Oocyte Maturation Research Articles

The global phosphorylation landscape of mouse oocytes during meiotic maturation.

Phosphorylation is a key post-translational modification regulating protein function and biological outcomes. However, the phosphorylation dynamics orchestrating mammalian oocyte development remains poorly understood. In the present study, we apply high-resolution mass spectrometry-based phosphoproteomics to obtain the first global in vivo quantification of mouse oocyte phosphorylation. Of more than 8000 phosphosites, 75% significantly oscillate and 64% exhibit marked upregulation during meiotic maturation, indicative of the dominant regulatory role. Moreover, we identify numerous novel phosphosites on oocyte proteins and a few highly conserved phosphosites in oocytes from different species. Through functional perturbations, we demonstrate that phosphorylation status of specific sites participates in modulating critical events including metabolism, translation, and RNA processing during meiosis. Finally, we combine inhibitor screening and enzyme-substrate network prediction to discover previously unexplored kinases and phosphatases that are essential for oocyte maturation. In sum, our data define landscape of the oocyte phosphoproteome, enabling in-depth mechanistic insights into developmental control of germ cells.

In Vitro Fertilization (IVF) Outcomes in Patients With Endometriosis Compared to Patients With Tubal Factor Infertility in Indonesia: A Retrospective Study.

Endometriosis is a disease characterized by dysmenorrhea, chronic pelvic pain, and infertility. The pathogenesis of endometriosis and its relationship to infertility are still not fully understood. In vitro fertilization (IVF) is considered an effective treatment for patients with endometriosis-associated infertility. This study compared the pregnancy rates of endometriosis patients who underwent IVF with those of patients with tubal obstruction. This was a retrospective cross-sectional study of 225 patients with endometriosis and tubal factor infertility who underwent IVF at Yasmin Clinic, Dr. Cipto Mangunkusumo National General Hospital, Jakarta, Indonesia, between January 2013 and August 2021. Demographic data, anti-Mullerian hormone (AMH) levels, the initial and total dose of recombinant follicle stimulating hormone (rFSH), the total dose of recombinant luteinizing hormone (rLH), stimulation duration, oocyte maturation rates, fertilization rates, embryo cleavage rates, and pregnancy rates (biochemical, clinical and ongoing) were obtained. AMH level, number of oocytes retrieved, and embryo cleavage rates were significantly lower in the endometriosis group. Initial and total doses of rFSH and total dose of rLH were higher, and the duration of stimulation was longer in the endometriosis group compared to the tubal factor group. In the endometriosis group, the biochemical (47.3% vs. 52.7%, p=0.375), clinical (43.1% vs. 56.9%, p=0.215), and ongoing (45.5% vs. 54.5%, p=0.511) pregnancy rates were lower than those in the tubal factor group. However, there were no statistically significant differences between the two groups. There was no significant difference in pregnancy rates between the short antagonist and ultra-long protocols (three months of downregulation). From multivariate analysis, only rLH supplementation was found to be significantly related to pregnancy outcomes in patients with endometriosis. AMH levels, number of oocytes retrieved, and embryo cleavage rates were lower in patients with endometriosis. However, pregnancy rates were not significantly different from patients with tubal factors. Supplementation with rLH may improve pregnancy rates in patients with endometriosis who have undergone IVF programs.

Progesterone induces meiosis through two obligate co-receptors with PLA2 activity.

The steroid hormone progesterone (P4) regulates multiple aspects of reproductive and metabolic physiology. Classical P4 signaling operates through nuclear receptors that regulate transcription. In addition, P4 signals through membrane P4 receptors (mPRs) in a rapid nongenomic modality. Despite the established physiological importance of P4 nongenomic signaling, the details of its signal transduction cascade remain elusive. Here, using Xenopus oocyte maturation as a well-established physiological readout of nongenomic P4 signaling, we identify the lipid hydrolase ABHD2 (α/β hydrolase domain-containing protein 2) as an essential mPRβ co-receptor to trigger meiosis. We show using functional assays coupled to unbiased and targeted cell-based lipidomics that ABHD2 possesses a phospholipase A2 (PLA2) activity that requires mPRβ. This PLA2 activity bifurcates P4 signaling by inducing clathrin-dependent endocytosis of mPRβ, resulting in the production of lipid messengers that are G-protein coupled receptors agonists. Therefore, P4 drives meiosis by inducing an ABHD2 PLA2 activity that requires both mPRβ and ABHD2 as obligate co-receptors.

Melatonin Protects Against Mitochondrial Dyshomeostasis and Ovarian Damage Caused by Chronic Unpredictable Mild Stress Through the eIF2α-AFT4 Signaling Pathway in Mice.

Stress is an emotional state caused by an unexpected external environmental change or stimulus, and several experiments have demonstrated its negative impact on ovarian function, ultimately affecting reproductive ability. Melatonin (MT) has been shown to facilitate oocyte maturation and enhance ovarian function by regulating mitochondrial function. However, the specific effect and underlying molecular mechanisms of MT on stress-induced ovarian dysfunction remain largely unknown. In this study, we established a mouse model of chronic unpredictable mild stress (CUMS) to investigate its impact on ovarian function. Our findings revealed that CUMS led to premature ovarian insufficiency (POI) in mice, characterized by a reduction in follicle numbers and decreased levels of anti-Müllerian hormone (AMH) and bone morphogenetic protein 15 (BMP15). Furthermore, CUMS caused decreased expression of mitochondrial fission protein 1 (FIS1) and enhanced level of mitochondrial fusion protein optic atrophy 1(OPA1), mitofusin1(MFN1), as well as nucleus-encoded protein succinate dehydrogenase complex A (SDHA), reflecting mitochondrial dyshomeostasis. Additionally, CUMS resulted in excessive autophagy and apoptosis. However, MT reversed these effects and improved ovarian damage. Importantly, the protective effects of MT were mediated through the inhibition of the eIF2α-AFT4 pathway. Overall, this study provides valuable insights into the treatment of POI caused by CUMS.

Maintaining mitochondrial DNA copy number mitigates ROS-induced oocyte decline and female reproductive aging

Oocytes play a crucial role in transmitting maternal mitochondrial DNA (mtDNA), essential for the continuation of species. However, the effects of mitochondrial reactive oxygen species (ROS) on mammalian oocyte maturation and mtDNA maintenance remain unclear. We investigated this by conditionally knocking out the Sod2 gene in primordial follicles, elevating mitochondrial matrix ROS levels from early oocyte stages. Our data indicates that reproductive aging in Sod2 conditional knockout females begins at 6 months, with oxidative stress impairing oocyte quality, particularly affecting OXPHOS complex II and mtDNA-encoded mRNA levels. Despite unchanged mtDNA mutation load, mtDNA copy numbers exhibited significant variations. Strikingly, reducing mtDNA copy numbers by reducing mtSSB protein, crucial for mtDNA replication, accelerated reproductive aging onset to three months, underscoring the critical role of mtDNA copy number maintenance under oxidative stress conditions. This research provides new insights into the relationship among mitochondrial ROS, mtDNA, and reproductive aging, offering potential strategies for delaying aging-related fertility decline.

Lack of effect of cAMP modulation during pre-maturation in vitro on development to the blastocyst stage and expression of specific genes associated with lineage commitment

Pharmacological elevation of cAMP of cultured cumulus-oocyte complexes (COC) before or coincident with initiation of maturation has been reported to improve outcomes for various systems for in vitro production of embryos. Here it was hypothesized that artificial elevation of cAMP in the oocyte for a 2-h period of pre-maturation would improve developmental competence of matured oocytes and result in increased blastocyst yield and alter expression of genes important for embryonic differentiation. Treated COC were cultured for 2 h with dibutyryl cAMP (dbcAMP), a membrane-permeable form of cAMP, and 3-isobutyl-1-methylxanthine (IBMX), which inhibits phosphodiesterases that convert cAMP to ATP. Subsequently, oocytes were matured and fertilized and the resultant embryos cultured for 7.5 d. There was no effect of treatment on the percent of oocytes or cleaved embryos becoming blastocysts or on transcript abundance of EOMES, GATA4, NANOG, SOX2, or SOX17 in the blastocyst. Results do not support the use of pharmacological enhancers of cAMP concentrations in the oocyte for improving the blastocyst yield following in vitro oocyte maturation, fertilization, and embryo culture.

Deoxynivalenol exposure disturbs the cytoplasmic maturation in porcine oocytes

Deoxynivalenol (DON) is a secondary metabolite of Fusarium fungi and belonged to trichothecenes, and it widely presents in various food commodities. Previous studies have highlighted its potent toxicity, adversely affecting the growth, development, and reproductive in both humans and animals. However, the potential impact of DON on porcine oocyte organelles remains elusive. In present study, we delved into the toxic effects of DON on mitochondria, endoplasmic reticulum, Golgi during the porcine oocyte maturation. Our findings revealed that DON exposure significantly impeded granulosa cell diffusion and the expulsion of the first polar body. Additionally, mitochondrial fluorescence intensity and membrane potential underwent notable alterations under DON exposure. Notably, lysosomal fluorescence intensity decreased significantly, suggesting protein degradation and potential autophagy, which was further corroborated by the enhanced fluorescence intensity of LC3. Furthermore, endoplasmic reticulum fluorescence intensity declined, and DON exposure elevated endoplasmic reticulum stress levels, evident from the upregulated expression of GRP78. Concurrently, we observed disruption in the fusiform cortex distribution of the Golgi apparatus, characterized by reduced Golgi apparatus fluorescence intensity and GM130 expression. Collectively, our results indicate that DON exposure profoundly affects the fundamental functions of porcine oocyte organelles during meiosis and maturation.

Developmental Competence of Somatic Cell Nuclear Transfer Embryos and Interspecies ICSI Zygotes From Bovine Small Antral Follicles.

Assisted reproductive technologies (ART) play a crucial role in conserving threatened wildlife species such as Bos gaurus. ART requires a large number of mature oocytes, and small antral follicles (SAFs) in the ovary are often used to obtain abundant sources of bovine oocytes. However, oocytes from SAFs often experience difficulty completing maturation and obtaining high quality and quantity of blastocyst formation compared to fully grown oocytes. This study aimed to increase the number of high-quality mature oocytes and improve their potential for ART applications in cloned and interspecies intracytoplasmic sperm injection (ICSI) embryos by utilising L-ascorbic acid (LAA) in pre invitro maturation (pre-IVM) culture. First, oocytes isolated from SAFs were cultured with the duration of pre-IVM 0, 6, 8, 10 h and different concentrations of LAA to determine good conditions for oocyte maturation. Then, mature oocytes were assessed for their developmental competence through parthenogenesis, cloned and interspecies ICSI embryos. The results showed that 8-h pre-IVM with 50 μg/mL LAA improved the maturation rate and developmental competence of parthenogenetic and clone embryos, especially, improving the high blastocyst quality by increasing cell number and expression of histone acetylation at lysine 9 (H3K9ac). In addition, the culture process improved the nuclear reprogramming of somatic cells after nuclear transfer into mature oocytes, resulting in an increased hatching rate of cloned embryos. It also enhanced the activation and the pronuclear formation rate of Gaurus-Taurus zygotes. Overall, the established pre-IVM culture method enhanced the meiotic and developmental competence of embryos. This procedure opened hope for the preservation of endangered species and other applications.

Effects of multisuperovulation on the transcription and genomic methylation of oocytes and offspring

BackgroundControlled ovarian stimulation is a common skill of assisted reproductive technologies (ARTs). In the clinic, some females would undergo more than one controlled ovarian stimulation cycle. However, few studies have focused on the influence of multi-superovulation on oocytes and offspring.ResultsHere, we found that multi-superovulation disrupted the transcriptome of oocytes and that the differentially expressed genes (DEGs) were associated mainly with metabolism and fertilization. The disruption of mRNA degradation via poly (A) size and metabolism might be a reason for the reduced oocyte maturation rate induced by repeated superovulation. Multi-superovulation results in hypo-genomic methylation in oocytes. However, there was an increase in the methylation level of CGIs. The DMRs are not randomly distributed in genome elements. Genes with differentially methylated regions (DMRs) in promoters are enriched in metabolic pathways. With increasing of superovulation cycles, the glucose and insulin tolerance of offspring is also disturbed.ConclusionsThese results suggest that multi-superovulation has adverse effects on oocyte quality and offspring health.

Selection and Regulatory Network Analysis of Differential CircRNAs in the Hypothalamus of Goats with High and Low Reproductive Capacity

The objectives of this investigation were to identify differentially expressed circular RNAs (circRNAs) in the hypothalamus of goats with high and low prolificacy and construct a circRNA-mRNA regulatory network to uncover key potential circRNAs that influence goat prolificacy. Transcriptome analysis was performed on hypothalamus samples from low-prolificacy (n = 5) and high-prolificacy (n = 6) Chuanzhong black goats to identify circRNAs that influence prolificacy in these goats. Differential expression analysis identified a total of 205 differentially expressed circRNAs, comprising 100 upregulated and 105 downregulated circRNAs in the high-prolificacy group compared with the low-prolificacy group. Enrichment analysis of these differentially expressed circRNAs indicated significant enrichment in Gene Ontology terms associated with mammalian oogenesis, negative regulation of neurotransmitter secretion, reproductive developmental processes, hormone-mediated signaling pathways, and negative regulation of hormone secretion. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis highlighted significant enrichment in the oxytocin signaling pathway, GnRH signaling pathway, and hormone-mediated oocyte maturation. The hypothalamus of low- and high-prolificacy goats contains circular RNAs (circRNAs), including chicirc_063269, chicirc_097731, chicirc_017440, chicirc_049641, chicirc_008429, chicirc_145057, chicirc_030156, chicirc_109497, chicirc_030156, chicirc_176754, and chicirc_193363. Chuanzhong black goats have the potential to influence prolificacy by modulating the release of serum hormones from the hypothalamus. A circRNA-miRNA regulatory network was constructed, which determined that miR-135a, miR-188-3p, miR-101-3p, and miR-128-3p may interact with differentially expressed circRNAs, thereby regulating reproductive capacity through the hypothalamic-pituitary-gonadal axis. The results of this study enhance our knowledge of the molecular mechanisms that regulate prolificacy in Chuanzhong black goats at the hypothalamic level.

Herbicide paraquat dichloride augments the expression of the c-abl-noxa-apoptotic pathway, instigating ovarian atresia in edible fish, Channa punctatus.

Ovarian cells of animals undergo atresia to regulate egg numbers and their release. However, unrestrained atretic activity decreases the chances of oocyte maturity and further process, ultimately resulting in a reduced population. Edible fishes are a critical source of nutrition and it is required to regulate their population. The application of herbicides at fish production sites is a threat to their population by altering female reproductive activity. In concern to this, here, this 60-day study investigates herbicide paraquat dichloride (PD)-induced atresia in ovarian cells of Channa punctatus (C. punctatus). Further, 96-h LC50 of PD for C. punctatus was calculated as 58.40mg/L. At the end of each exposure period, an increase in intracellular ROS in blood cells and activities of SOD and CAT in ovary tissue were observed in PD-treated fish with increasing concentration. The frequency of micronuclei in blood cells subsequently increased with the highest PD concentration. A significant (p < 0.05) increase in the relative expression of target genes was observed at the 30th and 60th day of the sampling periods in the fish treated with the highest concentration of PD. The histological study confirmed the occurrence of atretic ovary cells in PD-exposed fish. From the results it can be concluded that PD enhances the uncontrolled death of ovarian cells and has consequences of impairing the ovary health and reproductive potential of fish, hence reducing the fish population.

Folic acids promote in vitro maturation of bovine oocytes by inhibition of ferroptosis via upregulated glutathione and downregulated Fe2+ accumulation

Bovine embryos by in vitro fertilization have become the primary source of commercial embryo transfers globally. However, the developmental capacity of in vitro maturation (IVM) oocytes is considerably lower than that of in vivo maturation (IVO) oocytes, owing to the production of reactive oxygen species (ROS) via mitochondrial metabolism, which was higher in IVM oocytes than in IVO oocytes. To avoid the negative effects of ROS on embryo quality, folic acid (FA) was supplemented directly into the IVM medium to antagonize ROS production, however, the mechanisms remain unknown. In the present study, five levels of FA (0, 25, 50, 100, and 200 µM) were supplemented into the bovine oocyte culture medium. The maturation, cleavage, and blastocyst formation rates increased by 8.95 %, 6.94 %, and 4.36 %, respectively, in the 50 µM group compared to the 0 µM group. Moreover, 7904 differential genes were identified between 0 µM and 50 µM groups by transcriptome sequencing, and they were mainly enriched in 8 pathways. The glutathione, ROS, and Fe2+ levels in oocytes were found to be associated with ferroptosis. Our results revealed that 50 µM FA promoted the IVM of bovine oocytes and affected the expression of genes involved in the ferroptosis pathway. The downregulation of TFR1 and STEAP3 led to a decrease in intracellular Fe2+ accumulation, and the upregulation of GCL increased oocyte GSH levels, thereby reducing the production of ROS in the ferroptosis pathway. Our study provides a new insight into the molecular mechanisms by which FA promotes bovine oocyte development in vitro.

Methylmercury chloride inhibits meiotic maturation of mouse oocytes in vitro by disrupting the cytoskeleton

Methylmercury chloride (MMC) is a persistent heavy metal contaminant that can bioaccumulate in humans via the food chain, exerting detrimental effects on health. Nevertheless, the specific influence of MMC on oocyte meiotic maturation has yet to be elucidated. This research demonstrated that MMC exposure during the in vitro cultivation of mouse oocytes did not influence germinal vesicle breakdown but markedly decreased oocyte maturation rates. Subsequent analysis indicated that MMC exposure resulted in aberrant spindle morphology and disorganized chromosome alignment, alongside continuous activation of the spindle assembly checkpoint (SAC). However, MMC exposure didn't alter the localization pattern of microtubule-organizing center-associated proteins. MMC exposure considerably diminished the acetylation level of α-tubulin, signifying reduced microtubule stability. Additionally, MMC exposure disrupted the dynamic alterations of F-actin. MMC exposure didn't affect mitochondrial localization, mitochondrial membrane potential, adenosine triphosphate content or the concentrations of reactive oxygen species. Nonetheless, MMC exposure triggered DNA damage and modified histone modification levels. Consequently, the defects in oocyte maturation induced by MMC exposure can be attributed to impaired cytoskeleton dynamics and DNA damage. This study offers the first comprehensive elucidation of the negative impacts of MMC on oocyte maturation, highlighting the potential reproductive health risks associated with MMC exposure.

Culture of Immature Ovarian Follicles within Decellularized Ovary Enhances Oocyte Maturation and Improves In vitro Fertilization Results

The goal of this study is to improve methodologies that define the maturation of ovarian follicles and enhance in vitro fertilization by employing decellularized ovaries. Preantral follicles of mice were cultured for 14 days in both the decellularized ovary and two- dimensional (2D) conditions. The oocyte maturation rate, fertilization rate, and the subsequent embryo development rate were assessed in 2D and the decellularized ovary and compared to in vivo condition. Additionally, the gene expression profile of IGF1R, integrin αvβ3, Cox2, Caspase-3, Bax, and Bcl2 l1 was determined in blastocysts. The culture in the decellularized ovary showed a significantly higher number of MII oocytes in comparison to the 2D culture (P &lt; 0.05). Compared to in vivo, both the 2D and the decellularized ovary cultures exhibited significantly lower percentages of MII oocytes, 2PN, two-cell, cleavage, and blastocyst (P &lt; 0.05). In the decellularized ovary culture, significantly higher percentages of 2PN and blastocyst were observed (P &lt; 0.05) compared to the 2D culture. The gene expression level of IGF1R and Cox2 in blastocysts from both the 2D and the decellularized ovary cultures was markedly lower compared to in vivo. However, the gene expression levels of Integrin αv and β3 were comparable in blastocysts derived from in vivo and decellularized ovary-matured oocytes. Blastocysts derived from decellularized ovary-matured oocytes showed a higher bcl211 expression level compared to the blastocysts from 2D (P &lt; 0.05). Employing decellularized ovarian tissues methodologies for in vitro maturation of oocytes provides a promising avenue towards generating embryos with improved implantation potential.

TET1 overexpression affects cell proliferation and apoptosis in aging ovaries.

Along with the progress of society, human life expectancy has been increasing, and late marriage and late childbearing are the current trend. Since reproductive aging affects fertility, ovarian aging in women has become a major reproductive health issue in the current society. During ovarian aging, DNA methylation levels may change. The ten-eleven translocation (TET) protein family proteins TET1, TET2, and TET3 are important DNA demethylation enzymes, and differential expression of TET1, TET2, and TET3 may affect the proliferation and apoptosis of aging ovarian cells. The aim of this study was to investigate the role of TET1 in the regulation of ovarian aging. The expression of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) was analyzed by immunofluorescence (IF) in young and aging ovaries of six 6-8-week-old female mice and six 6-8-month-old female mice. Then, the expression pattern of the TET protein family in young and aging ovaries of mice was investigated. To determine the impact of TET1 on ovarian development, the aging of IOSE-80, KGN, and SKOV-3 cells was induced with D-galactosidase (D-gal). Cells were then transfected using the TET1 overexpression vector or si-TET1. We assessed the proliferation and apoptosis of aging cells after transfection and analyzed the regulatory effect of TET1 expression on aging cells. Additionally, we verified the Tet1 expression in Tet1-KO mice. The 5mC to 5hmC transition, oocyte maturation, and blastocyst rate were reduced in aging mice compared to young mice. In aging mice ovaries, the expression levels of Tet1, Tet2, and Tet3 were reduced significantly, with Tet1 being particularly pronounced. The overexpression of TET1 promoted proliferation and inhibited apoptosis in aging human ovarian cells. Furthermore, Tet1 expression was very low in Tet1-KO C57BL/6J mice ovaries. This study demonstrates that the expression levels of TET family proteins are low in aging ovaries, and the overexpression of TET1 can promote proliferation and inhibit apoptosis in aging ovarian cells.

Oocyte Competence, Embryological Outcomes and miRNA Signature of Different Sized Follicles from Poor Responder Patients

Poor ovarian response (POR) patients often face the risk of not having enough competent oocytes. Then, aspirating small follicles could serve as a strategy to increase their number. Many efforts have been addressed to associate follicular size with oocyte competence, but results are controversial. Therefore, our study aimed to evaluate oocyte maturation and developmental competence, along with a non-invasive oocyte-maturation-related miRNA signature in oocytes retrieved from both large and small follicles. A total of 178 follicles, from 31 POR patients, were aspirated and measured on the day of ovarian puncture. Follicular diameters, oocyte collection, oocyte maturation, fertilization, blastocysts, and good-quality blastocyst rates were recorded. Simultaneously, follicular fluids were collected to quantify their miRNA expression. The efficacy of oocyte retrieval along with oocyte maturation, fertilization, and blastulation rates tended to increase with follicular size, but few significant differences were found. Despite there being significantly more collected oocytes from follicles &gt; 11.5 mm compared to follicles ≤ 11.5 mm (p &lt; 0.05), oocytes from the latter were also mature, with no significant differences in the miRNA signature, but only those &gt; 13.5 mm demonstrated developmental competence. In conclusion, 11.5 mm follicles can produce mature oocytes, but only those larger than 13.5 mm yielded transferable embryos.

Eicosatrienoic acid enhances the quality of in vitro matured porcine oocytes by reducing PRKN-mediated ubiquitination of CISD2

Oocytes and early embryos are exposed to many uncontrollable factors that trigger endoplasmic reticulum (ER) stress during in vitro culture. Prevention of ER stress is an effective way to improve the oocyte maturation rate and oocyte quality. Increasing evidence suggests that dietary intake of sufficient n-3 polyunsaturated fatty acids (PUFAs) is associated with health benefits, particularly in the domain of female reproductive health. We found that supplementation of eicosatrienoic acid (ETA) during in vitro maturation (IVM) of oocyte significantly downregulated ER stress-related genes. Mitochondria-associated membranes (MAMs) are communications areas between the ER and mitochondria. Inositol 1,4,5-trisphosphate receptor (IP3R) is a key calcium channels in MAMs and, participates in the regulation of many cellular functions. Notably, the MAM area was significantly decreased in ETA-treated oocytes. CDGSH iron sulfur domain 2 (CISD2) is presents in MAMs, but its role in oocytes is unknown. ETA treatment significantly increased CISD2 expression, and siRNA-mediated knockdown of CISD2 blocked the inhibitory effect of ETA on IP3R. Transcriptomic sequencing and immunoprecipitation experiments showed that ETA treatment significantly decreased expression of the E3 ubiquitin ligase PRKN. PRKN induced ubiquitination and degradation of CISD2, indicating that the PRKN-mediated ubiquitin-proteasome system regulates CISD2. In conclusion, our study reveals the mechanism by which ETA supplementation during IVM alleviates mitochondrial calcium overload under ER stress conditions by decreasing PRKN-mediated ubiquitination of CISD2 and facilitating inhibition of IP3R by CISD2/BCL-2. This improves oocyte quality and subsequent embryo developmental competence prior to implantation.

Oleanolic acid promotes porcine oocyte maturation by activating the Nrf2/HO-1 signalling pathway

This study investigated the potential role and underlying mechanisms of oleanolic acid (OA), a pentacyclic triterpene with antioxidant and anti-inflammatory properties, in porcine oocytes during in vitro maturation (IVM). The results showed that supplementation with 5 μM OA during IVM resulted in a greater percentage of mature oocytes, parthenogenetically activated embryos and somatic cell nuclear-transferred embryos. This was evidenced by significant increases in the rate of first polar body expulsion, the expansion of cumulus granulosa cells and the total cell number in blastocysts. Further analysis revealed that OA promoted fatty acid accumulation and upregulated the mRNA expression of genes involved in fatty acid β-oxidation. OA significantly increased the intracellular mitochondrial membrane potential and ATP levels and effectively inhibited BAX/BCL2 and Cleaved Caspase3 protein expression. Notably, OA increased the protein levels of intracellular Nrf2 and HO-1, and the GSH levels and the activities of the antioxidant enzymes SOD and catalase (CAT), while reducing ROS levels. Mechanistically, OA activated the Nrf2/HO-1 signalling pathway, which is crucial for regulating the expression of antioxidant-related targets in IVM porcine oocytes. Our findings indicated that OA improved antioxidant capacity by activating the Nrf2/HO-1 signalling pathway, thereby promoting porcine oocyte maturation.

Antimony exposure affects oocyte quality and early embryo development via excessive mitochondrial oxidation and dysfunction

Antimony (Sb) is a metalloid, widely presents in the environment and associates with human health. In this study, we aimed to decipher whether Sb exposure is harmful to female reproduction and explore the underlying mechanisms. The ICR mice were exposed to 0, 5, 10, and 20 mg/kg acetate potassium Sb tartrate trihydrate by intraperitoneal injection for 10 days, then mouse oocytes were collected for further analysis. We first found a significant decrease in the proportion of MII-stage oocytes obtained from supernumerary ovulation in the fallopian tubes and early embryo development under Sb treatment. Then a series of tests showed Sb affects oocyte maturation by damaging the cytoskeleton of microtubule and actin. Moreover, the abnormal distribution of cortical granules and their component Ovastacin in oocytes, combined with reduced expression levels of Juno, affected sperm-oocyte binding and led to fertilization failure. Based on the sequencing results and experimental validation, it was demonstrated that Sb exposure impairs mitochondrial distribution and membrane potential, elevated levels of mitochondrial superoxide, finally caused energy supply deficits. Mitochondrial damage in oocytes after Sb exposure results in the excessive oxidative stress and early apoptosis. Taken together, these data suggest that Sb exposure decreases oocyte quality and female fertilization ability by impairing mitochondrial function and redox perturbation.

Antidepressants as new endocrine disruptors? – transcriptomic profiling in gonads of Mytilus trossulus exposed to norfluoxetine

In this study an impact of norfluoxetine (NFLU) on Mytilus trossulus gonads was investigated focusing on sex-related differences in hormonal changes, gene expression, and transcriptomic profiling. Sex-specific differences in gonadal serotonin levels were found. NFLU stimulates serotonin synthesis and/or transport in female gonads, potentially accelerating oocyte maturation and gamete release. In males, NFLU decreases serotonin level what likely leads to impeding sperm maturation and thus spawning delay. Transcriptomic analyses highlighted the presence of NFLU-induced changes in gene expression related to gametogenesis and neurotransmission. In females, NFLU upregulated genes associated with oocyte development and downregulated those involved in sperm maturation. NFLU-treated males exhibited mixed effects in their genes in relation to spermatogenesis. Additionally, sex-related differences in the expression of the CYP450 genes responsible for detoxification were found. Overall, norfluoxetine acts as an endocrine-disrupting chemical and impacts gonadal serotonin levels and gene expression, potentially disrupting reproductive success of M. trossulus.