Objective To investigate the effects of tissue inhibitor of matrix metalloproteinases-4(TIMP-4) on the activities of matrix
metalloproteinases(MMPs) and the collagen deposition.(Methods)Vascular smooth muscle cells(VSMCs) of rat thoracic aorta were cultured and divided into 3 groups: 2 groups to be transfected with
adenovirus vector containing green fluorescence protein(AdGFP) or adenovirus vector containing TIMP-4(AdTIMP-4),and one group un-transfected.Zymography and reverse zymography were used to detect the activities of MMP-2,MMP-9 and TIMP-4 in the supernatants.Male Wistar rats underwent balloon injury of common carotid artery and then divided into 3 groups: pure injury group,AdGFP transfection group,and AdTIMP-4.transfection group.Four and 28 days later 3 and 6 rats were killed in each group respectively to undergo microscopy and examination of the activities of MMP-2,MMP-9,and TIMP-4,and collagen quantity.Results The MMP-2 activity in the VSMC culture fluid supernatant of the AdTIMP-4 group was decreased dose-dependently,however,the activity of MMP-9 did not changed
significantly among the 3 groups.Bands of activated MMP-2 and MMP-9 could not be examined in the normal vessel tissues.Four hours after the injury,the activity of MMP-2 was significantly increased in the pure injury group and AdGFP group,however,was significantly decreased in the AdTIMP-4 group.Four days later no MMP activity could be detected in either group.The neoformation of tunica intima was inhibited by 66% in the AdTIMP-4 group,The collagen quantity per vessel cell was 12.1±1.0 in the AdGFP group,not significantly different from that of in the AdTIMP-4 group(11.9±1,P>0.05),and the collagen quantity per tunica adventitia cell in the AdTIMP-4 group was 118±13,not significantly different from that of the pure injury group(135±11,P>0.05).Conclusion The regulation of MMP/TIMP balance by TIMP-4 may control the metabolism of collagen and play an important role in the vascular repair process.