isolating-analyzing-cells-pancreas-mesenchyme-flow

Isolating and Analyzing Cells of the Pancreas Mesenchyme by Flow Cytometry

The pancreas is comprised of epithelial cells that are required for food digestion and blood glucose regulation. Cells of the pancreas microenvironment, ...

Sackler Faculty of Medicine, Tel Aviv University

β-Cells rely on the islet microenvironment for their functionality and mass. Pericytes, along with endothelial cells, make up the dense islet capillary network. However, although the role of endothelial cells in supporting β-cell homeostasis has been vastly investigated, the role of pericytes remains largely unknown. Here, we focus on contribution of pericytes to β-cell function. To this end, we used a transgenic mouse system that allows diphtheria toxin-based depletion of pericytes. Our results indicate that islets depleted of their pericytes have reduced insulin content and expression. Additionally, isolated islets displayed impaired glucose-stimulated insulin secretion, accompanied by a reduced expression of genes associated with β-cell function. Importantly, reduced levels of the transcription factors MafA and Pdx1 point to β-cell dedifferentiation in the absence of pericytes. Ex vivo depletion of pericytes in isolated islets resulted in a similar impairment of gene expression, implicating their direct, blood flow-independent role in maintaining β-cell maturity. To conclude, our findings suggest that pericytes are pivotal components of the islet niche, which are required for β-cell maturity and functionality. Abnormalities of islet pericytes, as implicated in type 2 diabetes, may therefore contribute to β-cell dysfunction and disease progression.

Islet Pericytes Are Required for β-Cell Maturity.

Pancreas development requires restrained Hedgehog (Hh) signaling activation. While deregulated Hh signaling in the pancreatic mesenchyme has been long suggested to be detrimental for proper organogenesis, this association was not directly shown. Here, we analyzed the contribution of mesenchymal Hh signaling to pancreas development. To increase Hh signaling in the pancreatic mesenchyme of mouse embryos, we deleted Patched1 (Ptch1) in these cells. Our findings indicate that deregulated Hh signaling in mesenchymal cells was sufficient to impair pancreas development, affecting both endocrine and exocrine cells. Notably, transgenic embryos displayed disrupted islet cellular composition and morphology, with a reduced β-cell portion. Our results indicate that the cell-specific growth rates of α- and β-cell populations, found during normal development, require regulated mesenchymal Hh signaling. In addition, we detected hyperplasia of mesenchymal cells upon elevated Hh signaling, accompanied by them acquiring smooth-muscle like phenotype. By specifically manipulating mesenchymal cells, our findings provide direct evidence for the non-autonomous roles of the Hh pathway in pancreatic epithelium development. To conclude, we directly show that regulated mesenchymal Hh signaling is required for pancreas organogenesis and establishment of its proper cellular composition.

Article	Year
Islet Pericytes Are Required for β-Cell Maturity. Diabetes\| PubMed ID: 27388217	2016
Pancreatic Mesenchyme Regulates Islet Cellular Composition in a Patched/Hedgehog-Dependent Manner. Scientific reports\| PubMed ID: 27892540	2016

Alona Epshtein

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