Reversal of diabetes in mice by implantation of human fibroblasts genetically engineered to release mature human insulin

Autoimmune destruction of pancreatic beta cells in type I, insulin-dependen t diabetes mellitus (IDDM) results in the loss of endogenous insulin secret ion, which is incompletely replaced by exogenous insulin administration, Th e functional restoration provided by allogeneic P-cell transplantation is l imited by adverse effects of immunosuppression, To pursue an insulin replac ement therapy based on autologous, engineered human non beta cells, we gene rated a retroviral vector encoding a genetically modified human proinsulin, cleavable to insulin in non-beta cells, and a human nonfunctional cell sur face marker. Here we report that this vector efficiently transduced primary human cells, inducing the synthesis of a modified proinsulin that was proc essed and released as mature insulin. This retrovirally derived insulin dis played in vitro biological activity, specifically binding to and phosphoryl ation of the insulin receptor, comparable to human insulin. In vivo, the tr ansplantation of insulin-producing fibroblasts reverted hyperglycemia in a murine model of diabetes, whereas proinsulin-producing cells were ineffecti ve. These results support the possibility of developing insulin production machinery in human non-beta cells for gene therapy of IDDM.