Search Results (99)

This study determined the optimal concentration of hydrogen peroxide (H₂O₂) for inducing oxidative stress in bovine oocytes prior to in vitro maturation (IVM). Ovaries were collected from local abattoirs, and cumulus–oocyte complexes (COCs) were aspirated, selected, and allocated into four groups, exposed to 0, 50, 75, or 100 µM H₂O₂, respectively, for 1 h in collecting medium. This was followed by IVM in TCM-199 at 38.5 °C in humidified atmosphere of 5% CO₂ for 23 h. Nuclear maturation was assessed by aceto-orcein staining. Exposure to increasing concentrations of H₂O₂ resulted in a clear, dose-dependent trend of decreased nuclear maturation rates. The control group (0 µM) exhibited the highest proportion of oocytes reaching the metaphase II (MII) stage (69.23 ± 8.45%), which remained comparable at 50 µM (67.50 ± 12.29%). A mild, though not statistically significant, decrease was observed at 75 µM (56.50 ± 2.33%). In contrast, treatment with 100 µM H₂O₂ led to a significant reduction in MII rate to 32.83 ± 7.64%, compared to all other groups. These findings indicated that exposure to 100 µM H₂O₂ for 1 h effectively induces oxidative stress in bovine oocytes and could serve as a standard in vitro model for future studies, investigating antioxidant supplementation during pre-IVM and IVM phases. Full article

In vitro maturation (IVM) of oocytes is a pivotal step in assisted reproductive technologies for livestock. However, oxidative stress (OS) and mitochondrial dysfunction during in vitro culture often lead to oocyte aging, thereby limiting the efficiency of the technologies. To address these challenges, this study investigated the regulatory effects of 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-Phosphocholine (POPC) on bovine oocyte IVM, aging, and developmental competence to determine the optimal concentration and explore underlying mechanisms. Cumulus–oocyte complexes (COCs) were collected from abattoir-derived bovine ovaries and cultured in IVM medium supplemented with 0 (control), 50, 100, 150, or 200 μmol/mL of POPC (n = 300 per group) at 38.5 °C under 5% CO₂ for 22 h. The optimal concentration was determined based on the first polar body extrusion rate, followed by in vitro fertilization (IVF), fluorescence staining, Smart-seq2 transcriptome sequencing, and quantitative PCR (qPCR) analysis. The results demonstrated that 150 μmol/mL of POPC yielded the highest maturation rate, significantly exceeding the control group (p < 0.05), and enhanced 2-4-cell cleavage rates after IVF. Furthermore, POPC markedly reduced intracellular reactive oxygen species (ROS) levels, increased glutathione (GSH) content, improved mitochondrial function, and restored normal spindle morphology. Transcriptomic analysis identified 350 upregulated and 280 downregulated differentially expressed genes (DEGs), which were enriched in pathways related to OS. qPCR validation confirmed upregulation of SIRT1/2 and BCL-2, along with downregulation of BAX and Caspase-1/3. Collectively, these findings suggest that 150 μmol/mL of POPC alleviates OS and activates the “SIRT–antioxidant–antiapoptotic” signaling axis, thereby providing valuable insights for optimizing assisted reproductive technologies in livestock. Full article

Acetamiprid (ACE), a widely used neonicotinoid insecticide, has raised concerns due to its potential reproductive toxicity. While its adverse effects on animal reproductive systems have been documented, the impact of ACE on mammalian oocytes remains poorly understood. This study aimed to investigate the potential effects of ACE exposure on porcine oocytes and evaluate whether alpha-tocopherol (α-TOC), a fat-soluble antioxidant, could alleviate ACE-induced oocyte damage. Porcine cumulus oocyte complexes (COCs) were exposed to ACE alone or co-treated with α-TOC for 44 h during in vitro maturation. ACE exposure significantly reduced the first polar body (PB1) excretion rate, arrested meiotic progression, and disrupted spindle assembly in porcine oocytes. Furthermore, ACE impaired mitochondrial function, evidenced by decreased mitochondrial membrane potential (MMP), while increasing intracellular reactive oxygen species (ROS) accumulation and lipid peroxidation (LPO). Additionally, ACE exposure induced intracellular iron overload and dysregulated ferroptosis-related genes, downregulating solute carrier family 7 member 11 (SLC7a11) and glutathione peroxidase 4 (GPX4) while upregulating transferrin receptor 1 (TfRC) and acyl-CoA synthetase long-chain family member 4 (ACSL4), contributing to the occurrence of oocyte ferroptosis. Notably, α-TOC co-treatment effectively alleviate oxidative stress and lipid peroxidation, thereby protecting oocytes from ACE-induced ferroptosis. Collectively, these findings indicate that oxidative stress-mediated ferroptosis may be a major contributing pathway through which ACE impairs oocyte maturation and suggest that α-tocopherol may serve as a protective agent against ACE-induced oocyte damage. Full article

Background/Objectives: Oocyte maturation is a process involving both nuclear and cytoplasmic development regulated by epigenetic changes in gene expression. Cyclin-B3 (CCNB3) and cyclin-A2 (CCNA2) genes are thought to be involved in oocyte maturation; however, the expression profiles and key function in Metaphase-I (MI) and Metaphase-II (MII) phases have yet to be fully elucidated. Small non-coding RNA sequences are involved in epigenetic regulation of specific transcriptional targets, whereas microRNAs (miRNAs) participate in the post-transcriptional and translational repression of target genes. This study examined the expression levels of CCNB3, CCNA2, and their associated miRNAs (miR-17, miR-106b, miR-190a, miR-1275) in cumulus oophorous complex (COC) cells derived from MI and MII oocytes of NOR and DOR IVF cases, with particular emphasis on elucidating their functions during the transition from MI to MII stage. Methods: Follicular fluid containing cumulus–oocyte complex (COC) cells obtained from oocytes of 120 cases in each group NOR MI (n = 30), NOR MII (n = 30), DOR MI (n = 30), and DOR MII (n = 30) who were admitted to the Istanbul Bahçeci Health Group Assisted Reproductive Treatment Center. Following total RNA isolation from COC cells, the gene and protein expression levels of CCNB3 and CCNA2, along with the expression of miR-17, miR-106b, miR-190a, and miR-1275, were assessed using (qPCR-based assay) and immunohistochemistry (IHC). To investigate the functional roles of COC cell populations, morphological analysis was performed using H&E staining. Additionally, metadata of the cases, including age, number of oocytes, fertilization, and embryonic development rates, were evaluated. Results: The expressions of miR-17 and miR-1275 were significantly elevated in both NOR MI and DOR MI groups compared to their respective NOR MII and DOR MII groups (p < 0.05). Additionally, miR-106b levels were higher in the NOR MII group relative to NOR MI (p < 0.05), while an increase was also observed in DOR MI compared to DOR MII (p < 0.05). No difference was observed in miR-190a expression between the NOR and DOR (p > 0.05). Based on the results of H and E staining, the NOR MI, NOR MII, DOR MI, and DOR MII groups exhibited distinct variations in cellular morphology, nuclear characteristics, cytoplasmic volume, and cell density. Conclusions: CCNB3 is predicted to be a potential candidate for determining MI between the NOR and DOR cases. On the other hand, only for the NOR MII cases could CCNA2 provide evidence of oocyte maturation. Moreover, we determined the relationship between related genes and miRNAs which target CCNA2 and CCNB3. Genetic and protein expression analysis across diverse molecular pathways and miRNAs yielded comprehensive preliminary data regarding the developmental stages of oocytes at the MI and MII phases, and their fertilization potential following maturation shows potential and warrants prospective validation with clinical performance evaluation. Full article

The aim was to evaluate the effectiveness of semen cryopreservation and oocyte vitrification in roe deer as a potential method of gamete preservation for endangered deer species. Sperm were isolated from the cauda epididymis of fourteen bucks (n = 14). The motility measure (CASA) and morphology of fresh semen (FS) and frozen–thawed semen (TS) were compared. A hyaluronic binding assay was used to distinguish between mature FS spermatozoa expressing hyaluronan receptors and immature FS lacking these receptors, and the mitochondrial membrane potential (MMP) in TS was determined (flow cytometry). A Sperm–Hyaluronan Binding Assay (HBA) showed a viability rate of 61.9% in FS and 78.2% in TS. Oocytes received from eight does (n = 8) underwent a viability test and vitrification, and fresh oocytes from the other eight does (n = 8) were fertilized with TS and embryos were cultured until the blastocyst stage. The number of isolated oocytes, cumulus–oocyte complexes (COCs), cleaved embryos, and expanded blastocysts was evaluated. Higher percentages of morphological factors (acrosome, head, midpiece, and tail shape) were observed in FS compared to TS, whereas the motility and progressive movement were greater in TS (p ≤ 0.001). The viability was 50.5% and MMP was 40.6% in TS. A total of 311 oocytes were collected and from 150 COCs and 125 blastocysts developed. The viability of thawed oocytes after vitrification was 81%. The viability of vitrified oocytes and cryopreserved sperm confirmed the effectiveness of freezing protocols and highlights the potential for their implementation in other deer species. Full article

To minimize the deleterious effects of oxidative stress and improve oocyte competence, we assessed the impact of melatonin during in vitro pre-maturation (pre-IVM) in bovine cumulus–oocyte complexes (COCs). We compared three groups: control (conventional IVM), pre-IVM control (without melatonin), and pre-IVM + MTn (with melatonin). The analyses included levels of reactive oxygen species (ROS), mitochondrial activity, oocyte lipid content, and the expression of genes related to oxidative stress and lipid metabolism in oocytes and cumulus cells. We also examined embryo quality by evaluating kinetics of development and gene expression. The pre-IVM + MTn group exhibited an increase (p ≤ 0.05) in ROS levels and a decrease (p ≤ 0.05) in lipid content, while maintaining mitochondrial activity similar (p > 0.05) to that of the control group. Regarding gene expression, the effect of pre-IVM, independent of melatonin, was characterized by a decrease in FABP3 transcripts in cumulus cells and reductions in GSS and NFE2L2 transcripts in oocytes (p ≤ 0.05). The pre-IVM + MTn group also displayed a decrease (p ≤ 0.05) in CAT and SOD2 transcript levels. In terms of embryonic development, the pre-IVM + MTn group achieved a higher blastocyst rate on D7 (p ≤ 0.05) compared to the control group (30.8% versus 25.8%), but with similar rates (p > 0.05) to the pre-IVM control group (30.8% versus 35.9%). However, there was a decrease in the levels of the PLAC8 transcript. This study indicates that, under the conditions tested, melatonin did not significantly benefit oocyte competence. Full article

The corpus luteum (CL) is a transient gland that can directly influence follicular dynamics and oocyte quality. The objective of this study was to evaluate the influence of the absence or presence of a small (≤3 mm), medium (4–8 mm), or large (>8 mm) CL in slaughterhouse ovaries on in vitro embryo production. Cumulus–oocyte complexes (COCs) were collected from each group of ovaries and matured in TCM-199 medium, plus hormones and fetal bovine serum. Fertilization was performed with fresh semen from a Katahdin ram of known fertility. Embryo development was carried out in commercial sequential media for 72 and 96 h, until the blastocyst stage. The number of follicles (2–6 mm in diameter) and COCs were influenced by the presence of CL, which was higher (p < 0.05) in the Large CL group (5.51 ± 0.33 and 3.62 ± 0.27) compared to the Without CL group (4.54 ± 0.19 and 2.62 ± 0.14, respectively), with no difference between the CL sizes. Likewise, the diameter and area of the COCs were higher in the Small CL group of ovaries compared to the Without CL group. In the Large CL group of ovaries, 9% more morulae (p < 0.05) were obtained compared to the Without CL group; in the Medium CL group, 13% more blastocysts were obtained compared to the Without CL group. However, in the hatching capacity and diameter of blastocysts, no statistical difference was evident (p > 0.05). In conclusion, the presence and size of the CL in the ovaries of slaughtered sheep influence the productive efficiency of embryos in vitro under the conditions in which the present study was carried out. Full article

The asynchrony of cytoplasmic and nuclear maturation in cumulus–oocyte complexes (COCs) due to prematurely declining concentrations of cyclic adenosine monophosphate (cAMP) has been shown to result in reduced oocyte developmental competence. The objective of this study was to evaluate the effect of pre-IVM treatment with cAMP modulators for different durations on the developmental potential of equine oocytes used for cloned embryo production. Collected COCs were transferred to cryovials filled with transport medium at 20–22 °C. Within the cryovials, the COCs were either untreated (Control) for 18 h or treated with 50 µM forskolin and 100 µM 3-isobutyl-1-methylxanthine for the first 4 h (Pre-IVM 4 h) or the entire 18 h (Pre-IVM 18 h). Oocytes were then transferred to maturation medium and incubated for a further 22–24 h at 38.5 °C in 5% CO₂ in air. Somatic cell nuclear transfer embryos were then produced using the meiotically mature oocytes and donor cells from six different fibroblast cell lines. The rates of maturation and embryo development did not differ significantly between the groups, though blastocyst formation tended to be inferior in the Pre-IVM 4 h group compared with the Control group (p = 0.06). Of 67 blastocysts produced, 23 were transferred to recipient mares on Day 4 or 5 post-ovulation. Regarding the pregnancy outcomes, no significant differences were found between the groups, and four viable foals were born, each derived from a different donor cell line. The findings expand on those from previous evaluations of this biphasic IVM system, and indicate that the cAMP-modulating treatments exert limited effects under the pre-IVM conditions used here. Full article

The efficiency of in vitro maturation (IVM) in Cavia porcellus remains suboptimal compared to other species. This study aimed to characterize the morphological and functional quality of oocytes based on the stage of the estrous cycle and the classification of the cumulus–oocyte complexes (COCs) from which they were derived. A total of 744 oocytes were recovered postmortem from females in the diestrus and periovulatory phases. Oocytes were evaluated for metabolic activity, lipid distribution, apoptosis, nuclear maturation, and diameter. Oocytes collected during diestrus exhibited larger diameters and more homogeneous lipid distribution, particularly in oocytes from Type A COCs. In contrast, a higher proportion of BCB+ oocytes and reduced rates of early apoptosis were observed during the periovulatory stage, suggesting enhanced metabolic competence. Nuclear maturation rates varied with both cycle stage and COC classification, with oocytes from Type A COCs showing higher maturation rates in diestrus. These findings indicate that both intrinsic (e.g., morphological quality) and extrinsic (e.g., estrous cycle stage) factors modulated oocyte competence. Selecting oocytes based on integrated morphological and physiological criteria may improve the efficiency of IVM protocols in this species. Full article

Triclosan (TCS) is an antimicrobial agent in a wide range of health care products. It has been found in various human bodily fluids and is a potential reproductive toxicant. However, the effect of TCS on early embryo development in mammalian species is limited. We therefore asked whether exposure to TCS affects mammalian cumulus–oocyte complexes (COCs), and if so, whether the effects persist into the early embryo. COCs, isolated from abattoir-derived bovine ovaries, were exposed to two environmentally relevant doses of TCS (1 and 10 nM) during in vitro maturation. When exposed to 1 nM TCS during in vitro maturation, progesterone release from bovine oocytes was elevated. Furthermore, altered pyruvate metabolism and mitochondrial dysfunction were also observed; specifically, O₂ consumption coupled to ATP production was significantly decreased in COCs after acute exposure to TCS prior to maturation, whereas proton leak from the respiratory chain was increased. Subsequently, TCS-exposed COCs were fertilised. Fewer oocytes were able to develop to blastocyst when exposed to 1 nM TCS during maturation compared to the Control group, and those that did reach the blastocyst displayed impaired glycolytic and amino acid metabolic activity. These findings indicate for the first time that oocytes exposed to TCS during the final stages of maturation give rise to embryos with impaired mitochondrial function, altered steroidogenesis, and disrupted metabolic activity. Full article

In vitro maturation (IVM) of oocytes retrieved from ovum pick-up (OPU) or ovarian tissue (OT) is a standard approach for patients with specific conditions where prior hormonal stimulation is contraindicated. However, the developmental competence of oocytes matured in vitro is still inferior to that of oocytes matured in vivo. Capacitation IVM (CAPA-IVM) includes an extra step of pre-maturation culture (PMC) with c-type natriuretic peptide (CNP) as a meiotic arrestor to better synchronize cytoplasmic and nuclear maturity in oocytes by allowing the cytoplasm additional time to acquire essential components critical for optimal competency. This study aims to evaluate the effect of CAPA-IVM on equine oocyte quality and developmental competence. Immature cumulus–oocyte complexes (COCs) were retrieved from slaughterhouse ovaries and matured in vitro either in CAPA-IVM (short 6 h, long 24 h pre-maturation) or standard IVM. Mature oocytes from each group were analyzed for calcium-releasing potential (n = 52) and single-oocyte proteomics (n = 44), and embryo development (n = 229) was assessed after fertilization with piezo-drilled intracytoplasmic sperm injection (ICSI). Genetic analysis of developed blastocysts (n = 41) was performed to detect chromosomal aberrations. Our findings demonstrate that CAPA-IVM of equine COCs yields significantly higher maturation rates than controls. Moreover, short CAPA-IVM with six hours pre-maturation culture showed substantially higher embryo development potential than the control group (20/69 vs. 9/63, respectively). Genetic analysis revealed a high euploidy rate in equine blastocysts regardless of the maturation conditions. Live calcium imaging of the fertilized oocytes demonstrated that the majority of oocytes displayed non-continuous calcium oscillation patterns, irrespective of maturation conditions. Single-oocyte proteomics reveals a comparable proteomic landscape between mature oocytes subjected to short CAPA-IVM and standard IVM. However, we identified four enriched gene sets with positive enrichment scores after short CAPA-IVM, related to cytoskeleton regulation, ribosomal function, and cytosolic components. Our findings indicate that CAPA-IVM holds the potential to improve oocyte quality and competence in horses. However, further fine-tuning of culture conditions would benefit the effective use of these IVM systems. Moreover, given that the mare serves as an excellent model for human reproduction, the molecular trends identified in this study could provide valuable insights for advancing human artificial reproductive technologies. Full article

Although prior studies have identified cumulus cells (CCs)-expressed genes and miRNAs that regulate cumulus expansion and/or CC apoptosis and may serve as markers for selecting competent oocytes and embryos, there remains an urgent need to identify CCs-expressed genes and miRNAs whose expression levels are directly correlated with oocyte developmental potential (DP). In this study, we first established CC models from mouse cumulus-oocyte complexes (COCs) that exhibited significantly different DP following in vitro or in vivo maturation. Subsequently, we performed mRNA/miRNA sequencing and functional analyses using these in vitro and in vivo CC models. We identified and validated Spp1, Fn1, Sdc1, and Ngf as DP-beneficial genes; Fos and Jun as DP-detrimental genes; and miR-7686-5p, miR-133a-3p, novel-miR-239, novel-miR-193, and miR-339-5p as DP-detrimental miRNAs. Finally, by employing a well-in-well activation/embryo culture system that enables tracking the COC origin of CCs and embryos, we further validated Spp1 and Ngf as DP-beneficial genes, Jun as the DP-detrimental gene, and miR-7686-5p, novel-miR-239, and miR-339-5p as DP-detrimental miRNAs. In conclusion, we identified and validated new sets of CCs-expressed genes and miRNAs whose expression levels were directly correlated with oocyte DP. These newly identified genes and miRNAs may serve as potential biomarkers for selecting competent oocytes and embryos. Full article

This study aimed to compare the morphometry, morphology, and maturation capacity of cattle oocytes subjected to vitrification using different vitrification and maturation media. In Experiment 1, a total of 900 oocytes were divided into three groups: (1) matured before vitrification, (2) non-vitrified, and (3) vitrified as immature oocytes using the straw vitrification method. Morphometric parameters, including oocyte diameter, ooplasm, zona pellucida width (ZPW), granulosa cell width (GRSW), and zona pellucida-granulosa cell width (ZP GRSW), were measured (µm) before and after cryopreservation. In Experiment 2, the maturation capacity of three in vitro maturation (IVM) media (VitroMat-Protect™, BO-IVM™, and TCM199) was evaluated based on cumulus–oocyte complex (COC) expansion and polar body (PB) extrusion. Morphological abnormalities such as fragmented polar bodies (FPBs), large vacuoles (LVs), degenerated oocytes (DOs), and cracked cytoplasm (CC) were recorded. While vitrification did not significantly affect the oocyte diameter, ooplasm, or ZPW, it significantly reduced the GRSW and ZP GRSW. BO-IVM™ supported the highest COC expansion rate, while TCM199 had the lowest. Among vitrified oocytes, the highest PB extrusion rates were observed in BO-IVM^TM (35.14 ± 5.01) and Vitromat-Protect^TM (24.60 ± 5.67) as compared to TCM199 (18.44 ± 8.00; p < 0.05). Oocytes with higher CC rates were observed in VitroMat-Protect™ (24.50 ± 10.53) and BO-IVM™ (31.42 ± 7.32) as compared to TCM199 (18.70 ± 7.04). In conclusion, the vitrification process affects the granulosa cells in both vitrified immature and mature oocytes. BO-IVM^TM and VitroMat-Protect^TM supported better oocyte maturation than TCM199, although vitrification increased FPB and CC rates. Full article

Oocytes are exposed to various stressors during in vitro maturation (IVM). Antioxidant supplementation during IVM can mitigate oxidative stress. We investigated the effects of supplementing IVM medium with novel flavonoid-enriched antioxidant nanoformulations, namely, EMD-300^® and EMP3-H200^®, on oocyte IVM and analyzed the expression of oxidative stress, apoptosis, and pluripotency genes in buffalo. Cumulus oocyte complexes (COCs) obtained from buffalo ovaries were matured in IVM medium supplemented with either EMD-300^® or EMP3-H200^® at 0.5% and 1.0% for 22 h. Following IVM, nuclear maturation, gene expression, and the levels of total antioxidant capacity (TAC) and malondialdehyde (MDA) were analyzed. Nuclear maturation was lower (p < 0.001) for the 1.0% EMD-300^® group than other groups. The expressions of the GPX4, SOD, CAT, and ATF6 genes were lower (p < 0.05) in the 0.5% EMD-300^® and EMP3-H200^® groups than in the control. OCT4 gene expression was higher (p < 0.05) for the treated groups than control group. The level of TAC in spent IVM medium was higher for the 0.5% EMD-300^® and EMP3-H200^® groups than for the control. However, the MDA concentrations were lower. In conclusion, supplementing IVM medium with EMD-300^® or EMP3-H200^® at 0.5% improved nuclear maturation of buffalo oocytes better than 1.0%. Our findings suggest that these compounds had antioxidant effects, which assures their ability in protecting oocytes against oxidative stress. Full article

Suboptimal culture conditions during in vitro maturation (IVM) affect oocyte developmental competence and the viability of the resulting embryo. Three-dimensional (3D) culture systems provide a more biologically appropriate environment compared to traditional two-dimensional (2D) cultures. The aim of this study was to evaluate the effect of liquid marble (LM) microbioreactors as a 3D culture system on IVM and the subsequent embryo development of prepubertal goat oocytes. The cumulus–oocyte complexes (COCs) recovered from prepubertal goat ovaries underwent IVM in drops under oil (the 2D system and the control group) and in the 3D LM system (the LM group). After IVM, oocytes were parthenogenetically activated and cultured until the blastocyst stage. The control and LM groups showed similar rates of nuclear maturation (52.17% and 44.12%) and blastocyst formation (10.64% and 10.10%). Reactive oxygen species and glutathione levels and the density of transzonal projections (TZPs) in oocytes did not differ between groups. The LM system increased mitochondrial activity and modified the organization of these organelles in the oocyte cytoplasm compared to the control group. The LM microbioreactor demonstrated the ability to improve the mitochondrial status of the oocytes and was not harmful for oocyte IVM and subsequent embryo development. Therefore, LM could be used as a 3D cost-effective culture system for the IVM of prepubertal goat oocytes. Full article