MMP9 and uveitis: PGE2 expression is thought to be part of the cascade that breaks down the blood–ocular barrier, since earlier studies have paralleled the rise in protein in the aqueous humor with the rise of PGE2 expression.8 MMP-9 is also likely to be a part of this process since it cleaves type IV collagen in basement membranes and allows the extravasion of leukocytes from the circulatory system into the aqueous humor during uveitis.10 We found that treatment with ME reduced PGE2 as measured by ELISA (Fig. 4) and qualitatively reduced immunostaining for MMP-9 (Fig. 5E).