Imaging Session:

Wednesday, September, 28th, 2022: 12:00 pm

Chairs: Raluca Niesner and Anja Hauser

Anna Pascual-Reguant

Activated fibrovascular niches orchestrate immunopathology in severe COVID-19 disease

AG Hauser, Immune Dynamics, Deutsches Rheuma-Forschungszentrum & Charité-Universitätsmedizin Berlin                                                                                                          

Post-acute lung sequelae of COVID-19 are challenging many survivors across the world, yet the mechanisms behind are poorly understood. We have analyzed post-mortem lung and lymph node tissue of COVID-19 cases and non-COVID-related pneumonia controls, by using several state-of-the-art imaging techniques, snRNAseq and spatial transcriptomics. We have stratified the COVID-19 donors based on disease duration and included a prolonged group (7 – 15 weeks of disease duration post-infection), where viral infection had been resolved. Nevertheless, prolonged COVID-19 lungs showed persistent tissue damage along with an increase in lymphocyte infiltration, features that recapitulate those previously reported for Long-COVID.
Our unique spatial approaches reveal that, upon endothelial dysfunction, activated fibrovascular niches emerge as crucial sites, where the molecular mechanisms driving a dysregulated interaction between immune cells and the surrounding tissue occur. We pinpoint two main factors, CCL18 and CCL21, which modulate the local stromal composition and favor endothelial to mesenchymal transition, resulting in the expansion of fibrovascular niches. This, in turn, results in an excessive accumulation of CCR7+ T cells, which become locally imprinted with an exhausted, T follicular helper-like phenotype, as opposed to the sustained T cell activation found in draining lymph nodes. The perpetuation of local chronic inflammation, which is independent of viral persistence, results in the formation of tertiary lymphoid structures as the ultimate manifestation of tissue repurposing.

I am a postdoctoral researcher in the Hauser Lab (Immune Dynamics) at the Deutsches Rheuma-Forschungszentrum and the Charité-Universitätsmedizin Berlin. I received my PhD from the Department of Biology, Chemistry and Pharmacy of Freie Universität Berlin. My research focuses on the in-depth and spatially resolved analysis of local immune responses using state-of-the-art, multiplexing techniques. I am interested in studying tissue niches, both at the protein and transcriptional level, as self-organized functional units that modulate local immunity and dictate tissue homeostasis and disease. I am particularly keen on sharing my enthusiasm for spatial immunology and microscopy with my colleagues and working in interdisciplinary environments.

Ruslan Dimitriev

Probing intestinal organoids oxygenation and metabolism using phosphorescence and fluorescence lifetime imaging microscopies

Tissue Engineering and Biomaterials Research Group, Dept. Human Structure and Repair, Ghent University, Ghent, Belgium

Success in studies of 3D (micro)tissues and organoids is often hampered by their intrinsic heterogeneity and dynamic gradients of biomolecules. Dynamics of cell metabolism, excretion products and O2 are hard to predict and are typically controlled by western blotting, next generation genome, RNA sequencing and traditional antibody-based microscopy methods. My team addresses the challenge of non-destructive quantitative multi-parametric imaging of 3D tissue models by using high-performance nanoparticles, new sensor chemistries and live fluorescence (FLIM) and phosphorescence (PLIM) lifetime imaging microscopies. In my talk I will briefly introduce the methodology of O2 sensing by PLIM and how this methodology can help visualizing live oxygenation of mouse adult stem cell derived intestinal organoids. Using this approach, complemented by the two-photon excited NAD(P)H autofluorescence imaging and other FLIM methods, we found that stem cell metabolism strongly depends on the nutrient availability in the growth medium. Collectively, presented methodology is highly useful for studies of the stem cell niche metabolism in the organoid cultures.

Ruslan I. Dmitriev is an Assistant Professor in the Department of Human Structure and Repair, Ghent University, Ghent, Belgium. He received his Ph.D. in bioorganic chemistry from the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, and continued his postdoctoral training at the University College Cork, Ireland. Before joining Ghent University in 2020, Ruslan was a staring investigator-research fellow at the Metabolic Imaging Group, University College Cork. Dr. Dmitriev’s research interests are in imaging of cellular oxygen gradients and cell metabolism in the three-dimensional tissue models, such as tumor and stem cell-derived spheroids and intestinal organoids, using multi-parameter live cell fluorescence lifetime imaging microscopy (FLIM) and high-performance protein-, bioconjugate- and nanoparticle-based biosensors. Dr. Dmitriev current work aims at developing advanced tools to study cell metabolic requirements in the tumor and stem cell-derived spheroids, intestinal organoids and addressing their heterogeneity using imaging-assisted tissue engineering tools.

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