ADVANCED SCIENCE, 2019
Photoactivatable Hsp47: A Tool to Regulate Collagen Secretion and Assembly
Collagen is the most abundant structural protein in mammals and is crucial for the mechanical integrity of tissues. Hsp47, an endoplasmic reticulum resident collagen‐specific chaperone, is involved in collagen biosynthesis and plays a fundamental role in the folding, stability, and intracellular transport of procollagen triple helices. This work reports on a photoactivatable derivative of Hsp47 that allows regulation of collagen biosynthesis within mammalian cells using light. … Read the scientific paper
Different integrins mediate haptotaxis of T lymphocytes towards either lower or higher adhesion zones
Guidance of cells by molecules anchored on a substrate, known as haptotaxis, is arguably crucial in development, immunology and cancer, however the exact cues and mechanisms driving cell orientation in vivo are hardly identified. Adhesive haptotaxis has been described in the case of mesenchymatous cells that develop strong pulling forces with their substrates and orient via a tug of war mechanism, a competition between cells pulling edges. In the case of amoeboid cells that migrate with minimal interaction with their substrate, existence of adhesive haptotaxis remains unclear. … Read the scientific paper
Mammalian Amoeboid Swimming is propelled by molecular and not protrusion-based paddling in Lymphocytes
Mammalian cells developed two main migration modes. The slow mesenchymatous mode, like fibroblasts crawling, relies on maturation of adhesion complexes and actin fiber traction, while the fast amoeboid mode, observed exclusively for leukocytes and cancer cells, is characterized by weak adhesion, highly dynamic cell shapes, and ubiquitous motility on 2D and in 3D solid matrix. In both cases, interactions with the substrate by adhesion or friction are widely accepted as a prerequisite for mammalian cell motility, which precludes swimming. … Read the scientific paper
Forces and constraints controlling podosome assembly and disassembly
Podosomes are a singular category of integrin-mediated adhesions important in the processes of cell migration, matrix degradation, and cancer cell invasion. Despite a wealth of biochemical studies, the effects of mechanical forces on podosome integrity and dynamics are poorly understood. Here, we show that podosomes are highly sensitive to two groups of physical factors. First, we describe the process of podosome disassembly induced by activation of myosin- IIA filament assembly. … Read the scientific paper
PLOS One, 2018
Live nanoscopic to mesoscopic topography reconstruction with an optical microscope for chemical and biological samples
Macroscopic properties of physical and biological processes like friction, wetting, and adhesion or cell migration are controlled by interfacial properties at the nanoscopic scale. In an attempt to bridge simultaneously investigations at different scales, we demonstrate here how optical microscopy in Wet-Surface Ellipsometric Enhanced Contrast (Wet-SEEC) mode offers imaging and measurement of thin films at solid/liquid interfaces in the range 1–500 nm with lateral optical resolution. … Read the scientific paper
Nano Lett, 2018
Optical magnetometry of single biocompatible micromagnets for quantitative magnetogenetic and magnetomechanical assays
The mechanical manipulation of magnetic nanoparticles is a powerful approach to probe and actuate biological processes in living systems. Implementing this technique in high-throughput assays can be achieved using biocompatible micomagnet arrays. Yet, the magnetic properties of these arrays are usually indirectly inferred from simulations or Stokes drag measurements, leaving unresolved questions about the actual profile of the magnetic fields at the micrometer scale and the exact magnetic forces that are applied. … Read the scientific paper
Extracellular matrix stiffness regulates force transmission pathways in multicellular ensembles of human airway smooth muscle cells.
For an airway or a blood vessel to narrow, there must be a connected path that links the smooth muscle (SM) cells with each other, and transmits forces around the organ, causing it to constrict. Currently, we know very little about the mechanisms that regulate force transmission pathways in a multicellular SM ensemble. Here, we used extracellular matrix (ECM) micropatterning to study force transmission in a two-cell ensemble of SM cells. … Read the scientific paper
The cytoskeleton as a smart composite material: A unified pathway linking microtubules, myosin-II filaments and integrin adhesions
The interrelationship between microtubules and the actin cytoskeleton in mechanoregulation of integrin-mediated adhesions is poorly understood. Here, we show that the effects of microtubules on two major types of cell-matrix adhesions, focal adhesions and podosomes, are mediated by KANK family proteins connecting the adhesion protein talin with microtubule tips. Both total microtubule disruption and microtubule uncoupling from adhesions by manipulations with KANKs trigger a massive assembly of myosin-IIA filaments. … Read the scientific paper
Tailoring 3D cell culture templates with common hydrogels.
3D cell culture aims at reconciliating the simplicity of in vitro models with the human like properties encountered in vivo. Soft permeable hydrogels have emerged as user-friendly materials to grow cells in more physiological conditions. With the intent on turning these homogeneous substrates into biomimetic templates, we introduce a generic solution compatible with the most biologically relevant and often frail materials. Here we take control of the chemical environment driving generic radical reactions to craft common gels with patterned light. … Read the scientific paper
Adv Biosys, 2018
A new approach to design artificial 3D micro-niches with combined chemical, topographical and rheological cues
The in vitro methods to recapitulate environmental cues around cells are usually optimized to test a specific property of the environment (biochemical nature or the stiffness of the extra cellular matrix (ECM), or nanotopography) for its capability to induce defined cell behaviors (lineage commitment, migration). Approaches that combine different environmental cues in 3D to assess the biological response of cells to the spatial organization of different biophysical and biochemical cues are growingly being developed. … Read the scientific paper
Lab Chip, 2018
In situ photopatterning of pressure-resistant hydrogel membranes with controlled permeabilities in PEGDA microfluidic channels.
We report the fabrication of highly permeable membranes in poly(ethylene glycol) diacrylate (PEGDA) channels, for investigating ultra- or micro-filtration, at the microfluidic scale. More precisely, we used a maskless UV projection setup to photopattern PEG-based hydrogel membranes on a large scale (mm–cm), and with a spatial resolution of a few microns. We show that these membranes can withstand trans-membrane pressure drops of up to 7 bar without any leakage, thanks to the strong anchoring of the hydrogel to the channel walls. … Read the scientific paper
Collagen assembly and turnover imaged with a CRISPR-Cas9 engineered Dendra2 tag
Electron microscopy has been the gold standard for studying collagen networks but dynamic information on how cells synthesise the networks has been lacking. Live imaging methods have been unable to distinguish newly-synthesised fibrils from pre-existing fibrils and intracellular collagen. Here, we tagged endogenous collagen-I using CRISPR-Cas9 with photoswitchable Dendra2 and demonstrate live cells synthesising, migrating on, and interacting with, collagen fibrils. … Read the scientific paper
Hum Mol Genet. 2016
Altered microtubule dynamics and vesicular transport in mouse and human MeCP2- deficient astrocytes.
Rett syndrome (RTT) is a rare X-linked neurodevelopmental disorder, characterized by normal post-natal development followed by a sudden deceleration in brain growth with progressive loss of acquired motor and language skills, stereotypic hand movements and severe cognitive impairment. Mutations in the methyl-CpG-binding protein 2 (MECP2) cause more than 95% of classic cases. … Read the scientific paper
Adv Mater. 2016
Multiprotein Printing by Light-Induced Molecular Adsorption.
Light-induced molecular adsorption of proteins (LIMAP) allows for quantitative sub-micrometer-resolution printing of multiple biomolecules. Surface-bound gradients are patterned within minutes over an entire glass cover-slip. LIMAP is used to perform selective immuno-assays, to dynamically control the adhesion of individual cells, and to achieve hierarchical co-cultures instrumental for tissue engineering. Read the scientific paper