Islet- and stem-cell-based tissue engineering in diabetes.

New sources of insulin-producing cells are needed to overcome the limited availability of islet tissue for transplantation to diabetic patients. The engineering of murine or human transformed beta-cell lines and of non beta-cells has progressed slowly in recent years, while significant achievements have been claimed in the differentiation of insulin-producing cells from embryonic and adult stem cells. Some of the results have been questioned, however, and the generated cells lack many characteristics of differentiated beta-cells. A much better understanding of the processes that govern the expansion and differentiation of stem cells is needed.