- Plastic & Recon Surgery
- Plastic Surgery
Fellowship:MD Anderson Cancer Center (2000) TX
Residency:New York University Med Ctr (1999) NY
Medical Education:Univ of California San Francisco (1989) CA
Residency:Massachusetts General Hospital (1997) MA
Board Certification: Plastic Surgery, American Board of Plastic Surgery (2001)
MD, UCSF, Medicine (1989)
Current Research and Scholarly Interests
Geoffrey Gurtner's Lab is interested in understanding the mecahnism of new blood vessel growth following injury and how pathways of tissue regeneration and fibrosis interact in wound healing.
SPY Intra-Operative Angiography & Skin Perfusion in Immediate Breast Reconstruction w/ Implants
Breast cancer is the most common malignancy among women, and over 180,000 women will be diagnosed with this disease in 2008. Last year, over 57,000 breast reconstructive procedures were performed, of which prosthetic reconstruction constituted 76%. Immediate reconstruction has been favored over delayed procedures for psychological and technical reasons. However, immediate breast reconstruction is associated with significantly higher complication rates (50-52%) than delayed procedures (32-36%), especially when a prosthetic technique is used. For prosthetic reconstructions, the most significant early complications include necrosis of the mastectomy skin flaps, infection, delayed wound healing and exposure of the implant. The published incidence of these complications ranges between 10% and 40% and is predominantly associated with malperfusion of mastectomy skin flaps. Thus, evaluation of skin perfusion and elimination of poorly vascularized areas could help reduce the high rate of complications in immediate breast reconstruction.
Evaluation of the Cook Biodesign Plastic Surgery Matrix
Patients with a desire for nipple reconstruction following breast cancer and breast reconstruction will receive a surgical procedure to reconstruct one or both nipples utilizing the COOK(r) Biodesign(r) Nipple Reconstruction Cylinder.
Stanford is currently not accepting patients for this trial. For more information, please contact Shannon Meyer, (650) 724 - 1953.
- Plastic Surgery
SURG 209 (Aut, Win, Spr, Sum)
Independent Studies (6)
- Directed Reading in Surgery
SURG 299 (Aut, Win, Spr, Sum)
- Early Clinical Experience in Surgery
SURG 280 (Aut, Win, Spr, Sum)
- Graduate Research
SURG 399 (Aut, Win, Spr, Sum)
- Medical Scholars Research
SURG 370 (Aut, Win, Spr, Sum)
- Plastic Surgery Tutorial
SURG 208 (Aut, Win, Spr, Sum)
- Undergraduate Research
SURG 199 (Aut, Win, Spr, Sum)
- Directed Reading in Surgery
- Prior Year Courses
Enhancement of mesenchymal stem cell angiogenic capacity and stemness by a biomimetic hydrogel scaffold
2012; 33 (1): 80-90
In this study, we examined the capacity of a biomimetic pullulan-collagen hydrogel to create a functional biomaterial-based stem cell niche for the delivery of mesenchymal stem cells (MSCs) into wounds. Murine bone marrow-derived MSCs were seeded into hydrogels and compared to MSCs grown in standard culture conditions. Hydrogels induced MSC secretion of angiogenic cytokines and expression of transcription factors associated with maintenance of pluripotency and self-renewal (Oct4, Sox2, Klf4) when compared to MSCs grown in standard conditions. An excisonal wound healing model was used to compare the ability of MSC-hydrogel constructs versus MSC injection alone to accelerate wound healing. Injection of MSCs did not significantly improve time to wound closure. In contrast, wounds treated with MSC-seeded hydrogels showed significantly accelerated healing and a return of skin appendages. Bioluminescence imaging and FACS analysis of luciferase+/GFP+ MSCs indicated that stem cells delivered within the hydrogel remained viable longer and demonstrated enhanced engraftment efficiency than those delivered via injection. Engrafted MSCs were found to differentiate into fibroblasts, pericytes and endothelial cells but did not contribute to the epidermis. Wounds treated with MSC-seeded hydrogels demonstrated significantly enhanced angiogenesis, which was associated with increased levels of VEGF and other angiogenic cytokines within the wounds. Our data suggest that biomimetic hydrogels provide a functional niche capable of augmenting MSC regenerative potential and enhancing wound healing.
View details for DOI 10.1016/j.biomaterials.2011.09.041
View details for Web of Science ID 000297399700009
View details for PubMedID 21963148
Focal adhesion kinase links mechanical force to skin fibrosis via inflammatory signaling
2012; 18 (1): 148-152
Exuberant fibroproliferation is a common complication after injury for reasons that are not well understood. One key component of wound repair that is often overlooked is mechanical force, which regulates cell-matrix interactions through intracellular focal adhesion components, including focal adhesion kinase (FAK). Here we report that FAK is activated after cutaneous injury and that this process is potentiated by mechanical loading. Fibroblast-specific FAK knockout mice have substantially less inflammation and fibrosis than control mice in a model of hypertrophic scar formation. We show that FAK acts through extracellular-related kinase (ERK) to mechanically trigger the secretion of monocyte chemoattractant protein-1 (MCP-1, also known as CCL2), a potent chemokine that is linked to human fibrotic disorders. Similarly, MCP-1 knockout mice form minimal scars, indicating that inflammatory chemokine pathways are a major mechanism by which FAK mechanotransduction induces fibrosis. Small-molecule inhibition of FAK blocks these effects in human cells and reduces scar formation in vivo through attenuated MCP-1 signaling and inflammatory cell recruitment. These findings collectively indicate that physical force regulates fibrosis through inflammatory FAK-ERK-MCP-1 pathways and that molecular strategies targeting FAK can effectively uncouple mechanical force from pathologic scar formation.
View details for DOI 10.1038/nm.2574
View details for Web of Science ID 000299018600041
Vascular anastomosis using controlled phase transitions in poloxamer gels
2011; 17 (9): 1147-U160
Vascular anastomosis is the cornerstone of vascular, cardiovascular and transplant surgery. Most anastomoses are performed with sutures, which are technically challenging and can lead to failure from intimal hyperplasia and foreign body reaction. Numerous alternatives to sutures have been proposed, but none has proven superior, particularly in small or atherosclerotic vessels. We have developed a new method of sutureless and atraumatic vascular anastomosis that uses US Food and Drug Administration (FDA)-approved thermoreversible tri-block polymers to temporarily maintain an open lumen for precise approximation with commercially available glues. We performed end-to-end anastomoses five times more rapidly than we performed hand-sewn controls, and vessels that were too small (<1.0 mm) to sew were successfully reconstructed with this sutureless approach. Imaging of reconstructed rat aorta confirmed equivalent patency, flow and burst strength, and histological analysis demonstrated decreased inflammation and fibrosis at up to 2 years after the procedure. This new technology has potential for improving efficiency and outcomes in the surgical treatment of cardiovascular disease.
View details for DOI 10.1038/nm.2424
View details for Web of Science ID 000294605100038
View details for PubMedID 21873986
Improving Cutaneous Scar Formation by Controlling the Mechanical Environment Large Animal and Phase I Studies
ANNALS OF SURGERY
2011; 254 (2): 217-225
To test the hypothesis that the mechanical environment of cutaneous wounds can control scar formation.Mechanical forces have been recognized to modulate myriad biologic processes, but the role of physical force in scar formation remains unclear. Furthermore, the therapeutic benefits of offloading cutaneous wounds with a device have not been rigorously tested.A mechanomodulating polymer device was utilized to manipulate the mechanical environment of closed cutaneous wounds in red Duroc swine. After 8 weeks, wounds subjected to different mechanical stress states underwent immunohistochemical analysis for fibrotic markers. In a phase I clinical study, 9 human patients undergoing elective abdominal surgery were treated postoperatively with a stress-shielding polymer on one side whereas the other side was treated as standard of care. Professional photographs were taken between 8 and 12 months postsurgery and evaluated using a visual analog scale by lay and professional panels. This study is registered with ClinicalTrials.gov, number NCT00766727.Stress shielding of swine incisions reduced histologic scar area by 6- and 9-fold compared to control and elevated stress states, respectively (P < 0.01 for both) and dramatically decreased the histologic expression of profibrotic markers. Closure of high-tension wounds induced human-like scar formation in the red Duroc, a phenotype effectively mitigated with stress shielding of wounds. In the study on humans, stress shielding of abdominal incisions significantly improved scar appearance (P = 0.004) compared with within-patient controls.These results indicate that mechanical manipulation of the wound environment with a dynamic stress-shielding polymer device can significantly reduce scar formation.
View details for DOI 10.1097/SLA.0b013e318220b159
View details for Web of Science ID 000292908700007
View details for PubMedID 21606834
An Information Theoretic, Microfluidic-Based Single Cell Analysis Permits Identification of Subpopulations among Putatively Homogeneous Stem Cells
2011; 6 (6)
An incomplete understanding of the nature of heterogeneity within stem cell populations remains a major impediment to the development of clinically effective cell-based therapies. Transcriptional events within a single cell are inherently stochastic and can produce tremendous variability, even among genetically identical cells. It remains unclear how mammalian cellular systems overcome this intrinsic noisiness of gene expression to produce consequential variations in function, and what impact this has on the biologic and clinical relevance of highly 'purified' cell subgroups. To address these questions, we have developed a novel method combining microfluidic-based single cell analysis and information theory to characterize and predict transcriptional programs across hundreds of individual cells. Using this technique, we demonstrate that multiple subpopulations exist within a well-studied and putatively homogeneous stem cell population, murine long-term hematopoietic stem cells (LT-HSCs). These subgroups are defined by nonrandom patterns that are distinguishable from noise and are consistent with known functional properties of these cells. We anticipate that this analytic framework can also be applied to other cell types to elucidate the relationship between transcriptional and phenotypic variation.
View details for DOI 10.1371/journal.pone.0021211
View details for Web of Science ID 000292033700046
View details for PubMedID 21731674
The molecular basis for impaired hypoxia-induced VEGF expression in diabetic tissues
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2009; 106 (32): 13505-13510
Diabetes is associated with poor outcomes following acute vascular occlusive events. This results in part from a failure to form adequate compensatory microvasculature in response to ischemia. Since vascular endothelial growth factor (VEGF) is an essential mediator of neovascularization, we examined whether hypoxic up-regulation of VEGF was impaired in diabetes. Both fibroblasts isolated from type 2 diabetic patients, and normal fibroblasts exposed chronically to high glucose, were defective in their capacity to up-regulate VEGF in response to hypoxia. In vivo, diabetic animals demonstrated an impaired ability to increase VEGF production in response to soft tissue ischemia. This resulted from a high glucose-induced decrease in transactivation by the transcription factor hypoxia-inducible factor-1alpha (HIF-1alpha), which mediates hypoxia-stimulated VEGF expression. Decreased HIF-1alpha functional activity was specifically caused by impaired HIF-1alpha binding to the coactivator p300. We identify covalent modification of p300 by the dicarbonyl metabolite methylglyoxal as being responsible for this decreased association. Administration of deferoxamine abrogated methylglyoxal conjugation, normalizing both HIF-1alpha/p300 interaction and transactivation by HIF-1alpha. In diabetic mice, deferoxamine promoted neovascularization and enhanced wound healing. These findings define molecular defects that underlie impaired VEGF production in diabetic tissues and offer a promising direction for therapeutic intervention.
View details for DOI 10.1073/pnas.0906670106
View details for Web of Science ID 000268877300065
View details for PubMedID 19666581
Wound repair and regeneration
2008; 453 (7193): 314-321
The repair of wounds is one of the most complex biological processes that occur during human life. After an injury, multiple biological pathways immediately become activated and are synchronized to respond. In human adults, the wound repair process commonly leads to a non-functioning mass of fibrotic tissue known as a scar. By contrast, early in gestation, injured fetal tissues can be completely recreated, without fibrosis, in a process resembling regeneration. Some organisms, however, retain the ability to regenerate tissue throughout adult life. Knowledge gained from studying such organisms might help to unlock latent regenerative pathways in humans, which would change medical practice as much as the introduction of antibiotics did in the twentieth century.
View details for DOI 10.1038/nature07039
View details for Web of Science ID 000255868400038
View details for PubMedID 18480812
Decreasing intracellular superoxide corrects defective ischemia-induced new vessel formation in diabetic mice
JOURNAL OF BIOLOGICAL CHEMISTRY
2008; 283 (16): 10930-10938
Tissue ischemia promotes vasculogenesis through chemokine-induced recruitment of bone marrow-derived endothelial progenitor cells (EPCs). Diabetes significantly impairs this process. Because hyperglycemia increases reactive oxygen species in a number of cell types, and because many of the defects responsible for impaired vasculogenesis involve HIF1-regulated genes, we hypothesized that HIF1 function is impaired in diabetes because of reactive oxygen species-induced modification of HIF1alpha by the glyoxalase 1 (GLO1) substrate methylglyoxal. Decreasing superoxide in diabetic mice by either transgenic expression of manganese superoxide dismutase or by administration of an superoxide dismutase mimetic corrected post-ischemic defects in neovascularization, oxygen delivery, and chemokine expression, and normalized tissue survival. In hypoxic fibroblasts cultured in high glucose, overexpression of GLO1 prevented reduced expression of both the EPC mobilizing chemokine stromal cell-derived factor-1 (SDF-1) and of vascular epidermal growth factor, which modulates growth and differentiation of recruited EPCs. In hypoxic EPCs cultured in high glucose, overexpression of GLO1 prevented reduced expression of both the SDF-1 receptor CXCR4, and endothelial nitric-oxide synthase, an enzyme essential for EPC mobilization. HIF1alpha modification by methylglyoxal reduced heterodimer formation and HIF1alpha binding to all relevant promoters. These results provide a basis for the rational design of new therapeutics to normalize impaired ischemia-induced vasculogenesis in patients with diabetes.
View details for DOI 10.1074/jbc.M707451200
View details for Web of Science ID 000254894700074
View details for PubMedID 18227068
Paracrine mechanism of angiogenesis in adipose-derived stem cell transplantation.
Annals of plastic surgery
2014; 72 (2): 234-241
INTRODUCTION: Adipose-derived stem cells (ASCs) have shown potential for cell-based therapy in the field of plastic surgery. However, the fate of ASCs after transplantation and the mechanism(s) of their biologic capabilities remain unclear. METHODS: We isolated and cultured ASCs from transgenic mice that express both luciferase and green fluorescent protein and injected the cells into the inguinal fat pads of wild-type mice. We tested 4 experimental groups, namely, ischemic fat pads with/without ASCs and control fat pads with/without ASCs. RESULTS: Transplanted ASCs were tracked with bioluminescence imaging. The luminescence gradually decreased over 28 days, indicating cell death after transplantation. More ASCs were retained in ischemic fat pads on day 7 compared to control fat pads. On day 14, adipose tissue vascular density was higher in the ASC transplantation groups compared to those without ASCs. On day 28, there was decreased atrophy of adipose tissue in ASC-treated ischemic fat pads. Transplanted ASCs were detected as nonproliferating green fluorescent protein-positive cells, whereas native endothelial cells adjacent to the transplanted ASCs were proliferative. Protein analysis demonstrated higher expression of hepatocyte growth factor and vascular endothelial growth factor in the ASC transplantation groups, suggesting a paracrine mechanism, which was confirmed by in vitro experiments with conditioned media from ASCs. CONCLUSIONS: Transplanted ASCs are preferentially retained in ischemic adipose tissue, although most of the cells eventually undergo cell death. They exert an angiogenic effect on adipose tissue mainly through a paracrine mechanism. Increased understanding of these effects will help develop ASCs as a tool for cell-based therapy.
View details for DOI 10.1097/SAP.0b013e318264fd6a
View details for PubMedID 23636112
Molecular analysis and differentiation capacity of adipose-derived stem cells from lymphedema tissue.
Plastic and reconstructive surgery
2013; 132 (3): 580-589
Many breast cancer patients are plagued by the disabling complication of upper limb lymphedema after axillary surgery. Conservative treatments using massage and compression therapy do not offer a lasting relief, as they fail to address the chronic transformation of edema into excess adipose tissue. Liposuction to address the adipose nature of the lymphedema has provided an opportunity for a detailed analysis of the stromal fraction of lymphedema-associated fat to clarify the molecular mechanisms for this adipogenic transformation.Adipose-derived stem cells were harvested from human lipoaspirate of the upper extremity from age-matched patients with lymphedema (n = 3) or subcutaneous adipose tissue from control patients undergoing cosmetic procedures (n = 3). Immediately after harvest, adipose-derived stem cells were analyzed using single-cell transcriptional profiling techniques. Osteogenic, adipogenic, and vasculogenic gene expression and differentiation were assessed by quantitative real-time polymerase chain reaction and standard in vitro differentiation assays.Differential transcriptional clusters of adipose-derived stem cells were found between lymphedema and subcutaneous fat. Interestingly, lymphedema-associated stem cells had a much higher adipogenic gene expression and enhanced ability to undergo adipogenic differentiation. Conversely, they had lower vasculogenic gene expression and diminished capability to form tubules in vitro, whereas the osteogenic differentiation capacity was not significantly altered.Adipose-derived stem cells from extremities affected by lymphedema appear to exhibit transcriptional profiles similar to those of abdominal adipose-derived stem cells; however, their adipogenic differentiation potential is strongly increased and their vasculogenic capacity is compromised. These results suggest that the underlying pathophysiology of lymphedema drives adipose-derived stem cells toward adipogenic differentiation.
View details for DOI 10.1097/PRS.0b013e31829ace13
View details for PubMedID 23985633
Enabling stem cell therapies for tissue repair: Current and future challenges
2013; 31 (5): 744-751
Stem cells embody the tremendous potential of the human body to develop, grow, and repair throughout life. Understanding the biologic mechanisms that underlie stem cell-mediated tissue regeneration is key to harnessing this potential. Recent advances in molecular biology, genetic engineering, and material science have broadened our understanding of stem cells and helped bring them closer to widespread clinical application. Specifically, innovative approaches to optimize how stem cells are identified, isolated, grown, and utilized will help translate these advances into effective clinical therapies. Although there is growing interest in stem cells worldwide, this enthusiasm must be tempered by the fact that these treatments remain for the most part clinically unproven. Future challenges include refining the therapeutic manipulation of stem cells, validating these technologies in randomized clinical trials, and regulating the global expansion of regenerative stem cell therapies.
View details for DOI 10.1016/j.biotechadv.2012.11.006
View details for Web of Science ID 000322058900020
View details for PubMedID 23178704
Wound healing: a paradigm for regeneration.
Mayo Clinic proceedings. Mayo Clinic
2013; 88 (9): 1022-1031
Human skin is a remarkably plastic organ that sustains insult and injury throughout life. Its ability to expeditiously repair wounds is paramount to survival and is thought to be regulated by wound components such as differentiated cells, stem cells, cytokine networks, extracellular matrix, and mechanical forces. These intrinsic regenerative pathways are integrated across different skin compartments and are being elucidated on the cellular and molecular levels. Recent advances in bioengineering and nanotechnology have allowed researchers to manipulate these microenvironments in increasingly precise spatial and temporal scales, recapitulating key homeostatic cues that may drive regeneration. The ultimate goal is to translate these bench achievements into viable bedside therapies that address the growing global burden of acute and chronic wounds. In this review, we highlight current concepts in cutaneous wound repair and propose that many of these evolving paradigms may underlie regenerative processes across diverse organ systems.
View details for DOI 10.1016/j.mayocp.2013.04.012
View details for PubMedID 24001495
A novel mouse model for frostbite injury.
Wilderness & environmental medicine
2013; 24 (2): 94-104
Frostbite injury occurs when exposure to cold results in frozen tissue. To screen drugs and other field therapies that might improve the outcome for a frostbite victim, it would be helpful to have a reliable and cost-effective preclinical in vivo model.We sought to create a novel mouse skin model of induced frostbite injury. This model would allow quantification of the surface area of involved skin, histology of the wound, rate of wound healing, and skin loss in a standardized fashion after the frostbite injury.Thirty-six mice were studied. Standardized 2.9-cm diameter circles were tattooed on the mouse dorsum. Magnets frozen in dry ice (-78.5°C) were used to create a frostbite injury on skin within the circle, either as a continuous 5-minute freeze or as 3 repeated freeze (1-minute) and thaw (3-minute) cycles. Appearance, healing rate, skin surface area loss, and histology were recorded until the wounds were healed.The amount of skin surface area loss was approximately 50% for both freeze methods. Although the time to surface skin healing was similar for both freeze methods, the initial healing rate was significantly (P = .001) slower in mice exposed to the freeze-thaw cycles compared with the continuous freeze model. Histopathology reflected inflammatory changes, cell death, and necrosis.This novel in vivo mouse model for frostbite allows quantification of affected skin surface area, histology, healing rate, and skin loss and has the potential of being utilized to screen future treatment modalities.
View details for DOI 10.1016/j.wem.2012.11.020
View details for PubMedID 23481507
Adipose-derived Stromal Cells Overexpressing Vascular Endothelial Growth Factor Accelerate Mouse Excisional Wound Healing
2013; 21 (2): 445-455
Angiogenesis is essential to wound repair, and vascular endothelial growth factor (VEGF) is a potent factor to stimulate angiogenesis. Here, we examine the potential of VEGF-overexpressing adipose-derived stromal cells (ASCs) for accelerating wound healing using nonviral, biodegradable polymeric vectors. Mouse ASCs were transfected with DNA plasmid encoding VEGF or green fluorescent protein (GFP) using biodegradable poly (?-amino) esters (PBAE). Cells transfected using Lipofectamine 2000, a commercially available transfection reagent, were included as controls. ASCs transfected using PBAEs showed enhanced transfection efficiency and 12-15-fold higher VEGF production compared with cells transfected using Lipofectamine 2000 (*P < 0.05). When transplanted into a mouse wild-type excisional wound model, VEGF-overexpressing ASCs led to significantly accelerated wound healing, with full wound closure observed at 8 days compared to 10-12 days in groups treated with ASCs alone or saline control (*P < 0.05). Histology and polarized microscopy showed increased collagen deposition and more mature collagen fibers in the dermis of wound beds treated using PBAE/VEGF-modified ASCs than ASCs alone. Our results demonstrate the efficacy of using nonviral-engineered ASCs to accelerate wound healing, which may provide an alternative therapy for treating many diseases in which wound healing is impaired.
View details for DOI 10.1038/mt.2012.234
View details for Web of Science ID 000314434600021
View details for PubMedID 23164936
Murine models of human wound healing.
Methods in molecular biology (Clifton, N.J.)
2013; 1037: 265-274
In vivo wound healing experiments remain the most predictive models for studying human wound healing, allowing an accurate representation of the complete wound healing environment including various cell types, environmental cues, and paracrine interactions. Small animals are economical, easy to maintain, and allow researchers to take advantage of the numerous transgenic strains that have been developed to investigate the specific mechanisms involved in wound healing and regeneration. Here we describe three reproducible murine wound healing models that recapitulate the human wound healing process.
View details for DOI 10.1007/978-1-62703-505-7_15
View details for PubMedID 24029941
Evidence that mast cells are not required for healing of splinted cutaneous excisional wounds in mice.
2013; 8 (3)
Wound healing is a complex biological process involving the interaction of many cell types to replace lost or damaged tissue. Although the biology of wound healing has been extensively investigated, few studies have focused on the role of mast cells. In this study, we investigated the possible role of mast cells in wound healing by analyzing aspects of cutaneous excisional wound healing in three types of genetically mast cell-deficient mice. We found that C57BL/6-Kit(W-sh/W-sh), WBB6F1-Kit(W/W-v), and Cpa3-Cre; Mcl-1(fl/fl) mice re-epithelialized splinted excisional skin wounds at rates very similar to those in the corresponding wild type or control mice. Furthermore, at the time of closure, scars were similar in the genetically mast cell-deficient mice and the corresponding wild type or control mice in both quantity of collagen deposition and maturity of collagen fibers, as evaluated by Masson's Trichrome and Picro-Sirius red staining. These data indicate that mast cells do not play a significant non-redundant role in these features of the healing of splinted full thickness excisional cutaneous wounds in mice.
View details for DOI 10.1371/journal.pone.0059167
View details for PubMedID 23544053
Cellular response to a novel fetal acellular collagen matrix: implications for tissue regeneration.
International journal of biomaterials
2013; 2013: 527957-?
Introduction. PriMatrix (TEI Biosciences Inc., Boston, MA, USA) is a novel acellular collagen matrix derived from fetal bovine dermis that is designed for use in partial- and full-thickness wounds. This study analyzes the cellular response to PriMatrix in vivo, as well as the ability of this matrix to facilitate normal tissue regeneration. Methods. Five by five mm squares of rehydrated PriMatrix were implanted in a subcutaneous fashion on the dorsum of wild-type mice. Implant site tissue was harvested for histology, immunohistochemistry (IHC), and flow cytometric analyses at multiple time points until day 28. Results. PriMatrix implants were found to go through a biological progression initiated by a transient infiltrate of inflammatory cells, followed by mesenchymal cell recruitment and vascular development. IHC analysis revealed that the majority of the implanted fetal dermal collagen fibers persisted through day 28 but underwent remodeling and cellular repopulation to form tissue with a density and morphology consistent with healthy dermis. Conclusions. PriMatrix implants undergo progressive in vivo remodeling, facilitating the regeneration of histologically normal tissue through a mild inflammatory and progenitor cell response. Regeneration of normal tissue is especially important in a wound environment, and these findings warrant further investigation of PriMatrix in this setting.
View details for DOI 10.1155/2013/527957
View details for PubMedID 23970899
The role of focal adhesion complexes in fibroblast mechanotransduction during scar formation.
Differentiation; research in biological diversity
Historically, great efforts have been made to elucidate the biochemical pathways that direct the complex process of wound healing; however only recently has there been recognition of the importance that mechanical signals play in the process of tissue repair and scar formation. The body's physiologic response to injury involves a dynamic interplay between mechanical forces and biochemical cues which directs a cascade of signals leading ultimately to the formation of fibrotic scar. Fibroblasts are a highly mechanosensitive cell type and are also largely responsible for the generation of the fibrotic matrix during scar formation and are thus a critical player in the process of mechanotransduction during tissue repair. Mechanotransduction is initiated at the interface between the cell membrane and the extracellular matrix where mechanical signals are first translated into a biochemical response. Focal adhesions are dynamic multi-protein complexes through which the extracellular matrix links to the intracellular cytoskeleton. These focal adhesion complexes play an integral role in the propagation of this initial mechanical cue into an extensive network of biochemical signals leading to widespread downstream effects including the influx of inflammatory cells, stimulation of angiogenesis, keratinocyte migration, fibroblast proliferation and collagen synthesis. Increasing evidence has demonstrated the importance of the biomechanical milieu in healing wounds and suggests that an integrated approach to the discovery of targets to decrease scar formation may prove more clinically efficacious than previous purely biochemical strategies.
View details for PubMedID 23623400
Adult stem cells in small animal wound healing models.
Methods in molecular biology (Clifton, N.J.)
2013; 1037: 81-98
This chapter broadly reviews the use of stem cells as a means to accelerate wound healing, focusing first on the properties of stem cells that make them attractive agents to influence repair, both alone and as vehicles for growth factor delivery. Major stem cell reservoirs are described, including adult, embryonic, and induced pluripotent cell sources, outlining the advantages and limitations of each source as wound healing agents, as well as the possible mechanisms responsible for wound healing acceleration. Finally, the chapter includes a materials and methods section that provides an in-depth description of adult tissue harvest techniques.
View details for DOI 10.1007/978-1-62703-505-7_5
View details for PubMedID 24029931
In vivo directed differentiation of pluripotent stem cells for skeletal regeneration
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (50): 20379-20384
Pluripotent cells represent a powerful tool for tissue regeneration, but their clinical utility is limited by their propensity to form teratomas. Little is known about their interaction with the surrounding niche following implantation and how this may be applied to promote survival and functional engraftment. In this study, we evaluated the ability of an osteogenic microniche consisting of a hydroxyapatite-coated, bone morphogenetic protein-2-releasing poly-L-lactic acid scaffold placed within the context of a macroenvironmental skeletal defect to guide in vivo differentiation of both embryonic and induced pluripotent stem cells. In this setting, we found de novo bone formation and participation by implanted cells in skeletal regeneration without the formation of a teratoma. This finding suggests that local cues from both the implanted scaffold/cell micro- and surrounding macroniche may act in concert to promote cellular survival and the in vivo acquisition of a terminal cell fate, thereby allowing for functional engraftment of pluripotent cells into regenerating tissue.
View details for DOI 10.1073/pnas.1218052109
View details for Web of Science ID 000312605600055
View details for PubMedID 23169671
Soft tissue mechanotransduction in wound healing and fibrosis
SEMINARS IN CELL & DEVELOPMENTAL BIOLOGY
2012; 23 (9): 981-986
Recent evidence suggests that mechanical forces can significantly impact the biologic response to injury. Integrated mechanical and chemical signaling networks have been discovered that enable physical cues to regulate disease processes such as pathologic scar formation. Distinct molecular mechanisms control how tensional forces influence wound healing and fibrosis. Conceptual frameworks to understand cutaneous repair have expanded beyond traditional cell-cytokine models to include dynamic interactions driven by mechanical force and the extracellular matrix. Strategies to manipulate these biomechanical signaling networks have tremendous therapeutic potential to reduce scar formation and promote skin regeneration.
View details for DOI 10.1016/j.semcdb.2012.09.010
View details for Web of Science ID 000311962800006
View details for PubMedID 23036529
- Introduction: Wound repair SEMINARS IN CELL & DEVELOPMENTAL BIOLOGY 2012; 23 (9): 945-945
Stem cell recruitment after injury: lessons for regenerative medicine
2012; 7 (6): 833-850
Tissue repair and regeneration are thought to involve resident cell proliferation as well as the selective recruitment of circulating stem and progenitor cell populations through complex signaling cascades. Many of these recruited cells originate from the bone marrow, and specific subpopulations of bone marrow cells have been isolated and used to augment adult tissue regeneration in preclinical models. Clinical studies of cell-based therapies have reported mixed results, however, and a variety of approaches to enhance the regenerative capacity of stem cell therapies are being developed based on emerging insights into the mechanisms of progenitor cell biology and recruitment following injury. This article discusses the function and mechanisms of recruitment of important bone marrow-derived stem and progenitor cell populations following injury, as well as the emerging therapeutic applications targeting these cells.
View details for DOI 10.2217/RME.12.82
View details for Web of Science ID 000310656000018
View details for PubMedID 23164083
Regenerative Surgery: Tissue Engineering in General Surgical Practice
WORLD JOURNAL OF SURGERY
2012; 36 (10): 2288-2299
Tissue engineering is a broad interdisciplinary field that aims to develop complex tissue and organ constructs through a combination of cell-, biomaterial-, and molecular-based approaches. This approach has the potential to transform the surgical treatment for diseases including trauma, cancer, and congenital malformations. A fundamental knowledge of key concepts in regenerative medicine is imperative for surgeons to maintain a leading role in developing and implementing these technologies. Researchers have started to elucidate the biologic mechanisms that maintain organ homeostasis throughout life, indicating that humans may have the latent capacity to regenerate complex tissues. By exploiting this intrinsic potential of the body, we can move even closer to developing functional, autologous replacement parts for a wide range of surgical diseases.
View details for DOI 10.1007/s00268-012-1710-1
View details for Web of Science ID 000309559800003
View details for PubMedID 22777416
Tissue engineering for the management of chronic wounds: current concepts and future perspectives
2012; 21 (10): 729-734
Chronic wounds constitute a significant and growing biomedical burden. With the increasing growth of populations prone to dysfunctional wound healing, there is an urgent and unmet need for novel strategies to both prevent and treat these complications. Tissue engineering offers the potential to create functional skin, and the synergistic efforts of biomedical engineers, material scientists, and molecular and cell biologists have yielded promising therapies for non-healing wounds. However, traditional paradigms for wound healing focus largely on the role of inflammatory cells and fail to incorporate more recent research highlighting the importance of stem cells and matrix dynamics in skin repair. Approaches to chronic wound healing centred on inflammation alone are inadequate to guide the development of regenerative medicine-based technologies. As the molecular pathways and biologic defects underlying non-healing wounds are further elucidated, multifaceted bioengineering systems must advance in parallel to exploit this knowledge. In this viewpoint essay, we highlight the current concepts in tissue engineering for chronic wounds and speculate on areas for future research in this increasingly interdisciplinary field.
View details for DOI 10.1111/j.1600-0625.2012.01542.x
View details for Web of Science ID 000310217000002
View details for PubMedID 22742728
- Delivery Strategies for Stem Cell-Based Therapy JOURNAL OF HEALTHCARE ENGINEERING 2012; 3 (1): 1-20
Stem cell niches for skin regeneration.
International journal of biomaterials
2012; 2012: 926059-?
Stem cell-based therapies offer tremendous potential for skin regeneration following injury and disease. Functional stem cell units have been described throughout all layers of human skin and the collective physical and chemical microenvironmental cues that enable this regenerative potential are known as the stem cell niche. Stem cells in the hair follicle bulge, interfollicular epidermis, dermal papillae, and perivascular space have been closely investigated as model systems for niche-driven regeneration. These studies suggest that stem cell strategies for skin engineering must consider the intricate molecular and biologic features of these niches. Innovative biomaterial systems that successfully recapitulate these microenvironments will facilitate progenitor cell-mediated skin repair and regeneration.
View details for DOI 10.1155/2012/926059
View details for PubMedID 22701121
- Stem Cells: Update and Impact on Craniofacial Surgery JOURNAL OF CRANIOFACIAL SURGERY 2012; 23 (1): 319-322
Therapeutic potential of bone marrow-derived mesenchymal stem cells for cutaneous wound healing.
Frontiers in immunology
2012; 3: 192-?
Despite advances in wound care, many wounds never heal and become chronic problems that result in significant morbidity and mortality to the patient. Cellular therapy for cutaneous wounds has recently come under investigation as a potential treatment modality for impaired wound healing. Bone marrow-derived mesenchymal stem cells (MSCs) are a promising source of adult progenitor cells for cytotherapy as they are easy to isolate and expand and have been shown to differentiate into various cell lineages. Early studies have demonstrated that MSCs may enhance epithelialization, granulation tissue formation, and neovascularization resulting in accelerated wound closure. It is currently unclear if these effects are mediated through cellular differentiation or by secretion of cytokines and growth factors. This review discusses the proposed biological contributions of MSCs to cutaneous repair and their clinical potential in cell-based therapies.
View details for DOI 10.3389/fimmu.2012.00192
View details for PubMedID 22787462
Enhancement of Human Adipose-Derived Stromal Cell Angiogenesis through Knockdown of a BMP-2 Inhibitor
PLASTIC AND RECONSTRUCTIVE SURGERY
2012; 129 (1): 53-66
Previous studies have demonstrated the role of noggin, a bone morphogenetic protein-2 inhibitor, in vascular development and angiogenesis. The authors hypothesized that noggin suppression in human adipose-derived stromal cells would enhance vascular endothelial growth factor secretion and angiogenesis in vitro and in vivo to a greater extent than bone morphogenetic protein-2 alone.Human adipose-derived stromal cells were isolated from human lipoaspirate (n = 6) noggin was knocked down using lentiviral techniques. Knockdown was confirmed and angiogenesis was assessed by tubule formation and quantitative real-time polymerase chain reaction. Cells were seeded onto scaffolds and implanted into a 4-mm critical size calvarial defect. In vivo angiogenic signaling was assessed by immunofluorescence and immunohistochemistry.Human adipose-derived stromal cells with noggin suppression secreted significantly higher amounts of angiogenic proteins, expressed higher levels of angiogenic genes, and formed more tubules in vitro. In vivo, calvarial defects seeded with noggin shRNA human adipose-derived stromal cells exhibited a significantly higher number of vessels in the defect site than controls by immunohistochemistry (p < 0.05). In addition, bone morphogenetic protein-2-releasing scaffolds significantly enhanced vascular signaling in the defect site.Human adipose-derived stromal cells demonstrate significant increases in angiogenesis in vitro and in vivo with both noggin suppression and BMP-2 supplementation. By creating a cell with noggin suppressed and by using a scaffold with increased bone morphogenetic protein-2 signaling, a more angiogenic niche can be created.
View details for DOI 10.1097/PRS.0b013e3182361ff5
View details for Web of Science ID 000298857100075
View details for PubMedID 21915082
Nonintegrating Knockdown and Customized Scaffold Design Enhances Human Adipose-Derived Stem Cells in Skeletal Repair
2011; 29 (12): 2018-2029
An urgent need exists in clinical medicine for suitable alternatives to available techniques for bone tissue repair. Human adipose-derived stem cells (hASCs) represent a readily available, autogenous cell source with well-documented in vivo osteogenic potential. In this article, we manipulated Noggin expression levels in hASCs using lentiviral and nonintegrating minicircle short hairpin ribonucleic acid (shRNA) methodologies in vitro and in vivo to enhance hASC osteogenesis. Human ASCs with Noggin knockdown showed significantly increased bone morphogenetic protein (BMP) signaling and osteogenic differentiation both in vitro and in vivo, and when placed onto a BMP-releasing scaffold embedded with lentiviral Noggin shRNA particles, hASCs more rapidly healed mouse calvarial defects. This study therefore suggests that genetic targeting of hASCs combined with custom scaffold design can optimize hASCs for skeletal regenerative medicine.
View details for DOI 10.1002/stem.757
View details for Web of Science ID 000297220000012
View details for PubMedID 21997852
Mechanical force prolongs acute inflammation via T-cell-dependent pathways during scar formation
2011; 25 (12): 4498-4510
Mechanical force significantly modulates both inflammation and fibrosis, yet the fundamental mechanisms that regulate these interactions remain poorly understood. Here we performed microarray analysis to compare gene expression in mechanically loaded wounds vs. unloaded control wounds in an established murine hypertrophic scar (HTS) model. We identified 853 mechanically regulated genes (false discovery rate <2) at d 14 postinjury, a subset of which were enriched for T-cell-regulated pathways. To substantiate the role of T cells in scar mechanotransduction, we applied the HTS model to T-cell-deficient mice and wild-type mice. We found that scar formation in T-cell-deficient mice was reduced by almost 9-fold (P < 0.001) with attenuated epidermal (by 2.6-fold, P < 0.01) and dermal (3.9-fold, P < 0.05) proliferation. Mechanical stimulation was highly associated with sustained T-cell-dependent Th2 cytokine (IL-4 and IL-13) and chemokine (MCP-1) signaling. Further, T-cell-deficient mice failed to recruit systemic inflammatory cells such as macrophages or monocytic fibroblast precursors in response to mechanical loading. These findings indicate that T-cell-regulated fibrogenic pathways are highly mechanoresponsive and suggest that mechanical forces induce a chronic-like inflammatory state through immune-dependent activation of both local and systemic cell populations.
View details for DOI 10.1096/fj.10-178087
View details for Web of Science ID 000298138100040
View details for PubMedID 21911593
Antimycotic Ciclopirox Olamine in the Diabetic Environment Promotes Angiogenesis and Enhances Wound Healing
2011; 6 (11)
Diabetic wounds remain a major medical challenge with often disappointing outcomes despite the best available care. An impaired response to tissue hypoxia and insufficient angiogenesis are major factors responsible for poor healing in diabetic wounds. Here we show that the antimycotic drug ciclopirox olamine (CPX) can induce therapeutic angiogenesis in diabetic wounds. Treatment with CPX in vitro led to upregulation of multiple angiogenic genes and increased availability of HIF-1?. Using an excisional wound splinting model in diabetic mice, we showed that serial topical treatment with CPX enhanced wound healing compared to vehicle control treatment, with significantly accelerated wound closure, increased angiogenesis, and increased dermal cellularity. These findings offer a promising new topical pharmacologic therapy for the treatment of diabetic wounds.
View details for DOI 10.1371/journal.pone.0027844
View details for Web of Science ID 000297789200029
View details for PubMedID 22125629
CD105 Protein Depletion Enhances Human Adipose-derived Stromal Cell Osteogenesis through Reduction of Transforming Growth Factor beta 1 (TGF-beta 1) Signaling
JOURNAL OF BIOLOGICAL CHEMISTRY
2011; 286 (45): 39497-39509
Clinically available sources of bone for repair and reconstruction are limited by the accessibility of autologous grafts, infectious risks of cadaveric materials, and durability of synthetic substitutes. Cell-based approaches for skeletal regeneration can potentially fill this need, and adipose tissue represents a promising source for development of such therapies. Here, we enriched for an osteogenic subpopulation of cells derived from human subcutaneous adipose tissue utilizing microfluidic-based single cell transcriptional analysis and fluorescence-activated cell sorting (FACS). Statistical analysis of single cell transcriptional profiles demonstrated that low expression of endoglin (CD105) correlated with a subgroup of adipose-derived cells with increased osteogenic gene expression. FACS-sorted CD105(low) cells demonstrated significantly enhanced in vitro osteogenic differentiation and in vivo bone regeneration when compared with either CD105(high) or unsorted cells. Evaluation of the endoglin pathway suggested that enhanced osteogenesis among CD105(low) adipose-derived cells is likely due to identification of a subpopulation with lower TGF-?1/Smad2 signaling. These findings thus highlight a potential avenue to promote osteogenesis in adipose-derived mesenchymal cells for skeletal regeneration.
View details for DOI 10.1074/jbc.M111.256529
View details for Web of Science ID 000296759800067
View details for PubMedID 21949130
Pullulan Hydrogels Improve Mesenchymal Stem Cell Delivery into High-Oxidative-Stress Wounds
2011; 11 (11): 1458-1466
Cell-based therapies for wound repair are limited by inefficient delivery systems that fail to protect cells from the acute inflammatory environment. Here, a biomimetic hydrogel system is described that is based on the polymer pullulan, a carbohydrate glucan known to exhibit potent antioxidant capabilities. It is shown that pullulan hydrogels are an effective cell delivery system and improve mesenchymal stem cell survival and engraftment in high-oxidative-stress environments. The results suggest that glucan hydrogel systems may prove beneficial for progenitor-cell-based approaches to skin regeneration.
View details for DOI 10.1002/mabi.201100180
View details for Web of Science ID 000297555500002
View details for PubMedID 21994074
Pushing Back: Wound Mechanotransduction in Repair and Regeneration
JOURNAL OF INVESTIGATIVE DERMATOLOGY
2011; 131 (11): 2186-2196
Human skin is a highly specialized mechanoresponsive interface separating our bodies from the external environment. It must constantly adapt to dynamic physical cues ranging from rapid expansion during embryonic and early postnatal development to ubiquitous external forces throughout life. Despite the suspected role of the physical environment in cutaneous processes, the fundamental molecular mechanisms responsible for how skin responds to force remain unclear. Intracellular pathways convert mechanical cues into biochemical responses (in a process known as mechanotransduction) via complex mechanoresponsive elements that often blur the distinction between physical and chemical signaling. For example, cellular focal adhesion components exhibit dual biochemical and scaffolding functions that are critically modulated by force. Moreover, the extracellular matrix itself is increasingly recognized to mechanically regulate the spatiotemporal distribution of soluble and matrix-bound ligands, underscoring the importance of bidirectional crosstalk between cells and their physical environment. It seems likely that a structural hierarchy exists to maintain both cells and matrix in mechanical homeostasis and that dysregulation of this architectural integrity may underlie or contribute to various skin disorders. An improved understanding of these interactions will facilitate the development of novel biophysical materials and mechanomodulatory approaches to augment wound repair and regeneration.
View details for DOI 10.1038/jid.2011.212
View details for Web of Science ID 000296240100012
View details for PubMedID 21776006
Wound healing and regenerative strategies
2011; 17 (6): 541-549
Wound healing is a complex biological process that affects multiple tissue types. Wounds in the oral cavity are particularly challenging given the variety of tissue types that exist in close proximity to one another. The goal of regenerative medicine is to facilitate the rapid replacement of lost or damaged tissue with tissue that is functional, and physiologically similar to what previously existed. This review provides a general overview of wound healing and regenerative medicine, focusing specifically on how recent advances in the fields of stem cell biology, tissue engineering, and oral disease could translate into improved clinical outcomes.
View details for DOI 10.1111/j.1601-0825.2011.01787.x
View details for Web of Science ID 000292985000001
View details for PubMedID 21332599
Comparative Healing of Human Cutaneous Surgical Incisions Created by the PEAK PlasmaBlade, Conventional Electrosurgery, and a Standard Scalpel
PLASTIC AND RECONSTRUCTIVE SURGERY
2011; 128 (1): 104-111
The authors investigated thermal injury depth, inflammation, and scarring in human abdominal skin by comparing the histology of incisions made with a standard "cold" scalpel blade, conventional electrosurgery, and the PEAK PlasmaBlade, a novel, low-thermal-injury electrosurgical instrument.Approximately 6 and 3 weeks before abdominoplasty, full-thickness incisions were created in the abdominal pannus skin of 20 women, using a scalpel (scalpel), the PlasmaBlade, and a conventional electrosurgical instrument. Fresh (0-week) incisions were made immediately before surgery. After abdominoplasty, harvested incisions were analyzed for scar width, thermal injury depth, burst strength, and inflammatory response.Acute thermal injury depth was reduced 74 percent in PlasmaBlade incisions compared with conventional electrosurgical instrument (p < 0.001). Significant differences in inflammatory response were observed at 3 weeks, with mean CD3 response (T-lymphocytes) 40 percent (p = 0.01) and 21 percent (p ? 0.12) higher for the conventional electrosurgical instrument and PlasmaBlade, respectively, compared with the scalpel. CD68 response (monocytes/macrophages) was 52 percent (p = 0.05) and 16 percent (p ? 0.35) greater for a conventional electrosurgical instrument and the PlasmaBlade, respectively. PlasmaBlade incisions demonstrated 65 percent (p < 0.001) and 42 percent (p < 0.001) stronger burst strength than a conventional electrosurgical instrument, with equivalence to the scalpel at the 3- and 6-week time points, respectively. Scar width was equivalent for the PlasmaBlade and the scalpel at both time points, and 25 percent (p = 0.01) and 12 percent (p = 0.15) less than for electrosurgery, respectively.PlasmaBlade incisions demonstrated reduced thermal injury depth, inflammatory response, and scar width in healing skin compared with electrosurgery. These results suggest that the PlasmaBlade may provide clinically meaningful advantages over conventional electrosurgery during human cutaneous wound healing.Therapeutic, II.(Figure is included in full-text article.).
View details for DOI 10.1097/PRS.0b013e31821741ed
View details for Web of Science ID 000292499600040
View details for PubMedID 21701326
- Regenerative Medicine CURRENT PROBLEMS IN SURGERY 2011; 48 (3): 148-212
- In brief: Regenerative medicine. Current problems in surgery 2011; 48 (3): 142-146
Engineered Pullulan-Collagen Composite Dermal Hydrogels Improve Early Cutaneous Wound Healing
TISSUE ENGINEERING PART A
2011; 17 (5-6): 631-644
New strategies for skin regeneration are needed to address the significant medical burden caused by cutaneous wounds and disease. In this study, pullulan-collagen composite hydrogel matrices were fabricated using a salt-induced phase inversion technique, resulting in a structured yet soft scaffold for skin engineering. Salt crystallization induced interconnected pore formation, and modification of collagen concentration permitted regulation of scaffold pore size. Hydrogel architecture recapitulated the reticular distribution of human dermal matrix while maintaining flexible properties essential for skin applications. In vitro, collagen hydrogel scaffolds retained their open porous architecture and viably sustained human fibroblasts and murine mesenchymal stem cells and endothelial cells. In vivo, hydrogel-treated murine excisional wounds demonstrated improved wound closure, which was associated with increased recruitment of stromal cells and formation of vascularized granulation tissue. In conclusion, salt-induced phase inversion techniques can be used to create modifiable pullulan-collagen composite dermal scaffolds that augment early wound healing. These novel biomatrices can potentially serve as a structured delivery template for cells and biomolecules in regenerative skin applications.
View details for DOI 10.1089/ten.tea.2010.0298
View details for Web of Science ID 000287801600005
View details for PubMedID 20919949
Surgical Approaches to Create Murine Models of Human Wound Healing
JOURNAL OF BIOMEDICINE AND BIOTECHNOLOGY
Wound repair is a complex biologic process which becomes abnormal in numerous disease states. Although in vitro models have been important in identifying critical repair pathways in specific cell populations, in vivo models are necessary to obtain a more comprehensive and pertinent understanding of human wound healing. The laboratory mouse has long been the most common animal research tool and numerous transgenic strains and models have been developed to help researchers study the molecular pathways involved in wound repair and regeneration. This paper aims to highlight common surgical mouse models of cutaneous disease and to provide investigators with a better understanding of the benefits and limitations of these models for translational applications.
View details for DOI 10.1155/2011/969618
View details for Web of Science ID 000286250000001
View details for PubMedID 21151647
The Role of Stem Cells in Cutaneous Wound Healing: What Do We Really Know?
PLASTIC AND RECONSTRUCTIVE SURGERY
2011; 127 (1): 10S-20S
Wound repair is a complex process involving the orchestrated interaction of multiple growth factors, cytokines, chemokines, and cell types. Dysregulation of this process leads to problems such as excessive healing in the form of keloids and hypertrophic scars and chronic, nonhealing wounds. These issues have broad global implications. Stem cells offer enormous potential for enhancing tissue repair and regeneration following injury. The rapidly developing fields of stem cell biology and skin tissue engineering create translational opportunities for the development of novel stem cell-based wound-healing therapies.
View details for DOI 10.1097/PRS.0b013e3181fbe2d8
View details for Web of Science ID 000286122400003
View details for PubMedID 21200267
Akt-mediated mechanotransduction in murine fibroblasts during hypertrophic scar formation
WOUND REPAIR AND REGENERATION
2011; 19 (1): 49-58
Although numerous factors are implicated in skin fibrosis, the exact pathophysiology of hypertrophic scarring remains unknown. We recently demonstrated that mechanical force initiates hypertrophic scar formation in a murine model, potentially enhancing cellular survival through Akt. Here, we specifically examined Akt-mediated mechanotransduction in fibroblasts using both strain culture systems and our murine scar model. In vitro, static strain increased fibroblast motility, an effect blocked by wortmannin (a phosphoinositide-3-kinase/Akt inhibitor). We also demonstrated that high-frequency cyclic strain was more effective at inducing Akt phosphorylation than low frequency or static strain. In vivo, Akt phosphorylation was induced by mechanical loading of dermal fibroblasts in both unwounded and wounded murine skin. Mechanically loaded scars also exhibited strong expression of ?-smooth muscle actin, a putative marker of pathologic scar formation. In vivo inhibition of Akt increased apoptosis but did not significantly abrogate hypertrophic scar development. These data suggest that although Akt signaling is activated in fibroblasts during mechanical loading of skin, this is not the critical pathway in hypertrophic scar formation. Future studies are needed to fully elucidate the critical mechanotransduction components and pathways which activate skin fibrosis.
View details for DOI 10.1111/j.1524-475X.2010.00643.x
View details for Web of Science ID 000286214600032
View details for PubMedID 21134033
Statistics in Medicine
PLASTIC AND RECONSTRUCTIVE SURGERY
2011; 127 (1): 437-444
The scope of biomedical research has expanded rapidly during the past several decades, and statistical analysis has become increasingly necessary to understand the meaning of large and diverse quantities of raw data. As such, a familiarity with this lexicon is essential for critical appraisal of medical literature. This article attempts to provide a practical overview of medical statistics, with an emphasis on the selection, application, and interpretation of specific tests. This includes a brief review of statistical theory and its nomenclature, particularly with regard to the classification of variables. A discussion of descriptive methods for data presentation is then provided, followed by an overview of statistical inference and significance analysis, and detailed treatment of specific statistical tests and guidelines for their interpretation.
View details for DOI 10.1097/PRS.0b013e3181f95dd2
View details for Web of Science ID 000285992100060
View details for PubMedID 21200241
- Diathermy or Surgical Scalpel for Abdominal Skin Incisions What Is the Impact On Clinical Practice? ANNALS OF SURGERY 2011; 253 (1): 14-15
Quantifying migration and polarization of murine mesenchymal stem cells on different bone substitutes by confocal laser scanning microscopy
JOURNAL OF CRANIO-MAXILLOFACIAL SURGERY
2010; 38 (8): 580-588
Cell migration is preceded by cell polarization. The aim of the present study was to evaluate the impact of the geometry of different bone substitutes on cell morphology and chemical responses in vitro.Cell polarization and migration were monitored temporally by using confocal laser scanning microscopy (CLSM) to follow green fluorescent protein (GFP)±mesenchymal stem cells (MSCs) on anorganic cancellous bovine bone (Bio-Oss(®)), ?-tricalcium phosphate (?-TCP) (chronOS(®)) and highly porous calcium phosphate ceramics (Friedrich-Baur-Research-Institute for Biomaterials, Germany). Differentiation GFP±MSCs was observed using pro-angiogenic and pro-osteogenic biomarkers.At the third day of culture polarized vs. non-polarized cellular sub-populations were clearly established. Biomaterials that showed more than 40% of polarized cells at the 3rd day of culture, subsequently showed an enhanced cell migration compared to biomaterials, where non-polarized cells predominated (p<0.003). This trend continued untill the 7th day of culture (p<0.003). The expression of vascular endothelial growth factor was enhanced in biomaterials where cell polarization predominated at the 7th day of culture (p=0.001).This model opens an interesting approach to understand osteoconductivity at a cellular level. MSCs are promising in bone tissue engineering considering the strong angiogenic effect before differentiation occurs.
View details for DOI 10.1016/j.jcms.2010.01.004
View details for Web of Science ID 000284971700006
View details for PubMedID 20189818
- The Basic Science of Vascular Biology: Implications for the Practicing Surgeon PLASTIC AND RECONSTRUCTIVE SURGERY 2010; 126 (5): 1527-1537
The basic science of vascular biology: implications for the practicing surgeon.
Plastic and reconstructive surgery
2010; 126 (5): 1528-1538
A thorough understanding of vascular biology will assist the reconstructive surgeon in both operative planning and development of novel surgical approaches to treat chronic wounds and tissue loss, and to optimize regenerative strategies for tissue reconstruction. In this review, several fundamental concepts of the basic science of vascular biology are discussed, with specific emphasis on the clinical implications most relevant to the reconstructive surgeon. Topics include the vascular physiology of tissue flaps and grafts, the principles of neovascularization including angiogenesis and vasculogenesis, and the basic concepts of bioengineering of vascularized tissue constructs for use in reconstruction. As basic science research increases our collective understanding of vascular physiology--specifically, in the areas of neovascularization and tissue engineering--reconstructive surgeons will be able to improve treatment of the sequelae of ischemic injuries, tissue loss, and chronic wounds.
View details for DOI 10.1097/PRS.0b013e3181ef8ccf
View details for PubMedID 21042110
PLASTIC AND RECONSTRUCTIVE SURGERY
2010; 126 (4): 1163-1171
Stem cells are self-renewing cells capable of differentiating into multiple cell lines and are classified according to their origin and their ability to differentiate. Enormous potential exists in use of stem cells for regenerative medicine. To produce effective stem cell-based treatments for a range of diseases, an improved understanding of stem cell biology and better control over stem cell fate are necessary. In addition, the barriers to clinical translation, such as potential oncologic properties of stem cells, need to be addressed. With renewed government support and continued refinement of current stem cell methodologies, the future of stem cell research is exciting and promises to provide novel reconstructive options for patients and surgeons limited by traditional paradigms.
View details for DOI 10.1097/PRS.0b013e3181ea42bb
View details for Web of Science ID 000282559100003
View details for PubMedID 20555302
Tissue Engineering in Plastic Surgery: A Review
PLASTIC AND RECONSTRUCTIVE SURGERY
2010; 126 (3): 858-868
Novel tissue- and organ-engineering strategies are needed to address the growing need for replacement biological parts. Collective progress in stem cell technology, biomaterials, engineering, and molecular medicine has advanced the state of regenerative medicine, yet many hurdles to clinical translation remain. Plastic surgeons are in an ideal position to capitalize on emerging technologies and will be at the forefront of transitioning basic science research into the clinical reconstructive arena. This review highlights fundamental principles of bioengineering, recent progress in tissue-specific engineering, and future directions for this exciting and rapidly evolving area of medicine.
View details for DOI 10.1097/PRS.0b013e3181e3b3a3
View details for Web of Science ID 000281606700016
View details for PubMedID 20811219
Bone formation and degradation of a highly porous biphasic calcium phosphate ceramic in presence of BMP-7, VEGF and mesenchymal stem cells in an ectopic mouse model
JOURNAL OF CRANIO-MAXILLOFACIAL SURGERY
2010; 38 (6): 423-430
Angiogenesis and mesenchymal stem cells (MSCs) promote osteogenesis. The aim of the present study was to evaluate whether bone morphogenetic protein (BMP-7) promoted osteoinduction could be enhanced by combining it with vascular endothelial growth factor (VEGF) or MSCs in highly porous biphasic calcium phosphate (BCP) ceramics.BCP ceramic blocks were implanted in an ectopic site in 24 mice (BMP-7 vs. BMP-7/VEGF; BMP-7 vs. BMP-7/MSCs and BMP-7 vs. Control; each group n=8). Specimens were analysed 12 weeks after surgery by environmental scanning electron microscopy (ESEM) and Giemsa staining.In all implanted scaffolds, newly formed bone was observed, even in the control site. No statistical differences in the amount of new bone were found in the presence of BMP-7 compared to BMP-7/VEGF (p=1.0) or BMP-7/MSCs (p=0.786). ESEM revealed a degradation of the scaffolds. A higher degradation was observed in areas where no bone-implant contact was present compared to areas where the ceramic was integrated in newly formed bone.Neither VEGF nor MSCs enhanced BMP-7 induced bone formation under the selected conditions. The present ceramic seemed to be osteoinductive and degradable, making this material suitable for bone tissue engineering.
View details for DOI 10.1016/j.jcms.2010.01.003
View details for Web of Science ID 000281172800003
View details for PubMedID 20189819
Strategies for organ level tissue engineering
2010; 6 (3): 151-157
The field of tissue engineering has made considerable strides since it was first described in the late 1980s. The advent and subsequent boom in stem cell biology, emergence of novel technologies for biomaterial development and further understanding of developmental biology have contributed to this accelerated progress. However, continued efforts to translate tissue-engineering strategies into clinical therapies have been hampered by the problems associated with scaling up laboratory methods to produce large, complex tissues. The significant challenges faced by tissue engineers include the production of an intact vasculature within a tissue-engineered construct and recapitulation of the size and complexity of a whole organ. Here we review the basic components necessary for bioengineering organs-biomaterials, cells and bioactive molecules-and discuss various approaches for augmenting these principles to achieve organ level tissue engineering. Ultimately, the successful translation of tissue-engineered constructs into everyday clinical practice will depend upon the ability of the tissue engineer to "scale up" every aspect of the research and development process.
View details for DOI 10.4161/org.6.3.12139
View details for Web of Science ID 000290266200003
View details for PubMedID 21197216
- The Plastic Surgery Research Council - Welcome from the Chairman PLASTIC AND RECONSTRUCTIVE SURGERY 2010; 125: 4-4
The SNaP System: Biomechanical and Animal Model Testing of a Novel Ultraportable Negative-Pressure Wound Therapy System
PLASTIC AND RECONSTRUCTIVE SURGERY
2010; 125 (5): 1362-1371
Negative-pressure wound therapy is traditionally achieved by attaching an electrically powered pump to a sealed wound bed and applying subatmospheric pressure by means of gauze or foam. The Smart Negative Pressure (SNaP) System (Spiracur, Inc., Sunnyvale, Calif.) is a novel ultraportable negative-pressure wound therapy system that does not require an electrically powered pump.Negative pressure produced by the SNaP System, and a powered pump, the wound vacuum-assisted closure advanced-therapy system (Kinetic Concepts, Inc., San Antonio, Texas), were compared in vitro using bench-top pressure sensor testing and microstrain and stress testing with pressure-sensitive film and micro-computed tomographic scan analysis. In addition, to test in vivo efficacy, 10 rats underwent miniaturized SNaP (mSNaP) device placement on open wounds. Subject rats were randomized to a system activation group (approximately -125 mmHg) or a control group (atmospheric pressure). Wound measurements and histologic data were collected for analysis.Bench measurement revealed nearly identical negative-pressure delivery and mechanical strain deformation patterns between both systems. Wounds treated with the mSNaP System healed faster, with decreased wound size by postoperative day 7 (51 percent versus 12 percent reduction; p < 0.05) and had more rapid complete reepithelialization (21 days versus 32 days; p < 0.05). The mSNaP device also induced robust granulation tissue formation.The SNaP System and an existing electrically powered negative-pressure wound therapy system have similar biomechanical properties and functional wound-healing benefits. The potential clinical efficacy of the SNaP device for the treatment of wounds is supported.
View details for DOI 10.1097/PRS.0b013e3181d62b25
View details for Web of Science ID 000276886600008
View details for PubMedID 20440156
Intraoperative Perfusion Mapping with Laser-Assisted Indocyanine Green Imaging Can Predict and Prevent Complications in Immediate Breast Reconstruction
PLASTIC AND RECONSTRUCTIVE SURGERY
2010; 125 (4): 1065-1073
Immediate breast reconstruction results in a superior cosmetic outcome. However, immediate breast reconstruction using both prosthetic and autologous techniques is associated with significantly higher complication rates than delayed procedures. These early postoperative complications are usually related to unrecognized ischemia of mastectomy skin and/or inadequate perfusion of autologous tissue used for reconstruction. Aside from clinical experience, there are no reliable tools to assist the novice surgeon with intraoperative assessment of tissue viability.Laser-assisted indocyanine green imaging was applied to determine and map tissue perfusion. Indocyanine green perfusion mapping was used in 24 consecutive breast reconstructions to define the perfusion of both mastectomy skin and autologous tissue. Areas of inadequate perfusion were then removed at the time of surgery. Postoperative complications occurring within 90 days after surgery were reviewed.In 24 consecutive breast reconstruction (16 tissue expanders, two latissimus dorsi flaps, and six deep inferior epigastric perforator/superficial inferior epigastric arteries), there was a 4 percent complication rate. Intraoperatively, the use of indocyanine green imaging allowed all poorly perfused skin to be removed completely in each case, minimizing the incidence of mastectomy flap necrosis, partial necrosis of autologous tissue, and impaired healing. For autologous reconstruction, patency of anastomoses could also be confirmed. This complication rate was significantly less than the 15.1 percent complication rate observed in 206 reconstructions in the previous consecutive 148 patients (p < 0.01) with similar demographics and risk factors.This early experience demonstrates an increased accuracy in predicting tissue necrosis (mastectomy flap, autologous tissue) as guided by indocyanine green imaging. Further prospective studies are warranted to quantify whether this technology can reduce health care costs by preventing complications in immediate breast reconstruction.
View details for DOI 10.1097/PRS.0b013e3181d17f80
View details for Web of Science ID 000276644000003
View details for PubMedID 20335859
- Discussion: Construction and Clinical Application of a Human Tissue-Engineered Epidermal Membrane PLASTIC AND RECONSTRUCTIVE SURGERY 2010; 125 (3): 910-912
HIF-1 alpha dysfunction in diabetes
2010; 9 (1): 75-79
Diabetic wounds are a significant public health burden, with slow or nonhealing diabetic foot ulcers representing the leading cause of non-traumatic lower limb amputation in developed countries. These wounds heal poorly as a result of compromised blood vessel formation in response to ischemia. We have recently shown that this impairment in neovascularization results from a high glucose-induced defect in transactivation of hypoxia-inducible factor-1alpha (HIF-1alpha), the transcription factor regulating vascular endothelial growth factor (VEGF) expression. HIF-1 dysfunction is the end result of reactive oxygen species-induced modification of its coactivator p300 by the glycolytic metabolite methylglyoxal. Use of the iron chelator-antioxidant deferoxamine (DFO) reversed these effects and normalized healing of humanized diabetic wounds in mice. Here, we present additional data demonstrating that HIF-1alpha activity, not stability, is impaired in the high glucose environment. We demonstrate that high glucose-induced impairments in HIF-1alpha transactivation persist even in the setting of constitutive HIF-1alpha protein overexpression. Further, we show that high glucose-induced hydroxylation of the C-terminal transactivation domain of HIF-1alpha (the primary pathway regulating HIF-1alpha/p300 binding) does not alter HIF-1alpha activity. We extend our study of DFO's therapeutic efficacy in the treatment of impaired wound healing by demonstrating improvements in tissue viability in diabetic mice with DFO-induced increases in VEGF expression and vascular proliferation. Since DFO has been in clinical use for decades, the potential of this drug to treat a variety of ischemic conditions in humans can be evaluated relatively quickly.
View details for Web of Science ID 000273236800025
View details for PubMedID 20016290
Meta Analysis of the Effectiveness of Surgical Scalpel or Diathermy in Making Abdominal Skin Incisions.
Annals of surgery
View details for PubMedID 21135686
SUPERCHARGED REVERSE PEDICLE ANTEROLATERAL THIGH FLAP IN RECONSTRUCTION OF A MASSIVE DEFECT: A CASE REPORT
2010; 30 (5): 397-400
Secondary reconstruction of lower extremity defects using local tissues is demanding and fraught with potential complications. Reconstructive efforts may be challenged by pre-existing scarring, paucity of recipient vessels, and patient co-morbidities limiting tolerance for prolonged and extensive surgery. We present a case of an 81-year-old male with a recurrent malignant melanoma invading the proximal and middle third of the tibia, who previously underwent reconstruction with the medial gastrocnemius muscle and a skin graft. After wide local re-excision and tibia fixation, a 12 cm x 28 cm reverse anterolateral thigh flap was used for soft tissue coverage. Because of the relatively large size of the flap based upon retrograde flow, we elected to supercharge the flap to augment its blood supply. Supercharging of the flap pedicle was accomplished by anastamosing the lateral circumflex femoral vessels to the anterior tibial vessels. The donor site wasclosed primarily. The flap survived entirely and successfully endured subsequent radiation therapy. Supercharging enhances reliability of the reverse anterolateral thigh flap, and thus, permits harvest of large tissue bulk for coverage of up to proximal two-thirds of the tibia.This is the first report describing successful supercharging of a large reverse anterolateral thigh flap which resulted in entire flap survival.
View details for DOI 10.1002/micr.20761
View details for Web of Science ID 000280085900010
View details for PubMedID 20238382
Imaging the Unfolded Protein Response in Primary Tumors Reveals Microenvironments with Metabolic Variations that Predict Tumor Growth
2010; 70 (1): 78-88
Cancer cells exist in harsh microenvironments that are governed by various factors, including hypoxia and nutrient deprivation. These microenvironmental stressors activate signaling pathways that affect cancer cell survival. While others have previously measured microenvironmental stressors in tumors, it remains difficult to detect the real-time activation of these downstream signaling pathways in primary tumors. In this study, we developed transgenic mice expressing an X-box binding protein 1 (XBP1)-luciferase construct that served as a reporter for endoplasmic reticulum (ER) stress and as a downstream response for the tumor microenvironment. Primary mammary tumors arising in these mice exhibited luciferase activity in vivo. Multiple tumors arising in the same mouse had distinct XBP1-luciferase signatures, reflecting either higher or lower levels of ER stress. Furthermore, variations in ER stress reflected metabolic and hypoxic differences between tumors. Finally, XBP1-luciferase activity correlated with tumor growth rates. Visualizing distinct signaling pathways in primary tumors reveals unique tumor microenvironments with distinct metabolic signatures that can predict for tumor growth.
View details for DOI 10.1158/0008-5472.CAN-09-2747
View details for Web of Science ID 000278404300011
View details for PubMedID 20028872
Comparative Healing of Surgical Incisions Created by the PEAK PlasmaBlade, Conventional Electrosurgery, and a Scalpel
PLASTIC AND RECONSTRUCTIVE SURGERY
2009; 124 (6): 1849-1859
The PEAK PlasmaBlade is a new electrosurgical device that uses pulsed radiofrequency to generate a plasma-mediated discharge along the exposed rim of an insulated blade, creating an effective cutting edge while the blade stays near body temperature.Full-thickness incisions were made on the dorsums of pigs with the PlasmaBlade, a conventional electrosurgical device, and a scalpel, and blood loss was quantified. Wounds were harvested at designated time points, tested for wound tensile strength, and examined histologically for scar formation and tissue damage.Bleeding was reduced significantly (59 percent) in PlasmaBlade incisions compared with scalpel incisions, and acute thermal damage from the PlasmaBlade (66 +/- 5 microm) was significantly less than both cut and coagulation mode electrosurgical incisions (456 +/- 35 microm and 615 +/- 22 microm, respectively). Histologic scoring for injury and wound strength was equivalent between the PlasmaBlade and scalpel incisions. By 6 weeks, the healed PlasmaBlade and scalpel incisions were approximately three times stronger, and scar cosmetic appearance was significantly better compared with electrosurgical incisions.The PlasmaBlade is a promising new surgical instrument that provides atraumatic, scalpel-like cutting precision and electrosurgical-like hemostasis, resulting in minimal bleeding, tissue injury, and scar formation.
View details for DOI 10.1097/PRS.0b013e3181bcee87
View details for Web of Science ID 000272615600015
View details for PubMedID 19952641
Human skin wounds: A major and snowballing threat to public health and the economy
WOUND REPAIR AND REGENERATION
2009; 17 (6): 763-771
ABSTRACT In the United States, chronic wounds affect 6.5 million patients. An estimated excess of US$25 billion is spent annually on treatment of chronic wounds and the burden is rapidly growing due to increasing health care costs, an aging population and a sharp rise in the incidence of diabetes and obesity worldwide. The annual wound care products market is projected to reach $15.3 billion by 2010. Chronic wounds are rarely seen in individuals who are otherwise healthy. In fact, chronic wound patients frequently suffer from "highly branded" diseases such as diabetes and obesity. This seems to have overshadowed the significance of wounds per se as a major health problem. For example, NIH's Research Portfolio Online Reporting Tool (RePORT; http://report.nih.gov/), directed at providing access to estimates of funding for various disease conditions does list several rare diseases but does not list wounds. Forty million inpatient surgical procedures were performed in the United States in 2000, followed closely by 31.5 million outpatient surgeries. The need for post-surgical wound care is sharply on the rise. Emergency wound care in an acute setting has major significance not only in a war setting but also in homeland preparedness against natural disasters as well as against terrorism attacks. An additional burden of wound healing is the problem of skin scarring, a $12 billion annual market. The immense economic and social impact of wounds in our society calls for allocation of a higher level of attention and resources to understand biological mechanisms underlying cutaneous wound complications.
View details for DOI 10.1111/j.1524-475X.2009.00543.x
View details for Web of Science ID 000271314900001
View details for PubMedID 19903300
- From Bedside to Bench and Back Again: Technology Innovation in Plastic Surgery PLASTIC AND RECONSTRUCTIVE SURGERY 2009; 124 (4): 1355-1356
- The mechanisms of action of vacuum assisted closure: More to learn SURGERY 2009; 146 (1): 40-51
Treating Chronic Wound Infections with Genetically Modified Free Flaps
PLASTIC AND RECONSTRUCTIVE SURGERY
2009; 123 (4): 1157-1168
The success of antimicrobial therapy has been impaired by the emergence of resistant bacterial strains. Antimicrobial peptides are ubiquitous proteins that are part of the innate immune system and are successful against such antibiotic-resistant microorganisms. The authors have previously demonstrated the feasibility of protein delivery via microvascular free flap gene therapy and here they examine this approach for recalcitrant infections.The authors investigated the production of the human cathelicidin antimicrobial peptide-LL37, delivered by ex vivo transduction of the rodent superficial inferior epigastric free flap with Ad/CMV-LL37. The vascular permeabilizing agent vascular endothelial growth factor (VEGF) was co-administered during ex vivo transduction with adenoviral vectors in an attempt to augment transduction efficiency. A rodent model of chronic wound/foreign body infection seeded with bioluminescent Staphylococcus aureus was used to assess the biological efficacy of delivering therapeutic antimicrobial genes using this technology.The authors were successful in demonstrating significant LL37 expression, which persisted for 14 days after ex vivo transduction with Ad/CMV-LL37. Transduction efficiency was significantly improved with the co-administration of 5 micrograms of VEGF during transduction without significantly increasing systemic dissemination of adenovirus or systemic toxicity. They were able to demonstrate in the rodent model of chronic wound/foreign body infections a significant reduction in bacterial loads from infected catheters following transduction with Ad/CMV-LL37 and increased bacterial clearance.This study demonstrates for the first time that microbicidal gene therapy via microvascular free flaps is able to clear chronic infections such as occurs with osteomyelitis resulting from trauma or an infected foreign body [corrected]
View details for DOI 10.1097/PRS.0b013e31819f25a4
View details for Web of Science ID 000265669400003
View details for PubMedID 19337084
Osteoblasts Stimulated With Pulsed Electromagnetic Fields Increase HUVEC Proliferation Via a VEGF-A Independent Mechanism
2009; 30 (3): 189-197
The clinically beneficial effect of low frequency pulsed electromagnetic fields (ELF-PEMF) on bone healing has been described, but the exact mechanism of action remains unclear. A recent study suggests that there is a direct autocrine mitogenic effect of ELF-PEMF on angiogenesis. The hypothesis of this study is that ELF-PEMF also has an indirect effect on angiogenesis by manipulation of vascular endothelial growth factor (VEGF)-A-based paracrine intercellular communication with neighboring osteoblasts. Conditioned media experiments measured fetal rat calvarial cell (FRC) and human umbilical vein endothelial cell (HUVEC) proliferation using tritiated thymidine uptake. We demonstrate that ELF-PEMF (15 Hz, 1.8 mT, for 8 h) has an indirect effect on the proliferation rate of both endothelial cells and osteoblasts in vitro by altering paracrine mediators. Conditioned media from osteoblast cells stimulated with ELF-PEMF increased endothelial proliferation 54-fold, whereas media from endothelial cells stimulated with ELF-PEMF did not affect osteoblast proliferation. We examined the role of the pro-angiogenic mediator VEGF-A in the mitogenic effect of ELF-PEMF-stimulated osteoblast media on endothelial cells. The production of VEGF-A by FRC as measured by ELISA was not changed by exposure to PEMF, and blocking experiments demonstrated that the ELF-PEMF-induced osteoblast-derived endothelial mitogen observed in these studies was not VEGF-A, but some other soluble angiogenic mediator.
View details for DOI 10.1002/bem.20459
View details for Web of Science ID 000264512900004
View details for PubMedID 19194859
Tissue engineering using autologous microcirculatory beds as vascularized bioscaffolds
2009; 23 (3): 906-915
Classic tissue engineering paradigms are limited by the incorporation of a functional vasculature and a reliable means for reimplantation into the host circulation. We have developed a novel approach to overcome these obstacles using autologous explanted microcirculatory beds (EMBs) as bioscaffolds for engineering complex three-dimensional constructs. In this study, EMBs consisting of an afferent artery, capillary beds, efferent vein, and surrounding parenchymal tissue are explanted and maintained for 24 h ex vivo in a bioreactor that preserves EMB viability and function. Given the rapidly advancing field of stem cell biology, EMBs were subsequently seeded with three distinct stem cell populations, multipotent adult progenitor cells (MAPCs), and bone marrow and adipose tissue-derived mesenchymal stem cells (MSCs). We demonstrate MAPCs, as well as MSCs, are able to egress from the microcirculation into the parenchymal space, forming proliferative clusters. Likewise, human adipose tissue-derived MSCs were also found to egress from the vasculature and seed into the EMBs, suggesting feasibility of this technology for clinical applications. We further demonstrate that MSCs can be transfected to express a luciferase protein and continue to remain viable and maintain luciferase expression in vivo. By using the vascular network of EMBs, EMBs can be perfused ex vivo and seeded with stem cells, which can potentially be directed to differentiate into neo-organs or transfected to replace failing organs and deficient proteins.
View details for DOI 10.1096/fj.08-114868
View details for Web of Science ID 000265506300026
View details for PubMedID 19001054
SDF-1 alpha Expression during Wound Healing in the Aged Is HIF Dependent
PLASTIC AND RECONSTRUCTIVE SURGERY
2009; 123 (2): 65S-75S
Age-related impairments in wound healing are associated with decreased neovascularization, a process that is regulated by hypoxia-responsive cytokines, including stromal cell-derived factor (SDF)-1 alpha. Interleukin-1 beta is an important inflammatory cytokine involved in wound healing and is believed to regulate SDF-1 alpha expression independent of hypoxia signaling. Thus, the authors examined the relative importance of interleukin (IL)-1 beta and hypoxia-inducible factor (HIF)-1 alpha on SDF-1 alpha expression in aged wound healing.Young and aged mice (n = 4 per group) were examined for wound healing using a murine excisional wound model. Wounds were harvested at days 0, 1, 3, 5, and 7 for histologic analysis, immunohistochemistry, enzyme-linked immunosorbent assay, and Western blot. An engineered wild-type and mutated SDF luciferase reporter construct were used to determine HIF transactivation.Aged mice demonstrated significantly impaired wound healing, reduced granulation tissue, and increased epithelial gap compared with young controls. Real-time polymerase chain reaction demonstrated reduced SDF-1 alpha levels in aged wounds that correlated with reduced CD31+ neovessels. Western blots revealed decreased HIF-1 alpha protein in aged wounds. However, both IL-1 beta and macrophage infiltrate were unchanged between young and aged animals. Using the wild-type and mutated SDF luciferase reporter construct in which the hypoxia response element was deleted, only young fibroblasts were able to respond to IL-1 beta stimulation, and this response was abrogated by mutating the HIF-binding sites. This suggests that HIF binding is essential for SDF-1 transactivation in response to both inflammatory and hypoxic stimuli.SDF-1 alpha deficiency observed during aged wound healing is attributable predominantly to decreased HIF-1 alpha levels rather than impaired IL-1 beta expression.
View details for DOI 10.1097/PRS.0b013e318191bdf4
View details for Web of Science ID 000263721600009
View details for PubMedID 19182665
Aging and Diabetes Impair the Neovascular Potential of Adipose-Derived Stromal Cells
PLASTIC AND RECONSTRUCTIVE SURGERY
2009; 123 (2): 475-485
Aging and diabetes are major risk factors for poor wound healing and tissue regeneration that reflect an impaired ability to respond to ischemic insults. The authors explored the intrinsic neovascular potential of adipose-derived stromal cells in the setting of advanced age and in type 1 and type 2 diabetes.Adipose-derived stromal cells isolated from young, aged, streptozotocin-induced, and db/db diabetic mice were exposed to normoxia and hypoxia in vitro. Vascular endothelial growth factor (VEGF) expression, proliferation, and tubulization were measured. Conditioned media harvested from adipose-derived stromal cell cultures were assessed for their ability to stimulate human umbilical vein endothelial cell proliferation (n = 3 and n = 3).Young adipose-derived stromal cells demonstrated significantly higher levels of VEGF production, proliferation, and tubulogenesis than those derived from aged, streptozotocin-induced, and db/db mice in both normoxia and hypoxia. Although aged and diabetic adipose-derived stromal cells retained the ability to up-regulate VEGF secretion, proliferation, and tubulogenesis in response to hypoxia, the response was blunted compared with young controls. Conditioned media derived from these cells cultured in normoxia in vitro also had a significantly greater ability to increase human umbilical vein endothelial cell proliferation compared with media harvested from aged, streptozotocin-induced, and db/db adipose-derived stromal cells. This effect was magnified in conditioned media harvested from hypoxic adipose-derived stromal cell cultures.This study demonstrates that aging and type 1 and type 2 diabetes impair intrinsic adipose-derived stromal cell function; however, these cells may still be a suitable source of angiogenic cells that can potentially improve neovascularization of ischemic tissues.
View details for DOI 10.1097/PRS.0b013e3181954d08
View details for Web of Science ID 000265669200006
View details for PubMedID 19182604
Intracranial Microvascular Free Flaps
JOURNAL OF RECONSTRUCTIVE MICROSURGERY
2009; 25 (2): 89-95
Large acquired intracranial defects can result from trauma or surgery. When reoperation is required because of infection or tumor recurrence, management of the intracranial dead space can be challenging. By providing well-vascularized bulky tissue, intracranial microvascular free flaps offer potential solutions to these life-threatening complications. A multi-institutional retrospective chart and radiographic review was performed of all patients who underwent microvascular free-flap surgery for salvage treatment of postoperative intracranial infections between 1998 and 2006. A total of six patients were identified with large intracranial defects and postoperative intracranial infections. Four patients had parenchymal resections for tumor or seizure and two patients had posttraumatic encephalomalacia. All patients underwent operative debridement and intracranial free-flap reconstruction using the latissimus dorsi muscle (N=2), rectus abdominis muscle (N=2), or omentum (N=2). All patients had titanium (N=4) or Medpor (N=2) cranioplasties. We concluded that surgery or trauma can result in significant intracranial dead space. Treatment of postoperative intracranial infection can be challenging. Vascularized free tissue transfer not only fills the void, but also provides a delivery system for immune cells, antibodies, and systemically administered antibiotics. The early use of this technique when intracranial dead space and infection coexist is beneficial.
View details for DOI 10.1055/s-0028-1090609
View details for Web of Science ID 000262933400002
View details for PubMedID 18925548
Mesenchymal Stem Cells Can Participate in Ischemic Neovascularization
PLASTIC AND RECONSTRUCTIVE SURGERY
2009; 123 (2): 45S-55S
Cells from the bone marrow contribute to ischemic neovascularization, but the identity of these cells remains unclear. The authors identify mesenchymal stem cells as a bone marrow-derived progenitor population that is able to engraft into peripheral tissue in response to ischemia.A murine model of skin ischemia was used. Bone marrow, blood, and skin were harvested at different time points and subjected to flow cytometric analysis for mesenchymal and hematopoietic markers (n = 3 to 7 per time point). Using a parabiotic model pairing donor green fluorescent protein (GFP)-positive with recipient wild-type mice, progenitor cell engraftment was examined in ischemic tissue by fluorescence microscopy, and engrafted cells were analyzed by flow cytometry for endothelial and mesenchymal markers. In vitro, the ability of both bone marrow- and adipose-derived mesenchymal stem cells to adopt endothelial characteristics was examined by analyzing (1) the ability of mesenchymal stem cells to take up DiI-acetylated low-density lipoprotein and Alexa Fluor lectin, and (2) phenotypic changes of mesenchymal stem cells co-cultured with GFP-labeled endothelial cells or under hypoxic/vascular endothelial growth factor stimulation.In vivo, the bone marrow mesenchymal stem cell population decreased significantly immediately after surgery, with subsequent engraftment of these cells in ischemic tissue. Engrafted cells lacked the panhematopoietic antigen CD45, consistent with a mesenchymal origin. In vitro, bone marrow- and adipose-derived mesenchymal stem cells took up DiI-acetylated low-density lipoprotein and Alexa Fluor lectin, and expressed endothelial markers under hypoxic conditions.The authors' data suggest that mesenchymal precursor cells can give rise to endothelial progenitors. Consequently, cell-based therapies augmenting the mesenchymal stem cell population could represent powerful alternatives to current therapies for ischemic vascular disease.
View details for DOI 10.1097/PRS.0b013e318191be4a
View details for Web of Science ID 000263721600007
View details for PubMedID 19182663
Taz is a transcriptional modulator of human adipose-derived stromal cell differentiation towards the osteogenic lineage
CRANIOFACIAL SURGERY 13: PROCEEDINGS OF THE THIRTEEN CONGRESS OF THE INTERNATIONAL SOCIETY OF CRANIOFACIAL SURGERY AND PARIS DISTRACTION SYMPOSIUM
View details for Web of Science ID 000303383400018
A Recommended Protocol for the Immediate Postoperative Care of Lower Extremity Free-Flap Reconstructions
JOURNAL OF RECONSTRUCTIVE MICROSURGERY
2009; 25 (1): 15-19
The success of lower extremity microsurgical reconstructions may be compromised postoperatively secondary to several factors, including thrombosis, infection, bleeding, and edema. To address edema, surgeons may use protocols for gradually dangling and/or wrapping the affected extremity. Such protocols vary widely among surgeons and are typically based on training and/or prior experience. To that end, we distributed surveys to five plastic surgeons who are experienced in microvascular lower extremity reconstruction at five different institutions. The surveys inquired about postoperative management protocols for lower extremity free flaps with regard to positioning, compression, initiation and progression of postoperative mobilization, nonweightbearing and weightbearing ambulation, assessment of flap viability, and flap success rate. These protocols were then evaluated for similarities to create a consensus of postoperative management guidelines. Progressive periods of leg dependency and compression therapy emerged as important elements. Although the consensus protocol developed in this study is considered safe by each participant, we do not intend for these recommendations to serve as a standard of care, nor do we suggest that any one particular protocol leads to improved outcomes. However, these recommendations may serve as a guide for less experienced surgeons or those without a protocol in place.
View details for DOI 10.1055/s-0028-1090600
View details for Web of Science ID 000262164000003
View details for PubMedID 18979418
IFATS Collection: Adipose Stromal Cells Adopt a Proangiogenic Phenotype Under the Influence of Hypoxia
2009; 27 (1): 266-274
Evolving evidence suggests a possible role for adipose stromal cells (ASCs) in adult neovascularization, although the specific cues that stimulate their angiogenic behavior are poorly understood. We evaluated the effect of hypoxia, a central mediator of new blood vessel development within ischemic tissue, on proneovascular ASC functions. Murine ASCs were exposed to normoxia (21% oxygen) or hypoxia (5%, 1% oxygen) for varying lengths of time. Vascular endothelial growth factor (VEGF) secretion by ASCs increased as an inverse function of oxygen tension, with progressively higher VEGF expression at 21%, 5%, and 1% oxygen, respectively. Greater VEGF levels were also associated with longer periods in culture. ASCs were able to migrate towards stromal cell-derived factor (SDF)-1, a chemokine expressed by ischemic tissue, with hypoxia augmenting ASC expression of the SDF-1 receptor (CXCR4) and potentiating ASC migration. In vivo, ASCs demonstrated the capacity to proliferate in response to a hypoxic insult remote from their resident niche, and this was supported by in vitro studies showing increasing ASC proliferation with greater degrees of hypoxia. Hypoxia did not significantly alter the expression of endothelial surface markers by ASCs. However, these cells did assume an endothelial phenotype as evidenced by their ability to tubularize when seeded with differentiated endothelial cells on Matrigel. Taken together, these data suggest that ASCs upregulate their proneovascular activity in response to hypoxia, and may harbor the capacity to home to ischemic tissue and function cooperatively with existing vasculature to promote angiogenesis.
View details for DOI 10.1634/stemcells.2008-0276
View details for Web of Science ID 000263032400030
View details for PubMedID 18974212
- Topical Lineage-Negative Progenitor-Cell Therapy for Diabetic Wounds (Invited Discussion) PLASTIC AND RECONSTRUCTIVE SURGERY 2009; 123 (1): 421-423
Hedgehog signaling is essential for normal wound healing
WOUND REPAIR AND REGENERATION
2008; 16 (6): 768-773
The hedgehog family of morphogens (sonic [Shh], Indian, and desert hedgehog) are central regulators of embryologic growth and tissue patterning. Although recent work implicates Shh in postnatal tissue repair and development, conclusive evidence is lacking. Here, we demonstrated the importance of Shh in wound repair, by examining the effects of cyclopamine, a specific inhibitor of the Shh signaling cascade, on tissue repair. Using a murine-splinted excisional wound model, which attenuates wound contraction in this loose-skinned rodent, we established that, by all measures (wound closure, epithelialization, granulation formation, vascularity, and proliferation), wound healing was profoundly impaired when Shh signaling was disrupted. Because embryonic disruption of Shh is associated with distinct phenotypic defects, our findings invite investigation of the potential role of Shh signaling under postnatal conditions associated with disregulated wound healing.
View details for DOI 10.1111/j.1524-475X.2008.00430.x
View details for Web of Science ID 000260445200070
View details for PubMedID 19128247
- Bisphosphonate-associated osteonecrosis of the jaw: Successful treatment at 2-year follow-up PLASTIC AND RECONSTRUCTIVE SURGERY 2008; 122 (2): 57E-59E
- "Priming" endothelial progenitor cells a new strategy to improve cell based therapeutics ARTERIOSCLEROSIS THROMBOSIS AND VASCULAR BIOLOGY 2008; 28 (6): 1034-1035
Using genetically modified microvascular free flaps to deliver local cancer immunotherapy with minimal systemic toxicity
PLASTIC AND RECONSTRUCTIVE SURGERY
2008; 121 (5): 1541-1553
Clinical use of cancer gene therapy has been prevented by the inability to deliver high levels of local transgene expression with acceptable host toxicity. The authors' laboratory has developed an ex vivo technique to genetically modify free flaps to deliver immunotherapy locally without systemic toxicity.Superficial inferior epigastric flaps were dissected in Fischer rats, perfused with a viral vector expressing the antitumor interleukin-12 (IL-12) for 1 hour, and re-anastomosed. Beneath the flaps was a bolus of 1 x 10(6) beta-human chorionic gonadotropin-secreting MADB-106 tumor cells. Tumor growth was monitored using beta-human chorionic gonadotropin levels (secreted by the tumor) and size. IL-12 expression in tissue was assessed by enzyme-linked immunosorbent assay. Tumor inflammatory infiltrate was assessed using immunohistologic staining (CD8 and CD161) and enzyme-linked immunosorbent assay (interferon-gamma). Serum levels of liver enzymes and histologic analysis were used to assess systemic toxicity.IL-12 expression was confirmed in the flap and surrounding tissue. The rate of tumor growth in the IL-12-treated group was significantly suppressed compared with the control group (p < 0.001). Liver enzyme levels remained normal, and histological evaluation of the liver, lung, and spleen revealed no evidence of inflammation in the treated group.Using genetically modified free flaps, the authors were able to deliver IL-12 directly into the local environment of a tumor and suppress its growth without eliciting toxic systemic effects. This technique could provide valuable adjuvant treatment after oncologic surgery for soft-tissue cancers, with the transduced flap reconstructing the defect and supplying a therapeutic agent to the resected tumor bed.
View details for DOI 10.1097/PRS.0b013e31816ff6aa
View details for Web of Science ID 000255435200004
View details for PubMedID 18453976
Diabetes increases p53-mediated apoptosis following ischemia
PLASTIC AND RECONSTRUCTIVE SURGERY
2008; 121 (4): 1135-1143
Diabetes impairs the ability of tissue to respond adequately to ischemia. The underlying mechanisms contributing to this impaired response remain unknown. Because increases in apoptosis have been linked to a spectrum of diabetic complications, the authors examined whether programmed cell death is involved in the pathogenesis of poor diabetic tissue responses to ischemia.Analysis for apoptosis and levels of proaptotic protein, p53, were performed on streptozocin-induced diabetic mice and wild-type controls in a murine model of soft-tissue ischemia (n = 6). In vitro, chronic hyperglycemic culture conditions were used to test inducibility and reversibility of the diabetic phenotype. Small interfering RNA was used to assess the role of p53.Ischemia-induced apoptosis and p53 levels were increased significantly in diabetic dermal fibroblasts both in vivo and in vitro. Chronic hyperglycemic culture was sufficient to induce the increased apoptotic phenotype, and this was not reversible with long-term normoglycemic conditions. Blocking p53 with small interfering RNA resulted in significant protection against ischemic apoptosis.These findings suggest that diabetes causes an increased apoptotic response to ischemia through a p53-mediated mechanism. This increase is not reversible by exposure to low-glucose conditions. This suggests that glycemic control alone will be unable to prevent tissue necrosis in diabetic patients and suggests novel therapeutic strategies for this condition.
View details for DOI 10.1097/01.prs.0000302499.18738.c2
View details for Web of Science ID 000254183600008
View details for PubMedID 18349630
Plastic surgical delivery systems for targeted gene therapy
ANNALS OF PLASTIC SURGERY
2008; 60 (3): 323-332
The expansion of gene therapy applications from inherited disorders to acquired conditions has been mirrored by an exponential rise in both experimental work and clinical trials. This review highlights current plastic surgical delivery systems and clinical applications for targeted gene therapy. We revisit some of the vectors used both experimentally and in clinical gene therapy trials, with an emphasis on developments in plastic surgical delivery systems resulting in improved targeting of therapeutic genes. In addition, we discuss a novel technique for the delivery of gene therapy using the ex vivo transduction of free flaps, developed in our laboratory. This delivery system achieves targeted high-level transgene expression with minimal demonstrable systemic toxicity. Advances in delivery systems are essential for translating basic research into clinical therapeutics.
View details for DOI 10.1097/SAP.0b013e31806917b0
View details for Web of Science ID 000253430300017
View details for PubMedID 18443515
Pulsed electromagnetic fields accelerate normal and diabetic wound healing by increasing endogenous FGF-2 release
PLASTIC AND RECONSTRUCTIVE SURGERY
2008; 121 (1): 130-141
Chronic wounds, particularly in diabetics, result in significant morbidity and mortality and have a profound economic impact. The authors demonstrate that pulsed electromagnetic fields significantly improve both diabetic and normal wound healing in 66 mice through up-regulation of fibroblast growth factor (FGF)-2 and are able to prevent tissue necrosis in diabetic tissue after an ischemic insult.Db/db and C57BL6 mice were wounded and exposed to pulsed electromagnetic fields. Gross closure, cell proliferation, and vascularity were assessed. Cultured medium from human umbilical vein endothelial cells exposed to pulsed electromagnetic fields was analyzed for FGF-2 and applied topically to wounds. Skin flaps were created on streptozocin-induced diabetic mice and exposed to pulsed electromagnetic fields. Percentage necrosis, oxygen tension, and vascularity were determined.Pulsed electromagnetic fields accelerated wound closure in diabetic and normal mice. Cell proliferation and CD31 density were significantly increased in pulsed electromagnetic field-treated groups. Cultured medium from human umbilical vein endothelial cells in pulsed electromagnetic fields exhibited a three-fold increase in FGF-2, which facilitated healing when applied to wounds. Skin on diabetic mice exposed to pulsed electromagnetic fields did not exhibit tissue necrosis and demonstrated oxygen tensions and vascularity comparable to those in normal animals.This study demonstrates that pulsed electromagnetic fields are able to accelerate wound healing under diabetic and normal conditions by up-regulation of FGF-2-mediated angiogenesis. They also prevented tissue necrosis in response to a standardized ischemic insult, suggesting that noninvasive angiogenic stimulation by pulsed electromagnetic fields may be useful to prevent ulcer formation, necrosis, and amputation in diabetic patients.
View details for DOI 10.1097/01.prs.0000293761.27219.84
View details for Web of Science ID 000252208700019
View details for PubMedID 18176216
Age decreases endothelial progenitor cell recruitment through decreases in hypoxia-inducible factor 1 alpha stabilization during ischemia
2007; 116 (24): 2818-2829
Advanced age is known to impair neovascularization. Because endothelial progenitor cells (EPCs) participate in this process, we examined the effects of aging on EPC recruitment and vascular incorporation.Murine neovascularization was examined by use of an ischemic flap model, which demonstrated aged mice (19 to 24 months) had decreased EPC mobilization (percent mobilized 1.4+/-0.2% versus 0.4+/-0.1%, P<0.005) that resulted in impaired gross tissue survival compared with young mice (2 to 6 months). This decrease correlated with diminished tissue perfusion (P<0.005) and decreased CD31+ vascular density (P<0.005). Gender-mismatched bone marrow transplantation demonstrated significantly fewer chimeric vessels in aged mice (P<0.05), which confirmed a deficit in bone marrow-mediated vasculogenesis. Age had no effect on total EPC number in mice or humans. Reciprocal bone marrow transplantations confirmed that impaired neovascularization resulted from defects in the response of aged tissue to hypoxia and not from intrinsic defects in EPC function. We demonstrate that aging decreased hypoxia-inducible factor 1alpha stabilization in ischemic tissues because of increased prolyl hydroxylase-mediated hydroxylation (P<0.05) and proteasomal degradation. This resulted in a diminished hypoxia response, including decreased stromal cell-derived factor 1 (P<0.005) and vascular endothelial growth factor (P<0.0004). This effect can be reversed with the iron chelator deferoxamine, which results in hypoxia-inducible factor 1alpha stabilization and increased tissue survival.Aging impairs EPC trafficking to sites of ischemia through a failure of aged tissues to normally activate the hypoxia-inducible factor 1alpha-mediated hypoxia response.
View details for DOI 10.1161/CIRCULATIONAHA.107.715847
View details for Web of Science ID 000251542200009
View details for PubMedID 18040029
Hypoxia-induced mediators of stem/progenitor cell trafficking are increased in children with hemangioma
ARTERIOSCLEROSIS THROMBOSIS AND VASCULAR BIOLOGY
2007; 27 (12): 2664-2670
The mechanism of neovascularization during the proliferative phase of infantile hemangioma is poorly understood. It is known that circulating bone marrow-derived endothelial progenitor cells (EPCs) form new blood vessels in ischemic tissues using mediators regulated by the transcription factor, HIF-1alpha. Mobilization of EPCs is enhanced by VEGF-A, matrix metalloproteinase (MMP)-9, and estrogen, whereas homing is secondary to localized expression of stromal cell-derived factor-1alpha (SDF-1alpha). We examined whether these mediators of EPC trafficking are upregulated during the proliferation of infantile hemangioma.Surgical specimens and blood samples were obtained from children with proliferating hemangioma and age-matched controls (n=10, each group). VEGF-A and MMP-9 levels were measured in blood, and tissue sections were analyzed for SDF-1alpha, MMP-9, VEGF-A, and HIF-1alpha. The role of estrogen as a modulator of hemangioma endothelial cell growth was also investigated. We found that all these mediators of EPC trafficking are elevated in blood and specimens from children with proliferating infantile hemangioma. In vitro, the combination of hypoxia and estrogen demonstrated a synergistic effect on hemangioma endothelial cell proliferation.These findings demonstrate that proliferating hemangiomas express known mediators of vasculogenesis and suggest that this process may play a role in the initiation or progression of this disease.
View details for DOI 10.1161/ATVBAHA.107.150284
View details for Web of Science ID 000251143300028
View details for PubMedID 17872454
Uniaxial mechanical strain: An in vitro correlate to distraction osteogenesis
JOURNAL OF SURGICAL RESEARCH
2007; 143 (2): 329-336
Distraction osteogenesis is a valuable clinical tool; however the molecular mechanisms governing successful distraction remain unknown. We have used a uniaxial in vitro strain device to simulate the uniaxial mechanical environment of the interfragmentary distraction gap.Using the Flexcell system, normal human osteoblasts were subjected to different levels of cyclical uniaxial mechanical strain. Cellular morphology, proliferation, migration, and the expression of angiogenic (vascular endothelial growth factor [VEGF] and fibroblast growth factor-2 [FGF-2]) and osteogenic (osteonectin, osteopontin, and osteocalcin) proteins and extracellular matrix molecules (collagen IalphaII) were analyzed in response to uniaxial cyclic strain.Osteoblasts exposed to strain assumed a fusiform spindle-shaped morphology aligning parallel to the axis of uniaxial strain and osteoblasts exposed to strain or conditioned media had a 3-fold increase in proliferation. Osteoblast migration was maximal (5-fold) in response to 9% strain. Angiogenic cytokine, VEGF, and FGF-2, increased 32-fold and 2.6-fold (P < 0.05), respectively. Osteoblasts expressed greater amounts of osteonectin, osteopontin, and osteocalcin (2.1-fold, 1.8-fold, 1.5-fold respectively, P < 0.01) at lower levels of strain (3%). Bone morphogenic protein-2 production increased maximally at 9% strain (1.6-fold, P < 0.01). Collagen I expression increased 13-, 66-, and 153-fold in response to 3, 6, and 9% strain, respectively.Uniaxial cyclic strain using the Flexcell device under appropriate strain parameters provides a novel in vitro model that induces osteoblast cellular and molecular expression patterns that simulate patterns observed in the in vivo distraction gap.
View details for DOI 10.1016/j.jss.2007.01.023
View details for Web of Science ID 000251281200021
View details for PubMedID 17950332
Mechanical load initiates hypertrophic scar formation through decreased cellular apoptosis
2007; 21 (12): 3250-3261
Hypertrophic scars occur following cutaneous wounding and result in severe functional and esthetic defects. The pathophysiology of this process remains unknown. Here, we demonstrate for the first time that mechanical stress applied to a healing wound is sufficient to produce hypertrophic scars in mice. The resulting scars are histopathologically identical to human hypertrophic scars and persist for more than six months following a brief (one-week) period of augmented mechanical stress during the proliferative phase of wound healing. Resulting scars are structurally identical to human hypertrophic scars and showed dramatic increases in volume (20-fold) and cellular density (20-fold). The increased cellularity is accompanied by a four-fold decrease in cellular apoptosis and increased activation of the prosurvival marker Akt. To clarify the importance of apoptosis in hypertrophic scar formation, we examine the effects of mechanical loading on cutaneous wounds of animals with altered pathways of cellular apoptosis. In p53-null mice, with down-regulated cellular apoptosis, we observe significantly greater scar hypertrophy and cellular density. Conversely, scar hypertrophy and cellular density are significantly reduced in proapoptotic BclII-null mice. We conclude that mechanical loading early in the proliferative phase of wound healing produces hypertrophic scars by inhibiting cellular apoptosis through an Akt-dependent mechanism.
View details for DOI 10.1096/fj.07-8218com
View details for Web of Science ID 000249781600025
View details for PubMedID 17504973
- Hypertrophic scar formation following burns and trauma: New approaches to treatment PLOS MEDICINE 2007; 4 (9): 1464-1470
db/db mice exhibit severe wound-healing impairments compared with other murine diabetic strains in a silicone-splinted excisional wound model
WOUND REPAIR AND REGENERATION
2007; 15 (5): 665-670
The pathophysiology of diabetic wound healing and the identification of new agents to improve clinical outcomes continue to be areas of intense research. There currently exist more than 10 different murine models of diabetes. The degree to which wound healing is impaired in these different mouse models has never been directly compared. We determined whether differences in wound impairment exist between diabetic models in order to elucidate which model would be the best to evaluate new treatment strategies. Three well-accepted mouse models of diabetes were used in this study: db/db, Akita, and streptozocin (STZ)-induced C57BL/6J. Using an excisional model of wound healing, we demonstrated that db/db mice exhibit severe impairments in wound healing compared with STZ and Akita mice. Excisional wounds in db/db mice show a statistically significant delay in wound closure, decreased granulation tissue formation, decreased wound bed vascularity, and markedly diminished proliferation compared with STZ, Akita, and control mice. There was no difference in the rate of epithelialization of the full-thickness wounds between the diabetic or control mice. Our results suggest that splinted db/db mice may be the most appropriate model for studying diabetic wound-healing interventions as they demonstrate the most significant impairment in wound healing. This study utilized a novel model of wound healing developed in our laboratory that stents wounds open using silicone splints to minimize the effects of wound contraction. As such, it was not possible to directly compare the results of this study with other studies that did not use this wound model.
View details for DOI 10.1111/j.1524-475X.2007.00273.x
View details for Web of Science ID 000249846800008
View details for PubMedID 17971012
Vascular delay revisited
PLASTIC AND RECONSTRUCTIVE SURGERY
2007; 119 (6): 1735-1744
The technique of vascular delay has been used by plastic surgeons for nearly 500 years and has proven useful for reliably transferring tissue and allowing for a greater volume of tissue to be reliably harvested. Delay procedures are an essential plastic surgical tool for a variety of aesthetic and reconstructive procedures. Despite the widespread use of vascular delay procedures, the mechanism by which this phenomenon occurs remains unclear. A number of groups have exhaustively examined microvascular changes that occur during vascular delay. Theories have been proposed ranging from the dilation of choke vessels to changes in metabolism and new blood vessel formation. Inherent in these theories is the concept that ischemia is able to act as the primary stimulus for vascular changes. The purpose of this review is to revisit the theories proposed to underlie the delay phenomenon in light of recent advances in vascular biology. In particular, the participation of bone marrow-derived endothelial progenitor cells in the delay phenomenon is explored. Greater understanding of the role these cells play in new blood vessel formation will be of considerable clinical benefit to high-risk patients in future applications of delay procedures.
View details for DOI 10.1097/01.prs.0000246384.14593.6e
View details for Web of Science ID 000246032200014
View details for PubMedID 17440348
Cyclic mechanical strain increases production of regulators of bone healing in cultured murine osteoblasts
JOURNAL OF THE AMERICAN COLLEGE OF SURGEONS
2007; 204 (3): 426-434
The adaptive response of bone to mechanical strain, for which angiogenesis is required, is underscored during fracture healing. Vascular endothelial growth factor (VEGF) and transforming growth factor beta-1 (TGF-beta1) are critical regulators of angiogenesis. The purpose of this study was to examine the effect of strain on the production of VEGF and TGF-beta1.MC3T3-E1 mouse osteoblasts underwent cyclic strain (low, 0.1 Hz, or high, 0.2 Hz) for 24 or 48 hours. VEGF and TGF-beta1 protein levels were determined by ELISA, and Northern blot analysis was performed for VEGF mRNA. Alkaline phosphatase (an osteoblast differentiation marker) activity was determined by functional enzymatic assay. All measurements were standardized for cell number by crystal violet colorimetric assay. Statistical significance was determined by t-test, ANOVA, and the Tukey-Kramer test.Protein production of VEGF and TGF-beta1 was dose-dependently elevated by strain (p < 0.05); alkaline phosphatase did not rise significantly. Northern blot analysis of strained osteoblast cells demonstrated increased VEGF mRNA. Cyclic strain was found to be progressively destructive in a dose-dependent manner, causing 51% and 70% decreases in cell number under low and high strain, respectively (p < 0.01).We demonstrated simultaneous, dose-dependent increases in VEGF and TGF-beta1 protein production by osteoblastic cells in response to increasing strain. VEGF mRNA also increased in response to strain. This strain-induced increase in angiogenic cytokines suggests a potential mechanism by which injured bone may recruit a new blood supply. But we also found increasing strain to increase cellular toxicity, suggesting that cyclic mechanical strain may select for a subpopulation of osteoblasts.
View details for DOI 10.1016/j.jamcollsurg.2006.11.019
View details for Web of Science ID 000244825200012
View details for PubMedID 17324777
Progress and potential for regenerative medicine
ANNUAL REVIEW OF MEDICINE
2007; 58: 299-312
Regenerative medicine focuses on new therapies to replace or restore lost, damaged, or aging cells in the human body to restore function. This goal is being realized by collaborative efforts in nonmammalian and human development, stem cell biology, genetics, materials science, bioengineering, and tissue engineering. At present, understanding existing reparative processes in humans and exploring the latent ability to regenerate tissue remains the focus in this field. This review covers recent work in limb regeneration, fetal wound healing, stem cell biology, somatic nuclear transfer, and tissue engineering as a foundation for developing new clinical therapies to augment and stimulate human regeneration.
View details for DOI 10.1146/annurev.med.58.085405.095329
View details for Web of Science ID 000244461500020
View details for PubMedID 17076602
Diabetes impairs endothelial progenitor cell-mediated blood vessel formation in response to hypoxia
PLASTIC AND RECONSTRUCTIVE SURGERY
2007; 119 (1): 59-70
Diabetics suffer from vascular dysfunction with increased risks of coronary artery disease and peripheral vascular disease secondary to an impaired ability to respond to tissue ischemia. Because endothelial progenitor cells are known to home to sites of ischemia and participate in new blood vessel growth, the authors examined the effects of diabetes on human endothelial progenitor cell function and peripheral tissue signaling in hypoxia, and determined whether these cells might be a useful cell-based therapy for diabetic vascular complications.Circulating human endothelial progenitor cells from type 2 diabetic patients and controls were isolated and subjected to in vitro adhesion, migration, and proliferation assays (n = 5). Cell mobilization and recruitment were studied in vivo in diabetic and nondiabetic environments (n = 6). Exogenous human diabetic and normal cells were analyzed for therapeutic efficacy in a murine ischemia model (n = 6).Adhesion, migration, and proliferation of human diabetic endothelial progenitor cells in response to hypoxia was significantly reduced compared with controls. In diabetic mice, cell mobilization from the bone marrow and recruitment into ischemic tissue was significantly reduced compared with controls. Normal cells injected systemically as replacement therapy in a diabetic mouse increased but did not normalize ischemic tissue survival.These findings suggest that diabetes causes defects in both the endothelial progenitor cell and peripheral tissue responses to hypoxia. These changes in endothelial progenitor cell function and signaling offer a novel explanation for the poor clinical outcome of type 2 diabetics following ischemic events. Based on these findings, it is unlikely that endothelial progenitor cell-based cellular therapies will be able to prevent diabetic complications.
View details for DOI 10.1097/01.prs.0000244830.16906.3f
View details for Web of Science ID 000243094700010
View details for PubMedID 17255657
Hypoxia, hormones, and endothelial progenitor cells in hemangioma.
Lymphatic research and biology
2007; 5 (4): 237-243
Hemangiomas are the most common tumor of infancy, and although the natural history of these lesions is well described, their etiology remains unknown. One current theory attributes the development of hemangiomas to placentally-derived cells; however, conclusive evidence to support a placental origin is lacking. While placental tissue and hemangiomas do share molecular similarities, it is possible that these parallels are the result of analogous responses of endothelial cells and vascular progenitors to similar environmental cues. Specifically, both tissue types consist of actively proliferating cells that exist within a low oxygen, high estrogen environment. The hypoxic environment leads to an upregulation of hypoxia inducible factor-1alpha (HIF-1alpha) responsive chemokines such as stromal cell derived factor-1alpha (SDF-1alpha) and vascular endothelial growth factor (VEGF), both of which are known to promote the recruitment and proliferation of endothelial progenitor cells. Increased hormone levels in the postpartum period further potentiate the growth of these lesions. In this model, increased stabilization of HIF-1 in concert with increased levels of estrogen create a milieu that promotes new blood vessel development, ultimately contributing to the pathogenesis of infantile hemangiomas.
View details for DOI 10.1089/lrb.2007.1014
View details for PubMedID 18370914
No evidence for maternal-fetal microchimerism in infantile hemangioma: A molecular genetic investigation
JOURNAL OF INVESTIGATIVE DERMATOLOGY
2006; 126 (11): 2533-2538
In this study, using the placental origin theory as a basis, we set out to explore whether hemangioma endothelial cells (HEC) were maternal in origin. We rigorously addressed this hypothesis using several molecular genetic techniques. Fluorescent in situ hybridization on surgical specimens of proliferating hemangiomas (n=8) demonstrated no XX-labeled HEC from resected tumors of male infants. This analysis was followed by PCR genotyping of HEC (n=11) using microsatellite markers where cellular components were genotyped and compared to genomic DNA of corresponding mother-child pairs. In the seven informative mother-child pairs, HEC matched the genotype of the child and not the maternal genotype. Concerned that HEC represented a mixed population of cells, we subsequently enriched for cells using the placental-specific endothelial cell (EC) marker, Fc gammaRII. Three informative mother-child pairs exhibited only the genotype of the child in our enriched cell population. Using sequence analysis, we identified an informative single nucleotide polymorphism in an exon of the placental-EC-specific protein, GLUT1. When comparing GLUT1 complementary DNA (cDNA) with mother-child DNA, the genotype of the cDNA matched the constitutional DNA of the child. Our results indicate that hemangiomas are not microchimeric in origin. This study provides further insight into the origin of a tumor whose pathogenesis remains elusive.
View details for DOI 10.1038/sj.jid.5700516
View details for Web of Science ID 000241359600023
View details for PubMedID 16902414
- Early-gestation fetal scarless wounds have less lysyl oxidase expression - Discussion PLASTIC AND RECONSTRUCTIVE SURGERY 2006; 118 (5): 1130-1131
Overview of the role for calreticulin in the enhancement of wound healing through multiple biological effects
JOURNAL OF INVESTIGATIVE DERMATOLOGY SYMPOSIUM PROCEEDINGS
2006; 11 (1): 57-65
Calreticulin (CRT), an intracellular chaperone protein crucial for the proper folding and transport of proteins through the endoplasmic reticulum, has more recent acclaim as a critical regulator of extracellular functions, particularly in mediating cellular migration and as a requirement for phagocytosis of apoptotic cells. Consistent with these functions, we show that the topical application of CRT has profound effects on the process of wound healing by causing a dose-dependent increase in epithelial migration and granulation tissue formation in both murine and porcine normal and impaired animal models of skin injury. These effects of CRTare substantiated, in vitro, as we show that CRT strongly induces cell migration/wound closure of human keratinocytes and fibroblasts, using a wound/scratch plate assay, and stimulates cellular proliferation of human keratinocytes, fibroblasts, and vascular endothelial cells, providing mechanistic insight into how CRT functions in repair. Similarly, in both animal models, the histology of the wounds show marked proliferation of basal keratinocytes and dermal fibroblasts, dense cellularity of the dermis with notably increased numbers of macrophages and well-organized collagen fibril deposition. Thus, CRT profoundly affects the wound healing process by recruiting cells essential for repair into the wound, stimulating cell growth, and increasing extracellular matrix production.
View details for DOI 10.1038/sj.jidsymp.5650011
View details for Web of Science ID 000253355800008
View details for PubMedID 17069011
Biologic brachytherapy: Ex vivo transduction of microvascular beds for efficient, targeted gene therapy
PLASTIC AND RECONSTRUCTIVE SURGERY
2006; 118 (1): 54-65
Gene therapy for cancer holds enormous therapeutic promise, but its clinical application has been limited by the inability to achieve targeted, high-level transgene expression with limited systemic toxicity. The authors have developed a novel method for delivering genes to microvascular free flaps (commonly used during reconstructive surgery) to avoid these problems.During the finite period in which a free flap is separated from the host (ex vivo), it can be perfused with extremely high titers of genetic material through the afferent artery, resulting in efficient transduction of the tissue. Before reanastomosis, unincorporated genetic material is flushed from the flap, minimizing systemic toxicity.In a rodent model using an adenoviral vector containing the lacZ reporter gene, high regional expression of beta-galactosidase was achieved in all the different cells in a microvascular free flap. Moreover, no beta-galactosidase staining was observed outside of the transduced flap, and viral sequence was undetectable by polymerase chain reaction analysis in other tissues. Further analysis confirmed that high-level transgene expression was precisely localized to the explanted tissue, with no collateral transduction.Targeting gene delivery with minimal systemic toxicity is essential for successful gene therapy. This form of "biological brachytherapy" provides a new opportunity to deliver targeted therapeutic transgenes to patients undergoing reconstructive surgery and allows microvascular free flaps to perform therapeutic and reconstructive functions.
View details for DOI 10.1097/01.prs.0000220466.27521.22
View details for Web of Science ID 000239048700009
View details for PubMedID 16816674
Skin graft vascularization involves precisely regulated regression and replacement of endothelial cells through both angiogenesis and vasculogenesis
PLASTIC AND RECONSTRUCTIVE SURGERY
2006; 117 (3): 836-844
Long-term survival of a skin graft is dependent on eventual revascularization. The authors' aim in the present study was to determine whether skin graft vascularization occurs by (1) simple reconnection of vessels, (2) ingrowth of recipient vasculature, (3) outgrowth of donor-derived vessels, and/or (4) recruitment of bone marrow-derived endothelial progenitor cells.Full-thickness skin grafts (1 x 1 cm) were transferred between wild-type FVB/N mice (n = 20) and transgenic tie2/lacZ mice (n = 20), where lacZ expression is controlled by the endothelial specific tie2 promoter, allowing differentiation of recipient and donor endothelial cells. The contribution of endothelial progenitor cells to skin graft neovascularization was determined using a bone marrow transplant model where tie2/lacZ bone marrow was transplanted into wild-type mice (n = 20).Vascular regression in the graft was observed at the periphery starting on day 3 and moving centrally through day 21, sparing graft vessels in the absolute center of the graft. At the same time, vascular ingrowth occurred from the wound bed to replace the regressing vessels. Furthermore, bone marrow-derived endothelial progenitor cells contributed to these new vessels starting as early as day 7. Surprisingly, the contribution of bone marrow-derived vessels to the overall process was approximately 15 to 20 percent of new endothelial cells.Replacement of the donor graft vasculature by endothelial and endothelial progenitor cells from the recipient along preexisting channels is the predominant mechanism for skin graft revascularization. This mechanism is likely similar for all nonvascularized free grafts and suggests novel strategies for optimizing the vascularization of tissue constructs engineered in vitro.
View details for DOI 10.1097/01.prs.0000201459.91559.7f
View details for Web of Science ID 000235942500019
View details for PubMedID 16525274
Hyperglycemia-induced reactive oxygen species and impaired endothelial progenitor cell function
ANTIOXIDANTS & REDOX SIGNALING
2005; 7 (11-12): 1476-1482
Vascular complications in diabetes are a significant source of human morbidity and mortality, affecting multiple organ systems and persisting despite tight glucose control. Many of these complications can be linked to impairments in vasculogenesis, the process by which circulating and bone marrow-derived endothelial progenitor cells (EPCs) contribute to new vessel formation. Recent evidence suggests that hyperglycemia alone, through the mitochondrial overproduction of reactive oxygen species (ROS), can induce changes in gene expression and cellular behavior in diabetes. In this review, we examine how hyperglycemia-induced overproduction of ROS could explain EPC impairments observed in diabetes. Experimentally, impairments in EPC function prevent new blood vessel growth and are potentially reversible by manipulations to decrease ROS. Novel strategies aimed at reducing hyperglycemia-induced ROS may be a useful adjuvant to antihyperglycemic therapies in the restoration of vasculogenesis and the prevention of diabetic complications.
View details for Web of Science ID 000233962500008
View details for PubMedID 16356110
Stem cells and distraction osteogenesis: Endothelial progenitor cells home to the ischemic generate in activation and consolidation
PLASTIC AND RECONSTRUCTIVE SURGERY
2005; 116 (4): 1053-1064
Ischemia is a limiting factor during distraction osteogenesis. The authors sought to determine the extent of ischemia in the distraction zone and whether endothelial progenitor cells home to the distraction zone and participate in local vasculogenesis.Laser Doppler imaging was used to assess the extent of blood flow in the distraction zone in gradually distracted, immediately distracted, and osteotomized rat mandibles during activation and consolidation. Animals (n = 50; 25 rats with unilateral gradual distraction and contralateral osteotomy as an internal control, and 25 rats with unilateral immediate distraction) were examined on postoperative days 4, 6, and 8 of activation, and after 1 and 2 weeks of consolidation. Endothelial progenitor cells isolated from human peripheral blood were labeled with fluorescent DiI dye, and 0.5 x 10 cells were injected intra-arterially under direct vision into each carotid artery at the start of activation in nude rats (n = 18) that then underwent the distraction protocol outlined above.Doppler flow analysis demonstrated relative ischemia during the activation period in the distraction osteogenesis group and increased blood flow in the osteotomized control group as compared with flow in a normal hemimandible [normal, 1 (standardized); distraction osteogenesis, 0.58 +/- 0.05; control, 2.58 +/- 0.21; p < 0.05 for both results]. We observed a significantly increased endothelial progenitor cell population at the generate site versus controls at midactivation and at 1 and 2 weeks of consolidation [25 +/- 1.9 versus 1 +/- 0.3 DiI-positive cells per high-power field (p < 0.05), 124 +/- 21 versus 8 +/- 4 DiI-positive cells per high-power field (p < 0.05), and 106 +/- 18 versus 9 +/- 3 DiI-positive cells per high-power field (p < 0.05), respectively].These data suggest that the distraction zone becomes relatively ischemic during activation and that endothelial progenitor cells home to the ischemic generate site during the activation phase and remain during the consolidation phase. Selective expansion of these stem cells may be useful in overcoming ischemic limitations of distraction osteogenesis. Moreover, their homing capability may be used to effect site-specific transgene delivery to the generate.
View details for DOI 10.1097/01.prs.0000178403.79051.70
View details for Web of Science ID 000232114400021
View details for PubMedID 16163094
Topical vascular endothelial growth factor reverses delayed wound healing secondary to angiogenesis inhibitor administration
WOUND REPAIR AND REGENERATION
2005; 13 (5): 506-512
The prevention of new blood vessel growth is an increasingly attractive strategy to limit tumor growth. However, it remains unclear whether anti-angiogenesis approaches will impair wound healing, a process thought to be angiogenesis dependent. Results of previous studies differ as to whether angiogenesis inhibitors delay wound healing. We evaluated whether endostatin at tumor-inhibiting doses delayed excisional wound closure. C57/BL6J mice were treated with endostatin or phosphate-buffered solution 3 days prior to the creation of two full-thickness wounds on the dorsum. Endostatin was administered daily until wound closure was complete. A third group received endostatin, but also had daily topical vascular endothelial growth factor applied locally to the wound. Wound area was measured daily and the wounds were analyzed for granulation tissue formation, epithelial gap, and wound vascularity. Endostatin-treated mice showed a significant delay in wound healing. Granulation tissue formation and wound vascularity were significantly decreased, but reepithelialization was not effected. Topical vascular endothelial growth factor application to wounds in endostatin-treated mice resulted in increased granulation tissue formation, increased wound vascularity, and wound closure approaching that of control mice. This study shows that the angiogenesis inhibitor endostatin delays wound healing and that topical vascular endothelial growth factor is effective in counteracting this effect.
View details for Web of Science ID 000231910600008
View details for PubMedID 16176459
Mechanical strain alters gene expression in an in vitro model of hypertrophic scarring
ANNALS OF PLASTIC SURGERY
2005; 55 (1): 69-75
Fibroblasts represent a highly mechanoresponsive cell type known to play key roles in normal and pathologic processes such as wound healing, joint contracture, and hypertrophic scarring. In this study, we used a novel fibroblast-populated collagen lattice (FPCL) isometric tension model, allowing us to apply graded biaxial loads to dermal fibroblasts in a 3-dimensional matrix. Cell morphology demonstrated dose-dependent transition from round cells lacking stress fibers in nonloaded lattices to a broad, elongated morphology with prominent actin stress fibers in 800-mg-loaded lattices. Using quantitative real-time RT-PCR, a dose dependent induction of both collagen-1 and collagen-3 mRNA up to 2.8- and 3-fold, respectively, as well as a 2.5-fold induction of MMP-1 (collagenase) over unloaded FPCLs was observed. Quantitative expression of the proapoptotic gene Bax was down-regulated over 4-fold in mechanically strained FPCLs. These results suggest that mechanical strain up-regulates matrix remodeling genes and down-regulates normal cellular apoptosis, resulting in more cells, each of which produces more matrix. This "double burden" may underlie the pathophysiology of hypertrophic scars and other fibrotic processes in vivo.
View details for DOI 10.1097/01.sap.0000168160.86221.e9
View details for Web of Science ID 000230322100024
View details for PubMedID 15985794
Sonographically guided percutaneous carpal tunnel release - An anatomic and cadaveric study
ANNALS OF PLASTIC SURGERY
2005; 55 (1): 52-56
Minimally invasive techniques have become the standard of care for multiple procedures. This paper demonstrates both the surgeons' capacity to perform an accurate anatomic evaluation of the hand and forearm (n=10) and the use of this anatomic information to accurately perform sonographically guided, percutaneous carpal tunnel release using a single-portal endoscope without direct or indirect visualization in a cadaver model (n=6). Open dissection was then performed to confirm complete ligament transection and to evaluate the surrounding structures for injury. In all 6 cadavers, the transverse carpal ligament was transected completely without injury to any surrounding structures. With further investigation, this novel technique may offer a less invasive, office-based method for the surgical treatment of carpal tunnel syndrome that may offer patients an expedited recovery.
View details for DOI 10.1097/01.sap.0000168281.77528.02
View details for Web of Science ID 000230322100018
View details for PubMedID 15985791
Adult vasculogenesis occurs through in situ recruitment, proliferation, and tubulization of circulating bone marrow-derived cells
2005; 105 (3): 1068-1077
Ischemia is a known stimulus for vascular growth. Bone marrow (BM)-derived endothelial progenitor cells (EPCs) are believed to contribute to new blood vessel growth, but the mechanism for this contribution is unknown. To elucidate how BM cells are able to form new blood vessels, a novel murine model of soft tissue ischemia was developed in lethally irradiated mice with BM reconstituted from either tie2/lacZ or ROSA/green fluorescent protein (GFP) mice (n = 24). BM-derived EPCs were recruited to ischemic tissue within 72 hours, and the extent of recruitment was directly proportional to the degree of tissue ischemia. At 7 days, there were persistently elevated levels of vascular endothelial growth factor (VEGF) (2.5-fold) and circulating VEGF receptor-2/CD11(-) (flk-1(+)/CD11(-)) cells (18-fold) which correlated with increased numbers of BM-derived EPCs within ischemic tissue. The cells were initially located extravascularly as proliferative clusters. By day 14, these clusters coalesced into vascular cords, which became functional vessels by day 21. In vitro examination of human EPCs from healthy volunteers (n = 10) confirmed that EPC proliferation, adhesion, and chemotaxis were all significantly stimulated in hypoxic conditions. We conclude that BM-derived cells produce new blood vessels via localized recruitment, proliferation, and differentiation of circulating cells in a sequence of events markedly different from existing paradigms of angiogenesis.
View details for DOI 10.1182/blood-2004-03-1051
View details for Web of Science ID 000226596700033
View details for PubMedID 15388583
Homing to hypoxia: HIF-1 as a mediator of progenitor cell recruitment to injured tissue
TRENDS IN CARDIOVASCULAR MEDICINE
2005; 15 (2): 57-63
The identification of bone marrow-derived endothelial progenitor cells has altered our understanding of new blood vessel growth and tissue regeneration. Previously, new blood vessel growth in the adult was thought to only occur through angiogenesis, the sprouting of new vessels from existing structures. However, it has become clear that circulating bone marrow-derived cells can form new blood vessels through a process of postnatal vasculogenesis, with endothelial progenitor cells selectively recruited to injured or ischemic tissue. How this process occurs has remained unclear. One common element in the different environments where vasculogenesis is believed to occur is the presence of a hypoxic stimulus. We have identified the chemokine stromal cell-derived factor-1 (SDF-1) and its receptor CXCR4 as critical mediators for the ischemia-specific recruitment of circulating progenitor cells. We have found that the endothelial expression of SDF-1 acts as a signal indicating the presence of tissue ischemia, and that its expression is directly regulated by hypoxia-inducible factor-1. Stromal cell-derived factor 1 is the only chemokine family member known to be regulated in this manner. Later events, including proliferation, patterning, and assembly of recruited progenitors into functional blood vessels, are also influenced by tissue oxygen tension and hypoxia. Interestingly, both SDF-1 and hypoxia are present in the bone marrow niche, suggesting that hypoxia may be a fundamental requirement for progenitor cell trafficking and function. As such, ischemic tissue may represent a conditional stem cell niche, with recruitment and retention of circulating progenitors regulated by hypoxia through differential expression of SDF-1.
View details for Web of Science ID 000229468900003
View details for PubMedID 15885571
Circulating endothelial progenitor cells and vascular anomalies.
Lymphatic research and biology
2005; 3 (4): 234-239
Recent findings regarding pathways of stem/progenitor cell involvement in adult blood vessel growth (postnatal vasculogenesis) suggest new theories for the pathogenesis of vascular anomalies. The somatic growth of vascular malformations and the mysterious pattern of proliferation and involution in infantile hemangioma can no longer be purely understood through the paradigm of angiogenesis. Molecular signals for postnatal vasculogenesis are being discovered in numerous animal models of cancer and ischemia, yet little research has addressed the importance of vasculogenesis in the growth of vascular anomalies. In this review, we discuss early studies that have investigated stem/progenitor cell involvement in the pathophysiology of infantile hemangioma and other congenital vascular anomalies.
View details for PubMedID 16379593
Progenitor cell trafficking is regulated by hypoxic gradients through HIF-1 induction of SDF-1
2004; 10 (8): 858-864
The trafficking of circulating stem and progenitor cells to areas of tissue damage is poorly understood. The chemokine stromal cell-derived factor-1 (SDF-1 or CXCL12) mediates homing of stem cells to bone marrow by binding to CXCR4 on circulating cells. SDF-1 and CXCR4 are expressed in complementary patterns during embryonic organogenesis and guide primordial stem cells to sites of rapid vascular expansion. However, the regulation of SDF-1 and its physiological role in peripheral tissue repair remain incompletely understood. Here we show that SDF-1 gene expression is regulated by the transcription factor hypoxia-inducible factor-1 (HIF-1) in endothelial cells, resulting in selective in vivo expression of SDF-1 in ischemic tissue in direct proportion to reduced oxygen tension. HIF-1-induced SDF-1 expression increases the adhesion, migration and homing of circulating CXCR4-positive progenitor cells to ischemic tissue. Blockade of SDF-1 in ischemic tissue or CXCR4 on circulating cells prevents progenitor cell recruitment to sites of injury. Discrete regions of hypoxia in the bone marrow compartment also show increased SDF-1 expression and progenitor cell tropism. These data show that the recruitment of CXCR4-positive progenitor cells to regenerating tissues is mediated by hypoxic gradients via HIF-1-induced expression of SDF-1.
View details for DOI 10.1038/nm1075
View details for Web of Science ID 000223055700041
View details for PubMedID 15235597
Electromagnetic fields increase in vitro and in vivo angiogenesis through endothelial release of FGF-2.
2004; 18 (11): 1231-1233
Pulsed electromagnetic fields (PEMF) have been shown to be clinically beneficial, but their mechanism of action remains unclear. The present study examined the impact of PEMF on angiogenesis, a process critical for successful healing of various tissues. PEMF increased the degree of endothelial cell tubulization (sevenfold) and proliferation (threefold) in vitro. Media from PEMF cultures had a similar stimulatory effect, but heat denaturation ablated this activity. In addition, conditioned media was able to induce proliferative and chemotactic changes in both human umbilical vein endothelial cells and fibroblasts, but had no effect on osteoblasts. Angiogenic protein screening demonstrated a fivefold increase in fibroblast growth factor beta-2 (FGF-2), as well as smaller increases in other angiogenic growth factors (angiopoietin-2, thrombopoietin, and epidermal growth factor). Northern blot analysis demonstrated an increase in FGF-2 transcription, and FGF-2 neutralizing antibody inhibited the effects of PEMF. In vivo, PEMF exposure increased angiogenesis more than twofold. We conclude that PEMF augments angiogenesis primarily by stimulating endothelial release of FGF-2, inducing paracrine and autocrine changes in the surrounding tissue. These findings suggest a potential role for PEMF in therapeutic angiogenesis.
View details for PubMedID 15208265
Quantitative and reproducible murine model of excisional wound healing
WOUND REPAIR AND REGENERATION
2004; 12 (4): 485-492
The goal of animal wound healing models is to replicate human physiology and predict therapeutic outcomes. There is currently no model of wound healing in rodents that closely parallels human wound healing. Rodents are attractive candidates for wound healing studies because of their availability, low cost, and ease of handling. However, rodent models have been criticized because the major mechanism of wound closure is contraction, whereas in humans reepithelialization and granulation tissue formation are the major mechanisms involved. This article describes a novel model of wound healing in mice utilizing wound splinting that is accurate, reproducible, minimizes wound contraction, and allows wound healing to occur through the processes of granulation and reepithelialization. Our results show that splinted wounds have an increased amount of granulation tissue deposition as compared to controls, but the rate of reepithelialization is not affected. Thus, this model eliminates wound contraction and allows rodents' wounds to heal by epithelialization and granulation tissue formation. Given these analogies to human wound healing, we believe that this technique is a useful model for the study of wound healing mechanisms and for the evaluation of new therapeutic modalities.
View details for Web of Science ID 000222725900012
View details for PubMedID 15260814
Ex vivo transduction of microvascular free flaps for localized peptide delivery
ANNALS OF PLASTIC SURGERY
2004; 52 (6): 581-584
Gene therapy is a promising modality for the treatment of soft tissue malignancies. Our laboratory has developed a novel technique of gene transfer using microvascular free flaps that addresses many of the current barriers preventing gene therapy from achieving widespread clinical use. Our previous work has demonstrated our ability to transduce free flaps with an adenovirus encoding the reporter gene lacZ. In this current study, we show that microvascular free flaps can be transduced with an adenovirus encoding the angiogenesis inhibitor endostatin with high levels of local flap expression. These transduced free flaps were able to serve as "biologic pumps" and were able to secrete endostatin into the serum as demonstrated by enzyme-linked immunosorbent assay. This form of "biologic brachytherapy" could provide a novel approach for the continuous delivery of therapeutic genes to a localized area while avoiding many of the practical obstacles currently limiting gene therapy.
View details for DOI 10.1097/01.sap.0000122652.81844.37
View details for Web of Science ID 000221715400010
View details for PubMedID 15166989
- Electromagnetic fields increase in vitro and in vivo angiogenesis through endothelial release of FGF-2 FASEB JOURNAL 2004; 18 (9): 1231-?
Bone morphogenic protein-2 gene therapy for mandibular distraction osteogenesis
ANNALS OF PLASTIC SURGERY
2004; 52 (6): 585-591
Distraction osteogenesis (DO) requires a long consolidation period and has a low but real failure rate. Bone morphogenic proteins (BMPs) accelerate bone deposition in fractures and critical-sized bone defects, but their effects on mandibular DO are unknown. We investigated the effect of local delivery of adenovirus containing the gene for BMP-2 (Adbmp-2) on mandibular DO in a rat model. Rats (n = 54) were distracted to 3 mm over 6 days. At the start of consolidation (POD 10), Adbmp-2 or adenovirus containing the lacZgene (AdlacZ) was injected directly into the distraction zone. After 1, 2, and 4 weeks of consolidation, mandibles were evaluated for amount of bone deposition. Adbmp-2-treated specimens demonstrated an increased amount of new bone formation by radiographic, histologic, and histomorphometric analysis. This study demonstrates that local, adenovirally-mediated delivery of BMP-2 can increase bone deposition during DO, potentially shortening consolidation and enhancing DO in poorly healing mandibles, such as occurs postirradiation.
View details for DOI 10.1097/01.sap.0000123.23.28874.1e
View details for Web of Science ID 000221715400011
View details for PubMedID 15166991
Topical vascular endothelial growth factor accelerates diabetic wound healing through increased angiogenesis and by mobilizing and recruiting bone marrow-derived cells
AMERICAN JOURNAL OF PATHOLOGY
2004; 164 (6): 1935-1947
Diminished production of vascular endothelial growth factor (VEGF) and decreased angiogenesis are thought to contribute to impaired tissue repair in diabetic patients. We examined whether recombinant human VEGF(165) protein would reverse the impaired wound healing phenotype in genetically diabetic mice. Paired full-thickness skin wounds on the dorsum of db/db mice received 20 microg of VEGF every other day for five doses to one wound and vehicle (phosphate-buffered saline) to the other. We demonstrate significantly accelerated repair in VEGF-treated wounds with an average time to resurfacing of 12 days versus 25 days in untreated mice. VEGF-treated wounds were characterized by an early leaky, malformed vasculature followed by abundant granulation tissue deposition. The VEGF-treated wounds demonstrated increased epithelialization, increased matrix deposition, and enhanced cellular proliferation, as assessed by uptake of 5-bromodeoxyuridine. Analysis of gene expression by real-time reverse transcriptase-polymerase chain reaction demonstrates a significant up-regulation of platelet-derived growth factor-B and fibroblast growth factor-2 in VEGF-treated wounds, which corresponds with the increased granulation tissue in these wounds. These experiments also demonstrated an increase in the rate of repair of the contralateral phosphate-buffered saline-treated wound when compared to wounds in diabetic mice never exposed to VEGF (18 days versus 25 days), suggesting that topical VEGF had a systemic effect. We observed increased numbers of circulating VEGFR2(+)/CD11b(-) cells in the VEGF-treated mice by fluorescence-activated cell sorting analysis, which likely represent an endothelial precursor population. In diabetic mice with bone marrow replaced by that of tie2/lacZ mice we demonstrate that the local recruitment of bone marrow-derived endothelial lineage lacZ+ cells was augmented by topical VEGF. We conclude that topical VEGF is able to improve wound healing by locally up-regulating growth factors important for tissue repair and by systemically mobilizing bone marrow-derived cells, including a population that contributes to blood vessel formation, and recruiting these cells to the local wound environment where they are able to accelerate repair. Thus, VEGF therapy may be useful in the treatment of diabetic complications characterized by impaired neovascularization.
View details for Web of Science ID 000221601000008
View details for PubMedID 15161630
Endostatin inhibits ischemia-induced neovascularization and increases ischemic tissue loss
ANNALS OF PLASTIC SURGERY
2004; 52 (5): 512-518
The impact of inhibitors of tumor angiogenesis (endostatin, angiostatin) on the neovascularization required for the healing of transferred tissue has not been examined. We investigated the effect of endostatin on the functional neovascularization of random pattern flaps. C57BL6 mice were pretreated with endostatin beginning 3 days prior to surgery (n = 10), and daily injections continued throughout the study. Dorsal random cutaneous flaps were raised in both treatment and control (saline-treated) groups. The remaining cranial attachment was divided on day 9. Oxygen tension (PO2) was measured using a microprobe on days 1, 3, 5 and 16. Flaps were harvested and the vasculature was stained with CD31 on day 16. We found that endostatin significantly decreased flap survival. Mice that were treated with endostatin had fewer CD31+ blood vessels, worse flap perfusion at all time points, and lower oxygen tensions throughout the length of the flap. These findings have potential implications for the patients undergoing antiangiogenesis therapy who require surgical reconstruction.
View details for DOI 10.1097/01.sap.0000123022.98361.c5
View details for Web of Science ID 000221283600014
View details for PubMedID 15096942
Reconstruction of a large mandibular defect utilizing temporary zygomatic-ramal fixation and bilateral Risdon incisions
JOURNAL OF CRANIOFACIAL SURGERY
2004; 15 (1): 16-19
Ameloblastoma is a benign, invasive, odontogenic tumor of the jaws that predominantly affects the mandible. Despite the benign nature of these lesions, there is a high rate of local recurrence after curettage, which usually requires resection. The traditional surgical approach for resection of ameloblastomas, via either mandibulotomy or mandibulectomy, has been through lower lip-splitting incisions, which are associated with significant functional and esthetic sequelae. A case is presented here in which less invasive Risdon and intraoral degloving incisions were used in combination with temporary zygomatic-ramal fixation to maintain occlusion after resection of a large mandibular ameloblastoma. The bilateral Risdon approach provided wide access to the mandible, allowing an angle-to-angle resection to be performed. This approach also provided adequate exposure for an osteocutaneous fibula free flap reconstruction to be performed, with 100% flap survival. At 1 year of follow-up, there were minimal functional and esthetic defects. This approach represents a less invasive alternative that provides access to the mandible for curative resection of benign tumors with minimal postoperative sequelae.
View details for Web of Science ID 000225848500006
View details for PubMedID 14704555
Selective recruitment of endothelial progenitor cells to ischemic tissues with increased neovascularization
PLASTIC AND RECONSTRUCTIVE SURGERY
2004; 113 (1): 284-293
Tissue ischemia remains a common problem in plastic surgery and one for which proangiogenic approaches have been investigated. Given the recent discovery of circulating endothelial stem or progenitor cells that are able to form new blood vessels, the authors sought to determine whether these cells might selectively traffic to regions of tissue ischemia and induce neovascularization. Endothelial progenitor cells were isolated from the peripheral blood of healthy human volunteers and expanded ex vivo for 7 days. Elevation of a cranially based random-pattern skin flap was performed in nude mice, after which they were injected with fluorescent-labeled endothelial progenitor cells (5 x 10(5); n = 15), fluorescent-labeled human microvascular endothelial cells (5 x 10(5); n = 15), or media alone (n = 15). Histologic examination demonstrated that endothelial progenitor cells were recruited to ischemic tissue and first appeared by postoperative day 3. Subsequently, endothelial progenitor cell numbers increased exponentially over time for the remainder of the study [0 cells/mm2 at day 0 (n = 3), 9.6 +/- 0.9 cells/mm2 at day 3 (n = 3), 24.6 +/- 1.5 cells/mm2 at day 7 (n = 3), and 196.3 +/- 9.6 cells/mm2 at day 14 (n = 9)]. At all time points, endothelial progenitor cells localized preferentially to ischemic tissue and healing wound edges, and were not observed in normal, uninjured tissues. Endothelial progenitor cell transplantation led to a statistically significant increase in vascular density in ischemic tissues by postoperative day 14 [28.7 +/- 1.2 in the endothelial progenitor cell group (n = 9) versus 18 +/- 1.1 in the control media group (n = 9) and 17.7 +/- 1.0 in the human microvascular endothelial cell group (n = 9; p < 0.01)]. Endothelial progenitor cell transplantation also showed trends toward increased flap survival [171.2 +/- 18 mm2 in the endothelial progenitor cell group (n = 12) versus 134.2 +/- 10 mm2 in the media group (n = 12) and 145.0 +/- 13 mm2 in the human microvascular endothelial cell group (n = 12)], but this did not reach statistical significance. These findings indicate that local tissue ischemia is a potent stimulus for the recruitment of circulating endothelial progenitor cells. Systemic delivery of endothelial progenitor cells increased neovascularization and suggests that autologous endothelial progenitor cell transplantation may have a role in the salvage of ischemic tissue.
View details for DOI 10.1097/01.PRS.0000091169.51035.A5
View details for Web of Science ID 000220063200040
View details for PubMedID 14707648
Microvascular free-tissue transfer for traumatic defects of the upper extremity: A 25-year experience
JOURNAL OF RECONSTRUCTIVE MICROSURGERY
2003; 19 (7): 455-461
Microvascular free-tissue transfer has been a major advance in the treatment of complex traumatic defects of the upper extremity. One hundred and fifty microvascular free-tissue transfers were performed in 133 patients with complex traumatic upper extremity defects at Bellevue Hospital Center from 1976 to 2000. The indication for microvascular free tissue transfers was exposure of vital structure (81 percent), bone defect (11 percent), and functional deficit (8 percent). The parascapular region was the most common donor site used (26 percent). Microvascular free-tissue transfer was performed either emergently at the time of injury (9.3 percent), during days 1 to 5 post injury (19.3 percent), during days 6 to 21 (19.3 percent), or after day 21 (52 percent). The overall flap failure rate was 9 percent. A decreased incidence of flap failure was observed in patients treated from 6 to 21 days post injury (3 percent p<0.05). The most common acute complication was infection at the recipient site, observed in 14 percent of patients overall. A decreased incidence of recipient-site infection was seen in patients who received free flaps at days 6 to 21 (3 percent; p<0.05). In long-term follow-up, the incidences of osteomyelitis and nonunion were lowest in patients treated from 6 to 21 days post injury (0.0 percent and 11 percent, respectively; p<0.05). During the last 10 years, the timing of reconstruction has been altered, and now preferentially microvascular free flaps are performed 6 to 21 days post injury. The treatment algorithm has been simplified and now only four different flaps are used in the majority of patients (70 percent). With this, the authors have witnessed a decrease in failure rates from 11 percent to 4 percent, a decrease in recipient-site infections from 16 percent to 10 percent and a decrease in osteomyelitis from 12 percent to 4 percent. The preferred timing for microvascular free-tissue transfers to the upper extremity is concluded to be 6 to 21 days post injury.
View details for Web of Science ID 000185905200003
View details for PubMedID 14634908
Reliable assessment of skin flap viability using orthogonal polarization imaging
PLASTIC AND RECONSTRUCTIVE SURGERY
2003; 112 (2): 547-555
Intraoperative evaluation of skin flap viability has primarily been dependent on clinical judgment. The purpose of this study was to determine whether an orthogonal polarization spectral imaging device could be used to accurately predict viability of random-pattern skin flaps. Orthogonal polarization spectral imaging is a newly developed technique that visualizes the microcirculation using reflected light without the use of fluorescent dyes and allows for noninvasive real-time observation of functional microvascular networks. In Sprague-Dawley rats (n = 24), three types of random skin flaps were designed with unknown zones of viability (n = 8 per group). After flap elevation, the skin flaps were evaluated by both clinical examination and orthogonal polarization spectral imaging. Areas of the flap determined to be nonviable by clinical examination were measured and marked. Orthogonal polarization spectral imaging was subsequently performed, and areas of the skin flap with stasis (i.e., cessation of red blood cell movement) in the dermal microcirculation on orthogonal polarization spectral imaging were measured and marked. The skin flaps were then secured in place. Flaps were evaluated on a daily basis for clinical signs of ischemia and necrosis. On postoperative day 7, the total amount of random skin flap necrosis was measured and recorded. Clinical examination of the random skin flaps significantly underestimated the actual amount of eventual flap necrosis, and as result was a very poor predictor of flap necrosis. By contrast, assessment of microcirculatory stasis using the orthogonal polarization spectral imaging device correlated well with the subsequent development of necrosis in all groups. In the three groups, the average amount of flap necrosis predicted by clinical examination deviated from actual necrosis by approximately 2 to 4 cm. However, the amount that orthogonal polarization spectral imaging differed from actual necrosis was 0.1 to 0.3 cm. Therefore, orthogonal polarization spectral imaging was an excellent predictor of eventual flap necrosis and much more accurate than clinical observation (p < 0.001). Intraoperative evaluation of axial and random pattern flap viability has traditionally been based on clinical examination as no other reliable, convenient test currently exists. The authors demonstrated that an orthogonal polarization spectral imaging device accurately predicts zones of necrosis in random pattern flaps by directly visualizing cessation of microcirculatory flow. Intraoperative stasis in the dermal microcirculation correlated precisely with subsequent flap necrosis. Orthogonal polarization spectral imaging was significantly more accurate than clinical examination, which consistently underestimated flap necrosis. The orthogonal polarization spectral imaging technique may have value in the intraoperative assessment of skin flap perfusion such as that required after skin-sparing mastectomy.
View details for DOI 10.1097/01.PRS.0000070968.42857.43
View details for Web of Science ID 000184532700022
View details for PubMedID 12900613
- Endothelial progenitor cells: The promise of vascular stem cells for plastic surgery PLASTIC AND RECONSTRUCTIVE SURGERY 2003; 111 (2): 846-854
Vascularized acellular dermal matrix island flaps for the repair of abdominal muscle defects
PLASTIC AND RECONSTRUCTIVE SURGERY
2003; 111 (1): 225-232
The potential widespread use of tissue-engineered matrices in soft-tissue reconstruction has been limited by the difficulty in fabricating and confirming a functional microcirculation. Acellular dermal matrix placed in a soft-tissue pocket acts as a scaffold to be incorporated by the host's fibrovascular tissue. A new method for noninvasive real-time observation of functional microvascular networks using orthogonal polarization spectral (OPS) imaging has recently been reported. Arterioles, venules, and capillaries can be directly visualized, and the movement of individual blood cells through them can be observed. The present study was performed to investigate the use of prefabricated acellular dermal matrix with an arteriovenous unit for the repair of abdominal muscle defects. OPS imaging was used to determine the presence of a functional microcirculation in the neovascularized matrix. In Sprague-Dawley rats, vascularized matrix was prefabricated by placing the superficial epigastric artery and vein on a 2-cm x 2-cm implant-type acellular dermal matrix in the thigh. Three weeks after implantation, the matrix-arteriovenous unit was elevated as an axial-type flap and a 2-cm x 2-cm full-thickness block of abdominal muscle immediately superior to the inguinal ligament was resected. Additional procedures were performed according to group: no repair (group 1, n = 20); repair with nonvascularized acellular dermal matrix (group 2, n = 20); repair with devascularized acellular dermal matrix (group 3, = 20); and repair with vascularized acellular dermal matrix (group 4, n = 20). OPS imaging (field of view, 1 mm in diameter; scan depth range, 0.2 mm) was performed on both sides of each flap on a total of 10 random distal regions before and after pedicle transection in group 3 and with the pedicle preserved in group 4. Hernia rate and duration of survival were compared for 21 days. OPS imaging showed directional blood cell movement through the capillary network in all areas scanned in group 4. No microvascular perfusion was observed after pedicle transection in group 3. Hernia rates of 100, 80, 90, and 0 percent were seen in groups 1, 2, 3, and 4, respectively. Median survival times of 9, 11.5, 9, and 21 postoperative days were noted in groups 1, 2, 3, and 4, respectively. Histopathologic analysis with factor VIII revealed full-thickness infiltration of the matrix by endothelial cells, signifying newly formed blood vessels. Repair of abdominal muscle defects using vascularized acellular dermal matrix resulted in no hernia and survival of all animals for the duration of study. However, repairs using avascular or devascularized matrix resulted in significant rates of hernia and decreased survival. Acellular dermal matrix can be prefabricated into vascularized tissue using an arteriovenous unit and used successfully to repair abdominal muscle defects. OPS imaging allowed for high-contrast direct visualization of microcirculation in previously acellular tissue following prefabrication with an arteriovenous unit.
View details for DOI 10.1097/01.PRS.0000034934.05304.ED
View details for Web of Science ID 000180191700039
View details for PubMedID 12496583
Mesenchymal stem cell homing in distraction osteogenesis: Promise for ex vivo expansion therapy and gene-delivery vehicles
CRANIOFACIAL SURGERY 10
View details for Web of Science ID 000227470500070
Increased circulating AC133+ CD34+ endothelial progenitor cells in children with hemangioma.
Lymphatic research and biology
2003; 1 (4): 301-307
Hemangioma is the most common soft-tissue tumor of infancy. Despite the frequency of these vascular tumors, the origin of hemangioma-endothelial cells is unknown. Circulating endothelial progenitor cells (EPCs) have recently been identified as vascular stem cells with the capacity to contribute to postnatal vascular development. We have attempted to determine whether circulating EPCs are increased in hemangioma patients and thereby provide insight into the role of EPCs in hemangioma growth.Peripheral blood mononuclear cells (PBMCs) were isolated from hemangioma patients undergoing surgical resection (N = 5) and from age-matched controls (N = 5) undergoing strabismus correction surgery. PBMCs were stained with fluorescent-labeled antibodies for AC133, CD34, and VEGFR2/KDR. Fluorescent-labeled isotype antibodies served as negative controls. Histologic sections of surgical specimens were stained with the specific hemangioma markers Glut1, CD32, and merosin, to confirm the diagnosis of common hemangioma of infancy. EPCs harvested from healthy adult volunteers were stained with Glut1, CD32, and merosin, to assess whether cultured EPCs express known hemangioma markers. Hemangioma patients had a 15-fold increase in the number of circulating CD34 AC133 dual-staining cells relative to controls (0.78+/-0.14% vs.0.052+/-0.017%, respectively). Similarly, the number of PBMCs that stained positively for both CD34 and KDR was also increased in hemangioma patients (0.49+/-0.074% vs. 0.19+/-0.041% in controls). Cultured EPCs stained positively for the known hemangioma markers Glut1, CD32, merosin.This is the first study to suggest a role for EPCs in the pathogenesis of hemangioma. Our results imply that increased levels of circulating EPCs may contribute to the formation of this vascular tumor.
View details for PubMedID 15624558
Cellular dysfunction in the diabetic fibroblast - Impairment in migration, vascular endothelial growth factor production, and response to hypoxia
AMERICAN JOURNAL OF PATHOLOGY
2003; 162 (1): 303-312
Although it is known that systemic diseases such as diabetes result in impaired wound healing, the mechanism for this impairment is not understood. Because fibroblasts are essential for wound repair, we compared the in vitro behavior of fibroblasts cultured from diabetic, leptin receptor-deficient (db/db) mice with wild-type fibroblasts from mice of the same genetic background in processes important during tissue repair. Adult diabetic mouse fibroblast migration exhibited a 75% reduction in migration compared to normal fibroblasts (P < 0.001) and was not significantly stimulated by hypoxia (1% O(2)), whereas wild-type fibroblast migration was up-regulated nearly twofold in hypoxic conditions (P < 0.05). Diabetic fibroblasts produced twice the amount of pro-matrix metalloproteinase-9 as normal fibroblasts, as measured by both gelatin zymography and enzyme-linked immunosorbent assay (P < 0.05). Adult diabetic fibroblasts exhibited a sevenfold impairment in vascular endothelial growth factor (VEGF) production (4.5 +/- 1.3 pg/ml versus 34.8 +/- 3.3 pg/ml, P < 0.001) compared to wild-type fibroblasts. Moreover, wild-type fibroblast production of VEGF increased threefold in response to hypoxia, whereas diabetic fibroblast production of VEGF was not up-regulated in hypoxic conditions (P < 0.001). To address the question whether these differences resulted from chronic hyperglycemia or absence of the leptin receptor, fibroblasts were harvested from newborn db/db mice before the onset of diabetes (4 to 5 weeks old). These fibroblasts showed no impairments in VEGF production under basal or hypoxic conditions, confirming that the results from db/db fibroblasts in mature mice resulted from the diabetic state and were not because of alterations in the leptin-leptin receptor axis. Markers of cellular viability including proliferation and senescence were not significantly different between diabetic and wild-type fibroblasts. We conclude that, in vitro, diabetic fibroblasts show selective impairments in discrete cellular processes critical for tissue repair including cellular migration, VEGF production, and the response to hypoxia. The VEGF abnormalities developed concurrently with the onset of hyperglycemia and were not seen in normoglycemic, leptin receptor-deficient db/db mice. These observations support a role for fibroblast dysfunction in the impaired wound healing observed in human diabetics, and also suggest a mechanism for the poor clinical outcomes that occur after ischemic injury in diabetic patients.
View details for Web of Science ID 000180009800031
View details for PubMedID 12507913
Endothelial progenitor cell trafficking in distraction osteogenesis in the activation and consolidation phases
CRANIOFACIAL SURGERY 10
View details for Web of Science ID 000227470500020
Gene therapy with bone morphogenic protein-2 in mandibular distraction osteogaiesis
CRANIOFACIAL SURGERY 10
View details for Web of Science ID 000227470500021
Human endothelial progenitor cells from type II diabetics exhibit impaired proliferation, adhesion, and incorporation into vascular structures.
2002; 106 (22): 2781-2786
The recent discovery of circulating endothelial progenitor cells (EPCs) has altered our understanding of new blood vessel growth such as occurs during collateral formation. Because diabetic complications occur in conditions in which EPC contributions have been demonstrated, EPC dysfunction may be important in their pathophysiology.EPCs were isolated from human type II diabetics (n=20) and age-matched control subjects (n=20). Proliferation of diabetic EPCs relative to control subjects was decreased by 48% (P<0.01) and inversely correlated with patient levels of hemoglobin A1C (P<0.05). Diabetic EPCs had normal adhesion to fibronectin, collagen, and quiescent endothelial cells but a decreased adherence to human umbilical vein endothelial cells activated by tumor necrosis factor-alpha (TNF-alpha) (P<0.05). In a Matrigel assay, diabetic EPCs were 2.5 times less likely to participate in tubule formation compared with controls (P<0.05).These findings suggest that type II diabetes may alter EPC biology in processes critical for new blood vessel growth and may identify a population at high risk for morbidity and mortality after vascular occlusive events.
View details for PubMedID 12451003
Reduction mammoplasty improves breast conservation therapy in patients with macromastia
AMERICAN JOURNAL OF SURGERY
2001; 181 (3): 215-220
Macromastia has been considered a contraindication to breast conservation therapy because of difficulties with radiation therapy. This study evaluates the feasibility of bilateral reduction mammoplasty as a component of breast conservation therapy for breast cancer patients with pendulous breasts.Of 153 patients undergoing reduction mammoplasty at the University of Texas M. D. Anderson Cancer Center, 28 were identified as breast cancer patients with macromastia receiving breast conservation therapy. Median follow-up was 23.8 months.Median patient age was 55 years. Nearly all patients were described as obese. Median weight of the reduction mammoplasty specimen on the cancerous side was 766 g. One patient (4%) required completion mastectomy for inadequate margin control. Major postoperative complications occurred in 2 patients (7%). There were no major postradiation complications. Patient survey revealed a satisfaction rate of 86%.Bilateral reduction mammoplasty is a reasonable and safe option for breast cancer patients with macromastia who desire breast conservation therapy.
View details for Web of Science ID 000168869400006
View details for PubMedID 11376574
Advances in head and neck reconstruction
PLASTIC AND RECONSTRUCTIVE SURGERY
2000; 106 (3): 672-682
Head and neck deformities, which can be caused by trauma, congenital defects, infections, or neoplasms, produce a stereotypical constellation of functional and aesthetic deficits, depending on the specific anatomic region. These deformities can be classified into six major anatomic categories: intraoral, mandibular, midfacial, cranial base, cutaneous, and scalp. This article presents a reliable approach to the reconstruction of these six areas that is used at the University of Texas M. D. Anderson Cancer Center. The emphasis is on an analysis of the unique functional and aesthetic problems presented by each of these specific anatomic lesions, and the reconstructive options are selected to maximize outcomes. The problems and limitations of current methods are discussed, and areas of potential development are explored.
View details for Web of Science ID 000088925700025
View details for PubMedID 10987478
Immunotargeting of liposomes to activated vascular endothelial cells: A strategy for site-selective delivery in the cardiovascular system
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1997; 94 (16): 8795-8800
Endothelial-selective delivery of therapeutic agents, such as drugs or genes, would provide a useful tool for modifying vascular function in various disease states. A potential molecular target for such delivery is E-selectin, an endothelial-specific cell surface molecule expressed at sites of activation in vivo and inducible in cultured human umbilical vein endothelial cells (HUVEC) by treatment with cytokines such as recombinant human interleukin 1beta (IL-1beta). Liposomes of various types (classical, sterically stabilized, cationic, pH-sensitive), each conjugated with mAb H18/7, a murine monoclonal antibody that recognizes the extracellular domain of E-selectin, bound selectively and specifically to IL-1beta-activated HUVEC at levels up to 275-fold higher than to unactivated HUVEC. E-selectin-targeted immunoliposomes appeared in acidic, perinuclear vesicles 2-4 hr after binding to the cell surface, consistent with internalization via the endosome/lysosome pathway. Activated HUVEC incubated with E-selectin-targeted immunoliposomes, loaded with the cytotoxic agent doxorubicin, exhibited significantly decreased cell survival, whereas unactivated HUVEC were unaffected by such treatment. These results demonstrate the feasibility of exploiting cell surface activation markers for the endothelial-selective delivery of biologically active agents via immunoliposomes. Application of this targeting approach in vivo may lead to novel therapeutic strategies in the treatment of cardiovascular disease.
View details for Web of Science ID A1997XQ12400090
View details for PubMedID 9238057
EFFECT OF CARBON-DIOXIDE PNEUMOPERITONEUM ON BACTEREMIA AND ENDOTOXEMIA IN AN ANIMAL-MODEL OF PERITONITIS
BRITISH JOURNAL OF SURGERY
1995; 82 (6): 844-848
Laparoscopy is increasingly used in conditions complicated by peritonitis. A theoretical concern is that carbon dioxide pneumoperitoneum may increase bacteraemia. This study examines the effect of carbon dioxide pneumoperitoneum on bacteraemia, endotoxaemia and physiological correlates of sepsis in an animal model of peritonitis. New Zealand white rabbits were assigned to three groups of six animals. Group 1 received an intraperitoneal inoculation of 10(9) colony-forming units of Escherichia coli followed by a 10-cm midline laparotomy. Group 2 received an identical bacterial inoculum followed by a 12-mmHg carbon dioxide pneumoperitoneum for 1 h. Group 3 received no bacteria but had a 12-mmHg carbon dioxide pneumoperitoneum for 1 h. Groups 1 and 2 had significantly higher levels of bacteraemia (P < 0.01) and endotoxaemia (P < 0.01) accompanied by significantly lower mean arterial pressures (P < 0.05) and higher heart rates (P < 0.05) compared with group 3. After 6 h groups 1 and 2 were significantly hypocarbic (P < 0.01), leucopenic (P < 0.01) and thrombocytopenic (P < 0.01). There was no difference between group 1 and group 2. A carbon dioxide pneumoperitoneum of 12 mmHg does not increase bacteraemia or endotoxaemia, nor does it adversely affect physiological or laboratory correlates of sepsis compared with laparotomy in this animal model of peritonitis.
View details for Web of Science ID A1995RC64400034
View details for PubMedID 7627528
TARGETED DISRUPTION OF THE MURINE VCAM1 GENE - ESSENTIAL ROLE OF VCAM-1 IN CHORIOALLANTOIC FUSION AND PLACENTATION
GENES & DEVELOPMENT
1995; 9 (1): 1-14
Vascular cell adhesion molecule-1 (VCAM-1) is expressed on vascular endothelium in a variety of inflammatory conditions and mediates leukocyte recruitment from blood into tissues. In this study we report a novel role for VCAM-1 in the formation of the umbilical cord and placenta during development. The murine VCAM1 gene was disrupted by targeted homologous recombination, and a distinct phenotype was found in VCAM-1-deficient embryos. At 8.5 days of gestation, the allantois failed to fuse to the chorion, resulting in abnormal placental development and embryonic death within 1-3 days. In addition, a role for VCAM-1 in early placental formation after chorioallantoic fusion was observed. In a minority of VCAM-1-deficient embryos, the allantois was able to fuse with the chorion, but the allantoic mesoderm was abnormally distributed over the chorionic surface. A small number of VCAM-1-deficient embryos survived, presumably by circumventing the placentation defects. They became viable and fertile adult mice with lack of VCAM-1 expression, normal organs, and an elevated number of circulating blood mononuclear leukocytes.
View details for Web of Science ID A1995QB81000001
View details for PubMedID 7530222
2-TEAM SYNCHRONOUS ESOPHAGECTOMY
BRITISH JOURNAL OF SURGERY
1994; 81 (11): 1620-1622
Between 1984 and 1992, 131 patients underwent two-team synchronous oesophagectomy for carcinoma. Some 95 per cent of tumours were successfully resected by this technique. In 5 per cent of patients the tumour was found to be irresectable at operation and gastric bypass was performed. The overall operative mortality rate was 8 per cent and the pulmonary complication rate 10 per cent. The actuarial survival rate was 55 per cent at 1 year, 22 per cent at 3 years and 16 per cent at 5 years. When compared with the traditional two-stage Lewis approach, two-team synchronous oesophagectomy was significantly faster (mean 222 versus 282 min), but was not significantly different with respect to blood loss, transfusion requirement, pulmonary complications or operative mortality rate. Patients undergoing two-team oesophagectomy had a significantly shorter hospital stay than those receiving the two-stage procedure (mean 16 versus 24 days).
View details for Web of Science ID A1994PQ50000015
View details for PubMedID 7827888
LOW-DENSITY LIPOPROTEIN UNDERGOES OXIDATIVE MODIFICATION INVIVO
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1989; 86 (4): 1372-1376
It has been proposed that low density lipoprotein (LDL) must undergo oxidative modification before it can give rise to foam cells, the key component of the fatty streak lesion of atherosclerosis. Oxidation of LDL probably generates a broad spectrum of conjugates between fragments of oxidized fatty acids and apolipoprotein B. We now present three mutually supportive lines of evidence for oxidation of LDL in vivo: (i) Antibodies against oxidized LDL, malondialdehyde-lysine, or 4-hydroxynonenal-lysine recognize materials in the atherosclerotic lesions of LDL receptor-deficient rabbits; (ii) LDL gently extracted from lesions of these rabbits is recognized by an antiserum against malondialdehyde-conjugated LDL; (iii) autoantibodies against malondialdehyde-LDL (titers from 512 to greater than 4096) can be demonstrated in rabbit and human sera.
View details for Web of Science ID A1989T274500059
View details for PubMedID 2465552
IMPROVED STATIC LUNG PRESERVATION WITH CORTICOSTEROIDS AND HYPOTHERMIA
JOURNAL OF HEART TRANSPLANTATION
1988; 7 (5): 348-352
With methylprednisolone as a chemical inhibitor of leukocytes, extended preservation was conducted with an isolated rabbit lung model. The heart-lung blocks of 39 New Zealand white rabbits were flushed in situ with 100 ml of Euro-Collins' solution, harvested, inflated (70%), and preserved at 4 degrees C. Lungs immediately reperfused with whole blood (control lungs, group 1) were compared with lungs preserved without methylprednisolone for 5, 12, and 24 hours (groups 2 to 4) and those preserved with methylprednisolone for 12 and 24 hours (groups 5 and 6, respectively). Methylprednisolone (30 mg/kg) was administered before harvest and was used as an additive to the flush and in the blood reperfusate. Hypothermia and Euro-Collins' flush alone provided adequate preservation for up to 5 hours; however, lung edema was evident by 12 hours of cold ischemia and became severe by 24 hours. By all measured parameters, the lungs in group 5 (treated with methylprednisolone) demonstrated values equal to or better than control lungs. By 24 hours of preservation the beneficial effects of the steroid treatment were no longer evident. Histologic evaluation revealed mild to moderate injury after 5 hours of cold ischemia; progressive edema and hemorrhage were found after 12 and 24 hours of preservation. This injury was significantly ameliorated by methylprednisolone treatment at 12 hours but not at 24 hours. This study suggests that static preservation for up to 5 hours is possible with hypothermia and a Euro-Collins' flush and that extended preservation to 12 hours is possible with pharmacologic dosages of methylprednisolone.(ABSTRACT TRUNCATED AT 250 WORDS)
View details for Web of Science ID A1988Q554200005
View details for PubMedID 3199247
Microsurgery Education in Residency Training Validating an Online Curriculum
LIPPINCOTT WILLIAMS & WILKINS. 2012: 410-414
Plastic surgery training has traditionally been modeled as an "apprenticeship," where faculty teach surgical skills to residents on live patients. Although this is a well-established process, the demand by the public and healthcare agencies for improved patient care, outcomes, and patient safety has led to the development of adjunct methods of teaching. The goal of this project is to assess the effectiveness of a web-based microsurgical curriculum.We developed an interactive Web site to teach essential microsurgical competencies. Residents were randomly divided into 2 cohorts: one experimental group completed this online resource and the other control group did not. Pre- and postassessments were administered, consisting of a written test and a recorded microsurgery skills session.A total of 17 plastic surgery residents of various training levels participated in the study. Residents who completed the web-based curriculum showed dramatic improvement in their knowledge and skills, with a 17-percentage point increase in their test scores (P = 0.01) compared with controls (P = 0.80). The experimental group was more likely to perform microanastomoses faster with an average of 4.5-minute improvement compared with 1.25-minute change among the control group. Residents performed self-assessments, and those who rated themselves as "very confident" had higher overall test scores (85% test score vs. 59%, P = 0.004), as well as shorter times to complete the microsurgical task (7.5 minutes vs. 13.6 minutes, P = 0.007). Overall, 62% of residents rated the online webpage as extremely valuable. The majority of residents reported the webpage improved their knowledge and markedly improved their microsurgical technique, which was confirmed by faculty experts.Our interactive Web-based curriculum is a novel resource, teaching microsurgery in an organized, competency-based manner, which we believe is the first Web site of this nature. An individualized, self-paced Web site is ideal for plastic surgery trainees of all levels. Overall, the widespread implementation of our proposed curriculum--online self-directed training combined with regular practice sessions--will establish a strong foundation of microsurgery knowledge and skills acquisition for all plastic surgery residents.
View details for DOI 10.1097/SAP.0b013e31823b6a1a
View details for Web of Science ID 000301800600019
View details for PubMedID 22421490
Effectiveness of the Asteame Nipple Guard (TM) in maintaining projection following nipple reconstruction: A prospective randomised controlled trial
ELSEVIER SCI LTD. 2010: 1592-1596
As the final step in breast reconstruction, nipple reconstruction is considered a minor surgical procedure. However, despite the multitude of techniques and postoperative dressings proposed, none have proven to resist the tendency of the reconstructed nipple to gradually flatten over time. A prospective randomized controlled trial was conducted assessing the value of using the Asteame Nipple Guard™ compared to standard gauze dressing in maintaining nipple projection postoperatively. A total of 30 nipple reconstructions in 22 patients were included in the study with randomisation of 15 nipples to each study arm. Nipple projection was measured at various time points postoperatively with calculation of the percent changes in nipple projection. The mean decrease in long-term nipple projection at 6 months in the experimental group was 46.6% vs. 71.8% in the control group (p<0.05). In conclusion, the Nipple Guard™ helps in maintaining nipple projection postoperatively.
View details for DOI 10.1016/j.bjps.2009.10.006
View details for Web of Science ID 000281655500003
View details for PubMedID 19897430