RAT HEPATIC LIPOCYTES SYNTHESIZE AND SECRETE TRANSIN (STROMELYSIN) INEARLY PRIMARY CULTURE

Background & Aims: Hepatic lipocyte proliferation and activation are p ivotal in liver fibrosis. Disruption of normal lipocyte-matrix interac tions may contribute to this process. The synthesis of transin, which degrades normal liver matrix, by culture-activated hepatic lipocytes w as investigated. Methods: Lipocytes were isolated by pronase/collagena se perfusion, density gradient centrifugation, and centrifugal elutria tion. Transin messenger RNA in lipocytes was analyzed by Northern blot ting. Transin activity was analyzed by zymography, Western blotting, i mmunocytochemistry, and quantitative [C-14]beta-casein degradation ass ay. Results: Transin messenger RNA was detected in early primary cultu re (3-5 days) but not in freshly isolated lipocytes or late primary cu lture. Zymography of lipocyte medium showed caseinolytic activity (rel ative molecular weight, 57 kilodaltons and 60 kilodaltons) inhibited b y ethylenediaminetetraacetic acid but not thiol or serine protease inh ibitors. Immunoblotting and immunocytochemistry confirmed the presence of transin in media and cells. Quantitative transin activity decrease d progressively with increasing duration of primary lipocyte culture a cid myofibroblastic transformation. Conclusions: Rat hepatic lipocytes express the transin gene and secrete its product during the early pha se of lipocyte activation in primary culture. Because this enzyme degr ades a wide spectrum of normal basement membrane proteins and activate s progelatinase B and interstitial collagenase, it may have an importa nt role in liver injury and fibrosis.