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R. R. Mohan, A. Sharma, C. Siddappa, S. Sinha, J. W. Cowden; Decorin, TGFβ1 and TGFβ2 Levels and Localization in the Normal and PRK-Treated Rabbit Corneas. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5699.
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Decorin, a proteoglycan, has been known to regulate TGFβ function. It was hypothesized that decorin plays important role in corneal wound healing and controls haze development in the cornea. To test the hypothesis we measured the levels and distribution of TGFβ1, TGFβ2 and decorin in the normal and PRK-treated rabbit corneas, determined the relationship between TGFβ and decorin expression in the cornea and studied their role in corneal wound healing and haze development.
New Zealand White rabbits were used. Photo refractive keratectomy (PRK) by creating a 6 mm ablation zone to -9 diopters with the Summit Apex excimer laser was performed in one eye and other eye served as a control. Corneas were collected 24 hours, 72 hours, 1 week, 2 weeks and 4 weeks after PRK. Immunocytochemistry, fluorescent and confocal microscopy were used to determine TGFβ and decorin expression.
Naive rabbit corneas showed high TGFβ levels in the epithelium and very low expression in the stroma and none in the endothelium. Decorin expression in the naïve corneas was confined to the stroma. PRK-treated rabbit corneas showed markedly high levels of TGFβ1and TGFβ2 in the stroma and epithelium at 24hours and 72hours and mild-to-moderately high levels at 2weeks and normal levels at 4weeks. The majority of the TGFβ1 expression was observed in the anterior and mid stroma whereas TGFβ2 in the anterior stroma. The increase in the decorin expression in the PRK-treated corneas compared to naïve corneas was observed only at 24 hours.
High TGFβ activity in the PRK-treated corneas is associated with the myofibroblast formation and haze development. Endogenous decorin expression is insufficient to block hyper TGFβ activity in PRK-treated rabbit corneas.
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