Abstract: The expression of matrix metalloproteinase-9 (MMP-9) after cerebral ischemia reperfusion injury can accelerate the damage of brain-blood barrier and plays an important role in brain edema after cerebral hemorrhage. The level of MMP-9 can reflex the severity of brain ischemia, indicate to the volume of infarct area and point out the prognosis of the disease. This article reviewed its source and expression,the gene regulation and polymorphism, hemorrhage transformation and nhibitors, and the mechanism was also analyzed.

Key words: matrix metalloproteinase-9, cerebral ischemia, review