Postmortem interval estimation of time since death: impact of non-histone binding proteins, immunohistochemical, and histopathological changes in vivo.

The postmortem interval (PMI) is one of the primary objectives and challenging tasks proposed for determining the time of death. This study aimed to estimate the PMI using serum levels of high mobility group box 1 (HMGB1), a biomarker of pyroptotic cell death, along with desmin immunohistochemical and histological analyses of the gastrocnemius muscle in rats at various time intervals. Serum and gastrocnemius muscle samples were collected at zero, 24-, 48-, 72-, and 96 hours postmortem from 50 rats maintained at 22 ± 2°C. The results revealed that the HMGB1 level peaked at 48 hours and dropped in a time-dependent manner afterward. Immunohistochemical analysis revealed a progressive decrease in desmin expression, with severe immunoreactivity (38.19%) at 0 hours, dropping to a minimal level (1.09%) 96 hours after death. Histological analysis of the gastrocnemius muscle at 96 hours revealed significant vacuolation, loss of normal architecture, reduced nuclear visibility, and complete autolysis of all myocytes. In conclusion, HMGB1 levels, desmin immunoreactivity, and histopathological alterations seen in the gastrocnemius muscle could be helpful, valuable, and potential markers for accurately determining PMIs in humans in future studies.