Redox Regulation and Oxidative Stress in Mammalian Oocytes and Embryos Developed In Vivo and In Vitro

Abstract

Oocytes and preimplantation embryos require careful regulation of the redox environment for optimal development both in vivo and in vitro. Reactive oxygen species (ROS) are generated throughout development as a result of cellular metabolism and enzyme reactions. ROS production can result in (i) oxidative eustress, where ROS are helpful signalling molecules with beneficial physiological functions and where the redox state of the cell is maintained within homeostatic range by a closely coupled system of antioxidants and antioxidant enzymes, or (ii) oxidative distress, where excess ROS are deleterious and impair normal cellular function. in vitro culture of embryos exacerbates ROS production due to a range of issues including culture-medium composition and laboratory culture conditions. This increase in ROS can be detrimental not only to assisted reproductive success rates but can also result in epigenetic and genetic changes in the embryo, resulting in transgenerational effects. This review examines the effects of oxidative stress in the oocyte and preimplantation embryo in both the in vivo and in vitro environment, identifies mechanisms responsible for oxidative stress in the oocyte/embryo in culture and approaches to reduce these problems, and briefly examines the potential impacts on future generations.

Relevance of Aquaporins for Gamete Function and Cryopreservation

“…Finally, in mouse oocytes, the transport of water and glycerol through the plasma membrane occurs via simple diffusion. While membrane channels are involved in the transit of water and cryoprotectants [ 121 , 122 ], the fact that mouse oocytes show low permeability to water and glycerol suggests that AQPs are not very abundant in these cells [ 123 ]. In spite of this, the treatment of mouse oocytes with mercury chloride, which inhibits all AQPs except AQP7, partially blocks water flow through the plasma membrane [ 124 , 125 ], thus suggesting that not only AQP7 but also other mercury-sensitive AQPs play an important function in water transport in mouse oocytes.…”

“…It is important to highlight that, in a similar fashion to that reported for sperm, the redox equilibrium is of high importance for oocyte integrity, since oxidative stress can damage oocyte structures which, in turn, may compromise their function [ 122 ]. Nevertheless, and to the best of our knowledge, no study has investigated the implication of AQPs in the transport of H 2 O 2 , either in mitochondria or through the plasma membrane, in mammalian oocytes.…”

Glutamine and norepinephrine in follicular fluid synergistically enhance the antioxidant capacity of human granulosa cells and the outcome of IVF-ET

“…Oxidative stress plays an important role in reproductive processes, including follicular development, oocyte maturation, ovulation and fertilization, as well as embryo implantation and embryo development 15 . Excessive generation of ROS, if not efficiently counterbalanced by antioxidative enzymes, may cause damage to oocytes and GCs, leading to poor oocyte quality 9 .…”

Effects of Dithiothreitol on Fertilization and Early Development in Sea Urchin

“…Nevertheless, further investigation is needed to understand to what extent the redox state of the egg cytoplasm is affected by the given conditions of DTT treatment and to identify the major targets of DTT that are accountable for our observations. Indeed, the importance of exquisite control of the redox state in oocytes and embryonic cells is increasingly being appreciated [ 75 ]. On the other hand, our observation of the apparently normal migration of female and male pronuclei in the eggs pretreated and fertilized in seawater containing DTT ( Figure 5 C) suggests that it is not likely that the centripetal movement of the cortical actin filaments makes a significant contribution to the transportation of the egg-engulfed sperm.…”