Postmortem mitochondrial membrane potential dynamics as a temperature-independent biomarker for early postmortem interval estimation.

Background: Accurate determination of postmortem interval (PMI) and cause of death (COD) is a critical challenge in forensic pathology, with significant implications for criminal investigations. Traditional PMI estimation methods are based on macroscopic changes and are influenced by environmental factors and investigator subjectivity. Recent advances in molecular biology have shown that certain cellular structures, such as mitochondria, retain functionality after death, making them potential biomarkers for forensic assessment. As mitochondria play a central role in cellular metabolism and respond dynamically to post-mortem hypoxia, investigation of mitochondrial membrane potential (ΔΨm) may provide a quantifiable and objective method for estimating PMI.

Results: We successfully isolated mitochondria from post-mortem tissues and cultured cells, confirming their purity and membrane integrity. Regression analysis showed a strong linear correlation between ΔΨm and PMI in brain, myocardium and skeletal muscle within the first 15-18 h postmortem, with skeletal muscle showing the highest correlation coefficient. ΔΨm values remained stable at different temperatures, suggesting that it is a robust biomarker for estimating PMI. In vitro experiments under hypoxic conditions revealed a transient increase in ΔΨm at 24 h, accompanied by ATP depletion, ROS accumulation and shifts in mitochondrial fission and fusion dynamics, indicating mitochondrial adaptation to oxygen deprivation.

Conclusions: These findings highlight ΔΨm as a promising temperature stable biomarker for early assessment of PMI. The observed mitochondrial adaptations suggest that ΔΨm-based models may improve forensic accuracy and provide insights into postmortem metabolic processes. Further validation with human postmortem samples is essential to refine these models and explore their applicability to COD determination.