Potential Contribution of Matrix Metalloproteinase-9 (MMP-9) to Cerebral Vasospasm After Experimental Subarachnoid Hemorrhage in Rats

This study investigated the possible involvement of matrix metalloproteinase 9 (MMP-9) in cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH) in rats. The CVS model was established by injection of fresh autologous nonheparinized arterial blood into the cisterna magna. Experiment 1 aimed to investigate the timecourse of the MMP-9 expression in the basilar artery after SAH. In Experiment 2, we chose the maximum time point of vasospasm (Day 3) and assessed the effect of SB-3CT (a selective MMP-9 inhibitor) on the regulation of cerebral vasospasm. The cross-sectional area of basilar artery was measured by H&E staining and the MMP-9 expression was assessed by immunohistochemistry analysis. The elevated expression of MMP-9 was detected in the basilar artery after SAH and peaked on day 3. After intracisternal administration of SB-3CT, the vasospasm was markedly attenuated after blood injection on day 3. Our results suggest that MMP-9 is increasingly expressed in a parallel time course to the development of cerebral vasospasm in this rat experimental model of SAH and that the administration of the specific MMP-9 inhibitor could prevent or reduce cerebral vasospasm caused by SAH.