Validation of Nasal Potential Difference Measurements in Gut-Corrected CF Knockout Mice

Abstract

Attempts at correcting the nasal potential difference (PD) in cystic fibrosis (CF) mice have long been used in preclinical gene and small molecule therapy development. However, in general, CF mice suffer from intestinal disease, are runted, and have high mortality rates; they are therefore difficult to work with, especially if large numbers are required. Because of this, large-scale PD studies in CF mice have not been performed. Working with CF mice has become substantially easier after the generation of the gut-corrected CF-knockout mouse. Fatty acid-binding promoter (FABp)-mediated expression of CFTR in the gut, but not the airways, prevents the intestinal disease of the CF knockout mouse. This model has given us the unique opportunity to systematically study PDs in large numbers of CF mice. The nose, but not the lungs, of these animals mimic the bioelectric defect seen in humans. We have therefore assessed the bioelectrics of the respiratory epithelium comparing FABp-CF and wild-type mice. The large body of data gathered in CF and wild-type mice allowed us, for the first time, to establish power calculations that should inform sample sizes required in gene and small molecule therapy development. In addition, we address the important issues of intra-animal variability as well as intra- and inter-operator variability for scoring the traces, and the effect of age and sex on nasal PD in CF mice. These data should allow a more informed use of CF animals in future studies.