Improvement of oocyte competence and in vitro oocyte maturation with EGF and IGF-I in Guinea pig model

In vitro maturation (IVM) system is an alternative method to superovulation protocols to obtain mature oocytes. Epidermal Growth Factor (EGF) and Insulin-like Growth Factor I (IGF-I) have been widely used in IVM medium in different species. Although the guinea pig is a valuable animal model for reproductive studies, IVM is rarely used. We aimed to establish a suitable in vitro production system using EGF and/or IGF-I during IVM to improve oocyte competence. Firstly, immunolocalization of EGF and IGF-I receptors in the ovary was assessed. An IVM dose-response experiment was performed with cumulus-oocyte complexes (COCs) supplemented with: 1) EGF [0, 10, 50, 100 ng/mL or 10% fetal calf serum (FCS)]; 2) IGF-I [0, 50, 100, 200 ng/mL or 10% FCS]; or 3) the concentrations of EGF and IGF-I which showed the best IVM index in the previous experiments, with or without Fetal Calf Serum (FCS). Cortical granule and mitochondria distribution patterns were determined in in vivo and in vitro-matured oocytes for the first time in this species. Apoptotic rate after IVM and oocyte competence by in vitro embryo development were evaluated. Immunohistochemistry results showed positive immunostaining of EGF and IGF receptors in corpus luteum, oocytes, granulosa and theca cells in follicles in all stages of development. Supplementation of IVM medium with 50 ng/mL EGF or 100 ng/mL IGF-I or their combination with FCS successfully led to oocyte nuclear and cytoplasmic maturation and reduced the apoptotic rate. Both growth factors improved oocyte competence during IVM in this species since early embryos were in vitro developed, showing better results when FCS was used in the IVM medium.

Impact of antioxidant supplementation during in vitro culture of ovarian preantral follicles: A review

The in vitro culture systems of ovarian preantral follicles have been developed for studying follicular and oocyte growth, for future use of immature oocytes as sources of fertilizable oocytes and for screening ovarian toxic substances. One of the key limitations of the in vitro culture of preantral follicles is the oxidative stress by accumulation of reactive oxygen species (ROS), which can impair follicular development and oocyte quality. Several factors are associated with oxidative stress in vitro, which implies the need for a rigorous control of the conditions as well as addition of antioxidant agents to the culture medium. Antioxidant supplementation can minimize or eliminate the damage caused by ROS, supporting follicular survival and development and producing mature oocytes competent for fertilization. This review focuses on the use of antioxidants and their role in preventing follicular damage caused by oxidative stress in the in vitro culture of preantral follicles.

Antioxidants supplementation improves the quality of in vitro produced ovine embryos with amendments in key development gene expressions

The present study assessed the effects of supplementation of different antioxidants on oocyte maturation, embryo production, reactive oxygen species (ROS) production and expression of key developmental genes. In this study, using ovine as an animal model, we tested the hypothesis that antioxidant supplementation enhanced the developmental competence of oocytes. Ovine oocytes aspirated from local abattoir-derived ovaries were subjected to IVM with different concentrations of antioxidants [(Melatonin, Ascorbic acid (Vit C), alpha-tocopherol (Vit E), Sodium selenite (SS)]. Oocytes matured without any antioxidant supplementation were used as controls. The oocytes were assessed for maturation rates and ROS levels. Further, embryo production rates in terms of cleavage, blastocysts and total cell numbers were evaluated after performing in vitro fertilization. Real-Time PCR analysis was used to evaluate the expression of stress related gene (SOD-1), growth related (GDF-9, BMP-15), and apoptosis-related genes (BCL-2 and BAX). We observed that maturation rates were significantly higher in alpha-tocopherol (100 μM; 92.4%) groups followed by melatonin (30 μM; 89.1%) group. However, blastocyst rates in ascorbic acid (100 μM; 19.5%), melatonin (30 μM; 18.4%), alpha-tocopherol (100 μM; 18.2%), and sodium selenite (20 μM; 16.9%) groups were significantly higher (P 0.05) than that observed in the control groups. Total cell numbers in blastocysts in the melatonin, ascorbic acid and alpha-tocopherol groups were significantly higher than those observed in sodium selenite and control groups. ROS production was reduced in groups treated with melatonin (30 μM), vitamin C (100 μM), sodium selenite (20 μM) and α-tocopherol (200 μM) compared with that observed in the control group. Supplementation of antioxidants caused the alterations in mRNA expression of growth, stress, and apoptosis related gene expression in matured oocytes. The results recommend that antioxidants alpha-tocopherol (200 μM), sodium selenite (40 μM), melatonin (30 μM) and ascorbic acid (100 μM) during IVM reduced the oxidative stress by decreasing ROS levels in oocytes, thus improving embryo quantity and quality.

Synergistic impact of α-linolenic acid and α-tocopherol on in vitro maturation and culture of buffalo oocytes

The objective of the current study was to investigate the synergistic impact of α-Tocopherol and α-Linolenic acid (100 µM) on IVM and IVC of Nili Ravi buffalo oocytes. Oocytes were obtained from the ovaries of slaughtered buffaloes within two hours after slaughter and brought to laboratory. Buffalo cumulus oocyte complexes were placed randomly in the five experimental groups included; GROUP 1: Maturation media (MM) + 100 µM ALA (control), GROUP 2: MM + 100 µM ALA + 50μM α-Tocopherol, GROUP 3: MM + 100 µM ALA + 100μM α-Tocopherol, GROUP 4: MM + 100 µM ALA + 200 μM α-Tocopherol and GROUP 5: MM + 100 µM ALA + 300 μM α-Tocopherol under an atmosphere of 5% CO2 in air at 38.5 °C for 22-24 h. Cumulus expansion and nuclear maturation status was determined (Experiment 1). In experiment 2, oocytes were matured as in experiment 1. The matured oocytes were then fertilized in Tyrode's Albumin Lactate Pyruvate (TALP) medium for about 20 h and cultured in synthetic oviductal fluid (SOF) medium to determine effect of α-Linolenic acid (100 µM) and α-Tocopherol in IVM medium on IVC of presumptive zygotes. To study the effect of α-Linolenic acid (100 µM) in IVM media and increasing concentration of α-tocopherol in the culture media on early embryo development (Experiment 3), the presumptive zygotes were randomly distributed into the five experimental groups with increasing concentration of α-tocopherol in culture media. Higher percentage of MII stage oocytes in experiment 1(65.2±2.0), embryos at morula stage in experiment 2 (30.4±1.5) and experiment 3 (22.2±2.0) were obtained. However, overall results for cumulus cell expansion, maturation of oocyte to MII stage and subsequent embryo development among treatments remain statistically similar (P > 0.05). Supplementation of α-tocopherol in maturation media having α-Linolenic acid and/or in embryo culture media did not further enhance in vitro maturation of oocyte or embryo production.

Effect of Ethanol on Parthenogenetic Activation and α-Tocopherol Supplementation during In Vitro Maturation on Developmental Competence of Summer-Collected Bovine Oocytes

The use of α-tocopherol during in vitro maturation (IVM) is an alternative to minimize the adverse effects of heat stress on oocyte competence. However, α-tocopherol is diluted in ethanol, which can induce oocyte parthenogenetic activation (PA). This study aimed to evaluate the role of ethanol concentration on PA and the effect of α-tocopherol supplementation during IVM on the developmental competence and the expression of key genes in blastocysts derived from summer-collected oocytes. All in vitro embryo production was conducted at 5% O₂, 5% CO₂ at 38.5 °C. Experiment 1: oocytes were cultured with or without 0.05% ethanol. As positive PA control matured oocytes were subjected to 3% or 7% ethanol for 7 min. Oocytes from all groups were placed in fertilization medium (22 h) and culture medium (9 days). Ethanol at 0.05% during IVM did not induce oocyte PA, however, 3% and 7% ethanol were effective parthenogenetic inductors. Experiment 2: oocytes were cultured in maturation medium supplemented with 0, 50, 100 and 200 μM α-tocopherol, diluted in 0.05% ethanol. After in vitro fertilization and embryo culture, we assessed blastocyst apoptotic index and the transcription of a panel of genes. The results showed that supplementation with 100 μM α-tocopherol reduced apoptotic index and increased the expression of SOD2. In conclusion, 100 μM α-tocopherol, diluted in 0.05% ethanol, can be used during IVM to embryonic quality.

Apoptosis and Cell Proliferation Markers in Inflammatory-Fibroproliferative Diseases of the Vessel Wall (Review)

Apoptosis is the main feature of inflammatory-fibroproliferative disorders of the vessel wall. Studies in animal models have shown that smooth muscle cells (SMCs) cultured from endarterectomy specimens from the affected area proliferate more slowly and display higher apoptotic indices than SMCs derived from the normal vessel wall. Apoptotic cells were found in the destabilized atherosclerotic plaques, as well as in the samples with restenosis of the reconstruction area.

Injury to the vessel wall causes two waves of apoptosis. The first wave is the rapid apoptosis in the media that occurs within a few hours after injury and leads to a marked reduction in the number of vascular wall cells. The second wave of apoptosis occurs much later (from several days to weeks) and is limited by the SMCs within the developing neointima. Up to 14% of the neointimal SMCs undergo apoptosis 20 days after balloon angioplasty. Ligation of the external carotid artery in a rabbit model led to a marked decrease in blood flow in the common carotid artery, which correlated with the increased apoptosis of endothelial cells and SMCs.

Angioplasty-induced death of SMCs is regulated by a redox-sensitive signaling pathway, and topical administration of antioxidants can minimize vascular cell loss. On the whole, studies show that apoptosis is prevalent in vascular lesions, controlling the viability of both inflammatory and vascular cells, determining the cellular composition of the vessel wall. The main markers of apoptosis (Fas, Fas ligand, p53, Bcl-2, Bax) and cell proliferation (toll receptor) have been considered in the current review.

Involvement of PINK1/Parkin-mediated mitophagy in mitochondrial functional disruption under oxidative stress in vitrified porcine oocytes

Vitrification is an effective technique for fertility preservation, but is known to lead to mitochondrial dysfunction in porcine oocytes. Mitophagy is induced to rebalance mitochondrial function, a process in which reactive oxygen species (ROS) plays a role. In this study, vitrified-warmed porcine oocytes were incubated for 4 h with the oxidant AAPH or antioxidant α-tocopherol to alter ROS levels. A series of tests suggested that vitrification damaged mitochondrial structure and caused dysfunction, including blurred mitochondrial cristae, decreased mitochondrial membrane potential, decreased mtDNA copy number and increased ROS generation. This dysfunction resulted in mitophagy and the loss of embryonic developmental potential. Incubation with AAPH or α-tocopherol altered mitochondrial function and mitophagy flux status in vitrified oocytes. The PINK1/Parkin pathway was involved in oxidative stress regulation in vitrified oocytes. Under AAPH-induced oxidative stress, increased fluorescence intensity of Parkin, increased expression of PINK1, Parkin, and LC3B-II, and decreased expression of MFN2 and p62 were observed, whereas the opposite effects were induced under α-tocopherol treatment. The inhibition of ROS by α-tocopherol benefitted mitochondrial homeostasis and alleviated PINK1/Parkin-mediated mitophagy, resulting in the recovery of embryonic developmental potential in vitrified porcine oocytes. Therefore, this study provides a new mechanism for the application of antioxidants to aid the cryopreservation of porcine oocytes.

Enhancing in vitro oocyte maturation competence and embryo development in farm animals: roles of vitamin-based antioxidants – a review

Oocyte/embryo in vitro culture is one of the most important assisted reproductive technologies used as a tool for maintaining genetic resources biodiversity and the inheritance of valuable genetic resources through generations. The success of such processes affects the final goal of the in vitro culture, getting viable and healthy offspring. In common in vitro oocyte maturation and/or embryo development techniques, the development of oocytes/embryos is carried out at 5% carbon dioxide and roughly 20% atmosphere-borne oxygen ratios in cell culture incubators due to their reduced cost in comparison with low atmospheric oxygen-tension incubators. These conditions are usually accompanying by the emergence of reactive oxygen species (ROS), which can extremely damage cell membrane integrity and other vital cellular organelles, as well as genetic material. The present review mainly focuses on the antioxidant roles of different vitamins on in vitro oocyte maturation competence and embryo development in farm animals. Because, the conditions of in vitro embryo production (IVEP) are usually accompanying by the emergence of reactive oxygen species (ROS), which can extremely damage cell membrane integrity and other vital cellular organelles as well as genetic material. The use of antioxidant agents may prevent the extreme augmentation of ROS generation and enhance in vitro matured oocyte competence and embryo development. Therefore, this review aimed to provide an updated outline of the impact of antioxidant vitamin (Vit) supplementations during in vitro maturation (IVM) and in vitro fertilization (IVF) on oocyte maturation and consequent embryo development, in various domestic animal species. Thus, the enrichment of the culture media with antioxidant agents may prevent and neutralize the extreme augmentation of ROS generation and enhance the in vitro embryo production (IVEP) outcomes.

Vitamin E regulates bovine granulosa cell apoptosis via NRF2-mediated defence mechanism by activating PI3K/AKT and ERK1/2 signalling pathways

High-yield dairy cows are usually subject to high-intensive cell metabolism and produce excessive reactive oxygen species (ROS). Once ROS is beyond the threshold of scavenging ability, it can induce oxidative stress, imperilling the reproductive performance of cows. The study was to investigate the effects of vitamin E (VE) on H₂ O₂ -induced proliferation and apoptosis of bovine granulosa cells and the underlying molecular mechanism. Granulosa cells were pretreated with VE for 24 hr and then treated with H₂ O₂ for 6 hr. The results showed that VE treatment decreased the intracellular ROS levels, increased the MDA content, and improved the antioxidant enzyme activity in a dose-dependent manner. Furthermore, VE treatment promoted the proliferation and inhibited apoptosis in granulosa cells by up-regulation of CCND1 and BCL2 levels and down-regulation of P21, BAX, and CASP3 levels. The cytoprotective effects of VE were attributed to the activation of the NRF2 signalling pathway. Knockdown of the NRF2 impaired the cytoprotective effects of VE on granulosa cells. Besides, the PI3K/AKT and ERK1/2, but not the p38 signalling pathway is involved in the regulation of VE-mediated cell proliferation and apoptosis. The PI3K/AKT inhibitor LY294002 and ERK1/2 inhibitor SCH772984 inhibited the VE-induced granulosa cell proliferation and promoted apoptosis, whereas the p38 inhibitor SB203580 had the opposite effects. These results were confirmed by proliferation and apoptosis-related gene expression at mRNA and protein levels. The results also showed that the PI3K/AKT inhibitor LY294002 and ERK1/2 inhibitor SCH772984 inhibited VE-induced NRF2, GCLC, GCLM, and HO-1 expression, whereas the p38 inhibitor SB203580 not. Overall, the results demonstrated that VE-regulated granulosa cell proliferation and apoptosis via NRF2-mediated defence system by activating the PI3K/AKT and ERK1/2 signalling pathway.

Impact of oxidative stress on oocyte competence for in vitro embryo production programs

Producing high-competent oocytes during the in vitro maturation (IVM) is considered a key step for the success of the in vitro production (IVP) of embryos. One of the known disruptors of oocyte developmental competence on IVP is oxidative stress (OS), which appears due to the imbalance between the production and neutralization of reactive oxygen species (ROS). The in vitro conditions induce supraphysiological ROS levels due to the exposure to an oxidative environment and the isolation of the oocyte from the follicle protective antioxidant milieu. In juvenile in vitro embryo transfer (JIVET), which aims to produce embryos from prepubertal females, the oocytes are more sensitive to OS as they have inherent lower quality. Therefore, the IVM strategies that aim to prevent OS have great interest for both IVP and JIVET programs. The focus of this review is on the effects of ROS on oocyte IVM and the main antioxidants that have been tested for protecting the oocyte from OS. Considering the importance that OS has on oocyte competence, it is crucial to create standardized antioxidant IVM systems for improving the overall IVP success.

Source and Follicular Fluid Treatment During the In Vitro Maturation of Recipient Oocytes Affects the Development of Cloned Pig Embryo

Pig cloning technique is valuable in agriculture, biomedicine, and life sciences. However, the full-term developmental efficiency of cloned pig embryos is only about 1%, which limits pig cloning application. The quality of recipient oocytes greatly affects the developmental competence of cloned pig embryos. Thus, this study investigated the effects of a recipient oocyte source (in vivo matured [IVVM] oocytes vs. slaughter house-derived in vitro matured [IVTM] oocytes), and follicular liquid treatment (slaughter house-derived immature follicle-derived fluid [IFF] vs. in vivo-matured follicle-derived fluid [MFF]) during the in vitro maturation (IVM) of oocytes on the development of the cloned pig embryos. Our results showed that using IVVM oocytes to replace IVTM oocytes as recipient oocytes, and using 10% MFF IVM medium to replace 10% IFF IVM medium could enhance the development of the cloned pig embryos. IFF and MFF contained different levels of oocyte quality-related proteins, resulting in different oocyte quality-related gene expression levels and reactive oxygen species levels between the 10% MFF medium-cultured oocytes and 10% IFF medium-cultured oocytes. This study provided useful information for enhancing the pig cloning efficiency by improving the quality of recipient oocytes.