Pharmacological correction of a defect in PPAR-gamma signaling ameliorates disease severity in Cftr-deficient mice.

Cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator (encoded by Cftr) that impair its role as an apical chloride channel that supports bicarbonate transport. Individuals with cystic fibrosis show retained, thickened mucus that plugs airways and obstructs luminal organs as well as numerous other abnormalities that include inflammation of affected organs, alterations in lipid metabolism and insulin resistance. Here we show that colonic epithelial cells and whole lung tissue from Cftr-deficient mice show a defect in peroxisome proliferator-activated receptor-gamma (PPAR-gamma, encoded by Pparg) function that contributes to a pathological program of gene expression. Lipidomic analysis of colonic epithelial cells suggests that this defect results in part from reduced amounts of the endogenous PPAR-gamma ligand 15-keto-prostaglandin E(2) (15-keto-PGE(2)). Treatment of Cftr-deficient mice with the synthetic PPAR-gamma ligand rosiglitazone partially normalizes the altered gene expression pattern associated with Cftr deficiency and reduces disease severity. Rosiglitazone has no effect on chloride secretion in the colon, but it increases expression of the genes encoding carbonic anhydrases 4 and 2 (Car4 and Car2), increases bicarbonate secretion and reduces mucus retention. These studies reveal a reversible defect in PPAR-gamma signaling in Cftr-deficient cells that can be pharmacologically corrected to ameliorate the severity of the cystic fibrosis phenotype in mice.

Airway gene transfer in mouse nasal-airways: importance of identification of epithelial type for assessment of gene transfer.

Mouse nasal airways are often used for the assessment of both reporter and cystic fibrosis transmembrane conductance regulator (CFTR) gene transfer to respiratory epithelia. However, the mouse nasal cavity is lined by both olfactory (OE) and respiratory epithelium (RE). Previous gene transfer studies have suggested that OE may be more efficiently transduced by adenoviral vectors than RE. However, to provide data pertinent to CFTR gene transfer in humans, measurements of CFTR function in mice by transepithelial potential difference (TPD) should be directed towards respiratory rather than olfactory epithelium. We report a new technique to mark the position of the TPD sensing cannula tip in the mouse nasal cavity that permitted us to correlate TPD measurements with epithelial cell type. Using this technique, we found TPD values did not discriminate between respiratory and olfactory epithelia. We next assessed relationships between anatomic regions accessed by the TPD cannula and epithelial type. The frequently used insertion depth of approximately 5 mm from the nose tip predominantly recorded the TPD from anterior dorsal olfactory epithelium. Measurement of the TPD of respiratory epithelium in our study was maximized by insertion of the TPD cannula probe to 2.5 mm depth. Because TPD measurements are not sensitive to epithelial type, adequate control of position and TPD catheter insertion depth are required to ensure accurate estimation of CFTR gene transfer into the target RE in the mouse nasal cavity.