Effects of gaseous atmosphere and antioxidants on the development and cryotolerance of bovine embryos at different periods ofin vitroculture

Abstract

This study examined the effects of antioxidant supplementation and O2 tension on embryo development, cryotolerance and intracellular reactive oxygen species (ROS) levels. The antioxidant supplementation consisted of 0.6 mM cysteine (CYST); 0.6 mM cysteine + 100 μM cysteamine (C+C); 100 IU catalase (CAT) or 100 μM β-mercaptoethanol (β-ME) for 3 or 7 days of in vitro culture (IVC). Two O2 tensions (20% O2 [5% CO2 in air] or 7% O2, 5% CO2 and 88% N2 [gaseous mixture]) were examined. After 7 days of antioxidant supplementation, the blastocyst frequencies were adversely affected (P < 0.05) by CYST (11.2%) and C+C (1.44%), as well as by low O2 tension (17.2% and 11.11% for 20% and 7% O2, respectively) compared with the control (26.6%). The blastocyst re-expansion rates were not affected (P > 0.05) by the treatments (range, 66-100%). After 3 days of antioxidant supplementation, the blastocyst frequencies were not affected (P > 0.05) by any of the antioxidants (range, 43.6-48.5%), but they were reduced by low O2 tension (P < 0.05) (52.1% and 38.4% for 20% and 7% O2, respectively). The intracellular ROS levels, demonstrated as arbitrary fluorescence units, were not affected (P > 0.05) by antioxidant treatment (range, 0.78 to 0.95) or by O2 tension (0.86 and 0.88 for 20% and 7% O2, respectively). The re-expansion rates were not affected (P > 0.05) by any of the treatments (range, 63.6-93.3%). In conclusion, intracellular antioxidant supplementation and low O2 tension throughout the entire IVC period were deleterious to embryo development. However, antioxidant supplementation up to day 3 of IVC did not affect the blastocyst frequencies or intracellular ROS levels.

Oxygen tension affects histone remodeling of in vitro–produced embryos in a bovine model

“…In fact, some studies report different results in which they report that lower O 2 tension yields better developmental rates in bovine embryos (for review see [19]). However, others have reported that higher O 2 tension could be most suitable for IVP in bovine [17], and other studies go further to suggest that low O 2 has negative effects on the rate of embryonic development [60]. As presented here, there are also studies showing that that varying O 2 level does not affect the rate of embryonic development during IVP [61,62].…”

Connexin 43 coupling in bovine cumulus cells, during the follicular growth phase, and its relationship to in vitro embryo outcomes

“…These studies used group culture dynamics and had differences in the media used, which may explain our differing results. Moreover, many studies have seen no or detrimental effects when comparing the culture of presumptive bovine embryos in 5% O 2 as opposed to in air (Mingoti, Castro, Mao, Sa Barretto, & Garcia, ; Rocha‐Frigoni, LeãoLeao, Nogueira, Accorsi, & Mingoti, ; Somfai et al, ). It has been suggested that when presumptive zygotes are cultured in the presence of cumulus cells they show improved blastocyst rates at higher O 2 levels than in the hypoxic 5% O 2 conditions (Corrêa, Rumpf, Mundim, Franco, & Dode, ).…”

Use of natural antioxidants in in vitro mammalian embryo production

“…This stress results from an imbalance between ROS and antioxidant substances, with a predominance of the former (ROCHA-FRIGONI et al, 2015). ROS are represented by a variety of molecules and free radicals produced from oxygen metabolism in biological systems.…”

“…From this radical, other biochemical reactions can lead to the formation of hydrogen peroxide (H 2 O 2 ) and the hydroxyl radical (•OH) (TAKAHASHI, 2012). All these oxygen-derived metabolites exhibit high instability and reactivity due to at least one unpaired electron in their outer orbit (ROCHA-FRIGONI et al, 2015).…”

“…These media must provide all the nutrients and factors necessary for the development of gametes and embryos, as well as maintain the balance of molecules that can harm the system (CROCOMO et al, 2012;SANTOS et al, 2017). In this regard, one of the main factors that can influence the success of IVEP is oxidative stress caused by the accumulation of reactive oxygen species (ROS) that impair the integrity of cells and their macromolecules thus interfering with in vitro development (ROCHA-FRIGONI et al, 2015).…”