Contribution of cytokeratin 19-expressing cells towards islet regeneration induced by multipotent stromal cell secreted proteins.

Abstract

Residual beta cell function has been documented in 'medalist' patients that have lived with Type 1 diabetes (T1D) for >50 years. In addition, endocrine cell neogenesis first occurs in the developing human embryo from a progenitor cells derived from pancreatic ductal epithelial structure. Thus, beta cell conversion from a dormant epithelial precursor remains a promising approach to regenerate islets during T1D. We have previously shown that intra-pancreatic (iPan) injection of Wnt pathway-stimulated conditioned media (Wnt+ CdM) generated from human bone marrow-derived multipotent stromal cells (MSC) contained islet regenerative factors that reduced hyperglycemia and recovered beta cell mass in streptozotocin-treated mice. However, the endogenous source of regenerated beta cells remains unknown. Herein, we employed cytokeratin 19 (CK19)-CreERT Rosa26-mTomato lineage-tracing mice to assess endocrine conversion of CK19+ cells during MSC CdM-induced islet regeneration. Mice iPan-injected with Wnt+ CdM demonstrated reduced blood glucose levels and improved glucose tolerance compared to mice injected with unconditioned basal media. CdM-injected mice also showed increased islet number and beta cell mass, as well as CK19+ cells within regenerating islets. The frequency of insulin+ cells that co-expressed tdTomato within dissociated pancreas samples observed via flow cytometry was 5-fold higher in Wnt+ CdM-injected mice (~5%) compared to basal media-injected controls (~1%). Collectively, in vivo lineage tracing revealed conversion of CK19+ cells to functional beta cells partially contributed to islet regeneration induced by Wnt activated MSC CdM. Future studies are required to delineate alternate cell types and mechanisms participating in islet regeneration induced by direct delivery of MSC-CdM.