Decidualization of human endometrial stromal cells in vitro: effects of progestin and relaxin on the ultrastructure and production of decidual secretory proteins*

Abstract

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)

Relaxin regulation of endometrial structure and function in the rhesus monkey

“…Thus, relaxin seems to be a powerful regulator of human endometrial decidualization, at least as influential as progesterone, if not more so. No evidence of secretory activity was shown by cells treated with only progesterone and estradiol, although secretory activity appears to be a prominent feature of decidualized endometrial stromal cells in vivo (21). Cells in the stromal cultures that were treated with relaxin in addition to progestin exhibited ultrastructural features characteristic of secretory cells.…”

“…Results from various studies provide abundant evidence that relaxin is a potent regulator of the differentiated function of human endometrial cells in vitro (14,(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). Relaxin stimulates the production of prolactin (16,17,19), insulin-like growth factor (18), and insulin-like growth factor binding protein 1 (IGFBP-1) (19), in progestin-primed endometrial stromal cells.…”

“…Relaxin stimulates the production of prolactin (16,17,19), insulin-like growth factor (18), and insulin-like growth factor binding protein 1 (IGFBP-1) (19), in progestin-primed endometrial stromal cells. Because prolactin and IGFBP-1 are considered the major secretory proteins of decidual cells (21), induction of the expression of these secretory proteins has been widely used as a biochemical marker of decidualization of endometrial stromal cells in vitro (22). Detailed studies of the regulation of IGFBP-1 promoter activity in endometrial stromal cells demonstrate that relaxin, not progesterone, is the major inducer of IGFBP-1 gene transcription (20).…”

“…A role for relaxin in human endometrial function is also supported by findings that relaxin binds specifically and with high affinity to human endometrial cells (15). In addition, a large body of evidence exists to demonstrate that relaxin has definitive effects on human endometrial cells in vitro (14,(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). Relaxin stimulates production of several endometrial products including prolactin, glycodelin, insulin-like growth factor binding protein 1 (IGFBP-1) and vascular endothelial growth factor in progestin-primed human endometrial cells in vitro.…”

Forkhead transcription factor FOXO1A is critical for induction of human decidualization

“…DNA microarray studies have shown that FOXO1A is targeted to the nucleus of human decidual cells (Christian et al 2002) and is one of the earliest and most induced genes during human decidualization (Brar et al 2001). In addition, transfection studies in human decidual cells have shown that overexpression of FOXO1A induces expression of the prolactin (Christian et al 2002) and insulin-like growth factor-binding protein 1 (IGFBP-1; Lane et al 1994, Tseng et al 1997, Kim et al 2005 genes, both of which are markedly induced during human decidualization. In a recent study, Kim and co-workers (2005) also reported that a FOXO1A small interfering RNA (siRNA) blocked IGFBP-1 expression in human uterine fibroblasts and HEC-1B cells, but they did not examine whether silencing of FOXO1A expression affects other markers of decidualization and is important in the induction of the decidualization process.…”