Direct effect of glucocorticoids on glucose-activated adult rat β-cells increases their cell number and their functional mass for transplantation

Compounds that increase beta-cell number can serve as beta-cell replacement therapies in diabetes. In vitro studies have identified several agents that can activate DNA synthesis in primary beta-cells but only in small percentages of cells and without demonstration of increases in cell number. We used whole well multiparameter imaging to first screen a library of 1,280 compounds for their ability to recruit adult rat beta-cells into DNA synthesis and then assessed influences of stimulatory agents on the number of living cells. The four compounds with highest beta-cell recruitment were glucocorticoid (GC) receptor ligands. The GC effect occurred in glucose-activated beta-cells and was associated with increased glucose utilization and oxidation. Hydrocortisone and methylprednisolone almost doubled the number of beta-cells in 2 wk. The expanded cell population provided an increased functional beta-cell mass for transplantation in diabetic animals. These effects are age dependent; they did not occur in neonatal rat beta-cells, where GC exposure suppressed basal replication and was cytotoxic. We concluded that GCs can induce the replication of adult rat beta-cells through a direct action, with intercellular differences in responsiveness that have been related to differences in glucose activation and in age. These influences can explain variability in GC-induced activation of DNA synthesis in rat and human beta-cells. Our study also demonstrated that beta-cells can be expanded in vitro to increase the size of metabolically adequate grafts.