MMP9 and glioma: For example, astrocytes from aging primate brains synthesize excess hyaluronic acid, supporting single-cell invasion and NF-κB activation18; aging astrocytes also produce excessive levels of fibronectin, which may promote cell survival and collective invasion19; and aging astrocytes express both MMP-2 and MMP-9, which are necessary factors glioma invasion of multiple brain regions20.