Abnormally located SSEA1+/SOX9+ endometrial epithelial cells with a basalis-like phenotype in the eutopic functionalis layer may play a role in the pathogenesis of endometriosis

STUDY QUESTION

Is endometriosis associated with abnormally located endometrial basalis-like (SSEA1+/SOX9+) cells in the secretory phase functionalis and could they contribute to ectopic endometriotic lesion formation?

SUMMARY ANSWER

Women with endometriosis had an abnormally higher number of basalis-like SSEA1+/SOX9+ epithelial cells present in the stratum functionalis and, since these cells formed 3D structures in vitro with phenotypic similarities to ectopic endometriotic lesions, they may generate ectopic lesions following retrograde menstruation.

WHAT IS KNOWN ALREADY

Endometrial basalis cells with progenitor potential are postulated to play a role in the pathogenesis of endometriosis and SSEA1 and nuclear SOX9 (nSOX9) mark basalis epithelial cells that also have some adenogenic properties in vitro. Induction of ectopic endometriotic lesions in a baboon model of endometriosis produces characteristic changes in the eutopic endometrium. Retrograde menstruation of endometrial basalis cells is proposed to play a role in the pathogenesis of endometriosis.

STUDY DESIGN, SIZE, DURATION

This prospective study included endometrial samples from 102 women with and without endometriosis undergoing gynaecological surgery and from six baboons before and after induction of endometriosis, with in vitro assays examining the differentiation potential of human basalis-like cells.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study was conducted at a University Research Institute. SSEA1 and SOX9 expression levels were examined in human endometrial samples from women aged 18-55 years (by immunohistochemistry (IHC) and qPCR) and from baboons (IHC). The differential gene expression and differentiation potential was assessed in freshly isolated SSEA1+ endometrial epithelial cells from women with and without endometriosis (n = 8/group) in vitro. In silico analysis of selected published microarray datasets identified differential regulation of genes of interest for the mid-secretory phase endometrium of women with endometriosis relative to that of healthy women without endometriosis.

MAIN RESULTS AND THE ROLE OF CHANCE

Women with endometriosis demonstrated higher number of basalis-like cells (SSEA1+, nSOX9+) in the functionalis layer of the eutopic endometrium compared with the healthy women without endometriosis in the secretory phase of the cycle (P < 0.05). Induction of endometriosis resulted in a similar increase in basalis-like epithelial cells in the eutopic baboon endometrium. The isolated SSEA1+ epithelial cells from the eutopic endometrium of women with endometriosis had higher expression of OCT4, NANOG, FUT4 mRNA (P = 0.05, P = 0.007, P = 0.018, respectively) and they differentiated into ectopic endometriotic gland-like structures in 3D culture, but not into mesodermal lineages (adipose or bone cells).

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Small sample size. Bioinformatics analysis and results depends on the quality of published microarray datasets and the stringency of patient selection criteria employed. Differentiation of SSEA-1+ cells was only examined for two mesodermal lineages (adipogenic and osteogenic).

WIDER IMPLICATIONS OF THE FINDINGS

Since endometrial epithelial cells with SSEA1+/nSOX9+ basalis-like phenotype generate endometriotic gland-like structures in vitro, they may potentially be a therapeutic target for endometriosis. An in depth analysis of the function of basalis-like eutopic endometrial epithelial cells might provide insights into their potential deregulation in other disorders of the endometrium including heavy menstrual bleeding and endometrial cancer where their function may be aberrant.

STUDY FUNDING/COMPETING INTEREST(S)

We acknowledge the support by Wellbeing of Women project grant RG1073 (D.K.H., C.E.G.) and R01 HD083273 from the National Institutes of Health (A.T.F.). We also acknowledge the support of Liverpool Women's Hospital Foundation Trust (J.D.), Institute of Translational Medicine (L.D.S., H.A.L., A.J.V., D.K.H.), University of Liverpool, the National Health and Medical Research Council of Australia ID 1042298 (C.E.G.) and the Victorian Government Operational Infrastructure Support Fund. All authors declare no conflict of interest.

cAMP-Response Element-Binding 3-Like Protein 1 (CREB3L1) is Required for Decidualization and its Expression is Decreased in Women with Endometriosis

Endometriosis is a major cause of infertility and pelvic pain, affecting more than 10% of reproductive-aged women. Progesterone resistance has been observed in the endometrium of women with this disease, as evidenced by alterations in progesterone-responsive gene and protein expression. cAMPResponse Element-Binding 3-like protein 1 (Creb3l1) has previously been identified as a progesterone receptor (PR) target gene in mouse uterus via high density DNA microarray analysis. However, CREB3L1 function has not been studied in the context of endometriosis and uterine biology. In this study, we validated progesterone (P4) regulation of Creb3l1 in the uteri of wild-type and progesterone receptor knockout (PRKO) mice. Furthermore, we observed that CREB3L1 expression was significantly higher in secretory phase human endometrium compared to proliferative phase and that CREB3L1 expression was significantly decreased in the endometrium of women with endometriosis. Lastly, by transfecting CREB3L1 siRNA into cultured human endometrial stromal cells (hESCs) prior to hormonal induction of in vitro decidualization, we showed that CREB3L1 is required for the decidualization process. Interestingly, phosphorylation of ERK1/2, critical factor for decidualization, was also significantly reduced in CREB3L1-silenced hESCs. It is known that hESCs from patients with endometriosis show impaired decidualization and that dysregulation of the P4-PR signaling axis is linked to a variety of endometrial diseases including infertility and endometriosis. Therefore, these results suggest that CREB3L1 is required for decidualization in mice and humans and may be linked to the pathogenesis of endometriosis in a P4-dependent manner.

Induction of Insulin-Like Growth Factor Binding Protein-1 Expression in Baboon Endometrial Stromal Cells by Cells of Trophoblast Origin

OBJECTIVE

To determine the influence of the conceptus on the induction of decidualization in endometrial stromal cells from the baboon.

METHODS

For in vivo studies, implantation sites from day 22 of pregnancy in the baboon were analyzed for insulin-like growth factor-II (IGF-II) and insulin-like growth factor binding protein-1 (IGFBP-1) mRNAs using in situ hybridization. For in vitro studies, Jeg-3 cells or primary cytotrophoblasts isolated from term placenta were cocultured with a monolayer of stromal cells from the baboon endometrium. Cytotrophoblasts were placed either directly on top of the stromal cell monolayer or in transwell cell culture inserts and cultured for 7 days. No exogenous hormones were added. Stromal cells were analyzed for IGFBP-1 mRNA and protein by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemistry.

RESULTS

Examination of early implantation sites in the baboon revealed a high expression of IGF-II mRNA in the invading cytotrophoblasts. Conversely, the stromal cells of the endometrium directly adjacent to the cytotrophoblasts expressed IGFBP-1 mRNA. Endometrial stromal cells cocultured with Jeg-3 cells or primary cytotrophoblasts for 7 days expressed IGFBP-1 mRNA and protein. This expression occurred in both the direct coculture system and coculture using the cell culture inserts. Cytotrophoblasts also induced the expression of prolactin in stromal fibroblasts following coculture.

CONCLUSIONS

The conceptus is capable of inducing decidualization of endometrial stromal cells. This is shown in both the in vivo and in vitro systems.

Altered expression of microRNA-451 in eutopic endometrium of baboons (Papio anubis) with endometriosis

STUDY QUESTION

Are microRNAs (miRs) altered in the eutopic endometrium (EuE) of baboons following the induction of endometriosis?

SUMMARY ANSWER

Induction of endometriosis causes significant changes in the expression of eight miRs, including miR-451, in the baboon endometrium as early as 3 months following induction of the disease.

WHAT IS KNOWN ALREADY

Endometriosis is one of the most common gynecological disorders and causes chronic pelvic pain and infertility in women of reproductive age. Altered expression of miRs has been reported in women and has been suggested to play an important role in the pathophysiology of several gynecological disorders including endometriosis.

STUDY DESIGN, SIZE, DURATION

EuE was obtained from the same group of baboons before and 3 months after the induction of endometriosis. The altered expression of miR-451 was validated in the eutopic and ectopic endometrium of additional baboons between 3 and 15 months following disease induction. Timed endometrial biopsies from women with and without endometriosis were also used to validate the expression of miR-451.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Total RNA was extracted from EuE samples before and after the induction of endometriosis, and miRNA expression was analyzed using a 8 × 15 K miR microarray. Microarray signal data were preprocessed by AgiMiRna software, and an empirical Bayes model was used to estimate the changes. The present study focused on quantitative RT-PCR validation of the microarray data, specifically on miR-451 and its target genes in both baboons (n = 3) and women [control (n = 7) and endometriosis (n = 19)]. Descriptive and correlative analysis of miR-451 and target gene expression was conducted using in situ hybridization and immunohistochemistry, while functional analysis utilized an in vitro 3' untranslated region (UTR) luciferase assay and overexpression of miR-451 in human endometrial and endometriotic cell lines.

MAIN RESULTS AND THE ROLE OF CHANCE

Induction of endometriosis results in the altered expression of miR-451, -141, -29c, -21, -424, -19b, -200a and -181a in the baboon endometrium. In the baboon, induction of endometriosis significantly decreased the expression of miR-451 at 3 months (P < 0.001), which was also associated with increased expression of its target gene YWHAZ (14.3.3ζ). A similar significant (P < 0.0001) decrease in miR-451 expression was observed in women with endometriosis. The 3' UTR luciferase assay confirmed the regulation of YWHAZ expression by miR-451. Furthermore, overexpression of miR-451 in 12Z cells (immortalized human endometriotic epithelial cell line) led to the decreased expression of its target YWHAZ and this was correlated with decreased cell proliferation.

LIMITATIONS, REASONS FOR CAUTION

The study focused only on miR-451 and one of its targets, namely YWHAZ. A single miR could target number of genes and a single gene could also be regulated by number of miRs; hence, it is possible that other miRs and their regulated genes may contribute to the pathophysiology of endometriosis.

WIDER IMPLICATIONS OF THE FINDINGS

Our data suggest that the presence of ectopic lesions in baboon causes changes in EuE miR expression as early as 3 months postinduction of the disease, and some of these changes may persist throughout the course of the disease. We propose that the marked down-regulation of miR-451 in both baboons and women with endometriosis increases the expression of multiple target genes. Increased expression of one of the target genes, YWHAZ, increases proliferation, likely contributing to the pathophysiology of the disease.

Lesion kinetics in a non-human primate model of endometriosis

BACKGROUND

Endometriosis is a common cause of pelvic pain and infertility in women of reproductive age. It is characterized by the presence of endometrial tissue outside the normal location, predominantly in the pelvic peritoneum causing severe abdominal pain. However, the severity of the symptoms of endometriosis does not always correlate with the anatomic severity of the disease. This lack of correlation may be due to morphological lesion variation during disease progression. This study examined lesion kinetics in a non-human primate model of endometriosis to better understand lesion dynamics.

METHODS

Endometriosis was experimentally induced in nine normal cycling female adult olive baboons (Papio anubis) by i.p. inoculation of autologous menstrual endometrium on Day 2 of menses for two consecutive menstrual cycles. Diagnostic laparoscopies were performed between Day 8-12 post-ovulation at 1, 3, 6, 9 and 12 months, followed by a necropsy at 15 months, after the second inoculation. In two animals, lesions were excised/ablated at 6 months and they were monitored for lesion recurrence and morphological changes by serial laparoscopy. Furthermore, five control animals underwent surgeries conducted at the same time points but without inoculation.

RESULTS

A total of 542 endometriotic lesions were observed. The location, macroscopic (different colours) and microscopic appearance confirmed distinct endometriosis pathology in line with human disease. The majority of the lesions found 1 month after tissue inoculation were red lesions, which frequently changed colour during the disease progression. In contrast, blue lesions remained consistently blue while white lesions were evident at the later stages of the disease process and often regressed. There were significantly lower numbers of powder burn, blister and multicoloured lesions observed per animal in comparison to black and blue lesions (P-value≤0.05). New lesions were continually arising and persisted up to 15 months post-inoculation. Lesions reoccurred as early as 3 months after removal and 69% of lesions excised/ablated had reoccurred 9 months later. Interestingly, endometriotic lesions were also found in the non-inoculated animals, starting at the 6-month time point following multiple surgeries.

CONCLUSIONS

Documentation of lesion turnover in baboons indicated that lesions changed their colour from red to white over time. Different lesion types underwent metamorphosis at different rates. A classification of lesions based on morphological appearance may help disease prognosis and examination of the effect of the lesion on disease symptoms, and provide new opportunities for targeted therapies in order to prevent or treat endometriosis. Surgical removal of endometriotic lesions resulted in a high incidence of recurrence. Spontaneous endometriosis developed in control baboons in the absence of inoculation suggesting that repetitive surgical procedures alone can induce the spontaneous evolution of the chronic disease. Although lesion excision/ablation may have short-term benefits (e.g. prior to an IVF cycle in subfertile women), for long-term relief of symptoms perhaps medical therapy is more effective than surgical therapy.

Endometrial stromal cells and immune cell populations within lymph nodes in a nonhuman primate model of endometriosis

Mounting evidence suggests that immunological responses may be altered in endometriosis. The baboon (Papio anubis) is generally considered the best model of endometriosis pathogenesis. The objective of the current study was to investigate for the first time immunological changes within uterine and peritoneal draining lymph nodes in a nonhuman primate baboon model of endometriosis. Paraffin-embedded femoral lymph nodes were obtained from 22 normally cycling female baboons (induced endometriosis n = 11; control n = 11). Immunohistochemical staining was performed with antibodies for endometrial stromal cells, T cells, immature and mature dendritic cells, and B cells. Lymph nodes were evaluated using an automated cellular imaging system. Endometrial stromal cells were significantly increased in lymph nodes from animals with induced endometriosis, compared to control animals (P = .033). In animals with induced endometriosis, some lymph node immune cell populations including T cells, dendritic cells and B cells were increased, suggesting an efficient early response or peritoneal drainage.

Aberrant expression of regulators of cell-fate found in eutopic endometrium is found in matched ectopic endometrium among women and in a baboon model of endometriosis

BACKGROUND

We have recently shown that women with endometriosis express an increased amount of telomerase and nucleolin, with concomitant loss of γ-H2AX in eutopic endometrium. To further examine these selected factors that regulate cell fate, in the pathogenesis of endometriosis, we studied the expression of telomerase, nucleolin, proliferating cell nuclear antigen and γ-H2AX in ectopic endometriotic deposits from women, and in matched eutopic and ectopic endometrial tissue from a baboon model of endometriosis.

METHODS

Ectopic active peritoneal endometriotic lesions were collected from seven symptomatic women. Endometriosis was induced in six baboons by intra-peritoneal autologous inoculation of menstrual endometrium. Eutopic and matched ectopic endometrial tissues were collected prior to and 6, 12 and 15 months after the induction of endometriosis as previously described. Eutopic endometrium was also obtained from eight healthy fertile control baboons. Immunohistochemistry was performed as previously described, and telomerase activity was confirmed using the telomeric repeat amplification protocol assay.

RESULTS

All active human endometriotic lesions expressed the proliferative markers but showed weak or absent staining for γ-H2AX. A similar expression pattern of these markers was seen in the ectopic lesions of the baboons with induced disease. In these baboons, the eutopic endometrium also showed intense immunoreactivity for all proliferative markers 6-12 months after induction with a parallel loss of γ-H2AX. The opposite staining pattern was seen in eutopic endometrium of healthy animals and in pre-induction endometrium of animals with induced disease.

CONCLUSIONS

Endometriotic lesions have excess proliferative potential; in baboons, these were present within 12 months of the initiation of the disease. In eutopic tissue, these changes appear to be induced by the development of endometriosis.

The endometrial response to chorionic gonadotropin is blunted in a baboon model of endometriosis

Endometriosis-associated infertility has a multifactorial etiology. We tested the hypothesis that the endometrial response to the early embryonic signal, human chorionic gonadotropin (hCG), alters over time in a nonhuman primate model of endometriosis. Animals with experimental or spontaneous endometriosis were treated with hCG (30 IU/d), from d 6 after ovulation for 5 d, via an oviductal cannula. Microarray analysis of endometrial transcripts from baboons treated with hCG at 3 and 6 months of disease (n=6) identified 22 and 165 genes, respectively, whose levels differed more than 2-fold compared with disease-free (DF) animals treated with hCG (P<0.01). Quantitative RT-PCR confirmed abnormal responses of known hCG-regulated genes. APOA1, SFRP4, and PAPPA, which are normally down-regulated by hCG were up-regulated by hCG in animals with endometriosis. In contrast, the ability of hCG to induce SERPINA3 was lost. Immunohistochemistry demonstrated dysregulation of C3 and superoxide dismutase 2 proteins. We demonstrate that this abnormal response to hCG persists for up to 15 months after disease induction and that the nature of the abnormal response changes as the disease progresses. Immunohistochemistry showed that this aberrant gene expression was not a consequence of altered LH/choriogonadotropin receptor distribution in the endometrium of animals with endometriosis. We have shown that endometriosis induces complex changes in the response of eutopic endometrium to hCG, which may prevent the acquisition of the full endometrial molecular repertoire necessary for decidualization and tolerance of the fetal allograft. This may in part explain endometriosis-associated implantation failure.

Extracellular matrix metalloproteinase inducer expression in the baboon endometrium: menstrual cycle and endometriosis

Extracellular matrix metalloproteinase inducer (EMMPRIN; BSG) regulates tissue remodeling through matrix metalloproteinases (MMPs). In human and non-human primates, endometrial remodeling is important for menstruation and the pathogenesis of endometriosis. We hypothesized that as in humans, BSG and MMPs are expressed in the endometrium of cycling baboons, and their expression is hormonally regulated by ovarian hormones, but endometriosis disrupts this regulation. BSG expression was evaluated in the baboon endometrium by q-PCR and immunohistochemistry. In the endometrium of control cycling animals, BSG mRNA levels were highest in late secretory stage tissue. BSG protein localized to glandular epithelial cells during the proliferative phase; whereas, secretory stage tissues expressed BSG in glandular and luminal epithelia with weak stromal staining. Several MMPs were differentially expressed throughout the menstrual cycle with the highest levels found during menstruation. In ovariectomized animals, BSG endometrial mRNA levels were highest with treatment of both estrogen and progesterone than that with only estrogen. Estrogen alone resulted in BSG protein localization primarily in the endometrial glandular epithelia, while estrogen and progesterone treatment displayed BSG protein localization in both the glandular and stromal cells. Exogenous hormone treatment resulted in differential expression patterns of all MMPs compared with the control cycling animals. In the eutopic endometrium of endometriotic animals, BSG mRNA levels and protein were elevated early but decreased later in disease progression. Endometriosis elevated the expression of all MMPs except MMP7 compared with the control animals. In baboons, BSG and MMP endometrial expression is regulated by both ovarian hormones, and their expression patterns are dysregulated in endometriotic animals.

Connexin expression pattern in the endometrium of baboons is influenced by hormonal changes and the presence of endometriotic lesions

Experimentally induced endometriosis in baboons serves as an elegant model to discriminate between endometrial genes which are primarily associated with normal endometrial function and those that are changed by the presence of endometriotic lesions. Since connexin genes are characteristic of the hormonally regulated differentiation of the endometrium, we have examined connexin expression in baboon endometrium to delineate if they are altered in response to the presence of endometriotic lesions. Connexin expression in the endometrium of cycling baboons is similar to that of the human endometrium with Connexin(Cx)43 being primarily seen in the stromal compartment and Cx26 and Cx32 being present predominantly in the epithelium. Although Cx32 is up-regulated during the secretory phase, Cx26 and Cx43 are down-regulated. In the baboon model of induced endometriosis a change in connexin pattern was evident in the presence of endometriotic lesions. In the secretory phase, Cx26 and Cx32 are no longer present in the epithelium but Cx26 is now observed primarily in the stromal cells. Infusion of chorionic gonadotrophin in a manner that mimics blastocyst transit in utero failed to rescue the aberrant stromal expression of Cx26 that is associated with the presence of endometriotic lesions suggesting an impairment of the implantation process. The altered connexin pattern coupled with a loss of the channel protein in the epithelium and a gain of Cx26 in the stromal compartment suggests that the presence of lesions changes the uterine environment and thereby the differentiation programme. This aberrant expression of connexins may be an additional factor that contributes to endometriosis-associated infertility.

The non-human primate model of endometriosis: research and implications for fecundity

The development of an animal model of endometriosis is crucial for the investigation of disease pathogenesis and therapeutic intervention. These models will enhance our ability to evaluate the causes for the subfertility associated with disease and provide a first-line validation of treatment modulators. Currently rodents and non-human primate models have been developed, but each model has their limitations. The aim of this manuscript is to summarize the current findings and theories on the development of endometriosis and disease progression and the effectiveness of therapeutic targets using the experimental induced model of endometriosis in the baboon (Papio anubis).

Altered expression of HOXA10 in endometriosis: potential role in decidualization

Endometriosis is a poorly understood gynaecologic disorder that is associated with infertility. In this study, we examined the expression of HOXA10 in the eutopic endometrium of baboons with induced endometriosis. A decrease in HOXA10 mRNA was observed after 3, 6, 12 and 16 months of disease, which reached statistical significance at 12 and 16 months. HOXA10 protein levels were decreased in both the epithelial and stromal cells of the endometrium. Furthermore, expression of beta3 integrin (ITGB3), which is upregulated by HOXA10, was decreased, whereas EMX2, a gene that is inhibited by HOXA10, was increased. Next, methylation patterns of the HOXA10 gene were analysed in the diseased and control animals. The F1 region on the promoter was found to be the most significantly methylated in the endometriosis animals and this may account for the decrease in HOXA10 expression. Finally, we demonstrate that stromal cells from the eutopic endometrium of baboons with endometriosis expressed significantly higher levels of insulin-like growth factor binding protein-1 (IGFBP1) mRNA than disease-free animals in response to estradiol, medroxyprogesterone acetate and dibutyryl cAMP (H + dbcAMP). The functional role of HOXA10 in IGFBP1 expression was further explored using human endometrial stromal cells (HSC). Overexpression of HOXA10 in HSC resulted in a decrease of IGFBP1 mRNA, whereas silencing HOXA10 caused an increase of IGFBP1 mRNA, even in the presence of H + dbcAMP. These data demonstrate that HOXA10 negatively influences IGFBP1 expression in decidualizing cells. Thus, the decrease in HOXA10 levels may in part be involved with the altered uterine environment associated with endometriosis.

A commentary on gestational programming and functions of HLA-G in pregnancy

HLA-G is an HLA class Ib gene that is highly expressed in human trophoblast cells. The single HLA-G mRNA is alternatively spliced to generate at least seven transcripts, three of which encode soluble isoforms. Many studies have shown that high levels of soluble antigens are associated with successful implantation and graft acceptance. To study expression, regulation and functions of two of the soluble isoforms, HLA-G5 and HLA-G6, we generated recombinant proteins in eukaryotic cells and developed monoclonal antibodies specific for each of the two proteins. In addition, we investigated the olive baboon Paan-AG gene as a potential functional correlate of HLA-G. Here, we present summaries of the studies that have been conducted in our laboratory using these tools and discuss the results within the context of the research on this topic that is ongoing in ours and other laboratories worldwide. Collectively, the data indicate that soluble HLA-G is a critical contributor to immune privilege in pregnancy and imply that this placenta-derived substance may impact other pathways leading to successful reproduction.

Identification of novel genes regulated by chorionic gonadotropin in baboon endometrium during the window of implantation

Chorionic gonadotropin (CG) is an early embryo-derived signal that is known to support the corpus luteum. An in vivo baboon model was used to study the direct actions of human CG (hCG) on the endometrium, during the periimplantation period. Endometrial gene expression was analyzed using microarrays. The endometrial biopsies were taken from hCG-treated (n = 5) and control (n = 6) animals on d 10 after ovulation. Class comparison identified 61 genes whose transcript levels differed between control and hCG-treated samples (48 increased, 13 decreased in mean expression level more than 2.5-fold; P < 0.01). Real-time PCR of transcript abundance confirmed up-regulation of several of these, including SerpinA3, matrix metalloproteinase 7, leukemia inhibitory factor (LIF), IL-6, and Complement 3 (P </= 0.05). Analysis of protein abundance in endometrial flushings showed increased LIF and IL-6 protein in uterine flushings from hCG-treated animals compared with controls. Complement C3 and Superoxide dismutase 2 that were also up-regulated, were further evaluated by immunocytochemistry. Complement C3 showed a marked increase in stromal staining in response to hCG, whereas and superoxide dismutase 2 localization was most markedly increased in the glandular epithelial cells. Expression of Soluble Frizzled Related Protein 4, the most highly down-regulated gene, was also validated by PCR. Our experiments have shown that hCG induces alterations in the endometrial expression of genes that regulate embryo attachment, extracellular matrix remodeling and the modulation of the immune response around the implanting blastocyst. Several of these genes, including LIF and gp130, have been shown to be essential for implantation in other species. This study provides strong evidence that the preimplantation embryo itself influences the development of the receptive endometrium via secreted paracrine signals.

Decidual stromal cell response to paracrine signals from the trophoblast: amplification of immune and angiogenic modulators

During the invasive phase of implantation, trophoblasts and maternal decidual stromal cells secrete products that regulate trophoblast differentiation and migration into the maternal endometrium. Paracrine interactions between the extravillous trophoblast and the maternal decidua are important for successful embryonic implantation, including establishing the placental vasculature, anchoring the placenta to the uterine wall, and promoting the immunoacceptance of the fetal allograph. To our knowledge, global crosstalk between the trophoblast and the decidua has not been elucidated to date, and the present study used a functional genomics approach to investigate these paracrine interactions. Human endometrial stromal cells were decidualized with progesterone and further treated with conditioned media from human trophoblasts (TCM) or, as a control, with control conditioned media (CCM) from nondecidualized stromal cells for 0, 3, and 12 h. Total RNA was isolated and processed for analysis on whole-genome, high-density oligonucleotide arrays containing 54,600 genes. We found that 1374 genes were significantly upregulated and that 3443 genes were significantly downregulated after 12 h of coincubation of stromal cells with TCM, compared to CCM. Among the most upregulated genes were the chemokines CXCL1 (GRO1) and IL8,CXCR4, and other genes involved in the immune response (CCL8 [SCYA8], pentraxin 3 (PTX3), IL6, and interferon-regulated and -related genes) as well as TNFAIP6 (tumor necrosis factor alpha-induced protein 6) and metalloproteinases (MMP1, MMP10, and MMP14). Among the downregulated genes were growth factors, e.g., IGF1, FGF1, TGFB1, and angiopoietin-1, and genes involved in Wnt signaling (WNT4 and FZD). Real-time RT-PCR and ELISAs, as well as immunohistochemical analysis of human placental bed specimens, confirmed these data for representative genes of both up- and downregulated groups. The data demonstrate a significant induction of proinflammatory cytokines and chemokines, as well as angiogenic/static factors in decidualized endometrial stromal cells in response to trophoblast-secreted products. The data suggest that the trophoblast acts to alter the local immune environment of the decidua to facilitate the process of implantation and ensure an enriched cytokine/chemokine environment while limiting the mitotic activity of the stromal cells during the invasive phase of implantation.

Morphological and glycosylation changes associated with the endometrium and ectopic lesions in a baboon model of endometriosis

BACKGROUND

Endometriosis is one of the most common causes of infertility and pelvic pain. A baboon model has recently been developed whereby the intrapelvic injection of menstrual endometrium results in the induction of endometriotic lesions. We have used this model to investigate changes in ultrastructure and glycosylation of endometria from normal and diseased baboons.

METHODS

Endometriosis was induced in eight female baboons; endometrial tissue and endometriotic lesions were removed on days 9-11 post ovulation between 3 and 16 months of disease and compared with endometrium from 17 control animals, using electron microscopy and lectin histochemistry.

RESULTS

Ultrastructurally, diseased endometrial glands showed abnormalities in secretory vacuoles and an intracellular accumulation of glycogen; in later stages of the disease, glands resembled those of the late secretory phase endometrium. The abnormalities were mirrored by changes in glycan expression. In early disease, there was an increased binding of lectin from Dolichos biflorus agglutinin (DBA) to fucosylated N-acetylglucosamine residues, whereas in later stages, this binding generally decreased in association with the appearance of a late secretory phenotype.

CONCLUSIONS

Endometriosis is accompanied by progressive changes in the gland architecture and biochemistry resulting in dyssynchrony within the window of uterine receptivity, which may result in the reduced fertility associated with this disease.

Extracellular matrix metalloproteinase inducer regulates metalloproteinases in human uterine endometrium

CONTEXT

Endometrial remodeling occurs during each menstrual cycle in women and also during the establishment of endometriosis. Both processes involve the production of metalloproteinases (MMPs) by uterine endometrial cells.

OBJECTIVE

The objective of this study was to determine whether tissue remodeling and endometrial invasion involve activation of MMPs by extracellular matrix metalloproteinase inducer (EMMPRIN).

MAIN OUTCOME MEASURES

EMMPRIN expression was examined by immunohistochemistry and real-time PCR in ectopic and eutopic endometria. For functional assays, human uterine fibroblasts were treated in the absence or presence of IL-1beta (10 ng/ml) or purified native EMMPRIN (0.5 or 1 microg/ml) for 24 h. Cellular RNA and conditioned medium were assayed by real-time PCR or immunoblotting.

RESULTS

EMMPRIN protein localized to epithelial and fibroblast cells of eutopic and ectopic endometria. The pattern of localization was regulated by ovarian hormones. EMMPRIN mRNA levels varied throughout the menstrual cycle in parallel with the cyclic changes in estradiol. EMMPRIN treatment (0.5 microg/ml) of human uterine fibroblast cells stimulated MMP-1 (5.23-fold) and MMP-2 (8.55-fold), but not MMP-3, mRNA levels over levels in control cells (P < 0.05). EMMPRIN treatment (1 microg/ml) stimulated endogenous EMMPRIN (1.6-fold) mRNA levels (P > 0.05). IL-1beta stimulated MMP-1 (5.6-fold), MMP-2 (2.8-fold), and MMP-3 (75-fold) gene expression, but not EMMPRIN, over levels in control cells (P < 0.05). Both EMMPRIN and IL-1beta treatments stimulated MMP-1, -2, and -3, but not EMMPRIN protein secretion, with 0.5 microg/ml producing the greatest response.

CONCLUSIONS

The ability of EMMPRIN to stimulate MMP secretion by endometrial fibroblasts indicates its potential role in uterine remodeling and the pathogenesis of endometriosis.

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 olive baboon (Papio anubis): a potential animal model to study the function of human leukocyte antigen-G (HLA-G)

The human class Ib major histocompatibility complex (MHC) molecule, HLA-G, is unique in its limited polymorphism, high expression in the placenta and generation of multiple transcripts by alternative splicing. The proteins encoded by these transcripts are believed to modulate maternal-fetal immunological relationships during pregnancy. The baboon placenta expresses Paan-AG, a novel MHC molecule that is evolutionarily related to the MHC-A locus but shares unique characteristics with HLA-G. In this brief review, we present evidence suggesting that Paan-AG may be the functional homologue of HLA-G, and propose that the baboon would compromise an excellent animal model for functional studies of HLA-G proteins in human pregnancy.

The induction of baboon glycodelin expression by progesterone is not through Sp1

Glycodelin is a major secretory product of the uterine glandular epithelial cells of the human and non-human primate during the late luteal phase of the menstrual cycle and early pregnancy. Since progesterone levels are elevated during these periods we sought to determine how progesterone modulates glycodelin gene expression. Co-transfection of various deletions of the baboon glycodelin promoter with the progesterone receptor (PR) into Ishikawa cells, a human endometrial cell line, revealed that full progesterone responsiveness is retained within the region -119/+48. In COS-1 cells, a kidney cell line, progesterone failed to elevate luciferase levels when various deletion constructs and the PR were co-transfected. Mutation of the Sp1 site in the -67/+48 region lowered basal expression but did not affect the ability of progesterone to increase expression of the luciferase reporter in Ishikawa cells. These findings suggest that Sp1 sites are not involved in the progesterone regulation of the baboon glycodelin gene. We propose that progesterone induces a factor that regulates glycodelin gene expression in the uterus since we failed to obtain a similar response in a non-uterine cell line.

IL-1beta during in vitro decidualization in primate

The sequence of biochemical and molecular events associated with decidualization in the primate remain unclear. In the baboon, the sequential changes during this period in vivo are characterized by the downregulation of alpha-smooth actin followed by induction of cyclooxygenase-2 (COX-2) at the implantation site and the expression of insulin growth factor binding protein-1 (IGFBP-1). IGFBP-1 is the predominant protein in decidualized cells and is considered to be biochemical marker of decidualization. In the baboon the expression of IGFBP-1 requires the presence of a conceptus in vivo or N(6), 2'-O-dibutyryladenosine 3:5'-cyclic monophosphate (dbcAMP) in the presence of hormones in vitro. In addition IL-1beta, as a possible conceptus-mediated factor, can induce IGFBP-1 expression in the presence of hormones following 3 days of incubation. However, if IL-1beta and dbcAMP are added together, IGFBP-1 expression is inhibited which resulted in IL-1beta being considered to be "inhibitory" to decidualization. Current data suggest that IL-1beta can activate multiple signaling pathways that either positively (no exogenous cAMP) or negatively (in presence of exogenous cAMP) regulate IGFBP-1 gene expression and decidualization in vitro. Signaling pathways activated by IL-1beta following 10 min of stimulation result in the phosphorylation of mitogen-activated protein kinase (MAPK, specifically p38 MAPK) and also lead to NF-kappaB activation. The expression of COX-2 and matrix metalloproteinase-3 (MMP-3) genes follows after 4-6 h. The steroid hormones, particularly progesterone, which are critical for IGFBP-1 expression, modulate the activity of IL-1beta by down-regulating MMP-3 activity. Disruption of actin filaments enhances IGFBP-1 induction during decidualization. IL-1beta induced MMP-3 may upregulate IGFBP-1 by initiation of cytoskeletal reorganization through degradation of extracellular matrix (ECM). Inhibition of IL-1beta induced pathways leads to reduction of IGFBP-1 expression, suggesting that IL-1beta may be involved in the events leading to decidualization in baboons.

Ultrastructure of epithelial plaque formation and stromal cell transformation by post-ovulatory chorionic gonadotrophin treatment in the baboon (Papio anubis)

BACKGROUND

To understand factors controlling endometrial responses to pregnancy, we have established a model using the baboon and examined the effects of infused human chorionic gonadotrophin (HCG) on the preparation of the luminal epithelium and stromal cell differentiation for the establishment of pregnancy.

METHODS

The ultrastructure of endometrium from normal day 10 post-ovulation animals, cycling females treated with either HCG or FSH (control), and a day 15 pregnant animal has been compared.

RESULTS

In the control endometrium, the luminal epithelium was smooth and regular, with underlying spindle shaped stromal cells. In pregnancy, the luminal epithelium underwent a plaque reaction, while stromal cells enlarged and developed filament-rich cell processes. Infusion of HCG produced changes similar to those seen in pregnancy, with generalized plaque formation and stromal decidualization, while in the animal treated with FSH there was no response.

CONCLUSIONS

This study indicates that infusion of HCG into the uterus can duplicate many of the responses of the endometrium to pregnancy, although in this case the plaque reaction involved the whole of the luminal epithelium, rather than only the implantation site as in pregnancy.

PRL-induced ERalpha gene expression is mediated by Janus kinase 2 (Jak2) while signal transducer and activator of transcription 5b (Stat5b) phosphorylation involves Jak2 and a second tyrosine kinase

In the rat corpus luteum of pregnancy, PRL stimulation of ER expression is a prerequisite for E2 to have any luteotropic effect. Previous work from our laboratory has established that PRL stimulates ERalpha expression at the level of transcription and that the transcription factor Stat5 (signal transducer and activator of transcription 5) mediates this stimulation. Since it is well established that PRL activates Stat5 through the tyrosine kinase, Janus kinase 2 (Jak2), the role of Jak2 in PRL regulation of ERalpha expression was investigated. In primary luteinized granulosa cells, the general tyrosine kinase inhibitors, genistein and AG18, and the Jak2 inhibitor, AG490, prevented PRL stimulation of ERalpha mRNA levels, suggesting that PRL signaling to the ERalpha gene requires Jak2 activity. However, using an antibody that recognizes the tyrosine-phosphorylated forms of both Stat5a and Stat5b (Y694/Y699), it was found that AG490 could inhibit PRL-induced Stat5a phosphorylation only and had little or no effect on Stat5b phosphorylation. These effects of AG490 were confirmed in COS cells overexpressing Stat5b. Also in COS cells, a kinase-negative Jak2 prevented PRL stimulation of ERalpha promoter activity and Stat5b phosphorylation while a constitutively active Jak2 could stimulate both in the absence of PRL. Furthermore, kinase-negative-Jak2, but not AG490, could inhibit Stat5b nuclear translocation and DNA binding. Therefore, it seems that in the presence of AG490, Stat5b remains phosphorylated, is located in the nucleus and capable of binding DNA, but is apparently transcriptionally inactive. These findings suggest that PRL may activate a second tyrosine kinase, other than Jak2, that is capable of phosphorylating Stat5b without inducing transcriptional activity. To investigate whether another signaling pathway is involved, the src kinase inhibitor PP2 and the phosphoinositol-3 kinase inhibitor (PI3K), LY294002, were used. Neither inhibitor alone had any major effect on PRL regulation of ERalpha promoter activity or on PRL-induced Stat5b phosphorylation. However, the combination of AG490 and LY294002 largely prevented PRL-induced Stat5b phosphorylation. These findings indicate that PRL stimulation of ERalpha expression requires Jak2 and also that PRL can induce Stat5b phosphorylation through two tyrosine kinases, Jak2 and one downstream of PI3K. Furthermore, these results suggest that the role of Jak2 in activating Stat5b may be through a mechanism other than simply inducing Stat5b phosphorylation.

The role of chorionic gonadotropin (CG) in blastocyst implantation

Implantation is a complex spatio-temporal interaction between the genotypically different embryo and the mother. Success of this event requires the synchronization of development and effective biochemical communications from both sides. Chorionic gonadotropin (CG), which is a major embryonic signal in the primate, is a glycoprotein hormone synthesized and secreted by the trophoblast. Various isoforms exist in plasma, urine, and blastocyst culture medium, a result of posttranslational modifications. The exponential secretion of CG and its long circulatory half-life extends the life span of corpus luteum to maintain the supply of progesterone during the first 6-8 weeks of pregnancy. To study the direct effects of CG in the uterus, we used the baboon (Papio anubis) as a non-human primate model. In vivo stimulation with CG during the window of uterine receptivity results in further morphologic and biochemical modifications of the receptive endometrium. These are characterized by the plaque reaction in the luminal epithelium, an increase in glycodelin expression and secretion by the glandular epithelium, and the differentiation of subepithelial stromal fibroblasts characterized by expression of the alpha smooth muscle actin (alpha SMA). Pretreatment with progesterone receptor antagonist (PRa) completely or partially inhibits these effects. The signal transduction pathway activated by CG in primate endometrial epithelial cells involves the protein kinase A (PKA)-independent phosphorylation of extracellular signal regulated kinase (ERK 1/2). This alternate signal transduction pathway may prevent CG Receptor (R) downregulation at the implantation site and enhance epithelial cell proliferation and differentiation. Thus, our results suggest that CG plays an important role in implantation in addition to its luteotrophic role.

Uterine receptivity in the baboon: modulation by chorionic gonadotropin

Embryonic signals not only rescue the corpus luteum but also modulate the uterine environment in preparation for implantation. Chorionic gonadotropin (CG), an early embryonic signal, is one such molecule. In vivo studies in the baboon show that CG alters the morphology and biochemical activity of the uterus, especially with respect to the three major cell types: luminal epithelium, glandular epithelium, and stromal fibroblasts. Further, CG and progesterone have a synergistic effect on the receptive endometrium. CG action on the endometrial cells is transduced via a seven transmembrane G protein-coupled receptor. Possible signaling pathways involved are discussed.

Activation of the luteinizing hormone/choriogonadotropin hormone receptor promotes ADP ribosylation factor 6 activation in porcine ovarian follicular membranes

Previously we demonstrated in a cell-free ovarian follicular plasma membrane model that agonist-dependent desensitization of the luteinizing hormone/choriogonadotropin receptor (LH/CG R) is GTP-dependent, mimicked by the addition of ADP-ribosylation factor (ARF) nucleotide binding site opener, which acts as a guanine nucleotide exchange factor for ARFs 1 and 6, and selectively inhibited by synthetic N-terminal ARF6 peptides. We therefore sought direct evidence that activation of the LH/CG R promotes activation of ARF1 and/or ARF6. Using a classic ARF activation assay, the cholera toxin-catalyzed ADP-ribosylation of G alpha(s), results show that LH/CG R activation stimulates an ARF protein by a brefeldin A-independent mechanism. Synthetic N-terminal inhibitory ARF6 but not ARF1 peptide blocks LH/CG R-stimulated ARF activity. LH/CG R activation also promotes the binding of a photoaffinity GTP analog to a protein that migrates on one- and two-dimensional polyacrylamide gel electrophoresis with ARF6. These results suggest that ARF6 is the predominant ARF activated by the LH/CG R. To activate ARF6, the LH/CG R does not appear to signal through the C-terminal regions of G alpha(i) or G alpha(q) or through the second or third intracellular loops or the N terminus of the cytoplasmic tail of the LH/CG R. Although exogenous recombinant ARNO promotes only a small increase in ARF6 activation in the presence of activated LH/CG R, hCG-stimulated ARF6 activation is reduced to basal levels by catalytically inactive ARF nucleotide binding-site opener. These results provide direct evidence that LH/CG R activation leads to the activation of membrane-delimited ARF6.

Heparin-binding EGF-like growth factor modulation by antiprogestin and CG in the baboon (Papio anubis)

The objectives of this study were to determine whether antiprogestin therapy or the infusion of human CG to mimic blastocyst transit in the baboon alters heparin-binding EGF-like growth factor expression during the window of implantation. During the menstrual cycle, heparin-binding EGF-like growth factor protein accumulation in the glandular epithelium was low in the proliferative phase and increased to maximal expression on d 5 and 10 postovulation. Stromal cells accumulated high levels of heparin-binding EGF-like growth factor in the proliferative phase, which decreased by d 5 postovulation. These transitional changes in both cell types were delayed when cycling baboons were treated with the antiprogestin ZK 137.316 during the luteal phase. The treatment with human CG had no effect on expression of heparin-binding EGF-like growth factor when compared with cycling baboons on d 10 postovulation and was comparable with that observed on d 18 and 22 of pregnancy. However, the superimposition of the antiprogestin with the human CG treatment also decreased expression in the epithelial cells. In summary, heparin-binding EGF-like growth factor accumulation in the epithelial glands is under the influence of progesterone and does not seem to be influenced by the paracrine secretion of trophoblast CG.

Early Implantation Events in the Baboon (Papio anubis) with Special Reference to the Establishment of Anchoring Villi

The development of the baboon anchoring villus has been studied from day 14 to day 48 of gestation, using light and electron microscopy. At day 14, cords of trophoblast could be seen streaming into the endometrium, invading maternal vessels and forming blood-filled lacunae; by 20 days gestation some of these had differentiated into distinctive anchoring villi, with an outer covering of syncytiotrophoblast and inner cytotrophoblast cells which differed from those of floating villi in that a subpopulation detached from the syncytium to form an interconnecting network of cells within the centre of the villus. Subsequent migration of cytotrophoblast into the endometrium formed the cytotrophoblastic shell while fibrillin-like extracellular matrix biosynthesis within the body of the villus provided a firm mechanical support. At the trophoblast-decidual interface, a zone of necrosis and phagocytosis initially developed, which became less extensive with time, so that by 40 days a stable interface was evident with only residual pockets of necrosis. During this period, there was differentiation of decidual cells which by 28 days developed characteristic pedunculated cell processes, and later became surrounded by a basal lamina. The factors that control detachment of cytotrophoblast from the syncytium and the biosynthesis of the specialized, fibrillar extracellular matrix, features that are not apparent in other placental villi, require further investigation, possibly by carefully controlled in vitro experimentation.

Structure of anchoring villi and the trophoblastic shell in the human, baboon and macaque placenta

Anchoring villi of first trimester placentae of the macaque, baboon and human were examined by light and electron microscopy. The anchoring villi of the baboon and macaque are similar in having more elongated cell columns than those of the human and in having more extracellular matrix between cytotrophoblast cells. These species also have a thicker and more uniform trophoblastic shell. The generative region of cytotrophoblast cells adjacent to the villous mesenchyme is similar in all three species, with the aspect of the core abutting this area being lined by a thickened basal lamina. Similarly, migratory cytotrophoblast cells form extracellular matrix in all three species, but matrix-rich regions of the anchoring villi and shell are more extensive in the non-human primates. The extracellular matrix and especially the material resembling fibrillin may serve to strengthen the villi, particularly the elongated villi of the non-human primate, and also may prevent maternal cells migrating into the trophoblastic shell. The baboon and macaque cytotrophoblast cells that form this matrix tend to be linked by gap and desmosomal junctions and are in contiguous arrays, whereas those in the human that are blocked from reaching normal decidua form abundant extracellular matrix but have no gap junctions. Whether the lack of extensive invasion of the endometrium by baboon and macaque cytotrophoblast cells is related to the increased amount of extracellular matrix, their greater distance from the mesenchymal core, or their intercellular linkages is not known. The investigation of isolated villi from the macaque or baboon, as has been extensively carried out in the human, might help to determine whether the cytotrophoblast cells are intrinsically different or are responding to different environmental cues.

Interleukin-1beta induces the expression of insulin-like growth factor binding protein-1 during decidualization in the primate

Since interleukin (IL)-1 can modulate fetal/maternal interactions, we hypothesized that IL-1beta is one potential embryonic cytokine that regulates the conceptus-induced decidual response in baboon stromal fibroblasts. Treatment of stromal fibroblasts with IL-1beta (10 ng/ml, 10 min) resulted in the phosphorylation of p38 mitogen-activated protein kinase and IkappaB-alpha. This suggests that IL-1beta induces multiple signaling pathways in stromal cells that result in the activation of mitogen-activated protein kinase cascade and the transcription factor NF-kappaB. After 4 h of stimulation, IL-1beta induced gene expression of cyclooxygenase-2 (COX-2) but not cyclooxygenase-1 (COX-1). PGE2 synthesis paralleled COX-2 messenger RNA expression. The addition of hormones [36 nM estradiol-17beta, 1 microM medroxyprogesterone acetate, and 100 ng/ml relaxin] to IL-1beta-treated cells induced insulin-like growth factor binding protein-1 (IGFBP-1) messenger RNA expression after 3 days of incubation. A specific COX-2 inhibitor, NS 398 (10 nM), partially inhibited IGFBP-1 protein synthesis. In contrast, the induction of IGFBP-1 by N6, 2'-O-dibutyryladenosine 3:5'-cyclic monophosphate (dbcAMP) and hormones was not affected by NS 398 treatment. Both dbcAMP and IL-1beta, in the presence of hormones, can independently induce IGFBP-1 gene expression and decidualization. However, if IL-1beta and dbcAMP were added together, IGFBP-1 expression was inhibited. These data suggest that IL-1beta can activate multiple signaling pathways that either positively or negatively regulate IGFBP-1 gene expression and decidualization.

Glycodelin-A expression in the uterine cervix

OBJECTIVE

Local immunosuppressive factors in the uterine cervix infected by human papillomavirus are felt to facilitate the malignant transformation process. Glycodelin-A is an immunosuppressive peptide found in several tissues of müllerian origin, most notably the pregnant and decidualized endometrium. Its expression in the uterine cervix has not been defined but could theoretically contribute to the immunopermissive environment of the cervix. To determine whether glycodelin-A is found in the cervix we examined the squamous and endocervical epithelia from both normal and neoplastic cervical specimens from 14 women.

METHODS

Immunohistochemisty identification of glycodelin-A was performed on archival paraffin-embedded sections from 10 hysterectomies and 4 cone biopsies. Sections were evaluated and staining was scored as negative, positive, or strongly positive with a separate score for the squamous and glandular components of the cervix.

RESULTS

Eleven of 14 cases, 79%, demonstrated positive staining of the squamous epithelium. Glycodelin-positive cases included hisologically normal (n = 4; 3 strongly positive, 1 positive) as well as dysplastic (n = 5; 1 strongly positive, 2 positive, and 2 negative) and malignant squamous cells (n = 5; 1 strongly positive, 3 positive, and 1 negative). Normal glandular epithelia were negative in all cases but 1, which demonstrated significant squamous and tubal metaplasia of the endocervical glands involved.

CONCLUSION

Glycodelin-A is found in the squamous epithelium of both the histologically normal and the neoplastic cervix. Further characterization of these results will focus on the possible immunosuppressive effect glycodelin-A may have in the cervix.

Modulation of the action of chorionic gonadotropin in the baboon (Papio anubis) uterus by a progesterone receptor antagonist (ZK 137. 316)

Signals from the developing mammalian blastocyst rescue the corpus luteum (CL) and modulate the uterine environment in preparation for implantation and early pregnancy. Our previous studies demonstrated that both short- and long-term administration of chorionic gonadotropin (CG) markedly alters the morphology and the biochemical activity of the receptive endometrium. Because the effects of CG were superimposed on a progesterone-primed endometrium, this study was undertaken to determine if the inhibition of progesterone action by progesterone receptor antagonists (PRa) in intact and ovariectomized baboons would alter the action of CG on the endometrium at the time of uterine receptivity. In the short-term hCG-treated baboons, the PRa reduced the epithelial plaque reaction, completely inhibited alpha-smooth muscle actin (alphaSMA) expression in stromal fibroblasts, and induced the reappearance of the progesterone (PR) and estrogen (ERalpha) receptors in epithelial cells. However, this treatment protocol had no effect on the expression of glycodelin in the glandular epithelium. In contrast, glycodelin expression in addition to alphaSMA was suppressed in the ovariectomized animals. In the long-term hCG-treated baboons, the PRa had a similar effect on both alphaSMA, PR, and ER. In addition, this treatment also resulted in an inhibition of glycodelin expression in the glandular epithelium. These results indicate that blocking the action of progesterone on the endometrium even for a short period of time has a profound effect on the hCG-induced response in stromal fibroblasts. In contrast, for the diminution of glandular epithelial function in the presence of an ovary requires prolonged inhibition of progesterone action, suggesting a potential paracrine effect on the endometrium from the CL in response to hCG.

Differential regulation of stromelysin-1 (matrix metalloproteinase-3) and matrilysin (matrix metalloproteinase-7) in baboon endometrium

OBJECTIVE

To investigate in vivo expression of matrix metalloproteinase enzymes (MMP), MMP-3 and MMP-7, by the baboon endometrium in relation to the process of tissue remodeling that accompanies menstruation in the primate.

METHODS

Endometrial tissues and uterine fluids obtained from reproductively intact cycling baboons, cycling baboons treated with an anti-progestin, and ovariectomized steroid-treated baboons were evaluated for MMP mRNA expression and protein production by using multiple analytic techniques.

RESULTS

The pattern of MMP protein production matched the pattern of MMP mRNA expression. In intact cycling baboons, MMP mRNA expression and protein production were specific to cell type and stage of the menstrual cycle. Endometrial stroma expressed minimal amounts of MMP-3 during the proliferative and secretory stages, whereas endometrial epithelia expressed MMP-7 during the proliferative stage. Expression of stromal MMP-3 and epithelial MMP-7 increased during early menses. Administration of anti-progestin beginning on the day of the LH surge increased MMP-7 but not MMP-3 expression at the mid secretory phase. Expression of MMP-3 and MMP-7 in the ovariectomized steroid-treated animals paralleled that of the intact cycling animals.

CONCLUSIONS

These results highlight the similarity of human and baboon endometrial MMP-3 and MMP-7 production, providing further evidence for use of the baboon as a model for studying events associated with hormonally regulated changes during the menstrual cycle. These results also demonstrate that endometrial epithelial MMP-7 is suppressed by progesterone in the baboon endometrium, but endometrial stromal MMP-3 is regulated by a different mechanism.

Implantation in the baboon: endometrial responses

Blastocyst implantation in the baboon usually occurs between 8 and 10 days post ovulation. Changes that occur within this window of receptivity and immediately following implantation can be divided into three distinct phases. The first phase, regulated by estrogen and progesterone, is characterized primarily by changes in both the luminal and glandular epithelial cells in preparation for blastocyst apposition and attachment. The second phase is the further modulation of these steroid induced changes in both epithelial and stromal cells by embryonic signals. The final phase is associated with trophoblast invasion and the remodeling of the endometrial stromal compartment. During the initial phase, the actions of estrogen and progesterone are dependent on the presence of specific receptors. Estrogen up-regulates both its own receptor (ER) and the progesterone receptor (PR), while progesterone down-regulates this expression pattern. However, the pattern of progesterone-induced down-regulation of ER and PR is confined to the epithelial cells and demonstrates a gradient effect from the functionalis to the basalis. What is most intriguing is that the loss of epithelial PR is closely correlated with the establishment of uterine receptivity. Coincident with the changes in ER and PR expression, epithelial cells undergo alterations in their cytoskeletal architecture and secretory profile. These changes can be counteracted by PR antagonist treatment during the luteal phase. Although estrogen and progesterone play a critical role in establishing the initial phase of uterine receptivity, it is becoming increasingly evident that the embryo induces functional receptivity in ruminants and rodents. In our studies in the primate, we demonstrate that chorionic gonadotrophin when infused in a manner that mimics blastocyst transit, has physiological effects on the three major cell types in the uterine endometrium. The luminal epithelium undergoes endoreplication and distinct epithelial plaques are evident. The glandular epithelium responds by inducing transcriptional and post-translational modifications in the major secretory product, glycodelin. The stromal fibroblasts initiate their differentiation process into a decidual phenotype and are characterized by the expression of actin filaments. In phase three, blastocyst attachment to the surface epithelium and subsequent implantation is associated with local remodeling of the maternal stroma, smooth muscle, and endothelium of the blood vessels by the trophoblast. In addition, there is a gradual diminution of the epithelial plaques on the luminal surface although the glandular epithelium remains highly secretory. The most dramatic effect is on the stromal fibroblasts, which in response to embryonic stimuli, differentiate into decidual cells, the major cell type of the gestational endometrium. This differentiation is characterized by the expression of insulin-like growth factor binding protein-1 (IGFBP-1) in these cells. The cytokine IL-1 beta is one possible embryonic signal. COX-2 is the rate-limiting enzyme for prostaglandin biosynthesis and transcription of this enzyme in response to the embryonic stimulus (IL-1 beta) results in an increase in prostaglandin biosynthesis in stromal fibroblasts at the site of implantation. Prostaglandins and PGE2 in particular, binds to its specific receptor (EP2 or EP4) and activates adenyl cyclase. The resulting increase in intracellular levels of cAMP can now activate IGFBP-1 gene transcription at the site of implantation. In summary, our studies have demonstrated that chorionic gonadotrophin, when infused into non-pregnant baboons during the window of uterine receptivity can induce epithelial responses that are similar to those observed in a fertile cycle. Stromal differentiation is initiated; however, decidualization requires a signal from the conceptus.

Blastocyst invasion and the stromal response in primates

One of the most remarkable processes associated with the establishment of pregnancy in the primate is the process of decidualization. This transformation of a stromal fibroblast to a fully differentiated decidual cell is required for implantation and embryo survival in early pregnancy. Although the morphological and biochemical characteristics of the primate decidual cell have been extensively studied, the precise cellular, biochemical and molecular signals required for this transformation have yet to be elucidated. During decidualization, stromal cells first proliferate and then differentiate. Based on our extensive in-vivo and ongoing in-vitro studies, we have suggested that the process of decidualization in the baboon can be divided into two distinct phases. The initial proliferative phase is characterized by the expression of the cytoskeletal protein alpha smooth muscle actin (alphaSMA) in the stromal fibroblasts and is independent of the presence of the conceptus. The second phase of differentiation is characterized by the expression of insulin-like growth factor binding protein-1 (IGFBP-1) and the down-regulation of alphaSMA in the decidualized stromal fibroblast. The expression of IGFBP-1 is dependent on the presence of the conceptus in vivo and is regulated by hormones and cAMP in vitro. We have postulated that, during the initial phase of stromal cell differentiation, alphaSMA expression is regulated by the interaction between stromal cell integrins with the secreted extracellular matrix proteins (ECM). In response to pregnancy a trophoblast 'factor', mediated by cAMP signal transduction, induces IGFBP-1 expression in decidualizing stromal fibroblasts. This induction of IGFBP-1 is associated with the disappearance of alphaSMA and de-novo protein synthesis. Our comparative studies suggest that the process of decidualization in the human and baboon involve similar mechanisms. However, the metabolic pathways required for decidualization in the two species appear to differ in their degree of sensitivity to external stimuli. This review focuses on the cellular events that may potentially regulate decidualization in the primate and its role in regulating trophoblast migration.

Expression of prolactin and its receptor in the baboon uterus during the menstrual cycle and pregnancy

PRL is known to be a major secretory product of the human decidua. However, the physiological role of decidual PRL during the menstrual cycle and pregnancy has not been fully defined, primarily due to the lack of an appropriate nonhuman primate model for in vivo studies. Therefore, this initial study examined the expression of PRL and its receptor in the baboon uterus during the cycle and pregnancy. PRL and PRL receptor messenger ribonucleic acid expression were detected by semiquantitative RT-PCR, and protein was localized by immunocytochemistry. PRL was shown to be expressed in myometrial smooth muscle during the follicular phase by both RT-PCR and immunocytochemistry. Expression of PRL messenger ribonucleic acid and protein was first observed in the epithelial cells of the deep basal glands during the late luteal phase. With the onset of pregnancy, PRL expression increased steadily and was evident primarily in the decidual tissue. In contrast to PRL, its receptor was expressed at constant levels in both the myometrium and endometrium during the cycle. An increase in receptor expression was evident in both the decidua and placenta throughout pregnancy. In summary, these results demonstrate that the baboon uterus is a site of both PRL production and action during the cycle and pregnancy. These studies establish the baboon as a nonhuman primate model to investigate the potential roles of PRL in implantation and maintenance of pregnancy.

Expression of cyclooxygenase-1 and -2 in the baboon endometrium during the menstrual cycle and pregnancy

Cyclooxygenase (COX) is the rate-limiting enzyme in the biosynthesis of PGs. PGs together with ovarian steroids play important regulatory roles in the establishment and maintenance of pregnancy in a number of different species. In the primate, little is known about the role of PGs in these processes. In this study, the uterine expression of COX-1 and COX-2 throughout the menstrual cycle [late follicular, day 5 postovulation (PO), day 10 PO, and day 14 PO] and pregnancy (days 12-18, day 39, day 51, and near term) was analyzed using semiquantitative RT-PCR, in situ hybridization, and immunocytochemistry. During the menstrual cycle, the highest expression of COX-1 occurred in luteal phase endometrium and was localized to the surface and glandular epithelium. The stromal cells did not express detectable levels of COX-1 at any time. COX-2 messenger RNA (mRNA) expression, as measured by RT-PCR, was evident at all stages of the menstrual cycle, and in situ hybridization showed specific localization for this mRNA in the epithelial cells during the cycle. Treatment of animals with the antiprogestin (ZK 137.316) for 9 days (beginning on the day of the LH surge) inhibited COX-1 expression in the epithelium when the tissue was analyzed on day 10 PO, whereas COX-2 expression disappeared in the epithelium and increased in the stroma. With the onset of pregnancy, COX-1 expression in epithelial cells decreased dramatically. In contrast, COX-2 continued to be detected on the surface epithelium and was also strongly expressed specifically in the stromal cells at the site of implantation. Immunocytochemical staining for COX-2 showed the same pattern of expression for the protein as the message. Finally, near-term decidua expressed very little COX-1 or COX-2 mRNA. These studies suggest that in the baboon endometrium, COX-1 expression is regulated primarily by progesterone, whereas regulation of COX-2 expression may involve additional mediators of embryonic origin at the site of implantation.

Localization of ubiquitin and ubiquitin cross-reactive protein in human and baboon endometrium and decidua during the menstrual cycle and early pregnancy

We have examined the distribution of ubiquitin and the related ubiquitin cross-reactive protein (UCRP) in paraffin-embedded sections of human and baboon endometrium and decidua by immunoperoxidase or immunofluorescence cytochemistry with antibodies raised against ubiquitin, UCRP, CD45, and insulin-like growth factor-binding protein-1. Anti-ubiquitin immunoreactivity was present in the nonpregnant endometrium, particularly in the glandular epithelial cells, and up-regulated in endometrial stromal cells as they decidualized at the beginning of pregnancy. Anti-UCRP immunoreactivity was absent from nonpregnant tissue but accumulated to high levels in decidual cells during pregnancy. Western blotting indicated that immunoreactivity was primarily due to the presence of ubiquitin and UCRP conjugated to other proteins, and that although levels of ubiquitin-protein conjugates do not change substantially during pregnancy, decidualization is accompanied by the appearance of conjugates of UCRP. Baboon uterine tissues demonstrated a similar distribution of the two proteins, which indicates that the baboon may be a useful model for study of the role of the ubiquitin system and UCRP in the establishment of pregnancy in humans.

Modulation of the baboon (Papio anubis) uterine endometrium by chorionic gonadotrophin during the period of uterine receptivity

This study was undertaken to determine the modulation of uterine function by chorionic gonadotrophin (CG) in a nonhuman primate. Infusion of recombinant human CG (hCG) between days 6 and 10 post ovulation initiated the endoreplication of the uterine surface epithelium to form distinct epithelial plaques. These plaque cells stained intensely for cytokeratin and the proliferating cell nuclear antigen. The stromal fibroblasts below the epithelial plaques stained positively for alpha-smooth muscle actin (alphaSMA). Expression of alphaSMA is associated with the initiation of decidualization in the baboon endometrium. Synthesis of the glandular secretory protein glycodelin, as assessed by Western blot analysis, was markedly up-regulated by hCG, and this increase was confirmed by immunocytochemistry, Northern blot analysis, and reverse transcriptase-PCR. To determine whether hCG directly modulated these uterine responses, we treated ovariectomized baboons sequentially with estradiol and progesterone to mimic the hormonal profile of the normal menstrual cycle. Infusion of hCG into the oviduct of steroid-hormone-treated ovariectomized baboons induced the expression of alphaSMA in the stromal cells and glycodelin in the glandular epithelium. The epithelial plaque reaction, however, was not readily evident. These studies demonstrate a physiological effect of CG on the uterine endometrium in vivo and suggest that the primate blastocyst signal, like the blastocyst signals of other species, modulates the uterine environment prior to implantation.

Insulin-like growth factor binding protein-1 expression in baboon endometrial stromal cells: regulation by filamentous actin and requirement for de novo protein synthesis

Stromal fibroblasts in the primate endometrium undergo dramatic morphological and biochemical changes in response to pregnancy. This transformation is characterized by the expression of insulin-like growth factor binding protein-1 (IGFBP-1). Stromal cells from the baboon endometrium of nonpregnant animals were cultured and subsequently treated with cytochalasin D to disrupt actin filaments. In response to cytochalasin D treatment, cells contracted and became rounded as early as 10 min after the initiation of treatment. When cytochalasin D was removed, cells reverted back to their original fibroblastic shape within 1 h. After cells were treated with cytochalasin D for 5 h, addition of (Bu)2cAMP and/or hormones (estradiol, medroxyprogesterone acetate, and relaxin) resulted in the expression of IGFBP-1 messenger RNA and protein within 24 h. Cells with an intact cytoskeleton did not express detectable levels of IGFBP-1 in response to hormones and/or (Bu)2cAMP. Furthermore, the addition of cycloheximide inhibited expression of IGFBP-1 in cytochalasin D-treated cells. Stromal cells were also isolated from early pregnant and simulated pregnant animals. Within 48 h, cells from both the pregnant and simulated pregnant animals produced IGFBP-1 in response to hormones and/or (Bu)2cAMP. In these studies, IGFBP-1 expression was also inhibited by cycloheximide. These studies suggest that induction of IGFBP-1 requires an intermediary protein and that alterations in the cytoskeleton may be involved.

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.

Regulation of the glycosylated beta-lactoglobulin homolog, glycodelin [placental protein 14:(PP14)] in the baboon (Papio anubis) uterus

In vitro studies indicate that glycodelin (PP14) synthesis by the human endometrium increases dramatically at the time of implantation and early pregnancy. It has been postulated that this protein may have an immunosuppressive function. Due to the limitations associated with in vivo studies in the human, this study was undertaken to study the regulation of the baboon glycodelin homolog in vivo during the menstrual cycle and early pregnancy. In nonpregnant baboons, between days 10-12 postovulation (n = 3) the mid and apical regions of the glandular epithelium showed a distinct punctate staining pattern, which increased between days 12-18 of pregnancy (n = 3). Between days 25-60 of pregnancy, staining intensity in the glandular epithelium decreased. The decrease was more apparent at the implantation site compared with the nonimplantation site. The immunostaining correlated with the synthesis of radiolabeled baboon glycodelin in explant culture. Northern blot analysis demonstrated two messenger RNA (mRNA) transcripts [1.0 and 1.7 kilobases (kb)] in the baboon uterus compared with a single 1.0-kb transcript in the human, and mRNA expression was consistent with protein localization and synthesis. The protein and mRNA expression was consistently higher in the deeper glands of the functionalis and basalis during early pregnancy. Because the increased expression of glycodelin in the baboon endometrium coincided with peak levels of CG, a simulated pregnant baboon model was used to confirm hormonal regulation. Exogenous human CG (hCG) followed by estrogen and progesterone treatment in intact and ovariectomized baboons up-regulated glycodelin expression between days 18-25 postovulation (n = 10). By day 32 postovulation (n = 3), glycodelin synthesis decreased. Estrogen and progesterone treatment in the absence of exogenous hCG did not result in an increase of glycodelin synthesis. Analysis of uterine flushings from hCG-treated animals revealed that a minimum of 7 days of hCG treatment was required for glycodelin to be detectable in the uterine lumen. These studies indicate that a posttranslationally modified glycodelin homolog is synthesized by the baboon uterus during early pregnancy and appears to be regulated directly by CG. This pattern of synthesis is comparable with that observed with in vitro studies in the human. Because glycodelin expression is associated with CG secretion, we suggest that this protein may have a functional role during implantation in the primate. Thus, the baboon may serve as a nonhuman primate model to elucidate the function of this protein in vivo.

Cyclic modulation of epithelial glycosylation in human and baboon (Papio anubis) endometrium demonstrated by the binding of the agglutinin from Dolichos biflorus

Glycoconjugate expression in endometrial epithelium varies in a cycle-dependent manner in many species and is probably fundamental to the establishment of a receptive uterine environment for the implanting embryo. We have examined the distribution of N-acetyl galactosamine (GalNAc)-containing sequences bound by Dolichos biflorus agglutinin (DBA) in the cycling endometrium of the human and baboon (Papio anubis). In the human, DBA binding was absent in the proliferative and early secretory phases of the cycle, increasing thereafter both in glands and on the surface epithelium. In contrast, DBA binding in the baboon was maximal in the proliferative phase, diminishing to almost indistinguishable levels in the late secretory phase. Treatment of early to mid-secretory-phase baboons with the antiprogestin Onapristone caused staining to revert to the proliferative-phase pattern, confirming the importance of progesterone in the decrease in DBA staining. Investigations with other GalNAc-binding lectins indicated that epithelial GalNAc residues were present throughout the cycle. Variation in steroidally dependent 1,2 fucosyl transferase activity may therefore be responsible for the appearance of the new, DBA-binding, nonreducing terminal structure GalNAcalpha1,3(Fucalpha1,2)-Galbeta1,4GlcNAcbeta1++ + in the human during the mid-secretory phase and in the baboon during the late proliferative phase.