Abstract
The original conformal coating method, the direct method (CC DM), affected the viability and biocompatibility of islets. I developed an augmented conformal coating method-emulsion method (CC EM)-which achieved hydrogel conformal coatings without compromising the viability or GSIS. These CC EM islets were tested in three sites in mouse, where the gonadal fat pad was found to be superior to the intramuscular and subcutaneous graft sites. Finally, the biocompatibility of CC EM islets in nonhuman primate omentum was found to be better than that of CC DM islets.
The variability in performance and limited supply of human donor pancreata necessitates the development of a safe, efficacious, and renewable stem cell-derived source of insulin-secreting cells. Due to reasonable concerns about stem cell-derived products, however, any stem cell islet product must be well characterized in vitro and in vivo. I found that stem cell (SC) islets exhibit batch to batch consistency in terms of morphology and similar size distribution to primary human islets. SC islets secrete insulin in response to glucose stimulation and were able to cure chemically-induced diabetes in an immunodeficient mouse model of type-1 diabetes for up to 180 days. SC islets were able to arrest hyperglycemia upon intraperitoneal glucose administration, and human C-peptide could be detected in the serum of recipients of SC islets. Importantly, we showed that the weight-normalized dose of SC islets is an important factor for predicting diabetes reversal in mice.
Finally, we demonstrated that human SC-islets reaggregated from cryopreserved cells display glucose-stimulated insulin secretion in vitro. Importantly, we showed that conformally coated SC-islets displayed comparable in vitro function to unencapsulated SC islets with conformal coating permitting physiological insulin secretion. Transplantation of SC islets into the gonadal fat pad of diabetic NODscid mice revealed that both unencapsulated and conformal coated SC islets could reverse diabetes and maintain human level euglycemia for more than ~80 days.