Canine oocyte nuclear maturation with Nano-ozone (NZS) supplementation: The alterations of antioxidant, and oxidant status and CDK1, cyclin B1 expressions

This study aims to evaluate the effects of nano-ozone solution (NZS) on canine oocyte nuclear maturation, associated with the alterations of antioxidant and oxidant status and cyclin-dependent kinase 1 (CDK1), cyclin B1 gene expressions. Oocytes were cultured in four distinct concentrations of NZS (0.5, 1, 2, and 5 µg/mL) and parthenogenetically activated. The rates of oocytes arrested at the Germinal Vesicle (GV), Germinal Vesicle Breakdown (GVBD), Metaphase I (MI), and Metaphase II (MII) stages were statistically different among groups (P < 0.05). The oocytes cultured in 1 µg/mL NZS yielded the best oocyte maturation rate at the MI and MII stages; however, the lowest maturation and high degeneration rates were observed in Group E. The measurements of Malondialdehyde (MDA), reduced Glutathione (GSH), Superoxide Dismutase (SOD), and Ferric Reducing/Antioxidant Power assay (FRAP) were performed from IVM culture media. No statistical difference was observed in SOD and MDA results (P > 0.05). GSH levels were statistically significant between Group A-Group E (p = 0.003), Group B-Group E (p = 0.045), and Group E-Group D (p = 0.021). The culture media in Group D and Group E had high FRAP concentrations and significantly differed between groups (P < 0.05). CDK1, and cyclin B1 genes, which are subunits of maturation-promoting factor (MPF), are upregulated in Group B and Group C, while are downregulated in oocytes of Group E. This study showed that low, controlled doses of NZS (1 µg/mL) supplementation could improve the meiotic competence of canine oocytes and lead to positive response in expressions of CDK1 and cyclin B1 on the gene level.

Vincristine-associated total antioxidant and oxidant status of ovaries and in vitro nuclear oocyte maturation in dogs with canine transmissible venereal tumor

The aim of this study is to evaluate the effects of scheduled vincristine sulfate therapy on canine oocyte quality and nuclear oocyte maturation, associated with total antioxidant and oxidant status of ovaries and Anti-Müllerian Hormone (AMH) concentrations in dogs with Canine Transmissible Venereal Tumor (CTVT). Six bitches suffering from CTVT and six healthy bitches were included in the study. Hemogram was carried out weekly. AMH measurements and ovariohysterectomy operations were performed after the termination of vincristine sulfate therapies. Tissue samples from ovaries were utilized for Malondialdehyde (MDA), reduced Glutathione (GSH), Superoxide Dismutase (SOD), Total Anti-oxidative Status (TAS), Total Oxidative Status (TOS) measurements, and Oxidative Stress Index (OSI) was calculated. Collected oocytes were evaluated for meiotic competence, after In Vitro Maturation (IVM) and parthenogenetic activation. No difference between the two groups was observed in hematologic parameters (P > 0.05). Meiotic stages of Germinal Vesicle Break Down (GVBD), Metaphase I (MI), and Metaphase II (MII) were significantly different between groups (P < 0.05). The number of oocytes reaching MII and meiotic resumption was lower in the CTVT group. Furthermore, AMH concentrations, oxidant parameters (OSI, TOS, and MDA), and antioxidant parameters (GSH, SOD, and TAS) were also statistically different between groups (P < 0.05). The results of this study show that vincristine sulfate application in the treatment of CTVT could alter oxidant/antioxidant status in ovaries. Apart from these, oocyte quality and IVM rates seem to decline related to gonadotoxicity. Moreover, AMH could be an important marker in the evaluation of oocyte qualities in bitches, as it is in women.

Effects of oxygen concentration on in vitro maturation of canine oocytes in a chemically defined serum-free medium

Canine oocytes require an extended period of culture (72 h) in vitro for nuclear maturation to the metaphase II stage, which also results in high degeneration. Canine cumulus oocyte complexes were isolated by slicing from ovaries collected after ovariohysterectomy and cultured in serum-free synthetic oviductal fluid incubated at low (5%) or high (20%) oxygen levels. Changes in oocyte nuclear maturation rates, H2O2 levels within the oocytes and mRNAs of reactive oxygen species inhibitory genes superoxide dismutase 1 and 2 (SOD1 and 2), glutathione reductase (GSR), glutathione peroxidase (GPX1), and catalase (CAT) were quantified. Higher meiotic resumption from germinal vesicle breakdown up to MII was observed in low O2 (41.8±13.1%) compared to high O2 (15.8±8.2%) (P=0.014) after 52 h of culture (n=112). Extension of the culture period up to 84 h at low O2 (n=457 oocytes) produced the highest meiotic resumption at 72 h (64.1±6.0%; P=0.008), compared with 52 h. Oocytes (n=110) cultured in high O2 contained higher levels of peroxidase measured using the 2′,7′-dichlorodihydrofluorescein diacetate fluorescence assay after 72 h of culture compared with low O2 (P=0.004). High O2-cultured oocytes also showed higher amounts of SOD1, SOD2, GSR, GPX1, and CAT mRNA. Vitamin E in high oxygen level was able to decrease degeneration (P=0.008) but had no improving effect on percentage of oocytes in MII. These results for the first time showed that low oxygen gas composition improves nuclear maturation rates and alleviates the oxidative stress for canine oocytes during in vitro maturation.