Roles of circular RNA in cardiac fibrosis

Heart failure is one of the leading causes of death and it often accompanies activation of quiescent cardiac myofibroblasts, which results in cardiac fibrosis and resulting cardiac remodeling. Circular RNA, one form of non-coding RNA discovered recently, is formed by backsplicing of 3' end to 5' end of exons and is known to be closely related to the variety of pathophysiological function as well as normal homeostasis. However, its roles in the cardiovascular diseases, especially in cardiac fibrosis, are not fully studied. Circular RNAs (circRNAs) are formed by backsplicing events of 3' end to 5' end. To identify circRNA candidates, RNA sequencing (RNA-seq) datasets were obtained from transverse aortic constriction (TAC)-induced hearts. Especially, we were interested in cardiac fibroblast-specific circRNAs that affect its differentiation and cardiac fibrosis. Thus, in the present study, by utilizing RNA sequencing analysis followed by diverse bioinformatic or biochemical studies, we identified and characterized circRNA that may affect the pathologic remodeling of heart. Overall design: Thoracic aortic constriction (TAC) is established method and is widely used to establish an animal model of pressure overload-induced cardiac hypertrophy and heart failure. Eight-week-old male C57BL/6J mice were anaesthetized by Avertin. The mice were then ventilated and the chest was opened to expose the thymus and aortic arch. A 7-0 silk suture were placed between the innominate and left carotid arteries. A 27-gauge needle put parallel to the transverse aorta and the suture was tied. After ligation, the needle was removed and the rib cage was closed using 4-0 silk suture. As a control, sham mice were subjected to same operation without ligation. One, four, and eight weeks later, the hearts were excised, and the Langendorff perfusion system was used to isolate cardiac fibroblasts and from hearts.