Investigation Of Rat Coronary Artery Microthrombopoiese Induced By Thromb Microparticles And Its Compensation

Objects: To construct a microcirculation disturbance model by blocking coronary artery capillaries with rat automicroembolus particles in order to imitate clinical angina pectoris stroke with nonsignificant stenosis of large coronary artery; investigate the expressions of fg12 prothrombinase (fg12) and von Willebrand factor (vWF) in ischemic myocardiums at different periods, explore the possible mechanism of microcirculation disturbance induced by blocking capillaries with coronary artery microemboli; at the same time observe the expressions of hypoxia inducing factor-1α(HIF1α) and vascular endothelial growth factor(VEGF) and the capillary density variability of myocardium, approach the influence of local hypoxia stimulus on the promotion on formation and construction of myocardium collateral circulation.Methods: SD rats were randomly classified into three groups as autothrombus, sodium chloride and normal control group. Automicroembolus particles were made from the blood of rat tail. The automicroembolus particle suspension was infused through aortic root to construct the coronary artery microcirculation disturbance model. Rat cardiac ventricle tissue samples were obtained after operation at the 1 hour, 1 day, 1 week, 2 week, 3 week and 4 week, and dyed by HE stain, then the microvascular thrombosis of coronary artery inside endocardium was observed by light microscope so as to decide whether this model has been successfully constructed. vWF level in plasma were tested by enzyme linked immunosorbent double antibody sandwich method (ELISA). The expressions of fg12 mRNA and HIF1αmRNA in ischemic myocardiums were examined with RT-PCR. The expressions of HIF1αprotein and VEGF protein and the changes of myocardium capillary density were detected with immunohistochemistry. Results: (1) The pathological results suggest that coronary artery microthrombus model has been successfully constructed, and with light microscope we find that there are mixed thrombus or white thrombus in small artery, small vein and capillary of myocardium. The quantity of microemboli in rat coronary artery of autothrombus group is much more than that of sodium chloride and normal control group (p<0.05). (2) The fg12 mRNA expression in ischemic myocardiums is highest at the first hour after coronary artery microembolization, then decreases obviously at 1 week, 2 week, 3 week and 4 week, but not to zero and has highly correlation with vWF level in plasma. (3) After 1 hour and 24 hour of coronary artery microembolization, ischemic myocardiums express HIF1αmRNA and HIF1αprotein, which mainly locate in myocardial cellular nucleus. (4) The VEGF protein expression is remarkably elevated at 2 week and 3 week, then at the 4 week is decreased to normal level. VEGF protein is expressed on myocardial cells and arterial smooth muscle cells, especially on vascular endothelial cell endochylema. (5) Myocardium capillary density at the 2 week and 3 week after coronary artery microembolization is notably increased, then at the 4 week it is decreased to normal level.Conclusions: (1) The successful construction of coronary artery automicrothrombus model provides an economic, convenient, effect and feasible experiment platform for the study on microcirculation disturbance mechanism. (2) The positive expression of fg12 mRNA suggests fg12 may play a role in coronary artery microthrombosis, which may be one of mechanisms of coronary artery primary thrombus, thus this can be an experiment foundation of the study on the role of fg12 in coronary artery microthrombus. The variation of homochronous vWF level indicates that classical intrinsic coagulation pathway induced by endothelium injury may play a role in microcirculation disturbance mechanism. (3) The expression elevations of HIF1αand its downstream gene VEGF in ischemic myocardium, and the obvious increase of myocardium capillary density demonstrate that coronary artery microthrombosis may lead to microcirculation disturbance, hypoxia stimulant signal may activate HIF1αtranscription and up-regulate VEGF expression, promote vascular endothelial cell proliferation and cell division, increase the formation of collateral circulation, elevate myocardium microvessel density, thus improve myocardium blood supply and heart function.