Effects of Rapamycin on corneal haze after photorefractive keratectomy in rabbits

Abstract

AIM: To investigate the effect of modulated autophagy activity on subepithelial haze after photorefractive keratectomy(PRK)in rabbits.METHODS: Totally 64 New Zealand white rabbits were randomly divided into 4 groups according to different postoperative medication after PRK operation, including simple PRK group, 14μmol/L DMSO group, 50μmol/L rapamycin group and 100μmol/L rapamycin group. According to the group situation, two hours after the operation, eye drops were given, 3 times a day for 7d. Another 16 rabbits were selected as normal control group. The postoperative inflammatory response and corneal epithelial healing were observed with slit-lamp microscope every day. Haze formation of each group at 1 and 4wk after PRK was collected by slit-lamp microscopy system. Eight rabbits in each group were killed by air embolization 1 and 4wk after PRK, and corneal tissue was extracted and frozen for later use. Immunohistochemistry was used to detect the expression levels of transforming growth factor-β1(TGF-β1), α-smooth muscle actin(α-SMA), and matrix metalloproteinase-2(MMP-2). Real-time PCR was used to detect the relative expression levels of autophage-5(ATG5), autophage-12(ATG12), B lymphocytoma gene-2(Bcl-2)and cysteine aspartic proteinase-3(Caspase3)genes.RESULTS: Corneal epithelium of all operative rabbits healed completely at 3-4d and no significant difference in healing time between the groups after operation(F=0.745, P=0.530). During the observation period, haze was the most obvious at 4wk after operation in all groups. The haze symptoms were more serious in the simple operation group and the 14μmol/L DMSO group, followed by the 50μmol/L rapamycin group. The haze symptoms in the 100μmol/L rapamycin group were significantly relieved than those in other groups. There was no significant difference in the haze grading with different time points after operation among all groups(all P<0.05). Immunohistochemistry showed that the expression of TGF-β1, MMP-2 and α-SMA was stronger in the operation group and 14μmol/L DMSO group, followed by 50μmol/L rapamycin group, and weakest in 100μmol/L rapamycin group than other groups at 1 and 4wk after operation(all P<0.05). The results of PCR showed that the relative expression of ATG5, ATG12 and Bcl-2 mRNA in 50μmol/L rapamycin group and 100μmol/L rapamycin group were significantly higher than those in simple operation group and 14μmol/L DMSO group at 1 and 4wk after operation(all P<0.05); The relative expression of Caspase3 mRNA in 50μmol/L rapamycin group and 100μmol/L rapamycin group was significantly lower than that in simple operation group and 14μmol/L DMSO group(all P<0.05).CONCLUSION: Rapamycin can enhance autophagy level and inhibit apoptosis level, thus reducing haze formation after PRK in rabbits.

Keywords

• photorefractive keratectomy
• haze
• rapamycin
• autophagy