DUAL EXPRESSION OF MATRIX METALLOPROTEINASE-2 AND MEMBRANE-TYPE-1 - MATRIX METALLOPROTEINASE IN FIBROTIC HUMAN LIVERS

We have previously reported increased expression of matrix metalloprot einase-2 (MMP-2) using a rat model of liver fibrosis, However we did n ot clarify how the precursor of MMP-2. (proMMP-2) was activated, There fore, we used human liver specimens with chronic hepatitis (CH) and li ver cirrhosis (LC) to examine expression of membrane-type-1-MMP (MT1-M MP), which has recently been determined to activate proMMP-2. Northern hybridization studies showed a 5.4- and 1.4-fold increase in MMP-2 ex pression in CH and LC, respectively, as compared with normal liver. MT 1-MMP gene expression simultaneously increased 4.0- and 1.4-fold in CH and LC, respectively. In situ hybridization using S-35-cRNA probes of MMP-2 and MT1-MMP showed prominent silver granules in elongated cells found in the lobules, periportal areas, and fibrous septa of CH and L C samples. These elongated cells expressed ct-smooth muscle actin by i mmunohistochemistry. Immunoelectron microscopic examination localized MMP-2 and MT1-MMP to the rough endoplasmic reticulum of stellate cells located in the lobules and periportal areas, or to fibroblasts in the fibrous septa, suggesting that MMP-2 and MT1-MMP were produced by the se cells. In addition, cytoplasmic and membranous immunodeposits of bo th MMPs were found in endothelial cells, Kupffer cells, capillary endo thelial cells, and lymphocytes, indicating that activation of proMMP-2 occurs locally, Increased expression of MMP-2 and MT1-MMP was detecte d in CH and LC, while dual over-expression was found in stellate cells and fibroblasts, possibly resulting in the increase of active MMP-2 i n and around these cells. These findings suggest that activated MMP-2 may remodel liver parenchyma during the process of liver fibrosis.