MMP9 and brain ischemia: It improved the cerebral nerve function score defect after cerebral ischemia/reperfusion, reduced the infarct volume ratio, alleviated cerebral edema, improved the pathological injury degree of cerebral infarction area, up-regulated the expression of tight protein ZO-1 and occludin, decreased the expression of matrix metal proteinase MMP-9 in the cerebral infarction area after cerebral ischemia/reperfusion, and reduced the inflammatory response.