Molecular Basis of Anti-fibrosis via Destruction of an Organ Self-repair System

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Myofibroblast formation and overproduction of extra-cellular matrix (ECM) are common events in the pathogenesis of tissue fibrosis under chronic injuries, such as liver cirrhosis, pulmonary fibrosis and cardiomyopathy. In the present study, we found that HGF directly targeted the interstitial myofibroblasts and reduced ECM accumulation using the animal model of pulmonary fibrosis, liver cirrhosis and dilated cardiomyopathy.1) Regression of pulmonary fibrosis by HGE :We used bleomycin-injected mice as a model of lung fibrosis and found that HGF elicited apoptotic changes in the myofibroblast cell population in vivo. Furthermore, we obtained in vitro evidence that : (i) HGF degraded ECM proteins (i.e., cell anchorage) around the myofibroblasts, via induction of proteinases such as MMP-9/-1/-2 ; (ii) under such ECM-deficient conditions, the myofibroblasts lose the anchorage then anoikis-like apoptotic cell death occurred. Importantly, an MMP-inhibitor diminished HGF-mediated apoptotic cell death of myofibroblasts, in vitro as well as in vivo, thus indicating that HGF-induced anti-fibrotic effects largely depended on inductions of MMPs by HGF. We published these results in FASEB-Journal 19 : 580 (2005)2) Reduction of interstitial fibrosis in liver cirrhosis and cardiomyopathy by HGF :In the rat model of liver cirrhosis, HGF enhanced myofibroblast apoptosis and inhibited proliferation of interstitial myofibroblasts. These effects were associated with the reduction of ECM-accumulated areas. In vitro, HGF counteracted the PDGF-mediated proliferation of the lipocyte-derived myofibroblasts. In the hamster model of cardiomyopathy, HGF reduced TGF-beta production in the interstitial myofibroblasts, followed by the reduction of ECM as well as improvement in the cardiac functions. These outcomes were published in Am-J-Pathol 166 : 1017 (2005) and in Am-J-Physiol 288 : H2131 (2005), respectively.