Cystic fibrosis airway mucus barrier (CF mucus barrier)

The cystic fibrosis (CF) airway mucus barrier is a pathological, highly viscous, and dehydrated secretion layer that accumulates in the lungs of CF patients due to dysfunctional CFTR-mediated ion transport (NIH, 2023). This barrier is primarily composed of hyper-concentrated mucins (MUC5AC and MUC5B), high levels of extracellular DNA from degraded neutrophils, and filamentous actin, which collectively create a mesh-like structure that impairs mucociliary clearance (PubMed, PMID: 30143479). In CF, this barrier serves as a niche for chronic bacterial infections, such as Pseudomonas aeruginosa, and protects pathogens from both the host immune system and exogenous antibiotics (Nature Reviews Disease Primers, 2016). Therapeutic interventions aim to modify the physical properties of this barrier—reducing its viscosity and elasticity—to facilitate clearance and improve lung function. Common strategies include the use of mucolytics to break down DNA or mucin crosslinks and osmotic agents to rehydrate the airway surface liquid (StatPearls, 2023). By altering the rheological properties of the sputum, these treatments help restore the lung's natural defense mechanisms and reduce the frequency of pulmonary exacerbations. This target is distinct from the CFTR protein itself, as it represents the downstream physical consequence of the disease that directly leads to airway obstruction. Effective management of this barrier is critical for preventing long-term lung damage and improving the quality of life for individuals with cystic fibrosis.

Other names

Cystic fibrosis sputumCF airway secretionsCF mucusCystic fibrosis bronchial mucusCF airway surface liquid

Therapeutic strategies target the CF airway mucus barrier through several mechanisms: enzymatic degradation of extracellular DNA (e.g., Dornase alfa), reduction of disulfide bonds in mucin polymers (e.g., N-acetylcysteine), and osmotic hydration to increase water content and improve rheology (e.g., hypertonic saline and mannitol).