A key role in the activation of MMP in the retina in glaucoma may be played by tissue plasminogen activator (tPA) and urokinase plasminogen activator (uPA): both levels were increased in the retinas of C57BL/6 mice after injection of staurosporine into the vitreous humor, and this accompanied increased MMP-9 activity and retinal ganglion cell death [188]. This evidence concerns the gene PLAU and glaucoma.