Thrombosis | EPFL Graph Search

Thrombosis (from Ancient Greek θρόμβωσις thrómbōsis "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thrombocytes) and fibrin to form a blood clot to prevent blood loss. Even when a blood vessel is not injured, blood clots may form in the body under certain conditions. A clot, or a piece of the clot, that breaks free and begins to travel around the body is known as an embolus. Thrombosis may occur in veins (venous thrombosis) or in arteries (arterial thrombosis). Venous thrombosis (sometimes called DVT, deep vein thrombosis) leads to a blood clot in the affected part of the body, while arterial thrombosis (and, rarely, severe venous thrombosis) affects the blood supply and leads to damage of the tissue supplied by that artery (ischemia and necrosis). A piece of either an arterial or a venous thrombus can break off as an embolu

Thrombosis efficacy induced by photodynamic therapy using different photosensitizers

Bernadette Pegaz-Toquet

Various human pathologies, such as cancers or, notably, exudative age-related macular degeneration (AMD), are characterized by an abnormal vascular proliferation (angiogenesis), which in the case of this type of AMD, can rapidly lead to blindness if no countermeasures are taken. In the past few years, it has become possible to stop - or at least to notably slow down - the evolution of AMD, by applying treatments based on photodynamic therapy (PDT), whereby, through the action of a molecule acting as photosensitizer (PS) which is targeted preferentially to the choroidal neovessels (CNV), the effects of this abnormal angiogenesis are stopped by provoking the closure of the neovessels. In particular, the PDT group at EPF-Lausanne has, in the past, already tested on the model of the chick embryo chorioallantoic membrane (known as the CAM model) several PSs of potential interest as substitute to the product currently considered as standard (Visudyne® , itself co-developed in this group) for the treatment of the CNV associated with AMD. The aim of this thesis was to study new molecules and/or formulations, potentially suitable as substitutes to the current photodynamic treatment of AMD, while diminishing its negative side-effects: general phototoxicity due to diffusion of the product out of the vasculature and further lack of selectivity leading to (undesirable) partial occlusion of the normal vasculature. In order to enable extrapolation and comparison of the results obtained, we have focused our attention on vascular effects only and administered the tested PSs under essentially similar conditions (formulation in DMSO; same delivery system through biodegradable nanoparticles built with the same polymer). In addition, the same animal model (the CAM model) was used throughout the entire study, the formulations being administered by intravenous injection. This model, importantly, allows for an easy and real-time semi-quantitative visualisation and recording of the vascular effects of a PS induced during a PDT session. In the first part of this work, we demonstrate that the tetra-phenylporphyrin molecule, when formulated in nanoparticles based on poly(D, L - lactic acid, of well defined size (ca. 200 nm or less) is a very interesting PS-candidate potentially suitable as a replacement of the currently used one. We show that inclusion of this PS in nanoparticles notably reduces the PDT's general phototoxicity. We believe therefore that this PS would deserve more thorough pre-clinical studies, on an animal model closer to the human case (for example, Ryan's model). The second part of this thesis aimed at elaborating a strategy allowing, in due time, for an improved selectivity of occlusion of the neovasculature, said strategy aiming at an active targeting of neovessels. Recently, a number of possible biochemical targets have been identified, including the so-called ανβ3 receptors, which are highly expressed at the level of the neovessels' endothelial cells. Our approach consisted in coupling a fluorescent molecule (fluorescein, easily visualized by epi-microscopy) to a protein (a kistrin) which contains the RGD peptide sequence, known for its affinity for the ανβ3 receptors. We have thus been able to demonstrate that the kistrin was effectively linked to these receptors and, therefore, that active targeting of the neovessels had indeed taken place. A complete proof of this concept by realizing the coupling of this kistrin with a PS molecule will be the next step in this research.

EPFL2007

The Angiotensin-Converting Enzyme 2/Angiotensin-(1-7)/Mas receptor axis: A potential target for treating thrombotic diseases

Danielle Gomes Passos Silva, Nikolaos Stergiopulos

Despite many therapeutic advances leading to increasingly effective drug treatments, thrombotic events (such as ischaemic stroke, pulmonary embolism, deep venous thrombosis and acute myocardial infarction) still represent a major worldwide cause of morbidity and mortality. Remarkable effort has been made to identify new drug targets. There is growing evidence indicating that the recently described counter-regulator axis of the renin-angiotensin system (RAS), composed of Angiotensin-Converting Enzyme 2 (ACE2), Angiotensin-(1-7) and the Mas receptor, has protective effects against thrombosis. In addition, it could be considered as a promising target for treating or preventing this disease. In this narrative review, we focused on the recent findings of the role of the ACE2/Angiotensin-(1-7)/Mas axis on the haemostatic process and its therapeutic potential.

Schattauer Gmbh-Verlag Medizin Naturwissenschaften2012

A Machine-Generated View of the Role of Blood Glucose Levels in the Severity of COVID-19

Francesco Casalegno, Jay Coggan, Cyrille Pierre Henri Favreau, Pierre-Alexandre Fonta, Anna-Kristin Kaufmann, Daniel Keller, Samuel Claude Kerrien, Emmanuelle Logette, Henry Markram, Enrico Scantamburlo, Mohameth François Sy

SARS-CoV-2 started spreading toward the end of 2019 causing COVID-19, a disease that reached pandemic proportions among the human population within months. The reasons for the spectrum of differences in the severity of the disease across the population, and in particular why the disease affects more severely the aging population and those with specific preconditions are unclear. We developed machine learning models to mine 240,000 scientific articles openly accessible in the CORD-19 database, and constructed knowledge graphs to synthesize the extracted information and navigate the collective knowledge in an attempt to search for a potential common underlying reason for disease severity. The machine-driven framework we developed repeatedly pointed to elevated blood glucose as a key facilitator in the progression of COVID-19. Indeed, when we systematically retraced the steps of the SARS-CoV-2 infection, we found evidence linking elevated glucose to each major step of the life-cycle of the virus, progression of the disease, and presentation of symptoms. Specifically, elevations of glucose provide ideal conditions for the virus to evade and weaken the first level of the immune defense system in the lungs, gain access to deep alveolar cells, bind to the ACE2 receptor and enter the pulmonary cells, accelerate replication of the virus within cells increasing cell death and inducing an pulmonary inflammatory response, which overwhelms an already weakened innate immune system to trigger an avalanche of systemic infections, inflammation and cell damage, a cytokine storm and thrombotic events. We tested the feasibility of the hypothesis by manually reviewing the literature referenced by the machine-generated synthesis, reconstructing atomistically the virus at the surface of the pulmonary airways, and performing quantitative computational modeling of the effects of glucose levels on the infection process. We conclude that elevation in glucose levels can facilitate the progression of the disease through multiple mechanisms and can explain much of the differences in disease severity seen across the population. The study provides diagnostic considerations, new areas of research and potential treatments, and cautions on treatment strategies and critical care conditions that induce elevations in blood glucose levels.

FRONTIERS MEDIA SA2021

Thrombosis efficacy induced by photodynamic therapy using different photosensitizers

Bernadette Pegaz-Toquet

EPFL2007

A Machine-Generated View of the Role of Blood Glucose Levels in the Severity of COVID-19

FRONTIERS MEDIA SA2021