Mucus Microrheology Measured on Human Bronchial Epithelium Culture

We describe an original method to measure mucus microrheology on human bronchial epithelium culture using optical tweezers. We probed rheology on the whole thickness of mucus above the epithelium and showed that mucus gradually varies in rheological response, from an elastic behavior close to the epithelium to a viscous one far away. Microrheology was also performed on mucus collected on the culture, on ex vivo mucus collected by bronchoscopy, and on another epithelium model. Differences are discussed and are related to mucus heterogeneity, adhesiveness, and collection method

Biophysical approach of the mucociliary function: Mucus rheology and beating coordination

International audienceThe 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

Mucus from human bronchial epithelial cultures: rheology and adhesion across length scales

International audienceMucus is a viscoelastic aqueous fluid that participates in the protective barrier of many mammals' epithelia. In the airways, together with cilia beating, mucus rheological properties are crucial for lung mucociliary function, and, when impaired, potentially participate in the onset and progression of chronic obstructive pulmonary disease (COPD). Samples of human mucus collected in vivo are inherently contaminated and are thus poorly characterized. Human bronchial epithelium (HBE) cultures, differentiated from primary cells at an air–liquid interface, are highly reliable models to assess non-contaminated mucus. In this paper, the viscoelastic properties of HBE mucus derived from healthy subjects, patients with COPD and from smokers are measured. Hallmarks of shear-thinning and elasticity are obtained at the macroscale, whereas at the microscale mucus appears as a heterogeneous medium showing an almost Newtonian behaviour in some extended regions and an elastic behaviour close to boundaries. In addition, we developed an original method to probe mucus adhesion at the microscopic scale using optical tweezers. The measured adhesion forces and the comparison with mucus-simulants rheology as well as mucus imaging collectively support a structure composed of a network of elastic adhesive filaments with a large mesh size, embedded in a very soft gel

Macro and Micro rheological characterization of Human bronchial mucus

International audienceThe mucociliary function of the bronchial epithelium ensures the continuous clearance of the respiratory system. This function relies on two main elements: mucus and cilia beating. 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). In addition, this methodology allows us to compare the rheological behavior of mucus samples corresponding to different pathologies

Biophysical approach of the mucociliary function: Mucus rheology and beating coordination

International audienceThe 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

Biophysical approach of the mucociliary function: Mucus rheology and beating coordination

National audienceThe 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