Increased expressions and activations of apoptosis-related factors in cell signaling during incised skin wound healing in mice: A preliminary study for forensic wound age estimation

Recent studies have demonstrated that apoptosis plays a pivotal role during skin wound healing and apoptosis-related factors in cell signaling regulate a variety of cellular function. In this study, the expressions of p38MAPK, and JNK, iNOS, eNOS were detected and the activations of caspase-6, -7, -8, -9, and calpain, another signaling pathway of apoptosis, were also investigated by immunohistochemical staining and Western blotting in mice. A time-dependent increase of each protein level was observed by immunohistochemistry and Western blot in mouse skin incision. p38MAPK level peaked at 12 h and 3 d, calpain level peaked at 1 d and 5 d, iNOS level peaked at 1 d and 10 d, while the peak levels of eNOS, caspase-6, -7, -8, and -9 occurred at 3 d and p-JNK at 1 d post-injury. In the early phase of wound healing, infiltrating polymorphonulcear cells were labeled with all the factors except caspase-8. Thereafter, infiltrating mononuclear cells and proliferating spindle-shaped fibroblastic cells showed positive staining for p38MAPK, JNK, calpain, caspases and NOS. The activation of caspase-8, -9, -6, and -7 as detected by Western blot indicated that caspase apoptotic pathway may take effect in cellular elimination during skin wound healing. From the viewpoint of forensic pathology, the time-dependent expressions of the factors in apoptotic pathway during skin incised wound healing may be used as potential markers for wound age estimation.