The dynamics of inflammatory cytokines in the healing process of mouse skin wound: a preliminary study for possible wound age determination

Abstract

The dynamics of inflammatory cytokines such as interleukin-1 alpha (IL-1 alpha), interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF alpha) during the healing process of mouse skin wounds were examined using the enzyme-linked immunosorbent assay and immunostaining. The applicability of this examination for wound age estimation is discussed from the perspective of forensic pathology. After wound induction, mice were sacrificed at intervals ranging from 0 to 240 h. The levels of TNF alpha and IL-1 beta began to elevate rapidly after wounding and reached a peak at 3 h. The IL-1 alpha level reached a peak at 6 h, and IL-6 peaked at 12 h. An infiltration of numerous leukocytes, indicating acute inflammation, was observed at 3 and 6 h, and the main source of the cytokines was immunohistochemically identified as neutrophils. These results indicate that TNF alpha and IL-1 beta play an important role in the commencement of inflammation. "Rebound" of cytokine levels, i.e. a re-increase, was observed at 72 h after wounding. Histological examination of the 72-h-old wound showed migration of fibroblasts and the formation of new granulation tissues, indicating the proliferative stage of the wound healing process. These experimental findings indicate that these cytokines have a close relationship to wound remodeling as well as to inflammation. From the viewpoint of forensic pathology, it is considered that inflammatory cytokines may become one of the markers for wound age estimation, but further studies are needed, especially those involving the investigation using human wound specimens with known time intervals after injury.