Oocyte-granulosa-theca cell interactions during preantral follicular development

Role of programmed cell death in mammalian ovarian follicular atresia

Programmed cell death (PCD) is a fundamental process in the development process of organisms, including apoptosis, autophagy, ferroptosis, and pyroptosis. In mammalian ovaries, 99 % of follicles undergo atresia, while only 1 % mature and ovulate, which limits the reproductive efficiency of mammals. The PCD process is closely related to the regulation of follicle development and atresia. Recently, an increasing number of studies have reported that autophagy, pyroptosis, and ferroptosis of PCD are involved in regulating granulosa cell apoptosis and follicular atresia. Granulosa cell apoptosis is a hallmark of follicular atresia. Therefore, an understanding of molecular mechanisms regulating PCD events is required for future advances in the diagnosis and management of various disorders of follicular atresia. This review summarizes recent work on apoptosis, autophagy, pyroptosis, and ferroptosis of PCD that affect granulosa cell survival and follicular atresia, and further elucidating the mechanisms of follicular atresia and providing new directions for improving the reproductive capacity of humans and animals.

Growth differentiation factor 9 activates the TGF-β pathway in follicle atresia of Muscovy ducks

Muscovy ducks' high broodiness hinders industry growth. Studying broodiness regulation contributes to the theoretical foundation for enhancing reproductive performance in Muscovy ducks. Experiment 1, a total of 18 Muscovy ducks were divided into 2 groups: Laying group (LO) and Broody group (BO). To collect ovaries for morphological and transcriptome analysis. Experiment 2, Primary Muscovy ducks granulosa cells (GC) were isolated and treated with or without GDF9 at appropriate concentrations as indicated. Experiment 3, GC were treated with or without GDF9 in the presence or absence of a receptor inhibitor. The cell viability, cell apoptosis rate and levels of TGF-β pathway were determined. In vivo, there was a gradual disappearance of follicles in the ovaries and accompanied by follicle atrophy and a concentration of cytoplasm in BO group. The transcriptome expression profile revealed a total of 1,185 up-regulated differentially expressed transcripts (DEs) and 1,258 down-regulated DEs in the BO group compared to the LO group. The up-regulated differentially expressed GDF9 is involved in regulating the TGF-β pathway, which is among the top 10 pathways identified through the KEGG pathway analysis (P < 0.05). Additionally, the fluorescence intensity of apoptosis is primarily observed in the granulosa layers of the ovary. Compared to the LO group, the mRNA level of TGF-β pathway and the protein of GDF9 and p-Smad2/3 were increased in ovary of the BO group (P < 0.05). In vitro, GDF9 supplementation demonstrated does-related promotion of GC (P < 0.01). Compared to CTRL group, 12 ng/mL GDF9 supplementation to GC increased the rate of cell apoptosis, the mRNA and protein expression of TGF-β pathway and the apoptosis-related genes. Pretreatment of GC with GDF9-receptor inhibitor largely abrogated the negative function of GDF9 treatment (P < 0.05). In summary, granulosa cell apoptosis leading to follicle atresia in broodiness of Muscovy ducks is associated with GDF9 activation of the TGF-β pathway. This discovery lays a solid foundation for understanding duck follicular development and enhancing egg production in Muscovy ducks.

Hydrogel Strategies for Female Reproduction Dysfunction

Infertility is an important issue for human reproductive health, with over half of all cases of infertility associated with female factors. Dysfunction of the complex female reproductive system may cause infertility. In clinical practice, female infertility is often treated with oral medications and/or surgical procedures, and ultimately with assisted reproductive technologies. Owing to their excellent biocompatibility, low immunogenicity, and adjustable mechanical properties, hydrogels are emerging as valuable tools in the reconstruction of organ function, supplemented by tissue engineering techniques to increase their structure and functionality. Hydrogel-based female reproductive reconstruction strategies targeting the pathological mechanisms of female infertility may provide alternatives for the treatment of ovarian, endometrium/uterine, and fallopian tube dysfunction. In this review, we provide a general introduction to the basic physiology and pathology of the female reproductive system, the limitations of current infertility treatments, and the lack of translation from animal models to human reproductive physiology. We further provide an overview of the current and future potential applications of hydrogels in the treatment of female reproductive system dysfunction, highlighting the great prospects of hydrogel-based strategies in the field of translational medicine, along with the significant challenges to be overcome.

Comparative transcriptome profile analysis of granulosa cells from porcine ovarian follicles during early atresia

At various stages of ovarian follicular development, more than 99% of follicles will be eliminated through a degenerative process called atresia. The regulatory mechanisms of atresia have been elucidated to some extent, involving hormones, growth factors, cytokines, and other factors. However, the stimuli initiating atresia in follicular granulosa cells remain unknown. In this study, we isolated the granulosa cells from porcine ovarian follicles (3-5 mm diameter) divided into healthy follicles (HFs) and early atretic follicles (EAFs). We applied high-throughput RNA sequencing to identify and compare differentially expressed genes (DEGs) between HFs and EAFs. A total of 31,694 genes were detected, of which 21,806 were co-expressed in six samples, and 243 genes (p < 0.05; FDR < 0.05) were differentially expressed (DEGs), including 123 downregulated and 120 upregulated in EAFs. GO analysis highlighted hormone metabolism, plasma membrane localization, and transporter activity. The pathway analysis indicated that 51 DEGs, involved in steroidogenesis, cell adhesion molecules, and TGF-beta signaling pathways, were highly related to atresia. Additionally, the interaction network of DEGs (p < 0.01; FDR < 0.05) using STRING highlighted LHR, ACACB, and CXCR4 as central nodes. In summary, this transcriptome analysis enriched our knowledge of the shifted mechanisms in granulosa cells during early atresia and provided novel perspectives into the atresia initiation.

Reproductive and developmental implications of micro- and nanoplastic internalization: Recent advances and perspectives

A growing body of evidence exhibits the ubiquitous presence and accumulation of micro- and nanoplastics (MNPs) in the air, drinking water, food, and even inside the body, which has raised concerns about their potential impact on reproductive and developmental health. To comprehensively examine the current state of knowledge regarding MNPs-induced reproductive and developmental toxicity, we conducted this systematic review by focusing on the prevalence of MNPs determined in reproductive tissues and their influences on parental reproduction and offspring development. Our findings demonstrate the detection of MNPs in various human reproductive tissues, including semen, placenta, and ovarian follicular fluid, as well as in reproductive tissues of diverse animal species. We show a potential relationship between MNP exposure and increased prevalence of infertility and adverse pregnancy outcomes based on the fact that MNPs exert detrimental effects on reproductive parameters, including sperm quality, ovarian function, and steroidogenesis. In male reproductive systems, MNPs disrupt testicular tissue structure, impair reproductive endocrinology, and reduce sperm quality. In females, MNPs affect ovarian tissue structure and function, interfere with hormone secretion, and impact the endometrium and embryo implantation. Additionally, MNPs cause developmental toxicity in animal models, affecting embryonic development and offspring health, and produce transgenerational effects. Notably, in-depth literature study suggests a crucial role for oxidative stress, inflammation, and epigenetic modification in MNPs-induced toxicity. In conclusion, we integrated systematic knowledge on MNPs-induced reproductive and developmental toxicity, and the systematic finding underscores future study to fully elucidate the risks posed by MNPs to reproductive and developmental health and to inform policy decisions and public health interventions aimed at mitigating their harmful effects.

Inducers and Inhibitors of Pyroptotic Death of Granulosa Cells in Models of Premature Ovarian Insufficiency and Polycystic Ovary Syndrome

Granulosa cells (GCs), the largest cell population and primary source of steroid hormones in the ovary, are the important somatic ovarian components. They have critical roles in folliculogenesis by supporting oocyte, facilitating its growth, and providing a microenvironment suitable for follicular development and oocyte maturation, thus having essential functions in maintaining female fertility and in reproductive health in general. Pyroptotic death of GCs and associated inflammation have been implicated in the pathogenesis of several reproductive disorders in females including Premature Ovarian Insufficiency (POI) and Polycystic Ovary Syndrome (PCOS). Here, I reviewed factors, either intrinsic or extrinsic, that induce or inhibit pyroptosis in GCs in various models of these disorders, both in vitro and in vivo, and also covered associated molecular mechanisms. Most of these studied factors influence NLRP3 inflammasome- and GSDMD (Gasdermin D)-mediated pyroptosis in GCs, compared to other inflammasomes and gasdermins (GSDMs). I conclude that a more complete mechanistic understanding of these factors in terms of GC pyroptosis is required to be able to develop novel strategies targeting inflammatory cell death in the ovary.

Effects of Melatonin and 3,5,3'-Triiodothyronine on the Development of Rat Granulosa Cells

Melatonin, as an endocrine neurotransmitter, can promote the development of the ovary. Meanwhile, it also has protective effect on the ovary as an antioxidant. Thyroid hormone (TH) is essential for normal human reproductive function. Many studies have shown that 3,5,3'-triiodothyronine (T3) regulates the development of ovarian granulosa cells. However, little is known about the specific mechanisms by which melatonin combines with T3 to regulate granulosa cell development. The aim of present study was to investigate the effects and the possible mechanisms of melatonin and T3 on ovarian granulosa cell development. In the present study, cell development and apoptosis were detected by CCK8, EdU and TUNEL, respectively. The levels of related proteins were analyzed by Western blotting. The results showed that oxidative stress (OS) and reactive oxygen species (ROS) were induced by H2O2 in granulosa cells, and cell apoptosis was also increased accompanied with the decreased cellular proliferation and viability. Melatonin protects granulosa cells from H2O2-induced apoptosis and OS by downregulating ROS levels, especially in the presence of T3. Co-treatment of cell with melatonin and T3 also promotes the expression of GRP78 and AMH, while inhibiting CHOP, Caspase-3, and P16. It was demonstrated that melatonin alone or in combination with T3 had positive effect on the development of granulosa cells. In addition, the AMPK/SIRT1 signaling pathway is involved in the process of melatonin/T3 promoting granulosa cell development.

Epigenetic modifications of gonadotropin receptors can regulate follicular development

The spatiotemporal transcription of follicle-stimulating hormone receptor (FSHR) and luteinizing hormone/human chorionic gonadotropin receptor (LHCGR) are crucial events for follicular development. However, their regulatory mechanisms are unclear. DNA methylation and histone acetylation are the main epigenetic modifications, and play important roles in transcriptional expression, which regulate cell responses including cell proliferation, senescence and apoptosis. This review will discuss the dynamic epigenetic modifications of FSHR and LHCGR that occur during the process of follicular development and their response to gonadotropins. In addition, some alteration patterns that occur during these epigenetic modifications, as well as their retrospect retrotransposons, which regulate the gene expression levels of FSHR and LHCGR will be discussed.

Hormonal and Allosteric Regulation of the Luteinizing Hormone/Chorionic Gonadotropin Receptor

Luteinizing hormone (LH) and human chorionic gonadotropin (CG), like follicle-stimulating hormone, are the most important regulators of the reproductive system. They exert their effect on the cell through the LH/CG receptor (LHCGR), which belongs to the family of G protein-coupled receptors. Binding to gonadotropin induces the interaction of LHCGR with various types of heterotrimeric G proteins (Gs, Gq/11, Gi) and β-arrestins, which leads to stimulation (Gs) or inhibition (Gi) of cyclic adenosine monophosphate-dependent cascades, activation of the phospholipase pathway (Gq/11), and also to the formation of signalosomes that mediate the stimulation of mitogen-activated protein kinases (β-arrestins). The efficiency and selectivity of activation of intracellular cascades by different gonadotropins varies, which is due to differences in their interaction with the ligand-binding site of LHCGR. Gonadotropin signaling largely depends on the status of N- and O-glycosylation of LH and CG, on the formation of homo- and heterodimeric receptor complexes, on the cell-specific microenvironment of LHCGR and the presence of autoantibodies to it, and allosteric mechanisms are important in the implementation of these influences, which is due to the multiplicity of allosteric sites in different loci of the LHCGR. The development of low-molecular-weight allosteric regulators of LHCGR with different profiles of pharmacological activity, which can be used in medicine for the correction of reproductive disorders and in assisted reproductive technologies, is promising. These and other issues regarding the hormonal and allosteric regulation of LHCGR are summarized and discussed in this review.

Extracellular vesicles and their content in the context of polycystic ovarian syndrome and endometriosis: a review

Extracellular vesicles (EVs), particles enriched in bioactive molecules like proteins, nucleic acids, and lipids, are crucial mediators of intercellular communication and play key roles in various physiological and pathological processes. EVs have been shown to be involved in ovarian follicular function and to be altered in two prevalent gynecological disorders; polycystic ovarian syndrome (PCOS) and endometriosis.Ovarian follicles are complex microenvironments where folliculogenesis takes place with well-orchestrated interactions between granulosa cells, oocytes, and their surrounding stromal cells. Recent research unveiled the presence of EVs, including exosomes and microvesicles, in the follicular fluid (FFEVs), which constitutes part of the developing oocyte's microenvironment. In the context of PCOS, a multifaceted endocrine, reproductive, and metabolic disorder, studies have explored the dysregulation of these FFEVs and their cargo. Nine PCOS studies were included in this review and two miRNAs were commonly reported in two different studies, miR-379 and miR-200, both known to play a role in female reproduction. Studies have also demonstrated the potential use of EVs as diagnostic tools and treatment options.Endometriosis, another prevalent gynecological disorder characterized by ectopic growth of endometrial-like tissue, has also been linked to aberrant EV signaling. EVs in the peritoneal fluid of women with endometriosis carry molecules that modulate the immune response and promote the establishment and maintenance of endometriosis lesions. EVs derived from endometriosis lesions, serum and peritoneal fluid obtained from patients with endometriosis showed no commonly reported biomolecules between the eleven reviewed studies. Importantly, circulating EVs have been shown to be potential biomarkers, also reflecting the severity of the pathology.Understanding the interplay of EVs within human ovarian follicles may provide valuable insights into the pathophysiology of both PCOS and endometriosis. Targeting EV-mediated communication may open avenues for novel diagnostic and therapeutic approaches for these common gynecological disorders. More research is essential to unravel the mechanisms underlying EV involvement in folliculogenesis and its dysregulation in PCOS and endometriosis, ultimately leading to more effective and personalized interventions.

Gonadotropin Activity during Early Folliculogenesis and Implications for Polycystic Ovarian Syndrome and Premature Ovarian Insufficiency: A Narrative Review

Female fertility depends on the ovarian reserve of follicles, which is determined at birth. Primordial follicle development and oocyte maturation are regulated by multiple factors and pathways and classified into gonadotropin-independent and gonadotropin-dependent phases, according to the response to gonadotropins. Folliculogenesis has always been considered to be gonadotropin-dependent only from the antral stage, but evidence from the literature highlights the role of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) during early folliculogenesis with a potential role in the progression of the pool of primordial follicles. Hormonal and molecular pathway alterations during the very earliest stages of folliculogenesis may be the root cause of anovulation in polycystic ovary syndrome (PCOS) and in PCOS-like phenotypes related to antiepileptic treatment. Excessive induction of primordial follicle activation can also lead to premature ovarian insufficiency (POI), a condition characterized by menopause in women before 40 years of age. Future treatments aiming to suppress initial recruitment or prevent the growth of resting follicles could help in prolonging female fertility, especially in women with PCOS or POI. This review will briefly introduce the impact of gonadotropins on early folliculogenesis. We will discuss the influence of LH on ovarian reserve and its potential role in PCOS and POI infertility.

The Roles of GDF-9, BMP-15, BMP-4 and EMMPRIN in Folliculogenesis and In Vitro Fertilization

Growth differentiation factor 9 (GDF-9) contributes to early ovarian development and oocyte survival. Higher concentrations of GDF-9 in follicular fluid (FF) are associated with oocyte nuclear maturation and optimal embryo development. In in vitro fertilization (IVF), GDF-9 affects the ability of the oocyte to fertilize and subsequent embryonic development. Bone morphogenetic protein 15 (BMP-15) is involved in the regulation of ovarian function and affects oocyte development. During IVF, BMP-15 contributes to the formation of competent blastocysts. BMP-15 may play a role in embryo implantation by affecting endometrial receptivity. Bone morphogenetic protein 4 (BMP-4) is involved in the regulation of follicle growth and development and affects granulosa cell (GC) differentiation. In relation to IVF, BMP-4 is important for embryonic development, influences cell fate and differentiation, and plays a role in facilitating embryo-endometrial interactions during the implantation process. Extracellular matrix metalloproteinase inducer (EMMPRIN) is associated with ovulation and follicle rupture, promotes the release of mature eggs, and affects the modification of the extracellular matrix of the follicular environment. In IVF, EMMPRIN is involved in embryo implantation by modulating the adhesive properties of endometrial cells and promotes trophoblastic invasion, which is essential for pregnancy to occur. The purpose of the current article is to review the studies and recent findings of GDF-9, BMP-15, BMP-4 and EMMPRIN as fundamental factors in normal follicular development and in vitro fertilization.

A Dose-Response Study on Functional and Transcriptomic Effects of FSH on Ex Vivo Mouse Folliculogenesis

Follicle-stimulating hormone (FSH) binds to its membrane receptor (FSHR) in granulosa cells to activate various signal transduction pathways and drive the gonadotropin-dependent phase of folliculogenesis. Both FSH insufficiency (due to genetic or nongenetic factors) and FSH excess (as encountered with ovarian stimulation in assisted reproductive technology [ART]) can cause poor female reproductive outcomes, but the underlying molecular mechanisms remain elusive. Herein, we conducted single-follicle and single-oocyte RNA sequencing analysis along with other approaches in an ex vivo mouse folliculogenesis and oogenesis system to investigate the effects of different concentrations of FSH on key follicular events. Our study revealed that a minimum FSH threshold is required for follicle maturation into the high estradiol-secreting preovulatory stage, and such threshold is moderately variable among individual follicles between 5 and 10 mIU/mL. FSH at 5, 10, 20, and 30 mIU/mL induced distinct expression patterns of follicle maturation-related genes, follicular transcriptomics, and follicular cAMP levels. RNA sequencing analysis identified FSH-stimulated activation of G proteins and downstream canonical and novel signaling pathways that may critically regulate follicle maturation, including the cAMP/PKA/CREB, PI3K/AKT/FOXO1, and glycolysis pathways. High FSH at 20 and 30 mIU/mL resulted in noncanonical FSH responses, including premature luteinization, high production of androgen and proinflammatory factors, and reduced expression of energy metabolism-related genes in oocytes. Together, this study improves our understanding of gonadotropin-dependent folliculogenesis and provides crucial insights into how high doses of FSH used in ART may impact follicular health, oocyte quality, pregnancy outcome, and systemic health.

Advancing Age May Decrease Mitochondrial Activity in Cumulus Cells

Background: The goal of this study was to compare mitochondrial activity in cumulus cells (CCs) between young and advancing-aged women, the factors that affect mitochondrial activity, and their association with blastocyst quality. Materials and methods: This prospective study included 80 infertile women who underwent ICSI between May and October 2023. Participants were divided into two groups: older and younger than 38. The oocyte mitochondrial activity from CCs was evaluated using MitoTracker, and the mean fluorescence intensity (MFI) was also evaluated. Results: The univariate and multivariate analyses revealed a significant difference in the MFI between the woman ≥ 38 age group and the lower age group (162.68 ± 79.87 vs. 228.39 ± 121.38; p-value = 0.005; 95%CI 19.97, 111.45). The factors that affected the MFI were women ≥ 38 years of age (p-value = 0.005; 95%CI -111.45, -19.91), total gonadotropin dosages (p-value = 0.006; 95%CI -0.08, 0.01), and gonadotropin-releasing hormone agonist (GnRHa) triggering (p-value = 0.006; 95%CI 36.46, 210.06). However, only women aged ≥38 years remained statistically significant after a multivariable regression analysis (p-value = 0.014; 95%CI -121.00, -14.30). In addition, only male age (mean age ± SD = 38.26 ± 5.13) was associated with high blastocyst quality in univariate and mixed multivariate analyses (OR 0.91; 95%CI 0.56, 3.04). The chemical pregnancy rate was not significantly different between the two age groups (34.5% vs. 56.7%; p-value = 0.162; 95%CI 0.2, 1.30). Conclusion: Advancing age decreased mitochondrial activity in CCs but did not affect blastocyst quality. By contrast, male age may be a predictor of high-grade blastocyst quality.

Altered Energy Metabolism, Mitochondrial Dysfunction, and Redox Imbalance Influencing Reproductive Performance in Granulosa Cells and Oocyte During Aging

Female fertility decreases during aging. The development of effective therapeutic strategies to address the age-related decline in oocyte quality and quantity and its accurate diagnosis remain major challenges. In this review, we summarize our current understanding of the study of aging and infertility, focusing primarily on the molecular basis of energy metabolism, mitochondrial function, and redox homeostasis in granulosa cells and oocytes, and discuss perspectives on future research directions. Mitochondria serve as a central hub sensing a multitude of physiological processes, including energy production, cellular redox homeostasis, aging, and senescence. Young granulosa cells favor glycolysis and actively produce pyruvate, NADPH, and other metabolites. Oocytes rely on oxidative phosphorylation fueled by nutrients, metabolites, and antioxidants provided by the adjacent granulosa cells. A reduced cellular energy metabolism phenotype, including both aerobic glycolysis and mitochondrial respiration, is characteristic of older female granulosa cells compared with younger female granulosa cells. Aged oocytes become more susceptible to oxidative damage to cells and mitochondria because of further depletion of antioxidant-dependent ROS scavenging systems. Molecular perturbations of gene expression caused by a subtle change in the follicular fluid microenvironment adversely affect energy metabolism and mitochondrial dynamics in granulosa cells and oocytes, further causing redox imbalance and accelerating aging and senescence. Furthermore, recent advances in technology are beginning to identify biofluid molecular markers that may influence follicular development and oocyte quality. Accumulating evidence suggests that redox imbalance caused by abnormal energy metabolism and/or mitochondrial dysfunction is closely linked to the pathophysiology of age-related subfertility.

miRNA profiling of granulosa cell-derived exosomes reveals their role in promoting follicle development

To explore whether granulosa cell (GC)-derived exosomes (GC-Exos) and follicular fluid-derived exosomes (FF-Exos) have functional similarities in follicle development and to establish relevant experiments to validate whether GC-Exos could serve as a potential substitute for follicular fluid-derived exosomes to improve folliculogenesis. GC-Exos were characterized. MicroRNA (miRNA) profiles of exosomes from human GCs and follicular fluid were analyzed in depth. The signature was associated with folliculogenesis, such as phosphatidylinositol 3 kinases-protein kinase B signal pathway, mammalian target of rapamycin signal pathway, mitogen-activated protein kinase signal pathway, Wnt signal pathway, and cyclic adenosine monophosphate signal pathway. A total of five prominent miRNAs were found to regulate the above five signaling pathways. These miRNAs include miRNA-486-5p, miRNA-10b-5p, miRNA-100-5p, miRNA-99a-5p, and miRNA-21-5p. The exosomes from GCs and follicular fluid were investigated to explore the effect on folliculogenesis by injecting exosomes into older mice. The proportion of follicles at each stage is counted to help us understand folliculogenesis. Exosomes derived from GCs were isolated successfully. miRNA profiles demonstrated a remarkable overlap between the miRNA profiles of FF-Exos and GC-Exos. The shared miRNA signature exhibited a positive influence on follicle development and activation. Furthermore, exosomes derived from GCs and follicular fluid promoted folliculogenesis in older female mice. Exosomes derived from GCs had similar miRNA profiles and follicle-promoting functions as follicular fluid exosomes. Consequently, GC-Exos are promising for replacing FF-Exos and developing new commercial reagents to improve female fertility.

Therapeutic Potential of Mesenchymal Stem Cells in PCOS

Polycystic ovary syndrome (PCOS) is a major reproductive endocrine disorder affecting different facets of a woman's life, comprising reproduction, metabolism, and mental health. Recently, several research groups have brought attention to the therapeutic capacity of mesenchymal stem cells (MSCs) for the treatment of female reproductive disorders. It is highlighted that the treatment with bone marrow mesenchymal stem cells (BMMSCs) considerably diminishes the levels of some inflammatory markers as well as essential genes for ovarian production of androgens, which are considerably higher in theca cells of PCOS women than in those of healthy cases. In addition, studies show that BMMSCs improve in vitro maturation (IVM) of germinal vesicles (GVs) and the number of antral follicles while lessening the number of primary and preantral follicles in mice with PCOS compared to healthy controls. Regarding adipose- derived mesenchymal stem cells (AdMSCs), these cells restore the ovarian structure, enhance the number of oocytes and corpora luteum, and diminish the number of aberrant cystic follicles in PCOS rats. Some research also indicates that umbilical cord mesenchymal stem cells (UC-MSCs) alleviate the inflammation of granulosa cells in women with PCOS. Therefore, due to the limited research on MSC therapy in PCOS, in this review, we summarize the current knowledge on the therapeutic potential of three types of MSCs: BMMSCs, AdMSCs, UC-MSCs and their secretome in the treatment of PCOS.

Chronic low-grade inflammation and ovarian dysfunction in women with polycystic ovarian syndrome, endometriosis, and aging

The ovarian microenvironment is critical for follicular development and oocyte maturation. Maternal conditions, including polycystic ovary syndrome (PCOS), endometriosis, and aging, may compromise the ovarian microenvironment, follicular development, and oocyte quality. Chronic low-grade inflammation can induce oxidative stress and tissue fibrosis in the ovary. In PCOS, endometriosis, and aging, pro-inflammatory cytokine levels are often elevated in follicular fluids. In women with obesity and PCOS, hyperandrogenemia and insulin resistance induce ovarian chronic low-grade inflammation, thereby disrupting follicular development by increasing oxidative stress. In endometriosis, ovarian endometrioma-derived iron overload can induce chronic inflammation and oxidative stress, leading to ovarian ferroptosis and fibrosis. In inflammatory aging (inflammaging), senescent cells may secrete senescence-associated secretory phenotype factors, causing chronic inflammation and oxidative stress in the ovary. Therefore, controlling chronic low-grade inflammation and fibrosis in the ovary would present a novel therapeutic strategy for improving the follicular microenvironment and minimizing ovarian dysfunction.

New insights into the role of LH in early ovarian follicular growth: a possible tool to optimize follicular recruitment

Evidence shows that LH participates in enhancing transition from the early stage to the antral stage of folliculogenesis. It has been demonstrated that functional LH receptors are expressed, albeit at a very low level and even in smaller follicles, during the phase that was traditionally considered to be gonadotrophin independent, suggesting a role for LH in accelerating the rate of progression of non-growing and primary follicles to the preantral/antral stage. Hypogonadotropic hypogonadism, together with other clinical conditions of pituitary suppression, has been associated with reduced functional ovarian reserve. The reduction in LH serum concentration is associated with a low concentration of anti-Müllerian hormone. This is the case in hypothalamic amenorrhoea, pregnancy, long-term GnRH-analogue therapy and hormonal contraception. The effect seems to be reversible, such that after pregnancy and after discontinuation of drugs, the functional ovarian reserve returns to the baseline level. Evidence suggests that women with similar primordial follicle reserves could present with different numbers of antral follicles, and that gonadotrophins may play a fundamental role in permitting a normal rate of progression of follicles through non-cyclic folliculogenesis. The precise role of gonadotrophins in early folliculogenesis, as well as their use to modify the functional ovarian reserve, must be investigated.

Testosterone supplementation improves estrogen synthesis of buffalo (Bubalus bubalis) granulosa cells

Granulosa cells (GCs) synthesize estrogens needed for follicular growth. However, the effects of androgen on estrogen production in buffalo GCs remain unclear. In this study, the impacts of testosterone on estrogen synthesis in buffalo GCs were examined. The results showed that testosterone that was added to cell medium at a concentration of 10-7  mol/L and applied to GCs for 48 or 72 h enhanced the estrogen synthesis of buffalo GCs. This study provides a theoretical basis for further exploration of ovarian endocrine mechanism for steroidogenesis.

Optimisation of hormonal treatment to improve follicular development in one-day-old mice ovaries cultured under in vitro condition

CONTEXT

Base medium containing knock-out serum replacement (KSR) has been found to support formation and maintenance of follicles in one-day-old mice ovaries, but has not been shown to properly support activation and growth of primordial follicles.

AIMS

The present study was conducted to tailor the hormonal content of base medium containing KSR to enhance development of primordial follicles in neonatal ovaries.

METHODS

One-day-old mice ovaries were initially cultured with base medium for four days, and then, different hormonal treatments were added to the culture media and the culture was proceeded for four additional days until day eight. Ovaries were collected for histological and molecular assessments on days four and eight.

KEY RESULTS

In experiment I, the main and interactive effects of FSH and testosterone were investigated and FSH promoted activation of primordial follicles and development of primary and preantral follicles, and upregulated genes of phosphoinositide 3-kinase (Pi3k ), KIT ligand (Kitl ), growth differentiation factor 9 (Gdf9 ) and follicle stimulating hormone receptor (Fshr ) (P Bmp15 ), Connexin-43 (Cx43 ) and luteinising hormone and choriogonadotropin receptor (Lhcgr ) (P P Lhcgr (P P >0.05).

CONCLUSIONS

Supplementation of culture medium containing KSR with gonadotropins, particularly hMG, could improve follicular growth and expression of factors regulating follicular development.

IMPLICATIONS

This study was a step forward in formulating an optimal medium for development of follicles in cultured one-day-old mice ovaries.

Hypoxia enhances steroidogenic competence of buffalo (Bubalus bubalis) granulosa cells

Granulosa cells (GCs) synthesize estrogens needed for follicular growth. However, the effects of hypoxia on steroidogenesis in buffalo GCs remain unclear. In this study, the impacts of hypoxic conditions (5% oxygen) on estrogen synthesis in buffalo GCs were examined. The results showed that hypoxia improved both the expression levels of estrogen synthesis-related genes (CYP11A1, CYP19A1, and 3β-HSD) and the secretion levels of estradiol in buffalo GCs. Hypoxic conditions promoted the sensitivity of buffalo GCs to FSH. Furthermore, inhibition of cAMP/PKA signaling pathway (H89, a cAMP/PKA signaling pathway inhibitor) reduced both the expression levels of estrogen synthesis-related genes (CYP11A1, CYP19A1, and 3β-HSD) and the secretion levels of estradiol in hypoxia-cultured buffalo GCs. Besides, inhibition of cAMP/PKA signaling pathway lowered the responsiveness of buffalo GCs to FSH under hypoxic conditions. The present study indicated that hypoxia enhanced the steroidogenic competence of buffalo GCs principal by affecting cAMP/PKA signaling pathway and subsequent sensitivity of GCs to FSH.

The Dose-Related Efficacy of Human Placenta-Derived Mesenchymal Stem Cell Transplantation on Antioxidant Effects in a Rat Model with Ovariectomy

Oxidative stress initiates various degenerative diseases, and it is caused by excessive reactive oxygen species (ROS) production. Oxidative stress is a key factor that causes infertility by inducing ovarian dysfunction, characterized by irregular hormone levels, lower quality of mature follicles, and loss of follicles. Hence, stem cell therapy has been actively studied as an approach to overcome the side effects of hormone replacement therapy (HRT) on ovarian dysfunction. However, there is a lack of evidence about the appropriate number of cells required for stem cell therapy. Therefore, based on the antioxidant effects investigated in this study, we focused on determining the appropriate dose of stem cells for transplantation in an animal model with ovarian dysfunction. One week after half-ovariectomy, placenta-derived mesenchymal stem cells (PD-MSCs, 1 × 105 cells, 5 × 105 cells, or 2.5 × 106 cells) were injected intravenously into the Tx groups through the tail vein. As a result, the mRNA expression of hAlu gradually increased as the transplanted cell concentration increased. Compared with no transplantation (NTx), the transplantation of PD-MSCs improved folliculogenesis, including the levels of secreted hormones and numbers of follicles, by exerting antioxidant effects. Also, the levels of oxidized glutathione in the serum of animal models after transplantation were significantly increased (* p < 0.05). These results indicated that PD-MSC transplantation improved ovarian function in half-ovariectomized rats by exerting antioxidant effects. According to our data, increasing the number of transplanted cells did not proportionally increase the effectiveness of the treatment. We suggest that low-dose PD-MSC transplantation has the same therapeutic effect as described in previous studies. These findings provide new insights for further understanding reproductive systems and provide evidence for related clinical trials.

Co-culture of human cryopreserved fragmented ovarian tissue with theca progenitor cells derived from theca stem cells

PURPOSE

Despite the significant advances in the in vitro development of human primordial follicles, it is still a challenging approach with great potential for improvements. Therefore, the present study aimed to investigate the effect of a feeder layer of human theca progenitor cells (hTPCs) on the development of primordial follicles embedded in human ovarian tissue.

METHODS

Fragments of frozen-thawed ovarian tissue were activated using the vanadate-derivative dipotassium bisperoxo (5-hydroxy-pyridine-2-carboxylic) oxovanadate (V) and kit ligand for 24 h. Then, the specimens were divided into the co-culture and mono-culture groups and were cultured with and without a hTPC feeder layer for 6 days, respectively. Afterward, the follicles were counted and classified, and the hormone levels and expression levels of apoptosis- and folliculogenesis-related genes were assessed.

RESULTS

Both culture groups showed significant follicle growth (P < 0.05). However, the co-culture group had a significantly higher number of growing follicles compared to the other group (P < 0.05). Moreover, the expression levels of ZP1, ZP2, ZP3, BMP-7, AMH, and GDF9 were significantly higher in the co-culture group compared to the other group (P < 0.05), while the expression levels of P53 and CASP3 were significantly lower (P < 0.05). Also, the concentrations of estradiol, progesterone, testosterone, and androstenedione were significantly higher in the co-culture group compared to the other group (P < 0.05).

CONCLUSION

The present study results provided novel evidence on the direct role of hTPCs in the growth and development of human primordial follicles. However, there is a need for future studies to illustrate the underlying mechanisms. Schematic summary of the results. According to our results, the expression of ZP1, ZP2, ZP3, and GDF9 in the oocytes, AMH in the granulosa cells, and BMP4 in the theca cells of the co-culture group were significantly higher than those of the mono-culture and non-culture groups, while the expression of apoptotic genes (BAX, CASP3, and P53) was significantly lower. Moreover, the co-culture group showed significantly increased levels of estradiol, progesterone, testosterone, and androstenedione in its culture media compared to the mono-culture groups.

The mechanisms that control the preantral to early antral follicle transition and the strategies to have efficient culture systems to promote their growth in vitro

Preantral to early antral follicles transition is a complex process regulated by endocrine and paracrine factors, as well as by a precise interaction among oocyte, granulosa cells and theca cells. Understanding the mechanisms that regulate this step of folliculogenesis is important to improve in vitro culture systems, and opens new perspectives to use oocytes from preantral follicles for assisted reproductive technologies. Therefore, this review aims to discuss the endocrine and paracrine mechanisms that control granulosa cell proliferation and differentiation, formation of the antral cavity, estradiol production, atresia, and follicular fluid production during the transition from preantral to early antral follicles. The strategies that promote in vitro growth of preantral follicles are also discussed.

miR-140-3p promotes follicle granulosa cell proliferation and steroid hormone synthesis via targeting AMH in chickens

Granulosa cells (GCs) are the ovary's most critical cells since they undergo cell differentiation and hormone synthesis changes closely associated with follicle development. While micro RNA 140-3p (miRNA-140-3p) has an apparent cell signaling role, particularly in cell proliferation, its biological role in chicken ovarian follicle growth and development remains elusive. This study explored miR-140-3p's effects on chicken GC proliferation and steroid hormone synthesis. MiR-140-3p dramatically increased GC proliferation, prevented apoptosis, increased progesterone synthesis, and enhanced gene expression related to steroid hormone synthesis. In addition, the anti-Müllerian hormone (AMH) gene was identified as a direct miR-140-3p target. MiR-140-3p abundance correlated negatively with AMH mRNA and protein levels in GCs. Our findings show that miR-140-3p influences chicken GC proliferation and steroid hormone synthesis by suppressing AMH expression.

Upregulated Ribosomal Pathway Impairs Follicle Development in a Polycystic Ovary Syndrome Mouse Model: Differential Gene Expression Analysis of Oocytes

Polycystic ovary syndrome (PCOS), a common endocrine disorder, is associated with impaired oocyte development, leading to infertility. However, the pathogenesis of PCOS has not been completely elucidated. This study aimed to determine the differentially expressed genes (DEGs) and epigenetic changes in the oocytes from a PCOS mouse model to identify the etiological factors. RNA-sequencing analysis revealed that 90 DEGs were upregulated and 27 DEGs were downregulated in mice with PCOS compared with control mice. DNA methylation analysis revealed 30 hypomethylated and 10 hypermethylated regions in the PCOS group. However, the DNA methylation status did not correlate with differential gene expression. The pathway enrichment analysis revealed that five DEGs (Rps21, Rpl36, Rpl36a, Rpl37a, and Rpl22l1) were enriched in ribosome-related pathways in the oocytes of mice with PCOS, and the immunohistochemical analysis revealed significantly upregulated expression levels of Rps21 and Rpl36. These results suggest that differential gene expression in the oocytes of mice in PCOS is related to impaired folliculogenesis. These findings improve our understanding of PCOS pathogenesis.

miR-202-5p Inhibits Lipid Metabolism and Steroidogenesis of Goose Hierarchical Granulosa Cells by Targeting ACSL3

miRNAs are critical for steroidogenesis in granulosa cells (GCs) during ovarian follicular development. We have previously shown that miR-202-5p displays a stage-dependent expression pattern in GCs from goose follicles of different sizes, suggesting that this miRNA could be involved in the regulation of the functions of goose GCs; therefore, in this study, the effects of miR-202-5p on lipid metabolism and steroidogenesis in goose hierarchical follicular GCs (hGCs), as well as its mechanisms of action, were evaluated. Oil Red O staining and analyses of intracellular cholesterol and triglyceride contents showed that the overexpression of miR-202-5p significantly inhibited lipid deposition in hGCs; additionally, miR-202-5p significantly inhibited progesterone secretion in hGCs. A bioinformatics analysis and luciferase reporter assay indicated that Acyl-CoA synthetase long-chain family member 3 (ACSL3), which activates long-chain fatty acids for the synthesis of cellular lipids, is a potential target of miR-202-5p. ACSL3 silencing inhibited lipid deposition and estrogen secretion in hGCs. These data suggest that miR-202-5p exerts inhibitory effects on lipid deposition and steroidogenesis in goose hGCs by targeting the ACSL3 gene.

Roles of endoplasmic reticulum stress in the pathophysiology of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder among reproductive-age women, affecting up to 15% of women in this group, and the most common cause of anovulatory infertility. Although its etiology remains unclear, recent research has revealed the critical role of endoplasmic reticulum (ER) stress in the pathophysiology of PCOS. ER stress is defined as a condition in which unfolded or misfolded proteins accumulate in the ER because of an imbalance in the demand for protein folding and the protein-folding capacity of the ER. ER stress results in the activation of several signal transduction cascades, collectively termed the unfolded protein response (UPR), which regulates various cellular activities. In principle, the UPR restores homeostasis and keeps the cell alive. However, if the ER stress cannot be resolved, it induces programmed cell death. ER stress has recently been recognized to play diverse roles in both physiological and pathological conditions of the ovary. In this review, we summarize current knowledge of the roles of ER stress in the pathogenesis of PCOS. ER stress pathways are activated in the ovaries of both a mouse model of PCOS and in humans, and local hyperandrogenism in the follicular microenvironment associated with PCOS is responsible for activating these. The activation of ER stress contributes to the pathophysiology of PCOS through multiple effects in granulosa cells. Finally, we discuss the potential for ER stress to serve as a novel therapeutic target for PCOS.

Identification of hub genes associated with follicle development in multiple births sheep by WGCNA

Sheep exhibit a distinct estrous cycle that includes four different phases: proestrus, estrus, late estrus, and luteal phase. As the estrous cycle repeats, follicular development regularly alternates. We thus investigated ovarian transcriptome data from each of the four phases using weighted gene co-expression network analysis (WGCNA) to identify modules, pathways, and genes essential to follicle growth and development. We clustered mRNA and long non-coding RNA (lncRNA) into different modules by WGCNA, and calculated correlation coefficients between genes and Stages of the estrous cycle. Co-expression of the black module (cor = 0.81, P<0.001) and the yellow module (cor = 0.61, P<0.04) was found to be critical for follicle growth and development. A total of 2066 genes comprising the black and yellow modules was used for functional enrichment. The results reveal that these genes are mainly enriched in Cell cycle, PI3K-Akt signaling pathway, Oocyte meiosis, Apoptosis, and other important signaling pathways. We also identified seven hub genes (BUB1B, MAD2L1, ASPM, HSD3B1, WDHD1, CENPA, and MXI1) that may play a role in follicle development. Our study may provide several important new markers allowing in depth exploration of the genetic basis for multiparous reproduction in sheep.

The Role of Circular RNAs in the Physiology and Pathology of the Mammalian Ovary

Circular RNAs (circRNAs) are an abundant class of endogenous non-coding RNAs (ncRNAs) generated from exonic, intronic, or untranslated regions of protein-coding genes or intergenic regions. The diverse, stable, and specific expression patterns of circRNAs and their possible functions through cis/trans regulation and protein-coding mechanisms make circRNA a research hotspot in various biological and pathological processes. It also shows practical value as biomarkers, diagnostic indicators, and therapeutic targets. This review summarized the characteristics, classification, biogenesis and elimination, detection and confirmation, and functions of circRNAs. We focused on research advances circRNAs in the mammalian ovary under conditions including ovarian cancer, polycystic ovarian syndrome (PCOS), and maternal aging, as well as during reproductive status, including ovarian follicle development and atresia. The roles of circRNAs in high reproductive traits in domestic animals were also summarized. Finally, we outlined some obstructive factors and prospects to work with circRNA, aiming to provide insights into the functional research interests of circRNAs in the reproduction and gynecology areas.

miR-10a-5p inhibits chicken granulosa cells proliferation and Progesterone(P4) synthesis by targeting MAPRE1 to suppress CDK2

The proliferation and steroid hormone synthesis of granulosa cells (GCs) are essential for ovarian follicle growth and ovulation, which are necessary to support the normal function of the follicle. Numerous studies suggest that miRNAs play key roles in this process. In this study, we report a novel role for miR-10a-5p that inhibits ovarian GCs proliferation and progesterone (P4) synthesis in chicken. Specifically, we found that miR-10a-5p significantly decreased the P4 secretion by quantitative real-time PCR (qRT-PCR), enzyme-linked immunosorbent assay (ELISA), and western blot. Moreover, we observed that miR-10a-5p can inhibit the proliferation of chicken GCs through the investigation of cell proliferation gene expression, cell counting kit 8 (CCK-8), cell cycle progression, and 5-ethynyl-2'-deoxyuridine (EdU) assay. Then we screened a target gene MAPRE1 of miR-10a-5p, which can promote P4 synthesis and proliferation of GCs. To explore how miR-10a-5p affects cell cycle by MAPRE1, we investigated the interaction between MAPRE1 and cyclin-dependent kinase 2 (CDK2) by Co-Immunoprecipitation (Co-IP), and then we found that MAPRE1 can form a complex with CDK2. In addition, miR-10a-5p was found to inhibit CDK2 expression by repressing the expression of MAPRE1. Overall, our results indicate that miR-10a-5p regulates the proliferation and P4 synthesis of chicken GCs by targeting MAPRE1 to suppress CDK2.

Effects of IGF-1 on the Three-Dimensional Culture of Ovarian Preantral Follicles and Superovulation Rates in Mice

Insulin-like growth factor-1 (IGF-1) plays a crucial role during folliculogenesis, which has been demonstrated by previous research. However, the optimal IGF-1 dosage in the three-dimensional (3D) culture system is unknown. Mouse secondary follicles (140−150 µm) were cultured for 6 days within an alginate bead in a medium supplemented with 0 (G0), 5 ng/mL (G5), 10 ng/mL (G10), or 50 ng/mL IGF-1 (G50). Secretions of 17β-estradiol and progesterone were significantly increased in G10 and G50 (p < 0.05). However, G50 significantly inhibited follicular growth (p < 0.05), while G10 showed a higher oocyte maturation rate. Thus, the 10 ng/mL IGF-1 was used in subsequent experiments. IGF-1 enhanced the function of granulosa cells (GCs) by upregulating expressions of Star, Cyp19a1, Hsd3b1, Fshr, and Lhcgr. Oocyte secretory function was promoted by upregulating expressions of Bmp-15, Gdf-9, and Fgf-8. Addition of IGF-1 showed anti-apoptotic effect. However, G10 did not improve fertilization rate of MII oocytes compared to G0. In an intraperitoneal injection experiment in mice, IGF-1 significantly increased the number of ovulated oocytes (p < 0.05). In conclusion, 10 ng/mL IGF-1 can promote the production of mature oocytes in the 3D culture medium and injection of IGF-1 before superovulation increases the number of ovulated oocytes.

miR-122-5p regulates proliferation and apoptosis of chicken granulosa cells of hierarchal follicles by targeting MAPK3

Chicken follicles plays a crucial role in the reproductive performance, especially in laying period. Recently, miR-122-5p has been found to be differentially expressed in the ovaries of rats with polycystic ovary syndrome and normal rats, indicating the potential role of miR-122-5p in the development of granulosa cells (GCs). In present study, we found that miR-122-5p was highly expressed in chicken atrophic ovaries. Herein, we investigated its function on GC proliferation and apoptosis of chicken in vitro. We found that overexpression of miR-122-5p significantly inhibited proliferation and promoted apoptosis of GCs, whereas the opposite effects were detected in miR-122-5p knockdown GCs. Meanwhile, mitogen-activated protein kinase 3 (MAPK3) was confirmed as a new target gene of miR-122-5p by bioinformatics software prediction and the dual-luciferase reporter assay verification. Furthermore, after knockdown of MAPK3, the function of MAPK3 for GC proliferation and apoptosis was opposite to that of miR-122-5p. Collectively, our results indicated that miR-122-5p impeded chicken GC proliferation and promoted apoptosis through the post-transcriptional downregulation of MAPK3.

CircRNA expression in chicken granulosa cells illuminated with red light

Red light (RL) can improve egg production in Jinghai Yellow hens. Circular RNAs (circRNAs) are novel, non-coding RNAs, but the molecular mechanism underlying circRNA function during follicular development in hens under monochromatic light has not been established. Herein, we compared expression profiles of granulosa cells (GCs) from small yellow follicles (SYFs) from hens under RL and white light (WL). A total of 2,468 circRNAs were identified, of which 22 were differentially expressed (DE) in the RL and WL groups. DE circRNA host genes were enriched in ovarian steroidogenesis, and MAPK and PI3K-Akt signaling pathways. Furthermore, DE circRNA_0320 and circRNA_0185 interacted with miR-143-3p, which targets the follicle-stimulating hormone receptor and is essential for GC differentiation and follicle development. These findings will facilitate further analysis of the molecular mechanism leading to GC development in hens raised under monochromatic light, which could lead to increased egg production.

Regulation of antral follicular growth by an interplay between gonadotropins and their receptors

Knowledge of the growth and maturation of human antral follicles is based mainly on concepts and deductions from clinical observations and animal models. To date, new experimental approaches and in vitro data contributed to a deep comprehension of gonadotropin receptors' functioning and may provide new insights into the mechanisms regulating still unclear physiological events. Among these, the production of androgen in the absence of proper LH levels, the programming of follicular atresia and dominance are some of the most intriguing. Starting from evolutionary issues at the basis of the gonadotropin receptor signal specificity, we draw a new hypothesis explaining the molecular mechanisms of the antral follicular growth, based on the modulation of endocrine signals by receptor-receptor interactions. The "heteromer hypothesis" explains how opposite death and life signals are delivered by gonadotropin receptors and other membrane partners, mediating steroidogenesis, apoptotic events, and the maturation of the dominant follicle.

Morphological Characteristics and Transcriptome Landscapes of Chicken Follicles during Selective Development

Ovarian follicle selection largely depends on the transition of granulosa cells from an undifferentiated to a fully differentiated state, which is accompanied by morphological and functional changes in follicles. The processes and transcriptional regulation of follicles during follicle selection are unclear; we thus used follicles from the prehierarchal to the hierarchal stage to investigate histology, reproductive endocrinology, and transcription. The morphology of follicles changed markedly during follicle selection. The numbers of large white, small yellow, and large yellow follicles (LWF, SYF, and LYF, respectively) were 11.83 ± 2.79, 6.83 ± 2.23, and 1.00, respectively, per ovary. LYF showed thicker granulosa cell layers than those of other prehierarchal follicles. Progesterone concentrations were significantly higher in LYF than that in LWF and SYF. In total, 16,823 genes were positively expressed in LWF, SYF, and LYF. Among follicle types, 1,290 differentially expressed genes were enriched regarding cell differentiation, blood vessel morphogenesis, and response to steroid hormones. Candidate genes associated with follicle selection participated in the Wnt signaling pathway, steroid hormone biosynthesis, and the TGF-β signaling pathway. We produced insights into crucial morphological characteristics of transcriptional regulation in follicle development. Our results provide an important basis for revealing the mechanism of follicle selection and potential impact on the poultry industry.

Oocyte quality and aging

It is well known that female reproduction ability decreases during the forth decade of life due to age-related changes in oocyte quality and quantity; although the number of women trying to conceive has today increased remarkably between the ages of 36 to 44. The causes of reproductive aging and physiological aspects of this phenomenon are still elusive. With increase in the women's age, during Assisted Reproductive Technologies (ART) we have perceived a significant decline in the number and quality of retrieved oocytes, as well as in ovarian follicle reserves. This is because of increased aneuploidy due to factors such as spindle apparatus disruption; oxidative stress and mitochondrial damage. The aim of this review paper is to study data on the potential role of the aging process impacting oocyte quality and female reproductive ability. We present the current evidence that show the decreased oocyte quality with age, related to reductions in female reproductive outcome. The aging process is complicated and it is caused by many factors that control cellular and organism life span. Although the factors responsible for reduced oocyte quality remain unknown, the present review focuses on the potential role of ovarian follicle environment, oocyte structure and its organelles. To find a way to optimize oocyte quality and ameliorate clinical outcomes for women with aging-related causes of infertility.

Whole Genome Transcriptomic Analysis of Ovary Granulosa Cells Revealed an Anti-Apoptosis Regulatory Gene DLGAP5 in Polycystic Ovary Syndrome

The mechanisms underlining pathogenesis of polycystic ovary syndrome (PCOS) remain largely unknown. Dysfunction of ovarian granulosa cells plays an important role. The present study performed the lncRNA and mRNA profiling by whole genome transcriptomic sequencing of ovary granulosa cells from women with PCOS and investigated the potential role of differentially expressed gens (DEGs) in the pathomechanism of PCOS. In total, 1,936 DEGs (30 upregulated and 1,906 downregulated mRNAs and lncRNAs) were identified in the ovary granulosa cells between control and PCOS group. Functional enrichment analysis showed that DEGs were mainly associated with cytokine-cytokine receptor interaction, neuroactive ligand-receptor interaction, and olfactory transduction. qRT-PCR validated the upregulation of DLGAP5 mRNA in ovary from PCOS group when compared to control group. Immunostaining and TUNEL assays showed that DLGAP5 protein level was increased while apoptosis was decreased in follicles of ovary in PCOS group. In vitro functional assays showed that DLGPA5 knockdown repressed viability and proliferation, but enhanced apoptosis and disrupted cell cycle in granulosa cells; while DLGAP5 overexpression had the opposite effects in granulosa cells. In conclusion, the study showed differentially expressed lncRNA and mRNA profile in the granulosa cells in ovaries of PCOS. Functional results demonstrated that DLGAP5 is a dysregulated candidate gene in the pathogenesis of PCOS, especially granulosa cell apoptosis and proliferation.

Role of Astaxanthin as a Stimulator of Ovarian Development in Nile Tilapia (Oreochromis niloticus) and Its Potential Regulatory Mechanism: Ameliorating Oxidative Stress and Apoptosis

A 60-day feeding experiment was performed to evaluate the effect of dietary astaxanthin on gonad development, the antioxidant system, and its inherent mechanism in female Nile tilapia (Oreochromis niloticus). Fish were fed with diets containing astaxanthin at five levels [0 mg/kg (control), 50 mg/kg, 100 mg/kg, 150 mg/kg, and 200 mg/kg]. At the end of experiment, the group fed with 150 mg/kg astaxanthin showed significantly increased specific growth rate, feed utilization, viscerosomatic index, and hepatosomatic index compared with the control group (P < 0.05). Gonad development was stimulated in the groups fed with 100 mg/kg and 150 mg/kg astaxanthin, and their gonadosomatic index and egg diameter were significantly higher than those of the control group and the group fed with 200 mg/kg astaxanthin. The ovaries of females in the groups fed with 100 mg/kg and 150 mg/kg astaxanthin were fully developed, the eggs were gray-yellow and uniform in size, and a large number of oocytes developed to stages IV and V. The serum levels of 17 β-estradiol, follicle-stimulating hormone, and luteinizing hormone were significantly higher in the groups fed with 100 mg/kg and 150 mg/kg astaxanthin than in the group fed with 200 mg/kg astaxanthin. Compared with the control and the other groups, the group fed with 150 mg/kg astaxanthin showed significantly higher transcript levels of genes encoding hormone receptors and higher catalase activity in ovarian tissues, lower malondialdehyde content, decreased apoptosis (reduced granulosa cell apoptosis and lower transcript levels of bax and caspase-3), and reduced follicular atresia. Gene ontology analyses revealed that cell division and the cell cycle were enriched with differentially expressed genes in the group fed with 150 mg/kg astaxanthin, compared with the control group. We concluded that dietary astaxanthin at a concentration of 150 mg/kg activates follicle development by inhibiting expression of mapk1 (involved in MAPK signaling) and increasing the expression genes involved in oocyte meiosis (chp2, ppp3ca, map2k1, and smc1a1) and progesterone-mediated oocyte maturation (igf1, plk1, and cdk1). In conclusion, female Nile tilapia fed with 150 mg/kg astaxanthin showed increased growth, reduced oxidative stress in ovarian tissue, lower levels of cell apoptosis, and improved oocyte development.

FSHR antagonists can trigger a PCOS-like state

Over the recent years, FSHR has become an important target for development of fertility regulating agents, as impairment of FSH-FSHR interaction can lead to subfertility or infertility. In our previous study, we identified a 9-mer peptide (FSHβ (89-97)) that exhibited FSHR antagonist activity. The histopathological and biochemical observations indicated, in addition to FSHR antagonism, a striking resemblance to a PCOS-like state. These observations led us to hypothesize that use of FSHR antagonists can trigger a PCOS-like state. In the present study, to validate this hypothesis, we performed qRT-PCR validation using ovarian tissue samples from our previous study. Expression of three genes known to be differentially expressed in PCOS was evaluated and found to be similar to the PCOS state. To further test the hypothesis, theoretical simulations were carried out by using the human menstrual cycle model available in the literature. Model simulations for FSHR antagonism were indicative of increased testosterone levels, increased ratio of luteinizing hormone/follicle stimulating hormone, and stockpiling of secondary follicles, which are typical characteristics of PCOS. The findings of this study will be relevant while reviewing the utility of FSHR antagonists for fertility regulation and reproductive medicine.Abbreviations: FSH: Follicle-stimulating hormone; FSHR: Follicle-stimulating hormone receptor; cAMP: Cyclic adenosine 3'5' monophosphate; PKA: Protein kinase A; PI3K: Phosphoinositide 3-kinase; PKB: protein kinase B; ERK1/2: Extracellular signal-regulated protein kinase 1/2; MAPK: Mitogen-activated protein kinases; T: testosterone; E2: estradiol; PCOS: Polycystic ovarian syndrome; LH: luteinizing hormone; Lhcgr: luteinizing hormone/choriogonadotropin receptor; CYP17A1: cytochrome P450 family 17 subfamily A member 1; Inhba: inhibin subunit beta A; qRT-PCR: Real-Time quantitative reverse transcription polymerase chain reaction; FSHβ: Follicle-stimulating hormone β subunit; Ct: Cycle threshold; Rn18s: Rattus norvegicus 18S ribosomal RNA.

Equine Chorionic Gonadotropin as an Effective FSH Replacement for In Vitro Ovine Follicle and Oocyte Development

The use of assisted reproductive technologies (ART) still requires strategies through which to maximize individual fertility chances. In vitro folliculogenesis (ivF) may represent a valid option to convey the large source of immature oocytes in ART. Several efforts have been made to set up ivF cultural protocols in medium-sized mammals, starting with the identification of the most suitable gonadotropic stimulus. In this study, Equine Chorionic Gonadotropin (eCG) is proposed as an alternative to Follicle Stimulating Hormone (FSH) based on its long superovulation use, trans-species validation, long half-life, and low costs. The use of 3D ivF on single-ovine preantral (PA) follicles allowed us to compare the hormonal effects and to validate their influence under two different cultural conditions. The use of eCG helped to stimulate the in vitro growth of ovine PA follicles by maximizing its influence under FBS-free medium. Higher performance of follicular growth, antrum formation, steroidogenic activity and gap junction marker expression were recorded. In addition, eCG, promoted a positive effect on the germinal compartment, leading to a higher incidence of meiotic competent oocytes. These findings should help to widen the use of eCG to ivF as a valid and largely available hormonal support enabling a synchronized in vitro follicle and oocyte development.

A low dose of bisphenol A stimulates estradiol production by regulating β-catenin-FOXL2-CYP19A1 pathway in human ovarian granulosa cells

Bisphenol A (BPA) is a well-known endocrine-disrupting chemical that interferes with normal steroid hormone production in various species. However, the underlying mechanism of the effect of BPA on steroid production in the human ovary is not well understood. In the present study, we found that BPA, at very low concentrations (10-11 to 10-8 M), significantly increased the expression of FOXL2, a transcriptional factor essential for proper ovarian development and function, in a human ovarian granulosa cell-derived cell line (KGN). Furthermore, BPA enhanced CYP19A1 (aromatase) expression levels and estradiol (E2) production, but these effects were not observed in FOXL2 knockout (KO) cells. In addition, we found that BPA upregulates β-catenin (CTNNB1) and stimulates nuclear translocation of CTNNB1, leading to transcriptional activation of FOXL2 mRNA. Furthermore, BPA failed to induce CYP19A1 and E2 production in CTNNB1-silenced KGN cells. Thus, we reveal a comprehensive molecular signaling cascade encompassing BPA-CTNNB1-FOXL2-CYP19A1-E2 that contributes to the endocrine-disrupting activities of BPA in human ovarian granulosa cells.

Effect of the spatial-temporal specific theca cell Cyp17 overexpression on the reproductive phenotype of the novel TC17 mouse

Background

In the ovarian follicle, the Theca Cells (TCs) have two main functions: preserving morphological integrity and, importantly, secreting steroid androgen hormones. TCs express the essential enzyme 17α-hydroxylase/17,20-desmolase (CYP17), which permits the conversion of pregnenolone and progesterone into androgens. Dysregulation of CYP17 enzyme activity due to an intrinsic ovarian defect is hypothesized to be a cause of hyperandrogenism in women. Androgen excess is observed in women with polycystic ovary syndrome (PCOS) resulting from excess endogenous androgen production, and in transgender males undergoing exogenous testosterone therapy after female sex assignment at birth. However, the molecular and morphological effects of Cyp17 overexpression and androgen excess on folliculogenesis is unknown.

Methods

In this work, seeking a comprehensive profiling of the local outcomes of the androgen excess in the ovary, we generated a transgenic mouse model (TC17) with doxycycline (Dox)-induced Cyp17 overexpression in a local and temporal manner. TC17 mice were obtained by a combination of the Tet-dependent expression system and the Cre/LoxP gene control system.

Results

Ovaries of Dox-treated TC17 mice overexpressed Cyp17 specifically in TCs, inducing high testosterone levels. Surprisingly, TC17 ovarian morphology resembled the human ovarian features of testosterone-treated transgender men (partially impaired folliculogenesis, hypertrophic or luteinized stromal cells, atretic follicles, and collapsed clusters). We additionally assessed TC17 fertility denoting a perturbation of the normal reproductive functions (e.g., low pregnancy rate and numbers of pups per litter). Finally, RNAseq analysis permitted us to identify dysregulated genes (Lhcgr, Fshr, Runx1) and pathways (Extra Cellular Matrix and Steroid Synthesis).

Conclusions

Our novel mouse model is a versatile tool to provide innovative insights into study the effects of Cyp17 overexpression and hyperandrogenism in the ovary.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03103-x.

circRNA-Mediated Inhibin-Activin Balance Regulation in Ovarian Granulosa Cell Apoptosis and Follicular Atresia

Ovarian granulosa cells (GC) play an essential role in the development and atresia of follicles. Emerging studies suggest that non-coding RNAs are involved in the regulation of GC apoptosis. Here, we aimed to analyze the function of ssc-circINHA-001, coded by the first exon of the inhibin subunit α gene (INHA), in resisting GC apoptosis and follicular atresia by enhancing the expression of the inhibin subunit β A (INHBA) through a cluster of miRNAs. A higher expression of ssc-circINHA-001 in healthy follicles compared to early atretic follicles was detected by qRT-PCR. Its circular structure was confirmed by RNase R treatment and reversed PCR. The function of ssc-circINHA-001 in GC resistance to apoptosis was detected by in vitro transfection of its si-RNA. Furthermore, the dual-luciferase reporter assay suggested that ssc-circINHA-001 adsorbed three miRNAs, termed miR-214-5p, miR-7144-3p, and miR-9830-5p, which share the common target INHBA. A low expression of ssc-circINHA-001 increased the levels of the free miRNAs, inhibited INHBA expression, and thus raised GCs apoptosis through a shift from the secretion of activin to that of inhibin. Our study demonstrated the existence of a circRNA–microRNAs–INHBA regulatory axis in follicular GC apoptosis and provides insight into the relationship between circRNA function and its coding gene in inhibin/activin balance and ovarian physiological functions.

Extracellular vesicles of bovine small follicular fluid promote ovarian cortical stromal cell proliferation and steroidogenesis

The aim of this study was to investigate the effects of extracellular vesicles (EVs) on the proliferation and steroid hormone synthesis of bovine ovarian cortical stromal cells in vitro. The release and uptake of EVs are the new mechanisms of cell-to-cell communication. Using reverse transcriptase polymerase chain reaction, enzyme-linked immunosorbent assay, TUNEL and other experiments, we found that EVs in bovine follicular fluid can promote the proliferation and synthesis of androstenedione and progesterone in ovarian cortical stromal cells. Moreover, 100 μg/ml EVs caused the most significant effect. We conclude that EVs at 100 μg/ml can significantly promote the proliferation and synthesis of androstenedione and progesterone in ovarian cortical stromal cells. This research is of great significance for further elucidating the regulatory role of follicular fluid EVs in follicular development and atresia and for research on the interaction of ovarian stromal cells, granulosa cells and oocytes.