Hypertonic saline releases the attached small intestinal cystic fibrosis mucus

Hypertonic saline inhalation has become a cornerstone in the treatment of cystic fibrosis (CF), but its effect on CF mucus is still not understood. In CF, mucus stagnates in the airways, causing mucus plugging, and forming a substrate for bacterial invasion. Using horizontal Ussing-type chambers to allow easy access to the tissue, we have recently shown that the small intestinal mucus of CF mice is attached to the epithelium and not freely movable as opposed to normal mucus, thus pointing to a similarity between the CF mucus in the ileum and airways. In the same type of system, we investigated how hypertonic saline affects mucus thickness, attachment and penetrability to fluorescent beads the size of bacteria in ileal explants from the cystic fibrosis transmembrane conductance regulator mutant (F508) mouse, in order to characterize how this common therapy affects mucus properties. Hypertonic saline (1.75-5%) detached the mucus from the epithelium, but the mucus remained impenetrable to beads the size of bacteria. This approach might be used to test other mucolytic interventions in CF.