291-LB: Possible Alpha-Cell Regeneration from Mucin-Producing Ducts in Zinc-Binding Site-Mutated CRY1-Expressing Diabetic Mice

C414A-CRY1 transgenic mice (TG) show the symptoms of diabetes due to cellular senescence-like phenotypes in their β-cells as we have reported at ADA Scientific Sessions in 2015. Due to the cellular phenotypes, structural remodeling in islets of TG progresses with age (S. Okano et al., ADA 2016-2022): the increase of the population ratios of α-cell to β-cell and of δ-cell to β-cell as well as the occurrence of fibrillation, angiogenesis and also the generation of mucin-producing intra-islet ductal cells (IIDCs) were observed. Contrary to normal ductal cells, IIDCs only weakly react with DBA lectin, indicating unique characters different from normal ductal cells (ADA 2019). Also, we have shown the results suggesting that δ-cells may play some role as the source for β-cells to supply new β-cells in TG (ADA 2022). To examine the possible roles of IIDCs to maintain of the amount of pancreatic endocrine cells under hyperglycemia for prolonged period in TG, in this study, we conducted detailed immune-staining experiments which focused on fully developed IIDCs, not small ones that still not fully developed. We distinguished IIDCs from normal ducts, PanINs as well as PDGs as the measure of the reactivity to DBA-lectin. Chromogranin A-positive cells were observed in IIDCs, but not in normal ducts, PanINs and PDGs. Then we examined IIDCs with anti-hormone antibodies. In the region of developed IIDCs, cytokeratin 17/19 and glucagon double-positive cells were predominantly observed. Only small portion of somatostatin-positive cells were clearly located adjacent to IIDCs. Cluster of β-cells were located apart from IIDCs. In addition, scrutinized observations suggested the delamination of glucagon-positive cells from the ductal epithelium of the IIDCs. Taken together, these results strongly suggest the possible neogenesis of endocrine cells in IIDCs, that is, IIDCs and their lining cells play roles as the source for endocrine cells, particularly for α, and also for δ cells. Disclosure S. Okano: None. A. Yasui: None. S. Kanno: None. Y. Sasaki: None. K. Satoh: None. M. Igarashi: None. O. Nakajima: None. Funding Grants-in-Aid for Scientific Research (19K07498); Tohoku University Institute of Development, Aging and Cancer