The mucociliary function of the bronchial epithelium ensures the continuous clearance of the respiratory system, which relies on two main elements: mucus and cilia beating coordination.We perform here a rheological characterization of mucus samples extracted from ALI (Air-liquid interface) cultures of bronchial epithelium. Our approach combines macro- and micro-rheology techniques with the aim of quantifying the mucus viscoelastic properties at different length scales (from the size of bronchial cilia up to the scale on which mucus is transported). This specific methodology allows us to compare samples corresponding to different patient pathologies.In addition, we will describe our method to quantitatively characterize the coordination between cilia and how density and spatial distribution influences this coordination and consequently the mucus motion, required for the mucoliary clearance.

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.

The bronchial epithelium mucociliary function ensuring the lung continuous clearance relies on mucus rheological properties and cilia beating coordination. Our biophysical approach aims at understanding two points. First, the biochemical and physical parameters affecting the mucus viscoelastic properties and evaluating its use as a marker for the diagnosis of respiratory diseases. Secondly the cilia coordination and its coupling with the mucus.We performed rheological experiments on mucus extracted from Air Liquid Interface (ALI) cultures of bronchial epithelium reconstituted from bronchial biopsies. Our approach consists in combining standard macro-rheology to micro-rheology performed with optical tweezers, in order to quantify the mucus flowing behavior at different scales, from the cilia up to the mucus layer length scales.Macro- and micro-rheology give different results. At the macro-scale, we obtain an elastic plateau (1 to 2 Pa), a shear-thinning behaviour and a very low yield stress (0.05-0.2 Pa). While at the micro-scale, we obtain a viscous flow, with a very low viscoelastic modulus (10-3-10-2 Pa). Nevertheless, by applying local forces at the interfaces, we observe an important adhesion and elasticity. Mucus adhesion should be taken into account to understand the differences between these different length scales and more generally to characterize the mucus properties. 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. Moreover, comparison of physical properties of mucus from the culture and directly extracted from patient lungs, provides an additional validation of the ALI model.Finally, the specific methodology we developed to quantify cilia activity and coordination, allows us to map, the cilia spatial distribution, the beating frequency and orientation of each cilium, and their standard deviation within a cilia cluster (cell). Local quantification of the cilia activity coupled to the measurement of the mucus velocity field, should help to evaluate the efficiency of the mucociliary function and to understand the mechanisms of clearance.

The mucociliary function of the bronchial epithelium ensures the continuous clearance of the respiratory system. This function relies on two main elements: mucus properties and cilia beating coordination. We work on high speed optical microscopy videos of Human bronchial epithelium from ALI (Air-liquid interface) cultures. We present here a technique based on the tracking of each cilium and on the spatiotemporal analysis of the obtained trajectories. To relate each cilium to its corresponding cell, a clustering method is used. The spatiotemporal coordination can than be quantified both, inside and in-between ciliated cells. In addition the physical parameters can be mapped to observe the heterogeneity of the cilia activity and compare different pathologies.