Recent Progress of Research Regarding the Applications of Stem Cells for Treating Diabetes Mellitus

At present, the number of diabetes patients has exceeded 537 million worldwide and this number continues to increase. Stem cell therapy represents a new direction for the treatment of diabetes; the use of stem cells overcomes some shortcomings associated with traditional therapies. Functional β cells play an important role in the pathogenesis of diabetes. As therapeutic targets, functional β cells are restored by a variety of stem cells, including pluripotent stem cells, mesenchymal cells, and urine-derived stem cells. Although all types of stem cells have their own characteristics, they mainly promote the repair and regeneration of β cells through directional differentiation, immunomodulation, and paracrine signaling after homing to the injured site. However, stem cell therapy still faces many obstacles, such as low long-term cell survival rate after transplantation, low maintenance time of blood glucose homeostasis, immune rejection, and tumorigenesis. Recently, genetically edited pluripotent stem cells and the cotransplantation of mesenchymal stem cells and islet cells have made significant progress in improving the efficacy of stem cell transplantation processes, also providing powerful tools for the study of the mechanisms underlying diabetes and disease modeling. In this review, we first focused on: (1) stem cells as a pool for the differentiation of insulin-producing cells; (2) stem cells as a source for regenerative repair of damaged islets and as a potential cotransplanted population with islets; (3) the potential of combining gene editing with stem cell therapy; and (4) selection of the stem cell transplantation approach. Based on these topics, we discuss the challenges within the field of adapting stem cell-supported and stem cell-derived transplantations and the promising routes for overcoming these problems.