Study of the potential role of extracellular vesicles in thrombosis associated with paroxysmal nocturnal hemoglobinuria and red blood cell concentrates transfusions

Promoters

Prof. François MULLIER, CHU UCL Namur, Hematology Laboratory

Prof. Jean-Michel DOGNE, UNamur, Department of Pharmacy

Jury

Prof. Sonia BRICHARD, UCL ; Prof. Bernard CHATELAIN, Université Catholique de Louvain CHU UCL Namur ; Prof. Christian CHATELAIN, Université de Namur ; Prof. Fanny DELETTRE, INSERM UMR France ; Prof. Jean-Michel DOGNE, Université de Namur ; Prof. Grigorios GEROTZIAFAS, Inserm U938 France ; Prof. Bernard MASEREEL, Université de Namur ; Prof. François MULLIER, Université Catholique de Louvain CHU UCL Namur ; Prof. Eric VANDENNESTE, UCL.

Summary

The impact of extracellular vesicles (EVs) in the physiopathology of thrombosis has been deeply studied. In paroxysmal nocturnal hemoglobinuria (PNH) patients, thrombosis is the main complication, thereby, it takes a big place in the patient’s management. These patients may also receive red blood cell (RBC) transfusion, however, the procoagulant activity inside the concentrates may be increased due to EV release with storage time.
The first aim of this thesis was the study of the EV responsibility in the pathogenesis of thrombosis in PNH. This purpose has been reached, first, by the analyze of the procoagulant activity in PNH patients at different time of treatment with eculizumab. Besides this study, a cellular model of the disease has been developed to assess the procoagulant activity of EVs released by PNH (-like) cells. The second aim of this thesis was the assessment of procoagulant activity EV-driven inside RBC concentrates through storage time. Two studies have been led in this purpose. For both, whole blood was collected in 12 healthy volunteers and RBC concentrates have been prepared. In the first study, EVs were sampled from packed-RBCs 13 times from day 0 to day 42. The amount and the procoagulant activity EV-driven were measured after 6 months of freezing. The second study was performed by implementing the limitation of the first one (i.e. the high number of samplings and the freezing of samples). In this purpose the samplings were decreased from 13 to 3 and the procoagulant activity has been measured both in fresh and frozen samples.
This work allowed highlighting a decrease of EV amount and activity during eculizumab treatment in PNH patients. In PNH-context, a role of procoagulant leucocytes derived EVs has also been shown thanks to the cellular model. Finally, it also permitted to be reassuring about thrombotic risk after the transfusion of old RBC concentrates.