Overlapping and distinct expression of progesterone receptors A and B in mouse uterus and mammary gland during the estrous cycle

A common allele increases endometrial Wnt4 expression, with antagonistic implications for pregnancy, reproductive cancers, and endometriosis

The common human SNP rs3820282 is associated with multiple phenotypes including gestational length and likelihood of endometriosis and cancer, presenting a paradigmatic pleiotropic variant. Deleterious pleiotropic mutations cause the co-occurrence of disorders either within individuals, or across population. When adverse and advantageous effects are combined, pleiotropy can maintain high population frequencies of deleterious alleles. To reveal the causal molecular mechanisms of this pleiotropic SNP, we introduced this substitution into the mouse genome by CRISPR/Cas 9. Previous work showed that rs3820282 introduces a high-affinity estrogen receptor alpha-binding site at the Wnt4 locus. Here, we show that this mutation upregulates Wnt4 transcription in endometrial stroma, following the preovulatory estrogen peak. Effects on uterine transcription include downregulation of epithelial proliferation and induction of progesterone-regulated pro-implantation genes. We propose that these changes increase uterine permissiveness to embryo invasion, whereas they decrease resistance to invasion by cancer and endometriotic foci in other estrogen-responsive tissues.

Validation of a new Custom Polyclonal Progesterone Receptor Antibody for Immunohistochemistry in the Female Mouse Brain

Immunohistochemical visualization of progesterone receptor (PR)-expressing cells in the brain is a powerful technique to investigate the role of progesterone in the neuroendocrine regulation of fertility. A major obstacle to the immunohistochemical visualization of progesterone-sensitive cells in the rodent brain has been the discontinuation of the commercially produced A0098 rabbit polyclonal PR antibody by DAKO. To address the unavailability of this widely used PR antibody, we optimized and evaluated 4 alternative commercial PR antibodies and found that each lacked the specificity and/or sensitivity to immunohistochemically label PR-expressing cells in paraformaldehyde-fixed female mouse brain sections. As a result, we developed and validated a new custom RC269 PR antibody, directed against the same 533-547 amino acid sequence of the human PR as the discontinued A0098 DAKO PR antibody. Immunohistochemical application of the RC269 PR antibody on paraformaldehyde-fixed mouse brain sections resulted in nuclear PR labeling that was highly distinguishable from background, specific to its antigen, highly regulated by estradiol, matched the known distribution of PR protein expression in the female mouse hypothalamus, and nearly identical to that of the discontinued A0098 DAKO PR antibody. In summary, the RC269 PR antibody is a specific and sensitive antibody to immunohistochemically visualize PR-expressing cells in the mouse brain.

Mixed-Culture Propagation of Uterine-Tissue-Resident Macrophages and Their Expression Properties of Steroidogenic Molecules

Tissue-resident macrophages (Mø) play tissue/organ-specific roles, and the physiological/pathological implications of uterine Mø in fertility and infertility are not yet fully understood. Herein, we report a simple propagation method for tissue-resident Mø by mixed culture with the respective tissue/organ-residing cells as the niche. We successfully propagated mouse uterine Mø by mixed culture with fibroblastic cells that exhibited properties of endometrial stromal cells. Propagated mouse uterine Mø were CD206- and arginase-1-positive; iNOS- and MHC-II-negative, indicating M2 polarization; and highly phagocytic, similar to endometrial Mø. Furthermore, uterine Mø were observed to express steroidogenic molecules including SRD5A1 and exhibited gap junction formation, likely with endometrial stromal cells. Accordingly, uterine Mø propagated by mixed culture may provide a new tool for studying immune-endocrine interactions related to fertility and infertility, particularly androgen's intracrine actions in preparing the uterine tissue environment to support implantation and pregnancy as well as in the etiology of endometriosis.

The Role of NF-κB in Endometrial Diseases in Humans and Animals: A Review

The expression of genes of various proinflammatory chemokines and cytokines is controlled, among others, by the signaling pathway of the nuclear factor kappaB (NF-κB) superfamily of proteins, providing an impact on immune system functioning. The present review addresses the influence and role of the NF-κB pathway in the development and progression of most vital endometrial diseases in human and animal species. Immune modulation by NF-κB in endometritis, endometrosis, endometriosis, and carcinoma results in changes in cell migration, proliferation, and inflammation intensity in both the stroma and epithelium. In endometrial cells, the NF-κB signaling pathway may be activated by multiple stimuli, such as bacterial parts, cytokines, or hormones binding to specific receptors. The dysregulation of the immune system in response to NF-κB involves aberrant production of chemokines and cytokines, which plays a role in endometritis, endometriosis, endometrosis, and endometrial carcinoma. However, estrogen and progesterone influence on the reproductive tract always plays a major role in its regulation. Thus, sex hormones cannot be overlooked in endometrial disease physiopathology. While immune system dysregulation seems to be NF-κB-dependent, the hormone-independent and hormone-dependent regulation of NF-κB signaling in the endometrium should be considered in future studies. Future goals in this research should be a step up into clinical trials with compounds affecting NF-κB as treatment for endometrial diseases.

A re-appraisal of mesenchymal-epithelial transition (MET) in endometrial epithelial remodeling

Mesenchymal-epithelial transition (MET) is a mechanism of endometrial epithelial regeneration. It is also implicated in adenocarcinoma and endometriosis. Little is known about this process in normal uterine physiology. Previously, using pregnancy and menses-like mouse models, MET occurred only as an epithelial damage/repair mechanism. Here, we hypothesized that MET also occurs in other physiological endometrial remodeling events, outside of damage/repair, such as during the estrous cycle and adenogenesis (gland development). To investigate this, Amhr2-Cre-YFP/GFP mesenchyme-specific reporter mice were used to track the fate of mesenchymal-derived (MD) cells. Using EpCAM (epithelial marker), EpCAM⁺YFP⁺ MD-epithelial cells were identified in all stages of the estrous cycle except diestrus, in both postpartum and virgin mice. EpCAM⁺YFP⁺ MD-epithelial cells comprised up to 80% of the epithelia during estrogen-dominant proestrus and significantly declined to indistinguishable from control uteri in diestrus, suggesting MET is hormonally regulated. MD-epithelial cells were also identified during postnatal epithelial remodeling. MET occurred immediately after birth at postnatal day (P) 0.5 with EpCAM⁺GFP⁺ cells ranging from negligible (0.21%) to 82% of the epithelia. EpCAM⁺GFP⁺ MD-epithelial cells declined during initiation of adenogenesis (P8, avg. 1.75%) and then increased during gland morphogenesis (P14, avg. 10%). MD-epithelial cells expressed markers in common with non-MD-epithelial cells (e.g., EpCAM, FOXA2, ESR1, PGR). However, MD-epithelial cells were differentially regulated postnatally and in adults, suggesting a functional distinction in the two populations. We conclude that MET occurs not only as an epithelial damage/repair mechanism but also during other epithelial remodeling events, which to our knowledge has not been demonstrated in other tissues.

CRC Therapy Identifies Indian Hedgehog Signaling in Mouse Endometrial Epithelial Cells and Inhibition of Ihh-KLF9 as a Novel Strategy for Treating IUA

Intrauterine adhesion (IUA) causes menstrual disturbance and infertility. There is no effective treatment available for moderate to severe IUA cases. Stem cell-based therapy has been investigated for treating IUA but is limited in clinical applications due to issues including the precise induction of differentiation, tumorigenesis, and unclear molecular mechanisms. In our recent study, we isolated and expanded the long-term cultures of conditional reprogrammed (CR) mouse endometrial epithelial cells. Treating IUA mice with these CR cells (CRCs) restored the morphology and structure of the endometrium and significantly improved the pregnancy rate. In this study, our data with high-throughput sequencing, CRISPR knockout Ihh^-/-CRCs, and transplantation identified for the first time that the Indian hedgehog (Ihh) gene plays a critical role in the regulation of endometrial epithelial cell proliferation. We also found that aberrant activated Ihh-krüppel-like factor 9 (KLF9) signaling contributes to the inhibition of normal progesterone receptor (PR) function in IUA mice. Thus, we hypothesized that inhibition of the Ihh-KLF9 pathway may be a novel strategy to treat IUA. Our data demonstrated that treatment with the hedgehog signaling inhibitor Vismodegib restored the morphology, structure, and microenvironment of the endometrium, and greatly improved the pregnancy rate in IUA mice. This study suggests a promising application of hedgehog inhibitors as a targeted drug in the IUA clinic.

Molecular Mechanism of Equine Endometrosis: The NF-κB-Dependent Pathway Underlies the Ovarian Steroid Receptors’ Dysfunction

Endometrosis is a frequently occurring disease decreasing mares’ fertility. Thus, it is an important disease of the endometrium associated with epithelial and stromal cell alterations, endometrium gland degeneration and periglandular fibrosis. Multiple degenerative changes are found in uterine mucosa, the endometrium. However, their pathogenesis is not well known. It is thought that nuclear factor-κB (NF-κB), a cell metabolism regulator, and its activation pathways take part in it. The transcription of the profibrotic pathway genes of the NF-κB in fibrotic endometria differed between the follicular (FLP) and mid-luteal (MLP) phases of the estrous cycle, as well as with fibrosis progression. This study aimed to investigate the transcription of genes of estrogen (ESR1, ESR2) and progesterone receptors (PGR) in equine endometria to find relationships between the endocrine environment, NF-κB-pathway, and fibrosis. Endometrial samples (n = 100), collected in FLP or MLP, were classified histologically, and examined using quantitative PCR. The phase of the cycle was determined through the evaluation of ovarian structures and hormone levels (estradiol, progesterone) in serum. The transcription of ESR1, ESR2, and PGR decreased with the severity of endometrial fibrosis and degeneration of the endometrium. Moreover, differences in the transcription of ESR1, ESR2, and PGR were noted between FLP and MLP in the specific categories and histopathological type of equine endometrosis. In FLP and MLP, specific moderate and strong correlations between ESR1, ESR2, PGR and genes of the NF-κB pathway were evidenced. The transcription of endometrial steroid receptors can be subjected to dysregulation with the degree of equine endometrosis, especially in both destructive types of endometrosis, and mediated by the canonical NF-κB pathway depending on the estrous cycle phase.

Chemical Effects on Breast Development, Function, and Cancer Risk: Existing Knowledge and New Opportunities

Population studies show worrisome trends towards earlier breast development, difficulty in breastfeeding, and increasing rates of breast cancer in young women. Multiple epidemiological studies have linked these outcomes with chemical exposures, and experimental studies have shown that many of these chemicals generate similar effects in rodents, often by disrupting hormonal regulation. These endocrine-disrupting chemicals (EDCs) can alter the progression of mammary gland (MG) development, impair the ability to nourish offspring via lactation, increase mammary tissue density, and increase the propensity to develop cancer. However, current toxicological approaches to measuring the effects of chemical exposures on the MG are often inadequate to detect these effects, impairing our ability to identify exposures harmful to the breast and limiting opportunities for prevention. This paper describes key adverse outcomes for the MG, including impaired lactation, altered pubertal development, altered morphology (such as increased mammographic density), and cancer. It also summarizes evidence from humans and rodent models for exposures associated with these effects. We also review current toxicological practices for evaluating MG effects, highlight limitations of current methods, summarize debates related to how effects are interpreted in risk assessment, and make recommendations to strengthen assessment approaches. Increasing the rigor of MG assessment would improve our ability to identify chemicals of concern, regulate those chemicals based on their effects, and prevent exposures and associated adverse health effects.

Loss of basigin expression in uterine cells leads to subfertility in female mice†

Basigin (BSG) is a transmembrane glycoprotein involved in cell proliferation, angiogenesis, and tissue remodeling. BSG has been shown to be essential for male and female reproduction although little is known about its role in normal uterine function. To study the potential function of BSG in the female reproductive tract, we generated mice with conditional knockout of Bsg in uterine cells using progesterone receptor-Cre and hypothesized that BSG is required for normal pregnancy in mice. Fertility study data showed that the conditional knockout mice had significantly reduced fertility compared to controls. Ovarian function of the conditional knockout mice appeared normal with no difference in the number of superovulated oocytes collected or in serum progesterone levels between the conditional knockout and the control mice. Uterine tissues collected at various times of gestation showed increased abnormalities in implantation, decidualization, placentation, and parturition in the conditional knockout mice. Uterine cross sections on Day 5 of pregnancy showed implantation failure and abnormal uterine epithelial differentiation in a large proportion of the conditional knockout mice. There was a compromised decidual response to artificial decidualization stimuli and decreased mRNA and protein levels for decidualization genes in the uteri of the conditional knockout mice. We also observed altered protein expression of monocarboxylate transporter 1 (MCT1), as well as impaired angiogenesis in the conditional knockout uteri compared to the controls. These results support that BSG is required for successful pregnancy through its functions in implantation and decidualization.

Uterine Epithelial Progesterone Receptor Governs Uterine Receptivity Through Epithelial Cell Differentiation

Progesterone receptor (PGR) is indispensable for pregnancy in mammals. Uterine PGR responds to the heightened levels of ovarian progesterone (P4) after ovulation and regulates uterine gene transcription for successful embryo implantation. Although epithelial and stromal P4-PGR signaling may interact with each other to form appropriate endometrial milieu for uterine receptivity and the subsequent embryo attachment, it remains unclear what the specific roles of epithelial P4-PGR signaling in the adult uterus are. Here we generated mice with epithelial deletion of Pgr in the adult uterus (Pgrfl/flLtfCre/+ mice) by crossing Pgr-floxed and Ltf-Cre mice. Pgrfl/flLtfCre/+ mice are infertile due to the impairment of embryo attachment. Pgrfl/flLtfCre/+ uteri did not exhibit epithelial growth arrest, suggesting compromised uterine receptivity. Both epithelial and stromal expressions of P4-responsive genes decreased in Pgrfl/flLtfCre/+ mice during the peri-implantation period, indicating that epithelial Pgr deletion affects not only epithelial but stromal P4 responsiveness. In addition, uterine LIF, an inducer of embryo attachment, was decreased in Pgrfl/flLtfCre/+ mice. The RNA-seq analysis using luminal epithelial specimens dissected out by laser capture microdissection revealed that the signaling pathways related to extracellular matrix, cell adhesion, and cell proliferation are altered in Pgr fl/flLtf Cre/+ mice. These findings suggest that epithelial PGR controls both epithelial and stromal P4 responsiveness and epithelial cell differentiation, which provides normal uterine receptivity and subsequent embryo attachment.

Constitutive expression of progesterone receptor isoforms promotes the development of hormone-dependent ovarian neoplasms

Differences in the relative abundances of the progesterone receptor (PGR) isoforms PGRA and PGRB are often observed in women with reproductive tract cancers. To assess the importance of the PGR isoform ratio in the maintenance of the reproductive tract, we generated mice that overexpress PGRA or PGRB in all PGR-positive tissues. Whereas few PGRA-overexpressing mice developed reproductive tract tumors, all PGRB-overexpressing mice developed ovarian neoplasms that were derived from ovarian luteal cells. Transcriptomic analyses of the ovarian tumors from PGRB-overexpressing mice revealed enhanced AKT signaling and a gene expression signature similar to those of human ovarian and endometrial cancers. Treating PGRB-overexpressing mice with the PGR antagonist RU486 stalled tumor growth and decreased the expression of cell cycle-associated genes, indicating that tumor growth and cell proliferation were hormone dependent in addition to being isoform dependent. Analysis of the PGRB cistrome identified binding events at genes encoding proteins that are critical regulators of mitotic phase entry. This work suggests a mechanism whereby an increase in the abundance of PGRB relative to that of PGRA drives neoplasia in vivo by stimulating cell cycling.

Systematic review of p38 mitogen-activated kinase and its functional role in reproductive tissues

Oxidative stress (OS) plays a role in uterine tissue remodeling during pregnancy and parturition. While p38 MAPK is an OS-response kinase, a precise functional role is unknown. Therefore, we conducted a systematic review of literature on p38 MAPK expression, activation, and function in reproductive tissues throughout pregnancy and parturition, published between January 1980 and August 2017, using four electronic databases (Web of Science, PubMed, Medline, and CoCHRANE). We identified 418 reports; 108 were selected for full-text evaluation and 74 were included in final review. p38 MAPK was investigated using feto-maternal primary or immortalized cells, tissue explants, and animal models. Western blot was most commonly used to report phosphorylated (active) p38 MAPK. Human placenta (27), chorioamniotic membranes (14), myometrium (13), decidua (8), and cervix (1) were the studied tissues. p38 MAPK's functions were tissue and gestational age dependent. Isoform specificity was hardly reported. p38 MAPK activity was induced by ROS or proinflammatory cytokines to promote cell signaling linked to cell fate, primed uterus, ripened cervix, and proinflammatory cytokine/chemokine production. In 35 years, reports on p38 MAPK's role during pregnancy and parturition are scarce and current literature is insufficient to provide a comprehensive description of p38 MAPK's mechanistic role during pregnancy and parturition.

Decreased epithelial progesterone receptor A at the window of receptivity is required for preparation of the endometrium for embryo attachment

The precise timing of progesterone signaling through its cognate receptor, the progesterone receptor (PGR), is critical for the establishment and maintenance of pregnancy. Loss of PGR expression in the murine uterine epithelium during the preimplantation period is a marker for uterine receptivity and embryo attachment. We hypothesized that the decrease in progesterone receptor A (PGRA) expression is necessary for successful embryo implantation. To test this hypothesis, a mouse model constitutively expressing PGRA (mPgrALsL/+) was generated. Expression of PGRA in all uterine compartments (Pgrcre) or uterine epithelium (Wnt7acre) resulted in infertility with defects in embryo attachment and stromal decidualization. Expression of critical PGRA target genes, indian hedgehog, and amphiregulin (Areg), was maintained through the window of receptivity while the estrogen receptor target gene, the leukemia inhibitory factor (Lif), a key regulator of embryo receptivity, was decreased. Transcriptomic and cistromic analyses of the mouse uterus at day 4.5 of pregnancy identified an altered group of genes regulating molecular transport in the control of fluid and ion levels within the uterine interstitial space. Additionally, LIF and its cognate receptor, the leukemia inhibitory factor receptor (LIFR), exhibited PGR-binding events in regions upstream of the transcriptional start sites, suggesting PGRA is inhibiting transcription at these loci. Therefore, downregulation of the PGRA isoform at the window of receptivity is necessary for the attenuation of hedgehog signaling, transcriptional activation of LIF signaling, and modulation of solutes and fluid, producing a receptive environment for the attaching embryo.

Estrogen and progesterone signalling in the normal breast and its implications for cancer development

The ovarian hormones estrogen and progesterone are master regulators of the development and function of a broad spectrum of human tissues, including the breast, reproductive and cardiovascular systems, brain and bone. Acting through the nuclear estrogen (ER) and progesterone receptors (PR), both play complex and essential coordinated roles in the extensive development of the lobular alveolar epithelial structures of the normal breast during puberty, the normal menstrual cycle and pregnancy. The past decade has seen major advances in understanding the mechanisms of action of estrogen and progesterone in the normal breast and in the delineation of the complex hierarchy of cell types regulated by ovarian hormones in this tissue. There is evidence for a role for both ER and PR in driving breast cancer, and both are favourable prognostic markers with respect to outcome. In this review, we summarize current knowledge of the mechanisms of action of ER and PR in the normal breast, and implications for the development and management of breast cancer.

Immunosuppression with tacrolimus improved implantation and rescued expression of uterine progesterone receptor and its co-regulators FKBP52 and PIASy at nidation in the obese and diabetic mice: Comparative studies with metformin

Diabesity is often associated with subfertility and recurrent miscarriages. Evidence links systemic and local uterine cytotoxicity to the pathogenesis of implantation failure (IF) in diabetes. Immunosuppression with tacrolimus improved pregnancy outcomes in obese and diabetic mice and repeated IF in women with elevated Th1/Th2 blood cell ratios. However the mode of action of tacrolimus in protecting against IF and the molecular mechanisms associated with recurrent miscarriages in the obese and diabetic subjects are yet to be elucidated. Here we administered tacrolimus (FK506) (0.1 mg/kg) for four consecutive weeks to the NONcNZO10/LtJ mice, a model of human PCOS, chronically fed with 60% kCal fat for 16 consecutive weeks to simulate human obesity-associated T2DM. Compared to those immunosuppressed with tacrolimus and their normative controls, high-fat fed (HFD) diabetic NONcNZO mice exhibited higher rates of peri- and post-implantation resorption and had aberrant expression of uterine IFNγ and progesterone receptor (PGR) and its immunophilin co-chaperone FKBP52 at nidation. Immature uterodomes and lack of activation of uterine STAT3 and NFκB at implantation were characteristics of IF in the HFD-dNONcNZO dams also low in the deciduogenic factors IL11 and GM-CSF. Therapeutic interventions with tacrolimus or metformin normalized the expression of decidual IFNγ, PGR and FKBP52, increased co-localization of protein inhibitor of activated STATy (PIASy) to PGR and resulted in the upregulation of uterine IL11and LIF. Rescued phosphorylation of STAT3 and NFκBp65 and uterodome maturation at nidation defined implantation success in treated dams. To our knowledge this is the first report to show that the impact of HFD on the hemochorial implantation is at least in part mediated through disruption of PGR signaling at nidation and that immunosuppression with tacrolimus or treatment with metformin restores PGR-mediated influences during implantation in the obese and diabetic subjects.

A Review of Mechanisms of Implantation

Implantation is a highly organized process that involves an interaction between a receptive uterus and a competent blastocyst. In humans, natural fecundity suggests that the chance of conception per cycle is relatively low (~30%) and two-third of lost pregnancies occur because of implantation failure. Defective implantation leads to adverse pregnancy outcomes including infertility, spontaneous miscarriage, intrauterine fetal growth restriction and preeclampsia. With use of advanced scientific technologies, gene expression analysis and genetically-engineered animal models have revealed critical cellular networks and molecular pathways. But, because of ethical restrictions and the lack of a mechanistic experiment, comprehensive steps in human implantation have still not been completely understood. This review primarily focuses on the recent advances in mechanisms of implantation. Because infertility is an emerging issue these days, gaining an understanding the molecular and hormonal signaling pathway will improve the outcome of natural pregnancy and assisted reproductive technology.

Molecular Signaling of Progesterone, Growth Hormone, Wnt, and HER in Mammary Glands of Dogs, Rodents, and Humans: New Treatment Target Identification

Mammary tumors are the most common form of neoplasia in the bitch. Female dogs are protected when they are spayed before the first estrus cycle, but this effect readily disappears and is already absent when dogs are spayed after the second heat. As the ovaries are removed during spaying, ovarian steroids are assumed to play an essential role in tumor development. The sensitivity toward tumor development is already present during early life, which may be caused by early mutations in stem cells during the first estrus cycles. Later on in life, tumors arise that are mostly steroid-receptor positive, although a small subset of tumors overexpressing human epidermal growth factor 2 (HER2) and some lacking estrogen receptor, progesterone receptor (PR), and HER2 (triple negative) are present, as is the situation in humans. Progesterone (P₄), acting through PR, is the major steroid involved in outgrowth of mammary tissue. PRs are expressed in two forms, the progesterone receptor A (PRA) and progesterone receptor B (PRB) isoforms derived from splice variants from a single gene. The dog and the whole family of canids have only a functional PRA isoform, whereas the PRB isoform, if expressed at all, is devoid of intrinsic biological activity. In human breast cancer, overexpression of the PRA isoform is related to more aggressive carcinomas making the dog a unique model to study PRA-related mammary cancer. Administration of P₄ to adult dogs results in local mammary expression of growth hormone (GH) and wing less-type mouse mammary tumor virus integration site family 4 (Wnt4). Both proteins play a role in activation of mammary stem cells. In this review, we summarize what is known on P₄, GH, and Wnt signaling in canine mammary cancer, how the family of HER receptors could interact with this signaling, and what this means for comparative and translational oncological aspects of human breast cancer development.

Competitive Agonists and Antagonists of Steroid Nuclear Receptors: Evolution of the Concept or Its Reversal

The mechanisms displaying pure and mixed steroid agonist/antagonist activity as well as principles underlying in vivo action of selective steroid receptor modulators dependent on tissue or cell type including interaction with various types of nuclear receptors are analyzed in this work. Mechanisms of in vitro action for mixed agonist/antagonist steroids are discussed depending on: specific features of their interaction with receptor hormone-binding pocket; steroid-dependent allosteric modulation of interaction between hormone-receptor complex and hormone response DNA elements; features of interacting hormone-receptor complex with protein transcriptional coregulators; level and tissue-specific composition of transcriptional coregulators. A novel understanding regarding context-selective modulators replacing the concept of steroid agonists and antagonists is discussed.

Expression of genes involved in progesterone receptor paracrine signaling and their effect on litter size in pigs

Background

Embryonic mortality during the period of implantation strongly affects litter size in pigs. Progesterone receptor (PGR) paracrine signaling has been recognized to play a significant role in embryonic implantation. IHH, NR2F2, BMP2, FKBP4 and HAND2 were proved to involve in PGR paracrine signaling. The objective of this study was to evaluate the expression of IHH, NR2F2, BMP2, FKBP4 and HAND2 in endometrium of pregnant sows and to further investigate these genes’ effect on litter size in pigs. Real-time PCR, western blot and immunostaining were used to study target genes/proteins expression in endometrium in pigs. RFLP-PCR was used to detect single nucleotide polymorphisms (SNPs) of target genes.

Results

The results showed that the mRNA and protein expression levels of IHH, NR2F2 and BMP2 were up-regulated during implantation period (P < 0.05 or P < 0.01). All target proteins were mainly observed in luminal epithelium and glandular epithelium. Interestingly, the staining of NR2F2 and HAND2 was also strong in stroma. SNPs detection revealed that there was a -204C > A mutation in promoter region of NR2F2 gene. Three genotypes were found in Large White, Landrace and Duroc sows. A total of 1847 litter records from 625 sows genotyped at NR2F2 gene were used to analyze the total number born (TNB) and number born alive (NBA). The study of the effect on litter size suggested that sows with genotype CC tend to have higher litter size.

Conclusions

These results showed the expression patterns of genes/proteins involved in PGR paracrine signaling over implantation time. And the candidate gene for litter size was identified from genes involved in this signaling. This study could be a resource for further studies to identify the roles of these genes for embryonic implantation in pigs.

Electronic supplementary material

The online version of this article (doi:10.1186/s40104-016-0090-z) contains supplementary material, which is available to authorized users.

Minireview: Progesterone Regulation of Proliferation in the Normal Human Breast and in Breast Cancer: A Tale of Two Scenarios?

Progesterone (P), which signals through the P receptor (PR), is critical in normal development of the breast, but its signaling axis is also a major driver of breast cancer risk. Here we review recent advances in the understanding of P signaling in the normal human breast, with a focus on the importance of the balance between autocrine and paracrine signaling. To date, most data (which derive largely from mouse models or human breast cancer cell line studies) have demonstrated that the vast majority of PR+ cells appear to act as "sensor" cells, which respond to P stimulation by translating these hormonal cues into paracrine signals. However, growing evidence suggests that, dependent on the cellular context, P may also signal in an autocrine manner in a subset of cells in the normal mouse mammary gland and human breast. It has been suggested that it may be dysregulation of this autocrine signaling, resulting in a "switch" from a predominance of paracrine signaling to autocrine signaling in PR+ cells, which is an early event during breast tumorigenesis. This review summarizes current evidence in the literature that demonstrates the mechanisms through which P acts in the normal human breast, as well as highlighting the important questions that remain unanswered.

Effects of ovarian hormone treatment on the gene expression of muscarinic acetylcholine receptors in the ovariectomized rat myometrium

We investigate the effects of ovarian hormone on the gene expression of muscarinic acetylcholine receptors (M1-M5) in the myometrium using real-time PCR and evaluate the relationships between their expression and that of ovarian hormone receptors (ERα, ERβ, and PgR). Wistar rats were sham operated (SO) or ovariectomized (OVX) and treated with vehicle, estradiol (E2), progesterone (P4), or both E2 and P4 for 2 days beginning on postoperative day 33. M1 and M4 mRNA expressions were not detected in the myometrium. M2 mRNA expression did not change significantly in the OVX and OVX+P4 groups compared to the SO group, but increased significantly in the OVX+E2 group and was normalized in the OVX+E2P4 group. M3 mRNA expression increased significantly in the OVX and OVX+P4 groups compared to the SO group, but was normalized in the OVX+E2 and OVX+E2P4 groups. M5 mRNA expression did not change significantly in all experimental groups. ERα mRNA expression increased significantly in the OVX, OVX+E2, and OVX+P4 groups compared to the SO group, but was normalized in the OVX+E2P4 group. The changes in ERβ mRNA expression were similar to those of M3 mRNA expression in all experimental groups. In contrast, the changes in PgR mRNA expression did not correspond with that of M2, M3, or M5 mRNA expression in any of the experimental groups. Additionally, we evaluated the relationship between the expression of muscarinic acetylcholine receptors and ovarian hormone receptors in estrus cycle. M2 mRNA expression increased significantly in diestus and metaestrus compared in proestrus and estrus. M3 mRNA expression increased significantly in only diestrus compared in the other stages. In contrast, M5 mRNA expression did not change in estrus cycle. The changes in ERα mRNA expression appeared to be similar to those of M2 in estrus cycle, but no significant difference was found. The changes in ERβ mRNA expression were similar to those of M3 mRNA expression. The change in PgR mRNA expression increased significantly in diestrus compared in metaestrus, but did not correspond with that of M2, M3, or M5 mRNA expression in estrus cycle. When acetylcholine sensitivity in the myometrium was compared between diestrus and estrus, the sensitivity is significantly lower in estrus than in diestrus. These results suggest that ovarian hormones influence the expression of M2 and M3 in the myometrium by regulating the expression of hormone receptors. E2 may upregulate M2 via ERα, but P4 may downregulate M2 by inhibiting ERα via PgR. E2 may downregulate M3 by inhibiting ERβ, but P4 may not regulate the expression of M3 and ERβ. M5 may be a constitutive muscarinic receptor in the myometrium because neither E2 nor P4 influence the expression of M5. The combination of E2 and P4 may contribute the reproduction by quieting down the acetylcholine-induced myometrial contraction.

Progesterone receptor and Stat5 signaling cross talk through RANKL in mammary epithelial cells

Progesterone (P4) stimulates proliferation of the mammary epithelium by a mechanism that involves paracrine signaling mediated from progesterone receptor (PR)-positive to neighboring PR-negative cells. Here we used a primary mouse mammary epithelial cell (MEC) culture system to define the molecular mechanism by which P4 regulates the expression of target gene effectors of proliferation including the paracrine factor receptor and activator of nuclear factor κB ligand (RANKL). MECs from adult virgin mice grown and embedded in three-dimensional basement-membrane medium resemble mammary ducts in vivo structurally and with respect to other properties including a heterogeneous pattern of PR expression, P4 induction of RANKL and other target genes in a PR-dependent manner, and a proliferative response to progestin. RANKL was demonstrated to have multiple functional P4-responsive enhancers that bind PR in a hormone-dependent manner as detected by chromatin immunoprecipitation assay. P4 also stimulated recruitment of signal transducer and activator of transcription (Stat)5a to RANKL enhancers through an apparent tethering with PR. Analysis of primary MECs from Stat5a knockout mice revealed that P4 induction of RANKL and a broad range of other PR target genes required Stat5a, as did P4-stimulated cell proliferation. In the absence of Stat5a, PR binding was lost at selective RANKL enhancers but was retained with others, suggesting that Stat5a acts to facilitate PR DNA binding at selective sites and to function as a coactivator with DNA-bound PR at others. These results show that RANKL is a direct PR target gene and that Stat5a has a novel role as a cofactor in PR-mediated transcriptional signaling in the mammary gland.

Functional role of progestin and the progesterone receptor in the suppression of spermatogenesis in rodents

Synthetic progestins such as levonorgestrel (LNG) are used in combination with testosterone (T) in male contraceptive clinical trials to suppress gonadotropins secretion, but whether progestins have additional direct effects on the testis are not known. This study aimed to examine the effect of a potent progestin, (LNG), alone or in combination with testosterone (T) on spermatogenesis in adult rats, and to evaluate the functional role of the progesterone receptors (PRs) in the testis. In comparison with a low dose of LNG treatment in adult rats for 4 weeks, T and T + LNG treatment decreased testicular sperm count to 64.1 and 40.2% of control levels respectively. LNG induced germ cell apoptosis at stages I-IV and XII-XIV; T increased apoptosis at stages VII-VIII; LNG + T treatment induced greater germ cell apoptosis at a wider range of seminiferous epithelial stages. RT-PCR and Western Blots showed that PR was present in testes and up-regulated during suppression of spermatogenesis induced by testicular hormonal deprivation. PR knockout (PRKO) mice had larger testes, greater sperm production, increased numbers of Sertoli and Leydig cells. Suppression of gonadotropin and intratesticular T by GnRH-antagonist treatment induced PR promoter driven LacZ expression in Leydig cells of PRKO mice. This suggests that GnRH-antagonist treatment while inducing germ cell apoptosis also up-regulates PR. We conclude that (i) LNG + T induced greater suppression of spermatogenesis through increase in germ cell apoptosis involving a wider range of seminiferous epithelial stages than either treatment alone, (ii) up-regulation of PR was associated with inhibition of spermatogenesis, (iii) PR knockout mice showed increased sperm production suggesting that testicular PR activated events play a physiological and pharmacological inhibitory role in the testis. These data support the hypothesis that in addition to its known suppressive effects on gonadotropins, progestins may have direct inhibitory actions on the testis.

The natural estrogenic compound diarylheptanoid (D3): in vitro mechanisms of action and in vivo uterine responses via estrogen receptor α

BACKGROUND

Diarylheptanoid (D3) isolated from the medicinal plant, Curcuma comosa, has estrogenic activity.

OBJECTIVE

We aimed to elucidate the mechanism(s) of D3 action and compare it with that of 17β-estradiol (E2) using both in vitro and in vivo uterine models.

METHODS

We used human uterine (Ishikawa) cells to determine the estrogenic action of D3 on the activation and nuclear translocation of estrogen receptor α (ERα). In addition, we further characterized the uterine response to D3 treatment in vivo.

RESULTS

D3 activated an estrogen responsive element (ERE) luciferase reporter through ERα, and molecular modeling suggested that D3 could be accommodated in the ERα binding pocket. Using modified ERα to assay ligand-dependent nuclear translocation, we observed D3-dependent ERα interaction and translocation. In mouse uteri, early- and late-phase estrogen-regulated gene responses were increased in D3-treated ovariectomized wild-type animals, in a manner similar to that of E2; no response was seen in ERα knockout animals. We observed a divergence in estrogen responses after D3 treatment: D3 induced robust DNA synthesis in uterine epithelial cells, linked to an increase in cell-cycle-related genes; however, no increase in uterine weight was observed 24 hr after treatment. D3 also affected uterine progesterone receptor expression patterns similar to E2. When D3 and E2 were administered together, we observed no additive or antagonistic effects of D3 on E2. Our findings suggest that D3 is a weak estrogenic agonist compound.

CONCLUSION

D3 is a weakly acting phytoestrogen that mimics the mitogenic responses produced by E2 in an ERα-dependent manner, but it is unable to increase uterine weight or enhance or antagonize the effects of estrogen.

Physiological and molecular determinants of embryo implantation

Embryo implantation involves the intimate interaction between an implantation-competent blastocyst and a receptive uterus, which occurs in a limited time period known as the window of implantation. Emerging evidence shows that defects originating during embryo implantation induce ripple effects with adverse consequences on later gestation events, highlighting the significance of this event for pregnancy success. Although a multitude of cellular events and molecular pathways involved in embryo-uterine crosstalk during implantation have been identified through gene expression studies and genetically engineered mouse models, a comprehensive understanding of the nature of embryo implantation is still missing. This review focuses on recent progress with particular attention to physiological and molecular determinants of blastocyst activation, uterine receptivity, blastocyst attachment and uterine decidualization. A better understanding of underlying mechanisms governing embryo implantation should generate new strategies to rectify implantation failure and improve pregnancy rates in women.

Deciphering the molecular basis of uterine receptivity

Uterine receptivity is defined as a limited time period during which the uterus enters into an appropriately differentiated state that is ready for the initiation of implantation by competent blastocysts. Although various cellular aspects and molecular pathways involved in uterine receptivity have been identified by gene expression studies and genetically engineered mouse models, a comprehensive understanding of the window of uterine receptivity is still missing. This review focuses on the recent progress in this area, with particular focus on the molecular basis of stromal-epithelial dialogue and crosstalk between the blastocyst and the uterus during implantation. A better understanding of the underlying mechanisms governing the window of uterine receptivity is hoped to generate new strategies to correct implantation failure and to improve pregnancy rates in women.

The biology of progesterone receptor in the normal mammary gland and in breast cancer

This paper reviews work on progesterone and the progesterone receptor (PR) in the mouse mammary gland that has been used extensively as an experimental model. Studies have led to the concept that progesterone controls proliferation and morphogenesis of the luminal epithelium in a tightly orchestrated manner at distinct stages of development by paracrine signaling pathways, including receptor activator of nuclear factor κB ligand (RANKL) as a major paracrine factor. Progesterone also drives expansion of stem cells by paracrine signals to generate progenitors required for alveologenesis. During mid-to-late pregnancy, progesterone has another role to suppress secretory activation until parturition mediated in part by crosstalk between PR and prolactin/Stat5 signaling to inhibit induction of milk protein gene expression, and by inhibiting tight junction closure. In models of hormone-dependent mouse mammary tumors, the progesterone/PR signaling axis enhances pre-neoplastic progression by a switch from a paracrine to an autocrine mode of proliferation and dysregulation of the RANKL signaling pathway. Limited experiments with normal human breast show that progesterone/PR signaling also stimulates epithelial cell proliferation by a paracrine mechanism; however, the signaling pathways and whether RANKL is a major mediator remains unknown. Work with human breast cancer cell lines, patient tumor samples and clinical studies indicates that progesterone is a risk factor for breast cancer and that alteration in progesterone/PR signaling pathways contributes to early stage human breast cancer progression. However, loss of PR expression in primary tumors is associated with a less differentiated more invasive phenotype and worse prognosis, suggesting that PR may limit later stages of tumor progression.

The progesterone receptor regulates implantation, decidualization, and glandular development via a complex paracrine signaling network

Many women are affected by infertility and reproductive-associated disease such as endometriosis or endometrial cancer. Successful pregnancy is dependent on a healthy uterus that is fit to receive and support a fertilized embryo. The uterus is an endocrine organ, responsive to the presence of the ovarian steroid hormones, estrogen and progesterone, which activate transcription of target genes through the binding of their cognate receptors, the estrogen receptor and the progesterone receptor. Progesterone signaling has been demonstrated to be critical for the initiation and continuance of pregnancy. Through the induction of Ihh, Wnt, and Bmp pathways within the epithelial and stromal compartments of the uterus, embryo attachment and implantation occur followed by decidualization of the surrounding stroma. Furthermore, these pathways have been shown to be involved in uterine glandular development. This review highlights the integral role of uterine progesterone-mediated paracrine signaling in gland development and pregnancy.

A phenotypic mouse model of basaloid breast tumors

Chemotherapeutic strategies that target basal-like breast tumors are difficult to design without understanding their cellular and molecular basis. Here, we induce tumors in mice by carcinogen administration, creating a phenocopy of tumors with the diagnostic and functional aspects of human triple negative disease (including EGFR expression/lack of erbB, estrogen-independent growth and co-clustering of the transcriptome with other basaloid models). These tumor strains are a complement to established mouse models that are based on mutations in Brca1 and/or p53. Tumors comprise two distinct cell subpopulations, basal and luminal epithelial cells. These cell fractions were purified by flow cytometry, and only basal cell fractions found to have tumor initiating activity (cancer stem cells). The phenotype of serially regenerated tumors was stable, and irrespective of tumor precursor cell. Tumors were passaged entirely in vivo and serial generations tested for their phenotypic stability. The relative chemo-sensitivity of basal and luminal cells were evaluated. Upon treatment with anthracycline, tumors were effectively de-bulked, but recurred; this correlated with maintenance of a high rate of basal cell division throughout the treatment period. Thus, these tumors grow as robust cell mixtures of basal bipotential tumor initiating cells alongside a luminal majority, and the cellular response to drug administration is dominated by the distinct biology of the two cell types. Given the ability to separate basal and luminal cells, and the discovery potential of this approach, we propose that this mouse model could be a convenient one for preclinical studies.

Intestinal tumorigenesis is not affected by progesterone signaling in rodent models

Clinical data suggest that progestins have chemopreventive properties in the development of colorectal cancer. We set out to examine a potential protective effect of progestins and progesterone signaling on colon cancer development. In normal and neoplastic intestinal tissue, we found that the progesterone receptor (PR) is not expressed. Expression was confined to sporadic mesenchymal cells. To analyze the influence of systemic progesterone receptor signaling, we crossed mice that lacked the progesterone receptor (PRKO) to the Apc^Min/+ mouse, a model for spontaneous intestinal polyposis. PRKO-Apc^Min/+mice exhibited no change in polyp number, size or localization compared to Apc^Min/+. To examine effects of progestins on the intestinal epithelium that are independent of the PR, we treated mice with MPA. We found no effects of either progesterone or MPA on gross intestinal morphology or epithelial proliferation. Also, in rats treated with MPA, injection with the carcinogen azoxymethane did not result in a difference in the number or size of aberrant crypt foci, a surrogate end-point for adenoma development. We conclude that expression of the progesterone receptor is limited to cells in the intestinal mesenchyme. We did not observe any effect of progesterone receptor signaling or of progestin treatment in rodent models of intestinal tumorigenesis.

Temporal expression pattern of progesterone receptor in the uterine luminal epithelium suggests its requirement during early events of implantation

OBJECTIVE

To determine the precise timing of progesterone receptor (PR) disappearing from the uterine luminal epithelium (LE) to help understand the significance of the dynamic PR expression in the LE during embryo implantation.

DESIGN

Experimental rodent models.

SETTING

University research laboratories.

ANIMAL(S)

Mice and hamsters.

INTERVENTION(S)

Pseudopregnancy and artificial decidualization.

MAIN OUTCOME MEASURE(S)

Blue dye injection for detecting embryo attachment; immunohistochemistry, immunofluorescence, and in situ hybridization for detecting gene expression.

RESULT(S)

Progesterone receptor remained expressed in the LE up to 6 hours after the initial detection of blue dye reaction in mice (day 3, 22:00 hours), but disappeared first from LE cells at the implantation site and subsequently from the entire LE layer by day 4, 06:00 hours, when uterine stromal decidualization had become obvious. Progesterone receptor remained highly expressed in the LE of day 4 at 11:00 hours in pseudopregnant mice, but it disappeared from the entire LE layer by day 4 at 06:00 hours in artificially decidualized pseudopregnant mice.

CONCLUSION(S)

Progesterone receptor disappears from the LE after implantation has initiated and before the histologic decidualization manifests, suggesting an active role of continued PR expression in the LE for the initial implantation process. The disappearance of PR expression in the LE is regulated by uterine factor(s) produced upon embryo attachment.

Progesterone induces adult mammary stem cell expansion

Reproductive history is the strongest risk factor for breast cancer after age, genetics and breast density. Increased breast cancer risk is entwined with a greater number of ovarian hormone-dependent reproductive cycles, yet the basis for this predisposition is unknown. Mammary stem cells (MaSCs) are located within a specialized niche in the basal epithelial compartment that is under local and systemic regulation. The emerging role of MaSCs in cancer initiation warrants the study of ovarian hormones in MaSC homeostasis. Here we show that the MaSC pool increases 14-fold during maximal progesterone levels at the luteal dioestrus phase of the mouse. Stem-cell-enriched CD49fhi cells amplify at dioestrus, or with exogenous progesterone, demonstrating a key role for progesterone in propelling this expansion. In aged mice, CD49fhi cells display stasis upon cessation of the reproductive cycle. Progesterone drives a series of events where luminal cells probably provide Wnt4 and RANKL signals to basal cells which in turn respond by upregulating their cognate receptors, transcriptional targets and cell cycle markers. Our findings uncover a dynamic role for progesterone in activating adult MaSCs within the mammary stem cell niche during the reproductive cycle, where MaSCs are putative targets for cell transformation events leading to breast cancer.

The effect of elevated progesterone and pregnancy status on mRNA expression and localisation of progesterone and oestrogen receptors in the bovine uterus

To investigate the effects of pregnancy or post-ovulatory progesterone (P4) supplementation on the expression of oestrogen and P4 receptors (ESRs and PGRs) in the bovine uterus, heifers (n=263) were randomly assigned to the following treatments: i) cyclic, normal P4; ii) cyclic, high P4; iii) pregnant, normal P4; and iv) pregnant, high P4 on days 5, 7, 13 and 16 of pregnancy/oestrous cycle. Elevated P4 was achieved through P4-releasing intravaginal device insertion on day 3 after oestrus, resulting in increased concentrations from day 3.5 to 8 (P<0.05) in the high groups than in the normal groups. Irrespective of treatment, PGR and ESR1 mRNA expressions were highest on days 5 and 7 and decreased on day 13 (P<0.05), while ESR2 mRNA expression increased on day 7 (P<0.05) and similar levels were maintained within the normal P4 groups subsequently. Expression in the high P4 groups decreased on day 13 (P<0.05). PGR-AB and PGR-B protein expressions were high in the luminal and superficial glands on days 5 and 7, but by day 13, expression had declined to very low or undetectable levels and high P4 concentration tended to decrease or decreased significantly (P<0.05) the expression in these regions on days 5 and 7. ESR1 protein expression was high, with no treatment effect. ESR2 protein was also highly expressed, with no clear effect of treatment. In conclusion, early post-ovulatory P4 supplementation advances the disappearance of PGR protein from the luminal epithelium on days 5 and 7, and decreases ESR2 mRNA expression during the mid-luteal phase, but has no effect on PGR or ESR1 mRNA expression.

Progesterone action in human tissues: regulation by progesterone receptor (PR) isoform expression, nuclear positioning and coregulator expression

Progesterone is a critical regulator of normal female reproductive function, with diverse tissue-specific effects in the human. The effects of progesterone are mediated by its nuclear receptor (PR) that is expressed as two isoforms, PRA and PRB, which are virtually identical except that PRA lacks 164 amino acids that are present at the N-terminus of PRB. Considerable in vitro evidence suggests that the two PRs are functionally distinct and in animals, tissue-specific distribution patterns of PRA and PRB may account for some of the diversity of progesterone effects. In the human, PRA and PRB are equivalently expressed in most target cells, suggesting that alternative mechanisms control the diversity of progesterone actions. PR mediates the effects of progesterone by association with a range of coregulatory proteins and binding to specific target sequences in progesterone-regulated gene promoters. Ligand activation of PR results in redistribution into discrete subnuclear foci that are detectable by immunofluorescence, probably representing aggregates of multiple transcriptionally active PR-coregulator complexes. PR foci are aberrant in cancers, suggesting that the coregulator composition and number of complexes is altered. A large family of coregulators is now described and the range of proteins known to bind PR exceeds the complement required for transcriptional activation, suggesting that in the human, tissue-specific coregulator expression may modulate progesterone response. In this review, we examine the role of nuclear localization of PR, coregulator association and tissue-specific expression in modulating progesterone action in the human.

Immunocytochemical localization of sex steroid hormone receptors in normal human mammary gland

The sex steroids, estrogens, progesterone, and androgens, all play a role in mammary development and function. To precisely identify the sites of action of these steroids, we studied the localization of the estrogen receptor alpha (ERalpha) and ERbeta, the progesterone receptor A (PRA) and PRB, and androgen receptors (AR) in the normal human mammary gland. Immunocytochemical localization of ERalpha, ERbeta, PRA, PRB, and AR was performed with reduction mammoplasty specimens from premenopausal women. ERalpha, PRA, PRB, and AR were localized mostly to the inner layer of epithelial cells lining acini and intralobular ducts, as well as to myoepithelial cells scattered in the external layer of interlobular ducts. AR was also found in some stromal cells. ERbeta staining was more widespread, resulting in epithelial and myoepithelial cells being labeled in acini and ducts as well as stromal cells. These results suggest that all sex steroids can directly act on epithelial cells to modulate development and function of the human mammary gland. Estrogens and androgens can also indirectly influence epithelial cell activity by an action on stromal cells.

Does the progesterone receptor genetic polymorphism +331G/A hPR influence the risk of venous thromboembolism among postmenopausal women using hormone therapy? The ESTHER Study

Hormone therapy (HT) increases venous thromboembolism (VTE) risk among postmenopausal women. Data on the influence of steroids receptors polymorphisms on this association remain scarce. Since progesterone receptor (hPR) is expressed in human veins and specific progestogens increase VTE risk, we investigated the impact of the functional +331G/A hPR polymorphism on the association of VTE with HT. Using the data of the ESTHER study, we showed that ORs for VTE in current users of progesterone or progestins were not significantly different by hPR+331G/A genotype status. hPR polymorphism appears not to have a significant effect on VTE risk related to HT.

Overexpression of progesterone receptor A isoform in mice leads to endometrial hyperproliferation, hyperplasia and atypia

A delicate balance in estrogen and progesterone signaling through their cognate receptors is characteristic for the physiologic state of the endometrium, and a shift in receptor isotype expression can be frequently found in human endometrial pathology. In this study, using a transgenic mouse model, we examined the mechanisms whereby alterations in progesterone receptor (PR) isotype expression leads to endometrial pathology. For an experimental model, we used transgenic mice (PR-A transgenics) carrying an imbalance in the native ratio of the two PR isoforms A and B (PR-A and PR-B) through the expression of additional A form and examined their uterine phenotype under different hormonal regimens, using various criteria. Uterine epithelial cell proliferation was augmented in PR-A transgenics and was abolished by PR antagonists. In particular, proliferative response to progesterone, independent of signaling through estrogen, was enhanced. Upon continuous exposure to estradiol and progesterone, the uteri in PR-A transgenics displayed gross enlargement, endometrial hyperplasia including atypical lesions, endometritis and pelvic inflammatory disease. Imbalanced expression of the two isoforms of PR in a transgenic model reveals multiple derangements in the regulation of uterine physiology, resulting in various pathologies including hyperplasias.

Discovery of candidate genes and pathways that may help explain fertility cycle stage dependent post-resection breast cancer outcome

Breast cancer relapse and death occur more often and sooner among young pre-menopausal women. Breast cancer resected during luteal phase cures about a quarter more women than if the operation is performed during follicular phase. We have identified candidate breast cancer gene signatures that may point to the potential mechanisms of cycle stage-dependent surgical cure. We performed whole murine genome microarrays on mammary tumors resected during pre-ovulatory (diestrus, follicular) and post-ovulatory (estrus, luteal) phases of the estrous cycle with known post-surgical cure or relapse (pulmonary metastasis) outcome. A set of genes whose expressions are differentially modulated by fertility cycle stage of tumor resection and also associate with prognosis were identified. These identified genes were validated by qRT-PCR. From two independent microarray studies, we identified 90 genes in mammary tumors whose expressions change significantly (up to 100-fold) across the estrous cycle, 69 genes that are associated with cure/relapse independent of cycle stage at resection, and 24 genes that change significantly (up to 12-fold) across the estrous cycle and also associate with the outcome. The mRNA expression patterns of these 24 identified genes were 100% validated by qRT-PCR in the same samples. We have identified candidate breast cancer genes and pathways that may point to the potential mechanisms by which the post-resection breast cancer outcome is influenced by the menstrual cycle phase of cancer resection. Since human breast cancer outcome is influenced by the menstrual cycle phase of breast cancer resection, we consider this study in a mouse breast cancer model to be a proof of principle that such signatures may well exist in human premenopausal breast cancer. It remains to be determined in human breast cancer whether woman to woman and/or tumor to tumor variability will mask cycle phase dependent and outcome predictive genomic signatures in human premenopausal breast cancer. The pathways identified by these studies are potential targets for the development of peri-surgical neoadjuvant therapies, which may delay or prevent relapse by preventing dormant micrometastatic tumor cells from escaping that dormant state post-operatively.

Hormone effects on specific and global brain functions

The first demonstration of how biochemical changes in neurons in specific parts of the brain direct a complete mammalian behavior derived from the effects of estrogens in hypothalamic neurons that facilitate lordosis behavior, the primary reproductive behavior of female quadrupeds (Pfaff. Estrogens and Brain Function. 1980; Pfaff. Drive: Neurobiological and Molecular Mechanisms of Sexual Motivation. 1999). Sex behaviors depend on sexual arousal that in turn depends on a primitive function: generalized CNS arousal (Pfaff. Brain Arousal and Information Theory. 2006). Here we summarize one of the ways in which a generalized arousal transmitter, norepinephrine, can influence the electrical excitability of ventromedial hypothalamic cells in a way that will foster female sex behavior.

Krüppel-Like Factor 9 Is a Negative Regulator of Ligand-Dependent Estrogen Receptor α Signaling in Ishikawa Endometrial Adenocarcinoma Cells

Estrogen and progesterone, acting through their respective receptors and other nuclear proteins, exhibit opposing activities in target cells. We previously reported that Krüppel-like factor 9 (KLF9) cooperates with progesterone receptor (PR) to facilitate P-dependent gene transcription in uterine epithelial cells. Here we evaluated whether KLF9 may further support PR function by directly opposing estrogen receptor (ER) signaling. Using human Ishikawa endometrial epithelial cells, we showed that 17β-estradiol (E2)-dependent down-regulation of ERα expression was reversed by a small interfering RNA to KLF9. Transcription assays with the E2-sensitive 4× estrogen-responsive element-thymidine kinase-promoter-luciferase reporter gene demonstrated inhibition of ligand-dependent ERα transactivation with ectopic KLF9 expression. E2 induced PR-A/B and PR-B isoform expression in the absence of effects on KLF9 levels. Addition of KLF9 small interfering RNA augmented E2 induction of PR-A/B while abrogating that of PR-B, indicating selective E2-mediated inhibition of PR-A by KLF9. Chromatin immunoprecipitation of the ERα minimal promoter demonstrated KLF9 promotion of E2-dependent ERα association to a region containing functional GC-rich motifs. KLF9 inhibited the recruitment of the ERα coactivator specificity protein 1 (Sp1) to the PR proximal promoter region containing a half-estrogen responsive element and GC-rich sites, but had no effect on Sp1 association to the PR distal promoter region containing GC-rich sequences. In vivo association of KLF9 and Sp1, but not of ERα with KLF9 or Sp1, was observed in control and E2-treated cells. Our data identify KLF9 as a transcriptional repressor of ERα signaling and suggest that it may function at the node of PR and ER genomic pathways to influence cell proliferation.

Differential hormonal regulation and function of progesterone receptor isoforms in normal adult mouse mammary gland

In normal mouse mammary gland, the mitogenic action of progesterone (P) is mediated by two P receptor (PR) isoforms, PRA and PRB. PRA is predominantly expressed in the adult virgin, and PRB is predominantly expressed during pregnancy. To investigate hormonal regulation of PR isoform expression and isoform-specific functions in vivo, adult ovariectomized BALB/c mice were treated for 3, 5, or 10 d with estrogen (E), P, or estrogen plus progesterone (E+P). Using an immunohistochemical approach with isoform-specific antibodies, we investigated hormonal regulation of PRA and PRB and their functional roles in proliferation and morphogenesis. Significant E-induced proliferation was only observed after 5 d at the distal tips of ducts; there was no sidebranching or alveologenesis. P induced proliferation that resulted in sidebranching and alveologenesis, but E+P treatment produced more proliferation sooner and more extensive sidebranching and alveologenesis. PRA levels were increased by E and decreased by P. Increased PRB levels were induced by treatment with P or E+P and coincided with the formation of alveoli. PRA was the predominant PR isoform expressed during sidebranching, and colocalization of PRA with 5-bromo-2'-deoxyuridine revealed that proliferation of PRA-positive and -negative cells was responsible for P-induced sidebranching. PRB was the predominant PR isoform expressed during alveologenesis, and colocalization of PRB with 5-bromo-2'-deoxyuridine showed that both PRB-positive and -negative cells proliferated during alveolar expansion. These results demonstrate different hormonal regulation of PRA and PRB levels in vivo and suggest that P can induce proliferation through either PRA or PRB via direct and paracrine mechanisms.