The study of ISO induced heart failure rat model

Objective: To find a more excellent large-dose isoproterenol (ISO) induced heart failure (HF) rat model.

Methods: 166 male Wistar rats were divided into four groups, normal group (n=10), 85/85 mg/kg group (n=50), 85/340 mg/kg group (n=50) and 340/340 mg/kg group (n=56). HF was induced by two subcutaneous injections of homologous ISO on 2 consecutive days. We calculated death rate of each ISO group on different time points. And all the survival ISO rats were examined by echocardiography separately on 2 weeks, 3 weeks and 4 weeks. We defined the EF<45% rats as heart failure, and calculated EF<45% rate of three ISO groups. 4 weeks after the last injection, all of the rats were sacrificed. H&E and Masson staining were used to evaluate inflammatory infiltration and myocardial fibrosis, and immunohistochemistry was used to measure the levels of IL-1, IL-6 and IL-17. We also treated adult rat cardiac fibroblasts with IL-1, IL-6, IL-17, or PBS for 24 h, and real-time PCR was used to measure the expressions of MMP-2 and MMP-9 in treated fibroblasts.

Results: Through 4-week observation, we found that the period within 2 days after the last injection was the most dangerous one for all the ISO rats, regardless of injection dose. Then, the death rate increased slowly. 4 weeks later, the death rates were respectively 30% in 85/85 mg/kg group, 60% in 85/340 mg/kg group, and 68% in 340/340 mg/kg group, and there were statistical differences among three experimental groups. Moreover, the EF<45% rate and cardiac fibrosis rate were 100% in 85/340 mg/kg group as same as 340/340 mg/kg group, and much higher than 85/85 mg/kg group. Furthermore, we also found that pro-inflammatory cytokines (IL-1, IL-6 and IL-17) increased in 85/340 mg/kg group compared with normal group, and above cytokines could induce MMP-2 and MMP-9 expression in cardiac fibroblasts.

Conclusion: 85/340 mg/kg ISO induced HF rat model was superior to the other two dose ISO induced HF rat models. Pro-inflammatory cytokines might contribute to HF and myocardial fibrosis through promotion of MMPs expression in cardiac fibroblasts.