Biology subjects

Louis, B.

Publications and source records attributed to Louis, B..

6 recordsLinked to original sources

bioRxiv2026

Synthetic Fibrous Hydrogels as Minimal Systems to Modulate Cell Migration Modes in 3D

Cell migration in three-dimensional (3D) environments is highly plastic and regulated by extracellular matrix (ECM) cues. Engineered biomaterials provide controllable platforms to investigate how specific matrix signals regulate cell behavior in 3D, yet how defined biochemical signals control migration modes remain unclear. Here, we present tunable fibrous polyisocyanide (PIC) hydrogels functionalized with integrin-binding RGD peptides, cadherin-mimetic HAVDI peptides, or no ligands to direct mesenchymal, hybrid, or amoeboid-like migration of human adipose-derived stem cells without altering matrix mechanics. Using live-cell tracking, 3D displacement microscopy, matrix remodeling analysis, and YAP nuclear localization, we show that ligand identity governs adhesion organization, force transmission, and mechanotransduction. RGD-functionalized matrices promote {beta}1-integrin clustering, extensive matrix remodeling, strong YAP activation and upregulation of migration-related genes. In contrast, non-adhesive matrices limit adhesion formation, resulting in weak force transmission and amoeboid-like behavior. HAVDI-functionalized matrices induce cadherin clustering and heterogeneous cellular responses, indicating that a hybrid migration mode arises from adhesion organization rather than a distinct transcriptional program. Together, these findings demonstrate that ligand identity alone is sufficient to program migration mode in a force-responsive 3D matrix and provide a versatile platform to dissect cell-matrix interactions in complex environments. Statement of significanceO_LICell migration in tissues is highly adaptable, yet precise control of migration modes in defined 3D biomaterials remains challenging. C_LIO_LIWe introduce fibrous PIC hydrogels presenting RGD, HAVDI, or no adhesive ligands to bias human stem cells toward mesenchymal-like, hybrid, or amoeboid-like migration states. C_LIO_LIBy linking ligand identity to adhesion organization, matrix remodeling, YAP mechanotransduction, and gene expression, this work provides a minimal platform to dissect and engineer 3D cell-matrix interactions C_LI

biophysics↗

bioRxiv2025

Quantitative Analysis of Cytoplasmic Viscosity in Colorectal Cancer Cells by Differential Dynamic Microscopy of Genetically Encoded Nanoparticles

The viscosity of the cytoplasm plays a key role in regulating molecular diffusion and cellular mechanics, yet quantifying it in living cells remains technically challenging. Genetically encoded multimeric nanoparticles (GEMs) have emerged as powerful probes for intracellular microrheology; however, current analyses rely on single-particle tracking, which is limited by probe density, imaging noise, and expression variability. Here, we combine GEMs with differential dynamic microscopy (DDM) to enable quantitative, non-invasive, and rapid measurement of intracellular viscosity using standard wide-field fluorescence imaging. DDM extracts particle dynamics from ensemble spatiotemporal intensity fluctuations, yielding reliable diffusion coefficients and viscosity values even in crowded or heterogeneous environments where tracking fails. Validation with fluorescent nanoparticles diffusing in water confirmed that DDM accurately reproduced theoretical viscosities across a wide range of particle sizes and concentrations. Comparison with single-particle tracking (SPT) demonstrated equivalent precision under dilute conditions and superior robustness under crowding. To showcase the potential of this approach, we applied GEM-DDM to colorectal cancer cell lines with different metastatic potentials. Cytoplasmic viscosity correlated with aggressiveness, increasing from 1.9-2.3 cP in poorly metastatic to 3.6-3.7 cP in highly metastatic lines, consistent with greater macromolecular crowding and cytoplasmic reorganization reported in aggressive cells. Together, these results establish GEM-DDM as a fast, reproducible, and accessible platform for intracellular microrheology, providing new opportunities to link the physical state of the cytoplasm to cell function and disease progression. Statement of significancePhysical properties such as cytoplasmic viscosity influence how molecules move and interact within cells, affecting metabolism, signalling, and disease progression. Measuring viscosity in living cells has been technically challenging and often invasive. Here, we introduce GEM-DDM as a quantitative, non-invasive image-based analysis method combining genetically encoded multimeric nanoparticles (GEMs) with differential dynamic microscopy (DDM) to measure intracellular viscosity using standard wide-field microscopy. We validate its accuracy against established single particle tracking (SPT) methods and demonstrate its biological relevance by showing that cytoplasmic viscosity increases with metastatic potential in cancer cells. This approach provides an accessible platform for studying how the physical state of cells influences their function and pathology.

biophysics↗

bioRxiv2025

Beyond One-Size-Fits-All: Tumor Biology Influences Nanoparticle Behaviour in Cancer Models

Nanoparticles (NPs) are a promising tool for cancer therapy, yet few have successfully reached clinical application. Current nanomedicine development pipelines are focused on optimizing physical properties of NPs, overlooking the impact of tumor biology on their behavior. Here, we show that the same NPs exhibit distinct accumulation and penetration patterns in 3D spheroids derived from four tumor models (representative of lung, colon, breast, and cervical cancer). We uncover an inverse relationship between NP uptake and penetration: tumors with slower internalization show deeper NP diffusion. Proteomic analysis revealed that tumor-specific expression of endocytic and extracellular matrix proteins underlies this variability. Our findings challenge the prevailing one-size-fits-all approach and highlight the need to integrate tumor biology into NP design. Tailoring NPs to the unique cellular and extracellular features of each tumor type will be critical for developing more effective and clinically relevant nanotherapies.

cell biology↗

bioRxiv2022

Synthetic fibrous hydrogels as a platform to decipher cell-matrix mechanical interactions

The interactions between cells and their direct environment are crucial for cell fate but biochemically and mechanically highly complex, and therefore, poorly understood. Despite recent advances that exposed the impact of a range of different factors, real progress remains challenging, since appropriate controllable matrices and quantitative analysis techniques that cover a range of time and length scales are unavailable. Here, we use a synthetic fibrous hydrogel with nonlinear mechanics to mimic and tailor the bi-directional cell-matrix interactions. Using advanced microscopy-based approaches, we acquire a comprehensive picture of how cellular traction forces, fiber remodeling, matrix stiffening, matrix properties and cellular behavior interact, highlighting for instance, the importance of a fibrous architecture and nonlinear mechanics of the matrix. Complete mapping of cell-matrix interactions at the cellular length scale provides indispensable information for the rational design of biomimetic materials to recreate realistic in vitro cell environments.

biophysics↗

bioRxiv2020

Functional and structural consequences of epithelial cell invasion by Bordetella pertussis adenylate cyclase toxin

Bordetella pertussis, the causative agent of whopping cough, produces an adenylate cyclase toxin (CyaA) that plays a key role in the host colonization by targeting innate immune cells which express CD11b/CD18, the cellular receptor of CyaA. CyaA is also able to invade non-phagocytic cells, via a unique entry pathway consisting in a direct translocation of its catalytic domain across the cytoplasmic membrane of the cells. Within the cells, CyaA is activated by calmodulin to produce high levels of cyclic adenosine monophosphate (cAMP) and alter cellular physiology. In this study, we explored the effects of CyaA toxin on the cellular and molecular structure remodeling of A549 alveolar epithelial cells. Using classical imaging techniques, biochemical and functional tests, as well as advanced cell mechanics method, we quantify the structural and functional consequences of the massive increase of intracellular cyclic AMP induced by the toxin: cell shape rounding associated to adhesion weakening process, actin structure remodeling for the cortical and dense components, increase in cytoskeleton stiffness, and inhibition of migration and repair. We also show that, at the low concentrations that may be found in vivo during B. pertussis infection, CyaA impairs the migration and wound healing capacities of the intoxicated alveolar epithelial cells. Our results suggest that the CyaA, beyond its major role in disabling innate immune cells, might also contribute to the local alteration of the epithelial barrier of the respiratory tract, that is an hallmark of pertussis.

cell biology↗

bioRxiv2018

High-throughput micro-patterning platform reveals Nodal-dependent dissection of peri-gastrulation-associated versus pre-neurulation associated fate patterning

In vitro models of post-implantation human development are valuable to the fields of regenerative medicine and developmental biology. Here, we report characterization of a robust in vitro platform that enabled high-content screening of multiple human pluripotent stem cell (hPSC) lines for their ability to undergo peri-gastrulation-like fate patterning upon BMP4 treatment of geometrically-confined colonies and observed significant heterogeneity in their differentiation propensities along a gastrulation associable and neuralization associable axis. This cell line associated heterogeneity was found to be attributable to endogenous nodal expression, with upregulation of Nodal correlated with expression of a gastrulation-associated gene profile, and Nodal downregulation correlated with a neurulation-associated gene profile expression. We harness this knowledge to establish a platform of pre-neurulation-like fate patterning in geometrically confined hPSC colonies that arises due to a stepwise activation of reaction-diffusion and positional-information. Our work identifies a Nodal signalling dependent switch in peri-gastrulation versus pre-neurulation-associated fate patterning in hPSC cells, provides a technology to robustly assay hPSC differentiation outcomes, and suggests conserved mechanisms of self-organized fate specification in differentiating epiblast and ectodermal tissues.

developmental biology↗