P-713 Preimplantation DNA methylation screening (PIMS) illustrates the outcome of assisted reproductive technology
Authors: Liu J , Gao Y , Yao X , Chen Z 
Published: June 2023

Abstract

Study question
It is unknown whether using DNA methylation can improve the outcome of ART and can exclude the imprinted gene diseases.

Summary answer
Our study provides a criterion on selecting blastocyst according to DNA methylome, which can improve live birth rate and decrease birth defect rate.

What is known already
How to select the embryos is one key factor that can determine the successful rate of ART. As aneuploidy exists in 20-30% of blastocysts, preimplantation genetic screening (PGS) has been widely used, which increases the live birth rate. Unfortunately, the live birth rate remains around 50% even with the help of PGS. DNA methylation is known to play important function during embryogenesis. Previous study has shown that a large proportion of human embryos have abnormal DNA methylome. However, whether DNA methylation pattern can affect the clinical outcome of ART has not been investigated in clinics.

Study design, size, duration
To determine whether PIMS method can increase live birth rate during ART, the whole genome DNA methylation of 3-5 biopsied cells from trophectoderm were measured. The methylation level and chromosome copy number variation (CNV) were analyzed by using the methylome data. elective single embryo transfer (eSET) will be performed for embryos with euploid chromosome. The live birth rate, pregnant rate and abortion rate will be examined. 182 families including 800 blastocysts were enrolled in PIMT.

Participants/materials, setting, methods
Eligible couples include advanced maternal age, recurrent pregnancy loss with unknown reason, recurrent implantation failure with unknown reason, severe oligoteratozoospermia. Eligible couples must have two or more good-quality blastocysts. We call a blastocyst as good quality if the blastocyst is 4BC or better according to the Gardner morphologic criteria on day 5-6 of embryo culture.

Main results and the role of chance
No one has ever performed clinical trial to investigate the impact of DNA methylation of blastocyst on the outcome of artificial assisted reproductive (ART). Here, we performed PIMS using the biopsied trophectoderm of 800 blastocysts. Chromosome copy number variation and DNA methylation pattern were analyzed by using methylome data. 162 of euploid embryos were transferred. Our data show that significant variation of DNA methylation level of blastocysts can be observed in both younger women (£37 years old) and older women (&gt;37 years). Blastocysts with global methylation level around 0.26 have the highest birth and pregnancy rate, but the lowest abortion rate. The higher the difference methylation value from 0.26 is, the lower the birth rate becomes. Furthermore, by using artificial intelligence method according to different methylated regions between the embryos succeeding in live-birth and those failing in live-birth, we can robustly predict the clinical outcome of blastocysts. PIMS method can find the abnormality of DNA methylation states in the imprinted control regions which can cause the imprinted diseases. Our study provides a criterion on selecting blastocyst according to DNA methylome during ART, which can potentially improve the live birth rate and decrease the birth defect rate.

Limitations, reasons for caution
Because of the low coverage of single cell DNA methylome, PIMS method cannot cover all imprinted control regions.

Wider implications of the findings
PIMS method can potentially find more human diseases which is caused by DNA methylation mutation.

Trial registration number
NCT03642574