Neurovascular proteases in brain injury, hemorrhage and remodeling after stroke.

Matrix metalloproteinases (MMPs) mediate tissue injury during acute stroke. Clinical data show that elevated MMPs in plasma of stroke patients may correlate with outcomes, suggesting its use as a biomarker. MMP-9 signal has also been detected in clinical stroke brain tissue samples. Because tissue plasminogen activator can upregulate MMPs via lipoprotein receptor signaling, these neurovascular proteolytic events may underlie some of the complications of edema and hemorrhage that plague thrombolytic therapy. However, in contrast to its deleterious actions in acute stroke, MMPs and other neurovascular proteases may play beneficial roles during stroke recovery. MMPs are increased in the subventricular zone weeks after focal stroke, and inhibition of MMPs suppress neurogenic migration from subventricular zone into damaged tissue. In peri-infarct cortex, MMPs may mediate neurovascular remodeling. Delayed inhibition of MMPs decrease markers of remodeling, and these phenomena may be related to reductions in bioavailable growth factors. Acute versus chronic protease profiles within the neurovascular unit are likely to underlie critical responses to stroke, therapy, and recovery.