Early postmortem interval (EPMI) estimation using differentially expressed gene transcripts

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.

Postmortem mitochondrial membrane potential dynamics as a temperature-independent biomarker for early postmortem interval estimation

BACKGROUND

Accurate determination of postmortem interval (PMI) and cause of death (COD) is a critical challenge in forensic pathology, with significant implications for criminal investigations. Traditional PMI estimation methods are based on macroscopic changes and are influenced by environmental factors and investigator subjectivity. Recent advances in molecular biology have shown that certain cellular structures, such as mitochondria, retain functionality after death, making them potential biomarkers for forensic assessment. As mitochondria play a central role in cellular metabolism and respond dynamically to post-mortem hypoxia, investigation of mitochondrial membrane potential (ΔΨm) may provide a quantifiable and objective method for estimating PMI.

RESULTS

We successfully isolated mitochondria from post-mortem tissues and cultured cells, confirming their purity and membrane integrity. Regression analysis showed a strong linear correlation between ΔΨm and PMI in brain, myocardium and skeletal muscle within the first 15-18 h postmortem, with skeletal muscle showing the highest correlation coefficient. ΔΨm values remained stable at different temperatures, suggesting that it is a robust biomarker for estimating PMI. In vitro experiments under hypoxic conditions revealed a transient increase in ΔΨm at 24 h, accompanied by ATP depletion, ROS accumulation and shifts in mitochondrial fission and fusion dynamics, indicating mitochondrial adaptation to oxygen deprivation.

CONCLUSIONS

These findings highlight ΔΨm as a promising temperature stable biomarker for early assessment of PMI. The observed mitochondrial adaptations suggest that ΔΨm-based models may improve forensic accuracy and provide insights into postmortem metabolic processes. Further validation with human postmortem samples is essential to refine these models and explore their applicability to COD determination.

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.

MiR-122, miR-133a, and miR-206 as potential biomarkers for post-mortem interval estimation

BACKGROUD

Accurate estimation of post-mortem interval (PMI) is crucial in forensic investigations. MicroRNAs (miRNAs or miRs) are small non-coding RNAs that remain relatively stable within the cell nucleus despite post-mortem changes.

OBJECTIVE

We assessed three target genes (miR-122, miR-133a, and miR-206) for PMI estimation using 72 healthy adult male BALB/c mice exposed to two different temperatures (4 and 21℃) at nine different time points over 10 days.

METHODS

Initially, the stability of the two reference genes (RNU6B and 5 srRNA) was evaluated using gene stability analysis tools (Delta Ct, Best Keeper, and Genorm) to select the optimal reference gene. RNU6B was found to be the most stable endogenous control. Subsequently, the expression patterns of miR-122, miR-133a, and miR-206 were analyzed within a 10-day PMI period using the heart, skeletal muscle, liver, and brain tissues.

RESULTS

At 4℃, miR-122 levels significantly decreased on days 8 and 10 in all tissues, with only the liver showing significant changes at 21℃. MiR-133a decreased over time in the heart, muscles, and brain, showing a dramatic decrease on days 8 and 10 in the heart and muscles at both temperatures. Although miR-206 levels decreased over time in muscles and liver at 4 ℃, these increased in the brain at 21 ℃, with no expression changes in other organs.

CONCLUSION

In summary, miR-122, miR-133a, and miR-206 are potential PMI markers in heart and skeletal muscle tissues.

An experimental study to estimate the early postmortem interval based on the degradation of lncRNAs in rat brain tissue

To study the degradation of lncRNAs in EPMI in rat brain tissue, this study provides a new direction for the estimation of EPMI. LncRNA high-throughput sequencing was performed on the brain tissues of hemorrhagic shock model rats at 0 h and 24 h, and the target lncRNAs were screened. Samples at 0, 1, 3, 6, 12, 18 and 24 h after death were collected, and miRNA-9 and miRNA-125b were used as reference genes. The relative expression levels of lncRNAs at each PMI were detected by RT-qPCR, and a functional model involving lncRNAs and EPMI was established. Samples were collected at 6, 9, 15, and 21 h after death for functional model verification. The expression of several lncRNAs decreased with the prolongation of EPMI, and the mathematical model established by several lncRNA indices exhibited good fit. The verification results of the multi-index joint function model are significantly better than those of the single-index function model, and the established model is more practical. There is a linear relationship between lncRNAs and EPMI, and the multi-index function model is significantly better than the single-index function model, which is important for EPMI inference in forensic pathology practice.

A miRNome analysis at the early postmortem interval

The postmortem interval (PMI) is the time elapsing since the death of an individual until the body is examined. Different molecules have been analyzed to better estimate the PMI with variable results. The miRNAs draw attention in the forensic field to estimate the PMI as they can better support degradation. In the present work, we analyzed the miRNome at early PMI in rats' skeletal muscle using the Affymetrix GeneChip™ miRNA 4.0 microarrays. We found 156 dysregulated miRNAs in rats' skeletal muscle at 24 h of PMI, out of which 84 were downregulated, and 72 upregulated. The miRNA most significantly downregulated was miR-139-5p (FC = -160, p = 9.97 × 10^-11), while the most upregulated was rno-miR-92b-5p (FC = 241.18, p = 2.39 × 10^-6). Regarding the targets of these dysregulated miRNAs, the rno-miR-125b-5p and rno-miR-138-5p were the miRNAs with more mRNA targets. The mRNA targets that we found in the present study participate in several biological processes such as interleukin secretion regulation, translation regulation, cell growth, or low oxygen response. In addition, we found a downregulation of SIRT1 mRNA and an upregulation of TGFBR2 mRNA at 24 h of PMI. These results suggest there is an active participation of miRNAs at early PMI which could be further explored to identify potential biomarkers for PMI estimation.

Role of molecular techniques in PMI estimation: An update

The time frames between death and reporting of the cadaver, known as post Mortem interval (PMI), is essential in investigation of homicide deaths, suspicious deaths, or other untimely deaths as well as natural deaths. Such information helps to connect the missing links in homicide or other relevant cases. Over the time several methods are developed which depends upon factors as several methods physiological, biochemical, entomological, and archaeological for the estimation of degradation of body with time. These methods lack precision, require expertise to achieve worthy results or authentic estimate. Although these methods are currently in use but, these evaluations are still unreliable and imprecise. Hence, we still need new methods for better estimation of PMI. Initially, the predictable morphological and chemical changes in cadaver are used as PMI indicators but, as the time since death increases, the above methods become less useful for as they can't pin point the time of death rather give a ballpark idea. With the advent of the field of molecular biology, the estimation of PMI is proposed to be executed by evaluating the degradation pattern of the biological markers (DNA, RNA, and Proteins). It is now proved that the DNA is fairly unwavering over long post-mortem phases, RNA is much more labile in nature, and sensitive to degradation in a tissue-specific manner. Thus, the main purpose (aim, agenda) of this document is to provide review that mainly focuses on potential use of RNA markers in estimation of PMI. For this Critical Review, the systematic evaluation of 47 studies is executed according to the chosen inclusion and exclusion criteria.

Insights into how environment shapes post-mortem RNA transcription in mouse brain

Most biological features that occur on the body after death were already deciphered by traditional medicine. However, the molecular mechanisms triggered in the cellular microenvironment are not fully comprehended yet. Previous studies reported gene expression alterations in the post-mortem condition, but little is known about how the environment could influence RNA degradation and transcriptional regulation. In this work, we analysed the transcriptome of mouse brain after death under three concealment simulations (air exposed, buried, and submerged). Our analyses identified 2,103 genes differentially expressed in all tested groups 48 h after death. Moreover, we identified 111 commonly upregulated and 497 commonly downregulated genes in mice from the concealment simulations. The gene functions shared by the individuals from the tested environments were associated with RNA homeostasis, inflammation, developmental processes, cell communication, cell proliferation, and lipid metabolism. Regarding the altered biological processes, we identified that the macroautophagy process was enriched in the upregulated genes and lipid metabolism was enriched in the downregulated genes. On the other hand, we also described a list of biomarkers associated with the submerged and buried groups, indicating that these environments can influence the post-mortem RNA abundance in its particular way.

Biomarkers of myocardial injury in rats after cantharidin poisoning: Application for postmortem diagnosis and estimation of postmortem interval

Postmortem diagnosis of cantharidin-induced myocardial injury and postmortem interval estimation (PMI) are the challenges in forensic science. Cardiac biomarkers play an important role in the prediction and diagnosis of myocardial injury and can be used to determine the PMI. Based on the evidence, we aimed to explore the biomarkers which may be used for the postmortem diagnosis of cantharidin-induced myocardial injury and PMI estimation using the study of the proteins expression of TN-T, VEGF and HIF-1α by ELISA. Results of this study suggested that postmortem pathological changes were difficult to identify due to the autolysis of myocardium 72 h after death in cantharidin poisoning group. The plasma levels of TN-T and HIF-1α/TN-T are cardiac biomarkers with higher diagnostic accuracy for postmortem diagnosis of cantharidin-induced myocardial injury, VEGF/HIF-1α promises to be a biomarker for PMI estimation. Further studies are needed to verify these biomarkers, based on population, for being a useful tool in postmortem diagnosis of cantharidin-induced myocardial injury and PMI estimation.