Forensic diagnosis of ante- and postmortem burn based on aquaporin-3 gene expression in the skin

Application of Aquaporins as Markers in Forensic Pathology: A Systematic Review of the Literature

The study of aquaporins (AQPs) in various forensic fields has offered a promising horizon in response to the need to have reliable elements for the identification of the manner of death and for the individuation of forensic markers for the timing of lesions and vitality of injury. In the literature, various tissues have been studied; the most investigated are the lungs, brain, kidneys, skin, and blood vessels. A systematic literature review on PubMed following PRISMA 2020 guidelines enabled the identification of 96 articles. In all, 34 of these were enrolled to identify Aquaporin-like (AQP-like) forensic markers. The analysis of the literature demonstrated that the most significant markers among the AQPs are as follows: for the brain, AQP4, which is very important in brain trauma and hypoxic damage; AQP3 in the skin lesions caused by various mechanisms; and AQP5 in the diagnosis of drowning. Other applications are in organ damage due to drug abuse and thrombus dating. The focus of this review is to collect all the data present in the literature about the forensic application of AQPs as forensic markers in the most important fields of application. In the current use, the individuation, validation, and application of markers in forensic investigation are very useful in real forensic applications in cases evaluated in court.

Homicides Disguised as Fire Deaths

Background

When conducting a forensic examination of burnt bodies, it is important to determine whether the victim was exposed to fire while alive or after death. The differential diagnosis between antemortem and postmortem burning is difficult and often cannot be made based on information obtained solely from the autopsy. The aim of the study is to review current literature on this topic and present clinical cases that illustrate how challenging the determination of vitality during the fire and manner of death can be.

Materials and methods

We present four cases of burnt homicide victims, illustrating the complexity of forensic determination of the cause of death in the fire and the importance of differential diagnosis of antemortem and postmortem exposure to flames.

Results

In the forensic assessment autopsy is a fundamental to determine the cause of death. When death is related to fire, particular findings during autopsy can help to suspect that the victim was alive. One of the main antemortem signs is the deposition of soot in the respiratory tract. Another important test is the toxicological analysis, which determines the level of carboxyhaemoglobin in the blood: a concentration of more than 50% indicates that the person died in the fire.

Conclusions

Forensic examination of burnt bodies requires a comprehensive and detailed assessment of all available data. The autopsy, together with additional diagnostic forensic methods, including histological examination, toxicological analysis and postmortem computed tomography, allows the exact cause of death to be determined.

Vitality markers in forensic investigations: a literature review

Determining whether an injury was sustained in life or not is one of the most important topics in forensic medicine. Morphological, cytological, and biological techniques are used to assess wound vitality. Several markers involved in vital and supravital reactions increase the accuracy of wound age estimation. This systematic review aimed to investigate the main vitality markers used in forensic medicine to date. This review was conducted by performing a systematic literature search on online resources (PubMed Central database and Google Scholar) until May 2022. We identified 46 articles published between 1987 and May 2022, analyzing a total of 53 markers. Based on the data of this review, the most studied vitality markers were adhesion molecules (fibronectin, p-selectin, CD 15), pro-inflammatory cytokines (IL-6, IL-1β, TNF-α), cathepsin D, tryptase, and microRNAs (miRNAs). The most interesting studies were based on animal models: the different markers were investigated through immunohistochemical and qRT-PCR methods. The experimental methods were usually based on skin incisions, ligature marks, and burned skin areas. To date, it has not been possible to identify any gold standard markers based on the criteria of efficacy, specificity, and reliability; however, studies are still in progress. In the future, the use of miRNAs is promising as well as the combination of multiple markers. In this way, it will be possible to increase the sensitivity and specificity to validate systems or models for determining wound vitality in forensic practice.

Forensic application of aquaporins

Aquaporins (AQPs) are a family of water channel proteins that primarily elicit the basic functions of water transport and osmotic homeostasis. To date, at least 17 mammalian AQPs have been identified, AQP-0 to -12 have been found in higher orders including human, and AQP-13 to -16 have been described in older lineages. Moreover, these proteins have recently been shown to regulate many biological processes through unique activities, such as cell proliferation, migration, apoptosis, and mitochondrial metabolism. Several studies have focused on the involvement of AQPs in cell biology aspect, showing that they are involved in a variety of physiological processes and pathophysiological conditions. Furthermore, in the field of forensic medicine, studies on whether AQPs can be a useful marker for diagnosing various causes of death have been conducted using autopsy samples and animal experiments, which have produced interesting results. Herein, we review certain observations regarding AQPs and discuss their potential to contribute to the future practice of forensic research.

Importance of Housekeeping Gene Optimization for the Analysis of mRNA Expression During Wound Healing in a Third-Degree Burn Injury Model

Wound healing evaluation methods in a third-degree burn injury model are categorized as histological (re-epithelialization and granulation tissue formation) and molecular (quantitative polymerase chain reaction). In general, mRNA expression is normalized to those of the housekeeping gene. Although the housekeeping gene expression is generally stable, it has been reported that the stability of these genes depends on the wound healing process and treatment method. In this study, we identified the most stable housekeeping gene (TATA-binding protein) for studying gene expression in a third-degree burn injury model, in which wound healing was promoted by grafting human amnion-derived mesenchymal cells. We investigated the wound healing effect of human amnion-derived mesenchymal cells in the injury model. The formation of granulation tissue, the differentiation from fibroblasts to myofibroblasts, and functional vascular structure were promoted in the full-thickness skin excision site by treatment with these cells. The expression of angiogenic, pro-inflammatory and anti-inflammatory related mRNA was measured and normalized to that of the housekeeping gene, showing that treatment with the cells promoted the infiltration of endothelial cells and differentiation of M1 and M2 macrophages. In conclusion, wound healing in a third-degree burn injury model can be accurately analyzed using the optimized housekeeping gene.

mRNA microarray analysis for the identification of potential biomarkers for vital reaction in burned skin: a preliminary pilot study

The identification of ante- and post-mortem burns is challenging in forensic pathology. In this study, microarray analysis was used to detect the mRNA expression profiles in the skin of an experimental burn mouse model; the results were validated using RT-qPCR. Differentially expressed mRNAs (DE-mRNAs) were assessed using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Our results revealed that mRNA expression of 501 genes was significantly different, of which 273 were upregulated and 228 were downregulated in ante-mortem burned mice skin. The expression levels of eight random mRNAs were consistent when measured using the microarray assay-based method and RT-qPCR. Genes from different functional categories and signalling pathways were enriched, including interleukin-20 binding, type IV hypersensitivity, negative regulation of acute inflammatory response, sensory organ development, endocytosis, neuroactive ligand-receptor interaction, and Jak-STAT signalling pathway. Only five of the eight mRNAs exhibited consistent changes in expression between burned skin samples of mice and human autopsy specimens. Our findings showed that DE-mRNAs revealed using microarray are potential biomarkers of ante-mortem burns. However, DE-mRNAs identified from experimental animal models cannot be directly extended to autopsy specimens without careful validation.

State-of-the-Art on Wound Vitality Evaluation: A Systematic Review

The vitality demonstration refers to determining if an injury has been caused ante- or post-mortem, while wound age means to evaluate how long a subject has survived after the infliction of an injury. Histology alone is not enough to prove the vitality of a lesion. Recently, immunohistochemistry, biochemistry, and molecular biology have been introduced in the field of lesions vitality and age demonstration. The study was conducted according to the preferred reporting items for systematic review (PRISMA) protocol. The search terms were "wound", "lesion", "vitality", "evaluation", "immunohistochemistry", "proteins", "electrolytes", "mRNAs", and "miRNAs" in the title, abstract, and keywords. This evaluation left 137 scientific papers. This review aimed to collect all the knowledge on vital wound demonstration and provide a temporal distribution of the methods currently available, in order to determine the age of lesions, thus helping forensic pathologists in finding a way through the tangled jungle of wound vitality evaluation.

Forensic Impact of the Omics Science Involved in the Wound: A Systematic Review

Background: In forensic autopsies, examining the wounds is one of the most critical aspects to clarify the causal relationship between the cause of death and the wounds observed on the corpse. However, on many occasions, it is difficult to differentiate antemortem injuries from post-mortem injuries, mainly when they occur very close to the moment of death. At present, various studies try to find biomarkers and clarify the molecular mechanisms involved in a wound due to the high variability of conditions in which they occur, thus being one of the most challenging problems in forensic pathology. This review aimed to study the omics data to determine the main lines of investigation emerging in the diagnosis of vital injuries, time of appearance, estimation of the age and vitality of the wound, and its possible contributions to the forensic field.

Methods: A systematic review of the human wound concerning forensic science was carried out by following PRISMA guidelines.

Results: This study sheds light on the role of omics research during the process of wounding, identifying different cytokines and other inflammatory mediators, as well as cells involved in the specific stage of the wound healing process, show great use in estimating the age of a wound. On the other hand, the expression levels of skin enzymes, proteins, metal ions, and other biomarkers play an essential role in differentiating vital and post-mortem wounds. More recent studies have begun to analyze and quantify mRNA from different genes that encode proteins that participate in the inflammation phase of a wound and miRNAs related to various cellular processes.

Conclusions: This study sheds light on the role of research in the molecular characterization of vital wounds, heralding a promising future for molecular characterization of wounds in the field of forensic pathology, opening up an important new area of research.

Systematic Review Registration: URL: https://www.crd.york.ac.uk/prospero/#myprospero, Identifier: CRD42021286623.

Mini Review: Forensic Value of Aquaporines

Forensic pathologists are routinely confronted with unclear causes of death or findings. In some scenarios, it can be difficult to answer the specific questions posed by criminal investigators or prosecutors. Such scenarios may include questions about wound vitality or causes of death when typical or landmark findings are difficult to find. In addition to the usual subsequent examinations to clarify unclear causes of death or special questions, immunohistochemical analysis has become increasingly important since its establishment in the early 40s of the 20th century. Since then, numerous studies have been conducted to determine the usefulness and significance of immunohistochemical investigations on various structures and proteins. These proteins include, for example, aquaporins, which belong to the family of water channels. They enable the transport of water and of small molecules, such as glycerol, through biological channels and so far, 13 classes of aquaporins could have been identified in vertebrates. The classic aquaporin channels 1, 2, 4 and 5 are only permeable to water. The aquaporin channels 3, 7, 9, and 10 are also called aquaglycerolporins since they can also transport glycerol. This mini review discusses the immunohistochemical research on aquaporins, their range of applications, and respective forensic importance, their current limitations, and possible further implementations in the future.

Application of CD83 and HSF5 to Identify Antemortem and Postmortem Skin Burns

OBJECTIVES

To explore the forensic application value of cluster of differentiation 83 (CD83) and heat shock transcription factor 5(HSF5) in identifying antemortem and postmortem skin burns.

METHODS

Through reverse transcription real-time quantitative polymerase chain reaction (RT-qPCR), CD83 and HSF5 mRNA levels in the skin tissues of antemortem and postmortem burned mice and human samples were detected quantitatively.

RESULTS

Compared with the control group and the postmortem burned group, the mRNA levels of CD83 and HSF5 in antemortem burned mice were higher. The high mRNA expressions of CD83 could be detected 96 h after death, and the mRNA expressions of HSF5 could be observed 72 h after death. Compared with undamaged skin, increased CD83 and HSF5 mRNA levels were detected in 11 out of 15 cases(P<0.05).

CONCLUSIONS

CD83 and HSF5 can be used in forensic practice as indicators for vital reaction in antemortem burn identification.

Aquaporin 1 and 3 as local vitality markers in mechanical and thermal skin injuries

Assessment of the vitality of an injury is one of to the main tasks in daily forensic casework. Aquaporins belong to the family of water channels. They enable the transport of water and of small molecules like glycerol through biological channels. So far, 13 classes of aquaporins are identified in vertebrates. The classical aquaporin channels 1, 2 and 4 are only permeable for water. The aquaporin channels 3, 7, 9 and 10 are also called aquaglycerolporins since they can also transport glycerol. Aquaporin 3 is expressed in epidermal keratinocytes. In the present investigation, the aquaporin 1 and 3 expression in mechanically and thermally damaged skin is investigated by immunohistochemistry. The study collective comprises 30 cases (63.3% male and 36.7% female) with an age range between 19 and 95 years (mean value 54.6 years). The skin injury comprises different kinds of blunt force, sharp force, strangulation marks, thermal injury, gunshot wounds and frost erythema. In all kinds of mechanical and trauma injury, an increased expression of aquaporin 3 in the keratinocytes of the epidermis was found. There is no correlation of the aquaporin 3 expression with age, sex, body mass index, duration of agonal period and postmortem interval. Concerning aquaporin 1, there were no differences between injured and uninjured skin. Aquaporin 3 is independently from the kind of skin injury and appears to be a valuable immunohistochemical parameter of vitality.

Unusual (self-)injuries in a case of hanging

A 41-year-old man was found by his wife in an atypical hanging situation in their apartment. As there was a known previous psychiatric illness and a history of suicide attempts, the investigative authorities assumed this case was a suicide. However, the autopsy revealed numerous findings that are unusual for a suicidal atypical hanging, including numerous cuts on the face, the arms and the penis. According to his wife, the deceased suffered from Asperger's syndrome with auto-aggressive behavior. He had allegedly injured himself with household scissors in the days before his death and had hit himself numerous times in the face the night before his death. His wife also revealed that she would injure him with scissors at his request. Even though the observed injury pattern in this case contradicted a self-infliction, the information given by the wife about the chronology of the occurrence of injuries could be reconciled with the findings of the immunohistochemical estimation of wound age. The circumstances that led to the hanging remained unresolved.

[Reliability of the immunohistochemical estimation of vitality and injury age: analysis and perspectives for study]

This review summarizes the literature data on the applicability of various immunohistochemical markers for the diagnosis of vitality and injury age. Current state of the problem of the reliability of the estimation of injury vitality, and the most promising immunohistochemical markers for further study are also considered.

Lethal hypothermia due to impalement

Impalement injuries in the region of large blood vessels can lead to extensive and even lethal blood loss. However, they can also lead to forced positions from which the affected persons cannot free themselves. This 85-year-old woman was found dead in a prone position in her garden. A metal bar had penetrated deeply into the front of her right thigh, while the other end of the bar was stuck firmly in the soil. The metal bar had merely displaced the woman's muscles and the larger blood vessels without causing major blood loss. There were typical findings of lethal hypothermia, including Wischnewski spots of the gastric mucosa and frost erythema on both knees and the left lower leg. The fall onto the metal bar caused an impalement injury leading to a forced position from which the woman could not free herself where she finally succumbed to lethal hypothermia.

Forensic application of epidermal AQP3 expression to determination of wound vitality in human compressed neck skin

In forensic practices, it is often difficult to determine wound vitality in compression marks of the neck with naked eyes. AQP1 and AQP3 are the major water channels associated with skin. Thus, we immunohistochemically examined the expression of AQP1 and AQP3 in neck skin samples to discuss their forensic applicability to determination of the wound vitality. Skin samples were obtained from 56 neck compression cases (hanging, 35 cases; strangulation, 21 cases). The intact skin from the same individual was taken as a control. Although AQP1 was immnunostained in dermal capillaries in both the neck compression marks and intact skin samples, there was no significant difference in the magnitude of AQP1 expression between both groups. On the contrary, AQP3-positive signals could be faintly detected in uninjured skin samples, and the positive signals seemed more intense in the keratinocytes in compression regions. Morphometrical analyses revealed that the ratio of AQP3-expressed keratinocytes was significantly enhanced in neck compression regions, compared with control groups. From the viewpoints of forensic pathology, immunohistochemical detection of AQP3 in the neck skin can be considered a valuable marker to diagnose the trace of antemortem compression.

The Veterinary Forensic Necropsy: A Review of Procedures and Protocols

Investigation of animal-related crime, and therefore submission of forensic cases to veterinary pathology facilities, is increasing, yet many veterinary pathologists are unfamiliar and often uncomfortable with involvement in the forensic necropsy. This article discusses various aspects of the forensic necropsy without specific attention to any particular species group or crime. General advice is given on procedures, documentation, and recording of the examination, and the article indicates how these features may differ from those used in investigation of natural disease. It also discusses evidence management, including recordkeeping, identification of evidence, labeling of photographs, and use of standard operating procedures and protocols. Various written and visual methods for documentation of the forensic necropsy are covered, and adjunctive topics such as sample collection, assessment, and description of wounds and taphonomy are included. Cause, mechanism, and manner of death are defined, and guidance to the use of these terms is given. The aim of this article is to offer guidance on procedural aspects of the forensic necropsy that will help those developing their forensic services, contribute to standardization of the provision of forensic veterinary pathology, and build the confidence of the "uncomfortable" forensic veterinary pathologist.

Detection of endothelial progenitor cells in human skin wounds and its application for wound age determination

Endothelial progenitor cells (EPCs), a newly identified cell type, are bone marrow-derived progenitor cells that co-express stem cell markers and vascular endothelial growth factor (VEGF) receptor (Flk-1). In this study, a double-color immunofluorescence analysis was carried out using anti-CD34 and anti-Flk-1 antibodies to examine the time-dependent appearance of EPCs, using 52 human skin wounds with different wound ages (Group I, 0-1 days; Group II, 2-6 days; Group III, 7-14 days; and Group IV, 17-21 days). In wound specimens with an age of less than one day, CD34(+)/Flk-1(+) EPCs were not detected. EPCs were initially observed in wounds aged two days, and their number was increased in lesions with advances in wound age. In morphometrical analysis, the average number of EPCs was the highest in the wounds of Group III. Especially, 20 out of 21 wounds aged 7-12 days had >20 EPCs, and all wound samples with postinfliction intervals of 14-21 days had <15 EPCs. These observations at least showed that >20 EPCs would indicate a wound age of 7-12 days. Taken together, our observations indicate the detection of EPCs would be useful for wound age determination.

Epidermal aquaporin-3 is increased in the cutaneous burn wound

INTRODUCTION

Aquaporins (AQP) are a family of transmembrane proteins that transport water and small solutes such as glycerol across cell membranes. It is a mediator of transcellular water flow and plays an important role in maintaining intra/extracellular fluid homeostasis by facilitating water transport in response to changing osmotic gradients. In the skin, AQPs permit rapid, regulated, and selective water permeability and have been demonstrated to play a role in skin hydration, cell proliferation, migration, immunity, and wound healing. However, the expression of AQP-3 in the cutaneous burn wound has never been elucidated. We sought to assess the expression of AQP-3 in patients with burn wounds.

METHODS

A fresh full thickness biopsy sample was taken from the center of the burn wound, the burn wound edge, and the graft donor site in 7 patients (n=21), approximately 3-7 days post injury. Fixed, paraffin embedded sections were stained using AQP-3 specific antibody and examined by immunofluorescence. Fresh samples were processed to quantify AQP-3 protein expression with Western blot analysis.

RESULTS

The central portion of the burn wound revealed destruction of the epidermis and dermis with no AQP-3 present. Along the burn wound edge where the epidermal architecture was disrupted, there was robust AQP-3 staining. Western blot analysis demonstrated deeper staining along the burn wound edge compared to unburned skin (control). Quantification of the protein shows a significant amount of AQP-3 expression along the burn wound edge (3.6±0.34) compared to unburned skin (2.1±0.28, N=7, *p<0.05). There is no AQP-3 expression in the burn wound center.

CONCLUSION

AQP-3 expression is increased in the burn wound following injury. While its role in wound healing has been defined, we report for the first time the effect of cutaneous burns on AQP-3 expression. Our data provides the first step in determining its functional role in burn wounds. We hypothesize that development of AQP3 targeted therapies may improve burn wound healing.