The early stages of follicular development: activation of primordial follicles and growth of preantral follicles

Three-Dimensionally Printed Agarose Micromold Supports Scaffold-Free Mouse Ex Vivo Follicle Growth, Ovulation, and Luteinization

Ex vivo follicle growth is an essential tool, enabling interrogation of folliculogenesis, ovulation, and luteinization. Though significant advancements have been made, existing follicle culture strategies can be technically challenging and laborious. In this study, we advanced the field through development of a custom agarose micromold, which enables scaffold-free follicle culture. We established an accessible and economical manufacturing method using 3D printing and silicone molding that generates biocompatible hydrogel molds without the risk of cytotoxicity from leachates. Each mold supports simultaneous culture of multiple multilayer secondary follicles in a single focal plane, allowing for constant timelapse monitoring and automated analysis. Mouse follicles cultured using this novel system exhibit significantly improved growth and ovulation outcomes with comparable survival, oocyte maturation, and hormone production profiles as established three-dimensional encapsulated in vitro follicle growth (eIVFG) systems. Additionally, follicles recapitulated aspects of in vivo ovulation physiology with respect to their architecture and spatial polarization, which has not been observed in eIVFG systems. This system offers simplicity, scalability, integration with morphokinetic analyses of follicle growth and ovulation, and compatibility with existing microphysiological platforms. This culture strategy has implications for fundamental follicle biology, fertility preservation strategies, reproductive toxicology, and contraceptive drug discovery.

In Vitro Growth of Human Follicles: Current and Future Perspectives

Ovarian tissue cryopreservation is gaining importance as a successful method to restore fertility to girls and young women at high risk of sterility. However, there are concerns regarding the safety of transplantation after ovarian tissue cryopreservation due to the high risk of reintroducing cancer cells and causing disease recurrence. In these cases, the development of culture systems that support oocyte development from the primordial follicle stage is required. Notable achievements have been reached in human follicle in vitro growth in the past decade. Currently, systems for the in vitro culture of ovarian tissue are based on two-dimensional substrates that do not support the survival of follicles or recapitulate the mechanical heterogenicity in the mammalian ovary. Recognition of the importance of special arrangements between cells has spurred research in three-dimensional culture systems, and the provision of a precise culture system that maximizes the diffusion of nutrients and gases through the follicles has raised interest in advanced biomimetic models. The current review critically examines various culture systems employed for the in vitro development of follicles, with a particular focus on solutions utilizing Organ-on-a-Chip (OOC) technology. The emphasis on OOC technology underscores its role as a promising avenue in ensuring the successful cultivation and maintenance of follicular structures during the culture period.

Cellular atlases of ovarian microenvironment alterations by diet and genetically-induced obesity

Obesity, which can arise from genetic or environmental factors, has been shown to cause serious damages to the reproductive system. The ovary, as one of the primary regulators of female fertility, is a complex organ comprised of heterogeneous cell types that work together to maintain a normal ovarian microenvironment (OME). Despite its importance, the effect of obesity on the entire ovary remains poorly documented. In this study, we performed ovary single-cell and nanoscale spatial RNA sequencing to investigate how the OME changed under different kinds of obesity, including high-fat diet (HFD) induced obesity and Leptin ablation induced obesity (OB). Our results demonstrate that OB, but not HFD, dramatically altered the proportion of ovarian granulosa cells, theca-interstitial cells, luteal cells, and endothelial cells. Furthermore, based on the spatial dynamics of follicular development, we defined four subpopulations of granulosa cell and found that obesity drastically disrupted the differentiation of mural granulosa cells from small to large antral follicles. Functionally, HFD enhanced follicle-stimulating hormone (FSH) sensitivity and hormone conversion, while OB caused decreased sensitivity, inadequate steroid hormone conversion, and impaired follicular development. These differences can be explained by the differential expression pattern of the transcription factor Foxo1. Overall, our study provides a powerful and high-resolution resource for profiling obesity-induced OME and offers insights into the diverse effects of obesity on female reproductive disorders.

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.

Making a good egg: human oocyte health, aging, and in vitro development

Mammalian eggs (oocytes) are formed during fetal life and establish associations with somatic cells to form primordial follicles that create a store of germ cells (the primordial pool). The size of this pool is influenced by key events during the formation of germ cells and by factors that influence the subsequent activation of follicle growth. These regulatory pathways must ensure that the reserve of oocytes within primordial follicles in humans lasts for up to 50 years, yet only approximately 0.1% will ever be ovulated with the rest undergoing degeneration. This review outlines the mechanisms and regulatory pathways that govern the processes of oocyte and follicle formation and later growth, within the ovarian stroma, through to ovulation with particular reference to human oocytes/follicles. In addition, the effects of aging on female reproductive capacity through changes in oocyte number and quality are emphasized, with both the cellular mechanisms and clinical implications discussed. Finally, the details of current developments in culture systems that support all stages of follicle growth to generate mature oocytes in vitro and emerging prospects for making new oocytes from stem cells are outlined.

Unraveling the Consequences of Oxygen Imbalance on Early Embryo Development: Exploring Mitigation Strategies

Although well-established and adopted by commercial laboratories, the in vitro embryo production system still requires refinements to achieve its highest efficiency. Early embryonic development is a dynamic event, demanding suitable conditions to provide a high number of embryos with quality and competence. The first step to obtaining an optimized in vitro environment is to know the embryonic metabolism and energy request throughout the different stages of development. Oxygen plays a crucial role in several key biological processes necessary to sustain and complete embryonic development. Nonetheless, there is still controversy regarding the optimal in vitro atmospheric concentrations during culture. Herein, we discuss the impact of oxygen tension on the viability of in vitro-produced embryos during early development. The importance of oxygen tension is addressed as its roles regarding essential embryonic traits, including embryo production rates, embryonic cell viability, gene expression profile, epigenetic regulation, and post-cryopreservation survival. Finally, we highlight the damage caused by in vitro unbalanced oxygen tensions and strategies to mitigate the harmful effects.

JAK/STAT3 pathway promotes proliferation of ovarian aggregate-derived stem cells in vitro

BACKGROUND

The accurate identification and isolation of ovarian stem cells from mammalian ovaries remain a major challenge because of the lack of specific surface markers and suitable in vitro culture systems. Optimized culture conditions for in vitro expansion of ovarian stem cells would allow for identifying requirements of these stem cells for proliferation and differentiation that would pave the way to uncover role of ovarian stem cells in ovarian pathophysiology. Here, we used three-dimensional (3D) aggregate culture system for enrichment of ovarian stem cells and named them aggregate-derived stem cells (ASCs). We hypothesized that mimicking the ovarian microenvironment in vitro by using an aggregate model of the ovary would provide a suitable niche for the isolation of ovarian stem cells from adult mouse and human ovaries and wanted to find out the main cellular pathway governing the proliferation of these stem cells.

RESULTS

We showed that ovarian aggregates take an example from ovary microenvironment in terms of expression of ovarian markers, hormone secretion and supporting the viability of the cells. We found that aggregates-derived stem cells proliferate in vitro as long-term while remained expression of germline markers. These ovarian stem cells differentiated to oocyte like cells in vitro spontaneously. Transplantation of these stem cells in to chemotherapy mouse ovary could restore ovarian structure. RNA-sequencing analysis revealed that interleukin6 is upregulated pathway in ovarian aggregate-derived stem cells. Our data showed that JAK/Stat3 signaling pathway which is activated downstream of IL6 is critical for ovarian stem cells proliferation.

CONCLUSIONS

We developed a platform that is highly reproducible for in vitro propagation of ovarian stem cells. Our study provides a primary insight into cellular pathway governing the proliferation of ovarian stem cells.

Review: Roles of follicle-stimulating hormone in preantral folliculogenesis of domestic animals: what can we learn from model species and where do we go from here?

The pituitary gonadotropin FSH is a glycoprotein critical for the development of ovarian follicles. Upon binding to its G protein-coupled membrane receptor located on the granulosa cells of ovarian follicles, FSH elicits a cascade of downstream intracellular responses to promote follicle growth, maturation and steroidogenic activity, leading to the acquisition of meiotic and developmental competence of the enclosed oocyte. The essential role of FSH for proper antral follicle development and fertility is indisputable; over the decades, increasing evidence has also pointed toward survival and growth-promoting effects elicited by FSH in earlier-stage preantral follicles, deeming these follicles FSH-responsive as opposed to the FSH-dependent antral follicles. Transgenic mouse models lacking GnRH1, Fshβ or Fshr clearly demonstrate this difference by showing that, morphologically, preantral follicles develop to the secondary stage without FSH signaling; however, exogenous expression or administration of FSH to hormone-deficient mice promotes preantral follicle development, with more pronounced effects seen in earlier stages (i.e., primary follicles). In hypophysectomized sheep, FSH administration also promotes the growth of primary-stage preantral follicles. However, in vivo studies in this area are more challenging to perform in domestic animals compared to rodents, and therefore most of the research to date has been done in vitro. Here, we present the existing evidence for a role of FSH in regulating the growth and survival of preantral follicles from data generated in rodents and domestic animals. We provide an overview of the process of folliculogenesis, FSH synthesis and cellular signaling, and the response to FSH by preantral follicles in vivo and in vitro, as well as interactions between FSH and other molecules to regulate preantral folliculogenesis. The widespread use of FSH in ovarian stimulation programs for assisted reproduction creates a real need for a better understanding of the effects of FSH beyond stimulation of antral follicle growth, and more research in this area could lead to the development of more effective fertility programs. In addition to its importance as an agricultural species, the cow provides a desirable model for humans regarding ovarian stimulation due to similar timing of folliculogenesis and follicle size, as well as similar ovarian architecture. The refinement of minimally invasive methods to allow the study of preantral folliculogenesis in live animals will be critical to understand the short- and long-term effects of FSH in ovarian folliculogenesis.

Cocktails of NSAIDs and 17α Ethinylestradiol at Environmentally Relevant Doses in Drinking Water Alter Puberty Onset in Mice Intergenerationally

Non-steroidal anti-inflammatory drugs (NSAIDs) and 17α-ethinyl-estradiol (EE2) are among the most relevant endocrine-disrupting pharmaceuticals found in the environment, particularly in surface and drinking water due to their incomplete removal via wastewater treatment plants. Exposure of pregnant mice to NSAID therapeutic doses during the sex determination period has a negative impact on gonadal development and fertility in adults; however, the effects of their chronic exposure at lower doses are unknown. In this study, we investigated the impact of chronic exposure to a mixture containing ibuprofen, 2hydroxy-ibuprofen, diclofenac, and EE2 at two environmentally relevant doses (added to the drinking water from fetal life until puberty) on the reproductive tract in F1 exposed mice and their F2 offspring. In F1 animals, exposure delayed male puberty and accelerated female puberty. In post-pubertal F1 testes and ovaries, differentiation/maturation of the different gonad cell types was altered, and some of these modifications were observed also in the non-exposed F2 generation. Transcriptomic analysis of post-pubertal testes and ovaries of F1 (exposed) and F2 animals revealed significant changes in gene expression profiles and enriched pathways, particularly the inflammasome, metabolism and extracellular matrix pathways, compared with controls (non-exposed). This suggested that exposure to these drug cocktails has an intergenerational impact. The identified Adverse Outcome Pathway (AOP) networks for NSAIDs and EE2, at doses that are relevant to everyday human exposure, will improve the AOP network of the human reproductive system development concerning endocrine disruptor chemicals. It may serve to identify other putative endocrine disruptors for mammalian species based on the expression of biomarkers.

Risk Assessment of Transgender People: Development of Rodent Models Mimicking Gender-Affirming Hormone Therapies and Identification of Sex-Dimorphic Liver Genes as Novel Biomarkers of Sex Transition

Transgender (TG) describes individuals whose gender identity differs from the social norms. TG people undergoing gender-affirming hormone therapy (HT) may be considered a sub-group of the population susceptible to environmental contaminants for their targets and modes of action. The aim of this study is to set appropriate HT doses and identify specific biomarkers to implement TG animal models. Four adult rats/group/sex were subcutaneously exposed to three doses of HT (plus control) selected starting from available data. The demasculinizing-feminizing models (dMF) were β-estradiol plus cyproterone acetate, at 0.09 + 0.33, 0.09 + 0.93 and 0.18 + 0.33 mg, respectively, five times/week. The defeminizing-masculinizing models (dFM) were testosterone (T) at 0.45, 0.95 and 2.05 mg, two times/week. Clitoral gain and sperm count, histopathological analysis of reproductive organs and liver, hormone serum levels and gene expression of sex-dimorphic CYP450 were evaluated. In the dMF model, the selected doses-leading to T serum levels at the range of the corresponding cisgender-induced strong general toxicity and cannot be used in long-term studies. In the dFM model, 0.45 mg of T represents the correct dose. In addition, the endpoints selected are considered suitable and reliable to implement the animal model. The sex-specific CYP expression is a suitable biomarker to set proper (de)masculinizing/(de)feminizing HT and to implement TG animal models.

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.

Automatic Evaluation for Bioengineering of Human Artificial Ovary: A Model for Fertility Preservation for Prepubertal Female Patients with a Malignant Tumor

Introduction: The in vitro culture of primordial follicles is the only available option for preserving fertility in prepubertal girls with malignant tumors. The cultivation of primordial follicles in scaffolds as artificial ovaries is a promising approach for this. Methods: Dissociated follicles were placed into an artificial ovarian scaffold composed of fibrinogen and thrombin. The follicles were cultured in a dish dedicated to live cell imaging and observed for growth using immunofluorescence and development via optical microscopy. The morphology of the follicles in the scaffold was three-dimensionally reconstructed using the Imaris software. Growth and development were also quantified. Results: The morphology of artificial ovaries began to degrade over time. Within approximately 7 days, primordial follicles were activated and grew into secondary follicles. A comparison of optical and confocal microscopy results revealed the superior detection of live cells using confocal microscopy. The three-dimensional reconstruction of the confocal microscopy data enabled the automatic enumeration and evaluation of the overall morphology of many follicles. Conclusions: The novel artificial ovary-enabled primordial follicles to enter the growth cycle after activation and grow into secondary follicles. The use of a fibrin scaffold as a carrier preserves the developmental potential of primordial germ cells and is a potentially effective method for preserving fertility in prepubertal girls.

Isolation of Female Germline Stem Cells from Mouse and Human Ovaries by Differential Adhesion

Spermatogonial stem cell (SSC) counterparts known as female germline stem cells (fGSCs) were found in the mammalian ovary in 2004. Although the existence of fGSCs in the mammalian postnatal ovary is still under controversy, fGSC discovery encourages investigators to better understand the various aspects of these cells. However, their existence is not accepted by all scientists in the field because isolation of fGSCs by fluorescent activated cell sorting (FACS) has not been reproducible. In this study, we used differential adhesion to isolate and enrich fGSCs from mouse and human ovaries and subsequently cultured them in vitro. fGSCs were able to proliferate in vitro and expressed germ cell-specific markers Vasa, Dazl, Blimp1, Fragilis, Stella, and Oct4, at the protein level. Moreover, mouse and human fGSCs were, respectively, cultured for more than four months and one month in culture. Both mouse and human fGSCs maintained the expression of germ cell-specific markers over these times. In vitro cultured fGSCs spontaneously produced oocyte-like cells (OLCs) which expressed oocyte-relevant markers. Our results demonstrated that differential adhesion allows reproducible isolation of fGSCs that are able to proliferate in vitro over time. This source of fGSCs can serve as a suitable material for studying mechanisms underlying female germ cell development and function.

Prenatal transportation stress did not impact ovarian follicle count for three generations of female Brahman offspring

As prenatal transportation stress altered behavior and adrenal glucocorticoid secretion of calves, we hypothesized that prenatal transportation stress would decrease ovarian reserve size and negatively impact female offspring fertility. The impact of prenatal transportation stress on ovarian follicle numbers in female offspring for three generations was studied. Brahman cows were transported for 2 h on day 60 ± 5, 80 ± 5, 100 ± 5, 120 ± 5, and 140 ± 5 of gestation. Ovaries were collected from offspring of transported or non-transported dams at multiple ages. Primordial, primary, secondary, and antral follicles were histologically analyzed. Antral follicle numbers were determined by ultrasound in a subset of offspring. Numbers of primordial, primary, secondary, and antral follicles were analyzed using the MIXED procedure, while the CORR procedure of SAS was used to determine the correlation between follicles observed by ultrasonography and histology. There were no differences (P > 0.05) in the number of primordial, primary, secondary, antral, or total follicles observed histologically due to treatment. Younger females had significantly greater numbers of follicles than older females (P < 0.0001). Antral follicles tended to be correlated with total histological ovarian follicles (P = 0.10). There was no difference in the number of antral follicles observed at ultrasound due to treatment (P = 0.3147), or generation (P = 0.6005) when controlling for age at observation. These results show that short-term transportation stress during early- to mid-gestation did not impact fertility as measured by ovarian follicle numbers in female Brahman offspring for three generations.

Bovine models for human ovarian diseases

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

Optimization of Follicle Isolation for Bioengineering of Human Artificial Ovary

Background: A functional artificial ovary is a promising strategy to recover fertility and restore endocrine function in cancer patients. The aim of this study is to optimize the follicle isolation protocol for cryopreserved human ovarian tissues. Methods: Each of the cryopreserved human ovarian cortex pieces (OCPs) from 10 patients was cut into two equal parts and randomly distributed into two treatment groups. Group 1: OCPs digested with Tumor Dissociation Enzyme (TDE); Group 2: OCPs digested with Liberase Dispase High (DH). The efficiency of both groups were evaluated in terms of yield, viability, morphology, and a short-term in vitro culture (IVC) in alginate scaffolds. Results: The TDE can isolate more primordial follicles and smaller diameter of follicles than Liberase DH. The TDE also enabled the isolation of more bright red follicles, higher percent of viable follicles, more morphologically normal follicles, and lower oxidative stress levels compared with Liberase DH. After eight days of IVC, follicles in the TDE group had a higher growth rate from Day 0 to Day 8, and higher viability on Day 8 than the Liberase DH Group. Conclusion: The TDE can be considered an alternative to Liberase DH, enables the isolation of a higher number of healthy follicles from human OCPs, and improves follicle survival after IVC in contrast to Liberase DH.

In vitro production of viable eggs from isolated mouse primary follicles by successive culture

To produce viable eggs from single primary follicles in vitro, primary follicles containing oocytes (average 39.0 ± 0.2 µm in diameter) were isolated from the ovaries of 1-week-old mice, and cultured in combination with culture membranes for the first 8 days up to the secondary follicle stage, followed by the next 12 days to the later stages. After culture with a combination of first and second culture membranes using high and low adhesion characteristics, the average oocyte diameters of the surviving follicles increased by almost two-fold in all four groups. Further, the oocyte maturation rate was the highest (74.1%) in the culture group with low adhesion with collagenase and high adhesion. In this culture group, when the O₂ concentration was changed from 20% in the first culture to 5% in the second culture, the cleavage rate increased to 47.5%, which was comparable to the level of the in vivo control (34.6%). Finally, 39 embryos at the 2- to 8-cell stages were transferred into the oviducts of three pseudopregnant females, and eight live pups (20.5%) were obtained. Of the eight pups, six survived for at least six months and were fertile. The present study shows successive in vitro cultures of single isolated primary follicles for the production of viable eggs. We believe that this culture system, with a combination of culture membranes under controlled O₂ conditions, is applicable to other mammalian species, including humans.

The immunoexpression patterns of fibroblast growth factors in the pregnant and postpartum rat ovary

Fibroblast growth factors (FGFs) are polypeptides involved in the regulation of oogenesis and folliculogenesis by inducing ovarian mitogenic, homeostatic and angiogenic activity. This study was aimed at determining the localisation of FGF ligands (FGF1 and FGF2) and FGF receptor 2 (FGFR2) in the rat ovary by immunohistochemical analyses, at pregnancy and the postpartum period. During pregnancy and the postpartum period, positive FGF1 immunoreactions were observed in the nucleus and cytoplasm of germinative epithelial cells, granulosa cells of follicles in different developmental stages, theca interna cells, interstitial cells, luteal cells and atretic follicles. FGF2 immunoreactivity was strong in the cytoplasm of the endothelial cells and smooth muscle cells of the ovarian blood vessels and in the smooth muscle cells of the ovarian cortex and medulla. Strong FGFR2 immunoreactivity was observed in the stromal cells surrounding the blood vessels and rete ovarii. Immunoreaction intensity of the FGF1, FGF2 and FGFR2 had relatively similar abundances between the periods examined. Considering that FGFs act as local regulators in oogenesis, folliculogenesis, follicular atresia, ovulation, corpus luteum formation and regression and angiogenesis, this study supports the idea that FGFs may also be involved in these physiological functions in rat ovaries during pregnancy and postpartum period.

Initial steps on mapping differentially expressed proteins in bovine preantral follicles and ovarian tissue: An approach using single-follicle MALDI-MS and mass spectrometry imaging (MSI) analysis

The molecular mechanisms regulating follicular development and ensuring primordial follicle activation remain undefined. To help elucidate these mechanisms, this proteomic study of bovine ovarian tissue identified the differential molecular profiles of preantral follicles together with the spatial distribution of the most abundant molecular components in the tissue. Isolated primordial, primary and secondary follicles were individually placed on a MALDI target plate for mass spectral acquisitions, with detection of different m/z ranges. Ovarian tissue was sectioned and analysed in the m/z 400-2,000 range. Results of the first analysis indicated a similarity pattern in the molecular protein profile among different follicular classes in the m/z ranges of 100-1000 and 25,000-200,000, but in the m/z ranges of 800-4000, 4000-20,000 and 15,000-70,000, primary and secondary follicles shared similar clustering profiles which were different from primordial follicles (p < .05). In the second analysis, it was possible to correlate some intense molecular components in the tissue from global mass spectrum with the ions detected in the first analysis. Molecular components at m/z 11,325 (±230) were also detected in primary and secondary follicles in the experiment with isolated follicles, in addition to ions at m/z 4,029 (±120), 13,799 (±70), 5,547 (±9), 15,313 (±200), 7,018 (±40) and 7,663 (±90) which were also intensely detected in primary and secondary follicles. The present proteomic approaches evaluated different mass ranges of preantral follicles in bovine ovarian tissue and also indicated the spatial distribution of the most abundant molecular components. This study hopes to pave the way for future research identifying and characterizing specific proteins involved in follicle activation in bovine follicles, in order to better understand folliculogenesis and potentially improve mammalian follicle culture systems.

Effects of sub-chronic oral exposure to pyrogenic synthetic amorphous silica (NM-203) in male and female Sprague-Dawley rats: focus on reproductive systems

Synthetic amorphous silica (SAS) consists of agglomerates and aggregates of primary particles in the nanorange (<100 nm) and it is the E551 authorized food additive. The potential risks for human health associated to dietary exposure to SAS are not completely assessed; in particular, data on male and female reproductive systems are lacking. A 90-day oral toxicity study with pyrogenic SAS nanomaterial NM-203 was carried out on the basis of the OECD test guideline 408 in the frame of the NANoREG project. Adult Sprague-Dawley rats of both sexes were orally treated for 90 days with 0, 2, 5, 10, 20 and 50 mg SAS/kg bw per day. Dose levels were selected to be as close as possible to the expected human exposure to food additive E551. The present paper provides specific information on potential effects on male and female reproductive systems, through the evaluation of serum biomarkers, sperm count, histopathological analysis of testis, epididymis, ovary and uterus and real-time PCR on uterus; potential genotoxic alterations were evaluated by comet assay on testis, sperm and ovary. NM-203 did not induce histophatological and genotoxic effects in male reproductive system. In female rats, ovary is not target of NM-203 and only tissue-specific effects on uterus were recorded up to 10 mg/kg bw per day. To our best knowledge, this is the first study providing data on male and female reproductive systems after long-term, repeated oral exposure at dose levels close to dietary human exposure, which identifies a limited concern only for female reproductive health.

Melatonin delays ovarian aging in mice by slowing down the exhaustion of ovarian reserve

Studies have shown that melatonin (MLT) can delay ovarian aging, but the mechanism has not been fully elucidated. Here we show that granulosa cells isolated from mice follicles can synthesize MLT; the addition of MLT in ovary culture system inhibited follicle activation and growth; In vivo experiments indicated that injections of MLT to mice during the follicle activation phase can reduce the number of activated follicles by inhibiting the PI3K-AKT-FOXO3 pathway; during the early follicle growth phase, MLT administration suppressed follicle growth and atresia, and multiple pathways involved in folliculogenesis, including PI3K-AKT, were suppressed; MLT deficiency in mice increased follicle activation and atresia, and eventually accelerated age-related fertility decline; finally, we demonstrated that prolonged high-dose MLT intake had no obvious adverse effect. This study presents more insight into the roles of MLT in reproductive regulation that endogenous MLT delays ovarian aging by inhibiting follicle activation, growth and atresia.

Stochastic nonlinear model for somatic cell population dynamics during ovarian follicle activation

In mammals, female germ cells are sheltered within somatic structures called ovarian follicles, which remain in a quiescent state until they get activated, all along reproductive life. We investigate the sequence of somatic cell events occurring just after follicle activation, starting by the awakening of precursor somatic cells, and their transformation into proliferative cells. We introduce a nonlinear stochastic model accounting for the joint dynamics of the two cell types, and allowing us to investigate the potential impact of a feedback from proliferative cells onto precursor cells. To tackle the key issue of whether cell proliferation is concomitant or posterior to cell awakening, we assess both the time needed for all precursor cells to awake, and the corresponding increase in the total cell number with respect to the initial cell number. Using the probabilistic theory of first passage times, we design a numerical scheme based on a rigorous finite state projection and coupling techniques to compute the mean extinction time and the cell number at extinction time. We find that the feedback term clearly lowers the number of proliferative cells at the extinction time. We calibrate the model parameters using an exact likelihood approach. We carry out a comprehensive comparison between the initial model and a series of submodels, which helps to select the critical cell events taking place during activation, and suggests that awakening is prominent over proliferation.

The effects of the anti-Müllerian hormone on folliculogenesis in rats: light and electron microscopic evaluation

In this study, we evaluated the effects of anti-Müllerian hormone on follicle development and oocyte quality with light and electron microscopy. Twenty-four adult female rats were divided into four groups. After estrous cycle synchronization, on the first day, control group rats were injected with 0.5 ml saline, 2^nd, 3^rd, and 4^th groups were injected 1 µgr, 2 µgr, and 5 µgr anti-Müllerian hormone, respectively. On the third day, intracardiac blood samples were taken for follicle-stimulating hormone, luteinizing hormone, estradiol, and progesterone serum level measurements. Ovaries were obtained for light and electron microscopic examinations. Secondary (antral) follicles were decreased while atretic follicles were increased in number parallel with an increased dose of anti-Müllerian hormone injection. Atresia of the follicles was demonstrated with apoptosis of granulosa cells characterized by apoptotic bodies and with paraptosis characterized by the vacuole formation in the cytoplasm, enlargement of granular endoplasmic reticulum cisternae and perinuclear cisternae in granulosa cells. Premature luteinization characterized by increased lipid droplets, mitochondria with tubular cristae, and smooth-surfaced endoplasmic reticulum in the cytoplasm of granulosa cells were detected in some growing follicles. In the anti-Müllerian hormone injected experimental groups, cystic follicles characterized by a large antrum, attenuated granulosa cell layer, and flattened granulosa cells that face the antrum were observed. Corpus luteum and stroma were similar in all groups. It was concluded that increasing doses of anti-Müllerian hormone caused increased atresia in developing follicles, premature luteinization of granulosa cells in some follicles, and cystic follicle formation in the further developing follicles.

Comparison of Metabolic Alterations in Serum and Milk Whey Between Inactive Ovaries and Estrus Dairy Cows

Inactive ovaries (IOs) affect the estrus cycle and timed artificial insemination (TAI) efficiency in dairy cows during early lactation. The objective of the experiment was to determine metabolic changes in the serum and milk whey of dairy cows with IO and estrus. Twenty-eight healthy postpartum Holstein cows in similar age, milk production, and body condition were selected at 30 days postpartum for tracking to 70 days postpartum, and estrus performance was recorded through Afi Farm® software. The ovarian status and follicular diameter of dairy cows were examined by an experienced breeder through B-ultrasound and rectal examination. Fourteen normal estrus cows were allocated to control group A and 14 cows with IO to group B, all at 30–70 days postpartum. The serum and milk whey in the two groups of cows at 70 days postpartum were used for non-targeted nuclear magnetic resonance (¹H-NMR) analysis to measure the different metabolites of cows with IO. In group B compared with group A at 70 days postpartum, there was an increase in the milk whey of six different metabolites including succinate, creatine phosphate, glycine, myo-inositol, glycolate, and orotate and a decrease in the milk whey of seven metabolites, including alanine, creatinine, o-phosphorylcholine, lactose, taurine, galactose, and glucose-1-phosphate. There was an increase in the serum of group B cows of four differential metabolites, including 3-hydroxybutyrate, acetate, glutamine, and glycine and a decrease in the serum of nine differential metabolites, including alanine, succinate, citrate, creatinine, o-phosphocholine, glucose, myo-inositol, tyrosine, and histidine compared with group A. Group B cows with IO had decreased glucose metabolism and impaired tricarboxylic acid cycle, increased lipid mobilization, and abnormal amino acid metabolism. The study provides a potential prevention strategy for IO in dairy cows in future.

A role for orphan nuclear receptor liver receptor homolog-1 (LRH-1, NR5A2) in primordial follicle activation

Liver receptor homolog-1 (NR5A2) is expressed specifically in granulosa cells of developing ovarian follicles where it regulates the late stages of follicle development and ovulation. To establish its effects earlier in the trajectory of follicular development, NR5A2 was depleted from granulosa cells of murine primordial and primary follicles. Follicle populations were enumerated in neonates at postnatal day 4 (PND4) coinciding with the end of the formation of the primordial follicle pool. The frequency of primordial follicles in PND4 conditional knockout (cKO) ovaries was greater and primary follicles were substantially fewer relative to control (CON) counterparts. Ten-day in vitro culture of PND4 ovaries recapitulated in vivo findings and indicated that CON mice developed primary follicles in the ovarian medulla to a greater extent than did cKO animals. Two subsets of primordial follicles were observed in wildtype ovaries: one that expressed NR5A2 and the second in which the transcript was absent. Neither expressed the mitotic marker. KI-67, indicating their developmental quiescence. RNA sequencing on PND4 demonstrated that loss of NR5A2 induced changes in 432 transcripts, including quiescence markers, inhibitors of follicle activation, and regulators of cellular migration and epithelial-to-mesenchymal transition. These experiments suggest that NR5A2 expression poises primordial follicles for entry into the developing pool.

Modulation of granulosa cell function via CRISPR-Cas fuelled editing of BMPR-IB gene in goats (Capra hircus)

BMPs are multifunctional growth factors implicated in regulating the ovarian function as key intra-ovarian factors. Biological effects of BMPs are mediated through binding with membrane bound receptors like BMPR-IB and initiating downstream Smad signaling pathway. FecB mutation, regarded as a loss of function mutation in the BMPR-IB gene was identified in certain sheep breeds having high fecundity. Similar type of fecundity genes in goats have not been discovered so far. Hence, the current study was designed to investigate the effects of BMPR-IB gene modulation on granulosa cell function in goats. The BMPR-IB gene was knocked out using CRISPR-Cas technology in granulosa cells and cultured in vitro with BMP-4 stimulation for three different durations In addition, the FecB mutation was introduced in the BMPR-IB gene applying Easi-CRISPR followed by BMP-4/7 stimulation for 72 h. Steroidogenesis and cell viability were studied to explore the granulosa cell function on BMPR-IB gene modulation. BMPRs were found to be expressed stage specifically in granulosa cells of goats. Higher transcriptional abundance of R-Smads, LHR and FSHR indicating sensitisation of Smad signaling and increased gonadotropin sensitivity along with a significant reduction in the cell proliferation and viability was observed in granulosa cells upon BMPR-IB modulation. The inhibitory action of BMP-4/7 on P4 secretion was abolished in both KO and KI cells. Altogether, the study has revealed an altered Smad signaling, steroidogenesis and cell viability upon modulation of BMPR-IB gene in granulosa cells similar to that are documented in sheep breeds carrying the FecB mutation.

Unique morphological characteristics in the ovary of cotton rat (Sigmodon hispidus)

Cotton rats (Sigmodon hispidus, CRs) are commonly used as animal models in biomedical research. However, the reproductive characteristics and ovarian development in the CRs has not been widely investigated. We have previously shown that female CRs, in particular, show several unique phenotypes associated with the urogenital system, such as chronic kidney disease and pyometra. Our investigation revealed unique morphologies in CR ovaries, particularly in oocytes. Cotton rat ovaries at 6-8 weeks of age were obtained from the Hokkaido Institute of Public Health, and their sections analyzed by light microscopy and transmission electron microscopy. Although the general histology and folliculogenesis of CR ovaries were similar to those of other experimental rodents, multi-oocyte follicles (MOFs) and double nucleated oocytes (DNOs) were also observed. Although MOFs were found at all stages of follicular development, a greater frequency of MOFs was observed in the primary and secondary stages. However, DNOs tended to be frequently observed in primordial follicles. Almost all MOF oocytes and a few DNOs possessed a clear zona pellucida, expressed DEAD (Asp-Glu-Ala-Asp) box polypeptide 4 and Forkhead box protein 2, a representative marker of oocytes and follicular epithelial cells. Thus, our investigations revealed the unique phenotypes of the CR ovary. As MOFs and DNOs are occasionally observed in human patients with infertility, the CR would be a useful animal model to study for gaining a better understanding of folliculogenesis and oocytogenesis, as well as their abnormalities in humans and other animals.

Preservation of female genetic resources in feline species

The development of assisted reproduction techniques (ART) specifically for felids has been propagated for two main reasons: (i) most felids are threatened and faced with extinction in all or part of their native habitats (IUCN Red List of Threatened Species, www.catsg.org), and (ii) the domestic cat (Felis catus) can serve as a research model for the implementation of advanced assisted reproductive techniques (ART) to be applied in exotic cats. Domestic cat ovaries can be freshly obtained from veterinary clinics and are frequently used for research on preservation of genetic resources in feline species. The presented review will summarize recent advances and obstacles in biobanking of female genetic resources and discuss alternative approaches which are under investigation.

NLRP7 is expressed in the ovine ovary and associated with in vitro pre-implantation embryo development

NLRP (NACHT, LRR and PYD domain-containing proteins) family plays pivotal roles in mammalian reproduction. Mutation of NLRP7 is often associated with human recurrent hydatidiform moles. Few studies regarding the functions of NLRP7 have been performed in other mammalian species rather than humans. In the current study, for the first time, the function of NLRP7 has been explored in ovine ovary. NLRP7 protein was mainly located in ovarian follicles and in in vitro pre-implantation embryos. To identify its origin, 763 bp partial CDS of NLRP7 deriving from sheep cumulus oocyte complexes (COCs) was cloned, it showed a great homology with Homo sapiens. The high levels of mRNA and protein of NLRP7 were steadily expressed in oocytes, parthenogenetic embryos or IVF embryos. NLRP7 knockdown by the combination of siRNA and shRNA jeopardized both the parthenogenetic and IVF embryo development. These results strongly suggest that NLRP7 plays an important role in ovine reproduction. The potential mechanisms of NLRP7 will be fully investigated in the future.

Effects o follicular fluid oxidative status on human mural granulosa cells, oocyte competency and ICSI parameters

PURPOSE

The aim of the present study was to understand the molecular and genetic alterations involved in follicular fluid oxidative process by investigating human mural granulosa cells and to find possible biomarkers for oocyte competency and ICSI outcome measures.

METHODS

A total of 166 patients were included in the study. Total antioxidant and oxidant levels of follicular fluids were measured on the day of oocyte pick-up and oxidative status were calculated. Expression profiles of three potential target proteins in cases of oxidative stress (Hsp70, Tgf-β, Notch1), DNA status and chromatin integrity of mural granulosa cells were analyzed.

RESULTS

TAS levels were positively correlated with the Hsp70 and Tgf-β expression patterns of mural granulosa cells. Mature oocyte rate and fertilization rates were affected negatively by the presence of oxidative stress and a significant positive correlation was found with the oxidative status and the fertilization rate, whereas no correlation with the remaining ICSI parameters in the overall group.

CONCLUSIONS

Oxidative stress detected in follicular fluid adversely affects fertilization rates post-ICSI however no effect on the remaining parameters including embryo quality, pregnancy, and implantation rates. DNA damage, chromatin integrity were increased, whereas Hsp70 and Tgf-ß were decreased in mural granulosa cells in cases of oxidative stress which may indirectly reflect the oocyte competency and may be used as biomarkers for ICSI outcome measures.

Pituitary porcine FSH, and recombinant bovine and human FSH differentially affect growth and relative abundances of mRNA transcripts of preantral and early developing antral follicles in goats

Three different sources of FSH (porcine pituitary, pFSH; recombinant bovine, rbFSH; and recombinant human, rhFSH) were compared during in vitro culture of preantral and early antral follicles of goats for 18 days. Treatments were: base medium supplemented with no FSH (control), 10, 50, or 100 mIU/mL pFSH (pFSH10, pFSH50, and pFSH100, respectively), 100 ng/mL rbFSH (rbFSH), and 50 mIU/mL rhFSH (rhFSH). There were evaluations of follicle morphology, antrum formation, growth rate, estradiol production, oocyte viability and chromatin configuration, and follicle wall relative abundance of mRNA transcript for MMP-9, TIMP-2, CYP17, CYP19A1, FSHR, Insulin-R, and BAX/BCL-2 ratio. Follicle degeneration rates were similar among all treatment groups at the end of culturing. When there were treatments with pFSH, however, there was a lesser (P < 0.05) percentage of intact follicles and estradiol production, and greater (P < 0.05) extrusion rates. Furthermore, with only pFSH10 (antral follicles) and pFSH100 (preantral and antral follicles) treatments, there was a lesser (P < 0.05) follicle growth. For preantral follicles, when there was addition of pFSH10, pFSH100, and rhFSH there was lesser (P < 0.05) oocyte meiotic resumption compared to control and rbFSH treatments. For antral follicles, when there were treatments with rhFSH and pFSH10 there was greater (P = 0.08 - P < 0.05) oocyte maturation. In conclusion, the source of FSH differentially affected gene expression, as indicated by mRNA abundances, and follicular dynamics of preantral and antral follicles in vitro. Addition of FSH during the in vitro culture improved the developmental outcomes only for antral follicles.

Increased chemotherapy-induced ovarian reserve loss in women with germline BRCA mutations due to oocyte deoxyribonucleic acid double strand break repair deficiency

OBJECTIVE

To assess whether woman who have BRCA mutations (WBM) experience more declines in ovarian reserve after chemotherapy treatment, as it induces oocyte death by deoxyribonucleic acid (DNA) damage, and BRCA mutations result in DNA damage repair deficiency.

DESIGN

Longitudinal cohort study.

SETTING

Academic centers.

PATIENT(S)

The 108 evaluable women with breast cancer were stratified into those never tested (negative family history; n = 35) and those negative (n = 59) or positive (n = 14) for a pathogenic BRCA mutation.

INTERVENTION(S)

Sera were longitudinally obtained before and 12-24 months after chemotherapy treatment, assayed for antimüllerian hormone (AMH), and adjusted for age at sample collection.

MAIN OUTCOME MEASURE(S)

Ovarian recovery, defined as the geometric mean of the after chemotherapy age-adjusted AMH levels compared with baseline levels.

RESULT(S)

Compared with the controls, the before chemotherapy treatment AMH levels were 24% and 34% lower in those negative or positive for BRCA mutations, consistent with accelerated ovarian aging in WBM. The WBM had a threefold difference in AMH recovery after chemotherapy treatment (1.6%), when compared with BRCA negative (3.7%) and untested/low risk controls (5.2%). Limiting the analysis to the most common regimen, doxorubicin and cyclophosphamide followed by paclitaxel, showed similar results. These findings were mechanistically confirmed in an in vitro mouse oocyte BRCA knockdown bioassay, which showed that BRCA deficiency results in increased oocyte susceptibility to doxorubicin.

CONCLUSION(S)

Women who have pathogenic BRCA mutations are more likely to lose ovarian reserve after chemotherapy treatment, suggesting an emphasis on fertility preservation. Furthermore, our findings generate the hypothesis that DNA repair deficiency is a shared mechanism between aging, infertility, and cancer.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00823654.

Dynamin 2-dependent endocytosis is essential for mouse oocyte development and fertility

During folliculogenesis, oocytes are dependent on metabolic and molecular support from surrounding somatic cells. Here, we examined the role of the dynamin (DNM) family of mechanoenzymes in mediating endocytotic uptake into growing follicular oocytes. We found DNM1 and DNM2 to be highly expressed in growing follicular oocytes as well as in mature germinal vesicle (GV) and metaphase II (MII) stage oocytes. Moreover, oocyte-specific conditional knockout (cKO) of DNM2 (DNM2Δ) led to complete sterility, with follicles arresting at the preantral stage of development. In addition, DNM2Δ ovaries were characterized by disrupted follicular growth as well as oocyte and follicle apoptosis. Further, the loss of DNM activity, either through DNM2 cKO or through pharmacological inhibition (Dyngo 6a) led to the impairment of endocytotic pathways in preantral oocytes as well as in mature GV and MII oocytes, respectively. Loss of DNM activity resulted in the redistribution of endosomes and the misslocalization of clathrin and actin, suggesting dysfunctional endocytosis. Notably, there was no observable effect on the fertility of DNM1Δ females. Our study has provided new insight into the complex and dynamic nature of oocyte growth during folliculogenesis, suggesting a role for DNM2 in mediating the endocytotic events that are essential for oocyte development.

Androgenic Modulation in the Primary Ovarian Growth of the Japanese eel, Anguilla japonica

Anguilla japonica seedling production is urgently required for eel aquaculture due to the species' severely dwindling population. This study aimed to understand androgenic modulation of the primary ovarian growth, a critical development phase in females, in this semelparous fish. Through histological analysis, primordial to primary follicle transition was observed before hormone injection, and eels injected with SPH + MT showed greater synchronous follicle development than those injected with SPH alone. An in vivo experiment revealed a positive correlation (p < 0.05, r = 0.94) between the mRNA expression of arα and increasing gonadal somatic index (GSI) < 0.75% before SPH injection. Another positive correlation was seen between arβ expression and GSI (p < 0.05, r = 0.97) after weekly SPH injections for three weeks. fshr expression was high in the SPH + MT-injected group. Significantly high fshr mRNA levels were found after weekly MT injections for two weeks (p < 0.05), whereas the expression levels dropped after flutamide injection. arα and arβ expressions revealed different patterns before and after SPH induction. In this study, androgen modulation was found with regard to ARs expressions during primary growth and the primordial to primary follicle transition prior to hormone induction. This modulation continuously affected fshr expression and vitellogenic development after SPH induction during ovarian growth in the Japanese eel.

Plasma Metabolic Characterisation of Dairy Cows with Inactive Ovaries and Oestrus During the Peak of Lactation

Introduction

Differential metabolites (DMs) between cows with inactive ovaries (IO) and oestrous (E) cows were screened and metabolic pathways of DMs associated with IO were determined.

Material and Methods

Cows at 50 to 60 days (d) postpartum from an intensive dairy farm were randomly selected and allocated into an E group (n = 16) or an IO group (n = 16) according to a pedometer and rectal examinations. Their plasma samples were analysed by liquid chromatography–mass spectrometry (LC–MS) to compare plasma metabolic changes between the E and IO groups. Multivariate pattern recognition was used to screen the DMs in the plasma of IO cows.

Results

Compared with normal E cows, there were abnormalities in 20 metabolites in IO cows, including a significantly decreased content (VIP > 1, P < 0.05) of cholic acid, p-chlorophenylalanine, and arachidonic acid, and a significantly increased content (VIP > 1, P < 0.05) of tyramine, betaine, L-phenylalanine, L-glutamate, D-proline, L-alanine, and L-pyrophosphate. Five DMs (cholic acid, D-proline, L-glutamate, L-alanine, and L-pyroglutamic acid) with higher variable importance in projection (VIP) values between groups were validated by ELISA with blind samples of re-selected cows (IO, 50 to 60 d postpartum) and the validated results were consistent with the LC–MS results.

Conclusion

The 20 DMs in IO cows during the peak of lactation indicated that the pathogenesis of IO was involved in complex metabolic networks and signal transduction pathways. This study provides a basis for further exploration of the pathogenesis and prevention of IO in cows in the future.

Identification and characterization of a specific 13-miRNA expression signature during follicle activation in the zebrafish ovary

Ovarian folliculogenesis is always of great interest in reproductive biology. However, the molecular mechanisms that control follicle development, particularly the early phase of follicle activation or recruitment, still remain poorly understood. In an attempt to decipher the gene networks and signaling pathways involved in such transition, we conducted a transcriptomic analysis (RNA-seq) on zebrafish primary growth (PG, stage I; inactive) and previtellogenic (PV, stage II; activated) follicles. A total of 118 unique microRNAs (miRNAs) (11 downregulated and 83 upregulated during PG/PV transition) and 56711 unique messenger RNAs (mRNAs) (1839 downregulated and 7243 upregulated during PG/PV transition) were identified. Real-time quantitative polymerase chain reaction analysis confirmed differential expression of 46 miRNAs from 66 candidates (66.67%). Among which, we chose to focus on 13 miRNAs (let-7a, -7b, -7c-5p, -7d-5p, -7h, -7i; miR-21, -23a-3p, -27c-3p, -107a-3p, -125b-5p, -145-3p, and -202-5p) that exhibited significant differential expression between PG and PV follicles (P ≤ 0.045*). With this 13-miRNA expression signature alone, PG follicles can be well differentiated from PV follicles by hierarchical clustering, suggesting their functional relevance during PG-to-PV transition. By overlaying predicted target genes and the differentially expressed mRNAs revealed by the RNA-seq analysis, especially those showing reciprocal miRNA-mRNA expression patterns, we shortlisted a panel of miRNA downstream targets for luciferase reporter validation. The reporter assay confirmed the interactions of let-7i:: atg4a (P = 0.01*), miR-202-5p::c23h20orf24 (P = 0.0004***), and miR-144-5p::ybx1 (P = 0.003**), implicating these potential miRNA-mRNA gene pairs in follicle activation during folliculogenesis. Our transcriptomic data analyses suggest that miRNA-mediated post-transcriptional control may represent an important mechanism underlying follicle activation.

Countering the effects of lead as an environmental toxicant on the microanatomy of female reproductive system of adult wistar rats using aqueous extract of Ficus vogelii

BACKGROUND

Lead without nutritional value is a widely studied occupational and environmental toxicant. Leads' toxic effects on female reproduction are decreased fertility, inability to sustain pregnancy and reduced pregnancy.

OBJECTIVE

This study aimed at examining the effect of oral administration of lead acetate (1.5 mg/kg) on the histology of female albino Wistar rats' ovary and Uterus and the extracts' protective role against toxicity.

METHODS

The experiment took 28 days involving 25 female Wistar rats divided into 5 groups A, B, C, D and E. A is an untreated group that received normal saline, D lead acetate group that received lead acetate solution, E received aqueous extract, B and C low and high dose of aqueous extract respectively and lead acetate solution.

RESULTS

The positive control group showed a significant increase in SOD at P ≤ 0.01 compared to the negative control. Group E showed significant decrease ovarian SOD. The organs weights were significantly reduced in group D. The changes seen in the organs include oedema, necrosis, optical empty spaces, denudations and fatty changes. Administrating the extract protected the organs against the lead acetate. These alterations are shown to cause infertility in female rats.

CONCLUSION

The results suggested that the extract has protective role against lead reproductive toxicity.

Anti-Müllerian hormone and ovarian aging in mares

Anti-Müllerian hormone (AMH) is used as a marker of follicle population numbers and potential fertility in several species including horses but limited data exist across the lifespan. No one has decreased ovarian reserve experimentally to investigate whether a corresponding, quantitative decrease in AMH results. Concentrations of AMH across the lifespan were compiled from 1101 equine females sampled from birth to >33 years of age. Young and old mares (averaging 6 and 19 years) were hemi-ovariectomized and circulating AMH was assessed before and daily thereafter for 15 days. The remaining ovary was removed later and blood was drawn again before and after this second surgery for AMH determination. Polynomial regression analysis and analysis of mares grouped by 5-year intervals of age demonstrated AMH concentrations to be higher in mares aged 5-10 and 10-15 years than 0-5 years of age and lower in mares after 20 years of age. There was high variability in AMH concentrations among neonatal fillies, some of which had concentrations typical of males. Hemi-ovariectomy was followed by a decrease of AMH, almost exactly halving concentrations in intact mares. Concentrations of AMH had returned to intact levels in old mares before complete ovariectomy, as if exhibiting ovarian compensatory hypertrophy, but recovery of AMH was not evident in young mares. AMH may reflect ovarian senescence in mares after 20 years of age but is too variable to do so in the first two decades of life. The ovarian endocrine response to hemi-ovariectomy in mares appears to change with age.

Autophagy in Ovarian Follicular Development and Atresia

Autophagy is a mechanism that exists in all eukaryotes under a variety of physiological and pathological conditions. In the mammalian ovaries, less than 1% of follicles ovulate, whereas the remaining 99% undergo follicular atresia. Autophagy and apoptosis have been previously found to be involved in the regulation of both primordial follicular development as well as atresia. The relationship between autophagy, follicular development, and atresia have been summarized in this review with the aim to obtain a more comprehensive understanding of the role played by autophagy in follicular development and atresia.

Influence of follicle-stimulating hormone concentrations on the integrity and development of bovine follicles cultured in vitro

This study investigated the in vitro culture of bovine follicles included in ovarian tissue for 2 or 6 days (D2 or D6), with the addition of different concentrations of follicle-stimulating hormone (FSH) (0, 10, 50, 100 or 200 ng/ml). Data were compared for follicular development, morphological integrity and diameter of follicles and oocytes. Ovaries (n = 10) from Nelore cows (n = 5) were divided into fragments (n = 11 per ovary) and were immediately fixed in Bouin’s solution (D0) or were individually cultured for 2 or 6 days in one of the described concentrations of FSH and then processed for histology. Compared with the rates of follicular development at D2 for minimal essential medium (MEM) (75.0%) and 50 ng/ml of FSH (71.1%), the best rates of follicular development at D2 were obtained with 10 (84.7%), 100 (87.5%) and 200 ng/ml of FSH (85.0%; P<0.05). After 6 days of cultivation, there were no differences among treatments regarding follicular growth. The morphological integrity of preantral follicles was better maintained by 100 ng/ml FSH for 2 and 6 days of cultivation (51.2 and 40.4%, respectively; P<0.05) than that for MEM (D2: 30.9%, D6: 20.8%), 10 (D2: 39.2%, D6: 22.8%), 50 (D2: 30.4%, D6: 28.8%) and 200 ng/ml FSH (D2: 45.2%, D6: 36.8%). FSH at 100 ng/ml provided the highest mean diameter averages: 34.5±10.8 µm at D2 and 33.2±12.5 µm at D6 (P<0.05). We concluded that the medium supplemented with 100 ng/ml FSH during in vitro culture provided appropriate conditions for the development and morphological integrity of preantral follicles in cattle.

The cAMP/PKA pathway: steroidogenesis of the antral follicular stage

Pituitary gonadotropins, follicle-stimulating (FSH) and luteinizing hormone (LH) promote follicular recruitment and support antral follicle growth, maturation and selection, resulting in ovulation of the dominant follicle. FSH and LH biological functions are mediated by G protein-coupled receptors, FSHR and LHCGR, resulting in the activation of a number of signaling cascades, such as the cyclic AMP/protein kinase A (cAMP/PKA) pathway. Some in-vitro data are consistent with the dual, proliferative and pro-apoptotic role of cAMP, leaving unanswered questions on how cAMP/PKA signaling is linked to the follicle fate. Progression of the antral stage is characterized by the presence of dynamic serum gonadotropin and estrogen levels, accompanying proliferation and steroidogenesis of growing as well as apoptosis of atretic follicles. These events are parallel to changes of FSHR and LHCGR density at the cell surface occurring throughout the antral stage, reasonably modulating the cAMP/PKA activation pattern, cell metabolism and functions. Understanding whether gonadotropins and receptor expression levels impact on the steroidogenic pathway and play a role in determining the follicular fate, may put new light on molecular mechanisms regulating human reproduction. The aim of the present review is to update the role of major players modulating the cAMP/PKA pathway and regulating the balance between proliferative, differentiating and pro-apoptotic signals.

Assessing recrudescence of photoregressed Siberian hamster ovaries using in vitro whole ovary culture

In vitro culture has been used to study different aspects of ovarian function; however, this technique has not been applied to study recrudescence, or the return of ovarian function in seasonally breeding species. In Siberian hamsters, exposure to inhibitory photoperiods induces declines in ovarian function, which are restored with photostimulation. Because these changes are mediated by changes in systemic gonadotropin (GT) secretion, we hypothesized that culturing photoregressed ovaries with GT would restore aspects of function and induce expression of key folliculogenic factors. Adult female Siberian hamsters were exposed to either long-day (LD; 16L:8D) or short-day (SD; 8L:16D) photoperiods for 14 weeks to maintain in vivo cyclicity or induce gonadal regression, respectively. Isolated ovaries were then cultured for 10 days with or without GT. Ovarian mass and messenger RNA (mRNA) expression of mitotic marker Pcna were increased in cultured SD ovaries (cSD) ovaries with GT as compared to without GT, with no changes noted among cultured LD (cLD) ovaries. Media estradiol and progesterone concentrations increased in both cLD and cSD ovaries cultured with GT as compared to without GT. No differences in follicle numbers or incidence of apoptosis were noted across groups. In addition, differential mRNA expression of folliculogenic growth factors ( Bmp-4, Ntf-3, Inh-α, Gdf-9, Igf-1, Has-2, and Cox-2) was observed in cSD treated with or without GT. Together, these results suggest that this in vitro model could be a useful tool to (a) study the return of function in photoregressed ovaries, and (b) to identify the specific roles folliculogenic factors play in ovarian recrudescence.

In vitro culture of isolated preantral and antral follicles of goats using human recombinant FSH: Concentration-dependent and stage-specific effect

The present study aimed to investigate a concentration-response curve of human recombinant FSH (hrFSH) for in vitro culture of isolated preantral and early antral follicles of goats. Isolated follicles were cultured for 18 days using the following treatments: basic culture medium (control); or control medium supplemented with 10, 50, and 100 mIU/mL of hrFSH. At the end of the culture, cumulus-oocyte complexes were recovered and subjected to in vitro maturation. The following endpoints were evaluated: follicle morphology, growth rate and antrum formation, oocyte viability and meiotic stage, and estradiol production, as well as relative expression of FSH receptor (FSHR), and steroidogenic enzyme (3β-HSD, CYP17, and CYP19A1) genes. In antral follicles, the FSH addition at 50 mIU/mL increased follicular diameter and growth rate, percentage of fully developed oocytes, and oocyte diameter (P <  0.05), and tended to increase the percentage of MII oocytes when compared to the control (P =  0.07). With preantral follicles, FSH addition at 100 mIU/mL increased relative abundance of mRNA for CYP19A1 when compared to the control (P <  0.05). At the same FSH concentrations of 100 and 50 mIU/mL, there was a greater relatively abundance of mRNA for 3β-HSD and CYP17 in preantral than in antral follicles (P <  0.05). For preantral and antral follicle comparisons when the same treatments were imposed, there were greater concentrations of estradiol for antral follicles (P <  0.05). In conclusion, hrFSH enhanced in a concentration-dependent manner the in vitro development of caprine antral follicles; however, there was no positive effect in the culture of preantral follicles.

Update on oogenesis in vitro

INTRODUCTION

Ovarian tissue is increasingly being collected from cancer patients and cryopreserved for fertility preservation. Alternately to the autologous transplantation, the development of culture systems that support oocyte development from the primordial follicle stage represent a valid strategy to restore fertility. The aim of this study is to review the most recent data regarding oogenesis in vitro and to provide an up-to-date on the contemporary knowledge of follicle growth and development in vitro.

EVIDENCE ACQUISITION

A comprehensive systematic MEDLINE search was performed since February 2018 for English-language reports by using the following terms: "ovary," "animal and human follicle," "in vitro growth and development," "ovarian tissue culture," "fertility preservation," "IVM," "oocyte." Previous published reviews and recent published original articles were preferred in order to meet our study scope.

EVIDENCE SYNTHESIS

Over time, many studies have been conducted with the aim to optimize the characteristics of ovarian tissue culture systems and to better support the three main phases: 1) activation of primordial follicles; 2) isolation and culture of growing preantral follicles; 3) removal from the follicle environment and maturation of oocyte cumulus complexes. While complete oocyte in vitro development has been achieved in mouse, with the production of live offspring, the goal of obtaining oocytes of sufficient quality to support embryo development has not been completely reached into higher mammals despite decades of effort.

CONCLUSIONS

Over the years, many improvements have been made on ovarian tissue cultures with the future purpose that patients will be provided with a greater number of developmentally competent oocytes for fertility preservation.

Progressive obesity alters ovarian insulin, phosphatidylinositol-3 kinase, and chemical metabolism signaling pathways and potentiates ovotoxicity induced by phosphoramide mustard in mice

Mechanisms underlying obesity-associated reproductive impairment are ill defined. Hyperinsulinemia is a metabolic perturbation often observed in obese subjects. Insulin activates phosphatidylinositol 3-kinase (PI3K) signaling, which regulates ovarian folliculogenesis, steroidogenesis, and xenobiotic metabolism. The impact of progressive obesity on ovarian genes encoding mRNA involved in insulin-mediated PI3K signaling and xenobiotic biotransformation [insulin receptor (Insr), insulin receptor substrate 1 (Irs1), 2 (Irs2), and 3 (Irs3); kit ligand (Kitlg), stem cell growth factor receptor (Kit), protein kinase B (AKT) alpha (Akt1), beta (Akt2), forkhead transcription factor (FOXO) subfamily 1 (Foxo1), and subfamily 3 (Foxo3a), microsomal epoxide hydrolase (Ephx1), cytochrome P450 family 2, subfamily E, polypeptide 1 (Cyp2e1), glutathione S-transferase (GST) class Pi (Gstp1) and class mu 1 (Gstm1)] was determined in normal wild-type nonagouti (a/a; lean) and lethal yellow mice (KK.CG-Ay/J; obese) at 6, 12, 18, or 24 weeks of age. At 6 weeks, ovaries from obese mice had increased (P < 0.05) Insr and Irs3 but decreased (P < 0.05) Kitlg, Foxo1, and Cyp2e1 mRNA levels. Interestingly, at 12 weeks, an increase (P < 0.05) in Kitlg and Kit mRNA, pIRS1Ser302, pAKTThr308, EPHX1, and GSTP1 protein level was observed due to obesity, while Cyp2e1 mRNA and protein were reduced. A phosphoramide mustard (PM) challenge increased (P < 0.05) ovarian EPHX1 protein abundance in lean but not obese females. In addition, lung tissue from PM-exposed animals had increased (P < 0.05) EPHX1 protein with no impact of obesity thereon. Taken together, progressive obesity affected ovarian signaling pathways potentially involved in obesity-associated reproductive disorders.

Comparison of the enzymatic efficiency of Liberase TM and tumor dissociation enzyme: effect on the viability of cells digested from fresh and cryopreserved human ovarian cortex

BACKGROUND

The aim of this study was to examine the effectiveness of Tumor Dissociation Enzyme (TDE) on the viability of follicles after digestion of fresh and cryopreserved ovarian cortex fragments (OCFs).

METHODS

Fresh and thawed OCF from 14 patients (29 ± 6 years), sized 20 to 210 mm³ were randomly distributed into four treatment groups and digested with 16% TDE or 0.05 mg/ml Liberase TM: Group 1, frozen OCF digested with TDE; Group 2, frozen OCF digested with LiberaseTM; Group 3, fresh OCF digested with TDE; and Group 4, fresh OCF digested with Liberase TM. Evaluation of follicle viability was performed under light microscope after staining with Neutral red. For visualization of viable and dead cells under a confocal laser scanning microscope, the follicles were stained with Calcein AM and ethidium homodimer-1.

RESULTS

The results showed that the number of retrieved follicles was significantly higher (990 vs 487; P < 0.01) in the TDE-treatment group compared to the Liberase TM-group. The presence of intense neutral red stained follicles was significantly higher in Group 1 and Group 3 compared to Group 2 and Group 4 (70.3% ± +/- 6.22 vs 53,1% ± 2.03 and 94.2% ± 6.6 vs 79.1% ± 2.1; P < 0.01). The percentage of Calcein AM stained follicles of class V1 was significantly higher in Group 1 and Group 3 compared to Group 2 and Group 4 (95.97% ± 7.8 vs 87.87% ± 2.4; 97.1% ± 6.8 vs 91.3% ± 2.3; P < 0.01).

CONCLUSION

The enzymatic digestion of ovarian cortex with TDE provides recovery of a higher number of healthy preantral follicles in contrast to earlier described Liberase TM procedure.

Neurotrophins and Trk receptors in the developing and adult ovary of Coturnix coturnix japonica

NGF, BDNF, NT-3 and their specific receptors TrkA, TrkB and TrkC are known to be involved in the development and maintenance of vertebrates' nervous system. However, these molecules play a role also in non-neuronal tissue, such as in the reproductive system. In this study we investigated the presence and localization of neurotrophins and Trk receptors to unravel their potential role in the developing and adult ovary of Japanese quail, a model species well suited for reproduction studies. Western blotting analysis on ovaries of three month old quails in the period of egg laying showed the presence of pro and mature forms of neurotrophins and splice variants of Trk receptors. Immunohistochemical investigation reported that in embryonic ovaries from the 9th day of incubation to the hatching NGF and NT-3 were observed in the cortical and medullar areas respectively, whereas Trk receptors were observed in both areas. In adult ovary, all NTs were detected in glandular stromal cells, NGF and NT-3 also in the nervous component. Regarding follicle components, NGF and BDNF were observed in oocytes and follicular cells. All TrK receptors were present in nervous components and only TrkA in glandular stromal cells. In follicles, TrkA was present in oocyte cytoplasm and TrkB in theca cells. The results suggest an involvement of the neurotrophin system in the quail ovary physiology, promoting the oocyte development and follicular organization in the embryo, as well as oocyte and follicular maturation in adults.

Expression of inhibitor proteins that control primordial follicle reserve decreases in cryopreserved ovaries after autotransplantation

PURPOSE

Even with 86 live births reported globally so far, the mechanism of primordial follicle loss following autotransplantation of the frozen-thawed ovarian tissue needs further evaluation. Pten, Tsc1, p27, and Amh are the inhibitor proteins that play crucial roles in suppressing the transition from the primordial follicle to primary state, maintaining the primordial follicle reserve. In this study, we aimed to evaluate whether the expression patterns of these proteins change and it may be related to the global primordial follicle loss after autotransplantation of the frozen-thawed ovarian tissue.

METHODS

Four groups were established in rats: fresh-control, frozen/thawed, fresh-transplanted, and frozen/thawed and transplanted. After slow freezing and thawing process, two ovarian pieces were transplanted into the back muscle of the same rat. After 2 weeks, grafts were harvested, fixed, and embedded into the paraffin block. Normal and atretic primordial/growing follicle count was performed in all groups. Ovarian tissues were evaluated for the dynamic expressions of the Pten, Tsc1, p27, and Amh proteins using immunohistochemistry, and H-score analyses were done.

RESULTS

Ovarian tissue cryopreservation does not change the expression patterns of inhibitory proteins that control ovarian reserve. Both in fresh and frozen/thawed autotransplanted groups, the expression of inhibitory proteins and Amh decreased significantly in primordial follicles and in growing follicles, respectively. In control group and in frozen/thawed group, primordial follicle counts were similar but decreased by almost half in both fresh-transplanted and frozen/thawed and transplanted groups.

CONCLUSIONS

One of the causes of primordial follicle loss after transplantation of ovarian graft may be decreased expression of the inhibitory proteins that guard the ovarian reserve and transplantation itself seems to be the major cause for disruption of inhibitory molecular signaling. Our findings highlight important molecular aspects for future clinical applications for fertility preservation in humans.