Oxygen- and glucose-deprived culture promotes cell proliferation and invasion of vascular smooth muscle cells

Abstract

Abstract. Excessive proliferation of vascular smooth muscle cells (VSMCs) is an important reason for the formation and development of many vascular remodeling diseases. In pathological conditions, necrosis of VSMCs may result in the release of inflammatory cytokines, which can lead to stimulation of other normal smooth muscle cells, and promote the proliferation of VSMCs. The purpose of this study was to investigate the effect of oxygen-and glucose-deprived (OGD) conditioned medium on VSMC cell proliferation and invasion. Following culture of VSMCs in OGD-conditioned medium, the cell cycle distributions were remarkably altered. The number of cells in the G0/G1 phase decreased, while the number of cells in G2/M and S phase increased. The expression of cell cycle proteins D1 (Cyclin D1) in VSMCs increased correspondingly. These results suggested that after being cultured in OGD medium, VSMCs can pass through the G0/G1 phase by up-regulation of Cyclin D1 expression, and promote cell proliferation. In addition, we found that the expression of matrix metalloproteinase (MMP)-2 and MMP-9 was increased in OGD medium cultured VSMCs. Using a Transwell invasion assay, we showed that the OGD medium enhanced VSMC cell invasion. These results suggest that MMP-2 and MMP-9 degraded the basement membrane and promoted VSMC invasion. Taken together, our data demonstrate that OGD-conditioned medium can promote VSMC proliferation and invasion by up-regulating Cyclin D1 and MMP-2 and MMP-9 expression, which may contribute to the formation and development of vascular remodeling diseases. IntroductionVascular remodeling diseases are characterized by vascular wall thickening and luminal stenosis due to endothelial injury, vascular smooth muscle cell (VSMC) proliferation, and matrix deposition. Excessive proliferation of VSMCs is an important contributor of the formation and development of many vascular remodeling diseases, such as hypertension, atherosclerosis, restenosis after angioplasty (1-3). Extracellular proliferation and stimulation delivered signal to the nucleus through transmembrane conductance, initiates proliferation related genes, and results in excessive proliferation of VSMCs (4-7). In vascular remodeling diseases especially restenosis after angioplasty, VSMC damage, apoptosis, and necrosis are common pathological processes due to ischemia and hypoxia and their mechanical angioplasty injury (8). In pathological conditions, necrosis of the VSMCs may release inflammatory cytokines that can lead to stimulation of other normal smooth muscle cells, thus promoting the proliferation of VSMC. Cell count, the percentage rate of the cell cycle and cell cycle proteins D1 (Cyclin D1) are important indicators of VSMCs proliferation.Matrix metalloproteinases (MMPs) are proteolytic enzymes, which can degrade most extracellular matrix components and other substrates (9). MMPs play an important role in cell invasion and metastasis by degrading extracellular matrix, such as collagen type I, laminin, fibronectin and other components. Specif...