Effects of early applying basic fibroblast growth factor on corneal haze after surface ablation surgery and its mechanism

Objective

To investigate the effects of early applying of basic fibroblast growth factor (bFGF) on corneal haze formation after surface ablation surgery in rabbits.

Methods

The right eyes of 60 healthy New Zealand white rabbits received photorefractive keratectomy (PRK) and were randomized into PRK+ normal saline group, PRK+ bFGF group and simple PRK group, with 20 rabbits in each group.Normal saline solution and bFGF were topically administered according to grouping, respectively, 3 times per day, 1 drop for each time until the sacrifice of the animals, and no drug was used in the PRK group.Another 8 normal rabbits were served as blank control group.The corneal healing response and haze formation were evaluated by anterior segment photography and anterior segment optical coherence tomography (AS-OCT) and graded based on Fantes criteria.Corneal histopathology was examined by hematoxylin-eosin staining.Immunohistochemistry was used to detect the expression of transforming growth factor-β₁(TGF-β₁), α-smooth muscle actin (α-SMA) and matrix metalloproteinase-2 (MMP-2) in cornea.This study protocol was approved by the Experimental Animal Ethic Committee of Affiliated Hospital of Binzhou Medical University (20180209-03). The use and care of the animals complied with the Statement of ARVO.

Results

The corneal epithelium was completely healed in 3-4 days following surgery and there was not significantly different in healing time among the three groups.(F=0.57, P=0.57). The haze grading was significantly different among different groups at different time points (F_group=41.736, P<0.01; F_time=129.445, P<0.01) and showed the highest score in the PRK+ bFGF group on the 28th day after operation.On the 7th day after surgery, AS-OCT image showed that the surface reflection of corneal epithelium was continuous and smooth and corneal epithelium was not tightly attached to the superficial stromal layer; the reflection of the superficial stromal layer was enhanced in all the operation groups.The proliferation of corneal epithelial cells and superficial stromal layer in the operation area were seen under the optical microscope, and the arrangement of collagen fibers in the stromal layer was disordered with the most obvious changes in the PRK+ bFGF group in comparison with the PRK+ normal saline group and the simple PRK group, and these findings became worse on postoperative 28 days.The corneal epithelial surface reflection in the blank control group was continuous and smooth.Immunohistochemistry showed that a few MMP-2 positive cells were seen in the blank control group.TGF-β₁, α-SMA and MMP-2 proteins were positively expressed in the corneas 7 days after surgery in the three groups, and their expressions were the most obvious in the PRK+ bFGF in comparison with the PRK+ normal saline group and the PRK group and were enhanced 28 days after operation, showing statistically differences (all at P<0.05).

Conclusions

Early application of bFGF following surface ablation surgery promotes the proliferation of corneal epithelial cells and irregular arrangement of collagen in the superficial stromal layer, which is associated with the expressions of haze-related factors TGF-β₁, α-SMA and MMP-2 in corneas.

Transforming growth factor β₁; α-smooth muscle actin; Matrix metalloproteinase 2; Basic fibroblast growth factor; Corneal haze; Surface ablation surgery