Combinations of growth factors enhance the potency of islets in vitro

OBJECTIVES: Recent studies have demonstrated the impressive expansion of β cells in vitro. But unfortunately, expanded β cells do not function in the same way as fully differentiated β cells. Therefore, we developed a condition that would allow islet cells to proliferate while maintaining their endocrine function. METHODS: We tested the different use of growth factors in a different culture period. And we tested the possibility of adult islets, which expanded during a short period, as a clinical source of islet cells by comparing the efficiency of transplantation of cultured islets with that of fresh islets. RESULTS: The islets showed a time-dependent increase in proliferative activity, reaching 32.2% on day 5. After 5 days of culture, the efficiency of transplantation of cultured islets was increased (2-fold) in comparison to that of noncultured islets. Moreover, islet transplantation immediately induced normoglycemia at a level equal to native islets. CONCLUSIONS: These findings suggest that adult β cells have the potential to proliferate while maintaining their endocrine function, which can be improved through careful regulation of proliferation and differentiation.