Thin layer mucus dynamics in ciliated cultures

Cystic fibrosis lung disease originates in the deep airways of the lung and these airways have a thinner mucus layer than in the upper airways. A thin mucus layer is also present and remains on airway cells in culture even when these are washed thoroughly. We hypothesized that this layer could modulate its attachment to the surface in response to local conditions and investigated the effects of changes in fluid height, mucus thickness, and exposure to a cationic polymer in such cultures. Three responses were found using confocal and DIC microscopy. In flat cultures, decreasing the fluid height caused an increase in mucus flow. In cultures viewed in profile in a flow‐through chamber, increasing mucus thickness through ATP‐induced secretion generated a layer that lifted the previously attached mucus and then carried it over the surface. Polylysine that could damage cultures with thin mucus dramatically condensed thicker mucus without harming the cells. These observations suggest that, unlike the upper airway mucus, a thin attached layer in the deep airways may shed in response to local conditions. Supported by National Heart, Lung, and Blood Institute grant HL‐084934‐04.