Sulforaphane Acts Through NFE2L2 to Prevent Hypoxia-Induced Apoptosis in Porcine Granulosa Cells via Activating Antioxidant Defenses and Mitophagy

Role of programmed cell death in mammalian ovarian follicular atresia

Programmed cell death (PCD) is a fundamental process in the development process of organisms, including apoptosis, autophagy, ferroptosis, and pyroptosis. In mammalian ovaries, 99 % of follicles undergo atresia, while only 1 % mature and ovulate, which limits the reproductive efficiency of mammals. The PCD process is closely related to the regulation of follicle development and atresia. Recently, an increasing number of studies have reported that autophagy, pyroptosis, and ferroptosis of PCD are involved in regulating granulosa cell apoptosis and follicular atresia. Granulosa cell apoptosis is a hallmark of follicular atresia. Therefore, an understanding of molecular mechanisms regulating PCD events is required for future advances in the diagnosis and management of various disorders of follicular atresia. This review summarizes recent work on apoptosis, autophagy, pyroptosis, and ferroptosis of PCD that affect granulosa cell survival and follicular atresia, and further elucidating the mechanisms of follicular atresia and providing new directions for improving the reproductive capacity of humans and animals.

Oxidative stress controls lncRNA-mediated sow granulosa cell functions in a FoxO1-dependent manner

BACKGROUND

Oxidative stress (OS) is involved in low female fertility by altering multi-omics such as the transcriptome, miRome, and lncRNome in follicular cells and follicular fluid. However, the mechanism by which OS affects multi-omics dynamics remains largely unknown. Here, we report that OS induces lncRNome dynamics in sow granulosa cells (sGCs), which is partially dependent on the transcription factor activity of its effector, FoxO1.

RESULTS

A total of 2,283 putative FoxO recognition elements (FREs) were identified in the promoters of 394 lncRNAs, accounting for 91.20% (394/432) of the lncRNAs regulated by OS. ChIP and reporter assays showed that the effector FoxO1 mediated OS regulation of lncRNA transcription in a transcription factor activity-dependent manner. In sGCs, OS induces the transcription and function (e.g., apoptosis) of NORSF (non-coding RNA involved in sow fertility), a nuclear lncRNA involved in sGC function via FoxO1. Furthermore, FoxO1 has been identified as a transcriptional activator of NORSF in sGCs that interacts with the FRE motif of its promoter. Meanwhile, OS downregulates the transcription of CYP19A1, which encodes an essential enzyme for estrogen synthesis and 17β-estradiol (E2) release by sGCs via the FoxO1 and NORSF axis. Phenotypically, dysregulation of NORSF transcription caused by 2 novel adjacent transitions in the promoter leads to decreased sow fertility.

CONCLUSION

These results suggest a model of OS-stimulated lncRNome dynamics in sGCs and a new signaling pathway of OS that influences sGC function and sow fertility.

Sulforaphane acts through the NFE2L2/AMPK signaling pathway to protect boar spermatozoa from cryoinjury by activating antioxidant defenses

During cryopreservation, a substantial portion of spermatozoa undergoes apoptosis due to cryoinjury, resulting in decreased fertility. Boar spermatozoa are highly sensitive to temperature, with low temperature triggering reactive oxygen species (ROS) generation, leading to oxidative stress and apoptosis. Sulforaphane (SFN), a potent natural compound found in cruciferous vegetables, is efficacious in mitigating oxidative stress. We here supplemented different SFN concentrations (0, 1.25, 2.5, 5, 10, and 20 μM) into the freezing extender to explore its effect on boar sperm during cryopreservation and determine the optimal SFN concentration. Supplementation of 5 μM SFN exhibited the highest sperm motility, motion performance, plasma membrane integrity, acrosome integrity, and antioxidant properties (total antioxidant capacity (T-AOC) and antioxidant enzyme activity) after freezing and thawing. Then, RT group, C group and C + SFN group were established to explore the effect of SFN on the cryopreservation-induced sperm apoptosis level and fertilizing capacity of post-thawed sperms. SFN effectively rescued the apoptosis and fertilizing capacity of post-thawed sperms. Mechanistically, SFN activated the redox-sensitive nuclear factor erythroid 2-related factor 2 (NRF2/NFE2L2) by promoting adenosine monophosphate-activated protein kinase (AMPK) phosphorylation. This activation improved antioxidant defenses, ultimately improving cryoinjury in boar spermatozoa. In summary, SFN suppressed cryopreservation-induced apoptosis of spermatozoa by activating antioxidant defenses and the AMPK/NFE2L2 signaling pathway. These findings suggest a novel approach for augmenting the cryoprotective efficiency and spermatozoa fertility after cryopreservation.

Sulforaphane Promotes Proliferation of Porcine Granulosa Cells via the H3K27ac-Mediated GDF8-ALK5-ERK Pathway

Follicle development, a crucial process in reproductive biology, hinges upon the dynamic proliferation of granulosa cells (GCs). Growth differentiation factor-8 (GDF8) is well-known as myostatin for inhibiting skeletal muscle growth, and it also exists in ovarian GCs and follicle fluid. However, the relationship between GCs proliferation and GDF8 remains elusive. Sulforaphane (SFN) is a potent bioactive compound, which in our study has been demonstrated to induce the expression of GDF8 in GCs. Meanwhile, we discover a novel role of SFN in promoting the proliferation of porcine GCs. Specifically, SFN enhances GCs proliferation by accelerating the progression of the cell cycle through the G1 phase to the S phase. By performing gene expression profiling, we showed that the promoting proliferative effects of SFN are highly correlated with the TGF-β signaling pathways and cell cycle. Among the ligand factors of TGF-β signaling, we identify GDF8 as a critical downstream effector of SFN, which acts through ALK5 to mediate SFN-induced proliferation and G1/S transition. In addition, we identify a noncanonical downstream pathway by which GDF8 induces the activation of MAPK/ERK to facilitate the cell cycle progression in GCs. Moreover, we reveal that the expression of GDF8 is regulated by SFN through epigenetic modifications of H3K27 acetylation. These findings not only provide mechanistic insights into the regulation of GCs proliferation but also establish a previously unrecognized role of GDF8 in follicle development, which have significant implications for developing strategies to improve female fertility.

In pre-clinical study fetal hypoxia caused autophagy and mitochondrial impairment in ovary granulosa cells mitigated by melatonin supplement

INTRODUCTION

Fetal hypoxia has long-term effects on postnatal reproductive functions and the mitochondrial impairments of ovarian granulosa cells may be one of the causes. Melatonin applied to mitigate mitochondrial dysfunction and autophagy in mammalian cells has been reported. However, the potential mechanisms by which fetal hypoxia damages reproductive function in neonatal female mice and the melatonin effects on this problem remain unclear.

OBJECTIVES

This research aimed to explore the mechanism that fetal hypoxia damages reproductive function in neonatal female mice and attempt to improve the reproductive function by treating with melatonin in vivo and in vitro.

METHODS

We established a fetal hypoxia model and confirmed that fetal hypoxia affects ovarian function by inducing GC excessive autophagy. Transcriptomic analysis, gene interference, cell immunofluorescence, immunohistochemistry and western blot were conducted to explore and verify the underlying mechanisms in mice GCs and KGN cells. Finally, melatonin treatment was executed on hypoxia-treated mice GCs and KGN cells and melatonin injection to fetal-hypoxia-treated mice to determine its effect.

RESULTS

The results of in vitro experiments found that fetal hypoxia led to mitochondrial dysfunction in ovarian GCs causing autophagic cell death. And the PI3K/Akt/FoxO pathway mediated the occurrence of this process by transcriptome analysis of ovarian GCs from normal and fetal hypoxia mice, which was further verified in mice GCs and KGN cells. Additionally, melatonin administration prevented autophagic injuries and mitochondrial impairments in hypoxia-treated mice GCs and KGN cells. Meanwhile, in vivo experiments by melatonin injection ameliorated oxidative stress of ovary in fetal-hypoxia-treated mice and improved their low fertility.

CONCLUSION

Our data found that fetal hypoxia causes ovarian GCs excessive autophagy leading to low fertility in neonatal female mice and mitigated by melatonin. These results provide a potential therapy for hypoxic stress-related reproductive disorders.

Modulation of keap-1/Nrf2/HO-1 and NF-ĸb/caspase-3 signaling pathways by dihydromyricetin ameliorates sodium valproate-induced liver injury

Nuclear factor erythroid factor 2 (Nrf2) is the key regulatory of the antioxidant response elements. Also, Nrf2 interacts with nuclear factor kappa B (NF-ĸB) to inhibit subsequent inflammatory cascade. Activation of Nrf2 signaling ameliorates drug-induced liver injury. Sodium valproate (SVP) is an anti-epilepsy drug with a hepatotoxic adverse effect that restricts its clinical use. In this study, coadministration of Dihydromyricetin (DHM), a natural flavonoid, with SVP to rats upregulated gene expression of Nrf2 and its downstream gene, heme oxygenase 1 (HO-1), while suppressed the Nrf2 repressor, Keap-1. Additionally, DHM led to downregulation of proinflammatory factors in liver tissues, including NF-ĸB, interleukin 1 beta (IL-1β), and tumor necrosis factor alpha (TNF-α). This was accompanied by a decrease in the proapoptotic protein (cleaved caspase-3) expression level. Furthermore, biochemical and histopathological studies showed that DHM treatment improved liver function and lipid profile while decreased inflammatory cell infiltration, congestion, and hepatocellular damage. According to our knowledge, prior research has not examined the protective effect of DHM on the liver injury induced by SVP. Consequently, this study provides DHM as a promising herbal medication that, when used with SVP, can prevent its induced hepatotoxicity owing to its potential anti-oxidative, anti-inflammatory, and anti-apoptotic properties.

Mitophagy in mammalian follicle development and health

Mitophagy, the cellular process that removes damaged mitochondria, plays a crucial role in maintaining normal cell functions. It is deeply involved in the entire process of follicle development and is associated with various ovarian diseases. This review aims to provide a comprehensive overview of mitophagy regulation, emphasizing its role at different stages of follicular development. Additionally, the study illuminates the relationship between mitophagy and ovarian diseases, including ovary aging (OA), primary ovarian insufficiency (POI), and polycystic ovary syndrome (PCOS). A detailed understanding of mitophagy could reveal valuable insights and novel strategies for managing female ovarian reproductive health.

Melatonin protects oogenesis from hypobaric hypoxia-induced fertility damage in mice

Environmental hypoxia adversely affects reproductive health in humans and animals at high altitudes. Therefore, how to alleviate the follicle development disorder caused by hypoxia exposure and to improve the competence of fertility in plateau non-habituated female animals are important problems to be solved urgently. In this study, a hypobaric hypoxic chamber was used for 4 weeks to simulate hypoxic conditions in female mice, and the effects of hypoxia on follicle development, proliferation and apoptosis of granulosa cells, reactive oxygen species (ROS) levels in MII oocyte and 2-cell rate were evaluated. At the same time, the alleviating effect of melatonin on hypoxic exposure-induced oogenesis damage was evaluated by feeding appropriate amounts of melatonin daily under hypoxia for 4 weeks. The results showed that hypoxia exposure significantly increased the proportion of antral follicles in the ovary, the number of proliferation and apoptosis granulosa cells in the follicle, and the level of ROS in MII oocytes, eventually led to the decline of oocyte quality. However, these defects were alleviated when melatonin was fed under hypoxia conditions. Together, these findings suggest that hypoxia exposure impaired follicular development and reduced oocyte quality, and that melatonin supplementation alleviated the fertility reduction induced by hypoxia exposure.

Follicular fluid meiosis-activating sterol prevents porcine ovarian granulosa cells from hypoxia-induced apoptosis via inhibiting STAT4 expression

Follicular fluid meiosis-activating sterol (FF-MAS) is a small molecule compound found in FF, named for its ability to induce oocyte resumption of meiosis. Granulosa cells (GCs) within the follicle are typically located in a hypoxic environment under physiologic conditions due to limited vascular distribution. Previous research suggests that hypoxia-induced cell cycle arrest and apoptosis in GCs may be crucial triggering factors in porcine follicular atresia. However, the impact of FF-MAS on GCs within follicles has not been explored so far. In this study, we uncovered a novel role of FF-MAS in facilitating GC survival under hypoxic conditions by inhibiting STAT4 expression. We found that STAT4 expression was upregulated in porcine GCs exposed to 1% O2. Both gain and loss of function assays confirmed that STAT4 was required for cell apoptosis under hypoxia conditions, and that the GC apoptosis caused by hypoxia was markedly attenuated following FF-MAS treatment through inhibition of STAT4 expression. Correlation analysis in vivo revealed that GC apoptosis was associated with increased STAT4 expression, while the FF-MAS content in follicular fluid was negatively correlated with STAT4 mRNA levels and cell apoptosis. These findings elucidate a novel role of FF-MAS-mediated protection of GCs by inhibiting STAT4 expression under hypoxia, which might contribute to the mechanistic understanding of follicular development.

IGF-I protects porcine granulosa cells from hypoxia-induced apoptosis by promoting homologous recombination repair through the PI3K/AKT/E2F8/RAD51 pathway

Severe hypoxia induced by vascular compromise (ovarian torsion, surgery), obliteration of vessels (aging, chemotherapy, particularly platinum drugs) can cause massive follicle atresia. On the other hand, hypoxia increases the occurrence of DNA double-strand breaks (DSBs) and triggers cellular damage repair mechanisms; however, if the damage is not promptly repaired, it can also induce the apoptosis program. Insulin-like growth factor-I (IGF-I) is a polypeptide hormone that plays essential roles in stimulating mammalian follicular development. Here, we report a novel role for IGF-I in protecting hypoxic GCs from apoptosis by promoting DNA repair through the homologous recombination (HR) process. Indeed, the hypoxic environment within follicles significantly inhibited the efficiency of HR-directed DNA repair. The presence of IGF-I-induced HR pathway to alleviate hypoxia-induced DNA damage and apoptosis primarily through upregulating the expression of the RAD51 recombinase. Importantly, we identified a new transcriptional regulator of RAD51, namely E2F8, which mediates the protective effects of IGF-I on hypoxic GCs by facilitating the transcriptional activation of RAD51. Furthermore, we demonstrated that the PI3K/AKT pathway is crucial for IGF-I-induced E2F8 expression, resulting in increased RAD51 expression and enhanced HR activity, which mitigates hypoxia-induced DNA damage and thereby protects against GCs apoptosis. Together, these findings define a novel mechanism of IGF-I-mediated GCs protection by activating the HR repair through the PI3K/AKT/E2F8/RAD51 pathway under hypoxia.

Melatonin-Mediated Suppression of mtROS-JNK-FOXO1 Pathway Alleviates Hypoxia-Induced Apoptosis in Porcine Granulosa Cells

Numerous studies have established that the hypoxic conditions within ovarian follicles induce apoptosis in granulosa cells (GCs), a pivotal hallmark of follicular atresia. Melatonin (N-acetyl-5-methoxytryptamine, MT), a versatile antioxidant naturally present in follicular fluid, acts as a safeguard for maintaining GCs' survival during stress exposure. In this study, we unveil an innovative protective mechanism of melatonin against hypoxia-triggered GC apoptosis by selectively inhibiting mitochondrial ROS (mtROS) generation. Specifically, under hypoxic conditions, a gradual accumulation of mitochondrial ROS occurred, consequently activating the JNK-FOXO1 pathway, and driving GCs toward apoptosis. The blocking of JNK or FOXO1 diminished hypoxia-induced GC apoptosis, but this effect was nullified in the presence of GSH, indicating that mtROS instigates apoptosis through the JNK-FOXO1 pathway. Consistent with this, hypoxic GCs treated with melatonin exhibited decreased levels of mtROS, reduced JNK-FOXO1 activation, and mitigated apoptosis. However, the protective capabilities of melatonin were attenuated upon inhibiting its receptor MTNR1B, accompanied by the decreased expression of antioxidant genes. Notably, SOD2, a key mitochondrial antioxidant gene modulated by the melatonin-MTNR1B axis, effectively inhibited the activation of mtROS-JNK-FOXO1 and subsequent apoptosis, whereas SOD2 knockdown abrogated the protective role of melatonin in hypoxic GCs. In conclusion, our study elucidates that melatonin, through MTNR1B activation, fosters SOD2 expression, effectively quelling mtROS-JNK-FOXO1-mediated apoptosis in follicular GCs under hypoxic stress.

Chemical mitophagy modulators: Drug development strategies and novel regulatory mechanisms

Maintaining mitochondrial homeostasis is a potential therapeutic strategy for various diseases, including neurodegenerative diseases, cardiovascular diseases, metabolic disorders, and cancer. Selective degradation of mitochondria by autophagy (mitophagy) is a fundamental mitochondrial quality control mechanism conserved from yeast to humans. Indeed, small-molecule modulators of mitophagy are valuable pharmaceutical tools that can be used to dissect complex biological processes and turn them into potential drugs. In the past few years, pharmacological regulation of mitophagy has shown promising therapeutic efficacy in various disease models. However, with the increasing number of chemical mitophagy modulator studies, frequent methodological flaws can be observed, leading some studies to draw unreliable or misleading conclusions. This review attempts (a) to summarize the molecular mechanisms of mitophagy; (b) to propose a Mitophagy Modulator Characterization System (MMCS); (c) to perform a comprehensive analysis of methods used to characterize mitophagy modulators, covering publications over the past 20 years; (d) to provide novel targets for pharmacological intervention of mitophagy. We believe this review will provide a panorama of current research on chemical mitophagy modulators and promote the development of safe and robust mitophagy modulators with therapeutic potential by introducing high methodological standards.

Effect of prolactin on cytotoxicity and oxidative stress in ovine ovarian granulosa cells

Background

Prolactin (PRL) has been reported to be associated with oxidative stress, which is an important contributor leading to cell apoptosis. However, little is known about the mechanisms underlying the effects of PRL on cytotoxicity and oxidative stress in ovine ovarian granulosa cells (GCs).

Methods

Ovine ovarian GCs were treated with 0, 4, 20, 100 and 500 ng/mL of PRL. Then, the cytotoxicity, cell viability, malondialdehyde (MDA), reactive oxygen species (ROS), superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) of GCs were detected. Additionally, 500 ng/mL PRL was chosen as the high PRL concentration (HPC) due to its high cytotoxicity and oxidative stress. Proteomic and metabonomic were performed to examine the overall difference in proteins and metabolic pathways between C (control: 0 ng/mL PRL) and P groups (500 ng/mL PRL).

Results

The results indicated that GCs treated with 4 ng/mL PRL significantly decreased (P < 0.05) the cytotoxicity, ROS and MDA, increased (P < 0.05) the cell viability, SOD and T-AOC, and the GCs treated with 500 ng/mL PRL showed the opposite trend (P < 0.05). Supplementation with 500 ng/mL PRL significantly increased the proteins of MT-ND1, MAPK12, UBA52 and BCL2L1, which were enriched in ROS and mitophagy pathways. Pathway enrichment analysis showed that the pentose phosphate pathway was significantly enriched in the P group.

Conclusion

A low concentration of PRL inhibited cytotoxicity and oxidative stress. HPC induced oxidative stress in ovine ovarian GCs via the pentose phosphate pathway by modulating the associated proteins MT-ND1 in ROS pathway and UBA52, MAPK12 and BCL2L1 in mitophagy pathway, resulting in cytotoxicity.

Mechanisms of and Potential Medications for Oxidative Stress in Ovarian Granulosa Cells: A Review

Granulosa cells are essential for follicle initiation and development, and their abnormal function or apoptosis is a crucial factor leading to follicular atresia. A state of oxidative stress occurs when the balance between the production of reactive oxygen species and the regulation of the antioxidant system is disturbed. Oxidative stress is one of the most important causes of the abnormal function and apoptosis of granulosa cells. Oxidative stress in granulosa cells causes female reproductive system diseases, such as polycystic ovary syndrome and premature ovarian failure. In recent years, studies have confirmed that the mechanism of oxidative stress in granulosa cells is closely linked to the PI3K-AKT signaling pathway, MAPK signaling pathway, FOXO axis, Nrf2 pathway, NF-κB signaling pathway, and mitophagy. It has been found that drugs such as sulforaphane, Periplaneta americana peptide, and resveratrol can mitigate the functional damage caused by oxidative stress on granulosa cells. This paper reviews some of the mechanisms involved in oxidative stress in granulosa cells and describes the mechanisms underlying the pharmacological treatment of oxidative stress in granulosa cells.

Sulforaphane suppresses paraquat-induced oxidative damage in bovine in vitro-matured oocytes through Nrf2 transduction pathway

Sulforaphane (SFN), a bioactive phytocompound extracted from cruciferous plants, has received increasing attention due to its vital cytoprotective role in eliminating oxidative free radical through activation of nuclear factor erythroid 2-related factor (Nrf2)-mediated signal transduction pathway. This study aims at a better insight into the protective benefit of SFN in attenuating paraquat (PQ)-caused impairment in bovine in vitro-matured oocytes and the possible mechanisms involved therein. Results showed that addition of 1 μM SFN during oocyte maturation obtained higher proportions of matured oocytes and in vitro-fertilized embryos. SFN application attenuated the toxicological effects of PQ on bovine oocytes, as manifested by enhanced extending capability of cumulus cell and increased extrusion proportion of first polar body. Following incubation with SFN, oocytes exposed to PQ exhibited reduced intracellular ROS and lipid accumulation levels, and elevated T-SOD and GSH contents. SFN also effectively inhibited PQ-mediated increase in BAX and CASPASE-3 protein expressions. Besides, SFN promoted the transcription of NRF2 and its downstream antioxidative-related genes GCLC, GCLM, HO-1, NQO-1, and TXN1 in a PQ-exposed environment, indicating that SFN prevents PQ-caused cytotoxicity through activation of Nrf2 signal transduction pathway. The mechanisms underlying the role of SFN against PQ-induced injury included the inhibition of TXNIP protein and restoration of the global O-GlcNAc level. Collectively, these findings provide novel evidence for the protective role of SFN in alleviating PQ-caused injury, and suggest that SFN application may be an efficacious intervention strategy against PQ cytotoxicity.

Cyanidin Alleviated CCl4-Induced Acute Liver Injury by Regulating the Nrf2 and NF-κB Signaling Pathways

Acute liver injury has multiple causes and can result in liver failure. In this study, we evaluated the hepatoprotective ability of cyanidin (Cy) and investigated its associated mechanisms. Cy administration significantly and dose-dependently ameliorated acute liver injury induced by carbon tetrachloride (CCl₄). High-dose Cy showed effects comparable to those achieved by the positive control (silymarin). Severe oxidative stress and inflammatory responses in the liver tissue induced by CCl₄ were significantly mitigated by Cy supplementation. The total antioxidant capacity and the activity of superoxide dismutase, catalase, and glutathione peroxidase were increased and the content of malondialdehyde, lipid peroxide, tumor necrosis factor α, interleukin-1β, and interleukin-6 were decreased. Additionally, the Nrf2 and NF-κB signaling pathways, which regulate antioxidative and inflammatory responses, were analyzed using quantitative real-time polymerase chain reaction and western blot assay. Cy treatment not only increased Nrf2 transcription and expression but also decreased NF-κB signaling. Moreover, molecular docking simulation indicated that Cy had high affinity for Keap1 and NF-κB/p65, which may promote nuclear translocation of Nrf2 and inhibit that of NF-κB. In summary, Cy treatment exerted antioxidative and anti-inflammatory effects and ameliorated liver injury by increasing Nrf2 and inhibiting the NF-κB pathway, demonstrating the potential of Cy as a therapeutic agent in liver injury.

The TGF-β/SMAD Signaling Pathway Prevents Follicular Atresia by Upregulating MORC2

In mammals, female fertility is determined by the outcome of follicular development (ovulation or atresia). The TGF-β/SMAD signaling pathway is an important regulator of this outcome. However, the molecular mechanism by which the TGF-β/SMAD signaling pathway regulates porcine follicular atresia has not been fully elucidated. Microrchidia family CW-type zinc finger 2 (MORC2) is anovel epigenetic regulatory protein widely expressed in plants, nematodes, and mammals. Our previous studies showed that MORC2 is a potential downstream target gene of the TGF-β/SMAD signaling pathway. However, the role of MORC2 in porcine follicular atresia is unknown. To investigate this, qRT-PCR, western blotting, and TdT-mediated dUTP nick-end labeling were performed. Additionally, the luciferase activity assay was conductedto confirm that the TGF-β/SMAD signaling pathway regulates MORC2. Our results demonstrate that MORC2 is animportant anti-apoptotic molecule that prevents porcine follicular atresia via a pathway involving mitochondrial apoptosis, not DNA repair. Notably, this studyrevealsthat the TGF-β/SMAD signaling pathway inhibits porcine granulosa cell apoptosis by up-regulating MORC2. The transcription factor SMAD4 regulated the expression of MORC2 by binding to its promoter. Our results will help to reveal the mechanism underlying porcine follicular atresia and improve the reproductive efficiency of sows.