Postmortem interval (PMI) determination by profiling of HAF mRNA degradation using RT-qPCR

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.

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.

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.