Molecular mechanisms underlying the activation of mammalian primordial follicles

Effects of chemical in vitro activation versus fragmentation on human ovarian tissue and follicle growth in culture

STUDY QUESTION

What is the effect of the chemical in vitro activation (cIVA) protocol compared with fragmentation only (Frag, also known as mechanical IVA) on gene expression, follicle activation and growth in human ovarian tissue in vitro?

SUMMARY ANSWER

Although histological assessment shows that cIVA significantly increases follicle survival and growth compared to Frag, both protocols stimulate extensive and nearly identical transcriptomic changes in cultured tissue compared to freshly collected ovarian tissue, including marked changes in energy metabolism and inflammatory responses.

WHAT IS KNOWN ALREADY

Treatments based on cIVA of the phosphatase and tensin homolog (PTEN)-phosphatidylinositol 3-kinase (PI3K) pathway in ovarian tissue followed by auto-transplantation have been administered to patients with refractory premature ovarian insufficiency (POI) and resulted in live births. However, comparable effects with mere tissue fragmentation have been shown, questioning the added value of chemical stimulation that could potentially activate oncogenic responses.

STUDY DESIGN SIZE DURATION

Fifty-nine ovarian cortical biopsies were obtained from consenting women undergoing elective caesarean section (C-section). The samples were fragmented for culture studies. Half of the fragments were exposed to bpV (HOpic)+740Y-P (Frag+cIVA group) during the first 24 h of culture, while the other half were cultured with medium only (Frag group). Subsequently, both groups were cultured with medium only for an additional 6 days. Tissue and media samples were collected for histological, transcriptomic, steroid hormone, and cytokine/chemokine analyses at various time points.

PARTICIPANTS/MATERIALS SETTING METHODS

Effects on follicles were evaluated by counting and scoring serial sections stained with hematoxylin and eosin before and after the 7-day culture. Follicle function was assessed by quantification of steroids by ultra-performance liquid chromatography tandem-mass spectrometry at different time points. Cytokines and chemokines were measured by multiplex assay. Transcriptomic effects were measured by RNA-sequencing (RNA-seq) of the tissue after the initial 24-h culture. Selected differentially expressed genes (DEGs) were validated by quantitative PCR and immunofluorescence in cultured ovarian tissue as well as in KGN cell (human ovarian granulosa-like tumor cell line) culture experiments.

MAIN RESULTS AND THE ROLE OF CHANCE

Compared to the Frag group, the Frag+cIVA group exhibited a significantly higher follicle survival rate, increased numbers of secondary follicles, and larger follicle sizes. Additionally, the tissue in the Frag+cIVA group produced less dehydroepiandrosterone compared to Frag. Cytokine measurement showed a strong inflammatory response at the start of the culture in both groups. The RNA-seq data revealed modest differences between the Frag+cIVA and Frag groups, with only 164 DEGs identified using a relaxed cut-off of false discovery rate (FDR) <0.1. Apart from the expected PI3K-protein kinase B (Akt) pathway, cIVA also regulated pathways related to hypoxia, cytokines, and inflammation. In comparison to freshly collected ovarian tissue, gene expression in general was markedly affected in both the Frag+cIVA and Frag groups, with a total of 3119 and 2900 DEGs identified (FDR < 0.001), respectively. The top enriched gene sets in both groups included several pathways known to modulate follicle growth such as mammalian target of rapamycin (mTOR)C1 signaling. Significant changes compared to fresh tissue were also observed in the expression of genes encoding for steroidogenesis enzymes and classical granulosa cell markers in both groups. Intriguingly, we discovered a profound upregulation of genes related to glycolysis and its upstream regulator in both Frag and Frag+cIVA groups, and these changes were further boosted by the cIVA treatment. Cell culture experiments confirmed glycolysis-related genes as direct targets of the cIVA drugs. In conclusion, cIVA enhances follicle growth, as expected, but the mechanisms may be more complex than PI3K-Akt-mTOR alone, and the impact on function and quality of the follicles after the culture period remains an open question.

LARGE SCALE DATA

Data were deposited in the GEO data base, accession number GSE234765. The code for sequencing analysis can be found in https://github.com/tialiv/IVA_project.

LIMITATIONS REASONS FOR CAUTION

Similar to the published IVA protocols, the first steps in our study were performed in an in vitro culture model where the ovarian tissue was isolated from the regulation of hypothalamic-pituitary-ovarian axis. Further in vivo experiments will be needed, for example in xeno-transplantation models, to explore the long-term impacts of the discovered effects. The tissue collected from patients undergoing C-section may not be comparable to tissue of patients with POI.

WIDER IMPLICATIONS OF THE FINDINGS

The general impact of fragmentation and short (24 h) in vitro culture on gene expression in ovarian tissue far exceeded the effects of cIVA. Yet, follicle growth was stimulated by cIVA, which may suggest effects on specific cell populations that may be diluted in bulk RNA-seq. Nevertheless, we confirmed the impact of cIVA on glycolysis using a cell culture model, suggesting impacts on cellular signaling beyond the PI3K pathway. The profound changes in inflammation and glycolysis following fragmentation and culture could contribute to follicle activation and loss in ovarian tissue culture, as well as in clinical applications, such as fertility preservation by ovarian tissue auto-transplantation.

STUDY FUNDING/COMPETING INTERESTS

This study was funded by research grants from European Union's Horizon 2020 Research and Innovation Programme (Project ERIN No. 952516, FREIA No. 825100), Swedish Research Council VR (2020-02132), StratRegen funding from Karolinska Institutet, KI-China Scholarship Council (CSC) Programme and the Natural Science Foundation of Hunan (2022JJ40782). International Iberian Nanotechnology Laboratory Research was funded by the European Union's H2020 Project Sinfonia (857253) and SbDToolBox (NORTE-01-0145-FEDER-000047), supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund. No competing interests are declared.

Research progress on Sirtuins (SIRTs) family modulators

Sirtuins (SIRTs) represent a class of nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylases that exert a crucial role in cellular signal transduction and various biological processes. The mammalian sirtuins family encompasses SIRT1 to SIRT7, exhibiting therapeutic potential in counteracting cellular aging, modulating metabolism, responding to oxidative stress, inhibiting tumors, and improving cellular microenvironment. These enzymes are intricately linked to the occurrence and treatment of diverse pathological conditions, including cancer, autoimmune diseases, and cardiovascular disorders. Given the significance of histone modification in gene expression and chromatin structure, maintaining the equilibrium of the sirtuins family is imperative for disease prevention and health restoration. Mounting evidence suggests that modulators of SIRTs play a crucial role in treating various diseases and maintaining physiological balance. This review delves into the molecular structure and regulatory functions of the sirtuins family, reviews the classification and historical evolution of SIRTs modulators, offers a systematic overview of existing SIRTs modulation strategies, and elucidates the regulatory mechanisms of SIRTs modulators (agonists and inhibitors) and their clinical applications. The article concludes by summarizing the challenges encountered in SIRTs modulator research and offering insights into future research directions.

ERβ Regulation of Indian Hedgehog Expression in the First Wave of Ovarian Follicles

Increased activation of ovarian primordial follicles in Erβ knockout (ErβKO) rats becomes evident as early as postnatal day 8.5. To identify the ERβ-regulated genes that may control ovarian primordial follicle activation, we analyzed the transcriptome profiles of ErβKO rat ovaries collected on postnatal days 4.5, 6.5, and 8.5. Compared to wildtype ovaries, ErβKO ovaries displayed dramatic downregulation of Indian hedgehog (Ihh) expression. IHH-regulated genes, including Hhip, Gli1, and Ptch1, were also downregulated in ErβKO ovaries. This was associated with a downregulation of steroidogenic enzymes Cyp11a1, Cyp19a1, and Hsd17b1. The expression of Ihh remained very low in ErβKO ovaries despite the high levels of Gdf9 and Bmp15, which are known upregulators of Ihh expression in the granulosa cells of activated ovarian follicles. Strikingly, the downregulation of the Ihh gene in ErβKO ovaries began to disappear on postnatal day 16.5 and recovered on postnatal day 21.5. In rat ovaries, the first wave of primordial follicles is rapidly activated after their formation, whereas the second wave of primordial follicles remains dormant in the ovarian cortex and slowly starts activating after postnatal day 12.5. We localized the expression of Ihh mRNA in postnatal day 8.5 wildtype rat ovaries but not in the age-matched ErβKO ovaries. In postnatal day 21.5 ErβKO rat ovaries, we detected Ihh mRNA mainly in the activated follicles in the ovaries' peripheral regions. Our findings indicate that the expression of Ihh in the granulosa cells of the activated first wave of ovarian follicles depends on ERβ.

Differential expression of follicular fluid exosomal microRNA in women with diminished ovarian reserve

PURPOSE

Decreased ovarian reserve function is mainly characterized by female endocrine disorders and fertility decline. Follicular fluid (FF) exosomal microRNAs (miRNAs) have been shown to regulate the function of granulosa cells (GCs). The present study explored differentially expressed miRNAs (DEmiRNAs) in patients with diminished ovarian reserve (DOR).

METHODS

FF was collected from 12 DOR patients and 12 healthy controls. DEmiRNAs between the two groups were identified and analyzed using high-throughput sequencing technology and validated by real-time quantitative PCR (RT-qPCR).

RESULTS

A total of 592 DEmiRNAs were identified using high-throughput miRNA sequencing, of which 213 were significantly upregulated and 379 were significantly downregulated. The sequencing results were further validated by RT-qPCR. These DEmiRNA target genes were mainly involved in the cancer pathway, phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway, regulation of actin cytoskeleton signaling pathway, and biological processes related to protein binding, nucleoplasm, cytoplasm, and cell membrane.

CONCLUSION

FF exosomal miRNAs are significantly differentially expressed in DOR patients versus non-DOR patients, underscoring their crucial role in regulating the pathogenesis of DOR.

Anti-Müllerian hormone induces autophagy to preserve the primordial follicle pool in mice

The reserve pool of primordial follicles (PMFs) is finely regulated by molecules implicated in follicular growth or PMF survival. Anti-Müllerian hormone (AMH), produced by granulosa cells of growing follicles, is known for its inhibitory role in the initiation of PMF growth. We observed in a recent in vivo study that injection of AMH into mice seemed to induce an activation of autophagy. Furthermore, injection of AMH into mice activates the transcription factor FOXO3A which is also known for its implication in autophagy regulation. Many studies highlighted the key role of autophagy in the ovary at different stages of folliculogenesis, particularly in PMF survival. Through an in vitro approach with organotypic cultures of prepubertal mouse ovaries, treated or not with AMH, we aimed to understand the link among AMH, autophagy, and FOXO3A transcription factor. Autophagy and FOXO3A phosphorylation were analyzed by western blot. The expression of genes involved in autophagy was quantified by RT-qPCR. In our in vitro model, we confirmed the decrease in FOXO3A phosphorylation and the induction of autophagy in ovaries incubated with AMH. AMH also induces the expression of genes involved in autophagy. Interestingly, most of these genes are known to be FOXO3A target genes. In conclusion, we have identified a new role for AMH, namely the induction of autophagy, probably through FOXO3A activation. Thus, AMH protects the ovarian reserve not only by inhibiting the growth of PMFs but also by enabling their survival through activation of autophagy.

BCAS2 regulates oocyte meiotic prophase I by participating in mRNA alternative splicing

Oocyte meiotic prophase I (MI) is an important event in female reproduction. Breast cancer amplified sequence 2 (BCAS2) is a component of the spliceosome. Previous reports have shown that BCAS2 is critical in male germ cell meiosis, oocyte development, and early embryo genome integrity. However, the role of BCAS2 in oocyte meiosis has not been reported. We used Stra8-GFPCre mice to knock out Bcas2 in oocytes during the pachytene phase. The results of fertility tests showed that Bcas2 conditional knockout (cKO) in oocytes results in infertility in female mice. Morphological analysis showed that the number of primordial follicles in the ovaries of 2-month-old (M) mice was significantly reduced and that follicle development was blocked. Further analysis showed that the number of primordial follicles decreased and that follicle development was slowed in 7-day postpartum (dpp) ovaries. Moreover, primordial follicles undergo apoptosis, and DNA damage cannot be repaired in primary follicle oocytes. Meiosis was abnormal; some oocytes could not reach the diplotene stage, and more oocytes could not develop to the dictyotene stage. Alternative splicing (AS) analysis revealed abnormal AS of deleted in azoospermia like (Dazl) and diaphanous related formin 2 (Diaph2) oogenesis-related genes in cKO mouse ovaries, and the process of AS was involved by CDC5L and PRP19.

Overview of Gene Expression Dynamics during Human Oogenesis/Folliculogenesis

The oocyte transcriptome follows a tightly controlled dynamic that leads the oocyte to grow and mature. This succession of distinct transcriptional states determines embryonic development prior to embryonic genome activation. However, these oocyte maternal mRNA regulatory events have yet to be decoded in humans. We reanalyzed human single-oocyte RNA-seq datasets previously published in the literature to decrypt the transcriptomic reshuffles ensuring that the oocyte is fully competent. We applied trajectory analysis (pseudotime) and a meta-analysis and uncovered the fundamental transcriptomic requirements of the oocyte at any moment of oogenesis until reaching the metaphase II stage (MII). We identified a bunch of genes showing significant variation in expression from primordial-to-antral follicle oocyte development and characterized their temporal regulation and their biological relevance. We also revealed the selective regulation of specific transcripts during the germinal vesicle-to-MII transition. Transcripts associated with energy production and mitochondrial functions were extensively downregulated, while those associated with cytoplasmic translation, histone modification, meiotic processes, and RNA processes were conserved. From the genes identified in this study, some appeared as sensitive to environmental factors such as maternal age, polycystic ovary syndrome, cryoconservation, and in vitro maturation. In the future, the atlas of transcriptomic changes described in this study will enable more precise identification of the transcripts responsible for follicular growth and oocyte maturation failures.

Impact of human ovarian tissue manipulation on follicles: evidence of a potential first wave of follicle activation during fertility preservation procedures

PURPOSE

The aim of this study was to investigate the impact of processing human ovarian tissue on follicle activation dynamics.

METHODS

Fresh ovarian tissue was retrieved from 9 women undergoing laparoscopic surgery for benign conditions. Biopsies from each patient were divided into 3 fragments, the first of which was immediately fixed in the operating room (T0) and the second and third just after processing at 25 (T25) and (T90) 90 min. To evaluate follicle activation, markers of the PI3K and Hippo signaling pathways were immunolabeled at each time point, targeting phospho-Akt (p-Akt) by immunohistochemistry and yes-associated protein (YAP) cellular localization in the granulosa cell layer by immunofluorescence.

RESULTS

Four hundred forty primordial follicles were evaluated for p-Akt and 420 for YAP. Significantly stronger p-Akt expression was observed at T25 (23.01 ± 13.45%; p=0.04) and T90 (38.99 ± 25.21%; p<0.001) than at T0 (2.72 ± 3.35%). A significant nucleus-to-cytoplasm shift in YAP was detected at T25 (1.21 ± 0.25; p=0.015 compared to T0 (0.95 ± 0.09), while T90 (1.10 ± 0.16) values were similar to T25.

CONCLUSION

Our data prove that ovarian tissue manipulation significantly impacts follicle dynamics by stimulating the PI3K and Hippo signaling pathways involved in primordial follicle activation. Further experimental evidence must nevertheless be gathered to understand and gain control of follicle activation mechanisms in non-physiological conditions (like ovarian tissue manipulation), in order to optimize fertility preservation and restoration strategies.

Preservation of fertility in female and male prepubertal patients diagnosed with cancer

Over the past two decades, the importance of fertility preservation has grown not only in the realm of medical and clinical patient care, but also in the field of basic and applied research in human reproduction. With advancements in cancer treatments resulting in higher rates of patient survival, it is crucial to consider the quality of life post-cure. Therefore, fertility preservation must be taken into account prior to antitumor treatments, as it can significantly impact a patient's future fertility. For postpubertal patients, gamete cryopreservation is the most commonly employed preservation strategy. However, for prepubertal patients, the situation is more intricate. Presently, ovarian tissue cryopreservation is the standard practice for prepubertal girls, but further scientific evidence is required in several aspects. Testicular tissue cryopreservation, on the other hand, is still experimental for prepubertal boys. The primary aim of this review is to address the strategies available for possible fertility preservation in prepubertal girls and boys, such as ovarian cryopreservation/transplantation, in vitro follicle culture and meiotic maturation, artificial ovary, transplantation of cryopreserved spermatogonia, and cryopreservation/grafting of immature testicular tissue and testicular organoids.

Differentially expressed transcripts study during pregnancy and postpartum anestrus of yak (Bos grunniens)

Background: Yak is the main livestock species in the plateau area, and its reproductive performance is low, usually two years or three years. A very few of yaks recover within a certain period of time after delivery and smoothly enter the next estrous cycle, while most of them enter the postpartum anestrus and show no estrus performance. However, the key biological factors and influencing mechanisms that cause postpartum anestrus in yaks are not clear. Objective: To study the expression of differential transcripts in ovaries of yak during pregnancy and postpartum anestrus. Methods: Each three yaks in pregnancy and anestrus under natural grazing conditions in Haiyan County, Qinghai Province were selected and slaughtered, and their ovaries were collected and sent to Biomarker Technologies. Oxford Nanopore Technologies single-molecule real-time electrical signal sequencing technology was used to perform full-length transcriptome sequencing. Astalavista software was used to identify the types of alternative splicing events in yak estrus and pregnancy, and TAPIS pipeline was used to identify alternative polyadenylation. Results: The results showed that there were 1751 differentially expressed transcripts (DETs) between pregnancy and anestrus in yak, of which 808 were upregulated and 943 were downregulated. GO analysis showed that the biological processes of DETs were mainly reproductive, reproductive and rhythmic processes. KEGG analysis showed that the DET cell junction-related adhesion junction protein (β-catenin) and amino terminal kinase (JNK) were involved in FAs (local adhesion). Phosphatidylinositol-3-kinase (PI3K) is involved in the PI3K/AKT/mTOR signaling pathway. Circadian rhythm output cycle failure (Clock) and brain and muscle tissue aromatic hydrocarbon receptor nuclear transporter-like protein 1 (Bmal1) are involved in circadian rhythm signaling pathway. Conclusion: This study found that β-catenin, JNK, PI3K, Clock and Bmal1 were closely related to postpartum anestrus in yak.

Stem-Cell-Derived Extracellular Vesicles: Unlocking New Possibilities for Treating Diminished Ovarian Reserve and Premature Ovarian Insufficiency

Despite advancements in assisted reproductive technology (ART), achieving successful pregnancy rates remains challenging. Diminished ovarian reserve and premature ovarian insufficiency hinder IVF success-about 20% of in vitro fertilization (IVF) patients face a poor prognosis due to a low response, leading to higher cancellations and reduced birth rates. In an attempt to address the issue of premature ovarian insufficiency (POI), we conducted systematic PubMed and Web of Science research, using keywords "stem cells", "extracellular vesicles", "premature ovarian insufficiency", "diminished ovarian reserve" and "exosomes". Amid the complex ovarian dynamics and challenges like POI, stem cell therapy and particularly the use of extracellular vesicles (EVs), a great potential is shown. EVs trigger paracrine mechanisms via microRNAs and bioactive molecules, suppressing apoptosis, stimulating angiogenesis and activating latent regenerative potential. Key microRNAs influence estrogen secretion, proliferation and apoptosis resistance. Extracellular vesicles present a lot of possibilities for treating infertility, and understanding their molecular mechanisms is crucial for maximizing EVs' therapeutic potential in addressing ovarian disorders and promoting reproductive health.

Overactivation or Apoptosis: Which Mechanisms Affect Chemotherapy-Induced Ovarian Reserve Depletion?

Dormant primordial follicles (PMF), which constitute the ovarian reserve, are recruited continuously into the cohort of growing follicles in the ovary throughout female reproductive life. Gonadotoxic chemotherapy was shown to diminish the ovarian reserve pool, to destroy growing follicle population, and to cause premature ovarian insufficiency (POI). Three primary mechanisms have been proposed to account for this chemotherapy-induced PMF depletion: either indirectly via over-recruitment of PMF, by stromal damage, or through direct toxicity effects on PMF. Preventative pharmacological agents intervening in these ovotoxic mechanisms may be ideal candidates for fertility preservation (FP). This manuscript reviews the mechanisms that disrupt follicle dormancy causing depletion of the ovarian reserve. It describes the most widely studied experimental inhibitors that have been deployed in attempts to counteract these affects and prevent follicle depletion.

PTEN inhibitor and kit ligand increase in vitro activation and survival of primordial follicles in alpaca

In mammals, activation of primordial follicles to primary follicle is a progressive and highly regulated process. There is evidence in mice that phosphatase and tensin homologue deleted on Chromosome 10 (PTEN) silencing is an important negative regulator of phosphatidylinositol 3-kinase (PI3K), which initiates activation of dormant follicles. The objective of the study was to evaluate the effect of the addition of PTEN inhibitor (bpV(HOpic)) (10 μM) and/or Kit Ligand (KL) (100 ng/mL) on the in vitro activation and survival of alpaca primordial follicles. Ovarian cortical fragments from 11 adult alpacas were cultured for 24 h in tissue culture medium (α-MEM+ ) supplemented with KL and bpV or the association of both. Subsequently, each sample was processed by classical histology and follicular counting and classification were performed. The results obtained show a reduction (p < 0.05) of primordial follicles in more than 50% in follicular tissue cultured in vitro in α-MEM+ or supplemented with bpV and/or KL versus the control (not cultured). Further, >25% increase in primary follicles in follicular tissue cultured in vitro in α-MEM+ or supplemented with KL and/or bpV versus control. However, the follicular survival rate showed a decrease of 20% in the cultured tissues, except for the α-MEM+ supplemented with KL and bpV. In conclusion, supplementation of bpV (HOpic) (10 μM) and KL (100 ng/mL) increased the activation in vitro of primordial follicles and survival after in vitro culture of alpaca ovarian tissue.

Chemotherapy-induced ovarian damage and protective strategies

More than 9.2 million women worldwide suffer from cancer, and about 5% of them are at reproductive age. Chemotherapy-induced impairment of fertility affects the quality of life of these women. Several chemotherapeutic agents have been proven to cause apoptosis and autophagy by inducing DNA damage and cellular stress. Injuries to the ovarian stroma and micro-vessel network are also considered as pivotal factors resulting in ovarian dysfunction induced by chemotherapeutic agents. Primordial follicle pool over-activation may also be the mechanism inducing damage to the ovarian reserve. Although many studies have explored the mechanisms involved in chemotherapy-induced reproductive toxicity, the exact molecular mechanisms have not been elucidated. It is essential to understand the mechanisms involved in ovarian damage, in order to develop potential protective treatments to preserve fertility. In this article, we reviewed the current knowledge on the mechanism of chemotherapy-induced ovarian damage and possible protective strategies that prevent the ovary from such damages.

The transcriptome reveals the molecular regulatory network of primordial follicle depletion in obese mice

OBJECTIVE

To explore the dynamic transcriptional regulatory network of primordial follicle fate in obese mice to elucidate the potential mechanism of primordial follicle depletion.

DESIGN

Experimental study and transcriptomic analysis.

ANIMALS

Healthy (n=15) and obese (n=15) female mice.

INTERVENTIONS

Six-week-old CD-1 mice were divided into healthy and high-fat diet groups and fed continuously for 12 weeks. The diet of healthy mice contained 10% fat. The diet of high-fat mice contained 60% fat.

MAIN OUTCOME MEASURES

Primordial to primary follicle transition rate, gene expression changes, enriched Kyoto Encyclopedia of Genes and Genomes pathways, and ferroptosis.

RESULTS

Primordial follicle depletion was increased in the ovaries of obese mice. We found that deposited fat around primordial and primary follicles of obese mice was higher than that for healthy mice. The proliferation of granulosa cells around primary follicles was increased in obese mice. In addition, we uncovered specific gene signatures associated with the primordial to primary follicle transition (PPT) in obese mice using laser capture microdissection RNA sequencing analysis. Gene set enrichment analysis indicated that ferroptosis, cell oxidation, vascular endothelial growth factor, and mammalian target of rapamycin signaling were increased significantly in the primordial follicles of obese mice. Notably, the ferritin, acyl CoA synthetase long-chain family member 4, and solid carrier family 7 member 11 associated proteins of the ferroptosis signaling pathway were significantly increased in the PPT phase of obese mice.

CONCLUSION

Our work suggests that ferroptosis is a key pathway activated within immature ovarian follicles in the context of obesity and that the process may be involved in the physiological regulation of the PPT as well.

FOXO3 and PTEN expression in the ovary of girls with extra-gonadal cancer with or without chemotherapy treatment prior to cryopreservation

BACKGROUND

FOXO3/pFOXO3 and PTEN expression is known to regulate the dormancy/activation of ovarian primordial follicles. How chemotherapy could influence the expression of FOXO3 and PTEN in pre- and post-menarcheal girls with extra-gonadal cancer remains unexplored.

METHODS

Ovarian samples were collected from 27 girls suffering from extra-gonadal cancer. Of these, 8 patients had received chemotherapy before the time of sample collection. Ovarian tissue collected at the time of surgery was fixed in 10% formaldehyde for FOXO3/pFOXO3 and PTEN immunohistochemistry or immunofluorescence, or stored at -80 °C for Western blot, or preserved in RNA later for RT-PCR.

RESULTS

PTEN was detected in a limited number of primordial follicle-enclosed oocytes in approximately fifty percent of the patients, regardless of whether they had received anti-cancer treatment or not. However, there was a significant decrease in PTEN detection in patients who underwent chemotherapy treatment prior to the retrieval of the sample. Both primordial follicle-enclosed oocytes that expressed FOXO3 and those that did not were identified in patients who were treated with chemotherapy and those who were not. FOXO3-positive primordial follicles exhibited either nuclear FOXO3 localization or cytoplasmic pFOXO3 localization. Furthermore, transitional primordial follicles that expressed nuclear FOXO3 and cytoplasmic pFOXO3 were also observed. Primary follicle-enclosed oocytes displayed cytoplasmic pFOXO3 localization, whereas in more advanced stages of folliculogenesis, the expression moved to the somatic stratum. No significant statistical differences were identified in the detection of FOXO3 and pFOXO3 in patients who had or had not received chemotherapy prior to sample collection.

CONCLUSION

Primordial follicles expressing and not expressing FOXO3 were equally present in both the ovaries of patients who underwent chemotherapy and those who did not. The expression of FOXO3 remained unaltered in response to chemotherapy treatment. Notably, the detection of PTEN was significantly reduced in the treated patients, thereby warranting in-depth investigation, given the limited sample size examined in the present study.

PARP1-catalyzed PARylation of YY1 mediates endoplasmic reticulum stress in granulosa cells to determine primordial follicle activation

Although only a small number of primordial follicles are known to be selectively activated during female reproductive cycles, the mechanisms that trigger this recruitment remain largely uncharacterized. Misregulated activation of primordial follicles may lead to the exhaustion of the non-renewable pool of primordial follicles, resulting in premature ovarian insufficiency. Here, we found that poly(ADP-ribose) polymerase 1 (PARP1) enzymatic activity in the surrounding granulosa cells (GCs) in follicles determines the subpopulation of the dormant primordial follicles to be awakened. Conversely, specifically inhibiting PARP1 in oocytes in an in vitro mouse follicle reconstitution model does not affect primordial follicle activation. Further analysis revealed that PARP1-catalyzed transcription factor YY1 PARylation at Y185 residue facilitates YY1 occupancy at Grp78 promoter, a key molecular chaperone of endoplasmic reticulum stress (ERS), and promotes Grp78 transcription in GCs, which is required for GCs maintaining proper ERS during primordial follicle activation. Inhibiting PARP1 prevents the loss of primordial follicle pool by attenuating the excessive ERS in GCs under fetal bisphenol A exposure. Together, we demonstrate that PARP1 in GCs acts as a pivotal modulator to determine the fate of the primordial follicles and may represent a novel therapeutic target for the retention of primordial follicle pool in females.

Rescue of follicle development after oocyte-induced ovary dysfunction and infertility in a model of POI

The mechanisms and aetiology underlying the development of premature ovarian insufficiency (POI) are poorly understood. However, the oocyte clearly has a role as demonstrated by the Double Mutant (DM) mouse model where ovarian dysfunction (6 weeks) is followed by POI (3 months) due to oocyte-specific deletion of complex and hybrid N- and O-glycans. The ovaries of DM mice contain more primary follicles (3a stage) accompanied by fewer developing follicles, indicating a block in follicle development. To investigate this block, we first analysed early follicle development in postnatal (8-day), pre-pubertal (3-week) and post-pubertal (6-week and 3-month) DM (C1galt1 F/F Mgat1 F/F:ZP3Cre) and Control (C1galt1 F/F Mgat1 F/F) mice. Second, we investigated if transplantation of DM ovaries into a "normal" endocrine environment would restore follicle development. Third, we determined if replacing DM ovarian somatic cells would rescue development of DM oocytes. At 3-week, DM primary 3a follicles contain large oocytes accompanied by early development of a second GC layer and increased GC proliferation. At 6-week, DM primary 3a follicles contain abnormally large oocytes, accompanied with decreased GC proliferation. Transplantation of DM ovaries into a 'normal' endocrine environment did not restore normal follicle development. However, replacing somatic cells by generating reaggregated ovaries (ROs) did enable follicle development to progress and thus highlighted intra-ovarian factors were responsible for the onset of POI in DM females. Thus, these studies demonstrate oocyte-initiated altered communication between GCs and oocytes results in abnormal primary follicles which fail to progress and leads to POI.

Integrated bioinformatics analysis elucidates granulosa cell whole-transcriptome landscape of PCOS in China

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common reproductive, neuroendocrine, and metabolic disorder in women of reproductive age that affects up to 5-10% of women of reproductive age. The aetiology of follicle development arrest and critical issues regarding the abnormal follicular development in PCOS remain unclear. The present study aims to systematically evaluate granulosa cell whole-transcriptome sequencing data to gain more insights into the transcriptomic landscape and molecular mechanism of PCOS in China.

METHODS

In the present study, the microarray datasets GSE138518, GSE168404, GSE193123, GSE138572, GSE95728, and GSE145296 were downloaded from the Gene Expression Omnibus (GEO) database. Subsequently, differential expression analysis was performed on the PCOS and control groups, followed by functional interaction prediction analysis to investigate gene-regulatory circuits in PCOS. Finally, hub genes and their associated ncRNAs were validated by qPCR in human-luteinized granulosa (hGL) cells and were correlated with the clinical characteristics of the patients.

RESULTS

A total of 200 differentially expressed mRNAs, 3 differentially expressed miRNAs, 52 differentially expressed lncRNAs, and 66 differentially expressed circRNAs were found in PCOS samples compared with controls. GO and KEGG enrichment analyses indicated that the DEGs were mostly enriched in phospholipid metabolic processes, steroid biosynthesis and inflammation related pathways. In addition, the upregulated miRNA hsa-miR-205-5p was significantly enriched in the ceRNA network, and two hub genes, MVD and PNPLA3, were regulated by hsa-miR-205-5p, which means that hsa-miR-205-5p may play a fundamental role in the pathogenesis of PCOS. We also found that MVD and PNPLA3 were related to metabolic processes and ovarian steroidogenesis, which may be the cause of the follicle development arrest in PCOS patients.

CONCLUSIONS

In summary, we systematically constructed a ceRNA network depicting the interactions between the ncRNAs and the hub genes in PCOS and control subjects and correlated the hub genes with the clinical characteristics of the patients, which provides valuable insights into the granulosa cell whole-transcriptome landscape of PCOS in China.

Scrambled eggs-Negative impacts of heat stress and chemical exposures on ovarian function in swine

Exposure to environmental toxicants and hyperthermia can hamper reproduction in female mammals including swine. Phenotypic manifestations include poor quality oocytes, endocrine disruption, infertility, lengthened time to conceive, pregnancy loss, and embryonic defects. The ovary has the capacity for toxicant biotransformation, regulated in part by the phosphatidylinositol-3 kinase signaling pathway. The impacts of exposure to mycotoxins and pesticides on swine reproduction and the potential for an emerging chemical class of concern, the per- and polyfluoroalkylated substances, to hamper porcine reproduction are reviewed. The negative impairments of heat stress (HS) on swine reproductive outcomes are also described and the cumulative effect of environmental exposures, such as HS, when present in conjunction with a toxicant is considered.

Inhibition of phosphodiesterase PDE8B reduces activation of primordial follicles in mouse ovaries

In the ovaries, cyclic adenosine 3',5'-monophosphate (cAMP) is a second messenger supporting the generation of steroids. Phosphodiesterases (PDEs) are regulators of intracellular cAMP, and therefore, potential regulators of ovarian function. Interestingly, the family of PDE genes are differentially expressed in human oocytes and granulosa cells from primordial and primary follicles, suggesting diverse roles. In this study, we addressed the functions of PDE3B and PDE8B in primordial follicle regulation using inhibitors of PDE3B and PDE8B in murine ovary primary in vitro cultures. Inhibition of PDE8B in ovarian cultures prevented primordial follicle activation, while inhibition of PDE3B had no effect on follicle distribution in the ovary, under the tested conditions. As cAMP levels may increase steroid levels, we assessed the protein levels of the steroidogenic acute regulatory protein (StAR) and aromatase enzymes, and found that inhibition of PDE3B reduced StAR protein levels, whereas inhibition of PDE8 did not alter StAR expression in our murine ovary culture system conditions. Our results showed that ketotifen-induced inhibition of PDE8B can decrease primordial follicle activation, whereas we observed no effect of follicle distribution, when PDE3B was inhibited. Expression of the StaR enzyme was not altered when PDE8B was inhibited, which might reflect not sufficient inhibition by ketotifen to induce StAR alterations, or redundant mechanisms.

Recombinant anti-Mullerian hormone treatment attenuates primordial follicle loss after ovarian cryopreservation and transplantation

PURPOSE

The foremost drawback of ovarian tissue cryopreservation and re-transplantation (OTCT) technique is the rapid loss of the primordial follicle (PF) pool. In recent studies, we have demonstrated that post-transplantation burnout of the PFs occurs due to the altered expression of the activatory and inhibitory proteins that control PF reserve, and rapamycin prevented it.

METHODS

Here, we investigated whether anti-Mullerian hormone administration in the bilateral oophorectomy and transplantation group and internal AMH in the unilateral oophorectomy and transplantation group protect follicle reserve by regulating the expression of the molecules that control follicle growth after OTCT in mice.

RESULTS

After 14 days of OTCT, PF reserve is significantly reduced in both unilateral oophorectomy and transplantation and bilateral oophorectomy and transplantation groups, while anti-Mullerian hormone treatment attenuates PF loss after bilateral oophorectomy and transplantation. The expression of KitL, Bmp-15, and p27 decreased after unilateral oophorectomy and transplantation and bilateral oophorectomy and transplantation, yet recombinant anti-Mullerian hormone treatment did not restore the expression of these proteins in the BLO-T group.

CONCLUSION

Exogenous recombinant anti-Mullerian hormone administration in the BLO-T group preserved the expressions of Tsc1 and Gdf-9 in PF and p-s6k and Gdf-9 in growing follicles after OTCT. Nonetheless, recombinant anti-Mullerian hormone administration did not affect granulosa cell proliferation and death rates in the growing follicles. These findings suggest a novel hormonal replacement strategy for fertility preservation by restoring anti-Mullerian hormone to regulate Tsc1 and p-s6k, thereby linking this hormone with the mTOR pathway and Gdf-9 signaling.

Ovarian rescue in women with premature ovarian insufficiency: facts and fiction

The ovary has a comparatively short functional lifespan compared with other organs, and genetic and pathological injuries can further shorten its functional life. Thus, preserving ovarian function should be considered in the context of women with threats to ovarian reserve, such as ageing, premature ovarian insufficiency (POI) and diminished ovarian reserve (DOR). Indeed, one-third of women with POI retain resting follicles that can be reactivated to produce competent oocytes, as proved by the in-vitro activation of dormant follicles. This paper discusses mechanisms and clinical data relating to new therapeutic strategies using ovarian fragmentation, stem cells or platelet-rich plasma to regain ovarian function in women of older age (>38 years) or with POI or DOR. Follicle reactivation techniques show promising experimental outcomes and have been successful in some cases, when POI is established or DOR diagnosed; however, there is scarce clinical evidence to warrant their widespread clinical use. Beyond these contexts, also discussed is how new insights into the biological mechanisms governing follicular dynamics and oocyte competence may play a role in reversing ovarian damage, as no technique modifies oocyte quality. Additional studies should focus on increasing follicle number and quality. Finally, there is a small but important subgroup of women lacking residual follicles and requiring oocyte generation from stem cells.

The hypergonadotropic hypogonadism conundrum of classic galactosemia

BACKGROUND

Hypergonadotropic hypogonadism is a burdensome complication of classic galactosemia (CG), an inborn error of galactose metabolism that invariably affects female patients. Since its recognition in 1979, data have become available regarding the clinical spectrum, and the impact on fertility. Many women have been counseled for infertility and the majority never try to conceive, yet spontaneous pregnancies can occur. Onset and mechanism of damage have not been elucidated, yet new insights at the molecular level are becoming available that might greatly benefit our understanding. Fertility preservation options have expanded, and treatments to mitigate this complication either by directly rescuing the metabolic defect or by influencing the cascade of events are being explored.

OBJECTIVE AND RATIONALE

The aims are to review: the clinical picture and the need to revisit the counseling paradigm; insights into the onset and mechanism of damage at the molecular level; and current treatments to mitigate ovarian damage.

SEARCH METHODS

In addition to the work on this topic by the authors, the PubMed database has been used to search for peer-reviewed articles and reviews using the following terms: 'classic galactosemia', 'gonadal damage', 'primary ovarian insufficiency', 'fertility', 'animal models' and 'fertility preservation' in combination with other keywords related to the subject area. All relevant publications until August 2022 have been critically evaluated and reviewed.

OUTCOMES

A diagnosis of premature ovarian insufficiency (POI) results in a significant psychological burden with a high incidence of depression and anxiety that urges adequate counseling at an early stage, appropriate treatment and timely discussion of fertility preservation options. The cause of POI in CG is unknown, but evidence exists of dysregulation in pathways crucial for folliculogenesis such as phosphatidylinositol 3-kinase/protein kinase B, inositol pathway, mitogen-activated protein kinase, insulin-like growth factor-1 and transforming growth factor-beta signaling. Recent findings from the GalT gene-trapped (GalTKO) mouse model suggest that early molecular changes in 1-month-old ovaries elicit an accelerated growth activation and burnout of primordial follicles, resembling the progressive ovarian failure seen in patients. Although data on safety and efficacy outcomes are still limited, ovarian tissue cryopreservation can be a fertility preservation option. Treatments to overcome the genetic defect, for example nucleic acid therapy such as mRNA or gene therapy, or that influence the cascade of events are being explored at the (pre-)clinical level.

WIDER IMPLICATIONS

Elucidation of the molecular pathways underlying POI of any origin can greatly advance our insight into the pathogenesis and open new treatment avenues. Alterations in these molecular pathways might serve as markers of disease progression and efficiency of new treatment options.

Exploration the role of INHBA in Hu sheep granulosa cells using RNA-Seq

Activin/inhibin is an important factor for the fecundity of Hu sheep, and it is involved in follicular development in ovaries. Inhibin subunit beta A (INHBA) participates in the synthesis of activin A and inhibin A. In this study, we also noted a positive correlation between INHBA level and the secretion of both activin A and inhibin A in culture medium. Nevertheless, both knockdown and overexpression of INHBA downregulated the expression of Inhibin Subunit Alpha (INHA). Based on RNA-Sequencing, we further examined the effect and molecular mechanism of INHBA knockdown in GCs on mRNA expression. A total of 1,687 differentially expressed genes (DEGs) were identified (Fold change ≥ 2; False-discovory-rates (FDR) ≤ 0.01), of which 602 genes were upregulated and 1,087 genes were downregulated in the INHBA interference group compared with the control groups. Gene Ontology (GO) enrichment indicated that these DEGs were mainly involved in the regulation of cell cycle, protein serine/threonine kinase activity, and actin cytoskeleton reorganization. Moreover, DEGs were significantly enriched in 40 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, including P53, progesterone-mediated oocyte maturation, and PI3K-AKT signaling pathways. We also noted a positive correlation between INHBA level and many PI3K/Akt/mTOR pathway-related genes at the gene or/and protein expression. Overall, this study may contribute to a better understanding of the roles of INHBA on GCs of prolific sheep, as well as the molecular effect of low INHBA expression on GCs, clarifying some reproductive failures.

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.

Epigenetic regulation in premature ovarian failure: A literature review

Premature ovarian failure (POF), or premature ovarian insufficiency (POI), is a multifactorial and heterogeneous disease characterized by amenorrhea, decreased estrogen levels and increased female gonadotropin levels. The incidence of POF is increasing annually, and POF has become one of the main causes of infertility in women of childbearing age. The etiology and pathogenesis of POF are complex and have not yet been clearly elucidated. In addition to genetic factors, an increasing number of studies have revealed that epigenetic changes play an important role in the occurrence and development of POF. However, we found that very few papers have summarized epigenetic variations in POF, and a systematic analysis of this topic is therefore necessary. In this article, by reviewing and analyzing the most relevant literature in this research field, we expound on the relationship between DNA methylation, histone modification and non-coding RNA expression and the development of POF. We also analyzed how environmental factors affect POF through epigenetic modulation. Additionally, we discuss potential epigenetic biomarkers and epigenetic treatment targets for POF. We anticipate that our paper may provide new therapeutic clues for improving ovarian function and maintaining fertility in POF patients.

Impacts of endometrioma on ovarian aging from basic science to clinical management

Endometriosis is a common reproductive disorder characterized by the presence of endometrial implants outside of the uterus. It affects ~1 in 10 women of reproductive age. Endometriosis in the ovary, also known as endometrioma (OMA), is the most frequent implantation site and the leading cause of reproductive failure in affected women. Ovarian aging is one of the characteristic features of OMA, however its underlying mechanism yet to be determined. Accumulated evidence has shown that pelvic and local microenvironments in women with OMA are manifested, causing detrimental effects on ovarian development and functions. Whilst clinical associations of OMA with poor ovarian reserve, premature ovarian insufficiency, and early menopause have been reported. Moreover, surgical ablation, fenestration, and cystectomy of OMA can further damage the normal ovarian reservoir, and trigger hyperactivation of primordial follicles, subsequently resulting in the undesired deterioration of ovarian functions. Nevertheless, there is no effective treatment to delay or restore ovarian aging. This review comprehensively summarised the pathogenesis and study hypothesis of ovarian aging caused by OMA in order to propose potential therapeutic targets and interventions for future studies.

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.

VX-765 has a Protective Effect on Mice with Ovarian Injury Caused by Chemotherapy

BACKGROUND

Malignant tumors continue to remain a main global public health issue. In the past 40 years, due to strides made in multi-disciplinary comprehensive treatment schemes for patients suffering from malignant tumors, especially chemotherapy schemes, the survival rate has been greatly improved in such patients. This group can be expected to maintain their fertility or have restored endocrine function following successful malignant tumor treatment. Therefore, focusing on the ovarian damage caused by chemotherapy in women of childbearing age is vital in order to protect their fertility and improve their quality of life.

OBJECTIVE

This study attempted to evaluate whether VX-765 possesses an ovarian protective effect in ovarian injury induced by chemotherapy in the mice model.

METHODS

Female C57BL/6J mice were administered with VX-765 gavage once a day for 21 consecutive days. Use of cyclophosphamide (Cy) began one week after the last gavage administration of VX- 765. Detailed classification of follicles at various levels was then quantified in each group. Immunohistochemistry and Western blot analysis were then used in order to analyze the expression of key proteins (FOXO3a, mTOR, RPS6 and AKT) as well as their phosphorylation of the PI3K / PTEN / AKT pathways in the ovary. The concentrations of AMH were measured by ELISA.

RESULTS

The follicles at all levels of Cy treated mice were less than those of the normal group (P < 0.05). Meanwhile, mice treated with VX-765 prior to receiving Cy treatment had more primordial follicles (PMF) than mice treated with Cy alone (P < 0.05). In early growing follicles (EGF) and antral follicles (AF), no difference was observed among the experimental groups (P > 0.05), however, they were lower than those in the normal group (P < 0.05). In mice treated with continuous Cy, the total follicle number (TF) of mice combined with VX-765 (C-Cy-Vx765) was higher than that of mice without VX-765, and the TF of the two groups was lower than that of the normal group (P < 0.05). The value of PMF/TF in C-Cy-Vx765 group was significantly higher than that in the other three groups, while that of EGF/TF was significantly lower (P < 0.05). Immunohistochemical results showed that the phosphorylated forms of the main proteins of the PI3K / PTEN / AKT pathway were found to be more positive in Cy treated mice. The Western blot analysis showed that when Cy and VX-765 were cotreated, the increased levels of these phosphorylated proteins decreased compared with those treated with Cy alone. The AMH level of infancy Cy and VX-765 co-treated mice was higher than that of infancy normal mice (P < 0.05). After the mice grew to sexual maturity, the AMH level of Cy and VX- 765 co-treated mice was still higher than that of Cy treated mice (P < 0.05), and there was no significant difference with normal mice (P > 0.05).

CONCLUSION

VX-765 can maintain the level of AMH and inhibit the recruitment of PMF, thus protecting mice from Cy induced gonadotropic toxicity. Accordingly, VX-765 may play a protective role in mice with ovarian injury caused by chemotherapy.

In vivo promotion of primordial follicle activation by stem cell factor treatment in mice with premature ovarian insufficiency and advanced age

Dormant primordial follicles (PFs) are the most abundant reproductive resource in mammalian ovaries. With advances in the mechanism of study of the regulation of PF activation, PFs have been used to improve fertility in clinical practice. As a central controlling element of follicle activation signaling, the pre-granulosa cell-secreted stem cell factor (SCF; also known as KIT ligand, KITL), which initiates the growth of dormant oocytes, is an ideal natural activator that stimulates follicle activation. However, no systematic study has been conducted to identify the activating effect of SCF in vivo and in vitro. In this study, by combining an in vitro whole ovary culture system and several mouse models, we provide a series of experimental evidence that SCF is an efficient activator for improving PF activation in mouse ovaries. Our in vitro study showed that SCF increased phosphatidylinositol 3-kinase (PI3K) signaling and PF activation ratio in neonatal ovaries. In vivo ovarian non-invasive topical administrations of SCF to the ovaries efficiently improved follicle activation and development, oocyte retrieval ratio and fertility in inducible premature ovarian insufficiency mouse models and aged mice. Our study suggests that SCF is an efficient growth factor that can be applied to improve PF activation.

Repeated Superovulation Accelerates Primordial Follicle Activation and Atresia

For humans, ARTs (assisted reproductive technologies) have become the most effective method to treat subfertility/infertility in clinic. To obtain enough oocytes during ART, ovarian stimulation is performed by exogenous hormones, and some patients undergo several ovarian stimulation cycles. Although some adverse effects of ARTs on women and offspring are reported, few studies are focused on the effects of multiple superovulation on ovarian reserve. In the present study, we found that repeated superovulation significantly reduced primordial follicle number and the serum AMH. Compared to the decreased antral follicle number, the expression of genes related to primordial follicle activation, such as Foxo3, Akt, and Rptor, and the atretic follicle number in ovaries were increased by superovulation times. We further found that repeated superovulation reduced the plasma level of FSH, LH, and estradiol, and increased the expression of genes related to apoptosis (Bax, Casp3 (caspase-3), Casp8, and Casp9) in granulosa cells, providing evidence that repeated superovulation disrupted the balance between survival and death in granulosa cells. In summary, our results suggest that repeated superovulation has adverse effects on folliculogenesis.

Ovarian Reserve Disorders, Can We Prevent Them? A Review

The ovarian reserve is finite and begins declining from its peak at mid-gestation until only residual follicles remain as women approach menopause. Reduced ovarian reserve, or its extreme form, premature ovarian insufficiency, stems from multiple factors, including developmental, genetic, environmental exposures, autoimmune disease, or medical/surgical treatment. In many cases, the cause remains unknown and resulting infertility is not ultimately addressed by assisted reproductive technologies. Deciphering the mechanisms that underlie disorders of ovarian reserve could improve the outcomes for patients struggling with infertility, but these disorders are diverse and can be categorized in multiple ways. In this review, we will explore the topic from a perspective that emphasizes the prevention or mitigation of ovarian damage. The most desirable mode of fertoprotection is primary prevention (intervening before ablative influence occurs), as identifying toxic influences and deciphering the mechanisms by which they exert their effect can reduce or eliminate exposure and damage. Secondary prevention in the form of screening is not recommended broadly. Nevertheless, in some instances where a known genetic background exists in discrete families, screening is advised. As part of prenatal care, screening panels include some genetic diseases that can lead to infertility or subfertility. In these patients, early diagnosis could enable fertility preservation or changes in family-building plans. Finally, Tertiary Prevention (managing disease post-diagnosis) is critical. Reduced ovarian reserve has a major influence on physiology beyond fertility, including delayed/absent puberty or premature menopause. In these instances, proper diagnosis and medical therapy can reduce adverse effects. Here, we elaborate on these modes of prevention as well as proposed mechanisms that underlie ovarian reserve disorders.

Signaling pathway intervention in premature ovarian failure

Premature ovarian failure (POF) is a multifactorial disease that refers to the occurrence of secondary amenorrhea, estrogen decrease, and gonadotropin increase in women under the age of 40. The prevalence of POF is increasing year by year, and the existing instances can be categorized as primary or secondary cases. This disease has adverse effects on both the physiology and psychology of women. Hormone replacement therapy is the recommended treatment for POF, and a multidisciplinary strategy is required to enhance the quality of life of patients. According to recent studies, the primary mechanism of POF is the depletion of ovarian reserve function as a result of increased primordial follicular activation or primordial follicular insufficiency. Therefore, understanding the processes of primordial follicle activation and associated pathways and exploring effective interventions are important for the treatment of POF.

Early postnatal alterations in follicular stress response and survival in a mouse model of Classic Galactosemia

Primary ovarian insufficiency is characterized by accelerated loss of primordial follicles, which results in ovarian failure and concomitant menopause before age 40. About 1-3% of females in the general population are diagnosed with POI; however, greater than 80% of females with the inherited disease Classic Galactosemia will develop POI. Classic Galactosemia is caused by mutations in the GALT gene encoding the enzyme galactose-1 phosphate uridylyltransferase. While dietary restriction of galactose is lifesaving in the neonatal period, the development of complications including primary ovarian insufficiency is not mitigated. Additionally, the pattern(s) of follicle loss have not been completely characterized. The chronic accumulation of aberrant metabolites such as galactose-1-phosphate and galactitol are suspected culprits in the development of the sequelae, yet the mechanisms remain elusive.Our group uses a GalT gene-trapped mouse model to study the pathophysiology of primary ovarian insufficiency in Classic Galactosemia. We recently showed that differences in the Integrated Stress Response pathway occur in mutant ovaries that likely contribute to their primary ovarian insufficiency phenotype. Using immunofluorescent staining of histological sections of ovaries at progressive ages, we saw evidence of altered Integrated Stress Response activity in granulosa cells and primordial oocytes consistent with accelerated primordial follicle growth activation, aberrant DNA damage and/or repair, and increased cellular stress/death. Overall, our findings indicate that abnormal Integrated Stress Response in the Classic Galactosemia model ovary results in accelerated primordial follicle growth activation, sometimes referred to as "burnout." These aberrant early events help further clarify when/how the primary ovarian insufficiency phenotype arises under galactosemic conditions.

Development of protective agents against ovarian injury caused by chemotherapeutic drugs

BACKGROUND

Chemotherapy is one of the causes of ovarian injury and infertility. Although assisted reproductive technology helps young female patients with cancer become pregnant, preventing chemotherapy-induced ovarian injury will often possess even more significant benefits.

OBJECTIVE

We aimed at demonstrating the hazardous effects and mechanisms of ovarian injury by chemotherapeutic agents, as well as demonstrating agents that protect the ovary from chemotherapy-induced injury.

RESULTS

Chemotherapeutic agents cause death or accelerate activation of follicles and damage to the blood vessels in the ovary, resulting in inflammation. These often require drug development to protect the ovaries from injury.

CONCLUSIONS

Our findings provide a basis for the development of drugs to protect the ovaries from injury. Although there are many preclinical studies on potential protective drugs, there is still an urgent need for a large number of clinical experiments to verify their potential use.

A New Understanding, Guided by Single-Cell Sequencing, of the Establishment and Maintenance of the Ovarian Reserve in Mammals

BACKGROUND

Oocytes are a finite and non-renewable resource that are maintained in primordial follicle structures. The ovarian reserve is the totality of primordial follicles, present from birth, within the ovary and its establishment, size, and maintenance dictates the duration of the female reproductive lifespan. Understanding the cellular and molecular dynamics relevant to the establishment and maintenance of the reserve provides the first steps necessary for modulating both individual human and animal reproductive health as well as population dynamics.

SUMMARY

This review details the key stages of establishment and maintenance of the ovarian reserve, encompassing germ cell nest formation, germ cell nest breakdown, and primordial follicle formation and activation. Furthermore, we spotlight several formative single-cell sequencing studies that have significantly advanced our knowledge of novel molecular regulators of the ovarian reserve, which may improve our ability to modulate female reproductive lifespans.

KEY MESSAGES

The application of single-cell sequencing to studies of ovarian development in mammals, especially when leveraging genetic and environmental models, offers significant insights into fertility and its regulation. Moreover, comparative studies looking at key stages in the development of the ovarian reserve across species has the potential to impact not just human fertility, but also conservation biology, invasive species management, and agriculture.

Reduced mitochondrial size in hippocampus and psychiatric behavioral changes in the mutant mice with homologous mutation of Timm8a1-I23fs49X

Background

Deafness-dystonia-optic neuronopathy (DDON) syndrome, a condition that predominantly affects males, is caused by mutations in translocase of mitochondrial inner membrane 8A (TIMM8A)/deafness dystonia protein 1 (DDP1) gene and characterized by progressive deafness coupled with other neurological abnormalities. In a previous study, we demonstrated the phenotype of male mice carrying the hemizygous mutation of Timm8a1-I23fs49X. In a follow-up to that study, this study aimed to observe the behavioral changes in the female mutant (MUT) mice with homologous mutation of Timm8a1 and to elucidate the underlying mechanism for the behavioral changes.

Materials and methods

Histological analysis, transmission electron microscopy (EM), Western blotting, hearing measurement by auditory brainstem response (ABR), and behavioral observation were compared between the MUT mice and wild-type (WT) littermates.

Results

The weight of the female MUT mice was less than that of the WT mice. Among MUT mice, both male and female mice showed hearing impairment, anxiety-like behavior by the elevated plus maze test, and cognitive deficit by the Morris water maze test. Furthermore, the female MUT mice exhibited coordination problems in the balance beam test. Although the general neuronal loss was not found in the hippocampus of the MUT genotype, EM assessment indicated that the mitochondrial size showing as aspect ratio and form factor in the hippocampus of the MUT strain was significantly reduced compared to that in the WT genotype. More importantly, this phenomenon was correlated with the upregulation of translation of mitochondrial fission process protein 1(Mtfp1)/mitochondrial 18 kDa protein (Mtp18), a key fission factor that is a positive regulator of mitochondrial fission and mitochondrial size. Interestingly, significant reductions in the size of the uterus and ovaries were noted in the female MUT mice, which contributed to significantly lower fertility in the MUT mice.

Conclusion

Together, a homologous mutation in the Timm8a1 gene caused the hearing impairment and psychiatric behavioral changes in the MUT mice; the latter phenotype might be related to a reduction in mitochondrial size regulated by MTP18.

AOP key event relationship report: Linking decreased androgen receptor activation with decreased granulosa cell proliferation of gonadotropin-independent follicles

We recently proposed to formally recognize Key Event Relationships (KERs) as building blocks of Adverse Outcome Pathways (AOPs) that can be independently developed and peer-reviewed. Here, we follow this approach and provide an independent KER from AOP345, which describes androgen receptor (AR) antagonism leading to decreased female fertility. This KER connects AR antagonism to reduced granulosa cell proliferation of gonadotropin-independent follicles (KER2273). We have developed both the KER and the two adjacent Key Events (KEs). A systematic approach was used to ensure that all relevant supporting evidence for KER2273 was retrieved. Supporting evidence for the KER highlights the importance of AR action during the early stages of follicular development. Both biological plausibility and empirical evidence are presented, with the latter also assessed for quality. We believe that tackling isolated KERs instead of whole AOPs will accelerate the AOP development. Faster AOP development will lead to the development of simple test methods that will aid screening of chemicals, endocrine disruptor identification, risk assessment, and subsequent regulation.

Identification of curcumin as a novel potential drug for promoting the development of small ovarian follicles for infertility treatment

In-vitro fertilization is an effective treatment for various causes of infertility. However, management of women with poor ovarian response or premature ovarian insufficiency remains challenging because these women have underdeveloped small ovarian follicles that do not respond to hormone treatment. In-vitro activation of small follicles has been developed but its efficiency has much room for improvement. In the current study, we provide several lines of evidence showing that curcumin, an FDA-approved traditional medicine, can specifically promote the development of mouse ovarian follicles from the primary to secondary stage, which greatly potentiates these small follicles for subsequent in-vivo development into antral follicles that can be ovulated. Mechanistically, we show that curcumin promotes the proliferation and differentiation of granulosa cells and the growth of oocytes by activating the phosphatidylinositol 3 kinase (PI3K) signaling pathway. Most importantly, we show that in-vitro treatment of human ovarian tissues with curcumin can promote the in-vivo survival and development of small human ovarian follicles, showing that curcumin can be used as a potential drug to increase the success rate of in-vitro activation of small human follicles. We thus identify curcumin as a novel potential drug for promoting the development of small human ovarian follicles for infertility treatment.

Iodoacetic acid exposure alters the transcriptome in mouse ovarian antral follicles

Iodoacetic acid (IAA) is an unregulated water disinfection byproduct that is an ovarian toxicant. However, the mechanisms of action underlying IAA toxicity in ovarian follicles remain unclear. Thus, we determined whether IAA alters gene expression in ovarian follicles in mice. Adult female mice were dosed with water or IAA (10 or 500 mg/L) in the water for 35-40 days. Antral follicles were collected for RNA-sequencing analysis and sera were collected to measure estradiol. RNA-sequencing analysis identified 1063 differentially expressed genes (DEGs) in the 10 and 500 mg/L IAA groups (false discovery rate FDR < 0.1), respectively, compared to controls. Gene Ontology Enrichment analysis showed that DEGs were involved with RNA processing and regulation of angiogenesis (10 mg/L) and the cell cycle and cell division (500 mg/L). Pathway Enrichment analysis showed that DEGs were involved in the phosphatidylinositol 3-kinase and protein kinase B (PI3K-Akt), gonadotropin-releasing hormone (GnRH), estrogen, and insulin signaling pathways (10 mg/L). Pathway Enrichment analysis showed that DEGs were involved in the oocyte meiosis, GnRH, and oxytocin signaling pathways (500 mg/L). RNA-sequencing analysis identified 809 DEGs when comparing the 500 and 10 mg/L IAA groups (FDR < 0.1). DEGs were related to ribosome, translation, mRNA processing, oxidative phosphorylation, chromosome, cell cycle, cell division, protein folding, and the oxytocin signaling pathway. Moreover, IAA exposure significantly decreased estradiol levels (500 mg/L) compared to control. This study identified key candidate genes and pathways involved in IAA toxicity and can help to further understand the molecular mechanisms of IAA toxicity in ovarian follicles.

Depletion of oocyte dynamin-related protein 1 shows maternal-effect abnormalities in embryonic development

Eggs contain about 200,000 mitochondria that generate adenosine triphosphate and metabolites essential for oocyte development. Mitochondria also integrate metabolism and transcription via metabolites that regulate epigenetic modifiers, but there is no direct evidence linking oocyte mitochondrial function to the maternal epigenome and subsequent embryo development. Here, we have disrupted oocyte mitochondrial function via deletion of the mitochondrial fission factor Drp1. Fission-deficient oocytes exhibit a high frequency of failure in peri- and postimplantation development. This is associated with altered mitochondrial function, changes in the oocyte transcriptome and proteome, altered subcortical maternal complex, and a decrease in oocyte DNA methylation and H3K27me3. Transplanting pronuclei of fertilized Drp1 knockout oocytes to normal ooplasm fails to rescue embryonic lethality. We conclude that mitochondrial function plays a role in establishing the maternal epigenome, with serious consequences for embryo development.

Targeting signaling pathways involved in primordial follicle growth or dormancy: potential application in prevention of follicular loss and infertility

INTRODUCTION

Premature ovarian failure (POF) is one of the important causes of infertility in females. To date, no efficient preventive pharmacological treatment has been offered to prevent POF. Therefore, it is necessary to focus on strategies that provide a normal reproductive lifespan to females at risk of developing POF.

AREAS COVERED

Recently, attention has been drawn to discovering pathways involved in primordial follicle activation, as the inhibition of this process might maintain the stock of primordial follicles and therefore, prevent POF. In vitro and animal studies have resulted in the discovery of several of these pathways that can be used to develop new treatments for POF. These studies show crosstalk of these pathways at different levels. One of the important crossing points of many of these pathways involves anti-Mullerian hormone (AMH). Herein, we discuss different aspects of this topic by reviewing related published articles indexed in PubMed and Web of Science as of December 2021.

EXPERT OPINION

Although the findings seem promising, most of the studies were conducted on animals, and the interaction between these factors and the possible outcomes of their administration in the long term are still unknown. Therefore, further investigation is necessary to assess these aspects.

Asynchronous embryonic germ cell development leads to a heterogeneity of postnatal ovarian follicle activation and may influence the timing of puberty onset in mice

Background

Ovarian follicles, which are the basic units of female reproduction, are composed of oocytes and surrounding somatic (pre) granulosa cells (GCs). A recent study revealed that signaling in somatic preGCs controlled the activation (initial recruitment) of follicles in the adult ovaries, but it is also known that there are two waves of follicle with age-related heterogeneity in their developmental dynamics in mammals. Although this heterogeneity was proposed to be crucial for female reproduction, our understanding of how it arises and its significance is still elusive.

Results

In the current study, by deleting the key secreted factor KIT ligand from preGCs and analyzing the follicle cell developmental dynamics, we revealed distinct patterns of activation and growth associated with the two waves of follicles in mouse ovary. Our results confirmed that activation of adult wave follicles is initiated by somatic preGCs and dependent on the KIT ligand. By contrast, activation of first wave follicles, which are awakened from germ cells before follicle formation, can occur in the absence of preGC-secreted KIT ligand in postnatal ovaries and appears to be oocyte-initiated. We also found that the asynchronous activity of phosphatidylinositol 3 kinases (PI3K) signaling and meiotic process in embryonic germ cells lead to the follicle heterogeneity in postnatal ovaries. In addition, we supplied evidence that the time sequence of embryonic germ cell development and its related first wave follicle growth are correlated to the time of puberty onset in females.

Conclusion

Taken together, our study provides evidence that asynchronous development of embryonic oocytes leads to the heterogeneity of postnatal ovarian follicle activation and development, and affects the timing of onset of puberty in females.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01318-y.

De novo programming: establishment of epigenome in mammalian oocytes

Innovations in ultrasensitive and single-cell measurements enable us to study layers of genome regulation in the view of cellular and regulatory heterogeneity. Genome-scale mapping allows to evaluate epigenetic features and dynamics in different genomic contexts, including genebodies, CGIs, ICRs, promoters, PMDs, and repetitive elements. The epigenome of early embryos, fetal germ cells, and sperm has been extensively studied for the past decade, while oocytes remain less clear. Emerging evidence now supports the notion that transcription and chromatin accessibility precede de novo DNA methylation in both human and mouse oocytes. Recent studies also start to chart correlations among different histone modifications and DNA methylation. We discussed the potential mechanistic hierarchy by which shapes oocyte DNA methylome, also provided insights into the convergent and divergent features between human and mice.

Effects of prenatal and lactational exposure to iodoacetic acid on the F1 generation of mice†

Water disinfection can generate water disinfection byproducts (DBPs). Iodoacetic acid (IAA) is one DBP, and it has been shown to be an ovarian toxicant in vitro and in vivo. However, it is unknown if prenatal and lactational exposure to IAA affects reproductive outcomes in female offspring. This study tested the hypothesis that prenatal and lactational exposure to IAA adversely affects reproductive parameters in F1 female offspring. Adult female CD-1 mice were dosed with water (control) or IAA (10, 100, and 500 mg/L) in the drinking water for 35 days and then mated with unexposed males. IAA exposure continued throughout gestation. Dams delivered naturally, and pups were continuously exposed to IAA through lactation until postnatal day (PND) 21. Female pups were euthanized on PND 21 and subjected to measurements of anogenital distance, ovarian weight, and vaginal opening. Ovaries were subjected to histological analysis. In addition, sera were collected to measure reproductive hormone levels. IAA exposure decreased vaginal opening rate, increased the absolute weight of the ovaries, increased anogenital index, and decreased the percentage of atretic follicles in female pups compared to control. IAA exposure caused a borderline decrease in the levels of progesterone and follicle-stimulating hormone (FSH) and increased levels of testosterone in female pups compared to control. Collectively, these data show that prenatal and lactational exposure to IAA in drinking water affects vaginal opening, anogenital index, the weight of the ovaries, the percentage of atretic follicles, and hormone levels in the F1 generation in mice.

Research and experimental verification of the molecular mechanism of berberine in improving premature ovarian failure based on network pharmacology

Based on the research methods of network pharmacology, this study analyzed the improvement effect of berberine (BBR) on premature ovarian failure (POF) and its molecular mechanism. Carry out GO and KEGG enrichment analysis by R language to obtain the potential targets and pathways of BBR in the improvement of POF. Use SD rats and ovarian granulosa cells (GCs) for experimental verification. ELISA was used to measure the content of related hormones in the serum, CCK-8 was used to measure cell viability, western blot was used to measure the content of the target protein in the ovaries and GCs, and q-RT-PCR was used to detect the expression of the target genes in the ovaries and GCs. Predicted by network pharmacology: PTEN, AKT1, FoxO1, FasL, and Bim are the targets with the highest relative correlation between BBR and POF. The results of experiments show that the treatment of low and medium doses of BBR can increase the ovarian index of rats; BBR can increase the levels of Estradiol (E₂) and Anti-Mullerian hormone (AMH) in the serum of rats and reduce the levels of Follicle stimulating hormone (FSH) and Luteinizing hormone (LH). BBR can increase the cell viability of GCs; BBR can inhibit the PTEN/AKT1/FoxO1 signaling pathway and its phosphorylation level and reduce the expression of Fas/FasL and Bim mRNA. Overall, BBR can promote the ovarian to maintain normal hormone levels, protect GCs, and enhance the function of POF.

The process of ovarian aging: it is not just about oocytes and granulosa cells

Ovarian age is classically considered the main cause of female reproductive infertility. In women, the process proceeds as an ongoing decline in the primordial follicle stockpile and it is associated with reduced fertility in the mid-thirties, irregular menstruation from the mid-forties, cessation of fertility, and, eventually, menopause in the early fifties. Reproductive aging is historically associated with changes in oocyte quantity and quality. However, besides the oocyte, other cellular as well as environmental factors have been the focus of more recent investigations suggesting that ovarian decay is a complex and multifaceted process. Among these factors, we will consider mitochondria and oxidative stress as related to nutrition, changes in extracellular matrix molecules, and the associated ovarian stromal compartment where immune cells of both the native and adaptive systems seem to play an important role. Understanding such processes is crucial to design treatment strategies to  slow down ovarian aging and consequently prolong reproductive lifespan and, more to this, alleviaingt side effects of menopause on the musculoskeletal, cardiovascular, and nervous systems.

Enhanced pro-apoptosis gene signature following the activation of TAp63α in oocytes upon γ irradiation

Specialized surveillance mechanisms are essential to maintain the genetic integrity of germ cells, which are not only the source of all somatic cells but also of the germ cells of the next generation. DNA damage and chromosomal aberrations are, therefore, not only detrimental for the individual but affect the entire species. In oocytes, the surveillance of the structural integrity of the DNA is maintained by the p53 family member TAp63α. The TAp63α protein is highly expressed in a closed and inactive state and gets activated to the open conformation upon the detection of DNA damage, in particular DNA double-strand breaks. To understand the cellular response to DNA damage that leads to the TAp63α triggered oocyte death we have investigated the RNA transcriptome of oocytes following irradiation at different time points. The analysis shows enhanced expression of pro-apoptotic and typical p53 target genes such as CDKn1a or Mdm2, concomitant with the activation of TAp63α. While DNA repair genes are not upregulated, inflammation-related genes become transcribed when apoptosis is initiated by activation of STAT transcription factors. Furthermore, comparison with the transcriptional profile of the ΔNp63α isoform from other studies shows only a minimal overlap, suggesting distinct regulatory programs of different p63 isoforms.