Time heals all wounds: Identification of RNA biomarkers for forensic wound age estimation in human skin tissue samples.

Estimating wound age can be crucial in forensic work for establishing a causal link between the injury and death, or for better characterizing the timing and circumstances of the injury. Conventional methods for estimating wound age are not always reliable and often fail to achieve sufficient accuracy. Animal studies have shown that RNA-based methods for wound age estimation can produce reliable and reproducible results. However, the transferability of wound markers identified in animal experiments to human samples is questionable, and a model based on human tissue needs to be developed. Twenty-three paired samples including the wounded tissue and the corresponding uninjured skin tissue were collected during routine autopsies with sharp injuries inflicted between a few seconds and 28 days prior to death. The samples underwent targeted transcriptome sequencing (targeting > 20.000 human RefSeq transcripts) and were analyzed for differentially expressed genes. The samples were grouped into three categories based on wound age: acute (< 1 day), intermediate (1-3 days) and prolonged (> 3 days). A functional analysis of the differentially expressed genes revealed various biological functions that can be attributed to the individual stages of wound healing. A total of 31 potential marker candidates were identified, 21 of which have not yet been described in the context of a temporospatial association with wound healing. Results demonstrate that the analysis of human material is essential for the development of a human-specific forensic predictive model. The candidate markers identified in this study represent a first step towards an RNA-based method for estimating wound age in humans.