Estimates of exposure to cold before death from immunohistochemical expression patterns of HSP70 in glomerular podocytes

Environmental factors such as outside temperature at the time of death are very important for forensic diagnoses and police investigations. In particular, death in a cold environment is associated with factors of forensic interest, including hypothermia, drowning in cold water, or postmortem body movement by a suspect. Hypothermia raises a special problem because of the difficulty of evaluation during autopsy. We describe here a unique method of estimating antemortem environmental temperature, involving the immunohistochemical analysis of HSP70 expression patterns in glomerular podocytes. Using this method, we found that HSP70 was present in glomerular podocytes at autopsy and that HSP70 was highly expressed, mainly in the nucleus of podocytes, in deaths associated with exposure to cold. Interestingly, this expression pattern was specific to death in a cold environment, including hypothermia and drowning in cold water. Analysis of the pattern of HSP70 expression in glomeruli may therefore be very useful in forensic diagnosis, for determining whether the antemortem environmental temperature was low. Moreover, immunohistochemical and real-time PCR assays of the molecular mechanism of HSP70 and HSF1 expression in glomeruli following exposure to cold indicated that HSP70 was rapidly translocated to the nucleus of podocytes following exposure to cold, but without new protein synthesis.