Mechanics and genetics

Olivier Cochet-Escartin, Hélène Delanoë-Ayari, Sylvain Monnier, Charlotte Rivière

We study how the physical and mechanical environment influences the molecular regulations at play in living systems. This type of mechano-genetic coupling is increasingly recognized as an important type of regulation in a variety of biological contexts. We mainly question the role of mechano-genetic feedbacks in three different situations:
Such studies require the control and observation of both the physical environment and the molecular dynamics at play. We therefore combine techniques from microfabrication and soft matter physics with cellular and molecular biology to observe and quantify, in vivo, these two aspects. The goal is to achieve comprehensive models of these important biological processes explicitly taking into account the interplay of mechanics and genetics as a central regulatory element of these processes.
Funding: Ligue régionale contre le cancer, Plan Cancer, Institut François Rabelais, Fondation pour la Recherche Médicale, Institut Lumière Matière (iLM), Fondation de Recherche Andre Marie Ampère (FRAMA)
Collaborations: Centre de Recherche contre le Cancer de Lyon, LiPhy Grenoble, Laboratoire de Régénération et Neurogenèse Adulte (Université de Genève), Porto Alegre (Brasil), Laboratoire de Biologie Moléculaire et Cellulaire (ENS Lyon).

Regeneration of Hydra:

We study the role of mechanical signals in the patterning of Hydra vulgaris. This organism is well known for its regenerative capacities allowing to trigger pattern formation at will through amputations or the preparation of cellular aggregates (Fig). We then ask how externally applying mechanical perturbations (pressure, shear) on a regenerating sample affects the regenerative process at the genetic, cellular and organism scale. 


Legend: A-B from (Technau and Steele 2011), C from (Cochet-Escartin et al. 2017). A: Schematic representation of an adult Hydra and its different organs. B: Structure of Hydra at the cellular scale, the two epithelial layers are shown in red and green respectively. C: Timelapse images of Hydra regeneration from an aggregate of cells expressing GFP in the ectoderm (shown in green) and DsRed2 in the endoderm (shown in purple). Scale: 200 mm up to 72h, 500 mm at 100h.

To do so, we use an interdisciplinary approach combining techniques from molecular biology to observe the dynamics of key patterning genes, soft matter physics to develop force sensors, microfluidics to apply mechanical perturbations (Video 1) and 3d microscopy to observe the entire regenerating sample.


Regenerating Hydra tissue piece under mechanical perturbations in a microfluidic device.


Effect of pressure on tumor organoids

We aim at understanding how constraints generated by tumor microenvironment can impact tumor development and the fate of cancer cells. Indeed tumors grow in a confined environment leading to compression and generation of stress within the tumor. We study how such stresses impact physical parameters of the tumor (cell size, mechanics and diffusion) and act on various biological processes such as cell growth, division and differentiation. We focus on the role of this kind of stress on cancer stem-like cells. Cancer stem-like cells are a crucial subpopulation of cancerous cells; they are thought to be partly responsible for tumor progression, resistance to therapies and cancer relapse. Those cells are very dynamic as they can change state according to environmental cues among them stresses and physical could play key roles.

To study the role of mechanical stress on cancer cells, we use 3D tumor spheroids made of cancerous cells or cancer stem cells as model systems to mimic early stage of tumor development.  We also develop microfabricated systems and microfluidics to reproduce in vitro the pressure tumors can bear in vivo. Eventually, those tools are combined with live and quantitative measurements to assess physical and biological properties of cells and organoids.

Legend: 2-photon imaging of spheroid compression submitted to osmo-mechanical pressure within a microfluidic device. Fluorescence (white and red) labels the space between the cells (dark) and show compression of the intercellular space.

Effect of 2D mechanical Confinement on Cancer Stem Cells

There are growing evidences that mechanics is playing a key role in tumor progression. However, while the effect of matrix stiffness is extensively studied in various biological context, few studies are focusing on the role of mechanical stresses. This type of stimuli remains poorly investigated due to a lack of standard in-vitro assays enabling cell analysis upon extended mechanical stimulation.

We have developed a flexible agarose-based microsystem that precisely confines cells for extended periods (Fig). It faithfully reproduces long-term in vitro confinement mimicking in vivo conditions, without affecting cell behavior by other means (ref biorxiv). This is a unique tool to analyze the role of long-term effect of mechanical confinement in normal and pathological conditions.

We are currently analyzing dynamic cell response to such mechanical confinement in various cancer cell models (Colon, Breast and Leukemia).

Key publications:

Cochet-Escartin, O., Locke, T. T., Shi, W. H., Steele, R. E., & Collins, E. M. S. (2017). Physical mechanisms driving cell sorting in Hydra. Biophysical journal113(12), 2827-2841.

A. PrunetS. LefortH. Delanoë-AyariB. LaperrousazG. SimonS. SaciF. ArgoulB. GuyotJ.-P. RieuS. GobertV. Maguer-SattaC. Rivière (2019), Development of a soft cell confiner to decipher the impact of mechanical stimuli on cells. 

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