Gaspard Pardon, Head of Platform on Google Scholar
EPFL Core facilities publications:
2024
Tracking single hiPSC-derived cardiomyocyte contractile function using CONTRAX an efficient pipeline for traction force measurement
Cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CMs) are powerful in vitro models to study the mechanisms underlying cardiomyopathies and cardiotoxicity. Quantification of the contractile function in single hiPSC-CMs at high-throughput and over time is essential to disentangle how cellular mechanisms affect heart function. Here, we present CONTRAX, an open-access, versatile, and streamlined pipeline for quantitative tracking of the contractile dynamics of single hiPSC-CMs over time. Three software modules enable: parameter-based identification of single hiPSC-CMs; automated video acquisition of >200 cells/hour; and contractility measurements via traction force microscopy. We analyze >4,500 hiPSC-CMs over time in the same cells under orthogonal conditions of culture media and substrate stiffnesses; +/− drug treatment; +/− cardiac mutations. Using undirected clustering, we reveal converging maturation patterns, quantifiable drug response to Mavacamten and significant deficiencies in hiPSC-CMs with disease mutations. CONTRAX empowers researchers with a potent quantitative approach to develop cardiac therapies.
Nature communications. 2024. Vol. 15, num. 1. DOI : 10.1038/s41467-024-49755-3.Investigation of the polyphenol load in the OMIC range in biological matrices with liquid chromatography coupled with mass spectrometry
It is well known that for analytic cost functions, gradient flow trajectories have finite length and converge to a single critical point. The gradient conjecture of R. Thom states that, again for analytic cost functions, whenever the gradient flow trajectory converges, the limit of its unit secants exists. One might think that already the convergence of the gradient flow trajectory to a critical point is enough to ensure that the unit secants have a limit, but this does not hold-the gradient conjecture is to a certain extend sharp. We provide a counterexample in case of the missing analyticity assumption, that is a smooth (non-analytic) cost function f, where the limit of unit secants does not exist. In addition, f satisfies even a strong geometric length-distance convergence property.
Ernahrung. 2024. Vol. 48, num. 5, p. 33 – 36.Cell Architecture and Dynamics of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes (hiPSC-CMs) on Hydrogels with Spatially Patterned Laminin and N-Cadherin
Published by American Chemical Society.Controlling cellular shape with micropatterning extracellular matrix (ECM) proteins on hydrogels has been shown to improve the reproducibility of the cell structure, enhancing our ability to collect statistics on single-cell behaviors. Patterning methods have advanced efforts in developing human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) as a promising human model for studies of the heart structure, function, and disease. Patterned single hiPSC-CMs have exhibited phenotypes closer to mature, primary CMs across several metrics, including sarcomere alignment and contractility, area and aspect ratio, and force production. Micropatterning of hiPSC-CM pairs has shown further improvement of hiPSC-CM contractility compared to patterning single cells, suggesting that CM-CM interactions improve hiPSC-CM function. However, whether patterning single hiPSC-CMs on a protein associated with CM-CM adhesion, like N-cadherin, can drive similar enhancement of the hiPSC-CM structure and function has not been tested. To address this, we developed a novel dual-protein patterning process featuring covalent binding of proteins at the hydrogel surface to ensure robust force transfer and force sensing. The patterns comprised rectangular laminin islands for attachment across the majority of the cell area, with N-cadherin “end caps” to imitate CM-CM adherens junctions. We used this method to geometrically control single-cell CMs on deformable hydrogels suitable for traction force microscopy (TFM) to observe cellular dynamics. We seeded α-actinin::GFP-tagged hiPSC-CMs on dual-protein patterned hydrogels and verified the interaction between hiPSC-CMs and N-cadherin end caps via immunofluorescent staining. We found that hiPSC-CMs on dual-protein patterns exhibited higher cell area and contractility in the direction of sarcomere organization than those on laminin-only patterns but no difference in sarcomere organization or total force production. This work demonstrates a method for covalent patterning of multiple proteins on polyacrylamide hydrogels for mechanobiological studies. However, we conclude that N-cadherin only modestly improves single-cell patterned hiPSC-CM models and is not sufficient to elicit increases in contractility observed in hiPSC-CM pairs.
ACS Applied Materials and Interfaces. 2024. Vol. 17, p. 174 – 186. DOI : 10.1021/acsami.4c11934.