Some other studies show that apoE4 significantly dampens Aβ-induced MMP-9 levels, possibly by downregulating the Rho-Rho kinase (ROCK) pathway, and reduction of astrocytic MMP-9 by apoE4 may affect Aβ clearance and promote Aβ deposition in AD [22, 23]. This evidence concerns the gene MMP9 and Alzheimer disease.