OBJECTIVE: This study was conducted to define the cellular site of expression of tissue inhibitor of metalloproteinase-1 and tissue inhibitor of metalloproteinase-2 in human amnion by an evaluation of the levels of messenger ribonucleic acids in separated amnion epithelial and mesenchymal cells and to ascertain whether amnion epithelial and mesenchymal cells maintained in culture continue to express tissue inhibitor of metalloproteinase messenger ribonucleic acids.

STUDY DESIGN: Human placentas and fetal membranes were obtained immediately after delivery. Amnion tissue was separated from chorion laeve and either frozen immediately (–80° C) or processed by differential enzymatic treatment to separate the epithelial and mesenchymal cells, which were frozen (−80° C) or else plated and maintained in monolayer culture. The levels of tissue inhibitor of metalloproteinase types 1 and 2 messenger ribonucleic acid were evaluated by Northern analyses of total ribonucleic acid extracted from amnion tissue, freshly separated epithelial and mesenchymal cells, and epithelial and mesenchymal cells in monolayer culture.

RESULTS: Tissue inhibitor of metalloproteinase types 1 and 2 messenger ribonucleic acids were detected by Northern analysis in freshly isolated amnion tissues from midtrimester and term pregnancies. The major species of tissue inhibitor of metalloproteinase-1 messenger ribonucleic acid was 0.9 kb in length; a minor species of approximately 3.5 kb also was present. Tissue inhibitor of metalloproteinase-2 messenger ribonucleic acids of 3.5 and 1.0 kb and of similar intensity were also detected. The levels of type 1 messenger ribonucleic acid were not different in amnion tissues obtained at term or during the midtrimester of pregnancy. The levels of tissue inhibitor of metalloproteinase type 2 messenger ribonucleic acids in amnion tissue most commonly were greater at term than in tissues obtained during the midtrimester. The level of type 1 messenger ribonucleic acid in mesenchymal cells was appreciably greater than that in epithelial cells, and this difference was maintained during culture of these cells. The level of type 2 messenger ribonucleic acid was similar in both cell types and was maintained during culture. The levels of type 1 or 2 messenger ribonucleic acids were not affected by treatment of amnion epithelial or mesenchymal cells in culture with a variety of test agents, including steroid hormones, cytokines, and growth factors.

CONCLUSION: The amnion mesenchymal cells are the primary source of tissue inhibitor of metalloproteinase-1 in human amnion, whereas both cell types have the potential to produce tissue inhibitor of metalloproteinase-2. (Am J Obstet Gynecol 1997;176:915-21.)