Project description:Pancreatic islet transplantation as a cure for type 1 diabetes (T1D) cannot be scaled up due to a scarcity of human pancreas donors. In vitro expansion of beta cells from mature human pancreatic islets provides an alternative source of insulin-producing cells. The exact nature of the expanded cells produced by diverse expansion protocols, and their potential for differentiation into functional beta cells, remain elusive. We performed a large-scale meta-analysis of gene expression in human pancreatic islet cells, which were processed using three different previously described protocols for expansion and attempted re-differentiation. All three expansion protocols induced dramatic changes in the expression profiles of pancreatic islets; many of these changes are shared among the three protocols. Attempts at re-differentiation of expanded cells induce a limited number of gene expression changes. Nevertheless, these fail to restore a pancreatic islet-like gene expression pattern. Comparison with a collection of public microarray datasets confirmed that expanded cells are highly comparable to mesenchymal stem cells. Genes induced in expanded cells are also enriched for targets of transcription factors important for pluripotency induction. The present data increases our understanding of the active pathways in expanded and re-differentiated islets. Knowledge of the mesenchymal stem cell potential may help development of drug therapeutics to restore beta cell mass in T1D patients. Experiment Overall Design: In this study, we have tested three different protocols to expand human pancreatic islets in monolayer and after attempted maneuvers to re-differentiate the expanded cells back to islets. We have characterized the resulting cells in detail by performing microarray analyses with fresh pancreatic islets, expanded islet cells and re-differentiated cells. Genes modified by either of three protocols have 70 to 80% overlap with the genes changed by the other two protocols. Although there are promising changes in the right direction, none of the three protocols could achieve a return to a functional islet state. The expanded cells highly resemble Mesenchymal Stem Cells (MSC), and similar gene regulatory networks seem to be active in both cell types. On the other hand, the expanded islet cells are different from MSC in that they seem to retain activity of some islet gene modules. The current results highlight the importance of designing new strategies that take into account the MSC potential of expanded cells.

Project description:β cell proliferation rates decline with age and adult β cells have limited self-duplicating activity for regeneration, which predisposes to diabetes. Here we show that, among MYC family members, Mycl was expressed preferentially in proliferating immature endocrine cells. Genetic ablation of Mycl caused a modest reduction in cell proliferation of pancreatic endocrine cells in neonatal mice. By contrast, systemic expression of Mycl in mice stimulated proliferation in pancreatic islet cells and resulted in expansion of pancreatic islets without forming tumors in other organs. Single-cell RNA sequencing and genetic tracing experiments revealed that the expression of Mycl provoked transcription signatures associated with immature proliferating endocrine cells and stimulated self-duplication in adult hormone-expressing cells. The expanded hormone-expressing cells ceased proliferation but persisted after withdrawal of Mycl expression. Remarkably, a subset of the expanded α cells gave rise to insulin-producing cells after the withdrawal. Moreover, transient Mycl expression in vivo was sufficient to normalize increased blood glucose levels in diabetic mice evoked by chemical ablation of β cells. In vitro expression of Mycl similarly provoked active replication without inducing apoptosis in adult hormone-expressing islet cells, even those from aged mice. Furthermore, the expanded islet cells functioned in diabetic mice after transplantation. Finally, we show that MYCL stimulated self-duplication of human adult cadaveric islet cells. Collectively, these results demonstrate that sole induction of Mycl expands adult β cells both in vivo and in vitro. Moreover, islet cell-specific reprogramming via transient Mycl transduction elicits endogenous expansion of insulin-producing cells in adult pancreas through both self-duplication of β cells and transdifferentiation ofα cells into insulin-producing cells, which may provide a regenerative strategy of β cells.

Dataset Information

Meta analysis of gene expression in human islets after in vitro expansion.

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