Snaili Is Involved In De Novo Cardaic Fibrosisi After Myocardial Infarction In Mice

BACKGROUND AND OBJECTIVE:Coronary artery disease, myocardial infarction, heart failure are serious cardiovascular diseases in the world that seriously affect human health. With the extensive and intensive researches of pathophysiology, cardiac fibrosis, associated with systolic and diastolic dysfunction, was concerned to cardiac remodeling process. During the process of cardiac fibrosis after myocardial infarction, there is a series of complex molecular signaling pathway activation, cell structure, phenotypic and functional changes. These changes includes: myocyte hypertrophy, apoptosis, fibroblast proliferation, re-expression of fetal gene and protein. Fibroblasts are the cells that were without have self-discipline, conductivity and contractility. The excessive production of fibroblasts is one of the decisive factors for impaired cardiac function and cardiac fibrosis. Nevertheless, the molecular mechanism by fibroblasts is not yet widespread. Recent studies had shown that the fibroblast might be producted by the inherent fibroblasts. Meanwhile, vascular endothelial cells are activated in certain pathological, molecular and humoral conditions and differentiate into a large number of fibroblasts through the epithelial mesenchymal transition (epithelial-mesenchynmal transition, EMT) pathways. And this was an important pathophysiological mechanism of organ fibrosis. Elisabeth first found that endothelial-to-mesenchymal transition (a type of EMT) contributed to cardiac fibrosis in2007, and then expound the EMT events regulated through TGF-β1and BMP7in the myocardial fibrosis. However, in the process of cardiac fibrosis in the EMT incident, which downstream signaling molecules can reduce cell polarity and adhesion, and promote the epithelial phenotype of cell migration and transformation? Which factor plays a leading role in these signaling molecules? All these problems remain unclear. We established the MI model by ligating on the left anterior descending coronary artery. And then we observed the pathological process of myocardial fibrosis after MI. The RNA expression patterns of Snaill Slug, twist, viminten and E-cadhernin in the infarct area were detected by Real-Time polymerase chain reaction (Real-Time PCR) analysis. Immunofluorescence was used to observe the spatedial and temporal expression patterns of those factors. And the protein expression trends between Snaill and periostin were certified by Western blotting. Confocal image fusion was used to investigate the Snaill co-staining with periostin.METHODS:(1) Myocardial infarction was induced in mice by permanent ligation of the left anterior descending artery (LAD). The day after operation, troponin-positive combined ECG ST-segment arched elevation prompted modeling success. Masson’s trichrome staining was performed for pathlogic observation.(2) Through the Real-Time PCR and immunofluorescence, we set the detection of EMT important regulatory transcription factor Snaill, Slug, twist, the epithelial phenotype marker protein E-Cadherin, the mesenchymal cell marker vimentin, as well as a cardiac fibrosis marker-periostin in mice after myocardial infarction within14days.(3) According to the second part of the results, Western blotting analysis was further made to certify protein expression trends of Snaill and periostin. And three-biomarker immunofluorescence and confocal microscopy image fusion were used to observe the co-expression between Snaill and periostin.RESULTS:(1) Thirty mice were used in this experment.19mice were succussful modeled. The success rate was63.33%, and the leading causes of death were:lung injury (16.67%), hemorrhagic shock (10.00%) anesthesia recovery failure (6.33%) and infection and other factors (3.67%). Masson staining shows the pathological changes in MI region within2weeks. After ligation of the coronary artery, cardiacmyocyte disorders, inflammatory response, collagen fibers to expand and preliminary determination were all presenced in14days after MI.(2) Snaill, Slug and twist are all activated after MI within in mice. Snaill was persistent activated mice within2weeks of in the infarcted area. Slug and twist were expredded within7days after MI. E-Cadherin was decrease and vimentin rose within14days after myocardial infarction. Periostin sustained increased after MI in mice with analogic trend with Snaill.(3) Protein quantitation indicated the expression of Snaill and periostin is basically consistent with the fluorescence intensity data. Mean while, Snaill and periostin were totally overlayed in the same mesenchymal cell at the7th day after MI in mice.CONCLUSIONS:The14days after MI is a critical time window for the prolifation of fibroblasts. Snaill, Slug, twist are all activated in the infarct area after MI in mice. Snaill is involved in the regulation of EMT in de novo cardiac fibrosis after MI. Slug and twist may possibly play a role in the regulation too. Snaill is a potential molecular target to make drug interventions for ventricular remodeling after MI.