| Study background and objective:: Human skin is the largest organ, directly contacts with the outside world, the skin has an important role for body to protect and barriers, and most vulnerable to mechanical injury,so in the practice of forensic medicine, timing of wound age is to be resolved Key issue for forensic workers. Because of this, the research of estimation on skin injury age, has been one of the hot issues at home and abroad for forensic pathology workers. E-selectin is one of the members of the SF of AM. Its distribution is very limited in the body,E-selectin is crined mainly by endothelial cells of the capillaries and post venule, and without storage in the cells. After only in trauma and inflammatory stimulation, E-selectin expresses on the surface of vascular endothelial cells, and has a specificity. After E-selectin expression, it participates in memory T lymphocyte, monocytes, eosinophils and basophils granulocyte of the gathering, and endothelial cell proliferation, migration, tubular capillary formation and the generation, but it is most important for E-selectin to lead in the blood neutrophil adhesion. E-selectin participates in repairing at the early dama -ge. It is most focused on the clinical aspects for research of E-selectin at home and abroad at present. For it, in the field of forensic medicine, it is very rare on the research for express -ion of E-selectin after skin damage different times and post -mortem stability. Especially on domestic, it is almost reported for E-selectin of timing of skin mechanical injury and repair age. Therefore, we established the model of skin incised wound in the head skin of rats and employed immunohistochemical and positive cell counting techniques to examine and analyze the expression of E-selectin in the healing process of wound and the identification of his antemortem wounds or postmortem injury to provide a new theoretical evidence for the wounding interval estimation of forensic pathology.Methods: For the experiment, rats were divided into experimental and control groups completely at random methods. The experimental group was divided into antemortem incision groups (killed at 0.5h,1h,2h,3h,5h,7h9h,12h,1d,3d,5d,7d after incision) and postmortem incision groups(0.5h,1h,3h), postmortem stability group at -20℃(6h,12h,1d,2d,3d,4d,5d,6d,7d after death)and at 25℃(6h,12h,1d,2d,3d after death), and the non-incised rats skin was used as contro1.In antemortem incision groups an wound was made in the head skin of rats and obtained at arranged time after death, postmortem stability groups were all killed at 1d after head skin incised wound。while in postmortem incision groups an incised wound was made at arranged time after death and obtained. Immunohistochemical and positive cell counting techniques were employed in vital skin incision groups and postmortem stability groups and post -mortem incision groups as well as the non-incised rats skin, to explore the expression of E-selectin during skin incised wound healing and the applicability of time-dependent expressions of E-selectin to determination of wound age. The samples surrounding the lesion were harvested at different time points. The skin tissue was fixed wit paraformaldehyde-phosphate buffered asline, paraffin wax embedded sections were prepared for HE staining and microscope observation.The expression of E-selectin protein at different time were detected by immuno -histochemistry method The data collected were analyzed by the statistical package of SPSS11.0 software.Results: 1.Observation of the HE staining: The infiltration of mass inflammation cells were observed within 12h wound sites most of which were neutrophils. furthermore, the gradual formation and proliferation of granulation tissue were observed in1～3d after incision and the major inflammation cells were mononuclear cells and macrophages. The gradual maturation of granulation tissue with extinction of inflammation cells and plerosis of the wounds were observed in 5～7d after incision. As compare as instantly rats of death after 1d head skin incised wound,at-20℃postmortem stability groups' incised head skin tissue were less changes between 6h and 5d; there were very small number of inflammatory cells within the structure less clear, karyopyknosis, Cui cracked, but the edge of a clear organizational structure between 6d and7d.Howere,at 25℃the site of skin injury in inflammatory cells, some organizations gradually necrosis ,autolysis and dissolved, as well as damage the edge of ambiguity between 6h and 3d.The postmortem incision groups and the normal control group had no alteration like that. 2. Observation of the immunohistochemical SABC staining: After incision within 1h, there was litter brown positive reaction on the capillary endothelial cells around margin of incised skin wound and then positive reaction sustained increased, till to 1d, positive expression reached a peak; gradually expression weakened after expression, in 7d there was a small amount of positive expression. As compare as instantly rats of death after 1d head skin incised wound,at-20℃postmortem stability groups, there were no significance changes between 6h and 7d, However, at 25℃,with the extension of time, organization and cell necrosis and dissolved, the expression of injury 1d executed immediately after a significant change the E-selectin positive expression gradually reduced between 6h and 2d, in 2d, there was mostly no positive expression.In the control group and death there were no E-selectin expression.3,positive cell count results: positive cells rate (PR value) 1h after injury till to 1d E-selectin positive expression gradually increased,1d after injury E-selectin positive expression reached a peak ,after injury 3d~7d,PR value decreased gradually.4,the results were: variance analysis show -ed that his wounds between the two neighboring E-selectin PR values are compared with significant differences(P<0.01). 1d trauma of his group and other groups time were significantly different (P <0.01).3 The results of positive cell counting tech -niques: In the vital skin incisions, the figures of PR began at 1h after incision,which increased subsequently, and peaked at 1d.Then the quantity of E-selectin expression decreased gradually and minimized in the specimens aged 7 days. In postmortem stability groups at -20℃,the expression of E-selectin show no significance difference between 1day and 7day.howere,at 25℃t he expression of E-selectin show significance difference between 1day and 3day.4.The results of statistical processing: The results of analysis of variance were indicated that there were significance levels between consecutive groups (P<0.01). Comparing of each groups indicated that there were significance levels between the group of 1d after injury and else groups (P<0.01). In postmortem stability groups at -20℃, Comparing of each groups indicated that there were no significance levels between the group of 1d after injury .Conclusion: The expression of E-selectin protein increased after rat skin incised wound was associated with time-related, with a certain regularity, and the rise - the peak - the decline in sequential change. It reached a peak after 1 d in skin incised injury. and after death E-selectin expression stability is greatly affected by the temperature, at - 20℃, its expression was stability; but at 25℃environment, the poor stability. During his lifetime and after his death E-selectin is not expressed. It is important mean to identificate antemortem wound and injury after death,it can be as a referenced index to estimate the injury interval in early time after skin injury.
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