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Oxygen tension in culture • History
- 20% O2 imposed by practical reasons • Theory
• Gametes/embryos are exposed to much lower O2 tension in vivo
• Unnecessarily high O2 tension in vitro could enhance oxidative damage, especially after a change in embryo metabolism occurring from the morula stage
Maternal antioxidant enzyme RNAs provide early ROS protection
Morin et al., 2017
Oygen consumption increases
Expression of antioxidant enzymes increases
Existing evidence indicates that use of 5% O2 is associated to improved clinical outcome
• (Overwhelming animal data consistently confirm that atmospheric oxygen is detrimental to embryo development)
• Cochrane meta‐analysis (Bontekoe et al., 2012)
- Lower O2 tension associated to higher live birt rate (OR 1.39;
95% CI 1.11 to 1.76; P = 0.005)
- Similar outcomes in favour of 5% O2 for clinical and ongoing PR
• Is there more to tell?
• Animal studies on 2% O2 are ongoing
• Preliminary human study (Kaser et al., 2016) is suggestive that a sequential 5% ‐ 2% O2 regimen is compatible with 40% blastulation rate (but cell no. may be affected!)
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PRECONGRESS COURSE 02 I BARCELONA, SPAIN – 1 JULY 2018 83
