Regeneration of beta cells in the native pancreata after syngeneic and allogeneic pancreas transplantations in spontaneously type 2 diabetic Torii rats.

BACKGROUND: We previously demonstrated that syngeneic pancreas transplantation has a potential to reverse diabetes even in a rat model of type 2 diabetes mellitus, namely Spontaneously Diabetic Torii (SDT; RT1a). The onset of diabetes was significantly delayed in the pancreas transplant recipients. We speculated that perfect diabetic control achieved by pancreas transplantation showed a beneficial effect on the native pancreata & recipients. MATERIALS AND METHODS: Twenty-five-week-old diabetic SDT rats were divided into 3 groups: untreated controls and syngeneic and allogeneic transplant recipients. We transplanted pancreaticoduodenal grafts from nondiabetic 10-week-old SDT rats and from 10-week-old allogeneic Dark Agouti (DA; RT1a) rats using daily administration of FK506. RESULTS: Untreated SDT rats showed disappearance of pancreatic and duodenal homeobox-1 (PDX-1) expression in the pancreas and a marked decrease in beta-cell mass. Among syngeneic and allogeneic pancreas transplant recipients, islet-like cell clusters were found in the native pancreata. The beta-cell mass at 40 weeks of age was significantly increased in the native pancreata of recipients compared with age-matched controls. Interestingly, we observed the reexpression of PDX-1 in the nuclei of islet-like cell clusters. CONCLUSIONS: Our results indicated the benefits of avoiding glucose toxicity by pancreas transplantation which induced PDX-1 expression in the native pancreata of type 2 diabetic recipients, resulting in regeneration of beta cells in the native pancreata.

Adenoviral-mediated overexpression of either membrane-bound human FasL or human decoy Fas can prolong pig islet xenograft survival in a rat transplant model.

The success of pancreatic islet transplantation is limited because of the severe shortage of allogeneic pancreas donors. Accordingly, pig islets are considered to be an attractive, promising alternative. However, cell-mediated immunity, especially CD8+ cytotoxic T lymphocyte (CTL)-mediated cytotoxicity, remains a formidable barrier to prevent long-term islet survival in xenograft recipients. Therefore, it is particularly important to explore methods to specifically prevent cell-mediated immunity against pig islets. Our group previously demonstrated that the overexpression of either membrane-bound human FasL or human decoy Fas antigen in pig endothelial cells prevented CTL xenocytotoxicity. In this study, we assessed the cytoprotective effects of adenoviral-mediated overexpression of either membrane-bound human FasL or human decoy Fas antigen in pig islets to inhibit CTL xenocytotoxicity. The CTL-mediated killing of pig islets infected with an adenoviral vector carrying either membrane-bound human FasL or human decoy Fas was significantly reduced compares with that of control pig islets transfected with adenoviral vector encoding enhanced green fluorescent protein (EGFP). Moreover, we transfected pig islets with these molecules to confirm their cytoprotective effects in in vivo studies. The significant long-term survival of pig islets expressing these molecules was elicited through days 3 to 5 posttransplantation. Thus, these results demonstrated that the remodeling of either death receptor or death ligand on pig islets by adenoviral gene transfer prevented innate cellular immunity against xeno-islet grafts facilitating long-term xenograft survival.

Adenoviral-mediated overexpression of membrane-bound human FasL and human decoy Fas protect pig islets against human CD8+ CTL-mediated cytotoxicity.

Pig islets are considered to be most suitable source of islets for xenotransplantation into patients with type 1 diabetes mellitus. However, cellular rejection, especially CD8+ CTL-mediated cytotoxicity, remains a formidable barrier preventing long-term xenograft survival. Our previous study demonstrated that human CD8+ CTLs were highly detrimental to xenograft cells and that this strong cytotoxicity of human CTLs was mediated mainly by the Fas/FasL apoptotic pathway. Furthermore, we exploited novel methods for inhibiting human CD8+ CTL-mediated xenocytotoxicity with overexpression of membrane-bound human FasL and human decoy Fas antigen in xenografted cells. In the present study, we assessed the cytoprotective effects of these novel inhibitory molecules overexpressed by an adenoviral-mediated system in pig islets. Isolated pig islets were transfected with adenovirus vector encoding either human decoy Fas or membrane-bound human FasL genes. Thirty percent to 60% of transfected pig islets expressed these molecules producing 60% to 88% suppression of CTL killing compared with parental pig islets. These data indicated that pig islet grafts isolated from transgenic pigs with either membrane-bound human FasL or human decoy Fas antigen genes may control the innate cellular response to xenografts, and creating a window of opportunity to facilitate xenograft survival.

Reliable and cost-effective system for surgical stent graft insertion.

For intraoperative stented graft implantation, we use a half-inch translucent soft polyvinyl tube as a sheath and an obturator from a two-stage venous cannula as a pushing rod. Ten centimeters of any kind of graft can be used for the stent graft itself. The stent we used was a self-expandable Gianturco double Z stent and was sutured inside the graft.