The mechanism of serum cell-free DNA release in postmortem subjects and novel markers to estimate the postmortem intervals

Cell-free DNA (cfDNA) is DNA released from dying cells into the serum. The aim of the present study is to elucidate the mechanism of cell-free DNA (cfDNA) release in postmortem subjects by assaying Cytokeratin 18 (M30 and M65), cyclophilin A (CyPA), and myeloperoxidase (MPO) levels and to evaluate whether these levels are useful as markers for estimating postmortem intervals. Serum (n = 54) was sampled from postmortem autopsied Japanese subjects. cfDNA was extracted and M30, M65, CyPA, and MPO in serum were assayed by enzyme-linked immunosorbent assay. Significantly higher serum levels of M30, M65, and MPO were observed in postmortem subjects than in living subjects. Although the difference was smaller, CyPA was also significantly higher in postmortem subjects than in living subjects. In addition, serum M30 and MPO levels were significantly correlated with cfDNA concentrations in postmortem subjects. Furthermore, M30 levels slightly increased according to the postmortem interval, and MPO levels at 2.5 days were significantly higher than those at <2 days. The result of regression analysis revealed a significant difference between M30/MPO levels and postmortem intervals. These findings suggested that elevated levels of cfDNA in postmortem subjects are released by apoptosis and neutrophils via NETosis and that M30 and MPO levels can be used as markers to estimate postmortem intervals.