Postmortem interval determination using mRNA markers and DNA normalization

Advancements in estimating post-mortem interval in medico-legal practice: A comprehensive review

Estimating the Post-Mortem Interval (PMI) is a crucial aspect of forensic investigations, aiding in the resolution of criminal cases, identifying missing persons, and understanding decomposition processes. This review provides an exhaustive analysis of recent advancements in PMI estimation techniques, encompassing both traditional and emerging methodologies. Included in the study is an exhaustive examination of well-established methodologies, including algor mortis, livor mortis, and rigor mortis, as well as their shortcomings and improvements. It also delves into innovative approaches, including forensic entomology, chemical and molecular biology, microbiology, artificial intelligence, etc. Furthermore, this article discusses the integration of multiple disciplines and the potential of interdisciplinary collaboration to enhance PMI accuracy and reliability. By synthesizing the latest research findings and technological innovations, this review aims to provide forensic practitioners, law enforcement agencies, and medico-legal professionals with a comprehensive understanding of the current state-of-the-art in PMI estimation, facilitating more effective crime scene investigations and judicial proceedings.

Estimation of the post-mortem interval: a review

Determination of the time of death and post-mortem interval (PMI) is a major task for Legal and Forensic Medicine, given the implications it entails. In this respect, depending on the proximity to the moment of death, this PMI estimation will be simpler or more complex. Traditionally, the estimation of the PMI has centred upon the analysis of corporeal rigidity, body temperature and the concentration of potassium within the vitreous humour. However, in recent years, innovative methodologies that facilitate an increasingly precise prediction of the PMI have been developed. Therefore, this article aims to compile and present a comprehensive overview of these PMI estimation techniques, in order to serve as a basic guide and reference point to understand the latest advances in this area, as well as to identify their limitations and to explore the potential future directions of this discipline.

Immunohistochemical and molecular study for differential diagnosis between freshwater and saltwater drowning

The postmortem identification of drowning in the field of forensic medicine is difficult due to unspecific autopsy findings, and usually, it is a "diagnosis of exclusion". A model of drowning in salt and fresh water was established to discuss the postmortem changes after drowning and the differences between saltwater drowning (SWD) and freshwater drowning (FWD). The organs (brain and 'lung) of 30 rats were extracted at three-time points (0 h, 24 h, and 48 h) after drowning. The histopathological, immunohistochemical,l, and molecular changes in the lung and brain of rats at different time points were investigated. Results show no significant difference in pathological findings between fresh and saltwater drowning. Casp3, JNK, and ERK all showed a rise in their postmortem expression in a time-dependent way; the expression of these three genes is much greater in cases of saltwater drowning compared to cases of freshwater drowning. So, it is concluded that after 24 h and 48 h from death, potent cellular oxidative stress occurred and caused the upregulation of the studied genes.

Comparative analysis of anticoagulant influence on PMI estimation based on porcine blood metabolomics profile measured using GC-MS

Introduction

Accurate post-mortem interval (PMI) estimation is essential in forensic investigations. Although various methods for PMI determination have been developed, only an approximate estimation is still achievable, and an accurate PMI indication is still challenging. Therefore, in this study, we employed gas chromatography-mass spectrometry (GC-MS)-based metabolomics to assess post-mortem changes in porcine blood samples collected with and without the addition of anticoagulant (EDTA). Our study aimed to identify metabolites dependent on the EDTA addition and time (taking into account the biodiversity of the studied organism) and those that are time-dependent but resistant to the addition of an anticoagulant.

Methods

The experiment was performed on blood samples collected from 16 animals (domestic pig, breed: Polish Large White), 8 with and 8 without EDTA addition. The moment of death (time 0) and 15 additional time points (from 3 to 168 h after death) were selected to examine changes in metabolites' levels in specific time intervals. We employed linear mixed models to study the relationship between metabolite intensities, time and presence of EDTA while accounting for the effect of individual pigs.

Results and Discussion

We confirmed that the intensity of 16 metabolites (mainly amino acids) significantly depends on PMI and the presence of EDTA. However, the intensity of the ideal biomarker(s) for PMI estimation should be determined only by the time after death and not by external factors such as the presence of the anticoagulant agent. Thus, we identified 41 metabolites with time-dependent intensities that were not susceptible to EDTA presence. Finally, we assessed the performance of these metabolites in a PMI predictive model. Citraconic acid yielded one of the lowest errors in general PMI estimation (32.82 h). Moreover, similar errors were observed for samples with and without EDTA (33.32 h and 32.34 h, respectively). Although the small sample size and information leak in predictive modelling prevent drawing definite conclusions, citraconic acid shows potential as a robust PMI estimator.

Seasonal mouse cadaver microbial study: rupture time and postmortem interval estimation model construction

The estimation of postmortem interval (PMI) has long been a focal point in the field of forensic science. Following the death of an organism, microorganisms exhibit a clock-like proliferation pattern during the course of cadaver decomposition, forming the foundation for utilizing microbiology in PMI estimation. The establishment of PMI estimation models based on datasets from different seasons is of great practical significance. In this experiment, we conducted microbiota sequencing and analysis on gravesoil and mouse intestinal contents collected during both the winter and summer seasons and constructed a PMI estimation model using the Random Forest algorithm. The results showed that the MAE of the gut microbiota model in summer was 0.47 ± 0.26 d, R2 = 0.991, and the MAE of the gravesoil model in winter was 1.04 ± 0.22 d, R2 = 0.998. We propose that, in practical applications, it is advantageous to selectively build PMI estimation models based on seasonal variations. Additionally, through a combination of morphological observations, gravesoil microbiota sequencing results, and soil physicochemical data, we identified the time of cadaveric rupture for mouse cadavers, occurring at around days 24-27 in winter and days 6-9 in summer. This study not only confirms previous research findings but also introduces novel insights, contributing to the foundational knowledge necessary to advance the utilization of microbiota for PMI estimation.

Dental DNA Mutations Occurring after Death: A Novel Method for Post-Mortem Interval (PMI) Estimation

Post-mortem interval (PMI) estimation remains one of the major challenges in forensic practice, especially for late PMIs beyond 7-10 days after the death of the subject. In 2022, an innovative method to investigate the occurrence of mutations induced by the death of a subject in the DNA of post-mortem dental pulps at different PMIs was developed, applying a next-generation sequencing (NGS) analysis. The present study aims to apply the same method of analysis to a small sample of teeth belonging to the same subject and analyzed at different PMIs/accumulated degree days (ADDs), and of teeth extracted from different subjects but analyzed at the same PMI/ADD to verify the repeatability of the results obtained in relation to the time elapsed since death. A total of 10 teeth were collected from 6 patients (3 males and 3 females) with PMI varying from 8 to 35 days, and ADD from 157.4 to 753.8. We found 1754 mutations in 56 genes, with more than 700 mutations having a prevalence > 5% and more than 300 variants considered of interest for the purposes of the study. Mutations that were not present at lower PMIs but manifested in later PMIs in pulps belonging to the same subject demonstrate that they can only have been acquired by the subject after death and according to the time elapsed since death. In total, 67 somatic mutations in 29 out of the 56 genes of the used panel occurred in a fashion that allows an association with specific PMI/ADD ranges (within 8 days, between 17 and 28, and beyond 30 days after death). The results suggest that temperature and humidity could influence the rate of DNA degeneration in dental pulps, thus PMI should be estimated in ADD more than days. The preliminary validation supports the hypothesis that the innovative method could be a useful tool for estimating the post-mortem interval even beyond the first week after death, but further analyses are needed to customize a specific genetic panel for forensic investigations and verify the influence of degenerative processes of soft tissues surrounding dental elements on DNA degeneration of pulps.

Potential Role of mRNA in Estimating Postmortem Interval: A Systematic Review

Although the postmortem interval estimation still represents one of the main goals of forensic medicine, there are still several limitations that weigh on the methods most used for its determination: for this reason, even today, precisely estimating the postmortem interval remains one of the most important challenges in the forensic pathology field. To try to overcome these limitations, in recent years, numerous studies have been conducted on the potential use of the mRNA degradation time for reaching a more precise post mortem interval (PMI) estimation. An evidence-based systematic review of the literature has been conducted to evaluate the state of the art of the knowledge focusing on the potential correlation between mRNA degradation and PMI estimation. The research has been performed using the electronic databases PubMed and Scopus. The analysis conducted made it possible to confirm the potential applicability of mRNA for reaching a more precise PMI estimation. The analysis of the results highlighted the usefulness of some mRNAs, such as β-actin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA, especially in short time frames, within a few hours or days of death. The matrices on which these analyses were conducted were also analyzed, resulting in less exposure to the external environment, including the heart, brain, and dental pulp. The major limitations were also reported, including the short time intervals analyzed in most of the articles, the lack of mathematical models, and the failure to report the error rate between the mRNA degradation time and PMI. Given the still small number of published articles, the lack of globally recognized standardized methods, and the numerous techniques used to evaluate the mRNA degradation times, numerous and larger studies are still necessary to reach more solid and shared evidence.

Catch me if you can-emission patterns of human bodies in relation to postmortem changes

The present study examines for the first time the emission patterns and olfactory signatures of 9 complete human corpses of different stages of decomposition. Air sampling was performed inside the body bags with solid sorbents and analysed by coupled gas chromatography-mass spectrometry after thermal desorption (TD-GC-MS). Furthermore, odour-related substances were detected by gas chromatography-olfactometry (GC-O). Sulfurous compounds (mainly dimethyl di- and trisulfide) were identified as most important to the odour perception. Around 350 individual organic substances were detected by TD-GC-MS, notably sulfurous and nitrogenous substances as well as branched alkanes, aldehydes, ketones, alcohols, carboxylic acids, carboxylic acid esters and ethers. A range of terpenes was detected for the first time in a characteristic emission pattern over all decomposition stages. Concentrations of the substances varied greatly, and no correlation between the emission patterns, the stage of decomposition and the cause of death could be found. While previous studies often analysed pig cadavers or only parts of human tissue, the present study shows the importance of analysing complete human corpses over a range of decomposition stages. Moreover, it is shown that using body bags as a kind of "emission test chamber" is a very promising approach, also because it is a realistic application considering the usual transport and store of a body before autopsy.

The impact of RNA stability and degradation in different tissues to the determination of post-mortem interval: A systematic review

Postmortem interval (PMI) in legal medicine is extremely important for both criminal and civil cases, and several sorts of techniques have been recommended. This systematic review solely focuses on approaches linked to RNA analysis, instead of including all proposed methods for determining the PMI. The term PMI will be used in this review to indicate the time between a person's death and the postmortem examination of the body. We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Guidelines when conducting this systematic review. The majority of studies on various tissues at various time intervals at various temperatures are non-human, and just a small number are on humans. The results are then provided using various statistical approaches. To calculate the PMI, post-mortem RNA degradation was examined using several tissues. The result so obtained had an opposite polarity. While some studies show that RNA stability in various tissues remained constant for several days after death, the other group of studies showed evident RNA degradation over time post-mortem, which was significantly influenced by temperature and other agonal factors. These factors have an impact on the multi-parametric mathematical model of ante and post-mortem factors on RNA degradation, as well as its applicability and feasibility. The estimation of PMI using RNA degradation can prove to be highly objective and efficient after controlling for the various factors and challenges that pose the estimation of RNA in forensic samples difficult.

Zapico S. Partners in Postmortem Interval Estimation: X-ray Diffraction and Fourier Transform Spectroscopy

The postmortem interval (PMI) is difficult to estimate in later stages of decomposition. There is therefore a need to develop reliable methodologies to estimate late PMI. This study aims to assess whether there is a correlation between changes in the mineral composition of human teeth and the estimation of PMI. X-ray diffraction (XRD) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy techniques were performed to address this challenge. Forty healthy human teeth obtained from odontological clinics were stored at different times (0, 10, 25, 50 years; N = 10/group). XRD and ATR-FTIR parameters related to the structure and composition of teeth were studied. Our results showed that the crystallinity index, crystal size index, mineral-to-organic matrix ratio (M/M) and carbonate/phosphate ratio (C/P) had the strongest association with PMI. For larger PMIs, there was a significant increase in crystallinity, crystal size and M/M ratio, while the C/P ratio showed a specific decrease with increasing PMI. According to our results, the parameters of crystallinity, crystal size, M/M ratio and C/P ratio can be considered highly accurate in determining a PMI of 10 years of data; crystallinity and mineral maturity can be considered useful in determining a PMI of 25 years; and crystallinity and mineral maturity can be considered highly accurate in determining a PMI of 50 years. A particular XRD index was identified as the most suitable parameter to estimate PMI: crystallinity. The joint use of XRD and ATR-FTIR analyses could be a promising alternative for dating human teeth.

Review of the current and potential use of biological and molecular methods for the estimation of the postmortem interval in animals and humans

We provide here an overview of the state of applied techniques in the estimation of the early period of the postmortem interval (PMI). The biological methods included consist of body cooling, CSF potassium, body cooling combined with CSF potassium, and tissue autolysis. For each method, we present its application in human and veterinary medicine and provide current methodology, strengths, and weaknesses, as well as target areas for improvement. We examine current and future molecular methods as they pertain to DNA and primarily to messenger RNA degradation for the estimation of the PMI, as well as the use of RNA in aging wounds, aging blood stains, and the identification of body fluids. Various types of RNA have different lengths, structures, and functions in cells. These differences in RNAs determine various intrinsic properties, such as their half-lives in cells, and, hence, their decay rate as well as their unique use for specific forensic tests. Future applications and refinements of RNA-based techniques provide opportunities for the use of molecular methods in the estimation of PMI and other general forensic applications.

High-throughput sequencing to evaluate the effects of methamphetamine on the succession of the bacterial community to estimate the postmortem interval

In forensic medical examinations, estimating the postmortem interval (PMI) is an important factor. Methamphetamine (MA) is a synthetic stimulant that is commonly abused, and estimation of the PMI after MA abuse has become one of the main tasks in forensic investigation. Microorganisms play a vital role in carrion decomposition. Analysing the bacterial succession patterns can be used as a forensic tool to estimate the PMI. The present study aimed to analyse bacterial succession changes during the decomposition of MA to estimate the PMI. We analysed bacterial communities in rabbits treated with three different concentrations of MA (0, 22.5, and 90 mg/kg) under the natural conditions of 20 °C and 70% humidity by sequencing 16S rRNA gene amplicons using the Illumina MiSeq system. We obtained 2 374 209 high-quality sequences and 2 937 operational taxonomic units (OTUs). The relative abundances of the bacterial communities varied markedly in response to different MA concentrations. Interestingly, in response to the different concentrations of MA, Bacteroidetes became disparate in the rectum in the late PMI. Increased numbers of bacterial taxa were identified in the rectum and buccal cavity samples, except at the highest concentration of MA in the rectum samples when PMI was 0-h, than were present in live rabbits. Meanwhile, the PMI correlated significantly with bacterial succession at different taxonomic levels. Our results suggested that bacterial community succession could be used as a "microbial clock" to estimate the PMI in cases of MA-related death; however, further study is required to gain a deeper understanding of this concept.

PMI estimation through metabolomics and potassium analysis on animal vitreous humour

INTRODUCTION

The estimation of post-mortem interval (PMI) remains a major challenge in forensic science. Most of the proposed approaches lack the reliability required to meet the rigorous forensic standards.

OBJECTIVES

We applied ¹H NMR metabolomics to estimate PMI on ovine vitreous humour comparing the results with the actual scientific gold standard, namely vitreous potassium concentrations.

METHODS

Vitreous humour samples were collected in a time frame ranging from 6 to 86 h after death. Experiments were performed by using ¹H NMR metabolomics and ion capillary analysis. Data were submitted to multivariate statistical data analysis.

RESULTS

A multivariate calibration model was built to estimate PMI based on 47 vitreous humour samples. The model was validated with an independent test set of 24 samples, obtaining a prediction error on the entire range of 6.9 h for PMI < 24 h, 7.4 h for PMI between 24 and 48 h, and 10.3 h for PMI > 48 h. Time-related modifications of the ¹H NMR vitreous metabolomic profile could predict PMI better than potassium up to 48 h after death, whilst a combination of the two is better than the single approach for higher PMI estimation.

CONCLUSION

The present study, although in a proof-of-concept animal model, shows that vitreous metabolomics can be a powerful tool to predict PMI providing a more accurate estimation compared to the widely studied approach based on vitreous potassium concentrations.

Combining with lab-on-chip technology and multi-organ fusion strategy to estimate post-mortem interval of rat

Background

The estimation of post-mortem interval (PMI) is one of the most important problems in forensic pathology all the time. Although many classical methods can be used to estimate time since death, accurate and rapid estimation of PMI is still a difficult task in forensic practice, so the estimation of PMI requires a faster, more accurate, and more convenient method.

Materials and methods

In this study, an experimental method, lab-on-chip, is used to analyze the characterizations of polypeptide fragments of the lung, liver, kidney, and skeletal muscle of rats at defined time points after death (0, 1, 2, 3, 5, 7, 9, 12, 15, 18, 21, 24, 27, and 30 days). Then, machine learning algorithms (base model: LR, SVM, RF, GBDT, and MLPC; ensemble model: stacking, soft voting, and soft-weighted voting) are applied to predict PMI with single organ. Multi-organ fusion strategy is designed to predict PMI based on multiple organs. Then, the ensemble pruning algorithm determines the best combination of multi-organ.

Results

The kidney is the best single organ for predicting the time of death, and its internal and external accuracy is 0.808 and 0.714, respectively. Multi-organ fusion strategy dramatically improves the performance of PMI estimation, and its internal and external accuracy is 0.962 and 0.893, respectively. Finally, the best organ combination determined by the ensemble pruning algorithm is all organs, such as lung, liver, kidney, and skeletal muscle.

Conclusion

Lab-on-chip is feasible to detect polypeptide fragments and multi-organ fusion is more accurate than single organ for PMI estimation.

It Is Premature to Use Postmortem Sperm for Reproductive Purposes: a Data-Driven Opinion

Postmortem sperm retrieval for reproductive purposes is an assisted reproduction procedure that offers women an opportunity to have a child using sperm retrieved from their deceased partners. The ethical issues of this procedure have been discussed in previous works. However, an assessment of the procedure using a scientific perspective is still lacking. Here, we aim to ascertain, using a biological standpoint, whether postmortem sperm should be rescued for reproductive purposes. Data suggest that it is premature to use postmortem sperm for reproductive purposes. This procedure should not be clinically applied until appropriate and comprehensive analyses have been completed. Such analyses should be focused not only on fertilization, embryo development, and pregnancy outcomes, but also on potential postmortem alterations of sperm DNA, RNAs, and proteins. In addition, genetic and epigenetic analyses of sperm, pre-implantation embryos, and newborns, as well as mental and physical health follow-up of the resulting offspring during a whole life cycle, using appropriate non-human mammalian models, are warranted.

rno-miR-203a-3p and Mex3B contribute to cell survival of iliopsoas muscle via the Socs3-Casp3 axis under severe hypothermia in rats

Forensic diagnosis of fatal hypothermia is considered difficult because no specific findings, such as molecular markers, have been identified. Therefore, determining the molecular mechanism in hypothermia and identifying novel molecular markers to assist in diagnosing fatal hypothermia are important. This study aimed to investigate microRNA (miRNA) and mRNA expression in iliopsoas muscle, which plays a role in homeostasis in mammals, to resolve the molecular mechanism in hypothermia. We generated rat models of mild, moderate, and severe hypothermia, then performed body temperature-dependent miRNA and mRNA expression analysis of the iliopsoas muscle using microarray and next-generation sequencing. Analysis showed that rno-miR-203a-3p expression was lower with decreasing body temperature, while Socs3 expression was significantly increased only by severe hypothermia. Luciferase reporter assays suggested that Socs3 expression is regulated by rno-miR-203a-3p. Socs3 and Mex3B small interfering RNA-mediated knockdown showed that suppressing Mex3B could induce the activation of Socs3, followed by a change in caspase 3/7 activity and adenosine triphosphate levels in iliopsoas muscle cells. These findings indicate that rno-miR-203a-3p and Mex3B are deactivated by a decrease in body temperature, whereby it contributes to suppressing apoptosis by accelerating Socs3. Accordingly, the rno-miR-203a-3p-Socs3-Casp3 or Mex3B-Socs3-Casp3 axis may be the part of the biological defense response to maintain homeostasis under extreme hypothermia.

Dental DNA as an Indicator of Post-Mortem Interval (PMI): A Pilot Research

Teeth have proven to be a reliable source of DNA for forensic analysis as the pulp is rich in cells and protected from damaging factors and contamination by dental hard tissues. The pilot study aims to evaluate the feasibility of Next-Generation sequencing analysis on dental pulp to detect genetic mutations in DNA caused by post-mortem cell necrosis. We used a 56-gene oncopanel kit on a sample of 17 teeth extracted from living patients. Time of the tooth avulsion was assumed as death of the individual and Post-mortem Interval (PMI) was the time elapse since the DNA extraction and analysis. Days and Accumulated Degree Days (ADD) were assumed as measures of PMI that ranged between 0 to 34 days. Only 38 of the 56 considered genes proved to be affected by mutations (101), thus being of forensic interest. More specifically, 14 mutations occurred only in a specific range of PMIs/ADD; 67 were detected (alone or as clusters of the same gene) at specific PMI/ADD; 22 occurred at every PMI/ADD, except for some specific intervals. Since dental pulp was not targeted by any oncological diseases and all teeth were intact, vital, and from patients with unremarkable medical history, it could be assumed that mutations were due to post-mortem DNA changes induced by pulp death and the increasing time elapse since death. This pilot study found encouraging results in the application of NGS analysis on dental DNA, especially for PMIs of several days for which the traditional tools for PMI estimation have limitations. Further research on a larger sample of PMI and validation research on a larger sample of PMI and validation of the results are indeed necessary.

Establishment of a co-analysis system for personal identification and body fluid identification: a preliminary report

Analysis of genetic markers can provide clues for case investigation. Short tandem repeat (STR) detection and analysis are widely used for both personal identification and parentage testing. However, DNA analysis currently cannot provide sufficient information for body fluid identification. Tissue or cell sources of samples can be identified by detecting body fluid-specific mRNA markers, which have been studied thoroughly. Integrating STR profiling and mRNA expression patterns can provide more information than conventional methods for investigations and the reconstruction of crime scenes; this can be achieved by DNA/RNA co-extraction technology, which is economical, efficient, and suitable for low-template samples. Here, we propose a co-analysis system based on the PowerPlex 16 kit. This system can simultaneously amplify 25 markers, including 15 STRs, one non-STR amelogenin, and nine mRNA markers (three blood-specific, two saliva-specific, two semen-specific, and two housekeeping gene markers). The specificity and sensitivity of the co-analysis system were determined and aged and degraded samples were used to validate the stability of the co-analysis system. Finally, different DNA/RNA ratios and various carriers were evaluated. The results showed that the DNA/RNA co-analysis system correctly identified different types of body fluid stains. The STR profiles obtained using the co-analysis system were identical to those obtained using the PP16 kit, which demonstrates that the mRNA primers used did not affect STR profiling. Complete STR and mRNA profiles could be obtained from 1/8 portions of buccal swabs, 1/16 portions of swabs of blood and semen samples, 0.1 cm² of blood samples, 0.25 cm² of semen samples, and 1.0 cm² saliva samples. Additionally, our findings indicate that complete STR and mRNA profiles can be obtained with this system from blood and semen samples when the DNA/RNA ratio is 1:1/32. This study suggests that the co-analysis system could be used for simultaneous personal identification and body fluid identification.

RNA marker modifications reveal the necessity for rigorous preparation protocols to avoid artifacts in epitranscriptomic analysis

The accurate definition of an epitranscriptome is endangered by artefacts resulting from RNA degradation after cell death, a ubiquitous yet little investigated process. By tracing RNA marker modifications through tissue preparation protocols, we identified a major blind spot from daily lab routine, that has massive impact on modification analysis in small RNAs. In particular, m6,6A and Am as co-varying rRNA marker modifications, appeared in small RNA fractions following rRNA degradation in vitro and in cellulo. Analysing mouse tissue at different time points post mortem, we tracked the progress of intracellular RNA degradation after cell death, and found it reflected in RNA modification patterns. Differences were dramatic between liver, where RNA degradation commenced immediately after death, and brain, yielding essentially undamaged RNA. RNA integrity correlated with low amounts of co-varying rRNA markers. Thus validated RNA preparations featured differentially modified tRNA populations whose information content allowed a distinction even among the related brain tissues cortex, cerebellum and hippocampus. Inversely, advanced cell death correlated with high rRNA marker content, and correspondingly little with the naïve state of living tissue. Therefore, unless RNA and tissue preparations are executed with utmost care, interpretation of modification patterns in tRNA and small RNA are prone to artefacts.

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

(1) 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.

Comparison of serum cell-free DNA between postmortem and living samples

Cell-free DNA (cfDNA) originates from apoptotic and/or necrotic cells. Few reports are available that examine cfDNA from postmortem samples. Therefore, this study investigated differences between postmortem and biogenic subjects in concentration and fragment distribution of serum cfDNA. We also clarified features of serum cfDNA in postmortem subjects. The results revealed that postmortem subjects had significantly higher cfDNA concentrations than healthy controls and patients with cardiac disease. Serum cfDNA concentrations increased slightly with postmortem interval in subjects who died of asphyxia, and they were slightly higher in subjects who died from internal vs. external causes. Microchip electrophoresis of serum cfDNA revealed a fragment larger than 10,000 bp in only two postmortem subjects; we speculate that the fragment may have originated from necrotic cells. A relatively high concentration of one 150-200 bp fragment was characteristic of postmortem samples. This fragment may have been derived from apoptosis or other processes. We also observed ladder fragments in some subjects who died from external causes. Although additional research is needed for verification, serum cfDNA concentrations and fragment patterns possibly be used as a tool to estimate postmortem intervals and cause of death.

Postmortem expression of apoptosis-related genes in the liver of mice and their use for estimation of the time of death

PURPOSE

A major challenge in forensic medicine is to estimate the postmortem interval (PMI). Several approaches had been tried to determine the time of death, including physical and chemical changes. This study aims to explore the postmortem changes in the expression of apoptosis-related genes in the liver of mice and to use these changes for estimation of the PMI.

METHODS

Hepatic tissue was collected from sacrificed mice immediately after death (the control group) and at 3, 6, 9, 12, 18, and 24 hours after death. Four apoptosisrelated genes were selected as target genes, which are Caspase 3 (Casp3), B cell leukemia/ lymphoma 2 (Bcl2), BCL2-associated X protein (Bax), and Transformation related protein 53 (Trp53), and their relative expression was measured using quantitative PCR. miR-122 was used as a reference gene for normalization of the Ct (threshold cycle) values of the target genes.

RESULTS

The results revealed that the postmortem expression of Casp3 increased in a time-dependent manner; the expression of Bax increased from 3 to 18 hours followed by a decrease at 24 hours after death; the expression of Bcl2 decreased in a time-dependent manner after death; the expression of Trp53 increased from 3 to 6 hours and then started to decrease from 9 to 24 hours after death.

CONCLUSION

Based on the observed changes in the expression level of these genes, mathematical models were established to estimate the PMI. Further research is needed to investigate these markers and mathematical models in human tissues.