Epithelia ciliés – transport et auto-organisation

Physics of the mucociliary clearance.

Principal investigators: E. Loiseau, A. Viallat,
Postdoc: O. Mesdjian
PhD student: A. Baby

Topology and dynamics of ciliated epithelia : fluid flow patterns and biological functions

From swimming microorganisms to major organs including the brain, the respiratory system and the reproductive tracts, ciliated cells are ubiquitous in living systems. Their multiple active cilia continuously consume chemical energy and beat unidirectionally to ensure motility of marine microorganisms, circulation of the cerebrospinal fluid in the central nervous system, mucociliary clearance of pathogens and pollutants from airways, flow generation to clear the skin of Xenopus embryo from pathogens. The generation of fluid flows at the tissue level requires a dense array of cilia that coordinate their beat directions at long range. Furthermore, cilia are exposed by ciliated cells in tight adhesion with their neighbors to form a connective tissue which has its own dynamics and constraints.

We focus on two main systems: the bronchial epithelium and Xenopus embryo. To identify the physical and biological mechanisms that govern the self-organisation of cilia and the patterning of the underlying tissue we combine topological active matter, cell biology and numerical simulations.

We develop new  methods and analysis tools, based on advanced optical microscopy and image processing, in order to quantify the mechanics, the hydrodynamics and the dynamic processes of ciliated epithelia, from the cellular scale to the tissue level, and up to an entire organism. We aim at identifying biophysical markers in respiratory diseases.

The airway epithelium is protected by the active transport at its surface of a layer of a complex fluid, the mucus. It is powered by the beats of billions of microscopic cilia carried by epithelial cells. These beats present a strong long-range orientational order but the physical mechanisms leading to the emergence and maintain of this collective dynamic order of ciliary beats is not known. They involve the mechanical cilia-mucus coupling mediated by long-range hydrodynamic interactions, and the active mechanotransductive response of ciliary beats. We study the long-range self-organization of ciliary activity and mucus flow patterns in reconstituted bronchial epithelium.