Novielli Chiara, Mandò Chiara, Tabano Silvia, Anelli Gaia M, Fontana Laura, Antonazzo Patrizio, Miozzo Monica, Cetin Irene
"L. Sacco" Department of Biomedical and Clinical Sciences, Laboratory of Maternal-Fetal Translational Research "Giorgio Pardi", Università degli Studi di Milano, via G.B. Grassi 74, 20157 Milano, Italy.
Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Via F. Sforza 35, 20122 Milano, Italy.
Placenta. 2017 Jul;55:63-70. doi: 10.1016/j.placenta.2017.05.008. Epub 2017 May 12.
Intrauterine growth restriction (IUGR) and preeclampsia (PE) are pregnancy disorders characterized by placental insufficiency with oxygen/nutrient restriction and oxidative stress, all influencing mitochondria functionality and number. Moreover, IUGR and PE fetuses are predisposed to diseases later in life, and this might occur through epigenetic alterations. Here we analyze content and methylation of mitochondrial DNA (mtDNA), for the first time in IUGR and PE singleton fetuses, to identify possible alterations in mtDNA levels and/or epigenetic control of mitochondrial loci relevant to replication (D-loop) and functionality (mt-TF/RNR1: protein synthesis, mt-CO1: respiratory chain complex).
We studied 35 term and 8 preterm control, 31 IUGR, 17 PE/IUGR and 17 PE human singleton pregnancies with elective cesarean delivery. Fetal cord blood was collected and evaluated for biochemical parameters. Extracted DNA was subjected to Real-time PCR to assess mtDNA content and analyzed for D-loop, mt-TF/RNR1 and mt-CO1 methylation by bisulfite conversion and pyrosequencing.
mtDNA levels were increased in all pathologic groups compared to controls. Mitochondrial loci showed very low methylation levels in all samples; D-loop methylation was further decreased in the most severe cases and associated to umbilical vein pO. mt-CO1 methylation levels inversely correlated to mtDNA content.
Increased mtDNA levels in IUGR, PE/IUGR and PE cord blood may denote a fetal response to placental insufficiency. Hypomethylation of D-loop, mt-TF/RNR1 and mt-CO1 loci confirms their relevance in pregnancy.
胎儿宫内生长受限（IUGR）和子痫前期（PE）是妊娠疾病，其特征为胎盘功能不全，伴有氧/营养物质限制和氧化应激，所有这些都会影响线粒体的功能和数量。此外，IUGR和PE胎儿在生命后期易患疾病，这可能通过表观遗传改变而发生。在此，我们首次分析了IUGR和PE单胎胎儿线粒体DNA（mtDNA）的含量和甲基化情况，以确定mtDNA水平和/或与复制（D环）及功能（mt-TF/RNR1：蛋白质合成，mt-CO1：呼吸链复合体）相关的线粒体基因座的表观遗传控制方面可能存在的改变。
我们研究了35例足月和8例早产对照、31例IUGR、17例PE/IUGR和17例PE的单胎妊娠，并进行择期剖宫产。采集胎儿脐带血并评估其生化参数。提取的DNA进行实时PCR以评估mtDNA含量，并通过亚硫酸氢盐转化和焦磷酸测序分析D环、mt-TF/RNR1和mt-CO1的甲基化情况。
与对照组相比，所有病理组的mtDNA水平均升高。所有样本中线粒体基因座的甲基化水平都非常低；在最严重的病例中，D环甲基化进一步降低，并与脐静脉pO相关。mt-CO1甲基化水平与mtDNA含量呈负相关。
IUGR、PE/IUGR和PE脐带血中mtDNA水平升高可能表明胎儿对胎盘功能不全的反应。D环、mt-TF/RNR1和mt-CO1基因座的低甲基化证实了它们在妊娠中的相关性。
