Granulosa cells of prepubertal cattle respond to gonadotropin signaling and upregulate genes that promote follicular growth and prevent cell apoptosis

Exogenous FSH/LH modulates TGF beta signaling genes in granulosa cells of Simmental heifers without affecting IVP results

Follicular wave synchronization and follicular superstimulation with FSH are commonly used in OPU-IVP programs to increase oocyte developmental competence. Factors like Growth Differentiation Factor 9 (GDF9) and Bone Morphogenetic Protein 15 (BMP15), from the TGF beta superfamily, are produced by the oocyte and modulate follicular function. The aim of this study was to analyze the FSH-induced effects on (1) embryo production in dual-purpose Simmental cattle, and (2) TGF beta-mediated effects on oocyte-granulosa cell communication. Simmental heifers (n = 12, age 484 ± 62 days) underwent two OPU-IVP cycles in a cross-over design. Follicular waves were synchronized using 0.5 mg cloprostenol on Day 0, followed by 10 μg buserelin on Day 2. Subsequently, half of the heifers were randomly assigned to receive FSH/LH (four injections of 75 IU FSHp and 75IU LHp, 12 h apart on Days 4 and 5) before the first OPU, while the remaining heifers received FSH/LH before the second OPU. At the time of OPU, i.e. 7 days after the start of synchronization, granulosa cells were collected for RT-qPCR analysis. FSH treatment did not affect the number of oocytes collected (17.3 vs. 13.3, P > 0.05), but increased the percentage of quality 1 oocytes compared to controls (45.7 % vs. 22.0 %, P < 0.001). Neither cleavage (86.4 % vs. 85.7 %), nor blastocyst (42.1 % vs. 39.3 %) rate, or the number of transferable embryos produced by IVP (4.1 vs 4.8) was influenced by FSH treatment (P > 0.05 in all cases). FSH treatment increased HIF1A and FSHR levels in granulosa cells, while STAR was decreased (P = 0.008 in all cases). FSH treatment did not affect BMP15 or GDF9 mRNA expression (P > 0.05) but appeared to modulate the expression of genes involved in the BMP signaling pathway. Transcriptional levels of BMP15 receptor (BMPR1A, P = 0.016), and its downstream signaling factor SMAD1 (P = 0.008) were affected by FSH treatment. Our results demonstrated no benefit of this FSH stimulation protocol on IVP results in Simmental heifers. Further, our results suggest that the effects of FSH on bovine oocytes during acquisition of developmental competence may be mediated through BMP, but do not involve the regulation of transcriptional availability of GDF9, providing new insights into possible paracrine effects of the oocyte on granulosa cells.

Allogenic Follicular Fosterage Technology: Problems, Progress and Potential

The allogeneic follicular fosterage (AFF) technique transfers cumulus-oocyte complexes (COCs) from pubertal female animals to the dominant follicles of adult female animals for further development, allowing the COCs to further develop in a completely in vivo environment. This article reviews the history of AFF and JIVET and their effects on oocyte and embryo development as well as freezing resistance. Improving the efficiency and reproducibility of AFF technology is crucial to its clinical application. This article discusses factors that affect the success rate of AFF, including differences in specific technical procedures and differences between pubertal and adult follicles. Designing standardized procedures and details to improve the synchronization of donor COCs and recipient follicle maturity and reducing the damage to COCs caused by follicular aspiration may be the direction for improving the success rate of AFF in the future.

Different types of bisphenols alter ovarian steroidogenesis: Special attention to BPA

Endocrine disruptors such as bisphenol A (BPA) and some of its analogues, including BPS, BPAF, and BPE, are used extensively in the manufacture of plastics. These synthetic chemicals could seriously alter the functionality of the female reproductive system. Although the number of studies conducted on other types of bisphenols is smaller than the number of studies on BPA, the purpose of this review study was to evaluate the effects of bisphenol compounds, particularly BPA, on hormone production and on genes involved in ovarian steroidogenesis in both in vitro (human and animal cell lines) and in vivo (animal models) studies. The current data show that exposure to bisphenol compounds has adverse effects on ovarian steroidogenesis. For example, BPA, BPS, and BPAF can alter the normal function of the hypothalamic-pituitary-gonadal (HPG) axis by targeting kisspeptin neurons involved in steroid feedback signals to gonadotropin-releasing hormone (GnRH) cells, resulting in abnormal production of LH and FSH. Exposure to BPA, BPS, BPF, and BPB had adverse effects on the release of some hormones, namely 17-β-estradiol (E2), progesterone (P4), and testosterone (T). BPA, BPE, BPS, BPF, and BPAF are also capable of negatively altering the transcription of a number of genes involved in ovarian steroidogenesis, such as the steroidogenic acute regulatory protein (StAR, involved in the transfer of cholesterol from the outer to the inner mitochondrial membrane, where the steroidogenesis process begins), cytochrome P450 family 17 subfamily A member 1 (Cyp17a1, which is involved in the biosynthesis of androgens such as testosterone), 3 beta-hydroxysteroid dehydrogenase enzyme (3β-HSD, involved in the biosynthesis of P4), and cytochrome P450 family 19 subfamily A member 1 (Cyp19a1, involved in the biosynthesis of E2). Exposure to BPA, BPB, BPF, and BPS at prenatal or prepubertal stages could decrease the number of antral follicles by activating apoptosis and autophagy pathways, resulting in decreased production of E2 and P4 by granulosa cells (GCs) and theca cells (TCs), respectively. BPA and BPS impair ovarian steroidogenesis by reducing the function of some important cell receptors such as estrogens (ERs, including ERα and ERβ), progesterone (PgR), the orphan estrogen receptor gamma (ERRγ), the androgen receptor (AR), the G protein-coupled estrogen receptor (GPER), the FSHR (follicle-stimulating hormone receptor), and the LHCGR (luteinizing hormone/choriogonadotropin receptor). In animal models, the effects of bisphenol compounds depend on the type of animals, their age, and the duration and dose of bisphenols, while in cell line studies the duration and doses of bisphenols are the matter.

Optimization of gonadotropin stimulation protocols for in vitro embryo production in prepubertal Mediterranean water buffalo

Embryos can be produced from prepubertal donor animals using laparoscopic ovum pickup and in vitro embryo production technologies (LOPU-IVEP). Together, these tools can shorten the interval between generations, rapidly accelerating the rate of genetic gain. Here, we assessed the impact of different gonadotropin stimulation protocols in Mediterranean water buffalo heifer calves aged between 2 and 6 months old. Following gonadotropin stimulation, LOPU was performed at two-week intervals, with animals receiving different protocols on subsequent LOPUs. After collection, the cumulus-oocyte complexes (COCs) were matured and fertilized in vitro, and embryos were cultured to the blastocyst stage followed by transfer into synchronized adult recipients. The number and size of follicles aspirated during LOPU, the number and quality of COCs recovered, as well as cleavage, embryo development and pregnancy rates were assessed. First, we evaluated the impact of using FSH with and without eCG (administered 24-h prior to LOPU) and found that a combination of FSH and eCG was able to significantly improve embryo development rates (20.6 ± 2.0% vs. 9.0 ± 3.6%; P < 0.05). Second, we compared this protocol to a slow-release formulation of FSH reconstituted in hyaluronan. In addition to requiring less work to prepare the animals for LOPU, this slow-release formulation yielded numerically higher, but not statistically different, average number of recovered COCs (14.4 ± 2.1 vs. 10.3 ± 2.0; P > 0.05) and embryo development rates (22.9 ± 4.7% vs. 14.1 ± 5.2%; P > 0.05) compared to FSH given every 12 h. Next, we compared the length of gonadotropin treatment over 3-, 4- and 5-days prior to LOPU and found that as the length of gonadotropin treatment increased, although the number of COCs recovered steadily decreased (14.1 ± 2.4 vs. 8.7 ± 1.0 vs. 6.9 ± 0.7; P < 0.05), the embryo development rates steadily increased (14.4 ± 3.9 vs. 27.3 ± 4.4 vs. 35.9 ± 7.0; P < 0.05), presumably due to an increase in the proportion of large follicles at the time of LOPU. Numerically, the 4-day treatment yielded more transferrable embryos per donor per LOPU (2.70 ± 0.5) than 3-day (1.94 ± 0.6) and 5-day (2.25 ± 0.5) treatments. Finally, following embryo transfer, 26 of 90 recipient females became pregnant (28.9%). Pregnancies were established from all treatments, which suggests that post-implantation development was not affected among the gonadotropin treatments assessed.

Factors Affecting the Efficiency of In Vitro Embryo Production in Prepubertal Mediterranean Water Buffalo

Embryos from prepubertal water buffalo can be produced using laparoscopic ovum pickup (LOPU) and in vitro embryo production (IVEP). However, to date, it is unclear what factors and environmental conditions can affect LOPU-IVEP efficiency in prepubertal animals, especially buffalo. In this study, we explored the impact of season, age and individual variation among female donor animals, as well as the effect of the sire used for in vitro fertilization. Donor animals between 2 and 6 months of age were stimulated using gonadotropins prior to LOPU, which was performed at two-week intervals. Following in vitro maturation and fertilization, the resulting embryos were then cultured to the blastocyst stage until they were either vitrified or transferred into recipient animals. The number of follicles available for aspiration and embryo development rates was stable throughout the year. As animals became older, there was a slight trend for fewer COCs recovered from LOPU and better embryo development. There was a large individual variation in both ovarian response and the developmental competence of oocytes among donors. The bull used for fertilization also had a significant impact on embryo development. Upon embryo transfer, pregnancy rates were not affected by the number of embryos transferred per recipient. The best pregnancy rates were achieved when transferring blastocysts, compared to compact morula or hatched blastocysts. Finally, vitrification had no effect on pregnancy rate compared to fresh embryos.

Bovine models for human ovarian diseases

During early embryonic development, late fetal growth, puberty, adult reproductive years, and advanced aging, bovine and human ovaries closely share molecular pathways and hormonal signaling mechanisms. Other similarities between these species include the size of ovaries, length of gestation, ovarian follicular and luteal dynamics, and pathophysiology of ovarian diseases. As an economically important agriculture species, cattle are a foundational species in fertility research with decades of groundwork using physiologic, genetic, and therapeutic experimental techniques. Many technologies used in modern reproductive medicine, such as ovulation induction using hormonal therapy, were first used in cows before human trials. Human ovarian diseases with naturally occurring bovine correlates include premature ovary insufficiency (POI), polycystic ovarian syndrome (PCOS), and sex-cord stromal tumors (SCSTs). This article presents an overview of bovine ovary research related to causes of infertility, ovarian diseases, diagnostics, and therapeutics, emphasizing where the bovine model can offer advantages over other lab animals for translational applications.

Transcriptomic comparison of ovarian granulosa cells between adult sheep and prepubertal lambs

BACKGROUND

The oocyte development ability of prepubertal animals is significantly lower than that of adult animals. Granulosa cells (GCs) have an important function on regulation of follicular and oocyte development. Therefore, analysis of GC characteristics can be used to explore the developmental mechanism of follicles and oocytes.

RESULTS

In order to understand the possible reasons for the differences in follicle and oocyte development between lambs and adult sheep, we utilized high-throughput sequencing technique to analyze the transcriptome of GCs from follicle-stimulating hormone (FSH) superstimulated adult ewes and prepubertal lambs. Adult ewes were treated with FSH for 3 days (group A) and lambs were FSH-treated for 2 days (group B) or 3 days (group C). Transcriptome analysis of GCs showed that there were 405 and 159 differentially expressed genes from A vs. B and A vs. C, respectively. The results indicated that prolonging the FSH-treatment of lambs made the GC state of lambs more similar to the adult ewes, but there were still a large number of differentially expressed genes between adult ewes and lambs. Further analysis showed that many differently expressed genes were implicated in cell proliferation and apoptosis, oocyte development and follicular ovulation. Cellular examination demonstrated that fatty acid binding protein 4 (FABP4), which was highly expressed in lamb GCs, had a potential of promoting cell apoptosis. Cytoplasmic phospholipase A2 (PLA2G4A), which was expressed lowly in lamb GCs, may be responsible for reduced synthesis of prostaglandins in cells and impaired follicle/oocyte development. In contrast, glutathione S-transferase β-1 (GSTT2B) and forkhead boxO6 (FOXO6) had no apparent effect on the proliferation and apoptosis of GCs.

CONCLUSIONS

Our study found dramatic transcriptomic differences in GCs between lambs and adult sheep, which may explain the possible reasons for the defects of follicle and oocyte development in lambs compared to adult sheep. Our data provides important information for further understanding the mechanism of follicular development in prepubertal animals and improving their oocyte developmental competence.

In Vitro Production of Embryos from Prepubertal Holstein Cattle and Mediterranean Water Buffalo: Problems, Progress and Potential

Laparoscopic ovum pick-up (LOPU) coupled with in vitro embryo production (IVEP) in prepubertal cattle and buffalo accelerates genetic gain. This article reviews LOPU-IVEP technology in prepubertal Holstein Cattle and Mediterranean Water Buffalo. The recent expansion of genomic-assisted selection has renewed interest and demand for prepubertal LOPU-IVEP schemes; however, low blastocyst development rates has constrained its widespread implementation. Here, we present an overview of the current state of the technology, limitations that persist and suggest possible solutions to improve its efficiency, with a focus on gonadotropin stimulations strategies to prime oocytes prior to follicular aspiration, and IVEP procedures promoting growth factor metabolism and limiting oxidative and endoplasmic reticulum stress.

PATL2 regulated the apoptosis of ovarian granulosa cells in patients with PCOS

AIM

PCOS often showed abnormal follicular development. Previous studies have found that the increased apoptosis of granulosa cells (GCs) is one of the key factors leading to follicular dysplasia. It has been found that the decrease or deletion of PATL2 function can significantly inhibit the development and maturation of human oocytes. We found that PATL2 was also expressed in human ovarian GCs, suggesting that PATL2 may be involved in the regulation of related biological events in GCs. This study aims to explore the function of PATL2 on regulation of GCs apoptosis, and the potential role of PATL2 in the development of PCOS-related abnormal follicles.

MATERIALS AND METHODS

The follicular GCs of PCOS patients and normal ovulating female patients were collected. Moreover, human granular cell line (KGN) was used for in vitro experiments.

RESULTS

(1) The maturation rate and fertilization rate of oocytes in the PCOS group were significantly lower than those in the normal control group (p＜0.05). (2) Flow cytometry and TUNEL staining showed that the apoptosis level of GCs in the PCOS group was significantly increased. (3) Immunofluorescence and Western Blot showed that the PATL2 expression level of GCs in the PCOS group was significantly reduced. (4) Knocking down the expression of PATL2 by siRNA significantly prevented the apoptosis of GCs.

CONCLUSIONS

Reduced PATL2 could resulted in the increased apoptosis level of ovarian GCs, which might be closely related to the occurrence and development of abnormal follicles in PCOS.

Bisphenol analogs AF, S and F: Effects on functional characteristics of porcine granulosa cells

In order to replace industrial functions of the restricted endocrine disruptor bisphenol A (BPA), its structural analogs are increasingly employed without adequate assessment of their biological actions. Our study examined effects of the bisphenols AF (BPAF), S (BPS) and F (BPF), on functions of porcine ovarian granulosa cells (GCs) with the focus on viability, steroid production (10^-9-10^-4M), and expression of factors (10^-9-10^-5M) important for the follicle development: vascular endothelial growth factor A (VEGFA), matrix metalloproteinase 9 (MMP9), forkhead box O1 (FOXO1), and aryl hydrocarbon receptor (AHR). Cell viability was not impaired by the bisphenol analogs, except for the highest BPAF concentration (10^-4M). While the lower concentrations of the bisphenols were without effect, each of them reduced follicle-stimulating hormone (FSH)-induced progesterone synthesis at the highest dose. Estradiol synthesis was sensitive to BPS, inhibitory effects of which were manifested from the concentration of 10^-6M. Treatment of GCs with the selected bisphenol concentrations did not result in marked alterations in steroidogenic enzyme expression. Bisphenols did not significantly modulate VEGFA mRNA expression or output either under basal or FSH-stimulated conditions. BPF at 10^-5M increased MMP9 expression in FSH-stimulated cells. FSH upregulated FOXO1 expression, however, none of the bisphenols significantly affected FOXO1 levels either in basal or in FSH-stimulated conditions. AHR mRNA expression remained unchanged after bisphenol treatment. Although the significant effects of BPAF, BPS and BPF appeared only at supraphysiological doses, the results obtained indicate that BPA analogs are not inert with regard to ovarian physiology.

The Roles of the miRNAome and Transcriptome in the Ovine Ovary Reveal Poor Efficiency in Juvenile Superovulation

Simple Summary

Using the technology of juvenile superovulation, more follicles can be acquired in juvenile animals than in adult animals. However, oocytes derived from the follicles of juvenile animals are usually of poor quality, meaning that they have lower levels of subsequent maturation and embryonic development. In the present study, we used an exogenous hormone treatment to stimulate Hu sheep in order to compare the differences in ovarian superovulation effects and serum hormone secretion in juvenile and adult sheep. Differentially expressed microRNA (miRNA) and messenger RNA (mRNA) from the ovaries of juvenile and adult Hu sheep were then investigated using high-throughput sequencing technology to reveal the formation mechanism of large numbers of follicles and poor oocyte quality in juvenile ovaries under superovulation treatment. We found that molecules of oar-miR-143 and follicle-stimulating hormone receptor (FSHR), among others, might regulate follicle formation, while oar-miR-485-3p, oar-miR-377-3p, and pentraxin 3 (PTX3), among others, may be associated with oocyte quality. The results will help us to identify miRNAs and mRNAs that could be used to predict ovarian superovulation potential and oocyte quality in the future.

Abstract

Juvenile superovulation can provide a wealth of oocyte material for embryo production, animal cloning, and genetic modification research, but embryos derived from juvenile oocytes show poor efficiency in subsequent developmental capacity. In order to reveal the formation mechanism of large numbers of follicles and poor oocyte quality in juvenile ovaries under superovulation treatment, differentially expressed microRNAs (miRNAs) and messenger RNAs (mRNAs) were characterized and investigated in the ovaries of lambs and adult sheep using high-throughput sequencing technology. The majority of differentially expressed miRNAs (337/358) were upregulated in lamb libraries. The expression levels of mRNAs related to hormone receptors (follicle-stimulating hormone receptor, FSHR; luteinizing hormone/choriogonadotropin receptor, LHCGR; estrogen receptor 1, ESR1), steroid hormone secretion (cytochrome P450 family 11 subfamily A member 1, CYP11A1; cytochrome P450 family 17 subfamily A member 1, CYP17A1; cytochrome P450 family 19 subfamily A member 1, CYP19A1), and oocyte quality (pentraxin 3, PTX3; BCL2 apoptosis regulator, BCL2; caspase 3, CASP3) were significantly different between the lamb and adult libraries. The miRNA aor-miR-143, which targets FSHR, was highly and differentially expressed, and PTX3 was predicted to be targeted by oar-miR-485-3p and oar-miR-377-3p in the ovine ovary. A considerable number of miRNAs were predicted to inhibit ESR1 expression in lamb ovaries. In conclusion, oar-miR-143 and FSHR molecules, among others, might regulate follicle formation, and oar-miR-485-3p, oar-miR-377-3p, and PTX3, among others, may be associated with oocyte quality. These identified miRNAs and mRNAs will be beneficial for the prediction of ovarian superovulation potential and screening of oocytes.

Melatonin enhances in vitro developmental competence of cumulus-oocyte complexes collected by ovum pick-up in prepubertal and adult dairy cattle

Bovine oocytes from prepubertal donors have been used for in vitro embryo production to decrease the generation interval. However, reduced cumulus-oocyte competence, mainly attributed to increased apoptosis, has been observed in oocytes/embryos collected from prepubertal donors. Here, we investigated the effects of the potent antioxidative molecule melatonin on cumulus-oocyte competence and embryo development in prepubertal and adult dairy cattle in vitro. A total of fifteen Holstein Friesian calves, six to ten months old (7.6 ± 1.34 months of age). And fifteen adult cows with one to four calvings (2.3 ± 0.96 calvings) were enrolled as ovum pick up (OPU) donors in this study. Cumulus-oocyte complexes (COCs) were cultured either in the presence or absence of melatonin (0.01 nM). The proportion of cleavage stages, blastocysts, and advanced blastocysts was determined. Embryo quality was assessed via differential staining to determine the total embryonic cells and allocation to the inner cell mass (ICM) and trophectoderm (TE) cells. Melatonin treatment yielded a greater percentage of blastocysts compared to the control group, i.e. oocytes from both adult cows (P = 0.0485; 24.8 ± 3.5% vs. 16.0 ± 3.4%, respectively), and from prepubertal donors (P = 0.0007; Melatonin 23.1 ± 5.1% vs. Control: 11.1 ± 3.5%). Adult cows had significantly (P = 0.0370) greater advanced blastocyst rates than those found in the prepubertal group (13.9%± vs. 7.0±%, respectively). Additionally, the number of ICM, total cells, and the ratios ICM: Total, ICM: TE, respectively, were greater (P < 0.05) after melatonin treatment compared with the control group (39.1 ± 2.8, 98.6 ± 5.7, 0.4 ± 0.01, and 0.7 ± 0.04 vs. 27.3 ± 2.9, 81.2 ± 5.8, 0.34 ± 0.01, and 0.52 ± 0.04, respectively). Blastocysts derived from adult cows had a greater number of TE (P = 0.01) and total embryonic cells (P = 0.0095) compared to the prepubertal donor group (63.5 ± 3.2 and 101.05 ± 4.8 vs. 48.9 ± 4.3 and 78.8 ± 6.5, respectively). Nevertheless, embryonic cell counting in embryos derived from prepubertal COCs equated to that observed from adult donors after melatonin exposure. In conclusion, these results indicate that the presence of melatonin during in vitro maturation improves cumulus-oocyte competence, embryo development, and quality by increasing the allocation of embryonic cells to the ICM compartment and the total number of embryonic cells in both adult and prepubertal bovine donors.

STAT4 targets KISS1 to promote the apoptosis of ovarian granulosa cells

Background

In mammals, it is known that the estradiol-17β (E2) is mainly synthetized in ovarian granulosa cells (GCs), and the excessive apoptosis of GCs induces the follicular atresia. Many studies have implicated the essential role of KISS1, with the pro-synthetic effect of E2 and the anti-apoptotic effect on GCs, in the mammalian folliculogenesis, and several STAT4 potential binding sites were previously predicted on the promoter of KISS1 in pigs. However, the biological effects of STAT4 on GCs and the molecular regulation between STAT4 and KISS1 remained largely unknown.

Methods

Using the porcine GCs as the cellular model, the overexpression plasmid, small interfering RNA, 5′-deletion and luciferase assay were applied to investigate the molecular mechanisms for STAT4 regulating the expression of KISS1.

Results

In this study, the STAT4 negatively regulated the mRNA and protein levels of KISS1 in porcine GCs, and the mRNA level of STAT4 was observed to significantly decrease from immature to mature follicles, which was inversed with that of KISS1. The relative luciferase activity of KISS1 promoter was significantly increased with deletion of the fourth potential binding site (− 305/− 295), and ChIP further confirmed that the STAT4 bound at − 305/− 295 region of KISS1. Besides, the STAT4 significantly regulated the mRNA levels of PDK1, FOXO3 and TSC2 of PI3K signaling pathway to promote the cell apoptosis and the percentage of cells at G0/G1 phase of cell cycle in GCs. Alternatively, the STAT4 significantly decreased the mRNA levels of CYP17, 3B-HSD, 17B-33 HSD, ESR1, and ESR2, as well as the concentration of E2 in GCs. Furthermore, interfering with the expression of STAT4 was observed to significantly stimulate the pro-synthetic effect of E2 and anti-apoptotic effect of KISS1 in GCs.

Conclusions

Collectively, the STAT4 might directly target at − 305/− 295 region of KISS1 to negatively regulate the transcription of KISS1, promote the cell apoptosis via PI3K signaling pathway, suppress the synthesis of E2 through the estrogen signaling pathway in porcine GCs. These proposed works could provide useful insight in further investigations on the molecular functionalities of STAT4 and KISS1 in the folliculogenesis of mammals.

Downregulation of gap junctional intercellular communication and connexin 43 expression by bisphenol A in human granulosa cells

Gap junctional intercellular communication (GJIC) is the transfer of ions, metabolites, and second messengers between neighboring cells through intercellular junctions. Connexin 43 (Cx43) was found to be the type of gap junction protein responsible for human granulosa cells (GCs) and oocyte communication, which is required for folliculogenesis and oocyte maturation. Bisphenol A (BPA), an estrogenic-like endocrine-disrupting chemical, is one of the most widely produced chemicals around the world. There are reports that the chemical might cause endometrial tumorigenesis and several female reproductive disorders. This study demonstrated that cell culture medium, containing antioxidants (N-acetyl-l-cysteine and l-ascorbic acid-2-phosphate), was able to enhance the survival and self-renewal of GCs. In addition, we found that BPA at environmentally relevant concentration (10^-7  M) reduced Cx43 expression and GJIC in GCs through estrogen receptor and mitogen-activated protein kinase pathways. The results of this study not only reveal the reproductive toxicity of BPA but also provide possible mechanisms by which BPA inhibited GJIC in GCs.

Functional effects of Tribbles homolog 2 in bovine ovarian granulosa cells†

Tribbles homologs (TRIB) 1, 2, and 3 represent atypical members of the serine/threonine kinase superfamily. We previously identified TRIB2 as a differentially expressed gene in granulosa cells (GCs) of bovine preovulatory follicles. The current study aimed to further investigate TRIB2 regulation and study its function in the ovary. GCs were collected from follicles at different developmental stages: small antral follicles (SF), dominant follicles (DF) at day 5 of the estrous cycle, and hCG-induced ovulatory follicles (OFs). RT-qPCR analyses showed greater expression of TRIB2 in GC of DF as compared to OF and a significant downregulation of TRIB2 steady-state mRNA amounts by hCG/LH, starting at 6 h through 24 h post-hCG as compared to 0 h. Specific anti-TRIB2 polyclonal antibodies were generated and western blot analysis confirmed TRIB2 downregulation by hCG at the protein level. In vitro studies showed that FSH stimulates TRIB2 expression in GC. Inhibition of TRIB2 using CRISPR/Cas9 resulted in a significant increase in PCNA expression and an increase in steroidogenic enzyme CYP19A1 expression, while TRIB2 overexpression tended to decrease GC proliferation. TRIB2 inhibition also resulted in a decrease in transcription factors connective tissue growth factor (CTGF) and ankyrin repeat domain-containing protein 1 (ANKRD1) expression, while TRIB2 overexpression increased CTGF and ANKRD1. Additionally, western blot analyses showed reduction in ERK1/2 (MAPK3/1) and p38MAPK (MAPK14) phosphorylation levels following TRIB2 inhibition, while TRIB2 overexpression increased p-ERK1/2 and p-p38MAPK. These results provide evidence that TRIB2 modulates MAPK signaling in GC and that TRIB2 could act as a regulator of GC proliferation and function, which could affect steroidogenesis during follicular development.