Comparison of tissue factor expression and activity in foetal and adult endothelial cells
Tissue factor (TF) is not usually expressed by endothelial cells but can be induced in these cells by inflammatory cytokines. Many studies have used human umbilical vein endothelial cells (HUVEC) as a model to examine the regulation of TF expression. However, there is a question as to whether this reflects TF expression in adult endothelial cells. This study compared TF expression and the release of TF-positive microvesicles in HUVEC and adult human dermal blood endothelial cells (HDBEC) in response to tumour necrosis factor α (TNFα) and interleukin-1 β (IL-1β). Cells were treated with the inflammatory cytokines and TF mRNA and total protein expression was examined by real-time RT-PCR and TF ELISA. Cell surface TF activity was measured in the calibrated automated thrombogram assay, as were microvesicle concentrations and microvesicle-associated TF activity. The TF antigen content of the microvesicles was determined by TF ELISA. Both HUVEC and HDBEC expressed increased levels of TF mRNA in response to TNFα and IL-1β within 2 h. TF antigen expression increased in both cell types, reaching a maximum at 6 h, with HUVEC expressing significantly higher levels compared with HDBEC in response to TNFα. However, increases in TF-specific thrombin generation were similar on both HUVEC and HDBEC and both cell types also released comparable levels of TF-positive microvesicles. HUVEC and HDBEC respond similarly to TNFα and IL-1β in terms of TF expression, and both are suitable models to examine cell surface TF activity and TF-positive microvesicle release in endothelial cells.