Development and Engineering of Ciliated Tissues: Unravelling the Role of Mechanical Forces with Smart Tissue Scaffolding

Thousands of motile hair-like appendages called cilia cover the epithelium of our lungs, clearing mucus and germs. Their spatial organization is essential for coordinating their collective function and establishing long-range transport. Mechanical forces contribute to cell polarity pathways and the establishment of the direction of cilia-driven flow.

In cultured cells lacking the in vivo mechanical environment, cilia are poorly aligned, and transport efficiency suffers. However, applying exogenous fluid flow within a controlled chamber can realign cilia in the direction of the flow, enhancing unidirectional fluid transport. We recently found that cilia realignment is coupled with cell rearrangements, suggesting that cilia hydrodynamics represent an important contribution to the internal mechanics of the tissue. Yet, the cellular mechanisms leading to cilia realignment remain an open question.

The PhD candidate will investigate the role of mechanical forces in the establishment of cilia orientational polarity, focusing on the yet unexplored coupling between the hydrodynamic forces generated by the cilia and the internal forces at a cellular and tissue level. Project Goals: Goal I: Quantification of flow-induced mechanical forces in ciliated tissues

Goal II: Identification of cellular responses to specific mechanical cues

Goal III: Identification of developmental mechanisms setting cilia orientational polarity, with an exploration of tissue engineering applications

Implementation: We will employ animal caps explanted from pre-gastrulation Xenopus embryos, which spontaneously develop into functional ciliated epithelia (organoids). Xenopus is a well-established model with a suite of genetic tools available to stain or interfere with cilia structures and cell mechanics.

The forces induced by the flow will be estimated from the strain of a flexible substrate (traction microscopy), shape changes of droplets injected into the tissues, and recoil dynamics following laser ablation at cellular edges. We will assay mechanotransduction by imaging calcium reporter (gcamp) and identify downstream events by interfering with ion channels like Piezo1.

To understand the observed cellular rearrangements induced by the measured forces, we will incorporate the contribution of cilia hydrodynamics into a model for tissue mechanics (e.g., vertex methods) and predict cellular dynamics.

To perturb the system and test causality of cellular response, we will develop a novel cell substrate that can stretch and buckle under magnetic fields to modulate forces in space and time.

To explore translational opportunities, we will conclude by examining the forces and cellular rearrangements leading to the recovery of cilia alignment following wounds.