Time-dependent appearances of myofibroblasts during the repair of contused skeletal muscle in rat and its application for wound age determination.

OBJECTIVE: To research the relation between the time-dependent appearances of myotibroblasts during the repair of contused skeletal muscle in rat and wound age determination. METHODS: A total of 35 SD male rats were divided into the control and six injured groups according to wound age as follows: 12 h, 1 d, 5 d, 7 d, 10 d and 14 d after injury. The appearances of myofibroblasts were detected by HE staining, immunohistochemistry and confocal laser scanning microscopy. Masson's trichrome staining was utilized to examine collagen accumulation in the contused areas. RESULTS: Immunohistochemical staining showed that α-SMA+ myofibroblasts were initially observed at 5 d post-injury. The average ratio of myofibroblasts was highest at 14 d post-injury, with all samples, ratios more than 50%. In the other five groups, the average of α-SMA positive ratios were less than 50%. The collagen stained areas in the contused zones, concomitant with myofibroblast appearance, were increasingly augmented along with advances of posttraumatic interval. CONCLUSION: The immunohistochemical detection of myofibroblasts can be applied to wound age determination. The myofibroblasts might be involved in collagen deposition during the repair of contused skeletal muscle in rat.