Role Of MicroRNA-29a In Activation And Proliferation Of Cardiac Fibroblasts In Rats

Objective Atrial fibrillation, as one of the most common clinical type of fast arrhythmias, whose mechanism has been a keystone of research in the field of cardiovascular domestic and overseas. The pathophysiology basis of atrial fibrillation is myocardial fibrosis which cause occurrence and development of atrial fibrillation and other arrhythmia. Related studies have shown that there is a certain correlation between myocardial fibrosis and so-called cardio-micro RNAs. This study was designed to investigate the change of micro RNA-29 a and its downstream protein VEGF-A expression in rat atrial tissue and cardiac fibroblasts to explore the effect of micro RNA-29 a mimics and inhibitor on activation and proliferation of cardiac fibroblasts. Then evaluating the micro RNA-29 a molecular mechanism in the process of myocardial fibrosis during atrial fibrillation.Methods The model of myocardial fibrosis was induced by isoprenaline(ISO). 60 male Sprague-Dawley rats were randomly divided into the blank control group and the model group which are repectively 30 and 30. Subcutaneous injection with 10 mg/kg?d ISO daily for 15 days among model group while the blank control group was treated with same amount of normal saline. The rats were killed after 14 days and obtained myocardial tissue specimens for each group respectively. Cardiac fibroblasts was transfected with micro RNA-29 a mimics, inhibitor and their negative control being used Lipofectamine? 2000 Reagent. After 24~48 h related parameters were evaluated. HE staining and Masson staining was used to calculate myocardial tissue collagen volume fraction(CVF); q RT-PCR was uesd to detect the expression of micro RNA-29 a and the m RNA of Col1A1 and VEGF-A; Western blot was used to determine the expression of Col1A1 and VEGF-A; MTT assay was used to measured the proliferation influence of the transfected cardiac fibroblasts by using micro RNA-29 a mimics, inhibitor and their negative control.Results Compared with blank control group, HE staining and Masson staining showed myocardial tissue obvious collagen proliferation and myocardial matrix collagen volume fraction(CVF) increasing significantly. Compared with the blank control group and negative control group repectively, micro RNA-29 a up-regulated in micro RNA-29 a mimics group while down-regulated in model group and micro RNA-29 a inhibitor group. Col1A1 expression was down-regulated in micro RNA-29 a mimics group while up-regulated in model group and micro RNA-29 a inhibitor group. VEGF-A expression was down-regulated in micro RNA-29 a mimics group while up-regulated in model group and micro RNA-29 a inhibitor group. The cardiac fibroblasts proliferation activity decreased significantly after transfected micro RNA-29 a mimics while increased in micro RNA-29 a inhibitor groups.Conclusion Atrial fibrillation and obvious myocardial fibrosis can be induced by subcutaneous injection of ISO in rats. In atrial tissue, over-expression of micro RNA-29 a could down-regulated VEGF-A expression suppressing myocardial fibrosis. Micro RNA-29 a mimics can significantly suppress cardiac fibroblasts proliferation activity while micro RNA-29 a inhibitor can enhance cardiac fibroblasts proliferation activity. Implicating micro RNA-29 a, potential target of cardiac fibrolasts proliferation, is a vital signaling molecule in mechanism of atrial fibrillation providing a new way of thinking in intervention and treatment in occurrence and development of myocardial fibrosis.