Intestinal current measurement detects age-dependent differences in CFTR function in rectal epithelium.

Objective: Intestinal current measurement (ICM) provides a sensitive bioassay for assessment of cystic fibrosis transmembrane conductance regulator (CFTR) function in rectal biopsies Methods: We investigated CFTR-mediated chloride secretion in rectal biopsies from 258 people without CF and 72 people with pancreatic-insufficient CF from 1 month to 68 years of age. Change in transepithelial short-circuit current in response to cyclic adenosine monophosphate (cAMP)-mediated (100 μM IBMX, 1 µM forskolin, basolateral) and cholinergic (100 μM carbachol, basolateral) stimulation was assessed as a readout for CFTR function using perfused micro-Ussing chambers. Furthermore, quantitative real-time PCR of Results: We found that CFTR-mediated chloride secretion across rectal tissues, as determined from cAMP-mediated as well as cholinergic chloride-secretory responses was highest during infancy and early childhood and declined with age in people without CF (both P < 0.001). Although, there was no difference in cAMP-mediated currents in people with CF, potassium-secretory responses induced by cholinergic stimulation were also reduced with increasing age. Transcript analyses showed that Conclusion: These results demonstrate that CFTR function in the rectal epithelium is reduced with increasing age and indicate that this change is likely due to a decline in the number of secretory colonocytes at the crypt base. These findings suggest that differences in CFTR expressing cells may explain increased functional responses to CFTR modulator therapies in children compared to adult people with CF.