Crucial role of Reg I from acinar-like cell cluster touching with islets (ATLANTIS) on mitogenesis of beta cells in EMC virus-induced diabetic mice.

Recently, we reported the presence of distinct cell clusters named acinar-like cell clusters touching Langerhans islets with thin interstitial surrounding (ATLANTIS) in human pancreas. A morphological study in humans demonstrated that ATLANTIS and islet cell clusters are found together in the microenvironment enclosed by a common basement membrane, and ATLANTIS releases vesicles containing Regenerating gene protein (REG Iα) to islet cell clusters. We examined 1) the presence or absence of ATLANTIS in homozygous Reg I (mouse homologue of human REG Iα) deficient (Reg I) and wild-type mice, and 2) the possible role of ATLANTIS in the regeneration of beta cell clusters after encephalomyocarditis (EMC) virus (D-variant) infection in Reg I and wild-type mice. ATLANTIS was found in both wild-type and Reg I mice. In both groups, mean blood glucose increased transiently to greater than 14.0 mmol/L at 5 days after EMC virus infection and recovered to baseline at 12 days. At 12 days after EMC virus infection, lower BrdU labeling indices were observed in islet beta cells of Reg I mice compared to wild-type mice. Beta cell volume 12 days after EMC virus infection in Reg I mice did not differ from that of wild-type mice. These results suggest that Reg I, which is released from ATLANTIS to islet beta cell clusters, has a crucial role in beta cell regeneration in EMC virus-induced diabetes. The presence of mechanism(s) other than that mediated by Reg I in beta cell restoration after destruction by EMC virus was also suggested.