Ubiquitin expression in skin wounds and its application to forensic wound age determination

The time-dependent expression of ubiquitin (Ub) was examined in murine skin wounds and 55 human skin wounds with different wound ages (groups I: 0-12 h, II: 1-5 days, III: 7-14 days and IV: 17-21 days). In murine skin wound specimens, neutrophils, macrophages and fibroblasts showed intensive Ub-positive reactions in the nuclei. In the human wound specimens with wound ages between 4 h and 1 day, neutrophils with strong intranuclear positive reactions for Ub were observed. With increasing wound ages, the nuclei of macrophages and fibroblasts were more intensively stained with anti-Ub antibody. Morphometrically, the intranuclear Ub-positive ratios were very low in group I. The skin wound specimens in groups II and IV showed Ub-positive ratios of >10%, and all samples in group III had Ub-positive ratios of >20%. These results suggest that a ratio of >10% for Ub indicates a wound age of at least 1 day. In contrast, Ub-positive ratios of less than 10% indicate a wound age of <1 day. Moreover, there was a significant difference in the Ub-positive ratio between group III and the other three groups. Thus, Ub-positive ratios considerably exceeding 30%, possibly indicate a wound age of 7-14 days. From the viewpoint of a forensic pathology application, the present study showed that Ub is suitable as a marker of wound age determination.