Multifaceted roles for IGFBP-1 in human endometrium during implantation and pregnancy

Impaired decidualization and relative increase of PROK1 expression in the decidua of patients with unexplained recurrent pregnancy loss showing insulin resistance

A recent meta-analysis revealed that patients with unexplained recurrent pregnancy loss (RPL) show higher insulin resistance compared to healthy controls. However, the etiology of RPL remains unknown. Prokineticin (PROK1), a pleiotropic uterine endometrial protein, is important for implantation and decidualization and is regulated by hypoxia and insulin. In this study, we investigated the decidualization status and the role of PROK1 in the decidua of patients with unexplained RPL showing insulin resistance. Thirty-two patients with unexplained RPL were included in this study. Following the diagnosis of a miscarriage, the decidua and villi of the patient were surgically collected. Fasting blood glucose and insulin levels were measured, and HOMA-β was calculated. Using IHC and ELISA, the expression of IGFBP-1, PRL and PROK1 in the decidua and IGF-2 in the villi were analyzed in patients with euploid miscarriage with a high HOMA-β index (n = 8) and compared to controls (euploid miscarriage with normal HOMA-β: n = 12, aneuploid miscarriage with normal HOMA-β: n = 12). The co-localization of PROK1 and IGFBP-1 was observed in the decidua by IHC. In the decidua of RPL patients with high HOMA-β, the expression levels of IGFBP-1 and PRL were significantly lower, whereas the PROK1/IGFBP-1 ratio was significantly higher compared to that of the controls. IGF-2 expression in villi was significantly lower in RPL patients with high HOMA-β. Impaired decidualization and excessive PROK1 production may have pathological implications in patients with unexplained RPL with insulin resistance, especially under the state of hyper insulin production.

Embryonic growth retardation and altered expression of IGF-II is reciprocal induced by phytocompounds during early gestation in mice

Methanolic crude extract of Scoparia dulcis (CESD) was orally administered to female mice during the early gestation (day 4-day 8) at a dose of 500 mg/kg/day. It induces embryo resorption and morphological changes of fetal maternal tissue. Histomorphology was studied by routine hematoxylin eosin stain. In situ immunofluorescence localization of IGF-II using Texas red showed an ordered expression of the growth factor in the maternal decidual cells, trophoblast cells and the embryo. Western blot analysis showed a gradual increase of IGF-II from D4 to D8 of control females. In contrast, the CESD-treated females showed resorption of embryo on D8 with disorganized in situ expression and lowered IGF-II in fetal maternal tissue. The phytocompounds present in the CESD could modulate either the ER or IGF-II receptors causing reduced IGF-II expression in the target tissues which lead to the failure of embryonic growth during periimplantation.

Chronic endometritis and altered embryo implantation: a unified pathophysiological theory from a literature systematic review

PURPOSE

Chronic endometritis (CE) is a frequent hysteroscopic and histological finding which affects embryo transfer implantation during IVF-ICSI cycles. In particular, CE impairs proper decidualization and, subsequently, implantation. Although this correlation has been clearly clarified, a pathophysiological explanation assembling all the studies performed has not been elucidated yet. For this reason, we have structured a systematic review considering all the original articles that evaluated a pathological element involved in CE and implantation impairment.

METHODS

The authors searched electronic databases and, after screening, collected 15 original articles. These were fully scanned and used to create a summary pathway.

RESULTS

CE is primarily caused by infections, which lead to a specific cytokine and leukocyte pattern in order to prepare the uterus to fight the noxa. In particular, the immunosuppression requested for a proper semi-allogenic embryo transfer implantation is converted into an immunoreaction, which hampers correct embryo implantation. Moreover, endometrial vascularization is affected and both irregular vessel density and luminal thickening and thrombosis reduce what we have first identified as endometrial flow reserve. Finally, incorrect uterine wave propagation could affect embryo contact with decidua.

CONCLUSION

This is the first summary of evidence on CE pathophysiology and its relationship with infertility. Understanding the CE pathophysiology could improve our knowledge in embryo transfer success.

Early pregnancy serum IGFBP-1 relates to lipid profile in overweight and obese women

Lower level of insulin-like growth factor-binding protein (IGFBP-1) has been observed in insulin resistance, while higher level of matrix metalloproteinase-8 (MMP-8) has been linked to obesity. The aim here was to study in overweight and obese women, typically manifesting with insulin resistance, whether IGFBP-1 and MMP-8 are related to and reflect systemic low-grade inflammation, metabolism and diet. Fasting serum from overweight and obese pregnant women (n = 100) in early pregnancy were analysed for IGFBP-1, phosphorylated IGFBP-1 (phIGFBP-1) and MMP-8. High-sensitivity CRP and GlycA were used as markers for low grade inflammation. GlycA and lipids were quantified using NMR. IGFBP-1 associated negatively with GlycA, evidenced by higher concentrations in the lowest quartile (median 1.53 (IQR 1.45–1.72)) compared to the highest (1.46 (1.39–1.55)) (P = 0.03). Several lipid metabolites, particularly HDL-cholesterol, correlated inversely with phIGFBP-1 (FDR<0.1). Nutritional status and diet contributed to the levels of IGFBP-1, demonstrated as an inverse correlation with maternal weight (Spearman r = -0.205, P = 0.04) and dietary intake of vitamin A (r = -0.253, P = 0.014) and a direct correlation with dietary intake of polyunsaturated fatty acids (Spearman r = 0.222, P = 0.03). MMP-8 correlated inversely with pyridoxine (r = -0.321, P = 0.002) and potassium (r = -0.220, P = 0.033). Maternal serum IGFBP-1 may contribute to maternal lipid metabolism in overweight and obese women during early pregnancy. These findings may be of importance in identification of metabolic disturbances preceding the adverse metabolic outcomes in pregnancy.

Embryo gene expression in pig pregnancy

Pregnancy is a complex process in which significant changes occur continually in both the corpora lutea and in the endometrium of the females and varies depending on the embryonic, pre-implantation or foetal stages. In the embryonic stages, the majority of genes expressed in the pig embryo correspond to the loss of cellular pluripotency. In contrast, the implantation consists of three phases: elongation of the conceptus, adhesion and union of the embryo to the endometrial epithelium. During these phases, many factors are expressed, including growth factors, molecules that facilitate adhesion and cytokines. All these changes are ultimately regulated by different lipid and hormonal substances, specifically by progesterone, oestradiol and prostaglandins, which regulate the expression of many proteins necessary for the development of the embryo, endometrial remodelling and embryo-maternal communication. This paper is a review of primary gene regulatory mechanisms in pigs during different stages of implantation.

Meta-analysis of studies on biochemical marker tests for the diagnosis of premature rupture of membranes: comparison of performance indexes

Background

Premature rupture of the membranes (PROM) is most commonly diagnosed using physical examination; however, accurate decision making in ambiguous cases is a major challenge in current obstetric practice. As this may influence a woman’s subsequent management, a number of tests designed to assist with confirming a diagnosis of PROM are commercially available. This study sought to evaluate the published data for the accuracy of two amniotic fluid-specific biomarker tests for PROM: insulin-like growth factor binding protein-1 (IGFBP-1 – Actim® PROM) and placental alpha microglobulin-1 (PAMG-1 – AmniSure®).

Methods

Main analysis included all PubMed referenced studies related to Actim® PROM and AmniSure® with available data to extract performance rates. To compare accuracy, a comparison of pooled indexes of both rapid tests was performed. Studies in which both tests were used in the same clinical population were also analysed. Membrane status, whether it was known or a suspected rupture, and inclusion or not of women with bleeding, were considered.

Results

All the available studies published in PubMed up to April 2013 were reviewed. Data were retrieved from 17 studies; 10 for Actim® PROM (n = 1066), four for AmniSure® (n = 1081) and three studies in which both biomarker tests were compared directly. The pooled analysis found that the specificity and positive predictive value were significantly higher for AmniSure® compared with Actim® PROM. However, when 762 and 1385 women with known or suspected rupture of membranes, respectively, were evaluated, AmniSure® only remained significantly superior in the latter group. Furthermore, when the two tests were compared directly in the same study no statistically significant differences were observed. Remarkably, women with a history or evidence of bleeding were excluded in all four studies for AmniSure®, in two Actim® PROM studies and in two of the three studies reporting on both tests.

Conclusions

No differences were observed in the performance of the two tests in studies where they were used under the same clinical conditions or in women with known membrane status. Although AmniSure® performed better in suspected cases of PROM, this may need further analysis as exclusion of bleeding may not be representative of the real clinical presentation of women with suspected PROM.

Differential expression of serum glycodelin and insulin-like growth factor binding protein 1 in early pregnancy

This prospective study evaluated whether serum glycodelin and insulin-like growth factor binding protein 1 (IGFBP-1) predict the likelihood of embryo implantation in recipients undergoing donor egg in vitro fertilization. We measured glycodelin and IGFBP-1 at 6 points from lining check to lutenizing hormone (LH) + 31. β-Human chorionic gonadotropin levels were first measured at LH + 17. The recipients were divided into those without embryo implantation (group 1, n = 6) and those with successful implantation (group 2, n = 30). Although this is a negative study in that neither glycodelin nor IGFBP-1 alone reflected endometrial (EM) receptivity, the glycodelin/IGFBP-1 ratio on the day of blastocyst transfer was higher in recipients who achieved pregnancy (P = .05). At LH + 17, glycodelin was higher (P = .04), and IGFBP-1 was lower (P = .004) in recipients who achieved pregnancy when compared to those who did not. These observations are likely due to EM changes induced by successful embryo implantation.

Chemerin is present in human cord blood and is positively correlated with birthweight

OBJECTIVE

Chemerin, a novel adipokine, has been implicated in adipogenesis, inflammation, and metabolism. The aims of this study were to determine the presence of chemerin in cord blood and its association with birthweight.

STUDY DESIGN

This cross-sectional study included the following: (1) twins with (n = 24) or without (n = 28) birthweight discordancy; and (2) singletons subclassified into small-for-gestational-age (SGA; n = 18); appropriate for gestational age (AGA; n = 33); and large-for-gestational-age (LGA; n = 8). Cord blood chemerin was determined. Parametric and nonparametric statistics were used for analysis.

RESULTS

The results of the study included the following: (1) within the discordant twins group, the median chemerin concentration was significantly lower in the SGA group than in their cotwins; (2) within singletons, the median chemerin concentration was significantly higher in the LGA than the AGA newborns; and (3) the regression model revealed that chemerin was independently associated with birthweight.

CONCLUSION

Cord blood chemerin is present in cord blood and its concentrations are positively correlated with birthweight. These novel findings support a role of adipokines in fetal growth.

Dioxin and endometrial progesterone resistance

Development of endometriosis likely requires multiple, interactive mechanisms involving both the endocrine and immune systems. Environmental toxicants, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are of particular interest as potential contributory agents in the development of this disease because they can disrupt both systems. Nevertheless, defining the potential role that environmental exposure to TCDD plays in the development of endometriosis requires a better understanding of how this toxicant affects the biological processes that promote the disease. Although the disease mechanism(s) responsible for progesterone resistance in the endometrium of endometriosis patients remains speculative, our studies indicate that developmental exposure of mice to TCDD leads to a progesterone-resistant phenotype in adult animals that can persist for several generations. These studies and others underscore the importance of developing a greater understanding of the mechanisms of TCDD action that relate to reproductive disorders such as endometriosis.

Insulin-like growth factor-binding protein-1 (IGFBP-1) in cervical secretions as a predictor of preterm delivery

OBJECTIVE

The objective of this study was to investigate the level of insulin-like growth factor-binding protein-1 (IGFBP-1) in cervical secretions and Bishop score as predictors of preterm delivery in asymptomatic pregnant women.

METHODS

This was a prospective study at the Clinic for Gynecology and Obstetrics at the University Clinical Center in Tuzla, on a sample of 80 healthy pregnant women at between 24 and 34 gestational weeks. After interview every woman underwent IGFBP-1 concentration measurement by the 'Actim Partus' test. The Bishop score was determined by the author (A.L) during vaginal examination. Rates among groups were compared using arithmetic mean and standard deviation, Student's t-test, Mann-Witney U-test, and Spearman-Rank correlation test. Statistical importance was determined at the variation levels of 5% and 1%.

RESULTS

Eight (10.00%) women in the study group had a positive Actim Partus test and six (7.50%) of them had a preterm delivery. The positive predictive value was 44.44% and negative predictive value was 98.59%. The specificity of the Bishop score in the study group was 83.78% and the sensitivity was 50.00%. The positive predictive value of the Bishop score in this group was 20.00% and the negative predictive value was 95.36%. There was no correlation between the Bishop score and Actim Partus test (p = 0.15).

CONCLUSIONS

If the concentration of IGFBP-1 is <10 microg/L (negative Actim Partus test) in asymptomatic pregnant women, the risk of preterm delivery is low. The Actim Partus test could be used as a screening test for preterm delivery in asymptomatic pregnant women.

Expression of ADAMTS-5/implantin in human decidual stromal cells: regulatory effects of cytokines

BACKGROUND

The restricted expression of ADAMTS-5 (A Disintegrin And Metalloproteinase with ThromboSpondin repeats-5) to the maternal-fetal interface in mice has led to this novel metalloproteinase being assigned the trivial name 'implantin'.

METHODS

As a first step in determining whether ADAMTS-5 also contributes to the implantation process in humans, we have examined the spatiotemporal expression of this ADAMTS subtype in the endometrium during the menstrual cycle and pregnancy by immunohistochemical analysis. A quantitative competitive PCR (QC-PCR) strategy and western blotting were subsequently used to determine whether interleukin (IL)-1beta and transforming growth factor (TGF)-beta1, two cytokines involved in the formation of the maternal-fetal interface, were capable of regulating ADAMTS-5 messenger RNA (mRNA) and protein levels in primary cultures of stromal cells isolated from first trimester decidual tissues.

RESULTS

ADAMTS-5 expression in the stroma of the human endometrium correlates with decidualization of this cellular compartment in vivo. IL-1beta was found to increase (P < 0.05) whereas TGF-beta1 decreased (P < 0.05) ADAMTS-5 mRNA and protein levels in decidual stromal cell cultures in a concentration- and time-dependent manner. These regulatory effects were attenuated by function-perturbing antibodies directed against either cytokine.

CONCLUSIONS

ADAMTS-5 expression is restricted to decidualized stromal cells of the human endometrium in vivo and is subject to regulation by cytokines in vitro.

Differential effects of interleukin-1beta and transforming growth factor-beta1 on the expression of the inflammation-associated protein, ADAMTS-1, in human decidual stromal cells in vitro

BACKGROUND

The pro-inflammatory cytokine, interleukin-1 beta (IL-1beta) promotes the proteolytic degradation of the extracellular matrix (ECM) of maternal decidua, a critical step in pregnancy that is counterbalanced by the expression of the anti-inflammatory cytokine, transforming growth factor-beta 1 (TGF-beta1). Recently, the inflammation-associated protein, ADAMTS-1, a member of the ADAMTS (A Disintegrin And Metalloproteinase with ThromboSpondin repeats) gene family of metalloproteinases has been assigned a central role in the formation and organization of tissues. In view of these observations, we have hypothesized that ADAMTS-1 contributes to the cytokine-mediated remodelling of decidual ECM.

METHODS

The spatiotemporal expression of ADAMTS-1 in human endometrium was examined by immunohistochemistry. A quantitative-competitive (QC)-PCR strategy and western blot analysis was then employed to determine whether IL-1beta and TGF-beta1 regulate ADAMTS-1 mRNA and protein expression levels in primary cultures of stromal cells isolated from first trimester decidua.

RESULTS

ADAMTS-1 expression is associated with decidualization of the endometrial stroma in vivo. IL-1beta increased whereas TGF-beta1 decreased ADAMTS-1 mRNA and protein levels in decidual stromal cell cultures in a concentration- and time-dependent manner. These regulatory effects were attenuated by function-perturbing antibodies specific for either cytokine.

CONCLUSION

IL-1beta and TGF-beta1 differentially regulate ADAMTS-1 expression in human decidual stromal cells.

Targeted disruption of LH receptor gene revealed the importance of uterine LH signaling

Numerous previous studies have demonstrated that LH and hCG can directly regulate several uterine functions. We investigated in the present study, whether uterine phenotype in LH receptor knockout animals resulted also from the absence of direct actions of LH in the uterus. The phenotype consisted of marked growth reduction of uterus, decreased thickness of endometrial and myometrial layers, number of endometrial glands, height of luminal epithelium and vascular space. Analysis of uterine gene expression by mouse genome U74Av2 Affymetrix genechips revealed a differential expression of 155 genes by more than 3-fold (range 3-53-fold) between null and wild-type animals. Of these, 89 genes decreased and 66 increased in uterus of null animals. Semi-quantitative RT-PCR confirmed the differential expression of several selected genes. The decreased genes can be clustered into 18 functional families and the increased into 15 functional families. Semi-quantitative RT-PCR, Western blotting and immunocytochemistry demonstrated a decreased expression of ERbeta, PR-A, PR-B and AR in uterus of null animals as compared with wild-type siblings. Twenty-one-day estradiol and progesterone replacement therapy did not normalize the decrease in the number of endometrial glands and several genes that either decreased or increased in expression. The partial success of therapy suggests that direct LH actions could be required to completely normalize the uterus. In summary, findings on the knockout model reaffirm that LH and hCG control uterine functions directly as well as indirectly through increasing ovarian synthesis of steroid hormones and both actions are required for normal uterine biology.

Implantation: Embryonic Signals and the Modulation of the Uterine Environment—A Review

Interaction between maternal endometrium and embryo during implantation is mediated through the multiple molecules and signalling cascades, which are still not fully understood. This complex sequence of events results in the transformation of stromal cells into decidual cells (decidualization). The conceptus is essential to regulate these changes in baboon stromal fibroblasts, possibly through production of cytokines by the implanting embryo. The role of interleukin-1 (IL-1) system during implantation and its contribution to decidualization is discussed in this review. Decidualized endometrial stromal cells are thought to contribute to establishment of a successful pregnancy by expressing a number of gene products. One of the major products of decidual cells is insulin-like growth factor binding protein-1 (IGFBP-1). The IGFBP-1 serves as a modulator of insulin-like growth factor (IGF) protein action in the interactions between the decidua and invading trophoblast. The delineation of the mechanisms involved in cooperative action of transcription factors FKHR and HOXA10 leading to IGFBP-1 expression, as well as interrelationship between IL-1 and IGF signalling cascades will contribute to the understanding of events leading to successful implantation.

The regional expression of insulin-like growth factor II (IGF-II) and insulin-like growth factor binding protein-1 (IGFBP-1) in the placentae of women with pre-eclampsia

Insulin-like growth factors and their binding proteins regulate cellular proliferation, differentiation and function, and play an important role in placental development. IGF-II and IGFBP-1 are abundantly expressed by cells at the maternal-fetal interface and mediate cell-to-cell communication between trophoblasts and decidua. Placentae of pre-eclamptic pregnancies show villous cytotrophoblast proliferation, increased syncytial sprout formation and impaired trophoblast invasion. We hypothesized that the expression of IGF-II and IGFBP-1 by cells at the maternal-fetal interface is altered in pre-eclampsia. We determined the regional abundance and cellular localization of IGF-II mRNA and IGFBP-1 mRNA and protein in placentae from normotensive control and pre-eclamptic pregnancies. IGF-II mRNA was expressed in both the chorionic villi and basal plate decidua regions. Increased IGF-II mRNA abundance was observed in the intermediate trophoblasts of peri-infarct regions. IGFBP-1 expression was present only in the decidua of the basal plate and membranes, and this expression was decreased significantly in pre-eclamptic placentae. The increased IGF-II expression in the intermediate trophoblast surrounding placental infarcts suggests a role for IGF-II in placental repair or remodelling. Decreased IGFBP-1 mRNA expression in the basal plate decidua suggests that the increased concentrations of IGFBP-1 the circulation of pre-eclamptic women is not of decidual origin. The altered IGF-II and IGFBP-1 expression at the fetomaternal interface may be important in the pathophysiology of pre-eclampsia.

Implantation defects in infertile women with endometriosis

The endometrium undergoes characteristic histologic changes during the menstrual cycle as it prepares for embryo implantation. Historic and current data suggest the presence of a defined period of maximal uterine receptivity during the mid-secretory phase occurring between days 7 and 10 postovulation. In recent years, we and others have sought to define biochemical markers of receptivity that might be used to better understand this time of endometrial differentiation. Based on the work with cell adhesion molecules, we have discovered three different integrins that are only coexpressed during this time in the cycle when embryos will successfully implant. By studying the regulation of one of these, the alpha(v)beta3 integrin, and its extracellular matrix ligand, osteopontin (OPN), we have defined two separate regulatory pathways that may regulate endometrial receptivity. While alpha(v)beta3 expression appears to be stimulated by EGF or heparin-binding EGF, osteopontin is stimulated by progesterone. We now believe the former pathway is a paracrine-mediated signal, while the latter is a direct effect of progesterone on the estrogen-primed endometrial epithelium. In women with endometriosis, it appears that alpha(v)beta3 expression is reduced, while OPN expression is unaffected. Interestingly, binding of OPN to the surface epithelium appears quite limited when alpha(v)beta3 expression is lacking. Such evidence continues to reinforce the notion that endometrium from some women with endometriosis is dysfunctional and may account for the reduction in cycle fecundity noted in this group of patients.

Expression of Wilms' tumor suppressor gene (WT1) in human endometrium: regulation through decidual differentiation

The Wilms' tumor suppressor gene (WT1) encodes a zinc-finger containing transcription factor that is selectively expressed in the developing urogenital tract and functions as a tissue-specific developmental regulator. In addition to its gene-regulatory function through DNA binding properties, WT-1 also regulates transcription by formation of protein-protein complexes. These properties place WT-1 as a major regulator of cell growth and differentiation. In view of these observations, we studied WT1 mRNA and protein in human endometrial extracts and in endometrial stromal cells (ESCs) differentiating into decidual cells in vitro, by RT-PCR and Western blotting, respectively. WT1 protein expression was also studied in situ in the proliferative and the secretory phase of the menstrual cycle in the early pregnant state. Analysis by PCR of total RNA prepared from human ESCs demonstrated the presence of WT1 mRNA and four WT1 mRNA splice variants. Western blot analysis of nuclear protein extracts from ESCs yielded one immunoreactive protein of the expected size (approximately 52-54 kDa) recognized by the WT1 antibody. Immunohistochemical staining showed that WT1 protein is localized only to nuclei of human endometrial stromal cells. It remains constant in the proliferative and the secretory phase of the menstrual cycle and is increased remarkably during decidualization in early pregnancy. ESCs decidualized in vitro were investigated for WT-1 expression, which confirmed that decidualizing stimuli (E2, medroxy-progesterone-acetate, and relaxin for 12 d or cAMP and progesterone for 1-4 d) induced WT-1 mRNA (P < 0.05) and increased protein levels (P < 0.05). These data indicate that in humans the WT1 gene is expressed in ESCs and its mRNA and protein levels remain constant in the proliferative and the secretory phase of the menstrual cycle and that WT1 mRNA and protein expression increases significantly in ESCs when these cells differentiate into decidual cells.

Molecular markers of implantation: clinical implications

The endometrium has been conventionally studied using histologic criteria. Our understanding of endometrial physiology has been advanced tremendously by research into the molecules that mediate its development and function. These molecules demonstrate a dynamic expression pattern through the menstrual cycle and have been implicated in endometrial growth, differentiation, and receptivity. These molecules include secreted proteins (endometrial bleeding-associated factor, glycodelin-A, insulin-like growth factor binding protein-1), cell-surface receptors (integrins), and nuclear transcription factors (HOXA10 and HOXA11). The homeobox genes Hoxa10 and Hoxa11 are necessary for implantation because mice with mutations in these genes exhibit a failure of implantation. HOXA10 and HOXA11 have been shown to be important for implantation in humans as well. Knowledge of endometrial molecular dynamics may now be used to enhance our ability to diagnose implantation defects. It may soon be possible to treat individual molecular defects by protein supplementation or gene therapy.

Endometrial receptivity and the window of implantation

Implantation is a highly co-ordinated event that involves both embryonic and endometrial participation. The endometrium expresses a sophisticated repertoire of proteins during the menstrual cycle many of which help to define a period of receptivity collectively known as the 'window of implantation'. Many of these factors, which are temporally aligned with this window, are now seen as chemical messengers that are recognized by the embryo and facilitate embryonic growth and differentiation. The use of such proteins as biomarkers has also advanced our understanding of the implantation process and may identify women with implantation failure and infertility. While the study of endometrial receptivity is still evolving, the field is growing rapidly and will probably enhance our ability to diagnose and treat couples with infertility, especially in the arena of assisted reproductive technologies (ART).

Distribution of IGFBP-rP1 in normal human tissues

IGFBP-rP1/mac25 is a recently described member of the insulin-like growth factor binding protein (IGFBP) family. It has structural homology to the other members of the IGFBP family but has a lower affinity for insulin-like growth factors (IGFs). In previous studies using RNA blot hybridization, it was shown that the expression of IGFBP-rP1/mac25 was ubiquitous in normal human tissues. In this report we show by immunohistochemistry that the expression of IGFBP-rP1/mac25 is actually restricted to certain organs and specific cell types. We used an antibody raised against a decapeptide of the C-terminal part of the protein that recognizes a approximately 37-kD protein under reduced conditions. The immunohistochemistry performed on normal human tissues showed a ubiquitous intense staining of peripheral nerves and a variable degree of positive staining in smooth muscle cells, including those from blood vessel walls, gut, bladder, and prostate. Cilia from the respiratory system, epididymis, and fallopian tube showed intense immunoreactivity. Most endothelial cells showed some positivity, whereas fat cells, plasma cells, and lymphocytes were negative. There was specific expression limited to certain cell types in the kidney, adrenal gland, and skeletal muscle, indicating a possible specialized function of IGFBP-rP1/mac25 in these organs. We further noted an opposite pattern of staining in the lining epithelium of breast (typically positive) and prostate glands (largely negative). The specific localization of IGFBP-rP1/mac25 as described implies a function of the protein. However, its regulation within the IGF axis or a possible direct action of IGFBP-rP1/mac25 remains to be demonstrated.

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.

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.