Extracellular DNA levels and cytokine profiles in preterm birth: a cohort study

The content of eight different cytokines, cell-free DNA (cfDNA) and cell-free fetal DNA (cffDNA) in women's plasma during preterm birth (PB) was studied. The purpose of this study was to identify the relationships between the investigated factors and determine their prognostic significance.

Venous blood samples were collected from 45 women with PB and 35 women with full-term labor at 22-31 and 32-36 weeks of gestation, as well as from 17 women during labor at 39-40 weeks of gestation. The concentration of IL-2, IL-4, IL-6, IL-8, IL-10, GM-CSF, IFN-γ and TNF-α cytokines in peripheral blood plasma was measured by multiplex method. The level of cfDNA and cffDNA was evaluated using PCR analysis.

It was found that, the level of IL-6, IL-8 and cfDNA in the blood was significantly increased in women with PB at 22-31 weeks of gestation (p = 0.044, p = 0.001, p < 0.001) and 32-36 weeks of gestation (p = 0.025, p = 0.001, p = 0.002) compared to women with physiological pregnancy at the same terms. The level of cffDNA (p = 0.014) was significantly increased in women with PB at 32-36 weeks of gestation. The IL-8 content had a significant correlation with the cfDNA level in women with PB at all stages of labor and with the cffDNA level in the group who gave birth at 32-36 weeks of gestation. There was no correlation between IL-8, cfDNA and cffDNA, but there was consistency with other cytokines at all studied terms and during delivery in the term-delivery group.

The results of the study suggest that cfDNA is a potential marker of PB and show that the aberrant relationship between cfDNA and IL-8 may be important in the genesis of PB.