Structural remodeling of left atrial induced by aging and atrial fibrillation involved in the changes in miRNAs expression

Objective The study was designed to decipher whether the structure remodeling of left atrial induced by aging and atrial fibrillation(AF)correlated with changes in miRNAs expression. Methods Dogs were divided into 3 groups randomly: adult and old groups in sinus rhythm (SR)and old group with chronic AF. AF model was induced by rapid atrial pacing. Expressions of miRNA-1, miRNA-21, miRNA-29 and miRNA-133 were measured by Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR). Pathohistological and ultrastructural changes were analyzed by light and electron microscopy. Apoptosis index of myocytes was detected by TdT-mediated dUTP nick end labeling(TUNEL). Results In sinus rhythm group, compared to the adult group, the expressions of miRNA-21, 29 were significantly increased(miRNA-21, 2.3671±0.3056 vs.1.3529±0.1921; miRNA-29, 2.1929±0.2726 vs.1.2430±0.1828, P<0.05), whereas the expressions of miRNA-1, miRNA-133 showed obviously down-regulation tendencye in the aged group(miRNA-1, 0.7518±0.1009 vs.1.2036±0.1328; miRNA-133, 1.0438±0.1282 vs.1.2705±0.2025, P<0.05). Compared to the aged group in sinus rhythm, the expressions of miRNA-1, miRNA-21, miRNA-29 were significantly increased in the old group in AF(miRNA-1, 1.2475±0.2091 vs.0.7518±0.1009; miRNA-21, 3.8251±0.316 vs. 2.3671±0.3056; miRNA-29; 3.4532±0.3076 vs.2.1929±0.2726, P<0.05). In contrast, the expressions of miRNA-133 showed obviously down-regulation tendency(miRNA-133, 0.7439+ 0.1026 vs.1.0438+ 0.1292, P<0.05). Samples of atrial tissue showed statistical significance changes(all P<0.05)in fibrosis degree, ultrastructural and apoptosis index with aging and/or in AF dogs. Conclusion These changes in miRNAs expression may be responsible for pathological atrialremodeling with aging and AF. Key words: Atrial fibrillation; Aging; Structuralremodelling; miRNAs