Tissue factor up‐regulation in proinflammatory conditions confers thrombin generation capacity to endothelial colony‐forming cells without influencing non‐coagulant properties in vitro

Background: Endothelial progenitor cells (EPC) are good candidates for cell‐based therapy in cardiovascular diseases. However, concerns have been raised about the potential risks of EPC‐based cell therapy, in terms of thrombogenicity particularly in inflammatory conditions, currently observed in such patients. Tissue factor (TF) can trigger coagulation and may support thrombogenicity. TF is also a key receptor in angiogenesis. Objective: The present study was designed to (i) evaluate the capacity of resting and tumour necrosis factor‐alpha (TNF)‐α‐stimulated late‐outgrowth endothelial colony‐forming cells (ECFCs) to express TF and (ii) investigate the effect of TF/FVII(a) interaction on procoagulant and non‐procoagulant activities of ECFCs in vitro. Methods: ECFCs from cord blood (cb) and adult peripheral blood (ab) were analyzed for TF expression and activity using reverse transcription‐polymerase chain reaction (RT‐PCR), flow cytometry, Western blot and a thrombin generation assay. Non‐procoagulant properties of TF‐expressing ECFCs were investigated in vitro using wound‐healing, cell proliferation, tube formation and spheroid‐based assays. Results: ECFCs expressed TF in response to TNF‐α. The up‐regulation of TF conferred to ECFCs a FVII(a)‐dependent thrombin generation activity. Compared with cb‐ECFC, ab‐ECFCs can display a higher level of constitutive TF expression and activity, with a notable heterogeneity among donors. TF/FVIIa interaction did not modify non‐procoagulant properties of TNF‐α stimulated cb‐ECFCs in vitro. Conclusions: Proinflammatory conditions up‐regulate TF expression in ECFCs. This expression confers to ECFCs a strong thrombin generation capacity without influencing their non‐coagulant properties. Our results suggest that EPC‐based cell therapy may be associated with prothrombotic risk which could be limited by inhibiting TF without affecting the proangiogenic capacity of the cells.