In Situ Analysis Reveals That CFTR Is Expressed in Only a Small Minority of [beta]-Cells in Normal Adult Human Pancreas

Context: Although diabetes affects 40% to 50% of adults with cystic fibrosis, remarkably little is known regarding the underlying mechanisms leading to impaired pancreatic [beta]-cell insulin secretion. Efforts toward improving the functional [beta]-cell deficit in cystic fibrosis-related diabetes (CFRD) have been hampered by an incomplete understanding of whether [beta]-cell function is intrinsically regulated by cystic fibrosis transmembrane conductance regulator (CFTR). Definitively excluding meaningful CFTR expression in human [beta]-cells in situ would contribute significantly to the understanding of CFRD pathogenesis. Objective: To determine CFTR messenger ribonucleic acid (mRNA) and protein expression within [beta]-cells in situ in the unmanipulated human pancreas of donors without any known pancreatic pathology. Design: In situ hybridization for CFTR mRNA expression in parallel with insulin immunohistochemical staining and immunofluorescence co-localization of CFTR with insulin and the ductal marker, Keratin-7 (KRT7), were undertaken in pancreatic tissue blocks from 10 normal adult, nonobese deceased organ donors over a wide age range (23-71 years) with quantitative image analysis. Results: CFTR mRNA was detectable in a mean 0.45% (range 0.17%-0.83%) of insulin-positive cells. CFTR protein expression was co-localized with KRT7. One hundred percent of insulin-positive cells were immunonegative for CFTR. Conclusions: For the first time, in situ CFTR mRNA expression in the unmanipulated pancreas has been shown to be present in only a very small minority (