Moderate concentrations of TNF- α induce BMP-2 expression in endothelial cells

Tumor necrosis factor-alpha (TNF-α) is best-known as a potent pro-inflammatory cytokine involved in many cardiovascular diseases. During vascular calcification, TNF-α has been reported topromote osteogenic differentiation of human vascular smooth muscle cells (VSMC) and mesenchymal stem cells (MSCs). In contrast, there is alack of data reporting the osteoinductive effect of TNF-α in endothelial cell. In this study, experiments were performed to investigate and determine theoptimum dose of TNF-α that induces expression of the osteoinductive factor bone morphogenetic protein (BMP-2) in endothelial cells. Human vein endothelial cells were treated with TNF-α at doses of 0, 2, 5, 10, or 20 ng/mL for2, 8, or 24 h time intervals. BMP-2 cell expression was evaluated using immunocytochemistry staining by calculating the percentage of BMP-2 positive cells. Apoptosiswas determined by counting the number ofpyknoticcells. In this study, we found that the optimum dose of TNF-α thatinduces BMP-2 expression in endothelial cells was 5 ng/mL at the 8 h time interval. Lower (2 ng/mL) orhigher (10 and 20 ng/mL) concentrations of TNF-α had minimal effects on BMP-2 expression. Moreover, higher concentrations of TNF-α treatment (10 and 20 ng/ml) at8 h and 24 h increased the presence of pyknotic endothelial cells, which representthefinal stage of apoptosis.