MMP2 and brain aneurysm: Comparing the gene expression of ruptured and unruptured cerebral aneurysms with genome-wide microarrays have been investigated, which shows the overexpression of collagenases (matrix metalloproteinase 2 and 9), pro-apoptotic genes and inducible nitric oxide (NO) synthetase in ruptured cerebral aneurysms, as well as downregulation of anti-apoptotic genes.