Determination of the blood level of mitochondrial DNA for the prediction of pregnancy complication

Background. Mitochondria play an important role in the regulation of cellular energy metabolism. During pregnancy, there is a higher mitochondrial functional activity, while at the same time with increased mitochondrial energy generation, there is an elevated production of reactive oxygen species and nitrogen, which is attended by a compensatory rise in the activity of antioxidant protection. In contrast, mitochondrial dysfunctions varying in nature lead to uncontrolled oxidative stress (OS) that damages cells and tissues, which is considered to be one of the leading factors for the pathogenesis of pregnancy complications, such as premature birth (PB), preeclampsia (PE), and fetal growth retardation (FGR). Based on the fact that pregnancy is associated with progressive OS, even in case of its physiological course, it has been suggested that changes in the number of mitochondrial DNA (mtDNA) copies in the blood of pregnant women can serve as a biological marker for the degree of OS induction and for the increased risk of this or that complication during pregnancy. Objective. To determine plasma mtDNA level in women during physiological and complicated pregnancy. Subjects and methods. The course of pregnancy and the outcomes of labor were analyzed in 142 were analyzed. According to the results of the analysis, all the examinees were divided into 4 groups: 1) women with physiological pregnancy (PP); 2) those with PB; 3) those with pregnancy complicated by PE; 4) those with pregnancy complicated by FGR. The plasma amount of mtDNA was determined by real-time polymerase chain reaction (PCR). The number of PCR products in the reaction was estimated by the Ct value that was defined as the nth cycle of the reaction, at which fluorescence reaches a predetermined threshold value. The amount of a PCR product of the target gene (mtDNA D-loop) was normalized relative to that of a PCR product of the nuclear β-microglobulin gene. The copy number of mtDNA was expressed in the standard units 2(-ΔС). Results and discussion. In complicated pregnancy, the level of mtDNA was found to be higher just in the first trimester. The amount of mtDNA was increased by 49% in pregnant women diagnosed with FGR (p < 0.01), by 48% in those with PB (p < 0.01), and by 25% in those who developed PE (p < 0.05) versus those with PP. The relative level of mtDNA was 153±32, 292±69, 205±84, and 299±101 in the PP, PB, PE, and FGR groups, respectively. ROC analysis showed that the sensitivity and specificity of the assay of blood mtDNA levels in pregnant women in the first trimester in the diagnosis of PB was 100% and 91%, respectively; those in that of PE and FGR were 71% and 64% and 83% and 90%, respectively. The blood mtDNA threshold values associated with an increased risk of PB, PE, and FGR were determined to be 2(-ΔС) ≥209, 2(-ΔС) ≥158, and 2(-ΔС) ≥221, respectively. Conclusion. The determination of plasma mtDNA levels in the first trimester of pregnancy allows identification of a group of women at an increased risk for PB, PE, and FGR.

physiological pregnancy, premature birth, preeclampsia, fetal growth retardation, pregnancy complications, mitochondria, mitochondrial DNA