Lhx8 regulates primordial follicle activation and postnatal folliculogenesis

Exocyst complex component 1 (Exoc1) loss in dormant oocyte disrupts c-KIT and growth differentiation factor (GDF9) subcellular localization and causes female infertility in mice

A limited number of female germ cells support reproduction in many mammals. The follicle, composed of oocytes and supporting granulosa cells, forms the basis of oogenesis. Crosstalk between oocytes and granulosa cells is essential for the formation, dormancy, re-awakening, and maturation of oocytes. The oocyte expresses c-KIT and growth differentiation factor-9 (GDF-9), which are major factors in this crosstalk. The downstream signalling pathways of c-KIT and GDF-9 have been well-documented; however, their intra-oocyte trafficking pathway remains unclear. Our study reveals that the exocyst complex, a heterotetrameric protein complex important for tethering in vesicular transport, is important for proper intra-oocyte trafficking of c-KIT and GDF9 in mice. We found that depletion of oocyte-specific EXOC1, a component of the exocyst complex, impaired oocyte re-awakening and cyst breakdown, and inhibited granulosa cell proliferation during follicle growth. The c-KIT receptor is localised on the oocyte plasma membrane. The oocyte-specific Kit conditional knockout mice were reported to exhibit impaired oocyte re-awakening and reduced oocyte cyst breakdown. GDF9 is a protein secreted extracellularly in the oocyte. Previous studies have shown that Gdf9 knockout mice impaired proliferation and granulosa cell multilayering in growing follicles. We found that both c-KIT and GDF9 abnormally stuck in the EXOC1-depleted oocyte cytoplasm. These abnormal phenotypes were also observed in oocytes depleted of exocyst complex members EXOC3 and EXOC7. These results clearly show that the exocyst complex is essential for proper intra-oocyte trafficking of c-KIT and GDF9. Inhibition of this complex causes complete loss of female fertility in mice. Our findings build a platform for research related to trafficking mechanisms of vital crosstalk factors for oogenesis.

Genomic Analysis and Functional Validation of Bidirectional Promoters in Medaka (Oryzias latipes)

Bidirectional promoters (BDPs) regulate the transcription of two adjacent, oppositely oriented genes, offering a compact structure with significant potential for multigene expression systems. Although BDPs are evolutionarily conserved, their regulatory roles and sequence characteristics vary across species, with limited studies in fish. Here, we systematically analyzed the distribution, sequence features, and expression patterns of BDPs in the medaka (Oryzias latipes) genome. A total of 1737 divergent gene pairs, representing 13% of medaka genes, were identified as potentially regulated by BDPs. These genes are enriched in essential biological processes, including organelle function, RNA processing, and ribosome biogenesis. Transcriptomic analysis revealed that co-regulation (co-expression and co-silencing) is a prominent feature of these gene pairs, with variability influenced by tissue and sex. Sequence analysis showed that medaka BDPs are compact, with most fragments under 400 bp and an average GC content of 42.06%. Validation experiments confirmed the bidirectional transcriptional activity of three histone-related BDPs in both medaka SG3 cells and embryos, demonstrating effective and robust regulatory efficiency. This study enhances our understanding of the genomic organization and transcriptional regulation in fish and provides a valuable reference for developing species-specific multigene expression systems in fish genetic engineering.

Cellular and molecular regulations of oocyte selection and activation in mammals

Oocytes, a uniquely pivotal cell population, play a central role in species continuity. In mammals, oogenesis involves distinct processes characterized by sequential rounds of selection, arrest, and activation to produce a limited number of mature eggs, fitting their high-survival yet high-cost fertility. During the embryonic phase, oocytes undergo intensive selection via cytoplasmic and organelle enrichment, accompanied by the onset and arrest of meiosis, thereby establishing primordial follicles (PFs) as a finite reproductive reserve. Subsequently, the majority of primary oocytes enter a dormant state and are gradually recruited through a process termed follicle activation, essential for maintaining orderly fertility. Following activation, oocytes undergo rapid growth, experiencing cycles of arrest and activation regulated by endocrine and paracrine signals, ultimately forming fertilizable eggs. Over the past two decades, advancements in genetically modified animal models, high-resolution imaging, and omics technologies have significantly enhanced our understanding of the cellular and molecular mechanisms that govern mammalian oogenesis. These advances offer profound insights into the regulatory mechanisms of mammalian reproduction and associated female infertility disorders. In this chapter, we provide an overview of current knowledge in mammalian oogenesis, with a particular emphasis on oocyte selection and activation in vivo.

Advances in the genetic etiology of female infertility

Human reproduction is a complex process involving gamete maturation, fertilization, embryo cleavage and development, blastocyst formation, implantation, and live birth. If any of these processes are abnormal or arrest, reproductive failure will occur. Infertility is a state of reproductive dysfunction caused by various factors. Advances in molecular genetics, including cell and molecular genetics, and high-throughput sequencing technologies, have found that genetic factors are important causes of infertility. Genetic variants have been identified in infertile women or men and can cause gamete maturation arrest, poor quality gametes, fertilization failure, and embryonic developmental arrest during assisted reproduction technology (ART), and thus reduce the clinical success rates of ART. This article reviews clinical studies on repeated in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) failures caused by ovarian dysfunction, oocyte maturation defects, oocyte abnormalities, fertilization disorders, and preimplantation embryonic development arrest due to female genetic etiology, the accumulation of pathogenic genes and gene pathogenic loci, and the functional mechanism and clinical significance of pathogenic genes in gametogenesis and early embryonic development.

Genome-wide association and functional annotation analysis for the calving interval in Nellore cattle

Calving interval (CI) measures the number of days between two consecutive calves of the same cow, and previous studies based on phenotype and pedigree data reported low heritability for this trait. However, the genetic architecture of CI in the Nellore breed was not evaluated based on genomic data. Thus, this study aimed to estimate the heritability based on genomic data and carry out a genome-wide association study (GWAS) for CI in the Nellore breed, using 12,599 pedigree records, 5078 CI records, and 3818 animals genotyped with 50k SNPchip panel. Both quality control and GWAS were performed in BLUPF90 family packages, which use the single-step genomic best linear unbiased predictor (ssGBLUP) method. The average CI was 427.6 days, with a standard deviation of 106.9 and a total range of 270-730 days. The heritability estimate was 0.04 ± 0.04. The p-values of GWAS analysis resulted in a genomic inflation factor (lambda) of 1.08. The only significant SNP (rs136725686) at the genome-wide level (p-value = 1.53E-06) was located on BTA13. Other 19 SNPs were significant at the chromosome-wide level, distributed on BTA1, 2, 3, 6, 10, 13, 14, 17, 18, 22, and 26. Functional annotation analysis found thirty-six protein-coding genes, including genes related to cell cycle (RAD21, BCAR3), oocyte function (LHX8, CLPX, UTP23), immune system (TXK, TEC, NFATC2), endocrine function (LRRFIP2, GPR158), estrous cycle (SLC38A7), and female fertility (CCK, LYZL4, TRAK1, FOXP1, STAC). Therefore, CI is a complex trait with small heritability in Nellore cattle, and various biological processes may be involved with the genetic architecture of CI in Nellore cattle.

HDAC6-dependent deacetylation of NGF dictates its ubiquitination and maintains primordial follicle dormancy

Rationale: Primordial follicles are limited in number and cannot be regenerated, dormant primordial follicles cannot be reversed once they enter a growth state. Therefore, the length of the female reproductive lifespan depends on the orderly progression and selective activation of primordial follicles, the mechanism of which remains unclear. Methods: We used human ovarian cortical biopsy specimens, granulosa cells from diminished ovarian reserve (DOR) patients, Hdac6-overexpressing transgenic mouse model, and RNA sequencing to analyze the crucial roles of histone deacetylase 6 (HDAC6) in fertility preservation and primordial follicle activation. Results: In the present study, we found that HDAC6 was highly expressed in most dormant primordial follicles. The HDAC6 expression was reduced accompanying reproductive senescence in human and mouse ovaries. Overexpression of Hdac6 delayed the rate of primordial follicle activation, thereby prolonging the mouse reproductive lifespan. Short-term inhibition of HDAC6 promoted primordial follicle activation and follicular development in humans and mice. Mechanism studies revealed that HDAC6 directly interacted with NGF, reducing acetylation modification of NGF and thereby accelerating its ubiquitination degradation. Consequently, the reduced NGF protein level maintained the dormancy of primordial follicles. Conclusions: The physiological significance of the high expression of HDAC6 in most primordial follicles is to reduce NGF expression and prevent primordial follicle activation to maintain female fertility. Reduced HDAC6 expression increases NGF expression in primordial follicles, activating their development and contributing to reproduction. Our study provides a clinical reference value for fertility preservation.

Mitochondrial Unfolded Protein Response Gene Clpp Is Required for Oocyte Function and Female Fertility

Mitochondrial unfolded protein stress response (mtUPR) plays a critical role in regulating cellular and metabolic stress response and helps maintain protein homeostasis. Caseinolytic peptidase P (CLPP) is one of the key regulators of mtUPR and promotes unfolded protein degradation. Previous studies demonstrated that global deletion of Clpp resulted in female infertility, whereas no impairment was found in the mouse model with targeted deletion of Clpp in cumulus/granulosa cells. These results suggest the need to delineate the function of Clpp in oocytes. In this study, we aimed to further explore the role of mtUPR in female reproductive competence and senescence using a mouse model. Oocyte-specific targeted deletion of Clpp in mice resulted in female subfertility associated with metabolic and functional abnormalities in oocytes, thus highlighting the importance of CLPP-mediated protein homeostasis in oocyte competence and reproductive function.

Regulation of Oocyte mRNA Metabolism: A Key Determinant of Oocyte Developmental Competence

The regulation of mRNA transcription and translation is uncoupled during oogenesis. The reason for this uncoupling is two-fold. Chromatin is only accessible to the transcriptional machinery during the growth phase as it condenses prior to resumption of meiosis to ensure faithful segregation of chromosomes during meiotic maturation. Thus, transcription rates are high during this time period in order to produce all of the transcripts needed for meiosis, fertilization, and embryo cleavage until the newly formed embryonic genome becomes transcriptionally active. To ensure appropriate timing of key developmental milestones including chromatin condensation, resumption of meiosis, segregation of chromosomes, and polar body extrusion, the translation of protein from transcripts synthesized during oocyte growth must be temporally regulated. This is achieved by the regulation of mRNA interaction with RNA binding proteins and shortening and lengthening of the poly(A) tail. This chapter details the essential factors that regulate the dynamic changes in mRNA synthesis, storage, translation, and degradation during oocyte growth and maturation.

ROCK1 is a multifunctional factor maintaining the primordial follicle reserve and follicular development in mice

The follicle is the basic structural and functional unit of the ovary in female mammals. The excessive depletion of follicles will lead to diminished ovarian reserve or even premature ovarian failure, resulting in diminished ovarian oogenesis and endocrine function. Excessive follicular depletion is mainly due to loss of primordial follicles. Our analysis of published human ovarian single-cell sequencing results by others revealed a significant increase in rho-associated protein kinase 1 (ROCK1) expression during primordial follicle development. However, the role of ROCK1 in primordial follicle development and maintenance is not clear. This study revealed a gradual increase in ROCK1 expression during primordial follicle activation. Inhibition of ROCK1 resulted in reduced primordial follicle activation, decreased follicular reserve, and delayed development of growing follicles. This effect may be achieved through the HIPPO pathway. The present study indicates that ROCK1 is a key molecule for primordial follicular reserve and follicular development.NEW & NOTEWORTHY ROCK1, one of the Rho GTPases, plays an important role in primordial follicle reserve and follicular development. ROCK1 was primarily expressed in the cytoplasm of oocytes and granulosa cell in mice. Inhibition of ROCK1 significantly reduced the primordial follicle reserve and delayed growing follicle development. ROCK1 regulates primordial follicular reserve and follicle development through the HIPPO signaling pathway. These findings shed new lights on the physiology of sustaining female reproduction.

Cyanidin-3-O-glucoside Mitigates the Ovarian Defect Induced by Zearalenone via p53-GADD45a Signaling during Primordial Follicle Assembly

Zearalenone (ZEN) is well known as a kind of endocrine disruptor whose exposure is capable of causing reproductive toxicity in animals. Cyanidin-3-O-glucoside (C3G) is a derivative of cyanidin and owns multiple biofunctions, and prior efforts have suggested that C3G has therapeutic actions for reproductive diseases. In this article, a ZEN exposure model during primordial follicle assembly was constructed using the in vitro culture platform of neonatal mouse ovaries. We investigated the protective effect of C3G on ZEN-induced ovarian toxicity during primordial follicle assembly in mice, as well as its potential mechanism. Interestingly, we observed that C3G could effectively protect the ovary from ZEN damage, mainly by restoring primordial follicle assembly, which upregulated the expression of LHX8 and SOHLH1 proteins and relieved ZEN-induced DNA damage. Next, to explore the mechanism by which C3G rescued ZEN-induced injury, we performed RNA sequencing (RNA-seq). The bioinformatic analysis illustrated that the rescue pathway of C3G was associated with p53-Gadd45a signaling and cell cycle. Then, western blotting and flow cytometry results revealed that C3G restored the expression levels of cyclin-dependent kinase 6 (CDK6) and cyclin D2 (CCND2) and regulated the ovarian cell cycle to normal. In conclusion, our findings manifested that C3G could alleviate ZEN-induced primordial follicle assembly impairment by restoring the cell cycle involved in p53-GADD45a signaling.

Gene expression and demographic analyses in women with the poor ovarian response: a computational approach

PURPOSE

Poor response to ovarian stimulation (POR) typically is reflected as decreased follicular response and low estradiol (E2) levels following ovarian stimulation by FSH/HMG. Many genes are involved in oocyte maturation, and demographic features and lifestyle can affect the oocyte maturity and developmental competence. The present study was conducted to investigate the magnitude of gene expression and lifestyle habits in POR women as compared to healthy women, using different statistical and computational methods.

METHODS

Fifty women in the two groups were studied. The study groups included POR women (n = 25) with 1-9 released oocytes, and the control group (normal women, n = 25) with 9-15 released oocytes. Quantitative PCR was used to estimate the expression of FIGLA, ZAR1, WNT4, LHX8, APC, H1FOO, MOS, and DMC1 genes in granulosa cells.

RESULTS

The results showed no significant difference in the magnitude of the studied genes' expression and linear discriminant analysis did not differentiate the studied groups based on all the genes together. Redundancy analysis (RDA) and latent factor mixed model (LFMM) results produce no significant association between the genes' expression magnitude and the geographical variables of the patients' local habitat. Linear discriminant analysis (LDA) of the demographic features differentiated the two groups of women.

CONCLUSION

Our results indicate that demographic features may have an effect on sample gene expression levels.

From in vivo to in vitro: exploring the key molecular and cellular aspects of human female gametogenesis

Human oogenesis is a highly complex and not yet fully understood process due to ethical and technological barriers that limit studies in the field. In this context, replicating female gametogenesis in vitro would not only provide a solution for some infertility problems, but also be an excellent study model to better understand the biological mechanisms that determine the formation of the female germline. In this review, we explore the main cellular and molecular aspects involved in human oogenesis and folliculogenesis in vivo, from the specification of primordial germ cells (PGCs) to the formation of the mature oocyte. We also sought to describe the important bidirectional relationship between the germ cell and the follicular somatic cells. Finally, we address the main advances and different methodologies used in the search for obtaining cells of the female germline in vitro.

cAMP controls the balance between dormancy and activation of primordial follicles in mouse ovaries

In mammalian ovaries, the balance between dormancy and activation of primordial follicles determines the female fecundity and endocrine homeostasis. Recently, several functional molecules and pathways have been reported to be involved in the activation of primordial follicles. However, the homeostasis regulatory mechanisms of primordial follicle activation are still scant. Our previous study has proved that a relatively higher concentration of cyclic AMP (cAMP) is required for primordial follicle formation. Here, we identified that cAMP also plays a vital role in the balance between dormancy and activation of primordial follicles. Our results showed that the concentration of cAMP remained stable in neonatal mouse ovaries, which is due to ADCY3, the synthetase of cAMP, and PDE3A, the hydrolytic enzyme of cAMP, were synchronously increased during the activation of primordial follicles in mouse ovaries. Once the concentration of cAMP in neonatal ovaries was either elevated or reduced in vitro, the activation of primordial follicles was either accelerated or decelerated accordingly. In addition, a higher concentration of cAMP in the ovaries of puberty mice improved primordial follicle activation in vivo. Finally, cAMP promoted primordial follicle activation via canonical mTORC1-PI3K signaling cascades and PKA signaling. In conclusion, our findings reveal that the concentration of cAMP acts as a key regulator in balancing the dormancy and activation of primordial follicles in the mouse ovary.

SP1 impacts the primordial to primary follicle transition by regulating cholesterol metabolism in granulosa cells

The primordial to primary follicle transition (PPT) in the ovary is critical to maintain sustainable reproductive resources in female mammals. However, it is unclear how granulosa cells (GCs) of the primary follicle participate in regulating PPT. This study focused on exploring the role of transcription factor Sp1 (SP1) in regulating PPT based on the fact that SP1 is pivotal for pregranulosa cell proliferation before primordial follicle formation. The results showed that mice fertility was prolonged when Sp1 was specifically depleted from GCs (GC- Sp1 ^-/- ). Besides, the PPT in GC- Sp1 ^-/- mice was reduced, resulting in more primordial follicles being preserved. Single-cell RNA-seq also indicated that the level of cholesterol metabolism was downregulated in GC- Sp1 ^-/- mice. Additionally, the PPT was promoted by either overexpression of ferredoxin-1 (FDX1), one of the key genes in mediating cholesterol metabolism or supplementing cholesterol for cultured fetal ovaries. Collectively, SP1 in GCs participates in the metabolism of cholesterol partially by regulating the transcription of Fdx1 during the PPT.

Follicle outcomes in human ovarian tissue: effect of freezing, culture, and grafting

OBJECTIVE

To study the effect of freezing, in vitro culture (IVC) and grafting to chorioallantoic membrane (CAM) on follicle outcomes in human ovarian tissue.

DESIGN

An experimental study.

SETTING

University-based research laboratory.

PATIENTS

Fresh and cryopreserved ovarian tissue from 10 patients was donated to research with their consent and institutional review board approval.

INTERVENTIONS

Fresh and frozen-thawed ovarian cortical pieces were in vitro-cultured and compared (fresh-IVC vs FT-IVC). The FT-IVC fragments were then examined against fragments grafted to CAM (FT-CAM). After both IVC and CAM grafting, ovarian cortical pieces (4×2×1 mm³) were analyzed on days 0, 1, and 6.

MAIN OUTCOME MEASURES

Follicle analyses included histology (count and classification) and immunohistochemistry (Ki67 [proliferation], caspase-3 [apoptosis], 1A and 1B light chain 3B [autophagy], p-Akt, FOXO1, and p-rpS6 [PI3K activation]). Droplet digital polymerase chain reaction further explored expression of PI3K pathway- and oocyte-related genes in tissue sections.

RESULTS

No major differences were detected between fresh-IVC and FT-IVC tissues in any conducted analyses. Although a significant drop was observed in primordial follicle (PF) proportions in the fresh-IVC and FT-IVC groups (d0 vs. d6, P<.002), they held steady in the FT-CAM group (d0 vs. d6, P>.05). The PF rates were also significantly higher in the FT-CAM group than the FT-IVC group on d6 (P=.02). Importantly, avian erythrocytes were already present in 30% of implants from d1. Apoptotic and autophagic follicle rates increased during IVC (P<.008), but remained significantly lower in the FT-CAM group (P<.01), confirming superior follicle preservation in CAM-grafted tissue. Upregulation of the PI3K/FOXO pathway was established in the IVC groups, demonstrating PF activation, whereas significant pathway downregulation was detected in the FT-CAM group (P<.03). The droplet digital polymerase chain reaction tests confirmed oocyte growth during IVC and follicle autophagy in all groups; however, the PI3K pathway appeared to be differentially modulated in tissues and follicles.

CONCLUSIONS

In vitro culture induces PF depletion with no additional impact of freezing. Grafting to CAM preserves the PF pool by curbing follicle activation, apoptosis, and autophagy, probably thanks to rapid graft revascularization and/or the circulating embryonic antimüllerian hormone. These findings highlight the importance of enhancing neoangiogenesis in ovarian grafts and investigating the potential benefits of administering antimüllerian hormone to prevent PF burnout.

Mechanisms of primordial follicle activation and new pregnancy opportunity for premature ovarian failure patients

Primordial follicles are the starting point of follicular development and the basic functional unit of female reproduction. Primordial follicles are formed around birth, and most of the primordial follicles then enter a dormant state. Since primordial follicles are limited in number and can't be renewed, dormant primordial follicles cannot be reversed once they enter the growing state. Thus, the orderly occurrence of primordial follicles selective activation directly affects the rate of follicle consumption and thus determines the length of female reproductive lifespan. Studies have found that appropriately inhibiting the activation rate of primordial follicles can effectively slow down the rate of follicle consumption, maintain fertility and delay ovarian aging. Based on the known mechanisms of primordial follicle activation, primordial follicle in vitro activation (IVA) technique has been clinically developed. IVA can help patients with premature ovarian failure, middle-aged infertile women, or infertile women due to gynecological surgery treatment to solve infertility problems. The study of the mechanism of selective activation of primordial follicles can contribute to the development of more efficient and safe IVA techniques. In this paper, recent mechanisms of primordial follicle activation and its clinical application are reviewed.

Maternal ochratoxin A exposure impairs meiosis progression and primordial follicle formation of F1 offspring

Ochratoxin A (OTA), a mycotoxin produced by Aspergillus and Penicillium fungi, widely contaminates feed, food and their raw materials. OTA has been proved to have hepatotoxicity and nephrotoxicity. Its reproductive toxicity needs to be further explored. We found that OTA inhibited the progression of meiosis, keeping more germ cells at leptotene and zygotene. Furthermore, OTA impaired primordial follicle formation, keeping more germ cells in cysts. Increased γH2AX suggested that DNA damage occurred both at the stages of meiosis and primordial follicle formation. The expression of RAD51 increased with the concentration of OTA at the stage of meiosis, while decreased later, suggesting the activated DNA repair induced by DNA damage then inhibited by persistent and excessive stress of DNA damage, which further induced apoptosis. DEGs caused by OTA were also mainly enriched in DNA damage and repair through RNA-seq analysis. Higher level of reactive oxygen species (ROS) and increased degree of oxidative damage marker 8-OHdG were both found in the ovaries exposed to OTA. We concluded that maternal OTA exposure affected meiosis progression and primordial follicle formation via oxidative damage and DNA repair. Clarification of the mechanism of OTA will contribute to the development of more effective detoxification strategies.

Heterozygous loss-of-function variants in LHX8 cause female infertility characterized by oocyte maturation arrest

PURPOSE

The genetic causes of oocyte maturation arrest leading to female infertility are largely unknown, and no population-based genetic analysis has been applied in cohorts of patients with infertility. We aimed to identify novel pathogenic genes causing oocyte maturation arrest by using a gene-based burden test.

METHODS

Through comparison of exome sequencing data from 716 females with infertility characterized by oocyte maturation arrest and 3539 controls, we performed a gene-based burden test and identified a novel pathogenic gene LHX8. Splicing event was evaluated using a minigene assay, expression of LHX8 protein was assessed in HeLa cells, and nuclear subcellular localization was determined in both HeLa cells and mouse oocytes.

RESULTS

A total of 5 heterozygous loss-of-function LHX8 variants were identified from 6 independent families (c.389+1G>T, c.412C>T [p.Arg138∗], c.282C>A [p.Cys94∗]; c.257dup [p.Tyr86∗]; and c.180del, [p.Ser61Profs∗30]). All the identified variants in LHX8 produced truncated LHX8 protein and resulted in loss of LHX8 nuclear localization in both HeLa cells and mouse oocytes.

CONCLUSION

By combining genetic evidence and functional evaluations, we identified a novel pathogenic gene LHX8 and established the causative relationship between LHX8 haploinsufficiency and female infertility characterized by oocyte maturation arrest.

Identification of Biomarkers for Predicting Ovarian Reserve of Primordial Follicle via Transcriptomic Analysis

Ovarian reserve (OR) is mainly determined by the number of primordial follicles in the ovary and continuously depleted until ovarian senescence. With the development of assisted reproductive technology such as ovarian tissue cryopreservation and autotransplantation, growing demand has arisen for objective assessment of OR at the histological level. However, no specific biomarkers of OR can be used effectively in clinic nowadays. Herein, bulk RNA-seq datasets of the murine ovary with the biological ovarian age (BOA) dynamic changes and single-cell RNA-seq datasets of follicles at different stages of folliculogenesis were obtained from the GEO database to identify gene signature correlated to the primordial follicle pool. The correlations between gene signature expression and OR were also validated in several comparative OR models. The results showed that genes including Lhx8, Nobox, Sohlh1, Tbpl2, Stk31, and Padi6 were highly correlated to the OR of the primordial follicle pool, suggesting that these genes might be used as biomarkers for predicting OR at the histological level.

Functional differentiation of two lhx8 paralogs and possible regulatory role of lhx8a in Japanese flounder (Paralichthys olivaceus)

Lhx8, belonging to the LIM-Homebox family, is involved in the tooth, nervous system, and primordial follicles development in mammals. However, little is known about the regulatory roles of lhx8 in teleosts. In this study, two lhx8 duplicates were identified in Paralichthys olivaceus, termed Polhx8a and Polhx8b, respectively. Bioinformatic analysis showed that Polhx8a was more likely to be a teleost-specific paralog. According to expression analysis, Polhx8a transcripts were almost exclusively concentrated in the oocytes, while Polhx8b was weakly expressed in the spleen, gill, and some facial organs, indicating sub-functionalization of this gene pair during evolution. Furthermore, Polhx8a mRNA level elevated from perinucleolar oocyte (PNO) stage to vitellogenic oocyte (VO) stage transition and changed after exogenous hormone stimulation, proving that Polhx8a was involved in the oocyte development and could be regulated by sex hormones. Yeast two-hybrid, bimolecular fluorescence complementation (BiFC) and co-immunoprecipitation (co-IP) experiments captured the positive protein interactions between PoLhx8a and the other two oocyte-specific transcription factors: PoFigla and PoNobox. After knocking down lhx8a in embryos or adult ovaries in vivo, the expression of oocyte-associated genes was significantly down-regulated (P < 0.05). Our findings suggest the evolution and functional differentiation of lhx8 genes, and shed light on the potential role of lhx8a in protein interactions and gene regulation in teleosts.

Human ovarian tissue in-vitro culture: primordial follicle activation as a new strategy for female fertility preservation

Cryopreservation and transplantation of ovarian tissue is the only fertility preservation option used for prepubertal girls and women who don't have a chance for embryo or oocyte vitrification. For women with aggressive cancer, hormone-responsive malignancies, autoimmune diseases, etc. ovary transplantation cannot be performed so an alternative technology called in-vitro follicle activation is thinkable. In this method, dormant primordial follicles are activated from the resting primordial pool by in-vitro culture and enter their growth phase. Different in-vitro culture media and supplements in addition to various culturing methods have been conducted for activating these dormant follicles. Furthermore, several signaling pathways such as Hippo, phosphatidylinositol-3-kinase, and mTOR influence follicle activation. Therefore, the addition of different activators of these signaling pathways can beneficially regulate this culture system. This review summarizes the findings on different aspects of human ovarian tissue culture strategies for in-vitro follicular activation, their medium, and different factors involved in this activation. Afterward, signaling pathways important for follicle activation and their clinical applications towards improving activation in culture are also reviewed.

Ovarian Stem Cells Differentiation into Primary Oocytes Using Follicle Stimulating Hormone, Basic Fibroblast Growth Factor, and Neurotrophin 3

Background:

In vitro obtaining oocytes can be an appropriate alternative for patients with gonadal insufficiency or cancer survivors. The purpose of the current research was isolating stem cells from ovarian cortical tissue as well as evaluating the effectiveness of follicle stimulating hormone (FSH), basic fibroblast growth factor (bFGF), and neurotrophin 3 (NT3) in differentiating to oocyte-like cells.

Methods:

A human ovary was dissected and cortical tissue pieces were cultured for cell isolation. Isolated cells were divided into 8 groups (3 cases in each group) of control, FSH, NT3, bFGF, FSH+NT3, FSH+bFGF, NT3+bFGF, and FSH+NT3+ bFGF. Pluripotency specific gene (OCT4-A and Nanog), initial germ cells (c-KIT and VASA) and PF growth initiators (GDF-9 and Lhx-8) were evaluated by qRTPCR. Experiments were performed in triplicate and there were 3 samples in each group. The results were analyzed using one-way ANOVA and p-value less than 0.05 was considered statistically significant.

Results:

Flow cytometry results showed that cells isolated from the ovarian cortex expressed markers of pluripotency. The results showed that the expression of Nanog, OCT4, GDF-9 and VASA was significantly increased in FSH+NT3 group, while treatment with bFGF caused significant expression of c-KIT and Lhx-8 (p<0.05). Also, according to the results, isolated cells treated with NT3 significantly increased c-KIT expression.

Conclusion:

According to our results, the ovarian cortex cells could be differentiated into primordial follicles if treated with the proper combination of FSH, bFGF, and NT3. These findings provided a new perspective for the future of in vitro gamete proudest.

Overexpression of Lin28a induces a primary ovarian insufficiency phenotype via facilitation of primordial follicle activation in mice

Lin28a is an RNA binding protein and increasing evidence has indicated its role in regulating female fertility. Lin28a has been reported to be involved in ovarian follicle activation. However, its role and mechanisms in regulating primordial follicle activation have not yet been explored. To test whether overexpression of Lin28a activates ovarian primordial follicles, studies were conducted in wild type (WT) and Lin28a Tg mice. Female Lin28a Tg mice at 4-month old exhibited significantly smaller litter size and fewer ovulated oocytes when compared with the WT mice. By 6-month of age, these parameters in Lin28a Tg mice were less than 20% of the WT mice. At postnatal day (PD) 14, the number of primordial follicles was significantly decreased but the number of primary follicles was significantly increased in the transgenic mice. The number of primordial follicles, secondary and antral follicles in these mice were drastically reduced at PD21. In the ovary of Lin28a Tg mice, there were activation of Wnt/β-catenin signaling and its downstream mTOR pathway. Interestingly, overexpression of Lin28a, which can also act as transcriptional activator, activated Wnt signaling through enhancing the transcription of Wnt co-receptor LRP5. In conclusion, overexpression of Lin28a induced a primary ovarian insufficiency phenotype in long term via facilitating Wnt/β-catenin signaling leading to activation of primordial follicles.

LIM Homeodomain (LIM-HD) Genes and Their Co-Regulators in Developing Reproductive System and Disorders of Sex Development

LIM homeodomain (LIM-HD) family genes are transcription factors that play crucial roles in a variety of functions during embryonic development. The activities of the LIM-HD proteins are regulated by the co-regulators LIM only (LMO) and LIM domain-binding (LDB). In the mouse genome, there are 13 LIM-HD genes (Lhx1-Lhx9, Isl1-2, Lmx1a-1b), 4 Lmo genes (Lmo1-4), and 2 Ldb genes (Ldb1-2). Amongst these, Lhx1 is required for the development of the müllerian duct epithelium and the timing of the primordial germ cell migration. Lhx8 is necessary for oocyte differentiation and Lhx9 for somatic cell proliferation in the genital ridges and control of testosterone production in the Leydig cells. Lmo4 is involved in Sertoli cell differentiation. Mutations in LHX1 are associated with müllerian agenesis or Mayer-Rokitansky-Kuster-Hauser (MRKH) syndrome. LHX9 gene variants are reported in cases with disorders of sex development (DSD). Mutations in LHX3 and LHX4 are reported in patients with combined pituitary hormone deficiency having absent or delayed puberty. A transcript map of the Lhx, Lmo, and Ldb genes reveal that multiple LIM-HD genes and their co-regulators are expressed in a sexually dimorphic pattern in the developing mouse gonads. Unraveling the roles of LIM-HD genes during development will aid in our understanding of the causes of DSD.

Redox imbalance in age-related ovarian dysfunction and perspectives for its prevention

The age at which women have their first child is increasing. This change represents a major health problem to society because advanced maternal age is related with a decay in fertility and an increase in the incidence of a variety of pregnancy complications and offspring health issues. The ovary stands as the main contributor for female reproductive ageing because of the progressive age-related decrease in follicle number and oocyte quality. Loss of redox homeostasis and establishment of an ovarian oxidative microenvironment are seen as major underlying causes for such downfall and impairment of ovarian function. Thus, the use of antioxidants to preserve fertility became an important field of research. In this review, new insights on mechanisms underlying the establishment of oxidative stress and its repercussions on ovarian ageing are addressed, along with the current state of knowledge on antioxidant supplementation and its contribution for healthy ageing and extension of ovarian lifespan.

Single-Oocyte Gene Expression Suggests That Curcumin Can Protect the Ovarian Reserve by Regulating the PTEN-AKT-FOXO3a Pathway

A better understanding of the mechanism of primordial follicle activation will help us better understand the causes of premature ovarian insufficiency (POI), and will help us identify new drugs that can be applied to the clinical treatment of infertility. In this study, single oocytes were isolated from primordial and primary follicles, and were used for gene profiling with TaqMan array cards. Bioinformatics analysis was performed on the gene expression data, and Ingenuity Pathway Analysis was used to analyze and predict drugs that affect follicle activation. An ovarian in vitro culture system was used to verify the function of the drug candidates, and we found that curcumin maintains the ovarian reserve. Long-term treatment with 100 mg/kg curcumin improved the ovarian reserve indicators of AMH, FSH, and estradiol in aging mice. Mechanistic studies show that curcumin can affect the translocation of FOXO3, thereby inhibiting the PTEN-AKT-FOXO3a pathway and protecting primordial follicles from overactivation. These results suggest that curcumin is a potential drug for the treatment of POI patients and for fertility preservation.

The inhibition of WIP1 phosphatase accelerates the depletion of primordial follicles

RESEARCH QUESTION

What role does wild-type p53-induced phosphatase 1 (WIP1) play in the regulation of primordial follicle development?

DESIGN

WIP1 expression was detected in the ovaries of mice of different ages by western blotting and immunohistochemical staining. Three-day-old neonatal mouse ovaries were cultured in vitro with or without the WIP1 inhibitor GSK2830371 (10 μM) for 4 days. Ovarian morphology, follicle growth and follicle classification were analysed and the PI3K-AKT-mTOR signal pathway and the WIP1-p53-related mitochondrial apoptosis pathway evaluated.

RESULTS

WIP1 expression was downregulated with age. Primordial follicles were significantly decreased in the GSK2830371-treated group, without a significant increase in growing follicles. The ratio of growing follicles to primordial follicles was not significantly different between the control and GSK2830371 groups, and no significant variation was observed in the PI3K-AKT-mTOR signal pathway. The inhibition of WIP1 phosphatase accelerated primordial follicle atresia by activating the p53-BAX-caspase-3 pathway.

CONCLUSIONS

These findings reveal that WIP1 participates in regulating primordial follicle development and that inhibiting WIP1 phosphatase leads to massive primordial follicle loss via interaction with the p53-BAX-caspase-3 pathway. This might also provide valuable information for understanding decreased ovarian reserve during ovarian ageing.

Revisiting the Impact of Local Leptin Signaling in Folliculogenesis and Oocyte Maturation in Obese Mothers

The complex nature of folliculogenesis regulation accounts for its susceptibility to maternal physiological fitness. In obese mothers, progressive expansion of adipose tissue culminates with severe hyperestrogenism and hyperleptinemia with detrimental effects for ovarian performance. Indeed, maternal obesity is associated with the establishment of ovarian leptin resistance. This review summarizes current knowledge on potential effects of impaired leptin signaling throughout folliculogenesis and oocyte developmental competence in mice and women.

Current mechanisms of primordial follicle activation and new strategies for fertility preservation

Premature ovarian insufficiency (POI) is characterized by symptoms caused by ovarian dysfunction in patients aged <40 years. It is associated with a shortened reproductive lifespan. The only effective treatment for patients who are eager to become pregnant is IVF/Embryo Transfer (ET) using oocytes donated by young women. However, the use of the technique is constrained by the limited supply of oocytes and ethical issues. Some patients with POI still have some residual follicles in the ovarian cortex, which are not regulated by gonadotropin. These follicles are dormant. Therefore, activating dormant primordial follicles (PFs) to obtain high-quality oocytes for assisted reproductive technology may bring new hope for patients with POI. Therefore, this study aimed to explore the factors related to PF activation, such as the intercellular signaling network, the internal microenvironment of the ovary and the environment of the organism. In addition, we discussed new strategies for fertility preservation, such as in vitro activation and stem cell transplantation.

The Efficacy and Safety of the mTOR Signaling Pathway Activator, MHY1485, for in vitro Activation of Human Ovarian Tissue

Background

Premature ovarian insufficiency (POI) is characterized by abnormal ovarian function before the age of 40. POI showed that primordial follicles developed in disorder. mTOR signaling plays a vital role in the process of follicle development. It has been verified that the mTOR signaling pathway activator, MHY1485, can promote primordial follicle development in mice. We considered that MHY1485 would be a promising fertility preservation method for POI patients.

Methods

The fragmented ovarian tissues of normal woman was cultured with activator MHY1485 in vitro, and then the control and activated ovaries were transplanted into the kidney capsules of ovariectomized mice. We then used the Infinium Human Methylation EPIC BeadChip to verify the DNA methylation level of ovarian tissues, thus exploring the effectiveness of them.

Results

MHY1485 stimulated mTOR, S6K1, and rpS6 phosphorylation. Cultured with MHY1485, ovarian weights increased and endocrine function was restored. The number of growing follicles was increased. The in vitro activation process did not induce histological changes or abnormal DNA methylation occurrence.

Conclusion

MHY1485 for in vitro activation (IVA) is effective for ovarian rejuvenation and is a potential therapeutic treatment for POI patients.

Signalling pathways and mechanistic cues highlighted by transcriptomic analysis of primordial, primary, and secondary ovarian follicles in domestic cat

In vitro growth (IVG) of dormant primordial ovarian follicles aims to produce mature competent oocytes for assisted reproduction. Success is dependent on optimal in vitro conditions complemented with an understanding of oocyte and ovarian follicle development in vivo. Complete IVG has not been achieved in any other mammalian species besides mice. Furthermore, ovarian folliculogenesis remains sparsely understood overall. Here, gene expression patterns were characterised by RNA-sequencing in primordial (PrF), primary (PF), and secondary (SF) ovarian follicles from Felis catus (domestic cat) ovaries. Two major transitions were investigated: PrF-PF and PF-SF. Transcriptional analysis revealed a higher proportion in gene expression changes during the PrF-PF transition. Key influencing factors during this transition included the interaction between the extracellular matrix (ECM) and matrix metalloproteinase (MMPs) along with nuclear components such as, histone HIST1H1T (H1.6). Conserved signalling factors and expression patterns previously described during mammalian ovarian folliculogenesis were observed. Species-specific features during domestic cat ovarian folliculogenesis were also found. The signalling pathway terms "PI3K-Akt", "transforming growth factor-β receptor", "ErbB", and "HIF-1" from the functional annotation analysis were studied. Some results highlighted mechanistic cues potentially involved in PrF development in the domestic cat. Overall, this study provides an insight into regulatory factors and pathways during preantral ovarian folliculogenesis in domestic cat.

Microenvironmental changes induced by placenta-derived mesenchymal stem cells restore ovarian function in ovariectomized rats via activation of the PI3K-FOXO3 pathway

Background

Translational studies have explored the therapeutic potential and feasibility of mesenchymal stem cells (MSCs) in several degenerative diseases; however, mechanistic studies of the function of these cells have been insufficient. As ovarian failure causes anovulation as well as ovarian steroid hormonal imbalances, the specific aims of this study were to analyze the therapeutic role of placenta-derived MSCs (PD-MSCs) in an ovarian failure ovariectomy (OVX) rat model and evaluate whether PD-MSC transplantation (Tx) improved folliculogenesis and oocyte maturation in the injured ovary through PI3K/Akt and FOXO signaling.

Methods

Blood and ovary tissue were collected and analyzed after various PD-MSC Tx treatments in an ovariectomized rat model. Changes in the expression of folliculogenesis- and ovary regeneration-related genes induced by PD-MSC treatments were analyzed by qRT-PCR, Western blotting, and histological analysis.

Results

The levels of hormones related to ovary function were significantly increased in the PD-MSC Tx groups compared with those in the nontransplantation group (NTx). The follicle numbers in the ovarian tissues were increased along with the increased expression of genes related to folliculogenesis in the PD-MSC Tx groups compared with the NTx groups. Furthermore, Tx PD-MSCs induced follicle maturation by increasing the phosphorylation of GSK3 beta and FOXO3 (p < 0.05) and shifting the balance of growth and apoptosis in oocytes.

Conclusions

Taken together, these results show that PD-MSC Tx can restore ovarian function and induce ovarian folliculogenesis via the PI3K/Akt and FOXO signaling pathway.

The Factors and Pathways Regulating the Activation of Mammalian Primordial Follicles in vivo

Mammalian ovaries consist of follicles as basic functional units. Each follicle comprised an innermost oocyte and several surrounding flattened granulosa cells. Unlike males, according to the initial size of the primordial follicle pool and the rate of its activation and depletion, a female's reproductive life has been determined early in life. Primordial follicles, once activated, will get into an irreversible process of development. Most follicles undergo atretic degeneration, and only a few of them could mature and ovulate. Although there are a lot of researches contributing to exploring the activation of primordial follicles, little is known about its underlying mechanisms. Thus, in this review, we collected the latest papers and summarized the signaling pathways as well as some factors involved in the activation of primordial follicles, hoping to lead to a more profound understanding of the cellular and molecular mechanisms of primordial follicle activation.

Pathways coordinating oocyte attrition and abundance during mammalian ovarian reserve establishment

The mammalian ovarian reserve is comprised of a finite pool of primordial follicles, representing the lifetime reproductive capacity of females. In most mammals, the reserve is produced during embryonic and early postnatal development with oocyte numbers peaking during mid-to-late gestation, and then experiencing a dramatic decline continuing until shortly after birth. Oocytes remaining after the bulk of this attrition are subsequently surrounded by a layer of somatic pre-granulosa cells with these units then referred to as "primordial follicles." The complex and varied cell death mechanisms intrinsic to this process are not only characteristic of, but also essential for, the proper formation of this pool of follicles, and as a result must be immaculately balanced to ensure long-term fertility and reproductive health. Too few follicles can lead to Primary Ovarian Insufficiency, resulting in fertility loss and other features of aging, such as an overall shorter lifespan. On the other hand, whereas an excess of follicles might extend reproductive lifespan, this might also be the underlying etiology of other ovarian pathologies. The last decade, in particular, has vastly expanded our understanding of oocyte attrition and determinants of ovarian reserve abundance. By continuing to decipher the intricacies underlying the cell death processes and development of the initial primordial follicle pool, we may be in a much better position to understand idiopathic cases of premature follicle depletion and improve ovarian health in reproductive-age women.

Evaluation of the epigenetic alterations and gene expression levels of HepG2 cells exposed to zearalenone and α-zearalenol

Zearalenone, produced by various Fusarium species, is a non-steroidal estrogenic mycotoxin that contaminates cereals, resulting in adverse effects on human health. We investigated the effects of zearalenone and its metabolite alpha zearalenol on epigenetic modifications and its relationship with metabolic pathways in human hepatocellular carcinoma cells following 24 h of exposure. Zearalenone and alpha zearalenol at the concentrations of 1, 10 and 50 μM significantly increased global levels of DNA methylation and global histone modifications (H3K27me3, H3K9me3, H3K9ac). Expression levels of the chromatin modifying enzymes EHMT2, ESCO1, HAT1, KAT2B, PRMT6 and SETD8 were upregulated by 50 μM of zearalenone exposure using PCR arrays, consistent with the results of global histone modifications. Zearalenone and alpha zearalenol also changed expression levels of the AhR, LXRα, PPARα, PPARɣ, L-fabp, LDLR, Glut2, Akt1 and HK2 genes, which are related to nuclear receptors and metabolic pathways. PPARɣ, a key regulator of lipid metabolism, was selected from among these genes for further analysis. The PPARɣ promoter reduced methylation significantly following zearalenone exposure. Taken together, the epigenetic mechanisms of DNA methylation and histone modifications may be key mechanisms in zearalenone toxicity. Furthermore, effects of zearalenone in metabolic pathways could be mediated by epigenetic modifications.

In utero exposure to acetaminophen and ibuprofen leads to intergenerational accelerated reproductive aging in female mice

Nonsteroidal anti-inflammatory drugs (NSAIDs) and analgesic drugs, such as acetaminophen (APAP), are frequently taken during pregnancy, even in combination. However, they can favour genital malformations in newborn boys and reproductive disorders in adults. Conversely, the consequences on postnatal ovarian development and female reproductive health after in utero exposure are unknown. Here, we found that in mice, in utero exposure to therapeutic doses of the APAP-ibuprofen combination during sex determination led to delayed meiosis entry and progression in female F1 embryonic germ cells. Consequently, follicular activation was reduced in postnatal ovaries through the AKT/FOXO3 pathway, leading in F2 animals to subfertility, accelerated ovarian aging with abnormal corpus luteum persistence, due to decreased apoptosis and increased AKT-mediated luteal cell survival. Our study suggests that administration of these drugs during the critical period of sex determination could lead in humans to adverse effects that might be passed to the offspring.

Lhx8 ablation leads to massive autophagy of mouse oocytes associated with DNA damage

Following proliferation of oogonia in mammals, great numbers of germ cells are discarded, primarily by apoptosis, while the remainder form primordial follicles (the ovarian reserve) that determine fertility and reproductive lifespan. More massive, rapid, and essentially total loss of oocytes, however, occurs when the transcription factor Lhx8 is ablated-though the cause and mechanism of germ cell loss from the Lhx8-/- ovaries has been unknown. We found that Lhx8-/- ovaries maintain the same number of germ cells throughout embryonic development; rapid decrease in the pool of oocytes starts shortly before birth. The loss results from activation of autophagy, which becomes overwhelming within the first postnatal week, with extracellular matrix proteins filling the space previously occupied by follicles to produce a fibrotic ovary. Associated with this process, as early as a few days before birth, Lhx8-/- oocytes failed to repair DNA damage-which normally occurs when meiosis is initiated during embryonic development; and DNA damage repair genes were downregulated throughout the oocyte short lifespan. Based on gene expression analyses and morphological changes, we propose a model in which lineage-restricted failure of DNA repair triggers germ cell autophagy, causing premature depletion of the ovarian reserve in Lhx8-/- mice.

Mitofusin 1 is required for female fertility and to maintain ovarian follicular reserve

Mitochondria are dynamic organelles that continually adapt their structure through fusion and fission in response to changes in their bioenergetic environment. Targeted deletion of mitochondrial fusion protein mitofusin1 (MFN1) in oocytes resulted in female infertility associated with failure to achieve oocyte maturation. Oocyte-granulosa cell communication was impaired, and cadherins and connexins were downregulated, resulting in follicle developmental arrest at the secondary follicle stage. Deletion of MFN1 in oocytes resulted in mitochondrial dysfunction and altered mitochondrial dynamics, as well as accumulation of ceramide, which contributed to increased apoptosis and a reproductive phenotype that was partially rescued by treatment with ceramide synthesis inhibitor myriocin. Absence of MFN1 and resulting apoptotic cell loss also caused depletion of ovarian follicular reserve, and a phenotype consistent with accelerated female reproductive aging.

Control of Mammalian Oocyte Development by Interactions with the Maternal Follicular Environment

Development of animal germ cells depends critically on continuous contact and communication with the somatic compartment of the gonad. In females, each oocyte is enclosed within a follicle, whose somatic cells supply nutrients that sustain basal metabolic activity of the oocyte and send signals that regulate its differentiation. This maternal microenvironment thus plays an indispensable role in ensuring the production of fully differentiated oocytes that can give rise to healthy embryos. The granulosa cells send signals, likely membrane-associated Kit ligand, which trigger oocytes within resting-stage primordial follicles to initiate growth. During growth, the granulosa cells feed amino acids, nucleotides, and glycolytic substrates to the oocyte. These factors are necessary for the oocyte to complete its growth and are delivered via gap junctions that couple the granulosa cells to the oocyte. In a complementary manner, growing oocytes also release growth factors, notably growth-differentiation factor 9 and bone morphogenetic protein 15, which are necessary for proper differentiation of the granulosa cells and for these cells to support oocyte growth. During the late stages of oocyte growth, cyclic GMP that is synthesized by the granulosa cells and diffuses into the oocyte is required to prevent its precocious entry into meiotic maturation. Finally, at the early stages of maturation, granulosa cell signals promote the synthesis of a subset of proteins within the oocyte that enhance their ability to develop as embryos. Thus, the maternal legacy of the follicular microenvironment is witnessed by the fertilization of the ovulated oocyte and subsequent birth of healthy offspring.

Mitofusin 2 plays a role in oocyte and follicle development, and is required to maintain ovarian follicular reserve during reproductive aging

Mitochondria change their shape through fusion and fission in order to adapt to their metabolic milieu. Mitofusin-2 (MFN2) is a key regulatory protein in this process, mediating mitochondrial fusion and interaction with endoplasmic reticulum. Targeted deletion of Mfn2 in oocytes resulted in mitochondrial dysfunction and female subfertility associated with impaired oocyte maturation and follicle development. Oocytes lacking MFN2 showed shortened telomeres and increased apoptosis, resulting in compromised oocyte quality and accelerated follicular depletion, consistent with a reproductive aging phenotype.

Gestational diabetes promotes germ cell cCyst breakdown and primordial follicle formation in newborn mice via the AKT signaling pathway

Type 1 diabetes (T1D) is a common disease in which pancreatic β cells are impaired due to auto-immunity, pregnancy in women with it is associated with increased risk of neonatal morbidity, mortality. However, the effects of gestational diabetes on the reproduction of newborn offspring are still poorly understood. Here, we determined the cyst breakdown and primordial follicle formation in neonatal offspring born by streptozotocin (STZ)-induced diabetic or non-diabetic female mice, and found that the germ cell cyst breakdown was promoted in neonatal offspring of STZ -induced diabetic mice at postnatal Day 1, which sequentially accelerated the primordial follicle formation. Further investigation revealed that, the expression level of PI3K and p-AKT were significantly increased in ovaries of offspring born by T1D mice. These results indicated that STZ -induced gestational diabetes promotes germ cell cyst breakdown and primordial follicle formation by regulating the PI3K/AKT signaling pathway in the newborn offspring. In addition, this effect can be rescued by an insulin supplement. Taken together, our results uncover the intergenerational effects of gestational diabetes on neonatal offspring folliculogenesis, and provide an experimental model for treating gestational diabetes and its complications in neonatal offspring.

Alterations in global DNA methylation and metabolism-related genes caused by zearalenone in MCF7 and MCF10F cells

Zearalenone (ZEN) is a non-steroidal estrogenic mycotoxin produced by Fusarium fungi. ZEN has endocrine disruptor effects and could impair the hormonal balance. Here, we aimed at investigating possible effects of ZEN on metabolism-related pathways and its relation to epigenetic mechanisms in breast adenocarcinoma (MCF7) and breast epithelial (MCF10F) cells. Using the MTT and neutral red uptake (NRU) cell viability tests, IC₅₀ values of ZEN after 24 h were found to be 191 μmol/L and 92.6 μmol/L in MCF7 cells and 67.4 μmol/L and 79.5 μmol/L in MCF10F cells. A significant increase on global levels of 5-methylcytosine (5-mC%) was observed for MCF7 cells, correlating with the increased expression of DNA methyltransferases. No alterations were observed on levels of 5-mC% and expression of DNA methyltransferases for MCF10F cells. Further, at least threefold upregulation compared to control was observed for several genes related to nuclear receptors and metabolism in MCF7 cells, while some of these genes were downregulated in MCF10F cells. The most notably altered genes were IGF1, HK2, PXR, and PPARγ. We suggested that ZEN could alter levels of global DNA methylation and impair metabolism-related pathways.

Persistent epigenetic changes in adult daughters of older mothers

Women of advanced maternal age account for an increasing proportion of live births in many developed countries across the globe. Offspring of older mothers are at an increased risk for a variety of subsequent health outcomes, including outcomes that do not manifest until childhood or adulthood. The molecular underpinnings of the association between maternal aging and offspring morbidity remain elusive. However, one possible mechanism is that maternal aging produces specific alterations in the offspring's epigenome in utero, and these epigenetic alterations persist into adulthood. We conducted an epigenome-wide association study (EWAS) of the effect of a mother's age on blood DNA methylation in 2,740 adult daughters using the Illumina Infinium HumanMethylation450 array. A false discovery rate (FDR) q-value threshold of 0.05 was used to identify differentially methylated CpG sites (dmCpGs). We identified 87 dmCpGs associated with increased maternal age. The majority (84%) of the dmCpGs had lower methylation in daughters of older mothers, with an average methylation difference of 0.6% per 5-year increase in mother's age. Thirteen genomic regions contained multiple dmCpGs. Most notably, nine dmCpGs were found in the promoter region of the gene LIM homeobox 8 (LHX8), which plays a pivotal role in female fertility. Other dmCpGs were found in genes associated with metabolically active brown fat, carcinogenesis, and neurodevelopmental disorders. We conclude that maternal age is associated with persistent epigenetic changes in daughters at genes that have intriguing links to health.

Proteomic analysis of mouse ovaries during the prepubertal stages

Postnatal folliculogenesis, primordial follicle activation and follicular development at early stage are important for normal ovarian function and fertility, and a comprehensive understanding of this process under physiological condition is necessary. To observe the regulation and mechanism of ovarian follicle development during the prepubertal stages, we collected the mouse ovaries from three time points, including 1 day, 7 days, and 4 weeks after birth. We then performed a proteomic analysis using tandem mass tags (TMT) labeling combined with a two-dimensional liquid chromatography-tandem mass spectrometry (2D LC-MS/MS) technique. A total of 706 proteins were determined to be significant differential abundance (P-SDA). Sixty upregulated proteins and 12 downregulated proteins that were P-SDA and 3 significant KEGG pathways (P < 0.05) were found at 7 days vs. 1 day after birth, while 237 upregulated proteins, 271 downregulated proteins and 42 significant KEGG pathways were found for 4 weeks vs. 7 days after birth. Some vital genes (Figla, Ooep, Padi6, Zp3, Hsd3b1, cyp11a1), key pathways (ECM-receptor interaction, focal adhesion, ovarian steroidogenesis, complement and coagulation cascades, PI3K/Akt/mTOR), and metabolic regulation (energy metabolism, lipid metabolism, metal ion metabolism) were found to be related to the postnatal folliculogenesis, primordial follicle activation and follicular development. Finally, qRT-PCR and western blotting verified some vital genes and further elucidated the developmental process of follicles, and the results may contribute to the understanding of the formation and activation of primordial follicle and follicular development. Significance: This study offers the first proteomic insights into mechanisms of follicle development under physiological condition during the prepubertal stages. By comparing P-SDA of mouse ovaries during various period of age, our data reveals that the regulation of primordial follicle formation and activation is significantly different from that of follicular development. These findings demonstrate that many unique molecular mechanisms underlie ovarian development could be used for ovarian disease research.

Fibroblast growth factor 21 coordinates adiponectin to mediate the beneficial effects of low-protein diet on primordial follicle reserve

Background

Global consumption of protein per capita is rising, while rates of infertility are increasing. However, a clear relationship between protein intake and reproductive health has not been demonstrated. The activation of the quiescent primordial follicles is the first step of folliculogenesis, and their activation must be tightly controlled to prevent premature exhaustion of the ovarian follicular reserve.

Methods

The primordial follicle reserve of wild-type or liver-specific ablation of fibroblast growth factor 21 (FGF21) in mice, subjected to limited or excessive protein diets or oral gavage test, were detected in vivo. Mouse ovary organ cultures were used to examine the direct role of metabolites or metabolic hormones on primordial follicle activation.

Findings

Mouse primordial follicle activation, was reduced by restricted protein intake and was accelerated by excessive protein intake, in an ovarian mTORC1 signaling-dependent manner. Furthermore, restricted or excessive protein intake resulted in an augmentation or decline of oocyte number and fertility at older age, respectively. Liver-specific ablation of FGF21, which resulted in a reduction of 87% in circulating FGF21, abrogated the preserving effect of low-protein intake on primordial follicle pool. Interestingly, FGF21 had no direct effect on the activation of primordial follicles, but instead required an adipokine adiponectin. Moreover, AdipoRon, an oral adiponectin receptor agonist, prevented the over-activation effect of excessive protein intake on primordial follicle activation.

Interpretation

Dietary protein consumption controlled ovarian primordial follicle reserve and fertility, which required coordination between FGF21 and adiponectin.

Fund

Natural Science Foundation of China (Grant 31772616).

Med12 regulates ovarian steroidogenesis, uterine development and maternal effects in the mammalian egg

The transcriptional factor MED12 is part of the essential mediator transcriptional complex that acts as a transcriptional coactivator in all eukaryotes. Missense gain-of-function mutations in human MED12 are associated with uterine leiomyomas, yet the role of MED12 deficiency in tumorigenesis and reproductive biology has not been fully explored. We generated a Med12 reproductive conditional knockout mouse model to evaluate its role in uterine mesenchyme, granulosa cells, and oocytes. Mice heterozygous for Med12 deficiency in granulosa cells and uterus (Med12fl/+ Amhr2-Cre) were subfertile, while mice homozygous for Med12 deficiency in granulosa cells and uterus (Med12fl/fl Amhr2-Cre) were infertile. Morphological and histological analysis of the Med12fl/fl Amhr2-Cre reproductive tract revealed atrophic uteri and hyperchromatic granulosa cells with disrupted expression of Lhcgr, Esr1, and Esr2. Med12fl/fl Amhr2-Cre mice estrous cycle was disrupted, and serum analysis showed blunted rise in estradiol in response to pregnant mare serum gonadotropin. Uterine atrophy was partially rescued by exogenous steroid supplementation with dysregulation of Notch1 and Smo expression in steroid supplemented Med12fl/fl Amhr2-Cre uteri, indicating intrinsic uterine defects. Oocyte-specific ablation of Med12 caused infertility without disrupting normal folliculogenesis and ovulation, consistent with maternal effects of Med12 in early embryo development. These results show the critical importance of Med12 in reproductive tract development and that Med12 loss of function does not cause tumorigenesis in reproductive tissues.

Gametogenesis: A journey from inception to conception

Gametogenesis, the process of forming mature germ cells, is an integral part of both an individual's and a species' health and well-being. This chapter focuses on critical male and female genetic and epigenetic processes underlying normal gamete formation through their differentiation to fertilization. Finally, we explore how knowledge gained from this field has contributed to progress in areas with great clinical promise, such as in vitro gametogenesis.

Cloning, tissue distribution and methylation analyses of Lhx9 in Chinese tongue sole (Cynoglossus semilaevis)

Lhx9 is a LIM-homeodomain protein related to gonad development and sex reversal. In this study, we cloned and characterized CS-Lhx9 in the gonads of the Chinese tongue sole (Cynoglossus semilaevis). The full-length cDNA of CS-Lhx9 was 3123 bp, including an ORF of 1149 bp encoding 383 amino acids which contains two LIM domains and a homeobox domain. CS-Lhx9 transcripts were primarily observed in the testis of male and neomale at 1 yah, but nearly undetectable in the ovary. During the development of gonad, CS-Lhx9 exhibited an increasing trend and appeared to reach its peak value of expression in testis at 1 yah. In situ hybridization was performed in male and neomale gonads at 210 dah and 1 yah. The results showed strong CS-Lhx9 signals in the spermatids and spermatozoa (germ cells). Methylation level of CS-Lhx9 promoter was higher in female and lower in male and neomale gonads, showing a negative correlation with CS-Lhx9 expression.

Biomechanics and mechanical signaling in the ovary: a systematic review

PURPOSE

Mammalian oogenesis and folliculogenesis share a dynamic connection that is critical for gamete development. For maintenance of quiescence or follicular activation, follicles must respond to soluble signals (growth factors and hormones) and physical stresses, including mechanical forces and osmotic shifts. Likewise, mechanical processes are involved in cortical tension and cell polarity in oocytes. Our objective was to examine the contribution and influence of biomechanical signaling in female mammalian gametogenesis.

METHODS

We performed a systematic review to assess and summarize the effects of mechanical signaling and mechanotransduction in oocyte maturation and folliculogenesis and to explore possible clinical applications. The review identified 2568 publications of which 122 met the inclusion criteria.

RESULTS

The integration of mechanical and cell signaling pathways in gametogenesis is complex. Follicular activation or quiescence are influenced by mechanical signaling through the Hippo and Akt pathways involving the yes-associated protein (YAP), transcriptional coactivator with PDZ-binding motif (TAZ), phosphatase and tensin homolog deleted from chromosome 10 (PTEN) gene, the mammalian target of rapamycin (mTOR), and forkhead box O3 (FOXO3) gene.

CONCLUSIONS

There is overwhelming evidence that mechanical signaling plays a crucial role in development of the ovary, follicle, and oocyte throughout gametogenesis. Emerging data suggest the complexities of mechanotransduction and the biomechanics of oocytes and follicles are integral to understanding of primary ovarian insufficiency, ovarian aging, polycystic ovary syndrome, and applications of fertility preservation.