The Role Of Alteration Of Cardiac Matrix Metalloproteinases And Tissue Inhibitors Of Metalloproteases, TGF-β1 And SMC Proliferation In Cardiac Allograft Vasculopathy

Background-The matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteases (TIMPs) system plays an important role in remodeling of the coronary wall in different diseases. However, in patients who developed cardiac allograft vasculopathy (CAV), their expression levels within the walls of allograft coronary arteries remains unknown.Methods and Results-To observe expression of MMPs/TIMPs in the thickening of neointimal in CAV and to determine their roles in the development of CAV. Coronary artery samples from explanted hearts of 20 idiopathic dilated cardiomyopathy (DCM) patients whom underwent cardiac transplantation and 24 CAV patients whom underwent re-transplantation were obtained. MMP-1,2,3,9,13,14 and TIMP-1 protein expressions were quantified by Western blot(WB), and MMP-1,2 and 3 were further analyzed by immunohistochemistry (IHC) staining. By WB, MMP-1 and MMP-3 were found to significantly be decreased while TIMP-1 and MMP-2 significantly increased in the media and intima of CAV compared to DCM. There were no significant differences of MMP-9 and MMP-14 between CAV and DCM. The lower levels of MMP-1 and MMP-3 expression was confirmed in media and intima of CAV by IHC; however, the intima of CAV showed small patches of distinctly higher MMP-1 expression areas. MMP-2 staining was significant higher in the intima of CAV and significant lower in the media of CAV compared to DCM. The distribution of MMP-2 staining was basically co-localized with smooth muscle cells (SMC) in thickened intima of CAV.Conclusions-The combination of increased MMP-2, TIMP-1 and decreased MMP-1, MMP-3 orchestrates the pathologic remodeling toward intimal hyperplasia in coronary artery wall of CAV. Background-Vascular smooth muscle cell (VSMC) plays a characteristic pathologic role of the intimal thickening in Cardiac Allograft Vasculopathy (CAV), however, its time-related changes and underlying mechanism remains unknown.Methods and Results-To observe the distribution of VSMC in the thickening of neointimal in CAV and to test the hypothesis that Transforming Growth Factor (TGF-β1) may play a pathogenesis role, coronary artery samples from explanted hearts of 20 idiopathic dilated cardiomyopathy (DCM) patients whom underwent cardiac transplantation and 27 CAV whom underwent re-transplantation were obtained. Active and latent form of TGF-β1 andα-SMA protein expressions were quantified by Western blot, and VSMC distribution in coronary artery wall were analyzed byα-SMA-positive area in immunofluorescent (IF) staining. Unlike mild intimal thickening with VSMC in DCM, VSMC was more heterogeneously distributed in thickened intima of CAV vs. DCM shown inα-SMA IF staining. Three different types of distribution of VSMC expression were observed:TypeⅠCAV(CⅠ):abundant VSMC and mild fibrotic throughout the intima; TypeⅡCAV(CⅡ):reducing VSMC confined in a circumferential layer adjacent to the medium, the inner part of intima shows fibrofatty lesion and/or fibrotic change; TypeⅢCAV(CⅢ):scarce or absent VSMC within whole neo-intima. Analysis of fluorescent image showed in CAV group:CⅠshowed highest percentage of SMC in both intima and media, CⅡwas the second, CⅢthe lowest, there was no significant difference between CⅠand DCM, but DCM was higher than CⅡand CⅢ. CⅢhad significant longer allograft survival time than CⅠ. By quantitative Western blot analysis, the latent TGF-β1 protein expression in all CAV groups was significant higher than DCM groups, however, CⅢhad lower active TGF-β1 level compare to DCM. In CAV, CⅠhad highestα-SMA and TGF-β1 level compared to other groups, CⅢthe lowest.α-SMA positively correlated with the active TGF-β1 (r=0.635, P<0.001) and latent TGF-β1 (r=0.531, P<0.01) in CAV. In CAV group, Allograft survival time was negatively correlated with theα-SMA (r=-0.457, P＜0.05) and recipient age.Conclusions-Elevation of TGF-β1 expression in lesion of CAV plays a important role of neointima formation, TGFβ1 is associated with the proliferation and differentiation of VSMC in CAV, high level of SMC proliferation and expression of A - TGF-β1 in coronary artery wall associated with the shorter allograft survival time in patients who develop CAV.