[Postmortem DNA and RNA synthesis. Preliminary studies in human cadavers]

Development and validation of an mRNA-based multiplex body fluid identification workflow and a rectal mucosa marker pilot study

Molecular identification of body fluids and tissues is crucial in order to understand the circumstances of crimes. For that reason, molecular investigations used to identify body fluids/tissues have increasingly been examined recently. Various studies have proved that messenger RNA (mRNA) profiling is a sensitive and robust method for body fluid/tissue identification. The forensically relevant body fluids/tissues blood, semen, saliva, vaginal secretion, menstrual blood and skin have all been detected successfully by applying suitable mRNA assay. However, rectal mucosa, which can be found as evidence in sexual assault cases, has been neglected in forensic investigations. So far there is no mRNA marker to detect rectal mucosa, although anal penetration occurs in a large number of sexual assaults (23.2% of female victims and 50% of male victims). In this study, specific and sensitive mRNA markers for forensically relevant body fluids were adapted and validated in an mRNA multiplex assay for routine casework. This included the implementation of a DNA/RNA re-extraction method for automated extraction that can be integrated into casework without loss of DNA. This re-extraction method and the mRNA multiplex assay were tested using casework samples. PCR-primers were designed for the identification of rectal mucosa and the more effective marker MUC12 was integrated into an extended multiplex assay. The result of our study is a highly specific and sensitive mRNA multiplex assay plus an automated DNA/RNA re-extraction method, that can be integrated into casework and identify rectal mucosa for the first time.

RNA/DNA co-analysis from bloodstains on aged polyvinyl-alcohol gloves prepared for securing evidence from the hands of victims of fatal gunshot injuries

In contrast to cumulative techniques (e.g., tape-lift) for qualitative gunshot residues (GSR) analysis, topographic methods are commonly applied to preserve the integrity of evidence from a shooter's or victim's hand in cases of gun-related crimes. Topographic sampling techniques employing adhesive foils, latex, or the polyvinyl alcohol (PVAL) method enable unambiguous sampling of biological and non-biological trace material while preserving its spatial distribution and relation to each other. The PVAL method in particular allows for a topographically veridic and quantitative conservation of traces of GSR and biological stains that are embedded in the PVAL glove, because it completely removes these traces from the hand. The present study investigated the success rates of STR profiling and the detection of blood and brain-specific gene expression from minimal traces of blood splatter as well as parallel to the positive detection of gunshot residues embedded in 17 PVAL gloves taken from the hands of deceased persons in the context of homicide cases in the period between 1996 and 2003. The water-soluble PVAL matrix is shown to be fully compatible with successful STR profiling and the detection of blood- and brain-specific miRNA expression, even after up to 20 years of storage, demonstrating that this sampling technique offers advantages compared to other more simplistic sampling methods like taping.

RNA/DNA co-analysis on aged bloodstains from adhesive tapes used for gunshot residue collection from hands

In cases of firearm related fatalities a systematic investigation at the scene of death is indispensable to differentiate between self-inflicted and homicidal gunshot injuries. A common method to preserve gunshot residues (GSR) is their collection using adhesive tapes. However, the biological material gathered at the same time by the tapes would be of special interest if backspatter, ejected from the entrance wound against the direction of fire, could be detected. In the present study we examined the success rate of co-analysis of RNA and DNA recovered from biological traces sampled with adhesive tapes. The material originated from eight cases of fatal gunshots, taken from the hands of suspects or victims, examined 5 to 19 years ago for GSR. For all types of adhesive tapes tested, quantity and quality of the co-extracted nucleic acids was insufficient for successful DNA profiling, but was sufficient for the detection of blood-specific micro RNA (miRNA). In summary, sampling trace evidence from the hands of persons involved in fatal gunshots with adhesive tapes has a long-term detrimental effect on biological traces.

Micro-RNA - A potential for forensic science?

Micro-RNAs (miRNAs) are a class of small non-coding RNA (ncRNA) molecules with a length of 18 to 24 nucleotides which play an essential regulative role for many cellular processes. Whereas mRNA-analysis has become a well established technique in many forensic laboratories, micro-RNA has only recently been introduced to forensic science. Herein we provide a short outline of biogenesis, mode of function and regulation of miRNAs and take a look at tissue and cell specific miRNA expression. After recapitulating the role of mRNA analysis in forensic science we compare it to miRNA analysis and discuss the results of two recent studies applying miRNA analysis to a forensic research setting. We conclude that analysis of miRNA and perhaps small non-coding RNAs in general clearly has potential for forensic applications and merits attention of forensic scientists.

Advances in the diagnosis of wound vitality: a review

The diagnosis of the vital origin of wounds in many cases remains an unsolved problem for the forensic pathologist. Practical experience enables the expert to diagnose the vital or postmortem origin of wounds on the basis of macroscopic examination. In some cases, optic microscopy is used to confirm the diagnosis. In many other cases, additional more sensitive and specific markers of vitality are required. In the past 50 years, comprehensive research on this topic has resulted in a better understanding of the acute inflammatory reaction. The development and application of sensitive and specific markers through research in the areas of histochemistry, enzymology, and biochemistry has provided a partial solution to the problems involved in wound vitality diagnosis. A review of this challenging area of forensic pathology, including an explanation of these methods and markers, is presented in this paper.

RNA and DNA synthesis of epidermal basal cells after wounding. Comparison of vital and postmortem investigations

Incision wounds were made on both of the pinnae of each rat, and two biopsies from both the ears were taken for examination after different survival times of the wounds. Two biopsies were taken from each ear, four from each animal, two intravitally and two postmortem after 24 hours storage at 8 degrees C. One each of the intravital and one each of the postmortem biopsies were prepared and evaluated for quantification of RNA and DNA synthesis rate using an in vitro incorporation model with 3H-cytidine and bromodeoxyuridine (BrdU) as markers. The intravital specimens showed a significant increase in 3H-cytidine incorporation in the basal cell layer after survival times of 10 to 24 hours. No increase in the rate of RNA synthesis in the basal cell layer as a function of wound age was seen in postmortem specimens. In both intravital and postmortem biopsies the labelling indices after BrdU exposition increased significantly in the period from 32 to 60 hours post-injury. This suggest that DNA synthesis induced during life continues after death. Applied to forensic practice, these findings point to the possibility of determining the vitality of a wound in postmortem tissue. The RNA synthesis, obviously, precedes the DNA synthesis after mechanical trauma.

Temporal course of intravital and postmortem proliferation of epidermal cells after mechanical injury. An immunohistochemical study using bromodeoxyuridine in rats

The temporal course of epidermal basal cell proliferation in the wound of the pinna of rats was studied using bromodeoxyuridine (BrdU) immunohistochemistry. Following incisional wounding, the animals were sacrificed at intervals ranging from 0 hours to 32 days. Two biopsies were taken from each animal, one intravitally and one postmortem after 24 hours storage at 8 degrees C. Specimens were incubated in a solution containing BrdU and embedded in paraffin. BrdU expression was demonstrated by a monoclonal antibody against BrdU. In both intravital and postmortem biopsies, the labelling indices increased significantly in the period from 32 to 60 hours post-injury. This suggests that DNS synthesis induced during life continues after death. Applied to forensic practice, the present findings point to the possibility of determining the vitality of a wound in postmortem tissue.

Histological and enzyme histochemical parameters for the age estimation of human skin wounds

Routine histological staining techniques form the basis of a forensic age estimation of human skin wounds and the determination of vitality is aided by the detection of neutrophilic granulocytes which appear earliest about 20-30 min after wounding. A clear granulocyte infiltration and a significant increase in the number of macrophages indicates a post infliction interval of at least several hours. Macrophages containing incorporated particles such as lipophages, erythrophages or siderophages appear earliest at a wound age of 2-3 days similarly to extracellular deposits of hemosiderin, whereas the rarely detectable iron-free pigment hematoidin and spot-like lymphocytic infiltrates in the granulation tissue appear approximately one week or more after wounding. A complete reepithelialization of surgically treated and primarily healing human skin lesions can be expected earliest 5 days after wound infliction and the absence of a complete new epidermal layer indicates a survival time of less than 21 days. Enzyme histochemical methods allow a wound age differentiation especially in the range of a few hours. An increase in nonspecific esterases can be observed earliest approximately 1 hour after wounding followed by other enzymes such as acid phosphatase (approximately 2 h), ATPase (approximately 4 h), aminopeptidase (approximately 4 h) or alkaline phosphatase (approximately 4 h). Positive results, however, cannot be regularly found. Therefore, the detection of reactive changes is useful for a wound age estimation whereas negative findings, which in general must be interpreted with caution, can provide information only in a limited number of histological parameters.

Time-dependent RNA synthesis in different skin layers after wounding. Experimental investigations in vital and postmortem biopsies

Incision wounds were made on the outer ear of rats and two biopsies were taken for examination after different survival times. In each case a biopsy was made of vital tissue and a second of postmortem tissue after refrigeration for 24 h. The biopsies were exposed to a solution containing the RNA precursor 3H-cytidine for 1 h, washed and fixed in formalin. Sections 5 microns thick were then autoradiographically prepared and automatically evaluated using Quantimet 920. The intravital specimens showed a significant increase in 3H-cytidine incorporation in the basal cell layer after survival times of 10-24 h. No increase was seen in the stratum corneum, corium or cartilage tissue. The investigated distance from the wound margin did not have any significant bearing on the results. The 3H-cytidine incorporation rate in postmortem tissue was practically identical with that of vital tissue, but no increase was observed in the rate of RNA synthesis in the basal cells as a function of the age of the wound. It may therefore be assumed that this method provides no additional information as to the age of wounds in postmortem examination.

Cytokinetics of epidermic cells in skin from human cadavers. I. Dependency on the postmortal interval

Punch biopsies taken from the extensor side of the thigh of 35 human cadavers were incubated in vitro with radioactively labeled thymidine (3H-thymidine = 3H-TdR, 14C-thymidine = 14C-TdR) to determine whether a relationship exists between changes in the proliferative activity of the skin and the postmortal interval after irreversible cardiac arrest. The cadavers were stored at 4 degrees C. Cadavers with indeterminable time of death or presence of intoxication, drug therapy with cytostatic agents, or a skin disease were excluded from the study. Single, double, or multiple biopsies were performed on the same cadaver; single labeling with 3H-TdR was done in all cases; double labeling with 3H-TdR and 14C-TdR in selected cases. No relevant changes in the labeling index (mean, 2.39 +/- 1.03%) were demonstrable within the examined postmortal interval of 77.75 h. The DNA synthesis time (ts) was, on the average, 4.75 +/- 1.44 h; a certain relationship to the postmortal interval existed since ts declined with increasing storage time. The potential doubling time (tpot) decreased accordingly, beginning with 181.7 h (mean storage time, 29.9 h) and ending with 137.7 h (mean storage time, 41.7 h). No statistically relevant differences, however, were established at the 1% level. Whereas both labeling index and tpot during the early postmortal interval are comparable with observations in live humans, ts was relatively short as compared to that for the epidermis of live humans.