Knockdown of Progesterone Receptor (PGR) in Macaque Granulosa Cells Disrupts Ovulation and Progesterone Production

Classification system of human ovarian follicle morphology: recommendations of the National Institute of Child Health and Human Development - sponsored ovarian nomenclature workshop

OBJECTIVE

To develop a consensus on histologic human ovarian follicle staging nomenclature, provide guidelines for follicle density calculation, and assess changes due to fixation to enhance communication among clinicians and ovarian biology researchers to gain a deeper understanding of human fertility.

SETTING

Beginning in March 2021, the Ovarian Nomenclature Workshop's Follicle Classification Working Subgroup was organized by the Pediatric and Adolescent Gynecology program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

METHODS

After the initial workshop held in May 2021, a Follicle Working Subgroup comprised of experts in reproductive endocrinology and ovarian biology held multiple meetings to develop the human follicle classification system and reported to the collective group during two follow up workshops.

RESULTS

The Follicle Working Subgroup recommends consolidation and expansion of the current classification systems to include six stages of normal preantral follicles, five stages of normal antral follicles, as well as categories of corpus lutea, abnormal preantral follicles, abnormal antral follicles, and other distinct follicle types. The new preantral staging added intermediate stages (primordial, transitional primordial, primary, transitional primary, secondary, and multilayer ovarian follicles). The antral follicle staging includes early, preselection, selection, dominance, and preovulatory follicles. Abnormal preantral follicles include those with an abnormal oocyte, granulosa cells, or both. We suggest a uniform way of calculating the mean follicle density in the number of follicles/mm2.

CONCLUSION

To establish a consensus in human ovarian follicle terminology, the Ovarian Follicle Working Subgroup of the National Institute of Child Health and Human Development Ovarian Nomenclature Workshop standardized follicle staging nomenclature and follicle density calculating systems so consistent common language can be used among ovarian biology researchers and clinicians.

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.

Cell Communications Between GCs and Macrophages Contribute to the Residence of Macrophage in Preovulatory Follicles

PROBLEM

There were not only granulosa cells (GCs) but also immune cells in preovulatory follicular fluid. The objective of this study was to explore the interactions between macrophages and GCs via adhesion molecules in preovulatory follicles and the regulatory mechanisms of the interactions.

METHOD OF STUDY

Flow cytometry and immunofluorescence were used to detect the expression of ITGB1 in macrophages and fibronectin (FN)1 in GCs in preovulatory follicles from 12 patients. The synthesis of FN1 protein in human ovarian GCs line (KGN) was detected by western blot. An adhesion experiment was performed to observe the changes of KGN cells adhesion to macrophages.

RESULTS

The progesterone levels 12 h after human chorionic gonadotropin (HCG) administration in the high proportion immune cells (high immune [HI]) group were significantly higher than that in the low proportion immune cells (low immune [LI]) group (p < 0.0001). The expression of ITGB1 in macrophages in the HI group was higher than in the LI group. The expression of FN1 in GCs in HI group was higher than in LI group (p < 0.01). Progesterone increased the synthesis of FN1 in KGN cells (p < 0.0001) and was suppressed by the elimination of PGR. The adhesion effect of KGN cells on macrophages was enhanced by progesterone (p < 0.0001).

CONCLUSION

After luteinizing hormone (LH)/HCG surge, progesterone promotes the expression of FN1 in GCs by acting on the receptor PGR, and then GCs enhance the adhesion of macrophages by FN1-ITGB1 interaction, further leading to the result that macrophages perform diverse functional activities to maintain tissue homeostasis during ovulation.

Effect of the gonadotropin surge on steroid receptor regulation in preovulatory follicles and newly formed corpora lutea in the cow

The objective of the study was to characterize the mRNA expression patterns of specific steroid hormone receptors namely, estrogen receptors (ESRRA-estrogen related receptor alpha and ESRRB-estrogen related receptor beta) and progesterone receptors (PGR) in superovulation-induced bovine follicles during the periovulation and subsequent corpus luteum (CL) formation. The bovine ovaries (n = 5 cow / group), containing preovulatory follicles or early CL, were collected relative to injection of the gonadotropin-releasing hormone (GnRH) at (I) 0 h, (II) 4 h, (III) 10 h, (IV) 20 h, (V) 25 h (preovulatory follicles) and (VI) 60 h (CL, 2-3 days after induced ovulation). In this experiment, we analyzed the steroid receptor mRNA expression and their localization in the follicle and CL tissue. The high mRNA expression of ESRRA, ESRRB, and PGR analyzed in the follicles before ovulation is significantly reduced in the group of follicles during ovulation (25 h after GnRH), rising again significantly after ovulation in newly formed CL, only for ESRRA and PGR (P < 0.05). Immunohistochemically, the nuclei of antral follicles' granulosa cells showed a positive staining for ESRRA, followed by higher activity in the large luteal cells just after ovulation (early CL). In contrast, the lower PGR immunopresence in preovulatory follicles increased in both small and large luteal cell nuclei after follicle ovulation. Our results of steroid receptor mRNA expression in this experimentally induced gonadotropin surge provide insight into the molecular mechanisms of the effects of steroid hormones on follicular-luteal tissue in the period close to the ovulation and subsequent CL formation in the cow.

Proteo-transcriptomic profiles reveal key regulatory pathways and functions of LDHA in the ovulation of domestic chickens (Gallus gallus)

BACKGROUND

In poultry, the smooth transition of follicles from the preovulatory-to-postovulatory phase impacts egg production in hens and can benefit the poultry industry. However, the regulatory mechanism underlying follicular ovulation in avians is a complex biological process that remains unclear.

RESULTS

Critical biochemical events involved in ovulation in domestic chickens (Gallus gallus) were evaluated by transcriptomics, proteomics, and in vitro assays. Comparative transcriptome analyses of the largest preovulatory follicle (F1) and postovulatory follicle (POF1) in continuous laying (CL) and intermittent laying (IL) chickens indicated the greatest difference between CL_F1 and IL_F1, with 950 differentially expressed genes (DEGs), and the smallest difference between CL_POF1 and IL_POF1, with 14 DEGs. Additionally, data-independent acquisition proteomics revealed 252 differentially abundant proteins between CL_F1 and IL_F1. Perivitelline membrane synthesis, steroid biosynthesis, lysosomes, and oxidative phosphorylation were identified as pivotal pathways contributing to ovulation regulation. In particular, the regulation of zona pellucida sperm-binding protein 3, plasminogen activator, cathepsin A, and lactate dehydrogenase A (LDHA) was shown to be essential for ovulation. Furthermore, the inhibition of LDHA decreased cell viability and promoted apoptosis of ovarian follicles in vitro.

CONCLUSIONS

This study reveals several important biochemical events involved in the process of ovulation, as well as crucial role of LDHA. These findings improve our understanding of ovulation and its regulatory mechanisms in avian species.

Atretic preovulatory follicles could be precursors of ovarian lutein cysts in the pig

Ovarian cysts contribute to reduced reproductive performance in pigs. Unfortunately, the mechanism of lutein cysts formation remains unknown. Here, we compared the endocrine and molecular milieus of intact, healthy preovulatory follicles (PF), gonadotropin (eCG/hCG)-induced healthy and atretic-like PF, as well as gonadotropin-provoked and spontaneous ovarian cysts in gilts. Several endocrine and molecular indicators and microRNA were compared in walls of PF and cysts. Intact and healthy PF, showed high estradiol/androstendione and low progesterone levels associated with CYP17A1, HSD17B1, and CYP19A1 elevation and reduced StAR/HSD3B1 protein expression. In contrast, low estradiol/androstendione and high progesterone concentrations, accompanied by decreased CYP17A1, HSD17B1, CYP19A1 and increased HSD3B1 protein abundance, appeared in atretic-like PF, gonadotropin-induced and spontaneous cysts. High progesterone receptor (PGR) protein abundance was maintained in intact and healthy PF, while it dropped in atretic-like PF, gonadotropins-induced and spontaneous cysts. The atretic PF showed high level of TNFα compared to healthy PF. In conclusion, follicular lutein cysts could be recruited from atretic-like PF with lost estrogenic milieu and inability to ovulate. Ovulatory cascade was presumably disrupted by a low PGR and high TNFα levels associated with earlier luteinization of follicular walls. These results suggest a novel mechanism of lutein ovarian cysts development in pigs and, perhaps, other species.

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

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

History, insights, and future perspectives on studies into luteal function in cattle

The corpus luteum (CL) forms following ovulation from the remnant of the Graafian follicle. This transient tissue produces critical hormones to maintain pregnancy, including the steroid progesterone. In cattle and other ruminants, the presence of an embryo determines if the lifespan of the CL will be prolonged to ensure successful implantation and gestation, or if the tissue will undergo destruction in the process known as luteolysis. Infertility and subfertility in dairy and beef cattle results in substantial economic loss to producers each year. In addition, this has the potential to exacerbate climate change because more animals are needed to produce high-quality protein to feed the growing world population. Successful pregnancies require coordinated regulation of uterine and ovarian function by the developing embryo. These processes are often collectively termed "maternal recognition of pregnancy." Research into the formation, function, and destruction of the bovine CL by the Northeast Multistate Project, one of the oldest continuously funded Hatch projects by the USDA, has produced a large body of evidence increasing our knowledge of the contribution of ovarian processes to fertility in ruminants. This review presents some of the seminal research into the regulation of the ruminant CL, as well as identifying mechanisms that remain to be completely validated in the bovine CL. This review also contains a broad discussion of the roles of prostaglandins, immune cells, as well as mechanisms contributing to steroidogenesis in the ruminant CL. A triadic model of luteolysis is discussed wherein the interactions among immune cells, endothelial cells, and luteal cells dictate the ability of the ruminant CL to respond to a luteolytic stimulus, along with other novel hypotheses for future research.

Intraovarian, Isoform-Specific Transcriptional Roles of Progesterone Receptor in Ovulation

Progesterone receptor (PGR) activity is obligatory for mammalian ovulation; however, there is no established direct functional pathway explaining how progesterone receptor completely and specifically regulates oocyte release. This study examined the overarching cell- and isoform-specific effects of the PGR within each cellular compartment of the ovary, using mice null for the PGR (PRKO), as well as isoform-specific null mice. The PGR was expressed in ovarian granulosa and stromal cells and although PRKO ovaries showed no visible histological changes in preovulatory ovarian morphology, follicle rupture did not occur. Reciprocal ovarian transplant experiments established the necessity of ovarian PGR expression for ovulation. Cumulus–oocyte complexes of PRKO mice exhibited normal morphology but showed some altered gene expression. The examination of mitochondrial activity showed subtle differences in PRKO oocytes but no differences in granulosa cell respiration, glycolysis or β-oxidation. Concurrently, RNA-seq identified novel functional pathways through which the PGR may regulate ovulation. PGR-A was the predominant transcriptionally active isoform in granulosa cells and 154 key PGR-dependent genes were identified, including a secondary network of transcription factors. In addition, the PGR regulated unique gene networks in the ovarian stroma. Collectively, we establish the effector pathways activated by the PGR across the ovarian cell types and conclude that PGR coordinates gene expression in the cumulus, granulosa and stromal cells at ovulation. Identifying these networks linking the PGR to ovulation provides novel targets for fertility therapeutics and nonhormonal contraceptive development.

Regulation of progesterone during follicular development by FSH and LH in sheep

Progesterone (P4) can participate in the development of female mammalian antral follicles through nuclear receptor (PGR). In this experiment, the differences of P4 synthesis and PGR expression in different developmental stages of sheep antral follicles (large > 5mm, medium 2-5mm, small < 2mm) were detected by enzyme-linked immunosorbent assay, immunohistochemistry, qRT-PCR and Western blotting. Secondly, sheep follicular granulosa cells were cultured in vitro. The effects of different concentrations of FSH and LH on P4 synthesis and PGR expression were studied. The results showed that acute steroid regulatory protein (StAR), cholesterol side chain lyase (P450scc) and 3β Hydroxysteroid dehydrogenase (3β-HSD) and PGR were expressed in antral follicles, and with the development of antral follicles in sheep, StAR, P450scc and the expression of 3β-HSD and PGR increased significantly. In vitro experiments showed that FSH and LH alone or together treatment could regulate P4 secretion and PGR expression in sheep follicular granulosa cells to varying degrees, hint P4 and PGR by FSH and LH, and LH was the main factor. Our results supplement the effects of FSH and LH on the regulation of P4 synthesis during follicular development, which provides new data for further study of steroid synthesis and function in follicular development.

Follicular hormone dynamics during the midcycle surge of gonadotropins in women undergoing fertility treatment

Changes in concentrations of intra-follicular hormones during ovulation are important for final oocyte maturation and endometrial priming to ensure reproductive success. As no human studies have investigated these changes in detail, our objective was to describe the dynamics of major follicular fluid (FF) hormones and transcription of steroidogenic enzymes and steroid receptors in human granulosa cells (GCs) during ovulation. We conducted a prospective cohort study at a public fertility clinic in 2016-2018. Fifty women undergoing ovarian stimulation for fertility treatment were included. From each woman, FF and GCs were collected by transvaginal ultrasound-guided follicle puncture of one follicle at two specific time points during ovulation, and the study covered a total of five time points: before ovulation induction (OI), 12, 17, 32 and 36 h after OI. Follicular fluid concentrations of oestradiol, progesterone, androstenedione, testosterone, 17-hydroxyprogesterone, anti-Mullerian hormone, inhibin A and inhibin B were measured using ELISA assays, and a statistical mixed model was used to analyse differences in hormone levels between time points. Gene expression of 33 steroidogenic enzymes and six hormone receptors in GCs across ovulation were assessed by microarray analysis, and selected genes were validated by quantitative reverse transcription PCR. We found that concentrations of oestradiol, testosterone, progesterone, AMH, inhibin A and inhibin B (P < 0.001) and gene expression of 12 steroidogenic enzymes and five receptors (false discovery rate < 0.0001) changed significantly during ovulation. Furthermore, we found parallel changes in plasma hormones. The substantial changes in follicular hormone production during ovulation highlight their importance for reproductive success.

Two waves of transcriptomic changes in periovulatory human granulosa cells

STUDY QUESTION

How does the human granulosa cell (GC) transcriptome change during ovulation?

SUMMARY ANSWER

Two transcriptional peaks were observed at 12 h and at 36 h after induction of ovulation, both dominated by genes and pathways known from the inflammatory system.

WHAT IS KNOWN ALREADY

The crosstalk between GCs and the oocyte, which is essential for ovulation and oocyte maturation, can be assessed through transcriptomic profiling of GCs. Detailed transcriptional changes during ovulation have not previously been assessed in humans.

STUDY DESIGN, SIZE, DURATION

This prospective cohort study comprised 50 women undergoing fertility treatment in a standard antagonist protocol at a university hospital-affiliated fertility clinic in 2016-2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

From each woman, one sample of GCs was collected by transvaginal ultrasound-guided follicle aspiration either before or 12 h, 17 h or 32 h after ovulation induction (OI). A second sample was collected at oocyte retrieval, 36 h after OI. Total RNA was isolated from GCs and analyzed by microarray. Gene expression differences between the five time points were assessed by ANOVA with a random factor accounting for the pairing of samples, and seven clusters of protein-coding genes representing distinct expression profiles were identified. These were used as input for subsequent bioinformatic analyses to identify enriched pathways and suggest upstream regulators. Subsets of genes were assessed to explore specific ovulatory functions.

MAIN RESULTS AND THE ROLE OF CHANCE

We identified 13 345 differentially expressed transcripts across the five time points (false discovery rate, <0.01) of which 58% were protein-coding genes. Two clusters of mainly downregulated genes represented cell cycle pathways and DNA repair. Upregulated genes showed one peak at 12 h that resembled the initiation of an inflammatory response, and one peak at 36 h that resembled the effector functions of inflammation such as vasodilation, angiogenesis, coagulation, chemotaxis and tissue remodelling. Genes involved in cell-matrix interactions as a part of cytoskeletal rearrangement and cell motility were also upregulated at 36 h. Predicted activated upstream regulators of ovulation included FSH, LH, transforming growth factor B1, tumour necrosis factor, nuclear factor kappa-light-chain-enhancer of activated B cells, coagulation factor 2, fibroblast growth factor 2, interleukin 1 and cortisol, among others. The results confirmed early regulation of several previously described factors in a cascade inducing meiotic resumption and suggested new factors involved in cumulus expansion and follicle rupture through co-regulation with previously described factors.

LARGE SCALE DATA

The microarray data were deposited to the Gene Expression Omnibus (www.ncbi.nlm.nih.gov/gds/, accession number: GSE133868).

LIMITATIONS, REASONS FOR CAUTION

The study included women undergoing ovarian stimulation and the findings may therefore differ from a natural cycle. However, the results confirm significant regulation of many well-established ovulatory genes from a series of previous studies such as amphiregulin, epiregulin, tumour necrosis factor alfa induced protein 6, tissue inhibitor of metallopeptidases 1 and plasminogen activator inhibitor 1, which support the relevance of the results.

WIDER IMPLICATIONS OF THE FINDINGS

The study increases our understanding of human ovarian function during ovulation, and the publicly available dataset is a valuable resource for future investigations. Suggested upstream regulators and highly differentially expressed genes may be potential pharmaceutical targets in fertility treatment and gynaecology.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by EU Interreg ÔKS V through ReproUnion (www.reprounion.eu) and by a grant from the Region Zealand Research Foundation. None of the authors have any conflicts of interest to declare.

Progesterone Receptor Serves the Ovary as a Trigger of Ovulation and a Terminator of Inflammation

Ovulation is triggered by the gonadotropin surge that induces the expression of two key genes, progesterone receptor (Pgr) and prostaglandin-endoperoxide synthase 2 (Ptgs2), in the granulosa cells of preovulatory follicles. Their gene products PGR and PTGS2 activate two separate pathways that are both essential for successful ovulation. Here, we show that the PGR plays an additional essential role: it attenuates ovulatory inflammation by diminishing the gonadotropin surge-induced Ptgs2 expression. PGR indirectly terminates Ptgs2 expression and PGE2 synthesis in granulosa cells by inhibiting the nuclear factor κB (NF-κB), a transcription factor required for Ptgs2 expression. When the expression of PGR is ablated in granulosa cells, the ovary undergoes a hyperinflammatory condition manifested by excessive PGE2 synthesis, immune cell infiltration, oxidative damage, and neoplastic transformation of ovarian cells. The PGR-driven termination of PTGS2 expression may protect the ovary from ovulatory inflammation.

A central role for cAMP/EPAC/RAP/PI3K/AKT/CREB signaling in LH-induced follicular Pgr expression at medaka ovulation†

Nuclear progestin receptor (PGR) is a ligand-activated transcription factor that has been identified as a pivotal mediator of many processes associated with ovarian and uterine function, and aberrant control of PGR activity causes infertility and disease including cancer. The essential role of PGR in vertebrate ovulation is well recognized, but the mechanisms by which PGR is rapidly and transiently induced in preovulatory follicles after the ovulatory LH surge are not known in lower vertebrates. To address this issue, we utilized the small freshwater teleost medaka Oryzias latipes, which serves as a good model system for studying vertebrate ovulation. In the in vitro ovulation system using preovulatory follicles dissected from the fish ovaries, we found that inhibitors of EPAC (brefeldin A), RAP (GGTI298), PI3K (Wortmannin), AKT (AKT inhibitor IV), and CREB (KG-501) inhibited LH-induced follicle ovulation, while the PKA inhibitor H-89 had no effect on follicle ovulation. The inhibitors capable of inhibiting follicle ovulation also inhibited follicular expression of Pgr and matrix metalloproteinase-15 (Mmp15), the latter of which was previously shown to not only be a downstream effector of Pgr but also a proteolytic enzyme indispensable for follicle rupture in medaka ovulation. Further detailed analysis revealed for the first time that the cAMP/EPAC/RAP/PI3K/AKT/CREB signaling pathway mediates the LH signal to induce Pgr expression in preovulatory follicles. Our data also showed that phosphorylated Creb1 is a transcription factor essential for pgr expression and that Creb1 phosphorylated by Akt1, rather than PKA, may be preferably used to induce pgr expression.

Neurotensin: A novel mediator of ovulation?

The midcycle luteinizing hormone (LH) surge initiates a cascade of events within the ovarian follicle which culminates in ovulation. Only mural granulosa cells and theca cells express large numbers of LH receptors, and LH-stimulated paracrine mediators communicate the ovulatory signal within the follicle. Recent reports identified the neuropeptide neurotensin (NTS) as a product of granulosa cells. Here, we demonstrate that granulosa cells were the primary site of NTS expression in macaque ovulatory follicles. Granulosa cell NTS mRNA and protein increased after human chorionic gonadotropin (hCG) administration, which substitutes for the LH surge. To identify ovulatory actions of NTS, a NTS-neutralizing antibody was injected into preovulatory macaque follicles. hCG administration immediately followed, and ovaries were removed 48 hours later to evaluate ovulatory events. Follicles injected with control IgG ovulated normally. In contrast, 75% of NTS antibody-injected follicles failed to ovulate, containing oocytes trapped within unruptured, hemorrhagic follicles. Serum progesterone was unchanged. Of the three NTS receptors, SORT1 was highly expressed in follicular granulosa, theca, and endothelial cells; NTSR1 and NTSR2 were expressed at lower levels. Excessive blood cells in NTS antibody-injected follicles indicated vascular anomalies, so the response of monkey ovarian endothelial cells to NTS was evaluated in vitro. NTS stimulated endothelial cell migration and capillary sprout formation, consistent with a role for NTS in vascular remodeling associated with ovulation. In summary, we identified NTS as a possible paracrine mediator of ovulation. Further investigation of the NTS synthesis/response pathway may lead to improved treatments for infertility and novel targets for contraception.

Insulin-like growth factor 2 is produced by antral follicles and promotes preantral follicle development in macaques†

Insulin-like growth factors (IGFs) are known for their involvement in endocrine and paracrine regulation of ovarian function. Although IGF2 is the predominant circulating and intraovarian form of IGFs in primate species, the stage-specific follicular expression, action, and regulation of IGF2 are not well defined. Therefore, experiments were conducted to investigate the follicular IGF production in response to steroid hormone regulation and the direct IGF actions on follicular development and function in vitro. Preantral follicles were isolated from rhesus macaque ovaries and cultured to the antral stage in media supplemented with follicle-stimulating hormone and insulin. Follicles were randomly assigned to treatment groups: (a) control, (b) trilostane (a steroid synthesis inhibitor), (c) trilostane + estradiol, (d) trilostane + progesterone, and (e) trilostane + dihydrotestosterone. Media was analyzed for IGF concentrations, which were correlated to follicle growth. Follicles produced IGF2, but not IGF1, at the antral stage. Steroid depletion decreased, whereas steroid replacement increased, IGF2 production by antral follicles. Media IGF2 levels correlated positively with antral follicle diameters. Macaque preantral follicles and granulosa cells were subsequently cultured without (control) and with recombinant human IGF2 supplementation. Follicle survival, growth, and paracrine factor production, as well as granulosa cell proliferation and gonadotropin receptor gene expression, were assessed. IGF2 addition increased follicle survival rates, diameters and inhibin B production, as well as granulosa cell proliferation. These data demonstrate that IGF2 produced by antral follicles, in response to steroid hormone regulation, could act as a paracrine factor that positively impacts preantral follicle development and function in primates.

Dissection of the Ovulatory Process Using ex vivo Approaches

Ovulation is a unique physiological phenomenon that is essential for sexual reproduction. It refers to the entire process of ovarian follicle responses to hormonal stimulation resulting in the release of mature fertilization-competent oocytes from the follicles and ovaries. Remarkably, ovulation in different species can be reproduced out-of-body with high fidelity. Moreover, most of the molecular mechanisms and signaling pathways engaged in this process have been delineated using in vitro ovulation models. Here, we provide an overview of the major molecular and cytological events of ovulation observed in frogs, primarily in the African clawed frog Xenopus laevis, using mainly ex vivo approaches, with the focus on meiotic oocyte maturation and follicle rupture. For the purpose of comparison and generalization, we also refer extensively to ovulation in other biological species, most notoriously, in mammals.

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.

Unconservative_15_2570409 suppresses progesterone receptor expression in the granulosa cells of Hu sheep

Female fertility potential depends on the number of mature follicles; however, the underlying molecular mechanisms remain unclear. Based on previously generated miRNA and mRNA sequencing data of healthy ovarian follicles (>5 mm in diameter) isolated from Hu sheep with different prolificacy, we investigated the roles of a novel miRNA (unconservative_15_2570409) and the progesterone receptor (PGR) gene in follicular development. During the periovulatory phase, the expression of unconservative_15_2570409 and PGR was lower and higher, respectively, in the >5 mm follicles of high prolificacy (HP) ewes than in those of low prolificacy (LP) ewes and in the >3 mm follicles than in the smaller follicles of the HP ewes. Subsequently, the granulosa cells (GCs) of Hu sheep were used as an in vitro model. PGR overexpression significantly increased the mRNA expression of steroidogenic acute regulatory protein (StAR), 3-beta-hydroxysteroid dehydrogenase/isomerase (3β-HSD), and cytochrome P450 family 19 subfamily A member 1 (CYP19A1), which promoted the secretion of progesterone (P₄) and estradiol (E₂). PGR knockdown significantly downregulated the levels of StAR and 3β-HSD mRNA and decreased the production of P₄, whereas no effects on CYP19A1 mRNA expression and E₂ levels were observed. We also found the negative regulatory effect of unconservative_15_2570409 on the mRNA and protein expression of PGR by targeting the 3'-untranslated region. The regulation of PGR levels resulted in a corresponding change in the ADAMTS1, PPAR-γ, and CTSL gene transcripts, which are important for follicular maturation and ovulation. Additionally, PGR, ADAMTS1, and PPAR-γ were predominantly localized in the GCs. Collectively, our results suggest that by regulating PGR expression and consequently affecting the expression of target genes and steroidogenesis, unconservative_15_2570409 plays a role in follicular development during the periovulatory stage, which provides novel insights into the molecular mechanisms affecting Hu sheep prolificacy.

GFP expression pattern in pituitary and gonads under the control of nuclear progesterone receptor promoter in transgenic zebrafish

BACKGROUND

The nuclear progesterone receptor (Pgr) is a ligand-dependent transcription factor primarily responsible for mediating progesterone actions relevant for reproduction across vertebrates. Information on the cellular localization of Pgr expression in the reproductive system is required for developing a comprehensive approach to elucidate the role of Pgr in reproduction.

RESULTS

We generated transgenic zebrafish Tg(pgr:eGFP) that express enhanced green fluorescent protein (eGFP) driven by promoter sequence of pgr gene. The tissue distribution pattern of egfp mRNA is consistent with the pgr mRNA expression in Tg(pgr:eGFP). In the pituitary, GFP signals are found in the proximal pars distalis. In order to better discern the cellular localization of GFP signals in gonads, Tg(pgr:eGFP) line was crossed with Tg(gsdf:nfsB-mCherry) line, specifically expressing nitroreductase-mCherry fusion protein in granulosa and Sertoli cells in ovary and testis, respectively. Imaging of testis tissue showed that GFP expression was confined to Leydig cells. In the ovary, GFP expression colocalized with the mCherry signal in granulosa cells. Intriguingly, we also identified some non-granulosa cells close to where blood vessels branched, expressing stronger GFP signals than granulosa cells.

CONCLUSIONS

Analyzing Tg(pgr:eGFP) expression in zebrafish provided leads toward new routes to study the role of Pgr in reproduction.

Ovulation and ovarian wound healing are impaired with advanced reproductive age

Aging is associated with reduced tissue remodeling efficiency and increased fibrosis, characterized by excess collagen accumulation and altered matrix degradation. Ovulation, the process by which an egg is released from the ovary, is one of the most dynamic cycles of tissue wounding and repair. Because the ovary is one of the first organs to age, ovulation and ovarian wound healing is impaired with advanced reproductive age. To test this hypothesis, we induced superovulation in reproductively young and old mice and determined the numbers of eggs ovulated and corpora lutea (CLs), the progesterone producing glands formed post-ovulation. Reproductively old mice ovulated fewer eggs and had fewer CLs relative to young controls. Moreover, reproductively old mice exhibited a greater number of oocytes trapped within CLs and expanded cumulus oocyte complexes within unruptured antral follicles, indicative of failed ovulation. In addition, post-ovulatory tissue remodeling was compromised with age as evidenced by reduced CL vasculature, increased collagen, decreased hyaluronan, decreased cell proliferation and apoptosis, impaired wound healing capacity, and aberrant morphology of the ovarian surface epithelium (OSE). These findings demonstrate that ovulatory dysfunction is an additional mechanism underlying the age-related loss of fertility beyond the reduction of egg quantity and quality.

mRNA and miRNA Transcriptome Profiling of Granulosa and Theca Layers From Geese Ovarian Follicles Reveals the Crucial Pathways and Interaction Networks for Regulation of Follicle Selection

Follicle development is characterized by the recruitment, growth, selection, and dominance of follicles, and follicle selection determines the lifetime reproductive performance. However, in birds, the molecular mechanisms underlying follicle selection still remain elusive. This study analyzed genome-wide changes in the mRNA and miRNA expression profiles in both the granulosa and theca layers of geese ovarian follicles before selection (4–6- and 8–10-mm follicles) and after selection (F5). The sequencing results showed that a higher number of both differentially expressed (DE) mRNAs and DE miRNAs were identified between 8–10-mm and F5 follicles compared with those between the 4–6- and 8–10-mm follicles, especially in the granulosa layer. Moreover, a Short Time-series Expression Miner analysis identified a large number of DE mRNAs and DE miRNAs that are associated with follicle selection. The functional enrichment analysis showed that DE genes in the granulosa layer during follicle selection were mainly enriched in five pathways related to junctional adhesion and two pathways associated with lipid metabolism. Additionally, an interaction network was constructed to visualize interactions among protein-coding genes, which identified 53 junctional adhesion- and 15 lipid regulation-related protein-coding genes. Then, a co-expression network between mRNAs and miRNAs in relation to junctional adhesion was also visualized and mainly included acy-miR-2954, acy-miR-218, acy-miR-2970, acy-miR-100, acy-miR-1329, acy-miR-199, acy-miR-425, acy-miR-181, and acy-miR-147. Furthermore, miRNA–mRNA interaction pairs related to lipid regulation were constructed including acy-miR-107, acy-miR-138, acy-miR-130, acy-miR-128, and acy-miR-101 during follicular selection. In summary, these data highlight the key roles of junctional adhesion and lipid metabolism during follicular selection and contribute to a better understanding of the mechanisms underlying follicle selection in birds.

Tissue-specific progesterone receptor-chromatin binding and the regulation of progesterone-dependent gene expression

Progesterone receptor (PGR) co-ordinately regulates ovulation, fertilisation and embryo implantation through tissue-specific actions, but the mechanisms for divergent PGR action are poorly understood. Here we characterised PGR activity in mouse granulosa cells using combined ChIP-seq for PGR and H3K27ac and gene expression microarray. Comparison of granulosa, uterus and oviduct PGR-dependent genes showed almost complete tissue specificity in PGR target gene profiles. In granulosa cells 82% of identified PGR-regulated genes bound PGR within 3 kb of the gene and PGR binding sites were highly enriched in proximal promoter regions in close proximity to H3K27ac-modified active chromatin. Motif analysis showed highly enriched PGR binding to the PGR response element (GnACAnnnTGTnC), but PGR also interacted significantly with other transcription factor binding motifs. In uterus PGR showed far more tendency to bind intergenic chromatin regions and low evidence of interaction with other transcription factors. This is the first genome-wide description of PGR action in granulosa cells and systematic comparison of diverse PGR action in different reproductive tissues. It clarifies finely-tuned contextual PGR-chromatin interactions with implications for more targeted reproductive medicine.

Chronically elevated androgen and/or consumption of a Western-style diet impairs oocyte quality and granulosa cell function in the nonhuman primate periovulatory follicle

PURPOSE

To investigate the impact of chronically elevated androgens in the presence and absence of an obesogenic diet on oocyte quality in the naturally selected primate periovulatory follicle.

METHODS

Rhesus macaques were treated using a 2-by-2 factorial design (n = 10/treatment) near the onset of menarche with implants containing either cholesterol (C) or testosterone (T, 4-5-fold increase above C) and a standard or "Western-style" diet alone (WSD) or in combination (T+WSD). Following ~ 3.5 years of treatment, females underwent controlled ovulation (COv, n = 7-10/treatment) cycles, and contents of the naturally selected periovulatory follicle were aspirated. Follicular fluid (FF) was analyzed for cytokines, chemokines, growth factors, and steroids. RNA was extracted from luteinizing granulosa cells (LGCs) and assessed by RNA-seq.

RESULTS

Only healthy, metaphase (M) I/II-stage oocytes (100%) were retrieved in the C group, whereas several degenerated oocytes were recovered in other groups (33-43% of T, WSD, and T+WSD samples). Levels of two chemokines and one growth factor were reduced (p < 0.04) in FF of follicles with a MI/MII oocyte in WSD+T (CCL11) or T and WSD+T groups (CCL2 and FGF2) compared to C and/or WSD. Intrafollicular cortisol was elevated in T compared to C follicles (p < 0.02). Changes in the expression pattern of 640+ gene products were detected in LGC samples from follicles with degenerated versus MI/MII-stage oocytes. Pathway analysis on RNAs altered by T and/or WSD found enrichment of genes mapping to steroidogenic and immune cell pathways.

CONCLUSIONS

Female primates experiencing hyperandrogenemia and/or consuming a WSD exhibit an altered intrafollicular microenvironment and reduced oocyte quality/competency, despite displaying menstrual cyclicity.

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.

Coordination of Ovulation and Oocyte Maturation: A Good Egg at the Right Time

Ovulation is the appropriately timed release of a mature, developmentally competent oocyte from the ovary into the oviduct, where fertilization occurs. Importantly, ovulation is tightly linked with oocyte maturation, demonstrating the interdependency of these two parallel processes, both essential for female fertility. Initiated by pituitary gonadotropins, the ovulatory process is mediated by intrafollicular paracrine factors from the theca, mural, and cumulus granulosa cells, as well as the oocyte itself. The result is the induction of cumulus expansion, proteolysis, angiogenesis, inflammation, and smooth muscle contraction, which are each required for follicular rupture. These complex intercellular communication networks and the essential ovulatory genes have been well defined in mouse models and are highly conserved in primates, including humans. Importantly, recent discoveries in regulation of ovulation highlight new areas of investigation.

Anti-Müllerian hormone is a survival factor and promotes the growth of rhesus macaque preantral follicles during matrix-free culture

Anti-Müllerian hormone (AMH) plays a key role during ovarian follicular development, with local actions associated with a dynamic secretion profile by growing follicles. While results for AMH effects on antral follicle growth and function are consistent among studies in various species, any effects on preantral follicle development remain controversial. Therefore, experiments were conducted to investigate the direct actions and role of AMH during follicle development at the preantral stage. Macaque-specific short-hairpin RNAs (shRNAs) targeting AMH mRNA were incorporated into adenoviral vectors to decrease AMH gene expression in rhesus macaque follicles. Secondary follicles were isolated from adult macaque ovaries and cultured individually in the ultra-low-attachment dish containing defined medium supplemented with follicle-stimulating hormone and insulin for 5 weeks. Follicles were randomly assigned to treatment groups: (a) control, (b) nontargeting control shRNA-vector, (c) AMH shRNA-vector, (d) AMH shRNA-vector + recombinant human AMH, and (e) recombinant human AMH. Follicle survival and growth were assessed. Culture media were analyzed for steroid hormone and paracrine factor concentrations. For in vivo study, the nontargeting control shRNA-vector and AMH shRNA-vector were injected into macaque ovaries. Ovaries were collected 9 days postinjection for morphology and immunohistochemistry assessment. Decreased AMH expression reduced preantral follicle survival and growth in nonhuman primates. Supplemental AMH treatment in the culture media promoted preantral follicle growth to the small antral stage in vitro with increased steroid hormone and paracrine factor production, as well as oocyte maturation. These data demonstrate that AMH is a critical follicular paracrine/autocrine factor positively impacting preantral follicle survival and growth in primates.

Intravenous neutralization of vascular endothelial growth factor reduces vascular function/permeability of the ovary and prevents development of OHSS-like symptoms in rhesus monkeys

Background

Ovarian hyperstimulation syndrome (OHSS) is a disorder associated with elevated serum VEGFA following chorionic gonadotropin (hCG) exposure in controlled ovarian stimulation (COS) cycles in women. In this study, we tested the effect of intravenous VEGFA neutralization on OHSS-like symptoms and vascular function in rhesus macaques during COS cycles.

Methods

Monkeys (n = 8) were treated with 3 COS protocols and assigned randomly to groups as follows: 1) COS alone (Control,n = 5); 2) COS + VEGF mAb Avastin 19 ± 5 h before hCG (Avastin pre-hCG; n = 6); 3) COS + Avastin 3–4 days post-hCG (Avastin post-hCG; n = 4); 4) COS + Simulated Early Pregnancy (SEPn = 3); or 5) COS + SEP + Avastin (SEP + Avastinn = 3). Follicles were aspirated 36 h post-hCG, fluid was collected from one follicle for analysis of steroid and vascular hormone content. Remaining follicles were aspirated, and luteinized granulosa cells (LGCs) cultured for 24 h. Ovarian/uterine vascular flow (VF) and blood volume (BV) were analyzed by contrast enhanced ultrasound (CEUS) before hCG bolus and 6–8 days post-hCG bolus/time of peak SEP response. Ovarian permeability to albumin was analyzed by Dynamic Contrast Enhanced-MRI (DCE-MRI) post-hCG.

Results

Abdominal fluid was present in 4/5 Control, 2/6 Avastin pre-hCG, and 3/4 Avastin post-hCG females. Neutralization of VEGFA before hCG reduced ovarian VF, BV, and permeability to albumin (P < 0.05), while only ovarian VF and permeability were reduced in Avastin-post hCG group (P < 0.05). There was no effect of Avastin on ovarian vascular function during COS + SEP. VEGF levels in follicular fluid were reduced 78-fold by Avastin pre-hCG, and LGCs exposed to Avastin in vivo also released 4-fold less VEGF into culture media (P < 0.05). Culture medium of LGCs exposed to VEGFA neutralization in vivo had lower levels of P4 and ANGPT1, and an increased ratio of ANGPT2/1 (P < 0.05). Uterine VF was reduced by SEP + Avastin in the basalis/junctional zone (P < 0.05).

Conclusions

Avastin treatment before hCG prevents the development of symptoms associated with ovarian hyperstimulation syndrome. In vitro data suggest neutralization of VEGFA alters expression of other vascular factors typically induced by hCG in the luteinizing follicle. Neutralization of VEGFA action alters the vascular function of the basalis zone of the uterus during simulated early pregnancy, indicating a potential effect on embryo implantation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13048-017-0340-5) contains supplementary material, which is available to authorized users.

Coordinated Regulation Among Progesterone, Prostaglandins, and EGF-Like Factors in Human Ovulatory Follicles

CONTEXT

In animal models, the luteinizing hormone surge increases progesterone (P4) and progesterone receptor (PGR), prostaglandins (PTGs), and epidermal growth factor (EGF)-like factors that play essential roles in ovulation. However, little is known about the expression, regulation, and function of these key ovulatory mediators in humans.

OBJECTIVE

To determine when and how these key ovulatory mediators are induced after the luteinizing hormone surge in human ovaries.

DESIGN AND PARTICIPANTS

Timed periovulatory follicles were obtained from cycling women. Granulosa/lutein cells were collected from in vitro fertilization patients.

MAIN OUTCOME MEASURES

The in vivo and in vitro expression of PGR, PTG synthases and transporters, and EGF-like factors were examined at the level of messenger RNA and protein. PGR binding to specific genes was assessed. P4 and PTGs in conditioned media were measured.

RESULTS

PGR, PTGS2, and AREG expressions dramatically increased in ovulatory follicles at 12 to 18 hours after human chorionic gonadotropin (hCG). In human granulosa/lutein cell cultures, hCG increased P4 and PTG production and the expression of PGR, specific PTG synthases and transporters, and EGF-like factors, mimicking in vivo expression patterns. Inhibitors for P4/PGR and EGF-signaling pathways reduced hCG-induced increases in PTG production and the expression of EGF-like factors. PGR bound to the PTGS2, PTGES, and SLCO2A1 genes.

CONCLUSIONS

This report demonstrated the time-dependent induction of PGR, AREG, and PTGS2 in human periovulatory follicles. In vitro studies indicated that collaborative actions of P4/PGR and EGF signaling are required for hCG-induced increases in PTG production and potentiation of EGF signaling in human periovulatory granulosa cells.

Progesterone receptor and prostaglandins mediate luteinizing hormone-induced changes in messenger RNAs for ADAMTS proteases in theca cells of bovine periovulatory follicles

Little is known about the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) family of extracellular proteases in ovarian follicles of non-rodent species, particularly in theca cells. In the present study, temporal changes in the abundance of mRNA encoding four ADAMTS subtypes and hormonal regulation of mRNA encoding two subtypes were investigated in theca interna cells during the periovulatory period in cattle. Gonadotropin-releasing hormone (GnRH) was injected into animals to induce a luteinizing hormone (LH)/follicle-stimulating hormone (FSH) surge, and follicles were obtained at 0 hr post-GnRH (preovulatory) or at 6, 12, 18, or 24 hr (periovulatory). ADAMTS1, -2, -7, and -9 transcript abundance was then determined in the isolated theca interna. ADAMTS1 and -9 mRNA levels were up-regulated at 24 hr post-GnRH, whereas ADAMTS2 mRNA was higher at 12-24 hr post-GnRH and ADAMTS7 mRNA increased transiently at 12 hr post-GnRH compared to other time points. Subsequent in vitro experiments using preovulatory theca interna (0 hr post-GnRH) showed that application of LH in vitro can mimic the effects of the gonadotropin surge on mRNAs encoding ADAMTS1 and -9 and that progesterone/progesterone receptor and/or prostaglandins may regulate the levels of mRNA encoding ADAMTS1 and -9 in theca interna, downstream of the LH surge. Time- and subtype-specific changes in ADAMTS mRNA abundance in vivo, and their regulation in vitro by hormones, indicate that ADAMTS family members produced by theca cells may play important roles in follicle rupture and the accompanying tissue remodeling in cattle. Mol. Reprod. Dev. 84: 55-66, 2017. © 2016 Wiley Periodicals, Inc.

Leukemia Inhibitory Factor Is Necessary for Ovulation in Female Rhesus Macaques

Although the requirement of pituitary-derived LH for ovulation is well documented, the intrafollicular paracrine and autocrine processes elicited by LH necessary for follicle rupture are not fully understood. Evaluating a published rhesus macaque periovulatory transcriptome database revealed that mRNA encoding leukemia inhibitory factor (LIF) and its downstream signaling effectors are up-regulated in the follicle after animals receive an ovulatory stimulus (human chorionic gonadotropin [hCG]). Follicular LIF mRNA and protein levels are below the limit of detection before the administration of hCG but increase significantly 12 hours thereafter. Downstream LIF receptor (LIFR) signaling components including IL-6 signal transducer, the receptor associated Janus kinase 1, and the transcription factor signal transducer and activator of transcription 3 also exhibit increased expression in the rhesus macaque follicle 12 hours after administration of an ovulatory hCG bolus. A laparoscopic ovarian evaluation 72 hours after the injection of a LIF antagonist (soluble LIFR) into the rhesus macaque preovulatory follicle and hCG administration revealed blocking LIF action prevented ovulation (typically occurs 36-44 h after hCG). Moreover, ovaries removed 52 hours after both hCG and intrafollicular soluble LIFR administration confirmed ovulation was blocked as evidenced by the presence of an intact follicle and a trapped cumulus-oocyte complex. These findings give new insight into the role of LIF in the primate ovary and could lead to the development of new approaches for the control of fertility.