| Co-Investigator(Kenkyū-buntansha) |
HAMAGUCHI Tomoya Osaka University Medical School, Medical Staff, 医学部・附属病院, 医員
HIGASHIYAMA Shigeki Osaka University Medical School, Assistant Professor, 医学部, 助手 (60202272)
NAMBA Mitsuyoshi Osaka University Medical School, Lecturer, 医学部, 講師 (00183533)
HANAFUSA Toshiaki Osaka University Medical School, Lecturer, 医学部, 講師 (60164886)
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| Research Abstract |
We tried to clarify the mechanism of differentiation of AR42J cells into insulin-secreting cells induced by betacellulin, and in vivo effects of betacellulin on the islet neogenesis and glucose intolerance in diabetic mice induced by selective perfusion of alloxan.In AR42J cells, stimulation with recombinant human betacellulin induced insulin immunoreactivlty and beta granule-like secretory vesicles in the cytoplasm.Phosphorylation of erbB receptor tyrosine was mainly occurred in erbB2 which could not bind directly to betacellulin, suggesting that crossactivation of erbB2 in the form of heterodimer is important for the intracellular differentiation signaling in AR42J cells into insulin-producing cells.However, it was difficult to clone the cells dominant negative for erbB2 by transfecting mutant form to confirm this result.We could not detect the betacellulin-specific receptor or binding protein on the cell surface of AR42J cells.
Betacellulin was expressed predominantly in the fetal and adult pancreas, and we found this factor was produced in duct cells and alpha cells of islets.In the pancreas of diabetic mice induced by selective perfusion of alloxan, islet neogenesis was observed mainly in the alloxan-perfused beta cell-depleted segment.Expression of insulin transscription factor, IPF1/PDX-1 was detected in the duct cells directly associated with newly formed islet-like cell clusters (ICCs).In ICCs, endocrine cells with double positive immunoreactivities to pancreatic hormones including insulin were observed, suggesting duct cells are important for the islet neogenesis in diabetic pancreas.Based on these findings, we examined in vivo effect of betacellulin by injecting recombinant human betacellulin in these diabetic mice.In the mice treated with betacellulin, the number of ICCs was increased, and the glucose intolerance was ameliorated.These results suggested betacellulin, as observed in AR42J cells, may act as beta cell differentiation factor in the pancreas.
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