Intra-vitreal injection of methotrexate in experimental endotoxin-induced uveitis in rabbit

Uveitis is a major cause of vision loss. Methotrexate (MTX) has been widely used in uveitis due to its relatively safe profile. The purpose of this study was to evaluate the effects of two different dosages of MTX via intra-vitreal administration for treatment of endotoxin induced uveitis (EIU) in an experimental model. Thirty-five healthy rabbits were randomly divided into four groups and all animals were tolerated intra-vitreal injections. The first group received normal saline (NS), the second group received normal saline plus Salmonella typhimurium lipopolysaccharide endotoxin (LPS), (NS+LPS), the third group received 400 μg MTX plus LPS (LPS+MTX 400) and the fourth group received 800 μg MTX plus LPS (LPS+MTX 800). Intra-ocular inflammation was evaluated by clinical examination scoring during 7 post-injection days and histopathological examination at the end of study. Kruskal-Wallis and Mann-Whitney U tests were used to compare the histopathological and clinical scores. According to the clinical examinations, all groups demonstrated higher uveitis score than group 1 on first post-injection day. Also, groups 2 and 3 showed greater uveitis score than group 4. On the third, fifth and seventh post-injection days, clinical uveitis score in groups 2, 3 and 4 was significantly higher than group 1. The mean histopathological inflammation intensity scores in groups 2, 3 and 4 were significantly higher than group 1. Single intra-vitreal injection of 400 μg and 800 μg of MTX did not show significant anti-inflammatory effects on EIU in rabbits.