Gene expression profiling reveals progesterone-mediated cell cycle and immunoregulatory roles of Hoxa-10 in the preimplantation uterus

LIF regulates the expression of miR-27a-3p and HOXA10 in bovine endometrial epithelial cells via STAT3 pathway

LIF is crucial in regulating embryo implantation, while HOXA10 is a marker gene for uterine receptivity. However, the specific mechanism of LIF regulating HOXA10 during cow embryo implantation has not been fully understood. To address this knowledge gap, the experiment involved treating bovine endometrial epithelial cells (BEECs) with LIF to investigate the relationship between LIF, miRNA, and HOXA10. The experimental findings revealed that applying LIF resulted in a substantial increase in the proliferation of endometrial epithelial cells. Moreover, the expressions of PI3K, AKT, HOXA10, CDK4, cyclinD1, and cyclinE1 were significantly elevated. Conversely, the expression of p21Cipl was significantly reduced. In the group that received a combination of LIF and a STAT3 inhibitor, the expression of PI3K/AKT remained significantly increased, but there was no significant change in the expression of HOXA10. When miRNA-27a-3p was overexpressed, it resulted in a decrease in both the RNA and protein expression of HOXA10. Conversely, inhibiting miRNA-27a-3p increased the RNA and protein expression of HOXA10. In the presence of LIF treatment, the expression of miRNA-27a-3p was reduced, while the expression of HOXA10 was increased. However, when LIF and a STAT3 inhibitor were combined, there was no significant change in the expression of miRNA-27a-3p or HOXA10. Consequently, LIF facilitated cell proliferation by activating the PI3K/AKT pathway. LIF controlled the expression of miRNA-27a-3p and HOXA10 in endometrial epithelial cells through STAT3, with miRNA-27a-3p negatively regulating the expression of HOXA10.

A Novel HOXA10-Associated 5-Gene-Based Prognostic Signature for Stratification of Short-term Survivors of Pancreatic Ductal Adenocarcinoma

PURPOSE

Despite the significant association of molecular subtypes with poor prognosis in patients with pancreatic ductal adenocarcinoma (PDAC), few efforts have been made to identify the underlying pathway(s) responsible for this prognosis. Identifying a clinically relevant prognosis-based gene signature may be the key to improving patient outcomes.

EXPERIMENTAL DESIGN

We analyzed the transcriptomic profiles of treatment-naïve surgically resected short-term survivor (STS) and long-term survivor (LTS) tumors (GSE62452) for expression and survival, followed by validation in several datasets. These results were corroborated by IHC analysis of PDAC-resected STS and LTS tumors. The mechanism of this differential survival was investigated using CIBERSORT and pathway analyses.

RESULTS

We identified a short-surviving prognostic subtype of PDAC with a high degree of significance (P = 0.018). One hundred thirty genes in this novel subtype were found to be regulated by a master regulator, homeobox gene HOXA10, and a 5-gene signature derived from these genes, including BANF1, EIF4G1, MRPS10, PDIA4, and TYMS, exhibited differential expression in STSs and a strong association with poor survival. This signature was further associated with the proportion of T cells and macrophages found in STSs and LTSs, demonstrating a potential role in PDAC immunosuppression. Pathway analyses corroborated these findings, revealing that this HOXA10-driven prognostic signature is associated with immune suppression and enhanced tumorigenesis.

CONCLUSIONS

Overall, these findings reveal the presence of a HOXA10-associated prognostic subtype that can be used to differentiate between STS and LTS patients of PDAC and inform on the molecular interactions that play a role in this poor prognosis.

Loss of HOXA10 causes endometrial hyperplasia progressing to endometrial cancer

Endometrial cancer is the fourth most common malignancy in women and the precursor lesion is endometrial hyperplasia. HOXA10 is a transcription factor that plays key roles in endometrial functions such as the endowment of receptivity, embryo implantation, and trophoblast invasion. Herein, using testicular transgenesis, we developed transgenic mice that expressed a shRNA against HOXA10 and there was a nearly 70% reduction in the expression of HOXA10 in these animals. We observed that downregulation of HOXA10 led to the development of endometrial hyperplasia in the young animals (3 months), and as they aged (>1 year), most animals developed well-differentiated endometrial adenocarcinoma. In the endometrium of animals with reduced HOXA10, there was increased proliferation and elevated levels of ERα and ERβ. In parallel, there was increased expression of Wnt4 and β-Catenin, SOX9, and YAP1. We propose that chronic reduction in HOXA10 expression disrupts multiple pathways in the uterus that aids in the development of endometrial hyperplasia which progresses to endometrial cancer with age.

Vitamin D Supplementation Improves Uterine Receptivity in a Rat Model of Vitamin D Deficiency: A Possible Role of HOXA-10/FKBP52 Axis

Synchronized uterine receptivity with the time of implantation is crucial for pregnancy continuity. Vitamin D (VD) deficiency has been linked to the failure of implantation. Therefore, we tested the link between the Homeobox transcription factor-10/immunophilin FK506-binding protein 52 (HOXA-10/FKBP52) axis and the uterine receptivity in VD-deficient rats. The effect of VD supplementation at different doses was also investigated. Forty-eight pregnant rats were divided into six groups (eight/group); normal control rats fed with standard chow (control), control rats supplemented with VD (equivalent dose of 400 IU/day) (control-D400). VD-deficient group (DEF) and the three VD deficiency groups with VD supplementation were equivalent to 400, 4,000, and 10,000 IU/day (DEF-D400, DEF-D4000, and DEF-D10000, respectively). The expression levels of HOXA-10/FKBP52, progesterone level, and histological evaluation of decidualization using osteopontin (OSN) and progesterone receptor (PGR) were estimated. An assessment of the uterine contractility was conducted for all rats. This study showed the downregulation of HOXA-10/FKBP52 together with increased amplitude and frequency of the uterine contractility in the DEF group compared to control. VD dose-dependent supplementation restored progesterone/receptor competency, upregulated the expressional response of HOXA-10 and its downstream FKBP52, and improved uterine receptivity and endometrial decidualization at the time of implantation that was documented by increased area% of OSN and the number of implantation beads.

Identification of HOXA10 target genes in human endometrial stromal cells by RNA-seq analysis

Homeobox A10 (HOXA10) is a transcription factor belonging to the homeobox gene family. It is highly expressed in endometrial stromal cells (ESCs) and plays essential roles in the proliferation and differentiation of endometrium, the establishment of endometrial receptivity and embryo implantation. However, little is known about the target genes and signaling pathways regulated by HOXA10 in ESCs. In this study, we identified 1830 transcripts regulated by HOXA10 in ESCs by RNA interference (RNAi) and RNA-sequencing (RNA-seq) analysis, of which 980 were positively regulated by HOXA10 and 850 were negatively regulated by HOXA10. Interestingly, matrix metallopeptidase-11 was downregulated by HOXA10 in stromal cells verified by quantitative real-time polymerase chain reaction and western blot analysis. Pathway analysis demonstrated that the target genes were enriched in various pathways, including cellular metabolism, DNA replication and repair, cell junction, and lysosome and signal transduction. The results of the present study provide novel insights into the mechanism underlying HOXA10 regulation in ESCs and may identify novel targets for the diagnosis and treatment of endometrium-related infertility.

Adenomyosis and Infertility-Review of Medical and Surgical Approaches

The aim of this review is to clarify the relative association between adenomyosis and infertility and the possible treatment for an infertile patient. Although adenomyosis is detected more often in women of late reproductive age, its influence on pregnancy rates is important, especially considering the tendency to delay pregnancy among women in developed countries. In this article, we present a critical analysis of the literature data concerning the impact of adenomyosis on fertility. The possible effects of treatment on the pregnancy rate will also be discussed. We conducted a literature search; publications from Pubmed, Embase and Cochrane databases published from 1982 to 2019 were retrieved using terms ’adenomyosis and infertility’ and ’adenomyosis and pregnancy outcomes’, extensively studied in the aspects of diagnosis, pathogenesis of infertility and possible treatment methods. Molecular studies have given deep insight into the pathogenesis of adenomyosis in the recent few years, but there is a huge discrepancy between in vitro studies and praxis. Oral contraceptive pills, anti-prostaglandins, oral or parenteral progestins, danazol and gonadotrophin-releasing hormone (GnRH) analogues have all been used to control menstrual pain and menorrhagia in women with adenomyosis, but they temporarily suppress the menstrual cycle. Additionally, endometrial ablation and hysterectomy used to alleviate pain caused by adenomyosis exclude pregnancy planning. The development of imaging techniques—ultrasound and MRI—enables the diagnosis of adenomyosis with very high accuracy nowadays, but the methods of treatment mentioned above have not given satisfactory results in women planning pregnancy. For these patients, the high-intensity-focused ultrasound method (HIFU) and combined treatment before assisted reproductive techniques can prove beneficial in adenomyosis patients.

Autophagy in the uterine vessel microenvironment: Balancing vasoactive factors

Autophagy, which has the literal meaning of self-eating, is a cellular catabolic process executed by arrays of conserved proteins in eukaryotes. Autophagy is dynamically ongoing at a basal level, presumably in all cells, and often carries out distinct functions depending on the cell type. Therefore, although a set of common genes and proteins is involved in this process, the outcome of autophagic activation or deficit requires scrutiny regarding how it affects cells in a specific pathophysiological context. The uterus is a complex organ that carries out multiple tasks under the influence of cyclic changes of ovarian steroid hormones. Several major populations of cells are present in the uterus, and the interactions among them drive complex physiological tasks. Mouse models with autophagic deficits in the uterus are very limited, but provide an initial glimpse at how autophagy plays a distinct role in different uterine tissues. Herein, we review recent research findings on the role of autophagy in the uterine mesenchyme in mouse models.

Postnatal exposure to endosulfan affects uterine development and fertility

Endosulfan is an organochlorine pesticide (OCP) used in large-scale agriculture for controlling a variety of insects and mites that attack food and non-food crops. Although endosulfan has been listed in the Stockholm Convention as a persistent organic pollutant to be worldwide banned, it is still in use in some countries. Like other OCPs, endosulfan is bioaccumulative, toxic and persistent in the environment. Human unintentional exposure may occur through air inhalation, dietary, skin contact, as well as, via transplacental route and breast feeding. Due to its lipophilic nature, endosulfan is rapidly absorbed into the gastrointestinal tract and bioaccumulates in the fatty tissues. Similar to other OCPs, endosulfan has been classified as an endocrine disrupting chemical (EDC). Endocrine action of endosulfan on development and reproductive function of males has been extensively discussed; however, endosulfan effects on the female reproductive tract have received less attention. This review provides an overview of: i) the fate and levels of endosulfan in the environment and human population, ii) the potential estrogenic properties of endosulfan in vitro and in vivo, iii) its effects on uterine development, and iv) the long-term effects on female fertility and uterine functional differentiation during early gestation.

An autophagic deficit in the uterine vessel microenvironment provokes hyperpermeability through deregulated VEGFA, NOS1, and CTNNB1

The uterus undergoes vascular changes during the reproductive cycle and pregnancy. Steroid hormone deprivation induces macroautophagy/autophagy in major uterine cell types. Herein, we explored the functions of uterine autophagy using the Amhr2-Cre-driven atg7 deletion model. Deletion of Atg7 was confirmed by functional deficit of autophagy in uterine stromal, myometrial, and vascular smooth muscle cells, but not in endothelial cells. atg7^d/d uteri exhibited enhanced stromal edema accompanied by dilation of blood vessels. Ovariectomized atg7^d/d uteri showed decreased expression of endothelial junction-related proteins, such as CTNNB1/beta-catenin, with increased vascular permeability, and increased expression of VEGFA and NOS1. Nitric oxide (NO) was shown to mediate VEGFA-induced vascular permeability by targeting CTNNB1. NO involvement in maintaining endothelial junctional stability in atg7^d/d uteri was confirmed by the reduction in extravasation following treatment with a NOS inhibitor. We also showed that atg7^d/d uterine phenotype improved the fetal weight:placental weight ratio, which is one of the indicators of assessing the status of preeclampsia. We showed that autophagic deficit in the uterine vessel microenvironment provokes hyperpermeability through the deregulation of VEGFA, NOS1, and CTNNB1.Abbreviations: ACTA2: actin, alpha 2, smooth muscle, aortic; Amhr2: anti-Mullerian hormone type 2 receptor; ANGPT1: angiopoietin 1; ATG: autophagy-related; CDH5: cadherin 5; CLDN5: claudin 5; COL1A1: collagen, type I, alpha 1; CSPG4/NG2: chondroitin sulfate proteoglycan 4; CTNNB1: catenin (cadherin associated protein), beta 1; DES: desmin; EDN1: endothelin 1; EDNRB: endothelin receptor type B; F3: coagulation factor III; KDR/FLK1/VEGFR2: kinase insert domain protein receptor; LYVE1: lymphatic vessel endothelial hyaluronan receptor 1; MAP1LC3B: microtubule-associated protein 1 light chain 3 beta; MCAM/CD146: melanoma cell adhesion molecule; MYL2: myosin, light polypeptide 2, regulatory, cardiac, slow; MYLK: myosin, light polypeptide kinase; NOS1/nNOS: nitric oxide synthase 1, neuronal; NOS2/iNOS: nitric oxide synthase 2, inducible; NOS3/eNOS: nitric oxide synthase 3, endothelial cell; OVX: ovariectomy; PECAM1/CD31: platelet/endothelial cell adhesion molecule 1; POSTN: periostin, osteoblast specific factor; SQSTM1: sequestosome 1; TEK/Tie2: TEK receptor tyrosine kinase; TJP1/ZO-1: tight junction protein 1; TUBB1, tubulin, beta 1 class VI; USC: uterine stromal cell; VEGFA: vascular endothelial growth factor A; VSMC: vascular smooth muscle cell.

Cypermethrin exposure during perinatal period affects fetal development and impairs reproductive functions of F1 female rats

Cypermethrin (CYP) is a ubiquitously present synthetic pyrethroid insecticide. It has endocrine disrupting activities which may adversely affect reproductive development and functions of offspring if exposed during critical developmental period. The present study was undertaken to delineate the effects of CYP exposure in pregnant female rats during perinatal period on the sexual maturation, hormonal regulation, reproductive development and fertility of F1 female offspring and its molecular mechanism of action. Pregnant rats (F0) were gavaged daily with 0, 1, 10, 25 mg/kg bw/day CYP and 10 μg/kg bw/day Diethylstilbestrol (DES; positive control) from gestation day (GD) 6 to postnatal day (PND) 21. The reproductive development and function parameters were evaluated at PND 45 and 75. Reduced body weight, delayed vaginal opening, and disrupted estrous cyclicity were observed at 25 mg/kg CYP dose. CYP exposure significantly affected the reproductive organ development and their functions at all doses. Significant alterations in ovarian and uterine histology such as luteinization, reduction of primordial follicular reserves, presence of multi-oocyte follicles and thin degenerative luminal and glandular uterine epithelium were observed at adulthood. Altered circulatory steroid hormone levels and expression of ovarian and uterine steroid hormone receptors were observed at PND 75 in the F1 female offspring. Expression of HOXA10 and α-SMA which are important for uterine integrity and functions, were found to be altered at PND 75. Increased pre-implantation loss (PIL%), post-implantation loss (POL%), and reduced litter size in F1 females when cohabitated with unexposed fertile male rats were observed. Overall, perinatal exposure of pregnant rats to CYP led to significant long lasting effects on the reproductive functions of F1 female offspring. The adverse effects were passed on to F2 generation via female germ line and posed developmental anomalies. The present finding necessitates additional molecular studies to understand its trans-generational mechanism of action via female germline.

The Role of Extracellular Vesicles and PIBF in Embryo-Maternal Immune-Interactions

Pregnancy represents a unique immunological situation. Though paternal antigens expressed by the conceptus are recognized by the immune system of the mother, the immune response does not harm the fetus. Progesterone and a progesterone induced protein; PIBF are important players in re-adjusting the functioning of the maternal immune system during pregnancy. PIBF expressed by peripheral pregnancy lymphocytes, and other cell types, participates in the feto-maternal communication, partly, by mediating the immunological actions of progesterone. Several splice variants of PIBF were identified with different physiological activity. The full length 90 kD PIBF protein plays a role in cell cycle regulation, while shorter splice variants are secreted and act as cytokines. Aberrant production of PIBF isoforms lead to the loss of immune-regulatory functions, resulting in and pregnancy failure. By up regulating Th2 type cytokine production and by down-regulating NK activity, PIBF contributes to the altered attitude of the maternal immune system. Normal pregnancy is characterized by a Th2-dominant cytokine balance, which is partly due to the action of the smaller PIBF isoforms. These bind to a novel form of the IL-4 receptor, and induce increased production of IL-3, IL-4, and IL-10. The communication between the conceptus and the mother is established via extracellular vesicles (EVs). Pre-implantation embryos produce EVs both in vitro, and in vivo. PIBF transported by the EVs from the embryo to maternal lymphocytes induces increased IL-10 production by the latter, this way contributing to the Th2 dominant immune responses described during pregnancy.

Homeobox genes for embryo implantation: From mouse to human

The proper development of uterus to a state of receptivity and the attainment of implantation competency for blastocyst are 2 indispensable aspects for implantation, which is considered to be a critical event for successful pregnancy. Like many developmental processes, a large number of transcription factors, such as homeobox genes, have been shown to orchestrate this complicated but highly organized physiological process during implantation. In this review, we focus on progress in studies of the role of homeobox genes, especially the Hox and Msx gene families, during implantation, together with subsequent development of post-implantation uterus and related reproductive defects in both mouse models and humans, that have led to better understanding of how implantation is precisely regulated and provide new insights into infertility.

The regulation of ovary and conceptus on the uterine natural killer cells during early pregnancy

Uterine natural killer (uNK) cells are short-lived, terminally differentiated and the most abundant lymphocytes in the uterus which play a crucial role in the spiral arteriole modification and establishment of successful pregnancy. Dysregulation of uNK cells has been linked to gestational implications such as recurrent pregnancy loss, preeclampsia and fetal growth retardation. There is evidence showing that progesterone and estrogen can regulate the recruitment, proliferation, differentiation and function of uNK cells via direct action on intracellular nuclear receptors or through intermediary cells in the uterus during early pregnancy. As the deepening of related research in this field, the role of conceptus in such regulation has received extensive attention, it utilizes endocrine signaling (hCG), juxtacrine signaling (HLA-C, HLA-E, HLA-G) and paracrine signaling (cytokines) to facilitate the activities of uNK cells. In addition, under the influence of ovarian hormones, conceptus can increase expression of PIBF and HLA-G molecules to reduce cytotoxicity of uNK cells and promote angiogenesis. In this review, we aim to concentrate on the novel findings of ovarian hormones in the regulation of uNK cells, emphasize the regulatory role of conceptus on uNK cells and highlight the proposed issues for future research in the field.

Decrease in Expression of HOXA10 in the Decidua After Embryo Implantation Promotes Trophoblast Invasion

An important step toward successful pregnancy involves invasion of the trophoblast cells into the decidua for placentation. Herein, we show that in the human and baboon decidua HOXA10 expression is downregulated after implantation and that this reduction is most prominent in the decidual cells juxtaposed to the invading placental villi. The supernatants derived from HOXA10-depleted human decidual cells increase the invasiveness of the trophoblast cell lines ACH-3P and JEG3 in vitro; this increase is due to higher expression and activity of matrix metalloproteases (MMPs) and reduced expression of tissue inhibitors of MMPs in both the cell lines. The proinvasive ability of HOXA10-depleted decidual cells is due to increased levels and secretion of leukemia inhibitor factor (LIF) and interleukin (IL)-6. Both these cytokines individually promote invasion of ACH-3P and JEG3 cell by increasing the activities of MMPs and decreasing mRNA levels of TIMPs. Finally, we demonstrate that the supernatants derived from HOXA10-depleted decidual cell-phosphorylated STAT3 (Tyr 705) and knocking down STAT3 in ACH-3P and JEG3 cells restrained the invasion mediated by supernatants derived from HOXA10-depleted decidual cells. These results imply that STAT3 activity is essential and sufficient to promote invasion in response to downregulation of HOXA10 in decidual cells. We propose that downregulation of HOXA10 in the decidual cells promotes the expression of LIF and IL-6, which, in a paracrine manner, activates STAT3 in the trophoblast cells, leading to an increase in MMPs to facilitate invasion.

Dydrogesterone and the immunology of pregnancy

Progesterone is indispensable for the maintenance of pregnancy, both via its endocrine effects and its role in creating a favorable immunological environment for the fetus. This review focuses on the immunological effects of progesterone. Progestogens have been shown to have very interesting effects on cytokine production and decidual natural killer (NK) cell activity. The orally-administered progestogen, dydrogesterone, has the ability to modulate cytokine production patterns in a manner that could be conducive to successful pregnancy. The adverse effects of progesterone deficiency and the beneficial effects of progesterone supplementation in pregnancy pathologies will be discussed.

HOXA-10 and E-cadherin expression in the endometrium of women with recurrent implantation failure and recurrent miscarriage

OBJECTIVE

To compare the expression of HOXA-10 and E-cadherin in the endometrium of women with recurrent implantation failure (RIF), women with recurrent miscarriage (RM), and women with proven fertility (normal control; NC).

DESIGN

Observational cohort study.

SETTING

University assisted reproductive unit.

PATIENT(S)

Fifty women were recruited: 18 NC, 12 unexplained RIF, and 20 RM.

INTERVENTIONS(S)

None.

MAIN OUTCOME MEASURE(S)

Endometrial biopsy was precisely timed 7 days after LH surge. The expression of HOXA-10 and E-cadherin were examined by means of immunohistochemistry. H-Scores of staining intensity in the glandular epithelium and stroma were measured.

RESULT(S)

HOXA-10 signal was mainly localized in the nuclei of stroma cells and the cytoplasm of glandular epithelium cells. E-Cadherin signal was found only in the cytoplasm of glandular epithelium cells. The HOXA-10 H-scores in the RIF group and the RM group were significantly lower than in the control group in both the glandular epithelium and stroma. The E-cadherin H-scores in the RM group were also significantly lower than in the control group. Interestingly, there was a positive correlation between HOXA-10 and E-cadherin H-scores in all of the women examined.

CONCLUSION(S)

There is a positive correlation between levels of HOXA-10 and E-cadherin expression in the endometrium, both of which are significantly reduced in women with RIF and RM compared with fertile control women. The findings suggest a potential role of HOXA-10 and E-cadherin in the implantation processes and altered expression in women with reproductive failure.

WINGLESS (WNT) signaling is a progesterone target for rat uterine stromal cell proliferation

Preparation of mammalian uterus for embryo implantation requires a precise sequence of cell proliferation. In rodent uterus, estradiol stimulates proliferation of epithelial cells. Progesterone operates as a molecular switch and redirects proliferation to the stroma by down-regulating glycogen synthase kinase-3β (GSK-3β) and stimulating β-catenin accumulation in the periluminal stromal cells. In this study, the WNT signal involved in the progesterone-dependent proliferative switch was investigated. Transcripts of four candidate Wnt genes were measured in the uteri from ovariectomized (OVX) rats, progesterone-pretreated (3 days of progesterone, 2mg/daily) rats, and progesterone-pretreated rats given a single dose (0.2µg) of estradiol. The spatial distribution of the WNT proteins was determined in the uteri after the same treatments. Wnt5a increased in response to progesterone and the protein emerged in the periluminal stromal cells of progesterone-pretreated rat uteri. To investigate whether WNT5A was required for proliferation, uterine stromal cell lines were stimulated with progesterone (1µM) and fibroblast growth factor (FGF, 50ng/mL). Proliferating stromal cells expressed a two-fold increase in WNT5A protein at 12h post stimulation. Stimulated stromal cells were cultured with actinomycin D (25µg/mL) to inhibit new RNA synthesis. Relative Wnt5a expression increased at 4 and 6 h of culture, suggesting that progesterone plus FGF preferentially increased Wnt5a mRNA stability. Knockdown of Wnt5a in uterine stromal cell lines inhibited stromal cell proliferation and decreased Wnt5a mRNA. The results indicate that progesterone initiates and synchronizes uterine stromal cell proliferation by increasing WNT5A expression and signaling.

The Multifaceted Actions of Leukaemia Inhibitory Factor in Mediating Uterine Receptivity and Embryo Implantation

Embryo implantation is mediated by the combined actions of the ovarian hormones E2 and P4 on the uterus. In addition, the pro-inflammatory cytokine, leukaemia inhibitory factor (LIF), plays a pivotal role in regulating uterine receptivity. LIF is expressed in the endometrial glands and has a robust action on the uterine luminal epithelium (LE). In mice, LIF is induced by nidatory E2 and functions to convert the LE from a non-receptive to an embryo-responsive state. LIF mediates its actions by activating the JAK-STAT pathway specifically in the LE. Activation of JAK-STAT pathway results in the induction of many additional pathways, including some 40 +  transcription factors, many of which initiate a cascade of changes affecting epithelial polarity, epithelial-mesenchymal interactions, angiogenesis, stromal cell decidualization, and inhibiting cell proliferation. This review discusses the role of LIF and the recent analysis of its action on the uterine LE in regulating endometrial receptivity and implantation.

Progesterone-Regulated Endometrial Factors Controlling Implantation

The steroid hormone progesterone (P), acting via the progesterone receptor (PR) isoforms, PR-A and PR-B, exerts a profound influence on uterine functions during early gestation. In recent years, chromatin immunoprecipitation-sequencing in combination with microarray-based gene expression profiling analyses have revealed that the PR isoforms control a substantially large cistrome and transcriptome during endometrial differentiation in the human and the mouse. Genetically engineered mouse models have established that several PR-regulated genes, such as Ihh, Bmp2, Hoxa10, and Hand2, are essential for implantation and decidualization. PR-A and PR-B also collaborate with other transcription factors, such as FOS, JUN, C/EBPβ and STAT3, to regulate the expression of many target genes that functions in concert to properly control uterine epithelial proliferation, stromal differentiation, angiogenesis, and local immune response to render the uterus 'receptive' and allow embryo implantation. This review article highlights recent work describing the key PR-regulated pathways that govern critical uterine functions during establishment of pregnancy.

Control of regional decidualization in implantation: Role of FoxM1 downstream of Hoxa10 and cyclin D3

Appropriate regulation of regional uterine stromal cell decidualization in implantation, at the mesometrial triangle and secondary decidual zone (SDZ) locations, is critical for successful pregnancy, although the regulatory mechanisms remain poorly understood. In this regard, the available animal models that would specifically allow mechanistic analysis of site-specific decidualization are strikingly limited. Our study found that heightened expression of FoxM1, a Forkhead box transcription factor, is regulated during decidualization, and its conditional deletion in mice reveals failure of implantation with regional decidualization defects such as a much smaller mesometrial decidua with enlarged SDZ. Analysis of cell cycle progression during decidualization both in vivo and in vitro demonstrates that the loss of FoxM1 elicits diploid cell deficiency with enhanced arrests prior to mitosis and concomitant upregulation of polyploidy. We further showed that Hoxa10 and cyclin D3, two decidual markers, control transcriptional regulation and intra-nuclear protein translocation of FoxM1 in polyploid cells, respectively. Overall, we suggest that proper regional decidualization and polyploidy development requires FoxM1 signaling downstream of Hoxa10 and cyclin D3.

Neonatal exposure to low doses of endosulfan induces implantation failure and disrupts uterine functional differentiation at the pre-implantation period in rats

We investigated whether neonatal exposure to low doses of endosulfan affects fertility and uterine functional differentiation at pre-implantation in rats. Newborn female rats received the vehicle, 0.2 µg/kg/d of diethylstilbestrol (DES), 6 µg/kg/d of endosulfan (Endo6) or 600 µg/kg/d of endosulfan (Endo600) on postnatal days (PND) 1, 3, 5, and 7. On PND90, the rats were mated to evaluate their reproductive performance on gestational day (GD) 19 and their ovarian steroid serum levels, endometrial proliferation and implantation-associated proteins on GD5. DES and endosulfan decreased the pregnancy rate and the number of implantation sites. On GD5, DES and endosulfan did not change the serum levels of 17β-estradiol (E2) and progesterone (P); the endometrial proliferation decreased, which was associated with silencing of Hoxa10 in the Endo600-treated rats. Both doses of endosulfan increased the progesterone receptor (PR) expression, whereas the higher dose led additionally to an increase in estrogen receptor alpha (ERα). In the Endo600-treated rats, the down-regulation of Hoxa10 was associated with a deregulation of the steroid receptor coregulators. Alterations in endometrial proliferation and the endocrine pathway of Hoxa10/steroid receptors/coregulators might be the mechanism of endosulfan-induced implantation failure.

Endometrial beta3 integrin profile reflects endometrial receptivity defects in women with unexplained recurrent pregnancy loss

BACKGROUND

The pathophysiology of recurrent pregnancy loss (RPL) is still unknown in 50% of the cases. Herein we measure the expression of beta3 integrin subunit, a well-known implantation marker, in women with or without RPL and correlate it with the histological dating of the endometrial tissue.

METHODS

LH-timed endometrial biopsies were obtained from cases (RPL; n = 21, age 33.9+/-4.7) and healthy controls (n = 29; age 29.8+/-4.1) during the mid-secretory phase (post ovulatory day: 8 to 10). Endometrial samples were timed histologically according to Noyes' criteria and underwent immunohistochemical staining for beta3 integrin expression. For statistical analysis the semi-quantitative HSCORE was assessed. Type I (beta3 negative in an out-of-phase endometrium) and Type II defect (beta3 negative in an in-phase endometrium) were also analysed. Statistical analysis was done with Student t-test, Mann Whitney U test, ANCOVA and chi square for trend. Significance was set as P < 0.05.

RESULTS

The mean (SD) age in controls was lower compared to cases [(29.8 (4.1) vs. 33.9 (4.7) - P = 0.001; Student t-test)]. The median (range) expression of beta3 integrin in controls and cases was 1.94 (0 to 3.5) vs. 0.82 (0 to 3.6), respectively (P = 0.001; Mann Whitney U test). Significance was still significant after adjusting for age (P = 0.03;ANCOVA). The normal positive staining > =0.7 of beta3 integrin subunit and in-phase endometrium was seen in 24 out of 29 (82.8%) controls, but in only 6 out of 21 (28.6%) of cases with RPL; Type I and II defects were seen in 10.3 and 6.9% of controls, while present in 52.4 and 19.1% of cases, respectively (P = 0.0005; chi-square).

CONCLUSIONS

Women with unexplained RPL had significantly reduced integrin expression compared to controls. Our findings underline the need for further molecular analysis of endometrial tissue in affected women.

Serum progesterone concentration on day of embryo transfer in donor oocyte cycles

PURPOSE

To evaluate the association between serum progesterone (P) levels on the day of embryo transfer (ET) and pregnancy rates in fresh donor IVF/ICSI cycles.

METHODS

Fresh donor cycles with day 3 ET from 10/2007 to 8/2012 were included (n = 229). Most cycles (93 %) were programmed with a gonadotropin releasing hormone (GnRH) agonist; oral, vaginal or transdermal estradiol was used for endometrial priming, and intramuscular P was used for luteal support (50-100 mg/day). Recipient P levels were measured at ET, and P dose was increased by 50-100 % if <20 ng/mL per clinic practice. The main outcome measure was rate of live birth (> = 24 weeks gestational age). Generalized estimating equations were used to account for multiple cycles from the same recipient, adjusted a priori for recipient and donor age.

RESULTS

Mean recipient serum P at ET was 25.5 ± 10.1 ng/mL. Recipients with P < 20 ng/mL at ET, despite P dose increases after ET, were less likely to achieve clinical pregnancy (RR = 0.75, 95 % CI = 0.60-0.94, p = 0.01) and live birth (RR = 0.77, 95 % CI = 0.60-0.98, p = 0.04), as compared to those with P ≥ 20 ng/mL. P dose increases were more often required in overweight and obese recipients.

CONCLUSIONS

Serum P levels on the day of ET in fresh donor IVF/ICSI cycles were positively correlated with clinical pregnancy and live birth rates. An increase in P dose after ET was insufficient to rescue pregnancy rates. Overweight and obese recipients may require higher initial doses of P supplementation. Future research is needed to define optimal serum P at ET and the interventions to achieve this target.

The immune privilege of testis and gravid uterus: same difference?

The fetus in the gravid uterus and the developing spermatogenic cells in the adult testis both comprise special challenges for the host immune system. Protection of the neoantigens of the fetus and male germ cells from immune attack, defined as immune privilege, is fundamental for the propagation of species. Immune privilege is not simply the absence of leukocytes, but involves immune and non-immune cells acting synergistically together at multiple levels to create a unique tolerogenic environment. A number of the pathways are shared by the testis and gravid uterus. Amongst them steroid hormones, namely testosterone in the male and progesterone in the female, seem to function as key molecules that govern the local production of immunoregulatory factors which finally control the overall immune environment.

Long-lasting effects of neonatal bisphenol A exposure on the implantation process

Successful implantation is the result of complex molecular interactions between the hormonally primed uterus and a mature blastocyst. This very carefully synchronized interplay of hormonal signals and feedback loops is potentially vulnerable to chemicals such as endocrine disruptors that may disrupt endocrine signaling. Bisphenol A (BPA) is one of the highest-volume chemicals produced worldwide. This chapter describes the effects of brief postnatal exposure to BPA on female reproductive performance and specifically on the uterine adaptations during the preimplantation period. We propose that an early alteration in Hoxa10 gene expression affects the functional differentiation of the preimplantation uterus as part of an altered endocrine signal transduction pathway. These molecular alterations could explain, at least in part, the adverse effects of BPA on uterine implantation. Exposure to endocrine disruptors, such as BPA, could contribute to the impaired female fertility noted over the past decades.

Gene Sets Net Correlations Analysis (GSNCA): a multivariate differential coexpression test for gene sets

MOTIVATION

To date, gene set analysis approaches primarily focus on identifying differentially expressed gene sets (pathways). Methods for identifying differentially coexpressed pathways also exist but are mostly based on aggregated pairwise correlations or other pairwise measures of coexpression. Instead, we propose Gene Sets Net Correlations Analysis (GSNCA), a multivariate differential coexpression test that accounts for the complete correlation structure between genes.

RESULTS

In GSNCA, weight factors are assigned to genes in proportion to the genes' cross-correlations (intergene correlations). The problem of finding the weight vectors is formulated as an eigenvector problem with a unique solution. GSNCA tests the null hypothesis that for a gene set there is no difference in the weight vectors of the genes between two conditions. In simulation studies and the analyses of experimental data, we demonstrate that GSNCA captures changes in the structure of genes' cross-correlations rather than differences in the averaged pairwise correlations. Thus, GSNCA infers differences in coexpression networks, however, bypassing method-dependent steps of network inference. As an additional result from GSNCA, we define hub genes as genes with the largest weights and show that these genes correspond frequently to major and specific pathway regulators, as well as to genes that are most affected by the biological difference between two conditions. In summary, GSNCA is a new approach for the analysis of differentially coexpressed pathways that also evaluates the importance of the genes in the pathways, thus providing unique information that may result in the generation of novel biological hypotheses.

AVAILABILITY AND IMPLEMENTATION

Implementation of the GSNCA test in R is available upon request from the authors.

The role of progesterone and the progesterone receptor in human reproduction and cancer

Insufficient progesterone, effect possibly more on immune factors rather than adequate endometrial development, can be an easy remedial cause of infertility by simply supplementing the luteal phase with either vaginal or intramuscular or oral (dydrogesterone) progesterone. Progesterone will also help to reduce miscarriage rates when follicle maturing drugs are used for those with regular menses but follicular maturation defects, or women with recurrent miscarriages. One mechanism of action seems to be related to production of an immunomodulatory protein, the progesterone-induced blocking factor either in the cytoplasm or in the circulation. PIBF inhibits cytotoxicity of natural killer cells. Cancer cells may 'borrow' the same mechanism to escape NK cell immunosurveillance.

Gamma-amino butyric acid and the A-type receptor suppress decidualization of mouse uterine stromal cells by down-regulating cyclin D3

Uterine decidualization, characterized by stromal cell proliferation and differentiation into polyploid decidual cells, is critical to the establishment of pregnancy in mice, although the mechanism underlying this process remains poorly understood. This study is the first to investigate the expression of gamma-amino butyric acid (GABA) and the GABA A-type receptor π subunit (GABPR) in the early-pregnancy mouse uterus and their roles in decidualization. The expression of GABRP was detected from Day 4 to 8 of pregnancy. The effects of GABA and GABA A-type receptor on cell proliferation and apoptosis were investigated using the Cell Titer 96® AQueous One Solution Cell Proliferation Assay and flow cytometry. The levels of cyclin D3 protein were measured in cultured stromal cells artificially induced to undergo decidualization, and treated with GABA and a GABA A-type receptor agonist or antagonist, respectively, at the same time. mRNA expression of gabrp in implantation sites was lower than that in inter-implanted sites. GABA and GABRP protein were localized in the luminal and glandular epithelium, stromal cells, and decidual cells. In vitro, GABPR protein level was decreased in cultured stromal cells during the decidualization process. The addition of GABA and the GABA A-type receptor agonist Muscimol inhibited stromal cell proliferation, promoted apoptosis, and arrested cells in S-phase, followed by decreased expression of cyclin D3. These results show that in mice, GABA was actively involved in inhibiting stromal cell proliferation and suppresses decidualization progress through GABA A-type receptors by down-regulating cyclin D3 level.

Overexpression of cyclin D3 improves decidualization defects in Hoxa-10(-/-) mice

Uterine decidualization, a crucial process for implantation, is a tightly regulated process encompassing proliferation, differentiation, and polyploidization of uterine stromal cells. Hoxa (Homeobox A)-10, a homeobox transcription factor, is highly expressed in decidualizing stromal cells. Targeted gene deletion experiments have demonstrated marked infertility resulting from severely compromised decidualization in Hoxa-10(-/-) mice. However, the underlying mechanism by which Hoxa-10 regulates stromal cell differentiation remains poorly understood. Cyclin D3, a G(1) phase cell-cycle regulatory protein involved in stromal cell proliferation and decidualization, is significantly reduced in Hoxa-10(-/-) mice. The expression of cyclin D3 in the pregnant mouse uterus parallels stromal cell decidualization. Here, we show that adenovirus-driven cyclin D3 replacement in Hoxa-10(-/-) mice improves stromal cell decidualization. To address our question of whether cyclin D3 replacement in Hoxa-10(-/-) mice can improve decidualization, both in vitro and in vivo studies were completed after the addition of cyclin D3 or empty (control) viral vectors. Immunostaining demonstrated increased proliferation and decidualization in both in vitro and in vivo studies, and in situ hybridization confirmed increased expression of decidualization markers in vivo. Placentation was demonstrated as well in vivo in the cyclin D3-replaced animals. However, fertility was not restored in Hoxa-10(-/-) mice after d 10 of pregnancy. Finally, we identified several downstream targets of cyclin D3 during decidualization in vitro via proteomics experiments, and these were confirmed using in situ hybridization in vivo. Collectively, these results demonstrate that cyclin D3 expression influences a host of genes involved in decidualization and can improve decidualization in Hoxa-10(-/-) mice.

Maternal ghrelin deficiency compromises reproduction in female progeny through altered uterine developmental programming

Ghrelin has a well-known role in the regulation of appetite, satiety, energy metabolism, and reproduction; however ghrelin has not been implicated in reproductive tract development. We examined the effect of ghrelin deficiency on the developmental programming of female fertility. We observed that female wild-type mice born of ghrelin heterozygote dams (i.e. exposed in utero to ghrelin deficiency) had diminished fertility and produced smaller litters. We demonstrate that exposure to in utero ghrelin deficiency led to altered developmental programming of the reproductive tract. The number of ovarian follicles, corpora lutea, and embryos produced were identical in both exposed and unexposed mice. However wild-type embryos transferred to uteri of mice exposed to in utero ghrelin deficiency had a 60% reduction in the rate of embryo implantation compared with those transferred to wild-type unexposed uteri. We identified significant alterations in the uterine expression of four genes critical for implantation and a defect in uterine endometrial proliferation. Taken together, these results demonstrate that the mechanism of subfertility was abnormal endometrial function. In utero exposure to decreased levels of ghrelin led to defects in developmental programming of the uterus and subsequent subfertility in wild-type offspring.

Progesterone-mediated immunomodulation in pregnancy: its relevance to leukocyte immunotherapy of recurrent miscarriage

Progesterone is crucial for the establishment and maintenance of pregnancy. Progesterone-regulated genes in the pregnant uterus control the development of endometrial receptivity as well as recruitment and differentiation of decidual NK cells, which in turn act on angiogenesis and trophoblast invasion. The link between progesterone and the immune system is established by lymphocyte progesterone receptors expressed in peripheral blood gammadelta T cells of pregnant women and in peripheral NK cells. Regulation of lymphocyte progesterone receptors is activation related, thus efficient recognition of fetal antigens is a requirement for the initiation of progesterone-dependent immunoregulatory mechanisms. Several immunological effects of progesterone are mediated by progesterone-induced blocking factor--the product of a progesterone-induced gene in lymphocytes. One part of unexplained recurrent miscarriages might have an immunological etiology. Immunization of the mothers with paternal or third-party leukocytes aims to correct the misregulated antifetal immune response. There are, however, serious concerns about this treatment, including the lack of information about the mode of action and possible adverse effects of the treatment, the failure to detect a significant effect of immunotherapy and the lack of a reliable generally accepted marker for patient selection. These concerns will be discussed in this review.

Regulation of tryptophan 2,3-dioxygenase by HOXA10 enhances embryo viability through serotonin signaling

Tryptophan 2,3-dioxygenase (TDO) is expressed in endometrium and catabolizes tryptophan, a precursor in the biosynthesis of serotonin. Tryptophan metabolism is an important mechanism for regulation of serotonin levels. Preimplantation mouse embryos are known to express serotonin receptors, specifically the 5-HT1D and 5-HT7 serotonin receptor subtypes. Here we demonstrate that Hoxa10 regulates endometrial TDO expression and improves embryo viability through increased serotonin production. Transfection of pcDNA-Hoxa10 to the murine uterus increased total TDO expression. In vitro, epithelial cell TDO expression was decreased after transfection with Hoxa10. Decreased glandular TDO in response to HOXA10 may augment serotonin production by increasing tryptophan availability. Conversely, stromal TDO expression increased with constitutive Hoxa10 expression. In mice, epithelial serotonin was increased in response to constitutive expression of Hoxa10. Embryo quality was impaired after treatment with Hoxa10 antisense. Blockade of serotonin receptors 1D and 7 also resulted in impaired embryo development, indicating an essential role for Hoxa10 induction of TDO and subsequent serotonin production in embryo development. Transfection of pcDNA-TDO also decreased the number of T cells in the endometrial stroma. We have shown a novel mechanism by which HOXA10 regulates endometrial TDO expression. In the endometrial stroma, HOXA10 increases TDO mRNA, which may increase tryptophan catabolism, allowing for immune tolerance at the time of embryo implantation. In endometrial glands, HOXA10 decreases TDO mRNA leading to increased serotonin that in turn acts to promote normal embryo development.

Regulatory effect of estrogen, progestin and HB-EGF on the expression of HOXA10 gene in Ishikawa cells

HOXA10 gene plays an essential role in differentiation of the endometrium and in human reproduction. The aim of this study was to investigate the regulatory effect of sex steroids and HB-EGF on HOXA10 gene in Ishikawa cells. Ishikawa cells were incubated with 17-beta estradiol (10(-8) mol/L), medroxyprogesterone acetate (MPA) (10(-6) mol/L), RU486 (10(-5) mol/L) or HB-EGF (10 ng/mL) for 48 h respectively. The expression of HOXA10 gene was detected by immunofluorescence, reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting. Our results showed that either estrogen alone, progestin alone or progestin combined with estrogen could significantly increase the expression of HOXA10 gene 48 h after the treatment (P<0.05). But estrogen combined with progestin and RU486 could inhibit the up-regulation by estrogen and progestin. HB-EGF could elevate the expression of HOXA10 gene 48 h after the treatment (P<0.05). It is concluded that both estrogen and progestin can up-regulate the expression of HOXA10 gene in Ishikawa cells, but RU486 can inhibit the effect and HB-EGF can elevate the expression level of HOXA10 gene.

Regional development of uterine decidualization: molecular signaling by Hoxa-10

Uterine decidualization, a key event in implantation, is critically controlled by stromal cell proliferation and differentiation. Although the molecular mechanism that controls this event is not well understood, the general consensus is that the factors derived locally at the site of implantation influence aspects of decidualization. Hoxa-10, a developmentally regulated homeobox transcription factor, is highly expressed in decidualizing stromal cells, and targeted deletion of Hoxa-10 in mice shows severe decidualization defects, primarily due to the reduced stromal cell responsiveness to progesterone (P(4)). While the increased stromal cell proliferation is considered to be an initiator of decidualization, the establishment of a full-grown functional decidua appears to depend on the aspects of regional proliferation and differentiation. In this regard, this article provides an overview of potential signaling mechanisms mediated by Hoxa-10 that can influence a host of genes and cell functions necessary for propagating regional decidual development.

Fetal rejection: infertility and immunity

Defective reaction toward fetal alloantigens could result in both recurrent spontaneous abortions (RSAs) and recurrent early pregnancy failures (REPFs), the latter existing in couples with unexplained infertility and multiple failures of implantation after in vitro fertilization embryo transfer. Immunological mechanisms leading to RSA and REPF seem to be different, although both syndromes probably have a genetic background that has not been identified so far. Despite the fact that antiphospholipid syndrome is a well-established cause of repeated pregnancy loss, the role of different autoantibodies existing in RSA and REPF patients needs to be elucidated. Immunotherapy is believed to correct the detrimental immune reactions; however, its real effectiveness and safety for the treatment of distinct forms of pregnancy loss need to be reconsidered.

Regulation of decidualization, interleukin-11 and interleukin-15 by homeobox A 10 in endometrial stromal cells

Cytokine production by the endometrial stromal and decidual cells is essential for successful differentiation of the endometrial stromal cells and uterine leukocytes to sustain pregnancy. Interleukin-11 and -15 (IL-11 and IL-15) secreted by the stromal and decidual cells are two key modulators of the process of decidualization and natural killer cell (NK) activity in the uterus and are essential for pregnancy. However, limited information exists on the maternal factors that regulate the production of these cytokines by the stromal cells. In this study, we investigated the role of homeobox A10 (HOXA10) in the regulation of expression of genes encoding the decidualization markers insulin-like growth factor binding protein-1 (IGFBP1), prolactin and the cytokines IL-11 and IL-15 by endometrial stromal and decidual cells in vitro. The results demonstrated that the expression of IGFBP1, Prolactin (PRL), HOXA10, IL11, and IL15 are co-regulated during steroid hormone-mediated decidualization of human endometrial stromal cells in vitro. In the predecidual cells, downregulation of HOXA10 by siRNA suppresses IGFBP1 and IL15, but increases IL11 expression. In the decidualized cells, knocking down HOXA10 inhibits IGFBP1 and PRL expression but elevates the expression of IL11 and IL15. In addition, our data also demonstrate that transient inhibition of HOXA10 expression in the predecidual cells does not influence its ability to subsequently decidualize or affect cytokine expression, suggesting that steroid hormone-mediated decidualization and cytokine production in vitro does not require HOXA10 preconditioning.

Uterine disorders and pregnancy complications: insights from mouse models

Much of our knowledge of human uterine physiology and pathology has been extrapolated from the study of diverse animal models, as there is no ideal system for studying human uterine biology in vitro. Although it remains debatable whether mouse models are the most suitable system for investigating human uterine function(s), gene-manipulated mice are considered by many the most useful tool for mechanistic analysis, and numerous studies have identified many similarities in female reproduction between the two species. This Review brings together information from studies using animal models, in particular mouse models, that shed light on normal and pathologic aspects of uterine biology and pregnancy complications.

Fetomaternal immunotolerance

Implantation of mammalian conceptus in uterine cavity is the result of evolutionary adaptation, through high level of physiological procedures to ensure its success. However the majority of pregnancy losses occur before or during implantation. It is expected that exploring and defining the molecular and physiological road map during the crucial time of implantation will enable us to decode and effectively treat fertility defects. Immunological, hormonal and molecular factors participate in the feto-maternal cross talk during implantation and designate the effectiveness of the process. The atypical expression of major histocompatibility complex and other protein-antigens, such as Fas/FasL and petformin in human trophoblast, the modified function of cellular constituents of the feto-maternal interface, as well as the specific role of some hormones and cytokines, represent substantive parameters of feto-maternal immunotolerance during implantation.

Progesterone in pregnancy; receptor-ligand interaction and signaling pathways

Progesterone is indispensable in creating a suitable endometrial environment for implantation, and also for the maintenance of pregnancy. Successful pregnancy depends on an appropriate maternal immune response to the fetus. Along with its endocrine effects, progesterone also acts as an "immunosteroid", by contributing to the establishment of a pregnancy protective immune milieu. Progesterone plays a role in uterine homing of NK cells and upregulates HLA-G gene expression, the ligand for NK inhibitory and activating receptors. At high concentrations, progesterone is a potent inducer of Th2-type cytokines as well as of LIF and M-CSF production by T cells. A protein called progesterone-induced blocking factor (PIBF), by inducing a Th2-dominant cytokine production mediates the immunological effects of progesterone. PIBF binds to a novel type of the IL-4 receptor and signals via the Jak/STAT pathway, to induce a number of genes, that not only affect the immune response, but might also play a role in trophoblast invasiveness.

HOXA10 signals on the highway through pregnancy

Implantation represents the remarkable synchronization between the development of the embryo and the differentiation of the endometrium. It depends on uterine-dependent and embryo-specific events, which are critically and sequentially coordinated. A plethora of molecules have been identified which play major roles before and after embryo implantation. In recent years HomeoboxA10 (HOXA10) has emerged as one of the most promising candidates which regulate the events occurring in the maternal compartment for successful establishment of pregnancy. HOXA10 is a transcription factor that is crucial for development and patterning of the uterus during embryogenesis. In the adult endometrium, HOXA10 is expressed in a menstrual cycle dependent manner and it is regulated by ovarian steroid hormones and embryonic signals, HOXA10 is required for uterine receptivity and implantation, and is a key regulator of decidualization. In the decidua, HOXA10 is involved in regulation of cell cycle and local immunomodulation. The present review summarizes the events that are regulated by HOXA10 in embryo implantation and decidualization.

Cell cycle regulatory control for uterine stromal cell decidualization in implantation

Uterine stromal cell decidualization is integral to successful embryo implantation, which is a gateway to pregnancy establishment. This process is characterized by stromal cell proliferation and differentiation into decidual cells with polyploidy. The molecular mechanisms that are involved in these events remain poorly understood. The current concept is that locally induced factors with the onset of implantation influence uterine stromal cell proliferation and/or differentiation through modulation of core cell cycle regulators. This review will aim to address the currently available knowledge on interaction between growth factor/homeobox and cell cycle regulatory signaling in the progression of various aspects of decidualization.

Stress affects uterine receptivity through an ovarian-independent pathway

BACKGROUND

Although stress is known to disturb natural fertility through the inhibition of the hypothalamic-pituitary-gonadal (HPG) axis, the impact of stress on infertile women who receive exogenous gonadal hormones is not well defined. This is probably due to lack of experimental models for evaluating the impacts of stress through an ovarian-independent pathway. The objective of this study was to investigate the possible impact of stress on uterine receptivity, independent of HPG axis dysfunction, using a mouse implantation model maintained with hormone supplementation.

METHODS

Blastocysts from donor mice were transferred into the uterine lumen of ovariectomized (OVX) Balb/c female recipient mice following supplementation with estradiol and progesterone. The recipients were divided into two groups: those exposed (stress group) or not exposed (control group) to intermittent sonic exposure prior to embryo transfer (ET). The number of implantation sites (IS) was compared between these groups. Microarray analysis was performed to elucidate stress-induced molecular alterations in uteri during the implantation period. Sequential gene expression of leukemia inhibitory factor (Lif), an estradiol-inducible gene, was also analyzed using real-time PCR.

RESULTS

A non-mating OVX model with satisfactory implantation rates was established. The number of IS in the stress group (n = 20) was significantly less than that in the control group (n = 18) (Mann-Whitney test, P = 0.0375). Implantation-related genes and ovarian-hormone-responsive genes were repressed in the stress group despite ovarian hormone supplementation. The expression of Lif was suppressed in the stress group.

CONCLUSIONS

Stress can cause decreased uterine receptivity through an ovarian-independent pathway.

Developmental exposure to Bisphenol a impairs the uterine response to ovarian steroids in the adult

Morphoregulator genes like members of the Hox gene family regulate uterine development and are associated with endocrine-related processes such as endometrial proliferation and differentiation in the adult uterus. Exposure to neonatal endocrine disruptors could affect signaling events governed by Hox genes, altering the developmental trajectory of the uterus with lasting consequences. We investigated whether neonatal exposure to bisphenol A (BPA) alters Hoxa10 and Hoxa11 mRNA uterine expression shortly after treatment as well as in the adult. Moreover, we studied whether xenoestrogen exposure may affect the adult uterine response to hormonal stimuli. Newborn females received vehicle, 0.05 mg/kg.d BPA, 20 mg/kg*d BPA, or diethylstilbestrol (0.2 microg/kg*d) on postnatal d 1, 3, 5, and 7). At postnatal d 8, real time RT-PCR assays showed a decrease in Hoxa10 and Hoxa11 expression in all xenoestrogen-treated groups. To evaluate the long-term effects, we used adult ovariectomized rats with hormonal replacement. The subepithelial stroma in BPA- and diethylstilbestrol-treated animals showed an impaired proliferative response to steroid treatment associated with a silencing of Hoxa10 but not associated with changes in the methylation pattern of the Hoxa10 promoter. BPA animals showed that the Hoxa10 reduction was accompanied by an increased stromal expression of the silencing mediator for retinoic acid and thyroid hormone receptor. The spatial coexpression of steroid receptors Hoxa10 and silencing mediator for retinoic acid and thyroid hormone receptor was established using immunofluorescence. Our data indicate that postnatal BPA exposure affects the steroid hormone-responsiveness of uterine stroma in adulthood. Whether this impaired hormonal response is associated with effects on uterine receptivity and decidualization is currently under investigation.

Endometrial gene expression in early pregnancy: lessons from human ectopic pregnancy

Human endometrium undergoes modifications in preparation for embryonic implantation. This study investigated in vivo the endocrine effects of pregnancy on the endometrium, using the model of ectopic pregnancy. Endometrial biopsies from 9 subjects with ectopic pregnancy (Preg) were compared with 8 and 6 samples of mid and late secretory endometrium, respectively. After hybridizing with Affymetrix HGU133 Plus 2 chips, data were analyzed using GeneSpring GX and Ingenuity Pathways Analysis. From 54,675 genes, 3021 genes were significantly differentiated when mid-secretory endometrium was compared with the Preg (Volcano plot; P < .05, >or=2-fold change).The complement and coagulation cascade, phospholid degradation, glycosphingolipid biosynthesis (globoseries), retinol metabolism, antigen presentation pathway, glycosphingolipid biosynthesis, and O-glycan biosynthesis were main significant canonical pathways found in Preg samples. Validation was done with reverse transcriptase polymerase chain reaction. In conclusion, the ectopic embryo has a significant impact, by an endocrine mechanism, on endometrium, when compared with the window of implantation.

Global analysis of genes regulated by HOXA10 in decidualization reveals a role in cell proliferation

Homeobox (HOX) A10 is essential for fertility as demonstrated in transgenic mice, specifically affecting implantation and decidualization. Its role in human decidualization, however, remains unknown. In this study, we used gene silencing followed by microarray analysis to decipher the role of HOXA10 during decidualization of human endometrial stromal cells (HESCs). HOXA10 was knocked down using siRNA oligonucleotide transfection and cells were treated with estradiol, medroxyprogesterone acetate and dibutyryl cAMP (H + cAMP) to induce decidualization. Genes significantly regulated were identified using the Affymetrix microarray chip. With this method, 2361 transcripts were significantly altered by 1.5-fold or higher (P < 0.05) with H + cAMP treatment only. Of these genes, 258 were significantly up-regulated by HOXA10 knockdown and 236 transcripts were significantly down-regulated by more than 1.5-fold, totaling 494 genes that were regulated by HOXA10 during decidualization. Data analysis using the Ingenuity System revealed that many of the genes regulated by HOXA10 knockdown during H + cAMP treatment were associated with cell cycle. Real-time PCR was used to confirm that HOXA10 knockdown decreased expression of the cell cycle genes CDC2 and CCNB2. In addition, a higher percentage of cells were arrested in the G2/M phase. Next, we observed that cell proliferation as measured by BrdU incorporation was decreased upon HOXA10 knockdown and H + cAMP treatment. Apoptosis, on the other hand, as measured by Annexin V staining was not influenced by siHOXA10 in decidualizing cells. Together, these data demonstrate that during decidualization of HESC, HOXA10 is actively involved in promoting cell proliferation through the regulation of hundreds of genes.

Gene expression profiling reveals putative HOXA10 downstream targets in the periimplantation mouse uterus

HOXA10 encodes a transcription factor required for endometrial receptivity and embryo implantation. The objective of this study was to identify and to characterize those molecular markers regulated by HOXA10 expression. The authors have identified putative HOXA10 target genes identified by microarray analysis employing a murine model of transient HOXA10 expression during the anticipated implantation window. Microarray analysis identified 40 statistically significant genes regulated by HOXA10 overexpression of which 31 genes were downregulated greater than 2-fold over control and 9 genes were upregulated. Cellular ontogenies of differentially expressed genes include cell adhesion molecules, signal transduction factors, and metabolic regulators. Semiquantitative real-time reverse transcriptase polymerase chain reaction confirmed regulation of selected candidate genes. Examples included clusterin (Clu), phoshoglycerate 3-dehydrogenase (3-Pgdh), and tumor-associated calcium signal transducer 2 (Tacstd2). Elucidation of these pathways will allow further characterization of the molecular mechanisms governing endometrial development, which also may function to enhance uterine receptivity.