Research Progress of Exosomes and Their Forensic Significance.

Exosomes are membranous tiny vesicles secreted by cells, which are widely found in the extracellular matrix and various body fluids and carry a variety of biologically functional molecules such as proteins, lipids, messenger RNA (mRNA) and microRNA (miRNA). Exosomes not only play important biological roles in the field of immunology and oncology, but also have potential application value in the field of forensic medicine. This article reviews the discovery, production and degeneration mechanism, biological functions, isolation and identification methods of exosomes, summarizes the research on exosomes and their significance in the field of forensic science, and discusses their applications in body fluid identification, individual identification, postmortem interval estimation to provide ideas for the application of exosomes in forensic work.

Research Progress on Accumulated Degree Days for PMI Estimation.

ABSTRACT: Among many factors that affect postmortem interval （PMI）, temperature is undoubtedly the most important factor, but simply considering temperature in estimation of PMI has limitations. Accumulated degree days （ADD） is an important indicator related to biological growth and development, which considers two major variables, environmental temperature and elapsed time. Therefore, the establishment of mathematical model of ADD and some evaluation indicators to estimate PMI, is obviously better than single temperature variable. This article briefly describes the research history of ADD, its application in PMI estimation, and the problems it faces, to provide reference for the further development of ADD to improve the accuracy of PMI estimation.

Application of Postmortem Biochemistry Analysis in Forensic Medicine.

In recent years, postmortem biochemistry analysis has gradually been applied to forensic practice, providing objective evidence for health conditions before death, disease pathophysiological processes and forensic diagnosis of postmortem interval and cause of death. It is of great significance to understand the change patterns of postmortem biochemical indicators and their applications in forensic medicine. This article reviews the research progress of postmortem biochemistry and its application in forensic medicine, it summarizes the existing problems of postmortem biochemistry analysis in forensic medicine of China and discusses the application prospect of postmortem biochemistry analysis in forensic medicine. This review is expected to provide references for forensic practitioners.

[Research Progress on Estimation of Postmortem Interval Using mRNA and ncRNA].

ABSTRACT: Postmortem interval （PMI） estimation has always been an important and difficult issue in the field of forensic pathology. In recent years, research progress on the estimation of PMI using RNA specific variation patterns after death has been made by researchers at home and aboard. This paper summarizes the specific application methods of messenger RNA and non-coding RNA for PMI estimation based on the literatures and discusses the existing problems and development trends, in order to provide technical reference for related studies and estimation practice.

[Estimation of Early Postmortem Interval of Asphyxial Death Rats at Different Ambient Temperatures by GC-MS-Based Metabolomics].

ABSTRACT: Objective To establish the orthogonal partial least square （OPLS） model for the estimation of early postmortem interval （PMI） of asphyxial death rats in four ambient temperatures based on gas chromatography-mass spectrometry （GC-MS） metabolomics. Methods The 96 rats were divided into four temperature groups （5 ℃, 15 ℃, 25 ℃ and 35 ℃）. Each temperature group was further divided into 3 h, 6 h, 12 h and 24 h after death, and 6 other rats were taken as the control group. The cardiac blood was collected at the set time points for the four temperature groups and 0 h after death for the control group for the metabolomics analysis by GC-MS. By OPLS analysis, the variable importance in projection （VIP）>1 and the result of Kruskal-Wallis test P<0.001 were used to screen out the differential metabolite related to PMIs in the cardiac blood of rats of different temperature groups. Then OPLS regression models of different temperature groups were established with these metabolites. At the same time, a prediction group for investigating the prediction ability of these models was set up. Results Through the analysis of OPLS, 18, 15, 24 and 30 differential metabolites （including organic acids, amino acids, sugars and lipids） were screened out from the rats in groups of 5 ℃, 15 ℃, 25 ℃ and 35 ℃, respectively. The prediction results of the four temperature group models showed that the prediction deviation of 5 ℃ model was larger than that of other groups. The prediction results of other temperature groups were satisfactory. Conclusion There are some differences in the changes of metabolites in cardiac blood of rats at different ambient temperatures. The influence of ambient temperature should be investigated in the study of PMI estimation by metabolomics, which may improve the accuracy of PMI estimation.

Rectal Temperature of Corpse and Estimation of Postmortem Interval.

ABSTRACT: Measurement of corpse temperature is mainly used for estimation of early postmortem interval, and rectal temperature is often used as a representative of body's core temperature in actual work because it is simple, quick and non-invasive. At present, the rectal temperature postmortem interval estimation method internationally accepted and widely used is HENSSGE's nomogram method, while many domestic scholars also deduced their own regression equations through a large number of case data. Estimation of postmortem interval based on rectal temperature still needs further study. The nomogram method needs to be optimized and extended, and quantification of its influencing factors needs to be dealt with more scientifically. There is still a lack of consensus on the probability and duration of the temperature plateau. There is no clear understanding of the probability and extent of the change in initial temperature caused by various causes. New methods and ideas enrich methodological research, but it still lacks systemicity and practicality. This article reviews the researches on estimation of postmortem interval based on rectal temperature in order to summarize the current situation of previous researches and seek new breakthrough points. Because the decline of body temperature can be easily influenced by many factors in vitro and vivo, and the influencing factors in different regions vary greatly, regionalization research and application may be a practical exploration to improve the accuracy of postmortem interval determination.

Relationship between Electrical Conductivity and Chemical Content of Rat Skeletal Muscle Impregnating Solution and Postmortem Interval.

ABSTRACT: Objective To study the mechanism of change of the electrical conductivity （EC） of rat skeletal muscle impregnating solution that occurs with the change of postmortem interval （PMI）. Methods Healthy Sprague-Dawley rats were killed and kept at about 25 ℃. Skeletal muscles were extracted at different PMI--immediate （0 d）, 1 d, 2 d, 3 d, 4 d, 5 d, 6 d, and 7 d, then mixed with deionized water to make impregnating solution with a mass concentration of 0.1 g/mL. The solution's EC and nine common chemicals in it, such as potassium ion, calcium ion, and chloride ion, were determined. Results EC increased gradually with the extending of PMI （P=0.024） during the 7 days after the rats' death. The content of uric acid （P=0.032）, urea nitrogen （P=0.013） and phosphorus （P=0.022） also increased during the extension. However, the content of magnesium ions decreased with extending of PMI （P=0.047）. The correlation between potassium ion, sodium ion, chlorine ion, calcium ion, creatinine and PMI were weak （P>0.05）. Conclusion The molecular basis of skeletal muscle EC change in rats after their death is the changes of uric acid, urea nitrogen, inorganic phosphorus and other chemical components. Furthermore, combine use of various indicators can improve the accuracy of the EC method to infer PMI.

Research Progress of Aquatic Corpse Decomposition and Postmortem Submersion Interval Estimation.

ABSTRACT: Human corpses can be found in a variety of aquatic environments. The decomposition of corpses in aquatic environments is different from those on land. A large number of factors influence the decomposition process in water, therefore postmortem submersion interval （PMSI） is difficult to estimate. To date, while studies on aquatic corpses are obviously fewer than those on terrestrial corpses, there are many problems in practical work. This review summarizes the stages and influencing factors of aquatic corpse decomposition, and introduces the relevant research progress of PMSI estimation based on decomposition stages, postmortem phenomena, aquatic insects, biofilm, and physical and chemical methods, in order to provide reference for aquatic decomposition researches and practices.