Expression and clinical significance of YKL-40 in choroidal neovascularization model in mice induced by laser

Abstract:

Objective：To explore the expression and significance of chitinase-3-like-1（YKL-40） in choroidal neovascularization （CNV） models in mice. Methods：Forty adult male C57BL/6J mice were divided into day 7 group and day 14 group post laser coagu－lation randomly according to the sampling time，with twenty mice in each group. The left eyes of mice were set as normal control and the right eyes were established CNV models by 532 nm laser photocoagulation. Retinal pigment epithelium（RPE）/choroidal flatmounts after cardiac perfusion with FITC-dextran and HE staining on the 7th and 14th day post laser were used to identify the CNV models. The mRNA levels of YKL-40 and vascular endothelial growth factor（VEGF） in neuroretina and RPE/choroidal complex were detected by real-time PCR. The localizations and expressions of YKL-40 in eyes of each group were determined by immunofluorescence staining. Results：Both RPE/choroidal flatmount and HE staining confirmed the success of model and the CNV formation on day 7 and day 14 after laser coagulation. Real-time PCR showed that in neuroretina the expressions of YKL-40 and VEGF[（1.939±0.209），（4.017±1.312）] were higher in day 7 group than control group[（1.002±0.076），（1.017±0.219）]，and the differences were significant（t=13.320，P=0.006；t=5.457，P=0.012）. However，in RPE/choroidal complex，no significant differences（t= -4.519，P=0.053；t=2.450，P=0.134） were observed between control group[（1.004±0.101），（1.021±0.240）] and day 7 group[（0.968±0.381），（1.192±0.354）]. Futhermore，the mRNA levels of YKL-40 and VEGF in day 14 group[（3.174±1.583），（3.045±1.430），（12.669±4.512），（8.254±2.968）] were higher than those in control group[（1.013±0.173），（1.043±0.371），（1.037±0.347），（1.078±0.462）] both in neuroretina and in RPE/choroidal complex tissues，and the differences were significant（t=4.777，P=0.041；t=3.508，P=0.039；t=4.827，P=0.040；t=12.800，P=0.006）. Pearson correlation analysis showed that the expression of YKL-40 was positively correlated with VEGF in CNV models. The immunofluorescence staining showed that YKL-40 were mainly expressed in the retinal ganglion cell layer，inner plexiform layer and inner nuclear layer of mice after laser. Both in day 7 group and day 14 group，the expressions of YKL-40[（0.141±0.004），（0.105±0.018）] were higher than control group（0.008±0.001），and the differences were significant（F=106.388，P=0.000）. Conclusion：The expression of YKL-40 is up-regulated during the process of CNV formation and is positively correlated with VEGF. Therefore，we infer that YKL-40 may play a critical role in the pathological process of CNV formation.