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Parathyroid Hormone Increases Epidermal Growth Factor Receptors in Cultured Human Trophoblastic Cells from Early and Term Placenta

Laboratoire de Physiopathologie du Développement, CNRS URA 1337-Ecole Normale Supérieure 75230 Paris Cedex 05 France

Address all correspondence and requests for reprints to: Eliane Alsat, Laboratoire de Physiopathologie du Développement, CNRS URA 1337-Ecole Normale Supérieure, 46, rue d’Ulm-8ème Etage, 75230 Paris Cedex 05, France.

The effect of PTH on the epidermal growth factor (EGF) receptor was analyzed during the in vitro differentiation of human cytotrophoblasts. The cytotrophoblasts were isolated by a trypsin-DNase method from first trimester and term placentas and purified on a Percoll gradient. In culture, these cells aggregated and fused together to form a syncytium. This in vitro differentiation was associated with a 2-fold increase in ¹²⁵I-EGF binding after 48 h of culture. The addition of 0.1 µM PTH (PTH-treated cells) to the culture medium induced a significant 2- to 3-fold increase (P < 0.005) in EGF binding. The effect was dose related with a maximum obtained at a 1 nM concentration.

Scatchard analyses revealed that PTH-treated cells possess a 2-fold higher number of high affinity sites as compared to control cells from early placenta (0.71 ± 0.06 pmol/mg protein and 0.34 ± 0.04 pmol/mg protein, respectively) and from term placenta 1.24 ± 0.10 pmol/mg protein and 0.61 ± 0.07 pmol/mg protein, respectively). The apparent Kd values for high affinity sites (0.15 nM) and for low affinity sites (4 nM) were not altered either by the gestational age of the cells or by PTH treatment.

With respect to the EGF-dependent phosphorylation in membranes of trophoblast cells in culture, it was found that the phosphorylation of two major proteins of 175 kilodaltons and 35 kilodaltons, is greatly increased in PTH-treated cell membranes in the presence of EGF. This PTH-induced effect on EGF receptors was associated with an augmented functional response of trophoblastic cells to EGF. PTH increased the EGF-stimulated secretion of hCG.

These results demonstrate that PTH increases the number of biologically active EGF receptors during the in vitro differentiation of human trophoblast cells. This PTH-induced effect suggests a role for this hormone in the regulation of the growth and the endocrine functions of these cells.

^*This study was supported with grants from le Comité de Paris de la Ligue Nationale Francaise contre le Cancer and from La Fondation pour la Recherche Médicale.

Received June 11, 1990.

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