Role of matrix metalloproteinase-9 in apoptosis of hippocampal neurons in rats during early brain injury after subarachnoid hemorrhage

This study investigated the possible involvement of matrix metalloproteinase 9 (MMP-9) in early brain injury (EBI) of subarachnoid hemorrhage (SAH) in rats. MMP-9 activities in hippocampus were examined at 6, 12, 24, 48 and 72 h after SAH. Laminin was detected by immunohistochemistry. Apoptosis of neurons in hippocampus was observed by TUNEL. Brain water content was also examined. MMP-9 activity and the number of apoptotic neurons increased from 12 to 72 h with a peak at 24 h. Laminin was found to decrease at 12 h, reached minimum at 24 h and began to increase from 48 h, which had a negative correlation with apoptotic neurons. The changes of brain water content were found to be coincidence with that of neuronal apoptosis. Our findings suggest that MMP-9 is probably involved in the pathophysiological events of EBI after SAH, through degrading laminin which leads to neuronal anoikis of hippocampus.