Wound age estimation based on chronological changes in chitinase 3-like protein 1 expression

Abstract

In forensic practice, wound age estimation is essential for making assessments of injuries; however, it remains challenging, and markers which correctly indicate wound age are required. Since our previous study showed that chitinase 3-like protein 3 (CHI3L3) expression changed chronologically in murine skin wounds, we hypothesized that other proteins of chitinase and chitinase-like protein (C/CLP) family, which CHI3L3 belongs to, might also have varied expression in wound healing. Therefore, we considered that some proteins of the C/CLP family could be used as markers of wound age estimation, and we aimed to test this hypothesis. Examinations of murine skin wounds revealed that the expression of chitinase 3-like protein 1 (CHI3L1) changed chronologically. CHI3L1 expression in human cadaver skin wounds, which was immunohistochemically analyzed by the average ratio of CHI3L1-expressed cells/total cells in 10 microscopic fields, was weak in wounds from days 0 to 1 after injury (0.11 ± 0.024; mean ± standard error of the mean); however, CHI3L1-positive cells appeared in wounds from days 2 to 3 (1.65 ± 0.19). The number of CHI3L1-expressed cells increased in wounds from days 4 to 6 (5.35 ± 0.35) but dropped from days 7 to 13 (1.53 ± 0.24). Receiver operating characteristic curve analysis indicated that wounds from days 4 to 6 after injury could be clearly distinguished from other wounds based on a cutoff value of 2.75, sensitivity of 92.31%, and specificity of 85.14%. Our findings suggest that CHI3L1 could be a reliable marker for wound age estimation in forensic practice.