Effect of low-level laser irradiation (llli) on expression of vascular endothelial growth factor (vegf) and inducible nitric oxide synthase (inos) in rats model of myocardial infarction

Objective: To observe the effect and significance of low-level laser irradiation (LLLI) on expression of vascular endothelial growth factor (VEGF) and inducible nitric oxide synthase (iNOS) in rat model of myocardium infarction (RMMI). Method: 110 SD rats were randomly divided into Sham, control and treatment group. Control and treatment group established rat model of myocardial infarction (RMMI) by ligation of left anterior descending artery while Sham group performed only threading around the same site of ligation. After 3 weeks of RMMI, irradiation was done at infarct region in the treatment group by using low level laser diode (635nm, 6mW, 125s, 0.96J / cm2), while the control group and the sham group were irradiating without putting the power on. 4 to 6 rats were euthanized at 1h, 24h, 48h, 72h and 7d after LLLI. The irradiated myocardial tissue were excised to measure the expression of VEGF and iNOS by using Western blot method. Results: After the LLLI treatment, VEGF expression continued to rise at 1h-48h in the treatment group, peak expression compared with the control group (2.27 ± 0.22:1.46 ± 0.19,P<0.05) there was a statistically significant difference. iNOS expression started to rise after exposure at 1h in the treatment group, peaked at 48h, compared with the control group (1.90 ± 0.18:1.4 ± 0.08,P<0.05) there was a statistically significant difference. 1 week after the 2nd thoracic irradiation, compared control group with the treatment group; left ventricular ejection fraction (LVEF) (%) (39.83 ± 1.64vs47.62 ± 2.75,P<0.05), left ventricular fractional shortening rates (LVFS) (%) (18.03 ± 1.25vs24.15 ± 2.53,P<0.05), there was a statistically significant difference; 1 week after LLLI, a new capillary density compared between the control group and the treatment group (69.50 ±14.50)/mm2 vs. (111.50 ± 9.00)/mm2,P<0.05, there was a statistically significant difference. Conclusion: LLLI can significantly increase expression of VEGF and iNOS in infarcted myocardium which can promote angiogenesis to improve the microcirculation of infarct zone and improve the cardiac function.