MMP2 and brain ischemia: Following localized cerebral ischemia, a significant increase in the activity of matrix metalloproteinases (MMPs) in the rat brain occurs in two temporal phases: first, an induced increase in MMP-9 from 4 h to 4 days, followed by a large increase in MMP-2 appearing on day 4, which may be related to MMP-2 in reactive microglial cells or macrophages (Planas et al., 2001).