Biology subjects

Boyreau, A.

Publications and source records attributed to Boyreau, A..

7 recordsLinked to original sources

bioRxiv2026

Back-illumination Phase Imaging Enables Nanoscale Drift Stabilization in Non-transparent Biological Tissues

High-resolution optical microscopy enables nanoscale investigation of molecular structures but is challenged by sample drift during long acquisitions, particularly in thick biological tissues where trans-illumination is unpractical. Precise stabilization at the nanoscale is critical for high-resolution imaging techniques like localization microscopy and single particle tracking. Here we introduce a method combining homogenized differential phase contrast imaging with cross-correlation-based analysis to achieve automated, precise 3D drift correction applicable under oblique back-illumination. We demonstrate its effectiveness in fixed and live organotypic brain slices, maintaining focus within tens of nanometers and enabling high-quality nanoscale mapping of extracellular structures based on single particle tracking. Furthermore, we illustrate its application to opaque liver tissues combined with near-infrared single particle tracking. Our label-free approach provides a versatile solution for stabilizing optical microscopes in thick non-transparent tissues, facilitating extended high-resolution imaging across increasingly complex biological samples.

biophysics↗

bioRxiv2025

Reversible superdeformability of hiPSC epithelial cortinoids

Epithelial cortinoids, fluid filled shells formed from induced pluripotent stem cells (iPSCs), must accommodate large deformations during growth and morphogenesis. Using inflation-deflation assays and high-resolution imaging, we find that these fluid-filled shells are weakly-pressurized and achieve extreme deformability through reversible soft modes of deformation accommodated by the cytoskeleton. We show that cytoskeletal elements such as actin localized along lateral cell edges undergo tilt and bend instabilities that buffer mechanical load by decoupling apico-basal stretching from lateral extension. These reversible instabilities act as elastic safety valves, permitting large shape changes without loss of epithelial hydraulic and topological integrity. A minimal theoretical and computational model demonstrates how tilt and bend reduce effective resistance to radial thinning and explains the observed pressure-strain softening. Thus, iPSC shells exploit reversible cytoskeletal instabilities as mechanical buffers, enabling robust tolerance of large deformations in developing epithelia.

biophysics↗

bioRxiv2025

A versatile microfluidic extrusion-based hydrogel platform for self-organization and long-term maintenance of engineered 3D lymphatic endothelium

Lymphatic endothelium is essential for interstitial fluid drainage, immune surveillance, and macromolecular transport. Existing in vitro models that accurately recapitulate its three-dimensional structure, barrier properties, and long-term stability are still limited. In this study, we propose a robust, adaptable, and scalable platform designed to generate engineered three-dimensional lymphatic endothelium using primary human dermal lymphatic endothelial cells (HDLECs). This system combines microfluidic extrusion-based fabrication allowing precise control of the tubular geometry with custom-optimized extracellular matrix-derived hydrogel. The capability to tune dimensions enables the creation of constructs that encompass physiologically relevant size ranges. Through a systematic matrix screen, we identified a unique four-component formulation--gelatin, Matrigel, hyaluronic acid, and fibrinogen--that supports the rapid self-assembly of HDLECs into stable, lumen-forming monolayers within one week. These engineered structures maintain viability and structural integrity for a minimum of 30 days under static culture conditions. Functional permeability assays demonstrated selective tracer uptake characteristics of lymphatic transport. Comparative studies with blood vascular endothelial cells indicate that the proposed platform preserves maintenance of lineage-specific expression profiles, junctional organization, and permeability properties under identical fabrication parameters. Altogether, this approach offers a reproducible and controlled system for studying three-dimensional endothelial architecture, transport mechanisms, and extracellular matrix remodeling across diverse endothelial phenotypes, thereby addressing a pivotal gap in the modeling of lymphatic vasculature. HighlightsO_LIA microfluidic extrusion platform allows primary human lymphatic endothelial cells to self-organize into 3D hollow tubes. C_LIO_LIThe internal dimensions of the hybrid cell/hydrogel constructs can be precisely controlled by tuning the flow rates. C_LIO_LIA custom-defined four-component extracellular matrix provides essential biochemical cues for stable monolayer formation and for the in vitro organization of lymphatic endothelial vessels. C_LIO_LIMatrix composition significantly influences cell proliferation and migration, thereby impacting on the spatial arrangement of the tissue. C_LIO_LIThe three-dimensional lymphatic tissue configuration sustains cell viability, consistent expression of lineage-specific markers, and barrier function which lasts for at least 30 days. C_LIO_LIThe system maintains morphological and functional properties not only for lymphatic endothelial cells, but also for blood endothelial cells in long-term culture conditions. C_LI

bioengineering↗

bioRxiv2024

Pheno-morphological screening and acoustic sorting of 3D multicellular aggregates using drop millifluidics

Three-dimensional multicellular aggregates like organoids and spheroids have become essential tools to study the biological mechanisms involved in the progression of diseases. In cancer research, they are now widely used as in vitro models for drug testing. However, their analysis still relies on tedious manual procedures, which hinders their routine use in large-scale biological assays. Here, we introduce a novel drop millifluidic approach to screen and sort large populations containing over one thousand multicellular aggregates. Our system utilizes real-time image processing to detect pheno-morphological traits in cellular aggregates. They are then encapsulated in millimetric drops, actuated on-demand using the acoustic radiation force. We demonstrate the performance of our system by sorting spheroids with uniform sizes from a heterogeneous population, and by isolating organoids from spheroids with different phenotypes. We anticipate that this work offers the potential to standardize drug testing on multicellular aggregates, which promises accelerated progress in biomedical research.

bioengineering↗

bioRxiv2024

zIncubascope: long-term quantitative imaging of multi-cellular assemblies inside an incubator

Recent advances in bioengineering have made it possible to develop increasingly complex biological systems to recapitulate organ functions as closely as possible in vitro. Monitoring the assembly and growth of multi-cellular aggregates, micro-tissues or organoids and extracting quantitative information is a crucial but challenging task required to decipher the underlying morphogenetic mechanisms. We present here an imaging platform designed to be accommodated inside an incubator which provides high-throughput monitoring of cell assemblies over days and weeks. We exemplify the capabilities of our system by investigating human induced pluripotent stem cells (hiPSCs) enclosed in spherical capsules, hiPSCs in tubular capsules and yeast cells in spherical capsules. Combined with a customized pipeline of image analysis, our solution provides insight into the impact of confinement on the morphogenesis of these self-organized systems.

bioengineering↗

bioRxiv2024

Identification of early-stage liver fibrosis by modifications in the interstitial space diffusive microenvironment using fluorescent single-walled carbon nanotubes

During liver fibrosis, recurrent hepatic injuries lead to accumulation of collagen and other extracellular matrix components in the interstitial space, ultimately disrupting liver functions. Early stages of liver fibrosis may be reversible, but opportunities for diagnosis at these stages are currently limited. Here, we show that the alterations of the interstitial space associated with fibrosis can be probed by tracking individual fluorescent single-walled carbon nanotubes (SWCNTs) diffusing in that space. In a mouse model of early liver fibrosis, we find that nanotubes generally explore elongated areas, whose length decrease as the disease progresses even in regions where histopathological examination does not reveal fibrosis yet. Furthermore, this decrease in nanotube mobility is a purely geometrical effect, as the instantaneous nanotube diffusivity stays unmodified. This work establishes the promise of SWCNTs both for the diagnosis of liver fibrosis at an early stage, and for more in-depth studies of the biophysical effects of the disease.

cancer biology↗

bioRxiv2021

The Incubascope : a simple, compact and large field of view microscope for long-term imaging inside an incubator

Optical imaging has rapidly evolved in the last decades. Sophisticated microscopes allowing optical sectioning for 3D imaging or sub-diffraction resolution are available. Due to price and maintenance issues, these microscopes are often shared between users in facilities. Consequently, long term access is often prohibited and does not allow to monitor slowly evolving biological systems or to validate new models like organoids. Preliminary coarse long-term data that do not require acquisition of terabytes of high-resolution images are important as a first step. By contrast with expansive all-in-one commercialized stations, standard microscopes equipped with incubator stages offer a more cost-effective solution despite imperfect long run atmosphere and temperature control. Here, we present the Incubascope, a custom-made compact microscope that fits into a table-top incubator. It is cheap and simple to implement, user-friendly and yet provides high imaging performances. The system has a field of view of 5.5 x 8 mm2, a 3 m resolution, a 10 frames/second acquisition rate, and is controlled with a Python-based graphical interface. We exemplify the capabilities of the Incubascope on biological applications such as the hatching of Artemia salina eggs, the growth of the slime mold Physarum polycephalum and of encapsulated spheroids of mammalian cells.

biophysics↗