| Background and objectiveAlong with the acceleration of China's urbanization process and the aging society,as well as the unhealthy lifestyle of the residents,the prevalence and mortality of cardiovascular disease in China is still rising,and the number of cardiovascular diseases is estimated to be 290 million.Cardiovascular deaths accounted for more than 40% of the deaths of residents,ranking first,with myocardial infarction accounting for more than 60% of cardiovascular deaths,and the overall increase.Myocardial infarction(MI)is a clinical syndrome in which coronary atherosclerotic plaque ruptures into a thrombus,coronary artery infarction,continuous myocardial ischemia,and hypoxia-induced necrosis.Treatment can be divided into drug therapy and revascularization.Regardless of the treatment method,it is closely related to the recovery of blood supply to infarcted myocardium.Therefore,the number of new blood vessels in the infarcted myocardium or the re-opening of the original obstructed blood vessels is of great significance for the repair of myocardial infarction.The formation of blood vessels refers to the formation of new blood vessels in a manner of budding or nesting by proliferation and migration of vascular endothelial cells.In recent years,with the deepening of research on pathophysiological changes in the process of MI,many scholars have thought of improving the production of MI for neovascularization in infarcted areas.In recent years,research on microRNAs has become a research hotspot in the medical field and has made important progress.MicroRNAs(miRNAs)are a class of endogenous highly conserved non-coding small RNAs in eukaryotes that regulate the expression of target genes.The study found that a variety of miRNAs are widely involved in various processes such as cell proliferation,differentiation,and apoptosis,including promoting angiogenesis,which has important physiological and pathological significance.miRNA-126 is an endothelial-specific miRNA that is highly expressed in all capillaries and large vascular endothelial cells,regulating angiogenesis and development by affecting vascular gene signaling pathways.Studies have confirmed that miRNA-126 is the most abundant miRNA in vascular endothelial cells,especially in highly vascularized mouse tissues such as heart and lung.miR-126 has a very positive role in maintaining vascular endothelial cell and vascular integrity in vivo.Low-level laser irradiation(LLLI)is a very mature physical therapy.It has been used in medicine for more than 40 years.At first,it was the first to be bold in the field of ophthalmology and orthopedics.Now it is in almost all disciplines.Widely used in the field,its safety and effectiveness have been confirmed and recognized by the academic community.LLLI produces biological effects rather than thermal effects,including biostimulatory effects such as stimulation,regulation,and activation.It mainly affects damaged tissues and is beneficial to damaged cells,including cell proliferation,adhesion improvement and prevention of apoptosis,and is basically harmless to intact cells.Although the specific mechanism of action and mechanism of action of LLLI are still in the research stage,a large number of basic research and clinical cases have confirmed that it can regulate many biological processes of cells and tissues in vitro.Studies have shown that LLLI can improve the microcirculation of the infarct area,have myocardial protection,and can also reduce the formation of collagen fibers and improve the process of ventricular remodeling.Therefore,this study established a rat myocardial infarction model to observe the changes of miR-126 expression in myocardial tissue before and after myocardial infarction,and used low-energy laser to irradiate the myocardial infarction area to observe the changes of expression of miR-126 before and after irradiation in the infarcted myocardium.And the changes of new capillary density after infarction,and then explore whether low-energy laser and miR-126 have synergistic effect in promoting angiogenesis,and provide experimental basis for low-energy laser to improve the blood supply of infarct tissue after acute myocardial infarction.Methods and methods(1)Animals and groupingThe experimental animals were 110 SPF male SD rats weighing 220-250 g and aged 6-8 weeks.They were randomly divided into 3 groups: 30 in the sham operation group,40 in the control group,and 40 in the laser group.The myocardial infarction animal model was established in the control group and the laser group.The MI model was maded by ligation of LAD.The sham operation group was made by threading the same position during the operation but not ligating,and the remaining steps were the same.(2)Screening myocardial infarction modelAfter 24 hours of modeling of rat myocardial infarction model,echocardiography was performed.The criteria for inclusion in the myocardial infarction model were: objective indicators: 1.LVEF <60%;2.LVFS <30%;subjective indicators: 3.The sonographer found that at least one level showed abnormal ventricular wall contraction.A successful myocardial infarction model must meet 2 or more.(3)Low level laser irradiationAfter screening,all rats were subjected to LLLI: diode laser therapeutic apparatus with a wavelength of 635 nm and a power adjustment of 6mW.The vertical distance of the transmitter from the infarcted myocardium surface was 15 mm,continuous irradiation for 125 s,and energy density of 0.96J/cm2.When the sham operation group and the control group are subjected to LLLI,the low energy laser is not powered.(4)Left heart function testIn the first screening of the rat myocardial infarction model,after the LLLI in the control group and the laser group,echocardiography was performed again before the myocardial tissue samples were obtained.The indicators and methods were the same as the first time.(5)Determination of miR-126 expressionAll the three groups were anesthetized by abdominal cavity at 24 h,7d and 14 d after low-energy laser irradiation.The heart was quickly opened and placed in a 0.9% NaCl injection at 4°C.The residual blood in the heart was discharged with the heart beat,ensuring no Residual,carefully collect the myocardial tissue at the edge of the infarct area with ophthalmic scissors and store in a refrigerator at-80°C.Detection of miR-126 expression by RT-qPCR.(6)Pathological analysis of infarcted myocardiumThree groups of rats were anesthetized by intraperitoneal injection 7 days after low-energy laser irradiation.The heart was quickly opened and placed in a 0.9% NaCl injection at 4°C.The residual blood in the heart was discharged with the heart beat to ensure no residue.TTC staining(2-3/group),H & E staining,CD31 immunohistochemistry for MVD.(7)Statistical analysisThe data were analyzed by SPSS 21.0 statistical software.The measurement data were expressed as meanąstandard deviation(xąs).The variance analysis was used to prove the homogeneity of each group.LSD-t test was used to analyze the correlation of measurement data.Level ?=0.05,p<0.05 indicates that the difference is statistically significant.Results(1)Establishment of rat myocardial infarction modelA total of 99 rats survived within 24 hours after surgery in the rat model of myocardial infarction,29 in the sham operation group,30 in the control group,and 35 in the laser group.The success rate of modeling surgery was 81.25%(65/80).After screening,28 of the control group met the standard,26 of the laser group met the standard,and the success rate of the myocardial infarction model was 67.5%(54/80).(2)Evaluation and comparison of left heart functionAfter 7 days of laser irradiation,the LVEF and LVFS were significantly increased after irradiation,and the difference was statistically significant.After 7 days of low-energy laser irradiation,compared to the control group,the LVEF and LVFS of the laser group were obviously enhanced.The difference was statistically significant.(3)Infarcted myocardium miR-126 expressionThe results of miR-126 amplification showed that the expression of miR-126 in the laser group was significantly higher than that in the control group.The expression of miR-126 in the sham operation group did not change with the passage of time,and the overall stability was relatively stable.After low-energy laser irradiation,the expression of miR-126 in the control group and the laser group was lower than that in the sham operation group at 24 h,7d,and 14 d,while the laser group was higher than the control group;the expression of miR-126 was highest in the control group at 7d,laser The same was true in the group;the expression of miR-126 was lower than 24 h in the control group at 14 d,but there was no statistical significance in the laser group at 14 d and 24 h.(4)Comparison of myocardial infarction areaAccording to the results of TTC staining,compared with the control group,we found that the myocardial infarction area of the laser group was obviously decreased.The difference was significantly statistical.(5)Myocardial histopathology test results 1.HE staining resultsIn the sham operation group,the cardiomyocytes were arranged neatly,the cell structure was basically normal,and no inflammatory cell infiltration was observed.In the control group,a large number of regional necrosis accompanied by a large number of inflammatory cell infiltration;the degree of myocardial necrosis and edema in the laser group were compared with the control group.Improved,reduced inflammatory cell infiltration.2.Immunohistochemical test resultsThe microvessel density(MVD)in rat myocardial tissue was detected by CD31 immunohistochemistry.The results showed that the microvessel density in the myocardial tissue of the laser group was obviously increased.The difference was significantly statistical..(6)Correlation between MVD and miR-126 expression levels in laser groupCorrelation analysis between the expression of MVD in infarcted myocardium and the corresponding miR-126 in the laser group showed that the expression of MVD and miR-126 in the infarcted myocardium of the laser group was positively correlated.ConclusionsLow level laser can promote angiogenesis of infarcted myocardium after myocardial infarction in rats.After neovascularization,the blood supply of infarcted myocardium is increased,the myocardial infarct size is reduced,the inflammatory response during infarction is reduced,and myocardial apoptosis is reduced.Left heart function,to achieve the purpose of myocardial protection.Low level laser can increase the expression of miRNA-126 in infarcted myocardium,which is positively correlated with angiogenesis,which may be the mechanism of low-energy laser affecting angiogenesis. |
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