Abstract: Objective To observe the effect of Polygonatum sibiricum polysaccharides(PSP) on myocardial fibrosis in diabetic cardiomyopathy rats and to explore its possible mechanism.Methods Healthy male Sprague-Dawkey rats were randomly divided into normal group,model group,and 250,500,1000 mg/kg PSP groups and all the rats were fed with normal diet for 12 consecutive weeks.General conditions of the rats in each group were observed;fasting blood glucose (FBG),blood biochemical indexes,hemodynamic indexes were detected and heart mass index (HMI),left ventricular mass index (LVMI),and left ventricular end-diastolic pressure (LVEDP)were determined.Hematoxylin-eosin staining was used to observe the changes of myocardial morphology;Masson staining was used to observe the distribution of collagen fiber;the expressions of the bone morphogenetic protein-7(BMP-7),transforming growth factor beta 1 (TGF-β1),Smad2/3 and Smad7 were detected with immunohistochemistry.Results Compared with those of the control group,the FBG (24.81±2.30 mmol/L),HMI (4.16±1.14),LVMI (2.85±0.09) and LVEDP of the rats in the model group were increased (all P < 0.05).Immunohistochemistry results showed that the expressions of TGF-β1 and Smad2/3 protein were significantly increased (P < 0.05);the expressions of BMP-7 and Smad7 protein were significantly reduced(P < 0.05);HE and Masson staining showed that the cardiac tissues were serious damaged for the rats in the model group.Compared with those of the model group,the FBG (13.28±2.08 mmol/L),HMI (3.21±0.07),LVMI (2.09±0.02),and LVEDP were decreased (all P < 0.05);the expressions of TGF-β1 and Smad2/3 protein were significantly reduced (both P < 0.05);the expressions of BMP-7 and Smad7 protein were significantly increased (both P < 0.05);and the pathological changes of cardiac tissue were improved for the rats in 1 000 mg/kg PSP treatment group.Conclusion PSP can improve myocardial fibrosis in diabetic rats and its mechanism may be related to the promoted expression of BMP-7 in cardiac tissue,which affects the TGF-β1 /Smads signal pathway.