In situ analysis reveals that CFTR is expressed in only a small minority of β-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 (<1%) of normal adult beta-cells. These data signal a need to move away from studying endocrine-intrinsic mechanisms and focus on elucidation of exocrine-endocrine interactions in human cystic fibrosis.