Type IV collagenases in human amniotic fluids and amnion epithelial cells

Abstract

Gelatin zymograms revealed in human second trimester amniotic fluids a constant M r 66000 proteolytically active polypeptide that in immunoblotting was recognized by antiserum against the human fibroblast gelatinase/type IV collagenase. Isolated cultured human amnion epithelial cells produced the M r 66000 proteinase and frequently a M r 92000 one. The production of the former was enhanced by transforming growth factor-β and that of the latter by tetradecanoyl phorbol acetate. Immunoprecipitation experiments indicated that the M r 66000 amnion epithelial cell proteinase was identical with that round in the amniotic fluids and that the M r 92000 one corresponded to the human macrophage/granulocyte gelatinase/type IV collagenase. Approximate quantifications of the M r 66 000 proteinase in amniotic fluids and sera from same individuals were assessed by comparison of dilution series of the samples and standard enzyme preparations in zymography. These measurements indicated that the amount of the proteinase in the amniotic fluids was about 5–10 μg/ml representing 0.1–0.2% of total proteins. In sera the corresponding figures were 30–40 μg/ml and 0.03–0.06%, respectively. Thus the relative concentration of the M r 66000 proteinase in amniotic fluids was approx. 3–4-fold that in sera, suggesting local production of the protein. The proteinase may be produced by amnion epithelial cells that under so far unknown physiologic stimulus also may start secreting the M r 92000 enzyme.