MMP9 and brain ischemia: These ischemia-induced protective microglia are called M2 microglia, and their protective effect is considered to be due to the secretion of remodelling factors, such as VEGF and BDNF, matrix metalloproteinase-9 (MMP-9), and transforming growth factor-beta (TGF-β) after ischemia17, 20, 21, 22, 23, 24, 25, that may facilitate anti-inflammation, angiogenesis, and axonal outgrowth after cerebral ischemia.