Biology subjects

Leclech, C.

Publications and source records attributed to Leclech, C..

7 recordsLinked to original sources

bioRxiv2025

Adaptation of endothelial cells to microenvironment topographical cues through lysyl oxidase like-2-mediated basement membrane scaffolding

Basement membrane (BM) provides structural support and signaling platform for blood vessels. While its major structural components are required for vascular morphogenesis, integrating BM regulators, like the lysyl oxidase LOXL2, and BM assembly in cell response to microenvironement cues remain poorly understood. Here we study the early deposition and supramolecular assembly of BM components using correlative atomic force and fluorescence microscopy. The fibrillar deposition of fibronectin is gradually remodeled and associates with the collagen IV meshwork as it organizes into BM. We demonstrate that LOXL2 is deposited with both proteins and participates in their remodeling. Alteration of BM scaffolding by LOXL2-depletion affects focal adhesion maturation and cytoskeleton remodeling. This altered BM organization maintains stress fibers, affects the distribution and activation of mechanosensors and alters cell barrier properties. Furthermore, using 3D micro-printed substrates, we demonstrate that BM assembly regulates endothelial cell response to topographical constraint. We therefore propose a mechanism directly linking the scaffolding of BM components and adaptation to the topographical signals from the microenvironment.

cell biology↗

bioRxiv2025

A Morphodynamic Network Model to Describe Cell Organization and Nematic Ordering in Monolayers

To robustly model nematic ordering in cell monolayers, it is crucial to accurately capture cell geometries, which in turn direct the formation of patterns in cell alignment. In this regard, existing agent-based models (ABMs), such as vertex and Voronoi models, lack generality. Current models often fail to accommodate complex cell geometries (such as elongated or non-convex cells) or implement thermodynamically well-posed rules for cell rearrangements. These features are essential for describing the biophysics of morphogenetic processes where irregular cell shapes and dynamic cell rearrangements play central roles. To address the limitations of existing models, we present a novel computational framework, termed the morphodynamic network model (MNM), for simulating confluent cell monolayers. The MNM is a cell center-based ABM in which the cell centers (nodes) are connected to form a dynamic triangulation (network). The node positions and network structure, recording connections between neighboring cells, evolve according to a split-step approach. First, node positions are updated with the network structure (or topology) fixed, then the network topology is updated with node positions fixed. We apply the MNM to study the morphodynamic behavior of cell monolayers, including fluidization, elasto-visco-plastic responses, nematic ordering, and substrate-induced cell alignment. The MNM is designed to capture complex behaviors and morphologies, offering a flexible and robust tool for studying multicellular phenomena.

biophysics↗

bioRxiv2024

A Variational Autoencoder Model for Clustering of Cell Nuclei on Microgroove Substrates: Potential for Disease Diagnosis

Various diseases including laminopathies and certain types of cancer are associated with abnormal nuclear mechanical properties that influence cellular and nuclear deformations in complex environments. Recently, microgroove substrates designed to mimic the anisotropic topography of the basement membrane have been shown to induce significant 3D nuclear deformations in various adherent cell types. Importantly, these deformations are different in myoblast cells derived from laminopathy patients from those in cells derived from normal individuals. Here we assess the ability of a variational autoencoder (VAE) and a Gaussian Mixture Model (GMM) to cluster patches of nuclei of both wildtype myoblast cells and myoblast cells with laminopathy-associated mutations cultured on microgroove substrates, and we explore the impact of image processing parameters on clustering performance. We show that a standard VAE with GMM is able to cluster nuclei based on their morphologies and degrees of deformations and that these clusters correspond to either wildtype myoblasts or myoblasts with LMNA mutations. The current results suggest that combining deep learning techniques with microgroove substrates enables automatic classification of nuclear deformations and thus provides a promising approach for easy and rapid diagnosis of pathologies that involve abnormalities in nuclear deformation.

cell biology↗

bioRxiv2024

Microgroove substrates unveil topography-driven, dynamic 3D nuclear deformations

Navigating complex extracellular environments requires extensive deformation of cells and their nuclei. Nuclear deformations are intricately linked to nuclear structure and mechanical properties, and abnormalities in nuclear mechanics contribute to various diseases including laminopathies and cancer. Most in vitro systems used to study nuclear deformations are typically designed to generate strong whole-cell confinement relevant for specific cell types such as immune or cancer cells. Here, we use microgroove substrates as a model of anisotropic basement membrane topography and we report that adherent cells including endothelial cells and myoblasts exhibit significant 3D (in-plane and out-of-plane) nuclear deformations, with partial to complete penetration into the microgrooves. These deformations are dynamic with nuclei cyclically entering and exiting the microgrooves. AFM measurements show that these deformation cycles are accompanied by transient changes in nuclear mechanical properties. We also show that nuclear penetration into the grooves is principally driven by cell-substrate adhesion, without the need for cytoskeleton-associated forces. Finally, we demonstrate that myoblasts from patients with LMNA mutations exhibit abnormal nuclear deformations which can be rapidly identified and quantified using automated image analysis. We therefore propose the use of microgrooves as a novel simple, tunable, and high throughput system to study nuclear deformations in adherent cells, with the potential to serve as a functional diagnostic platform for pathological alterations in nuclear mechanics.

cell biology↗

bioRxiv2022

Distinct contact guidance mechanisms in single endothelial cells and in monolayers

In many tissues, cell shape and orientation are controlled by a combination of internal and external biophysical cues. Anisotropic substrate topography is a ubiquitous cue that leads to cellular elongation and alignment, a process termed contact guidance, whose underlying mechanisms remain incompletely understood. Additionally, whether contact guidance responses are similar in single cells and in cellular monolayers is unknown. Here, we address these questions in vascular endothelial cells (ECs) that in vivo form a monolayer that lines blood vessels. Culturing single ECs on microgrooved substrates that constitute an idealized mimic of anisotropic basement membrane topography elicits a strong, groove depth-dependent contact guidance response. Interestingly, this response is greatly attenuated in confluent monolayers. While contact guidance in single cells is principally driven by persistence bias of cell protrusions in the direction of the grooves and is surprisingly insensitive to actin stress fiber disruption, cell shape and alignment in dense EC monolayers are driven by the organization of the basement membrane secreted by the cells, which leads to a loss of interaction with the microgrooves. The findings of distinct contact guidance mechanisms in single ECs and in EC monolayers promise to inform strategies aimed at designing topographically patterned endovascular devices.

cell biology↗

bioRxiv2021

Topography-induced large-scale anti-parallel collective migration in vascular endothelium

Collective migration of vascular endothelial cells is central for embryonic development, angiogenesis, and wound closure. Although physical confinement of cell assemblies has been shown to elicit specific patterns of collective movement in various cell types, endothelial migration in vivo often occurs without confinement. Here we show that unconfined endothelial cell monolayers on microgrooved substrates that mimic the anisotropic organization of the extracellular matrix exhibit a new type of collective movement that takes the form of a periodic pattern of anti-parallel cell streams. We further establish that the development of these streams requires intact cell-cell junctions and that stream sizes are particularly sensitive to groove depth. Finally, we show that modeling the endothelial cell sheet as an active fluid with the microgrooves acting as constraints on cell orientation predicts the occurrence of the periodic anti-parallel cell streams as well as their lengths and widths. We posit that in unconfined cell assemblies, physical factors that constrain or bias cellular orientation such as anisotropic extracellular matrix cues or directed flow-derived shear forces dictate the pattern of collective cell movement.

biophysics↗

bioRxiv2018

Topographical cues control the morphology and dynamics of migrating cortical interneurons

In mammalian embryos, cortical interneurons travel long distances among complex three-dimensional tissues before integrating into cortical circuits. Several molecular guiding cues involved in this migration process have been identified, but the influence of physical parameters remains poorly understood. In the present study, we have investigated in vitro the influence of the topography of the microenvironment on the migration of primary cortical interneurons released from mouse embryonic explants.\n\nWe found that arrays of 10 m-sized PDMS micro-pillars, either round or square, influenced both the morphology and the migratory behavior of interneurons. Strikingly, most interneurons exhibited a single and long leading process oriented along the diagonals of the square pillared array, whereas leading processes of interneurons migrating in-between round pillars were shorter, often branched and oriented in all available directions. Accordingly, dynamic studies revealed that growth cone divisions were twice more frequent in round than in square pillars. Both soma and leading process tips presented forward directed movements within square pillars, contrasting with the erratic trajectories and more dynamic movements observed among round pillars. In support of these observations, long interneurons migrating in square pillars displayed tight bundles of stable microtubules aligned in the direction of migration.\n\nOverall, our results show that micron-sized topography provides global spatial constraints promoting the establishment of two different morphological and migratory states. Remarkably, both states belong to the natural range of migratory behaviors of cortical interneurons, highlighting the potential importance of topographical cues in the guidance of these embryonic neurons, and more generally in brain development.

cell biology↗