Stem cells in the treatment of diabetes

Clinical islet transplantation trials based on cadaveric allogenic islets have demonstrated that it is indeed possible to restore near-physiological insulin secretion capacity in a type I diabetic patient through transplantation of insulin-producing cells. In order to develop this form of therapy to become available for the vast majority of patients with diabetes, new sources of transplantable insulin-producing cells need to be identified. Stem cells provide the best potential to achieve this goal. Controversial results have been presented concerning the existence and nature of pancreatic islet stem or precursor cells. An increasing body of evidence suggests that the pancreatic and hepatic cell types (hepatocytes, islet, acinar and ductal cells) have remarkable plasticity and can de- and trans-differentiate into each other under appropriate conditions. Elucidation of the molecular mechanisms regulating these processes could lead to clinically applicable ways of either inducing pancreatic islet regeneration in situ or to expanding the insulin-producing cells in vitro for transplantation. The emergence of human embryonic stem cells has led to an active area of research aiming to achieve targeted differentiation of these cells into a safely transplantable beta-like cell. After initial excitement, it appears that much basic research is still required before this goal could be achieved.