Glucocorticoid metabolism in equine follicles and oocytes

Characterization of preovulatory follicular fluid secretome and its effects on equine oocytes during in vitro maturation

In vitro maturation (IVM) of oocytes is clinically used in horses to produce blastocysts but current conditions used for horses are suboptimal. We analyzed the composition of equine preovulatory follicular fluid (FF) secretome and tested its effects on meiotic competence and gene expression in oocytes subjected to IVM. Preovulatory FF was obtained, concentrated using ultrafiltration with cut-off of 10 kDa, and stored at -80 °C. The metabolic and proteomic composition was analyzed, and its ultrastructural composition was assessed by cryo-transmission microscopy. Oocytes obtained post-mortem or by ovum pick up (OPU) were subjected to IVM in the absence (control) or presence of 20 or 40 μg/ml (S20 or S40) of secretome. Oocytes were then analyzed for chromatin configuration or snap frozen for gene expression analysis. Proteomic analysis detected 255 proteins in the Equus caballus database, mostly related to the complement cascade and cholesterol metabolism. Metabolomic analysis yielded 14 metabolites and cryo-transmission electron microscopy analysis revealed the presence of extracellular vesicles (EVs). No significant differences were detected in maturation rates among treatments. However, the expression of GDF9 and BMP15 significantly increased in OPU-derived oocytes compared to post-mortem oocytes (fold increase ± SEM: 9.4 ± 0.1 vs. 1 ± 0.5 for BMP15 and 9.9 ± 0.3 vs. 1 ± 0.5 for GDF9, respectively; p < 0.05). Secretome addition increased the expression of TNFAIP6 in S40 regardless of the oocyte source. Further research is necessary to fully understand whether secretome addition influences the developmental competence of equine oocytes.

Glucocorticoids and Their Receptor Isoforms: Roles in Female Reproduction, Pregnancy, and Foetal Development

Alterations in the hypothalamic-pituitary-adrenal (HPA) axis and associated changes in circulating levels of glucocorticoids are integral to an organism's response to stressful stimuli. Glucocorticoids acting via glucocorticoid receptors (GRs) play a role in fertility, reproduction, placental function, and foetal development. GRs are ubiquitously expressed throughout the female reproductive system and regulate normal reproductive function. Stress-induced glucocorticoids have been shown to inhibit reproduction and affect female gonadal function by suppressing the hypothalamic-pituitary-gonadal (HPG) axis at each level. Furthermore, during pregnancy, a mother's exposure to prenatal stress or external glucocorticoids can result in long-lasting alterations to the foetal HPA and neuroendocrine function. Several GR isoforms generated via alternative splicing or translation initiation from the GR gene have been identified in the mammalian ovary and uterus. The GR isoforms identified include the splice variants, GRα and GRβ, and GRγ and GR-P. Glucocorticoids can exert both stimulatory and inhibitory effects and both pro- and anti-inflammatory functions in the ovary, in vitro. In the placenta, thirteen GR isoforms have been identified in humans, guinea pigs, sheep, rats, and mice, indicating they are conserved across species and may be important in mediating a differential response to stress. Distinctive responses to glucocorticoids, differential birth outcomes in pregnancy complications, and sex-based variations in the response to stress could all potentially be dependent on a particular GR expression pattern. This comprehensive review provides an overview of the structure and function of the GR in relation to female fertility and reproduction and discusses the changes in the GR and glucocorticoid signalling during pregnancy. To generate this overview, an extensive non-systematic literature search was conducted across multiple databases, including PubMed, Web of Science, and Google Scholar, with a focus on original research articles, meta-analyses, and previous review papers addressing the subject. This review integrates the current understanding of GR variants and their roles in glucocorticoid signalling, reproduction, placental function, and foetal growth.

NR3C1 and glucocorticoid-regulatory genes mRNA and protein expression in the endometrium and ampulla during the bovine estrous cycle

The bovine reproductive tract exhibits changes during the estrous cycle modulated by the interplay of steroid hormones. Glucocorticoids can be detrimental when stress-induced but are relevant at baseline levels for appropriate reproductive function. Here, an analysis of quantitative real-time PCR was performed to study the bovine glucocorticoid-related baseline gene transcription in endometrial and ampullar tissue samples derived from three time points of the estrous cycle, stage I (Days 1-4), stage III (Days 11-17) and stage IV (Days 18-20). Our results revealed expression differences during stages, as expression observed in the ampulla was higher during the post-ovulatory phase (stage I), including the glucocorticoid receptor NR3C1, and some of its regulators, involved in glucocorticoid availability (HSD11B1 and HSD11B2) and transcriptional actions (FKBP4 and FKBP5). In contrast, in the endometrium, higher expression of the steroid receptors was observed during the late luteal phase (stage III), including ESR1, ESR2, PGRMC1 and PGRMC2, and HSD11B1 expression decreased, while HSD11B2 increased. Moreover, at protein level, FKBP4 was higher expressed during the late luteal phase, and NR3C1 during the pre-ovulatory phase (stage IV). These results suggest that tight regulation of the glucocorticoid activity is promoted in the ampulla, when reproductive events are taking place, including oocyte maturation. Moreover, most expression changes in the endometrium were observed during the late luteal phase, and may be related to the embryonic maternal recognition. In conclusion, the glucocorticoid regulation changes across the estrous cycle and may be playing a role on the reproductive events occurring in the bovine ampulla and endometrium.

Epigenetic Changes in Equine Embryos after Short-Term Storage at Different Temperatures

Simple Summary

In embryos subjected to assisted reproductive techniques, epigenetic modifications may occur that can influence embryonic development and establishment of pregnancy. In horses, the storage temperature during transport of fresh embryos before transfer is a major concern. The aim of this study was, therefore, to determine the effects of two storage temperatures (5 °C and 20 °C) on equine embryos, collected at day seven after ovulation and stored for 24 h, concerning morphological development, expression of candidate genes associated with embryo growth and development, maternal recognition of pregnancy, methylation, apoptosis and gene-specific and global DNA methylation. Temperature during storage did not affect embryo size. There were no changes in pH and lipid peroxidation of the medium irrespective of group. mRNA expression and gene-specific DNA methylation of genes related to growth and development, maternal recognition of pregnancy, DNA methylation and apoptosis in stored embryos (5 °C and 20 °C) were altered when compared to fresh embryos. Therefore, our study demonstrates for the first time the gene-specific and global DNA methylation status of fresh equine embryos collected on days seven and eight after ovulation. Short-term storage, regardless of temperature, may compromise embryo development after transfer.

Abstract

In embryos subjected to assisted reproductive techniques, epigenetic modifications may occur that can influence embryonic development and the establishment of pregnancy. In horses, the storage temperature during transport of fresh embryos before transfer is a major concern. The aim of this study was, therefore, to determine the effects of two storage temperatures (5 °C and 20 °C) on equine embryos, collected at day seven after ovulation and stored for 24 h, on: (i) morphological development; (ii) expression of candidate genes associated with embryo growth and development, maternal recognition of pregnancy, methylation and apoptosis, and (iii) gene-specific and global DNA methylation. Embryos (n = 80) were collected on day seven or day eight after ovulation and assigned to four groups: day seven control (E7F, fresh); day seven, stored for 24 h at 5 °C (E5C); day seven, stored for 24 h at 20 °C (E20C) and day eight control (E8F, fresh 24h time control). The embryos and the storage medium (EquiHold, holding medium, Minitube, Tiefenbach, Germany) from all treatment groups were analyzed for (i) medium temperature, pH, and lipid peroxidation (malondialdehyde; MDA) and (ii) embryo morphology, mRNA expression and DNA methylation (immunohistochemistry and gene-specific DNA methylation). The size of embryos stored at 5 °C was larger (p < 0.01), whereas embryos stored at 20 °C were smaller (p < 0.05) after 24 h. There were no changes in pH and MDA accumulation irrespective of the group. The mRNA expression of specific genes related to growth and development (POU5F1, SOX2, NANOG), maternal recognition of pregnancy (CYP19A1, PTGES2), DNA methylation (DNMT1, DNMT3A, DNMT3B) and apoptosis (BAX) in the E5C and E20C were either up or downregulated (p < 0.05) when compared to controls (E7F and E8F). The immune expression of 5mC and 5hmC was similar among treatment groups. Percentage of methylation in the CpG islands was lower in the specific genes ESR1, NANOG and DNMT1 (p < 0.001) in E20C embryos when compared to E8F (advanced embryo stage). Therefore, our study demonstrates for the first time the gene-specific and global DNA methylation status of fresh equine embryos collected on days seven and eight after ovulation. Although our results suggest some beneficial effects of storage at 20 °C in comparison to 5 °C, the short-term storage, regardless of temperature, modified gene expression and methylation of genes involved in embryo development and may compromise embryo viability and development after transfer.

Endocrine and Electrolyte Balances during Periovulatory Period in Cycling Mares

Simple Summary

This study provides new evidence on the physiological mechanisms involved in the electrolyte balance during periovulatory period in cycling mares. The interrelationships among adrenocorticotropic hormone (ACTH), cortisol (CORT), aldosterone (ALD) and electrolytes (sodium—Na⁺, potassium—K⁺ and chloride—Cl⁻) were evaluated. The simultaneous increase in ACTH, CORT and ALD toward the time of ovulation could suggest the involvement of the adrenocortical pituitary axis in the ovulatory mechanisms, contributing at the same time to the maintenance of electrolyte homeostasis.

Abstract

In cycling females, the periovulatory period is characterized by stimulation of the hypothalamic pituitary adrenal (HPA) axis. The aim of present study was to analyze the pattern and interrelationships among adrenocorticotropic hormone (ACTH), cortisol (CORT), aldosterone (ALD) and electrolytes (sodium—Na⁺, potassium—K⁺ and chloride—Cl⁻) during periovulatory period in cycling mares. Venous blood samples were obtained daily from a total of 23 Purebred Spanish broodmares, aged 7.09 ± 2.5 years, from day −5 to day +5 of estrous cycle, considering day 0, the day of ovulation. Plasma ACTH was measured by a fluorescent immunoassay kit, serum CORT and ALD by means of a competitive ELISA immunoassay, and plasma Na⁺, K⁺ and Cl⁻ were quantified by an analyzer with selective electrodes for the three ions. ACTH showed higher concentrations at day 0 compared to days −5 to −1 and +1 to +3 (p < 0.05). CORT showed higher concentrations at day 0 compared to days −5 to −2 and +1 to +5 (p < 0.05). ALD showed higher concentrations at day 0 compared to days −5 to −2 (p < 0.05) and +2 (p < 0.05). Na⁺ and Cl⁻ showed higher concentrations at day 0, compared to day −5 and +5. K⁺ showed lower concentrations at day 0 compared to day +1 (p < 0.05). The significant correlations obtained between ACTH and CORT (r = 0.20) and between ACTH and ALD (r = 0.32) suggest that although ACTH may have an effect both on CORT and ALD, there are other very important determinants that could be considered. Hence, it is possible to presume that the pituitary adrenocortical response and ALD may be involved in the ovulatory mechanisms without a direct relation with electrolyte pattern.

Reduced growth capacity of preimplantation mouse embryos in chronic unpredictable stress model

Psychological stress can affect female reproduction by deteriorating oocyte quality, but the molecular mechanism is unclear. In this study, we used the chronic unpredictable stress model to study the effect of psychological stress on mouse oocyte competence during preimplantation stage, and RNA sequencing in single oocytes to analyze differential gene expression at the transcription level. Stress changed the serum levels of glucocorticoids and reduced oocyte developmental potential, depending on the strength of the stress. Strong stress (two stressors per day) reduced the fertilization rate and induced significant apoptosis in blastocysts. Moderate stress (one stressor per day) reduced the cleavage rate and blastocyst formation rate. Weak stress (one stressor every 2 days) did not have any significant negative effect on the fertilization, cleavage, and blastocyst formation. Hatching rate was not affected by stress, but stress retarded the development of the expanded blastocysts and inhibited the embryo development at early stages. Transcriptome analysis revealed that stress disturbed the expression of cell cycle regulators and apoptotic genes. The hub genes identified through protein-protein interaction analysis include Msln, Ceacam12, Psg16, Psg17, and Psg23, which are all carcinoembryonic or related genes involved in cell adhesion, proliferation, and migration. Thus, stress was inhibitory on fertilization and early embryo development in mice.

Seminal Plasma Triggers the Differential Expression of the Glucocorticoid Receptor (NR3C1/GR) in the Rabbit Reproductive Tract

Rabbits are interesting as research animal models for reproduction, due to their condition of species of induced ovulation, with the release of endogenous gonadotropin-releasing hormone (GnRH) due to coitus. Glucocorticoid (GC) signaling, crucial for physiological homeostasis, is mediated through a yet unclear mechanism, by the GC receptor (NR3C1/GR). After mating, the female reproductive tract undergoes dynamic modifications, triggered by gene transcription, a pre-amble for fertilization and pregnancy. This study tested the hypothesis that when ovulation is induced, the expression of NR3C1 is influenced by sperm-free seminal plasma (SP), similarly to after mating (whole semen), along the different segments of the internal reproductive tract of female rabbits. Semen (mating) was compared to vaginal infusion of sperm-free SP (Experiment 1), and changes over time were also evaluated, i.e., 10, 24, 36, 68, and 72 h post-mating, corresponding to specific stages, i.e., ovulation, fertilization, and the interval of early embryo development up to the morula stage (Experiment 2). All does were treated with GnRH to induce ovulation. Samples were retrieved from seven segments of the reproductive tract (from the cervix to infundibulum), at 20 h post-mating or sperm-free SP infusion (Experiment 1) or at 10, 24, 36, 68, and 72 h post-mating (Experiment 2). Gene expression of NR3C1 was analyzed by qPCR. Results showed an increase in NR3C1 expression in the infundibulum compared to the other anatomical regions in the absence of spermatozoa when sperm-free SP infusion was performed (Experiment 1). Moreover, during the embryo transport through the oviduct, the distal isthmus was time-course upregulated, especially at 72 h, when morulae are retained in this anatomical region, while it was downregulated in the distal uterus at 68 h (Experiment 2). The overall results suggest that NR3C1, the GC receptor gene, assessed in the reproductive tract of does for the first time, shows differential expression changes during the interval of oviductal and uterine embryo transport that may imply a relevant role of the GC action, not only close to the site of ovulation and fertilization, but also in the endometrium.

Supportive techniques to investigate in vitro culture and cryopreservation efficiencies of equine ovarian tissue: A review

During the reproductive lifespan of a female, only a limited quantity of oocytes are naturally ovulated; therefore, the mammalian ovary possesses a substantial population of preantral follicles available to be handled and explored in vitro. Hence, the manipulation of preantral follicles enclosed in ovarian tissue aims to recover a considerable population of oocytes of high-value animals for potential application in profitable assisted reproductive technologies (ARTs). For this purpose, the technique of preantral follicle in vitro culture (IVC) has been the most common research tool, achieving extraordinary results with offspring production in the mouse model. Although promising outcomes have been generated in livestock animals after IVC of preantral follicles, the quantity and quality of embryo production with those oocytes are still poor. In recent years, the mare has become an additional model for IVC studies due to remarkable similarities with women and livestock animals regarding in vivo and in vitro ovarian folliculogenesis. For a successful IVC system, several factors should be carefully considered to provide an optimum culture environment able to support the viability and growth of preantral follicles enclosed in ovarian tissue. The cryopreservation of the ovarian tissue is another important in vitro manipulation technique that has been used to preserve the reproductive potential in humans and, in the future, may be used in highly valuable domestic animals or endangered species. Several improvements in cryopreservation protocols are necessary to support the utilization of ovarian tissue of different species in follow-up ARTs (e.g., ovarian fragment transplantation). This review aims to provide an update on the most current advances regarding supportive in vitro techniques used in equids to evaluate and manipulate preantral follicles and ovarian tissue, as well as methodological approaches used during IVC and cryopreservation techniques.

Natural Mating Differentially Triggers Expression of Glucocorticoid Receptor (NR3C1)-Related Genes in the Preovulatory Porcine Female Reproductive Tract

Mating initiates dynamic modifications of gene transcription in the female reproductive tract, preparing the female for fertilization and pregnancy. Glucocorticoid signaling is essential for the homeostasis of mammalian physiological functions. This complex glucocorticoid regulation is mediated through the glucocorticoid receptor, also known as nuclear receptor subfamily 3 group C member 1 (NR3C1/GR) and related genes, like 11β-hydroxysteroid dehydrogenases (HSD11Bs) and the FK506-binding immunophilins, FKBP5 and FKBP4. This study tested the transcriptome changes in NR3C1/GR regulation in response to natural mating and/or cervical deposition of the sperm-peak ejaculate fraction collected using the gloved-hand method (semen or only its seminal plasma), in the preovulatory pig reproductive tract (cervix to infundibulum, 24 h after mating/insemination/infusion treatments). Porcine cDNA microarrays revealed 22 NR3C1-related transcripts, and changes in gene expression were triggered by all treatments, with natural mating showing the largest differences, including NR3C1, FKBP5, FKBP4, hydroxysteroid 11-beta dehydrogenase 1 and 2 (HSD11B1, HSD11B2), and the signal transducer and activator of transcription 5A (STAT5A). Our data suggest that natural mating induces expression changes that might promote a reduction of the cortisol action in the oviductal sperm reservoir. Together with the STAT-mediated downregulation of cytokine immune actions, this reduction may prevent harmful effects by promoting tolerance towards the spermatozoa stored in the oviduct and perhaps elicit spermatozoa activation and detachment after ovulation.

Glucocorticoid receptor isoforms and effects of glucocorticoids in ovulated mouse oocytes and preimplantation embryos†

To investigate possible involvement of glucocorticoid receptor (GR) in mediating effects of maternal stress or therapeutically administered glucocorticoids on early embryo, we analyzed the expression of GR subtypes in ovulated mouse oocytes and preimplantation embryos. RT-PCR analysis results showed that GRα and GRγ transcripts are relatively highly expressed in mouse oocytes, and both transcripts are present at lower amounts in preimplantation embryos. We also detected low expression of two other splice variants, GRβ and a transcript orthologous to the human GR-P subtype, mainly at the blastocyst stage. Using western blot analysis, we detected several GR protein bands that differed in size between oocytes and preimplantation embryos. To compare the effects of corticosterone (a major endogenous glucocorticoid in rodents) and dexamethasone (a synthetic glucocorticoid) on early embryos, we cultured mouse preimplantation embryos in the presence of these glucocorticoids. Corticosterone showed a strong inhibitory effect on embryo development (starting from a 50 μM concentration), without a significant influence on apoptosis incidence. On the other hand, dexamethasone induced apoptosis in early embryo cells (starting from a 1.5 μM concentration), and its effect on embryo development was less detrimental than that found with the same dose of corticosterone. In summary, our results showed that different GR subtypes are expressed in ovulated mouse oocytes and preimplantation embryos and that the composition of GR subtypes changes during early embryo development. Moreover, we found significant differences in the effects of the two glucocorticoids on early embryo development, which might be associated with activation of different GR subtypes.

Intrafollicular and systemic serotonin, oestradiol and progesterone concentrations in cycling mares

The hypothesis that a local serotonergic network might also exist in the follicle of mares remains poorly documented, with exception for humans and laboratory species. For this reason, the aim of the present study was to clarify this possibility, investigating intrafollicular serotonin concentrations of the cycling mare at ovulation time. Sixty ovaries collected from 30 clinically healthy mares of slaughterhouse meat production with clinically normal reproductive tracts after slaughtering were evaluated. Blood samples were taken prior to sacrifice. Follicles were classified in three categories in relation to size, as small (20-30 mm), medium (31-40 mm) and large (>41 mm), and the follicular fluid samples were extracted from each follicle. Intrafollicular and systemic serotonin (5-HT), oestradiol-17β (E₂ ) and progesterone (P₄ ) were determined by means of enzyme-linked immunosorbent assay and RIA, respectively. Intrafollicular 5-HT, E₂ and P₄ concentrations were higher than systemic ones (p < .05). 5-HT concentrations increased in larger compared to medium follicles, without differences compared to small size follicles (p < .05). 5-HT and E₂ (r = .79) and 5-HT and P₄ (r = .79; p < .05) were positively correlated. 5-HT and P₄ concentrations in follicular fluid increased progressively with the increase in follicular size (p < .05). Follicle diameter and E₂ (r = .85) and P₄ (r = .68) were correlated (p < .05). Since serotonin interacts with steroids, its role on steroidogenesis during growth of the dominant follicle may be suggested.

Activation of HSD11B1 in the bovine cumulus-oocyte complex during IVM and IVF

The bovine cumulus-oocyte complex (COC) is capable of converting cortisone, an inert glucocorticoid to active cortisol. This mechanism is mediated by 11β-hydroxysteroid oxidoreductase type 1 (HSD11B1), whose expression dramatically increases in the mature COC. In this study, we investigate the time course expression of HSD11B1 and the enzyme activity in the bovine COC undergoing maturation and fertilization in relation to key events taking place in the COC. Bovine COCs were subjected to in vitro maturation (IVM) and fertilization (IVF). The activities of HSD11B1 and HSD11B2, which mediates the opposite reaction, were measured using a radiometric conversion assay. In parallel studies, cumulus expansion, P4 production and the expression of genes associated with ovulation were measured. The reductive activity of HSD11B1 increased in the latter half of IVM and remained high during IVF, whereas the oxidative activity of HSD11B2 remained unchanged over both periods. Consequently, the net glucocorticoid metabolism in the bovine COC shifted from inactivation to activation around the time of ovulation and fertilization. The increase in HSD11B1 expression lagged behind that of P4 increase and cumulus expansion but ahead of the expressions of genes responsible for PGE2 synthesis. The reductive activity of HSD11B1 was well correlated with the cumulus expansion rate. This outcome indicates that the ability of the cumulus to activate glucocorticoids is related to its ability to synthesize hyaluronan. These results also indicate that the activation of HSD11B1 is an integral part of the sequential events taking place at the ovulation and fertilization in the bovine COC.

Cellular and molecular mechanisms of the preovulatory follicle differenciation and ovulation: What do we know in the mare relative to other species

Terminal follicular differentiation and ovulation are essential steps of reproduction. They are induced by the increase in circulating LH, and lead to the expulsion from the ovary of oocytes ready to be fertilized. This review summarizes our current understanding of cellular and molecular pathways that control ovulation using a broad mammalian literature, with a specific focus to the mare, which is unique in some aspects of ovarian function in some cases. Essential steps and key factors are approached. The first part of this review concerns LH, receptors and signaling, addressing the description of the equine gonadotropin and cloning, signaling pathways that are activated following the binding of LH to its receptors, and implication of transcription factors which better known are CCAAT-enhancer-binding proteins (CEBP) and cAMP response element-binding protein (CREB). The second and major part is devoted to the cellular and molecular actors within follicular cells during preovulatory maturation. We relate to 1) molecules involved in vascular permeability and vasoconstriction, 2) involvement of neuropeptides, such as kisspeptin, neurotrophins and neuronal growth factor, neuropeptide Y (NPY), 3) the modification of steroidogenesis, steroids intrafollicular levels and enzymes activity, 4) the local inflammation, with the increase in prostaglandins synthesis, and implication of leukotrienes, cytokines and glucocorticoids, 5) extracellular matrix remodelling with involvement of proteases, antiproteases and inhibitors, as well as relaxin, and finaly 6) the implication of oxytocine, osteopontin, growth factors and reactive oxygen species. The third part describes our current knowledge on molecular aspect of in vivo cumulus-oocyte-complexe maturation, with a specific focus on signaling pathways, paracrine factors, and intracellular regulations that occur in cumulus cells during expansion, and in the oocyte during nuclear and cytoplasmic meiosis resumption. Our aim was to give an overall and comprehensive map of the regulatory mechanisms that intervene within the preovulatory follicle during differentiation and ovulation.

Expanded equine cumulus-oocyte complexes exhibit higher meiotic competence and lower glucose consumption than compact cumulus-oocyte complexes

Equine cumulus-oocyte complexes (COCs) are classified as compact (cCOC) or expanded (eCOC) and vary in their meiotic competence. This difference could be related to divergent glucose metabolism. To test this hypothesis in the present study, eCOCs, cCOCs and expanded or compact mural granulosa cells (EC and CC respectively) were matured in vitro for 30h, at which time maturation rate, glucose metabolism and the expression of genes involved in glucose transport, glycolysis, apoptosis and meiotic competence were determined. There were significant differences between eCOCs and cCOCs in maturation rate (50% vs 21.7% (n=192 and 46) respectively; P<0.001), as well as mean (±s.e.m.) glucose consumption (1.8±0.5 vs 27.9±5.9 nmol per COC respectively) and pyruvate (0.09±0.01 vs 2.4±0.8 nmol per COC respectively) and lactate (4.7±1.3 vs 64.1±20.6 nmol per COC respectively; P<0.05 for all) production. Glucose consumption in EC and CC did not differ significantly. Expression of hyaluronan-binding protein (tumour necrosis factor alpha induced protein 6; TNFAIP6) was increased in eCOCs and EC, and solute carrier family 2 member 1 (SLC2A1) expression was increased in eCOCs, but there were no differences in the expression of glycolysis-related enzymes and solute carrier family 2 member 3 (SLC2A3) between the COC or mural granulosa cell types. The findings of the present study demonstrate that metabolic and genomic differences exist between eCOCs and cCOCs and mural granulosa cells in the horse.

Effects of FSH addition to an enriched medium containing insulin and EGF after long-term culture on functionality of equine ovarian biopsy tissue

The effect of FSH supplementation on an enriched cultured medium containing insulin (10 ng/mL) and EGF (50 ng/mL) was investigated on in vitro culture of equine ovarian biopsy tissue. Ovarian tissue fragments were collected from mares (n = 10) and distributed in the following treatments: noncultured control, cultured control, and cultured + FSH. Both treated groups were cultured for 7 or 15 days. The end points evaluated were: follicular morphology, estradiol levels in the culture medium, fluorescence intensity for TUNEL, EGFR and Ki-67 detection, and gene expression of GDF-9, BMP-15, and Cyclin-D2 in the ovarian tissue. After seven days of culture, medium supplemented with FSH had a similar (P > 0.05) percentage of morphologically normal follicles compared to the noncultured control group. Estradiol levels increased (P < 0.05) from Day 7 to Day 15 of culture for both treated groups. No difference (P > 0.05) was observed for TUNEL and EGFR intensity between the noncultured control group and the treated groups after 15 days of culture. Ki-67 intensity did not differ (P > 0.05) between treated groups after 15 days of culture, but decreased (P < 0.05) when compared with the noncultured control group. Similar (P > 0.05) mRNA expression for GDF-9, BMP-15, and Cyclin-D2 was observed among all treatments after 15 days of culture. In conclusion, an enriched medium supplemented or not with FSH was able to maintain the functionality of equine ovarian biopsy tissue after a long-term in vitro culture.