Cells

HDFs were bought from ScienCell Research Laboratories (USA). The supplier company guaranteed, via Cell Applications (USA), that the HDFs expressed fibronectin and were negative for immune deficiency virus, hepatitis B virus, hepatitis C virus, mycoplasma, bacteria, yeasts and fungi. The standard culture medium for the HDFs was Dulbecco's minimum essential medium (DMEM) (89% v/v; Life Technologies Italia, Italy) supplemented with heat-inactivated (at 56°C for 30 minutes) foetal bovine serum (FBS) (10% v/v; Life Technologies Italia) and penicillin–streptomycin solution (1% v/v; Lonza, Italy).

HDMVECs isolated from adult skin capillaries were sourced from Cell Applications (USA). The seller pledged that such cells were free from bacteria, yeasts, fungi and mycoplasma, and that they expressed the factor VIII-related antigen. HDMVECs were grown in endothelial cell growth basal medium (PromoCell, Germany) supplemented with 10% v/v inactivated FBS; for the experiments, the standard FBS was changed to bovine exosome-depleted FBS.