Cystic Fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane regulator (CFTR) gene. About 2000 mutations have been described so far. We set up the ex vivo model of human nasal epithelial cells (HNECs) to test the effect of novel mutations and to evaluate the effect of molecular therapies in cells from patients with CF bearing specific genotypes. We improved the sampling (by brushing), culture and analysis of HNECs using several techniques to study the effect of CFTR mutations. We performed 223 brushings from patients with CF and controls. Using cultured cells we: i) demonstrated the widely heterogeneous expression of CFTR in patients and in controls; ii) defined the splicing effect of a CFTR mutation; iii) assessed the CFTR gating activity of HNECs from patients bearing different mutations; iv) demonstrated that butyrate significantly enhances CFTR expression; v) described the genotype-phenotype correlation and the results of either in vitro and ex vivo studies performed on HNECs in a large group of patients with CF carrying CFTR complex alleles.
According to our data we can conclude:
1) the HNEC brushing is performed without anesthesia and it is well tolerated by children and adults;
2) once sampled, HNECs may be stored up to 48 hours before culture. This allows multicenter studies;
3) the HNECs culture is a suitable model to study the molecular effect of novel CFTR mutations and/or mutations of uncertain significance;
4) the ex-vivo model of HNECs may be used to evaluate, before the use in humans, the effect of novel drugs on cells bearing specific CFTR mutations;
5) our procedure may be used for the quantitative measurement of the CFTR gating activity of the HNECs from patients with different genotypes. It may help to classify:
i) CF patients bearing two severe mutations, with an activity <10%;
ii) CF patients bearing at least a mild mutation, with an activity of 10-30%;
iii) CF carriers (heterozygous subjects) with an activity between 40-70%