Impact of the extracellular matrix physical properties on immune responses against infection – InfEx
Unveiling the Molecular Dialogue Between Immune Cells and Their Matrix Environment
The extracellular matrix is profoundly remodeled during inflammation or infection, altering the physical properties of tissues such as topography and stiffness. Immune cells navigating through these tissues are then subjected to mechanical constraints that differ from their native conditions, which can affect not only their migration but also their function.
The objective of our project was to (1) understand how the matrix is remodeled during inflammation and (2) characterize the consequences on the immune response.
To fulfill their functions, immune cells continuously integrate chemical and physical signals from their environment. While many studies have highlighted the role of chemical mediators in immune responses, the physical changes in tissues have been less explored. The main objectives of this project were to: 1. Characterize, through tissue imaging and image analysis approaches, the biophysical properties of the extracellular matrix under different conditions, whether homeostatic or inflammatory; 2. Assess the biological consequences on immune cell migration, localization, and activation; 3. Identify the molecular mechanisms involved; 4. Determine the consequences for the immune response at the organism level.
Our study was conducted by combining various approaches: imaging (videomicroscopy, confocal and two-photon microscopy), transcriptomics, and computational analysis.
1. To understand how mechanical confinement affects the migration and function of dendritic cells, we performed:
• Dynamic imaging using two-photon microscopy, allowing simultaneous visualization of collagen structure and dendritic cell migration;
• Videomicroscopy tracking of dendritic cells under different physical confinement heights, along with bulk transcriptomic analysis;
• Tracking of dendritic cell migration from the periphery to the draining lymph node using flow cytometry.
2. To characterize the physical determinants of the matrix that control the local accumulation of T lymphocytes and neutrophils, we:
• Imaged collagen fiber structure using second harmonic generation, along with T lymphocytes and neutrophils;
• Developed a dedicated image analysis pipeline, resulting in the creation of a machine learning model capable of predicting the localization of T lymphocytes and neutrophils based solely on the topographical features of the fibers.
1. Matrix-induced nuclear deformations support the tolerogenic response of dendritic cells
Real-time imaging of skin dendritic cells revealed that during migration, these cells undergo deformation and pass through pores measuring 2 to 4 µm in diameter—smaller than the size of their nucleus. Our study established the consequences of these deformations: activation of the cPLA2 (phospholipase A2) pathway and expression of the chemokine receptor CCR7, enabling dendritic cell migration to the draining lymph node. The activation threshold of this mechanism is finely regulated by cytoskeletal proteins that maintain nuclear envelope tension. Dendritic cells activated in this mechanically driven manner adopt a tolerogenic profile through the activation of a specific transcriptional program.
These findings were published in Nature Immunology in 2024 (Alraies et al., Nat Immunol. 2024 Jul;25(7):1193–1206. doi: 10.1038/s41590-024-01856-3).
2. Collagen matrix topography dictates the local accumulation of T lymphocytes and neutrophils
Through the development of a specific collagen fiber analysis strategy, we demonstrated that collagen topography alone can predict the sites of local accumulation of T lymphocytes and neutrophils. Our approach revealed a differential topographical tropism for these two cell types.
These results are currently under revision and available on bioRxiv (Fusilier et al., doi.org/10.1101/2025.01.17.633527).
We are now focusing on understanding the mechanisms by which mechanical constraints control gene expression in dendritic cells, with particular attention to the role of transposable elements. We are also exploring the consequences of this process in various pathophysiological contexts.
In parallel, we are actively investigating how the topography of extracellular matrix fibers molecularly regulates the migration of T lymphocytes and neutrophils. Our study will later extend to other matrix characteristics such as stiffness, composition, and the combination of multiple parameters.
Since the beginning of medicine, changes in physical properties of tissues have been known to be a sign of pathology. These changes are linked to modifications of the extracellular matrix (ECM), which constitutes the tissue scaffold and continuously provides key mechanical and biochemical cues to cells. We wish to investigate how the physical properties of the ECM are modified during inflammation and infection and impact on immune cell migration and function. We propose to (1) evaluate the alterations of the extracellular matrix after infection; (2) assess the impact of mechanical properties on the monocytes, dendritic cells and T cells in vitro and (3) determine the influence of the ECM properties on immune response in vivo. This project will provide the first comprehensive view of the impact of ECM physical properties on immune responses against inflammation and infection. We anticipate that our results will contribute to the design of new therapeutic strategies.
Project coordination
Hélène Moreau (IMMUNITE ET CANCER, U932)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Partnership
IC IMMUNITE ET CANCER, U932
Help of the ANR 389,307 euros
Beginning and duration of the scientific project:
December 2020
- 36 Months
