Activin effects on follicular growth in in vitro preantral follicle culture

Epigenetic modifications of gonadotropin receptors can regulate follicular development

The spatiotemporal transcription of follicle-stimulating hormone receptor (FSHR) and luteinizing hormone/human chorionic gonadotropin receptor (LHCGR) are crucial events for follicular development. However, their regulatory mechanisms are unclear. DNA methylation and histone acetylation are the main epigenetic modifications, and play important roles in transcriptional expression, which regulate cell responses including cell proliferation, senescence and apoptosis. This review will discuss the dynamic epigenetic modifications of FSHR and LHCGR that occur during the process of follicular development and their response to gonadotropins. In addition, some alteration patterns that occur during these epigenetic modifications, as well as their retrospect retrotransposons, which regulate the gene expression levels of FSHR and LHCGR will be discussed.

Altered ovarian reserve in Ewe lambs exposed to a glyphosate-based herbicide

Glyphosate-based herbicides (GBHs) are considered endocrine disruptors that affect the female reproductive tract of rats and ewe lambs. The present study aimed to investigate the impact of neonatal exposure to a low dose of a GBH on the ovarian follicular reserve of ewe lambs and the response to a gonadotropic stimulus with porcine FSH (pFSH). To this end, ewe lambs were orally exposed to an environmentally relevant GBH dose (1 mg/kg/day) or vehicle (Control) from postnatal day (PND) 1 to PND14, and then some received pFSH (50 mg/day) between PND41 and 43. The ovaries were dissected, and follicular types and gene expression were assessed via RT-PCR. The treatments did not affect the body weight of animals, but pFSH increased ovarian weight, not observed in GBH-exposed lambs. GBH-exposed lambs showed decreased Estrogen receptor-alpha (56%), Progesterone receptor (75%), Activin receptor II (ACVRII) (85%), and Bone morphogenetic protein 15 (BMP15) (88%) mRNA levels. Control lambs treated with pFSH exhibited downregulation of Follistatin (81%), ACVRII (77%), BMP15 (93%), and FSH receptor (FSHr) (72%). GBH-exposed lambs treated with pFSH displayed reduced ACVRII (68%), BMP15 (81%), and FSHr (50%). GBH-exposed lambs also exhibited decreased Anti-Müllerian hormone expression in primordial and antral follicles (27%) and (54%) respectively) and reduced Bone morphogenetic protein 4 (31%) expression in primordial follicles. Results suggest that GBH disrupts key follicular development molecules and interferes with pFSH action in ovarian receptors, decreasing the ovarian reserve. Future studies should explore whether this decreased ovarian reserve impairs adult ovarian function and its response to superovulation stimuli.

Bioengineered 3D ovarian model for long-term multiple development of preantral follicle: bridging the gap for poly(ε-caprolactone) (PCL)-based scaffold reproductive applications

BACKGROUND

Assisted Reproductive Technologies (ARTs) have been validated in human and animal to solve reproductive problems such as infertility, aging, genetic selection/amplification and diseases. The persistent gap in ART biomedical applications lies in recapitulating the early stage of ovarian folliculogenesis, thus providing protocols to drive the large reserve of immature follicles towards the gonadotropin-dependent phase. Tissue engineering is becoming a concrete solution to potentially recapitulate ovarian structure, mostly relying on the use of autologous early follicles on natural or synthetic scaffolds. Based on these premises, the present study has been designed to validate the use of the ovarian bioinspired patterned electrospun fibrous scaffolds fabricated with poly(ε-caprolactone) (PCL) for multiple preantral (PA) follicle development.

METHODS

PA follicles isolated from lamb ovaries were cultured on PCL scaffold adopting a validated single-follicle protocol (Ctrl) or simulating a multiple-follicle condition by reproducing an artificial ovary engrafted with 5 or 10 PA (AO5PA and AO10PA). The incubations were protracted for 14 and 18 days before assessing scaffold-based microenvironment suitability to assist in vitro folliculogenesis (ivF) and oogenesis at morphological and functional level.

RESULTS

The ivF outcomes demonstrated that PCL-scaffolds generate an appropriate biomimetic ovarian microenvironment supporting the transition of multiple PA follicles towards early antral (EA) stage by supporting follicle growth and steroidogenic activation. PCL-multiple bioengineering ivF (AO10PA) performed in long term generated, in addition, the greatest percentage of highly specialized gametes by enhancing meiotic competence, large chromatin remodeling and parthenogenetic developmental competence.

CONCLUSIONS

The study showcased the proof of concept for a next-generation ART use of PCL-patterned scaffold aimed to generate transplantable artificial ovary engrafted with autologous early-stage follicles or to advance ivF technologies holding a 3D bioinspired matrix promoting a physiological long-term multiple PA follicle protocol.

The mechanisms that control the preantral to early antral follicle transition and the strategies to have efficient culture systems to promote their growth in vitro

Preantral to early antral follicles transition is a complex process regulated by endocrine and paracrine factors, as well as by a precise interaction among oocyte, granulosa cells and theca cells. Understanding the mechanisms that regulate this step of folliculogenesis is important to improve in vitro culture systems, and opens new perspectives to use oocytes from preantral follicles for assisted reproductive technologies. Therefore, this review aims to discuss the endocrine and paracrine mechanisms that control granulosa cell proliferation and differentiation, formation of the antral cavity, estradiol production, atresia, and follicular fluid production during the transition from preantral to early antral follicles. The strategies that promote in vitro growth of preantral follicles are also discussed.

Activin A attenuates apoptosis of granulosa cells in atretic follicles through ERβ-induced autophagy

It is well known that about 99% of ovarian follicles in mammals suffer from a degenerative process known as atresia, which is a huge waste of genetic resource in female animals. Studies have shown that activin A (ACT-A) is located in ovarian granulosa cells and has different effects in granulosa cell depending on species. Although granulosa cells play a critical role during follicular atresia, the mechanism of action of ACT-A in bovine ovarian granulosa cells (BGC) is poorly understood. In this study, we firstly determined the apoptosis of BGCs isolated from growth follicles and atretic follicles, respectively. Then, BGC isolated from atretic follicles were used as a model to elucidate the role of ACT-A in cattle ovary. The results showed that apoptosis occurred in both growing follicles and atretic follicles, and the percentage of apoptotic cells in atretic follicles was higher than that in growing follicles. The current results indicated that ACT-A can attenuate apoptosis of BGC through maintaining the function of BGC in atretic follicles. Increased ERβ induced by ACT-A promoted BGC autophagy but had no effect on apoptosis. In summary, this study suggests that ACT-A attenuates BGC apoptosis in atretic follicles by ERβ-mediated autophagy signaling.

Therapeutic Potential of In Vitro-Derived Oocytes for the Restoration and Treatment of Female Fertility

Considerable progress has been made with the development of culture systems for the in vitro growth and maturation (IVGM) of oocytes from the earliest-staged primordial follicles and from the more advanced secondary follicles in rodents, ruminants, nonhuman primates, and humans. Successful oocyte production in vitro depends on the development of a dynamic culture strategy that replicates the follicular microenvironment required for oocyte activation and to support oocyte growth and maturation in vivo while enabling the coordinated and timely acquisition of oocyte developmental competence. Significant heterogeneity exists between the culture protocols used for different stages of follicle development and for different species. To date, the fertile potential of IVGM oocytes derived from primordial follicles has been realized only in mice. Although many technical challenges remain, significant advances have been made, and there is an increasing consensus that complete IVGM will require a dynamic, multiphase culture approach. The production of healthy offspring from in vitro-produced oocytes in a secondary large animal species is a vital next step before IVGM can be tested for therapeutic use in humans.

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.

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.

miR-181a promotes porcine granulosa cell apoptosis by targeting TGFBR1 via the activin signaling pathway

Activin/Smad3 signaling plays a pivotal role in follicle development and atresia. However, the precise mechanisms underlying this process are not yet fully understood. Herein, we identified miR-181a as a central component of activin/Smad3-mediated follicle atresia. miR-181a was strikingly upregulated in porcine atretic follicles, which induced the apoptosis of porcine granulosa cells (GCs) in vitro. Furthermore, the transforming growth factor-β type 1 receptor (TGFBR1) was confirmed as a direct target of miR-181a by bioinformatics analysis and luciferase assays. Transfection with an miR-181a agomir repressed the TGFBR1 mRNA and protein levels. In addition, TGFBR1 overexpression repressed GC apoptosis, whereas TGFBR1 inhibition promoted GC apoptosis. miR-181a overexpression downregulated the phosphorylation of Smad3 and blocked the activation of TGF-β signaling. Moreover, activin A downregulated miR-181a expression and upregulated the TGFBR1 and p-Smad3 protein levels. Collectively, these data suggest that miR-181a regulates porcine GC apoptosis by targeting TGFBR1 via the activin signaling pathway.