Successes and disappointments with clinical islet transplantation

Islet transplantation is considered a therapeutic option for patients with type 1 diabetes who have life–threatening hypoglycemic episodes. After the procedure, the frequency and severity of hypoglycemic episodes generally decrease and the majority of patients have sustained graft function as indicated by detectable levels of C-peptide. However, true insulin independence is seldom achieved and generally not long–lasting. Apart from the low insulin-independence rates, reasons for concern regarding this procedure are the side effects of the immunosuppressive therapy, alloimmunization, and the high costs. Moreover, whether islet transplantation prevents the progression of diabetic micro- and macrovascular complications more effectively than standard insulin therapy is largely unknown. Areas of current research include the development of less toxic immunosuppressive regimens, the control of the inflammatory reaction immediately after transplantation, the identification of the optimal anatomical site for islet infusion, and the possibility to encapsulate transplanted islets to protect them from the alloimmune response. Nowadays, islet transplantation is still an experimental procedure, which is only indicated for a highly selected group of type 1 diabetic patients with life–threatening hypoglycemic episodes.