Follicle dynamics: visualization and analysis of follicle growth and maturation using murine ovarian tissue culture

Advancing fertility preservation in prepubertal mice: Efficacy of ovarian tissue culture and in vitro growth in mature oocyte development

AIM

This study aimed to evaluate the ovarian tissue culture and in vitro follicle growth as safer alternatives to cryopreservation for generating in vitro fertilization (IVF)-ready mature oocytes from prepubertal mice without the risk of cancer cell contamination.

METHODS

Ovaries from prepubertal B6D2F1 mice were cultured in α-minimum essential medium supplemented with an estrogen receptor antagonist, ICI 182780. Culture duration was investigated to identify the optimal timeframe for follicle growth and oocyte maturation. Follicles were isolated mechanically or using 1 mg/mL collagenase and cultured in Matrigel matrix or polyvinylpyrrolidone. Oocyte development at metaphase II was induced by in vitro maturation, followed by IVF.

RESULTS

The optimal culture duration was 2-4 days, and tissues cultured beyond this period showed significant follicular degeneration. ICI 182780 supplementation resulted in the recovery of 20.5 follicles per ovary compared with 9.5 follicles in non-supplemented cultures (p < 0.05). Of the 452 isolated follicles, 237 (52.4%) showed growth, 150 (33.2%) underwent germinal vesicle breakdown, and 18 (4.0%) reached metaphase II. However, none of the metaphase II oocytes were successfully fertilized after IVF. Matrigel demonstrated a significantly higher in vitro maturation rate compared with polyvinylpyrrolidone in a comparative analysis of culture matrices (p < 0.001).

CONCLUSIONS

This study highlighted ovarian tissue culture and in vitro growth as effective strategies for producing mature oocytes from prepubertal mice. Further studies are required to overcome fertilization hurdles and understand the mechanisms that improve post-IVF embryo viability.

In vitro culture of mechanically isolated murine primary follicles in the presence of human platelet lysate PLTMax

OBJECTIVE

To develop a system for the culture of murine preantral ovarian follicles using Human Serum Albumin (HSA) and Human Platelet Lysate (PLTMax).

METHODS

Mechanically isolated preantral follicles (N=146) were obtained from Swiss mice and cultured in DMEM:F12 medium for ten days in a 96-well plate with conical bottom. The medium was supplemented with penicillin, streptomycin, and equine chorionic gonadotropin. Additional proteins were tested in 4 test groups: G1: human serum albumin (HSA), G2: human platelet lysate (PLTM), and G3 and G4: HSA + PLTMax at lower and higher concentrations, respectively. Cellular vitality and oocyte morphology were evaluated on day 11 of culture.

RESULTS

The highest follicular growth (3.4 fold) was achieved in HSA (G1), while a significantly lower (1.8 fold) growth was achieved in the presence of PLTM (G2, G4) and even further reduced (1.2 fold) when HSA and PLTM were combined (G3). Cellular vitality was close to 70-80% among the four groups, and the highest number of intact oocytes were found in G1.

CONCLUSIONS

PLTM did not improve follicular development and oocyte maturation compared to HSA but preserved cell vitality.

In-depth analysis of transcriptomes in ovarian cortical follicles from children and adults reveals interfollicular heterogeneity

The ovarian cortical reserve of follicles is vital for fertility. Some medical treatments are toxic to follicles, leading to premature ovarian insufficiency. Ovarian tissue cryopreservation is an established method to preserve fertility in adults and even applied in prepuberty despite unproven efficacy. Here, we analyze transcriptomes of 120 cortical follicles from children and adults for detailed comparison. We discover heterogeneity with two main types of follicles in both age groups: one with expected oocyte-granulosa profiles and another with predicted role in signaling. Transcriptional changes during growth to the secondary stage are similar overall in children and adults, but variations related to extracellular matrix, theca cells, and miRNA profiles are found. Notably, cyclophosphamide dose correlates with interferon signaling in child follicles. Additionally, morphology alone is insufficient for follicle categorization suggesting a need for additional markers. Marker genes for early follicle activation are determined. These findings will help refine follicular classification and fertility preservation techniques across critical ages.

Knockdown of DNMT1 Induces SLCO3A1 to Promote Follicular Growth by Enhancing the Proliferation of Granulosa Cells in Mammals

In female mammals, the proliferation and apoptosis of granulosa cells (GCs) have been shown to determine the fate of follicles. DNA methyltransferases (DNMTs) and SLCO3A1 have been reported to be involved in the survival of GCs and follicular growth. However, the molecular mechanisms enabling DNMTs to regulate the expression of SLCO3A1 to participate in follicular growth are unclear. In this study, we found that the knockdown of DNMT1 enhanced the mRNA and protein levels of SLCO3A1 by regulating the chromatin accessibility probably. Moreover, SLCO3A1 upregulated the mRNA and protein levels of MCL1, PCNA, and STAR to promote the proliferation of GCs and facilitated cell cycle progression by increasing the mRNA and protein levels of CCNE1, CDK2, and CCND1, but it decreased apoptosis by downregulating the mRNA and protein levels of CASP3 and CASP8. Moreover, SLCO3A1 promoted the growth of porcine follicles and development of mice follicles. In conclusion, the knockdown of DNMT1 upregulated the mRNA and protein levels of SLCO3A1, thereby promoting the proliferation of GCs to facilitate the growth and development of ovarian follicles, and these results provide new insights into investigations of female reproductive diseases.

Rehmannioside D mitigates disease progression in rats with experimental-induced diminished ovarian reserve via Forkhead Box O1/KLOTHO axis

This study aims to explore the impact of Rehmannioside D (RD) on ovarian functions of rats with diminished ovarian reserve (DOR) and its underlying mechanisms of action. A single injection of cyclophosphamide was performed to establish a DOR rat model, and fourteen days after the injection, the rats were intragastrically administrated with RD for two weeks. Rat estrus cycles were tested using vaginal smears. Ovarian tissues were histologically evaluated, the number of primordial, mature, and atretic follicles was calculated, and the apoptotic rate of granulosa cells. Follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E₂) levels were determined by ELISA assays. Protein levels of Forkhead Box O1 (FOXO1), KLOTHO, Bcl-2, and Bax were investigated in ovarian tissues of DOR rats. The binding between FOXO1 and KLOTHO was verified by ChIP assay. High-dose administration of RD into DOR rats improved their estrus cycles, increased ovarian index, enhanced the number of primordial and mature follicles, reduced the number of atretic follicle number, and ovarian granulosa cell apoptosis in addition to inhibiting FSH and LH levels and upregulating E₂ expression. FOXO1 and KLOTHO were significantly suppressed in DOR rats. FOXO1 knockdown partially suppressed the protective effects of RD on DOR rats, and KLOTHO overexpression could restore RD-induced blockade of DOR development despite knocking down FOXO1. FOXO1 antibody enriched KLOTHO promoter, and the binding between them was reduced in DOR group compared to that in sham group. RD improved ovarian functions in DOR rats and diminished granulosa cell apoptosis via the FOXO1/KLOTHO axis.

Linking mitochondrial dynamics and fertility: promoting fertility by phoenixin through modulation of ovarian expression of GnRH receptor and mitochondrial dynamics proteins DRP-1 and Mfn-2

Obesity is linked to reproductive disorders. Novel neuropeptide phoenixin demonstrated many therapeutic actions. In this study, we aim to evaluate phoenixin’s potential effect in obesity-induced infertility through modulating mitochondrial dynamics. Ninety adult female rats were divided to 4 groups: (I), fed with normal pellet diet; (II), given phoenixin; (III), fed with high-fat diet. Rats that developed obesity and infertility were divided to 2 groups: (III-A), received no further treatment; (III-B), given phoenixin. Our results showed that phoenixin treatment in obese infertile rats significantly decreased serum levels of insulin and testosterone and ovarian levels of dynamin-related protein1(Drp1),reactive oxygen species ROS, TNF-α, MDA, and caspase-3. Phoenixin treatment also significantly increased serum estrogen progesterone, LH, and FSH together with ovarian levels of GnRH receptor (GnRHR), mitofusin2(Mfn2), mitochondrial transmembrane potential (ΔΨm), and electron transport chain (ETC) complex-I significantly when compared with obese group. Ovarian histopathological changes were similarly improved by phoenixin. Our data demonstrate phoenixin’s role in improving obesity-induced infertility.

miR-221-3p regulates apoptosis of ovarian granulosa cells via targeting FOXO1 in older women with diminished ovarian reserve (DOR)

In our earlier study, we showed that the expression of microRNA‐221‐3p (miR‐221‐3p) was significantly lower in women of advanced age with diminished ovarian reserve (DOR) compared with young women with normal ovarian reserve (NOR). Therefore, in this study, we aimed to explore how miR‐221‐3p regulates apoptosis of granulosa cells and the pathogenesis of DOR. Bioinformatics prediction and dual‐luciferase reporter assay were conducted to identify the target gene of miR‐221‐3p. miR‐221‐3p expression was manipulated by transfecting KGN cells with miR‐221‐3p mimics, inhibitor, and negative control. Following transfection, apoptosis of granulosa cells was determined by flow cytometry, and the expression of the target gene was measured by quantitative real‐time polymerase chain reaction (qRT‐PCR) and western blot analysis (WB). In addition, the expression of the target gene in granulosa cells of DOR patients and NOR patients was measured. miR‐221‐3p were found to directly bind the 3ʹ untranslated region of Forkhead box O1 (FOXO1). Transfection with miR‐221‐3p mimics significantly decreased the apoptosis rate of KGN cells compared with transfection with miR‐221‐3p inhibitors. The expression level of miR‐221‐3p was negatively correlated with the messenger RNA and protein levels of the FOXO1 gene. Besides, FOXO1 expression was upregulated in DOR patients. In conclusion, these results provide evidence that downregulation of miR‐221‐3p expression promotes apoptosis of granulosa cells by upregulating FOXO1 expression, thus serving an important role in DOR pathogenesis.

The Ameliorating Effects of Bushen Huatan Granules and Kunling Wan on Polycystic Ovary Syndrome Induced by Dehydroepiandrosterone in Rats

Aim

To investigate the effects of Bushen Huatan Granules (BHG) and Kunling Wan (KW), the two Chinese medicines, on the regulation of polycystic ovary syndrome (PCOS) and their underlying mechanisms.

Materials and Methods

PCOS rat model was established by subcutaneous injection of dehydroepiandrosterone (DHEA) (6 mg/100 g/day) for 20 days, followed by treatment with BHG (0.75, 1.49, and 2.99 g/kg) or KW (0.46, 0.91, and 1.82 g/kg) by gavage for 4 weeks. Estrous cycle was detected by vaginal smears. Follicles development was assessed by histology. Levels of testosterone and insulin in serum were tested by ELISA. Apoptosis of Granulosa cells (GCs) was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling staining. Pathways associated with apoptosis were detected with western blot. Pregnancy outcome was also assessed. GCs were pre-treated with 10^–5 M testosterone in vitro for 24 h, then incubated with serum from rats receiving BHG (1.49 g/kg) or KW (1.82 g/kg). The parameters concerning apoptosis, mitochondrial function and endoplasmic reticulum stress were assessed.

Results

Post-treatment with either BHG or KW ameliorated DHEA-induced irregular estrous cycles, follicles development abnormalities, increase of testosterone and insulin in serum, and the apoptosis of GCs. Post-treatment with BHG decreased the expression of cleaved caspase-9/caspase 9, release of cytochrome C from mitochondria, and mitochondria reactive oxygen species production, increased activities of complex I, II, IV of ovarian tissue. Post-treatment with KW decreased the levels of caspase-12, GRP78, C/EBP homologous protein, phosphorylation of IRE-I, x-box-binding protein 1s, as well as phosphorylation of proline-rich receptor-like protein kinase, phosphorylation of eukaryotic translation initiation factor 2α and ATF4 of ovarian tissue and GCs. Both BHG and KW ameliorated pregnancy outcome.

Conclusion

This study demonstrated BHG or KW as a potential strategy for treatment of PCOS induced by DHEA, and suggested that the beneficial role of the two medicines were mediated by different pathway with the effect of BHG being correlated with the regulation of mitochondria, while the effect of KW being attributable to protection of endoplasmic reticulum stress.

Effect of the neuropeptide phoenixin and its receptor GPR173 during folliculogenesis

Folliculogenesis is a complex process, defined by the growth and development of follicles from the primordial population. Granulosa cells (GCs) play a vital role in every stage of follicular growth through proliferation, acquisition of gonadotropic responsiveness, steroidogenesis and production of autocrine/paracrine factors. A recently discovered hypothalamic neuropeptide phoenixin is involved in the regulation of the reproductive system. Phoenixin acts through its receptor, G protein-coupled receptor 173 (GPR173), to activate the cAMP/PKA pathway leading to the phosphorylation of CREB (pCREB). Here, we demonstrated the expression patterns of phoenixin and GPR173 in human ovary and explored its role in folliculogenesis. Phoenixin and GPR173 were both expressed in the human ovarian follicle, with increased expression in GCs as the follicle grows. Phoenixin treatment at 100 nM for 24 h induced the proliferation of human non-luteinized granulosa cell line, HGrC1 and significantly increased the expression levels of CYP19A1, FSHR, LHR and KITL, but decreased NPPC expression levels. These effects were suppressed by GPR173 siRNA. The expression level of CREB1, pCREB and estradiol (E2) production in the culture medium was significantly enhanced by phoenixin treatment in a concentration-dependent manner. Phoenixin also significantly increased the follicular area in a murine ovarian tissue culture model, leading to an increased number of ovulated oocytes with a higher level of maturation. Taken together, our data demonstrate that phoenixin is an intraovarian factor that promotes follicular growth through its receptor GPR173 by accelerating proliferation of GCs, inducing E2 production and increasing the expression of genes related to follicle development.

Newly Identified Regulators of Ovarian Folliculogenesis and Ovulation

Each follicle represents the basic functional unit of the ovary. From its very initial stage of development, the follicle consists of an oocyte surrounded by somatic cells. The oocyte grows and matures to become fertilizable and the somatic cells proliferate and differentiate into the major suppliers of steroid sex hormones as well as generators of other local regulators. The process by which a follicle forms, proceeds through several growing stages, develops to eventually release the mature oocyte, and turns into a corpus luteum (CL) is known as “folliculogenesis”. The task of this review is to define the different stages of folliculogenesis culminating at ovulation and CL formation, and to summarize the most recent information regarding the newly identified factors that regulate the specific stages of this highly intricated process. This information comprises of either novel regulators involved in ovarian biology, such as Ube2i, Phoenixin/GPR73, C1QTNF, and α-SNAP, or recently identified members of signaling pathways previously reported in this context, namely PKB/Akt, HIPPO, and Notch.

The Effects of Cholesterol Metabolism on Follicular Development and Ovarian Function

Cholesterol is an important substrate for the synthesis of ovarian sex hormones and has an important influence on follicular development. The cholesterol in follicular fluid is mainly derived from plasma. High-density lipoprotein (HDL) and lowdensity lipoprotein (LDL) play important roles in ovarian cholesterol transport. The knockout of related receptors in the mammalian HDL and LDL pathways results in the reduction or absence of fertility, leading us to support the importance of cholesterol homeostasis in the ovary. However, little is known about ovarian cholesterol metabolism and the complex regulation of its homeostasis. Here, we reviewed the cholesterol metabolism in the ovary and speculated that regardless of the functioning of cholesterol metabolism in the system or the ovarian microenvironment, an imbalance in cholesterol homeostasis is likely to have an adverse effect on ovarian structure and function.

Protective effects of mangafodipir against chemotherapy-induced ovarian damage in mice

BACKGROUND

Given the seriousness of chemotherapy-induced ovarian injury in female cancer patients, the preservation of fertility, including through the use of cryopreservation technology and pharmaceuticals, requires investigation. Previous studies have shown that damage to the ovaries is related to oxidative stress caused by anticancer drugs. Therefore, superoxide dismutase (SOD) may represent a key factor in the pharmacological protection of the ovaries. The aim of our study was to identify the effects of mangafodipir, a manganese chelate and SOD-mimetic, on suppression of apoptosis in granulosa cells and primordial follicle activation induced by anticancer drugs.

METHODS

Cell viability assays using methyltrichlorosilane solutions and immunoblotting for cleaved caspase-3 were performed in in vitro experiments with the simultaneous addition of mangafodipir to human non-luteinized granulosa cell line (HGrC) cultures treated with hydrogen peroxide (H₂O₂), cisplatin, or paclitaxel. Count and morphological analyses of follicles at each developing stage in the ovaries and immunohistochemistry for cleaved caspase-3, Ki67 and 4-hydroxynonenal, a marker for oxidative stress, were also performed using mangafodipir-injected 6-week-old female ICR mice treated with cisplatin or paclitaxel. Further, mangafodipir was injected into 6-week-old female BALB/c mice inoculated with ES-2 to analyze whether mangafodipir inhibits the anti-tumor effects of cisplatin or paclitaxel treatment.

RESULTS

Mangafodipir attenuated apoptosis induced by H₂O₂ and anticancer drugs in vitro. Mangafodipir also decreased the expression of 4-hydroxynonenal and reduced cisplatin- and paclitaxel-induced apoptosis in granulosa cells in vivo. In addition, mangafodipir inhibited the loss of primordial follicles. Tumor xenograft studies in mice showed that mangafodipir did not affect anticancer drug antitumor effects.

CONCLUSIONS

Oxidative stress might be one of the mechanisms of cisplatin- and paclitaxel-induced the loss of primordial follicles. Mangafodipir can reduce cisplatin- and paclitaxel-induced apoptosis in granulosa cells and primordial follicle activation partially via its SOD activity. At the same time, mangafodipir might have other potential mechanisms to inhibit the activation of primordial follicles. Further, mangafodipir attenuated the ovarian damage caused by cisplatin and paclitaxel without affecting their antitumor activities. Mangafodipir, therefore, though its efficacy might be limited, may be a new option for the preservation of fertility during anticancer treatment.

Ovarian Tissue Culture to Visualize Phenomena in Mouse Ovary

Mammalian females periodically ovulate an almost constant number of oocytes during each estrus cycle. To sustain such regularity and periodicity, regulation occurs at the hypothalamic-pituitary-gonadal axis level and on developing follicles in the ovary. Despite active studies, follicle development mechanisms are not clear because of the several steps involved from the dormant primordial follicle activation to ovulation, and because of the regulation complexity that differs at each follicular stage. To investigate the mechanisms of follicle development, and the dynamics of follicles throughout the estrus cycle, we developed a mouse ovarian tissue culture model that can be used to observe follicle development using a microscope. Systematic follicle development, periodical ovulation, and follicle atresia can all be reproduced in the cultured ovary model, and the culture conditions can be experimentally modulated. Here, we demonstrate the usefulness of this method in the study of the regulatory mechanisms of follicle development and other ovarian phenomena.