Targeted modulation of adult human proliferation: Towards ex vivo expansion for diabetes treatment

Diabetes Mellitus is characterized by abnormally high blood sugar levels, which is caused by either an autoimmune destruction of insulin-producing beta-cells within the islets of Langerhans, or the inability to cope with an increased demand for insulin in the presence of insulin-resistance. Attempts at replenishing the beta-cells by pancreatic islet cell transplantation have been hampered by the lack of human islet cells for transplantation. One method to derive islet cells for transplantation would be to enhance the ability of these beta cells to grow ex vivo before transplantation. However, there have been difficulties encountered in attempting this expansion involving low proliferation rates, changing cell phenotypes and culture dominance of undesired cell types. Here we sought to solve some of these problems and increase the amount of islet cells by improving the process of islet isolation, as well as modulating cell cycle proteins. We looked at using technologies that could possibly be applied to the clinic as well as lentiviral vectors. We applied siRNA to the cell cycle inhibiting proteins Rb and P53 as well as applied TAT fusion proteins derived from Cyclin D, cdk4 and SV40T to demonstrate an induction of limited proliferation in human and rodent cells. Also, novel lentiviral vectors were designed to isolate phenotypically stable proliferating beta cells.