Abstract: Objective To investigate the expression of caspase-6 in rat skin contusion and its surrounding areas during repairment. Methods Immunohistochemical SP method and Western blot technique were used to study the expression and activation of caspase-6 in rat skin contusion and its surrounding areas. Results Weak expression of caspase-6 was detected in cytoplasms of polymorphonuchear cells (PMNs) infiltrated in the injured area at 3 hours post-contusion. The ratio of the caspase-6 positive cells was low (25.78±1.38)%. The expression of caspase-6 was increased prominently (47.70±5.14)% at 12 hours post-contusion. Almost all of the PMNs,mononuclear cells (MNCs) and fibroblastic cells (FBCs) were caspase-6 positive with both cytoplasm and nucleus staining (54.58±5.64)% on post-contusion day 3. The expression of caspase-6 decreased gradually thereafter. The expression of the 34-kDa pro-caspase-6 was detected by Western blot in both control and the post-contusion groups with time dependent dynamics. Conclusion These results suggest that caspase-6 may play a major role in trauma-induced inflammatory response. Since caspase-6 shows a timely dependent expression in PMNs,MNCs and FBCs during skin injury repair in rat,it may be used as a marker for the contusion age determination,

Key words: forensic pathology, skin contusion, caspase-6, contusion age determination