P-535 DNA methylation abnormalities induced by advanced maternal age in villi in early pregnancy prime a high-risk state for spontaneous abortion
Authors: Chen W , Meng Q , Lingyue H 
Published: June 2023

Abstract

Study question
What’s the epigenetic effect of advanced maternal age (AMA, &gt; =35 at delivery) on human villus in early pregnancy and its relationship with spontaneous abortion (SA)?

Summary answer
AMA-induced local changes in DNA methylome would perturb villous transcriptome and trophoblast cellular function, which may partly explain increased risk of SA in AMA pregnancy.

What is known already
The proportion of AMA in living births has increased in many countries over recent decades. However, AMA has been regarded as an independent risk factor for many pregnancy complications, including SA, which are closely associated with placental dysfunction in early pregnancy. Currently, researches about the epigenetic influence of AMA has been extremely limited, and only one study in mice tried to explore the DNA methylation alterations of eight ICRs in AMA placenta. The DNA methylation pattern of the human placenta in AMA pregnancy is still blank, and a comprehensive genome-wide investigation of AMA’s influence is urgently needed.

Study design, size, duration
We profiled the DNA methylome of 24 human chorionic villi samples (CVSs) from early pregnancies in AMA and young maternal age (YMA) and 11 CVSs from early spontaneous abortion cases, and the transcriptome of 10 CVSs from AMA and YMA pregnancies. Trophoblast cellular impairment were investigated by repressing target gene in trophoblast cell lineage.

Participants/materials, setting, methods
CVSs from early pregnancies were collected, the DNA methylome were profiled, using reduced representation bisulfite sequencing (RRBS), and the transcriptome were profiled. with mRNA sequencing(mRNA-seq). Single-cell villous transcriptional altas presented the expression patterns of targeted AMA-/SA-related genes. Cellular function experiment werewas performed after the knockdown of GNE expression in HTR8-S/Vneo cells.

Main results and the role of chance
AMA-induced local DNA methylation changes, defined as AMA-related differentially methylated regions (DMRs), might be derived from the abnormal expression of genes taking part in DNA demethylation, such as GADD45B. These DNA methylation changes were significantly enriched in the processes involved in Notch signaling and extracellular matrix organization, and reflected in the transcriptional alterations in the corresponding biological processes and specific genes, too. Furthermore, the DNA methylation level of special AMA-related DMRs not only significantly changed in AMA, but also showed more excessive defects in CVS from spontaneous abortion (SA), including four AMA-related DMRs whose nearby genes were overlapping AMA-related differentially expressed genes (DEGs) (CDK11A, C19orf71, COL5A1, and GNE). The decreased DNA methylation level of DMR near GNE was positively correlated with the downregulated expression of GNE in AMA. Single-cell altas further revealed the comparatively high expression of GNE in trophoblast lineage, and the knockdown of GNE in HTR8-S/Vneo cells significantly impaired cellular proliferation and migration. Our study provides valuable resources to investigate AMA-induced epigenetic abnormalities and bring a new insight for explaining the increased risks of pregnancy complications in AMA pregnancy.

Limitations, reasons for caution
The samples size was still small, a larger cohort study would be helpful to verify our findings in future. Meanwhile, though the high co-relationships between the expression of specific DEGs and the DNA methylation level of nearby DMRs, the detailed mechanisms in gene expression regulation need to be further explored.

Wider implications of the findings
It deepened our understanding of the influences of AMA and provided novel evidence to develop strategies for the diagnosis, providence and even therapy for pregnancy complications in AMA.

Trial registration number
not applicable