| Type 1 diabetes is an autoimmune disorder characterized by destruction of the insulin-producing beta-cells in the Islets of Langerhans of the pancreas. Exogenous insulin treatment is used to manage type 1 diabetes, however transplantation of insulin-producing tissue provides a more physiological control of blood glucose levels. Neonatal porcine islets (NPIs) are an attractive source of xenotransplantable tissue due to their abundance and ease of isolation. In addition, NPIs are composed of about 50% ductal cells, thought to be endocrine precursor cells, indicating a capacity to grow and mature post-transplantation. However, along with the robust immune response to xenogenic tissue, the potential for transmission of foreign pathogens through xenotransplantation poses a barrier.; This study had four aspects. In the first portion, a novel model of in vitro NPI maturation was developed, shortening the lag time to achieve euglycemia after transplantation of immature tissue, and providing a reproducible model to study islet development. Secondly, an in vivo model of NPI transplantation was utilized to characterize the development and maturation of this tissue after transplantation. The model helps elucidate conditions for optimal tissue transplantation, as well as timing of signals involved in NPI development. In the third segment, overexpression of Pdx-1 by adenoviral transfection was found to show high levels of PDX-1 protein in NPIs, however this was not sufficient to induce precursors to differentiate into beta-cells. Still, these results provide a starting point for the pursuit of factors which, if provided at the right time point, may induce maturation of NPIs.; Lastly, the concern of porcine endogenous retrovirus (PERV) transmission from NPIs was addressed. In previous studies, PERV nucleic acid has been detected in peripheral tissues of transplanted mice, thus raising concern that the virus is spreading in the recipient. In this study, it was found that PERV nucleic acid in peripheral tissues was associated with the presence of porcine cells due to migration post-transplantation. When migration of porcine cells was prevented, no PERV nucleic acid was detected in peripheral tissues.; Taken together, these studies further characterize NPIs as a potential source of transplantable insulin-producing tissue, complementing previous work, and providing tools for future studies. |
