Mucus is important for maintaining healthy lungs. Inhaled particles, including bacteria and viruses, get trapped in mucus and then cilia—tiny hair like projections on the surface of the airway cells—sweep the mucus out of the airway.
In lungs affected by cystic fibrosis (CF), the mucus is abnormal and the lung-clearing process breaks down. This deficit may contribute to lung infections and inflammation that cause serious, life-shortening illness in people with CF.
In a new study, published in Proceedings of the National Academy of Sciences (PNAS) Early Edition, University of Iowa researchers led by Michael Welsh, MD, director of the UI Pappajohn Biomedical Institute, professor of internal medicine in the UI Carver College of Medicine, and a Howard Hughes Medical Institute investigator, and Lynda Ostedgaard, PhD, investigated how CF alters the structure of mucus produced in airway passages. The study focused on two gel-forming mucin proteins, MUC5B and MUC5AC, that are the major components of airway mucus. Studying these two proteins in pigs, the researchers found that they have distinct and different structures and origins. MUC5B is produced by submucosal glands in the form of strands, while MUC5AC is secreted by goblet cells as wispy threads and thin sheets. The study also showed that once these two types of mucus protein emerge onto the airway surface, they combine so that the MUC5B strands are partly covered with MUC5AC sheets. This overall structure may be helpful for capturing and clearing inhaled particles.