The reproductive efficiency of dairy cows decreases significantly in hot climates. Exposure to heat stress causes damage to different stages of the reproductive cycle including a decrease in the quality of oocytes. Antioxidant supplementation has been introduced as one of the main approaches to alleviate the effects of free radical damage associated with heat stress. Gamma-oryzanol (ORY), a component of rice bran oil, is introduced as a novel antioxidant. As a supplement of culture media for maturation, the effect of ORY on the development of heat-shocked bovine cumulus–oocyte complexes was evaluated in this study. At the end of maturation in vitro using the heat-shock model, a higher proportion of metaphase II oocytes (0.78 ± 0.03 vs 0.42 ± 0.03) and lower metaphase I and germinal vesicle breakdown (0.10 ± 0.02 vs 0.38 ± 0.03) were recorded for the treated group (N = 205) in comparison with the control (N = 203) (P < 0.05). Moreover, the treatment exerted upregulation of NRF2, SOD, CAT and GPX transcripts in matured oocytes and GPX in CCs, along with a considerable increase in the cleavage (0.52 ± 0.04 vs 0.33 ± 0.03) and total blastocyst rates (0.30 ± 0.03 vs 0.14 ± 0.02) (P < 0.05). These results showed that ORY increased the mRNA expression of the transcripts associated with antioxidant enzymes and enhanced the developmental potential of heat-shocked bovine oocytes and warranted further studies to explore this antioxidant’s influence on improving dairy cattle’s reproductive efficiency during heat stress.

Aneuploidy in oocytes is a leading cause of implantation failure, miscarriage and congenital disorders. During meiosis, proper timing of chromosome segregation is regulated by the spindle assembly checkpoint (SAC) and the anaphase-promoting complex/cyclosome (APC/C). However, how pharmacological manipulation of these regulatory pathways affects aneuploidy remains incompletely understood. In this study, we investigated whether SAC inhibition by reversine induces aneuploidy in mouse oocytes and whether partial inhibition of APC/C by proTAME can alleviate these errors. Germinal vesicle (GV) oocytes were matured in vitro in the presence of various concentrations of reversine. To optimize the timing of treatment, oocytes were exposed to reversine for 0, 3, 5 or 7 h, followed by culture with or without proTAME. A proTAME-only group (2.5 nM) was also included. Chromosome spreads were analyzed at the metaphase II (MII) stage to determine aneuploidy rates. Reversine (5 nM) yielded an MII maturation rate of 80.5% but induced a high aneuploidy rate of 77.0%. Sequential treatment with 2.5 nM proTAME significantly reduced aneuploidy to 33.3%. In contrast, proTAME alone led to 79.0% aneuploidy, suggesting its effect is contingent upon prior SAC disruption. These results indicate that reversine compromises chromosomal integrity, while appropriately timed, low-dose proTAME can partially rescue segregation errors. Our findings underscore the potential of pharmacologically regulating APC/C activity to reduce aneuploidy and enhance oocyte quality, offering new avenues for improving outcomes in assisted reproductive technologies.

Circadian rhythms are intrinsic, endogenously generated cycles that regulate various physiological processes, including reproductive functions. These rhythms are orchestrated by a network of core clock genes and are influenced by external environmental cues, primarily the light–dark cycle. Disruptions in circadian rhythms can have profound effects on fertility in both males and females, impacting processes such as the estrous cycle, ovulation, sperm production, implantation and pregnancy maintenance. This review comprehensively explores the molecular mechanisms underlying circadian rhythms and their influence on reproductive health, integrating evidence from both animal models and human studies. We delve into the intricate interplay between circadian genes, hormonal regulation and environmental factors, underscoring the critical importance of circadian integrity for optimal reproductive outcomes. The potential therapeutic implications of maintaining circadian rhythms are also discussed, highlighting novel avenues for enhancing reproductive health.

This work investigated the effect of zinc oxide nanoparticles functionalized with curcumin (ZnO(np)+CUR) supplementation during the in vitro maturation (IVM) of bovine oocytes on the in vitro embryo production and the cellular antioxidant response. A total of 1,625 cumulus-oocyte complexes (COCs) were cultured in the maturation medium in the absence (0 µM - control) or presence of different concentrations of ZnO(np)+CUR (3 µM, 6 µM or 12 µM). After IVM, COCs were destined either to 1) in vitro embryo production or 2) analysis of reactive oxygen species production, superoxide dismutase (SOD) activity, catalase (CAT) activity and total antioxidant capacity (FRAP). The results demonstrated that the addition of 6 and 12 µM ZnO(np)+CUR during in vitro maturation showed a higher rate of blastocyst production when compared to the control (p < 0.05). However, only 12 µM ZnO(np)+CUR treatment showed higher rates of embryo production when compared to 3µM ZnO(np)+CUR treatment. Supplementation of IVM medium with 6 µM ZnO(np)+CUR reduced ROS production (p < 0.05) compared to control and 12 µM ZnO(np)+CUR treatments. Also, the treatment containing ZnO(np)+CUR at 12 µM had lower SOD activity after IVM than control treatment. In conclusion, the best outcome for in vitro embryo production was obtained when 6 and 12 µM ZnO(np)+CUR was added during IVM of bovine oocytes. However, this improvement in in vitro embryo production was not associated with either the reduction of ROS production or SOD and CAT activities.