The thematic developed by of the Team 1 concerns haemostasis and thrombosis. Since the team has joined U698 in 2005, the relations between the vascular wall and the actors of the haemostatic system are at the centre of our studies with the constant will to implement new technologies.

One major axis relates to platelets. We have conducted or participated to studies aimed to determine the mechanisms of their activation, events involved in their production and to analyse the platelet proteome. We are particularly involved in the study of the platelet membrane glycoprotein VI (GPVI), that we have contributed to demonstrate as being the major platelet receptor for collagen. We have documented the key role of GPVI in platelet aggregation on a surface of collagen and of atherosclerosis plaques and in the procoagulant properties of collagen activated platelets. The development of a potentially therapeutic humanized antibody fragment is in progress. The structure function relationship of the receptor has been studied by a strategy combining molecular modelling, phage display, mutagenesis ant the construction of recombinant chimeric proteins. We have been the first to demonstrate the functional implication of the two Ig-like loops of the GPVI extracellular domain in the binding to collagen. We have developed new tools for the diagnosis of platelet disorders on one hand and for therapeutics on the other hand. GPVI appears as an attractive target to develop new antithrombotic drugs acting at the initial phase of thrombus formation, specific of platelets and with a limited bleeding risk. Antagonists of GPVI (monoclonal antibodies and scFvs) have thus been obtained and characterized and patents. The antithrombotic effect of one selected antibody has been analysed in vitro and ex vivo in cynomolgus monkeys. Active recombinant humanized antibody fragments have been obtained patent.

Platelet interactions with the damaged vascular wall are susceptible to change according to the rheological conditions. The reproduction ex vivo of the shear forces generated in arteries is applied on platelets using two different methodological approaches (a viscosimeter and perfusion chambers). GPIb is a main actor in shear induced effects and its interaction with vWF and thrombin has been investigated. The measurement of shear induced platelet aggregation has been validated in the follow up of treatments by anti platelet agents and the molecular mechanisms triggered by the shear are under investigation.

Thrombin is another major thematic of the team. Besides the characterisation of inherited structural abnormalities of prothrombin, we have initiated a new project in order to determine the role of the major tissue inhibitor of thrombin protease nexin 1 (PN-1) in vascular biology. We have demonstrated for the first time that PN-1 is expressed by the vascular smooth muscle cells and that its expression is regulated in pathological conditions. PN-1 protects cells against thrombin and proteases of the fibrinolytic system and PN-1 has additional independent effects on cell adhesion and migration. PN-1 is bound to the cell membrane via glycosaminoglycan and this is particularly relevant on endothelial cells at the level of which we have for the first time identified highly active complexes of PN-1 with the thrombin regulatory protein thrombomodulin.

Besides the study of patients presenting with platelet pathology, the team is involved in several clinical studies in strong relation with the basic research activity. The measurement of platelet activation markers and of the intrinsic potential to generate thrombin are at the centre of studies conducted in collaboration with the cardiology and neurology clinical teams on acute arterial thrombosis (acute coronary syndromeand cerebral infarction). In a prospective study comparing STEMI patient with and without spontaneous coronary reperfusion, persistent occlusion related with markers related to high thrombin and plasmin production but not with markers of platelet activation. Besides, neutrophil activation was found to play a key role in the acute activation of coagulation during severe heatstroke. These activities were supported by several grants including the recurrent unit budget from Inserm and University Paris 7 and grants from the Fondation de France and Fondation pour la Recherche Médicale.