The role of matrix metalloproteinases in Alzheimer's disease and small vessel disease.

Matrix metalloproteinases (MMPs) are a family of enzymes participating in maintenance and remodeling of the extracellular matrix. Their many types are involved in diverse, sometimes contrasting physiological processes, and they are ubiquitously present throughout the CNS. In this mini-review we focused on MMP-2, MMP-3, MMP-9, and MMP-14, highlighting their importance in pathways linked to Alzheimer's disease and small vessel disease. Despite overlapping roles in modulating brain-blood barrier impairment, neuroinflammation, and the accumulation of disease-specific proteins like amyloid-β and tau, they show somewhat distinct expression patterns in different cells and differ in their primary influences on disease mechanisms. Although our knowledge is still very limited, there is evidence linking them to imaging manifestations of cerebral vessel disease and suggesting they could be a target for therapeutic interventions.