Effect of progestin, antiprogestin, and relaxin on the accumulation of prolactin and insulin-like growth factor-binding protein-1 messenger ribonucleic acid in human endometrial stromal cells

Regulation of the human relaxin genes H1 and H2 by steroid hormones

Relaxin, a peptide hormone important to the outcome of human pregnancy is expressed in a tissue specific manner as two genes known as relaxins H1 and H2, in addition to a third human relaxin H3, expressed primarily in the brain. The H1 and H2 genes are highly homologous, differentially expressed in reproductive tissues and appear to activate the same receptor, but their regulation is poorly understood. Based upon the known physiology of these hormones and the response elements in their 5'- and 3'-flanking regions, the possibility that progesterone and/or the glucocorticoids might influence their differential expression was therefore investigated. The changes in the mRNA levels of the relaxin genes in response to either medroxyprogesterone acetate (MPA) or dexamethasone (Dex) were analyzed by RT-PCR using a choriocarcinoma cell line (JAR) as a model system, because the expression of these genes in any primary human cell type is too low for such a study. The addition of 0.5 microM MPA to JAR cells, significantly upregulated the mRNA of only the relaxin H2, while the addition of 0.5 microM Dex significantly upregulated the mRNAs for both the relaxins, after 6h of treatment. Promoter assays indicated an early activation of transcription (1 h), which by 6 h had decreased. Progesterone and/or glucocorticoids could exert their effects via the GRE motif found on the 5'-flanking region of the relaxin genes. The H1-GRE differs from the H2-GRE by a single nucleotide, which may affect H1-GRE binding to the progesterone receptor (PR) but not the glucocorticoid receptor (GR). The antiprogestin RU486 inhibited the binding of the GR to both H1-GRE and H2-GRE, while it enhanced the binding of the PR to these GREs. As determined by gel shift assays, this GRE motif could bind to both the PR and GR and was therefore considered to be functional. Thus, both progesterone and glucocorticoids are capable of differentially regulating the expression of the two human relaxin genes in a model system.

Relaxin regulation of endometrial structure and function in the rhesus monkey

Despite the documented importance of the protein hormone relaxin in reproduction in various mammalian species, the role of relaxin in human reproduction is poorly understood, largely because of the lack of studies in women or in suitable non-human primate models. Here we describe the establishment of a non-human primate model of early human pregnancy and its use in defining the actions of relaxin. Results demonstrate that relaxin exerts dramatic uterine effects including pronounced increase in uterine weight and stimulation of endometrial angiogenesis and resident endometrial lymphocyte number. In addition, relaxin decreases endometrial levels of matrix metalloproteinases 1 and 3 and increases levels of their endogenous inhibitor, tissue inhibitor of metalloproteinase 1, resulting in maintenance of endometrial collagen content. Relaxin significantly inhibits endometrial levels of estrogen receptor alpha, but not beta, and of progesterone receptor isoforms A and B. The findings that relaxin stimulates new blood vessel formation and increases cytokine-containing lymphocyte number while maintaining endometrial connective tissue integrity are consistent with a significant role of relaxin in the establishment and/or maintenance of early pregnancy.

Activation of the protein kinase A pathway in human endometrial stromal cells reveals sequential categorical gene regulation

Decidualization of endometrial stromal cells is a prerequisite for human implantation and occurs in vivo in response to progesterone and involves activation of the protein kinase A (PKA) pathway. The objective of this study was to determine the molecular signatures and patterns of gene expression during stimulation of this pathway with an analog of cAMP. Endometrial stromal cells from two subjects were treated with or without 8-Br-cAMP (1 mM) for 0, 2, 12, 24, 36, and 48 h and were processed for microarray analysis, screening for 12,686 genes and ESTs. Most abundantly upregulated genes included neuropeptides, immune genes, IGF family members, cell cycle regulators, extracellular matrix proteases, cholesterol trafficking, cell growth and differentiation, hormone signaling, and signal transduction. Most abundantly downregulated genes included activator of NF-kappaB, actin/tropomyosin/calmodulin binding protein, cyclin B, IGFBP-5, alpha1 type XVI collagen, lipocortin III, l-kynurenine hydrolase, frizzle-related protein, and cyclin E2. RT-PCR validated upregulation of IGFBP-1, preprosomatostatin, and IL-11, and Northern analysis validated their kinetic upregulation. RT-PCR confirmed downregulation of IGFBP-5, cyclin B, and TIL-4. K-means analysis revealed four major patterns of up- and downregulated genes, and genes within each ontological group were categorized into these four kinetic patterns. Within each ontological group different patterns of temporal gene expression were observed, indicating that even genes within one functional category are regulated differently during activation of the PKA pathway in human endometrial stromal cells. Overall, the data demonstrate kinetic reprogramming of genes within specific functional groups and changes in genes associated with nucleic acid binding, cell proliferation, decreased G protein signaling, increased STAT pathway signaling, structural proteins, cellular differentiation, and secretory processes. These changes are consistent with cAMP modulating early events (0-6 h) primarily involving cell cycle regulation, subsequent events (12-24 h) involving cellular differentiation (including changes in morphology and secretory phenotype), and late events (24-48 h) mediating more specialized function, including immune modulators, in the human endometrial stromal cell.

Action of mifepristone on the expression of insulin-like growth factor binding protein-1 mRNA and protein during the early luteal phase in the human oviduct

OBJECTIVE

To investigate the effects of the antiprogestin mifepristone on the expression of insulin-like growth factor binding protein-1 (IGFBP-1) mRNA and protein during the early luteal phase in the human oviduct.

DESIGN

Prospective case-control study.

SETTING

University hospital.

PATIENT(S)

Fourteen healthy women with regular menstrual cycles who were admitted to the hospital for voluntary sterilization by the laparoscopic technique.

INTERVENTION(S)

Treatment with 200 mg of mifepristone was administered on day LH+2. Fallopian tube samples were obtained on days LH+4 to LH+6.

MAIN OUTCOME MEASURE(S)

Expression of IGFBP-1 was identified using immunhistochemistry, and mRNA levels were determined with semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULT(S)

Immunoreactivity for IGFBP-1 was primarily localized to the cytoplasm of the oviductal epithelial cells. Messenger RNA for IGFBP-1 was identified in total RNA extracted from the same fallopian tube samples. There was a significant increase in the expression of IGFBP-1 immunostaining and mRNA after treatment with mifepristone.

CONCLUSION(S)

These data further illustrate the complex actions of mifepristone and support the view that changes in the oviductal environment after treatment with mifepristone may be detrimental to normal gamete transport and function and contribute to the contraceptive action of mifepristone.

Deletion, but not antagonism, of the mouse growth hormone receptor results in severely decreased body weights, insulin, and insulin-like growth factor I levels and increased life span

GH participates in growth, metabolism, and cellular differentiation. To study these roles, we previously generated two different dwarf mouse lines, one expressing a GH antagonist (GHA) and the other having a disrupted GH receptor and binding protein gene (GHR -/-). In this study we compared the two dwarf lines in the same genetic background (C57BL/6J). One of the most striking differences between the mouse lines was their weight gain profile after weaning. The weights of the GHA dwarfs gradually approached controls over time, but the weights of the GHR -/- dwarfs remained low throughout the analysis period. Additionally, fasting insulin and glucose levels were reduced in the GHR -/- mice but normal in the GHA mice. IGF-I and IGF binding protein 3 (IGFBP-3) levels were significantly reduced, but by different degrees, in both mouse lines, but IGFBP-1 and -4 levels were reduced and IGFBP-2 levels increased in GHR -/- mice but unaltered in GHA mice. Finally, life span was significantly extended for the GHR -/- mice but remained unchanged for GHA dwarfs. These results suggest that the degree of blockade of GH signaling can lead to dramatically different phenotypes.

Complex regulation of decidualization: a role for cytokines and proteases--a review

Decidualization of the endometrial stroma is a precondition for successful establishment of pregnancy. While the local molecular mechanisms driving decidualization are still largely unknown, a number of autocrine/paracrine factors have been identified as differentiation factors in this process. These include the cytokines, interleukin 11, activin A and monoclonal non-specific suppressor factor beta (MNSFbeta). Furthermore, locally produced proteases, including proprotein convertase 6 and matrix metalloproteinases, enable expansion of the tissue and processing of regulatory molecules. This article reviews recent work from our laboratory on the roles of these factors in decidualization.

Oestrogen and progestin responses in human endometrium

Our understanding of the mechanisms of the actions of oestrogens and progestins have evolved from the simple concept of nuclear receptor-mediated regulation of transcription to a highly sophisticated, finely tuned interplay between various coregulators, other signaling cascades and transcription factors. The net result of these complex regulatory mechanisms is a steroid-, cell-, or tissue-specific action of oestrogens and progestins, their antagonists or selective modulators of their receptors. In this review, we have attempted to shed some light on the regulation of the actions of oestrogens and progestins on the human endometrium.

Relaxin activates the MAP kinase pathway in human endometrial stromal cells

The reproductive hormone, relaxin, is structurally similar to insulin and insulin-like growth factor (IGF). Although a number of cellular responses to relaxin have been described, intracellular signaling mechanisms that link relaxin receptor engagement to alterations in gene expression remain uncharacterized. In the present study, relaxin treatment of a well-characterized target, human endometrial stromal cells, resulted in rapid activation of p42/44 mitogen-activated protein (MAP) kinase, as well as of MAPK (or ERK) kinase (MEK). Using a selective chemical inhibitor of MEK, it was further demonstrated that MEK phosphorylation is critical for relaxin-induced MAP kinase activation. Relaxin treatment also induced MAP kinase activation in THP-1 monocytic cells and in human smooth muscle cells, indicating that it may be a major signaling transducer utilized by the relaxin receptor. In contrast to insulin or IGF-1, relaxin did not trigger the PI 3-kinase/Akt pathway, perhaps accounting in part for relaxin's unique biological profile. Relaxin was also found to cause activation of the transcription factor CREB, a substrate of the MAP kinase pathway. Finally, activation of the MAP kinase pathway was shown to be essential for optimal stimulation of expression of the gene for vascular endothelial growth factor.

Hox proteins activate the IGFBP-1 promoter and suppress the function of hPR in human endometrial cells

Previous studies have shown that progestin activates the transcription of IGFBP-1 (insulin-like growth factor binding protein-1). Four regions in the IGFBP-1 promotor have been identified to enhance the transcription. Two of the regions, located at -73 to -65 bp and -319 to -311 bp formed identical DNA-protein complexes with the nuclear extracts of endometrial stromal/decidual cells. To identify the binding protein(s) in endometrial cells that interact with these two regions, we have used the TGTCAATTA repeats (-319 to -11 bp of the IGFBP-1 promoter) to screen the human decidual cDNA library by yeast one-hybrid system. We found that Hox A10, HoxA11, HoxB2, HoxB4, and HoxD11 interacted with the TGTCAATTA repeats in yeast cells. Among these hox genes, the full-length coding region of HoxA10, HoxA11, and HoxB4 were used for functional analysis in three types of endometrial cells, undifferentiated endometrial stromal cells, decidual cells (differentiated stromal cells) and endometrial adenocarcinoma cell line (HEC1-B). All these endometrial cells produce IGFBP-1. Transient transfection assay showed that HoxA10 expression vector increased the promoter activity (the IGFBP-1 proximal promoter containing TGC/TCAATTA and two functional PRE sites) in endometrial stromal cells and in HEC-1B cells, but not in decidual cells. HoxB4 enhanced the promoter activity only in decidual cells, while HoxA11 had no apparent effect in all three types of cells. To evaluate whether Hox proteins would interact with progesterone receptor (hPR), cells were transfected with the promoter construct, Hox and hPR expression vectors. hPR alone activated the IGFBP-1 promoter activity, but expression of Hox gene suppressed the activation. Hox proteins also suppressed the hPR enhanced promoter activities of MMTV (containing consensus-PRE sites) and glycodelin (GdA, containing Sp1 site which mediates the hPR function). These data showed that Hox genes selectively activate the transcription of the IGFBP-1 and GdA genes in different types of endometrial cells. Hox genes, however, suppress the hPR enhanced activities. In addition, we found that HoxB4 expression was induced by estrogen and progestin. Other investigators have shown that HoxA10 and 11 were stimulated by progestin. These findings show that Hox proteins are molecular mediators of the steroid hormones during endometrial cell development.

Relaxin gene and protein expression and its regulation of procollagenase and vascular endothelial growth factor in human endometrial cells

Extensive evidence demonstrates pronounced effects of relaxin on the differentiation of human endometrial cells in vitro. In vivo data in rhesus monkeys suggest a role for relaxin in the development of endometrial vascular architecture. In women, pregnancy can be established and maintained in the absence of circulating relaxin. Thus, local synthesis by the endometrium is necessary if relaxin plays a physiological role in human endometrial function. Although relaxin protein and the prorelaxin C peptide have been localized to human endometrium, no data for relaxin synthesis have been provided to date. We therefore assessed relaxin mRNA and protein levels in cultured, defined human endometrial cells. Reverse transcriptase-polymerase chain reaction (RT-PCR) techniques were used to demonstrate the presence of relaxin mRNA in human stromal and glandular epithelial cells. Secretion of the protein into the media of cultured cells of both types was also detected. Relaxin stimulated the expression of vascular endothelial growth factor in glandular epithelial and stromal cells that were isolated from tissue that had been taken during the secretory phase of the cycle. Relaxin inhibited the expression of procollagenase from both glandular epithelial cells, with a more marked inhibition demonstrated from cells that were isolated from tissue that had been taken during the secretory phase, and from stromal cells. These data demonstrate that human endometrial cells synthesize relaxin, and they support the concept that relaxin fosters endometrial conditions that are required for implantation in women.

Partial characterization of the CCAAT box in the promoter of the hLGFBP-1 gene: interaction with negatively acting transcription factors in decidualized human endometrial stromal cells

The CCAAT cis-element and its adjacent DNA sequence (-82 to -52 bp) in the human insulin-like growth factor binding protein-1 gene (IGFBP-1) promoter are active in both decidualized human endometrial stromal cells and HepG2 cells. In HepG2 cells, CCAAT activity is mediated by interacting with hepatocyte nuclear factor, HNF-1. In endometrial cells, this region is protected by the nuclear extracts of endometrial decidual cells, however, the transactivator which interacts with the region has not been identified. This study was carried out to characterize and identify the stromal/decidual nuclear proteins that interact with the IGFBP-1 CCAAT motif. Gel shift analysis showed that the CCAAT motif (-82 to -52 bp) formed three specific complexes (CI, CII, and CIII) by extracts from human endometrial decidual or stromal cells. The intensity of CIII formed by the nuclear extracts of decidual cells was less compared to that formed by stromal cells whereas CI/CII was found to be opposite. To evaluate the transcription factors that bind to this region, a number of known CCAAT binding proteins were tested. Among them, the CCAAT binding proteins NF-Y (alpha2(1) collagen promoter CCAAT binding protein) and CBF (hsp70 promoter CCAAT binding protein), were characterized by the gel shift assay. The NF-Y consensus binding sequence (the alpha2(1) collagen promoter) and NF-YA,B antibody abolished or shifted CIII. Although the CBF consensus binding sequence (the hsp70 promoter) eliminated all three complexes, the antibody to CBF had no effect on all three complexes. The nuclear extracts of the endometrial stromal/decidual cells did not form a band corresponding to the HNF-1/CCAAT complex. These results indicate that the CCAAT motif binds to NF-Y and the CI/CII binding protein (remains to be identified) but not HNF-1 in endometrium. Systematic mutation in the CCAAT motif showed that NF-Y(CIII binding protein) bound to the 12 bp sequence GGCGCTGCCAAT(-79 to -68 bp) and the CI/CII binding protein bound to 9 bp, TGCCAATCA(-74 to -66 bp). These findings indicate that the CCAAT motif is a composite element. The CCAAT mediated function was analyzed in decidualized endometrial stromal cells. Mutations in the CCAAT motif increased the promoter activity. The maximum activity was found in mutants which abolished the NF-Y complex. The CCAAT core sequence mutants in which both CIII and CI/CII were abolished, also increased the promoter activity. Results indicated that NF-Y and the CI/CII binding protein, yet to be identified, interact with the composite CCAAT element in the IGFBP-1 promoter to repress the promoter activity in endometrial decidual cells.

Trophic effects of relaxin on reproductive tissue: role of the IGF system

Although the growth promoting actions of relaxin on the reproductive tract have been well documented, the means by which relaxin stimulates reproductive tissue growth has not been identified. This report is an overview of studies from our laboratory investigating the role of the insulin-like growth factor (IGF) system in relaxin-induced growth of ovarian and uterine tissues. In the pig ovary, concentrations of relaxin that promote both theca and granulosa cell (GC) DNA synthesis in vitro also significantly (P < 0.05) increased GC IGF-I secretion. When IGF-I activity was blocked in the presence of an IGF-I antibody, the trophic effects of relaxin on GC [3H]thymidine incorporation into DNA were inhibited. However, there was no effect of relaxin on GC IGF binding proteins or IGF-I receptor. In the uterus, in vivo relaxin administration to prepubertal pigs resulted in the stimulation of growth and increases in uterine luminal IGF-I, IGF-II, and IGF binding proteins-2 and -3 secretion (P < 0.05). Thus, the trophic effects of relaxin on ovarian granulosa cells and the uterus involve tissue-specific changes in the IGF system. Additional studies are necessary to better understand the contribution of relaxin to follicular growth and uterine accommodation. These include characterization of the relaxin receptor and post-receptor binding events, as well as the potential impact of relaxin on other growth factor systems and how these systems interact to ultimately drive reproductive tissue growth.

Activation of the insulin-like growth factor binding protein-1 promoter by progesterone receptor in decidualized human endometrial stromal cells

Insulin-like growth factor binding protein-1 (IGFBP-1) is induced extensively when human endometrial stromal cells are decidualized by progestin and relaxin in a long-term primary culture system. The purpose of this study is to investigate whether progesterone receptor (PR) directly activates the IGFBP-1 gene promoter. In decidualized stromal cells, activity of the IGFBP-1 promoter (from -1.2 kb to +68 bp) containing putative progesterone-response elements (PREs) was increased 80-fold. Mutation of either 5' or 3' half-site of the putative PRE1 site (from -193 to -179 bp) reduced the promoter activity. Mutations that converted PRE1 closer to consensus PRE increased the promoter activity. In undifferentiated stromal cells, mutations of PRE sites had no effect on the promoter activity. When a PR expression vector (hPR1) was cotransfected, progestin increased promoter activity derived from p275CAT but not from p1.2CAT, suggesting that the function of PRE1 was repressed by the region from -1.2 kb to -275 bp in the promoter. Progestin did not increase promoter activity derived from p275CAT without cotransfection of hPR1, suggesting that endogenous PR alone is insufficient to activate PRE1. In summary, results indicate that the PRE1 site of the IGFBP-1 promoter mediates a direct activation of PR on transcription specifically in decidualized stromal cells.

Cadherin-11 is a hormonally regulated cellular marker of decidualization in human endometrial stromal cells

Cultured human endometrial stromal cells respond to the gonadal steroids, progesterone and 17beta-estradiol, with morphological and biochemical changes that are characteristic of decidualization in vivo. To date, the cellular mechanisms involved in the terminal differentiation of human endometrial stromal cells into decidual cells remain poorly understood. We have recently determined that the novel cadherin subtype, known as cadherin-11, is expressed by endometrial stromal cells undergoing decidualization during the luteal phase of the menstrual cycle and the decidua of pregnancy. In these studies, we have examined cadherin-11 mRNA and protein expression levels in human endometrial stromal cells undergoing steroid-mediated decidualization in vitro. Progesterone or a combination of progesterone and 17beta-estradiol increased stromal cadherin-11 mRNA and protein expression levels with time in culture. Maximum levels of cadherin-11 expression in these cell cultures correlated with a marked increase in IGFBP-1 mRNA levels, a biochemical marker of decidualization. In contrast, 17beta-estradiol had no effect on stromal cad-11 mRNA and protein expression or the levels of the IGFBP-1 mRNA transcript. Taken together, these observations demonstrate that cadherin-11 mRNA and protein expression levels are up-regulated during the terminal differentiation of endometrial stromal cells-suggesting that this cell adhesion molecule may serve as a useful cellular marker for decidualization.

Treatment of human endometrial stromal cells with chorionic gonadotropin promotes their morphological and functional differentiation into decidua

Human endometrial stromal cells contain luteinizing hormone (LH)/human chorionic gonadotropin (hCG) receptors and treatment with highly purified hCG results in an up-regulation of cyclooxygenase-2 (COX-2) gene expression and increased production of prostaglandin (PG) E2. Since PGE2 promotes the differentiation of endometrial stromal cells into decidua, we tested the hypothesis that LH and hCG themselves may promote this process. The results revealed that these hormones can promote morphological as well as functional differentiation. While their action on morphological differentiation did not require the presence of estradiol (E2) and progesterone (P4), they did require them for the functional differentiation. The hCG effect was mimicked by LH, but not by follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH) or alpha and beta subunits of hCG, suggesting that the hCG action was hormone specific and requires the conformation of native hormone. The hCG treatment also increased the steady state PRL mRNA levels. This increase was due to an increase in the transcription rate of the gene rather than a decrease in the degradation of PRL transcripts. In summary, we conclude that hCG and LH can increase the morphological as well as functional differentiation of human endometrial stromal cells into decidua. This is one of the newly discovered actions of LH and hCG that may be important for the implantation of blastocyst and maintenance of pregnancy.

Immunohistochemical analysis of insulin-like growth factor-binding proteins -1, -2, and -3 in implantation sites of the mouse

PURPOSE

Our purpose was to analyze potential interactions between the embryo and the maternal endometrial interface in vivo by analyzing immunolocalization of insulin-like growth factor-binding proteins (IGFBPs) -1, -2, and -3 in implantation sites of the mouse.

METHODS

Six-week-old B6D2F1 female mice underwent superovulation followed by mating and sacrifice at timed intervals. Formalin-fixed paraffin-embedded tissue was used for avidin-biotin immunocytochemical localization of IGFBPs utilizing standard methodology.

RESULTS

Immunostaining at 1.5 days post coitum revealed light staining in the epithelial glandular cells and faint staining in decidual stroma for both IGFBP-1 and IGFBP-2. At 7.5-10.5 days post coitum, there was moderate-dense immunostaining in the decidualized stromal cells at the implantation site for all three IGFBPs, whereas light immunostaining was seen in nonimplantation site decidua.

CONCLUSIONS

Compartmentalization of immunostaining for IGFBP-1, -2, and -3 within decidualized stroma suggests that these proteins may be regulated by trophoblastic and/or embryonic signals.

Effect of insulin-like growth factors (IGFs) and IGF-binding proteins on in vitro sperm motility

OBJECTIVE

Previous studies have shown that exogenous growth hormone (GH) produces increases in sperm motility when given to subfertile men. Previous studies have also demonstrated the presence of IGFs and IGFBPs in seminal plasma. We have therefore investigated the effects of insulin-like growth factor-I (IGF-I), IGF-II, IGF-binding protein 2 (IGFBP-2) and intact IGFBP-3 on in vitro sperm motility.

DESIGN AND METHODS

Using computer-aided sperm analysis, we investigated the effects of IGFs and IGFBPs on the in vitro sperm motility parameters: curvilinear velocity (CV), progressive velocity (PV), linearity (Ln), straightness (St), amplitude of lateral head movement (ALH), and beat frequency (BF). Washed motile sperm selected by the 'swim-up' method, from normozoospermic samples, were incubated at 37 degrees C in 5% CO2 in air with IGF-I, IGF-II, IGFBP-2, IGFBP-3, or control Earle's media, and were examined at time 0 and after 60 min incubation. Changes in motility parameters after 60 min incubation were compared with controls by analysis of variance (ANOVA).

RESULTS

Compared to controls, statistically significant changes occurred at time 60 min after incubation: IGF-I decreased CV and ALH significantly (P < 0.05), but IGFBP-3 increased Ln, St, BF, and decreased ALH significantly (P < 0.05). In contrast, IGF-II, IGFBP-2, and a combination of IGF-I/IGFBP-3, had no significant effects.

CONCLUSIONS

IGF-I and IGFBP-3 have differing and opposing effects on in vitro sperm motility parameters and thus may have a role in modulating in vivo sperm motility.

Comparative studies on the in vitro decidualization process in the baboon (Papio anubis) and human

The process of decidualization involves the morphological and functional transformation of stromal fibroblasts to decidual cells. The objective of this study was to define appropriate in vitro culture conditions required for decidualization of baboon stromal cells. Parallel studies were also done with human endometrial stromal cells for comparative analysis. Human stromal cells produced prolactin and insulin-like growth factor-binding protein (IGFBP)-1 in response to hormones (estradiol-17beta [36 nM], medroxyprogesterone acetate [1 microM], and relaxin [100 ng/ml]), and production was enhanced in the presence of 0.1 mM dibutyryl cAMP (dbcAMP). By contrast, baboon cells did not produce any detectable levels of prolactin, even in the presence of hormones and dbcAMP. IGFBP-1 expression in baboon stromal cells was detectable by Day 6 of hormone and dbcAMP treatment and increased exponentially thereafter. In both human and baboon stromal cells, alpha smooth muscle actin (alphaSMA) expression, an early marker for decidualization in the baboon in vivo, was induced spontaneously under normal culture conditions. Furthermore, a decrease in alphaSMA expression was observed in cells producing high levels of IGFBP-1. Human cells produced significant levels of IGFBP-1 (p < or = 0.01) in response to short-term dbcAMP treatment (48 h) after 2 and 12 days of hormone treatment. However, baboon stromal cells required 17 days of hormonal treatment before cells became responsive to short-term dbcAMP treatment (p < or = 0.01). Finally, human endometrial stromal cells expressed the protein kinase A regulatory subunits RIalpha, RIbeta, RIIalpha, and RIIbeta whereas baboon stromal cells expressed RIalpha, RIIalpha, and RIIbeta. No difference in the mRNA expression of these isoforms was observed in decidualized or nondecidualized cells of either human or baboon endometrium. Our observations indicate that baboon stromal cells can be induced to decidualize in vitro and that this requires dbcAMP in addition to hormones. This is the first report demonstrating in vitro decidualization in a nonhuman primate.

Differentiation-dependent and cell-specific regulation of the hIGFBP-1 gene in human endometrium

We analyzed IGFBP-1 gene promoter activity by transient transfection during the progressive decidualization of human endometrial stromal cells. A time study over a 13-day culture period showed that the promoter activity increased exponentially to > 10(4) fold in cells treated with MPA and RLX correlating with the secretion rate and steady-state mRNA levels of the endogenous gene. Deletion analysis showed that two regions in the IGFBP-1 gene promoter are responsible for the activation of the IGFBP-1 gene. The basal promoter region between -1 and -300 bp contains multiple sections of functional elements homologous either to CRE, PRE, or CCAAT. The major difference of IGFBP-1 gene activation in endometrium and the hepatic system lies in the distal promoter region, between -2.6 and -3.4 kb, which mediates 95% of the total promoter activity derived from -3.3 kb to +68 bp. Functional and binding analysis in the distal promoter region showed that multiple Sp1 elements interacting with a novel Sp3 transcription factor activates the hIGFBP-1 gene promoter.

Progesterone receptor (PR) inhibits expression of insulin-like growth factor-binding protein-1 (IGFBP-1) in human endometrial cell line HEC-1B: characterization of the inhibitory effect of PR on the distal promoter region of the IGFBP-1 gene

Progestin has been shown to have both stimulatory and inhibitory effects on the expression of insulin-like growth factor binding protein-1 (IGFBP-1) in human endometrial cells. In this study, progestin was found to reduce levels of secreted IGFBP-1 and IGFBP-1 messenger RNA and IGFBP-1 promoter activity after stably transfecting a progesterone receptor (PR; B form) expression vector into HEC-1B cells. Deletion analysis of the IGFBP-1 promoter revealed that PR specifically inhibited promoter activity derived from a 59-bp distal BsaHI/RsaI fragment. It was concluded that PR inhibited the promoter activity through protein-protein interactions based on the facts that 1) no progesterone-responsive element was revealed by a series block mutation in the BsaHI/RsaI fragment; 2) PR bound by the antiprogesterone ZK98299 inhibited IGFBP-1 promoter activity; 3) a DNA-binding mutant of PR inhibited the IGFBP-1 promoter activity; and 4) in an in vivo competition assay, the DNA-binding domain of PR did not release the inhibitory effect of intact PR. Analysis of PR deletion mutants indicated that both transcriptional activation domains of PR (TAF-1 and TAF-2) were involved in the inhibition of IGFBP-1 expression. Thus, our data may explain the superinduction of IGFBP-1 in human endometrial cells after progestin withdrawal or progestin replacement with antiprogestin.

The role of relaxin in glycodelin secretion

Glycodelin is a glycoprotein named for its unique carbohydrate structure. Glycodelin is produced by the secretory endometrium during the late luteal phase and returns to baseline during menses of the ensuing cycle, whereas in conceptive cycles it rapidly increases. Although progesterone and possibly estradiol are required for glycodelin production, they are not directly involved in the synthesis and release of this protein. Their role may be development of the endometrial secretory glandular elements, whereas other factors are required to initiate and maintain glycodelin secretion. The pattern of relaxin secretion during the luteal phase and early pregnancy is similar to that of glycodelin, but their profiles have not been determined simultaneously. To investigate the relationship of relaxin and glycodelin, two studies were conducted. In the first study, relaxin, glycodelin, and ovarian steroids were measured in daily serum samples from nonconceptive and conceptive natural cycles. Profiles of relaxin and glycodelin were closely associated, with the onset of relaxin preceding glycodelin secretion by 1-2 days in nonconceptive cycles, and the pregnancy-associated increases in each hormone differing by about 2 days. The second study tested the hypothesis that relaxin stimulates glycodelin secretion. Samples were obtained from patients injected with human relaxin for 28 days. In subjects demonstrating ovarian cyclicity, glycodelin secretion was elevated, but it was not detected in subjects without ovarian cyclicity or in placebo-treated control subjects. This study reveals a close temporal and quantitative relationship between relaxin and glycodelin profiles in the late luteal phase and early pregnancy. It also demonstrates that relaxin administration can stimulate glycodelin production from a developed endometrium. This is the first report of a nonsteroidal ovarian factor that controls glycodelin secretion, and these results suggest a function for relaxin during early pregnancy. Glycodelin is a potent inhibitor of sperm zona pellucida binding by virtue of its extensive carbohydrate structure, but it is normally at a nadir in the periovulatory period. The data demonstrate that relaxin can stimulate glycodelin secretion throughout the menstrual cycle, including the periovulatory period, when relaxin-induced glycodelin secretion could have a contraceptive effect.

Immunoregulatory properties of growth hormone and prolactin

Reciprocal communication between the neuroendocrine and immune systems is critical to the establishment of host homeostatic and defence mechanisms. The production and utilisation of common ligands and their receptors by cells of the immune and neuroendocrine systems constitutes a biochemical information circuit between and within the immune and neuroendocrine systems. Although the structures of the various signalling components appear to be similar in both systems, the regulation of their synthesis may be different. Growth hormone and prolactin have similar and marked influences on the function/activity of each of the major immune cell types, both in vitro and in vivo. The underlying molecular mechanisms are just beginning to be unravelled, and it is anticipated that further work in this rapidly developing field will establish abnormal pituitary and/or lymphocyte growth hormone and prolactin synthesis and function as a contributory factor to a number of pathologic situations, including leukaemia and autoimmunity.

Activation of the human IGFBP-1 gene promoter by progestin and relaxin in primary culture of human endometrial stromal cells

We have studied the activity for the insulin-like growth factor binding protein-1 (IGFBP-1) gene promoter in human endometrial stromal cells by transient transfection. The promoter activity derived from p3.6CAT or p3.6Luc (3400 bp IGFBP-1 promoter 5' to the reporter gene chloramphenicol acetyltransferase or luciferase) was minimal in unstimulated cells. A time study over 13 days of culture showed that the promoter activity increased exponentially to > 10(4) fold in cells treated with medroxyprogesterone acetate (MPA) and relaxin (RLX). Induction of the IGFBP-1 gene promoter activity by hormones was similar to the secretion pattern of IGFBP-1 in endometrial stromal cells. MPA alone caused a moderate induction, 3-40-fold increase over the control. Deletion analysis showed that two regions in the IGFBP-1 gene promoter were responsible for the activation of the IGFBP-1 gene. The basal promoter region, termed bp1-A (+68 bp to -1.205 kb), contains multiple sections of regulatory sequence including a cis-element CCAAT (-72 bp). A DNase I protection assay in the bp-1A region revealed four distinct binding regions, one of which contained the CCAAT box region. Another promoter region, termed bp1-B (-2.6 to -3.4 kb), mediated 95% of the total promoter activity in endometrial stromal cells. The bp1-B region also contains multiple regulatory sequences. Mutation and DNase I protection assay suggest that Sp1-like binding site at -2.63 kb was a regulatory site responsible for the activation of IGFBP-1 gene promoter.

Identification of a distal regulatory sequence of the human IGFBP-1 gene promoter and regulation by the progesterone receptor in a human endometrial adenocarcinoma cell line

The activity of the insulin-like growth factor binding protein-1 (IGFBP-1) gene promoter was studied in the human endometrial adenocarcinoma cell line HEC-1B. Basal promoter activity was directed by the region +68 to -207 bp, similar to observations in the hepatoma HepG2 cell line. A distal regulatory sequence approximately -2.6 kb from the transcription initiation site strongly enhanced the activity of the IGFBP-1 gene promoter in HEC-1B cells, but not in HepG2 cells. Sequence analysis revealed that this active region resides in 105 bp between -2,628 to -2,732 bp (the Rsa I-Cla I fragment). This region contains many putative active motifs homologous to known cis elements. Additional deletion and mutation in the Rsa I-Cla I fragment showed that the activity was confined to a 58-bp DNA fragment. In cells treated with progestin and co-transfected with progesterone receptor vector hPR1, the CAT activity derived from constructs containing the Rsa I-Cla I fragment was reduced in a dose-dependent manner. The active DNA fragment also stimulated the activity of the heterologous TK/CAT promoter in HEC-1B cells, while the PR complex inhibited this activity by 50%. These observations indicate that most of the regulation of the IGFBP-1 gene in HEC-1B cells is derived from the distal promoter region confined to the Rsa I-Cla I fragment and that the same region mediates an inhibitory effect from the progesterone receptor.

Fetal membrane rupture is associated with the presence of insulin-like growth factor-binding protein-1 in vaginal secretions

OBJECTIVE

Our purpose was to determine whether detection of insulin-like growth factor-binding protein-1 in vaginal secretions could be used in the diagnosis of fetal membrane rupture.

STUDY DESIGN

Consenting patients (n = 105) with complaints suspicious of membrane rupture between 24 and 42 weeks of gestation who had no evidence of placenta previa were enrolled in the study. The diagnosis of membrane rupture required at least two of the following findings on vaginal examination: pooling of fluid, positive Nitrazine paper (Bristol-Myers Squibb, Cherry Hill, N.J.) test, or microscopic evidence of ferning. A swab of the posterior vaginal fornix was obtained, placed in sample buffer, and analyzed for insulin-like growth factor-binding protein-1 by immunoassay. Data analysis included chi 2 analysis, Student t test, or Mann-Whitney U test and linear regression and receiver operating characteristic curve analysis.

RESULTS

A total of 78 (74.3%) patients met the criteria for membrane rupture. There was a highly significant difference in mean vaginal insulin-like growth factor-binding protein-1 concentrations between patients with and without clinical evidence of membrane rupture (553.6 +/- 731.4 micrograms/L vs 3.0 +/- 7.3 micrograms/L, p = 0.0002). Receiver operating characteristic curve analysis demonstrated that the optimal identification of patients with membrane rupture was achieved with an insulin-like growth factor-binding protein-1 value > 3 micrograms/L (sensitivity 74.4%, 95% confidence interval 64.7% to 84.0%; specificity 92.6%, 95% confidence interval 82.7% to 102.5%; positive predictive value 96.7%, 95% confidence interval 92.1% to 101.2%; negative predictive value 55.6%, 95% confidence interval 41.0% to 70.1%).

CONCLUSIONS

The presence of vaginal insulin-like growth factor-binding protein-1 is highly predictive of membrane rupture, identifying 74.4% of affected patients with a very low false-positive rate.

Growth factors and growth modulators in human uterine endometrium: their potential relevance to reproductive medicine

OBJECTIVE

To provide an up-to-date, comprehensive review on the presence and regulation of growth factors (GFs), GF receptors, and GF regulatory proteins in human endometrium in an effort to understand the potential roles of these proteins in endometrial cell mitosis and differentiation and in endometrial-trophoblast interactions.

DESIGN

Relevant studies were identified through a computerized bibliographic search (MEDLINE; BRS Information Technologies, a division of Maxwell Online, Inc., McLean, VA) and through manual scanning of recent relevant journals.

RESULTS

Several GFs, their receptors, and regulatory proteins have been identified in endometrium, and cellular localization and steroid-dependence of these proteins as well as action of several growth modulators on endometrial cell function have been studied. Epidermal growth factor, transforming growth factor (TGF)-alpha, platelet-derived growth factor, insulin-like growth factors (IGFs) and their binding proteins, fibroblast growth factor (FGF), TGF-beta, colony-stimulating factor (CSF)-1, and interferon-gamma regulate mitosis of endometrial cellular components in vitro. Endothelin-1 may participate in vasoconstriction and FGF may participate in angiogenesis in this tissue in vivo. Interleukins-1 and -6 are believed to be involved in endometrial T-cell activation, and TGF-beta, CSF-1, the interleukins, and the IGFs likely mediate endometrial-trophoblast interactions. The role of tumor necrosis factor in endometrium remains uncertain.

CONCLUSIONS

Current evidence supports the thesis that GFs play a central role in cyclic mitosis and differentiation of endometrial cellular components, recruitment of macrophages in decidualizing endometrium, endometrial-trophoblast interactions, early pregnancy maintenance, tissue shedding in the absence of implantation, and endometrial functionalis regeneration.

Direct effect of gonadotropins on decidualization of human endometrial stroma cells

Decidualization of stromal cells isolated from proliferative human endometrium was achieved by adding to the culture medium human gonadotropins (FSH, FSH + LH, hCG). In addition to changes in the morphology of the stromal cells to the decidual phenotype, decidualization was evident from the expression of prolactin (PRL), demonstrated immunocytochemically, by Western blotting analysis, and by measuring its output into the medium through solid phase enzyme immunoassay. Gonadotropins also induced cAMP formation in the endometrial stromal cells under the same experimental conditions. This finding suggests that the mechanism by which gonadotropins promote decidualization of human endometrial stromal cells in vitro involves the introduction of cAMP, a compound that we have found to elicit the expression of PRL in this system. PRL is likely to be a key intermediate in the process of decidualization since it is by itself capable of inducing differentiation of the endometrial stromal cells to the decidual phenotype. Awareness of direct actions of gonadotropins on the endometrial cells and, in particular, of the decidualizing effects of FSH (Metrodin), FSH+LH (Pergonal) and hCG may contribute to the understanding of physiologic as well as pathophysiologic conditions relevant to endometrial functions and fertility.

Insulin-like growth factor regulation of human endometrial stromal cell function: coordinate effects on insulin-like growth factor binding protein-1, cell proliferation and prolactin secretion

The insulin-like growth factor (IGF) autocrine/paracrine system is believed to be involved in endometrial differentiation, but there is limited information on the specific cellular functions regulated by IGFs in uterine tissues and their regulation of IGF-binding proteins (IGFBPs). We have investigated the regulation by insulin, IGF-I, and IGF-II, of IGFBP secretion in human endometrial stromal cells decidualized in vitro, and examined the interrelationship between the induced changes in IGFBP levels and the biological responses of stromal cells to IGFs. IGFBPs in conditioned media were analyzed by Western ligand blotting, and IGFBP-1 was quantified by an immunoenzymometric assay (IEMA). In the absence of peptides, decidualized stromal cells secreted 25.5 +/- 3.2 micrograms/day per 10(6) cells of IGFBP-1. Insulin caused a dose-dependent reduction of IGFBP-1 secretion (half-maximal inhibition at < 1 ng/ml) to a maximum of 1% of control values. Northern analysis using a specific cDNA probe showed the expression in decidualized stromal cells of a single 1.5 kb transcript for IGFBP-1, which was absent in insulin-treated cells. The effects of IGF-I and IGF-II on IGFBP-1 secretion were biphasic, with initial stimulation (200-250%) that peaked at 1 and 10 ng/ml, respectively, followed by inhibition at higher concentrations (half maximal inhibition at 3 ng/ml and 30 ng/ml, respectively). The decrease in IGFBP-1 levels in decidualized stromal cultures was associated with the induction of mitogenesis by IGF-I and IGF-II, while IGF effects on prolactin secretion paralleled those of IGFBP-1 secretion, with stimulation (243-324%) in the low concentration range followed by inhibition at higher concentrations. These data indicate that endometrial stromal cell IGFBP-1 is regulated by insulin, at concentrations that are compatible with insulin acting via its own receptor, while the effects of IGF-I and IGF-II on IGFBP-1 secretion, are suggestive of their acting probably through the type I IGF receptor. The present study describes distinct effects of the IGFs on stromal cell IGFBPs, that correlate with changes in the proliferative and secretory responses of decidualized stromal cells to the IGFs. Our findings suggest that complex IGF-IGFBP interactions may participate in the regulation of endometrial cell function, and support a role for IGF-II in stromal cell mitogenesis during decidualization, and as a local regulator of decidual cell function during the late secretory phase and early pregnancy.

Sequential appearance of relaxin, prolactin and IGFBP-1 during growth and differentiation of the human endometrium

Relaxin (RLX) is a product of the human corpus luteum, pregnancy decidua and placenta, prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP-1) are products of the cyclic endometrium and of the pregnancy decidua. All three proteins are thought to function interdependently in endometrium/decidua as local factors within the uterus without reaching the systemic circulation. In this study, the avidin-biotin immunoperoxidase method for immunolocalization with monoclonal or polyclonal antibodies has been applied to serial sections of endometria obtained from patients at different stages of the menstrual cycle and in early and late gestation. This allowed the cellular localization of the three proteins to be followed simultaneously through the reproductive stages from cyclic endometrium to term gestational decidua. The production, as opposed to sequestration of RLX from an ovarian source was demonstrated by the application in parallel of an antibody to the processed hormone and its connecting peptide. RLX was shown localized to the glandular and luminal epithelia in the proliferative and secretory phases. The decidualized stromal cells also immunostained for RLX in the late secretory phase and in early and late pregnancy. PRL was localized first to the glandular epithelium and then stroma, appearing after RLX, IGFBP-1 appeared later in the secretory phase and predominantly in the decidualized stromal cells confirming previous studies. In contrast, all three proteins were immunostained in early pregnancy and increased to term gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

HNF1 activates transcription of the human gene for insulin-like growth factor binding protein-1

Insulin-like growth factor binding protein-1 (IGFBP-1) is expressed primarily in the liver, kidney, and uterus. Basal IGFBP-1 promoter activity in human HEP G2 hepatoma cells is dependent upon a proximal promoter element that binds hepatic nuclear factor 1 (HNF1), a protein that is likely to be an important factor regulating the expression of many genes in liver and kidney. To test whether HNF1 activates IGFBP-1 transcription, HEP G2 cells and HeLa cells were cotransfected transiently with HNF1 expression vectors and with IGFBP-1 promoter/chloramphenicol acetyltransferase reporter gene constructs. HNF1 increased IGFBP-1 promoter activity in both HEP G2 and HeLa cells. Gel mobility-shift assays and additional transfections in HeLa cells showed that expressed full-length and carboxy-terminal truncated forms of HNF1 could each bind the HNF1 cis element of the IGFBP-1 promoter; however, significant trans-activation only occurred in the presence of the full-length HNF1 protein, similar to past experience with these two HNF1 forms and the albumin promoter. Further studies showed that IGFBP-1 promoter constructs containing mutations with high or low affinity for HNF1 responded to HNF1 expression with increased or decreased activity, respectively, relative to the native promoter. These studies suggest that HNF1 and/or related proteins play a role in hepatic, and perhaps also renal, expression of IGFBP-1.