Expression of matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1 in atrial tissue in the elderly dogs with persistent atrial fibrillation

Objective To investigate matrix metalloproteinase-9(MMP-9) and tissue inhibitor of metalloproteinase-1(TIMP-1) expression in atrial tissue in the elderly dogs with persistent atrial fibrillation and to analyze the relationship of MMP-9 and TIMP-1 expression with atrial fibrillation and fibrosis.Methods Eighteen healthy Beagle dogs were randomly divided into adult normal sinus rhythm group(n=5),elderly normal sinus rhythm group(n=5),adult persistent atrial fibrillation group(n=4) and elderly persistent atrial fibrillation group(n=4).Masson staining was used to determine the stage of fibrosis.The expressions of MMP-9 mRNA and TIMP-1 mRNA were detected with RT-PCR in left atrium.The level of protein expression was determined with Western blot technique.Results Compared with adult normal sinus rhythm group,atrial fibrosis was more severe(P0.01),TIMP-1 mRNA and protein expressions decreased(P0.05,P0.01),and MMP-9 protein increased(P0.01) in the other three groups.MMP-9 mRNA expression increased in elderly normal sinus rhythm group and elderly persistent atrial fibrillation group compared with adult normal sinus rhythm group(P0.05).The atrial fibrosis was more severe,collagen volume fraction increased more significantly(P0.05),and TIMP-1 protein expression decreased(P0.01) in elderly persistent atrial fibrillation group compared with adult persistent atrial fibrillation group.Conclusion The imbalanced expression of MMP-9 and TIMP-1 gene is properly one of the important mechanisms of atrial fibrosis induced by collagen metabolism and aging atrial fibrillation.It is correlated with the occurrence of aging atrial fibrillation.