Increased generation of reactive oxygen species in embryos cultured in vitro

RNAseq analysis of oocyte maturation from the germinal vesicle stage to metaphase II in pig and human

During maturation oocytes at the germinal vesicle (GV) stage progress to metaphase II (MII). However, during in vitro maturation a proportion often fail to progress. To understand these processes, we employed RNA sequencing to examine the transcriptome profile of these three groups of oocytes from the pig. We compared our findings with similar public oocyte data from humans. The transcriptomes in oocytes that failed to progress was similar to those that did. We found in both species, the most upregulated genes in MII oocytes were associated with chromosome segregation and cell cycle processes, while the most down regulated genes were relevant to ribosomal and mitochondrial pathways. Moreover, those genes involved in chromosome segregation during GV to MII transition were conserved in pig and human. We also compared MII and GV oocyte transcriptomes at the isoform transcript level in both species. Several thousands of genes (including DTNBP1, MAPK1, RAB35, GOLGA7, ATP1A1 and ATP2B1) identified as not different in expression at a gene transcript level were found to have differences in isoform transcript levels. Many of these genes were involved in ATPase-dependent or GTPase-dependent intracellular transport in pig and human, respectively. In conclusion, our study suggests the failure to progress to MII in vitro may not be regulated at the level of the genome and that many genes are differentially regulated at the isoform level, particular those involved ATPase- or GTPase-dependent intracellular transport.

Increased ROS levels in mitochondrial outer membrane protein Mul1-deficient oocytes result in abnormal preimplantation embryogenesis

Reactive oxygen species (ROS) are associated with oocyte maturation inhibition, and N-acetyl-l-cysteine (NAC) partially reduces their harmful effects. Mitochondrial E3 ubiquitin ligase 1 (Mul1) localizes to the mitochondrial outer membrane. We found that female Mul1-deficient mice are infertile, and their oocytes contain high ROS concentrations. After fertilization, Mul1-deficient embryos showed a DNA damage response (DDR) and abnormal preimplantation embryogenesis, which was rescued by NAC addition and ROS depletion. These observations clearly demonstrate that loss of Mul1 in oocytes increases ROS concentrations and triggers DDR, resulting in abnormal preimplantation embryogenesis. We conclude that manipulating the mitochondrial ROS levels in oocytes may be a potential therapeutic approach to target infertility.

Embryos from Prepubertal Hyperglycemic Female Mice Respond Differentially to Oxygen Tension In Vitro

Reduced oxygen during embryo culture in human ART prevents embryo oxidative stress. Oxidative stress is also the major mechanism by which maternal diabetes impairs embryonic development. This study employed induced hyperglycemia prepubertal mice to mimic childhood diabetes to understand the effects of varying oxygen tension during in vitro embryonic development. The oocytes were fertilized and cultured at low (≈5%) oxygen (LOT) or atmospheric (≈20%) oxygen tension (HOT) for up to 96 h. Embryo development, apoptosis in blastocysts, inner cell mass (ICM) outgrowth proliferation, and Hif1α expression were assessed. Though the oocyte quality and meiotic spindle were not affected, the fertilization rate (94.86 ± 1.18 vs. 85.17 ± 2.81), blastocyst rate (80.92 ± 2.92 vs. 69.32 ± 2.54), and ICM proliferation ability (51.04 ± 9.22 vs. 17.08 ± 3.05) of the hyperglycemic embryos were significantly higher in the LOT compared to the HOT group. On the other hand, blastocysts from the hyperglycemic group, cultured at HOT, had a 1.5-fold increase in apoptotic cells compared to the control and lower Hif1α transcripts in ICM outgrowths compared to the LOT. Increased susceptibility of embryos from hyperglycemic mice to higher oxygen tension warrants the need to individualize the conditions for embryo culture systems in ART clinics, particularly when an endogenous maternal pathology affects the ovarian environment.

Culture of Human Embryos at High and Low Oxygen Levels

One of the parameters potentially affecting the in vitro growth of preimplantation embryos is the oxygen concentration in the culture environment. An increased oxygen concentration causes the generation of ROS which in turn can cause damage to the cells and seriously disrupt the embryonic development. Previous studies have assessed oxygen concentrations in the fallopian tubes of several mammals of between 5 and 8%, while the oxygen levels in the uterus were found to be even lower; similar measurements have been confirmed in humans. In addition, studies in mammalian embryos showed that low oxygen concentrations improve embryo development. Multiple studies on the effect of the oxygen concentration on human embryos have been conducted so far with diverse methodologies and objectives. Data from these have been included in three meta-analyses. All meta-analyses indicate the potential benefit in favor of a low oxygen concentration, though data are considered to be of a low methodological quality and further studies are considered necessary. However, based on the existing evidence, it is suggested that a low oxygen concentration should be adopted in the routine of the IVF laboratory, especially in the case of blastocyst culture.

Heat Stress as a Barrier to Successful Reproduction and Potential Alleviation Strategies in Cattle

In recent decades, the adverse effects of global warming on all living beings have been unanimously recognized across the world. A high environmental temperature that increases the respiration and rectal temperature of cattle is called heat stress (HS), and it can affect both male and female reproductive functions. For successful reproduction and fertilization, mature and healthy oocytes are crucial; however, HS reduces the developmental competence of oocytes, which compromises reproduction. HS disturbs the hormonal balance that plays a crucial role in successful reproduction, particularly in reducing the luteinizing hormone and progesterone levels, which leads to severe problems such as poor follicle development with a poor-quality oocyte and problems related to maturity, silent estrus, abnormal or weak embryo development, and pregnancy loss, resulting in a declining reproduction rate and losses for the cattle industry. Lactating cattle are particularly susceptible to HS and, hence, their reproduction rate is substantially reduced. Additionally, bulls are also affected by HS; during summer, semen quality and sperm motility decline, leading to compromised reproduction. In summer, the conception rate is reduced by 20-30% worldwide. Although various techniques, such as the provision of water sprinklers, shade, and air conditioning, are used during summer, these methods are insufficient to recover the normal reproduction rate and, therefore, special attention is needed to improve reproductive efficiency and minimize the detrimental effect of HS on cattle during summer. The application of advanced reproductive technologies such as the production of embryos in vitro, cryopreservation during the hot season, embryo transfer, and timed artificial insemination may minimize the detrimental effects of HS on livestock reproduction and recover the losses in the cattle industry.

Unraveling the Consequences of Oxygen Imbalance on Early Embryo Development: Exploring Mitigation Strategies

Although well-established and adopted by commercial laboratories, the in vitro embryo production system still requires refinements to achieve its highest efficiency. Early embryonic development is a dynamic event, demanding suitable conditions to provide a high number of embryos with quality and competence. The first step to obtaining an optimized in vitro environment is to know the embryonic metabolism and energy request throughout the different stages of development. Oxygen plays a crucial role in several key biological processes necessary to sustain and complete embryonic development. Nonetheless, there is still controversy regarding the optimal in vitro atmospheric concentrations during culture. Herein, we discuss the impact of oxygen tension on the viability of in vitro-produced embryos during early development. The importance of oxygen tension is addressed as its roles regarding essential embryonic traits, including embryo production rates, embryonic cell viability, gene expression profile, epigenetic regulation, and post-cryopreservation survival. Finally, we highlight the damage caused by in vitro unbalanced oxygen tensions and strategies to mitigate the harmful effects.

Female Reproductive Aging and Oxidative Stress: Mesenchymal Stem Cell Conditioned Medium as a Promising Antioxidant

The recent tendency to delay pregnancy has increased the incidence of age-related infertility, as female reproductive competence decreases with aging. Along with aging, a lowered capacity of antioxidant defense causes a loss of normal function in the ovaries and uterus due to oxidative damage. Therefore, advancements have been made in assisted reproduction to resolve infertility caused by reproductive aging and oxidative stress, following an emphasis on their use. The application of mesenchymal stem cells (MSCs) with intensive antioxidative properties has been extensively validated as a regenerative therapy, and proceeding from original cell therapy, the therapeutic effects of stem cell conditioned medium (CM) containing paracrine factors secreted during cell culture have been reported to be as effective as that of direct treatment of source cells. In this review, we summarized the current understanding of female reproductive aging and oxidative stress and present MSC-CM, which could be developed as a promising antioxidant intervention for assisted reproductive technology.

Transcriptome profiling reveals the underlying mechanism of grape post-harvest pathogen Penicillium olsonii against the metabolites of Bacillus velezensis

Introduction

Pathogen infection influences the post-harvest shelf life of grape berries. In a preliminary study, metabolites produced by Bacillus velezensis significantly inhibited the growth of the grape postharvest pathogen Penicillium olsonii.

Methods

To investigate the mechanism of interaction between B. velezensis and P. olsonii, a draft genome was generated for P. olsonii WHG5 using the Illumina NovaSeq platform, and the transcriptomic changes in WHG5 were analyzed in response to the exposure to B. velezensis metabolites (10% v/v).

Results

The expression levels of genes associated with sporulation, including GCY1, brlA, and abaA, were down-regulated compared with those of the control. In addition, spore deformation and abnormal swelling of the conidiophore were observed. The expression of crucial enzymes, including fructose 2,6-bisphosphate and mannitol-2-dehydrogenase, was down-regulated, indicating that the glycolytic pathway of WHG5 was adversely affected by B. velezensis metabolites. The KEGG pathway enrichment analysis revealed that glutathione metabolism and the antioxidant enzyme system were involved in the response to B. velezensis metabolites. The down-regulation of the pathogenesis-related genes, PG1 and POT1, suggested that B. velezensis metabolites decreased the pathogenicity of P. olsonii. B. velezensis metabolites disrupted the homeostasis of reactive oxygen species in P. olsonii by affecting glucose metabolism, resulting in spore deformation and disruption of growth. In addition, the expression of key pathogenesis-related genes was down-regulated, thereby reducing the pathogenicity of P. olsonii.

Disscusion

This study provides insights into the responses of P. olsonii to B. velezensis metabolites and identifies potential target genes that may be useful in biocontrol strategies for the suppression of post-harvest spoilage in grapes.

Metabolomic Profile of Children Conceived With Medically Assisted Technologies

CONTEXT

Assisted reproductive technologies (ART) and non-in vitro fertilization fertility treatments (NIFT) are treatments for infertility. These technologies may have long-term health effects in children such as increased hypertension, glucose intolerance, and hypertriglyceridemia. Few studies have compared children born following ART and NIFT to those conceived spontaneously by subfertile couples.

OBJECTIVE

This work aimed to describe metabolic differences in children conceived by ART and NIFT compared to children conceived spontaneously by infertile couples.

METHODS

Children conceived by parent(s) receiving infertility care at the University of California, San Francisco, between 2000 and 2017 were invited to participate in the Developmental Epidemiological Study of Children born through Reproductive Technology (DESCRT). Serum metabolomic analyses were conducted using samples from 143 enrolled children (age range 4-12 years, 43% female) conceived using NIFT or ART (with fresh or frozen embryos with and without intracytoplasmic sperm injection [ICSI]) and children conceived spontaneously by subfertile couples. Principal component analysis and multivariable regression were used to compare the distribution of metabolites between groups.

RESULTS

There was no separation in metabolites based on treatment or sex. NIFT-conceived children showed no differences compared to spontaneously conceived controls. Only spontaneously conceived children had different metabolomics profiles from children conceived from fresh ART, frozen ART, and all ICSI. Pantoate and propionylglycine levels were elevated in fresh ART compared to the spontaneous group (P < .001). Propionylglycine levels were elevated in the ICSI (both fresh and frozen) vs the spontaneous group (P < .001). Finally, 5-oxoproline levels were decreased in frozen ART compared to the spontaneous group (P < .001).

CONCLUSION

NIFT-conceived children did not show any metabolic differences compared with spontaneously conceived children. The metabolic differences between ART-conceived children and children conceived spontaneously were small but unlikely to be clinically significant but should be examined in future studies.

OXIDATIVE STRESS AND REPRODUCTIVE FUNCTION: Reactive oxygen species in the mammalian pre-implantation embryo

In brief

Reactive oxygen species are generated throughout the pre-implantation period and are necessary for normal embryo formation. However, at pathological levels, they result in reduced embryo viability which can be mediated through factors delivered by sperm and eggs at conception or from the external environment.

Abstract

Reactive oxygen species (ROS) occur naturally in pre-implantation embryos as a by-product of ATP generation through oxidative phosphorylation and enzymes such as NADPH oxidase and xanthine oxidase. Biological concentrations of ROS are required for crucial embryonic events such as pronuclear formation, first cleavage and cell proliferation. However, high concentrations of ROS are detrimental to embryo development, resulting in embryo arrest, increased DNA damage and modification of gene expression leading to aberrant fetal growth and health. In vivo embryos are protected against oxidative stress by oxygen scavengers present in follicular and oviductal fluids, while in vitro, embryos rely on their own antioxidant defence mechanisms to protect against oxidative damage, including superoxide dismutase, catalase, glutathione and glutamylcysteine synthestase. Pre-implantation embryonic ROS originate from eggs, sperm and embryos themselves or from the external environment (i.e. in vitro culture system, obesity and ageing). This review examines the biological and pathological roles of ROS in the pre-implantation embryo, maternal and paternal origins of embryonic ROS, and from a clinical perspective, we comment on the growing interest in combating increased oxidative damage in the pre-implantation embryo through the addition of antioxidants.

Oxidative Stress and Oocyte Cryopreservation: Recent Advances in Mitigation Strategies Involving Antioxidants

Oocyte cryopreservation is widely used in assisted-reproductive technology and animal production. However, cryopreservation not only induces a massive accumulation of reactive oxygen species (ROS) in oocytes, but also leads to oxidative-stress-inflicted damage to mitochondria and the endoplasmic reticulum. These stresses lead to damage to the spindle, DNA, proteins, and lipids, ultimately reducing the developmental potential of oocytes both in vitro and in vivo. Although oocytes can mitigate oxidative stress via intrinsic antioxidant systems, the formation of ribonucleoprotein granules, mitophagy, and the cryopreservation-inflicted oxidative damage cannot be completely eliminated. Therefore, exogenous antioxidants such as melatonin and resveratrol are widely used in oocyte cryopreservation to reduce oxidative damage through direct or indirect scavenging of ROS. In this review, we discuss analysis of various oxidative stresses induced by oocyte cryopreservation, the impact of antioxidants against oxidative damage, and their underlying mechanisms. We hope that this literature review can provide a reference for improving the efficiency of oocyte cryopreservation.

Murine blastocysts generated by in vitro fertilization show increased Warburg metabolism and altered lactate production

In vitro fertilization (IVF) has resulted in the birth of over 8 million children. Although most IVF-conceived children are healthy, several studies suggest an increased risk of altered growth rate, cardiovascular dysfunction, and glucose intolerance in this population compared to naturally conceived children. However, a clear understanding of how embryonic metabolism is affected by culture condition and how embryos reprogram their metabolism is unknown. Here, we studied oxidative stress and metabolic alteration in blastocysts conceived by natural mating or by IVF and cultured in physiologic (5%) or atmospheric (20%) oxygen. We found that IVF-generated blastocysts manifest increased reactive oxygen species, oxidative damage to DNA/lipid/proteins, and reduction in glutathione. Metabolic analysis revealed IVF-generated blastocysts display decreased mitochondria respiration and increased glycolytic activity suggestive of enhanced Warburg metabolism. These findings were corroborated by altered intracellular and extracellular pH and increased intracellular lactate levels in IVF-generated embryos. Comprehensive proteomic analysis and targeted immunofluorescence showed reduction of lactate dehydrogenase-B and monocarboxylate transporter 1, enzymes involved in lactate metabolism. Importantly, these enzymes remained downregulated in the tissues of adult IVF-conceived mice, suggesting that metabolic alterations in IVF-generated embryos may result in alteration in lactate metabolism. These findings suggest that alterations in lactate metabolism are a likely mechanism involved in genomic reprogramming and could be involved in the developmental origin of health and disease.

Importance of Antioxidant Supplementation during In Vitro Maturation of Mammalian Oocytes

The in vitro embryo production (IVEP) technique is widely used in the field of reproductive biology. In vitro maturation (IVM) is the first and most critical step of IVEP, during which, the oocyte is matured in an artificial maturation medium under strict laboratory conditions. Despite all of the progress in the field of IVEP, the quality of in vitro matured oocytes remains inferior to that of those matured in vivo. The accumulation of substantial amounts of reactive oxygen species (ROS) within oocytes during IVM has been regarded as one of the main factors altering oocyte quality. One of the most promising approaches to overcome ROS accumulation within oocytes is the supplementation of oocyte IVM medium with antioxidants. In this article, we discuss recent advancements depicting the adverse effects of ROS on mammalian oocytes. We also discuss the potential use of antioxidants and their effect on both oocyte quality and IVM rate.

Use of giant unilamellar lipid vesicles as antioxidant carriers in in vitro culture medium of bovine embryos

Giant unilamellar vesicles (GUVs) are composed of lipophilic layers and are sensitive to the action of reactive oxygen species (ROS). The use of GUVs as microcarriers of biological macromolecules is particularly interesting since ROS produced by gametes or embryos during in vitro culture can induce the opening of pores in the membrane of these vesicles and cause the release of their content. This study investigated the behavior of GUVs [composed of 2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(lissamine rhodamine B sulfonyl)] in co-culture with in vitro produced bovine embryos, as well as their embryotoxicity and effectiveness as cysteine carriers in culture medium. Embryonic developmental rates were unaffected, demonstrating the absence of toxicity of GUVs co-cultured with the embryos. No increase of intracellular ROS levels was observed in the embryos co-cultured with GUVs, indicating that the higher lipid content of the culture environment resulting from the lipid composition of the GUV membrane itself did not increase oxidative stress. Variations in the diameter and number of GUVs demonstrated their sensitivity to ROS produced by embryos cultured under conditions that generate oxidative stress. Encapsulation of cysteine in GUVs was found to be more effective in controlling the production of ROS in embryonic cells than direct dilution of this antioxidant in the medium. In conclusion, the use of GUVs in in vitro culture was found to be safe since these vesicles did not promote toxic effects nor did they increase intracellular ROS concentrations in the embryos. GUVs were sensitive to oxidative stress, which resulted in structural changes in response to the action of ROS. The possible slow release of cysteine into the culture medium by GUV rupture would therefore favor the gradual supply of cysteine, prolonging its presence in the medium. Thus, the main implication of the use of GUVs as cysteine microcarriers is the greater effectiveness in preventing the intracytoplasmic increase of ROS in in vitro produced bovine embryos.

Oxidative Stress and Assisted Reproduction: A Comprehensive Review of Its Pathophysiological Role and Strategies for Optimizing Embryo Culture Environment

Oxidative stress (OS) due to an imbalance between reactive oxygen species (ROS) and antioxidants has been established as an important factor that can negatively affect the outcomes of assisted reproductive techniques (ARTs). Excess ROS exert their pathological effects through damage to cellular lipids, organelles, and DNA, alteration of enzymatic function, and apoptosis. ROS can be produced intracellularly, from immature sperm, oocytes, and embryos. Additionally, several external factors may induce high ROS production in the ART setup, including atmospheric oxygen, CO2 incubators, consumables, visible light, temperature, humidity, volatile organic compounds, and culture media additives. Pathological amounts of ROS can also be generated during the cryopreservation-thawing process of gametes or embryos. Generally, these factors can act at any stage during ART, from gamete preparation to embryo development, till the blastocyst stage. In this review, we discuss the in vitro conditions and environmental factors responsible for the induction of OS in an ART setting. In addition, we describe the effects of OS on gametes and embryos. Furthermore, we highlight strategies to ameliorate the impact of OS during the whole human embryo culture period, from gametes to blastocyst stage.

In Vivo and In Vitro Matured Oocytes From Mice of Advanced Reproductive Age Exhibit Alternative Splicing Processes for Mitochondrial Oxidative Phosphorylation

The mean age of women seeking infertility treatment has gradually increased over recent years. This has coincided with the emergence of in vitro maturation (IVM), a method used in assisted reproductive technology for patients with special requirements. However, when compared with conventional in vitro fertilization, IVM is associated with poor embryonic development potential and low live birth rates, thus limiting the widespread application of this technique. In this study, we performed RNA-sequencing transcriptomic assays and identified a total of 2,627 significant differentially expressed genes (DEGs) between IVM oocytes and in vivo matured oocytes from mice of advanced reproductive age. Next, Kyoto Encyclopedia of Genes and Genomes pathway analysis was used to identify the potential functions of the DEGs. The most significantly enriched pathway was oxidative phosphorylation (OXPHOS). In addition, we constructed a protein-protein interaction network to identify key genes and determined that most of the hub genes were mtDNA-encoded subunits of respiratory chain complex I. Antioxidant supplementation lead to an increase in ATP production and reduced the gene expression profile of the OXPHOS pathway in the IVM group. Moreover, alternative splicing (AS) events were identified during in vivo or in vitro oocyte maturation; data showed that skipped exons were the most frequent type of AS event. A number of genes associated with the OXPHOS pathway exhibited alterations in AS events, including Ndufa7, Ndufs7, Cox6a2, Ndufs5, Ndufb1, and Uqcrh. Furthermore, the process of IVO promoted the skipping of exon 2 in Ndufa7 and exon 3 in Ndufs7 compared with the IVM oocytes, as determined by semi-quantitative RT-PCR. Collectively, these findings provide potential new therapeutic targets for improving IVM of aged women who undergo infertility treatment.

Cellular and Molecular Nature of Fragmentation of Human Embryos

Embryo fragmentation represents a phenomenon generally characterized by the presence of membrane-bound extracellular cytoplasm into the perivitelline space. Recent evidence supports the cellular and molecular heterogeneity of embryo fragments. In this narrative review, we described the different embryo fragment-like cellular structures in their morphology, molecular content, and supposed function and have reported the proposed theories on their origin over the years. We identified articles related to characterization of embryo fragmentation with a specific literature search string. The occurrence of embryo fragmentation has been related to various mechanisms, of which the most studied are apoptotic cell death, membrane compartmentalization of altered DNA, cytoskeletal disorders, and vesicle formation. These phenomena are thought to result in the extrusion of entire blastomeres, release of apoptotic bodies and other vesicles, and micronuclei formation. Different patterns of fragmentation may have different etiologies and effects on embryo competence. Removal of fragments from the embryo before embryo transfer with the aim to improve implantation potential should be reconsidered on the basis of the present observations

Tripronuclear Zygotes in IVF Laboratory Quality Control: Experimental Evaluation and Potential Applications

This study set out to evaluate quality control within a new in vitro fertilization (IVF) laboratory environment and of new incubators based on the culture results of tripronuclear zygotes. The representative environmental indicators within new and old IVF laboratories were monitored, and tripronuclear zygotes were cultured in the two laboratories; the results were analyzed and compared. Subsequently, tripronuclear (3PN) zygotes were cultured in both new and old incubators and the culture results were compared. No differences were found in embryo development between 3PN zygotes in the old and new laboratories. However, in the quality control test, the degeneration rate and developmental arrest rate in the new incubator early phase group were significantly increased when compared with the old incubators. Moreover, the grade I embryo rate also decreased significantly. Nevertheless, all the above comparisons in the new incubator later phase group showed no statistical significance as compared to those observed in old incubators. Tripronuclear zygotes are sensitive to the environment in IVF laboratories and can be considered useful during quality control trials of new IVF laboratories and new equipment including incubators.

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.

Oral melatonin supplementation during in vitro fertilization treatment: a systematic PRISMA review and meta-analysis of randomized controlled trials

OBJECTIVE

High levels of reactive oxygen species (ROS) have been suspected of reducing the success rate of assisted reproductive technology (ART). Melatonin has anti-oxidative properties and could therefore be of interest as a supplement in in vitro-fertilization (IVF) protocols. The objective of this study was to evaluate if a melatonin supplementation given in vivo to women undergoing IVF-treatment can improve the outcome.

METHODS

A systematic literature search was performed on PubMed, Embase and Cochrane. The methodological quality of the included studies was assessed using the version 2 of the Cochrane risk-of-bias tool (RoB2). Primary outcome was clinical pregnancy rate (CPR). Secondary outcomes were total number of oocytes, number of mature oocytes, embryo quality, biochemical pregnancy rate, miscarriage rate and live birth rate (LBR).

RESULTS

Seven randomized controlled trials (RCT) were included. The meta-analysis demonstrated a significantly higher mature oocyte count when melatonin was used (Mean Diff. = 1,82; 95% CI 0.37-3.27; p = .01). All seven studies showed a trend for increase in CPR, although not significant. No other measured outcomes showed a significant improvement. Two studies had 'low risk', three 'some concerns' and two studies had 'high risk' of bias.

CONCLUSION

This meta-analysis including RCT indicates that an oral melatonin supplement during IVF-treatment can increase the number of mature oocytes, and a trend for increase CPR, albeit not significant. Most of the included studies were small. The methodological quality in three of the seven studies was moderate and two were low. Further investigations are needed to support the positive findings.

Peroxiredoxin 6 Plays Essential Role in Mediating Fertilization and Early Embryonic Development in Rabbit Oviduct

The oviduct is a site for early reproductive events including gamete maturation, fertilization, and early embryo development. Secretory cells lining the oviduct lumen synthesize and secrete proteins that interact with gametes and developing embryos. Although previous studies have identified some of the secretory proteins in the oviduct, however, knowledge and their precise specific functions in the oviduct are poorly understood. In this study, by using proteomic approach, we identified a secretory protein, Peroxiredoxin 6 (PRDX6), and evaluated its role in mediating early pregnancy events, fertilization, and embryo development in rabbit oviduct. The expression of PRDX6 was significantly higher in ampulla and isthmus sections of the oviduct in mated animal groups compared to non-mated controls. Furthermore, significant reduction in number of embryos recovered from PRDX6 siRNA-transfected oviductal horn was observed compared to the control contralateral horn. Moreover, in animals receiving PRDX6 siRNA in their oviductal horn, the number of implanted blastocysts was significantly less in the uterus as observed on day 9 post-coital (p.c.). Further, during embryo-rabbit oviduct epithelial cell (ROEC) co-culture, siRNA-mediated PRDX6 silencing attenuated the early embryonic development. Mechanistically, increased levels of ROS and expression of oxidative stress- and inflammation-related proteins were found in PRDX6 siRNA-treated ROEC cells as compared to control cells, implicating that ablation of PRDX6 in the oviduct creates a stress-induced micro-environment detrimental to early embryonic development in oviduct. Taken together, our data suggest that PRDX6 maintains an optimal micro-environment conducive to successful embryo development and can be considered as a candidate to evaluate its therapeutic potential in IVF strategies.

The antioxidant dieckol reduces damage of oxidative stress-exposed porcine oocytes and enhances subsequent parthenotes embryo development

This study investigated the effect of the antioxidant dieckol, a component of Ecklonia cava, on maturation and developmental competence of porcine oocytes exposed to oxidative stress in vitro. Oocytes were matured in in vitro maturation (IVM) medium containing various concentrations of dieckol. The blastocyst formation rate was highest in the 0.5 μM dieckol-treated (0.5 DEK) group. The reactive oxygen species level was decreased, and the level of glutathione and expression of antioxidant genes (NFE2L, SOD1, and SOD2) at metaphase II were increased in the 0.5 DEK group. Abnormal spindle organization and chromosome misalignment were prevented in the 0.5 DEK group. Expression of maternal markers (CCNB1 and MOS) and activity of p44/42 mitogen-activated protein kinase were increased in the 0.5 DEK group. After parthenogenetic activation, the total number of cells per blastocyst was increased and the percentage of apoptotic cells was decreased in the 0.5 DEK group. Expression of development-related genes (CX45, CDX2, POU5F1, and NANOG), antiapoptotic genes (BCL2L1 and BIRC5), and a proapoptotic gene (CASP3) were altered in the 0.5 DEK group. These results indicate that the antioxidant dieckol improves IVM and subsequent development of porcine oocytes and can be used to improve the quality of oocytes under peroxidation experimental conditions.

Lipid peroxidation in bull semen influences sperm traits and oxidative potential of Percoll®-selected sperm

Although bovine embryo in vitro production (IVP) is a common assisted reproductive technology, critical points warrant further study, including sperm traits and oxidative status of sperm for in vitro fertilization (IVF). Our aim was to evaluate whether the lipid peroxidation index of commercial bull semen is influenced by sperm traits and oxidative status of sperm populations selected using Percoll® gradient. Semen straws from 48 batches from 14 Nelore bulls were thawed individually, analyzed for motility and subjected to Percoll selection. After Percoll, the lipid peroxidation index of the extender was evaluated, whereas selected sperm were analyzed for motility, acrosome and membrane integrity, mitochondrial membrane potential, chromatin resistance and oxidative potential under IVF conditions. Batches were divided retrospectively in four groups according to lipid peroxidation index. Sperm from Group 4 with the lowest index of lipid peroxidation had, after Percoll selection, greater plasma membrane integrity (81.3%; P = 0.004), higher mitochondrial potential (81.1%; P = 0.009) and lower oxidative potential (135.3 ng thiobarbituric acid reactive substances (TBARS)/ml; P = 0.026) compared with Group 1 with highest lipid peroxidation index (74.3%, 73% and 213.1 ng TBARS/ml, respectively). Furthermore, we observed negative correlations for the lipid peroxidation index with motility, membrane integrity and mitochondrial potential, and positive correlations with oxidative potential. In conclusion, oxidative stress in semen straws, as determined using lipid peroxidation in the extender, is associated with sperm traits and their oxidative potential under IVF conditions. These results provided further insights regarding the importance of preventing oxidative stress during semen handling and cryopreservation, as this could affect sperm selected for IVF. Finally, Percoll selection did not completely remove sperm with oxidative markers.

Dimethyl Sulfoxide: Morphological, Histological, and Molecular View on Developing Chicken Liver

Dimethyl sulfoxide (DMSO) is widely used as a solvent for small hydrophobic drug molecules. However, the safe volume allowing to avoid its embryotoxic effect has been poorly studied. In this study, we documented the effects of dimethyl sulfoxide (DMSO) in the developing chicken embryo at morphological, histological, and molecular levels. We focused on the developing chicken liver as the main organ involved in the process of detoxification. In our study, 100% DMSO was administered subgerminally onto the eggshell membrane (membrana papyracea) at various volumes (5, 10, 15, 20, 25, 30, 35, and 50 µL) on 4th embryonic day (ED). We focused on histopathological alterations of the liver structure, and noticed the overall impact of DMSO on developing chicken embryos (embryotoxicity, malformation). At the molecular level, we studied cytochrome P450 complex (CYP) isoform's activities in relation to changes of CYP1A5, CYP3A37, and CYP3A80 gene expression. Total embryotoxicity after application of different doses of DMSO on ED 4, and the embryo lethality increased with increasing DMSO amounts. Overall mortality after DMSO administration ranged below 33%. Mortality was increased with higher amounts of DMSO, mainly from 20 µL. The highest mortality was observed for the highest dose of DMSO over 35 µL. The results also showed a decrease in body weight with increased application volumes of DMSO. At the histological level, we observed mainly the presence of lipid droplets and dilated bile canaliculi and sinusoids in samples over the administration of 25 µL of DMSO. While these findings were not statistically significant, DMSO treatment caused a significant different up-regulation of mRNA expression in all studied genes. For CYP1A5, CYP3A37, and CYP3A80 DMSO volumes needed were 15 µL, 10 µL, and 20 µL, respectively. A significant down-regulation of all studied CYP isoform was detected after application of a DMSO dose of 5 µL. Regarding the morphological results, we can assume that the highest safe dose of DMSO without affecting chicken embryo development and its liver is up to 10 µL. This conclusion is corroborated with the presence of number of malformations and body weight reduction, which correlates with histological findings. Moreover, the gene expression results showed that even the lowest administered DMSO volume could affect hepatocytes at the molecular level causing down-regulation of cytochrome P450 complex (CYP1A5, CYP3A37, CYP3A80).

Cellular and molecular alterations of buffalo oocytes cultured under two different levels of oxygen tension during in vitro maturation

This study was conducted to monitor the cellular and molecular changes of buffalo cumulus-oocytes complexes (COCs) cultured under high or low oxygen levels. Morphologically good quality COCs (n = 1627) were screened using brilliant cresyl blue (BCB) staining and placed into three groups (BCB+, BCB- and control). All groups of COCs were cultured under low (5%) or high (20%) oxygen tensions. Intracellular and molecular changes including oocyte ultrastructure, lipid contents, mitochondrial activity and transcript abundance of genes regulating different pathways were analyzed in the matured oocyte groups. The results revealed that oxygen tension did not affect cumulus expansion rates, however the BCB+ group had a higher (P ≤ 0.05) expansion rate compared with the BCB- group. BCB- oocytes recorded the lowest meiotic progression rate (P ≤ 0.05) under high oxygen levels that was linked with an increased level of reactive oxygen species (ROS) compared with the BCB+ oocytes. Ultrastructure examination indicated that BCB+ oocytes had a higher rate of cortical granules migration compared with BCB- under low oxygen tension. In parallel, our results indicated the upregulation of NFE2L2 in groups of oocytes cultured under high oxygen tension that was coupled with reduced mitochondrial activity. In contrast, the expression levels of MAPK14 and CPT2 genes were increased (P ≤ 0.05) in groups of oocytes cultured under low compared with high oxygen tension that was subsequently associated with increased mitochondrial activity. In conclusion, data from the present investigation indicated that low oxygen tension is a favourable condition for maintaining the mitochondrial activity required for nuclear maturation of buffalo oocytes. However, low-quality oocytes (BCB-) responded negatively to high oxygen tension by reducing the expression of gene-regulating metabolic activity (CPT2). This action was an attempt by BCB- oocytes to reduce the increased levels of endogenously produced ROS that was coupled with decreased expression of the gene controlling meiotic progression (MAPK14) in addition to nuclear maturation rate.

Effect of oxygen tension and antioxidants on the developmental competence of buffalo oocytes cultured in vitro

Aim:

Oxidative stress (OS) is one of the major disruptors of oocyte developmental competence, which appears due to the imbalance between the production and neutralization of reactive oxygen species (ROS).

Materials and Methods:

In Experiment 1, buffalo oocytes were in vitro matured, fertilized, and cultured at 38.5°C under 5% CO₂ + 20% O₂ in standard CO₂ incubator (OS) or under 5% O₂ + 5% CO₂ + 90% N₂ (Multi-gas incubator, low O₂). In Experiment 2, buffalo cumulus oocytes complexes (COCs) were matured in Basic maturation medium (BMM) composed of TCM199+ 10% FCS+ 10 µg/ml FSH+ 50 µg/ml gentamicin (control group) or in BMM supplemented with 50 μM ascorbic acid (ascorbic acid group) or 3.0 mM glutathione (glutathione group) or 10^-5 M melatonin (melatonin group) and cultured at 38.5°C under 20% O₂ for 24 h. Matured buffalo oocytes in control, ascorbic acid, or melatonin groups were fertilized and zygotes were cultured for 8 days under the same conditions.

Results:

In both experiments, maturation, cleavage, and blastocyst rates were recorded. Results showed that culture of buffalo oocytes under low O₂ (5% O₂) significantly increased maturation, cleavage, and blastocyst rates (p<0.05). Meanwhile, under 20% O₂, addition of 10^-5 M melatonin or 50 μM ascorbic acid to in vitro maturation (IVM) medium significantly improved cumulus cell expansion, nuclear maturation rates of buffalo oocytes (p<0.05), and increased cleavage and blastocyst rates (p<0.05).

Conclusion:

About 5% O₂ is the optimum condition for in vitro production of buffalo embryos, and addition of 10^-5 M melatonin to IVM medium for oocytes cultured under 20% O₂ could alleviate the adverse effect of high oxygen tension and increased embryo yield.

Human Adipose-Derived Stem Cells' Paracrine Factors in Conditioned Medium Can Enhance Porcine Oocyte Maturation and Subsequent Embryo Development

An essential requirement for the success of in vitro maturation (IVM) of the oocyte is to provide an optimal microenvironment similar to in vivo conditions. Recently, somatic cell-based coculture or supplementation of a conditioned medium during IVM has been performed to obtain better quality of oocytes, because they mimic the in vivo reproductive tract by secreting paracrine factors. In this study, human adipose-derived stem cells (ASC) and their conditioned medium (ASC-CM) were applied to IVM of porcine oocytes to evaluate the effectiveness of ASC on oocyte development and subsequent embryo development. In results, both ASC and ASC-CM positively influence on oocyte maturation and embryo development by regulating growth factor receptors (VEGF, FGFR, and IGFR), apoptosis (BCL2), cumulus expansion (PTGS2, HAS2, and TNFAIP6), and oocyte maturation-related genes (GDF9 and BMP15). In particular, the fluorescence intensity of GDF9 and BMP15 was markedly upregulated in the oocytes from the ASC-CM group. Furthermore, significantly high levels of growth factors/cytokine including VEGF, bFGF, IGF-1, IL-10, and EGF were observed in ASC-CM. Additionally, the ASC-CM showed active scavenging activity by reducing the ROS production in a culture medium. Consequently, for the first time, this study demonstrated the effect of human ASC-CM on porcine oocyte development and the alteration of mRNA transcript levels in cumulus–oocyte complexes.

Induction of Oxidative Stress and Mitochondrial Dysfunction by Juglone Affects the Development of Bovine Oocytes

Juglone, a major naphthalenedione component of walnut trees, has long been used in traditional medicine as an antimicrobial and antitumor agent. Nonetheless, its impact on oocyte and preimplantation embryo development has not been entirely clarified. Using the bovine model, we sought to elucidate the impact of juglone treatment during the in vitro maturation (IVM) of oocytes on their maturation and development of embryos. Results showed a severe reduction in oocyte nuclear maturation and cumulus expansion and a significant increase in mitochondrial dysfunction and reactive oxygen species (ROS) levels in cumulus-oocyte complexes (COCs) treated with juglone (12.5, 25.0, and 50.0 µM). In addition, RT-qPCR showed downregulation of the expansion-related (HAS2, TNFAIP6, PTX3, and PTGS2) and mitochondrial (ATPase6 and ATP5F1E) genes in juglone-treated COCs. Moreover, the development rates of day 4 total cleavage and 8-16 cell stage embryos, as well as day 8 blastocysts, were significantly reduced following exposure to juglone. Using immunofluorescence, the apoptotic marker caspase-9 was overexpressed in oocytes exposed to juglone (25.0 µM) compared to the untreated control. In conclusion, our study reports that exposing bovine oocytes to 12.5-50.0 µM of juglone can reduce their development through the direct induction of ROS accumulation, apoptosis, and mitochondrial dysfunction.

Anethole Supplementation During Oocyte Maturation Improves In Vitro Production of Bovine Embryos

Oxidative stress is one of the most detrimental factors that affect oocyte developmental competence and embryo development in vitro. The impact of anethole supplementation to in vitro maturation (IVM) media on oocyte maturation and further bovine in vitro embryo production was investigated. Oocytes of slaughterhouse-derived bovine ovaries were placed in IVM with anethole at different concentrations of 30 (AN30), 300 (AN300), and 2000 μg/mL (AN2000), or without (control treatment). The oocytes were assessed for maturation rates, and for reactive oxygen species (ROS) and ferric reducing antioxidant power (FRAP) levels, and mitochondrial membrane potential. Embryo development was assessed by cleavage and blastocyst rates, and embryo cell number. The percentage of metaphase II oocytes were similar among the treatments (range, 77%-96%). Anethole at 300 μg/mL was the only treatment that yielded higher cleavage and embryo development (morula and blastocyst) rates compared to the control treatment. The ROS production in the oocytes after maturation did not differ among treatments. However, oocytes treated with anethole at 300 μg/mL had higher (P < .05) FRAP and mitochondrial membrane potential compared to the control treatment. Furthermore, AN300 treatment increased (P < .05) the average number of total cells in blastocysts compared to the control and AN30 treatments. The use of anethole at 300 μg/mL during IVM is suggested to improve the quantity and quality of bovine embryos produced in vitro. The beneficial effects of anethole on embryonic developmental competence in vitro seems to be related to its capacity to regulate the redox balance and improve mitochondrial function in oocytes and embryos.

Hemoglobin: potential roles in the oocyte and early embryo†

Hemoglobin (Hb) is commonly known for its capacity to bind and transport oxygen and carbon dioxide in erythroid cells. However, it plays additional roles in cellular function and health due to its capacity to bind other gases including nitric oxide. Further, Hb acts as a potent antioxidant, quenching reactive oxygen species. Despite its potential roles in cellular function, the preponderance of Hb research remains focused on its role in oxygen regulation. There is increasing evidence that Hb expression is more ubiquitous than previously thought, with Hb and its variants found in a myriad of cell types ranging from macrophages to spermatozoa. The majority of nonerythroid cell types that express Hb are situated within hypoxic environments, suggesting Hb may play a role in hypoxia-inducible factor-regulated gene expression by controlling the level of oxygen available or as an adaptation to low oxygen providing a mechanism to store oxygen. Oocyte maturation and preimplantation embryo development occur within the low oxygen environments of the antral follicle and oviduct/uterus, respectively. Interestingly, Hb was recently found in human cumulus and granulosa cells and murine cumulus-oocyte complexes and preimplantation embryos. Here, we consolidate and analyze the research generated todate on Hb expression in nonerythroid cells with a particular focus on reproductive cell types. We outline future directions of this research to elucidate the role of Hb during oocyte maturation and preimplantation embryo development and finally, we explore the potential clinical applications and benefits of Hb supplementation during the in vitro culture of gametes and embryos.

Quercetin supports bovine preimplantation embryo development under oxidative stress condition via activation of the Nrf2 signalling pathway

Nrf2 is a master regulator for antioxidant machinery against oxidative stress in bovine preimplantation embryos. The endogenous or exogenous modulation of Nrf2-KEAP1 system in bovine embryos may contribute to the understanding of the mechanisms behind the response of embryos to stress conditions. Therefore, here we aimed to investigate the protective effect of quercetin on bovine preimplantation embryos exposed to higher atmospheric oxygen concentration. For that, blastocysts, which were developed from zygotes cultured in media supplemented with or without quercetin under high oxygen level (20%), were subjected intracellular ROS level and mitochondrial analysis, and determining blastocyst formation rate and total cell number. Moreover, mRNA and protein expression level of Nrf2 and selected downstream antioxidant genes were investigated in the resulting blastocysts. Quercetin supplementation in vitro culture did not affect cleavage and blastocyst rate until day 7. However, quercetin supplementation resulted in higher blastocyst total cell number and reduction of intracellular ROS level accompanied by increasing mitochondrial activity compared with control group in both day 7 and day 8 blastocysts. Moreover, quercetin supplementation induced mRNA and protein of Nrf2 with subsequent increase in the expression of downstream antioxidants namely: NQO1, PRDX1, CAT and SOD1 antioxidants. In conclusion, quercetin protects preimplantation embryos against oxidative stress and improves embryo viability through modulation of the Nrf2 signalling pathway.

Elimination of stress factors by continuous embryo culture and its influence on in vitro fertilization outcomes

Recently, infertility has become one of the most important endemic conditions, affecting approximately 15-20 % of couples worldwide. Among others, the careerist lifestyle, the increasing maternal age and the parallel increment in the aneuploidy rate of embryos play a crucial role in this phenomenon. In this study, embryological parameters and pregnancy outcomes were investigated in IVF cycles using either sequential embryo culture or a single step culture system. By sequential media, oocytes/embryos are needlessly exposed to the potentially negative effects of light exposure, temperature decrement and altered oxygen tension. In comparison with sequential media, single step media induced 1.28, 1.21 and 1.21-fold increments in implantation, biochemical pregnancy and clinical pregnancy rates, respectively. Pregnancy outcomes showed strong maternal age-dependency, so the difference between the two investigated culture systems was equalized by the increasing maternal ages (35-44 years) and the supposed incidence of embryo aneuploidy. Nevertheless, the significant enlargements in the outcomes of the younger ages (25-34) induced by the single step cultures suggest that, beside the resultant maternal aneuploidy, aneuploidy (reduced pregnancy rates) may evolve from exposure to the mentioned environmental stress factors.

The antioxidant dimethylthiourea improves IVF efficiency and decreases cumulus cell apoptosis in pigs

Abattoir ovaries, which are the main source of oocytes for reproductive biotechnologies, arrive at the laboratory under ischaemic conditions. Reoxygenation generates reactive oxygen species (ROS) in ischaemic tissues, which could affect oocyte quality. The aim of this study was to evaluate the effect of supplementation of media with dimethylthiourea (DMTU) during the collection and washing of cumulus-oocyte complexes (COC) on ROS levels, COC apoptosis and oocyte nuclear and cytoplasmic maturation. Thus, the collection (TCM-199) and washing (TCM-199 with 10% porcine follicular fluid, sodium pyruvate and antibiotics) media were supplemented with 1 and 10mM DMTU. In the control group, the media were not supplemented with DMTU. Intracellular ROS levels decreased significantly in the DMTU-treated groups (P<0.05). Although no effects on rate of nuclear maturation were observed, DMTU significantly increased sperm penetration rates without increasing polyspermy (P<0.05). The addition of 10mM DMTU to the collection and washing media enhanced IVF efficiency. DMTU did not modify the early or late apoptosis of oocytes. Both concentrations of DMTU significantly increased viability and decreased the apoptosis of cumulus cells (P<0.05). These results suggest that the addition of 1 or 10mM of DMTU to the media during the collection and washing of porcine COCs is useful for decreasing cumulus apoptosis mediated by ROS and for optimising the IVF of porcine oocytes.

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.

Oxygen concentration alters mitochondrial structure and function in in vitro fertilized preimplantation mouse embryos

STUDY QUESTION

Does the oxygen concentration in the culture medium [either physiologic (5%) or atmospheric (20%)] affect mitochondrial ultrastructure and function in preimplantation mouse embryos generated by IVF?

SUMMARY ANSWER

Embryos cultured in 20% oxygen show increased mitochondrial abnormalities compared to embryos cultured in 5% oxygen.

WHAT IS KNOWN ALREADY

ART are widely used and have resulted in the birth of more than 8 million children. A variety of media and oxygen concentrations are used to culture embryos. Embryos cultured under physiological O2 tension (5%) reach the blastocyst stage faster and have fewer alterations in gene expression when compared with embryos cultured under atmospheric oxygen conditions (20%). The mechanisms by which oxygen tension affects preimplantation development remain unclear, but mitochondria are believed to play an important role. The aim of this study was to evaluate how mitochondrial ultrastructure and function in IVF embryos were affected by culture under physiologic (5%) or atmospheric (20%) oxygen concentrations.

STUDY DESIGN, SIZE, DURATION

Zygotes, 2-cell, 4-cell, morula and blastocyst were flushed out of the uterus after natural fertilization and used as controls. IVF was performed in CF1 x B6D2F1 mice and embryos were cultured in Potassium simplex optimized medium (KSOM) with amino acids (KAA) under 5% and 20% O2 until the blastocyst stage. Embryo development with the addition of antioxidants was also tested.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Mitochondrial function was assessed by measuring mitochondrial membrane potential, reactive oxygen species (ROS) production, ATP levels, and the expression of selected genes involved in mitochondrial function. Mitochondria ultrastructure was evaluated by transmission electron microscopy (TEM).

MAIN RESULTS AND THE ROLE OF CHANCE

Embryos cultured under 20% O2 had fewer mitochondria and more vacuoles and hooded (abnormal) mitochondria compared to the other groups (P < 0.05). At the blastocyst stage the mitochondria of IVF embryos cultured in 20% O2 had lower mtDNA copy number, a denser matrix and more lamellar cristae than controls. Overall IVF-generated blastocysts had lower mitochondrial membrane potential, higher ROS levels, together with changes in the expression of selected mitochondrial genes (P < 0.05). ATP levels were significantly lower than controls only under 5% O2, with the 20% O2 IVF group having intermediate levels. Unexpectedly, adding antioxidant to the culture medium did not improve development.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Findings in mice embryos might be different from human embryos.

WIDER IMPLICATIONS OF THE FINDINGS

This study suggests that changes in the mitochondria may be part of the mechanism by which lower oxygen concentration leads to better embryo development and further emphasize the importance of mitochondria as a locus of reprogramming.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by R01 HD 082039 to PFR, the Department of Life, Health and Environmental Sciences, University of L'Aquila, Italy (RIA 2016-2018) and the Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, La Sapienza University of Rome, Italy (University grants 2016-2017). The authors declare no competing interests.

Supplementation of insulin-transferrin-sodium selenite in culture medium improves the hypothermic storage of bovine embryos produced in vitro

Hypothermic storage of gametes and embryos at 4 °C can be used as an alternative to cryopreservation, but hypothermic preservation can maintain embryo viability for a short duration only. This study investigated the effect of insulin-transferrin-sodium selenite (ITS) in embryo culture medium on hypothermic storage of bovine embryos at 4 °C. Day 7 bovine embryos were subjected to hypothermic storage in tissue culture medium 199 supplemented with 50% fetal bovine serum and 25 mM HEPES for different time durations. After recovery, the embryos were assessed for survival and hatching rate and gene and protein expression levels. Supplementation of embryo culture medium with ITS significantly increased (P < 0.05) the survival and hatching ability of blastocysts stored at 4 °C for 72 h compared to the control group (100% and 76.3% vs 68.5% and 40.5%, respectively). Furthermore, the beneficial effects of ITS on embryos were associated with greater (P < 0.05) total cell number per blastocyst and lesser apoptotic cells number. Moreover, embryos cultured in ITS had lower intracellular lipid content. The protein expression of sirt1 was greater (P < 0.05) in the ITS group, however, caspase3 protein expression was significantly lesser (P < 0.05) in the ITS group. Quantitative reverse transcription PCR indicated that the mRNA levels of SIRT1 and HSP70 were (P < 0.05) increased upon culture with ITS; however, the mRNA levels of the pro-apoptotic genes BAX and CASP3 were reduced (P < 0.05). Taken together, these data suggest that supplementation of embryo culture medium with ITS improves in vitro bovine embryo quality and survival following hypothermic storage.

Reactive oxygen species in reproduction: harmful, essential or both?

The process of embryonic development is crucial and radically influences preimplantation embryo competence. It involves oocyte maturation, fertilization, cell division and blastulation and is characterized by different key phases that have major influences on embryo quality. Each stage of the process of preimplantation embryonic development is led by important signalling pathways that include very many regulatory molecules, such as primary and secondary messengers. Many studies, both in vivo and in vitro, have shown the importance of the contribution of reactive oxygen species (ROS) as important second messengers in embryo development. ROS may originate from embryo metabolism and/or oocyte/embryo surroundings, and their effect on embryonic development is highly variable, depending on the needs of the embryo at each stage of development and on their environment (in vivo or under in vitro culture conditions). Other studies have also shown the deleterious effects of ROS in embryo development, when cellular tissue production overwhelms antioxidant production, leading to oxidative stress. This stress is known to be the cause of many cellular alterations, such as protein, lipid, and DNA damage. Considering that the same ROS level can have a deleterious effect on the fertilizing oocyte or embryo at certain stages, and a positive effect at another stage of the development process, further studies need to be carried out to determine the rate of ROS that benefits the embryo and from what rate it starts to be harmful, this measured at each key phase of embryonic development.

Transcriptome profiling of in vitro-matured oocytes from a korean native cow (hanwoo) after cysteamine supplementation

This study elucidated the molecular markers that decrease oocyte quality during in vitro culture, restricting optimal developmental potential. Here, we evaluated the transcriptomic differences between cysteamine-treated and non-treated bovine cumulus oocyte complexes (COCs) after 22 h of co-culture in the maturation media using RNA sequencing. In total, 39,014 transcripts were sequenced between cysteamine-treated and non-treated mature COCs. We evaluated the relative expression of 21,472 genes, with 59 genes showing differential expression between the two COC groups. The cysteamine-treated group had 36 up-regulated gene transcripts and 23 down-regulated gene transcripts. Moreover, gene ontology (GO) enrichment analysis revealed that multiple biological processes were significantly enriched after cysteamine supplementation. Differentially expressed genes appeared to maintain normal oocyte physiology, regulation of apoptosis, differentiation, ossification or bone formation, cardiac and muscle physiology, hormonal secretion, and membrane construction for further embryonic development. In conclusion, cysteamine affects the mRNA level of COCs during oocyte maturation by upregulating potential molecular markers and downregulating genes that affect further embryonic development.

Effects of dynamic oxygen concentrations on the development of mouse pre- and peri-implantation embryos using a double-channel gas supply incubator system

Objective

We aimed to evaluate the effects of different oxygen conditions (20% [high O₂], 5% [low O₂] and 5% decreased to 2% [dynamic O₂]) on mouse pre- and peri-implantation development using a novel double-channel gas supply (DCGS) incubator (CNC Biotech Inc.) to alter the oxygen concentration during in vitro culture.

Methods

The high-O₂ and low-O₂ groups were cultured from the one-cell to the blastocyst stage under 20% and 5% oxygen concentrations, respectively. In the dynamic-O₂ group, mouse embryos were cultured from the one-cell to the morula stage under 5% O₂ for 3 days, followed by culture under 2% O₂ to the blastocyst stage. To evaluate peri-implantation development, the blastocysts from the three groups were individually transferred to a fibronectin-coated dish and cultured to the outgrowth stage in droplets.

Results

The blastocyst formation rate was significantly higher in the low-O₂ and dynamic-O₂ groups than in the high-O₂ group. The total cell number was significantly higher in the dynamic-O₂ group than in the low-O₂ and high-O₂ groups. Additionally, the apoptotic index was significantly lower in the low-O₂ and dynamic-O₂ groups than in the high-O₂ group. The trophoblast outgrowth rate and spread area were significantly higher in the low-O₂ and dynamic-O₂ groups than in the high-O₂ group.

Conclusion

Our results showed that a dynamic oxygen concentration (decreasing from 5% to 2%) had beneficial effects on mouse pre- and peri-implantation development. Optimized, dynamic changing of oxygen concentrations using the novel DCGS incubator could improve the developmental competence of in vitro cultured embryos in a human in vitro fertilization and embryo transfer program.

Loss of methylation of H19-imprinted gene derived from assisted reproductive technologies can be mitigated by cleavage-stage embryo transfer in mice

PURPOSE

Studies on rodents have shown that assisted reproductive technologies (ARTs) are associated with perturbation of genomic imprinting in blastocyst-stage embryos. However, the vulnerable developmental window for ART influence on the genomic imprinting of embryos is still undetermined. The purpose of this study was to establish the specific embryonic development stage at which the loss of methylation of H19 imprinting control regions (ICRs) was caused by ART occurrence. Additionally, we explored protocols to safeguard against possible negative impacts of ART on embryo H19 imprinting.

METHODS

Mouse embryos were generated under four different experimental conditions, divided into four groups: control, in vitro culture (IVC), in vitro fertilization (IVF), and intracytoplasmic sperm injection (ICSI). The methylation levels of H19 ICR of the grouped or individual embryos were analyzed by bisulfite-sequencing PCR.

RESULTS

Our data showed that the loss of methylation of H19 ICR in mouse blastocysts was inflicted to a similar extent by IVC, IVF, and ICSI. Specifically, we observed a significant loss of methylation of H19 ICR between the mouse 8-cell and morula stages. In addition, we revealed that the transfer of mouse embryos generated by ARTs in the uterus at the 8-cell stage induced the occurrence of methylation patterns in the blastocysts closer to the in vivo ones.

CONCLUSIONS

Our findings indicate that the loss of methylation of H19 ICR caused by ARTs occurs between the 8-cell and the morula stages, and the transfer of cleavage embryos to the uterus mitigates the loss methylation of H19 derived by mice ARTs.

Influence of N-acetyl-L-cysteine against bisphenol a on the maturation of mouse oocytes and embryo development: in vitro study

BACKGROUND

Bisphenol A (BPA), an endocrine disruptor, is a widely used chemical that has adverse effects on animal development and reproduction. The current research aimed to evaluate the effect of BPA on the in vitro maturation (IVM) and subsequent embryo development of mouse oocytes following in vitro fertilization (IVF).

METHODS

IVM was performed in the presence of different concentrations (0, 20, 50, or 100 μg/mL) of BPA. Nuclear maturation, IVF efficiency and embryonic development were determined. The levels of reactive oxygen species (ROS) and glutathione (GSH) in the BPA (50 μg/mL) group were evaluated. We explored the ability of N-acetyl-L-cysteine (NAC) in the IVM medium to rescue the BPA-induced damage by examining changes in nuclear maturation, IVF rate, blastocyst formation, ROS levels and GSH content.

RESULTS

Compared with the control, BPA (50 μg/mL) supplementation during oocyte IVM significantly inhibited nuclear maturation and decreased fertilization and blastocyst formation rates. In addition, BPA exposure increased ROS levels and decreased GSH content in oocytes. The addition of NAC weakened the BPA-induced suppression of nuclear maturation, relieved the BPA-induced downregulation of the fertilization and blastocyst formation rates, and mitigated the increased ROS levels and decreased GSH content.

CONCLUSION

BPA affects mouse oocyte maturation and subsequent early embryonic developmental competence following IVF by increasing intracytoplasmic oxidative stress in mature oocytes. NAC can reduce these harmful effects to a certain extent.

Hesperidin improves the follicular development in 3D culture of isolated preantral ovarian follicles of mice

IMPACT STATEMENT

It has been stated that hesperidin has many pharmacological effects, such as anti-inflammatory and antioxidant effects, antimicrobial activity, and anti-carcinogenic activity; but hesperidin and its derivatives have been under investigation as anti-fertility factors for a very long time. However, our results show that hesperidin can improve mice follicular growth and maturation during in vitro 3D culture. Hesperidin as an antioxidant factor could enhance the mRNA expression levels of two important genes involved in folliculogenesis, PCNA, and FSH-R. Our results prove for the first time that hesperidin not only has deleterious effects on follicular development but can also increase rates of in vitro fertilization and embryo development.

Individual culture and atmospheric oxygen during culture affect mouse preimplantation embryo metabolism and post-implantation development

RESEARCH QUESTION

Does single embryo culture under atmospheric or reduced oxygen alter preimplantation metabolism and post-implantation development compared with culture in groups?

DESIGN

Mouse embryos were cultured under 5% or 20% oxygen, individually or in groups of 10. Spent media were analysed after 48, 72 and 96 h of culture. Blastocysts were assessed by outgrowth assay or transferred to pseudo-pregnant recipients, and fetal and placental weight, length and morphology were assessed.

RESULTS

Compared with group culture, individually cultured blastocysts had lower net consumption of glucose and aspartate and higher glutamate production. Atmospheric oxygen reduced uptake of glucose and aspartate and increased production of glutamate and ornithine compared with 5% oxygen. Combining 20% oxygen and single culture resulted in further metabolic changes: decreased leucine, methionine and threonine consumption. Under 5% oxygen, individual culture decreased placental labyrinth area but had no other effects on fetal and placental development or outgrowth size compared with group culture. Under 20% oxygen, however, individual culture reduced outgrowth size and fetal and placental weight compared with group-cultured embryos.

CONCLUSIONS

Preimplantation metabolism of glucose and amino acids is altered by both oxygen and individual culture, and fetal weight is reduced by individual culture under atmospheric oxygen but not 5% oxygen. This study raises concerns regarding the increasing prevalence of single embryo culture in human IVF and adds to the existing evidence regarding the detrimental effects of atmospheric oxygen during embryo culture. Furthermore, these data demonstrate the cumulative nature of stress during embryo culture and highlight the importance of optimizing each element of the culture system.

Anethole Supplementation During Oocyte Maturation Improves In Vitro Production of Bovine Embryos

Oxidative stress is one of the most detrimental factors that affect oocyte developmental competence and embryo development in vitro. The impact of anethole supplementation to in vitro maturation (IVM) media on oocyte maturation and further bovine in vitro embryo production was investigated. Oocytes of slaughterhouse-derived bovine ovaries were placed in IVM with anethole at different concentrations of 30 (AN30), 300 (AN300), and 2000 μg/mL (AN2000), or without (control treatment). The oocytes were assessed for maturation rates, and for reactive oxygen species (ROS) and ferric reducing antioxidant power (FRAP) levels, and mitochondrial membrane potential. Embryo development was assessed by cleavage and blastocyst rates, and embryo cell number. The percentage of metaphase II oocytes were similar among the treatments (range, 77%-96%). Anethole at 300 µg/mL was the only treatment that yielded higher cleavage and embryo development (morula and blastocyst) rates compared to the control treatment. The ROS production in the oocytes after maturation did not differ among treatments. However, oocytes treated with anethole at 300 µg/mL had higher ( P < .05) FRAP and mitochondrial membrane potential compared to the control treatment. Furthermore, AN300 treatment increased ( P < .05) the average number of total cells in blastocysts compared to the control and AN30 treatments. The use of anethole at 300 μg/mL during IVM is suggested to improve the quantity and quality of bovine embryos produced in vitro. The beneficial effects of anethole on embryonic developmental competence in vitro seems to be related to its capacity to regulate the redox balance and improve mitochondrial function in oocytes and embryos.

Antioxidant hesperetin improves the quality of porcine oocytes during aging in vitro

The citrus flavonoid hesperetin has a variety of pharmacological actions, including antioxidant, antiinflammatory, and anticancer activities. This study investigated whether hesperetin prevents aging of oocytes in vitro in which it determined the maturation of nuclear and cytoplasm and the developmental capacity of embryo by modulating the reactive oxygen species (ROS) level. Porcine oocytes were matured in vitro for 44 hr (control) and for an additional 24 hr in the presence of 0, 1, 10, 100, and 250 μM hesperetin (aging, H-1, H-10, H-100, and H-250, respectively). Although there was no difference in the rate of maturation among all the groups, both the control and H-100 groups significantly increased in the rate of cleavage and blastocyst formation compared to the aging group. The H-100 group significantly decreased ROS activity and increases the level of glutathione (GSH) and expression of the antioxidant genes (PRDX5, NFE2L, SOD1, and SOD2) compared with the aging group. The H-100 groups prevented aberrant spindle organization and chromosomal misalignment, blocked the decrease in the level of phosphorylated-p44/42 mitogen-activated protein kinase and increased the messenger RNA expression of cytoplasmic maturation factor genes (GDF9, CCNB1, BMP15, and MOS). Subsequently, both the control and H-100 groups significantly increased the total cell number and decreased the apoptosis cells at the blastocyst stage compared with aging group. The results indicate that hesperetin improves the quality of porcine oocytes by protecting them against oxidative stress during aging in vitro.

Considerations Regarding Embryo Culture Conditions: From Media to Epigenetics

There are numerous reports on embryo culture media and conditions in the laboratory, as the subject is multifaceted and complex, reflecting the variation in practice. In this scoping review, we attempt to approach the topic of culture media and conditions from the practitioners' perspective aiming to highlight, in a comprehensive fashion, important aspects regarding the options available, introduce points of debate and controversy, while maintaining the viewpoint of the practicing embryologist's concerns.

Female Reproductive Performance in the Mouse: Effect of Oral Melatonin

Although melatonin has some of the broadest ranges of actions on the physiology of vertebrates, especially on their reproductive processes, the mechanism by which melatonin regulates animal reproduction is still incompletely understood. This study was designed to determine the effect of oral melatonin on the reproductive performance of female mice. Female ICR mice (7 weeks old) were given melatonin-containing water (3, 30 and 300 μg/mL; melatonin) or water only (control) until 10 weeks of age. Then, some of the mice were successfully mated (confirmed by vaginal plugs), and the number of live births and their weights were recorded. Some mice were used for a histological analysis of the number of follicles in the ovaries. Others were used for oocyte collection after superovulation, and in vitro fertilization (IVF) was performed. The mRNA expression of the apopotosis-related genes (BAX, BCL2) in the IVF embryos were analyzed. After melatonin administration, the mice showed similar serum melatonin levels to that of the control. The number of antral follicles per mm² unit area in the 30 μg/mL melatonin-treated group (14.60) was significantly higher than that of the control (7.78), which was lower than that of the 3 μg/mL melatonin-treated group (12.29). The litter size was significantly higher in the 3 μg/mL melatonin-treated group (15.5) than in the control (14.3). After IVF, the hatched blastocyst formation rate in the 30 μg/mL melatonin-treated group (85.70%) was significantly higher than that of the control (72.10%), and it was the same for the BCL2/BAX expression ratio. Although oral melatonin did not appear to have an effect on the serum melatonin rhythm in the mouse, melatonin did increase litter size at the 3 μg/mL dose level, and improved the developmental competency of IVF embryos at the 30 μg/mL level.