Construction Of Mouse Model Of Surgical Ventricular Restoration And Analysis Of Non-coding RNAs Changes In Reponse To The Surgery

BackgroundLeft ventricular remodeling(LVR)is a pathophysiological change after myocardial infarction(MI)and also an important cause of heart failure(HF)after MI.Current studies revealed that reversing LVR effectively could postpone the process of post-MI HF and improve the prognosis of patients with MI;therefore,effective interventions have become the focus of treatment of patients with MI.Classic methods to reverse LVR include drug therapy,coronary artery bypass grafting and mitral valve repair.However,for patients with severe LVR,especially when the left ventricular end systolic volume index(LVESVI)is more than 60ml/m2(normal LVESVI in adult is about 25Ml/m2),the effect of classical treatment on intervening LVR is limited;therefore,more effective methods should be used.Surgical ventricular restoration(SVR)is one of the surgical methods to reverse MI-induced LVR by artificially reducing left ventricular volume and altering the geometrical configuration of left ventricle(LV).Although numerous studies hold a positive attitude towards this operation and believe that the clinical efficacy of this procedure,as well as the short-term and long-term follow-up results of patients are satisfactory,some studies have doubt about its clinical efficacy and think that this operation may lead to complications such as LV diastolic dysfunction and right ventricular(RV)systolic dysfunction,thereby affecting the prognosis of patients.One of the reasons that restrict the accurate evaluation of its clinical value is the lack of animal experiments with good homogeneity and controllable confounding factors.In order to clarify the specific effects of SVR on cardiac pathophysiology and molecular biology,and provide theoretical basis for clinical practice,we constructed mouse model of SVR and analyzed characteristic changes of the heart after SVR by using various techniques.The expression profiles and functional changes of noncoding(ncRNAs)after SVR were obtained and analyzed by whole transcriptome sequencing and bioinformatics.MethodsWe first constructed MI model in male C57BL/6 mice by ligating left anterior descending branch of the coronary artery.Electrocardiogram and TTC staining were used to verify the success and stability of MI surgery.At the 4 weeks after MI,SVR was performed on MI mice with LVESVI>12 ml/m2(normal LVESVI in mice is about 5ml/m2),the needle was inserted at the position that slightly higher than that of the ligation line of MI,and put out at the junction site of the infarcted myocardium and the normal myocardium near the apex of heart to suture the infarcted myocardium.Histology,two-dimensional echocardiography,cardiac catheterization and speckle-tracking were used to analyze the changes of cardiac morphology,structure and function.The expression profiles of microRNAs(miRNAs),long noncoding RNAs(lncRNAs)and circular RNAs(circular RNAs)in the heart tissues of mice in each group were obtained by full transcriptome sequencing at the 3 weeks after SVR,followed by gene ontology(GO)functional analysis and Kyoto Encyclopedia of Genes and Genomes(KEGG)pathway analysis of the target genes of different ncRNAs between the MI group and SVR group.ResultsSVR effectively improved the LV shape,structure and systolic function,but it had significant effect on LV diastolic function and RV systolic function.At the 3 weeks after SVR,LV gradually recovered from spherical shape to normal elliptical shape in SVR group,LVESVI was significantly lower than that in the MI group((11±1)ml/m2 vs.(21±1)ml/m2),left ventricular ejection fraction(LVEF)was markedly higher than that in the MI group((32±2)%vs.(8±1)%)and the strain of each of the myocardial segment was also improved compared with MI group;While the mitral valve E/A ratio,tricuspid annular plane systolic excursion and other indexes were not different from those in the MI group.Cardiac catheters also suggested that SVR could only improve LV systolic function.In addition,histology showed that the degree of myocardial fibrosis in the SVR group was significantly lower than that in the MI group((22±1)%vs.(46±1)%).Whole transcriptome sequencing showed that there were 57 differential expressed miRNAs,18 differential expressed lncRNAs and 29 differential expressed circRNAs between the SVR group and the MI group,respectively.Among them,the target genes of differential expressed miRNAs were mainly involved in the regulation of cell proliferation,apoptosis and metabolism by regulating cAMP signaling pathway,lysosome and other signalings.The target genes of differential expressed lncRNAs were mainly involved in the inflammatory response after SVR by regulating cytokine-cytokine receptor interaction,chemokine signaling pathway and other signalings.Most of the target genes of different circRNAs were related to the intracellular structure of cardiomyocytes,such as myosin Ⅱ comlex and myocardial fiber components,therefore affecting the structure and contractile function of cardiomyocytes after SVR.ConclusionsSVR could effectively reverse LVR and improve LV systolic function,but it had no significant effect on LV diastolic function and RV systolic function.The target genes of miRNAs,lncRNAs and circRNAs that changed significantly after SVR were mainly involved in the regulation of cell proliferation,apoptosis and metabolism,inflammatory response,structure and contraction function of cardiacmyocytes respectively.