Progesterone is critical for the development of mouse embryos

Deciphering the role of PGRMC2 in the human endometrium during the menstrual cycle and in vitro decidualization using an in vitro approach

STUDY QUESTION

What is the human endometrial non-classical progesterone receptor (PGR) membrane component 2 (PGRMC2) expression pattern throughout the menstrual cycle and what role does it play during decidualization?

SUMMARY ANSWER

Endometrial PGRMC2 expression fluctuates during the human menstrual cycle and is abundantly expressed in human endometrial stromal cells (hEnSCs) during in vitro decidualization, process where PGRMC2 is involved in embryo implantation-related pathways.

WHAT IS KNOWN ALREADY

The endometrial response to progesterone is mediated by the classical and non-classical PGRs. We previously demonstrated that PGR membrane component 1 (PGRMC1) is critical for endometrial function, embryo implantation, and future placentation, however, the role(s) of PGRMC2, which is structurally similar to PGRMC1, have not been studied in the human endometrium.

STUDY DESIGN, SIZE, DURATION

This prospective study comprehensively evaluated the endometrial expression of PGRMC2 throughout the human menstrual cycle and during in vitro decidualization of hEnSCs (isolated from 77 endometrial biopsies that were collected from 66 oocyte donors), using immunohistochemistry, RT-qPCR, western blot, transcriptomic, and proteomic analyses. In addition, functional analysis was carried out to validate the implication of PGRMC2 in hEnSCs during embryo invasion using an in vitro outgrowth model.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In vitro decidualization of hEnSCs was induced using co-treatment with cAMP and medroxyprogesterone 17-acetate progestin, and evaluated by measuring prolactin by ELISA and F-actin immunostaining. RT-qPCR was employed to compare expression with other PGRs. To reveal the function of PGRMC2 during the decidualization process, we specifically knocked down PGRMC2 with siRNAs and performed RNA-seq and quantitative proteomics techniques (SWATH-MS). The common differentially expressed genes (DEGs) and proteins (DEPs) were considered for downstream functional enrichment analysis. Finally, to verify its implication in the trophoblast invasion, an outgrowth model was carried out where hEnSCs with silenced PGRMC2 were co-cultured with human trophoblastic spheroids (JEG-3) following in vitro decidualization.

MAIN RESULTS AND THE ROLE OF CHANCE

In contrast to PGRMC1 and classical PGRs, endometrial PGRMC2 gene expression was significantly lower during the late- versus mid-secretory phase (P < 0.05). Accordingly, the elevated PGRMC2 protein abundance observed in the endometrial epithelial glands throughout the menstrual cycle dropped in the late secretory phase, when abundance decreased in all endometrial compartments. Nevertheless, PGRMC2 protein increased during the mid-secretory phase in stromal and glandular cells, and PGRMC2 mRNA (P < 0.0001) and protein (P < 0.001) levels were significantly enhanced in the membranes/organelles of decidualized hEnSCs, compared to non-decidualized hEnSCs. Notably, PGRMC1 and PGRMC2 mRNA were significantly more abundant than classical PGRs throughout menstrual cycle phases and in decidualized and non-decidualized hEnSCs (P < 0.05). RNA-seq and proteomics data revealed 4687 DEGs and 28 DEPs, respectively, in decidualized hEnSCs after PGRMC2 silencing. While functional enrichment analysis showed that the 2420 upregulated genes were mainly associated with endoplasmic reticulum function, vesicular transport, morphogenesis, angiogenesis, cell migration, and cell adhesion, the 2267 downregulated genes were associated with aerobic respiration and protein biosynthesis. The protein enrichment analysis showed that 4 upregulated and 24 downregulated proteins were related to aerobic respiration, cellular response, metabolism, localization of endoplasmic reticulum proteins, and ribonucleoside biosynthesis routes. Finally, PGRMC2 knockdown significantly compromised the ability of the decidualized hEnSCs to support trophoblast expansion in an outgrowth model (P < 0.05).

LARGE-SCALE DATA

Transcriptomic data are available via NCBI's Gene Expression Omnibus (GEO) under GEO Series accession number GSE251843 and proteomic data via ProteomeXchange with identifier PXD048494.

LIMITATIONS, REASONS FOR CAUTION

The functional analyses were limited by the discrete number of human endometrial biopsies. A larger sample size is required to further investigate the potential role(s) of PGRMC2 during embryo implantation and maintenance of pregnancy. Further, the results obtained in the present work should be taken with caution, as the use of a pure primary endometrial stromal population differentiated in vitro does not fully represent the heterogeneity of the endometrium in vivo, nor the paracrine communications occurring between the distinct endometrial cell types.

WIDER IMPLICATIONS OF THE FINDINGS

The repression of endometrial PGRMC2 during the late- versus mid-secretory phase, together with its overexpression during decidualization and multiple implications with embryo implantation not only highlighted the unknown roles of PGRMC2 in female reproduction but also the potential to exploit PGRMC2 signaling pathways to improve assisted reproduction treatments in the future.

STUDY FUNDING/COMPETING INTEREST(S)

This research was funded by Instituto de Salud Carlos III (ISCIII) granted to F.D. (PI20/00405 and PI23/00860), co-funded by the European Union. Y.M.-L. was supported by a predoctoral research grant from Generalitat Valenciana (ACIF/2019/262). R.G.-M. was supported by Generalitat Valenciana (CIAPOT/2022/15). P.d.C. was supported by a predoctoral grant for training in research into health (PFIS FI20/00086) from the Instituto de Salud Carlos III. I.D.-H. was supported by the Spanish Ministry of Science, Innovation and Universities (FPU18/01550). A.P. was supported by the Instituto de Salud Carlos III (PFIS FI18/00009). This research was also supported by IVI Foundation-RMA Global (1911-FIVI-103-FD). The authors declare no conflict of interest.

Melatonin promotes progesterone secretion in sheep luteal cells by regulating autophagy via the AMPK/mTOR pathway

The corpus luteum is primarily responsible for the production and secretion of progesterone. Melatonin has been established to regulate autophagy and induce progesterone secretion in luteal cell. However, whether melatonin affects progesterone secretion by interfering with autophagy is yet to be reported. In the present study, the expression levels of melatonin receptors (MT1 and MT2), autophagy-related protein Beclin1 (Bec1), microtubule-associated protein light chain 3 B (LC3B), progesterone and steroidogenic acute regulatory protein (StAR), and cytochrome P450scc (CYP11A1) were analyzed in the corpus luteum of sheep at different stages (early, middle, and late); specifically, enzyme-linked immunosorbent assays, immunohistochemical staining, and western blotting were utilized for this expression analysis. In addition, to determine whether melatonin regulated progesterone secretion via the regulation of autophagy, luteal cells were cultured before being exposed to different concentrations of melatonin (0.01-100 nM) and the autophagy inhibitor chloroquine (50 μM). Next, luteal cells were treated with the melatonin receptor inhibitors 4-phenyl-2-propionamidotetralin (1 μM) and luzindole (1 μM) before detecting Bec1, LC3B2, AMPK/mTOR, and progesterone secretion levels to ascertain whether the effect of melatonin on autophagy and progesterone secretion is mediated by its corresponding receptors in luteal cells. Finally, to determine the significance of the AMPK/mTOR pathway in this process, an AMPK inhibitor, Compound C (10 μM), was added to luteal cells. Overall, the highest expression of melatonin receptors, autophagy and progesterone secretion was observed in the middle-phase corpus luteum; additionally, melatonin promoted autophagy, at least partially, through its receptor-mediated AMPK/mTOR pathway, which thereby promoting progesterone secretion in luteal cells in vitro. Ultimately, this study is the first to clarify the important role of autophagy in the melatonin-mediated regulation of progesterone secretion in the corpus luteum of sheep; it also lays a foundation for further exploration into the role of melatonin in regulating sheep's ovarian function.

Galea spixii embryos have potential to produce steroid hormones

Estrogens and progestogens are hormones produced by maternal organs and it is required for recognition and maintenance of pregnancy. In addition, the embryo may also be a source. For this, the aim was to identify steroidogenic expression on Galea spixii embryos early in the embryonic period. Embryos were collected on Days 10 and 15 of gestation; some were fixed in 4% paraformaldehyde for morphological and immunohistochemical analysis (P450arom), whereas others had RNA extracted to determine presence of CYP19a1 gene. In addition, for immunochemistry, maternal ovaries were collected as positive control tissues. Maternal tissues had positive staining for aromatase, whereas none of the embryos stained for P450 aromatase. Based on qPCR reactions, CYP19a1 gene were expressed in all embryos. Galea spixii embryos expressed steroidogenic genes during the post-implantation period, indicating they have the potential to produce steroid hormones.

Progesterone Receptor Modulates Extraembryonic Mesoderm and Cardiac Progenitor Specification during Mouse Gastrulation

Progesterone treatment is commonly employed to promote and support pregnancy. While maternal tissues are the main progesterone targets in humans and mice, its receptor (PGR) is expressed in the murine embryo, questioning its function during embryonic development. Progesterone has been previously associated with murine blastocyst development. Whether it contributes to lineage specification is largely unknown. Gastrulation initiates lineage specification and generation of the progenitors contributing to all organs. Cells passing through the primitive streak (PS) will give rise to the mesoderm and endoderm. Cells emerging posteriorly will form the extraembryonic mesodermal tissues supporting embryonic growth. Cells arising anteriorly will contribute to the embryonic heart in two sets of distinct progenitors, first (FHF) and second heart field (SHF). We found that PGR is expressed in a posterior–anterior gradient in the PS of gastrulating embryos. We established in vitro differentiation systems inducing posterior (extraembryonic) and anterior (cardiac) mesoderm to unravel PGR function. We discovered that PGR specifically modulates extraembryonic and cardiac mesoderm. Overexpression experiments revealed that PGR safeguards cardiac differentiation, blocking premature SHF progenitor specification and sustaining the FHF progenitor pool. This role of PGR in heart development indicates that progesterone administration should be closely monitored in potential early-pregnancy patients undergoing infertility treatment.

Overweight and Fertility: What We Can Learn from an Intergenerational Mouse Obesity Model

The aim of this study was to evaluate the effects of being overweight on the ability to conceive, fertilization rate, and in vivo development of embryos in regularly cycling, spontaneously ovulating, and naturally mated female mice. The study was based on statistical analysis of data collected during 14 experiments with identical design, performed on 319 control and 327 obese mice, developed in an intergenerational model of obesity induction which eliminates the impact of aging and high-fat feeding. Six-week-old mice with a vaginal sperm plug were slaughtered on embryonic days 2, 3, or 4, and the flushed contents of the oviducts and uteri were assessed by stereomicroscopy. The results showed no association between being overweight and the proportion of ovulating or fertilized females. On the other hand, a strong association was found between being overweight and ovulation yield. On embryonic day 2, significantly higher numbers of eggs were recovered from the oviducts of fertilized obese mice. Maternal overweight status was also associated with higher developmental capacities of preimplantation embryos. In conclusion, contrary to studies based on the high-fat-diet model, in female mice fed regular chow, being overweight was associated with an increased ovulation quota and higher developmental rate of fertilized oocytes. Being overweight did not impact ability to conceive. On the other hand, as documented in our previous studies, the quality of oocytes and blastocysts recovered from overweight mice developed in an intergenerational model of obesity was low.

Progesterone and Inflammatory Response in the Oviduct during Physiological and Pathological Conditions

Progesterone has been shown to be a potent suppressor of several inflammatory pathways. During pregnancy, progesterone levels increase, allowing for normal pregnancy establishment and maintenance. The dysregulation of progesterone, as well as inflammation, leads to poor pregnancy outcomes. However, it is unclear how progesterone imbalance could impact inflammatory responses in the oviduct and subsequently result in early pregnancy loss. Therefore, in this review, we describe the role of progesterone signaling in regulating the inflammatory response, with a focus on the oviduct and pathological conditions in the Fallopian tubes.

Varied effects of doxorubicin (DOX) on the corpus luteum of C57BL/6 mice during early pregnancy

Certain chemotherapeutic drugs are toxic to ovarian follicles. The corpus luteum (CL) is normally developed from an ovulated follicle for producing progesterone (P4) to support early pregnancy. To fill in the knowledge gap about effects of chemotherapy on the CL, we tested the hypothesis that chemotherapy may target endothelial cells and/or luteal cells in the CL to impair CL function in P4 steroidogenesis using doxorubicin (DOX) as a representative chemotherapeutic drug in mice. In both mixed background mice and C57BL/6 mice, a single intraperitoneal injection of DOX (10 mg/kg) on 0.5 days post coitum (D0.5, post-ovulation) led to ~58% D3.5 mice with serum P4 levels lower than the serum P4 range in the PBS-treated control mice. Further studies in the C57BL/6 ovaries revealed that CLs from DOX-treated mice with low P4 levels had less defined luteal cords and disrupted collagen IV expression pattern, indicating disrupted capillary, accompanied with less differentiated luteal cells that had smaller cytoplasm and reduced StAR expression. DOX-treated ovaries had increased granulosa cell death in the growing follicles, reduced PCNA-positive endothelial cells in the CLs, enlarged lipid droplets and disrupted F-actin in the luteal cells. These novel data suggest that the proliferating endothelial cells in the developing CL may be the primary target of DOX to impair the vascular support for luteal cell differentiation and subsequently P4 steroidogenesis. This study fills in the knowledge gap about the toxic effects of chemotherapy on the CL and provides critical information for risk assessment of chemotherapy in premenopausal patients.

Effect of Exposure to Seminal Plasma Through Natural Mating in Cattle on Conceptus Length and Gene Expression

A growing body of evidence suggests that paternal factors have an impact on offspring development. These studies have been mainly carried out in mice, where seminal plasma (SP) has been shown to regulate endometrial gene expression and impact embryo development and subsequent offspring health. In cattle, infusion of SP into the uterus also induces changes in endometrial gene expression, however, evidence for an effect of SP on early embryo development is lacking. In addition, during natural mating, the bull ejaculates in the vagina; hence, it is not clear whether any SP reaches the uterus in this species. Thus, the aim of the present study was to determine whether SP exposure leads to improved early embryo survival and developmental rates in cattle. To this end, Day 7 in vitro produced blastocysts were transferred to heifers (12-15 per heifer) previously mated to vasectomized bulls (n = 13 heifers) or left unmated (n = 12 heifers; control). At Day 14, heifers were slaughtered, and conceptuses were recovered to assess size, morphology and expression of candidate genes involved in different developmental pathways. Additionally, CL volume at Day 7, and weight and volume of CL at Day 14 were recorded. No effect of SP on CL volume and weight not on conceptus recovery rate was observed. However, filamentous conceptuses recovered from SP-exposed heifers were longer in comparison to the control group and differed in expression of CALM1, CITED1, DLD, HNRNPDL, PTGS2, and TGFB3. In conclusion, data indicate that female exposure to SP during natural mating can affect conceptus development in cattle. This is probably achieved through modulation of the female reproductive environment at the time of mating.

Progesterone receptor membrane component 1 (PGRMC1)-mediated progesterone effect on preimplantation development of in vitro produced porcine embryos

Progesterone is a steroid hormone well known for its significant role in the reproduction process of mammals. Numerous studies have reported on the regulation of progesterone during implantation, pregnancy and parturition, but there are fewer studies on progesterone in relation to the early stages of embryo development. In the present study, we investigated the effects of progesterone during the development of in vitro produced porcine embryos. First, gene expression of various progesterone receptors in the in vitro produced porcine embryos were analyzed. PGRMC1 and PGRMC2 (progesterone receptor membrane component 1 and 2) showed distinct expression. Next, the embryos were treated with two concentrations of progesterone (10 nM and 100 nM) for two different durations (from day 0 and from day 4) to compare the developmental rates, cell numbers, and apoptosis rates of day 7 blastocysts. The experimental groups in both durations showed similarly increased blastocyst cell numbers and decreased apoptosis rates when treated with 100 nM progesterone. Furthermore, the expression levels of PGRMC1, PGRMC2, PAIRBP1 (plasminogen activator inhibitor RNA-binding protein 1), and apoptosis-related genes were examined in blastocysts and showed significant increases in the 100 nM treatment group compared to the control group. Subsequently, the embryos were treated with the PGRMC1 inhibitor, AG-205, and developmental rates, cell numbers, and apoptosis rates of day 7 blastocysts were compared. In addition, 100 nM progesterone was treated simultaneously with AG-205 to test if the inhibition effect is relieved by progesterone. Groups treated with 1 μM and 2 μM AG-205 showed decreased cell numbers and increased apoptosis rates in day 7 blastocysts compared to the control group. We also confirmed the recovery of inhibition by 100 nM progesterone. In conclusion, the present study indicated that progesterone positively affects the development of in vitro produced preimplantation porcine embryos by increasing cell proliferation and decreasing apoptosis via PGRMC1-involved actions. However, the detailed mechanisms of PGRMC1 need further elucidation.