CELL-FREE MEMBRANE-BOUND AND MEMBRANE-UNBOUND MITOCHONDRIAL DNA IN MATERNAL CIRCULATION IN PREECLAMPSIA

PURPOSE: Cell-free circulating mitochondrial DNA (CFCmtDNA) is a damage-associated molecular pattern (DAMP) that activates Toll-like receptor-9 (TLR-9). Previous studies suggested that CFCmtDNA may be a potential pathogenic trigger or a contributor to the maintenance of preeclampsia. The main objectives of this study were 1) to determine absolute concentrations of CFCmtDNA, in membrane-bound and -unbound states, independent of nuclear DNA (nDNA) changes, in cases with preeclampsia and healthy controls and 2) to implement a penalized regression analysis to establish the contribution of CFCmtDNA to preeclampsia diagnosis and its interaction with commonly collected patient characteristics. METHODS: Plasma CFCmtDNA (MT-ND5 gene) concentrations were quantified using an absolute quantification protocol. DNase I concentrations in maternal plasma were measured using an enzyme-linked immunosorbent assay and TLR-9 activity was monitored using SEAP reporter 293 cells expressing the human TLR-9 gene. RESULTS: Concentrations of CFCmtDNA were reduced in preeclampsia compared to healthy controls both in lysis buffer-treated samples (P=0.02) and in samples not treated with lysis buffer (P< 0.0001). Even though CFCmtDNA concentrations were reduced, plasma from women with preeclampsia induced greater TLR-9 activation than plasma from gestational age matched controls (P< 0.01). Multivariate analysis showed that high concentrations of nDNA and DNase I, a prior history of preeclampsia, and a lower concentration of CFCmtDNA are predictors of preeclampsia diagnosis. CONCLUSIONS: In conclusion, our data demonstrate an increased immunostimulatory potential of CFCmtDNA and upregulation of DNA degradation mechanisms in women with preeclampsia at the third trimester.