Effect of LLLI on Expression of Micro RNA-21 and Ventricular Remodeling inRats after AMI

Objective: To assess the effects of low-level laser irradiation (LLLI) on the expression of micro RNA-21 and ventricular remodelling in the model of rat myocardial infarction. Methods: 110 adult-female SD rats were randomly divided into sham operation (30), control (40), and treatment (40) groups. MI model was prepared by ligation of left anterior descending artery in the control and treatment groups while simply threading at the same site of MI model in sham group. LLLI treated using (635 nm, 6mW, 125s, 0.96 J/cm2) after three weeks of MI at infarct region in the treatment group. At 1 h, 24 h, 48 h, 72 h and 7 d after LLLI treatment, the expression of miR-21 at the infracted myocardial tissue were detected using qRT-PCR. At the end of 4 weeks after MI, hearts were harvested for histological analysis. Results: MiR-21 expression in the treatment group was lower than both sham group as well as the control group (P<0.05). LVEF (%) and LVFS (%) in the treatment group before and after LLLI; (39.37 ± 1.35 vs. 47.62 ± 2.75, P<0.05; (19.23 ± 3.12) vs (24.15± 2.53), P<0.05). Collagen fiber content in treatment group were significantly lower than control group (28.79 ± 2.06%) vs (69.22 ± 3.64%), (P<0.05). Conclusion: LLLI treatment of myocardial infarction can significantly down regulate the expression of tissue miR-21 in the infarct region, increase left ventricular function and decrease collagen fiber content suggesting the beneficial effect of LLLI on delaying myocardial fibrosis, reduce the pathological ventricular remodelling (VR) after MI.