A Low Oxygen Atmosphere during IVF Accelerates the Kinetic of Formation of In Vitro Produced Ovine Blastocysts

Abstract

Among the factors that affect in vitro embryo development, oxygen atmosphere is considered to be of great influence. In this study, we evaluated the influence of two different oxygen atmospheres during in vitro fertilization (IVF) of ovine oocytes on their developmental capacity and quality assessed by cryotolerance. Cumulus oocyte complexes derived from ovaries of slaughtered sheep were matured in vitro and subsequently fertilized under low (5%) or high (20%) oxygen atmospheres, and cultured in SOF + aa + 0.4% BSA in 5% CO2 and 5% O2 up to blastocyst stage. The cleavage rates obtained in the fertilization system at 20% O2 were significantly higher than those obtained in the 5% O2 fertilization system (61.2% vs 50.8%; p < 0.01). The distribution of cleaved oocytes at 22, 26 and 40 h of culture intervals was not different in the low or high O2 atmosphere (31.4%, 26.4% and 42.1% vs 28.0%, 29.3% and 42.7% respectively). Blastocysts output on the 6th day post-fertilization (dpf) was significantly higher when oocytes were fertilized under 5% O2 concentration (63.04% in 5% O2 vs 47.36% in 20% O2), while on the 7th dpf the higher number of blastocysts was obtained in the 20% O2 system (35.10%.in 20% O2 vs 26.09% in 5% O2). After vitrification no differences were observed between low or high oxygen atmosphere in the viability rates of blastocysts obtained on day 6 (93.6% vs 96.5%), on day 7 (46.3% vs 41.7%) and on day 8 (11.1% vs 6.6%). After differential staining, no significant differences were observed in the total cell number and inner cell mass and trophoblastic cells ratio of blastocysts produced on 6 dpf (189.6 +/- 51.3 and 0.260 +/- 0.07 vs 223.3 +/- 45.6 and 0.277 +/- 0.09), on 7 dpf (168.3 +/- 25.1 and 0.316 +/- 0.06 vs 172.1 +/- 33,6 and 0.320 +/- 0.06) and on 8 dpf (121.2 +/- 23,8 and 0.302 +/- 0.03 vs 117.0 +/- 35.1 and 0.313 +/- 0.04) under low or high oxygen atmosphere respectively). In conclusion, our data suggest that low oxygen atmosphere during IVF affects positively the production of high quality ovine blastocysts.

Effect of vitamin A supplementation at different gaseous environments on in vitro development of pre-implantation sheep embryos to the blastocyst stage

“…Thompson et al (1990) reported that culturing sheep and cattle embryos at 5% to 10% O 2 levels was optimal for embryo development in vitro. Similar observations were also made by Bernardi et al (1996) and Leoni et al (2007). In this context, this study was carried out to determine the antioxidant potential of vitamin A (all-trans retinol) in sheep in vitro oocyte and embryo culture under conditions of low and high O 2 concentrations, respectively.…”

Unveiling mRNA Changes During Meiotic Progression and Pre-Implantation Development: Help from Large Animal Models

“…A positive association between the time of first cleavage post-insemination in vitro and developmental competence has been clearly demonstrated, with those oocytes cleaving earliest being more likely to reach the blastocyst stage than their later-cleaving counterparts [74][75][76]. In our model of differential developmental competence, ovine blastocysts deriving from prepubertal oocytes showed a delay in development compared to adult ones.…”

Effect of α-tocopherol supplementation on in vitro maturation of sheep oocytes and in vitro development of preimplantation sheep embryos to the blastocyst stage

“…Higher developmental rates were observed in embryos cultured in vitro under 5% O 2 environment than those cultured under 20% O 2 environment [23]. Greater rates of cleavage and blastocyst-output seventh day post fertilization were reported in embryos obtained from oocytes fertilized at 20% oxygen atmosphere [24]. Also, the antioxidant hypotaurine was reported to exert beneficial effects on in vitro bovine embryo development in both 5% and 20% oxygen atmospheres [25].…”