Transcriptional effect of the LH surge in bovine granulosa cells during the peri-ovulation period

Supplementation with L-kynurenine during in vitro maturation improves bovine oocytes developmental competence through its antioxidative action

Oxidative stress impairs the developmental potential of oocytes during in vitro maturation (IVM). L-kynurenine (L-KYN), an endogenous metabolite, exhibits antioxidant, anti-inflammatory and neuroprotective effects. This work aimed to evaluate the potential effects of L-KYN on bovine oocyte IVM and its mechanisms. Different concentrations of L-KYN (0, 10, 50, 100, and 200 μmol/L) were supplemented to bovine oocyte IVM medium. Results shown a notable enhancement in the oocyte maturation rate and the subsequent zygote cleavage and blastocyst formation rate when the L-KYN concentration reached 100 μmol/L. Further analysis revealed that this treatment effectively down-regulated expression levels of genes to cumulus cell apoptosis (Bax and Caspase3), up-regulated expression levels of genes to cumulus cell expansion (HAS2, PTX3, and PTGS2) and oocyte antioxidant (GPX4 and CAT). L-KYN supplementation also effectively increased glutathione (GSH) levels, promoted oocytes mitochondrial activity, enhanced DNA repairability, deceased reactive oxygen species (ROS) levels, and reduced apoptosis. In conclusion, adding 100 μmol/L of L-KYN to IVM medium could enhance bovine oocyte quality and the subsequent embryonic development. L-KYN could be a potential antioxidant supplement for bovine oocyte maturation in vitro.

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.

Transcriptome profiling reveals transcriptional regulation of Protegrin-1 on immune defense and development in porcine granulosa cells

Protegrin-1 (PG1) is an antimicrobial peptide (AMP) that has garnered increasing attention due to its potent immune defense activity. Our previous studies demonstrated the ability of PG1 to enhance proliferation and inhibit apoptosis of porcine granulosa cells (GCs) under oxidative stress. GCs play a crucial role in ovary follicular development. However, the specific function and underlying mechanisms of AMP in follicular development still need further elucidation. The present study aimed to comprehensively explore the biological effects of PG1 on porcine GCs using transcriptome profiling by RNA sequencing technology. Isolated GCs were incubated with or without PG1 for 24 h and transcriptome-wide analysis was exerted to identify differentially expressed genes (DEGs). The results of expression analysis revealed 1,235 DEGs, including 242 up-regulated genes and 993 down-regulated genes (|log2 (FoldChange)| > 1; adjusted P-value < 0.05). The expression levels of 7 selected DEGs were validated by quantitative reverse transcription-polymerase chain reaction (RT-qPCR) analysis, which was consistent with the RNA-sequencing data. Among the significant DEGs, several genes associated with GC function and ovarian follicle development were identified, such as estrogen receptor 2 (ESR2), growth and differentiation factor 6 (GDF6), cell division cycle 20 homolog (CDC20), Notch3, ephrin and Eph receptor system, Egl nine homolog 3 (EGLN3), and BCL2 like 14 (BCL2L14). Gene Ontology (GO) analysis revealed that the top three significant GO terms were inflammatory response, defense response, and granulocyte migration. Additionally, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis presented that DEGs were mainly enriched in the immune system, infectious disease, signaling molecules and interaction, and immune disease. Furthermore, Ingenuity Pathway Analysis (IPA) predicted that the top activated pathway was Liver X Receptor (LXR)/ Retinoid X Receptor (RXR) Activation which is known to be associated with female reproduction. Predicted protein-protein interactions (PPIs) analysis identified complement C3 (C3) as the top node with the highest degree of network connection and revealed that DEGs in the sub-networks were involved in cytokine-cytokine receptor interaction, neuroactive ligand-receptor interaction, chemokine signaling pathway, and metabolic process. In conclusion, this study expanded the understanding of the effects of PG1 on porcine GCs at the transcriptomic level and provided a theoretical basis for further investigation into the role of PG1 in immune defense and mammalian ovarian follicular development.

Metabolite abundance in bovine preovulatory follicular fluid is influenced by follicle developmental progression post estrous onset in cattle

Introduction: Preovulatory follicle response to the luteinizing hormone (LH) surge leads to metabolic, molecular, and functional changes in the oocyte and somatic follicular cells from the onset of estrus to ovulation. Follicular fluid contains metabolites, miRNAs, proteins, and hormones that are byproducts of follicular metabolism and support cellular processes of oocyte, cumulus, and granulosa constituents. Numerous studies have highlighted the importance of follicular fluid composition to support fertility, but critical gaps exist toward understanding dynamic modifications in the follicular fluid metabolome from estrous onset to ovulation. The hypothesis was that abundance of follicular fluid metabolites is dependent on follicle progression post LH surge and variability in follicular fluid metabolome profiles indicate key processes required for preparation of the follicle and oocyte for optimal fertility. The objective was to generate preovulatory follicular fluid metabolome profiles and discern differences in the metabolome of preovulatory follicular fluid samples collected at onset of estrus, 11 h post estrous onset, and 18 h post estrous onset. Methods: Estrus was synchronized in non-lactating Jersey cows (n=40) and follicular fluid was collected immediately after the first observed standing mount (hr 0) or at approximately h 11 or 18 after the first standing mount. Ultra-High-Performance Liquid Chromatography-High Resolution Mass Spectrometry was performed on preovulatory follicular fluid samples (n = 9 collected at hr 0, 9 at h 11, and 10 at h 18) and a multiple linear model was performed to determine if time post estrous onset impacted metabolite abundance. Results: Metabolites influenced by time post estrous onset were tested for enrichment in KEGG pathways. Ninety metabolites were identified in follicular fluid samples. Twenty metabolites differed in abundance among timepoints post estrous onset (p ≤ 0.05). Pathways corresponding to amino acid and energy metabolism were enriched with metabolites impacted by time post estrous onset (FDR ≤ 0.10). Discussion: Results from the current study indicate early response to the LH surge to increase bioavailability of amino acids and metabolites used by the cumulus and granulosa cells for energy production and shuttled into the oocyte to support meiotic maturation. Such metabolites may later be used by the ovulatory follicle for protein production.

The PGE2/Ptger4b pathway regulates ovulation by inducing intracellular actin cytoskeleton rearrangement via the Rho/Rock pathway in the granulosa cells of periovulatory follicles in the teleost medaka

We have previously shown that the prostaglandin E₂/Ptger4b receptor system is involved in ovulation in teleost medaka and induces intracellular actin cytoskeleton rearrangement in the granulosa cells of preovulatory follicles. In this study, we investigated the signaling pathways through which prostaglandin E₂ induces a change in the actin cytoskeleton. Treating preovulatory follicles with GW627368X (Ptger4b antagonist), a Rho inhibitor, or Y-27632 [Rho-associated protein kinase (Rock) inhibitor] inhibited not only in vitro follicle ovulation but also intracellular actin cytoskeleton rearrangement. Active Rhoa-c and Rock1 were detected in follicles immediately before ovulation. GW627368X also inhibited Rhoa-c activation and cytoskeleton rearrangement. PGE₂-induced actin cytoskeleton rearrangement was not observed in the Ptger4b-, Rhoa-c-, or Rock1-deficient OLHNI-2 cells. These results indicate that the PGE₂/Ptger4b pathway regulates intracellular actin cytoskeleton rearrangement via the Rho/Rock pathway in the granulosa cells of preovulatory follicles during medaka ovulation.

Follicular Hyperstimulation Dysgenesis: New Explanation for Adverse Effects of Excessive FSH in Ovarian Stimulation

High follicle-stimulating hormone (FSH) doses during ovarian stimulation protocols for assisted reproductive technologies (ART) are detrimental to ovulatory follicle function and oocyte quality. However, the mechanisms are unclear. In a small ovarian reserve heifer model, excessive FSH doses lead to phenotypic heterogeneity of ovulatory size follicles, with most follicles displaying signs of premature luteinization and a range in severity of abnormalities. By performing whole transcriptome analyses of granulosa cells, cumulus cells, and oocytes from individual follicles of animals given standard or excessive FSH doses, we identified progressive changes in the transcriptomes of the 3 cell types, with increasing severity of follicular abnormality with the excessive doses. The granulosa and cumulus cells each diverged progressively from their normal phenotypes and became highly similar to each other in the more severely affected follicles. Pathway analysis indicates a possible dysregulation of the final stages of folliculogenesis, with processes characteristic of ovulation and luteinization occurring concurrently rather than sequentially in the most severely affected follicles. These changes were associated with disruptions in key pathways in granulosa and cumulus cells, which may account for previously reported reduced estradiol production, enhanced progesterone and oxytocin production and diminished ovulation rates. Predicted deficiencies in oocyte survival, stress response, and fertilization suggest likely reductions in oocyte health, which could further compromise oocyte quality and ART outcomes.

Metabolic and antioxidant status during transition is associated with changes in the granulosa cell transcriptome in the preovulatory follicle in high-producing dairy cows at the time of breeding

In this study, we hypothesized that early postpartum (pp) metabolic and oxidative stress conditions in dairy cows (particularly those with severe negative energy balance, NEB) are associated with long-term changes in granulosa cell (GC) functions in the preovulatory follicle at the time of breeding. Blood samples were collected at wk 2 and wk 8 pp from 47 healthy multiparous cows. Follicular fluid (FF) and GC were collected from the preovulatory follicle after estrous synchronization at wk 8. Several metabolic and antioxidant parameters were measured in blood and FF, and their correlations were studied. Subsequently, 27 representative GC samples were selected for RNA sequencing analysis. The GC gene expression data of LH-responsive genes and the estradiol:progesterone ratio in FF were used to identify pre- and post-LH surge cohorts. We compared the transcriptomic profile of subgroups of cows within the highest and lowest quartiles (Q4 vs. Q1) of each parameter, focusing on the pre-LH surge cohort (n = 16, at least 3 in each subgroup). Differentially expressed genes (DEG: adjusted P-value < 0.05, 5% false discovery rate) were determined using DESeq2 analysis and were functionally annotated. Blood and FF β-carotene and vitamin E concentrations at wk 2, but not at wk 8, were associated with the most pronounced transcriptomic differences in the GC, with up to 341 DEG indicative for lower catabolism, increased oxidoreductase activity and signaling cascades that are known to enhance oocyte developmental competence, increased responsiveness to LH, and a higher steroidogenic activity. In contrast, elevated blood NEFA concentrations at wk 2 (and not at wk 8) were associated with a long-term carryover effect detectable in the GC transcriptome at wk 8 (64 DEG). These genes are related to response to lipids and ketones, oxidative stress, and immune responses, which suggests persistent cellular stress and oxidative damage. This effect was more pronounced in cows with antioxidant deficiencies at wk 8 (up to 148 DEG), with more genes involved in oxidative stress-dependent responses, apoptosis, autophagy and catabolic processes, and mitochondrial damage. Interestingly, within the severe NEB cows (high blood NEFA at wk 2), blood antioxidant concentrations (high vs. low) at wk 8 were associated with up to 194 DEG involved in activation of meiosis and other signaling pathways, indicating a better oocyte supportive capacity. This suggests that the cow antioxidant profile at the time of breeding might alleviate, at least in part, the effect of NEB on GC functions. In conclusion, these results provide further evidence that the metabolic and oxidative stress in dairy cows early postpartum can have long-term effects on GC functions in preovulatory follicles at the time of breeding. The interplay between the effects of antioxidants and NEFA illustrated here might be useful to develop intervention strategies to minimize the effect of severe NEB on fertility.

Ankyrin-repeat and SOCS box-containing protein 9 (ASB9) regulates ovarian granulosa cells function and MAPK signaling

Ankyrin-repeat and SOCS box-containing proteins (ASB) interact with the elongin B-C adapter via their SOCS box domain and with the cullin and ring box proteins to form E3 ubiquitin ligase complexes within the protein ubiquitination pathway. ASB9 in particular is a differentially expressed gene in ovulatory follicles (OFs) induced by the luteinizing hormone (LH) surge or hCG injection in ovarian granulosa cells (GC) while downregulated in growing dominant follicles. Although ASB9 has been involved in biological processes such as protein modification, the signaling network associated with ASB9 in GC is yet to be fully defined. We previously identified and reported ASB9 interactions and binding partners in GC including PAR1, TAOK1, and TNFAIP6/TSG6. Here, we further investigate ASB9 effects on target binding partners regulation and signaling in GC. CRISPR/Cas9-induced inhibition of ASB9 revealed that ASB9 regulates PAR1, TAOK1, TNFAIP6 as well as genes associated with proliferation and cell cycle progression such as PCNA, CCND2, and CCNE2 while CCNA2 was not affected. Inhibition of ASB9 was also associated with increased GC number and decreased caspase3/7 activity, CASP3 expression, and BAX/BCL2 ratio. Furthermore, ASB9 induction in OF in vivo 24 h post-hCG is concomitant with a significant decrease in phosphorylation levels of MAPK3/1 while pMAPK3/1 levels increased following ASB9 inhibition in GC in vitro. Together, these results provide strong evidence for ASB9 as a regulator of GC activity and function by modulating MAPK signaling likely through specific binding partners such as PAR1, therefore controlling GC proliferation and contributing to GC differentiation into luteal cells.

Genome wide effects of oleic acid on cultured bovine granulosa cells: evidence for the activation of pathways favoring folliculo-luteal transition

BACKGROUND

Metabolic stress, as negative energy balance on one hand or obesity on the other hand can lead to increased levels of free fatty acids in the plasma and follicular fluid of animals and humans. In an earlier study, we showed that increased oleic acid (OA) concentrations affected the function of cultured bovine granulosa cells (GCs). Here, we focus on genome wide effects of increased OA concentrations.

RESULTS

Our data showed that 413 genes were affected, of which 197 were down- and 216 up-regulated. Specifically, the expression of FSH-regulated functional key genes, CCND2, LHCGR, INHA and CYP19A1 and 17-β-estradiol (E2) production were reduced by OA treatment, whereas the expression of the fatty acid transporter CD36 was increased and the morphology of the cells was changed due to lipid droplet accumulation. Bioinformatic analysis revealed that associated pathways of the putative upstream regulators "FSH" and "Cg (choriogonadotropin)" were inhibited and activated, respectively. Down-regulated genes are over-represented in GO terms "reproductive structure/system development", "ovulation cycle process", and "(positive) regulation of gonadotropin secretion", whereas up-regulated genes are involved in "circulatory system development", "vasculature development", "angiogenesis" or "extracellular matrix/structure organization".

CONCLUSIONS

From these data we conclude that besides inhibiting GC functionality, increased OA levels seemingly promote angiogenesis and tissue remodelling, thus suggestively initiating a premature fulliculo-luteal transition. In vivo this may lead to impeded folliculogenesis and ovulation, and cause sub-fertility.

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.

Investigating Markers of Reprogramming Potential in Somatic Cell Lines Derived from Matched Donors

Somatic cell biobanking and related technologies, somatic cell nuclear transfer (SCNT), and induction of pluripotent stem cells offer significant promise for wildlife conservation, but have yet to achieve optimal success. Inefficiency and variability in outcome have been linked to incomplete nuclear reprogramming, highlighting the importance of donor cell contribution. Studies show significant differences in SCNT outcome in donor cell lines within and between individuals, highlighting the necessity for a standardized characterization method to evaluate cell line reprogramming potential. Stringently standardized bovine fibroblast cell lines were generated and assessed for inter- and intraindividual variability on cellular (morphology, chromosome number, apoptotic incidence; Experiment 1) and molecular (pluripotency and epigenetic-related gene expression; Experiment 2) levels encompassing putative biomarkers of reprogramming potential. Cellular parameters were similar across cell lines. While some statistically significant differences were observed in DNMT1, DNMT3B, and HAT1, but not HDAC1, their biological relevance could not be determined with the information at hand. This study lays the foundation for understanding cellular characteristics in cultured cell lines; however, further studies are required to determine any correlation with reprogramming potential.

Integrated analysis of miRNA-mRNA interaction in ovaries of Turpan Black Sheep during follicular and luteal phases

To investigate the regulatory mechanism of the follicular-luteal phase transition in Turpan black sheep (Ovis aries), the genome-wide expression patterns of microRNAs (miRNAs) and genes were investigated in ovaries of six sheep (3 years and single lamb with 3 consecutive births) during follicular and luteal phases of the oestrous cycle. Bioinformatic analysis was used to screen potential miRNAs and genes related to Turpan black sheep ovarian function. RT-qPCR was used to validate the sequencing results. In total, we identified 139 known and 71 novel miRNAs in the two phases with miRNA-seq, and a total of 19 miRNAs were significantly differentially expressed, of which 7 were up-regulated and 12 were down-regulated in the follicular phase compared with luteal phase. A total of 150 genes were significantly differentially expressed, including 63 up-regulated and 87 down-regulated in the follicular phase compared with the luteal phase by RNA-seq data analysis. Those DEGs were significantly enriched in 103 GO terms and several KEGG pathways, including metabolic pathway, ovarian steroidogenesis, steroid hormone biosynthesis and oestrogen signalling pathway. In addition, we created a miRNA-mRNA regulatory network to further elucidate the mechanism of follicular-luteal transition. Finally, we identified key miRNAs and genes including miR-143, miR-99a, miR-150, miR-27a, miR-125b, STAR, STAT1, which might play crucial roles in reproductive hormone biosynthesis and follicular development. The miRNA-mRNA interactive network clearly illustrates molecular basis involving in follicular-luteal transition.

Contribution of the immune system to follicle differentiation, ovulation and early corpus luteum formation

Much of what we know about the involvement of the immune system in periovulatory follicle differentiation, ovulation and subsequent formation of the corpus luteum in cattle is drawn from the findings of studies in several mammalian livestock species. By integrating published histological data from cattle, sheep and pigs and referring back to the more comprehensive knowledge bank that exists for mouse and humans we can sketch out the key cells of the immune system and the cytokines and growth factors that they produce that are involved in follicle differentiation and luteinization, ovulation and early follicle development. These contributions are reviewed and the key findings, discussed.

Gonadotropin regulation of ankyrin-repeat and SOCS-box protein 9 (ASB9) in ovarian follicles and identification of binding partners

Ankyrin-repeat and SOCS-box protein 9 (ASB9) is a member of the large SOCS-box containing proteins family and acts as the specific substrate recognition component of E3 ubiquitin ligases in the process of ubiquitination and proteasomal degradation. We previously identified ASB9 as a differentially expressed gene in granulosa cells (GC) of bovine ovulatory follicles. This study aimed to further investigate ASB9 mRNA and protein regulation, identify binding partners in GC of bovine ovulatory follicles, and study its function. GC were obtained from small follicles (SF: 2–4 mm), dominant follicles at day 5 of the estrous cycle (DF), and ovulatory follicles, 24 hours following hCG injection (OF). Analyses by RT-PCR showed a 104-fold greater expression of ASB9 in GC of OF than in DF. Steady-state levels of ASB9 in follicular walls (granulosa and theca cells) analyzed at 0, 6, 12, 18 and 24 hours after hCG injection showed a significant induction of ASB9 expression at 12 and 18 hours, reaching a maximum induction of 10.2-fold at 24 hours post-hCG as compared to 0 hour. These results were confirmed in western blot analysis showing strongest ASB9 protein amounts in OF. Yeast two-hybrid screening of OF-cDNAs library resulted in the identification of 10 potential ASB9 binding partners in GC but no interaction was found between ASB9 and creatine kinase B (CKB) in these GC. Functional studies using CRISPR-Cas9 approach revealed that ASB9 inhibition led to increased GC proliferation and modulation of target genes expression. Overall, these results support a physiologically relevant role of ASB9 in the ovulatory follicle by targeting specific proteins likely for degradation, contributing to reduced GC proliferation, and could be involved in the final GC differentiation into luteal cells.

A Tissue Culture Model of Estrogen-producing Primary Bovine Granulosa Cells

Ovarian granulosa cells (GC) are the major source of estradiol synthesis. Induced by the preovulatory luteinizing hormone (LH) surge, cells of the theca and, in particular, of the granulosa cell layer profoundly change their morphological, physiological, and molecular characteristics and form the progesterone-producing corpus luteum that is responsible for maintaining pregnancy. Cell culture models are essential tools to study the underlying regulatory mechanisms involved in the folliculo-luteal transformation. The presented protocol focuses on the isolation procedure and cryopreservation of bovine GC from small- to medium-sized follicles (< 6 mm). With this technique, a nearly pure population of GC can be obtained. The cryopreservation procedure greatly facilitates time management of the cell culture work independent of a direct primary tissue (ovaries) supply. This protocol describes a serum-free cell culture model that mimics the estradiol-active status of bovine GC. Important conditions that are essential for a successful steroid-active cell culture are discussed throughout the protocol. It is demonstrated that increasing the plating density of the cells induces a specific response as indicated by an altered gene expression profile and hormone production. Furthermore, this model provides a basis for further studies on GC differentiation and other applications.

Transcriptome analysis of granulosa cells after conventional vs long FSH-induced superstimulation in cattle

BACKGROUND

Prolongation of superstimulatory treatment appears to be associated with a greater superovulatory response and with greater oocyte maturation in cattle. A genome-wide bovine oligo-microarray was used to compare the gene expression of granulosa cells collected from ovarian follicles after differing durations of the growing phase induced by exogenous FSH treatment. Cows were given a conventional (4-day) or long (7-day) superstimulatory treatment (25 mg FSH im at 12-h intervals; n = 6 per group), followed by prostaglandin treatment with last FSH and LH treatment 24 h later. Granulosa cells were harvested 24 h after LH treatment.

RESULTS

The expression of 416 genes was down-regulated and 615 genes was up-regulated in the long FSH group compared to the conventional FSH group. Quantification by RT-PCR of 7 genes (NTS, PTGS2, PTX3, RGS2, INHBA, CCND2 and LRP8) supported the microarrays data. Multigene bioinformatic analysis indicates that markers of fertility and follicle maturity were up-regulated in the long FSH group.

CONCLUSION

Using the large gene expression dataset generated by the genomic analysis and our previous associated with the growth phase and gene expression changes post LH, we can conclude that a prolonged FSH-induced growing phase is associated with transcriptomic characteristics of greater follicular maturity and may therefore be more appropriate for optimizing the superovulatory response and developmental competence of oocytes in cattle.

Lactate promotes specific differentiation in bovine granulosa cells depending on lactate uptake thus mimicking an early post-LH stage

BACKGROUND

The LH-induced folliculo-luteal transformation is connected with alterations of the gene expression profile in cells of the granulosa layer. It has been described that hypoxic conditions occur during luteinization, thus favoring the formation of L-lactate within the follicle. Despite being a product of anaerobic respiration, L-lactate has been shown to act as a signaling molecule affecting gene expression in neuronal cells. During the present study, we tested the hypothesis that L-lactate may influence differentiation of follicular granulosa cells (GC).

METHODS

In a bovine granulosa cell culture model effects of L- and D-lactate, of increased glucose concentrations and of the lactate transport inhibitor UK5099 were analyzed. Steroid hormone production was analyzed by RIA and the abundance of key transcripts was determined by quantitative real-time RT-PCR.

RESULTS

L-lactate decreased the production of estradiol and significantly affected selected genes of the folliculo-luteal transition as well as genes of the lactate metabolism. CYP19A1, FSHR, LHCGR were down-regulated, whereas RGS2, VNN2, PTX3, LDHA and lactate transporters were up-regulated. These effects could be partly or completely reversed by pre-treatment of the cells with UK5099. The non-metabolized enantiomer D-lactate had even more pronounced effects on gene expression, whereas increased glucose concentrations did not affect transcript abundance.

CONCLUSIONS

In summary, our data suggest that L-lactate specifically alters physiological and molecular characteristics of GC. These effects critically depend on L-lactate uptake, but are not triggered by increased energy supply. Further, we could show that L-lactate has a positive feedback on the lactate metabolism. Therefore, we hypothesize that L-lactate acts as a signaling molecule in bovine and possibly other monovular species supporting differentiation during the folliculo-luteal transformation.

Gene expression profiling of upregulated mRNAs in granulosa cells of bovine ovulatory follicles following stimulation with hCG

BACKGROUND

Ovulation and luteinization of follicles are complex biological processes initiated by the preovulatory luteinizing hormone surge. The objective of this study was to identify genes that are differentially expressed in bovine granulosa cells (GC) of ovulatory follicles.

METHODS

Granulosa cells were collected during the first follicular wave of the bovine estrous cycle from dominant follicles (DF) and from ovulatory follicles (OF) obtained 24 h following injection of human chorionic gonadotropin (hCG). A granulosa cell subtracted cDNA library (OF-DF) was generated using suppression subtractive hybridization and screened.

RESULTS

Detection of genes known to be upregulated in bovine GC during ovulation, such as ADAMTS1, CAV1, EGR1, MMP1, PLAT, PLA2G4A, PTGES, PTGS2, RGS2, TIMP1, TNFAIP6 and VNN2 validated the physiological model and analytical techniques used. For a subset of genes that were identified for the first time, gene expression profiles were further compared by semiquantitative RT-PCR in follicles obtained at different developmental stages. Results confirmed an induction or upregulation of the respective mRNAs in GC of OF 24 h after hCG-injection compared with those of DF for the following genes: ADAMTS9, ARAF, CAPN2, CRISPLD2, FKBP5, GFPT2, KIT, KITLG, L3MBLT3, MRO, NUDT10, NUDT11, P4HA3, POSTN, PSAP, RBP1, SAT1, SDC4, TIMP2, TNC and USP53. In bovine GC, CRISPLD2 and POSTN mRNA were found as full-length transcript whereas L3MBLT3 mRNA was alternatively spliced resulting in a truncated protein missing the carboxy-terminal end amino acids, ⁷⁷⁴KNSHNEL⁷⁸⁰. Conversely, L3MBLT3 is expressed as a full-length mRNA in a bovine endometrial cell line. The ⁷⁷⁴KNSHNEL⁷⁸⁰ sequence is well conserved in all mammalian species and follows a SAM domain known to confer protein/protein interactions, which suggest a key function for these amino acids in the epigenetic control of gene expression.

CONCLUSIONS

We conclude that we have identified novel genes that are upregulated by hCG in bovine GC of OF, thereby providing novel insight into peri-ovulatory regulation of genes that contribute to ovulation and/or luteinization processes.

miRNA-mRNA network involved in folliculogenesis interactome: systems biology approach

At later phases of folliculogenesis, the mammalian ovarian follicle contains layers of granulosa cells surrounding an antral cavity. To better understand the molecular basis of follicular growth and granulosa cell maturation, we study transcriptome profiling of granulosa cells from small (<5 mm) and large (>10 mm) bovine follicles using simultaneous method of Affymetrix microarrays (24,128 probe sets) and RNA-Seq data sets. This study proposes a computational method to discover the functional miRNA-mRNA regulatory modules, that is, groups of miRNAs and their target mRNAs that are believed to take part cooperatively in post-transcriptional gene regulation under specific conditions. The reconstructed network was named Integrated miRNA-mRNA Bipartite Network. 277 genes and 6 key modules were disclosed through clustering for mRNA master list. The 66 genes are among the genes that belong to at least two modules. All these genes, being involved in at least one of the phenomena, namely cell survival, proliferation, metastasis and apoptosis, have an overexpression pattern (P < 0.01). For miRNA master list, a total of 172 sequences were differentially expressed (P < 0.01) between dominant (large) and each of subordinate (small) follicles. Within the follicle, these miRNAs were predominantly expressed in mural granulosa cells. Finally, predicted and validated targets of these miRNAs enriched in dominant (large) follicles were identified, which are mapped to signaling pathways involved in follicular cell proliferation, steroidogenesis, PI3K/AKT/mTOR and Ras/Raf/MEK/ERK. The identification of miRNAs and their target mRNAs and the construction of their regulatory networks may give new insights into biological procedures.

Stable reference genes in granulosa cells of bovine dominant follicles during follicular growth, FSH stimulation and maternal aging

The aim of the present study was to determine a set of reference genes in granulosa cells of dominant follicles that are suitable for relative gene expression analyses during maternal and follicular aging. Granulosa cells of growing and preovulatory dominant follicles were collected from aged and young cows (maternal aging study) and from FSH-stimulated follicles developing under different durations of FSH treatment (follicular aging study). The mRNA levels of the two commonly used reference genes (GAPDH, ACTB) and four novel genes (UBE2D2, EIF2B2, SF3A1, RNF20) were analysed using cycle threshold values. Results revealed that mRNA levels of GAPDH, ACTB, EIF2B2, RNF20, SF3A1 and UBE2D2 were similar (P>0.05) between dominant follicle type, age and among follicles obtained after FSH-stimulation, but differed (P=0.005) due to mRNA processing (i.e. with versus without amplification). The stability of reference genes was analysed using GeNorm, DeltaCT and NormFinder programs and comprehensive ranking order was determined using RefFinder. The mRNA levels of GAPDH and ACTB were less stable than those of UBE2D2 and EIF2B2. The geometric mean of multiple genes (UBE2D2, EIF2B2, GAPDH and SF3A1) is a more appropriate reference control than the use of a single reference gene to compare relative gene expression among dominant and FSH-stimulated follicles during maternal and/or follicular aging studies.

MicroRNA Mediating Networks in Granulosa Cells Associated with Ovarian Follicular Development

Ovaries, which provide a place for follicular development and oocyte maturation, are important organs in female mammals. Follicular development is complicated physiological progress mediated by various regulatory factors including microRNAs (miRNAs). To demonstrate the role of miRNAs in follicular development, this study analyzed the expression patterns of miRNAs in granulosa cells through investigating three previous datasets generated by Illumina miRNA deep sequencing. Furthermore, via bioinformatic analyses, we dissected the associated functional networks of the observed significant miRNAs, in terms of interacting with signal pathways and transcription factors. During the growth and selection of dominant follicles, 15 dysregulated miRNAs and 139 associated pathways were screened out. In comparison of different styles of follicles, 7 commonly abundant miRNAs and 195 pathways, as well as 10 differentially expressed miRNAs and 117 pathways in dominant follicles in comparison with subordinate follicles, were collected. Furthermore, SMAD2 was identified as a hub factor in regulating follicular development. The regulation of miR-26a/b on smad2 messenger RNA has been further testified by real time PCR. In conclusion, we established functional networks which play critical roles in follicular development including pivotal miRNAs, pathways, and transcription factors, which contributed to the further investigation about miRNAs associated with mammalian follicular development.

Induction of altered gene expression profiles in cultured bovine granulosa cells at high cell density

BACKGROUND

In previous studies it has been shown that bovine granulosa cells (GC) cultured at a high plating density dramatically change their physiological and molecular characteristics, thus resembling an early stage of luteinization. During the present study, these specific effects on the GC transcriptome were comprehensively analysed to clarify the underlying mechanisms.

METHODS

GC were cultured in serum free medium with FSH and IGF-1 stimulation at different initial plating density. The estradiol and progesterone production was determined by radioimmunoassays and the gene expression profiles were analysed by mRNA microarray analysis after 9 days. The data were statistically analysed and the abundance of selected, differentially expressed transcripts was re-evaluated by qPCR. Bioinformatic pathway analysis of density affected transcripts was done using Ingenuity Pathway Analysis.

RESULTS

The data showed that at high plating density the expression of 1510 annotated genes, represented by 1575 transcript clusters, showed highly altered expression levels. Nearly two-thirds were up- and one third down-regulated. Within the top up-regulated genes VNN2, RGS2 and PTX3 could be identified, as well as HBA or LOXL2. Down-regulated genes included important key genes of folliculogenesis like CYP19A1 and FSHR. Ingenuity pathway analysis identified "AMPK signaling" as well as "cAMP-mediated signaling" as major pathways affected by the alteration of the expression profile. Main putative upstream regulators were TGFB1 and VEGF, thus indicating a connection with cell differentiation and angiogenesis. A detailed cluster analysis revealed one single cluster that was highly associated with the upstream regulator beta-estradiol. Within this cluster key genes of steroid biosynthesis were not included, but instead, other genes importantly involved in follicular development, like OXT and VEGFA as well as the three most down-regulated genes TXNIP, PAG11 and ARRDC4 were identified.

CONCLUSIONS

From these data we hypothesize that high density conditions induce a stage of differentiation in cultured GC that is similar to early post-LH conditions in vivo. Furthermore we hypothesize that specific cell-cell-interactions led to this differentiation including transformations necessary to promote angiogenesis.

Competence Classification of Cumulus and Granulosa Cell Transcriptome in Embryos Matched by Morphology and Female Age

Objective

By focussing on differences in the mural granulosa cell (MGC) and cumulus cell (CC) transcriptomes from follicles resulting in competent (live birth) and non-competent (no pregnancy) oocytes the study aims on defining a competence classifier expression profile in the two cellular compartments. Design: A case-control study. Setting: University based facilities for clinical services and research. Patients: MGC and CC samples from 60 women undergoing IVF treatment following the long GnRH-agonist protocol were collected. Samples from 16 oocytes where live birth was achieved and 16 age- and embryo morphology matched incompetent oocytes were included in the study.

Methods

MGC and CC were isolated immediately after oocyte retrieval. From the 16 competent and non-competent follicles, mRNA was extracted and expression profile generated on the Human Gene 1.0 ST Affymetrix array. Live birth prediction analysis using machine learning algorithms (support vector machines) with performance estimation by leave-one-out cross validation and independent validation on an external data set.

Results

We defined a signature of 30 genes expressed in CC predictive of live birth. This live birth prediction model had an accuracy of 81%, a sensitivity of 0.83, a specificity of 0.80, a positive predictive value of 0.77, and a negative predictive value of 0.86. Receiver operating characteristic analysis found an area under the curve of 0.86, significantly greater than random chance. When applied on 3 external data sets with the end-point outcome measure of blastocyst formation, the signature resulted in 62%, 75% and 88% accuracy, respectively. The genes in the classifier are primarily connected to apoptosis and involvement in formation of extracellular matrix. We were not able to define a robust MGC classifier signature that could classify live birth with accuracy above random chance level.

Conclusion

We have developed a cumulus cell classifier, which showed a promising performance on external data. This suggests that the gene signature at least partly include genes that relates to competence in the developing blastocyst.

Effects of intramuscular administration of folic acid and vitamin B12 on granulosa cells gene expression in postpartum dairy cows

The fertility of dairy cows is challenged during early lactation, and better nutritional strategies need to be developed to address this issue. Combined supplementation of folic acid and vitamin B12 improve energy metabolism in the dairy cow during early lactation. Therefore, the present study was undertaken to explore the effects of this supplement on gene expression in granulosa cells from the dominant follicle during the postpartum period. Multiparous Holstein cows received weekly intramuscular injection of 320 mg of folic acid and 10 mg of vitamin B12 (treated group) beginning 24 (standard deviation=4) d before calving until 56 d after calving, whereas the control group received saline. The urea plasma concentration was significantly decreased during the precalving period, and the concentration of both folate and vitamin B12 were increased in treated animals. Milk production and dry matter intake were not significantly different between the 2 groups. Plasma concentrations of folates and vitamin B12 were increased in treated animals. Daily dry matter intake was not significantly different between the 2 groups before [13.5 kg; standard error (SE)=0.5] and after (23.6 kg; SE=0.9) calving. Average energy-corrected milk tended to be greater in vitamin-treated cows, 39.7 (SE=1.4) and 38.1 (SE=1.3) kg/d for treated and control cows, respectively. After calving, average plasma concentration of β-hydroxybutyrate tended to be lower in cows injected with the vitamin supplement, 0.47 (SE=0.04) versus 0.55 (SE=0.03) for treated and control cows, respectively. The ovarian follicle ≥12 mm in diameter was collected by ovum pick-up after estrus synchronization. Recovered follicular fluid volumes were greater in the vitamin-treated group. A microarray platform was used to investigate the effect of treatment on gene expression of granulosa cells. Lower expression of genes involved in the cell cycle and higher expression of genes associated with granulosa cell differentiation before ovulation were observed. Selected candidate genes were analyzed by reverse transcription quantitative PCR. Although the effects of intramuscular injections of folic acid and vitamin B12 on lactational performance and metabolic status of animals were limited, ingenuity pathway analysis of gene expression in granulosa cells suggests a stimulation of cell differentiation in vitamin-treated cows, which may be the result of an increase in LH secretion.

Transcriptomic analysis of cyclic AMP response in bovine cumulus cells

Acquisition of oocyte developmental competence needs to be understood to improve clinical outcomes of assisted reproduction. The stimulation of cumulus cell concentration of cyclic adenosine 3'5'-monophosphate (cAMP) by pharmacological agents during in vitro maturation (IVM) participates in improvement of oocyte quality. However, precise coordination and downstream targets of cAMP signaling in cumulus cells are largely unknown. We have previously demonstrated better embryo development after cAMP stimulation for first 6 h during IVM. Using this model, we investigated cAMP signaling in cumulus cells through in vitro culture of cumulus-oocyte complexes (COCs) in the presence of cAMP raising agents: forskolin, IBMX, and dipyridamole (here called FID treatment). Transcriptomic analysis of cumulus cells indicated that FID-induced differentially expressed transcripts were implicated in cumulus expansion, steroidogenesis, cell metabolism, and oocyte competence. Functional genomic analysis revealed that protein kinase-A (PKA), extracellular signal regulated kinases (ERK1/2), and calcium (Ca(2+)) pathways as key regulators of FID signaling. Inhibition of PKA (H89) in FID-supplemented COCs or substitution of FID with calcium ionophore (A23187) demonstrated that FID activated primarily the PKA pathway which inhibited ERK1/2 phosphorylation and was upstream of calcium signaling. Furthermore, inhibition of ERK1/2 phosphorylation by FID supported a regulation by dual specific phosphatase (DUSP1) via PKA. Our findings imply that cAMP (FID) regulates cell metabolism, steroidogenesis, intracellular signaling and cumulus expansion through PKA which modulates these functions through optimization of ERK1/2 phosphorylation and coordination of calcium signaling. These findings have implications for development of new strategies for improving oocyte in vitro maturation leading to better developmental competence.

The contribution of the maternal immune system to the establishment of pregnancy in cattle

Immune cells play an integral role in affecting successful reproductive function. Indeed, disturbed or aberrant immune function has been identified as primary mechanisms behind infertility. In contrast to the extensive body of literature that exists for human and mouse, studies detailing the immunological interaction between the embryo and the maternal endometrium are quite few in cattle. Nevertheless, by reviewing the existing studies and extrapolating from sheep, pig, mouse, and human data, we can draw a reasonably comprehensive picture. Key contributions of immune cell populations include granulocyte involvement in follicle differentiation and gamete transfer, monocyte invasion of the peri-ovulatory follicle and their subsequent role in corpus luteum formation and the pivotal roles of maternal macrophage and dendritic cells in key steps of the establishment of pregnancy, particularly, the maternal immune response to the embryo. These contributions are reviewed in detail below and key findings are discussed.

Transcriptome profiling of granulosa and theca cells during dominant follicle development in the horse

Several aspects of equine ovarian physiology are unique among domestic species. Moreover, follicular growth patterns are very similar between horses and humans. This study aimed to characterize, for the first time, global gene expression profiles associated with growth and preovulatory (PO) maturation of equine dominant follicles. Granulosa cells (GCs) and theca interna cells (TCs) were harvested from follicles (n = 5) at different stages of an ovulatory wave in mares corresponding to early dominance (ED; diameter ≥22 mm), late dominance (LD; ≥33 mm) and PO stage (34 h after administration of crude equine gonadotropins at LD stage), and separately analyzed on a horse gene expression microarray, followed by validation using quantitative PCR and immunoblotting/immunohistochemistry. Numbers of differentially expressed transcripts (DETs; ≥2-fold; P < 0.05) during the ED-LD and LD-PO transitions were 546 and 2419 in GCs and 5 and 582 in TCs. The most prominent change in GCs was the down-regulation of transcripts associated with cell division during both ED-LD and LD-PO. In addition, DET sets during LD-PO in GCs were enriched for genes involved in cell communication/adhesion, antioxidation/detoxification, immunity/inflammation, and cholesterol biosynthesis. In contrast, the largest change in TCs during the LD-PO transition was an up-regulation of genes involved in immune activation, with other DET sets mapping to GPCR/cAMP signaling, lipid/amino acid metabolism, and cell proliferation/survival and differentiation. In conclusion, distinct expression profiles were identified between growing and PO follicles and, particularly, between GCs and TCs within each stage. Several DETs were identified that have not been associated with follicle development in other species.

Granulosa cell function and oocyte competence: Super-follicles, super-moms and super-stimulation in cattle

The review presents an overview of studies that examined the effects of follicular aging and maternal aging in the bovine model. The first of three main sections is a discussion of the developmental competence of oocytes from (1) the ovulatory follicle of 2-wave and 3-wave estrous cycles, (2) dominant follicles that develop under high or low LH pulse frequency, and (3) natural versus FSH-stimulated ovulatory follicles. The second section highlights the effects of maternal aging. Maternal aging in cattle is associated with (1) elevated circulating FSH concentrations, (2) reduced response to superstimulatory treatment, and (3) markedly decreased early embryonic development in cows >12 year of age. The third and final section on superstimulation protocols addresses the effects of the duration of FSH stimulation and withdrawal (i.e., FSH "starvation" or "coasting") on oocyte competence. Ovarian superstimulation for 4 days altered the expression of genes related to angiogenesis, and activated oxidative stress-response genes. Extending the duration of FSH stimulation from 4 to 7 days resulted in a greater and more synchronous ovulatory response and optimal oocyte maturation. The highest rates of blastocyst development in vitro were obtained when FSH support was discontinued for 44 to 68h and granulosa cell SMAD7 mRNA was predictive of this period. Longer periods of FSH starvation resulted in a loss of oocyte competence or ovulatory capability. By extending the bovine model to the transcriptome level, new approaches and treatments may be devised to resolve subfertility in women and animals.

Characterization of microRNAs differentially expressed during bovine follicle development

Several different miRNAs have been proposed to regulate ovarian follicle function; however, very limited information exists on the spatiotemporal patterns of miRNA expression during follicle development. The objective of this study was to identify, using microarray, miRNA profiles associated with growth and regression of dominant-size follicles in the bovine monovular ovary and to characterize their spatiotemporal distribution during development. The follicles were collected from abattoir ovaries and classified as small (4-8  mm) or large (12-17  mm); the latter were further classified as healthy or atretic based on estradiol and CYP19A1 levels. Six pools of small follicles and individual large healthy (n=6) and large atretic (n=5) follicles were analyzed using Exiqon's miRCURY LNA microRNA Array 6th gen, followed by qPCR validation. A total of 17 and 57 sequences were differentially expressed (greater than or equal to twofold; P<0.05) between large healthy and each of small and large atretic follicles respectively. Bovine miRNAs confirmed to be upregulated in large healthy follicles relative to small follicles (bta-miR-144, bta-miR-202, bta-miR-451, bta-miR-652, and bta-miR-873) were further characterized. Three of these miRNAs (bta-miR-144, bta-miR-202, and bta-miR-873) were also downregulated in large atretic follicles relative to large healthy follicles. Within the follicle, these miRNAs were predominantly expressed in mural granulosa cells. Further, body-wide screening revealed that bta-miR-202, but not other miRNAs, was expressed exclusively in the gonads. Finally, a total of 1359 predicted targets of the five miRNAs enriched in large healthy follicles were identified, which mapped to signaling pathways involved in follicular cell proliferation, steroidogenesis, prevention of premature luteinization, and oocyte maturation.

Effects of steroid ablation and progestin replacement on the transcriptome of the primate corpus luteum during simulated early pregnancy

Previous microarray analyses indicated that a portion of the transcriptome in the macaque corpus luteum (CL) of the menstrual cycle was regulated indirectly by luteinizing hormone via the local actions of steroid hormones, notably progesterone (P). The current study was designed to investigate this concept in the CL of early pregnancy by analyzing chorionic gonadotrophin (CG)-regulated genes that are dependent versus independent of local steroid action. Exogenous human chorionic gonadotropin treatment simulating early pregnancy (SEP) began on Day 9 of the luteal phase in female rhesus monkeys with and without concurrent administration of the 3-β-hydroxysteroid dehydrogenase inhibitor trilostane (TRL) with or without the synthetic progestin R5020. Compared with SEP treatment alone, TRL altered 50 mRNA transcripts on Day 10, rising to 95 on Day 15 (P<0.05, ≥2-fold change in gene expression). Steroid-sensitive genes were validated; notably effects of steroid ablation and P replacement varied by day. Expression of some genes previously identified as P-regulated in the macaque CL during the menstrual cycle were not significantly altered by steroid ablation and P replacement during CG exposure in SEP. These data indicate that the majority of CG-regulated luteal transcripts are differentially expressed independently of local steroid actions. However, the steroid-regulated genes in the macaque CL may be essential during early pregnancy, based on previous reports that TRL treatment initiates premature structural regression of the CL during SEP. These data reinforce the concept that the structure, function and regulation of the rescued CL in early pregnancy differs from the CL of the menstrual cycle in primates.

Differential gene expression of granulosa cells after ovarian superstimulation in beef cattle

Microarray analysis was used to compare the gene expression of granulosa cells from dominant follicles with that of those after superstimulatory treatment. Cows were allocated randomly to two groups (superstimulation and control, n=6/group). A new follicular wave was induced by ablation of follicles ≥5 mm in diameter, and a progesterone-releasing device controlled internal drug release (CIDR) was placed in the vagina. The superstimulation group was given eight doses of 25 mg FSH at 12-h intervals starting from the day of wave emergence (day 0), whereas the control group was not given FSH treatment. Both groups were given prostaglandin F2α twice, 12 h apart, on day 3 and the CIDR was removed at the second injection; 25 mg porcine luteinizing hormone (pLH) was given 24 h after CIDR removal, and cows were ovariectomized 24 h later. Granulosa cells were collected for RNA extraction, amplification, and microarray hybridization. A total of 190 genes were downregulated and 280 genes were upregulated. To validate the microarray results, five genes were selected for real-time PCR (NTS, FOS, THBS1, FN1, and IGF2). Expression of four genes increased significantly in the three different animals tested (NTS, FOS, THBS1, and FN1). The upregulated genes are related to matrix remodeling (i.e. tissue proliferation), disturbance of angiogenesis, apoptosis, and oxidative stress response. We conclude that superstimulation treatment i) results in granulosa cells that lag behind in maturation and differentiation (most of the upregulated genes are markers of the follicular growth stage), ii) activates genes involved with the NFE2L2 oxidative stress response and endoplasmic reticulum stress response, and iii) disturbs angiogenesis.

Involvement of miRNAs in equine follicle development

Previous evidence from in vitro studies suggests specific roles for a subset of miRNAs, including miR-21, miR-23a, miR-145, miR-503, miR-224, miR-383, miR-378, miR-132, and miR-212, in regulating ovarian follicle development. The objective of this study was to determine changes in the levels of these miRNAs in relation to follicle selection, maturation, and ovulation in the monovular equine ovary. In Experiment 1, follicular fluid was aspirated during ovulatory cycles from the dominant (DO) and largest subordinate (S) follicles of an ovulatory wave and the dominant (DA) follicle of a mid-cycle anovulatory wave (n=6 mares). Follicular fluid levels of progesterone and estradiol were lower (P<0.01) in S follicles than in DO follicles, whereas mean levels of IGF1 were lower (P<0.01) in S and DA follicles than in DO follicles. Relative to DO and DA follicles, S follicles had higher (P≤0.01) follicular fluid levels of miR-145 and miR-378. In Experiment 2, follicular fluid and granulosa cells were aspirated from dominant follicles before (DO) and 24 h after (L) administration of an ovulatory dose of hCG (n=5 mares/group). Relative to DO follicles, L follicles had higher follicular fluid levels of progesterone (P=0.05) and lower granulosa cell levels of CYP19A1 and LHCGR (P<0.005). Levels of miR-21, miR-132, miR-212, and miR-224 were increased (P<0.05) in L follicles; this was associated with reduced expression of the putative miRNA targets, PTEN, RASA1, and SMAD4. These novel results may indicate a physiological involvement of miR-21, miR-145, miR-224, miR-378, miR-132, and miR-212 in the regulation of cell survival, steroidogenesis, and differentiation during follicle selection and ovulation in the monovular ovary.

Research resource: preovulatory LH surge effects on follicular theca and granulosa transcriptomes

The molecular mechanisms that regulate the pivotal transformation processes observed in the follicular wall following the preovulatory LH surge, are still not established, particularly for cells of the thecal layer. To elucidate thecal cell (TC) and granulosa cell (GC) type-specific biologic functions and signaling pathways, large dominant bovine follicles were collected before and 21 hours after an exogenous GnRH-induced LH surge. Antral GCs (aGCs; aspirated by follicular puncture) and membrane-associated GCs (mGCs; scraped from the follicular wall) were compared with TC expression profiles determined by mRNA microarrays. Of the approximately 11 000 total genes expressed in the periovulatory follicle, only 2% of thecal vs 25% of the granulosa genes changed in response to the LH surge. The majority of the 203 LH-regulated thecal genes were also LH regulated in GCs, leaving a total of 57 genes as LH-regulated TC-specific genes. Of the 57 thecal-specific LH-regulated genes, 74% were down-regulated including CYP17A1 and NR5A1, whereas most other genes are being identified for the first time within theca. Many of the newly identified up-regulated thecal genes (eg, PTX3, RND3, PPP4R4) were also up-regulated in granulosa. Minimal expression differences were observed between aGCs and mGCs; however, transcripts encoding extracellular proteins (NID2) and matrix modulators (ADAMTS1, SASH1) dominated these differences. We also identified large numbers of unknown LH-regulated GC genes and discuss their putative roles in ovarian function. This Research Resource provides an easy-to-access global evaluation of LH regulation in TCs and GCs that implicates numerous molecular pathways heretofore unknown within the follicle.

Gene expression profiling of granulosa cells from PCOS patients following varying doses of human chorionic gonadotropin

PURPOSE

Human chorionic gonadotrophin (hCG) has been used to induce ovulation and oocyte maturation. Although the most common dose of hCG used in IVF is 10,000 IU, there are reports that suggest 5,000 IU is sufficient to yield similar results. The objective of this study is to evaluate the dose dependent differences in gene expression of granulosa cells following various doses of hCG treatment.

METHODS

Patients with polycystic ovarian syndrome (PCOS) were stimulated for IVF treatment. The hCG injection was either withheld or given at 5,000 or 10,000 IU. Granulosa cells from the follicular fluids have been collected for RNA isolation and analyzed using Affymetrix genechip arrays.

RESULTS

Unsupervised hierarchical clustering based on whole gene expression revealed two distinct groups of patients in this experiment. All untreated patients were clustered together whereas hCG-treated patients separated to a different group regardless of the dose. A large number of the transcripts were similarly up- or down-regulated across both hCG doses (2229 and 1945 transcripts, respectively). However, we observed dose-dependent statistically significant differences in gene expression in only 15 transcripts.

CONCLUSIONS

Although hCG injection caused a major change in the gene expression profile of granulosa cells, 10,000 IU hCG resulted in minimal changes in the gene expression profiles of granulosa cells as compared with 5,000 IU. Thus, based on our results, we suggest the use of 10,000 IU hCG should be reconsidered in PCOS patients.

Fibroblast growth factor 2 induces the precocious development of endothelial cell networks in bovine luteinising follicular cells

The transition from follicle to corpus luteum represents a period of intense angiogenesis; however, the exact roles of angiogenic factors during this time remain to be elucidated. Thus, the roles of vascular endothelial growth factor (VEGF) A, fibroblast growth factor (FGF) 2 and LH in controlling angiogenesis were examined in the present study. A novel serum-free luteinising follicular angiogenesis culture system was developed in which progesterone production increased during the first 5 days and was increased by LH (P < 0.01). Blockade of signalling from FGF receptors (SU5402; P < 0.001) and, to a lesser extent, VEGF receptors (SU1498; P < 0.001) decreased the development of endothelial cell (EC) networks. Conversely, FGF2 dose-dependently (P < 0.001) induced the precocious transition of undeveloped EC islands into branched networks associated with a twofold increase in the number of branch points (P < 0.001). In contrast, VEGFA had no effect on the area of EC networks or the number of branch points. LH had no effect on the area of EC networks, but it marginally increased the number of branch points (P < 0.05) and FGF2 production (P < 0.001). Surprisingly, progesterone production was decreased by FGF2 (P < 0.01) but only on Day 5 of culture. Progesterone production was increased by SU5402 (P < 0.001) and decreased by SU1498 (P < 0.001). These results demonstrate that FGF and VEGF receptors play a fundamental role in the formation of luteal EC networks in vitro, which includes a novel role for FGF2 in induction of EC sprouting.

DNA methylation and histone modifications are associated with repression of the inhibin α promoter in the rat corpus luteum

The transition from follicle to corpus luteum after ovulation is associated with profound morphological and functional changes and is accompanied by corresponding changes in gene expression. The gene encoding the α subunit of the dimeric reproductive hormone inhibin is maximally expressed in the granulosa cells of the preovulatory follicle, is rapidly repressed by the ovulatory LH surge, and is expressed at only very low levels in the corpus luteum. Although previous studies have identified transient repressors of inhibin α gene transcription, little is known about how this repression is maintained in the corpus luteum. This study examines the role of epigenetic changes, including DNA methylation and histone modification, in silencing of inhibin α gene expression. Bisulfite sequencing reveals that methylation of the inhibin α proximal promoter is low in preovulatory and ovulatory follicles but is elevated in the corpus luteum. Increased methylation during luteinization is observed within the cAMP response element in the promoter, and EMSA demonstrate that methylation of this site inhibits cAMP response element binding protein binding in vitro. Chromatin immunoprecipitation reveals that repressive histone marks H3K9 and H3K27 trimethylation are increased on the inhibin α promoter in primary luteal cells, whereas the activation mark H3K4 trimethylation is decreased. The changes in histone modification precede the alterations in DNA methylation, suggesting that they facilitate the recruitment of DNA methyltransferases. We show that the DNA methyltransferase DNMT3a is present in the ovary and in luteal cells when the inhibin α promoter becomes methylated and observe recruitment of DNMT3a to the inhibin promoter during luteinization.

Impact of the LH surge on granulosa cell transcript levels as markers of oocyte developmental competence in cattle

In the case of in vitro embryonic production, it is known that not all oocytes detain the developmental capacity to form an embryo. This capacity appears to be acquired through completion of folliculogenesis, during which the oocyte and follicular cells influence their respective destinies. The differentiation status of granulosa cells (GCs) could therefore offer an indicator of oocyte quality. The aim of this study was to compare mRNA transcript abundance in GCs associated with oocytes that subsequently reach or not the blastocyst stage. GCs were collected from cattle following an ovarian stimulation protocol that did or did not include the administration of LH. GCs were classified according to the developmental stage achieved by the associated oocytes. Transcript abundance was measured by microarray. Follicles (n=189) obtained from cows before and after the LH surge were essentially similar and the rates of oocytes reaching the blastocyst stage were not significantly different (52 vs 41%), but blastocyst quality was significantly better in the post-LH-surge group. In GCs from the pre-LH-surge group and associated with developmentally competent oocytes, 18 overexpressed and 22 underexpressed transcripts were found, including novel uncharacterized transcripts, whereas no differentially expressed transcripts were associated with developmentally different oocytes in the post-LH-surge group. The novel transcriptomic response associated with LH appeared to mask the difference. Based on oocyte developmental competence, the period prior to the LH surge appears best suited for studying competence-associated mRNA transcripts in bovine follicle cells.