Biology subjects

Galland, F.

Publications and source records attributed to Galland, F..

4 recordsLinked to original sources

bioRxiv2023

Extended-depth of field random illumination microscopy, EDF-RIM, provides super-resolved projective imaging

The ultimate aim of fluorescence microscopy is to achieve high-resolution imaging of increasingly larger biological samples. Extended depth of field presents a potential solution to accelerate imaging of large samples when compression of information along the optical axis is not detrimental to the interpretation of images. We have implemented an Extended Depth of Field (EDF) approach in a Random Illumination Microscope (RIM). RIM uses multiple speckled illuminations and variance data processing to double the resolution. It is particularly adapted to the imaging of thick samples as it does not require the knowledge of illumination patterns. We demonstrate highly-resolved projective images of biological tissues and cells. Compared to a sequential scan of the imaged volume with conventional 2D-RIM, EDF-RIM allows an order of magnitude improvement in speed and light dose reduction, with comparable resolution. As the axial information is lost in an EDF modality, we propose a method to retrieve the sample topography for samples that are organized in cell sheets.

bioengineering↗

bioRxiv2022

Optimizing sampling for surface localization in 3D-scanning microscopy

3D-scanning fluorescence imaging of living tissue is in demand for less phototoxic acquisition process. For the imaging of biological surfaces, adaptive and sparse scanning schemes have been proven to efficiently reduce the light dose by concentrating acquisitions around the surface. In this paper, we focus on optimizing the scanning scheme at constant photon budget, when the problem is to estimate the position of a biological surface whose intensity profile is modeled as a Gaussian shape. We propose an approach based on the Cramer-Rao Bound to optimize the positions and number of scanning points, assuming signal-dependant Gaussian noise. We show that the optimization problem can be reduced to a few parameters, allowing to define quasi-optimal acquisition strategies, first when no prior knowledge on the surface location is available, and then when the user has a prior on this location.

biophysics↗

bioRxiv2022

Type III interferons induce pyroptosis in gut epithelial cells and delay tissue restitution upon acute intestinal injury.

Tissue damage and repair are hallmarks of the inflammatory process. Despite a wealth of information focused on the mechanisms that govern tissue damage, mechanistic insight on how inflammatory immune mediators affect the restitution phase is lacking. Here, we investigated how interferons influence tissue restitution after damage of the intestinal mucosa driven by inflammatory or physical injury. We found that type III, but not type I, interferons serve a central role in the restitution process. Type III interferons induce the upregulation of ZBP1, caspase activation, and cleavage of gasdermin C, and drive epithelial cell death by pyroptosis, thus delaying tissue restitution. We also found that this pathway is transcriptionally regulated in IBD patients. Our findings highlight a new molecular signaling cascade initiated by the immune system that affects the outcome of the immune response by delaying tissue repair and that may have important implications for human inflammatory disorders.

immunology↗

bioRxiv2022

Adaptive scans allow targeted cell-ablations on curved cell sheets

The mechanical actuation of cells by active forces from the cytoskeleton drives tissue morphogenesis. To understand these forces, multicellular laser dissection has become an essential tool for severing tissue locally and inferring tension from the recoil of surrounding structures. However, conventional laser dissection is limited by 2D steering, which is inadequate for embryos and developing tissues that are intrinsically 3D structures. In this study, we introduce a flexible near-infrared (NIR) fs-pulsed laser dissection system that allows for dissection trajectories to proceed in 3D and adapt to the curved surfaces of cell sheets, which are prominent structures in embryos. Trajectories are computed through an unsupervised search for the surface of interest. Using this technique, we demonstrate sectioning of multicellular domains on curved tissue, which was not possible with regular NIR laser scanning. We apply the developed strategy to map mechanical stresses in the imaginal disc of the developing Drosophila wing. Our targeted, adaptive scans can be used in other non-linear processes, such as two-photon fluorescence imaging or optogenetics. Overall, this new laser dissection system offers an innovative solution for studying complex 3D structures and their mechanical properties.

biophysics↗