The study of the inhibiting effect of pirfenidone on rat corneal neovascularization by acute alkali burn

Abstract

Objective To study the inhibitory actin of pirfenidone (PFD) on corneal neovascularization (CNV) in rat caused by acute alkali burn. Methods Alkali burn was used to prepare a CNV model. Then twenty adult healthy Sprague Dawley (SD) rats were equally divided into PFD and phosphate buffered saline (PBS) two groups. The PFD group was treated with pirfenidone eye drops 3 mg/ml and PBS group was treated with phosphate buffered saline, the treatments were administered daily 4 times and continued for 14 days. The level of corneal inflammation reaction, corneal opacity, and the growth of CNV were analyzed by the slit-lamp microscopy. At the 14th day of post-therapy all rats were killed and remove their corneas. The structure of corneal tissue by hematoxyli-eoitaiig (HE) staining. The MVD was observed by immunohistochemical CD34 staining. Corneal inflammation reaction and the growth of CNV at different time periods, the comparison between PFD and PBS two groups adopt two factor repeated measurement of variance analysis. Results At the 14th day, the corneal opacity of PFD group was (1.00±0.00) scores, the corneal opacity of PBS group was (3.40±0.52) scores, PFD group compared with PBS group, the corneal opacity was effectively inhibited (t=-14.697, P<0.05). At the 7th day and the 14th day, the level of corneal inflammation reaction of PFD group were (3.50±0.53) scores and (2.2±0.42) scores, the level of corneal inflammation reaction of PBS group were (4.9±0.57) scores and (3.3±0.48) scores, PFD group compared with PBS group, the corneal inflammation reaction were effectively inhibited (t=-5.715, -5.425; P<0.05). For PFD group, With the extension of time, increased corneal transparency and inflammation decline. The 7th day compared with the third day, the difference was statistically significant (t=7.56, P<0.05). The 14th day compared with the third day and the 7th day, the differences were all statistically significant (t=13.17, 6.08; P<0.05). For PBS group, The 7th day compared with the third day, the difference was statistically significant (t=2.64, P<0.05). The 14th day compared with the third day and the 7th day, the differences were all statistically significant (t=8.74, 6.79; P<0.05). At the third day, the 7th day and the 14th day, the CNV areas of PFD group were (6.06±0.93) square millimeters, (17.94±1.89) square millimeters and (23.89±1.84) square millimeters, the CNV areas of PBS group were (9.08±1.42) square millimeters, (27.11±2.02) square millimeters and (31.01±2.04) square millimeters, PFD group compared with PBS group, the differences were all statistically significant (t=-5.609, -10.452, -8.202; P<0.05). HE staining showed that the corneal tissue in PBS group have many inflammatory cell infiltration and the proliferation of fibrous tissue, however, the morphology and structure of corneal tissues in the PFD group was no significant pathological changes. Immunohistochemical CD34 stainings showed that the MVD of PFD group was (3.17±1.17) bars per square millimeter, the MVD of PBS group was (10.83±2.48) bars per square millimeter, PFD group compared with PBS group, the difference was statistically significant (t=-6.842, P<0.05). Conclusion PFD can significantly reduce inflammation reaction and inhibit the growth of corneal neovascularization, which may provides a new methods for the treatment of corneal neovascularization. Key words: Pirfenidone; Corneal neovascularization; Alkali burn