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Oxygen Tension on Human Embryonic Development

2019-06-02 23:09:17 | BioPortfolio

Summary

In mammals, uterine environment is at low oxygen concentration (2-8% O2). Thus, human embryo culture under low O2 tension (5%) is now recommended by European Society of Human Reproduction and Embryology (ESHRE) revised guidelines for good practices in in vitro fertilization (IVF) labs. Indeed, hypoxia seems to improve embryo quality at cleavage and blastocyst stages, presumably by reducing damages of oxidative stress (OS). Nevertheless, recent meta-analyses concluded only with a low evidence to a superiority of hypoxia on IVF/ICSI outcomes. Furthermore, a study on mouse embryos suggested a negative impact of OS only at cleavage stage. The aim of the present prospective randomized study was to investigate this hypothesis for the first time in human embryos.

Description

In mammals, uterine environment is at low oxygen tension, between 2 and 8% O2 . However, most IVF labs perform embryo culture at atmospheric tension (around 20% O2). Several randomized studies in human embryos have reported the superiority of hypoxia (5%) in terms of embryo quality and blastulation rates. This fact might be explained by a more physiological environment, probably inducing a decrease in oxidative stress (OS), which has a harmful impact on embryo development. Other studies have also suggested that before compaction, OS damages might be irreversible.

Wale et Gardner have investigated this impact of oxygen tension on mouse embryo development, by comparing four culture conditions: (i) group 1: culture exclusively at 5% O2 ; (ii) group 2: culture at 5% from Day 0 to Day 2, then at 20% from Day 2 to Day 4; (iii) group 3: at 20% then at 5% from Day 2; (iv) and group 4: culture exclusively at 20% Interestingly, no difference in terms of blastulation had been reported between groups 1 and 2, suggesting the OS might impact only at cleavage stage, and that switching culture under atmospheric conditions from Day 2/3 might not influence embryo development thereafter.

Hence, all those investigations suggest that embryo culture using trigas incubators (5% O2, 6% CO2 and 89% N2) would be preferable. However, this system is very expensive, notably due to a high N2 consumption, and requires a more complicated logistics (e.g. N2 levels monitoring). Yet, Wale and Gardner's results imply that sequential culture conditions (trigas from Day 0 to Day 2/3, then conventional incubator at 20% O2 until blastocyst stage) could be an valuable option, reducing the costs and, essentially, without any detrimental impact on embryo development.

The present study has two main objectives: (i) to confirm the improvement in embryo quality under low oxygen tension and (ii) to demonstrate the negative impact of OS only at cleavage stage in human embryos, as assumed by Wale and Gardner. For that purpose, we designed an original prospective randomized study comparing three culture conditions: (i) culture excusively at 20% O2 (Day 0 to Day 6) (Group A); (ii) culture exclusively at 5% O2 (Day 0 to Day 6) (Group B); (iii) culture at 5% from Day 0 to Day 3, then at 20% from Day 3 to Day 6) (Group C). Inclusion criteria and outcome measures are detailed in the following sections.

Study Design

Conditions

Infertility

Intervention

20% oxygen, 5% oxygen, 20 % and 5 % oxygen

Status

Completed

Source

Assistance Publique - Hôpitaux de Paris

Results (where available)

View Results

Links

Published on BioPortfolio: 2019-06-02T23:09:17-0400

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Medical and Biotech [MESH] Definitions

The rate at which oxygen is used by a tissue; microliters of oxygen STPD used per milligram of tissue per hour; the rate at which oxygen enters the blood from alveolar gas, equal in the steady state to the consumption of oxygen by tissue metabolism throughout the body. (Stedman, 25th ed, p346)

Stable oxygen atoms that have the same atomic number as the element oxygen, but differ in atomic weight. O-17 and 18 are stable oxygen isotopes.

Molecules or ions formed by the incomplete one-electron reduction of oxygen. These reactive oxygen intermediates include SINGLET OXYGEN; SUPEROXIDES; PEROXIDES; HYDROXYL RADICAL; and HYPOCHLOROUS ACID. They contribute to the microbicidal activity of PHAGOCYTES, regulation of signal transduction and gene expression, and the oxidative damage to NUCLEIC ACIDS; PROTEINS; and LIPIDS.

Unstable isotopes of oxygen that decay or disintegrate emitting radiation. O atoms with atomic weights 13, 14, 15, 19, and 20 are radioactive oxygen isotopes.

An excited state of molecular oxygen generated photochemically or chemically. Singlet oxygen reacts with a variety of biological molecules such as NUCLEIC ACIDS; PROTEINS; and LIPIDS; causing oxidative damages.

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