Expression of messenger ribonucleic acid for epidermal growth factor (EGF), transforming growth factor-alpha (TGF alpha), and EGF receptor in human amnion cells: possible role of TGF alpha in prostaglandin E2 synthesis and cell proliferation.

The amnion plays important structural and functional roles in the maintenance of pregnancy and the initiation of parturition. Recently, we reported that epidermal growth factor (EGF) activates prostaglandin (PG) production and cell growth in cultured amnion cells. In this study, we showed the expression of EGF, transforming growth factor-alpha (TGF alpha), and EGF receptor protein and messenger ribonucleic acid in amnion cells, using an immunofluorescence technique and the reverse transcription-polymerase chain reaction. Next, we studied the effect of TGF alpha on intracellular Ca2+ mobilization and PGE2 production in amnion cells. TGF alpha induced an increase in the intracellular Ca2+ concentration in amnion cells, and this increase was significantly reduced when the cells were incubated with cobalt chloride (a Ca2+ channel blocker; 2.5 mmol/L) or EGTA (a Ca2+ chelator; 5 mmol/L). TGF alpha enhanced PGE2 production, and this increase was significantly inhibited when the cells were incubated with indomethacin (a cyclooxygenase inhibitor; 10 mumol/L), cobalt chloride (2.5 mmol/L), or EGTA (5 mmol/L). We also investigated the effect of TGF alpha on the growth of cultured human amnion cells by using flow cytometric analysis of the DNA content. TGF alpha induced DNA synthesis by human amnion cells, and indomethacin inhibited the TGF alpha-induced DNA synthesis. These results suggest that 1) EGF/TGF alpha are expressed and produced in amnion cells; 2) these endogenous factors may regulate the proliferation of amnion cells in an autocrine or paracrine manner; and 3) these growth factors may exert their effects via intracellular Ca2+ mobilization and PGE2 production.