Regulation of embryonic development and apoptotic-related gene expression by brain-derived neurotrophic factor in two different culture conditions in ovine

In vitro production of small ruminant embryos: latest improvements and further research

This review presents the latest advances in and main obstacles to the application of invitro embryo production (IVEP) systems in small ruminants. This biotechnology is an extremely important tool for genetic improvement for livestock and is essential for the establishment of other biotechnologies, such as cloning and transgenesis. At present, the IVEP market is almost non-existent for small ruminants, in contrast with the trends observed in cattle. This is probably related to the lower added value of small ruminants, lower commercial demand and fewer qualified professionals interested in this area. Moreover, there are fewer research groups working on small ruminant IVEP than those working with cattle and pigs. The heterogeneity of oocytes collected from growing follicles in live females or from ovaries collected from abattoirs remains a challenge for IVEP dissemination in goats and sheep. Of note, although the logistics of oocyte collection from live small ruminant females are more complex than in the bovine, in general the IVEP outcomes, in terms of blastocyst production, are similar. We anticipate that after appropriate training and repeatable results, the commercial demand for small ruminant invitro -produced embryos may increase.

Transcriptional profile of ovine oocytes matured under lipopolysaccharide treatment in vitro

Lipopolysaccharide (LPS) derived from gram negative bacteria cell wall is known to cause ruminal acidosis and/or infectious diseases such as metritis and mastitis which has a significant negative impact on the reproductive performance. This study aimed to investigate the effect of LPS on oocyte maturation and subsequent development in vitro. Ovine cumulus oocyte complexes (COCs) were matured in a medium supplemented with 0 (control), 0.01, 0.1, 1 and 10 μg/mL LPS. Nuclear maturation, cleavage and blastocyst rate, mitochondrial membrane potential (ΔΨm), intracellular reactive oxygen species (ROS) content and changes to the transcript abundance were evaluated. In case of the maturation rate, the percentage of oocytes reaching the MII stage was lower following exposure to 10 μg/mL LPS in comparison to the control group (P < 0.05). Moreover, the blastocyst rate decreased in case of 1 and 10 μg/mL LPS when compared to the control group (P < 0.05). ROS overproduction accompanied by a decreased ΔΨm were recorded in LPS treated oocytes in comparison to the control group (P < 0.05). The 3' tag digital gene expression profiling method revealed that 7887 genes were expressed while only seven genes exhibited changes in the transcript abundance following exposure to LPS. Tripartite motif containing 25 (TRIM25), Tripartite motif containing 26 (TRIM26), Zona Pellucida glycoprotein 3 (ZP3), Family with sequence similarity 50-member A (FAM50A), Glyoxalate and hydroxy pyruvate reductase (GRHPR), NADH ubiquinase oxireductase subunit A8 (NDUFA8) were down-regulated (P < 0.05), while only Centrin 3 (CETN3) was up-regulated (P < 0.05). Our findings show that LPS has undesirable effects on the maturation competence of ovine oocytes and subsequent embryo development. In addition, the transcriptomic profiling results may shed more light on the molecular mechanisms of LPS-induced infertility in ruminants.

In vitro supplementation of trans-10, cis-12 conjugated linoleic acid ameliorated deleterious effect of heat stress on bovine oocyte developmental competence

Environmental stresses, such as heat stress (HS), have been shown to have diverse effects on the developmental competence of oocytes. The aim of this study was to determine the effect of exogenous conjugated linoleic acid (CLA) supplementation in maturation medium on bovine oocyte maturation and developmental competence under HS condition. Accordingly, cumulus-oocyte complexes (COCs) were cultured at 41 °C and 38.5 °C for the first and second 12 h of maturation in the presence of 0 (PC), 50 (CLA50-HS) and 100 (CLA100-HS) μM CLA. Also, a group of COCs were cultured at 38.5 °C for 24 h of maturation without CLA supplementation as negative control (NC). Nuclear maturation, level of intracellular glutathione (GSH), reactive oxygen species (ROS) content, cleavage and blastocyst rates as well as relative expression of BAX, and BCL2 genes in blastocysts were investigated. Our finding for the PC and NC groups revealed that HS decreased the percentage of MII oocytes, cleavage and blastocyst rates (P < 0.05). Moreover, HS lead to an increase in ROS levels and relative expression of BAX gene, decreased the intracellular content of GSH and relative expression of BCL2 gene (P < 0.05). However, the cleavage and blastocyst rates tended to increase in the CLA-supplemented groups compared to PC group (p < 0.10). Also, ROS and GSH levels in the matured oocytes decreased and increased in the CLA50-HS group compared to the PC group (P < 0.05), respectively. The ratio of expression levels of BAX to BCL2 genes was not different between the PC and CLA50-HS groups (P > 0.05). These findings suggest that HS has undesirable effects on the maturation competence of bovine oocyte and subsequent embryo development while administration of CLA can ameliorate some of adverse effects of HS.

Supplementation with CTGF, SDF1, NGF, and HGF promotes ovine in vitro oocyte maturation and early embryo development

The strategies for improving the in vitro maturation (IVM) of domestic animal oocytes focus on promoting nuclear and cytoplasmic maturation. The identification of paracrine factors and their supplementation in the culture medium represent effective approaches for oocyte maturation and embryo development. This study investigated the effects of paracrine factor supplementation including connective tissue growth factor (CTGF), nerve growth factor (NGF), hepatocyte growth factor (HGF), and stromal derived factor 1 (SDF1) on ovine oocytes and early parthenogenetic embryos using an in vitro culture system. First, we identified the optimal concentrations of CTGF (30 ng/mL), SDF1 (10 ng/mL), NGF (3 ng/mL), and HGF (100 ng/mL) for promoting oocyte maturation, which combined, induced nuclear maturation in 94.19% of oocytes. This combination also promoted cumulus cell expansion and inhibited oocyte/cumulus apoptosis, while enabling a larger proportion (33.04%) of embryos to develop into blastocysts than in the controls and prevented embryo apoptosis. These novel findings demonstrate that the paracrine factors CTGF, SDF1, NGF, and HGF facilitate ovine oocyte and early parthenogenetic embryo development in vitro. Thus, supplementation with these factors may help optimize the IVM of ovine oocytes and early parthenogenetic embryo development strategies.

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.

Melatonin Improves The Developmental Competence of Goat Oocytes

Background

DNA methylation is one the epigenetic mechanisms, which is critically involved in gene expression. This phenomenon is mediated by DNA methyl-transferases and is affected by environmental stress, including in vitro maturation (IVM) of oocytes. Melatonin, as an antioxidant, may theoretically be involved in epigenetic regulation via reductions of reactive oxygen species. This study was performed to investigate DNA methylation and the possibility of goat oocyte development after treatment with different concentrations of melatonin.

MATERIALS AND METHODS

This experimental study was performed to investigate DNA methylation and the possibility of goat oocyte development after treatment with different concentrations of melatonin. For this purpose, oocytes with granulated cytoplasm were selected and co-cultured with at least two layers of cumulus cells in maturation medium with 10^-6 M, 10^-9 M, 10^-12 M and 0-M (as control group) of melatonin. Nucleus status, glutathione content and developmental competence of the oocytes in each experimental group were assessed. Also, expression of genes associated with DNA methylation, including DNA methyltransferase 1 (DNMT1), DNA methyltransferase 3b (DNMT3b) and DNA methyltransferase 3a (DNMT3a) was evaluated by quantitative real time-polymerase chain reaction (RT-PCR).

RESULTS

According to our findings, the percentage of oocytes that reached the M-II stage significantly increased in the 10-12 M group (P<0.05). Also, a significant elevation of glutathione content was observed in melatonin-treated oocytes (P<0.05). Analysis of blastocyst formation revealed that developmental competence of the oocytes was higher than the control group (P<0.05). It was observed that melatonin treatment decreased expression levels of DNA methyltransferases (DNMTs) and global DNA methylation (P<0.05). In addition, the expression of melatonin receptor1A (MTNR1A) was detected in both cumulus and oocyte by RT-PCR.

CONCLUSION

The results suggested that in goat model melatonin affects DNA methylation pattern, leading to an improvement in the developmental competence of the oocytes.