Increased Insulin Secretion from Insulin-Secreting Cells by Construction of Mixed Multicellular Spheroids

We previously have shown that multicellular spheroids containing insulin-secreting cells are an effective therapy for diabetic mice. Here we attempted to increase insulin secretion by incorporating other cell types into spheroids. Multicellular spheroids of mouse MIN6 pancreatic beta cells were formed in microwells alone and with aortic vascular endothelial MAEC cells or embryo fibroblast NIH3T3 cells. mRNA expression of insulin genes and insulin secretion of MIN6 cells in each spheroid were measured by real-time PCR and an insulin ELIZA kit. Moreover, collagen IV expression in each spheroid was analyzed by western blot. In all cases, uniformly sized (about 300 mu m) multicellular spheroids were obtained. MAEC or NIH3T3 cell incorporation into MIN6 spheroids significantly increased mRNA expression of insulin genes and insulin secretion. In addition, collagen IV expression, which was reported to enhance insulin secretion from pancreatic beta cells, also increased in their spheroids. The formation of mixed multicellular spheroids containing collagen IV-expressing cells can improve the insulin secretion from insulin-secreting MIN6 cells, and mixed multicellular spheroids can be a potent therapeutic option for patients with type I diabetes mellitus.