WS06.6 Mucociliary transport is impaired in cystic fibrosis pig airways

Abstract

Objectives The basic defect in cystic fibrosis (CF) is well characterized, but the link between defects in the CF transmembrane conductance regulator (CFTR) and the phenomenon of stagnant mucus is not well understood. We have shown that the ileal mucus in CFTR mutant mice adheres to the epithelium, is denser, and is less penetrable than that of wildtype mice and that addition of 115 mM NaHCO 3 to mucus partially normalizes this mucus phenotype. Using this knowledge of effects on ileal mucus, we are developing an airway experimental set-up. Methods Excised airways from CFTR knockout (CF) and wildtype (WT) pigs are pinned to a chamber, alcian blue mucosal stain is added to visualize the mucus and the transport is recorded. During the experiment, mucus is collected for proteomics using masspectrometry. Scanning electron microscopy is used to visualize the properties of the mucus, and transmission electron microscopy is used to study mucin secretion in detail. Results Average clearance rates of strands in CF pig airways are lower than in WT pig airways. Preliminary results suggest that the initial defect in newborn pigs involves clearance of Muc5b from the glands. Furthermore, we show that removal of bicarbonate from WT airways reduces the average clearance rate to the level of CF airways. Conclusion Evidence suggests the importance of bicarbonate in the proper unpacking and secretion of mucins. Thus, restoration of bicarbonate to the apical surface of the epithelium in combination with osmolytes may induce proper mucin unpacking in CF epithelia, and therefore could relieve the mucus obstruction that causes clinical problems for cystic fibrosis patients.