Biophysics of airway defense: revisiting the role of mucus rheology

The airways are protected by mucus, a complex fluid that is transported from the lungs to the throat by the coordinated beating of millions of microscopic cilia. This process, known as mucociliary clearance, is a primary defense mechanism of the respiratory tract. It constitutes an active transport system whose dysfunction is associated with airway obstruction and chronic respiratory diseases.

In this seminar, I will present an experimental framework based on human bronchial epithelium cultured at the air–liquid interface to investigate the relationship between mucus mechanical properties and transport efficiency. This system exhibits self-organized mucus flows at the tissue scale, which we exploit to define a robust and quantitative measure of transport. Combined with in situ microrheology, we show that efficient transport can be maintained across a broad spectrum of rheological properties, from viscoelastic fluids to elastic solids. These results indicate that bulk mucus rheology alone does not account for transport efficiency. To gain insight into the underlying mechanism, we use ciliary beat dynamics as a mechanical probe to reveal the role of the interfacial layer mediating force transmission. These findings provide new insights into the mechanisms governing mucociliary clearance.