MMP9 and cholesteatoma: Moreover, MMP-9 is considered to be an important neuroinflammatory factor that can be regulated by endogenous tissue inhibitors of metalloproteinases (TIMP)-1, and an imbalanced MMP-9 or TIMP-1 or MMP-9/TIMP-1 ratio is associated with a variety of diseases such as inflammation-accompanied cholesteatoma, chronic venous disease, atherosclerosis, and colo-rectal disease [21, 22].