Endocrine Abstracts

JOINT69

In pregnancy, the placental trophoblasts secrete a large amount of pregnancy-specific glycoprotein 1 (PSG1) into the maternal circulation. However, the exact role of PSG1 in pregnancy remains elusive. Human chorionic gonadotropin (hCG) is a hormone produced primarily by syncytiotrophoblastic cells of the placenta during pregnancy. The hormone stimulates the corpus luteum to produce progesterone to maintain the pregnancy. By using primary human placental trophoblasts, we demonstrated that like the expression of hCG, the expression of PSG1 was also significantly increased during syncytialization of placental trophoblasts. Knock-down of PSG1 expression did not affect hCG beta subunit mRNA levels, but increased intracellular hCG accumulation in trophoblasts while decreased extracellular hCG abundance, suggesting that PSG1 maintains hCG secretion in human placental trophoblasts. Induction of endoplasmic reticulum (ER) stress with thapsigargin (Tg) reduced PSG1 secretion along with increased intracellular hCG in trophoblasts and decreased extracellular hCG. In conclusion, we have demonstrated a novel of PSG1 in the maintenance of hCG secretion in human placental trophoblasts which may be impaired by ER stress. This novel function of PSG1 indicates that PSG1 participates in pregnancy maintainence by stimulating hCG secretion.