FVIII interacts with cell surface to regulate endothelial cell functionality

Haemophilia A (HA) is a rare bleeding disorder caused by factor 8 (F8) mutations. Clinical manifestations are spontaneous bleedings that primarily consist of hemarthrosis and intracranial haemorrhages. To date, the impairment of vessel stability in HA patients and the correlation between FVIII and endothelial functionality is poorly understood. Here we show that FVIII plays a role in endothelial cell functionality. Blood Outgrowth endothelial cells (BOECs) knockout generated by CRISPR/Cas9, HA BOECs and HA iPSCs-derived ECs showed alteration of vessel-formation, endothelial cell migration, and vessel permeability. Importantly, the impaired EC phenotype was rescued by treatment with recombinant human FVIII or by lentiviral vector (LV) expressing FVIII. The FVIII function on endothelium was confirmed in vivo in a mouse model of severe HA which showed that an altered angiogenesis and vesselpermeability could be treated by exogenous FVIII. BOECstranscriptomic profiles revealed that FVIIIregulates the expression of endothelial basement membrane and extracellular matrix genes. Furthermore, exogenous expression of Nidogen2, identified as a FVIII regulated gene, restored the extracellular matrix integrity and EC functionality of HA ECs. In conclusion, FVIII is not only a coagulation factor but also an endothelial cell autocrine factor which promotes vessel stability.