| Type 1 diabetes, characterized by abnormal glycemic control, results from the destruction of beta cells within the pancreas of diabetic patients. Widespread islet transplantation, a clinical therapeutic option for type 1 diabetic patients, is limited by the shortage of donor islet tissue and a need for lifelong immunosuppression. For these reasons, alternate sources of islets are being investigated, as well as the impact of immunosuppressive drugs on these sources.; Mesenchymal stem cells (MSCs) derived from the bone marrow may potentially differentiate into pancreatic beta cells. Several differentiation strategies were developed, and their efficacies determined with respect to stimulating differentiation towards the beta cell fate. MSCs, induced to express the transcription factors ngn3 and Pdx1, and cultured with selective stimulatory growth factors, showed islet-like morphological and genetic changes. Cells formed spherical clusters and expressed the genes for Pax6, Nkx6.l, and NeuroD. These methods, however, did not result in cellular insulin.; Using a novel differentiation strategy to mimic the sequence of genetic events which occurs during normal pancreatic embryogenesis, we sought to enhance the differentiation of the MSCs. To achieve this, cells were transduced with multiple adenoviruses containing vectors for Pdx1, ngn3, NeuroD, or Pax6. In vitro, cells formed islet-like clusters and initiated expression of ngn3, NeuroD, glucagon, synaptophysin, Pax6, and Nkx6.1, however differentiation to the insulin-producing phenotype did not occur. Transplanting cell in vivo resulted in enhanced differentiation, with the detection of human c-peptide---a surrogate marker for insulin production.; Umbilical and mobilized peripheral blood may be MSC sources, and we investigated the efficacy of isolating MSCs from these two populations. Each population consisted of adherent cells with typical MSC phenotype, however these cells did not express classic MSC surface markers. Furthermore, cells transduced with ngn3 did not express ngn3 or other pancreatic transcription factors.; Finally, we investigated the impact of the immunosuppressive drug Sirolimus on the proliferation of pancreatic islets and ductal cells. We found that in human ductal cells, hypothesized to be adult pancreatic stem cells, and in neonatal porcine islets, which contain 57% ductal cells, that cell expansion was inhibited by 50% and 28% respectively. |
