Engineering a vascularized bioartificial pancreas for stem cell derived islet maturation

Background: A possible therapy for type 1 diabetes is pancreatic islet encapsulation, which allows physiological insulin secretion while protecting the transplant against immunological rejection. The effectiveness of encapsulation devices at therapeutic scale is limited by the physical barrier created by encapsulation that restricts oxygen and nutrient transport. Additionally, graft integration into the host vasculature is a slow process that can take several weeks during which oxygen deprivation can result in significant loss of the graft. Devices allowing both immunoprotection and direct vascularization post-transplantation should improve therapeutic efficiency. Methods: By combining 3D printing of sacrificial lattices and polyurethane dip coating, we have created a vascularized biomedical device that can be filled with hydrogel and is intended for anastomosis to the host blood arteries. Pancreatic pseudoislets were first differentiated from human pluripotent stem cells using a multistage protocol yielding ~75% pancreatic progenitors (PDX1+/NKX6.1+ cells; stage 4) and respectively ~25% and ~30% of alpha cells and beta cells at the end of the protocol. To investigate the maturation of pseudoislets inside the device, immature pseudoislets (Stage 6) were cultured for 10 days either in suspension, immobilized in alginate within the device or as slabs. Results: After 10 days of perfused immobilized culture within the device, pseudoislets were highly viable and stained positive for the insulin granule marker dithizone. Flow cytometry analysis demonstrated comparable yield of alpha (glucagon+) and beta (C-peptitde+) cells within the device compared to suspension controls. Pseudoislet maturation efficiency was not significantly different in the encapsulation system as compared to suspension controls based on mRNA-level expression of endocrine commitment markers (NEUROD1, Chromogranin A, NKX6.1). Conclusion: These results show promise for the development of an implantable vascularized pancreas for the treatment of type 1 diabetes. Canadian Institutes of Health Research (CIHR). ThéCell Network.