Gamete origin in relation to early embryo development

Attenuation of Oxidative Stress and Regulation of AKT Signaling by Vanillic Acid during Bovine Pre-Implantation Embryo Development

Vanillic acid (VA) has shown antioxidant and anti-inflammatory activities in different cell types, but its biological effects in the context of early embryo development have not yet been clarified. In the current study, the impact of VA supplementation during in vitro maturation (IVM) and/or post-fertilization (in vitro culture; IVC) on redox homeostasis, mitochondrial function, AKT signaling, developmental competence, and the quality of bovine pre-implantation embryos was investigated. The results showed that dual exposure to VA during IVM and late embryo culture (IVC3) significantly improved the blastocyst development rate, reduced oxidative stress, and promoted fatty acid oxidation as well as mitochondrial activity. Additionally, the total numbers of cells and trophectoderm cells per blastocyst were higher in the VA-treated group compared to control (p < 0.05). The RT-qPCR results showed down-regulation of the mRNA of the apoptosis-specific markers and up-regulation of AKT2 and the redox homeostasis-related gene TXN in the treated group. Additionally, the immunofluorescence analysis showed high levels of pAKT-Ser473 and the fatty acid metabolism marker CPT1A in embryos developed following VA treatment. In conclusion, the study reports, for the first time, the embryotrophic effects of VA, and the potential linkage to AKT signaling pathway that could be used as an efficacious protocol in assisted reproductive technologies (ART) to improve human fertility.

Leonurine improves bovine oocyte maturation and subsequent embryonic development by reducing oxidative stress and improving mitochondrial function

It is acknowledged that excessive reactive oxygen species (ROS) level attributes greatly to the compromised developmental potential of oocytes matured in vitro. Although agents were applied to alleviate ROS levels, results were varied because of the distinct antioxidative activity and cell toxicity. Leonurine (LEO), extracted from the natural Chinese herb motherwort, is considered to be a potent free radical scavenger. Yet, it is undetermined whether LEO is benefit for oocyte development during in vitro maturation (IVM). In the present study, the effect of LEO on the quality of bovine oocyte as well as the underlying mechanism was investigated. We found that maturation rate (P < 0.01), subsequent blastocyst formation rate (P < 0.05), and the total blastocyst cell number (P < 0.05) after parthenogenetic activation were significantly increased in the group treated with 20 μM LEO. Moreover, a dramatic decline in ROS (P < 0.01), decreased lipid content (P < 0.01), elevated MMP level (P < 0.05), increased ATP content (P < 0.05), and reduced mitochondrial temperature (P < 0.01) were observed in oocytes treated with LEO. Furthermore, the expression level of anti-apoptotic protein BCL2 was significantly higher in LEO treated oocytes (P < 0.01), and the ratio of BAX/BCL2 was obvious decreased (P < 0.01). Finally, we found that LC3B intensity was significantly reduced (P < 0.05) while the rate of EdU positive nuclei was markedly increased (P < 0.05) in embryos derived from LEO-treated oocytes. Our results demonstrate that LEO exhibits a potent protective role in the acquisition of oocyte development capacity against oxidative stress during IVM, and provides a new solution for optimizing the in vitro culture system of bovine embryos.

Non-invasive oocyte quality assessment

Oocyte quality is perhaps the most important limiting factor in female fertility; however, the current methods of determining oocyte competence are only marginally capable of predicting a successful pregnancy. We aim to review the predictive value of non-invasive techniques for the assessment of human oocytes and their related cells and biofluids that pertain to their developmental competence. Investigation of the proteome, transcriptome, and hormonal makeup of follicular fluid, as well as cumulus-oocyte complexes are currently underway; however, prospective randomized non-selection-controlled trials of the future are needed before determining their prognostic value. The biological significance of polar body morphology and genetics are still unknown and the subject of debate. The predictive utility of zygotic viscoelasticity for embryo development has been demonstrated, but similar studies performed on oocytes have yet to be conducted. Metabolic profiling of culture media using human oocytes are also limited and may require integration of automated, high-throughput targeted metabolomic assessments in real time with microfluidic platforms. Light exposure to oocytes can be detrimental to subsequent development and utilization of time-lapse imaging and morphometrics of oocytes is wanting. Polarized light, Raman microspectroscopy, and coherent anti-Stokes Raman scattering are a few novel imaging tools that may play a more important role in future oocyte assessment. Ultimately, the integration of chemistry, genomics, microfluidics, microscopy, physics, and other biomedical engineering technologies into the basic studies of oocyte biology, and in testing and perfecting practical solutions of oocyte evaluation, are the future for non-invasive assessment of oocytes.

Oocyte Morphometric Assessment and Gene Expression Profiling of Oocytes and Cumulus Cells as Biomarkers of Oocyte Competence in Sheep

Oocyte quality is crucial for subsequent embryo development and so it is a major challenge in assisted reproductive technologies. The aim of the present work was to evaluate the morphometric parameters of oocytes (experiment 1) and the relative gene expression of oocytes and cumulus cells (CCs) (experiment 2) as biomarkers of oocyte quality after individually culturing them (one oocyte or embryo/drop). In experiment 1, individually matured oocytes were measured and classified into small, intermediate, and large oocytes after a cluster analysis, based on total diameter (with zona pellucida, ZP), oocyte diameter (without ZP), and ZP thickness. These oocytes were individually fertilized in vitro and cultured. The embryo development was evaluated up to the blastocyst stage. According to the total diameter, oocyte diameter, and ZP thickness, the blastocyst rate decreased in the small oocytes group (3.1 ± 3.1, 14.1 ± 9.4, and 26.7 ± 3.9, respectively) compared to the intermediate (29.4 ± 5.2, 30.5 ± 10.1, and 28.6 ± 9.6, respectively) and large oocytes groups (54.2 ± 13.5, 44.4 ± 3.9, and 67.6 ± 12.4, respectively). In addition, the probability of reaching the blastocyst stage was positively related to the total diameter (p < 0.001), oocyte diameter (p < 0.05), and ZP thickness (p < 0.001). Furthermore, the relative gene expression of BAX, BCL2, GDF9, and GJA1 was lower in oocytes classified as large. In experiment 2, the mRNA transcript relative abundance pattern of genes in CCs was evaluated according to oocyte total diameter and developmental stage reached. CCs from oocytes classified as large and oocytes capable of developing to the blastocyst stage had a lower relative expression of BAX, STAR, and PTGS2, while a higher expression of HAS2 and SDC2 transcript was observed for those oocytes. In conclusion, oocyte morphometric parameters and gene expression analysis in oocytes and CCs provide methods for the identification of the most competent oocytes for assisted reproductive technologies in sheep.

Effects of Donor Cell Types on the Development of Bovine Embryos Using Cytoplasm Injection Cloning Technology

Cytoplasm injection cloning technology (CICT) is an efficient technique for evaluating the developmental potential of cloned embryos. In this study, we investigated the effects of donor cell type on the developmental potential and quality of cloned bovine embryos. Adult fibroblasts (AFs) and embryonic cells (ECs) were used as donor cells to clone bovine embryos using CICT. We initially used AF cells to develop cloned embryos and then cultured the cloned day-8 blastocysts for 10 days to obtain ECs as donor cells for second embryo cloning. We found that the bovine blastocysts cloned using AF cells had significantly reduced developmental rates, embryo quality, and ratios of inner cell mass (ICM) to the total number of cells compared to those using ECs as donor cells. Furthermore, there were significant differences in the DNA methyltransferase-, histone deacetylation-, apoptosis-, and development-related genes at the blastocyst stage in embryos cloned from AFs compared to those in embryos cloned from ECs. Our results suggest that using ECs as donor cells for nuclear transfer enhances the quantity and quality of cloned embryos. However, further investigation is required in terms of determining pregnancy rates and developing cloned embryos from different donor cell types.

Meta-analysis to determine effects of treatment with FSH when there is progestin-priming on in-vitro embryo production using ovum pick-up in Bos taurus cows

Treatments with follicle stimulating hormone (FSH) to enhance ovarian follicular development before ovum pick-up (OPU) are important for improving in-vitro embryo production (IVEP) procedures in cows, however, their procedural efficacy needs to be evaluated. The objective of the present study was to use meta-analytic methods to determine the effects of FSH treatments prior to OPU when there is progestin-priming on ovarian functions and IVEP in parous Bos taurus cows (n = 243). The literature was systematically reviewed and data from eight experiments, with 23 treatment means including 448 OPU sessions, were used for analyses. All eight experiments included a group of cows in which there was no FSH treatment (CON), and treatment with FSH before OPU to conduct IVEP. Mixed models were fitted using MIXED and GLIMMIX procedures of SAS. Additionally, classical meta-analytical statistics were also fitted using METAN and METAREG procedures of STATA. Models included fixed effects of treatment (i.e., CON and FSH) and random effect of the experiment, and data were weighted using the inverse of the SEM squared to account for precision of each experiment. Number of medium sized follicles, quality of oocytes, and transferable embryos were greater (P < 0.05) in FSH-treated as compared with cows of the CON group, without indications of publication bias or heterogeneity of data. Taken together, the results from the present study lead to the recommendation for treatments with FSH prior to OPU for IVEP when there was progestin-priming imposed to obtain a large number of transferable embryos for economic sustainability of commercial embryo transfer programs in parous non-lactating Bos taurus cows.

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.

A combination of bovine serum albumin with insulin-transferrin-sodium selenite and/or epidermal growth factor as alternatives to fetal bovine serum in culture medium improves bovine embryo quality and trophoblast invasion by induction of matrix metalloproteinases

This study investigated the use of bovine serum albumin (BSA) plus insulin-transferrin-sodium selenite (ITS) and/or epidermal growth factor (EGF) as alternatives to fetal bovine serum (FBS) in embryo culture medium. The developmental ability and quality of bovine embryos were determined by assessing their cell number, lipid content, gene expression and cryotolerance, as well as the invasion ability of trophoblasts. The percentage of embryos that underwent cleavage and formed a blastocyst was higher (P<0.01) in medium containing ITS plus EGF and BSA than in medium containing FBS. Culture with ITS plus EGF and BSA also increased the hatching ability of blastocysts and the total cell number per blastocyst. Furthermore, the beneficial effects of BAS plus ITS and EGF on embryos were associated with a significantly reduced intracellular lipid content, which increased their cryotolerance. An invasion assay confirmed that culture with ITS plus EGF and BSA significantly improved the invasion ability of trophoblasts. Real-time quantitative polymerase chain reaction analysis showed that the mRNA levels of matrix metalloproteinase-2 (MMP2) and MMP9, acyl-CoA synthetase long-chain family member 3, acyl-coenzyme A dehydrogenase long-chain and hydroxymethylglutaryl-CoA reductase significantly increased upon culture with ITS plus EGF and BSA. Moreover, protein expression levels of matrix metalloproteinase-2 and -9 increased (P<0.01) in medium supplemented with ITS plus EGF and BSA compared with medium supplemented with FBS. Taken together, these data suggest that supplementation of medium with ITS plus EGF and BSA improves invitro bovine embryo production, cryotolerance and invasion ability of trophoblasts.

Oocyte maturation with royal jelly increases embryo development and reduces apoptosis in goats

Royal jelly (RJ) was supplemented to goat oocyte in vitro maturation (IVM) medium at three different concentrations (2.5, 5, and 10 mg/ml). Maturation rate, embryo cleavage, and blastocyst rate were recorded. Gene expression of apoptosis-related transcripts was investigated in matured oocytes. Percentage of oocytes that reached MII-stage was increased in RJ-treated groups compared to the control group. Glutathione (GSH) content of mature oocytes was enhanced when RJ was added to IVM medium at any supplementation compared with control. Percentage of cleaved embryos and blastocysts was higher in the RJ-treated groups at a concentration of 5 than in the 2.5 mg/ml and control group. Total number of cells per blastocyst was not different in the control and RJ-treated group at 5 mg/ml. However, number of apoptotic cells per blastocyst was higher in the control group than in the RJ-treated group at 5 mg/ml. Expression profile of Bax, and p53 was down-regulated while Bcl-2 was up-regulated in oocytes treated with RJ at 5 and 10 mg/ml compared with the control group. Addition of RJ at concentrations of 5 mg/ml improved embryo production through increasing maturation rate. RJ seems to improve the IVM microenvironment by reducing expression of genes inducing apoptosis, enhancing GSH content, and reducing incidence of apoptosis in blastocysts.

Improvement of in vitro-produced bovine embryo treated with coagulansin-A under heat-stressed condition

Heat stress has large effects on reproduction including conception rate in cattle. In this study, we examined the effects of coagulansin-A (coa-A), a steroidal lactone, on acquired thermo tolerance during in vitro production of bovine embryos. Oocytes were incubated in in vitro maturation (IVM) media with or without coa-A at two different temperatures, 40.5˚C and 42˚C, for 20 h. The treatment of coa-A significantly improved blastocyst development only at 40.5˚C (P < 0.05). Interestingly, immunofluorescence analysis demonstrated that coa-A induced heat shock protein 70 (HSP70) and phosphatidylinositol-3-kinase (PI3K), but significantly attenuated nuclear factor kappa B (NF-κB) and cyclooxygenase-2 (COX2). To determine the expression patterns of related genes at the transcription level, qRT-PCR was performed. Expression of HSP70 and PI3K was elevated, whereas expression of NF-κB, COX2 and inducible nitric oxide synthase (iNOS) was significantly (P < 0.05) downregulated in the coa-A-treated group compared with the control group. Moreover, pro-apoptotic genes were downregulated, and antiapoptic genes were upregulated in the coa-A group. We also counted the total cell number and apoptotic nuclei at the blastocyst and found that more cell numbers (143.1 ± 1.5) and less apoptotic damages (6.4 ± 0.5) in the coa-A treatment group comparing to control group (131.4 ± 2.0 and 10.8 ± 0.5), indicating the enhanced embryo quality. In conclusion, our results demonstrate that the coa-A not only improved the blastocyst development in vitro but also increased their resistance to heat stress condition through induction of HSP70/PI3K.

Coagulansin-A has beneficial effects on the development of bovine embryos in vitro via HSP70 induction

Treatment with the steroidal lactone, coagulansin-A, improves bovine oocyte maturation and embryo development in vitro by inducing heat shock protein 70 (HSP70), which reduces the levels of reactive oxygen species (ROS), DNA damage and inflammation.

Coagulansin-A (withanolide) is the steroidal lactone obtained from Withania coagulans which belong to Solanaceae family. The present study investigated the effects of coagulansin-A on bovine oocyte maturation and embryo development in vitro. All these oocytes were aspirated from the ovaries obtained from Korean Hanwoo cows at a local abattoir. To determine whether coagulansin-A has beneficial effects on bovine oocyte maturation in vitro, 355 oocytes per group (control and treated) in seven replicates were subjected with different concentrations (1, 2.5, 5, 7.5 and 10 μM) of coagulansin-A. The coagulansin-A was added in the in vitro maturation (IVM) media followed by in vitro fertilization (IVF) and then in vitro culture (IVC). Only treatment with 5 μM coagulansin-A remarkably (P<0.05) improved embryos development (Day 8 blastocyst) having 27.30 and 40.01% for control and coagulansin-A treated groups respectively. Treatment with 5 μM coagulansin-A significantly induced activation of heat shock protein 70 (HSP70) (P<0.05). Immunofluorescence analysis revealed that 5 μM coagulansin-A treatment also significantly inhibited oxidative stress and inflammation during bovine embryo development in vitro by decreasing 8-oxoguanosine (8-OxoG) (P<0.05) and nuclear factor-κB (NF-κB) (P<0.05). The expressions of HSP70 and NF-κB were also conformed through real-time PCR (RT-PCR). Additionally, the terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assay confirmed that coagulansin-A treatment significantly improved the embryo quality and reduced bovine embryo DNA damage (P<0.05). The present study provides new information regarding the mechanisms by which coagulansin-A promotes bovine embryo development in vitro.

Influence of sperm fertilising concentration, sperm selection method and sperm capacitation procedure on the incidence of numerical chromosomal abnormalities in IVF early bovine embryos

The occurrence of numerical chromosomal aberrations, widely described as a major cause of mortality in in vitro-produced (IVP) embryos, has been linked to several factors. In the present study we investigated the effect of sperm fertilising concentration and semen handling (sperm selection and capacitation) before IVF on the rate of numerical chromosomal abnormalities in bovine embryos. In all, 466 IVP cattle embryos were karyotyped throughout three sequential experiments, analysing the effects of sperm fertilising concentration (0.1, 1.0 or 10×10(6) spermatozoa mL(-1)), selection method (unselected or Percoll-selected spermatozoa) and capacitation medium (bovine serum albumin (BSA), heparin or their combination). The percentage of normal (diploid) and aberrant (haploid, polyploid or aneuploid) embryos was noted in each experiment. The rate of numerical chromosomal abnormalities was mainly affected by sperm fertilising concentration (P<0.01) and, to a lesser extent, by the sperm capacitation medium (P<0.05). Polyploidy and haploidy rates were only affected by sperm fertilising concentration (P<0.05). Interestingly, the sperm selection technique used in the present study did not reduce the incidence of chromosome abnormalities in IVP cattle embryos (P>0.05). Finally, aneuploidy rates were not affected during the experiments (P>0.05), which suggests that they are not related to sperm-related factors. On the basis of these results, we conclude that sperm fertilising concentration is the 'paternal' key factor that affects the rate of numerical chromosomal abnormalities in IVP bovine embryos. By making small adjustments to fertilising protocols, the rate of cytogenetically aberrant embryos can be markedly reduced.

The ART of selecting the best embryo: A review of early embryonic mortality and bovine embryo viability assessment methods

Animal reproductive biotechnology is continually evolving. Significant advances have been made in our understanding of early embryonic mortality and embryo development in domestic animals, which has improved the selection and success of in vitro technologies. Yet our knowledge is still relatively limited such that identifying a single embryo with the highest chance of survival and development for transfer remains challenging. While invasive methods such as embryo biopsy can provide useful information regarding the genetic status of the embryos, morphological assessment remains the most common evaluation. A recent shift, however, favors alternative, adjunct approaches for non-invasive assessment of an embryo's viability and developmental potential. Various analytical techniques have facilitated the evaluation of cellular health through the metabolome, the assessment of end products of cellular metabolism, or by analyzing spent media for small RNAs. This review discusses the application of noninvasive approaches for ascertaining the health and viability of in vitro-produced bovine embryos. A comparative analysis of noninvasive techniques for embryo assessment currently being investigated in cattle and humans is also discussed.

Developmental competence of equine oocytes: impacts of zona pellucida birefringence and maternally derived transcript expression

In the present study, equine oocytes were classified into groups of presumably high and low developmental competence according to cumulus morphology, as well as oocyte ability to metabolise brilliant cresyl blue (BCB) stain. All oocytes were evaluated individually in terms of morphometry, zona pellucida birefringence (ZPB) and relative abundance of selected candidate genes. Oocytes with an expanded cumulus (Ex), representing those with presumably high developmental competence, had a significantly thicker zona (18.2 vs 17.3µm) and a significantly higher ZPB (64.6 vs 62.1) than oocytes with a compacted cumulus (Cp). Concurrently, oocytes classified as highly developmentally competent (BCB+) had a significantly thicker zona (18.8 vs 16.1µm) and significantly higher ZPB (63.1 vs 61.3) compared with oocytes classified as having low developmental competence. Expression of TFAM, STAT3 and CKS2 was significantly higher in Ex compared with Cp oocytes, whereas expression of COX1, ATPV6E and DNMT1 was lower. Together, the data reveal that developmentally competent equine oocytes are larger in size, have higher ZPB values and exhibit a typical genetic signature of maternally derived transcripts compared with oocytes with lower in vitro developmental competence.

Expression and cellular distribution of zona pellucida glycoproteins in canine oocytes before and after in vitro maturation

This study was aimed at investigating zona pellucida glycoproteins (ZP) ZP2, ZP3 mRNA expression as well as ZP3, ZP4 (ZPB) protein distribution before and after in vitro maturation (IVM) in canine oocytes. The cumulus–oocyte complexes (COCs) were recovered from 27 anoestrous mongrel bitches and matured for 72 h in TCM199 medium. The canine COCs were analysed before and after IVM. Using real-time quantitative polymerase chain reaction (RQ-PCR), both groups of oocytes were analysed for detection of ZP2 and ZP3 mRNA profiles as well as using confocal microscopic analysis for observation of ZP3 and ZP4 protein distribution. In post-IVM canine oocytes an increase in transcript content of ZP2 and ZP3 genes as well as a decrease in ZP3 and ZP4 protein levels were observed when compared with pre-IVM oocytes. Moreover, the ZP4 protein before IVM was significantly distributed in the peripheral area of cytoplasm, whereas after IVM it was localized rather than in the entire cytoplasm. In contrast, the ZP3 protein was found both before and after IVM was distributed in the peripheral area of the cytoplasm. In conclusion, we suggest that the expression of ZP2 and ZP3 genes is associated with the maturation stage of canine oocytes, as higher mRNAs levels were found after IVM. However, a decreased expression of ZP3 and ZP4 proteins after IVM suggests maturation-dependent down-regulation of these protein translations, which may result in disturbed fertilization.

Rapidly cleaving bovine two-cell embryos have better developmental potential and a distinctive mRNA pattern

Mammalian embryos that rapidly reach the two-cell stage in culture have a higher probability of becoming viable blastocysts. Our goal was to separate two-cell bovine embryos based on their zygotic cleavage timing, and to assess their global mRNA levels. Following in vitro fertilization, all embryos that cleaved by 29.5 hpi (early) were cultured separately from those that divided at 46 hpi (late). The blastocyst rates were 46.1 ± 3.7% and 6.1 ± 3.4% for early- and late-cleavers, respectively (P < 0.01). Seven replicates of selected two-cell embryos were collected at each time point for microarray characterization (n = 4) and quantitative reverse-transcriptase PCR (n = 3); the rest were left in culture for blastocyst evaluation. A total of 774 and 594 probes were preferentially present in early- and late-cleaving embryos, respectively (fold change ± 1.5, P < 0.05), with important contrasts related to cell cycle, gene expression, RNA processing, and protein degradation functions. A total of 12 transcripts were assessed by quantitative PCR, of which ATM, ATR, CTNNB1, MSH6, MRE11A, PCNA, APC, CENPE, and GRB2 were in agreement with the hybridization results. Since most of these molecules are directly or indirectly associated with cell-cycle regulation, DNA damage response, and transcription control, our results strongly suggest key roles for those biological functions in mammalian preimplantation development.

Mitochondrial content and gene expression profiles in oocyte-derived embryos of cattle selected on the basis of brilliant cresyl blue staining

The aim of this study was to investigate the developmental rate, lipid and mitochondrial distribution and gene expression in oocyte-derived embryos selected on the basis of brilliant cresyl blue (BCB) staining. Lipid content and mitochondrial distribution in Day 8 blastocysts were evaluated by fluorescence intensity, while gene expression was analyzed by real-time PCR. The proportion of blastocysts (30.9%) was greater (P<0.05) in BCB+ than in BCB- oocytes (13%) but not different (P>0.05) from the control group (28.2%). Total cell number was also greater in BCB+ (155.1 ± 36.2) than in BCB- (116.6 ± 40.5) and control (127.5 ± 35.7) blastocysts. Furthermore, the apoptotic cell number was less in BCB+ (3.7 ± 4.4) than in BCB- blastocysts (8.7 ± 8.7) but not different from the control group (5.9 ± 3.9). BCB+ embryos contained more mitochondria compared to BCB- embryos (P<0.05). There was no significant difference in intercellular lipid accumulation in embryos from all groups. Interferon-τ (IFNτ), transforming growth factor β1 (TGFB1) and secreted seminal-vesicle Ly-6 protein 1 (SSLP1) gene expression was greater in BCB+ than in BCB- blastocysts. By contrast, Bcl2-associated X protein (BAX) and heterogeneous nuclear ribonucleoprotein A2/B1 (HNRNPA2B1) gene expression was greater in BCB- than in BCB+ and control embryos. In conclusion, oocyte-derived embryos selected on the basis of BCB staining showed differences in developmental rate, quality, mitochondrial content and target gene expression compared to control embryos.

Effects of oocyte quality, incubation time and maturation environment on the number of chromosomal abnormalities in IVF-derived early bovine embryos

Chromosomal aberrations are one of the major causes of embryo developmental failures in mammals. The occurrence of these types of abnormalities is higher in in vitro-produced (IVP) embryos. The aim of the present study was to investigate the effect of oocyte morphology and maturation conditions on the rate of chromosomal abnormalities in bovine preimplantational embryos. To this end, 790 early cattle embryos derived from oocytes with different morphologies and matured under different conditions, including maturation period (24 v. 36 h) and maturation media (five different serum supplements in TCM-199), were evaluated cytogenetically in three sequential experiments. The rates of normal diploidy and abnormal haploidy, polyploidy and aneuploidy were determined in each embryo. Throughout all the experiments, the rate of chromosomal abnormalities was significantly (P < 0.05) affected by oocyte morphology and maturation conditions (maturation time and culture medium). Lower morphological quality was associated with a high rate of chromosome abnormalities (P < 0.05). Moreover, polyploidy was associated with increased maturation time (P < 0.01), whereas the maturation medium significantly (P < 0.05) affected the rates of haploidy and polyploidy. In general, supplementing the maturation medium with oestrous cow serum or fetal calf serum resulted in higher rates of chromosomal aberrations (P < 0.05) compared with the other serum supplements tested (bovine steer serum, anoestroues cow serum, bovine amniotic fluid and bovine serum albumin). On the basis of the results of the present study, we conclude that the morphological quality of oocytes and the maturation conditions affect the rate of chromosomal abnormalities in IVP bovine embryos.

Effect of dibutyryl cyclic adenosine monophosphate on reactive oxygen species and glutathione of porcine oocytes, apoptosis of cumulus cells, and embryonic development

The present study was conducted to investigate the effect of dibutyryl cyclic adenosine monophosphate (dbcAMP) supplemented into porcine maturation medium on reactive oxygen species (ROS) and glutathione (GSH) levels of oocytes, and apoptosis of cumulus cells (CC). In addition, the effect of dbcAMP on embryonic development following in vitro fertilization (IVF) or parthenogenetic activation (PA) was determined. Cumulus-oocyte complexes (COCs) were cultured in 0 mM (control), 0.5 mM, 1 mM, 5 mM, or 10 mM dbcAMP-supplemented medium for 22 h, then for another 22 h without dbcAMP. GSH and ROS levels of oocytes were assessed at 44 h of culture by dichlorohydrofluorescein diacetate or 4-chloromethyl-6,8-difluoro-7-hydroxycoumarin staining, respectively. Additionally, COCs were cultured in 0.5 mM or 1 mM dbcAMP and then fertilized in vitro or activated parthenogenetically. Embryonic development and blastocyst cell numbers and apoptosis levels on day 8 of culture were investigated. CC apoptosis at 44 h of culture and blastocyst apoptosis were assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. GSH levels in the 0.5 mM dbcAMP and control groups were increased (P < 0.05), while levels of oocyte ROS and CC apoptosis in the control, 0.5 mM, and 1 mM dbcAMP groups were significantly lower than the levels in other groups. Cleavage and blastocyst rates, cell numbers, and apoptosis levels were not significantly different in embryos derived by either IVF or PA among the groups, with the exception of significantly increased apoptotic levels in IVF blastocysts produced from oocytes treated with 1 mM dbcAMP. In conclusion, dbcAMP treatment during in vitro maturation (IVM) did not improve embryonic development under our study's parameters compared with control conditions, although 0.5 mM dbcAMP showed significantly higher GSH levels and lower blastocyst apoptotic levels compared with 1 mM dbcAMP.

Zona pellucida birefringence correlates with developmental capacity of bovine oocytes classified by maturational environment, COC morphology and G6PDH activity

In the present study we aimed to analyse structural changes during in vitro maturation of the bovine zona pellucida (ZP) by scanning electron microscopy (SEM) ands zona pellucida birefringence (ZPB). Here we show that alterations during in vitro maturation invasively analysed by SEM are reflected in ZPB. In vivo-matured oocytes displayed significantly lower birefringence parameters and significantly higher blastocyst rates compared with in vitro-derived oocytes (39.1% vs 21.6%). The same was observed for in vitro-matured oocytes with cumulus-oocyte complex (COC) Quality 1 (Q1) compared with Q3-COCs with respect to zona birefringence and developmental capacity. Immature oocytes with Q1-COCs displayed higher ZPB values and a higher developmental capacity to the blastocyst stage (27.7% vs 16.9%) compared with immature Q3-COCs. Considering in vitro-matured oocytes, only those with Q1-COC showed a trend for ZPB similar to in vivo-matured oocytes. Therefore, a decreasing trend for ZPB during in vitro maturation seems to be typical for high-quality oocytes and successful cytoplasmic maturation. In accordance, fully-grown immature oocytes reached significantly higher blastocyst rates (32.0% vs 11.5%) and lower ZPB values compared with still-growing ones. In conclusion, we successfully evaluated the applicability of zona imaging to bovine oocytes: alterations during in vitro maturation invasively analysed by scanning electron microscopy were reflected in the birefringence of the zona pellucida of bovine oocytes affecting developmental capacity at the same value. Therefore ZPB measurement by live zona imaging has potential to become a new tool to assess correctness of in vitro maturation and to predict developmental competence.

Oocyte quality determines bovine embryo development after fertilisation with hydrogen peroxide-stressed spermatozoa

Exposure of gametes to specific stressors at sublethal levels can enhance the gametes’ subsequent performance in processes such as cryopreservation. In the present study, bull spermatozoa were subjected to H2O2 for 4 h at 100-, 200- and 500-μM levels; computer-assisted sperm analysis (CASA) and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) assay were used for evaluation of subsequent sperm motility and DNA integrity, respectively. Exposure of spermatozoa to H2O2 did not affect sperm motility but DNA integrity was negatively affected by 500 μM H2O2 compared with mock-exposed spermatozoa, whereas both motility and DNA integrity were affected compared with untreated spermatozoa. Nevertheless, insemination of oocytes with spermatozoa exposed to 200 μM H2O2 increased fertilisation, cleavage and blastocyst rates (P < 0.05). Furthermore, the higher blastocyst yield after fertilisation of oocytes with spermatozoa exposed to 200 μM H2O2 was related to oocyte diameter, with large–medium oocytes yielding higher blastocyst rates, while small-diameter oocytes consistently failed to develop into blastocysts. In conclusion, the results indicate that exposure of spermatozoa to 200 μM H2O2 before sperm–oocyte interaction may enhance in vitro embryo production in cattle. However, this increased embryo production is largely dependent on the intrinsic quality of the oocytes.

Expression pattern of apoptotic genes in vitrified-thawed bovine oocytes

This study describes a method for quantification of transcripts from low numbers of bovine oocytes using real time RT-PCR. The objective was to evaluate the expression pattern of apoptotic genes (Fas, FasL, Bax and Bcl-2) in vitrified-thawed oocytes. Oocytes were evaluated at germinal vesicle stage; at 15 h of maturation; after vitrification and warming at 15 h of maturation and at 9 h of additional maturation. All transcripts showed an increase in at least 1.2-fold change post-vitrification warming, but the levels tended to decrease at 9 h of maturation post-vitrification warming. Transcript abundance for Fas mRNA was 1.4-fold for oocytes after vitrification and warming. The level of Fas mRNA upon maturation was 0.8-fold. The increase in the abundance of FasL mRNA was 2.1, while it was 0.5-fold relative to control. Vitrification resulted in 1.5-fold change in Bax mRNA expression in oocytes. After 9 h of maturation post-vitrification warming, the level for Bax mRNA was 0.6-fold. The mRNA for Bcl-2 was nearly the same after vitrification and warming. The abundance of mRNA for Bcl-2 was 1.2-fold in vitrified oocytes and fell (p = 0.05) to 0.5 at 9 h of maturation post-vitrification and warming. The up-regulation of apoptotic genes in vitrified oocytes may be an early indicator of reduced developmental competence following vitrification. Yet, results from terminal deoxynucleotidyl transferase dUTP nick end labelling and caspase assays did not support the evidence of apoptosis in embryos derived from large numbers of vitrified oocytes.

The effects of cysteine addition during in vitro maturation on the developmental competence, ROS, GSH and apoptosis level of bovine oocytes exposed to heat stress

In the present study, we investigated the effects of various concentrations of cysteine (0.0, 0.6, 1.2 and 1.8 mM) added to the maturation medium on nuclear maturation and subsequent embryonic development of bovine oocytes exposed to heat stress (HS: set at 39.5 °C for 5 h, 40.0 °C for 5 h, 40.5 °C for 6 h, and 40.0 °C for 4 h versus 38.5 °C for 20 h as the control group). This regime mimicked the circadian rhythm of the vaginal temperature of lactating dairy cows during the summer season in southwestern Japan. Moreover, we also evaluated the oocyte's reactive oxygen species (ROS) and glutathione (GSH) levels and the apoptosis levels of the oocytes and cumulus cells in the presence or absence of 1.2 mM cysteine. As a result, HS in the without-cysteine group significantly suppressed (p < 0.05) both the nuclear maturation rate up to the metaphase (M)II stage and the blastocyst formation rate compared with that of the control group. In addition, this group showed significantly higher (p < 0.05) ROS levels and significantly lower (p < 0.05) GSH levels than those of the control group. Moreover, the level of TdT-mediated dUTP nick end labelling (TUNEL)-positive cumulus cells in the HS without-cysteine group was significantly higher (p < 0.05) than that of the control group. However, the addition of 1.2 mM cysteine to the maturation medium restored not only the nuclear maturation, blastocyst formation rates and GSH contents, but also increased the ROS and TUNEL-positive levels of the cumulus cells, but not oocytes, to that of the control group. These results indicate that the addition of 1.2 mM cysteine during in vitro maturation (IVM) may alleviate the influence of heat stress for oocyte developmental competence by increasing GSH content and inhibiting the production of oocyte ROS followed by apoptosis of cumulus cells.

Predictive value of oocyte morphology in human IVF: a systematic review of the literature

BACKGROUND

Non-invasive selection of developmentally competent human oocytes may increase the overall efficiency of human assisted reproduction and is regarded as crucial in countries where legal, social or religious factors restrict the production of supernumerary embryos. The purpose of this study was to summarize the predictive value for IVF success of morphological features of the oocyte that can be obtained by light or polarized microscopic investigations.

METHODS

Studies about oocyte morphology and IVF/ICSI outcomes were identified by using a systematic literature search.

RESULTS

Fifty relevant articles were identified: 33 analysed a single feature, 9 observed multiple features and investigated the effect of these features individually, 8 summarized the effect of individual features. Investigated structures were the following: meiotic spindle (15 papers), zona pellucida (15 papers), vacuoles or refractile bodies (14 papers), polar body shape (12 papers), oocyte shape (10 papers), dark cytoplasm or diffuse granulation (12 papers), perivitelline space (11 papers), central cytoplasmic granulation (8 papers), cumulus–oocyte complex (6 papers) and cytoplasm viscosity and membrane resistance characteristics (2 papers). None of these features were unanimously evaluated to have prognostic value for further developmental competence of oocytes.

CONCLUSIONS

No clear tendency in recent publications to a general increase in predictive value of morphological features was found. These contradicting data underline the importance of more intensive and coordinated research to reach a consensus and fully exploit the predictive potential of morphological examination of human oocytes.

Cumulus cell features and nuclear chromatin configuration of in vitro matured canine COCs and the influence of in vivo serum progesterone concentrations of ovary donors

Phenotype integrity is viewed as an indicator of cumulus-oocyte complex (COC) viability. The objectives of this study were: (a) to observe the influence of cumulus investment expansion on the nuclear chromatin configuration of canine oocytes matured in vitro; (b) to examine the relationship between cumulus cell (CC) expansion and its morphology after in vitro maturation (IVM); (c) to ascertain the influence of in vivo serum progesterone (SP) concentrations of ovary donors on oocyte nuclear maturation, CC phenotypes and degrees of CC expansion of in vitro matured COCs. After 48 h of IVM in modified TCM 199, CCs from grade 1 and 2 COCs were stained with propidium iodide. Oocyte chromatin configuration was visualized by Hoechst 33342 stain. Results showed that oocyte IVM was not influenced by degree of CC expansion (D1, D2 and D3) in COCs. From the CC types (C1, C2 and C3), number of C1 types was higher at D1 expansion and differed from those observed at D2 and D3 expansions. Additionally, rates of apoptosis in D1 CCs were lower than those observed in D2 CCs (p < 0.05). Oocyte nuclear maturation was not influenced by in vivo SP concentrations of ovary donors. On the other hand, D3 expansion prevailed in COCs from bitches at SP > 2.5 ng/ml (p < 0.001). Moreover, in vitro CC apoptosis was associated both with low (0-1 ng/ml) and with high (>5 ng/ml) in vivo SP levels. These findings indicate that morphology of CCs from in vitro matured dog oocytes gives valuable information on viability of COCs and could possibly be used as a parameter in predicting the quality of oocytes destined for in vitro fertilization (IVF) and their outcomes.