| BackgroundArterial intimal thickening occurs in restenosis following angioplasty has generally been attributed to proliferation, migration of vascular smooth muscle cells (VSMCs) into the intima and vascular remodeling. Control the migration is important wherever one wishes to inhibit restenosis. Most attention has been focused on the role of diffusible chemical signals such as growth factor or other materials. However, a potential alternative control is through the ability of electric fields to modify cell behavior. Physiological electric fields (EFs) have been measured in many developing and regenerating systems, and these electric fields influence cell shape, cell motility and tissue architecture. Electric fields of 1-2 V/cm have been shown to orient the movements of a wide variety of cells in vitro. Because similar electrical potentials occur across wounds in mammalian skin and cornea and even larger electric fields (up to 5 V/cm) have been measured in developing limb buds, it has been proposed that endogenous, trans-tissue electric fields play a significant role in directing cell movements during vertebrate development and wound repair. If endothelium cells or vascular smooth muscle cells respond to physiological electric fields, similar approaches may be used to control blood vessel outgrowth during restenosis following angioplasty. However, the mechanism by which electric fields direct cell movement is not yet understood, and the effects on VSMCs are entirely unknown.PurposeTo demonstrate that: 1)direct current electric fields influence VSMCs shape, orient the migration and effect the proliferation; 2) orientation and directed migration of cultured VSMCs in physiological electric fields are growth factor and receptor dependent; 3) VSMCs migrate significantly faster in the presence of AngⅡand electric fields combined; AT1R are necessary for directed migration of cultured VSMCs in physiological electric fields; 4) physiological electric fields direct cell migration by eliciting an intracellular signal that creates new sites for actin assembly in the cytoplasm.Methods1) A electrophoresis apparatus was designed for applying the direct current electric fields to the cell cultures. 2) VSMCs, which got from the aorta of rat, were cultured by routine method. 3) Cultures of VSMCs were exposed to a direct current electric field for a few hours. Interval photographs were taken and analyzed. 4) The migration of VSMCs exposed to physiological electric fields in the presence DMEM, DMEM + FBS, DMEM + growth factor, DMEM + AngⅡ, DMEM + FBS+ AngⅡ was taken and analyzed. 4) The expression of PCNA, PDGFR, AT1R and AT2R in VSMCs was evaluated by immunohistochemistry or immunofluorescence. 5) filament actin(F-actin) distribution in VSMCs was stained by FITC-phalloidin and evaluated by confocal microscopy.Results1. A electrophoresis apparatus is designed for applying the physiological electric field to the cell cultures. It is formed by a direct current power source , electrodes and a cell culture chamber. It can be operated to charaterize the effects of electric field on cultured cells. 2. Cultured rat aortic cells are idenfied as VSMCs by morphology and immunohistochemistry stain.3. In media containing 10% FBS, VSMCs show marked galvanotropic response. Cells migrate cathodally at 100-250mV/mm. Both the dissociated cells and cell sheets have similer response to electric fields. Microscopic imaging shows that the field stimulates protrusions from surfaces that face the cathode. Cells migrate to the negative pole faster over 72 hours. Cells migrate cathodally when serum is present in the medium. PDGF-BB, bFGF and TGF-β1, elements within serum are necessary for VSMCs direct migration. AngⅡ promotes electric fields directed migration of cells. 4. VSMCs are exposed to electric fields of 150~250mV/mm for up to 72 hours. There areo no significant change of PCNA expression in VSMCs during electric fields exposure .5. Electric fields induce VSMCs PDGFR up-regulated expression. The expression rate of AT1...
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