Résumé
The bronchial epithelium mucociliary function ensuring the lung continuous clearance relies on mucus rheological properties and cilia beating coordination. We focus on two points: first, the biochemical and physical parameters affecting the mucus viscoelastic properties; secondly, the cilia coordination and its coupling with the mucus.We performed rheological experiments on mucus extracted from Air Liquid Interface cultures of bronchial epithelium reconstituted from bronchial biopsies. We combine standard macro-rheology to micro-rheology performed with optical tweezers, to quantify the mucus flowing behaviour at two scales: the mucus layer thickness and the cilia or bacteria scale. Macro- and micro-rheology give different results: an elastic plateau (1-2 Pa) at the macro-scale; a viscous flow (10-3-10-2 Pa) at the micro-scale but with an important adhesion and elasticity at the interfaces. We also perform original experiments using optical tweezers directly on the epithelium, to access the viscoelastic response in the various mucus layers. We obtain an increased elasticity in the vicinity to the epithelium.Finally, the study of the physical mucus properties coupled with the specific methodology we developed to quantify cilia activity, coordination and mucus velocity field, should help to evaluate the efficiency of the mucociliary function and to understand the mechanisms of clearance.