Abstract
Type 1 diabetes results from destruction of the majority of the pancreatic beta cells by beta cell-specific autoimmune responses; therefore, expansion of the beta-cell mass in vivo is a possible approach to its treatment. Betacellulin (BTC) is known to promote beta-cell growth and differentiation. We investigated whether transient, constitutive expression, and secretion of BTC would regenerate sufficient numbers of pancreatic beta cells to restore normoglycemia in diabetic animals. We constructed a recombinant adenoviral vector (rAd-BTC) containing the cytomegalovirus promoter/enhancer, beta-globin chimeric intron, and albumin leader sequence to facilitate secretion, followed by BTC (1-80) complementary DNA (cDNA) encoding mature BTC. A single intravenous (i.v.) administration of rAd-BTC resulted in complete remission of streptozotocin (STZ)-induced diabetes within 2 weeks in mice. The mice remained normoglycemic for >100 days; glucose tolerance tests showed kinetics similar to normal, nondiabetic mice. Pancreatic insulin content, beta-cell mass, and serum insulin levels in rAd-BTC-treated mice were significantly higher than in the controls. Treatment of autoimmune diabetic mice with rAd-BTC in combination with an immune suppressor resulted in remission of diabetes. We conclude that transient expression of BTC by rAd-BTC administration results in prolonged remission of diabetes in mice, by the regeneration of sufficient numbers of beta cells in the pancreas.