Cytoplasmic Maturation Research Articles

Follicular fluid exosome-derived miR-339-5p enhances in vitro maturation of porcine oocytes via targeting SFPQ, a regulator of the ERK1/2 pathway

In this study, we aimed to investigate cytoplasmic maturation and miRNA expression of mature oocytes cultured in porcine follicular fluid exosomes. We also examined the effect of miR-339-5p on oocyte maturation. Twenty eight differentially expressed miRNAs were detected using miRNA-seq. We then transfected cumulus oocyte complexes with miR-339-5p mimics and inhibitor during culture. The results showed that exosomes increased endoplasmic reticulum levels and the amount of lipid droplets, and decreased ROS levels, lipid droplet size, and percentage of oocytes with abnormal cortical granule distribution. Overexpressing miR-339-5p significantly decreased cumulus expansion genes, oocyte maturation-related genes, target gene proline/glutamine-rich splicing factor (SFPQ), ERK1/2 phosphorylation levels, oocyte maturation rate, blastocyst rate, and lipid droplet number, but increased lipid droplet size and the ratio of oocytes with abnormal cortical granule distribution. Inhibiting miR-339-5p reversed the decrease observed during overexpression. Mitochondrial membrane potential and ROS levels did not differ significantly between groups. In summary, exosomes promote oocyte cytoplasmic maturation and miR-339-5p regulating ERK1/2 activity through SFPQ expression, thereby elevating oocyte maturation and blastocyst formation rate in vitro.

Smart seq2 revealed distinct molecular responses during invitro porcine oocyte maturation before or after the addition of mogroside V.

Oocyte maturation involves both nuclear and cytoplasmic maturation. Mogroside V (MV) has been shown to enhance nuclear maturation, mitochondrial content, and developmental potential of porcine oocyte during invitro maturation (IVM). However, the impact of MV on cytoplasmic maturation and its underlying mechanisms are not understood. This study aimed to assess the effect of MV on cytoplasmic maturation. Germinal vesicle (GV) oocytes treated with MV exhibited a noticeable increase in cortical granules (CGs) formation. Additionally, MV enhanced the expression of NNAT and improved glucose uptake in mature oocytes. Further insights were gained through Smart-seq2 analysis of RNA isolated from 100 oocytes. A total of 11,274 and 11,185 transcripts were identified in oocytes treated with and without MV, respectively. Among quantified genes, 438 differentially expressed genes (DEGs) were identified for further analysis. Gene Ontology (GO) enrichment analysis indicated that these DEGs were primarily involved in DNA repair regulation, cellular response to DNA damage, intracellular components, and organelles. Furthermore, the DEGs were significantly enriched in three KEGG pathways: fatty acid synthesis, pyruvate metabolism, and WNT signalling. To validate the results, lipid droplets (LD) and triglyceride (TG) were examined. MV led to an increase in the accumulation of LD and TG production in mature oocytes. These findings suggest that MV enhances cytoplasmic maturation by promoting lipid droplet synthesis. Overall, this study provides valuable insights into the mechanisms through which MV improves oocyte quality during IVM. The results have significant implications for research in livestock reproduction and offer guidance for future studies in this field.

Bone morphogenetic protein 15 gene disruption affects the in vitro maturation of porcine oocytes by impairing spindle assembly and organelle function

Bone morphogenetic protein 15 (BMP15) plays a crucial role in the porcine follicular development. However, its exact functions in the in vitro maturation (IVM) of porcine oocytes remain largely unknown. Here, through cytoplasmic injection of a preassembled crRNA–tracrRNA–Cas9 ribonucleoprotein complex, we achieved BMP15 disruption in approximately 54 % of the cultured porcine oocytes. Editing BMP15 impaired the IVM of porcine oocytes, as indicated by the significantly increased abnormal spindle assembly and reduced first polar body (PB1) extrusion. The editing also impaired cytoplasmic maturation of porcine oocytes, as reflected by reduced abundant of Golgi apparatus and impaired functions of mitochondria. The impaired IVM of porcine oocytes by editing BMP15 possibly was associated with the attenuated SMAD1/5 and EGFR-ERK1/2 signaling in the cumulus granulosa cells (CGCs) and the inhibited MOS/ERK1/2 signaling in oocytes. The attenuated MOS/ERK1/2 signaling may contribute to the inactivation of maturation promoting factor (MPF) and the increased abnormal spindle assembly, leading to reduced PB1 extrusion. It also may contribute to reduced Golgi apparatus formation, and impaired functions of mitochondria. These findings expand our understanding of the regulatory role of BMP15 in the IVM of porcine oocytes and provide a basis for manipulation of porcine reproductive performance.

Fibronectin 1 supports oocyte in vitro maturation in pigs

Oocyte in vitro maturation (IVM) based on the follicular fluid (FF) environment can exploit untapped resources, however, what FF factors regulate oocyte maturation remains unclear. This work demonstrated that serum and FF significantly promoted oocyte polar body extrusion (PBE) and subsequent embryo development, and FF was especially effective. Fibronectin 1 (FN1) was predicted as one potential candidate to regulate oocyte maturation by proteomics. FN1 transcription obviously decreased, and the protein expression significantly increased and migrated to plasma membrane or even outside during oocyte IVM. Treatment with 10 ng/mL FN1 significantly improved oocyte PBE rate. FN1 significantly upregulated the percentage of regular spindle morphology, downregulated the γ-H2AX level, decreased the levels of ROS and apoptosis, and increased GSH and mitochondrion contents by ameliorating the expression of corresponding genes. Moreover, FN1 significantly increased the p-PI3K level to enhance the activation of PI3K signaling pathway. In conclusion, this study discovers and confirms that FN1 is one factor in FF that significantly enhances oocyte maturation, and the underlying mechanism is that FN1 ameliorates oocyte nuclear and cytoplasmic maturation by promoting the activation of PI3K signaling pathway.

Inhibition of HSP90AA1 induces abnormalities in bovine oocyte maturation and embryonic development.

HSP90AA1 is a ubiquitous molecular chaperone that can resist cellular stress, such as oxidative stress and apoptosis, and mediate the efficacy and protein folding of normal cells during heat stress, as well as many other functions. This study further reveals the role of HSP90AA1 in bovine oocyte maturation and early embryonic development. HSP90AA1, a highly abundant and ubiquitous molecular chaperone, plays important roles in various cellular processes including cell cycle control, cell survival, and hormone signaling pathways. In this study, we investigated the functions of HSP90AA1 in bovine oocyte and early embryo development. We found that HSP90AA1 was expressed at all stages of development, but was mainly located in the cytoplasm, with a small amount distributed in the nucleus. We then evaluated the effect of HSP90AA1 on the in vitro maturation of bovine oocytes using tanespimycin (17-AAG), a highly selective inhibitor of HSP90AA1. The results showed that inhibition of HSP90AA1 decreased nuclear and cytoplasmic maturation of oocytes, disrupted spindle assembly and chromosome distribution, significantly increased acetylation levels of α-tubulin in oocytes and affected epigenetic modifications (H3K27me3 and H3K27ac). In addition, H3K9me3 was increased at various stages during early embryo development. Finally, the impact of HSP90AA1 on early embryo development was explored. The results showed that inhibition of HSP90AA1 reduced the cleavage and blastocyst formation rates, while increasing the fragmentation rate and decreasing blastocyst quality. In conclusion, HSP90AA1 plays a crucial role in bovine oocyte maturation as well as early embryo development.

The Impact of Follicular Fluid on the in vitro Maturation of Camel Oocytes

Background: The objective of this research is to find out how much of an impact adding camel follicular fluid (CFF) to camel oocytes in vitro maturation (IVM) medium has on getting meiosis back on track. Methods: Ovaries from camels were obtained at the central slaughterhouse in Riyadh, Kingdom of Saudi Arabia (KSA). Oocytes were extracted from follicles ranging in size from 2 to 8 mm. Camel oocytes were cultivated in a maturation medium containing varying amounts of camel follicular fluid: 0% (control), 2.5% and 5% for a duration of 32-36 hours. Result: According to the result, the maturation rate of oocytes was considerably (p.05) lower in the 2.5% CFF and 5% CFF groups compared to the control group. It is advised that greater CFF concentrations of camel oocytes be added to the IVM culture in order to improve nuclear and cytoplasmic maturation and boost oocyte competency.

Description of a new quantitative method to assess mitochondrial distribution pattern in mature equine oocytes

The Mitochondrial distribution pattern or MDP in mammalian oocytes serves as an indicator of their cytoplasmic maturity, with a heterogeneous pattern associated with mature cytoplasm. Currently, MDP assessment involves fluorescent labelling of mitochondria followed by visual evaluation, as no quantitative method exists. Our objective was to develop a quantitative approach to assess MDP in mature equine oocytes. Equine oocytes, obtained by ovum pick up (OPU) were matured in vitro, and only metaphase II oocytes were used in the study (n = 56). Following denudation, oocytes were fixed, stained with MitoTracker™ Red CMXRos (50 nM in TCM-199 with Hank´s salts and 10% FBS) for 15 min at 38 °C, and then incubated with 2.5 µg/ml Hoechst 33342 for 10 min at 38 °C. Confocal microscope images were acquired, and the oocyte’s MDP was visually classified as either homogeneous (HoD; n = 17) or heterogeneous (HeD; n = 39). For quantitative analysis, Fiji-ImageJ software was employed. Background subtraction was performed, and a 1-pixel line along the diameter was drawn to calculate the intensity profile. Fluorescence intensities were normalized, and ratios of peripheral to central fluorescence intensity were determined. Student´s t-test was used for comparations; MDP ratio was (mean ± standard error of the mean): 0.8 ± 0.02 for HoD and 0.3 ± 0.02 for HeD (p < 0.001). These results demonstrate concordance between quantitative and qualitative MDP assessment in mature equine oocytes. Our study describes a new approach to quantify mitochondrial distribution pattern and cytoplasmic maturation in mature equine oocytes.

Could the presence and proportion of three/multiple pronuclei (3PN/MPN) zygotes indicate the cytoplasmic maturation state of oocyte cohort in conventional IVF patients?

Although abnormally fertilized zygotes with three or multiple pronuclei (3 PN/MPN) are commonly believed to be associated with improper maturation of the oocyte cytoplasm in conventional IVF cycles, no studies investigated the association between the proportion of MPN zygotes and the maturation state of the oocyte cohort. We compared the cytoplasmic maturity of oocytes from conventional IVF cycles with different proportions of 3 PN/MPN zygotes. A total of 1428 conventional IVF patients with ≥6 oocytes retrieved and fresh embryos transferred were divided into 4 groups according to the proportions of 3 PN/MPN zygotes. The pregnancy outcomes and the proportion of nuclear immature oocytes were analyzed to suggest the cytoplasmic maturation state of the oocyte cohort. Our results showed that the group with a low proportion of 3 PN/MPN zygotes had a higher clinical pregnancy rate (CPR) than those without 3 PN/MPN zygotes (P < 0.05). However, the live birth rate (LBR) was not significantly different between the two groups. The implantation rate (IR), CPR, and LBR did not differ between the low-proportion and high-proportion 3 PN/MPN groups. The proportion of nuclear immature oocytes on day 1 was highest in the group without 3 PN/MPN zygotes (23.8 %) and gradually decreased with an increased proportion of 3 PN/MPN zygotes (P < 0.001). Therefore, the presence of 3 PN/MPN zygotes after conventional IVF may indicate a more mature cytoplasmic state of the oocyte cohort, and the increased proportion of 3 PN/MPN zygotes is associated with an increased maturation state of the whole oocyte cohort. The occurrence and proportion of 3 PN/MPN zygotes may serve as an indicator for the cytoplasmic maturity of the oocyte cohort and help clinicians evaluate the efficiency of ovarian stimulation and optimize the stimulation protocols in subsequent cycles.

Epigen enhances the developmental potential of in vitro fertilized embryos by improving cytoplasmic maturation

Numerous growth factors contribute to oocyte maturation and embryonic development in vivo; however, only a few are understood. One such factor is epigen, a new member of the epidermal growth factor (EGF) family that is secreted by the granulosa cells of immature oocytes. We hypothesized that epigen may play a role in oocyte maturation, specifically in the nuclear and cytoplasmic aspects. This study aimed to investigate the effects of epigen on porcine oocyte maturation and embryo development in vitro. In this study, three different concentrations of epigen (3, 6, and 30 ng/mL) were added to tissue culture medium-199 (TCM-199) during in vitro maturation of porcine oocytes. A control group that did not receive epigen supplementation was also included. Mature porcine oocytes were fertilized, and the resulting zygotes were cultured until day 7. The levels of intracellular glutathione (GSH) and reactive oxygen species (ROS) were measured in the in vitro matured oocytes. At the same time, the expression patterns of genes related to apoptosis were detected in day 7 blastocysts (BLs) using real-time quantitative PCR Apoptosis was detected by annexin-V assays in mature oocytes. Data were analyzed using ANOVA and Duncan's test on SPSS, and results are presented as mean ± SEM. The group that received 6 ng/mL epigen had a significantly lower rate of germinal vesicle breakdown (GVBD) than the control group without affecting the nuclear maturation among the experimental groups. Among the treatment groups, the 6 ng/mL epigen group showed significantly higher levels of intracellular GSH and lower ROS production. Supplementation with 6 ng/mL epigen significantly improved blastocyst (BL) formation rates compared to those in the control and 3 ng/mL groups. Additionally, the blastocyst expansion rate was significantly higher with epigen supplementation (6 ng/mL). In the fertilization experiment, the group supplemented with 6 ng/mL epigen exhibited significantly higher levels of monospermy and fertilization efficiency and lower levels of polyspermy than the control group. This study indicated that adding epigen at a concentration of 6 ng/mL can significantly enhance the developmental potential of porcine oocytes fertilized in vitro. Specifically, the study found that epigen improves cytoplasmic maturation, which helps prevent polyspermy and emulates monospermic penetration.

In vitro maturation of African catfish (Clarias gariepinus, Burchell, 1822) oocytes results in viable larvae

In this study, we describe a protocol for in vitro maturation and ovulation of African catfish (Clarias gariepinus) postvitellogenic ovarian follicles, resulting in fertilizable and developmentally competent eggs. Such culture systems enable detailed studies of fish oocyte development and present a useful tool in assisted reproduction of fish. The maturation-inducing effects of 17α,20β-dihydroxy-4-pregnen-3-one (DHP), human chorionic gonadotropin (hCG) and recombinant human insulin-like growth factor 1 (rhIGF-1) were evaluated based on their ability to promote ooplasm translucency and germinal vesicle breakdown (GVBD), which indicates meiosis resumption. Among the tested groups, only follicles exposed to DHP underwent GVBD in a time-dependent manner, with the highest rates (>80%) observed within 10 to 12 h of incubation. Furthermore, adding rhIGF-1 or hCG prior to or during incubations with DHP did not influence the GVBD outcome. This suggested that the oocytes acquired maturational competence prior to isolation, as high concentrations of DHP (1 μg/ml) were alone sufficient to induce complete nuclear and cytoplasmic maturation; however, only 4 ± 3% of these oocytes ovulated in culture. To promote ovulation, we incorporated prostaglandins (PGs) as an additional incubation step following DHP-induced maturation. Exposure to both prostaglandin F2α (PGF2α) and prostaglandin E2 (PGE2) led to increased rupture of the follicular layer, most notably in groups with 5 μg/ml PGF2α (71 ± 8%). In addition to identifying optimal hormonal stimulation, effects of culture media pH in combination with media supplementation—in the form of bovine serum albumin (BSA) and fetal bovine serum (FBS)—were considered. Compared to results in media with pH of 7.5, significantly less follicles matured and ovulated in a more alkaline environment (pH 8.5), regardless of supplement type and concentration. Although the presence of FBS (5–20%) slightly improved ovulation rates, this benefit was not reflected in the fertilization outcomes. In vitro matured and ovulated oocytes obtained in non-supplemented media (pH 7.5) maintained their developmental competence and were successfully fertilized. The hatching rate was 39%, after which the survival rate of larvae was 8% at 72 h post fertilization (hpf).

Ядерно-цитоплазматическое созревание ооцитов Sus Scrofa Domesticus в условиях сверхнизких температур

Abstract. Vitrification of female gametes is the most important tool for solving the strategic tasks of cellular reproductive technologies in animal husbandry, veterinary medicine and biomedicine: replication of elite individuals (cloning, transgenesis), biodiversity conservation, organ xenotransplantation. The aim of this study was to evaluate the parameters of nuclear cytoplasmic maturation (chromatin status and mitochondrial activity) and developmental competence of donor porcine oocytes subjected to intra- (IOV) or extra-ovarian (EOV) vitrification and cultured in various maturation systems. Methods. Donor pig oocytes (6–8 months old) were vitrified extra- or intraovarially using cryoprotective agents (DMSO, ethylene glycol, trehalose, sucrose). The composition of cryoprotective agents was supplemented with 0.001 % highly dispersed silica nanoparticles (HDSns). Oocytes were thawed in trehalose solutions in TS-199 with 10 % of fetal bovine serum (FBS). Oocytes were cultured for 44 hours in media supplemented with granulosa cells (106 cells per ml of medium) and/or 0.001% of HDSns at 38.5 °C, in an atmosphere of 5 % CO2. Fertilization in vitro was carried out in accordance with the recommendations presented by us earlier [17. p. 17]. The functional activity of mitochondria and the status of chromatin in oocytes were assessed by double staining using MitoTracker Orange CMTMRos and Hoechst 33258 dyes. Results. The level of matured oocytes was 61 % at EOV and 29 % at IOV, and the level of cleavage embryos in EOV was in 11 % (31 % vs. 20 %, P &lt; 0.05) higher than at IOV when HDSns with granulosa cells were added in culture media. The maximum indicators of the functional activity of mitochondria among devitrified oocytes were in the group of EOV oocytes have cultured in media supplemented with HDSns and granulosa cells (152 ± 14.9 μA). Scientific novelty. The protocols for intra- and extra-ovarian vitrification of porcine oocytes have been modernized. Addition to cryoprotective agents and culture media of HDSns and co-culture of devitrified oocytes with granulosa cells significantly increased the fertility rates of devitrified gametes.

Transient suppression of Wnt signaling in poor-quality buffalo oocytes improves their developmental competence.

One of the most evolutionary conserved communication systems, the Wnt signaling pathway is a major gene regulatory pathway that affects the developmental competence of oocytes and regulates most embryonic developmental processes. The present study was undertaken to modulate the canonical Wnt (Wingless/integration) signaling pathway in the poor-quality (colorless cytoplasm after Brilliant Cresyl Blue staining, BCB-) buffalo cumulus-oocyte complexes (COCs) to improve their in vitro maturation (IVM) and embryo production (IVEP) rates. The expression of key Wnt pathway genes was initially assessed in the good (blue cytoplasm after Brilliant Cresyl Blue staining, BCB+) and poor quality (BCB-) buffalo COCs to establish a differential activity of the Wnt pathway. The BCB- COCs were supplemented with the Wnt pathway inhibitor, Dickkopf-related protein 1 (DKK1) and later subjected to IVM and IVEP along with the BCB+ and BCB- controls. The cumulus expansion index (CEI), rate of nuclear maturation (mean percentage of oocytes in the MII stage) and embryo production, and the expression of developmentally important genes were evaluated to assess the effect of Wnt pathway inhibition on the development competence of these poor-quality oocytes. The Wnt pathway genes exhibited a significantly higher expression (p < 0.05) in the poor-quality BCB- oocytes compared to the good-quality BCB+ oocytes during the early maturation stages. The supplementation of BCB- COCs with 100 ng/mL DKK1 effectively inhibited the expression of the key mediators of the Wnt pathway (β-catenin and dishevelled homolog 1, DVL1). DKK1 supplemented BCB- COCs exhibited significantly improved cytoplasmic and nuclear maturation indices, development rates and significantly elevated expression (p < 0.05) of genes implicated in germinal vesicle breakdown (GVBD) and embryonic genome activation (EGA) vis-à-vis BCB- control COCs. These data indicate that inhibition of the Wnt pathway during the initial course of oocyte maturation can improve the development competence of poor-quality buffalo oocytes.

The follicle-stimulating hormone triggers rapid changes in mitochondrial structure and function in porcine cumulus cells

Oocyte maturation is a key process during which the female germ cell undergoes resumption of meiosis and completes its preparation for embryonic development including cytoplasmic and epigenetic maturation. The cumulus cells directly surrounding the oocyte are involved in this process by transferring essential metabolites, such as pyruvate, to the oocyte. This process is controlled by cyclic adenosine monophosphate (cAMP)-dependent mechanisms recruited downstream of follicle-stimulating hormone (FSH) signaling in cumulus cells. As mitochondria have a critical but poorly understood contribution to this process, we defined the effects of FSH and high cAMP concentrations on mitochondrial dynamics and function in porcine cumulus cells. During in vitro maturation (IVM) of cumulus-oocyte complexes (COCs), we observed an FSH-dependent mitochondrial elongation shortly after stimulation that led to mitochondrial fragmentation 24 h later. Importantly, mitochondrial elongation was accompanied by decreased mitochondrial activity and a switch to glycolysis. During a pre-IVM culture step increasing intracellular cAMP, mitochondrial fragmentation was prevented. Altogether, the results demonstrate that FSH triggers rapid changes in mitochondrial structure and function in COCs involving cAMP.

Cytoplasmic and Nuclear Maturation of Intact and Reconstructed Oocytes Controlling the Developmental Competence of Embryos

Cytoplasmic and Nuclear Maturation of Intact and Reconstructed Oocytes Controlling the Developmental Competence of Embryos

Evaluation of the expression level of microRNA-21, microRNA-15a, microRNA-372 in human follicular fluid stem cells-derived oocyte-like cells (OLCs).

Today, researchers have succeeded in achieving oocyte-like cells through the in vitro differentiation of stem cells. MicroRNAs are key regulators of oocyte development. In this study we decided to evaluate the expression pattern of microRNA-21, microRNA-15a, and microRNA-372 in oocyte-like cells, to determine the maturation stage of oocyte-like cells. Human follicular fluid samples were collected and centrifuged, and their cells were divided into 3 groups; day 7 as control group, days 14 and 21. During this period, the cells were evaluated for their morphological appearance and viability by inverted microscopy. RNA isolation was performed and cDNA was reversely transcribed by specific stem-loop RT primers. Real-time RT-PCR was used to detect microRNA expression. The relative expression of microRNA-21 and microRNA-15a on day 21 was significantly down-regulated compared to the control group (day 7), but microRNA-372 did not show a significant difference. Also, on day 14 compared to the control group (day 7), microRNA-21 did not show a significant difference; but microRNA-15a and microRNA-372 were significantly down-regulated. MicroRNA-21 and microRNA-15a on day 21 compared to day 14 revealed down-regulated levels, but microRNA-372 revealed up-regulated levels. Our results showed significant decreases in the expression of microRNA-21 and microRNA-15a in oocyte-like cells, as well as in oocytes, which may lead to cytoplasmic maturation, germinal vesicle break down and the completion of meiosis І. In addition, down-regulation expression of microRNA-372 maybe a confirmation that mesenchymal stem cells have differentiated into germ cells, and these cells were differentiated into oocyte-like cells.

Nuclear-cytoplasmic asynchrony in oocyte maturation caused by TUBB8 variants via impairing microtubule function: a novel pathogenic mechanism

BackgroundTUBB8, a crucial gene encoding microtubule protein, plays a pivotal role in cellular processes. Deleterious TUBB8 variants have been shown to significantly hinder oocyte maturation. In this study, we conducted an in vitro investigation using TUBB8 mutant mouse oocytes to elucidate the pathogenic mechanisms of TUBB8 variants in oocyte nuclear and cytoplasmic maturation.MethodsA mutant model was successfully established in mouse oocytes via microinjection to further investigate the effects of four novel discovered TUBB8 mutations on the nuclear and cytoplasmic maturation of mouse oocytes. Immunofluorescence and confocal microscopy were performed to observe the cortical polarity and spindle and of mutant oocytes. Active mitochondrial staining was performed to analyze mitochondrial distribution patterns. Endoplasmic reticulum and Ca2+ staining were conducted to assess ER distribution and cytoplasmic calcium ion concentration in oocytes.ResultsIn mouse oocytes, TUBB8 variants (p.A313V, p.C239W, p.R251Q, and p.G96R) resulted in a reduction of the first polar body extrusion rate, disruption of spindle assembly, and abnormal chromosome distribution. Additionally, these variants induced oocyte organelle abnormalities, including anomalies in mitochondrial redistribution and endoplasmic reticulum stress compared to the wild-type.ConclusionDeleterious TUBB8 variants could disrupt microtubule function, affecting critical processes such as spindle assembly, chromosome distribution, and organelle rearrangement during oocyte meiosis. These disruptions culminate in compromised nuclear-cytoplasmic maturation, consequently giving rise to oocyte maturation defects.

"Meiosis arrester" C-natriuretic peptide directly stimulates oocyte mtDNA accumulation and is implicated in aging-associated oocyte mtDNA loss.

C-natriuretic peptide (CNP) is the central regulator of oocyte meiosis progression, thus coordinating synchronization of oocyte nuclear-cytoplasmic maturation. However, whether CNP can independently regulate cytoplasmic maturation has been long overlooked. Mitochondrial DNA (mtDNA) accumulation is the hallmark event of cytoplasmic maturation, but the mechanism underlying oocyte mtDNA replication remains largely elusive. Herein, we report that CNP can directly stimulate oocyte mtDNA replication at GV stage, and deficiency of follicular CNP may contribute largely to lower mtDNA copy number in invitro matured oocytes. The mechanistic study showed that cAMP-PKA-CREB1 signaling cascade underlies the regulatory role of CNP in stimulating mtDNA replication and upregulating related genes. Of interest, we also report that CNP-NPR2 signaling is inhibited in aging follicles, and this inhibition is implicated in lower mtDNA copy number in oocytes from aging females. Together, our study provides the first direct functional link between follicular CNP and oocyte mtDNA replication, and identifies its involvement in aging-associated mtDNA loss in oocytes. These findings, not only update the current knowledge of the functions of CNP in coordinating oocyte maturation but also present a promising strategy for improving invitro fertilization outcomes of aging females.

PSIII-4 Effect of Photobiomodulation Treatment on Atp Concentrations in Bovine Oocytes During Maturation

Abstract Oocyte cytoplasmic maturation is critical in determining the success of subsequent embryo development. It has been proposed that light in the red-to-near infrared optical region (~600–1000 nm) enhances cellular metabolic activity through activation of the mitochondrial respiratory chain, increasing intracellular ATP concentrations, and has the potential to modify the oocyte metabolome. Previous research indicated a greater cleavage rate and similar blastocyst rates for bovine oocytes treated with photobiomodulation at hours 16 and 20 from the start of maturation compared with control. For the present study, two separate experiments were conducted to determine ATP concentration in oocytes during maturation after photobiomodulation treatment. A standardized in vitro maturation (IVM) protocol and commercial media (IVF Bioscience) were used. Briefly, bovine ovaries were obtained at a local slaughterhouse, cumulus oocyte complexes (COCs) were collected by aspiration of small (2 to 6 mm) follicles. For experiment 1, compact COCs were cultured in in vitro maturation media (n = 30/well) and treated with no light (control); light (660-665nm) for 10 minutes at hour 16 from start of maturation (L-16) and light for 10 minutes at hour 20 from the start of maturation (L-20). At hour 24 of in vitro maturation, COCs were vortexed to remove cumulus, stained with BioTracker ATP-Red Live Cell Dye (Sigma-Aldrich SCT045), imaged with Cytation-1 (Agilent Technologies Inc.) in 6 replicates. For experiment 2, COCs were cultured in in vitro maturation media (n = 40/well) and treated with no light (control) and light (660-665nm) for 10 minutes at hour 16 from start of maturation (L-16). At hours 18, 20, 22 and 24 of in vitro maturation, COCs were vortexed to remove cumulus, stained with BioTracker ATP-Red Live Cell Dye, and imaged with Cytation-1 in 4 replicates. For experiment 1, one-way ANOVA and Student’s T-Test were performed (JMP software 16.0); in experiment 2, each well was considered as an experimental unit in a model of repeated measures, main effects of time and treatment, blocked by replicate (Mixed procedure, SAS Institute Inc.). In experiment 1, there was a significant (P &amp;lt; 0.05) effect of treatment; ATP concentrations were greater in L-16 than control, and L-20 was intermediate. ATP concentrations were 19,579.3a ± 596.5, 21,652.0b ± 602.7 and 19,710.9ab ± 570.6 relative fluorescence units (RFU) for control, L-16, and L-20 respectively. In experiment 2, there was a significant (P &amp;lt; 0.05) effect of treatment and no significant effect of time. Overall ATP concentrations were 25,668 ± 894.6 and 28,332 ± 894.6 RFU for control and L-16 respectively. In conclusion, photobiomodulation treatment with LED 660-665nm for 10 minutes at hour 16 from start of oocyte maturation increases intracellular ATP concentrations from hour 18 to 24 of maturation.

Heavy Metals in Follicular Fluid Affect the Ultrastructure of the Human Mature Cumulus-Oocyte Complex.

It is known that exposure to heavy metal such as lead (Pb) and cadmium (Cd) has several adverse effects, particularly on the human reproductive system. Pb and Cd have been associated with infertility in both men and women. In pregnant women, they have been associated with spontaneous abortion, preterm birth, and impairment of the development of the fetus. Since these heavy metals come from both natural and anthropogenic activities and their harmful effects have been observed even at low levels of exposure, exposure to them remains a public health issue, especially for the reproductive system. Given this, the present study aimed to investigate the potential reproductive effects of Pb and Cd levels in the follicular fluid (FF) of infertile women and non-smokers exposed to heavy metals for professional reasons or as a result of living in rural areas near landfills and waste disposal areas in order to correlate the intrafollicular presence of these metals with possible alterations in the ultrastructure of human cumulus-oocyte complexes (COCs), which are probably responsible for infertility. Blood and FF metals were measured using atomic absorption spectrometry. COCs corresponding to each FF analyzed were subjected to ultrastructural analyses using transmission electron microscopy. We demonstrated for the first time that intrafollicular levels of Pb (0.66 µg/dL-0.85 µg/dL) and Cd (0.26 µg/L-0.41 µg/L) could be associated with morphological alterations of both the oocyte and cumulus cells' (CCs) ultrastructure. Since blood Cd levels (0.54 µg/L-1.87 µg/L) were above the current reference values established by the guidelines of the Agency for Toxic Substances and Disease Registry (ATSDR) and the Environmental Protection Agency (EPA) (0.4 µg/L), whereas blood Pb levels (1.28 µg/dL-3.98 µg/dL) were below the ATSDR reference values (≤5 µg/dL), we believe that these alterations could be due especially to Cd, even if we cannot exclude a possible additional effect of Pb. Our results highlighted that oocytes were affected in maturation and quality, whereas CCs showed scarcely active steroidogenic elements. Regressing CCs, with cytoplasmic alterations, were also numerous. According to Cd's endocrine-disrupting activity, the poor steroidogenic activity of CCs might correlate with delayed oocyte cytoplasmic maturation. So, we conclude that levels of heavy metals in the blood and the FF might negatively affect fertilization, embryo development, and pregnancy, compromising oocyte competence in fertilization both directly and indirectly, impairing CC steroidogenic activity, and inducing CC apoptosis.

Aberrant protamination in sperm correlates to anomalous nuclear and cytoplasmic architectures in infertile males with sperm dysmorphology.

Aberrant sperm protamination is linked to sperm dysmorphology and nuclear chromatin condensation. Yet, its effects on sperm cytoplasmic maturation remain largely unexplored. The relationships of protamines, sperm morphology, DNA damage, and cytoplasmic remodeling were illustrated in this study to provide fresh perspectives on the mechanisms of male infertility. A total of 205 infertile males were allocated into 5 groups according to the percentage of spermatozoa exhibiting abnormal morphology within their samples. Sperm concentration, motility, abnormal sperm morphology, cytoplasmic droplets (CDs), and excess residual cytoplasm (ERC) were analyzed according to the World Health Organization manual (2010). Sperm nuclear vacuoles (NVs) were determined by propidium iodide (PI) staining. Sperm protamine expressions (P1 and P2) were detected by western blot. DNA damage was measured by acridine orange test (AOT) to calculate the proportion of sperm with single-strand DNA breaks (SSBs). Our data showed that sperm concentration and motility in infertile males significantly decreased with the severity of abnormal sperm morphology (both P < 0.01). P1 level, P1/P2 ratio, and SSB rate increased with the severity of sperm dysmorphology, whilst the P2 level decreased (all P < 0.01). NVs, CDs, and ERC were more common in males with sperm dysmorphology and positively correlated with the SSB rate (all P < 0.01). The relationships between the SSB rate and the P1/P2 ratio were also significant ( P < 0.01). Aberrant protamination may cause sperm dysmorphology and compromise male fertility by impairing sperm's nucleus and cytoplasm maturation, with the P1/P2 ratio potentially serving as a valuable indicator of sperm quality and male fertility.