O-007 Association of successful embryo development and pregnancy outcome with redox state as measured by human non-mercaptalbumin in embryo culture medium
Authors: Kusumoto Y , Sato M , Yasukawa K , Uranbileg B , Ikeda H , Yatomi Y 
Published: June 2023

Abstract

Study question
Is the redox state in the embryo culture medium, as measured by oxidized albumin, associated with successful embryo development and pregnancy outcome?

Summary answer
The level of oxidized albumin in the culture medium was the most important variable in predicting blastocyst formation andwas associated with miscarriage after transfer.

What is known already
Human serum albumin (HSA), the most abundant protein in the plasma, exerts important antioxidant activities against oxidative damage. HSA exists as oxidized human non-mercaptalbumin (HNA) and reduced human mercaptalbumin. HNA is attracting attention because of its novel role as a marker reflecting oxidative state, and HNA levels are known to increase in oxidative stress diseases such as kidney disease, diabetes, liver disease or Parkinson's disease. On the other hand, in human IVF, most culture medium are supplemented with HSA as a protein source, but no previous studies have examined the relationship between HNA and IVF outcomes.

Study design, size, duration
We followed the pregnancy outcomes for 40 cycles of single blastocyst transfer out of the retrospective study, which enrolled a total of 173 embryos cultured to the blastocyst stage from a total of 91 patients who underwent IVF/ICSI cycle between February 2018 and July 2018.

Participants/materials, setting, methods
Prior to using the medium for embryo culture, the redox state was assessed with HNA level. HNA level, patient age, IVF/ICSI and oocyte maturity were analyzed as factors associated with blastocyst formation on day 5 and 6 after fertilization, and a machine learning model was developed by using the Random Forest (RF) algorithm to predict blastocyst formation. We also examined whether the factors made a difference in pregnancy outcomes.

Main results and the role of chance
The median %HNA in the culture medium was 89.36% (range, 80.12% to 94.84%), which was much higher than the value for blood in healthy humans, (approximately 25%). Blastocyst formation was observed in 41.04% (71/173) embryos. In both univariate and multivariate analyses, successful blastocyst development was associated with a lower %HNA in the culture medium (p = 0.001), a younger patient age (p &lt; 0.001), and the use of standard IVF (p = 0.007). A prediction model for successful blastocyst formation was developed using a RF algorithm with four factors (%HNA, patient age, fertilizationmethod, and oocyte maturation stage). The RF model developed using 70% of samples (training set, n = 121) was validated in the remaining testing set (n = 52) and produced an area under the curve of 0.761, where %HNA in the culture medium was the most important variable for the prediction of blastocyst formation, followed by patient age. The HNA levels were significantly higher in the group of embryos that resulted in miscarriage after blastocyst transfer (93.15% vs. 89.28%, P = 0.0498).

Limitations, reasons for caution
This study was conducted in G-TL medium only. Further studies are needed to elucidate the association of %HNA and embryo development, and to predict the transfer success rate by using other commonly used media.

Wider implications of the findings
In the IVF medium, which is supposed to mimic the body environment, the %HNA showed a high oxidized state compared to the body itself; it is suggesting it may cause unsuccessful IVF results and lower live birth rate. Controlling the oxidation level may help to create a more appropriate environment.

Trial registration number
not applicable