1842-P: Enhanced TGF-ß1 Signaling in the Ducts of Cystic Fibrosis Pancreas Increases Basal Insulin Secretion by Islets

Cystic fibrosis (CF) is a multi-organ disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. CFTR protein is most highly expressed in pancreatic ductal epithelium, where loss of its function leads to ductal plugging, acinar destruction, and eventual diabetes. We hypothesize that exocrine pancreas remodeling in CF alters ductal paracrine signals to the endocrine pancreas. To test this hypothesis, we established primary ductal epithelium grown at an air-liquid interface (ALI) from WT and CFTR-KO ferret pancreas. Carbachol or IBMX/Forskolin (I/F) stimulated basolateral and apical secretions were analyzed for differentially secreted proteins using quantitative mass spectroscopy. Upon carbachol secretion 39 apical and 15 basolateral proteins were differentially secreted (P<0.05) by CFTR-KO ducts. Similarly, 26 and 6 differentially secreted proteins (P<0.05) were identified from I/F stimulated apical and basolateral secretions, respectively. TGF-β1 was one of the top upstream regulators of the differentially secreted proteins, P=5.02E-13 by Ingenuity Pathway Analysis. Single molecule fluorescence in situ hybridization of TGF-β1 mRNA on CFTR-KO and WT ferret pancreas indicated increased expression in CFTR-KO ducts compared to age matched controls. Likewise, expression of IGFBP7, a TGF-β1 signaling target, was augmented in fibroblasts surrounding pancreatic ducts and also in endocrine cells in CFTR-KO pancreas relative to controls. In cultured WT ferret islets, IGFBP7 treatment enhanced basal insulin secretion (2-fold, P<0.05) and attenuated glucose stimulated insulin secretion. This IGFBP7-dependent insulin secretion phenotype was similar to that observed in cultured CFTR-KO islets, suggesting TGF-β1 signaling may be partly responsible for altered insulin secretion in CF. Disclosure P. Rotti: None. I. Apak-Evans: None. Y. OMalley: None. A. Norris: None. A. Uc: None. J. Engelhardt: None. Funding National Institutes of Health