OBJECTIVETo investigate the correlation of genomic DNA methylation level with unexplained early spontaneous abortion and analyze the role of DNMT1, DNMT3A and DNMT3B.

METHODSForty-five villus samples from spontaneous abortion cases (with 33 maternal peripheral blood samples) and 44 villus samples from induced abortion (with 34 maternal peripheral blood samples) were examined with high-pressure liquid chromatography (HPLC) to measure the overall methylation level of the genomic DNA. The expressions of DNMT mRNAs were detected using fluorescence quantitative-PCR in the villus samples from 33 induced abortion cases and 30 spontaneous abortion cases.

RESULTSGenomic DNA methylation level was significantly lower in the villus in spontaneous abortion group than in induced abortion group (P<0.01), but similar in the maternal blood samples between the two groups (P>0.05). The mean mRNA expression levels of DNMT1 and DNMT3A in the villus were significantly lower in spontaneous abortion group than in induced abortion group (P<0.05), but DNMT3B expression showed no significant difference between them (P>0.05).

CONCLUSIONInsufficient genomic DNA methylation in the villus does exist in human early spontaneous abortion, and this insufficiency is probably associated with down-regulated expressions of DNMT1 and DNMT3A.