Differential expression of matrix-metalloproteinase-1 and -2 genes in normal and fibrotic human liver

Altered degradation of extracellular matrix has been implicated in the pathogenesis of hepatic fibrosis. We investigated levels and cellular sites of gene expression of two major collagen-degrading enzymes, matrix-metalloproteinase (MMP)-1 (fibroblast type-interstitial collagenase) and MMP-2 (72-kd gelatinase, type IV collagenase) in five normal and 18 fibrotic human livers as well as in cultured human hepatic fat-storing cells by Northern blot analysis and in situ hybridization. Fat-storing cells expressed both MMP-1 and MMP-2 RNA in vitro. In vivo, MMP-1 was undetectable in mesenchymal and parenchymal cells of all liver specimens, whereas MMP-2 transcripts were expressed in all livers by vimentin-positive, CD68-negative mesenchymal cells. Mesenchymal cells of all fibrotic livers displayed high transcript levels of transforming growth factor-beta 1, which is known to modulate MMP expression. Along with de novo fibrogenesis and possibly influenced by transforming growth factor-beta 1, expression of MMP-2 in the absence of MMP-1 expression may be responsible for the quantitative and qualitative changes of extracellular matrix observed in chronic liver disease.