Caspase 9 and Caspase 3 Immunohistochemical Pattern in Skeletal and Cardiac Muscles at Different Times after Death: An Experimental Study on PMI Estimation

Background: The estimation of the post mortem interval (PMI) is a challenge for forensic
pathologists because data emerging from methods commonly applied are not always conclusive,
since several conditions exist that may affect the reliability of these parameters. Thus, new approaches
have been proposed to overcome such a limit. In recent years, several studies have been performed
on proteins analyzing their expression/degradation patterns in relation to the progressing of the
post mortem interval. (2) Methods: The immunoreactivity patterns of two apoptosis mediators—
Caspase 9 and Caspase 3—have been tested in order to evaluate their potential role as markers
of the post mortem interval. The immunohistochemical analysis was performed on samples of
skeletal and cardiac muscles obtained from rats at 0, 4, 8, 12, 24 and 72 h after death. (3) Results:
The observed immunoreactivity patterns of both Caspase 9 and Caspase 3 showed a significant
correlation with increasing post mortem interval either in skeletal or cardiac muscles, while the
comparison of the immunoreactivity patterns of the two apoptotic mediators within each tissue
appeared consistent with a preliminary activation of the “initiator” Caspase 9, which, in turn,
subsequently activates the “executioner” Caspase 3. (4) Conclusion: The different expressions and
decrease immunohistochemically observed on both caspases with progressing PMI support the
usefulness of the combined analysis for post mortem interval estimation