Endothélium | EPFL Graph Search

vignette|Comparaison de l'endothélium vasculaire sain et dysfonctionnel. L'endothélium vasculaire est la couche la plus interne des vaisseaux sanguins, celle en contact avec le sang. Les dégradations pathologiques de l'endothélium sont dites « endothélites » ou endothéliites ( Kérato-endothélite, quand le phénomène se déclare dans l’œil, à la suite d'un herpès, un zona ophtalmique, un lupus, une piqure d'abeille, une greffe de cornée ou kératoplastie...). L'endothélite est une réponse immunitaire de type inflammatoire : les vaisseaux sanguins deviennent alors inflammés et un œdème des tissus environnants peut survenir (y compris du tissu conjonctif) se traduisant notamment par une irritation et une douleur pour le patient. Dans la cornée, une endothélite peut entraîner une perte irréversible de la vision. Les oreillons et certains virus (ex : cytomégalovirus, coronavirus) peuvent, dans certaines circonstances, en être des causes.Des facteurs aggravant ou prédisposant à un dysfonct

CO-REGULATION OF ENDOTHELIAL AND MYOGENIC CELL FATES THROUGH INTERCELLULAR CROSSTALK IN SKELETAL MUSCLE

Umji Lee

Skeletal muscle is one of the most dynamic organs in the human body, which has a vigorous potential to regenerate and adapt to environmental changes. Depending on environments, skeletal muscle enables essential life activities to survive by controlling movement and metabolism. The functional and structural adaptations of skeletal muscle crosstalk with other physiological systems enabling nutrition and oxygen delivery, and the elimination of metabolic waste products. The work in this dissertation focuses on the intercellular signals produced by myogenic cells to dynamically remodel skeletal muscle during exercise or muscle repair, and the reciprocal signals from the local niche and the systemic environment that regulate myogenic cell fate and metabolism according to physiological needs. This complex crosstalk is dissected in three specific chapters where we study the crosstalk of myogenic cells with endothelial cells and the vasculature to coordinate local niche interactions and systemic crosstalks. First, we demonstrate that an exercise-induced myokine called apelin is produced by muscle fiber and mediates intercellular signaling to endothelial cells through the apelin receptor. In addition, through a yeast one-hybrid screen of transcription factor binding to the apelin promoter, we identified the myogenic transcription factor TEA domain family member 1 (Tead1) as a regulator of Apln transcription. We observed via single-cell transcriptomic analysis of regenerating skeletal muscle that Aplnr (Apelin receptor) is enriched in muscle endothelial cells, whereas Tead1 is enriched in myogenic cells. Myofiber-specific over-expression of Tead1 suppresses apelin secretion at the whole-body level, and apelin secretion via Tead1 knock-down in muscle cells stimulates endothelial cell proliferation in co-cultures. By showing that apelin peptide supplementation in vivo enhances endothelial cell expansion following muscle injury, we conclude that paracrine crosstalk in which apelin secretion controlled by Tead1 in myogenic cells influences endothelial remodeling during skeletal muscle repair. Secondly, we show how tissue-resident support cells affect muscle progenitor activation in different metabolic environments. Skeletal muscle progenitors (SKMP) reside in close proximity to supportive cell types in the stem cell niche and dynamically interact with each other to adapt to environmental changes. Here, we studied how different niche cell types affect SKMPs in response to glycemic levels. Using co-cultures of SKMPs and niche cells, we discovered that endothelial cells synergistically enhance SKMP proliferation in a low glycemic environment, while fibroblasts and macrophages had no effect. We observed that the crosstalk between SKMPs and endothelial cells was mediated by direct cell-cell contacts independent of soluble paracrine signals. Transcriptomic analysis revealed that the endothelial alpha/beta hydrolase N-Myc Downstream Regulated1 (NDRG1) is induced by a low glycemic environment and is associated with biological adhesion. SKMPs co-cultured with Ndrg1 knock-down endothelial cells lose their synergistic functional relationship in response to glucose levels. Therefore, our findings suggest that Ndrg1 is a key mediator of endothelial cell-mediated glycemic control of SKMPs and provides a link between systemic energy levels and the skeletal muscle stem cell niche. Lastly, I developed intravital imaging to monitor muscle stem cells and vasculature.

EPFL2021

Proteins interacting with PfEMP1 in P. falciparum infected erythrocyte

Damien Jacot

During infection in humans, P. falciparum invades and refurbishes the red blood cells (RBCs) in order to persist and proliferate. Parasite survival depends on expression of a parasite encoded cytoadherence ligand at the surface of the infected RBC called PfEMP1 (P. falciparum erythrocyte membrane protein 1). PfEMP1 comprises a N-terminal extracellular part, which mediates binding to receptors at the host endothelium. It also contains a C-terminal part which is conserved among all PfEMP1 molecules. This acidic terminal segment (ATS) anchors PfEMP1 to the membrane of infected RBCs and has a role for trafficking. To bring proteins to the RBC surface, P. falciparum builds its own trafficking machinery de novo since the erythrocytes do not contain secretory organelles. These new structures include parasite derived compartments called Maurer's clefts (MCs) located at the RBC periphery. The resident MCs protein MAHRP1 (membrane-associated histidine-rich protein 1) has been shown to be critical for PfEMP1 trafficking. A MAHRP1 KO strain had no PfEMP1 on the RBC surface but accumulated PfEMP1 within the parasite. MAHRP1 is a 28.9kDa protein with 249 amino acids containing a N-terminal, a transmembrane, and a C-terminal domain comprising histidine-rich repeats. To re-establish PfEMP1 trafficking, the MAHRP1 KO parasite line was complemented with various truncated HA-tagged fragments of MAHRP1. Immunofluorescent assays (IFAs) showed that the Cterminal domain with the histidine-rich repeats was not essential for PfEMP1 trafficking.

{MAHRP1}_{1-130}

and

{MAHRP1}_{1-169}

were exported to MCs and restored trafficking of PfEMP1. Shorter MAHRP1 fragments were not exported to MCs and PfEMP1 transport remained impaired. New transfection constructs were designed including the C-terminal part to identify important domain(s) of MAHRP1 for PfEMP1 trafficking. To identify other proteins interacting with PfEMP1, the ATS domain of PfEMP1 was recombinantly expressed and used in pull-down experiments. In these experiments using parasite lysates, PF14_0377 was identified as a potential interaction partner. This protein has been described as putative, vesicular-associated membrane protein. To subsequently assess the interaction(s) and the localization(s), PF14_0377 was cloned and transfected in 3D7 for IFAs. Due to time restrictions all these new transfectants could not be analyzed completely

2009

Standardization and Validation of Fluorescence-Based Quantitative Assay to Study Human Platelet Adhesion to Extracellular-Matrix in a 384-Well Plate

François Cuenot, Cindy Marie Elodie Khawand, Tom Yohan Abraham Lachkar, Augusto Martins Lima, Damian Salim Saint Auguste, Nikolaos Stergiopulos

Platelets play a crucial role in the immunological response and are involved in the pathological settings of vascular diseases, and their adhesion to the extracellular matrix is important to bring leukocytes close to the endothelial cells and to form and stabilize the thrombus. Currently there are several methods to study platelet adhesion; however, the optimal parameters to perform the assay vary among studies, which hinders their comparison and reproducibility. Here, a standardization and validation of a fluorescence-based quantitative adhesion assay to study platelet-ECM interaction in a high-throughput screening format is proposed. Our study confirms that fluorescence-based quantitative assays can be effectively used to detect platelet adhesion, in which BCECF-AM presents the highest sensitivity in comparison to other dyes.

2020