- How Good Ideas Die: Understanding Common Pitfalls of Medtech Innovation MEDICAL INNOVATION: CONCEPT TO COMMERCIALIZATION 2018: 117–27
Polymeric delivery of therapeutic RAE-1 plasmid to the pancreatic islets for the prevention of type 1 diabetes
JOURNAL OF CONTROLLED RELEASE
2012; 162 (3): 606-611
The activating receptor NKG2D plays an important role in the development of type-1 diabetes. Exploiting a natural phenomenon observed in tumors, plasmid DNA encoding for a soluble ligand to NKG2D (sRAE-1γ) was isolated and engineered into a plasmid expression system. A polymeric gene delivery system was developed to deliver the soluble RAE-1 plasmid to the pancreatic islets. The bioreducible cationic polymer poly(cystamine bisacrylamide-diamino hexane) (p(CBA-DAH)) was modified with poly(ethylene glycol) (PEG) and the targeting peptide CHVLWSTRC, known to target the EphA2 and EphA4 receptors. We observed a higher uptake of the targeting polymer Eph-PEG-p(CBA-DAH) in the pancreas of NOD mice compared to non-targeting controls. To evaluate the efficacy of preventing diabetes, the Eph-PEG-p(CBA-DAH)/RAE-1 complex (polyplex) was intravenously injected into 6-week-old female NOD mice. Within 17 weeks blood glucose levels were stabilized in animals injected with polyplex, while those treated without therapeutic plasmid developed progressive hyperglycemia. Additionally, the degree of insulitis and the infiltration of CD8⁺ T-cells in the polyplex treated group were improved over the targeting polymer only treated group. The current study suggests that the therapy of the Eph-PEG-p (CBA-DAH) delivering therapeutic sRAE-1 gene may be used to protect β-cells from autoimmune destruction and prevent type-1 diabetes.
View details for DOI 10.1016/j.jconrel.2012.08.008
View details for Web of Science ID 000310506900016
View details for PubMedID 22910142
View details for PubMedCentralID PMC3455144
EphA2 targeting peptide tethered bioreducible poly(cystamine bisacrylamide-diamino hexane) for the delivery of therapeutic pCMV-RAE-1 gamma to pancreatic islets
JOURNAL OF CONTROLLED RELEASE
2012; 158 (1): 115-122
The pathogenesis of type-1 diabetes is complicated, and a clear, single mechanism has yet to be identified. Reports have indicated that the activating receptor NKG2D plays an important role in the development of disease. Exploiting a natural phenomenon observed in tumors, plasmid DNA encoding for a soluble ligand to NKG2D (sRAE-1γ) was isolated and engineered into a plasmid expression system. A polymeric gene delivery system was developed to deliver the soluble RAE-1 plasmid locally to the pancreatic islets for the prevention of type-1 diabetes. The bioreducible cationic polymer poly(cystamine bisacrylamide-diamino hexane) (p(CBA-DAH)) was modified with poly(ethylene glycol) (PEG) and the targeting peptide CHVLWSTRC, known to target the EphA2 and EphA4 receptors. The PEG serves to improve stability and tissue selectivity, while the peptide will target EphA2 and A4, overexpressed in the pancreatic microvasculature. The targeting polymer Eph-PEG-p(CBA-DAH) shows selective uptake by the target cell line, indicative of the targeting properties that will be seen in systemic administration. Using the delivery system, the therapeutic plasmid can be delivered to the pancreas, reduce interactions between the beta-cells and infiltrating NKG2D positive lymphocytes, and effectively protect beta-cells from autoimmune destruction and prevent type 1 diabetes.
View details for DOI 10.1016/j.jconrel.2011.10.022
View details for Web of Science ID 000302605900014
View details for PubMedID 22062690
View details for PubMedCentralID PMC3289743
Mixtures of Poly(triethylenetetramine/cystamine bisacrylamide) and Poly(triethylenetetramine/cystamine bisacrylamide)-g-poly(ethylene glycol) for Improved Gene Delivery
2010; 21 (10): 1753-1761
Branched disulfide-containing poly(amido ethyleneimines) (SS-PAEIs) are biodegradable polymeric gene carrier analogues of the well-studied, nondegradable, and often toxic branched polyethylenimines (bPEIs), but with distinct advantages for cellular transgene delivery. Clinical success of polycationic gene carriers is hampered by obscure design and formulation requirements. This present work reports synthetic and formulation properties for a graft copolymer of poly(ethylene glycol) (PEG) and a branched SS-PAEI, poly(triethylentetramine/cystaminebisacrylamide) (p(TETA/CBA)). Several laboratories have previously demonstrated the advantages of PEG conjugation to gene carriers, but have also shown that PEG conjugation may perturb plasmid DNA (pDNA) condensation, thereby interfering with nanoparticle formation. With this foundation, our studies sought to mix various amounts of p(TETA/CBA) and p(TETA/CBA)-g-PEG2k to alter the relative amount of PEG in each formulation used for polyplex formation. The influence of different PEG/polycation amounts in the formulations on polymer/nucleic acid nanoparticle (polyplex) size, surface charge, morphology, serum stability and transgene delivery was studied. Polyplex formulations were prepared using p(TETA/CBA)-g-PEG2k, p(TETA/CBA), and mixtures of the two species at 10/90 and 50/50 volumetric mixture ratios (wt/wt %), respectively. As expected, increasing the amount of PEG in the formulation adversely affects polyplex formation. However, optimal polymer mixtures could be identified using this facile approach to further clarify design and formulation requirements necessary to understand and optimize carrier stability and biological activity. This work demonstrates the feasibility to easily overcome typical problems observed when polycations are modified and thus avoids the need to synthesize multiple copolymers to identify optimal gene carrier candidates. This approach may be applied to other polycation-PEG preparations to alter polyplex characteristics for optimal stability and biological activity.
View details for DOI 10.1021/bc900522x
View details for Web of Science ID 000283101000006
View details for PubMedID 20882996
View details for PubMedCentralID PMC2958694
Congenital cholesteatoma of the mastoid temporal bone
2007; 117 (8): 1389-1394
Congenital mastoid cholesteatomas are rare lesions of the temporal bone. The clinical presentation of these lesions is variable, making them difficult to identify preoperatively. We evaluated our series of mastoid congenital cholesteatomas (CCs) in an effort to better define the clinical presentation, imaging characteristics, and surgical challenges specific to this lesion.Retrospective chart and radiologic study review.The medical records of patients with the diagnosis of mastoid CC on radiologic imaging over a 15-year period were reviewed. All had surgical and pathologic confirmation. Eight patients underwent preoperative computed tomography (CT). Six also underwent magnetic resonance (MR) scanning. Demographic information, clinical presentation, imaging results, and operative findings were recorded.Nine patients with the diagnosis of mastoid CC satisfying the inclusion criteria were found. Clinical findings were variable, with the most common presentation being an incidental finding. Imaging findings were more uniform. All CT scans demonstrated an expansile, well-circumscribed mass centered within the mastoid portion of the temporal bone. All MR scans showed a well-circumscribed mass with high intensity on T2-weighted images with precontrasted T1 sequences showing the lesion to be isointense or slightly hyperintense to cerebrospinal fluid (CSF). Operative findings included lateral mastoid cortex erosion, sigmoid sinus exposure, ossicular destruction, facial nerve exposure, and associated postauricular abscess. Management of these lesions is reviewed.Congenital mastoid cholesteatomas have a variable and nonspecific clinical presentation. Surgical challenges arise from the indolent nature of this clinical entity, which belies the extent of otologic involvement. Imaging with CT and magnetic resonance imaging are diagnostic, defines the extent of these lesions, and facilitates preoperative surgical planning.
View details for DOI 10.1097/MLG.0b013e3180645d50
View details for Web of Science ID 000248510800014
View details for PubMedID 17607152
Mesenchymal stem cells enhance angiogenesis in mechanically viable prevascularized tissues via early matrix metalloproteinase upregulation
2006; 12 (10): 2875-2888
Angiogenesis, the sprouting of new blood vessels from existing vasculature, is a complex biological process of interest to both the treatment of numerous pathologies and the creation of thick engineered tissues. In the context of tissue engineering, one potential solution to the diffusion limitation is to create a vascular network in vitro that can subsequently anastomose with the host after implantation, allowing the implantation of thicker, more complex tissues. In this study, the ability of endothelial cells to sprout and form stable vascular networks in 3-dimensional (3D) fibrin matrices was investigated as a function of matrix density in a prevascularized tissue model. The results demonstrate that while increasing matrix density leads to a nearly 7-fold increase in compressive stiffness, vascular sprouting is virtually eliminated in the most dense matrix condition. However, the addition of human mesenchymal stem cells (HMSCs) to the denser matrices reverses this effect, resulting in an up to a 7-fold increase in network formation. Although the matrix metalloproteinases (MMPs) MMP-2, MMP-9, and MT1-MMP are all upregulated early on with the addition of HMSCs, MT1-MMP appears to play a particularly important role in the observed angiogenic response among these proteases. This study provides a means to design stiffer prevascularized tissues utilizing naturally derived substrates, and its results may yield new mechanistic insights into stem cell-based angiogenic therapies.
View details for Web of Science ID 000242045600017
View details for PubMedID 17518656