Abstract： Objective To study the effects of hepatocyte growth factor (HGF) on angiotensin Ⅱ(Ang Ⅱ )-induced synthesis and degradation of cardiac fibroblast collagen in neonatal mice.Methods Cardiac fibroblasts (CFs) of neonatal Sprague-Dawley (SD) rats were isolated by differential adhesion, and were identified by immunocytochemistry.The cells were assigned to normal control group (group C) , 10-6 mol/L Ang Ⅱ group (group A), 10μg/L HGF + 10-6 mol/L Ang Ⅱ group (group H1) and 100μg/L HGF +10-6 mol/L Ang Ⅱ group (group H2).All the groups were treated for 48 h.Hydroxyproline assay was used to determine the collagen protein level.RT-PCR was used to detect the expression of ColⅠ, ColⅢ, matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-l) mRNA, and Western blotting was employed to measure Col I protein.In addition, MMP-1 activity was evaluated by collagenase Ⅰ activity assay kit.Results After intervention for 48 h, the collagen protein levels in groups A and H1 were significantly higher compared with group C [ (39.08±2.71) mg/L vs (37.45±4.22) mg/L vs (23.73 ±±1.62) mg/L, all P＜0.05] and the collagen protein level in group H2 [(26.03±3.04) mg/L] was lower than those of groups A and Hl(P＜0.05), but was not statistically different from group C.The expression levels of Col Ⅰ ,Col M and TIMP-1 showed an order of group A＞group HI＞group H2> group C (all P＜0.05), and for MMP-1 mRNA, group A ＜ group H1 ＜ group H2 ＜ group C (all P＜0.05).The levels of Col I protein expression showed an order of group A＞group HI＞group H2＞group C (89.90±4.29 vs 68.21?1.43 vs 36.08?.8 vs 30.14?.36, all P＜0.05).The expression and activity of MMP-1 mRNA in group A and H1 were obviously lower than those in group C (all P＜0.05), while group H2 were comparable to group C in these data.Conclusion HGF re-regulates MMP-1-TIMP-1 balance and ameliorates myocardiac fibrosis mainly by activating collagen degradation.