Objective:To explore the expression of MMP-2 and MMP-9 in rat skin after injury and its relationship with the wound time

in order to supply an experimental evidence for the prediction of injury time.Methods:After a model of incision of rat’s skin was set

immuno-histochemistry technique and auto-image analysis were used to study the expression of MMP-2 and MMP-9 at different post-traumatic time intervals in both antemortem and post-mortem groups.Results:The expression of MMP-2 and MMP-9 in ante mortem group was higher than that in the normal control group(P<0.05).However

in post-mortem injury group

there were no significant changes in anti-MMP-2 and MMP-9 immuno-reactivities in the area of injury and around the area of injury

compared with the normal control group(P>0.05).Further

the expression of MMP-2 could be detected as increasing at 0.5 h

and reached maximum on 3 d

maintained the high level to the 5th day

then decreased gradually

returned to norma1 lastly on 12～14 d.Compared with MMP-2

the expression of MMP-9 could be detected increasing at l h

and reached maximum on 3 d

maintained the high level to the 5th day

then decreased gradually

returned to norma1 lastly on 12～14 d .From 0.5 h to 3 d of wound interva1

the expression of MMP isoforms were identified in a large number of infiltrating neutrophilic granulocytes

afterwards the fibroblastic cells(FBCs) and the vascular endothelial cells accounted for the most part of the MMP-2and MMP-9 positive cells.Conclusion:The expression of MMP-2 and MMP-9 in rat’s skin is time dependent after skin injury

which could be used as a bio-marker to determine the time of injury.