Matrix metalloproteinase-19 expressed in cerebral amyloid angiopathy

Background. Cerebral amyloid angiopathy (CAA) is a frequent finding in the brains of patients with Alzheimer's disease (AD). CAA may be complicated with CAA-associated intracerebral haemorrhage (CAAH). Previous studies have revealed matrix metalloproteinase (MMP) expression in a mouse model of CAA and in human intracerebral haemorrhage. Here we studied the involvement of MMPs in human CAA and CAAH. Material and methods. To investigate the putative expression of MMPs in human CAA and CAAH (Step 1), immunohistochemistry (IHC) against MMPs-1, -2, -7, -9, -19 and -26 was applied on tissue microarray (TMA) constructed of cerebral samples from 29 individuals with AD, 15 with CAAH and 2 controls. The findings in TMA were confirmed (Step 2) in tissue samples from 64 individuals, 45 presenting with CAA (including 36 with CAAH) and 19 without CAA (including 11 with hypertensive cerebral haemorrhage). Results. In Step 1, immunoreactivity against MMPs-19 and -26 was detected in cerebral blood vessels in CAA. The results were confirmed in Step 2, where CAA (p < 0.001) and intracerebral haemorrhage (p==0.045) were associated with vascular immunoreactivity against MMP-19. Multivariate analysis showed that the association between vascular MMP-19 and intracerebral haemorrhage was dependent from CAA. MMP-26 associated with CAA (p==0.021) but not with intracerebral haemorrhage. Conclusion. This is the first human study showing local MMP-19 immunoreactivity in the A beta beta-amyloid-laden blood vessels in CAA, suggesting that MMPs may be involved in CAA.