The effects of epidermal growth factor (EGF) on the in vitro development of isolated goat secondary follicles and the relative mRNA expression of EGF, EGF-R, FSH-R and P450 aromatase in cultured follicles

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

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

Potential therapeutic drug targets and pathways prediction for premature ovarian insufficiency -Based on network pharmacologic method

ETHNOPHARMACOLOGICAL RELEVANCE

The incidence of premature ovarian insufficiency (POI) is gradually increasing, the proportion is rising especially in female infertility patients. The risk of death of POI patients with cardiovascular disease also increases significantly. The cause of POI is complex and unclear, and clinical treatment is still in the exploratory stage, are two major constraints of treating POI. Traditional Chinese medicine (TCM) is widely used in the treatment of POI, and it is a good way to combine the development of modern new drugs with the help of TCM to predict the therapeutic targets.

AIM OF THE STUDY

In this study, four herbs commonly used in clinical treatment of POI, namely Radix Paeoniae, Polygonatum sibiricum, Rehmannia glutinosa and Eucommia ulmoides were selected to predict their mechanism in the treatment of POI, using network pharmacology methods. Then verify the predicted targets by animal test. Aim to find more effective POI potential core treatment targets and main pathways.

MATERIALS AND METHODS

We screened the active ingredients of drugs from the TCM System Pharmacology Analysis Platform (TCMSP), Performed target prediction of active ingredients from databases such as SwissTargetPrediction and compare and analyze the POI-related targets retrieved from them to obtain potential targets for drug treatment of POI. Used STRING database to construct a protein interaction network, Cytoscape 3.7.2 software to construct an active ingredient-target-pathway network, and DAVID database to conduct the Kyoto Encyclopedia of Genes and Genomes (KEGG) on the intersection targets and gene ontology (GO) enrichment analysis.

RESULTS

The result is: there were 25 key targets for the treatment of POI with Radix Paeoniae Alba, 31 for the treatment of POI by Eucommia ulmoides, 28 for the treatment of POI by Polygonatum sibiricum, and 8 key targets for the treatment of Rehmannia glutinosa. The intersection targets of four herbs were defined as the core targets, which are CYP19A1, EGF, ESR1, ESR2, MDM2, AR, PCYP17A1, PPARG. Four Chinese herbs treat POI mainly through HIF-1 signaling pathway, PI3K-Akt signaling pathway, FoxO signaling pathway, Estrogen signaling pathway etc. A mouse model of POI was constructed based on the results of network pharmacology to verify the predicted targets. The results showed that the protein expression of the core target changed, and the estrogen level was increased by reducing the expression of peroxisome proliferator-activated receptor gamma (PPARG).

CONCLUSIONS

This study predicts the mechanism of multiple herbs in the treatment of POI, screens out more potential therapeutic drug targets and main pathways of POI treatment and provides new ideas for the subsequent development of POI therapeutic drugs.

Matrix-free three-dimensional culture of bovine secondary follicles to antral stage: Impact of media formulation and epidermal growth factor (EGF)

Disrupted/disordered ovarian steroidogenesis is associated with several fertility disorders such as polycystic ovary syndrome in humans and cystic ovarian disease in cattle. Methods to interrogate theca cell processes as part of follicular development are necessary to further research into treatments for these types of disorders. Multilayer follicles of dairy-breed cows were placed into culture in a novel matrix-free 3D system using round bottom low-attachment plates. Follicles were first cultured in the presence of two types of media previously used for in vitro follicle maturation (basal α-MEM and basal T-199). After the optimal media was identified, impact of supplementation of epidermal growth factor (EGF) on growth and survival of bovine secondary follicles to antral stage was evaluated. No differences were observed in growth and survival of follicles cultured in basal α-MEM media or basal T-199 media, although T-199 media's high phenol red content made assessment of follicles difficult. Further studies were then performed with α-MEM media. Three cohorts of follicles were observed based on time to antrum formation: ≤ 5 days (fast), 6-19 days (slow), or survived but did not form an antrum by 21 days (no). Supplementation of EGF to the basal α-MEM media dramatically improved follicle survival rates in culture (defined as follicles that either formed an antrum or did not form an antrum but did not die during 21 day culture period) from 29% to 95.7% (Chi-square p < 0.0001). However, in follicles that survived to form an antrum there were no differences in proportion of fast, slow and no antrum follicles after addition of EGF (Chi-square p > 0.7). Fast antrum follicles treated with EGF plateaued in size earlier in culture compared to controls (p = 0.013). Slow and no antrum follicles were larger in diameter during EGF culture than controls (p's < 0.0001). Many follicles cultured in this matrix-free system that formed an antrum approached 1.5-2 mm in size, an improvement from previous single follicle culture methods used for bovine pre-antral follicles in vitro. In addition, follicles displayed functional steroidogenesis in vitro producing measureable levels of estradiol and androstenedione. This matrix-free 3D culture system provides an excellent in vitro model to explore processes associated with folliculogenesis in cattle.

Regulatory role of melatonin on epidermal growth factor receptor, Type I collagen α1 chain, and caveolin 1 in granulosa cells of sheep antral follicles

We investigated the expression of epidermal growth factor receptor (EGFR), Type I collagen α1 chain (COL1A1), and caveolin 1 (CAV1) during follicular development and examined the regulatory role of melatonin (MLT) on EGFR, COL1A1, and CAV1 in sheep antral ovaries. The expression was detected in granulosa and theca cells by immunohistochemistry. Quantitative real-time polymerase chain reaction and Western blotting were used to examine the expression levels of EGFR, COL1A1, and CAV1 in small (≤2 mm), medium (2-5 mm), and large (≥5 mm) follicles. The mRNA and protein levels of EGFR, COL1A1, and CAV1 were found to be the highest in large follicles. Furthermore, cultured granulosa cells were treated with MLT (10^-7 -10^-11  M), luzindole (nonselective MT1 and MT2 receptor antagonist, 10^-7  M), and 4-phenyl-2-propanamide tetraldehyde (4P-PDOT, MT2 selective antagonist, 10^-7  M) to detect the regulatory role of MLT on EGFR, COL1A1, and CAV1. Results indicated COL1A1 and CAV1 were at least partially regulated by MLT through MT1 and MT2 pathways, whereas EGFR was not. This study provided a reference for further studies on MLT regulatory role on EGFR, COL1A1, and CAV1 during sheep follicular development and elucidated the physiological mechanism of MLT regulator production.

Regulation of aromatase in cancer

The regulation of aromatase, an enzyme involved in the biosynthesis of estrogen in normal and cancer cells, has been associated with growth factor signaling and immune response modulation. The tissue-specific regulatory roles of these factors are of particular importance as local aromatase expression is strongly linked to cancer development/progression and disease outcomes in patients. Therefore, aromatase has become a chemotherapeutic target and aromatase inhibitors (AIs) are used in the clinic for treating hormone-dependent cancers. Although AIs have shown promising results in the treatment of cancers, the emerging increase in AI-resistance necessitates the development of new and improved targeted therapies. This review discusses the role of tumor and stromal-derived growth factors and immune cell modulators in regulating aromatase. Current single-agent and combination therapies with or without AIs targeting growth factors and immune checkpoints are also discussed. This review highlights recent studies that show new connections between growth factors, mediators of immune response, and aromatase regulation.

Advances in in vitro folliculogenesis in domestic ruminants

The in vitro follicle culture (IVFC) represents an outstanding tool to enhance our understanding of the control of folliculogenesis and to allow the future use of a large number of immature oocytes enclosed in preantral follicles (PFs) in assisted reproductive techniques in humans as well as in others mammalian species including the ruminants. So far, the best results of IVFC were reported from mice with the production of live offspring from primordial follicles cultured in vitro. Live birth has been obtained after the in vitro culture of bovine early antral follicles. However, in other ruminant species, these results have been limited to the production of a variable number of mature oocytes and low percentages of embryos after in vitro culture of goat, buffalo and sheep isolated secondary preantral follicles. The present review presents and discusses the main findings, limitations, and prospects of in vitro folliculogenesis in ruminants focusing on bovine, caprine, and ovine species.

Effects of epidermal growth factor and progesterone on development, ultrastructure and gene expression of bovine secondary follicles cultured in vitro

The aims of this study were to investigate the effects of epidermal growth factor (EGF) and progesterone on the development, viability and the gene expression of bovine secondary follicle culture in vitro for 18 days. Secondary follicles (∼0.2 mm) were isolated from ovarian cortex and individually cultured at 38.5 °C, with 5% CO₂ in air, for 18 days, in TCM-199⁺ (n = 63) alone (control medium) or supplemented with 10 ng/mL progesterone (n = 64), 10 ng/mL EGF (n = 61) or both EGF and progesterone (n = 66). The effects of these treatments on growth, antrum formation, viability, ultrastructure and mRNA levels for GDF-9, c-MOS, H1foo and cyclin B1 were evaluated, significantly different (p < 0.05). The results showed that there was a progressive increase in follicular diameter in all treatments, but only follicles cultured in medium supplemented with EGF had increased significantly in diameter when compared to follicles cultured in the control medium at the end of the culture period, significantly different (p < 0.05). A positive interaction between EGF and progesterone was not observed. In addition, the presence of EGF, progesterone or both in culture medium did not influence the rate of follicle survival and antrum formation. However, the presence of only progesterone in cultured medium increased the expression of mRNAs for GDF9 and cyclin B1 in oocytes. EGF also significantly increased the levels of mRNAs for cMOS and GDF9 when compared to follicles cultured in control medium. Ultrastructural analyzes showed that cultured follicles in all treatments maintained the integrity of granulosa cells. In conclusion, the EGF promotes the development of secondary follicles cultured in vitro for 18 days and increases the expression of cMOS and GDF9, while progesterone alone or in association with EGF have not a positive effect on follicular growth. However, progesterone increases the expression of GDF9 and cyclin B1 in oocytes.

Effect of anti-apoptotic drug Z-VAD-FMK on in vitro viability of dog follicles

It is recognized that ovarian follicular atresia is associated with apoptosis, and the most important effector of cell death is caspase-3. The aim of this study was to investigate the influence of anti-apoptotic drug Z-VAD-FMK on in vitro follicle growth in the domestic dog. Ovaries were obtained from peri-pubertal and adult domestic dogs, and cortical fragments recovered and incubated on 1.5% (w/v) agarose gel blocks within a 24-well culture plate containing Minimum Essential Medium Eagle-Alpha Modification (αMEM) supplemented with 4.2 μg/mL insulin, 3.8 μg/mL transferrin, 5 ng/mL selenium, 2 mM L-glutamine, 100 μg/mL of penicillin G sodium, 100 μg/mL of streptomycin sulfate, 0.05 mM ascorbic acid, 10 ng/mL of FSH and 0.1% (w/v) polyvinyl alcohol in humidified atmosphere of 5% CO₂ and 5% O₂. The cortices were randomly allocated in six treatments: 1) 10 ng/mL EGF (EGF V0); 2) 10 ng/mL of EGF plus 1 mM Z-VAD-FMK (EGF V1); 3) 10 ng/mL of EGF and 10 mM Z-VAD-FMK (EGF V10); 4) 1 mM Z-VAD-FMK; 5) 10 mM Z-VAD-FMK and (6) no EGF and Z-VAD-FMK supplementation (Control). The cortices were processed for histology and assessed for viability (based on morphology), density of structurally normal follicles, and diameter immediately after collection (non-culture Control) or after 3 or 7 days of in vitro incubation. Evaluation of mRNA expression of Cas3 in fresh cortices and those incubated for 3 days was performed using real-time PCR. Histological analysis revealed that in vitro incubation decreased (P < 0.05) follicle viability and density compared to the fresh, non-culture control. Addition of 10 μM of Z-VAD-FMK alone to the culture medium sustained follicle viability at Day 3, but did not impact follicle diameter when compared to the other treatment groups (p < 0.001); however, the beneficial benefit of this anti-apoptotic drug diminished after 7 days of incubation. Furthermore, Z-VAD-FMK supplementation did not impact Cas3 expression. The findings demonstrated that dog ovarian tissues are highly susceptible to in vitro incubation and Z-VAD-FMK supported short-term survival of dog follicles enclosed within the ovarian cortex.

Molecular evidence that follicle development is accelerated in vitro compared to in vivo

In this study, we systematically compared the morphological, functional and molecular characteristics of granulosa cells and oocytes obtained by a three-dimensional in vitro model of ovine ovarian follicular growth with those of follicles recovered in vivo. Preantral follicles of 200 µm diameter were recovered and cultured up to 950 µm over a 20-day period. Compared with in vivo follicles, the in vitro culture conditions maintained follicle survival, with no difference in the rate of atresia. However, the in vitro conditions induced a slight decrease in oocyte growth rate, delayed antrum formation and increased granulosa cell proliferation rate, accompanied by an increase and decrease in CCND2 and CDKN1A mRNA expression respectively. These changes were associated with advanced granulosa cell differentiation in early antral follicles larger than 400 µm diameter, regardless of the presence or absence of FSH, as indicated by an increase in estradiol secretion, together with decreased AMH secretion and expression, as well as increased expression of GJA1, CYP19A1, ESR1, ESR2, FSHR, INHA, INHBA, INHBB and FST. There was a decrease in the expression of oocyte-specific molecular markers GJA4, KIT, ZP3, WEE2 and BMP15 in vitro compared to that in vivo. Moreover, a higher percentage of the oocytes recovered from cultured follicles 550 to 950 µm in diameter was able to reach the metaphase II meiosis stage. Overall, this in vitro model of ovarian follicle development is characterized by accelerated follicular maturation, associated with improved developmental competence of the oocyte, compared to follicles recovered in vivo.

Ovine secondary follicles vitrified out the ovarian tissue grow and develop in vitro better than those vitrified into the ovarian fragments

Cryopreservation of preantral follicles is a promising technique to preserve female fertility. The aim of this study was to evaluate the effect of vitrification on the development of secondary follicles included in ovarian tissue or isolated after microdissection. An important end point included is the capacity of grown oocytes to resume meiosis. Sheep ovarian cortexes were cut into fragments and split into three different groups: (1) fresh (control): secondary follicles isolated without any previous vitrification; (2) follicle-vitrification (follicle-vit): secondary follicles vitrified in isolated form; and (3) tissue-vitrification (tissue-vit): secondary follicles vitrified within fragments of ovarian tissue (in situ former) and subsequently subjected to isolation. From the three groups, isolated secondary follicles were submitted to IVC for 18 days. After IVC, cumulus-oocyte complexes (COCs) were harvested from follicles. As an additional control group, in vivo grown, in vivo-grown COCs were collected from antral ovarian follicles. All, recovered COCs were matured and the chromatin configuration was evaluated. Data were analyzed by ANOVA, and the means were compared by Student-Newman-Keuls test, and by chi-square. Differences were considered to be significant when P < 0.05. Isolated preantral follicles from all treatments had normal morphology, antrum formation, and low follicle degeneration after IVC. The growth rate between control and follicle-vit did not differ (P > 0.05), and was higher (P < 0.05) than for tissue-vit. The percentage of follicles that decreased diameter during IVC was significantly higher in tissue-vit than the in follicle-vit. Recovery rate of oocytes from normal follicles was higher in follicle-vit than in tissue-vit. Furthermore, oocyte viability was lower in tissue-vit than other treatments, and follicle-vit did not differ from control and in vivo grown. The percentage of oocytes meiosis resuming was not different between treatments except for in vivo grown. After vitrification, only follicle-vit showed metaphase I oocyte. We conclude that secondary follicles vitrified after isolation displayed a better follicular growth rate, oocyte viability, percentage of oocytes reaching the metaphase I stage, and fewer follicles with decreased diameter after IVC.

Is the mouse follicle culture a good model for the goat with respect to the development of preantral follicles in vitro?

The present study evaluated the efficiency of using 2 culture media developed for mice and for goats in the in vitro preantral follicle culture of each species. Murine and caprine secondary follicles were cultured in vitro with human recombinant follicle-stimulating hormone (murine medium) or with bovine recombinant follicle-stimulating hormone in association with growth hormone (caprine medium). The results showed that murine follicles cultured in caprine medium had lower (P < 0.05) rates of follicular survival and growth, whereas for caprine follicles, these variables were not affected by the type of medium used (P > 0.05). After in vitro maturation, a higher (P < 0.05) number of oocytes that resumed meiosis were observed in the murine medium for both species. In contrast, only in the caprine species estradiol production was significantly superior when the caprine medium was used. Higher progesterone production was observed in the presence of the murine medium only for murine follicles (P < 0.05). In conclusion, murine and caprine preantral follicles cultured under the same in vitro culture medium conditions respond differently; caprine oocytes grown in vitro in the presence of the murine medium show the greatest developmental competence among the tested combinations. Therefore, under the present experimental conditions, the mouse follicle culture has proved be a good model for the development of new culture media for caprine preantral follicles.

Alginate hydrogel matrix stiffness influences the in vitro development of caprine preantral follicles

This study examined caprine follicular development in different concentrations of alginate matrix to determine the optimal conditions for culture. Caprine preantral follicles were cultured in a two-dimensional system (control) or a three-dimensional encapsulated system in 0.25%, 0.5%, or 1% alginate (ALG 0.25, ALG 0.5, and ALG 1, respectively). A higher percentage of morphologically normal follicles developed in ALG 0.5 and ALG 1 than in ALG 0.25 or the control (P < 0.05). The rate of antrum formation, however, was higher in ALG 0.25 than in ALG 0.5 and ALG 1 conditions (P < 0.05), but similar to the control. Follicles cultured in ALG 0.25 had higher growth rates and meiotic resumption than those cultured in ALG 0.5, ALG 1, or the control (P < 0.05). Moreover, follicles cultured in ALG 0.25 had higher levels of estradiol and progesterone than those cultured in ALG 0.5, ALG 1, or the control, as well as higher levels of CYP19A1 and HSD3B mRNA. In conclusion, a three-dimensional system that uses ALG 0.25 fosters the in vitro development of caprine preantral follicles and increases the rate of meiotic resumption.