| Objective: Wound healing is a complex biological response which is generally composed of inflammatory, proliferative and maturation phases. It is well known that various kinds of biological substances are closely related with the wound healing process such as the promotion of inflammatory reactions, the formation of granulation tissue and angiogenesis. In forensic pathology, the expression of these biological substances in skin wounds was applied to wound age determination . One of the proposed functions is the chemoattracting cytokines also named chemokines which participate in the migration, activation and chemotaxis for leucocytes and play an important role in inflammation. MIP-1αas the CC subtribe of chemokines is about 8KD molecular weight。The production of MIP-1αis induced by bacterial or viral infection and other inflammatory cytokines like IL-1 and TNF-α. For cellular sources of MIP-1αit has already been reported that they are produced by macrophages,neutrophils, fibroblasts, endothelial cells and some tumour cells. MIP-1αproduces a marked biological effect by the combination of its acceptors and target cells .The target cells of MIP-1αare macrophages,neutrophils,eosinophils,NK cells,DC cells and so on. The biological role of MIP-1αis predominantly recruiting and chemotaxis for immunocytes such as macrophages,neutrophils,NK cells, restrainting the growth of hematopoietic stem cell and the infection of HIV. The present researchs of MIP-1αare mostly concentrated in clinical experiments,however,as we know the report of MIP-1αabout time estimation during skin incised wound healing in forensic medicine is rare . Therefore,we established the model of an incised wound in the dorsal skin of mouse and employed immunohistochemical and positive cell counting techniques to examine and analyze the expression of MIP-1αin the healing process of wound to provide a new theoretical evidence for the wounding interval estimation of forensic pathology.Methods: For the experiment, mice were divided into experiment and normal control groups completely at random and then experiment group is divided into antemortem incision groups (killed at 1h, 3h, 6h, 12h, 1d, 3d, 6d, 10d, 14d after incision) and postmortem incision groups(0.5 h,1 h,3 h,6h), and the non-incised mouse skin was used as contro1.In antemortem incision groups an wound was made in the dorsal skin of mouse and obtained at arranged time after death, 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 incision groups as well as the non-incised mouse skin,to explore the expression of MIP-1αduring skin incised wound healing and the applicability of time-dependent expressions of MIP-1αto determination of wound age.Results: 1.Observation of the HE staining: The infiltration of mass inflammation cells were observed within 1d wound sites most of which were neutrophils.Furthermore, the gradual formation and proliferation of granulation tissue were observed in 3～6d 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 10～14d after incision. The postmortem incision groups and the normal control group had no alteration like that. 2. Observation of the immunohistochemical SABC staining: Afer incision within 1d, strong MIP-1α-positive reactions were observed in the infiltration inflammation cells mostly in neutrophils and scattered mononuclear cells and macrophages. With increasing wound age, the strong MIP-1α-positive reactions were observed in the gradual formation and proliferation of granulation tissue in 3d after incision , with the maijor positive staining were observed in mass mononuclear cells and macrophages and some fibroblasts. In 10～14d after injury, still, the MIP-1α-positive reactions could been observed in some fibroblasts but the range and intensity of staining were weakened. In the postmortem incision groups(0.5h,1h group)and the normal control group MIP-1αwas only detected weak expression in the epidermal cells, hair follicle and sebaceous gland.However,the postmortem incision groups(3h,6h group)had no alteration like else groups. 3. The results of positive cell counting techniques: In the vital skin incisions, the figures of PR began at 6h after incision,which increased subsequently,and peaked at 3d.Then, the quantity of MIP-1αexpression decreased gradually and minimized in the specimens aged 14 days. 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 3d after injury and else groups (P<0.01).Conclusion: 1.The quantity of expression of MIP-1αvaried regularly in antemortem incision groups. It showed a process of upgrade-climactic-descendent expression,and peaked at 3d. 2. The cells of MIP-1α-positive expression varied regularly. It showed that in antemortem incision groups MIP-1α-positive expression was mainly in neutrophils in earlier period, then in mass mononuclear cells and macrophages at peaked time, finally in some fibroblasts in late phase. However in the postmortem incision groups(0.5h,1h group)and the normal control group MIP-1αwas only detected in some epidermal cells, hair follicle and sebaceous gland .3. The time-dependent expression of MIP-1αduring skin incised wound healing may be used as a useful reference marker,and the expression of early postmortem incision is also significantly valuable for forensic medicine.
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