Molecular pathology of pulmonary edema in forensic autopsy cases with special regard to fatal hyperthermia and hypothermia.

Fatalities due to an extreme ambient temperature might present with poor or nonspecific pathologies; thus, the diagnosis of the cause of death in such cases is one of the most difficult tasks in forensic pathology. The present study investigated the molecular pathology of alveolar damage involving pulmonary edema with special regard to hyperthermia (heatstroke) and hypothermia (cold exposure) in forensic autopsy cases (total, n=122; within 48 h postmortem). Intrapulmonary mRNA and immunohistochemical expressions of matrix metalloproteinases (MMPs), intercellular adhesion molecule-1 (ICAM-1), claudin-5 (CLDN-5) and aquaporins (AQPs) were examined. Relative mRNA quantification using Taqman real-time PCR assay demonstrated higher expressions of all markers except for AQP-5 in fatal hyperthermia, and higher expression of MMP-9 in fatal hypothermia. Acute cardiac death, mechanical asphyxiation, fire fatality and intoxication did not present any characteristic findings. In immunostaining, only MMPs showed evident differences among the causes of death: MMP-9 was intensely positive in most cases of hyperthermia and hypothermia, but MMP-2 expression was evident only in hyperthermia. These findings suggest alveolar damage involving pulmonary edema, characteristic of fatal hyperthermia and hypothermia. Systematic analysis of gene expressions using real-time PCR might be a useful procedure in forensic death investigation.