Cell free DNA and miRNA analysis by quantitative real-time polymerase chain reaction in postmortem interval determination

For the first time, French scientist Emanuelle Fodere named the diagnosis of death as somatic death and defined it as irreversible loss of spontaneous circulation, spontaneous breathing and central nervous system. The time after death is defined as the postmortem interval (PMI). Knowing the time of death is important in forensic cases. Postmortem changes are evaluated in two separate groups as early and late period. After death due to different reasons, similar changes occur in the body such as algor mortis, rigor mortis, livor mortis and putrefication. Physiological and biochemical changes such as the degree of freezing of the blood, measurement of beard and hair, measurement of stomach content, blood sugar measurement, bone marrow cells, measurement of blood pH and also used in the field of forensic entomology are used as traditional methods in forensic medicine. Traditional methods and entomological data can be affected by environmental conditions and cause errors in the determination of time of death. Genetic materials that are less affected by environmental conditions have been included in PMI studies recently. In the study, quantitative analyzes of the levels of extracellular free DNA and selected miRNAs were made in serum samples taken from rats at different time intervals, and the possible correlation between the postmortem period and the postmortem interval determination were investigated. Analysis results Ct, ΔCt and ΔΔCt and fold change were evaluated separately, and mir-16 and mir-122 had a statistically lower ΔCt mean than other miRNAs at all times; mir-16 had lower mean ΔΔCt at 24 and 48 hours; In the fold chage changes, it was observed that mir-16 had the highest mean at the 24th hour. In the study conducted for the elapsed time after death and extracellular free DNA determination, it was observed that our reference genes, GAPDH and ACTB, decreased over time and had a statistically higher mean at 0, 6, and 12 hours than at 24 and 48 hours. This study is the first quantitative study on the possible effect of extracellular free DNA in postmortem interval determination.