Engineering hypoimmune stem cell-derived beta cells.

In type 1 diabetes (T1D), autoimmune targeting destroys insulin-producing β cells in the pancreas, creating a chronic state of insulin deficiency. Islet transplantation presents a regenerative cell therapy approach that can re-establish insulin production and intrinsic glycemic control. However, islet transplantation is currently limited by a lack of cadaveric human islet donors and a requirement for life-long immune suppression following transplant. Developments in stem cell maturation and differentiation protocols have enabled production of insulin-producing cells 'on demand', thereby addressing the pancreatic donor tissue shortage. Continued reliance on immune suppression to avoid graft rejection, however, can result in opportunistic infection and malignancy, thus remaining a major obstacle for wide-spread application of insulin-producing β cell transplantation. As such, there has been significant interest in identifying alternative strategies for avoiding graft rejection without immune suppression including encapsulation and co-transplantation of accessory immunomodulating cells. However, these approaches are limited by incomplete immune isolation as well as concerns over maintenance of effector function and graft survival in vivo, respectively. Genetically engineering hypoimmune stem cell-derived β cells has thus emerged as a promising strategy for improving islet transplantation outcomes. These approaches leverage our understanding of pathways involved in immune regulation to selectively protect the transplanted insulin-producing cells without affecting systemic immune function. This review will summarize recent bioengineering approaches for generating hypoimmune stem cell-derived β cells. It will also discuss relevant safety concerns and potential genetic targets for future investigation that take inspiration from the development of immune evasive primary islets and chimeric antigen receptor (CAR) T cells.