Steroid metabolism and hormonal dynamics in normal and malignant ovaries

The ovaries are key steroid hormone production sites in post-pubertal females. However, current research on steroidogenic enzymes, endogenous hormone concentrations and their effects on healthy ovarian function and malignant development is limited. Here, we discuss the importance of steroid enzymes in normal and malignant ovaries, alongside hormone concentrations, receptor expression and action. Key enzymes include STS, 3β-HSD2, HSD17B1, ARK1C3, and aromatase, which influence ovarian steroidal action. Both androgen and oestrogen action, via their facilitating enzyme, drives ovarian follicle activation, development and maturation in healthy ovarian tissue. In ovarian cancer, some data suggest STS and oestrogen receptor α may be linked to aggressive forms, while various oestrogen-responsive factors may be involved in ovarian cancer metastasis. In contrast, androgen receptor expression and action vary across ovarian cancer subtypes. For future studies investigating steroidogenesis and steroidal activity in ovarian cancer, it is necessary to differentiate between disease subtypes for a comprehensive understanding.

Estradiol Signaling at the Heart of Folliculogenesis: Its Potential Deregulation in Human Ovarian Pathologies

Estradiol (E2) is a major hormone controlling women fertility, in particular folliculogenesis. This steroid, which is locally produced by granulosa cells (GC) within ovarian follicles, controls the development and selection of dominant preovulatory follicles. E2 effects rely on a complex set of nuclear and extra-nuclear signal transduction pathways principally triggered by its nuclear receptors, ERα and ERβ. These transcription factors are differentially expressed within follicles, with ERβ being the predominant ER in GC. Several ERβ splice isoforms have been identified and display specific structural features, which greatly complicates the nature of ERβ-mediated E2 signaling. This review aims at providing a concise overview of the main actions of E2 during follicular growth, maturation, and selection in human. It also describes the current understanding of the various roles of ERβ splice isoforms, especially their influence on cell fate. We finally discuss how E2 signaling deregulation could participate in two ovarian pathogeneses characterized by either a follicular arrest, as in polycystic ovary syndrome, or an excess of GC survival and proliferation, leading to granulosa cell tumors. This review emphasizes the need for further research to better understand the molecular basis of E2 signaling throughout folliculogenesis and to improve the efficiency of ovarian-related disease therapies.

Secretory products of the corpus luteum and preeclampsia

BACKGROUND

Despite significant advances in our understanding of the pathophysiology of preeclampsia (PE), there are still many unknowns and controversies in the field. Women undergoing frozen-thawed embryo transfer (FET) to a hormonally prepared endometrium have been found to have an unexpected increased risk of PE compared to women who receive embryos in a natural FET cycle. The differences in risk have been hypothesized to be related to the absence or presence of a functioning corpus luteum (CL).

OBJECTIVE AND RATIONALE

To evaluate the literature on secretory products of the CL that could be essential for a healthy pregnancy and could reduce the risk of PE in the setting of FET.

SEARCH METHODS

For this review, pertinent studies were searched in PubMed/Medline (updated June 2020) using common keywords applied in the field of assisted reproductive technologies, CL physiology and preeclampsia. We also screened the complete list of references in recent publications in English (both animal and human studies) on the topics investigated. Given the design of this work as a narrative review, no formal criteria for study selection or appraisal were utilized.

OUTCOMES

The CL is a major source of multiple factors regulating reproduction. Progesterone, estradiol, relaxin and vasoactive and angiogenic substances produced by the CL have important roles in regulating its functional lifespan and are also secreted into the circulation to act remotely during early stages of pregnancy. Beyond the known actions of progesterone and estradiol on the uterus in early pregnancy, their metabolites have angiogenic properties that may optimize implantation and placentation. Serum levels of relaxin are almost undetectable in pregnant women without a CL, which precludes some maternal cardiovascular and renal adaptations to early pregnancy. We suggest that an imbalance in steroid hormones and their metabolites and polypeptides influencing early physiologic processes such as decidualization, implantation, angiogenesis and maternal haemodynamics could contribute to the increased PE risk among women undergoing programmed FET cycles.

WIDER IMPLICATIONS

A better understanding of the critical roles of the secretory products of the CL during early pregnancy holds the promise of improving the efficacy and safety of ART based on programmed FET cycles.

Prolyl oligopeptidase regulates progesterone secretion via the ERK signaling pathway in murine luteal cells

Prolyl oligopeptidase (POP), one of the most widely distributed serine endopeptidases, is highly expressed in the ovaries. However, the physiological role of POP in the ovaries is not clear. In this study, we investigated the significance of POP in the corpus luteum. Murine luteal cells were cultured in vitro and treated with a POP selective inhibitor, (2S)-1[[(2 S)-1-(1-oxo-4-phenylbutyl)-2-pyrrolidinyl carbonyl]-2-pyrrolidinecarbonitrile (KYP-2047). We found that KYP-2047 treatment decreased progesterone secretion. In contrast, POP overexpression increased progesterone secretion. Three essential steroidogenic enzymes, including p450 cholesterol side-chain cleavage enzyme (CYP11A), 3β-hydroxysteroid dehydrogenase (3β-HSD), and the steroidogenic acute regulatory protein (StAR), were regulated by POP. Further studies showed that POP overexpression increased ERK1/2 phosphorylation and increased the expression of steroidogenic factor 1 (SF1), while KYP-2047 treatment decreased ERK1/2 phosphorylation and SF1 expression. To clarify the role of ERK1/2 signaling in POP-regulated progesterone synthesis, U0126-EtOH, an inhibitor of the ERK signaling pathway, was used to treat luteal cells. We found that U0126-EtOH decreased progesterone production and the expression of steroidogenic enzymes and SF1. POP overexpression did not reverse the effects of U0126-EtOH. Overall, POP regulates progesterone secretion by stimulating the expression of CYP11A, 3β-HSD, and StAR in luteal cells. ERK signaling and downstream SF1 expression contribute to this process.

Functional and Morphological Characterization of Small and Large Steroidogenic Luteal Cells From Domestic Cats Before and During Culture

The current study aimed to isolate, culture and characterize small (SLC) and large (LLC) steroidogenic cells from the corpora lutea (CL) of non-pregnant domestic cats. Isolation of feline SLC was based on an enzymatic digestion of luteal tissue, whereas LLC were obtained by mechanical disruption of CL. To assess function of both cell types, progesterone secretion and mRNA expression of selected genes involved in steroid and prostaglandin synthesis were measured, as well as relative transcript abundance of hormone receptors and anti-oxidative enzymes, before and during culture. The cells were cultured for 3 or 5 days without gonadotropins. Isolated feline SLC and LLC had different sizes (12 ± 3 μm vs. 34 ± 5 μm, respectively), morphologies (amount of lipid droplets) and behaved differently in culture. SLC attached and proliferated or spread quickly, but lost their steroidogenic function during culture (significant decrease in progesterone secretion and expression of steroidogenic genes). The expression of receptors for gonadotropins and prolactin also decreased. Prostaglandin synthase (PTGS2) decreased steadily over time, whereas mRNA expression of PGE2 synthase (PGES) increased. The gene expression of anti-oxidative enzyme glutathione peroxidase 4 (GPX4), also increased during culture, but not of superoxide dismutase 1 (SOD1). In comparison to SLC, LLC did not attach to culture plates, secreted more progesterone per inoculated cells and maintained steroidogenic function during culture. Expression of prostaglandin synthases (PTGS2 and PGES) was almost non-detectable. The gene expression of hormone receptors for prostaglandin F2 alpha (PTGFR), gonadotropins (LHCHR and FSHR), and prolactin (PRLR), as well as of anti-oxidative enzymes (GPX4, SOD1), increased over time. To conclude, we successfully isolated and cultured different types of feline steroidogenic luteal cells and comprehensively characterized both isolated cell types. This knowledge can be used to better understand the CL lifecycle in felines more broadly, and the established cell cultures will provide a foundation for future studies on luteolytic and luteotrophic factors in the domestic cat, and for comparison with other feline species, particularly lynx.

Daytime Variation in Serum Progesterone During the Mid-Luteal Phase in Women Undergoing In Vitro Fertilization Treatment

OBJECTIVE

To investigate whether mid-luteal serum progesterone (P₄) exhibits significant fluctuations during a 12-h daytime period in women undergoing in vitro fertilization (IVF) and to explore whether the extent of these fluctuations could impact the interpretation of luteal progesterone levels in a clinical setting.

DESIGN

Explorative pilot study.

SETTING

Public hospital-based fertility unit.

PATIENTS

Ten women undergoing IVF treatment.

INTERVENTION

Seven days after oocyte pick-up, patients underwent frequent repeated blood sampling (every 60 min for 12 h and during two of these hours, every 15 min). Serum samples were analyzed for progesterone, estradiol, and luteinizing hormone (LH).

MAIN OUTCOME MEASURES

Daytime fluctuations in s-progesterone and s-estradiol.

RESULTS

There was a significant positive correlation between median P₄ levels and the magnitude of P₄ variations-women with median P₄ < 60 nmol/l had clinically stable P₄ levels throughout the day, while patients with median P₄ > 250 nmol/l exhibited periodic P₄ peaks of several hundred nanomoles per liter. These endogenous P₄ fluctuations were observed irrespective of the type of stimulation protocol or mode of triggering of final oocyte maturation and despite the fact that LH was under the detection limit at the time of measurement. Simultaneously, large fluctuations were seen in s-estradiol.

CONCLUSION

Monitoring of early to mid-luteal P₄ levels in IVF cycles may be valuable in the planning of individualized luteal phase support in the attempt to increase reproductive outcomes. The prerequisite for luteal phase monitoring is, however, that the validity of a single measured P₄ value is reliable. We show for the first time, that a single P₄ measurement in the low progesterone patient quite accurately reflects the corpus luteum function and that the measurement can be used to detect IVF patients with a need of additional exogenous luteal P₄ administration.

Effect of steroid hormones, estrogen and progesterone, on epithelial mesenchymal transition in ovarian cancer development

As the primary female sex steroid hormones, estrogens and progesterone play important roles to regulate growth, differentiation, and function of a broad range of target tissues in the human body and maintain the function of female reproductive tissues. Ovarian cancer is the most cause of cancer death in gynecological malignancy. Despite enormous outcomes in the understanding of ovarian cancer pathology, this disease has resulted in poor survival rates since most patients are asymptomatic until the disease has been metastasized. The exact molecular events leading to metastasis of ovarian tumor cells have not yet been well elucidated, although it is recognized that the acquisition of capacity for migration and invasiveness would be a necessary prerequisite. During metastasis, epithelial-mesenchymal transition (EMT) is an important process, in which epithelial cells lose their intracellular adhesion and cell polarity and acquire increased motility and invasive properties to become mesenchymal like cells. The process of cancer cells to undergo EMT is regulated through the up- and down- regulation of a multiple cellular markers and signaling proteins. In this review, we focused the roles of women sex steroid hormones, estrogen and progesterone, in ovarian cancer, especially the ovarian cancer undergoing EMT and metastatic process. All things considered, we may suggest that progesterone is a potent hormone which inhibits the growth of human ovarian cancer cells and development to metastasis whereas estrogen may act as a risk factor of ovarian cancer progression and that progesterone therapy may be an alternative clinically effective tool for the treatment of human ovarian cancer.

Estrogen promotes luteolysis by redistributing prostaglandin F2α receptors within primate luteal cells

Prostaglandin F2α (PGF2α) has been proposed as a functional luteolysin in primates. However, administration of PGF2α or prostaglandin synthesis inhibitors in vivo both initiate luteolysis. These contradictory findings may reflect changes in PGF2α receptors (PTGFRs) or responsiveness to PGF2α at a critical point during the life span of the corpus luteum. The current study addressed this question using ovarian cells and tissues from female cynomolgus monkeys and luteinizing granulosa cells from healthy women undergoing follicle aspiration. PTGFRs were present in the cytoplasm of monkey granulosa cells, while PTGFRs were localized in the perinuclear region of large, granulosa-derived monkey luteal cells by mid-late luteal phase. A PTGFR agonist decreased progesterone production in luteal cells obtained at mid-late and late luteal phases, but did not decrease progesterone production by granulosa cells or luteal cells from younger corpora lutea. These findings are consistent with a role for perinuclear PTGFRs in functional luteolysis. This concept was explored using human luteinizing granulosa cells maintained in vitro as a model for luteal cell differentiation. In these cells, PTGFRs relocated from the cytoplasm to the perinuclear area in an estrogen- and estrogen receptor-dependent manner. Similar to our findings with monkey luteal cells, human luteinizing granulosa cells with perinuclear PTGFRs responded to a PTGFR agonist with decreased progesterone production. These data support the concept that PTGFR stimulation promotes functional luteolysis only when PTGFRs are located in the perinuclear region. Estrogen receptor-mediated relocation of PTGFRs within luteal cells may be a necessary step in the initiation of luteolysis in primates.

Differential interactions of antiretroviral agents with LXR, ER and GR nuclear receptors: potential contributing factors to adverse events

BACKGROUND AND PURPOSE

Antiretroviral (ARV) drugs activate pregnane X receptors and constitutive androstane receptors, increasing the risk of drug interactions due to altered drug metabolism and disposition. The closely related liver X receptors (LXRα/β), oestrogen receptors (ERα/β) and glucocorticoid receptor (GR) regulate many endogenous processes such as lipid/cholesterol homeostasis, cellular differentiation and inflammation. However, ARV drug activation of these nuclear receptors has not been thoroughly investigated.

EXPERIMENTAL APPROACH

The ability of an ARV drug library to activate LXRα/β, ERα/β and GR was assessed using a combined in silico and in vitro approach encompassing computational docking and molecular descriptor filtering, cell-free time-resolved fluorescence resonance energy transfer co-activator assays to assess direct binding to ligand-binding domains (LBDs), cell-based reporter assays and target gene expression.

KEY RESULTS

Direct LBD interactions with LXRα and/or LXRβ were predicted in silico and confirmed in vitro for darunavir, efavirenz, flavopiridol, maraviroc and tipranavir. Likewise, efavirenz was also predicted and confirmed as a ligand of ERα-LBD. Interestingly, atazanavir and ritonavir also activated LXRα/β in reporter assays, while tipranavir enhanced transcriptional activity of ERα. Effects on ER and LXR target gene expression were confirmed for efavirenz and tipranavir.

CONCLUSIONS AND IMPLICATIONS

There was good agreement between in silico predictions and in vitro results. However, some nuclear receptor interactions identified in vitro were probably due to allosteric effects or nuclear receptor cross-talk, rather than direct LBD binding. This study indicates that some of the adverse effects associated with ARV use may be mediated through 'off-target' effects involving nuclear receptor activation.

Glucocorticoid regulation of SLIT/ROBO tumour suppressor genes in the ovarian surface epithelium and ovarian cancer cells

The three SLIT ligands and their four ROBO receptors have fundamental roles in mammalian development by promoting apoptosis and repulsing aberrant cell migration. SLITs and ROBOs have emerged as candidate tumour suppressor genes whose expression is inhibited in a variety of epithelial tumours. We demonstrated that their expression could be negatively regulated by cortisol in normal ovarian luteal cells. We hypothesised that after ovulation the locally produced cortisol would inhibit SLIT/ROBO expression in the ovarian surface epithelium (OSE) to facilitate its repair and that this regulatory pathway was still present, and could be manipulated, in ovarian epithelial cancer cells. Here we examined the expression and regulation of the SLIT/ROBO pathway in OSE, ovarian cancer epithelial cells and ovarian tumour cell lines. Basal SLIT2, SLIT3, ROBO1, ROBO2 and ROBO4 expression was lower in primary cultures of ovarian cancer epithelial cells when compared to normal OSE (P<0.05) and in poorly differentiated SKOV-3 cells compared to the more differentiated PEO-14 cells (P<0.05). Cortisol reduced the expression of certain SLITs and ROBOs in normal OSE and PEO-14 cells (P<0.05). Furthermore blocking SLIT/ROBO activity reduced apoptosis in both PEO-14 and SKOV-3 tumour cells (P<0.05). Interestingly SLIT/ROBO expression could be increased by reducing the expression of the glucocorticoid receptor using siRNA (P<0.05). Overall our findings indicate that in the post-ovulatory phase one role of cortisol may be to temporarily inhibit SLIT/ROBO expression to facilitate regeneration of the OSE. Therefore this pathway may be a target to develop strategies to manipulate the SLIT/ROBO system in ovarian cancer.

Microarray analysis of the primate luteal transcriptome during chorionic gonadotrophin administration simulating early pregnancy

To explore chorionic gonadotrophin (CG)-regulated gene expression in the primate corpus luteum (CL), adult female rhesus macaques were treated in a model of simulated early pregnancy (SEP). Total RNA was isolated from individual CL after specific intervals of exposure (1, 3, 6 and 9 days) to recombinant hCG in vivo and hybridized to Affymetrix™ GeneChip Rhesus Macaque Genome Arrays. The mRNA levels of 1192 transcripts changed ≥2-fold [one-way ANOVA, false discovery rate (FDR) correction; P< 0.05] during SEP when compared with Day 10 untreated controls. Real-time PCR validation indicated that 15 of 17 genes matched in expression pattern between PCR and microarray. Protein levels of three genes identified as CG-sensitive, CYP19A1 (aromatase), PGRMC1 (progestin-binding protein) and STAR (steroidogenic acute regulatory protein) were quantified by western blot analysis. To further analyze global changes in gene expression induced by CG exposure, luteal gene expression was compared between SEP (rescued) and regressing CL, utilizing previously banked GeneChip data from the luteal phase of the menstrual cycle. Expression patterns and mRNA levels were analyzed between time-matched intervals. Transcripts for 7677 mRNAs differed in expression patterns ≥2-fold (one-way ANOVA, FDR correction; P< 0.05) between the hCG-exposed (SEP) CL and regressing CL. Regressed CL (at menses) were most unlike all other CL. Pathway analysis of significantly affected transcripts was performed; the pathway most impacted by CG exposure was steroid biosynthesis. Further comparisons of the genome-wide changes in luteal gene expression during CG rescue and luteolysis in the natural menstrual cycle should identify additional key regulatory pathways promoting primate fertility.

Induction of G protein-coupled estrogen receptor (GPER) and nuclear steroid hormone receptors by gonadotropins in human granulosa cells

Estradiol and progesterone mediate their actions by binding to classical nuclear receptors, estrogen receptor α (ERα) and estrogen receptor β (ERβ) and progesterone receptor A and B (PR-A and PR-B) and the non-classical G protein-coupled estrogen receptor (GPER). Several animal knock-out models have shown the importance of the receptors for growth of the oocyte and ovulation. The aim of our study was to identify GPER in human granulosa cells (GC) for the first time. Moreover, the effect of different doses of gonadotropins on estrogen and progesterone receptors in the human ovary should be investigated as follicle stimulating hormone (FSH) and luteinizing hormone (LH) are also responsible for numerous mechanisms in the ovary like induction of the steroid biosynthesis. Human GC were cultured in vitro and stimulated with different doses of recombinant human FSH or LH. Receptor expression was analyzed by immunocytochemistry and quantitative real-time RT-PCR. GPER could be identified for the first time in human GC. It could be shown that high concentrations of LH increase GPER protein expression. Furthermore FSH and LH increased ERβ, PR-A and PR-B significantly on protein level. These findings were verified for high doses of FSH and LH on mRNA level. ERα was not affected with FSH or LH. We assume that gonadotropins induce GPER, ERβ and PR in luteinized granulosa cells.

Estrogens and androgens affect human luteal cell function

OBJECTIVE

To evaluate estrogens (Es)--E2, estrone (E1), and estriol--and androgens--T and androstendione (A)-effect on P, prostaglandin (PG) F2α, PGE2, and vascular endothelial growth factor (VEGF) release and on VEGF expression in human luteal cells. To elucidate whether androgens effects were direct or mediated by their conversion in Es, an aromatase inhibitor was used. Finally, the luteal effect of the non-aromatizable dihydrotestosterone was evaluated.

DESIGN

Prospective laboratory study.

SETTING

University hospital.

PATIENT(S)

Corpora lutea (CLs) were obtained from 36 normally menstruating patients in the midluteal phase of the menstrual cycle.

INTERVENTION(S)

The human luteal cells were isolated from CLs and primary cultures were established.

MAIN OUTCOME MEASURE(S)

P and PG release were assayed by enzyme immunoassay; VEGF secretion by ELISA; VEGF messenger RNA (mRNA) expression by real-time polymerase chain reaction (PCR).

RESULT(S)

P and PGF2α secretion were decreased by Es and androgens. The VEGF release was increased by Es and androgens, whereas VEGF mRNA expression was not. The aromatase inhibitor counteracted T and A luteal effects.

CONCLUSION(S)

Both Es and androgens could participate in the regulation of human luteal function. The effect of T and A seems to be mediated by their conversion to Es, whereas for dihydrotestosterone, both direct androgenic and indirect estrogenic luteal effects could coexist.

The differential transcriptome and ontology profiles of floating and cumulus granulosa cells in stimulated human antral follicles

Communication between various ovarian cell types is a prerequisite for folliculogenesis and ovulation. In antral follicles granulosa cells divide into two distinct populations of mural and cumulus granulosa cells (CGC), enveloping the antrum and surrounding the oocyte, respectively. Both cell types, with the mural compartment in excess, contribute to the floating granulosa cell (FGC) population in the follicular fluid. The aim of this study was to compare the transcriptomes of FGC and CGC in stimulated antral follicles obtained from 19 women undergoing IVF-ICSI procedure. FGC were obtained from follicular fluid during the follicle puncture procedure and CGC were acquired after oocyte denudation for micromanipulation. Gene expression analysis was conducted using the genome-wide Affymetrix transcriptome array. The expression profile of the two granulosa cell populations varied significantly. Out of 28 869 analysed transcripts 4480 were differentially expressed (q-value < 10(-4)) and 489 showed > or =2-fold difference in the expression level with 222 genes up-regulated in FGC and 267 in CGC. The transcriptome of FGC showed higher expression of genes involved in immune response, hematological system function and organismal injury, although CGC had genes involved in protein degradation and nervous system function up-regulated. Cell-to-cell signalling and interaction pathways were noted in both cell populations. Furthermore, numerous novel transcripts that have not been previously described in follicular physiology were identified. In conclusion, our results provide a solid basis for future studies in follicular biology that will help to identify molecular markers for oocyte and embryo viability in IVF.

HCG up-regulates hypoxia inducible factor-1 alpha in luteinized granulosa cells: implications for the hormonal regulation of vascular endothelial growth factor A in the human corpus luteum

Vascular endothelial growth factor (VEGF)-dependent angiogenesis is essential for normal luteal development. Although it is believed that hypoxia is the primary inducer of VEGF, in the corpus luteum it is up-regulated by human chorionic gonadotrophin (hCG). As hypoxia-inducible factor (HIF)1A has been shown to regulate VEGFA under ligand-stimulated conditions, we hypothesized that the effect of hCG on luteal VEGFA was mediated through HIF1A. We studied the effect of hCG on VEGFA and HIF1A expression in human luteinized granulosa cells in vitro and in human corpora lutea in vivo. HCG up-regulated VEGFA (P < 0.05) and HIF1A (P < 0.001) in vitro and VEGFA (P < 0.05) and HIF1A (P < 0.05) in vivo. There was a correlation between HIF1A and VEGFA in vivo (P < 0.005) and in vitro (P < 0.05). Nuclear HIF1A in granulosa-lutein cells was highest during luteal formation and absent from the fully functional corpus luteum (P < 0.05). Both VEGFA (P < 0.001) and HIF1A (P < 0.01) were up-regulated by dibutyryl-cAMP, through a PKA pathway. Hypoxia increased VEGFA (P < 0.001) and HIF1A (P < 0.05) expression and hCG further augmented VEGFA (P < 0.001) and HIF1A (P < 0.01) under hypoxic conditions. However, progesterone increased hCG-stimulated VEGFA but had no effect on HIF1A expression. The expression of HIF1A is therefore hormonally regulated in luteal cells in vitro and in vivo and may regulate VEGFA expression under normoxic and hypoxic conditions. However, the differential effects of progesterone suggest that not all regulation of VEGFA is associated with an up-regulation of HIF1A.