Time-dependent changes in local and serum levels of inflammatory cytokines as markers for incised wound aging of skeletal muscles

Abstract

Wound age estimation is an important research field in forensic pathology. The expression levels of cytokines in the incised skeletal muscle were analyzed using a mouse model to explore the applicability for wound aging. A 5-mm long incisional wound was made at the biceps femoris muscle, and the muscle and serum were sampled at 6, 12, 24 and 48 hours after injury. Using a multiplex bead-based immunoassay, we measured the tissue levels of nine cytokines (IL-1β, IL-6, IL-7, CCL2, CCL3, CCL4, CXCL1, CXCL2, and CXCL10), which are all involved in the pathways of inflammatory response and tissue injury. Immunoassay of post-injury muscle samples revealed significant increases in the levels of six cytokines, except for CCL3, CCL4 and IL-7, at 6 hours after injury. The elevated tissue levels of these six cytokines were maintained during 48 hours after injury, although the levels of IL-6 and CXCL1 were significantly decreased at 12 hours. In case of CCL3, its tissue levels were increased only at 12 hours. By contrast, CCL4 and IL-7 levels were increased only at 48 hours. Moreover, serum levels of most cytokines, except for CXCL1, remained unchanged during 24 hours after injury, followed by significant increases at 48 hours. Serum CXCL1 levels were increased at 6 hours and then decreased to the basal levels. Thus, the significant increase in the muscle levels of CXCL1 and IL-7 was observed at 6 and 48 hours after injury, respectively. Measuring muscle CXCL1 and IL-7 levels is helpful for estimating incised wound aging.