Abstract
Purpose :
Visually regulated eye growth (emmetropization) is associated with some choroidal changes consistent with that of inflammation. In response to imposed myopic defocus the choroid thickens, exhibits increased vascular permeability, and increases the synthesis of a number of proteins associated with the acute phase response, including ovotransferrin, apolipoprotein A-1 and interleukin 6 (IL6). This study was undertaken to determine whether treatment with the anti-inflammatory drug, dexamethasone (DEX), could alter the emmetropization process.
Methods :
DEX or vehicle was administered daily to chicks during the development of monocular form deprivation myopia during the last 7 days of a 17 day deprivation period (4 mg/kg, IP). On the last day of treatment, occluders were removed and chicks were allowed to experience unrestricted vision for ≈20 hrs (“recovery”). Choroids and sclera were isolated from recovering and fellow control eyes. Gene expression of Il6 was quantified using Taqman™ PCR and normalized to GAPDH. Scleral proteoglycan synthesis (an indicator of eye growth in chicks) was evaluated by CPC-precipitation of 35SO4-labelled glycosaminoglycans.
Results :
DEX treatment resulted in a significant decrease in choroidal IL6 gene expression in recovering eyes, compared to recovering eyes of vehicle treated chicks (↓85%; p = 0.0029, Mann Whitney Test). No significant differences were detected in IL6 gene expression in choroids from control eyes between DEX and vehicle treated chicks (p = 0.4958, Mann Whitney Test). DEX treatment resulted in a significant decrease in scleral proteoglycan synthesis in control eyes, compared to control eyes of vehicle treated chicks (↓59%, p =0.0001, t-test). Despite the suppression of scleral proteoglycan synthesis observed in control eyes of DEX-treated chicks, DEX treatment resulted in a significant increase in scleral proteoglycan synthesis in recovering eyes relative to fellow controls (↑185%, p= 0.0028, paired t-test). No differences were detected in scleral proteoglycan synthesis between recovering and control eyes of vehicle treated chicks (p=0.1374, paired t-test).
Conclusions :
DEX treatment reduced choroidal gene expression of IL6 in recovering eyes, resulting in a disinhibition of scleral proteoglycan synthesis during recovery from induced myopia. These results provide additional support for a role of inflammation in visually regulated eye growth.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.