Islet cell transplantation for the treatment of diabetes mellitus

Diabetes mellitus is estimated to affect at least 16 million individuals in the United States and 135 million persons worldwide. It is a significant c ause of morbidity and early mortality. The related expenses are astronomica l with at least 15% of healthcare expenditures in the United States being u sed for the treatment of diabetes and its complications, a figure that appr oaches US$100 billion annually. The Diabetes Control and Complications Tria l (DCCT) convincingly showed that intensive glucose management delays the o nset and slows the progression of diabetic complications. Numerous studies have shown that pancreas transplantation not only delays the onset and prog ression of diabetic complications, but in some cases reverses some of the e ffects of diabetes. Human islet cell transplantation provides an alternativ e, less invasive alternative to whole organ transplantation. Human islet al lotransplantation would only exacerbate the organ shortage, as recipients u sually require islets from more than one pancreas. Xenotransplantation of p orcine islets is a more attractive option; however, the recipient's immune response to xenografted tissue would be a formidable obstacle. Microencapsu lation of the islets is a method of immunoisolation that would prevent the need for immunosuppressive drugs and the risks associated with their long-t erm use and have the potential to make xenoislet transplantation a clinical reality.