Objective: Endothelial-derived molecules involved in thrombosis and hemostasis have been investigated mainly in arteries and in experimental animals. The actual presence and integral function of these molecules in the human deep venous system have received less attention. Our aim was to evaluate expression of certain prothrombotic and antithrombotic genes in the normal human deep veins of the lower extremities.

Methods: Macroscopically intact and competent valve-containing segments of human deep veins were prospectively collected from patients who had undergone above-knee amputation. Vein samples were separated into 4 zones: zone 1 - post-valve (downstream, proximal) vein wall; zone 2 - the valve cusp; zone 3 - pre-valve (upstream, distal) vein wall; and zone 4 - vein wall within the valve cusp (cusp removed). RT-qPCR for principal genes involved in coagulation, fibrinolysis, and inflammation was performed to quantify mRNA. Selected protein gene products were measured by the western blot assay. One additional valve-containing segment underwent mass spectrometry analysis to investigate global differences in the proteome between the study zones.

Results: Seventeen valve-containing vein segments were analyzed. Significant upregulation of antithrombotic (PROCR, THBD, TFPI), prothrombotic (VWF), and pro-inflammatory (SELP, ICAM1) genes was found in the valve cusp compared to the vein wall (p<.05). PROCR and THBD demonstrated the highest level of up-regulation in the valve cusp. PROCR, SERPINE1, and SELP were upregulated in the valve cusp at the protein level (p<.05). Messenger-RNA composition in the vein wall within the valve cusp was similar to the pre-valve and post-valve vein wall for all genes, except for 2-times overexpressed ICAM1 (p<.05). Substantial differences within the proteome between the study zones were observed with mass spectrometry.

Conclusions: Biological properties of the valve cusp, vein wall within the valve cusp, and vein wall beyond the valve cusp are different. Endothelium of the valve cusps of a normal competent deep venous valve may be naturally less thrombogenic compared to the vein wall. Endothelium of the valve cusp may have a higher potential to interact with white blood cells compared to the vein wall. Mass spectrometry demonstrates substantial differences in the proteome between the vein wall and the valve cusps that were not anticipated before.

Keywords: gene expression; human deep veins; physiology; valve cusp; venous valve.