Mineralocorticoid Synthesis During the Periovulatory Interval in Macaques1

New insights into the ovulatory process in the human ovary

BACKGROUND

Successful ovulation is essential for natural conception and fertility. Defects in the ovulatory process are associated with various conditions of infertility or subfertility in women. However, our understanding of the intra-ovarian biochemical mechanisms underlying this process in women has lagged compared to our understanding of animal models. This has been largely due to the limited availability of human ovarian samples that can be used to examine changes across the ovulatory period and delineate the underlying cellular/molecular mechanisms in women. Despite this challenge, steady progress has been made to improve our knowledge of the ovulatory process in women by: (i) collecting granulosa cells across the IVF interval, (ii) creating a novel approach to collecting follicular cells and tissues across the periovulatory period from normally cycling women, and (iii) developing unique in vitro models to examine the LH surge or hCG administration-induced ovulatory changes in gene expression, the regulatory mechanisms underlying the ovulatory changes, and the specific functions of the ovulatory factors.

OBJECTIVE AND RATIONALE

The objective of this review is to summarize findings generated using in vivo and in vitro models of human ovulation, with the goal of providing new insights into the mechanisms underlying the ovulatory process in women.

SEARCH METHODS

This review is based on the authors' own studies and a search of the relevant literature on human ovulation to date using PubMed search terms such as 'human ovulation EGF-signaling', 'human ovulation steroidogenesis', 'human ovulation transcription factor', 'human ovulation prostaglandin', 'human ovulation proteinase', 'human ovulation angiogenesis' 'human ovulation chemokine', 'human ovulatory disorder', 'human granulosa cell culture'. Our approach includes comparing the data from the authors' studies with the existing microarray or RNA-seq datasets generated using ovarian cells obtained throughout the ovulatory period from humans, monkeys, and mice.

OUTCOMES

Current findings from studies using in vivo and in vitro models demonstrate that the LH surge or hCG administration increases the expression of ovulatory mediators, including EGF-like factors, steroids, transcription factors, prostaglandins, proteolytic systems, and other autocrine and paracrine factors, similar to those observed in other animal models such as rodents, ruminants, and monkeys. However, the specific ovulatory factors induced, their expression pattern, and their regulatory mechanisms vary among different species. These species-specific differences stress the necessity of utilizing human samples to delineate the mechanisms underlying the ovulatory process in women.

WIDER IMPLICATIONS

The data from human ovulation in vivo and in vitro models have begun to fill the gaps in our understanding of the ovulatory process in women. Further efforts are needed to discover novel ovulatory factors. One approach to address these gaps is to improve existing in vitro models to more closely mimic in vivo ovulatory conditions in humans. This is critically important as the knowledge obtained from these human studies can be translated directly to aid in the diagnosis of ovulation-associated pathological conditions, for the development of more effective treatment to help women with anovulatory infertility or, conversely, to better manage ovulation for contraceptive purposes.

REGISTRATION NUMBER

N/A.

The intrafollicular concentrations of biologically active cortisol in women rise abruptly shortly before ovulation and follicular rupture

STUDY QUESTION

What is the temporal activity and the concentration in follicular fluid (FF) of the anti-inflammatory steroid cortisol during the ovulatory process in humans?

SUMMARY ANSWER

Intrafollicular concentrations of cortisol become massively upregulated close to ovulation concomitant with an exceptionally high biological activity securing a timely and efficient termination of inflammatory processes.

WHAT IS KNOWN ALREADY

Ovulation has been described as a local, controlled inflammatory process resulting in the degeneration of the follicle wall which facilitate oocyte extrusion. Ovulation also affects the glucocorticoid metabolism of granulosa cells (GCs) and although de novo synthesis of cortisol only occurs in the adrenal cortex, the mid-cycle surge has been shown to induce a change from high expression of HSD11B2, inactivating cortisol to cortisone, to high expression of HSD11B1 which reversibly catalyses cortisol production from cortisone. Furthermore, high concentrations of progesterone and 17OH-progesterone within follicles may cause dislodging of cortisol from cortisol binding protein (CBP) thereby activating the biological activity of cortisol.

STUDY DESIGN, SIZE, DURATION

This prospective cohort study included 50 women undergoing fertility treatment according to a standard antagonist protocol at a university hospital-affiliated fertility clinic in Denmark.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women donated FF and GCs from one follicle for research purpose aspirated at one of four time points during the process of final maturation of follicles: T = 0 h, T = 12 h, T = 17 h, T = 32 h. A second sample was collected at oocyte pick up at T = 36 h. The concentration of cortisol and cortisone together with a range of sex steroids was measured by LC-MS/MS in FF collected at the five time points mentioned above. Whole genome microarray data, validated by q-PCR analysis, was used to evaluate gene expression of CYP11B1, CYP21A2, HSD11B1, HSD11B2, and NR3C1 in GCs at the same time points.

MAIN RESULTS AND THE ROLE OF CHANCE

The concentration of cortisol was significantly increased from a few nM at 0 h to around 100-140 nM (P ≤ 0.0001) at 32-36 h, whilst cortisone was almost constant from 0 to 17 h at a concentration of between 90 and 100 nM being significantly reduced to 25-40 nM (P ≤ 0.0001) at 32-36 h. This was paralleled by a 690-fold upregulation of HSD11B1 from 0 to 12 h increasing to a more than 20.000-fold change at 36 h. HSD11B2 was quickly downregulated 15- to 20-fold after ovulation induction. Concentrations of progesterone and 17OH-progesterone increased during the ovulatory process to high levels which in essence displaces cortisol from its binding protein CBP due to similar binding affinities. Furthermore, a significant decrease in 11-deoxycortisol expression was seen, but CYP11B1 expression was below detection limit in GCs.

LIMITATIONS, REASONS FOR CAUTION

The study included women undergoing ovarian stimulation and results may differ from the natural cycle. More observations at each specific time point may have strengthened the conclusions. Furthermore, we have not been able to measure the actual active biological concentration of cortisol.

WIDER IMPLICATIONS OF THE FINDINGS

For the first time, this study collectively evaluated the temporal pattern of cortisol and cortisone concentrations during human ovulation, rendering a physiological framework for understanding potential dysregulations in the inflammatory reaction of ovulation.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by the University Hospital of Copenhagen, Rigshospitalet, and Novo Nordisk Foundation grant number NNF21OC00700556. Interreg V ÔKS through ReproUnion (www.reprounion.eu); Region Zealand Research Foundation. The funders had no role in study design, collection of data, analyses, writing of the article, or the decision to submit it for publication. The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Progesterone modulates HSD11B1-mediated cortisol production in luteinized bovine granulosa cells

Progesterone (P4) and cortisol production increase in luteinized granulosa cells (LGCs) during the periovulatory period, but their interaction is not well established. Therefore, we investigated their interaction in cultured bovine LGCs. Granulosa cells were collected from follicles of 2-5 mm in diameter and cultured in DMEM/F-12 supplemented with 10% fetal calf serum for up to 14 days. P4 production and the expression of steroidogenic acute regulatory protein (STAR), cholesterol side-chain cleavage enzyme (CYP11A1), and 3β-hydroxysteroid dehydrogenase type 1 (HSD3B1) rapidly increased until day 10 and remained high thereafter. No de novo production of cortisol from P4 was detected during the culture period. The expression of 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1), which converts cortisone to cortisol, increased dramatically on day two, decreased until day 8, and remained relatively constant. To investigate how P4 and cortisol influence each other's production, LGCs were treated with trilostane (a P4 synthesis inhibitor), nomegestrol acetate (NA, a synthetic progestogen), P4, and/or cortisol for 24 h on days 6 and 12 of culture. Trilostane suppressed P4 and STAR expression while elevating HSD11B1 and HSD3B1 expression and cortisol production. Concomitant treatment with NA or P4 dose-dependently decreased cortisol production and HSD11B1 and HSD3B1 expression but elevated STAR expression in both days 6 and 12. Conversely, cortisol treatment increased HSD11B1 and HSD3B1 expression and decreased STAR expression without influencing P4 production. These results indicate that progestogens suppress cortisol production by modulating HSD11B1 expression and that progestogens and cortisol differentially regulate STAR, HSD3B1, and HSD11B1 expression in bovine LGCs.

Dysregulation of steroid metabolome in follicular fluid links phthalate exposure to diminished ovarian reserve of childbearing-age women

The widespread use of phthalates (PAEs) has drawn increasing attention due to their endocrine disruption and reproductive toxicity, while the steroid metabolome is essential for follicular development. However, the mechanism by which PAE exposure affects ovarian reserve through the steroid metabolome remains unclear. This study recruited 264 childbearing-age women in Tianjin (China) from April 2019 to August 2020 in a cross-sectional design. Target metabolome analysis of 16 steroids was performed in follicular fluid (FF) to compare diminished ovarian reserve (DOR) against normal ovarian reserve (NOR) women and differential steroids were identified using binary logistic analyses. Further analysis of eleven PAE metabolites (mPAEs) in FF was conducted, and the retrieved oocyte number (RON) representing ovarian reserve was counted. Multiple linear regression and quantile-based g-computation (qgcomp) models were used to associate individual mPAEs and mPAE mixture with the DOR-related differential steroids in FF. Mediation analysis was used to discuss the mediating effect of DOR-related steroids on the association between mPAEs and RON. Androstenedione (A4), corticosterone (CORT), cortisol (COR) and cortisone were significantly down-regulated in FF from women with DOR. Nine mPAEs with detection frequencies greater than 60% and median concentrations of 0.02-4.86 ng/mL were incorporated into statistical models. Negative associations with COR and CORT were found for mono-ethyl phthalate (mEP), mono-(2-ethyl-5-oxohexyl) phthalate (mEOHP), and mono-2-ethylhexyl phthalate (mEHP). A positive association with cortisone was found for mEOHP, mEHP, monobutyl phthalate (mBP), and mono (2-isobutyl) phthalate (miBP). The qgcomp and mediation analyses revealed that mEP and mEOHP not only significantly contributed to the decline of COR and CORT in the mixed exposure but also indirectly reduced RON through the mediating effects of COR and CORT. In conclusion, PAE exposure may decrease ovarian reserve by downregulating COR and CORT.

From Ligands to Behavioral Outcomes: Understanding the Role of Mineralocorticoid Receptors in Brain Function

Stress is a normal response to situational pressures or demands. Exposure to stress activates the hypothalamic-pituitary-adrenal (HPA) axis and leads to the release of corticosteroids, which act in the brain via two distinct receptors: mineralocorticoid receptors (MR) and glucocorticoid receptors (GR). Persistent HPA axis overactivation or dysregulation can disrupt an individual's homeostasis, thereby contributing to an increased risk for mental illness. On the other hand, successful coping with stressful events involves adaptive and cognitive processes in the brain that render individuals more resilient to similar stressors in the future. Here we review the role of the MR in these processes, starting with an overview of the physiological structure, ligand binding, and expression of MR, and further summarizing its role in the brain, its relevance to psychiatric disorders, and related rodent studies. Given the central role of MR in cognitive and emotional functioning, and its importance as a target for promoting resilience, future research should investigate how MR modulation can be used to alleviate disturbances in emotion and behavior, as well as cognitive impairment, in patients with stress-related psychiatric disorders.

Cortisol/glucocorticoid receptor: a critical mediator of the ovulatory process and luteinization in human periovulatory follicles

STUDY QUESTION

Do cortisol/glucocorticoid receptors play an active role in the human ovary during ovulation and early luteinization?

SUMMARY ANSWER

The ovulatory hCG stimulation-induced glucocorticoid receptor signaling plays a crucial role in regulating steroidogenesis and ovulatory cascade in human periovulatory follicles.

WHAT IS KNOWN ALREADY

Previous studies reported an increase in cortisol levels in the human follicular fluid after the LH surge or ovulatory hCG administration. However, little is known about the role of cortisol/glucocorticoid receptors in the ovulatory process and luteinization in humans.

STUDY DESIGN, SIZE, DURATION

This study was an experimental prospective clinical and laboratory-based study. An in vivo experimental study was accomplished utilizing the dominant ovarian follicles from 38 premenopausal women undergoing laparoscopic sterilization. An in vitro experimental study was completed using the primary human granulosa/lutein cells (hGLC) from 26 premenopausal women undergoing IVF.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study was conducted in a private fertility clinic and academic medical centers. Dominant ovarian follicles were collected before the LH surge and at defined times after hCG administration from women undergoing laparoscopic sterilization. Primary hGLC were collected from women undergoing IVF. hGLC were treated without or with hCG in the absence or presence of RU486 (20 µM; dual antagonist for progesterone receptor and glucocorticoid receptor) or CORT125281 (50 µM; selective glucocorticoid receptor antagonist) for 12 or 36 h. The expression of genes involved in glucocorticoid receptor signaling, steroidogenesis, and ovulatory cascade was studied with RT-quantitative PCR and western blotting. The production of cortisol, corticosterone, and progesterone was assessed by hormone assay kits.

MAIN RESULTS AND THE ROLE OF CHANCE

hCG administration upregulated the expression of hydroxysteroid 11-beta dehydrogenase 1 (HSD11B1), nuclear receptor subfamily 3 group C member 1 (NR3C1), FKBP prolyl isomerase 5 (FKBP5), and FKBP prolyl isomerase 4 (FKBP4) in human ovulatory follicles and in hGLC (P < 0.05). RU486 and CORT125281 reduced hCG-induced increases in progesterone and cortisol production in hGLC. The expression of genes involved in glucocorticoid receptor signaling, steroidogenesis, and the key ovulatory process was reduced by RU486 and/or CORT125281 in hGLC.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The role of cortisol/glucocorticoid receptors demonstrated using the hGLC model may not fully reflect their physiological roles in vivo.

WIDER IMPLICATIONS OF THE FINDINGS

Successful ovulation and luteinization are essential for female fertility. Women with dysregulated cortisol levels often suffer from anovulatory infertility. Deciphering the functional role of glucocorticoid receptor signaling in human periovulatory follicles enhances our knowledge of basic ovarian physiology and may provide therapeutic insights into treating infertility in women.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by P01HD71875 (to M.J., T.E.C., and M.B.) and R01HD096077 (to M.J.) from the Foundation for the National Institutes of Health and the BTPSRF of the University of Kentucky Markey Cancer Center (P30CA177558). The authors report no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Luteinizing hormone receptor promotes angiogenesis in ovarian endothelial cells of Macaca fascicularis and Homo sapiens†

Angiogenesis within the ovarian follicle is an important component of ovulation. New capillary growth is initiated by the ovulatory surge of luteinizing hormone (LH), and angiogenesis is well underway at the time of follicle rupture. LH-stimulated follicular production of vascular growth factors has been shown to promote new capillary formation in the ovulatory follicle. The possibility that LH acts directly on ovarian endothelial cells to promote ovulatory angiogenesis has not been addressed. For these studies, ovaries containing ovulatory follicles were obtained from cynomolgus macaques and used for histological examination of ovarian vascular endothelial cells, and monkey ovarian microvascular endothelial cells (mOMECs) were enriched from ovulatory follicles for in vitro studies. mOMECs expressed LHCGR mRNA and protein, and immunostaining confirmed LHCGR protein in endothelial cells of ovulatory follicles in vivo. Human chorionic gonadotropin (hCG), a ligand for LHCGR, increased mOMEC proliferation, migration and capillary-like sprout formation in vitro. Treatment of mOMECs with hCG increased cAMP, a common intracellular signal generated by LHCGR activation. The cAMP analog dibutyryl cAMP increased mOMEC proliferation in the absence of hCG. Both the protein kinase A (PKA) inhibitor H89 and the phospholipase C (PLC) inhibitor U73122 blocked hCG-stimulated mOMEC proliferation, suggesting that multiple G-proteins may mediate LHCGR action. Human ovarian microvascular endothelial cells (hOMECs) enriched from ovarian aspirates obtained from healthy oocyte donors also expressed LHCGR. hOMECs also migrated and proliferated in response to hCG. Overall, these findings indicate that the LH surge may directly activate ovarian endothelial cells to stimulate angiogenesis of the ovulatory follicle.

MC2R/MRAP2 activation could affect bovine ovarian steroidogenesis potential after ACTH treatment

Stressors activate the hypothalamic-pituitary-adrenal (HPA) axis, reducing fertility by interfering with the mechanisms that regulate the timing of events within the follicular phase of the estrous cycle. In the HPA axis, melanocortin 2 receptor (MC2R) mediates responses to adrenocorticotropic hormone (ACTH) in concert with melanocortin receptor accessory protein 2 (MRAP2). The aims of the present study were: (1) to evaluate the effects of ACTH administered in cows in the preovulatory period on the expression of the MC2R/MRAP2 complex in the dominant follicle; and (2) to analyze the involvement of Extracellular signal Regulated Kinase 1 (ERK1) signaling in the activation of MC2R and the expression of key enzymes involved in the biosynthesis of glucocorticoids (GCs) in the dominant follicle. To this end, 100 IU ACTH was administered to Holstein cows from a local dairy farm during pro-estrus every 12 h for four days until ovariectomy, which was performed before ovulation. Protein immunostaining of MC2R was higher in the dominant follicles of ACTH-treated cows (p < 0.05). Also, Western blot analysis showed higher activation of the ERK1 signaling pathway in ACTH-treated cows (p < 0.05). Finally, immunohistochemistry performed in the dominant follicles of ACTH-treated cows detected higher expression of CYP17A1 and CYP21A2 (p < 0.05). These results suggest that the bovine ovary is able to respond locally to ACTH as a consequence of stress altering the expression of relevant steroidogenic enzymes. The results also confirm that the complete GC biosynthesis pathway is present in bovine dominant follicle and therefore GCs could be produced locally.

Hypogonadism induced by surgical stress and brain trauma is reversed by human chorionic gonadotropin in male rats: A potential therapy for surgical and TBI-induced hypogonadism?

INTRODUCTION

Hypogonadotropic hypogonadism (HH) is an almost universal, yet underappreciated, endocrinological complication of traumatic brain injury (TBI). The goal of this study was to determine whether the developmental hormone human chorionic gonadotropin (hCG) treatment could reverse HH induced by a TBI.

METHODS

Plasma samples were collected at post-surgery/post-injury (PSD/PID) days -10, 1, 11, 19 and 29 from male Sprague-Dawley rats (5- to 6-month-old) that had undergone a Sham surgery (craniectomy alone) or CCI injury (craniectomy + bilateral moderate-to-severe CCI injury) and treatment with saline or hCG (400 IU/kg; i.m.) every other day.

RESULTS

Both Sham and CCI injury significantly decreased circulating testosterone (T), 11-deoxycorticosterone (11-DOC) and corticosterone concentrations to a similar extent (79.1% vs. 80.0%; 46.6% vs. 48.4%; 56.2% vs. 32.5%; respectively) by PSD/PID 1. hCG treatment  returned circulating T to baseline concentrations by PSD/PID 1 (8.9 ± 1.5 ng/ml and 8.3 ± 1.9 ng/ml; respectively) and was maintained through PSD/PID 29. hCG treatment significantly, but transiently, increased circulating progesterone (P4) ~3-fold (30.2 ± 10.5 ng/ml and 24.2 ± 5.8 ng/ml) above that of baseline concentrations on PSD 1 and PID 1, respectively. hCG treatment did not reverse hypoadrenalism following either procedure.

CONCLUSIONS

Together, these data indicate that (1) craniectomy is sufficient to induce persistent hypogonadism and hypoadrenalism, (2) hCG can reverse hypogonadism induced by a craniectomy or craniectomy +CCI injury, suggesting that (3) craniectomy and CCI injury induce a persistent hypogonadism by decreasing hypothalamic and/or pituitary function rather than testicular function in male rats. The potential role of hCG as a cheap, safe and readily available treatment for reversing surgery or TBI-induced hypogonadism is discussed.

Metabolomics analysis of follicular fluid coupled with oocyte aspiration reveals importance of glucocorticoids in primate periovulatory follicle competency

Gonadotropin administration during infertility treatment stimulates the growth and development of multiple ovarian follicles, yielding heterogeneous oocytes with variable capacity for fertilization, cleavage, and blastocyst formation. To determine how the intrafollicular environment affects oocyte competency, 74 individual rhesus macaque follicles were aspirated and the corresponding oocytes classified as failed to cleave, cleaved but arrested prior to blastulation, or those that formed blastocysts following in vitro fertilization. Metabolomics analysis of the follicular fluid (FF) identified 60 unique metabolites that were significantly different between embryo classifications, of which a notable increase in the intrafollicular ratio of cortisol to cortisone was observed in the blastocyst group. Immunolocalization of the glucocorticoid receptor (GR, NR3C1) revealed translocation from the cytoplasm to nucleus with oocyte maturation in vitro and, correlation to intrafollicular expression of the 11-hydroxy steroid dehydrogenases that interconvert these glucocorticoids was detected upon an ovulatory stimulus in vivo. While NR3C1 knockdown in oocytes had no effect on their maturation or fertilization, expansion of the associated cumulus granulosa cells was inhibited. Our findings indicate an important role for NR3C1 in the regulation of follicular processes via paracrine signaling. Further studies are required to define the means through which the FF cortisol:cortisone ratio determines oocyte competency.

Nuclear receptors: Key regulators of somatic cell functions in the ovulatory process

The development of the ovarian follicle to its culmination by ovulation is an essential element of fertility. The final stages of ovarian follicular growth are characterized by granulosa cell proliferation and differentiation, and steroid synthesis under the influence of follicle-stimulating hormone (FSH). The result is a population of granulosa cells poised to respond to the ovulatory surge of luteinizing hormone (LH). Members of the nuclear receptor superfamily of transcription factors play indispensable roles in the regulation of these events. The key regulators of the final stages of follicular growth that precede ovulation from this family include the estrogen receptor beta (ESR2) and the androgen receptor (AR), with additional roles for others, including steroidogenic factor-1 (SF-1) and liver receptor homolog-1 (LRH-1). Following the LH surge, the mural and cumulus granulosa cells undergo rapid changes that result in expansion of the cumulus layer, and a shift in ovarian steroid hormone biosynthesis from estradiol to progesterone production. The nuclear receptor best associated with these events is LRH-1. Inadequate cumulus expansion is also observed in the absence of AR and ESR2, but not the progesterone receptor (PGR). The terminal stages of ovulation are regulated by PGR, which increases the abundance of the proteases that are directly responsible for rupture. It further regulates the prostaglandins and cytokines associated with the inflammatory-like characteristics of ovulation. LRH-1 regulates PGR, and is also a key regulator of steroidogenesis, cellular proliferation, and cellular migration, and cytoskeletal remodeling. In summary, nuclear receptors are among the panoply of transcriptional regulators with roles in ovulation, and several are necessary for normal ovarian function.

Aldosterone enhances progesterone biosynthesis regulated by bone morphogenetic protein in rat granulosa cells

Aldosterone (Aldo) is involved in various cardiovascular diseases such as hypertension and heart failure. Aldo levels are known to be increased in patients with polycystic ovary syndrome, and expression of the mineralocorticoid receptor (MR) has also been detected in the ovary. However, the effect of Aldo on reproductive function has yet to be elucidated. Here, we examined the effects of Aldo on follicular steroidogenesis using primary culture of rat granulosa cells by focusing on the ovarian bone morphogenetic protein (BMP) system acting as a luteinizing inhibitor. We found that Aldo treatment increased FSH-induced progesterone production in a concentration-responsive manner. Consistent with the effects on steroidogenesis, Aldo increased mRNA levels of progesterogenic factor and enzymes including StAR and P450scc, whereas Aldo failed to change FSH-induced estradiol and cAMP synthesis or P450arom expression by granulosa cells. Progesterone production and StAR expression induced by FSH and Aldo were reversed by co-treatment with spironolactone, suggesting the involvement of geonomic MR action. Aldo treatment attenuated Smad1/5/9 phosphorylation and Id1 transcription induced by BMP-6. Furthermore, Aldo enhanced the expression of inhibitory Smad6 in the presence of BMP-6. In addition, BMP-6 downregulated MR expression, while Aldo modulated the mRNA levels of endogenous BMP-6 and BMP type-II receptors, indicating the existence of a feedback loop between the BMP system and MR in granulosa cells. 　Collectively, the results indicated that Aldo predominantly enhances FSH-induced progesterone production by inhibiting BMP-Smad signaling, suggesting a novel role of Aldo in ovarian steroidogenesis and a functional link between MR and BMP pathways in granulosa cells.

Expression of genes encoding mineralocorticoid biosynthetic enzymes and the mineralocorticoid receptor, and levels of mineralocorticoids in the bovine follicle and corpus luteum

Unlike sex steroids, mineralocorticoids have attracted limited attention in ovarian physiology. Recent studies on primates have indicated possible local synthesis and action of mineralocorticoids in the ovary. Here, we examined developmental changes in the levels of mineralocorticoids and expression of genes encoding their biosynthetic enzymes and receptor in the bovine ovary. The follicles and corpora lutea (CL) were collected from F1 heifers. Expression levels of 21α-hydroxylase (CYP21A2), 11β-hydroxylase-1 (CYP11B1), and the mineralocorticoid receptor (NR3C2) in granulosa cells (GC), thecal layers (TL), and CL tissues were quantified by real-time PCR, whereas mineralocorticoids in the follicular fluid were measured by enzyme immunoassay (EIA). TL and GC expressed CYP21A2 and NR3C2, whereas CYP11B1 was expressed at very low or undetectable levels. The expression levels of these genes were not significantly different among small/large and healthy/atretic follicles but were higher in TL than in GC. CYP21A2 and NR3C2 were expressed in all CL stages with higher expression observed in the mid-stage. CYP11B1 expression was only apparent in the mid-stage CL. Aldosterone was detected in all follicles, and its concentration was not significantly different among the follicular groups. In paired large-healthy/atretic follicles, the concentration of deoxycorticosterone, a precursor of aldosterone, was approximately ten-fold higher than that of aldosterone and not significantly different between healthy and atretic follicles. In conclusion, the presence of mineralocorticoids and expression of NR3C2 in the bovine follicle together with the developmental change in the expression of CYP21A2, CYP11B1, and NR3C2 in the CL suggest possible endocrine/paracrine/autocrine roles of mineralocorticoids in the bovine ovary.

Human granulosa cells function as innate immune cells executing an inflammatory reaction during ovulation: a microarray analysis

Ovulation has been compared to a local inflammatory reaction. We performed an in silico study on a unique, PCR validated, transcriptome microarray study to evaluate if known inflammatory mechanisms operate during ovulation. The granulosa cells were obtained in paired samples at two different time points during ovulation (just before and 36 hours after ovulation induction) from nine women receiving fertility treatment. A total of 259 genes related to inflammation became significantly upregulated during ovulation (2-80 fold, p<0.05), while specific leukocyte markers were absent. The genes and pathway analysis indicated NF-KB-, MAPK- and JAK/STAT signalling (p<1.0E-10) as the major pathways involved in danger recognition and cytokine signalling to initiate inflammation. Upregulated genes further encoded enzymes in eicosanoid production, chemo-attractants, coagulation factors, cell proliferation factors involved in tissue repair, and anti-inflammatory factors to resolve the inflammation again. We conclude that granulosa cells, without involvement from the innate immune system, can orchestrate ovulation as a complete sterile inflammatory reaction.

Ovulation: Parallels With Inflammatory Processes

The midcycle surge of LH sets in motion interconnected networks of signaling cascades to bring about rupture of the follicle and release of the oocyte during ovulation. Many mediators of these LH-induced signaling cascades are associated with inflammation, leading to the postulate that ovulation is similar to an inflammatory response. First responders to the LH surge are granulosa and theca cells, which produce steroids, prostaglandins, chemokines, and cytokines, which are also mediators of inflammatory processes. These mediators, in turn, activate both nonimmune ovarian cells as well as resident immune cells within the ovary; additional immune cells are also attracted to the ovary. Collectively, these cells regulate proteolytic pathways to reorganize the follicular stroma, disrupt the granulosa cell basal lamina, and facilitate invasion of vascular endothelial cells. LH-induced mediators initiate cumulus expansion and cumulus oocyte complex detachment, whereas the follicular apex undergoes extensive extracellular matrix remodeling and a loss of the surface epithelium. The remainder of the follicle undergoes rapid angiogenesis and functional differentiation of granulosa and theca cells. Ultimately, these functional and structural changes culminate in follicular rupture and oocyte release. Throughout the ovulatory process, the importance of inflammatory responses is highlighted by the commonalities and similarities between many of these events associated with ovulation and inflammation. However, ovulation includes processes that are distinct from inflammation, such as regulation of steroid action, oocyte maturation, and the eventual release of the oocyte. This review focuses on the commonalities between inflammatory responses and the process of ovulation.

Detection and activity of 11 beta hydroxylase (CYP11B1) in the bovine ovary

Glucocorticoids (GCs) such as cortisol and corticosterone are important steroid hormones with different functions in intermediate metabolism, development, cell differentiation, immune response and reproduction. In response to physiological and immunological stress, adrenocorticotropic hormone (ACTH) acts on the adrenal gland by stimulating the synthesis and secretion of GCs. However, there is increasing evidence that GCs may also be synthesized by extra-adrenal tissues. Here, we examined the gene and protein expression of the enzyme 11β-hydroxylase P450c11 (CYP11B1), involved in the conversion of 11-deoxycortisol to cortisol, in the different components of the bovine ovary and determined the functionality of CYP11B1in vitro.CYP11B1mRNA was expressed in granulosa and theca cells in small, medium and large antral ovarian follicles, and CYP11B1 protein was expressed in medium and large antral follicles. After stimulation by ACTH, we observed an increased secretion of cortisol by the wall of large antral follicles. We also observed a concentration-dependent decrease in the concentration of cortisol in response to metyrapone, an inhibitor of CYP11B1. This decrease was significant at 10−5 µM metyrapone. In conclusion, this study demonstrated for the first time the presence of CYP11B1 in the bovine ovary. This confirms that there could be a local synthesis of GCs in the bovine ovary and therefore a potential endocrine responder to stress through these hormones.

11-Ketotestosterone Is a Major Androgen Produced in Human Gonads

CONTEXT

11-ketotestosterone (11-KT) is a novel class of active androgen. However, the detail of its synthesis remains unknown for humans.

OBJECTIVE

The objective of this study was to clarify the production and properties of 11-KT in human. Design, Participants, and Methods: Expression of cytochrome P450 and 11β-hydroxysteroid dehydrogenase types 1 and 2 (key enzymes involved in the synthesis of 11-KT) were investigated in human gonads. The production of 11-KT was investigated in Leydig cells. Plasma concentrations of testosterone and 11-KT were measured in 10 women and 10 men of reproductive age. Investigation of its properties was performed using breast cancer-derived MCF-7 cells.

RESULTS

Cytochrome P450 and 11β-hydroxysteroid dehydrogenase types 1 and 2 were detected in Leydig cells and theca cells. Leydig cells produced 11-KT, and relatively high levels of plasma 11-KT were measured in both men and women. There was no sexual dimorphism in the plasma levels of 11-KT, even though testosterone levels were more than 20 times higher in men than in women. It is noteworthy that the levels of testosterone and 11-KT were similar in women. In a luciferase reporter system, 11-KT activated human androgen receptor-mediated transactivation. Conversely, 11-KT did not activate estrogen receptor-mediated transactivation in aromatase-expressed MCF-7 cells, whereas testosterone did following conversion to estrogen. 11-KT did not affect the estrogen/estrogen receptor -mediated cell proliferation of MCF-7 cells. Furthermore, it significantly inhibited cell proliferation when androgen receptor was transfected into MCF-7 cells.

CONCLUSIONS

The current study indicates that 11-KT is produced in the gonads and represents a major androgen in human. It can potentially serve as a nonaromatizable androgen.

Glucocorticoid metabolism in the bovine cumulus-oocyte complex matured in vitro

Glucocorticoid action in target organs is regulated by relative activities of 11β-HSD type 1 (HSD11B1) that mainly converts cortisone to active cortisol and type 2 (HSD11B2) that inactivates cortisol to cortisone. HSD11Bs have been shown to be expressed in the ovary of various species. However, little is known about the expression and activity of HSD11Bs in the bovine cumulus-oocyte complex (COC). In the present study, we investigated the expression and activities of HSD11Bs in in vitro-matured (IVM) bovine COCs. Bovine COCs were matured in M199 supplemented with or without FSH and FCS. The expression of HSD11B1 and HSD11B2 was measured by using quantitative RT-PCR in denuded oocytes (DO) and cumulus cells (CC). Reductive and oxidative activities of HSD11Bs were determined by radiometric conversion assay using labeled cortisol, cortisone or dexamethasone in intact COCs, DO or CC in the presence or absence of 11-keto-progesterone (11kP), a selective inhibitor of HSD11B2. The presence of HSD11Bs in the oocyte was examined by immunofluorescence microscopy. Oocytes exclusively expressed HSD11B2 and its expression and activity were largely unchanged during IVM. CC, on the other hand, exclusively expressed HSD11B1 and its expression and activity were upregulated as IVM progressed. As a result, the net glucocorticoid metabolism shifted from inactivation to activation towards the end of IVM. These results indicate that the bovine COC is capable of modulating local glucocorticoid concentration and, by doing so, may create an environment that is favorable to ovulating oocyte for maturation, fertilization and subsequent development.

Altered theca and cumulus oocyte complex gene expression, follicular arrest and reduced fertility in cows with dominant follicle follicular fluid androgen excess

Aspiration of bovine follicles 12-36 hours after induced corpus luteum lysis serendipitously identified two populations of cows, one with High androstenedione (A4; >40 ng/ml; mean = 102) and another with Low A4 (<20 ng/ml; mean = 9) in follicular fluid. We hypothesized that the steroid excess in follicular fluid of dominant follicles in High A4 cows would result in reduced fertility through altered follicle development and oocyte maternal RNA abundance. To test this hypothesis, estrous cycles of cows were synchronized and ovariectomy was performed 36 hours later. HPLC MS/MS analysis of follicular fluid showed increased dehydroepiandrosterone (6-fold), A4 (158-fold) and testosterone (31-fold) in the dominant follicle of High A4 cows. However, estrone (3-fold) and estradiol (2-fold) concentrations were only slightly elevated, suggesting a possible inefficiency in androgen to estrogen conversion in High A4 cows. Theca cell mRNA expression of LHCGR, GATA6, CYP11A1, and CYP17A1 was greater in High A4 cows. Furthermore, abundance of ZAR1 was decreased 10-fold in cumulus oocyte complexes from High A4 cows, whereas NLRP5 abundance tended to be 19.8-fold greater (P = 0.07). There was a tendency for reduction in stage 4 follicles in ovarian cortex samples from High A4 cows suggesting that progression to antral stages were impaired. High A4 cows tended (P<0.07) to have a 17% reduction in calving rate compared with Low A4 cows suggesting reduced fertility in the High A4 population. These data suggest that the dominant follicle environment of High A4 cows including reduced estrogen conversion and androgen excess contributes to infertility in part through altered follicular and oocyte development.

21-Hydroxylase-derived steroids in follicles of nonobese women undergoing ovarian stimulation for in vitro fertilization (IVF) positively correlate with lipid content of luteinized granulosa cells (LGCs) as a source of cholesterol for steroid synthesis

CONTEXT

Mineralocorticoid synthesis by the nonhuman primate periovulatory follicle enhances luteinization. Whether a similar event occurs in women undergoing in vitro fertilization (IVF) is unknown.

OBJECTIVE

The objective of the study was to determine whether human luteinized granulosa cells (LGCs) produce mineralocorticoids derived from 21-hydroxylase activity and also express mRNA for 21-hydroxylase and the mineralocorticoid receptor.

DESIGN

This was a prospective cohort study.

SETTING

The study was conducted at an academic center.

PATIENTS

LGC lipid content and follicle fluid (FF) hormone analysis was performed on 27 nonobese IVF women. LGCs from six additional nonobese IVF women were used for gene expression studies.

INTERVENTION

At oocyte retrieval, FF was aspirated from the first follicle (≥16 mm in size) of each ovary and pooled LGCs were collected.

MAIN OUTCOME MEASURES

FF steroid analysis was performed by liquid chromatography-tandem mass spectrometry. LGCs were stained with lipid fluorescent dye BODIPY FL C16 to estimate lipid content by confocal microscopy as a cholesterol source for steroidogenesis in vivo. Quantitative real-time PCR was performed using LGCs to detect 21-hydroxylase and mineralocorticoid receptor mRNA expression. Pearson correlation coefficients determined associations between FF steroid levels and LGC lipid content.

RESULTS

FF levels of the 21-hydroxylase-derived steroids, 11-deoxycorticosterone [DOC, 39.97, median (13.94-63.02) ng/mL] and 11-deoxycortisol [11DOC, 2.07 (0.69-5.01) ng/mL], along with the 21-hydroxylase precursor 17-hydroxyprogesterone [1268.21 (493.26-3558.39) ng/mL], positively correlated with LGC lipid content (84 ± 43 fluorescent units/sample) (P ≤ .05, all steroids). 21-Hydroxylase and mineralocorticoid receptor mRNA expression was detected in LGCs.

CONCLUSIONS

Human LGCs likely synthesize 21-hydroxylase-derived mineralocorticoids from cholesterol-containing lipid in vivo to promote postovulatory luteinization via mineralocorticoid receptor-mediated events.

Identification of new ovulation-related genes in humans by comparing the transcriptome of granulosa cells before and after ovulation triggering in the same controlled ovarian stimulation cycle

STUDY QUESTION

Which genes and molecular mechanisms are involved in the human ovulatory cascade and final oocyte maturation?

SUMMARY ANSWER

Up-regulated genes in granulosa cells (GC) represented inflammation, angiogenesis, extracellular matrix, growth factors and genes previously associated with ovarian cancer, while down-regulated genes mainly represented cell cycle and proliferation.

WHAT IS KNOWN ALREADY

Radical changes occur in the follicle during final follicle maturation after the ovulatory trigger: these range from ensuring an optimal milieu for the oocyte in meiotic arrest to the release of a mature oocyte and remodeling into a corpus luteum. A wide range of mediators of final follicle maturation has been identified in rodents, non-human primates and cows.

STUDY DESIGN, SIZE, DURATION

Prospective cohort study including 24 women undergoing ovarian stimulation with the long gonadotrophin-releasing hormone agonist protocol during 2010-2012 at Holbæk Fertility Clinic. Nine paired samples of GC and 24 paired samples of follicular fluid (FF) were obtained before and after recombinant human chorionic gonadotrophin (rhCG) administration.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Nine paired (nine arrays before rhCG and nine arrays after rhCG) samples of GC mRNA were amplified and hybridized to Affymetrix Human Gene 1.0 ST GeneChip arrays, compared and bioinformatically analyzed. Eleven selected genes were validated by quantitative reverse transcriptase PCR. FF hormones were analyzed by enzyme-linked immunosorbent assay.

MAIN RESULTS AND THE ROLE OF CHANCE

Eleven hundred and eighty-six genes were differentially expressed (>2-fold, P<0.0001, false discovery rate <0.0012) when comparing GC isolated before and 36 h after hCG, among those were genes known to be expressed at ovulation, i.e. ADAMTS1 and HAS2. Many new ovulation-related genes were revealed, such as CD24, ANKRD22, CLDN11 and FBXO32. FF estrogen, androstenedione and anti-Müllerian hormone decreased significantly while progesterone increased, accompanied by radical changes in the expression of steroidogenic genes (CYP17A, CYP19A, HSD11B1 and HSD11B2, StAR). Genes related to inflammation, angiogenesis, extracellular matrix formation, growth factors and cancer were up-regulated while cell cycle genes were massively down-regulated. Seventy-two genes previously described in connection with ovarian cancer were among the highly regulated genes. In silico analysis for top upstream regulators of the ovulatory trigger suggested--besides LH--TNF, IGF1, PGR, AR, EGR1 (early growth response 1), ERK1/2 (extracellular signal regulated kinase 1/2) and CDKN1A (cyclin-dependent kinase inhibitor 1A) as potential mediators of the LH/hCG response.

LIMITATIONS, REASONS FOR CAUTION

The present dataset was generated from women under hormonal stimulation. However, comparison with a macaque natural cycle whole follicle ovulation dataset revealed major overlap, supporting the idea that the ovulation-related genes found in this study are relevant in the human natural cycle.

WIDER IMPLICATIONS OF THE FINDINGS

These data will serve as a research resource for genes involved in human ovulation and final oocyte maturation. Ovulation-related genes might be good candidate biomarkers of follicle and oocyte health. Further, some of the ovulation-related genes may serve as future ovarian cancer biomarkers.

STUDY FUNDING/COMPETING INTEREST(S)

Grants from the Research Fund of Region Sjælland are gratefully acknowledged. None of the authors declared any conflict of interest.

TRIAL REGISTRATION NUMBER

Not applicable.

Prostate androgen-regulated mucin-like protein 1: a novel regulator of progesterone metabolism

The LH surge reprograms preovulatory follicular cells to become terminally differentiated luteal cells which produce high levels of progesterone and become resistant to apoptosis. PARM1 (prostate androgen regulated mucin-like protein 1) has been implicated in cell differentiation and cell survival in nonovarian cells, but little is known about PARM1 in the ovary. This study demonstrated that the LH surge induced a dramatic increase in Parm1 expression in periovulatory follicles and newly forming CL in both cycling and immature rat models. We further demonstrated that hCG increases Parm1 expression in granulosa cell cultures. The in vitro up-regulation of Parm1 expression was mediated by hCG-activated multiple signaling pathways and transcriptional activation of this gene. Parm1 knockdown increased the viability of cultured granulosa cells but resulted in a decrease in progesterone levels. The inhibitory effect of Parm1 silencing on progesterone was reversed by adenoviral mediated add-back expression of Parm1. Parm1 silencing had little effect on the expression of genes involved in progesterone biosynthesis and metabolism such as Scarb1, Ldlr, Vldlr, Scp2, Star, Cyp11a1, Hsd3b, and Srd5a1, while decreasing the expression of Akr1c3. Analyses of culture media steroid levels revealed that Parm1 knockdown had no effect on pregnenolone levels, while resulting in time-dependent decreases in progesterone and 20α-dihydroprogesterone and accelerated accumulation of 5α-pregnanediol. This study revealed that the up-regulation of Parm1 expression promotes progesterone and 20α-dihydroprogesterone accumulation in luteinizing granulosa cells by inhibiting progesterone catabolism to 5α-pregnanediol. PARM1 contributes to ovulation and/or luteal function by acting as a novel regulator of progesterone metabolism.

Follicle growth, ovulation, and luteal formation in primates and rodents: A comparative perspective

Ovarian function has a great deal of functional overlap between species; antral follicles grow in response to FSH, ovulation involves proteolysis, and the steroidogenic pathway is largely the same. However, embedded in these similarities are important differences that reflect the evolutionary and natural history of species and may focus future research into these critical areas. This review compares ovarian function of rats and mice with primates, focusing on estradiol and follicle growth, steroidogenesis and rupture during the periovulatory interval, and the formation of a functional corpus luteum, drawing the conclusion that careful comparison of species yields more functional information about both than studying them in isolation.

Mechanisms of ligand specificity of the mineralocorticoid receptor

The mineralocorticoid receptor (MR) differs from the other steroid receptors in that it responds to two physiological ligands, aldosterone and cortisol. In epithelial tissues, aldosterone selectivity is determined by the activity of 11β-hydroxysteroid dehydrogenase type 2, while in other tissues, including the heart and regions of the central nervous system, cortisol is the primary ligand for the MR where it may act as an antagonist. Clinical trials have demonstrated the potential of MR antagonists in the treatment of cardiovascular disease, though their use has been limited by concurrent hyperkalaemia. In order to better target the MR, an understanding of the structural determinants of tissue- and ligand-specific MR activation is needed. Interactions of the MR have been identified, which exhibit ligand discrimination and/or specificity. These interactions include those of the ligand-binding domain with ligand, with the N-terminal domain and with putative co-regulatory molecules. Agonist and antagonist binding have been characterised using chimeras between the human MR and the glucocorticoid receptor or the zebra fish MR together with molecular modelling. The interaction between the N-terminus and the C-terminus is aldosterone dependent but is unexpectedly antagonised by cortisol and deoxycorticosterone in the human MR. Nuclear receptor-mediated transactivation is critically dependent on, and modulated by, co-regulatory molecules. Proteins that interact with the MR in the presence of either aldosterone or cortisol, but not both, have been identified. The successful identification of ligand-specific interactions of the MR may provide the basis for the development of novel MR ligands with tissue specificity.

The mislabelling of deoxycorticosterone: making sense of corticosteroid structure and function

Over the 70 or so years since their discovery, there has been continuous interest and activity in the field of corticosteroid functions. However, despite major advances in the characterisation of receptors and coregulators, in some ways we still lack clear insight into the mechanism of receptor activation, and, in particular, the relationship between steroid hormone structure and function remains obscure. Thus, why should deoxycorticosterone (DOC) reportedly be a weak mineralocorticoid, while the addition of an 11β-hydroxyl group produces glucocorticoid activity, yet further hydroxylation at C18 leads to the most potent mineralocorticoid, aldosterone? This review aims to show that the field has been confused by the misreading of the earlier literature and that DOC, far from being relatively inactive, in fact has a wide range of activities not shared by the other corticoids. In contrast to the accepted view, the presence of an 11β-hydroxyl group yields, in corticosterone or cortisol, hormones with more limited functions, and also more readily regulated, by 11β-hydroxysteroid dehydrogenase. This interpretation leads to a more systematic understanding of structure-function relationships in the corticosteroids and may assist more rational drug design.

Dynamics of intra-follicular glucose during luteinization of macaque ovarian follicles

Glucose is important to the maturation of the oocyte and development of the embryo, while hyperglycemia results in profound reproductive and developmental consequences. However, the normal physiology of glucose in the ovary remains poorly understood. The goal of this study was to determine intra-follicular glucose dynamics during the periovulatory interval in non-human primates undergoing controlled ovarian stimulation protocols. Follicular fluid and mural granulosa cells were isolated before or up to 24h after an ovulatory hCG bolus, and the human granulosa-lutein cell line hGL5 was used. Intra-follicular glucose increased 3h after hCG, and remained at that level until 12h when levels decline back to pre-hCG concentrations. Pyruvate and lactate concentrations in the follicle were not strongly altered by hCG. Mural granulosa cell expression of hexokinase 1 and 2, and glucose-6-phosphate dehydrogenase mRNA decreased following hCG, while glycogen phosphorylase (liver form) increased following hCG. Glucose uptake by hGL5 cells was delayed until 24h following stimulation. In summary, intra-follicular glucose increases following an ovulatory stimulus and mural granulosa cells do not appear able to utilize it, sparing the glucose for the cumulus-oocyte complex.

hCG-induced down-regulation of PPARγ and liver X receptors promotes periovulatory progesterone synthesis by macaque granulosa cells

An ovulatory stimulus induces the rapid and dramatic increase in progesterone synthesis by the primate ovarian follicle. However, little is known about the early events leading to the shift from estrogen to progesterone production. Because steroidogenesis represents an aspect of cholesterol metabolism, it was hypothesized that transcription factors regulating cholesterol balance would be among the earliest to change in response to an ovulatory stimulus. Granulosa cells were isolated from rhesus monkey follicles following controlled ovarian stimulation protocols before or up to 24 hr after an ovulatory human chorionic gonadotropin (hCG) bolus. The peroxisome proliferator-activated receptor-γ (PPARG) and the liver X receptors [nuclear receptor (NR)1H2, NR1H3] decreased within 3 hr of hCG, as did the reverse cholesterol transporters ATP-binding cassette (ABC)A1 and ABCG1. Treatment of granulosa cells isolated before an ovulatory stimulus with hCG and rosiglitizone resulted in an increase in NR1H3 and ABCG1, and decreased steroidogenic acute regulatory (STAR) protein and scavenger receptor-BI (SCARB1). A liver X receptor agonist attenuated hCG-induced progesterone synthesis in vitro and increased the expression of ABCA1 and ABCG1, and suppressed STAR, P450 side-chain cleavage A1, hydroxysteroid dehydrogenase 3B, and SCARB1. These data suggest that an initial action of LH/CG on the primate preovulatory follicle is to rapidly reduce the expression of PPARG, resulting in reduced NR1H3 with the consequence shifting the balance from cholesterol efflux via ABCA1 and ABCG1 to cholesterol uptake (SCARB1) and metabolism (STAR, P450 side-chain cleavage A1, hydroxysteroid dehydrogenase 3B). That the regulation of PPARG and the liver X receptors occurs within 3 hr strongly indicates that early events in the primate luteinizing follicle are critical to successful ovulation and luteal formation.

Deficiency of scavenger receptor class B type I negatively affects progesterone secretion in human granulosa cells

Our goal was to examine the effect of deficiency of the lipoprotein receptor, scavenger receptor class B type I (SR-BI), on progesterone secretion in human granulosa cells (HGL5). Scrambled or SR-BI small interfering RNA [knockdown (KD)] cells were exposed to dimethylsulfoxide [DMSO, vehicle for forskolin (Fo)], Fo, serum, high-density lipoprotein, low-density lipoprotein (LDL), or Fo plus lipoproteins or serum for 24 h. Progesterone secretion was lower in all of the SR-BI KD cells regardless of treatment. We examined progesterone secretion in SR-BI KD, LDL receptor KD, and double KD cells incubated with DMSO, Fo, LDL, or Fo + LDL for 6-24 h. As compared with scrambled cells, progesterone secretion was lower in SR-BI and double KD cells regardless of treatment; whereas progesterone secretion was only lower in LDL receptor KD cells incubated with LDL and Fo + LDL. We measured phosphorylation of hormone-sensitive lipase (pHSL) expression, intracellular total cholesterol (TC) mass, and progesterone secretion in scrambled and SR-BI KD cells incubated with DMSO or Fo for 2-24 h. The expression of pHSL was similar between the cells and conditions. The mean change in TC mass and progesterone secretion was lower in SR-BI KD cells exposed to DMSO and Fo. Incubating SR-BI KD cells with 22-hydroxy cholesterol did not overcome the reduction in progesterone secretion. At different time points, RNA expression of steroidogenic acute regulatory protein, side-chain cleavage, and 3β-hydroxysteroid dehydrogenase was significantly lower in SR-BI KD cells incubated with Fo. In conclusion, SR-BI protein deficiency, in part, might explain progesterone deficiency in some infertile women.

Dynamics of the transcriptome in the primate ovulatory follicle

Experiments were designed to evaluate changes in the transcriptome (mRNA levels) in the ovulatory, luteinizing follicle of rhesus monkeys, using a controlled ovulation model that permits analysis of the naturally selected, dominant follicle at specific intervals (0, 12, 24 and 36 h) after exposure to an ovulatory (exogenous hCG) stimulus during the menstrual cycle. Total RNA was prepared from individual follicles (n= 4-8/timepoint), with an aliquot used for microarray analysis (Affymetrix Rhesus Macaque Genome Array) and the remainder applied to quantitative real-time PCR (q-PCR) assays. The microarray data from individual samples distinctly clustered according to timepoints, and ovulated follicles displayed markedly different expression patterns from unruptured follicles at 36 h. Between timepoint comparisons revealed profound changes in mRNA expression profiles. The dynamic pattern of mRNA expression for steroidogenic enzymes (CYP17A, CYP19A, HSD3B2, HSD11B1 and HSD11B2), steroidogenic acute regulatory protein (StAR) and gonadotrophin receptors [LH/choriogonadotrophin receptor (LHCGR), FSH receptor (FSHR)] as determined by microarray analysis correlated precisely with those from blinded q-PCR assays. Patterns of mRNA expression for epidermal-growth-factor-like factors (amphiregulin, epiregulin) and processes [hyaluronan synthase 2 (HAS2), tumor necrosis factor alpha-induced protein 6 (TNFAIP6)] implicated in cumulus-oocyte maturation/expansion were also comparable between assays. Thus, several mRNAs displayed the expected expression pattern for purported theca (e.g. CYP17A), granulosa (CYP19A, FSHR), cumulus (HAS2, TNFAIP6) cell and surface epithelium (HSD11B)-related genes in the rodent/primate pre-ovulatory follicle. This database will be of great value in analyzing molecular and cellular pathways associated with periovulatory events in the primate follicle (e.g. follicle rupture, luteinization, inflammatory response and angiogenesis), and for identifying novel gene products controlling mammalian fertility.

Progressive obesity leads to altered ovarian gene expression in the Lethal Yellow mouse: a microarray study

Background

Lethal yellow (LY; C57BL/6J A^y/a) mice exhibit adult-onset obesity, altered metabolic regulation, and early reproductive senescence. The present study was designed to test the hypothesis that obese LY mice possess differences in expression of ovarian genes relative to age-matched lean mice.

Methods

90- and 180-day-old LY and lean black (C57BL/6J a/a) mice were suppressed with GnRH antagonist (Antide^®), then stimulated with 5 IU eCG. cRNA derived from RNA extracts of whole ovarian homogenates collected 36 h post-eCG were run individually on Codelink Mouse Whole Genome Bioarrays (GE Healthcare Life Sciences).

Results

Fifty-two genes showed ≥ 2-fold differential (p < 0.05) expression between 180-day-old obese LY and lean black mice. LY mice exhibited elevated ovarian expression of agouti (350×), leptin (6.5×), and numerous genes involved in cholesterol/lipid transport and metabolism, e.g. lanosterol synthase, Cyp51, and steroidogenic acute regulatory protein (Star). Fewer genes showed lower expression in LY mice, e.g. angiotensinogen. In contrast, none of these genes showed differential expression in 90-day-old LY and black mice, which are of similar body weight. Interestingly, 180-day-old LY mice had a 2-fold greater expression of 11beta-hydroxysteroid dehydrogenase type 1 (Hsd11b1) and a 2-fold lesser expression of 11beta-hydroxysteroid dehydrogenase type 2 (Hsd11b2), differences not seen in 90-day-old mice. Consistent with altered Hsd11b gene expression, ovarian concentrations of corticosterone (C) were elevated in aging LY mice relative to black mice, but C levels were similar in young LY and black mice.

Conclusion

The data suggest that reproductive dysfunction in aging obese mice is related to modified intraovarian gene expression that is directly related to acquired obesity.

Immunohistochemical demonstration of the mineralocorticoid receptor, 11beta-hydroxysteroid dehydrogenase-1 and -2, and hexose-6-phosphate dehydrogenase in rat ovary

An IHC survey using several monoclonal antibodies against different portions of the rat mineralocorticoid receptor (MR) molecule demonstrated significant specific MR immunoreactivity in the ovary, prompting further study of the localization of MR and of determinants of extrinsic MR ligand specificity, 11beta-hydroxysteroid dehydrogenase (11beta-HSD) types 1 and 2, and hexose-6-phosphate dehydrogenase (H6PDH). MR expression (real-time RT-PCR and Western blot) did not differ significantly in whole rat ovaries at early diestrus, late diestrus, estrus, and a few hours after ovulation. MR immunostaining was most intense in corporal lutea cells, light to moderate in oocytes and granulosa cells, and least intense in theca cells. Light immunoreactivity for 11beta-HSD2 occurred in most cells, with some mural granulosa cells of mature follicles staining more strongly. The distribution of immunoreactivity for 11beta-HSD1 and H6PDH required to generate NADPH, the cofactor required for reductase activity of 11beta-HSD1, was similar, with the most-intense staining in the cytoplasm of corporal lutea and theca cells and light or no staining in the granulosa and oocytes. MR function in the ovary is as yet unclear, but distinct patterns of distribution of 11beta-HSD1 and -2 and H6PDH suggest that the ligand for MR activation in different cells of the ovary may be differentially regulated.

Expression of the insulin-like growth factor and insulin systems in the luteinizing macaque ovarian follicle

OBJECTIVE

To determine intrafollicular hormone levels and characterize the mRNA expression of the insulin-like growth factor (IGF) receptors, IGF binding proteins (IGFBP), and pregnancy-associated plasma protein-A (PAPP-A) in granulosa cells before and after an ovulatory hCG stimulus.

DESIGN

Experimental animal study.

SETTING

Academic medical center.

ANIMAL(S)

Adult rhesus macaques.

INTERVENTION(S)

Animals received exogenous FSH to promote the development of multiple preovulatory follicles. Follicles were aspirated before (0 hours) or 3, 6, 12, or 24 hours after an ovulatory hCG bolus.

MAIN OUTCOME MEASURE(S)

IGF1, IGF2, and insulin levels in follicular fluid were determined by radioimmunoassay. Messenger RNA (mRNA) levels in granulosa cells were determined by real-time reverse transcriptase-polymerase chain reaction. IGFBPs and PAPP-A in follicular fluid were determined by Western blot analysis and enzyme-linked immunosorbent assay.

RESULT(S)

IGF1, IGF2, and insulin in follicular fluid did not change during luteinization. IGF1R, IGFBP1, and IGFBP2 mRNAs were unchanged by hCG. IGF2R, IGFBP3, -5, and -6 and PAPP-A mRNA levels increased after hCG administration, while insulin receptor and IGFBP4 mRNA levels decreased after hCG administration. IGFBP3 and -6 and PAPP-A protein increased after hCG administration.

CONCLUSION(S)

Dynamic changes in the expression of the IGFBPs and PAPP-A suggest tight regulation of IGF action during ovulation and corpus luteum formation.

Expression of scavenger receptor-BI and low-density lipoprotein receptor and differential use of lipoproteins to support early steroidogenesis in luteinizing macaque granulosa cells

An ovulatory hCG stimulus to rhesus macaques undergoing controlled ovarian stimulation protocols results in a rapid and sustained increase in progesterone synthesis. The use of lipoproteins as a substrate for progesterone synthesis remains unclear, and the expression of lipoprotein receptors [very-low-density lipoprotein receptor (VLDLR), low-density lipoprotein receptor (LDLR), and scavenger receptor-BI (SR-BI)] soon after human chorionic gonadotropin (hCG) (<12 h) has not been characterized. This study investigated lipoprotein receptor expression and lipoprotein (VLDL, LDL, and HDL) support of steroidogenesis during luteinization of macaque granulosa cells. Granulosa cells were aspirated from rhesus monkeys undergoing controlled ovarian stimulation before or up to 24 h after an ovulatory hCG stimulus. The expression of VLDLR decreased within 3 h of hCG, whereas LDLR and SR-BI increased at 3 and 12 h, respectively. Granulosa cells isolated before hCG were cultured for 24 h in the presence of FSH or FSH plus hCG with or without VLDL, LDL, or HDL. Progesterone levels increased in the presence of hCG regardless of lipoprotein addition, although LDL, but not HDL, further augmented hCG-induced progesterone. Other cells were cultured with FSH or FSH plus hCG without an exogenous source of lipoprotein for 24 h, followed by an additional 24 h culture with or without lipoproteins. Cells treated with hCG in the absence of any lipoprotein were unable to maintain progesterone levels through 48 h, whereas LDL (but not HDL) sustained progesterone synthesis. These data suggest that an ovulatory stimulus rapidly mobilizes stored cholesterol esters for use as a progesterone substrate and that as these are depleted, new cholesterol esters are obtained through an LDLR- and/or SR-BI-mediated mechanism.

Cyp11b1 is induced in the murine gonad by luteinizing hormone/human chorionic gonadotropin and involved in the production of 11-ketotestosterone, a major fish androgen: conservation and evolution of the androgen metabolic pathway

We have shown previously that Cyp11b1, an 11beta-hydroxylase responsible for glucocorticoid biosynthesis in the adrenal gland, was induced by cAMP in androgen-producing Leydig-like cells derived from mesenchymal stem cells. We found that Cyp11b1 was induced in male Leydig cells, or female theca cells, when human chorionic gonadotropin was administered in immature mice. Expression of Cyp11b1 in rodent gonads caused the production of 11-ketotestosterone (11-KT), a major fish androgen, which induces male differentiation or spermatogenesis in fish. As in teleosts, plasma concentrations of 11-KT were elevated in human chorionic gonadotropin-treated mice. In contrast to teleosts, however, plasma concentrations of 11-KT were similar in both sexes, despite levels of testosterone, a precursor substrate, being about 20 times higher in male mice. Because expression of 11beta-hydroxysteroid dehydrogenase type 2, was much higher in the mouse ovary than in the testis, conversion of testosterone into 11-KT may occur more efficiently in the ovary. In a luciferase reporter system that was responsive to and activated by androgens, 11-KT efficiently activated mammalian androgen receptor-mediated transactivation. Our results suggest that the androgen metabolic pathway is conserved between teleosts and mammals, despite sexual dominance and reproductive functions of 11-KT being altered during evolution.

Why are mineralocorticoid receptors so nonselective?

Mineralocorticoid receptors (MR) bind aldosterone, cortisol, and progesterone with equal high affinity. Attention has focused on the role of MR in epithelial fluid and electrolyte homeostasis; from a variety of studies, however, MR are largely constitutively occupied by cortisol, with aldosterone an evolutionary latecomer, and MR pressed into service in epithelia to respond selectively to aldosterone through the co-expression of 11beta hydroxysteroid dehydrogenase type 2. The pathophysiologic--and to a lesser extent the physiologic--roles of constitutively cortisol-occupied MR in nonepithelial tissues (eg, cardiomyocytes, neurons) are beginning to be delineated; the implications of the maintained high affinity of MR for progesterone, and their possible role as primarily progesterone sensors in reproductive (and other) tissues, await exploration.

Regulation of granulosa cell proliferation and EGF-like ligands during the periovulatory interval in monkeys

BACKGROUND

This study seeks to clarify cell cycle dynamics of granulosa cells following hCG and elucidate the expression of epidermal growth factor (EGF)-like ligands during luteinization.

METHODS

Granulosa cells were obtained from rhesus macaques undergoing controlled ovarian stimulation protocols before or after an ovulatory hCG bolus. Cell cycle characteristics were determined by flow cytometry and levels of EGF receptor (EGFR), amphiregulin (AREG), epiregulin (EREG) and betacellulin (BTC) mRNAs were measured by real-time RT-PCR.

RESULTS

The proportion of cells in S-phase was 7.5% prior to hCG and did not decline until 24 h after hCG (3.1%). EGFR protein and BTC mRNA did not change following hCG, whereas AREG and EREG mRNA increased starting at 3 and 12 h post-hCG, respectively, and remained elevated thereafter.

CONCLUSIONS

Cell cycle transit of macaque granulosa cells does not change until 24 h after an ovulatory stimulus, whereas the EGF-like ligands EREG and AREG are increased rapidly. This suggests that luteinizing granulosa cells are refractory to mitogenic stimulation by EGFR ligands.