ObjectiveTo establish a rat model of myocardial fibrosis and investigate its pathogenetic characteristics, and provide an animal model of myocardial fibrosis (MF) for clinical research. MethodOne hundred male Wistar rats were randomly divided into two groups:the model group (n =92) and the sham group (n=8). The rats in the model group were subjected to heart coronary artery ligation (CAL). Heart specimens were taken at different time points from 1 to 8 weeks. Pathological changes and collagen distribution were examined by histopathology using HE and Masson staining. The hydroxyproline content and expression of collagen and TGF-β1 in the heart tissue were quantitatively determined. The sham operated rats served as controls. ResultsOn the 7th day after CAL, compared with the control rats, the heart tissue of rats in the model group showed seveve inflammatory reaction:disrupture and degeneration of cardiomyocytes, significant increase of collagen content (P<0.01), hydroxyproline content (P<0.05), expression of TGF-β1 (P<0.01), and those changes were kept at a high level during the experiment. The fibrosis reached a peak on the 42nd day, and then it showed a tendency of improvement. No abnormal changes were seen in the myocardium of control rats. ConclusionsA reliable rat model of myocardial fibrosis can be successfully established by coronary artery ligation. Its mechanism may be related to the overexpression of TGF-β1.