Study on changes of MMP-3 expression after brain contusion in rats.

To investigate the mechanism and to explore the applicability of MMP-3 (matrix metalloproteinase-3) to determine the age of brain contusion, expression of MMP-3 was studied by immunochemistry and Western blot techniques on model of brain contusion in rats. Brain contusion was performed by falling weight in adult male Sprague-Dawley rats after anesthetized with diethyl ether, then maintained with 2% pentobarbital sodium (30 mg/kg). Samples were collected at 6 and 12 h, 1, 3, 5, 7, 10 and 14 days after the contusion. Histopathological examination and immunostaining of MMP-3 were conducted using paraffin sections. Protein of MMP-3 bands was visualized by ECL kit in Western blot. Result showed that: No staining in control and sham operation group. The staining of MMP-3 positive appeared 6 h after contusion, and it becomes stronger 24 h after contusion, the staining reached the maximum at 5 days post-contusion, then it decrease, positive staining could still be observed at 14 days after contusion. No MMP-3 expression was detected in control and sham group by Western blot analysis. Brain contusion caused the appearance of a band of 45 ku molecular weight, which corresponds to an active form of MMP-3. Conclusions were drew that there is no expression of MMP-3 in normal brain, that the expression of MMP-3 appears 6h after TBI, and that there is a relationship between the expression of MMP-3 and the time course after TBI, and MMP-3 would be used as an indicator for estimating the age of traumatic brain contusion in forensic pathology.