Abstract
Bovine embryos are typically cultured at reduced oxygen tension to lower the impact of oxidative stress on embryo development. However, oocyte in vitro maturation (IVM) is performed at atmospheric oxygen tension since low oxygen during maturation has a negative impact on oocyte developmental competence. Lycopene, a carotenoid, acts as a powerful antioxidant and may protect the oocyte against oxidative stress during maturation at atmospheric oxygen conditions. Here, we assessed the effect of adding 0.2 μM lycopene (antioxidant), 5 μM menadione (pro-oxidant), and their combination on the generation of reactive oxygen species (ROS) in matured oocytes and the subsequent development, quality, and transcriptome of the blastocysts in a bovine in vitro model. ROS fluorescent intensity in matured oocytes was significantly lower in the lycopene group, and the resulting embryos showed a significantly higher blastocyst rate on day 8 and a lower apoptotic cell ratio than all other groups. Transcriptomic analysis disclosed a total of 296 differentially expressed genes (Benjamini–Hochberg-adjusted p < 0.05 and ≥ 1-log2-fold change) between the lycopene and control groups, where pathways associated with cellular function, metabolism, DNA repair, and anti-apoptosis were upregulated in the lycopene group. Lycopene supplementation to serum-free maturation medium neutralized excess ROS during maturation, enhanced blastocyst development and quality, and modulated the transcriptomic landscape.
Highlights
Reactive oxygen species (ROS) are reactive molecules with high pro-oxidative potential that are responsible for oxidative stress [1]
We showed that when lycopene was supplemented in the presence of menadione, lycopene may help the oocytes to partially restore their developmental capacity in a prooxidant environment
Lycopene supplementation changed the transcriptomic landscape of the resultant embryos by upregulating pathways associated with cellular function, metabolism, DNA repair, and anti-apoptosis
Summary
Reactive oxygen species (ROS) are reactive molecules with high pro-oxidative potential that are responsible for oxidative stress [1]. During in vitro embryo production (IVEP), it is challenging to recreate a balanced oxidative environment due to the high oxygen tensions to which the oocytes are exposed during manipulation and in vitro maturation (IVM). IVM is routinely performed under 5% carbon dioxide (CO2 ) and 21% oxygen (O2 ) in air [5], which is higher than the conditions that prevail within the ovarian follicle [6]. Greater oxygen tension during IVM may increase ROS production, provoke intracellular damage to the oocyte, and affect its competence for embryonic development. To overcome the damage associated with excessive ROS, exogenous antioxidants may be helpful to protect against oxidative stress during in vitro manipulations [7]. A carotenoid, is a natural antioxidant found mainly in ripe tomatoes, watermelon, and pink grapefruit [8]
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