Liver fibrosis (scarring) develops as a consequence of a variety of chronic inflammatory liver diseases, and if untreated, will progress into cirrhosis and liver failure. With the dramatic increased prevalence of non-alcoholic fatty liver disease and chronic hepatitis C worldwide, it is expected that the health care impact and cost of liver cirrhosis will dramatically increase in the next 10-20 years. Unfortunately, no therapy currently available directly regulates the process of liver fibrosis. Hepatic stellate cells (HSCs) have been regarded as a central cellular mediator of fibrosis during chronic liver injury. Upon activation, they transform into myofibroblast-like cells that promote the accumulation of extracellular matrix proteins, eventually distorting liver architecture and impairing liver function. Recent studies on a known extracellular matrix-regulating protease, tissue-type plasminogen activator (t-PA), have shown that it can play a role in modulating tissue fibrosis development [1-3]. Preliminary studies presented in this proposal indicate that exogenous administration of active t-PA can antagonize and reverse the pro-fibrotic phenotype of hepatic stellate cells in vitro. Therefore, this proposal is directed at testing the hypothesis that t-PA normally suppresses the myofibroblast-like cell differentiation of HSCs following acute hepatic injury and that the loss of this function results in fibrosis/cirrhosis.
The aims of this study are: 1) to investigate the potential proteolytic functions of t-PA in suppressing liver fibrosis 2) to determine the potential signaling functions of t-PA in suppressing liver fibrosis, and 3) to determine the changes that occur in tissue distribution of the PAs and their interacting partners between normal and chronically injured liver. Should the stated hypothesis prove correct, targeted administration of t-PA may be a novel strategy for the treatment and/or prevention of liver cirrhosis resulting from a variety of etiologies (e.g. NALFD, chronic hepatitis, genetic disorders, and alcoholism). Since t-PA is already FDA-approved for clinical use, the impact of this project is tremendous in terms of potential expedited development of therapies for liver cirrhosis patients who currently have limited treatment options.