Age-dependent high-yield isolation of primordial, primary, and early secondary follicles from the bovine ovarian cortex

In brief

Preantral follicles constitute the largest follicle reserve in the mammalian ovary. This study assesses a mechanical isolation method to maximize the number of follicles retrieved from a defined cortex volume.

Abstract

Primordial, primary, and secondary follicles (collectively defined as preantral follicles) constitute the most abundant source of gametes inside the mammalian ovarian cortex. The massive isolation of preantral follicles and the refinement of stage-specific protocols for in vitro follicle growth would provide a powerful tool to boost the rescue and restoration of fertility in assisted reproduction interventions in human medicine, animal breeding, and vulnerable species preservation. Nevertheless, together with an efficient culture system, the most significant limitation to implementing in vitro follicle growth is the lack of an efficient method to isolate viable and homogeneous subpopulations of primordial, primary, and secondary follicles suitable for in vitro culture. Our study provides a strategy for high-yielding mechanical isolation of primordial, primary, and early secondary follicles from a limited portion of the ovarian cortex in the bovine animal model. In the first part of the study, we refined a mechanical isolation protocol of preantral follicles, adopting specific methodological strategies to separate viable and distinct subpopulations of primordial (oblate and prolate forms), primary, and early secondary follicles from 0.16 cm3 of the ovarian cortex. In the second part of the study, we tested the effectiveness of the isolation protocol, considering the individual's age as a critical factor, bearing in mind the progressive decrease in the ovarian reserve that naturally accompanies the reproductive life span. Our study provides a way for designing quantitative and conservative fertility preservation approaches to preserve organ function and minimize the invasiveness of the interventions, also considering age-related differences.

Mesenchymal stem cells promote ovarian reconstruction in mice

BACKGROUND

Studies have shown that chemotherapy and radiotherapy can cause premature ovarian failure and loss of fertility in female cancer patients. Ovarian cortex cryopreservation is a good choice to preserve female fertility before cancer treatment. Following the remission of the disease, the thawed ovarian tissue can be transplanted back and restore fertility of the patient. However, there is a risk to reintroduce cancer cells in the body and leads to the recurrence of cancer. Given the low success rate of current in vitro culture techniques for obtaining mature oocytes from primordial follicles, an artificial ovary with primordial follicles may be a good way to solve this problem.

METHODS

In the study, we established an artificial ovary model based on the participation of mesenchymal stem cells (MSCs) to evaluate the effect of MSCs on follicular development and oocyte maturation. P2.5 mouse ovaries were digested into single cell suspensions and mixed with bone marrow derived mesenchymal stem cells (BM-MSCs) at a 1:1 ratio. The reconstituted ovarian model was then generated by using phytohemagglutinin. The phenotype and mechanism studies were explored by follicle counting, immunohistochemistry, immunofluorescence, in vitro maturation (IVM), in vitro fertilization (IVF), real-time quantitative polymerase chain reaction (RT-PCR), and Terminal-deoxynucleotidyl transferase mediated nick end labeling(TUNEL) assay.

RESULTS

Our study found that the addition of BM-MSCs to the reconstituted ovary can enhance the survival of oocytes and promote the growth and development of follicles. After transplanting the reconstituted ovaries under kidney capsules of the recipient mice, we observed normal folliculogenesis and oocyte maturation. Interestingly, we found that BM-MSCs did not contribute to the formation of follicles in ovarian aggregation, nor did they undergo proliferation during follicle growth. Instead, the cells were found to be located around growing follicles in the reconstituted ovary. When theca cells were labeled with CYP17a1, we found some overlapped staining with green fluorescent protein(GFP)-labeled BM-MSCs. The results suggest that BM-MSCs may participate in directing the differentiation of theca layer in the reconstituted ovary.

CONCLUSIONS

The presence of BM-MSCs in the artificial ovary was found to promote the survival of ovarian cells, as well as facilitate follicle formation and development. Since the cells didn't proliferate in the reconstituted ovary, this discovery suggests a potential new and safe method for the application of MSCs in clinical fertility preservation by enhancing the success rate of cryo-thawed ovarian tissues after transplantation.

Cell polarity opposes Jak/STAT-mediated Escargot activation that drives intratumor heterogeneity in a Drosophila tumor model

In proliferating neoplasms, microenvironment-derived selective pressures promote tumor heterogeneity by imparting diverse capacities for growth, differentiation, and invasion. However, what makes a tumor cell respond to signaling cues differently from a normal cell is not well understood. In the Drosophila ovarian follicle cells, apicobasal-polarity loss induces heterogeneous epithelial multilayering. When exacerbated by oncogenic-Notch expression, this multilayer displays an increased consistency in the occurrence of morphologically distinguishable cells adjacent to the polar follicle cells. Polar cells release the Jak/STAT ligand Unpaired (Upd), in response to which neighboring polarity-deficient cells exhibit a precursor-like transcriptomic state. Among the several regulons active in these cells, we could detect and further validate the expression of Snail family transcription factor Escargot (Esg). We also ascertain a similar relationship between Upd and Esg in normally developing ovaries, where establishment of polarity determines early follicular differentiation. Overall, our results indicate that epithelial-cell polarity acts as a gatekeeper against microenvironmental selective pressures that drive heterogeneity.

Hsa-mir-548 family expression in human reproductive tissues

BACKGROUND

Hsa-miR-548ba expressed in ovarian granulosa cells targets PTEN and LIFR, which are essential for ovarian follicle activation and growth. The expression pattern of hsa-miR-548ba correlates with its host gene follicle-stimulating hormone receptor (FSHR), and FSH has a positive influence on hsa-miR-548ba expression. However, hsa-miR-548ba is a member of a large hsa-mir-548 family with potentially overlapping targets. The current study aims to investigate the co-expression of hsa-mir-548 family members in FSHR-positive reproductive tissues and to explore the potential co-regulation of pathways.

RESULTS

For the above-described analysis, small RNA sequencing data from public data repositories were used. Sequencing results revealed that hsa-miR-548ba was expressed at the highest level in the ovarian granulosa cells and uterine myometrial samples together with another twelve and one hsa-miR-548 family members, respectively. Pathway enrichment analysis of microRNA targets in the ovarian samples revealed the hsa-miR-548ba and hsa-miR-548b-5p co-regulation of RAB geranylgeranylation in mural granulosa cells. Moreover, other hsa-mir-548 family members co-regulate pathways essential for ovarian functions (PIP3 activates AKT signalling and signalling by ERBB4). In addition to hsa-miR-548ba, hsa-miR-548o-3p is expressed in the myometrium, which separately targets the peroxisome proliferator-activated receptor alpha (PPARA) pathway.

CONCLUSION

This study reveals that hsa-mir-548 family members are expressed in variable combinations in the reproductive tract, where they potentially fulfil different regulatory roles. The results provide a reference for further studies of the hsa-mir-548 family role in the reproductive tract.

Upregulation of Low-Density Lipoprotein Receptor of the Steroidogenesis Pathway in the Cumulus Cells Is Associated with the Maturation of Oocytes and Achievement of Pregnancy

The maturation of the oocyte is influenced by cumulus cells (CCs) and associated with pregnancy rate, whereas the influencing factors have not been completely elucidated in the CCs. In this study, we identified new regulators of CCs for high-quality oocytes and successful pregnancies during assisted reproductive techniques. CCs were collected from cumulus–oocyte complexes (COCs) in young (≤33 years old) and old (≥40 years old) women undergoing intracytoplasmic sperm injection (ICSI) procedures. We screened for factors differentially expressed between young vs. old CCs and pregnancy vs. non-pregnancy using whole mRNA-seq-next-generation sequencing (NGS). We characterized the transcriptome of the CCs to identify factors critical for achieving pregnancy in IVF cycles. Women in the young and old pregnancy groups exhibited the up- and downregulation of multiple genes compared with the non-pregnancy groups, revealing the differential regulation of several specific genes involved in ovarian steroidogenesis in CCs. It was shown that the low-density lipoprotein (LDL) receptor to the steroidogenesis pathway was upregulated in CCs with higher maturity rates of oocytes in the pregnancy group. In conclusion, a higher pregnancy rate is related to the signaling pathway of steroidogenesis by the LDL receptor in infertile women undergoing IVF procedures.

Single-cell transcriptome and cell-specific network analysis reveal the reparative effect of neurotrophin-4 in preantral follicles grown in vitro

BACKGROUND

In-vitro-grow (IVG) of preantral follicles is essential for female fertility preservation, while practical approach for improvement is far from being explored. Studies have indicated that neurotrophin-4 (NT-4) is preferentially expressed in human preantral follicles and may be crucial to preantral follicle growth.

METHODS

We observed the location and expression of Tropomyosin-related kinase B (TRKB) in human and mouse ovaries with immunofluorescence and Western blot, and the relation between oocyte maturation and NT-4 level in follicular fluid (FF). Mice model was applied to investigate the effect of NT-4 on preantral follicle IVG. Single-cell RNA sequencing of oocyte combined with cell-specific network analysis was conducted to uncover the underlying mechanism of effect.

RESULTS

We reported the dynamic location of TRKB in human and mouse ovaries, and a positive relationship between human oocyte maturation and NT-4 level in FF. Improving effect of NT-4 was observed on mice preantral follicle IVG, including follicle development and oocyte maturation. Transcriptome analysis showed that the reparative effect of NT-4 on oocyte maturation might be mediated by regulation of PI3K-Akt signaling and subsequent organization of F-actin. Suppression of advanced stimulated complement system in granulosa cells might contribute to the improvement. Cell-specific network analysis revealed NT-4 may recover the inflammation damage induced by abnormal lipid metabolism in IVG.

CONCLUSIONS

Our data suggest that NT-4 is involved in ovarian physiology and may improve the efficiency of preantral follicle IVG for fertility preservation.

Effects of Er:YAG laser treatment on re-vascularization and follicle survival in frozen/thawed human ovarian cortex transplanted to immunodeficient mice

PURPOSE

The huge loss of ovarian follicles after transplantation of frozen/thawed ovarian tissue is considered a major drawback on the efficacy of the procedure. Here we investigate whether Er:YAG laser treatment prior to xenotransplantation can improve re-vascularization and subsequently follicle survival in human ovarian tissue.

METHODS

A total of 99 frozen/thawed human ovarian cortex pieces were included of which 72 pieces from 12 woman were transplanted to immunodeficient mice. Tissues from each woman were included in both an 8-day and an 8-week duration study and treated with either full-beam laser (L1) or fractionated laser (L2), or served as untreated controls. Vascularization of the ovarian xenografts were evaluated after 8 days by qPCR and murine Cd31 immunohistochemical analysis. Follicle densities were evaluated histologically 8 weeks after xenografting.

RESULTS

Gene expression of Vegf/VEGF was upregulated after L1 treatment (p=0.002, p=0.07, respectively), whereas Angpt1, Angpt2, Tnf-α, and Il1-β were significantly downregulated. No change in gene expression was found in Cd31/CD31, ANGPT1, ANGPT2, ANGTPL4, XBP1, or LRG1 after any of the laser treatments. The fraction of Cd31 positive cells were significantly reduced after L1 and L2 treatment (p<0.0001; p=0.0003, respectively), compared to controls. An overall negative effect of laser treatment was detected on follicle density (p=0.03).

CONCLUSIONS

Er:YAG laser treatment did not improve re-vascularization or follicle survival in human ovarian xenografts after 8 days and 8 weeks grafting, respectively. However, further studies are needed to fully explore the potential angiogenic effects of controlled tissue damage using different intensities or lasers.

Comparison of open and a novel closed vitrification system with slow freezing for human ovarian tissue cryopreservation

PURPOSE

To investigate the differences concerning post-thawing/warming follicle survival, DNA damage and apoptosis in human ovarian tissues cryopreserved by slow freezing, open, or closed vitrification methods.

METHODS

A total of 50 pieces of 5 × 5 × 1 mm ovarian cortical pieces were harvested (5 donor ovaries; mean age 31 ± 6.62 years). From each donor, one cortical piece was used as baseline; the remaining were randomly assigned to slow freezing (SF), vitrification using open device (VF-open), or closed device (VF-closed) groups. After 8-10 weeks of cryostorage, tissues were evaluated 4 h after thawing/warming. Histological analysis was evaluated for follicle survival (primordial and primary follicle densities) by H&E staining. The percentages of primordial and primary follicles with DNA double-strand breaks (γH2AX) and apoptotic cell death pathway activation (AC3) were immunohistochemically assessed. Data were analysed using one-way ANOVA and LSD post hoc comparison.

RESULTS

Compared to the baseline, primordial follicle (pdf) densities significantly declined in all cryopreserved groups (SF, VF-open, and VF-closed, P < 0.05). However, the total and non-apoptotic pdf densities were similar among SF, VF-open, and VF-closed. SF and VF with either open or closed devices did not increase the percentages of primordial or primary follicles with DNA double-strand breaks (DSBs) or apoptosis compared to the baseline or among the freezing methods in the present study.

CONCLUSION

Based on the intact primordial follicle survival, DNA damage, and apoptosis rates after thawing/warming, SF vs VF with either open or newly developed closed devices appear to be comparable.

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

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

Protocol for evaluating autophagy using LysoTracker staining in the epithelial follicle stem cells of the Drosophila ovary

We have outlined the approach of visualizing autophagy specifically in the epithelial follicle stem cells of the Drosophila ovary using the LysoTracker dye. The advantage of using this protocol is that it details several techniques, including ovary dissection, immunofluorescence, and western blotting, that positively identify autophagy changes in a very small population of cells. One of the limitations of this protocol is that it needs to be combined with other genetic manipulations and positive markers of the autophagy pathway. For complete details on the use and execution of this protocol, please refer to Singh et al., (2018).

Corticotropin-releasing hormone reduces basal estradiol production in zebrafish follicular cells

Corticotropin-releasing hormone (CRH) plays a key regulatory role in coordinating the regulation of endocrine, autonomic nervous, immune, and reproductive systems. Two CRH (CRHα and CRHβ) and their receptors (CRHR1 and CRHR2) had been identified in zebrafish. However, their functions remained uncovered in the ovary of zebrafish. Therefore, this study aimed to determine whether CRH acts directly on the ovary to regulate steroidogenesis in cultured zebrafish follicular cells. Firstly, CRH and its receptors are expressed in the zebrafish ovary. The expression profile of CRHβ fluctuated during ovarian development in zebrafish, and the highest CRHα mRNA levels were observed at the mature follicle. The highest CRHR1 and CRHR2 mRNA levels existed in mid-vitellogenic (MV) and early vitellogenic (EV) stages, respectively. In primary cultured zebrafish follicular cells, both of the CRHα and CRHβ inhibited expression of hsd17b3 mRNA levels and decreased content of estradiol (E2) in the medium. Furthermore, CRH activated p38 MAPK and p38 MAPK inhibitor SB203580 attenuated the phosphorylation of p38 MAPK induced by CRHα. Simultaneously, SB203580 changed the effect of CRH on cyp19a1a expression but not hsd17b1 and hsd17b3. SB203580 alone or combined with CRH inhibited the E2 content. Finally, the CRHR inhibitor α-helical 9-41 also blocked the phosphorylation of p38 MAPK induced by CRHα but did not change the inhibitory effect of CRH on the mRNA expression of the steroidogenic gene and the content of E2 in the culture medium. Taken together, our findings suggest that the anti-steroidogenic effects of CRH may be mediated partly through activation of the p38 MAPK signaling pathway.

Indel mutations within the bovine HSD17B3 gene are significantly associated with ovary morphological traits and mature follicle number

Given the intensive selection for increased milk production, it is imperative that the problem of declining fertility in dairy cows be reversed. In female mammals their reproductive traits and functioning is controlled by a finely tuned process balancing estrogens and androgens, in which androgens (e.g., testosterone) as a precursor substance can participate in estrogen synthesis by activating 17β-hydroxysteroid dehydrogenase (17betaHSD). Being a key catalyst for testosterone synthesis, we hypothesized HSD17B3 gene is involved in the ovary's development and thereby capable of influencing cows' fecundity. Herein, to investigate the relationship between polymorphisms of the HSD17B3 gene and cow fertility, we characterized three insertion/deletion (indels) polymorphisms of this gene in 1110 healthy bovine ovaries. Their respective minimum allelic frequency (MAF) ranged from 0.180 to 0.482. For the ovary morphological traits, correlations revealed that both P1-D_15-bp and P4-D_19-bp demonstrated significant associations with ovarian height (P = 0.007 and 0.004, respectively), while P5-I_5-bp was found to be significantly associated with the ovarian weight (P = 0.024). For ovarian volume, a significant correlation was uncovered between it and both polymorphisms of P4-D_19-bp (P = 0.036) and P5-I_5-bp (P = 0.045). Cows with either the DD genotype of P4-D_19-bp or P5-I_5-bp tended to have greater ovarian volume, a result consistent with their relationship to ovarian weight (P5-I_5-bp) or height (P4-D_19-bp). For the mature follicle traits, polymorphisms of P4-D_19-bp were found significantly associated with the number of mature follicles (P = 0.045). Furthermore, expression levels of HSD17B3 differed significantly between the maximal and minimum groups of ovarian weight or volume, and the transcription factors GATA-1 and USF were predicted to bind P1-D_15-bp and P4-D_19-bp, respectively. This suggested the detected intron mutations could affect HSD17B3's transcription by regulating the binding of transcription factors, thereby affecting ovarian weight and other reproductive traits. As a potential effective molecular marker loci significantly related to traits of ovary and follicle, these three indels could be used in practical molecular marker-assisted selection (MAS) breeding programs, to optimize female fertility and enhance economic efficiency in the dairy cow industry.

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

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

Evidence and manipulation of O-GlcNAcylation in granulosa cells of bovine antral follicles†

Glucose is a preferred energy substrate for metabolism by bovine granulosa cells (GCs). O-linked N-acetylglucosaminylation (O-GlcNAcylation), is a product of glucose metabolism that occurs as the hexosamine biosynthesis pathway (HBP) shunts O-GlcNAc sugars to serine and threonine residues of proteins. O-GlcNAcylation through the HBP is considered a nutrient sensing mechanism that regulates many cellular processes. Yet little is known of its importance in GCs. Here, O-GlcNAcylation in GCs and its effects on GC proliferation were determined. Bovine ovaries from a slaughterhouse, staged to the mid-to-late estrous period were used. Follicular fluid and GCs were aspirated from small (3-5 mm) and large (>10 mm) antral follicles. Freshly isolated GCs of small follicles exhibited greater expression of O-GlcNAcylation and O-GlcNAc transferase (OGT) than large follicles. Less glucose and more lactate was detectable in the follicular fluid of small versus large follicles. Culture of GCs revealed that inhibition of the HBP via the glutamine fructose-6-phosphate aminotransferase inhibitor, DON (50 μM), impaired O-GlcNAcylation and GC proliferation, regardless of follicle size. Direct inhibition of O-GlcNAcylation via the OGT inhibitor, OSMI-1 (50 μM), also prevented proliferation, but only in GCs of small follicles. Augmentation of O-GlcNAcylation via the O-GlcNAcase inhibitor, Thiamet-G (2.5 μM), had no effect on GC proliferation, regardless of follicle size. The results indicate GCs of bovine antral follicles undergo O-GlcNAcylation, and O-GlcNAcylation is associated with alterations of glucose and lactate in follicular fluid. Disruption of O-GlcNAcylation impairs GC proliferation. Thus, the HBP via O-GlcNAcylation constitutes a plausible nutrient-sensing pathway influencing bovine GC function and follicular growth.

Interactions between serum FSH, inhibin B and antral follicle count in the decline of serum AMH during the menstrual cycle in late reproductive age

Objective

To investigate the hormonal interrelationships during the menstrual cycle in women of late reproductive age with suppressed serum AMH and antral follicle count (AFC).

Methods

Serum hormones (AMH, FSH, LH, estradiol, progesterone, inhibin A, inhibin B), AFC (2-10 mm) and AMH/AFC ratio (an estimate of AMH/follicle) were assessed every 2-3 days across the menstrual cycle in 26 healthy ovulatory women aged 18-50 years.

Results

An 11-fold fall in AMH/AFC was observed in women aged ≥45 years compared to those 18-45 years (P < .001). Although women ≥45 years exhibited normal menstrual cycle patterns of serum estradiol, progesterone, LH and inhibin A, FSH was elevated (P < .001) and inhibin B suppressed (P < .001) compared to the younger group. Overall FSH was inversely correlated (r = .55, P < .05) and AMH directly correlated (r = .88, P < .01) with AFC; however, these relationships were curvilinear and more pronounced when AFC was low. Inhibin B was directly linearly correlated (r = .70, P < .01) with AFC across both high and low AMH/follicle groups.

Conclusions

It is hypothesized that the marked fall in AMH/follicle in late reproductive age is attributed to the change in the hormonal interplay between the pituitary and ovary. The fall in AFC leads to a decrease in inhibin B and a concomitant increase in FSH by a recognized feedback mechanism. It is postulated the elevated FSH suppresses AMH either directly or indirectly through oocyte-specific growth factors leading to a marked fall in AMH/follicle. We propose that pituitary-ovarian and intra-ovarian regulatory systems underpin the accelerated fall in AMH/follicle during the transition to menopause.

TGF-β1-induced collagen promotes chicken ovarian follicle development via an intercellular cooperative pattern

Follicle development is a complex process under strict regulation of diverse hormones and cytokines including transforming growth factor β (TGF-β) superfamily members. TGF-β is pivotal for the regulation of ovarian functions under physiological and pathological conditions. In this study, effect of TGF-β1 on chicken follicle development was examined through investigating the accumulation and action of collagen, an indispensable member of the extracellular matrix (ECM) involved in this process. The granulosa cells (GCs) and theca cells (TCs) were separated from growing follicles of the laying chicken for treatment of TGF-β1 and analysis of expression of ECM components and key proteins in intracellular signaling pathways. Results showed that collagen was mainly distributed in the follicular theca layer and was produced with the formation of the granulosa layer during ovarian development. Collagen accumulation increased with follicle growth and treatment of GCs with TGF-β1 elicited an increased expression of collagen. After production from GCs, collagen was transferred to the neighboring TCs to promote cell proliferation and inhibit apoptosis. Treatment of collagen remarkably increased expression of p-ERK, mitogen-activated protein kinase (MAPK), and p-MAPK, but treatment with hydroxylase inhibitor (to break collagen structure) reversed these alterations. In conclusion, during follicle growth collagen was secreted by GCs under TGF-β1 stimulation and was subsequently collaboratively transferred to neighboring TCs to increase cell proliferation and thus to promote follicle development via an intercellular cooperative pattern during development of chicken growing follicles.

Bicaudal C is required for the function of the follicular epithelium during oogenesis in Rhodnius prolixus

The morphology and physiology of the oogenesis have been well studied in the vector of Chagas disease Rhodnius prolixus. However, the molecular interactions that regulate the process of egg formation, key for the reproductive cycle of the vector, is still largely unknown. In order to understand the molecular and cellular basis of the oogenesis, we examined the function of the gene Bicaudal C (BicC) during oogenesis and early development of R. prolixus. We show that R. prolixus BicC (Rp-BicC) gene is expressed in the germarium, with cytoplasmic distribution, as well as in the follicular epithelium of the developing oocytes. RNAi silencing of Rp-BicC resulted in sterile females that lay few, small, non-viable eggs. The ovaries are reduced in size and show a disarray of the follicular epithelium. This indicates that Rp-BicC has a central role in the regulation of oogenesis. Although the follicular cells are able to form the chorion, the uptake of vitelline by the oocytes is compromised. We show evidence that the polarity of the follicular epithelium and the endocytic pathway, which are crucial for the proper yolk deposition, are affected. This study provides insights into the molecular mechanisms underlying oocyte development and show that Rp-BicC is important for de developmental of the egg and, therefore, a key player in the reproduction of this insect.

Three-dimensional and two-dimensional relationships of gangliogenesis with folliculogenesis in mature mouse ovary: a Golgi-Cox staining approach

The present study was set out to investigate two-dimensional (2D) and three-dimensional (3D) evaluations of ovarian nervous network development and the structural relationship between folliculogenesis and gangliogenesis in mouse ovaries. Adult mice ovarian tissue samples were collected from follicular and luteal phases after cardiac perfusion. Ovarian samples were stained by a Golgi-Cox protocol. Following staining, tissues were serially sectioned for imaging. Neural filaments and ganglia were present in the ovaries. In both 2D and 3D studies, an increase in the number and area of ganglia was seen during the follicular growth. The same pattern was also seen in corpora lutea development. However, in some cases such as ratio of ganglia number to follicle area, the ratio of ganglia area to follicular area, 2D findings were different compared with the 3D results. 3D analysis of ovarian gangliogenesis showed the possible direct effect of them on folliculogenesis. Golgi-Cox staining was used in this study for 3D evaluation in non-brain tissue. The results of 3D analysis of the present study showed that, in some cases, the information provided by 2D analysis does not match the reality of ovarian neuronal function. This confirmed the importance of 3D analysis for evaluation of ovarian function.

Extracellular vesicles and female reproduction

Extracellular vesicles (EVs) are nano-sized membrane bound complexes that have been identified as a mean for intercellular communication between cells and tissues both in physiological and pathological conditions. These vesicles contain numerous molecules involved in signal transduction including microRNAs, mRNAs, DNA, proteins, lipids, and cytokines and can affect the behavior of recipient cells. Female reproduction is dependent on extremely fine-tuned endocrine regulation, and EVs may represent an added layer that contributes to this regulation. This narrative review article provides an update on the research of the role of EVs in female reproduction including folliculogenesis, fertilization, embryo quality, and implantation. We also highlight potential pitfalls in typical EV studies and discuss gaps in the current literature.

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.

Dual Trigger for Final Follicular Maturation Improves Cumulative Live-Birth Rate in Ovarian Stimulation for Freeze-All In Vitro Fertilization/Intracytoplasmic Sperm Injection Cycles

STUDY QUESTION

Does dual trigger in freeze-all in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycles improve the cumulative live-birth outcome compared with human chorionic gonadotropin (hCG) trigger?

SUMMARY ANSWER

Dual trigger for final follicular maturation improves the cumulative pregnancy and live-birth rates compared with hCG trigger in freeze-all IVF/ICSI cycles.

WHAT IS KNOWN ALREADY

Dual trigger could increase the numbers of oocytes and mature oocytes and improve pregnancy rates.

STUDY DESIGN SIZE DURATION

This retrospective cohort analysis included data from 4438 freeze-all IVF/ICSI cycles between January 2012 and December 2017.

PARTICIPANTS/MATERIALS SETTING METHODS

Women aged 20-49 years who underwent ovarian stimulation and oocyte retrieval for autologous IVF/ICSI with a freeze-all policy in our centre were enrolled. Data on number of oocytes retrieved, number of mature oocytes, clinical pregnancy rate, live-birth rate, cumulative pregnancy rate, and cumulative live-birth rate (CLBR) were assessed and compared between patients who underwent a dual trigger and hCG trigger. Multivariate logistic regression was performed to identify and adjust for factors known to independently affect the CLBR.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 4438 IVF/ICSI cycles were analyzed, including 1445 cycles with single hCG trigger and 2993 cycles with dual trigger. The cumulative biochemical pregnancy rate (60.8% vs. 68.1%, P<0.001; odds ratio (OR): 0.727; 95% confidence interval (CI): 0.638-0.828), cumulative clinical pregnancy rate (52.9% vs. 58.5%, P<0.001; OR: 0.796; 95%CI: 0.701-0.903), and CLBR (44.3% vs. 50.5%, P<0.001; OR: 0.781; 95%CI: 0.688-10.886) were all significantly lower in the hCG-trigger group compared with the dual-trigger group. The clinical pregnancy rate (48.2% vs. 58.2%, P=0.002; OR: 0.829; 95%CI: 0.737-0.934) and embryo implantation rate (34.4% vs. 38.9%, P<0.001; OR: 0.823; 95%CI: 0.750-0.903) in each transfer cycle were also significantly lower in the hCG-trigger group compared with the dual-trigger group. After controlling for all potential confounding variables, the trigger method was identified as an independent factor affecting the CLBR. The OR and 95%CI for hCG trigger were 0.780 and 0.641-0.949 (P=0.013).

LIMITATIONS REASONS FOR CAUTION

The data used to analyse the effect of dual trigger on cumulative pregnancy and live-birth outcomes were retrospective, and the results may thus have been subject to inherent biases. Further prospective randomized controlled trials are required to verify the beneficial effects of dual trigger.

WIDER IMPLICATIONS OF THE FINDINGS

Dual trigger had a positive effect on CLBRs, suggesting that it could be used as a routine trigger method in freeze-all cycles.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by grants from National Key Research and Development Program of China (2018YFC1004800), the Natural Science Program of Zhejiang (LY19H040009), the National Natural Science Foundation of China (No. 81601236). No authors have competing interests to declare.

Mathematical Modeling and Simulation Provides Evidence for New Strategies of Ovarian Stimulation

New approaches to ovarian stimulation protocols, such as luteal start, random start or double stimulation, allow for flexibility in ovarian stimulation at different phases of the menstrual cycle. It has been proposed that the success of these methods is based on the continuous growth of multiple cohorts ("waves") of follicles throughout the menstrual cycle which leads to the availability of ovarian follicles for ovarian controlled stimulation at several time points. Though several preliminary studies have been published, their scientific evidence has not been considered as being strong enough to integrate these results into routine clinical practice. This work aims at adding further scientific evidence about the efficiency of variable-start protocols and underpinning the theory of follicular waves by using mathematical modeling and numerical simulations. For this purpose, we have modified and coupled two previously published models, one describing the time course of hormones and one describing competitive follicular growth in a normal menstrual cycle. The coupled model is used to test ovarian stimulation protocols in silico. Simulation results show the occurrence of follicles in a wave-like manner during a normal menstrual cycle and qualitatively predict the outcome of ovarian stimulation initiated at different time points of the menstrual cycle.

Can frozen-thawed human ovary withstand refreezing-rethawing in the form of cortical strips?

PURPOSE

The aim of this study was to elucidate whether ovarian tissue is able to withstand a double freezing-thawing procedure.

METHODS

Human ovarian cortical biopsies from 4 thawed whole ovaries were divided into 4 experimental subgroups: (a) frozen-thawed non-grafted group, (b) frozen-thawed xenografted group, (c) refrozen-rethawed non-grafted group, and (d) refrozen-rethawed xenografted group. Xenografting was performed using 8 severe combined immunodeficient mice for a total duration of 21 days. The following analyses were conducted: classic hematoxylin and eosin staining, Ki67 immunolabeling, transmission electron microscopy, Masson's green trichrome, and double CD34 immunostaining.

RESULTS

Morphologically normal preantral follicles were detected in all groups. We observed a dramatic decline of more than 65% in early preantral follicle survival rates after grafting of both frozen-thawed (p < 0.0001) and refrozen-rethawed (p < 0.0001) ovarian tissue. However, mean follicle densities remained comparable between the frozen-thawed and refrozen-rethawed non-grafted groups, as well as both grafted groups. Equivalent proportions of proliferating early preantral follicles were identified in frozen-thawed and refrozen-rethawed samples, whether the tissue was grafted or not. Furthermore, we did not observe any significant difference in atretic follicle rates between any of the four groups, and the ultrastructural quality of follicles appeared unaffected by the refreezing procedure. Similar proportions of fibrosis were noted in the frozen-thawed and refrozen-rethawed groups, irrespective of grafting. Finally, no significant differences were witnessed in terms of vascularization.

CONCLUSION

We were able to demonstrate, for the first time, that refrozen-rethawed ovarian tissue has the same functional characteristics as frozen-thawed ovarian tissue.

Role of GnRH and GnIH in paracrine/autocrine control of final oocyte maturation

The control of oocyte growth and its final maturation is multifactorial and involves a number of hypothalamic, hypophyseal, and peripheral hormones. In this study, we investigated the direct actions of the gonadotropin-releasing hormone (GnRH) and the gonadotropin-inhibitory hormone (GnIH), which are expressed in the ovarian follicles, on final oocyte maturation in zebrafish, in vitro. Our study demonstrates the expression of GnRH and GnIH in the ovarian follicles of zebrafish (Danio rerio) at different stages of development and provides information on the direct action of these hormones on final oocyte maturation. Treatment with both GnRH and GnIH peptides stimulated the germinal vesicle breakdown (GVBD) of the late-vitellogenic oocyte. Both the GnRH and GnIH treatments showed no significant change in the caspase-3 activity of pre-vitellogenic and mid-vitellogenic oocytes, while they displayed different responses in the late-vitellogenic follicles. The GnRH treatment increased caspase-3 activity, whereas the GnIH reduced caspase-3 activity in the late-vitellogenic follicles. We also investigated the effects of GnRH and GnIH on the hCG-induced resumption of meiosis and caspase activity in vitro. GnRH and GnIH were found to have a similar effect on the hCG-induced resumption of meiosis, while they showed the opposite effect on caspase-3 activity. Furthermore, we investigated the effects of concomitant treatment of GnRH and GnIH peptides with hCG. The results demonstrated that the presence of both GnRH3 and GnIH are necessary for the normal induction of final oocyte maturation by gonadotropins. The findings support the hypothesis that GnIH and GnRH peptides produced in the ovary are part of a complex multifactorial regulatory system that controls zebrafish final oocyte maturation in paracrine/autocrine manner working in concert with gonadotropin hormones.

Ovarian follicular dynamics, progesterone concentrations, pregnancy rates and transcriptional patterns in Bos indicus females with a high or low antral follicle count

We evaluated the effect of the antral follicle count (AFC) on ovarian follicular dynamics, pregnancy rates, progesterone concentrations, and transcriptional patterns of genes in Nelore cattle (Bos taurus indicus) after a timed artificial insemination (TAI) programme. Cows were separated based on the AFC, and those with a high AFC showed a larger (P < 0.0001) ovarian diameter and area than those with a very low AFC. Females with a very low AFC exhibited a larger (P < 0.01) diameter of the dominant follicle at TAI (13.6 ± 0.3 vs. 12.2 ± 0.4 mm) and a tendency (P = 0.06) to have different serum progesterone concentrations (2.9 ± 0.3 vs. 2.1 ± 0.3 ng/mL; on day 18, considering day 0 as the beginning of the synchronization protocol) than those with a high AFC. The pregnancy rate was higher (P ≤ 0.05) in animals with a very low (57.9%) and low (53.1%) AFC than in those with a high AFC (45.2%). The expression of genes related to intercellular communication, meiotic control, epigenetic modulation, cell division, follicular growth, cell maintenance, steroidogenesis and cellular stress response was assessed on day 5. In females with a low AFC, 8 and 21 genes in oocytes and cumulus cells, respectively, were upregulated (P < 0.05), while 3 and 6 genes in oocytes and cumulus cells, respectively, were downregulated. The results described here will help elucidate the differences in ovarian physiology and the reproductive success of Bos indicus females with a low or high AFC.

Gradient in cytoplasmic pressure in germline cells controls overlying epithelial cell morphogenesis

It is unknown how growth in one tissue impacts morphogenesis in a neighboring tissue. To address this, we used the Drosophila ovarian follicle, in which a cluster of 15 nurse cells and a posteriorly located oocyte are surrounded by a layer of epithelial cells. It is known that as the nurse cells grow, the overlying epithelial cells flatten in a wave that begins in the anterior. Here, we demonstrate that an anterior to posterior gradient of decreasing cytoplasmic pressure is present across the nurse cells and that this gradient acts through TGFβ to control both the triggering and the progression of the wave of epithelial cell flattening. Our data indicate that intrinsic nurse cell growth is important to control proper nurse cell pressure. Finally, we reveal that nurse cell pressure and subsequent TGFβ activity in the stretched cells combine to increase follicle elongation in the anterior, which is crucial for allowing nurse cell growth and pressure control. More generally, our results reveal that during development, inner cytoplasmic pressure in individual cells has an important role in shaping their neighbors.

The optimized research of the in vitro culture of preantral follicles in mice

OBJECTIVE

Efficiency of preantral follicle culture in vitro is low and is dependent on species, development stage, and follicle-stimulating hormone (FSH) concentration. Here, we optimized the preantral follicle in vitro culture system in mice.

METHODS

The primary follicles (PM follicles, 80-100 μm diameter ) and early secondary follicles (ES follicles, 110-130 μm diameter) isolated from 14-day female mice were cultured in mediums containing 10 mIU/mL or 100 mIU/mL r-FSH. The follicle growth and oocyte maturation were observed. Estradiol (E2) was detected by ELISA. FSH receptor (FSHR), Ki-67, 3β-HSD, CYP17, and CYP19 levels were detected by immunofluorescence and Western blot.

RESULTS

The antrum formation and oocyte maturation rates of ES follicles were significantly higher than those of PM follicles (P < .05). They were also significantly higher in ES follicles with 100 mIU/mL r-FSH than with 10 mIU/mL r-FSH (P < .05). A higher FSHR level was found in ES follicles. Meanwhile, with 10 mIU/mL r-FSH, the ES follicles exhibited a pattern of flat growth, whereas a pattern of stereoscopic spatial growth was observed with 100 mIU/mL r-FSH. The 100 mIU/mL r-FSH stimulated granulosa cell proliferation more significantly than 10 mIU/mL r-FSH. Moreover, FSH significantly promoted ES follicle granulosa cell proliferation compared to PM follicular granulosa cells. The secretion of E2 and the expressions of 3β-HSD, CYP 17, and CYP 19 in ES follicles with 100 mIU/mL r-FSH were significantly higher than those with 10 mIU/mL r-FSH.

CONCLUSIONS

The 100 mIU/mL r-FSH ideally promotes the development of ES follicles, whose growth pattern can more reasonably simulate the growth of follicles in vivo.

Characterizing the effects of tonic 17β-estradiol administration on spatial learning and memory in the follicle-deplete middle-aged female rat

17β-estradiol (E2)-containing hormone therapy is a safe, effective way to alleviate unwanted menopause symptoms. Preclinical research has focused upon the role of E2 in learning and memory using a surgically menopausal rodent model whereby the ovaries are removed. Given that most women retain their reproductive tract and undergo a natural menopause transition, it is necessary to understand how exogenous E2 impacts a structurally intact, but follicle-deplete, system. In the current study, 8 month old female rats were administered the ovatoxin 4-vinylcyclohexene diepoxide (VCD), which accelerates ovarian follicular depletion, to model the human menopause transition. After follicular depletion, at 11 months old, rats were administered Vehicle or tonic E2 treatment for 12 days prior to behavioral evaluation on spatial working and reference memory tasks. Results demonstrated that E2 had both enhancing and impairing effects on taxed working memory depending upon the learning or retention phases of the water radial-arm maze, with no impact on reference memory. Relationships between memory scores and circulating estrogen levels were specific to follicle-depleted rats without E2 treatment. Collectively, findings demonstrate the complexity of E2 administration in a follicle-depleted background, with cognitive effects specific to working memory; furthermore, E2 administration altered circulating hormonal milieu and relationships between hormone profiles and memory. In sum, menopausal etiology impacts the parameters of E2 effects on cognition, complementing prior work with other estrogen compounds. Deciphering estrogenic actions in a system wherein the reproductive tract remains intact with follicle-depleted ovaries, thus modeling the majority or menopausal women, is critical for translational perspectives.

Effect of animal-sourced bioactive peptides on the in vitro development of mouse preantral follicles

The aim of this study was to investigate the effect of bioactive peptides (BAPT) from animal sources on the development of mouse preantral follicles in vitro. Preantral follicles were isolated and randomly divided into the following groups: an untreated group (control) and three groups supplemented with 20, 40 and 60 μg/mL BAPT, respectively. After establishing the in vitro follicle culture, the gene expression levels and hormone levels were quantified. After in vitro maturation, the developmental rates, reactive oxygen species (ROS) production levels and mitochondrial distributions of MII oocytes were investigated, followed by the analyses of embryonic developmental rates after in vitro fertilization.The results showed that BAPT promoted the growth of mouse preantral follicles. Notably, after 14 d of in vitro culture, the levels of 17 β-estradiol and progesterone were up-regulated with BAPT treatments. Moreover, the expression levels of Oct4, Bmp15, GDF9, FOXO3, Zp3, FOXL2, Inhibin alpha, SOD2, Catalase, GPx and Bcl-2 in the developing follicles were significantly up-regulated after BAPT treatments (P < 0.05), while BAPT significantly inhibited the expression levels of BAX (P < 0.05). Following BAPT treatments, the ROS production levels of MII oocytes were decreased while the mitochondrial distributions were significantly enhanced. Furthermore, increased maturation rates, fertilization and embryonic developmental rates were found in these BAPT-treated groups (P < 0.05).These results demonstrated that BAPT significantly improved the development of preantral follicles in vitro by reducing ROS-dependent cellular damages and by enhancing mitochondrial distributions, thereby promoting the further applications of animal-derived BAPT in biomedical research.

The ovarian stroma as a new frontier

Historically, research in ovarian biology has focused on folliculogenesis, but recently the ovarian stroma has become an exciting new frontier for research, holding critical keys to understanding complex ovarian dynamics. Ovarian follicles, which are the functional units of the ovary, comprise the ovarian parenchyma, while the ovarian stroma thus refers to the inverse or the components of the ovary that are not ovarian follicles. The ovarian stroma includes more general components such as immune cells, blood vessels, nerves, and lymphatic vessels, as well as ovary-specific components including ovarian surface epithelium, tunica albuginea, intraovarian rete ovarii, hilar cells, stem cells, and a majority of incompletely characterized stromal cells including the fibroblast-like, spindle-shaped, and interstitial cells. The stroma also includes ovarian extracellular matrix components. This review combines foundational and emerging scholarship regarding the structures and roles of the different components of the ovarian stroma in normal physiology. This is followed by a discussion of key areas for further research regarding the ovarian stroma, including elucidating theca cell origins, understanding stromal cell hormone production and responsiveness, investigating pathological conditions such as polycystic ovary syndrome (PCOS), developing artificial ovary technology, and using technological advances to further delineate the multiple stromal cell types.

Tube-like structures within the ovarian follicle of Hydrolagus colliei indicate the early origins of follicle cell processes

Follicle cell processes (FCP) are actin-based, tube-like structures that connect the developing oocyte to the follicle cells throughout oogenesis. They were first described in Selachians (sharks) where their suggested roles were facilitating the transport of metabolites to the developing oocyte and providing structural support to the large egg cells of sharks, an early stage in the evolution of viviparity. Subsequent studies found that FCP are absent in Rajiformes (skates), suggesting that FCP may have been novel structures specific to the sharks. Here, FCP in Hydrolagus colliei, a Chimaeriform, were described. The FCP of H. colliei differ morphologically from those previously described in sharks, but as they also contain actin, they presumably play similar roles provisioning the developing oocyte and providing structural support. The presence of FCP in the order Chimaeriformes suggests that their origin predates the split of the elasmobranchs and the holocephalans.

A Preliminary Study on the Characteristics of microRNAs in Ovarian Stroma and Follicles of Chuanzhong Black Goat during Estrus

microRNAs (miRNAs) play a significant role in ovarian follicular maturity, but miRNA expression patterns in ovarian stroma (OS), large follicles (LF), and small follicles (SF) have been rarely explored. We herein aimed to identify miRNAs, their target genes and signaling pathways, as well as their interaction networks in OS, LF, and SF of Chuanzhong black goats at the estrus phase using small RNA-sequencing. We found that the miRNA expression profiles of LF and SF were more similar than those of OS—32, 16, and 29 differentially expressed miRNAs were identified in OS vs. LF, OS vs. SF, and LF vs. SF, respectively. Analyses of functional enrichment and the miRNA-targeted gene interaction network suggested that miR-182 (SMC3), miR-122 (SGO1), and miR-206 (AURKA) were involved in ovarian organogenesis and hormone secretion by oocyte meiosis. Furthermore, miR-202-5p (EREG) and miR-485-3p (FLT3) were involved in follicular maturation through the MAPK signaling pathway, and miR-2404 (BMP7 and CDKN1C) played a key role in follicular development through the TGF-β signaling pathway and cell cycle; nevertheless, further research is warranted. To our knowledge, this is the first study to investigate miRNA expression patterns in OS, LF, and SF of Chuanzhong black goats during estrus. Our findings provide a theoretical basis to elucidate the role of miRNAs in follicular maturation. These key miRNAs might provide candidate biomarkers for the diagnosis of follicular maturation and will assist in developing new therapeutic targets for female goat infertility.

Decellularization and recellularization of the ovary for bioengineering applications; studies in the mouse

BACKGROUND

Fertility preservation is particularly challenging in young women diagnosed with hematopoietic cancers, as transplantation of cryopreserved ovarian cortex in these women carries the risk for re-introducing cancer cells. Therefore, the construction of a bioengineered ovary that can accommodate isolated small follicles was proposed as an alternative to minimize the risk of malignancy transmission. Various options for viable bioengineered scaffolds have been reported in the literature. Previously, we reported three protocols for producing mouse ovarian scaffolds with the decellularization technique. The present study examined these scaffolds further, specifically with regards to their extracellular composition, biocompatibility and ability to support recellularization with mesenchymal stem cells.

MATERIAL AND METHODS

Three decellularization protocols based on 0.5% sodium dodecyl sulfate (Protocol 1; P1), or 2% sodium deoxycholate (P2), or a combination of the two detergents (P3) were applied to produce three types of scaffolds. The levels of collagen, elastin and sulfated glycosaminoglycans (sGAGs) were quantified in the remaining extracellular matrix. Detailed immunofluorescence and scanning electron microscopy imaging were conducted to assess the morphology and recellularization efficiency of the constructs after 14 days in vitro utilizing red fluorescent protein-labelled mesenchymal stem cells.

RESULTS

All protocols efficiently removed the DNA while the elastin content was not significantly reduced during the procedures. The SDS-protocol (P1) reduced the sGAG and the collagen content more than the SDC-protocol (P2). All scaffolds were biocompatible and recellularization was successful, particularly in several P2-derived scaffolds. The cells were extensively distributed throughout the constructs, with a denser distribution observed towards the ovarian cortex. The cell density was not significantly different (400 to 550 cells/mm²) between scaffold types. However, there was a tendency towards a higher cell density in the SDC-derived constructs. Scanning electron microscope images showed fibrous scaffolds with a dense repopulated surface structure.

CONCLUSIONS

While there were differences in the key structural macromolecules between protocols, all scaffolds were biocompatible and showed effective recellularization. The results indicate that our SDC-protocol might be better than our SDS-protocol. However, additional studies are necessary to determine their suitability for attachment of small follicles and folliculogenesis.

Drosophila Insulin-Like Peptide 8 (DILP8) in Ovarian Follicle Cells Regulates Ovulation and Metabolism

In Drosophila melanogaster eight insulin-like peptides (DILP1-8) are encoded on separate genes. These DILPs are characterized by unique spatial and temporal expression patterns during the lifecycle. Whereas, functions of several of the DILPs have been extensively investigated at different developmental stages, the role of DILP8 signaling is primarily known from larvae and pupae where it couples organ growth and developmental transitions. In adult female flies, a study showed that a specific set of neurons that express the DILP8 receptor, Lgr3, is involved in regulation of reproductive behavior. Here, we further investigated the expression of dilp8/DILP8 and Lgr3 in adult female flies and the functional role of DILP8 signaling. The only site where we found both dilp8 expression and DILP8 immunolabeling was in follicle cells around mature eggs. Lgr3 expression was detected in numerous neurons in the brain and ventral nerve cord, a small set of peripheral neurons innervating the abdominal heart, as well as in a set of follicle cells close to the oviduct. Ovulation was affected in dilp8 mutants as well as after dilp8-RNAi using dilp8 and follicle cell Gal4 drivers. More eggs were retained in the ovaries and fewer were laid, indicating that DILP8 is important for ovulation. Our data suggest that DILP8 signals locally to Lgr3 expressing follicle cells as well as systemically to Lgr3 expressing efferent neurons in abdominal ganglia that innervate oviduct muscle. Thus, DILP8 may act at two targets to regulate ovulation: follicle cell rupture and oviduct contractions. Furthermore, we could show that manipulations of dilp8 expression affect starvation resistance suggesting effects on metabolism. Possibly this reflects a feedback signaling between ovaries and the CNS that ensures nutrients for ovary development. In summary, it seems that DILP8 signaling in regulation of reproduction is an ancient function, conserved in relaxin signaling in mammals.

Role of anti-Müllerian hormone and testosterone in follicular growth: a cross-sectional study

BACKGROUND

Anti-Müllerian hormone (AMH) is now considered the best serum biomarker of ovarian reserve, while basal sex hormones are classic markers used for assessing ovarian reserve. The interaction between AMH and sex hormones are complicated and not sufficiently addressed. In this study, we took diminished ovarian reserve (DOR) and polycystic ovarian syndrome (PCOS) as two extremes of ovarian reserve (deficient and excessive respectively) to investigate the role of AMH and sex hormones in follicular growth.

METHODS

A retrospective cross-sectional survey was performed. The patients assessed AMH and basal sex hormones in the Second Hospital of Zhejiang University from April 2016 to March 2019 were involved in this study. Serum AMH and sex hormone concentrations were tested with electrochemiluminescence method. Stepwise linear regression and binary logistic regression was used to determine the predictors of AMH level and to explore the involved factors determining DOR and PCOS.

RESULTS

In the present study, we found that age and follicle-stimulating hormone (FSH) were main negative correlation factors, and luteinizing hormone (LH) and testosterone (T) were main positive factors of AMH. In DOR group, age, FSH and estradiol (E₂) increased and T decreased, while in PCOS group, LH and T increased. Binary logistic regression found that age, weight, FSH, E₂, and T were the significant factors which independently predicted the likelihood of DOR, and that age, body mass index (BMI), AMH, LH, and T predicted the likelihood of PCOS.

CONCLUSIONS

Our study demonstrated that age, FSH, and T were factors that most closely correlated with AMH level, and T was involved in both DOR and PCOS. Since DOR and PCOS are manifested with insufficient AMH and excessive AMH respectively, it is suggested that total testosterone correlated with AMH closely and plays an important role in follicular growth. More attention should be given to testosterone level during controlled ovarian hyperstimulation (COH) process.

Role of 3-D Transvaginal Ultrasonography in Women Undergoing in Vitro Fertilization/Intra-cytoplasmic Sperm Injection

Both 2-D and 3-D transvaginal ultrasonography are effective imaging modalities for assessment of ovarian reserve. Our aim was to compare both modalities in assessment of ovarian reserve of women undergoing in vitro fertilization/intra-cytoplasmic sperm injection (IVF/ICSI). Fifty women were scheduled according to their menstrual cycle to be examined by both 2-D and 3-D transvaginal ultrasonography. We found that the average time for computerized analysis of the 3-D ultrasound data was significantly shorter than that for analysis of the 2-D ultrasound data, for both total antral follicle count and ovarian volume. However, there were no statistically significant differences between the methods in total antral follicle count and ovarian volume. We conclude that, where available, 3-D ultrasonography can be used for assessment of ovarian reserve in addition to the biochemical marker, particularly in overcrowded in vitro fertilization centers that need to save time.

Microanalysis of Fish Ovarian Follicular Atresia: A Possible Synergic Action of Somatic and Immune Cells

The present study describes in detail the morphological characteristics of the process of ovarian follicular atresia in Redbelly tilapia (Coptodon zillii) during the nonbreeding season using light and electron microscopy and immunohistochemistry. The follicular regression process was initiated with shrinkage and disintegration of the nuclear membrane of oocytes resulting in dispersing of chromatin within the ooplasm, followed by marked hyperplasia and hypertrophy of follicular and granulosa cells, which exhibited a strong phagocytic activity to engulf the liquefied yolk particles. Rodlet cells and granulocytes were recorded on the follicular wall and invaded the regressed follicles. Rodlet cells expressed a strong immunoreactivity to matrix metalloperoxidase (MMP-9) and α-smooth muscle actin, while neutrophils expressed a strong reactivity to Myeloperoxidase-3 (MPO). In the advanced stage of follicular atresia, the yolk was almost phagocytized and resorbed and the regressed follicle lost its integrity and appeared to be formed of a cellular mass of phagocytic cells. Transmission electron microscopy revealed the presence of neutrophils, eosinophils, and dendritic cells within the atretic follicle in between these phagocytic cells. Moreover, numerous lysosomes, granules, and phagosomes were observed within the cytoplasm of both phagocytic cells and granulocytes. Telocytes were also demonstrated within the highly thickened richly vascularized theca layer during the late stages of follicular atresia. Immunohistochemical staining for caspase-3 established the participation of apoptosis in the advanced stages of follicular regression. Immune cells, rodlet cells, and telocytes in combination with follicular cells play an essential role in follicular atresia. In conclusion, the present study provides a new evidence on the role of both somatic and immune cells in the phenomenon of ovarian follicular atresia in Redbelly tilapia (Coptodon zillii) during the nonbreeding season.

Distinct activities of Scrib module proteins organize epithelial polarity

A polarized architecture is central to both epithelial structure and function. In many cells, polarity involves mutual antagonism between the Par complex and the Scribble (Scrib) module. While molecular mechanisms underlying Par-mediated apical determination are well-understood, how Scrib module proteins specify the basolateral domain remains unknown. Here, we demonstrate dependent and independent activities of Scrib, Discs-large (Dlg), and Lethal giant larvae (Lgl) using the Drosophila follicle epithelium. Our data support a linear hierarchy for localization, but rule out previously proposed protein-protein interactions as essential for polarization. Cortical recruitment of Scrib does not require palmitoylation or polar phospholipid binding but instead an independent cortically stabilizing activity of Dlg. Scrib and Dlg do not directly antagonize atypical protein kinase C (aPKC), but may instead restrict aPKC localization by enabling the aPKC-inhibiting activity of Lgl. Importantly, while Scrib, Dlg, and Lgl are each required, all three together are not sufficient to antagonize the Par complex. Our data demonstrate previously unappreciated diversity of function within the Scrib module and begin to define the elusive molecular functions of Scrib and Dlg.

Corticosterone and testosterone treatment influence expression of gene pathways linked to meiotic segregation in preovulatory follicles of the domestic hen

Decades of work indicate that female birds can control their offspring sex ratios in response to environmental and social cues. In laying hens, hormones administered immediately prior to sex chromosome segregation can exert sex ratio skews, indicating that these hormones may act directly on the germinal disc to influence which sex chromosome is retained in the oocyte and which is discarded into an unfertilizable polar body. We aimed to uncover the gene pathways involved in this process by testing whether treatments with testosterone or corticosterone that were previously shown to influence sex ratios elicit changes in the expression of genes and/or gene pathways involved in the process of meiotic segregation. We injected laying hens with testosterone, corticosterone, or control oil 5h prior to ovulation and collected germinal discs from the F1 preovulatory follicle in each hen 1.5h after injection. We used RNA-sequencing (RNA-seq) followed by DESeq2 and gene set enrichment analyses to identify genes and gene pathways that were differentially expressed between germinal discs of control and hormone-treated hens. Corticosterone treatment triggered downregulation of 13 individual genes, as well as enrichment of gene sets related to meiotic spindle organization and chromosome segregation, and additional gene sets that function in ion transport. Testosterone treatment triggered upregulation of one gene, and enrichment of one gene set that functions in nuclear chromosome segregation. This work indicates that corticosterone can be a potent regulator of meiotic processes and provides potential gene targets on which corticosterone and/or testosterone may act to influence offspring sex ratios in birds.

Peroxisome Proliferator-Activated Receptor Gamma Modulator Promotes Neonatal Mouse Primordial Follicle Activation In Vitro

Peroxisome proliferator-activated receptor gamma (PPARγ) is known as a regulator of cellular functions, including adipogenesis and immune cell activation. The objectives of this study were to investigate the expression of PPARγ and identify the mechanism of primordial follicle activation via PPARγ modulators in mouse ovaries. We first measured the gene expression of PPARγ and determined its relationship with phosphatase and tensin homolog (PTEN), protein kinase B (AKT1), and forkhead box O3a (FOXO3a) expression in neonatal mouse ovaries. We then incubated neonatal mouse ovaries with PPARγ modulators, including rosiglitazone (a synthetic agonist of PPARγ), GW9662 (a synthetic antagonist of PPARγ), and cyclic phosphatidic acid (cPA, a physiological inhibitor of PPARγ), followed by transplantation into adult ovariectomized mice. After the maturation of the transplanted ovaries, primordial follicle growth activation, follicle growth, and embryonic development were evaluated. Finally, the delivery of live pups after embryo transfer into recipient mice was assessed. While PPARγ was expressed in ovaries from mice of all ages, its levels were significantly increased in ovaries from 20-day-old mice. In GW9662-treated ovaries in vitro, PTEN levels were decreased, AKT was activated, and FOXO3a was excluded from the nuclei of primordial follicles. After 1 month, cPA-pretreated, transplanted ovaries produced the highest numbers of oocytes and polar bodies, exhibited the most advanced embryonic development, and had the greatest blastocyst formation rate compared to the rosiglitazone- and GW9662-pretreated groups. Additionally, the successful delivery of live pups after embryo transfer into the recipient mice transplanted with cPA-pretreated ovaries was confirmed. Our study demonstrates that PPARγ participates in primordial follicle activation and development, possibly mediated in part by the PI3K/AKT signaling pathway. Although more studies are required, adapting these findings for the activation of human primordial follicles may lead to treatments for infertility that originates from poor ovarian reserves.

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.

Estrogen regulation of germline stem cell differentiation as a mechanism contributing to female reproductive aging

Progressive loss of ovarian estrogen (E2) production is a hallmark feature of, if not a driving force behind, reproductive aging and the menopause. Recent genetic studies in mice have shown that female germline or oogonial stem cells (OSCs) contribute to maintenance of adult ovarian function and fertility under physiological conditions through support of de-novo oogenesis. Here we show that mouse OSCs express E2 receptor-α (ERα). In the presence of E2, ERα interacts with the stimulated by retinoic acid gene 8 (Stra8) promoter to drive Stra8 expression followed by oogenesis. Treatment of mice with E2 in vivo increases Stra8 expression and oogenesis, and these effects are nullified by ERα (Esr1), but not ERβ (Esr2), gene disruption. Although mice lacking ERα are born with a normal quota of oocytes, ERα-deficient females develop premature ovarian insufficiency in adulthood due to impaired oogenesis. Lastly, mice treated with reversible ER antagonists show a loss of Stra8 expression and oocyte numbers; however, both endpoints rebound to control levels after ceasing drug treatment. These findings establish a key physiological role for E2-ERα signaling in promoting OSC differentiation as a potential mechanism to maintain adequate numbers of ovarian follicles during reproductive life.

A single-cell atlas of adult Drosophila ovary identifies transcriptional programs and somatic cell lineage regulating oogenesis

Oogenesis is a complex developmental process that involves spatiotemporally regulated coordination between the germline and supporting, somatic cell populations. This process has been modeled extensively using the Drosophila ovary. Although different ovarian cell types have been identified through traditional means, the large-scale expression profiles underlying each cell type remain unknown. Using single-cell RNA sequencing technology, we have built a transcriptomic data set for the adult Drosophila ovary and connected tissues. Using this data set, we identified the transcriptional trajectory of the entire follicle-cell population over the course of their development from stem cells to the oogenesis-to-ovulation transition. We further identify expression patterns during essential developmental events that take place in somatic and germline cell types such as differentiation, cell-cycle switching, migration, symmetry breaking, nurse-cell engulfment, egg-shell formation, and corpus luteum signaling. Extensive experimental validation of unique expression patterns in both ovarian and nearby, nonovarian cells also led to the identification of many new cell type-and stage-specific markers. The inclusion of several nearby tissue types in this data set also led to our identification of functional convergence in expression between distantly related cell types such as the immune-related genes that were similarly expressed in immune cells (hemocytes) and ovarian somatic cells (stretched cells) during their brief phagocytic role in nurse-cell engulfment. Taken together, these findings provide new insight into the temporal regulation of genes in a cell-type specific manner during oogenesis and begin to reveal the relatedness in expression between cell and tissues types.

The cytoskeletal motor proteins Dynein and MyoV direct apical transport of Crumbs

Crumbs (Crb in Drosophila; CRB1-3 in mammals) is a transmembrane determinant of epithelial cell polarity and a regulator of Hippo signalling. Crb is normally localized to apical cell-cell contacts, just above adherens junctions, but how apical trafficking of Crb is regulated in epithelial cells remains unclear. We use the Drosophila follicular epithelium to demonstrate that polarized trafficking of Crb is mediated by transport along microtubules by the motor protein Dynein and along actin filaments by the motor protein Myosin-V (MyoV). Blocking transport of Crb-containing vesicles by Dynein or MyoV leads to accumulation of Crb within Rab11 endosomes, rather than apical delivery. The final steps of Crb delivery and stabilisation at the plasma membrane requires the exocyst complex and three apical FERM domain proteins - Merlin, Moesin and Expanded - whose simultaneous loss disrupts apical localization of Crb. Accordingly, a knock-in deletion of the Crb FERM-binding motif (FBM) also impairs apical localization. Finally, overexpression of Crb challenges this system, creating a sensitized background to identify components involved in cytoskeletal polarization, apical membrane trafficking and stabilisation of Crb at the apical domain.

Germline stem cell aging in the Drosophila ovary

The age-related decline of adult stem cells leads to loss of tissue homeostasis and contributes to organismal aging. Though the phenotypic hallmarks of aging are well-characterized at the organ or tissue level, the molecular processes that govern stem cell aging remain unclear. This review seeks to highlight recent research in stem cell aging in the Drosophila ovary and connect the discoveries in the fly to ongoing questions in stem cell aging.

A single-cell atlas of the developing Drosophila ovary identifies follicle stem cell progenitors

Addressing the complexity of organogenesis at a system-wide level requires a complete understanding of adult cell types, their origin, and precursor relationships. The Drosophila ovary has been a model to study how coordinated stem cell units, germline, and somatic follicle stem cells maintain and renew an organ. However, lack of cell type-specific tools have limited our ability to study the origin of individual cell types and stem cell units. Here, we used a single-cell RNA sequencing approach to uncover all known cell types of the developing ovary, reveal transcriptional signatures, and identify cell type-specific markers for lineage tracing. Our study identifies a novel cell type corresponding to the elusive follicle stem cell precursors and predicts subtypes of known cell types. Altogether, we reveal a previously unanticipated complexity of the developing ovary and provide a comprehensive resource for the systematic analysis of ovary morphogenesis.

Signal transduction in the early Drosophila follicle stem cell lineage

The follicle stem cell (FSC) lineage in the Drosophila ovary is a highly informative model of in vivo epithelial stem cell biology. Studies over the past 30 years have identified roles for every major signaling pathway in the early FSC lineage. These pathways regulate a wide variety of cell behaviors, including self-renewal, proliferation, survival and differentiation. Studies of cell signaling in the follicle epithelium have provided new insights into how these cell behaviors are coordinated within an epithelial stem cell lineage and how signaling pathways interact with each other in the native, in vivo context of a living tissue. Here, we review these studies, with a particular focus on how these pathways specify differences between the FSCs and their daughter cells. We also describe common themes that have emerged from these studies, and highlight new research directions that have been made possible by the detailed understanding of the follicle epithelium.

Follicular Output Rate and Follicle-to-Oocyte Index of Low Prognosis Patients According to POSEIDON Criteria: A Retrospective Cohort Study of 32,128 Treatment Cycles

OBJECTIVE

To investigate ovarian sensitivity in subgroups of patients with a low prognosis, as defined by the POSEIDON criteria, undergoing in vitro fertilization treatment and measures to improve ovarian sensitivity in these patients.

DESIGN

We conducted a retrospective cohort analysis.

SETTING

The study was conducted at an IVF clinic in a public hospital.

PATIENTS

A total of 32,128 fresh IVF cycles from January 2014 to October 2018 at a single IVF clinic were included in the analysis. Patients with a low prognosis were categorized into four groups based on the POSEIDON criteria.

INTERVENTIONS

None.

MAIN OUTCOME MEASURE

The primary outcome measures were the follicular output rate (FORT) and the follicle-to-oocyte index (FOI).

RESULTS

The FORTs in the order from the highest to the lowest were 1.18 in group 3, 0.98 in group 4, 0.76 in group 1, and 0.68 in group 2. The trend in the FOI values was consistent with that in the FORTs. Among patients with poor ovarian sensitivity, 58.41% of patients with FORTs ≥ 0.30 in the second cycle underwent an adjustment to the ovarian stimulation (OS) protocol and 41.59% underwent an adjustment to the gonadotropin (Gn) starting dose. Among patients with normal ovarian sensitivity, 43.56% of those with FORTs ≥ 0.80 in the second cycle underwent an adjustment to the OS protocol and 56.44% underwent an adjustment to the Gn starting dose.

CONCLUSION

Ovarian sensitivity was the highest in group 3 (young women with poor ovarian reserve), followed by groups 4 (women at advanced age with poor ovarian reserve) and 1 (young women with good ovarian reserve), and it was the lowest in group 2 (women at advanced age with good ovarian reserve). For patients with poor ovarian sensitivity, it is preferred to recommend an adjustment to the OS protocol, while for those with normal ovarian sensitivity, adjusting the Gn starting dose is preferred.

In vitro growth of immature bovine follicles and oocytes

The limitation in the supply of mature, fertilisable oocytes constitutes a major impediment to increasing the success of assisted reproduction, stem cell derivation and cloning in domestic species. Techniques are being developed to grow immature oocytes invitro that have the potential to increase the supply of oocytes. Mouse oocytes can be cultured from initial stages of development to maturity, and live young have been produced, but for domestic species, such as cows, with long growth periods, invitro systems that allow complete growth of oocytes contained within primordial follicles to maturity is technically challenging and has not yet been achieved. For cows, several culture systems have been developed that support specific developmental stages, but a multistep culture system will be required for complete growth invitro. This review highlights the steps that will be required to achieve the goal of growing oocytes invitro.

Commentary on the Recent FSH Collection: Known Knowns and Known Unknowns

Follicle-stimulating hormone (FSH) is a dimeric glycoprotein secreted by the anterior pituitary gonadotrope that is necessary for reproductive function in mammals. FSH primarily regulates granulosa cells and follicular growth in females, and Sertoli cell function in males. Since its identification in the 1930s and sequencing in the 1970s, significant progress has been made in elucidating its regulation and downstream function. Recent advances provide deeper insight into FSH synthesis, and effects in the gonads suggest potential roles in extragonadal tissues and examine pharmacological approaches and clinical applications in infertility treatment that now affect 18% of couples. These advances were discussed in detail in a number of reviews published in the last 2 years in Endocrinology. In this brief commentary, we summarize these reviews and point to the outstanding questions that should be answered in the near future to bridge a gap in our understanding of this hormone.