Postmortem muscle protein degradation in humans as a tool for PMI delimitation

Abstract

Forensic estimation of time since death relies on diverse approaches, including measurement and comparison of environmental and body core temperature and analysis of insect colonization on a dead body. However, most of the applied methods have practical limitations or provide insufficient results under certain circumstances. Thus, new methods that can easily be implemented into forensic routine work are required to deliver more and discrete information about the postmortem interval (PMI). Following a previous work on skeletal muscle degradation in the porcine model, we analyzed human postmortem skeletal muscle samples of 40 forensic cases by Western blotting and casein zymography. Our results demonstrate predictable protein degradation processes in human muscle that are distinctly associated with temperature and the PMI. We provide information on promising degradation markers for certain periods of time postmortem, which can be useful tools for time since death delimitation. In addition, we discuss external influencing factors such as age, body mass index, sex, and cause of death that need to be considered in future routine application of the method in humans.

A field study to evaluate PMI estimation methods for advanced decomposition stages

“…Comparing degradation patterns of tropomyosin, this protein turned out to be very stable towards decomposition, as it has been shown previously for humans and pigs [10,26]. The significant loss of native cardiac troponin T (cTnT) after day 5, in comparison, partly contradicts previously described results in pigs, where this change occurred after 9 to 10 days postmortem at 21°C under controlled laboratory conditions [10].…”

“…Qualitative changes of protein band patterns such as occurring degradation products or the loss of native protein bands can be valuable clues for PMI estimation. However, to date, there is only limited reference data for humans [26] and available data regarding the porcine animal model exclusively originate from controlled laboratory studies [10]. To provide further reference data, we tested the method in uncontrolled field conditions by comparing results of this animal study to already available reference data from controlled environments.…”

“…The study of skeletal muscle protein decay is promising [10] and offers some advantages: its immediate use following death, the high abundance of muscle tissue in human bodies, and the ease of sampling. Although this method has already proven its potential in human application [26,27], it requires additional validation, especially on behalf of possible influencing factors. Last but not the least, decomposition scoring systems are still of little help in forensic practice [28,29].…”

Potential use of GAPDH m-RNA in estimating PMI in brain tissue of albino rats at different environmental conditions

“…The earliest changes after death (within the first 24 h postmortem) include the development and regression of rigor mortis, the progression of livor mortis and algor mortis. Although these methods are applied to assess the PMI in daily forensic work, there are still great inaccuracies and limitations (Pittner et al, 2016). Several days postmortem, forensic entomology has shown to provide valuable information about the time since death.…”

Interdisziplinarität in der Forensik

“…Diese durch Spaltung verursachten Veränderungen der Proteinprofile können sogar statistisch je einem spezifischen postmortalen Zeitraum zugeordnet werden, so dass über ein vorliegendes Proteinmuster (z.B. Protein 1 ist bereits abgebaut, Proteine 2 und 3 sind erhalten) Rückschlüsse auf die Liegezeit gezogen werden können . In bestimmten Fällen kann die neu entwickelte Methode bereits in der rechtsmedizinischen Routine angewandt werden.…”