Biology subjects

D'Ortona, U.

Publications and source records attributed to D'Ortona, U..

4 recordsLinked to original sources

bioRxiv2026

Disentangling mucus rheology and transport efficiency in human airways

The protection of the respiratory tract relies on a layer of mucus that is transported along the epithelial surface by the beating of millions of microscopic cilia. This mechanism, called mucociliary clearance, is defective in chronic respiratory diseases. Since these pathologies alter mucus rheology, mucus transport efficiency is hypothesized to rely on its mechanical properties. Yet, this link is difficult to test due to limited experimental models. Here, we introduce an experimental framework that enables us to identify conditions associated with efficient mucus transport or arrest. Strikingly, we show that cilia are able to efficiently propel mucus with properties ranging from a viscoelastic fluid to an elastic solid, revealing that bulk mucus rheology is not the critical determinant of clearance failure. Instead, we demonstrate that the efficiency of mucociliary clearance is governed by the hydration of a thin fluid layer at the cilia-mucus interface. Finally, we use a hydrodynamic model informed by measurements on ciliary beat patterns to infer the properties of this critical layer under both transported and arrested mucus conditions. This work not only offers a novel understanding of the fundamental physical mechanism of mucus transport, but also provides a well-defined and quantitative assay to test effects of mucolytic agents or drugs on mucus clearance.

biophysics↗

bioRxiv2021

Longitudinal to transverse metachronal wave transitions in an in-vitro model of ciliated bronchial epithelium

Myriads of cilia beat on ciliated epithelia, which are ubiquitous in life. When ciliary beats are synchronized, metachronal waves emerge, whose direction of propagation depends on the living system in an unexplained way. We show on a reconstructed human bronchial epithelium in-vitro that the direction of propagation is determined by the ability of mucus to be transported at the epithelial surface. Numerical simulations show that longitudinal waves maximise the transport of mucus while transverse waves, observed when the mucus is rigid and still, minimize the energy dissipated by the cilia.

biophysics↗

bioRxiv2020

Hydrodynamic model of directional ciliary-beat organization in human airways

In the lung, the airway surface is protected by mucus, whose transport and evacuation is ensured through active ciliary beating. The mechanisms governing the long-range directional organization of ciliary beats, required for effective mucus transport, are much debated. Here, we experimentally show on human bronchial epithelium reconstituted in-vitro that the dynamics of ciliary-beat orientation is closely connected to hydrodynamic effects. To examine the fundamental mechanisms of this self-organization process, we build a two-dimensional model in which the hydrodynamic coupling between cilia is provided by a streamwise-alignment rule governing the local orientation of the ciliary forcing. The model reproduces the emergence of the mucus swirls observed in the experiments. The predicted swirl sizes, which scale with the ciliary density and mucus viscosity, are in agreement with in-vitro measurements. A transition from the swirly regime to a long-range unidirectional mucus flow allowing effective clearance occurs at high ciliary density and high mucus viscosity. In the latter case, the mucus flow tends to spontaneously align with the bronchus axis due to hydrodynamic effects.

biophysics↗

bioRxiv2019

Active mucus-cilia hydrodynamic coupling drives self-organisation of human bronchial epithelium

The respiratory tract is protected by mucus, a complex fluid transported along the epithelial surface by the coordinated beating of millions of microscopic cilia, hence the name of mucociliary clearance. Its impairment is a strong marker of severe chronic respiratory diseases. Yet, the relationship between ciliary density and the spatial scale of mucus transport, as well as the mechanisms that drive ciliary-beat orientations during ciliogenesis are much debated. Here, we show on polarized human bronchial epithelia that mucus swirls and circular orientational order of the underlying ciliary beats emerge and grow during ciliogenesis, until a macroscopic mucus transport is achieved for physiological ciliary densities. By establishing that the macroscopic ciliary-beat order is lost and recovered by removing and adding mucus respectively, we demonstrate that cilia/mucus hydrodynamic interactions govern the collective dynamics of ciliary-beat directions. We propose a two-dimensional model that predicts a phase diagram of mucus transport in accordance with the experiments. It paves the way to a predictive in-silico modeling of bronchial mucus transport in health and disease.

biophysics↗