Abstract: Objective To study the percentages of polymorphonuclear leukocytes （PMN）, mononuclear cells （MNC） and fibroblastic cells （FBC） in different post-traumatic intervals after skeletal muscle mechanical injury in rats. Methods The rat model of skeletal muscle mechanical injury was established. The rats were divided into injured groups （6 h, 12 h, 1 d, 3 d, 7 d, 10 d and 14 d after injury） and control group. The percentages of PMN, MNC and FBC in different post-traumatic intervals after skeletal muscle mechanical injury were assessed with HE staining and image analysis. Results At post-injury 6-12 h, the percentages of PMN and MNC infiltration appeared in injured sites and that of PMN reached peak. At 1 d, the percentage of MNC infiltration appeared and reached peak, while that of PMN decreased. At 3-7 d, the percentage of FBC gradually increased, while that of PMN and MNC decreased. At 10-14 d, the percentage of FBC reached peak. Conclusion The percentages of PMN, MNC and FBC in injured zones showed time-dependent changes, which might be used as reference index for determination of age of skeletal muscle injury.

Key words:  forensic pathology, wounds and injuries, muscle, skeletal, polymorphonuclear leucocytes, mononuclear cells, fibroblastic cells, rats