The results showed that normal Circle of Willis arteries exhibited either minimal or negative staining for SPARC, MMP-2 and MMP-9 (Fig. 2A–C); however, human intracranial aneurysms stained extensively for both SPARC and MMP-2/-9 (Table 2, Fig. 3A–C). Here, MMP9 is linked to Dilatation of the cerebral artery.