Placental imprinting gene methylation profiles of fetuses with intrauterine growth restriction

Intrauterine growth restriction (IUGR) is a condition characterized by the failure of the fetus to achieve its genetically determined growth potential, and it is associated with significant perinatal morbidity and mortality. Fetal growth is a complex process regulated by a variety of factors, including those of maternal, placental, and fetal origin. The etiology of fetal growth restriction (FGR) is multifactorial, involving varying degrees of genetic and environmental factors. Investigating epigenetic alterations in the placenta can contribute to understanding the molecular mechanisms underlying intrauterine impaired fetal growth and the increased susceptibility to diseases later in life. Several studies have shown that proper epigenetic regulation of both imprinted and non-imprinted genes in the placenta is critical for placental development and fetal growth, and that imprinted genes are highly expressed in the placenta. This study aims to analyze the DNA methylation profiles of imprinted genes in placental tissue samples from fetuses diagnosed with IUGR and to investigate the effects of epigenetic mechanisms on fetal growth. In this retrospective case-control study, a total of 85 pregnancies delivered between 2015 and 2023 were examined. The study group consisted of 46 pregnancies diagnosed with FGR, while the control group included 39 pregnancies with appropriate birth weight for gestational age. Genomic DNA was extracted from paraffin-embedded placental tissue blocks using the GeneAll® Exgene™ Clinic SV mini kit. The DNA samples obtained were analyzed for methylation levels of imprinted genes using the SALSA® MS-MLPA® (methylation-specific multiplex ligation-dependent probe amplification) technique with the Probemix ME034-C1 Multi-locus Imprinting kit. Statistical analysis revealed significantly lower methylation levels in the H19 (Position 3) and GRB10 (Position 1) gene regions in the IUGR group compared to controls (p = 0.048 and p = 0.035, respectively). When comparing copy number variations in the gene regions covered by the assay — including three probes each for H19 and PEG3, two probes each for KCNQ1OT1, MEST, MEG3, MEG8, SNRPN, PLAGL1, GRB10, and GNASXL, and one probe each for NESP55, GNAS-AS1, and GNAS A/B — no statistically significant differences were observed (p > 0.05). Examination of demographic data showed significant differences between groups in gestational age at birth, birth weight, preterm birth rate, and neonatal intensive care unit admission. These findings suggest that epigenetic dysregulation, particularly altered methylation of imprinted genes such as H19 and GRB10, may contribute to the development of IUGR. Our study highlights the potential of placental imprinting gene methylation as a biomarker for better understanding the mechanisms of fetal growth.