Maintained MPF Level after Oocyte Vitrification Improves Embryonic Development after IVF, but not after Somatic Cell Nuclear Transfer

The effect of vitrification after warming on the expressions of p38, CDK1, and cyclin B in immature goat oocytes followed by in vitro maturation

Background and Aim

The combination of vitrification techniques and in vitro maturation can reduce oocyte competence. Mitogen-activated protein kinase and maturation-promoting factor are significant in oocyte meiotic maturation regulation. This study aimed to analyze vitrification's effect, after warming followed by in vitro maturation, on the expressions of protein 38 (p38), cyclin-dependent kinase 1 (CDK1), and cyclin B and oocyte maturation level.

Materials and Methods

Immature goat oocytes were soaked in vitrification and warming solutions. The procedure was followed by in vitro maturation and in vitro maturation without post-warming vitrification as a control. These oocytes, along with their cumulus, were vitrified using hemistraw in liquid nitrogen. Oocyte maturation was carried out in a maturation medium that was added with 10 μg/mL of FSH, 10 μg/mL of LH, and 1 μg/mL E₂ for 22 h. The expressions of p38, CDK1, and cyclin B were observed using immunocytochemical methods, which were assessed semiquantitatively according to the modified Remmele method. The oocyte maturation level was observed using the aceto-orcein staining method based on the achievement of chromosomes up to the metaphase II stage and/or the formation of the polar body I.

Results

p38 expression in vitrified oocytes after warming, followed by in vitro maturation, increased insignificantly (p≥0.05), with the acquisition of 3.91±2.69 and 2.69±0.50 in the control oocytes. CDK1 expression in vitrified oocytes decreased significantly (p≤0.05) after warming, followed by in vitro maturation, with the acquisition of 2.73±1.24 and 7.27±4.39 in the control oocytes. Cyclin B expression in vitrified oocytes decreased insignificantly (p≥0.05) after warming, followed by in vitro maturation, with the acquisition of 3.09±1.4 and 4.18±2.61 in the control oocytes. The proportion of vitrified oocyte maturation levels after warming, followed by in vitro maturation, decreased significantly (p≤0.05), with the acquisition of 45.45% and 77.27% in the control oocytes.

Conclusion

This study concluded that vitrification after warming resulted in an insignificant increase in p38 expression, a significant decrease in CDK1 expression, an insignificant decrease in cyclin B expression, and a significant reduction in oocyte maturation levels.

Elevation of MPF and MAPK gene expression, GSH content and mitochondrial distribution quality induced by melatonin promotes porcine oocyte maturation and development in vitro

The MPF and MAPK genes play crucial roles during oocyte maturation processes. However, the pattern of MPF and MAPK gene expression induced by melatonin (MT) and its correlation to oocyte maturation quality during the process of porcine oocyte maturation in vitro remains unexplored. To unravel it, in this study, we cultured the porcine oocytes in maturation medium supplemented with 0, 10⁻⁶, 10⁻⁹, and 10⁻¹² mol/L melatonin. Later, we analyzed the MPF and MAPK gene expression levels by RT-PCR and determined the maturation index (survival and maturation rate of oocytes). The GSH content in the single oocyte, and cytoplasmic mitochondrial maturation distribution after porcine oocyte maturation in vitro was also evaluated. We also assessed the effects of these changes on parthenogenetic embryonic developmental potential. The oocytes cultured with 10⁻⁹mol/L melatonin concentration showed higher oocyte maturation rate, and MPF and MAPK genes expression levels along with better mitochondrial distribution than the 0, 10⁻⁶, and 10⁻¹² mol/L melatonin concentrations (p < 0.05). No significant difference was observed in the survival rates when the oocytes were cultured with different melatonin concentrations. The expression of the MPF gene in the oocytes cultured with 10⁻⁶ mol/L melatonin was higher than with 10⁻¹² and 0 mol/L melatonin, and the expression of the MAPK gene in 10⁻⁶ and 10⁻¹² group was higher than the control (p < 0.05). As far as the embryonic developmental potential is concerned, the cleavage and blastocyst rate of oocytes cultured with 10⁻⁶ and 10⁻⁹ mol/L melatonin was significantly higher than the 10⁻¹² mol/L melatonin and control. In conclusion, 10⁻⁹–10⁻⁶ mol/L melatonin significantly induced the MPF and MAPK gene expression; besides, it could also be correlated with GSH content of single oocyte, mitochondrial maturation distribution, and the first polar body expulsion. These changes were also found to be associated with parthenogenetic embryo developmental potential in vitro.

Anti-apoptotic Regulation Contributes to the Successful Nuclear Reprogramming Using Cryopreserved Oocytes

Cryopreservation has a negative effect on the quality of oocytes and may be closely associated with increased levels of reactive oxygen species (ROS) and apoptotic events. The purpose of the present study was to evaluate the detrimental effects on the developmental competence of somatic cell nuclear transferred (SCNT) mouse embryos using vitrified (cryopreserved) oocytes and to evaluate the recovery effects of melatonin on cryo-damage in cloned embryos. Development of SCNT embryos using cryopreserved oocyte cytoplasm (SCNT-CROC) was inferior to those using fresh cytoplasm (SCNT-FOC). Using RNA-sequencing analysis, we found upregulation of eight pro-apoptotic-related genes (Cyct, Dapk2, Dffb, Gadd45g, Hint2, Mien1, P2rx7, and Pmaip) in the SCNT-CROC group. Furthermore, the addition of melatonin, an agent that reduces apoptosis and ROS production, enhanced blastocyst formation rates in the SCNT-CROP group when compared with the melatonin-untreated group. Additionally, melatonin treatment increased the derivation efficiency of pluripotent stem cells from cloned embryos using cryopreserved oocyte.

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Cloned mouse embryos using cryopreserved oocytes have shown increased apoptosis

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The addition of melatonin reduces apoptosis and ROS production

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Melatonin enhances development of the SCNT embryos using cryopreserved oocytes

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This system will be helpful in the derivation and application of human SCNT-ESC line

Caffeine and oocyte vitrification: Sheep as an animal model

Oocyte cryopreservation is valuable way of preserving the female germ line. Vitrification of immature ovine oocytes decreased the levels of both maturation promoting factor (MPF) and mitogen-activated protein kinase (MAPK) in metaphase II (MII) oocytes after IVM. Our aims were 1) to evaluate the effects of vitrification of ovine GV-oocytes on spindle assembly, MPF/MAP kinases activities, and preimplantation development following IVM and IVF, 2) to elucidate the impact of caffeine supplementation during IVM on the quality and development of vitrified/warmed ovine GV-oocytes. Cumulus-oocyte complexes (COCs) from mature ewes were divided into vitrified, toxicity and control groups. Oocytes from each group were matured in vitro for 18 h in caffeine free IVM medium and denuded oocytes were incubated in maturation medium supplemented with 10 mM (+) or without (−) caffeine for another 6 h. At 24 h.p.m., oocytes were evaluated for spindle configuration, MPF/MAP kinases activities or fertilized and cultured in vitro for 7 days. Caffeine supplementation did not significantly affect the percentages of oocytes with normal spindle assembly in all the groups. Caffeine supplementation during IVM did not increase the activities of both kinases in vitrified groups. Cleavage and blastocyst development were significantly lower in vitrified groups than in control. Caffeine supplementation during the last 6 h of IVM did not significantly improve the cleavage and blastocyst rates in vitrified group. In conclusion, caffeine treatment during in vitro maturation has no positive impact on the quality and development of vitrified/warmed ovine GV-oocytes after IVM/IVF and embryo culture.