Ascorbic acid: role in preservation of corneal structure in chronically ultraviolet B irradiated guinea pigs.

H. M. SERRA,; CAFARO T A,; SUAREZ MF; QUINTAR A; MALDONADO, C; J. A. URRETS-ZAVALIA

Congreso; ARVO; 2011

Purpose: One of the primary sources of environmental stress for the anterior eye is solar radiation, specifically in the ultraviolet B (UVB)-range. This kind of damages induced by UVB can be controlled by antioxidant systems, such as ascorbic acid (AA), which is highly concentrated in corneal tissue. This study was conducted to investigate the possible protective role of a high dose ascorbic acid (AA) diet in the cornea of guinea pigs chronically exposed to UVB irradiation. Methods: Sixteen healthy male guinea pigs (Ssi:AL), aged 3 to 5 months old were used and were randomly divided into 2 groups of 8 animals each according to the level of AA in their diet: a high level AA diet group (HAA), and a low level AA diet group (LAA). Four animals from each group were exposed to 0.12 J/cm2 of UVB irradiation for 40 minutes/day for 9 months (HAA-UV, LAA-UV), and the remaining animals from both groups were not exposed to UVB irradiation. After treatment, the corneal thickness was measured in vivo with ultrasound pachymetry and the superficial layers of the cornea were studied by means of transmission electron microscopy.  Results: Although corneal thickness increased significantly in UVB exposed groups (p<0.001) there was not difference between HAA-UV vs LAA-UV groups. The LAA-UV group showed different abnormalities in the epithelium (disorganized cell layers and irregular cell shapes) and stroma (high expression of TGFβ, present of grouped myofibroblast, apoptotic cells and disorganized collagen layers). These changes were much less pronounced in the HAA-UV group. Conclusions: This study showed that a high dose of AA in the diet had a protective effect on guinea pig corneas chronically exposed to UVB irradiation.