For examples, MMP-9 was observed in neuritic plaques, neurofibrillary tangles, cytoplasm of neurons, and vascular walls in hippocampus and cortex; MMP-9 level was even significantly elevated in serum from patients with MCI due to AD compared with control (Lorenzl et al., 2003, 2008). This evidence concerns the gene MMP9 and Alzheimer disease.