Potential Forensic Application of Receptor for Advanced Glycation End Products (RAGE) as a Novel Biomarker for Estimating Postmortem Interval

Applicable Forensic Biomarker for Drowning Diagnosis: Extracellular Signal-Regulated Kinase 2 (ERK2)

Drowning is a common cause of accidental death worldwide, and it continues to be a serious public health problem. However, diagnosing drowning is a challenging task in forensic investigation because it is difficult to prove actual drowning and other submerged deaths with the autopsy techniques that are currently in use. Here, we show biomarkers that may be helpful for the diagnosis of drowning. We divided the experimental animals into four groups (drowning, postmortem submersion, hypoxia, and control) to evaluate the expression patterns of extracellular signal-regulated kinase 1/2 (ERK1/2). On gene expression analysis, only ERK2 was found to be significantly increased in the drowning groups compared to the other cases. In the immunoblot analysis, phosphorylated ERK2 (p-ERK2) was found to be upregulated in the drowning groups. Immunohistochemical staining also showed that p-ERK in alveolar cells revealed a granular pattern in the drowning groups. However, the expression pattern of ERK2 over time after drowning differed between the freshwater and seawater drowning groups. Taken together, these results indicate that ERK2 may be useful for distinguishing between drowning and postmortem submersion if the postmortem interval (PMI) of drowning is short. Conversely, if the PMI is long from the time that death occurs until the discovery of dead bodies, it is possibly more helpful for identifying between freshwater and seawater drowning.

New Trends in Immunohistochemical Methods to Estimate the Time since Death: A Review

The identification of a reliable and accurate post-mortem interval (PMI) is a major challenge in the field of forensic sciences and criminal investigation. Several laboratory techniques have recently been developed that offer a better contribution to the estimation of PMI, in addition to the traditional physical or physico-chemical (body cooling, lividity, radiocarbon dating, rigor mortis), chemical (autolysis), microbiological (putrefaction), entomological, as well as botanical parameters. Molecular biology (degradation pattern of macromolecules such as proteins, DNA, RNA), biochemical analysis of biological fluids (such as blood, cerebrospinal fluid, and vitreous humor), and immunohistochemistry are some of the most recent technological innovations. A systematic review of the literature was performed with the aim of presenting an up-to-date overview on the correlation between the immunohistochemical (IHC) expression of specific antigenic markers at different PMIs. The systematic review was performed according to PRISMA guidelines. Scopus and PubMed were used as search engines from January 1, 1998 to March 1, 2022 to evaluate the effectiveness of immunohistochemistry in estimating PMI. The following keywords were used: (immunohistochemical) OR (immunohistochemistry) AND (time since death) OR (post-mortem interval) OR (PMI). A total of 6571 articles were collected. Ultimately, 16 studies were included in this review. The results of this systematic review highlighted that IHC techniques, in association with traditional methods, add, in Bayesian terms, additional information to define a more accurate time of death and PMI. However, current IHC results are numerically limited and more data and studies are desirable in the near future.

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.

Postmortem Protein Degradation as a Tool to Estimate the PMI: A Systematic Review

Objectives: We provide a systematic review of the literature to evaluate the current research status of protein degradation-based postmortem interval (PMI) estimation. Special attention is paid to the applicability of the proposed approaches/methods in forensic routine practice. Method: A systematic review of the literature on protein degradation in tissues and organs of animals and humans was conducted. Therefore, we searched the scientific databases Pubmed and Ovid for publications until December 2019. Additional searches were performed in Google Scholar and the reference lists of eligible articles. Results: A total of 36 studies were included. This enabled us to consider the degradation pattern of over 130 proteins from 11 different tissues, studied with different methods including well-established and modern approaches. Although comparison between studies is complicated by the heterogeneity of study designs, tissue types, methods, proteins and outcome measurement, there is clear evidence for a high explanatory power of protein degradation analysis in forensic PMI analysis. Conclusions: Although only few approaches have yet exceeded a basic research level, the current research status provides strong evidence in favor of the applicability of a protein degradation-based PMI estimation method in routine forensic practice. Further targeted research effort towards specific aims (also addressing influencing factors and exclusion criteria), especially in human tissue will be required to obtain a robust, reliable laboratory protocol, and collect sufficient data to develop accurate multifactorial mathematical decomposition models.

Development of 18S rRNA gene arrays for forensic detection of diatoms

Diatom test is the most commonly used method to diagnose drowning in forensic laboratories. However, microscopic examination and identification of diatom frustules is time-consuming and requires taxonomic expertise. At present, the identification of drowning is still a challenge in forensic casework. In this study, we developed a novel diatom microarray based on the detection of specific 18S rRNA gene fragments of diatom species. The array covers 169 diatom species which were documented as commonly found in a wide range of fresh waters in China. Diatom arrays were prepared from species specific oligonucleotide probes targeting to variable regions of the 18S rRNA gene. We also developed an auxiliary sample preparation method for isolation of diatom DNA from tissues, which enabled detection of diatom species in real forensic samples as well as environmental waters. We applied the diatom arrays to analyze six drowned cases and eight environmental samples. The diatom arrays showed much better sensitivity and more consistent results than those of the conventional SEM methods. We discovered major discrepancies between results generated by the diatom arrays and the routinely used SEM based diatom tests. We verified the results of our diatom arrays by species specific PCR and Sanger sequencing and found that the currently used SEM diatom test method has a serious deficiency in sensitivity due to high loss rate of frustules in the sample preparation procedure. We anticipate that the application of diatom arrays will transform current forensic practice of diagnosing drowning deaths.

Diatomological mapping of water bodies in Chongqing section of the Yangtze River and Jialing River

The diagnosis of drowning is one of the most difficult in forensic medicine. Forensic diatomology has been proposed to be useful in solving the diagnosis of drowning and considered to be a reliable indicator of the site of drowning. The Yangtze River and Jialing River are the main rivers in the Chongqing area (China), and a large number of corpses are found in the rivers every year. However, the distribution of diatoms in the rivers was not fully studied. In the presented study, a Microwave Digestion-Vacuum Filtration-Scanning Electron Microscopy (MD-VF-SEM) method was performed to acquire the qualitative and quantitative data of diatoms of water samples collected from 10 different sites of the Yangtze River and Jialing River in Chongqing section during different seasons. Our study not only created the diatomological maps of water bodies in Chongqing section of the Yangtze River and Jialing River for the first time but also identified some seasonal and site-specific diatoms that can be taken as markers of particular sites or seasons of drowning. The results of our study may provide forensic scientists helpful reference in solving the drowning cases.