Dr. Dunn obtained his B.S. degree in Biology and Chemical Engineering from the California Institute of Technology and his M.D. and Ph.D. degrees from Harvard and Massachusetts Institute of Technology. He trained in General Surgery at the UCLA School of Medicine and in Pediatric Surgery at the Riley Hospital for Children in Indianapolis. He was the Professor and Chief of Pediatric Surgery at UCLA, with a joint appointment in the Department of Bioengineering until 2016. Dr. Dunn is the Susan B. Ford Surgeon-in-Chief at the Lucile Packard Children's Hospital, the John A. and Cynthia Fry Gunn Director of Pediatric Surgery, and Professor of Surgery and Bioengineering at the Stanford School of Medicine.
- Pediatric Surgery
- Short Bowel Syndrome
- Intestinal Motility Disorders
Chief of Pediatric Surgery, Department of Surgery, Stanford (2016 - Present)
Surgeon-in-Chief, Lucile Packard Children's Hospital (2016 - Present)
Boards, Advisory Committees, Professional Organizations
Member, Child Health Research Institute Executive Committee (2016 - Present)
Ex-officio, Lucile Packard Children's Hospital Board of Directors (2016 - Present)
B.S., California Institute of Technology, Biology and Chemical Engineering (1985)
M.D., Harvard Medical School, Medicine (1992)
Ph.D., Massachusetts Institute of Technology, Medical Engineering (1992)
Residency: UCLA Health Sciences (1999) CA
Board Certification: General Surgery, American Board of Surgery (2000)
Fellowship: Riley Hospital for Children at Indiana University Health (2001) IN
Board Certification: Pediatric Surgery, American Board of Surgery (2002)
James Dunn. "United States Patent 9,138,336 Expandable distension device for hollow organ growth", Sep 22, 2015
Current Research and Scholarly Interests
Intestinal lengthening for short bowel syndrome
Intestinal stem cell therapy for intestinal failure
Skin derived precursor cell therapy for enteric neuromuscular dysfunction
Intestinal tissue engineering
- Senior Capstone Design I
BIOE 141A (Aut)
Graduate and Fellowship Programs
Pediatric Surgery (Fellowship Program)
Tumescent Injections in Subcutaneous Pig Tissue Disperse Fluids Volumetrically and Maintain Elevated Local Concentrations of Additives for Several Hours, Suggesting a Treatment for Drug Resistant Wounds.
2020; 37 (3): 51
PURPOSE: Bolus injection of fluid into subcutaneous tissue results in accumulation of fluid at the injection site. The fluid does not form a pool. Rather, the injection pressure forces the interstitial matrix to expand to accommodate the excess fluid in its volume, and the fluid becomes bound similar to that in a hydrogel. We seek to understand the properties and dynamics of externally tumesced (swollen) subcutaneous tissue as a first step in assessing whether tumescent antibiotic injections into wounds may provide a novel method of treatment.METHODS: Subcutaneous injections of saline are performed in live and dead pigs and the physical properties (volume, expansion ratio, residence time, apparent diffusion constant) of the resulting fluid deposits are observed with diffusion-weighted magnetic resonance imaging, computed tomography, and 3D scanning.RESULTS: Subcutaneous tissue can expand to a few times its initial volume to accommodate the injected fluid, which is dispersed thoroughly throughout the tumescent volume. The fluid spreads to peripheral unexpanded regions over the course of a few minutes, after which it remains in place for several hours. Eventually the circulation absorbs the excess fluid and the tissue returns to its original state.CONCLUSIONS: Given the evidence for dense fluid dispersal and several-hour residence time, a procedure is proposed whereby tumescent antibiotic injections are used to treat drug-resistant skin infections and chronic wounds that extend into the subcutaneous tissue. The procedure has the potential to effectively treat otherwise untreatable wounds by keeping drug concentrations above minimum inhibitory levels for extended lengths of time.
View details for DOI 10.1007/s11095-020-2769-2
View details for PubMedID 32043171
- Electroacupuncture to Increase Neuronal Stem Cell Growth MEDICAL ACUPUNCTURE 2020; 32 (1): 16–23
Electroacupuncture to Increase Neuronal Stem Cell Growth.
2020; 32 (1): 16–23
Background: Neuropathic intestinal disorders continue to pose a significant burden, and current treatment options do not target the underlying cellular deficiencies. The goal of this study is to determine whether acupuncture and electroacupuncture (EA) can affect the growth of neuronal cells. Methods: Three groups of Lewis rats received 25 minutes of acupuncture twice a week for 10 weeks. The 3 groups of rats received treatment with either sham acupuncture (SA), real acupuncture (RA), or EA. After 10 weeks of treatment, skin and intestinal tissue were collected and analyzed for histology and mRNA expression of neuronal marker genes. Results: Compared with rats that received SA, rats that received RA and EA showed a significant increase in the mRNA expression levels of multiple neuronal genes in the skin. No significant histologic changes were seen. Conclusions: Acupuncture and EA result in significant changes in the expression of genes implicated as markers for neural stem cells, neural cell development, and neurons. This may, therefore, provide a novel avenue for developing treatments in patients suffering from intestinal aganglionic and neuropathic diseases.
View details for DOI 10.1089/acu.2019.1381
View details for PubMedID 32104523
View details for PubMedCentralID PMC7041333
- Cutaneous Patches to Monitor Myoelectric Activity of the Gastrointestinal Tract in Postoperative Pediatric Patients PEDIATRIC GASTROENTEROLOGY HEPATOLOGY & NUTRITION 2019; 22 (6): 518–26
Optimization of In-Continuity Spring-Mediated Intestinal Lengthening.
Journal of pediatric surgery
BACKGROUND: Spring-mediated intestinal lengthening has been studied in numerous animal models to effectively achieve up to a 3-fold increase in length. In this study we are interested in optimizing this method of spring lengthening.METHODS: Juvenile mini-Yucatan pigs underwent laparotomy for spring implantation. Springs were secured by plicating the intestine around the springs. In one set of experiments, varying degrees of plication were compared to determine the necessary narrowing needed to confine the spring. In another set of experiments, dissolvable sutures were used for the plication to allow for spontaneous spring passage postoperatively. Intestinal segments were retrieved and evaluated for lengthening and histological changes.RESULTS: Pigs tolerated their diet advancement to a regular diet postoperatively. 10% plication resulted in a 1.3-fold increase in length, while 50% plication resulted in a 2.7-fold increase in length (p<0.05). At two months postoperatively, the majority of springs had safely passed out of the intestine. All lengthened intestine showed significant growth histologically.CONCLUSIONS: A 50% reduction in lumen diameter achieves optimal spring-mediated intestinal lengthening. Springs can safely pass out of the intestine, thus avoiding a second operation for spring removal. These results may be important in developing future therapies for short bowel syndrome.LEVEL OF EVIDENCE: Level I experimental study.
View details for DOI 10.1016/j.jpedsurg.2019.09.072
View details for PubMedID 31676077
Autologous Transplantation of Skin-Derived Precursor Cells in a Porcine Model.
Journal of pediatric surgery
BACKGROUND: Hirschprung's disease is characterized by aganglionic bowel and often requires surgical resection. Cell-based therapies have been investigated as potential alternatives to restore functioning neurons. Skin-derived precursor cells (SKPs) differentiate into neural and glial cells in vitro and generate ganglion-like structures in rodents. In this report, we aimed to translate this approach into a large animal model of aganglionosis using autologous transplantation of SKPs.METHODS: Juvenile pigs underwent skin procurement from the shoulder and simultaneous chemical denervation of an isolated colonic segment. Skin cells were cultured in neuroglial-selective medium and labeled with fluorescent dye for later identification. The cultured SKPs were then injected into the aganglionic segments of colon, and the specimens were retrieved within seven days after transplantation. SKPs in vitro and in vivo were assessed with histologic samples for various immunofluorescent markers of multipotency and differentiation. SKPs from the time of harvest were compared to those at the time of injection using PCR.RESULTS: Prior to transplantation, 72% of SKPs stained positive for nestin and S100b, markers of neural and glial precursor cells of neural crest origin, respectively. Markers of differentiated neurons and gliocytes, TUJ1 and GFAP, were detected in 47% of cultured SKPs. After transplantation, SKPs were identified in both myenteric and submucosal plexuses of the treated colon. Nestin co-expression was detected in the SKPs within the aganglionic colon in vivo. Injected SKPs appeared to migrate and express early neuroglial differentiation markers.CONCLUSIONS: Autologous SKPs implanted into aganglionic bowel demonstrated immunophenotypes of neuroglial progenitors. Our results suggest that autologous SKPs may be potentially useful for cell-based therapy for patients with enteric nervous system disorders.TYPE OF STUDY: Basic science.
View details for DOI 10.1016/j.jpedsurg.2019.09.075
View details for PubMedID 31704043
Growth of Small Intestinal Layers Proximal and Distal to the Intestine Undergoing Distraction Enterogenesis
ELSEVIER SCIENCE INC. 2019: S204
View details for Web of Science ID 000492740900390
Biomechanical signaling and collagen fiber reorientation during distraction enterogenesis.
Journal of the mechanical behavior of biomedical materials
2019; 101: 103425
Distraction enterogenesis has been extensively studied as a potential treatment for short bowel syndrome, which is the most common subset of intestinal failure. Spring distraction uses an intraluminal axial mechanical force to stimulate the growth and elongation of the small intestine. The tissue close to the distracted intestinal segment may also experience signaling to grow. In this study we examined the effects of distraction enterogenesis at different post-operative days on the thickness of small intestinal layers in the intestine proximal and distal to the distracted segment, as well as how the submucosal collagen fibers were reoriented. It was observed that not only different layers of intestine wall in distracted segment showed thickening due to the applied mechanical force but also adjacent tissues in both distal and proximal directions were impacted significantly where they showed thickening as well. The orientation of collagen fibers in submucosa layer was also significantly impacted due to the mechanical force in both distracted and adjacent tissue. The effect of the applied mechanical force on the main distracted tissue and the radial growth of the adjacent tissue strongly suggest actions of paracrine signaling.
View details for DOI 10.1016/j.jmbbm.2019.103425
View details for PubMedID 31541857
Biomechanics of small intestine during distraction enterogenesis with an intraluminal spring.
Journal of the mechanical behavior of biomedical materials
2019; 101: 103413
During recent years, distraction enterogenesis has been extensively studied as a treatment for short bowel syndrome, which is the most common cause of intestinal failure. Although different strategies such as parenteral nutrition and surgical lengthening have been used to manage the difficulties that patients with SBS deal with, these treatments are associated with high complication rates. Distraction enterogenesis uses mechanical force to increase the length and stimulate growth of the small intestine. In this study we combine in vivo experiments with computational modeling to explore the biomechanics of spring dependent distraction enterogenesis. We hypothesize that the self-expanding spring provides mechanical force for elastic tissue lengthening and triggers cellular proliferation. The additional growth of the intestine suggests signaling between mechanical stress and tissue response. We developed a computational modeling platform to test the correlation of applied mechanical force and tissue growth. We further validated our computational models with experimental measurements using spring-mediated distraction enterogenesis in a porcine model. This modeling platform can incorporate patient biometrics to estimate an individual's tissue response to spring mediated distraction enterogenesis.
View details for DOI 10.1016/j.jmbbm.2019.103413
View details for PubMedID 31518947
A Wireless Implantable System for Facilitating Gastrointestinal Motility.
2019; 10 (8)
Gastrointestinal (GI) electrical stimulation has been shown in several studies to be a potential treatment option for GI motility disorders. Despite the promising preliminary research progress, however, its clinical applicability and usability are still unknown and limited due to the lack of a miniaturized versatile implantable stimulator supporting the investigation of effective stimulation patterns for facilitating GI dysmotility. In this paper, we present a wireless implantable GI modulation system to fill this technology gap. The system consists of a wireless extraluminal gastrointestinal modulation device (EGMD) performing GI electrical stimulation, and a rendezvous device (RD) and a custom-made graphical user interface (GUI) outside the body to wirelessly power and configure the EGMD to provide the desired stimuli for modulating GI smooth muscle activities. The system prototype was validated in bench-top and in vivo tests. The GI modulation system demonstrated its potential for facilitating intestinal transit in the preliminary in vivo chronic study using porcine models.
View details for DOI 10.3390/mi10080525
View details for PubMedID 31395845
- Long-Term Outcomes in Children With Intestinal Failure-Associated Liver Disease Treated With 6 Months of Intravenous Fish Oil Followed by Resumption of Intravenous Soybean Oil JOURNAL OF PARENTERAL AND ENTERAL NUTRITION 2019; 43 (6): 708–16
- Intravenous Fish Oil and Serum Fatty Acid Profiles in Pediatric Patients With Intestinal Failure-Associated Liver Disease JOURNAL OF PARENTERAL AND ENTERAL NUTRITION 2019; 43 (6): 717–25
The cellular regulators PTEN and BMI1 help mediate NEUROGENIN-3-induced cell cycle arrest.
The Journal of biological chemistry
Neurogenin-3 (NEUROG3) is a helix-loop-helix (HLH) transcription factor involved in the production of endocrine cells in the intestine and pancreas of humans and mice. However, the human NEUROG3 loss-of-function phenotype differs subtly from that in mice, but the reason for this difference remains poorly understood. Because NEUROG3 expression precedes exit of the cell cycle and the expression of endocrine cell markers during differentiation, we investigated the effect of lentivirus-mediated overexpression of the human NEUROG3 gene on the cell cycle of BON4 cells and various human non-endocrine cell lines. NEUROG3 overexpression induced a reversible cell cycle exit, whereas expression of a neuronal lineage homolog, NEUROG1, had no such effect. In endocrine lineage cells, the cellular quiescence induced by short-term NEUROG3 expression required cyclin-dependent kinase inhibitor 1A (CDKN1A)/p21 CIP1 expression. Expression of endocrine differentiation markers required sustained NEUROG3 expression in the quiescent, but not in the senescent, state. Inhibition of the phosphatase and tensin homolog (PTEN) pathway reversed quiescence by inducing cyclin-dependent kinase 2 (CDK2) and reducing p21CIP1 and NEUROG3 protein levels in BON4 cells and human enteroids. We discovered that NEUROG3 expression stimulates expression of CDKN2a/p16 INK4aand BMI1 proto-oncogene polycomb ring finger (BMI1), with the latter limiting expression of the former, delaying the onset of CDKN2a/p16 INK4a-driven cellular senescence. Furthermore, NEUROG3 bound to the promoters of both CDKN1a/p21 CIP1 and BMI1 genes, and BMI1 attenuated NEUROG3 binding to the CDKN1a/p21 CIP1 promoter. Our findings reveal how human NEUROG3 integrates inputs from multiple signaling pathways and thereby mediates cell cycle exit at the onset of differentiation.
View details for DOI 10.1074/jbc.RA119.008926
View details for PubMedID 31341016
Delayed appearance of mature ganglia in an infant with an atypical presentation of total colonic and small bowel aganglionosis: a case report.
2019; 19 (1): 93
BACKGROUND: Total colonic and small bowel aganglionosis (TCSA) occurs in less than 1% of all Hirschsprung's disease patients. Currently, the mainstay of treatment is surgery. However, in patients with TCSA, functional outcomes are often poor. A characteristic transition zone in TCSA can be difficult to identify which may complicate surgery and may often require multiple operations.CASE PRESENTATION: We present the case of a male infant who was diagnosed with biopsy-proven total colonic aganglionosis with extensive small bowel involvement as a neonate. The patient was diverted at one month of age based on leveling biopsies at 10cm from the Ligament of Treitz. At 7months of age, during stoma revision for a prolapsed stoma, intra-operative peristalsis was observed in nearly the entire length of the previously aganglionic bowel, and subsequent biopsies demonstrated the appearance of mature ganglion cells in a previously aganglionic segment.CONCLUSIONS: TCSA remains a major challenge for pediatric surgeons. Our case introduces new controversy to our understanding of aganglionosis. Our observations warrant further research into the possibility of post-natal ganglion maturation and encourage surgeons to consider a more conservative surgical approach.
View details for PubMedID 30953480
- Intestinal Electrical Stimulation to Increase the Rate of Peristalsis JOURNAL OF SURGICAL RESEARCH 2019; 236: 153–58
Intravenous Fish Oil and Serum Fatty Acid Profiles in Pediatric Patients With Intestinal Failure-Associated Liver Disease.
JPEN. Journal of parenteral and enteral nutrition
BACKGROUND: Intravenous fish oil (FO) treats pediatric intestinal failure-associated liver disease (IFALD). There are concerns that a lipid emulsion composed of omega-3 fatty acids will cause an essential fatty acid deficiency (EFAD). This study's objective was to quantify the risk for abnormal fatty acid concentrations in children treated with FO.METHODS: Inclusion criteria for this prospective study were children with intestinal failure. Intravenous soybean oil (SO) was replaced with FO for no longer than 6 months. Serum fatty acids were analyzed using linear and logistic models, and compared with age-based norms to determine the percentage of subjects with low and high concentrations.RESULTS: Subjects (n=17) started receiving FO at a median of 3.6 months (interquartile range 2.4-9.6 months). Over time, alpha-linolenic, linoleic, arachidonic, and Mead acid decreased, whereas docosahexaenoic and eicosapentaenoic acid increased (P<0.001 for all). Triene-tetraene ratios remained unchanged (P=1). Although subjects were 1.8 times more likely to develop a low linoleic acid while receiving FO vs SO (95% CI: 1.4-2.3, P<0.01), there was not a significant risk for low arachidonic acid. Subjects were 1.6 times more likely to develop high docosahexaenoic acid while receiving FO vs SO; however, this was not significant (95% CI: 0.9-2.6, P=0.08).CONCLUSION: In this cohort of parenteral nutrition-dependent children, switching from SO to FO led to a decrease in essential fatty acid concentrations, but an EFAD was not evident. Low and high levels of fatty acids developed. Further investigation is needed to clarify if this is clinically significant.
View details for PubMedID 30900274
Double plication for spring-mediated in-continuity intestinal lengthening in a porcine model
MOSBY-ELSEVIER. 2019: 389–92
Short bowel syndrome is a condition with substantial morbidity and mortality, yet definitive therapies are lacking. Distraction enterogenesis uses mechanical force to "grow" new intestine. In this study, we examined whether intestinal plication can be used to safely achieve spring-mediated intestinal lengthening in a functioning segment of jejunum in its native position.A total of 12 juvenile, miniature Yucatan pigs underwent laparotomy to place either compressed springs or expanded springs within a segment of jejunum (n = 6 per group). The springs were secured within the jejunum by performing intestinal plication to narrow the intestinal lumen around the spring. After 3 weeks, the jejunum was retrieved and examined for lengthening and for histologic changes.There were no intraoperative or postoperative complications, and the pigs tolerated their diets and gained weight. Segments of jejunum containing expanded springs showed no significant change in length over the 3 weeks. In contrast, jejunum containing compressed springs showed nearly a 3-fold increase in length (P < .001). Histology of the retrieved jejunum showed a significant increase in thickness of the muscularis propria and in crypt depth relative to normal jejunum.Intestinal plication is effective in securing endoluminal springs to lengthen the jejunum. This approach is a clinically relevant model because it allows for normal GI function and growth of animals during intestinal lengthening, which may be useful in lengthening intestine in patients with short bowel syndrome.
View details for PubMedID 30217395
Cutaneous Patches to Monitor Myoelectric Activity of the Gastrointestinal Tract in Postoperative Pediatric Patients.
Pediatric gastroenterology, hepatology & nutrition
2019; 22 (6): 518–26
Limited means exist to assess gastrointestinal activity in pediatric patients postoperatively. Recently, myoelectric gastrointestinal activity recorded by cutaneous patches has been shown in adult patients to be predictive of clinical return of gastrointestinal function postoperatively. The aim of this case series is to demonstrate the feasibility of this system in pediatric patients and to correlate myoelectric signals with return of bowel function clinically.Pediatric patients undergoing abdominal surgery were recruited to have wireless patches placed on the abdomen within two hours postoperatively. Myoelectric data were transmitted wirelessly to a mobile device with a user-interface and forwarded to a cloud server where processing algorithms identified episodes of motor activity, quantified their parameters and nominally assigned them to specific gastrointestinal organs based on their frequencies.Three patients (ages 5 months, 4 year, 16 year) were recruited for this study. Multiple patches were placed on the older subjects, while the youngest had a single patch due to space limitations. Rhythmic signals of the stomach, small intestine, and colon could be identified in all three subjects. Patients showed gradual increase in myoelectric intestinal and colonic activity leading up to the first recorded bowel movement.Measuring myoelectric intestinal activity continuously using a wireless patch system is feasible in a wide age range of pediatric patients. The increase in activity over time correlated well with the patients' return of bowel function. More studies are planned to determine if this technology can predict return of bowel function or differentiate between physiologic ileus and pathologic conditions.
View details for DOI 10.5223/pghn.2019.22.6.518
View details for PubMedID 31777717
View details for PubMedCentralID PMC6856497
Intestinal epithelial replacement by transplantation of cultured murine and human cells into the small intestine.
2019; 14 (5): e0216326
Adult intestinal epithelial stem cells are a promising resource for treatment of intestinal epithelial disorders that cause intestinal failure and for intestinal tissue engineering. We developed two different animal models to study the implantation of cultured murine and human intestinal epithelial cells in the less differentiated "spheroid" state and the more differentiated "enteroid" state into the denuded small intestine of mice. Engraftment of donor cells could not be achieved while the recipient intestine remained in continuity. However, we were able to demonstrate successful implantation of murine and human epithelial cells when the graft segment was in a bypassed loop of jejunum. Implantation of donor cells occurred in a random fashion in villus and crypt areas. Engraftment was observed in 75% of recipients for murine and 36% of recipients for human cells. Engrafted spheroid cells differentiated into the full complement of intestinal epithelial cells. These findings demonstrate for the first time successful engraftment into the small bowel which is optimized in a bypassed loop surgical model.
View details for DOI 10.1371/journal.pone.0216326
View details for PubMedID 31150401
- Intestinal lengthening via multiple in-continuity springs W B SAUNDERS CO-ELSEVIER INC. 2019: 39–43
Long-Term Outcomes in Children With Intestinal Failure-Associated Liver Disease Treated With 6 Months of Intravenous Fish Oil Followed by Resumption of Intravenous Soybean Oil.
JPEN. Journal of parenteral and enteral nutrition
BACKGROUND: Intravenous soybean oil (SO) is a commonly used lipid emulsion for children with intestinal failure (IF); however, it is associated with IF-associated liver disease (IFALD). Studies have demonstrated that intravenous fish oil (FO) is an effective treatment for IFALD. However, there is a lack of long-term data on children who stop FO and resume SO. This study's objective was to investigate our institution's outcomes for children with IFALD treated with 6months of FO and who then restarted SO.METHODS: Inclusion criteria for FO included children with IFALD. Parenteral nutrition (PN)-dependent children resumed SO after FO and were prospectively followed for 4.5 years or until death, transplant, or PN discontinuation. The primary outcome was the cumulative incidence rate (CIR) for cholestasis after FO.RESULTS: Forty-eight subjects received FO, and conjugated bilirubin decreased over time (-0.22mg/dL/week; 95% confidence interval [CI]: -0.25, -0.19; P< .001). The CIR for cholestasis resolution after 6months of FO was 71% (95% CI: 54%, 82%). Twenty-seven subjects resumed SO and were followed for a median of 16months (range 3-51months). While the CIR for enteral autonomy after 3 years of follow-up was 40% (95% CI: 17%, 26%), the CIR for cholestasis and transplant was 26% (95% CI: 8%, 47%) and 6% (95% CI: 0.3%, 25%), respectively.CONCLUSION: In this study, FO effectively treated cholestasis, and SO resumption was associated with cholestasis redevelopment in nearly one-fourth of subjects. Long-term FO may be warranted to prevent end-stage liver disease.
View details for PubMedID 30411372
Intestinal lengthening via multiple in-continuity springs.
Journal of pediatric surgery
BACKGROUND: Short bowel syndrome is a debilitating condition with few effective treatments. Spring-mediated distraction enterogenesis can be used to lengthen intestine. The purpose of this study is to determine whether multiple springs in series can safely increase the total amount of lengthening.METHODS: Juvenile mini-Yucatan pigs each received three nitinol springs placed within their jejunum. Plication was used to narrow the intestine around each spring to secure them. Compressed springs were used in the experimental group, while uncompressed springs were used in the control group. The intestine was examined 3 weeks later for lengthening and histologic changes.RESULTS: All pigs tolerated diets postoperatively with continued weight gain, and no dilation or obstruction of the intestine was observed. Segments of intestine that contained compressed springs had a significant increase in length from 2.5 cm to 3.9 ± 0.2 cm per spring, compared to segments containing control springs that showed no change (p < 0.001).CONCLUSIONS: Intestinal plication can be safely used to secure multiple springs in series to achieve intestinal lengthening without compromising intestinal function. Using several springs at once allows for a greater amount of total lengthening. This is a promising model that has potential in the treatment of short bowel syndrome.
View details for PubMedID 30361072
Disrupting the LINC complex in smooth muscle cells reduces aortic disease in a mouse model of Hutchinson-Gilford progeria syndrome
SCIENCE TRANSLATIONAL MEDICINE
2018; 10 (460)
Hutchinson-Gilford progeria syndrome is a disorder of premature aging in children caused by de novo mutations in LMNA that lead to the synthesis of an internally truncated form of prelamin A (commonly called progerin). The production of progerin causes multiple disease phenotypes, including an unusual vascular phenotype characterized by the loss of smooth muscle cells in the arterial media and fibrosis of the adventitia. We show that progerin expression, combined with mechanical stress, promotes smooth muscle cell death. Disrupting the linker of the nucleoskeleton and cytoskeleton (LINC) complex in smooth muscle cells ameliorates the toxic effects of progerin on smooth muscle cells and limits the accompanying adventitial fibrosis.
View details for PubMedID 30257952
View details for PubMedCentralID PMC6166472
Bioengineering functional smooth muscle with spontaneous rhythmic contraction in vitro
2018; 8: 13544
Oriented smooth muscle layers in the intestine contract rhythmically due to the action of interstitial cells of Cajal (ICC) that serve as pacemakers of the intestine. Disruption of ICC networks has been reported in various intestinal motility disorders, which limit the quality and expectancy of life. A significant challenge in intestinal smooth muscle engineering is the rapid loss of function in cultured ICC and smooth muscle cells (SMC). Here we demonstrate a novel approach to maintain the function of both ICC and SMC in vitro. Primary intestinal SMC mixtures cultured on feeder cells seeded electrospun poly(3-caprolactone) scaffolds exhibited rhythmic contractions with directionality for over 10 weeks in vitro. The simplicity of this system should allow for wide usage in research on intestinal motility disorders and tissue engineering, and may prove to be a versatile platform for generating other types of functional SMC in vitro.
View details for PubMedID 30202095
Double plication for spring-mediated intestinal lengthening of a defunctionalized Roux limb
JOURNAL OF PEDIATRIC SURGERY
2018; 53 (9): 1806–10
Spring-mediated distraction enterogenesis has been shown to increase the length of an intestinal segment. The goal of this study is to use suture plication to confine a spring within an intestinal segment while maintaining luminal patency to the rest of the intestine.Juvenile mini-Yucatan pigs underwent placement of nitinol springs within a defunctionalized Roux limb of jejunum. A 20 French catheter was passed temporarily, and sutures were used to plicate the intestinal wall around the catheter at both ends of the encapsulated spring. Uncompressed springs placed in plicated segments and springs placed in nonplicated segments served as controls. The intestine was examined approximately 3 weeks after spring placement.In the absence of plication, springs passed through the intestine within a week. Double plication allowed the spring to stay within the Roux limb for 3 weeks. Compared to uncompressed springs that showed no change in the length of plicated segments, compressed springs caused a significant 1.7-fold increase in the length of plicated segments.Intestinal plication is an effective method to confine endoluminal springs. The confined springs could lengthen intestine that maintains luminal patency. This approach may be useful to lengthen intestine in patients with short bowel syndrome.Level I Experimental Study.
View details for PubMedID 29352575
- Fluid flow in tumescent subcutaneous tissue observed with 3D scanning: massage accelerates injection dispersal BIOMEDICAL PHYSICS & ENGINEERING EXPRESS 2018; 4 (4)
- Mechanically induced development and maturation of human intestinal organoids in vivo NATURE BIOMEDICAL ENGINEERING 2018; 2 (6): 429–42
Mechanisms for intestinal regeneration
CURRENT OPINION IN PEDIATRICS
2018; 30 (3): 424–29
The purpose of this review is to briefly summarize the notable structures and pathways in intestinal epithelial growth before presenting the current main areas of active research in intestinal regeneration. As a rapidly advancing field, a number of breakthroughs have recently been made related to the culture of intestinal stem cells (ISCs) and to the engineering of intestinal tissue.ISCs can be derived from fibroblasts and can be cultured in hydrogels under xenogeneic-free conditions. Intestinal organoids can be cultured with neural crest cells to form small intestinal tissues with neuromuscular networks. Endoluminal devices can be placed inside the native intestine to exert mechanical force to induce novel tissue growth.A number of recent advances in the field of intestinal regeneration are encouraging and suggest that novel therapies for a wide range of intestinal disorders may be developed in the near future. There are still a number of obstacles before such stem cell therapies can be safely used in humans.
View details for PubMedID 29538044
Bioengineered intestinal muscularis complexes with long-term spontaneous and periodic contractions
2018; 13 (5): e0195315
Although critical for studies of gut motility and intestinal regeneration, the in vitro culture of intestinal muscularis with peristaltic function remains a significant challenge. Periodic contractions of intestinal muscularis result from the coordinated activity of smooth muscle cells (SMC), the enteric nervous system (ENS), and interstitial cells of Cajal (ICC). Reproducing this activity requires the preservation of all these cells in one system. Here we report the first serum-free culture methodology that consistently maintains spontaneous and periodic contractions of murine and human intestinal muscularis cells for months. In this system, SMC expressed the mature marker myosin heavy chain, and multipolar/dipolar ICC, uniaxonal/multipolar neurons and glial cells were present. Furthermore, drugs affecting neural signals, ICC or SMC altered the contractions. Combining this method with scaffolds, contracting cell sheets were formed with organized architecture. With the addition of intestinal epithelial cells, this platform enabled up to 11 types of cells from mucosa, muscularis and serosa to coexist and epithelial cells were stretched by the contracting muscularis cells. The method constitutes a powerful tool for mechanistic studies of gut motility disorders and the functional regeneration of the engineered intestine.
View details for PubMedID 29718926
Subcutaneous cefazolin to reduce surgical site infections in a porcine model
JOURNAL OF SURGICAL RESEARCH
2018; 224: 156–59
Surgical site infections (SSIs) pose a significant health and financial burden. A key aspect of appropriate prophylaxis is the administration of antibiotics intravenously (IV). However, subcutaneous administration of antibiotics is not well described in the literature. During surgery, we hypothesize that subcutaneous injection may provide better protection against SSIs. To better understand the kinetics after subcutaneous injection, we describe the serum concentrations of cefazolin in a porcine model.Juvenile mini-Yucatan pigs were administered 20 mL of 25 mg/kg cefazolin subcutaneously, and serial blood samples were taken for 3 h. Blood samples were analyzed for cefazolin concentration using chromatography. Pharmacokinetic data were calculated based on the blood serum concentrations.Maximum serum concentrations of cefazolin were achieved 42.6 ± 2.0 min after the time of injection and were found to be 18.8 ± 7.4 μg/mL. The elimination rate constant was 0.0033 ± 0.0016 min-1 and the half-life was 266 ± 149 min. The area under the curve was 4940 ± 1030 μg × min/mL. The relative bioavailability of subcutaneous injection was 95% +5%/-20%.Subcutaneous administration of cefazolin achieves a significantly lower maximum serum concentration than IV injection. As a result, higher doses of antibiotic can be injected locally without incurring systemic toxicity. Subcutaneous administration will therefore result in higher concentrations of antibiotic for a longer time at the incision site compared with standard IV administration. This strategy of antibiotic delivery may be more effective in preventing SSIs. Further studies are needed to detail the exact effect of subcutaneous antibiotic injection on SSI rates.
View details for PubMedID 29506833
Mechanically induced development and maturation of human intestinal organoids in vivo.
Nature biomedical engineering
2018; 2 (6): 429–42
The natural ability of stem cells to self-organize into functional tissue has been harnessed for the production of functional human intestinal organoids. Although dynamic mechanical forces play a central role in intestinal development and morphogenesis, conventional methods for the generation of intestinal organoids have relied solely on biological factors. Here, we show that the incorporation of uniaxial strain, by using compressed nitinol springs, in human intestinal organoids transplanted into the mesentery of mice induces growth and maturation of the organoids. Assessment of morphometric parameters, transcriptome profiling, and functional assays of the strain-exposed tissue revealed higher similarities to native human intestine, with regards to tissue size and complexity, and muscle tone. Our findings suggest that the incorporation of physiologically relevant mechanical cues during the development of human intestinal tissue enhances its maturation and enterogenesis.
View details for PubMedID 30151330
View details for PubMedCentralID PMC6108544
A Wireless Implant for Gastrointestinal Motility Disorders.
2018; 9 (1)
Implantable functional electrical stimulation (IFES) has demonstrated its effectiveness as an alternative treatment option for diseases incurable pharmaceutically (e.g., retinal prosthesis, cochlear implant, spinal cord implant for pain relief). However, the development of IFES for gastrointestinal (GI) tract modulation is still limited due to the poorly understood GI neural network (gut⁻brain axis) and the fundamental difference among activating/monitoring smooth muscles, skeletal muscles and neurons. This inevitably imposes different design specifications for GI implants. This paper thus addresses the design requirements for an implant to treat GI dysmotility and presents a miniaturized wireless implant capable of modulating and recording GI motility. This implant incorporates a custom-made system-on-a-chip (SoC) and a heterogeneous system-in-a-package (SiP) for device miniaturization and integration. An in vivo experiment using both rodent and porcine models is further conducted to validate the effectiveness of the implant.
View details for PubMedID 30393295
View details for PubMedCentralID PMC6187657
- INTERSTITIAL MATRIX PREVENTS THERAPEUTIC ULTRASOUND FROM CAUSING INERTIAL CAVITATION IN TUMESCENT SUBCUTANEOUS TISSUE ULTRASOUND IN MEDICINE AND BIOLOGY 2018; 44 (1): 177–86
- A Wireless Implant for Gastrointestinal Motility Disorders MICROMACHINES 2018; 9 (1)
Three-dimensionally printed surface features to anchor endoluminal spring for distraction enterogenesis.
2018; 13 (7): e0200529
Spring-mediated distraction enterogenesis has been studied as a novel treatment for short bowel syndrome (SBS). Previous approaches are limited by multiple surgeries to restore intestinal continuity. Purely endoluminal devices require a period of intestinal attachment for enterogenesis. The purpose of this study is to modify the device to prevent premature spring migration in a porcine model. Two models were created in juvenile mini-Yucatan pigs for the placement of three-dimensionally printed springs. (1) Two Roux-en-y jejunojenostomies with two Roux limbs were made. A spring with bidirectional hooked surface features was placed in one Roux limb and a spring with smooth surface was placed in the other Roux limb. (2) The in-continuity model had both hooked and smooth surface springs placed directly in intestinal continuity. Spring location was evaluated by weekly radiographs, and the intestine was retrieved after 2 to 4 weeks. Springs with smooth surfaces migrated between 1 to 3 weeks after placement in both porcine models. Springs with bidirectional hooked surface features were anchored to the intestine for up to 4 weeks without migration. Histologically, the jejunal architecture showed significantly increased crypt depth and muscularis thickness compared to normal jejunum. Bidirectional features printed on springs prevented the premature migration of endoluminal springs. These novel spring anchors allowed for their endoluminal placement without any sutures. This approach may lead to the endoscopic placement of the device for patients with SBS.
View details for PubMedID 30001433
- Lgr5 Stem Cell Proliferation from Spring-Mediated Distraction Enterogenesis in a Mouse Model ELSEVIER SCIENCE INC. 2017: S152–S153
Feasibility and scalability of spring parameters in distraction enterogenesis in a murine model
JOURNAL OF SURGICAL RESEARCH
2017; 215: 219–24
Distraction enterogenesis has been investigated as a novel treatment for short bowel syndrome (SBS). With variable intestinal sizes, it is critical to determine safe, translatable spring characteristics in differently sized animal models before clinical use. Nitinol springs have been shown to lengthen intestines in rats and pigs. Here, we show spring-mediated intestinal lengthening is scalable and feasible in a murine model.A 10-mm nitinol spring was compressed to 3 mm and placed in a 5-mm intestinal segment isolated from continuity in mice. A noncompressed spring placed in a similar fashion served as a control. Spring parameters were proportionally extrapolated from previous spring parameters to accommodate the smaller size of murine intestines. After 2-3 wk, the intestinal segments were examined for size and histology.Experimental group with spring constants, k = 0.2-1.4 N/m, showed intestinal lengthening from 5.0 ± 0.6 mm to 9.5 ± 0.8 mm (P < 0.0001), whereas control segments lengthened from 5.3 ± 0.5 mm to 6.4 ± 1.0 mm (P < 0.02). Diameter increased similarly in both groups. Isolated segment perforation was noted when k ≥ 0.8 N/m. Histologically, lengthened segments had increased muscularis thickness and crypt depth in comparison to normal intestine.Nitinol springs with k ≤ 0.4 N/m can safely yield nearly 2-fold distraction enterogenesis in length and diameter in a scalable mouse model. Not only does this study derive the safe ranges and translatable spring characteristics in a scalable murine model for patients with short bowel syndrome, it also demonstrates the feasibility of spring-mediated intestinal lengthening in a mouse, which can be used to study underlying mechanisms in the future.
View details for PubMedID 28688651
- Feasibility and Scalability of Spring Parameters in Distraction Enterogenesis in a Murine Model LIPPINCOTT WILLIAMS & WILKINS. 2017: S30
- Spring-Mediated Intestinal Lengthening in a Porcine Model LIPPINCOTT WILLIAMS & WILKINS. 2017: S29–S30
New insights and interventions for short bowel syndrome.
Current pediatrics reports
2017; 5 (1): 1-5
This review summarizes recent innovations in the treatment of patients with short bowel syndrome.The use of surgical procedures, growth factor stimulation, and bioengineering approaches to increase absorptive surface area of the intestine is examined. While the morphology of the intestine is clearly altered by these interventions, it is less clear that the overall function of the intestine is improved.Continued innovations will likely bring about new therapeutic options for patients with short bowel syndrome. Careful evaluations of the impact of these interventions await controlled clinical trials.
View details for DOI 10.1007/s40124-017-0119-6
View details for PubMedID 28367359
A novel culture system for adult porcine intestinal crypts
CELL AND TISSUE RESEARCH
2016; 365 (1): 123-134
Porcine models are useful for investigating therapeutic approaches to short bowel syndrome and potentially to intestinal stem cell (ISC) transplantation. Whereas techniques for the culture and genetic manipulation of ISCs from mice and humans are well established, similar methods for porcine stem cells have not been reported. Jejunal crypts were isolated from murine, human, and juvenile and adult porcine small intestine, suspended in Matrigel, and co-cultured with syngeneic intestinal subepithelial myofibroblasts (ISEMFs) or cultured without feeder cells in various culture media. Media containing epidermal growth factor, noggin, and R-spondin 1 (ENR medium) were supplemented with various combinations of Wnt3a- or ISEMF-conditioned medium (CM) and with glycogen synthase kinase 3 inhibitor (GSK3i), and their effects were studied on cultured crypts. Cell lineage differentiation was assessed by immunohistochemistry and quantitative polymerase chain reaction. Cultured porcine cells were serially passaged and transduced with a lentiviral vector. Whereas ENR medium supported murine enteroid growth, it did not sustain porcine crypts beyond 5 days. Supplementation of Wnt3a-CM and GSK3i resulted in the formation of complex porcine enteroids with budding extensions. These enteroids contained a mixture of stem and differentiated cells and were successfully passaged in the presence of GSK3i. Crypts grown in media supplemented with porcine ISEMF-CM formed spheroids that were less well differentiated than enteroids. Enteroids and spheroids were transfected with a lentivirus with high efficiency. Thus, our method maintains juvenile and adult porcine crypt cells long-term in culture. Porcine enteroids and spheroids can be successfully passaged and transduced by using lentiviral vectors.
View details for DOI 10.1007/s00441-016-2367-0
View details for Web of Science ID 000378877600011
View details for PubMedID 26928041
Basic fibroblast growth factor eluting microspheres enhance distraction enterogenesis
JOURNAL OF PEDIATRIC SURGERY
2016; 51 (6): 960-965
The purpose of this study was to determine if distraction enterogenesis using self-expanding polycaprolactone (PCL) springs is a potential therapy for short bowel syndrome. Sustained release basic fibroblast growth factor (bFGF) microspheres have been shown to induce angiogenesis and intestinal regeneration in tissue engineered scaffolds. We hypothesized that the provision of bFGF-loaded microspheres would increase angiogenesis and thereby enhance the process of enterogenesis.A 10-mm segment of rodent jejunum was isolated and an encapsulated PCL spring inserted. Blank or bFGF-loaded microspheres were delivered to the segment. After 4weeks, jejunal segments were assessed for lengthening, morphology, quantification of blood vessels, and ganglia.Lengthened intestinal segments receiving bFGF microspheres demonstrated significantly increased microvascular density compared to those with blank microspheres. There were also significantly more submucosal and myenteric ganglia in the segments that received bFGF microspheres. Segments achieved similar lengthening and final muscular thickness in both blank and bFGF groups, but the bFGF microsphere caused a significant increase in luminal diameter of the jejunal segment.Sustained release bFGF microspheres enhanced distraction enterogenesis through improved vascularity. The synergy of growth factors such as bFGF with distraction enterogenesis may yield improved results for the future treatment of patients with short bowel syndrome.
View details for DOI 10.1016/j.jpedsurg.2016.02.065
View details for Web of Science ID 000378908600018
View details for PubMedID 26995517
Long-term renewable human intestinal epithelial stem cells as monolayers: A potential for clinical use
JOURNAL OF PEDIATRIC SURGERY
2016; 51 (6): 995-1000
Current culture schema for human intestinal stem cells (hISCs) frequently rely on a 3D culture system using Matrigel™, a laminin-rich matrix derived from murine sarcoma that is not suitable for clinical use. We have developed a novel 2D culture system for the in vitro expansion of hISCs as an intestinal epithelial monolayer without the use of Matrigel.Cadaveric duodenal samples were processed to isolate intestinal crypts from the mucosa. Crypts were cultured on a thin coat of type I collagen or laminin. Intestinal epithelial monolayers were supported with growth factors to promote self-renewal or differentiation of the hISCs. Proliferating monolayers were sub-cultured every 4-5days.Intestinal epithelial monolayers were capable of long-term cell renewal. Less differentiated monolayers expressed high levels of gene marker LGR5, while more differentiated monolayers had higher expressions of CDX2, MUC2, LYZ, DEF5, and CHGA. Furthermore, monolayers were capable of passaging into a 3D culture system to generate spheroids and enteroids.This 2D system is an important step to expand hISCs for further experimental studies and for clinical cell transplantation.1 Experimental.
View details for DOI 10.1016/j.jpedsurg.2016.02.074
View details for Web of Science ID 000378908600025
View details for PubMedID 26995514
View details for PubMedCentralID PMC4921284
Mechanical lengthening in multiple intestinal segments in-series
JOURNAL OF PEDIATRIC SURGERY
2016; 51 (6): 957-959
Current models of mechanical intestinal lengthening employ a single device in an isolated segment. Here we demonstrate that polycaprolactone (PCL) springs can be deployed in-series to lengthen multiple intestinal segments simultaneously to further increase overall intestinal length.A Roux-en-y jejunojejunostomy with a blind Roux limb was created in the proximal jejunum of rats. Two encapsulated 10-mm PCL springs were placed in-series into the Roux limb and were secured with clips. After 4weeks, the lengthened segments were retrieved for histological analyses.Lengthening two intestinal segments simultaneously was achieved by placing two PCL springs in-series. The total combined length of the lengthened segments in-series was 45±4mm. The two jejunal segments with PCL springs (25±2 and 20±2mm) were significantly longer than control segments without the spring (14±1mm, p<0.05).Spring-mediated lengthening can be achieved using multiple springs placed sequentially. The use of the Roux-en-y surgical model allowed easy insertion of springs in a blind Roux limb and arrange them in-series. Combined with relengthening techniques, we can use these methods to increase the length of small intestine to reach clinical significance.1 Experimental.
View details for DOI 10.1016/j.jpedsurg.2016.02.058
View details for Web of Science ID 000378908600017
View details for PubMedID 27013424
Development of Functional Microfold (M) Cells from Intestinal Stem Cells in Primary Human Enteroids
2016; 11 (1)
Intestinal microfold (M) cells are specialized epithelial cells that act as gatekeepers of luminal antigens in the intestinal tract. They play a critical role in the intestinal mucosal immune response through transport of viruses, bacteria and other particles and antigens across the epithelium to immune cells within Peyer's patch regions and other mucosal sites. Recent studies in mice have demonstrated that M cells are generated from Lgr5+ intestinal stem cells (ISCs), and that infection with Salmonella enterica serovar Typhimurium increases M cell formation. However, it is not known whether and how these findings apply to primary human small intestinal epithelium propagated in an in vitro setting.Human intestinal crypts were grown as monolayers with growth factors and treated with recombinant RANKL, and assessed for mRNA transcripts, immunofluorescence and uptake of microparticles and S. Typhimurium.Functional M cells were generated by short-term culture of freshly isolated human intestinal crypts in a dose- and time-dependent fashion. RANKL stimulation of the monolayer cultures caused dramatic induction of the M cell-specific markers, SPIB, and Glycoprotein-2 (GP2) in a process primed by canonical WNT signaling. Confocal microscopy demonstrated a pseudopod phenotype of GP2-positive M cells that preferentially take up microparticles. Furthermore, infection of the M cell-enriched cultures with the M cell-tropic enteric pathogen, S. Typhimurium, led to preferential association of the bacteria with M cells, particularly at lower inoculum sizes. Larger inocula caused rapid induction of M cells.Human intestinal crypts containing ISCs can be cultured and differentiate into an epithelial layer with functional M cells with characteristic morphological and functional properties. This study is the first to demonstrate that M cells can be induced to form from primary human intestinal epithelium, and that S. Typhimurium preferentially infect these cells in an in vitro setting. We anticipate that this model can be used to generate large numbers of M cells for further functional studies of these key cells of intestinal immune induction and their impact on controlling enteric pathogens and the intestinal microbiome.
View details for DOI 10.1371/journal.pone.0148216
View details for Web of Science ID 000369528400076
View details for PubMedID 26820624
Concise Review: The Potential Use of Intestinal Stem Cells to Treat Patients With Intestinal Failure.
Stem cells translational medicine
: Intestinal failure is a rare life-threatening condition that results in the inability to maintain normal growth and hydration status by enteral nutrition alone. Although parenteral nutrition and whole organ allogeneic transplantation have improved the survival of these patients, current therapies are associated with a high risk for morbidity and mortality. Development of methods to propagate adult human intestinal stem cells (ISCs) and pluripotent stem cells raises the possibility of using stem cell-based therapy for patients with monogenic and polygenic forms of intestinal failure. Organoids have demonstrated the capacity to proliferate indefinitely and differentiate into the various cellular lineages of the gut. Genome-editing techniques, including the overexpression of the corrected form of the defective gene, or the use of CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 to selectively correct the monogenic disease-causing variant within the stem cell, make autologous ISC transplantation a feasible approach. However, numerous techniques still need to be further optimized, including more robust ex vivo ISC expansion, native ISC ablation, and engraftment protocols. Large-animal models can to be used to develop such techniques and protocols and to establish the safety of autologous ISC transplantation because outcomes in such models can be extrapolated more readily to humans.The field of intestinal stem cell biology has exploded over the past 5 years with discoveries related to in vivo and in vitro stem cell identity and function. The goal of this review article is to highlight the potential use of these cells to treat various epithelial disorders of the gut and discuss the various roadblocks that will be encountered in the coming years.
View details for DOI 10.5966/sctm.2016-0153
View details for PubMedID 27638919
2016; 32: 1-4
This review summarizes bioengineering innovations in the treatment of patients with short bowel syndrome. Bioengineering approaches aim to increase the overall intestinal tissue mass. While the morphology of the intestine is clearly altered by these interventions, it remains to be shown that the overall function of the intestine is improved. Continued innovations will likely bring about new therapeutic options for patients with short bowel syndrome. Careful evaluations of the impact of these interventions await controlled clinical trials.
View details for PubMedID 28564517
Scalability of an endoluminal spring for distraction enterogenesis.
Journal of pediatric surgery
2016; 51 (12): 1988–92
Techniques of distraction enterogenesis have been explored to provide increased intestinal length to treat short bowel syndrome (SBS). Self-expanding, polycaprolactone (PCL) springs have been shown to lengthen bowel in small animal models. Their feasibility in larger animal models is a critical step before clinical use.Juvenile mini-Yucatan pigs underwent jejunal isolation or blind ending Roux-en-y jejunojejunostomy with insertion of either a PCL spring or a sham PCL tube. Extrapolated from our spring characteristics in rodents, proportional increases in spring constant and size were made for porcine intestine.Jejunal segments with 7mm springs with k between 9 and 15N/m demonstrated significantly increased lengthening in isolated segment and Roux-en-y models. Complications were noted in only two animals, both using high spring constant k>17N/m. Histologically, lengthened segments in the isolated and Roux models demonstrated significantly increased muscularis thickness and crypt depth. Restoration of lengthened, isolated segments back into continuity was technically feasible after 6weeks.Self-expanding, endoluminal PCL springs, which exert up to 0.6N force, safely achieve significant intestinal lengthening in a translatable, large-animal model. These spring characteristics may provide a scalable model for the treatment of SBS in children.
View details for DOI 10.1016/j.jpedsurg.2016.09.023
View details for PubMedID 27665493
Mouse model of endoscopically ablated enteric nervous system
JOURNAL OF SURGICAL RESEARCH
2016; 200 (1): 117-121
Current transgenic animal models of Hirschsprung disease are restricted by limited survival and need for special dietary care. We used small animal colonoscopy to produce chemically ablated enteric nervous system in the distal colon and rectum of normal mice.Adult C57BL/6 mice underwent colonoscopy with submucosal injection of 75-100 μL of saline (n = 2) or 0.002% (n = 2), 0.02% (n = 15), or 0.2% (n = 2) benzalkonium chloride (BAC). Each mouse received 1-3 injections in the distal colon and rectum. Mice were sacrificed on postprocedure day 7 or 28. Injection sites were analyzed histologically and with immunostaining for β-tubulin III.Submucosal injection of 0.02% BAC resulted in megacolon and obliteration of 82 ± 8.8% of myenteric ganglia at the injection site on postprocedure day 7 compared with normal colon. This effect was sustained until day 28. Injection of 0.002% BAC had little effect on the myenteric neuronal network at these time points. Multiple injections of 0.002% or 0.02% BAC (up to three injections per mouse) were well tolerated. Injection of 0.2% BAC caused acute toxicity or death.A novel model of chemically ablated enteric nervous system in the mouse colon and rectum is introduced. This model can be valuable in evaluating targeted cell delivery therapies for Hirschsprung disease.
View details for DOI 10.1016/j.jss.2015.07.034
View details for Web of Science ID 000366840700018
View details for PubMedID 26299595
Spring-mediated distraction enterogenesis in-continuity.
Journal of pediatric surgery
2016; 51 (12): 1983–87
Distraction enterogenesis has been investigated as a novel treatment for patients with short bowel syndrome (SBS) but has been limited by loss of intestinal length during restoration and need for multiple bowel surgeries. The feasibility of in-continuity, spring-mediated intestinal lengthening has yet to be demonstrated.Juvenile mini-Yucatan pigs underwent in-continuity placement of polycaprolactone (PCL) degradable springs within jejunum. Methods used to anchor the spring ends to the intestine included full-thickness sutures and a high-friction surface spring. Spring constant (k) was 6-15N/m. Bowel was examined for length and presence of spring at 1 to 4weeks.Animals tolerated in-continuity lengthening without bowel obstruction for up to 29days. In-continuity jejunum with springs demonstrated intestinal lengthening by 1.47-fold ±0.11. Five springs had detached prematurely, and lengthening could not be assessed. Histologically, in-continuity jejunum showed significantly increased crypt depth and muscularis thickness in comparison to normal jejunum.Self-expanding endoluminal springs placed in continuity could lengthen intestine without obstruction in a porcine model. This is the first study showing safety and efficacy of a self-expanding endoluminal device for distraction enterogenesis. This is proof-of-concept that in-continuity spring lengthening is feasible and demonstrates its therapeutic potential in SBS.Level 3.
View details for DOI 10.1016/j.jpedsurg.2016.09.024
View details for PubMedID 27692863
A multicenter study to standardize reporting and analyses of fluorescence-activated cell-sorted murine intestinal epithelial cells
AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY
2013; 305 (8): G542-G551
Fluorescence-activated cell sorting (FACS) is an essential tool for studies requiring isolation of distinct intestinal epithelial cell populations. Inconsistent or lack of reporting of the critical parameters associated with FACS methodologies has complicated interpretation, comparison, and reproduction of important findings. To address this problem a comprehensive multicenter study was designed to develop guidelines that limit experimental and data reporting variability and provide a foundation for accurate comparison of data between studies. Common methodologies and data reporting protocols for tissue dissociation, cell yield, cell viability, FACS, and postsort purity were established. Seven centers tested the standardized methods by FACS-isolating a specific crypt-based epithelial population (EpCAM+/CD44+) from murine small intestine. Genetic biomarkers for stem/progenitor (Lgr5 and Atoh 1) and differentiated cell lineages (lysozyme, mucin2, chromogranin A, and sucrase isomaltase) were interrogated in target and control populations to assess intra- and intercenter variability. Wilcoxon's rank sum test on gene expression levels showed limited intracenter variability between biological replicates. Principal component analysis demonstrated significant intercenter reproducibility among four centers. Analysis of data collected by standardized cell isolation methods and data reporting requirements readily identified methodological problems, indicating that standard reporting parameters facilitate post hoc error identification. These results indicate that the complexity of FACS isolation of target intestinal epithelial populations can be highly reproducible between biological replicates and different institutions by adherence to common cell isolation methods and FACS gating strategies. This study can be considered a foundation for continued method development and a starting point for investigators that are developing cell isolation expertise to study physiology and pathophysiology of the intestinal epithelium.
View details for DOI 10.1152/ajpgi.00481.2012
View details for PubMedID 23928185
A nomenclature for intestinal in vitro cultures
AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY
2012; 302 (12): G1359-G1363
Many advances have been reported in the long-term culture of intestinal mucosal cells in recent years. A significant number of publications have described new culture media, cell formations, and growth patterns. Furthermore, it is now possible to study, e.g., the capabilities of isolated stem cells or the interactions between stem cells and mesenchyme. However, at the moment there is significant variation in the way these structures are described and named. A standardized nomenclature would benefit the ability to communicate and compare findings from different laboratories using the different culture systems. To address this issue, members of the NIH Intestinal Stem Cell Consortium herein propose a systematic nomenclature for in vitro cultures of the small and large intestine. We begin by describing the structures that are generated by preparative steps. We then define and describe structures produced in vitro, specifically: enterosphere, enteroid, reconstituted intestinal organoid, induced intestinal organoid, colonosphere, colonoid, and colonic organoid.
View details for DOI 10.1152/ajpgi.00493.2011
View details for Web of Science ID 000305398600001
View details for PubMedID 22461030
View details for PubMedCentralID PMC3378093
Risk Factors for Parenteral Nutrition-associated Liver Disease Following Surgical Therapy for Necrotizing Enterocolitis
JOURNAL OF PEDIATRIC GASTROENTEROLOGY AND NUTRITION
2011; 52 (5): 595-600
The aim of the study was to prospectively determine risk factors for the development of parenteral nutrition-associated liver disease (PNALD) in infants who underwent surgery for necrotizing enterocolitis (NEC), the most common cause of intestinal failure in children.: From February 2004 to February 2007, we diagnosed 464 infants with NEC, of whom 180 had surgery. One hundred twenty-seven patients were available for full analysis. PNALD was defined as serum direct bilirubin ≥ 2 mg/dL or ALT ≥ 2 × the upper limit of normal in the absence of sepsis after ≥ 14 days of exposure to PN.Median gestational age was 26 weeks and 68% were boys. Seventy percent of the cohort developed PNALD and the incidence of PNALD varied significantly across the 6 study sites, ranging from 56% to 85% (P = 0.05). Multivariable logistic regression analysis identified small-bowel resection or creation of jejunostomy (odds ratio [OR] 4.96, 95% confidence interval [CI] 1.97-12.51, P = 0.0007) and duration of PN in weeks (OR 2.37, 95% CI 1.56-3.60, P < 0.0001) as independent risk factors for PNALD. Preoperative exposure to PN was also associated with the development of PNALD; the risk of PNALD was 2.6 (95% CI 1.5-4.7; P = 0.001) times greater in patients with ≥ 4 weeks of preoperative PN compared with those with less preoperative PN use. Breast milk feedings, episodes of infection, and gestational age were not related to the development of PNALD.The incidence of PNALD is high in infants with NEC undergoing surgical treatment. Risk factors for PNALD are related to signs of NEC severity, including the need for small-bowel resection or proximal jejunostomy, as well as longer exposure to PN. Identification of these and other risk factors can help in the design of clinical trials for the prevention and treatment of PNALD and for clinical assessment of patients with NEC and prolonged PN dependence.
View details for DOI 10.1097/MPG.0b013e31820e8396
View details for Web of Science ID 000289671900018
View details for PubMedID 21464752
View details for PubMedCentralID PMC3444282
Risk Factors for Intestinal Failure in Infants with Necrotizing Enterocolitis: A Glaser Pediatric Research Network Study
JOURNAL OF PEDIATRICS
2010; 157 (2): 203-U50
To determine risk factors for intestinal failure (IF) in infants undergoing surgery for necrotizing enterocolitis (NEC).Infants were enrolled in a multicenter prospective cohort study. IF was defined as the requirement for parenteral nutrition for >or= 90 days. Logistic regression was used to identify predictors of IF.Among 473 patients enrolled, 129 had surgery and had adequate follow-up data, and of these patients, 54 (42%) developed IF. Of the 265 patients who did not require surgery, 6 (2%) developed IF (OR 31.1, 95% CI, 12.9 - 75.1, P < .001). Multivariate analysis identified the following risk factors for IF: use of parenteral antibiotics on the day of NEC diagnosis (OR = 16.61, P = .022); birth weight < 750 grams, (OR = 9.09, P < .001); requirement for mechanical ventilation on the day of NEC diagnosis (OR = 6.16, P = .009); exposure to enteral feeding before NEC diagnosis (OR=4.05, P = .048); and percentage of small bowel resected (OR = 1.85 per 10 percentage point greater resection, P = .031).The incidence of IF among infants undergoing surgical treatment for NEC is high. Variables characteristic of severe NEC (low birth weight, antibiotic use, ventilator use, and greater extent of bowel resection) were associated with the development of IF.
View details for DOI 10.1016/j.jpeds.2010.02.023
View details for Web of Science ID 000279871700011
View details for PubMedID 20447649
View details for PubMedCentralID PMC3217834