Blockade of Toll-like Receptor 2 Expression and Membrane Translocation in Rat Corneal Epithelial Cells by Glucocorticoid (TobraDex) After Penetrating Keratoplasty

Purpose: To evaluate the role of Toll-like receptor (TLR) 2 and the effect of glucocorticoid on immune rejection of penetrating keratoplasty. Methods: Allograft corneal transplantation was performed between host Sprague Dawley (SD) and Wistar donor rats. The expression of TLR2 messenger RNA (mRNA) and protein in corneas was determined by reverse transcription-polymerase chain reaction (RTPCR), immunohistochemistry, and immunofluorescence on days 5, 7, and 9 after operation. Three groups were included: allograft, allograft treated with TobraDex (Alcon, Rijksweg, Belgium), and isograft. Normal rat corneas were included as an additional control. Results: Various degrees of congregation of inflammatory cells and neovascularization of grafts were confirmed by histopathology. Immunohistochemistry revealed that TLR2 was expressed in epithelial, stromal, and endothelial cells of normal tissue, and in all of the grafts. Immunofluorescence analysis of TLR2 showed membrane staining of epithelial cells in the allografts on days 7 and 9. This was absent in the isografts and the allografts treated with TobraDex. TLR2 mRNA was detected in normal corneas, and levels were increased in all of the grafts, as determined by quantitative reverse transcription-polymerase chain reaction. By day 9 after transplantation, a 3.6-fold increase in TLR2 mRNA was observed in the allografts compared with the isografts or the allografts treated with TobraDex, which was statistically significant, at P < 0.005. Conclusions: Expression of TLR2 in the rat cornea was significantly increased and concurred with the allograft rejection, but was effectively blocked by treatment with TobraDex.