Loss of imprinting and aberrant methylation of IGF2 in placentas from pregnancies complicated with fetal growth restriction.

The objective of this study was to investigate the hypothesis that the altered epigenetic mechanisms that regulate IGF2 imprinting in placentas from fetal growth restricted (FGR) pregnancies affect IGF2 expression leading to impaired fetal growth. We investigated gene transcription, genotyping and the methylation patterns of IGF2 from 31 and 17 placentas from FGR-complicated and normal pregnancies, respectively. A statistically significant decrease in IGF2 mRNA levels was observed in the placentas from the FGR pregnancies. Loss of imprinting (LOI) was only detected in the abnormal placentas. The evaluation of the percentage of the methylated reference (PMR) of two different potentially differentially methylated regions (DMR) demonstrated significant PMR values in both sites for the normal and FGR pregnancies with no significant differences. Our results suggest the involvement of the IGF2 imprinted gene in placental function and fetal growth and the possible association of epigenetic alterations with the pathophysiology of fetal growth restriction.