Pancreatic Pericytes Support ß-Cell Function in a Tcf7l2-Dependent Manner.

Polymorphism in TCF7L2, a component of the canonical Wnt signaling pathway, has a strong association with ß-cell dysfunction and type 2 diabetes through a mechanism that has yet to be defined. ß-Cells rely on cells in their microenvironment, including pericytes, for their proper function. Here, we show that Tcf7l2 activity in pancreatic pericytes is required for ß-cell function. Transgenic mice in which Tcf7l2 was selectively inactivated in their pancreatic pericytes exhibited impaired glucose tolerance due to compromised ß-cell function and glucose-stimulated insulin secretion. Inactivation of pericytic Tcf7l2 was associated with impaired expression of genes required for ß-cell function and maturity in isolated islets. In addition, we identified Tcf7l2-dependent pericytic expression of secreted factors shown to promote ß-cell function, including bone morphogenetic protein 4 (BMP4). Finally, we show that exogenous BMP4 is sufficient to rescue the impaired glucose-stimulated insulin secretion of transgenic mice, pointing to a potential mechanism through which pericytic Tcf7l2 activity affects ß-cells. To conclude, we suggest that pancreatic pericytes produce secreted factors, including BMP4, in a Tcf7l2-dependent manner to support ß-cell function. Our findings thus propose a potential cellular mechanism through which abnormal TCF7L2 activity predisposes individuals to diabetes and implicates abnormalities in the islet microenvironment in this disease.