Regulation of Insulin-Like Growth Factor-Binding Protein-1 Synthesis and Secretion by Progestin and Relaxin in Long Term Cultures of Human Endometrial Stromal Cells*

Abstract

The decidualized endometrium during the first trimester of pregnancy synthesizes and secretes a 32-kDa insulin-like growth factor-binding protein (termed hIGFBP-1) at high levels. IGFBP-1 is the major soluble protein product of this tissue and is principally localized to the differentiated endometrial stromal cell, the decidual cell. In the present study long term culture of stromal cells from the nonpregnant endometrium have been employed to elucidate the hormonal requirements for IGFBP-1 production. Immunoreactive IGFBP-1 was undetectable in control cultures. However, inclusion of medroxyprogesterone acetate (MPA) induced rates of 0.35 +/- 0.09 microgram/0.1 mg cell DNA.day (mean +/- SEM; n = 5) after 20-30 days. In these cultures cells exhibited morphological changes consistent with decidual cell differentiation. In all cultures removal of MPA after exposure for 10-16 days, with or without subsequent inclusion of relaxin (RLX), increased production of IGFBP-1 450- to 4600-fold to rates of 150-710 micrograms/0.1 mg cell DNA.day or 26-131 micrograms/10(6) cells.day on days 24-26. The rates tended to be higher with the inclusion of RLX and were sustained in contrast to cultures without RLX, where rates fell by day 30. Individual cultures responded differently to RLX when added from the initiation of culture, with either a response similar to MPA alone or a cyclical change in production, achieving maximal rates of 190-290 micrograms/0.1 mg cell DNA.day. Cultures in which RLX alone induced high IGFBP-1 high production were obtained from endometrium during the progesterone-dominated luteal phase. In cultures exhibiting high rates of immunoreactive IGFBP-1 production, the protein represented their major secretory protein product. This was confirmed by [35S]methionine incorporation and the presence of IGFBP-1 as the predominant protein in serum-free culture medium. The immunoreactive IGFBP-1 isolated from culture medium was found to be identical, by a number of criteria, with IGFBP-1 derived from decidual tissue. These results were consistent with a primary role of progestin exposure, whether in vivo or in vitro, in converting endometrial stromal cells to cells potentially able to exhibit the high rates of IGFBP-1 production typical of the decidualized endometrium of pregnancy.

Effect of single post-ovulatory administration of mifepristone (RU486) on transcript profile during the receptive period in human endometrium

“…Circulating relaxin (RLX) levels rise during the luteal phase (Bond et al 2004, Hayes 2004 and its detection in the endometrium during natural cycles coincide with the period of endometrial receptivity (Yki-Jarvinen et al 1985) suggesting a role in the early events of embryo implantation. Several studies show that RLX exerts a wide range of effects on the human endometrium mediating differentiation, vascularization and immunomodulation in this tissue (Goldsmith & Weiss 2009 Bell et al 1991), glycodelin (Tseng et al 1999) and vascular endothelial growth factor (VEGF; Unemori et al 1999, Palejwala et al 2002. The results obtained in the present study cannot distinguish between genes that are regulated by P 4 and those whose transcript levels are regulated by the presence of estrogens, relaxin or other factors.…”

IGFs and IGF-binding proteins in the regulation of human ovarian and endometrial function

“…In contrast, there is no difference in circulating IGFBP-1 levels between IUCD (without progestin) users and non-IUCD users (Seleem et al 1996). Studies using cell cultures have also shown that progesterone (medroxyprogesterone acetate) stimulates IGFBP-1 secretion in cultured endometrial stromal cells (Bell et al 1991). These findings further confirm that synthesis of endometrial IGFBP-1 is progesterone dependent ( Julkunen et al 1988, Rutanen & Pekonen 1991).…”

Hox transcription factors and their elusive mammalian gene targets

“…Insulin-like growth factor binding protein-1 (IGFBP-1) is highly expressed during decidualisation and this expression is progesterone-dependent, as is Hoxa10 (Bell et al, 1991). HOXA10 activates the IGFBP-1 promoter in various types of endometrial cells (Gao et al, 2002) in cooperation with FKHR, a member of the FOXO subfamily of forkhead (fkh) transcription factors (Kim et al, 2003).…”