Prolactin (PRL) and insulin-like growth factor-binding protein (IGFBP-1) are two major secretory proteins of human endometrial/decidual cells. We have characterized the mRNA of PRL and IGFBP-1 and studied the effect of progestin, medroxyprogesterone acetate (MPA), anti-progestin (RU486), and relaxin (RLX) on the levels of these two mRNA transcripts in a long-term culture of human endometrial stromal cells. Northern blot analysis showed that the size of PRL mRNA was 1.15 kb and that of IGFBP-1 mRNA, 1.6 kb. Primer extension of endometrial/decidual IGFBP-1 mRNA showed two transcription initiation sites identical to those found in HepG2 human hepatoma cell line. The levels of mRNA in control samples remained low, approximately 2 pg PRL and approximately 5 pg IGFBP-1/microgram RNA at various times of culture. When stromal cells were treated with MPA for 28 days, PRL mRNA gradually increased 100-fold whereas IGFBP-1 mRNA exponentially increased approximately 1000-fold compared to control values and leveled after 25 days in culture. The timing of maximal stimulation was shortened by withdrawing MPA or by replacing MPA with RU486. After removal of MPA, levels of both mRNAs increased and each peaked after approximately 10 days, with PRL showing a 2-fold and IGFBP-1 a 20-fold increase compared to cells treated with MPA continuously. Replacing MPA by RU486 caused a rapid increase of PRL mRNA (2-3-fold) in 2-3 days followed by a gradual reduction to less than 20% of peak levels over the next 3 days. IGFBP-1 mRNA levels increased 30- and 100-fold in 1-2 days followed by a reduction to less than 20% of peak levels over the next 24 h. The reduction of mRNA levels by RU486 was reversed when cells were rechallenged with MPA. Relaxin alone caused a transient stimulation of PRL and IGFBP-1 mRNA. Maximal stimulation occurred between 10 and 20 days of culture and was 100-fold for PRL and 1000-fold for IGFBP-1 relative to control values. Cells treated with MPA and RLX in sequence had higher mRNA levels than cells treated with MPA continuously or cells subjected to MPA withdrawal. Maximal mRNA levels reached 0.4 ng PRL and approximately 8 ng IGFBP-1/microgram total RNA, approximately 0.04% and 0.8% of cellular RNA. The mRNA levels under various hormonal manipulations were similar to the previously published synthesis and secretion patterns of PRL and IGFBP-1 proteins in this system.(ABSTRACT TRUNCATED AT 400 WORDS)

Decidual cells arise by proliferation and differentiation of endometrial stromal cells of the uterus after appropriate stimulation by ovarian hormones. Previously we have shown that progestin and relaxin stimulate the secretion of several decidual-cell-specific secretory proteins in a long-term primary cell culture system. We now report the effects of progestin and relaxin on the morphology of stromal cells in association with the production rate of two major decidual secretory proteins, prolactin and insulin-like growth factor binding protein-1 (IGFBP-1). Stromal cells were cultured in RPMI 1640 and 2% fetal bovine serum for 22 days under control conditions (no hormone), with relaxin or medroxyprogesterone acetate (MPA), or MPA plus relaxin. Cells treated with MPA alone or MPA plus porcine relaxin grew to a high density with many areas of heaping while control cells and cells grown in medium containing relaxin alone formed discontinuous layers. The cytoplasm was distinguished by aggregates of rough endoplasmic reticulum and secretory granules. Surfaces of cells treated with MPA plus relaxin had clusters of short blunt processes containing secretory granules. The processes were rarely seen in cells exposed to MPA alone and completely absent in control cells or cells exposed to relaxin alone. Intercellular space was greatly widened in cells treated with MPA alone or MPA plus relaxin. There were many extended gap junctions in MPA- and relaxin-treated cells in contrast to controls.(ABSTRACT TRUNCATED AT 250 WORDS)

The present study showed that in undifferentiated endometrial stromal cells, progestin increases the RLX receptor content to enhance the effect of RLX on the target gene (IGFBP-1). In decidual cells, RLX alone up-regulates its receptor, resulting in a large scale induction of IGFBP-1. TGFbeta1 has an inhibitory effect on LGR7 and IGFBP-1.