Degradation of Kidney and Psoas Muscle Proteins as Indicators of Post-Mortem Interval in a Rat Model, with Use of Lateral Flow Technology

We investigated potential protein markers of post-mortem interval (PMI) using rat kidney and psoas muscle. Tissue samples were taken at 12 h intervals for up to 96 h after death by suffocation. Expression levels of eight soluble proteins were analyzed by Western blotting. Degradation patterns of selected proteins were clearly divided into three groups: short-term, mid-term, and long-term PMI markers based on the half maximum intensity of intact protein expression. In kidney, glycogen synthase (GS) and glycogen synthase kinase-3 beta were degraded completely within 48 h making them short-term PMI markers. AMP-activated protein kinase alpha, caspase 3 and GS were short-term PMI markers in psoas muscle. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was a mid-term PMI marker in both tissues. Expression levels of the typical long-term PMI markers, p53 and beta-catenin, were constant for at least 96 h post-mortem in both tissues. The degradation patterns of GS and caspase-3 were verified by immunohistochemistry in both tissues. GAPDH was chosen as a test PMI protein to perform a lateral flow assay (LFA). The presence of recombinant GAPDH was clearly detected in LFA and quantified in a concentration-dependent manner. These results suggest that LFA might be used to estimate PMI at a crime scene.