The Roles Of MMP-9 And TIMP-1 During The Progression Of Skin Sclerosis In Mouse Model And Effects Of Simvastatin On The Sclerotic Skin In Mouse Model

Objective:To investigate the dynamic trends of protein expressions of MMP-9 and its inhibitor,TIMP-1,during the progression of skin sclerosis in mice so as to get insight of the roles played by MMP-9 and TIMP-1 in skin sclerosis and the effect of simvastatin on the mouse model of sclerotic skin.Methods:The mouse model of sclerotic skin was established by local injections of bleomycin(BLM) at a concentration of 600μg/ml,100μl once per day for 4 weeks, in the back of BALB/c mice.Simvastatin was given orally to the mouse model simultaneously or after 4 weeks' injection of BLM.After administration of sinvastatin for 4 weeks,the skin sections were collected for histopathological examination,measurement of dermal thickness, determination of hydroxyproline contents,measurement of the levels of procollagena 1(Ⅰ) mRNA expression by RT-PCR and MMP-9 and TIMP-1 protein expression by Western blot..Results: As compared with the PBS injected mice,the protein expressions of MMP-9 and TIMP-1 were both increased in the BLM-treated group;and more obvious expression of MMP-9 was noticed in the 1^st-2^nd weeks.From 3^rd-4(th) weeks after local injections in the BLM-treated group,TIMP-1 expressions were increased dramatically,especially at the 4^th weeks after local injections.The hydroxyproline contents were also gradually increased,as compared with those in the normal control group.TIMP-1 expressions were gradually elevated in parallel with the increase of hydroxyproline contents and the induction of dermal sclerosis.As compared with the PBS injected mice,the dermal thickness and the amount of hydroxyproline was increased remarkably (P＜0.01,0.01,respectively),the level of procollagena 1(Ⅰ) mRNA and MMP-9 and TIMP-1 protein expression was increased significantly in mice injected with bleomycin.As comparison with those of the normal saline(NS) -treated mice injected with bleomycin,the levels of procollagena 1(Ⅰ) mRNA,MMP-9 and TIMP-1 protein expression was decreased significantly (P＜0.01,0.01,0.01,respectively) in simvastatin-treated mice administered at the beginning,but not decrease after sclerosis induced;The dermal thickness and the amount of hydroxyproline were significantly decreased(P＜0.05,0.01,respectively) in simvastatin-treated mice administered at the time sclerosis was induced;Except for the improvement of the levels of procollagena 1(Ⅰ) mRNA expression(P＜0.05),another three parameters were of no improvement when simvastatin was given after sclerosing formation,as compared with those of NS-treated mice injected with bleomycin.When the administration of simvastatin started at the beginning, compared with that of the NS-treated mice injected with BLM,the dermal thickness was decreased remarkably(P＜0.05),and the amount of hydroxyproline in skin was also markedly decreased(P＜0.01).When the administration of simvastatin started after sclerosis had been induced,no significant improvement was observed on the dermal thickness or hydroxyproline contents.Conclusion:During the skin sclerosis induced by BLM in mice,the inflammation is the most important alteration with enhanced MMP-9 expression in the early stage.While in the late stage,the main change is displayed as sclerosis,characterized by increased TIMP-lexpression.These findings suggest that the enhanced production of MMP-9 may contribute to fibrogenic remodeling during the progression of skin sclerosis in mice;TIMP-1 is involved in the pathogenesis of skin sclerosis and it is important for fibrogenesis.Orally simvastatin can suppress the expression of procollagena 1(Ⅰ) mRNA,MMP-9 and TIMP-1 protein,and improve sclerosis in bleomycin-treated mice in the early stage rather than in the stage when sclerosis has already formed.These findings suggest that simvastatin has potential as a drug for the treatment of scleroderma especially in the early phase.