Effect of Periplaneta americana Extract on Corneal Fibrosis and Epithelial Healing After Rabbit Lamellar Keratectomy

Purpose: To evaluate Periplaneta americana extract (PAE) effects on corneal epithelial healing and fibrosis after superficial lamellar keratectomy (SLK) in rabbits. Methods: SLK was performed on the right eyes of 48 New Zealand White rabbits, randomized into three treatment groups (n = 16/group): normal saline (NS), Tobradex eye drops (TE), and PAE group. Corneal opacity and epithelial defect area were quantified using slit-lamp imaging at postoperative days 3, 7, 14, and 28 (D3, D7, D14, and D28) and scored via the grading system. We performed histopathological analysis to visualize tissue structure and immunohistochemistry (IHC) localize and quantify TGF-β1 protein in corneal tissues. Results: Significant intergroup differences in corneal epithelial defect area and opacity were observed on D3 and D7 (all P < 0.05). The TE group exhibited the largest epithelial defects but mildest corneal opacity, whereas the PAE group demonstrated the smallest epithelial defects and significantly reduced opacity compared to the NS group (P < 0.05). Time-dependent variations in epithelial defect area were noted across all groups (P < 0.05). The NS and TE groups displayed progressive corneal opacity increases, whereas the opacity of the PAE group peaked at D7 before declining. Histological analysis revealed epithelial detachment, stromal edema, and inflammatory infiltration in all groups, with the TE group showing milder inflammation. TGF-β1 expression levels initially increased followed by a decline in the NS and PAE groups, in contrast to the inverse trend of the TE group. No statistically significant differences in late-phase corneal opacity or TGF-β1 levels were observed between groups (all P > 0.05). Conclusions: During the early phase after SLK, PAE accelerated corneal tissue regeneration, inhibited corneal scarring, and partially restored corneal clarity. This biphasic regulatory effect may be attributed to promoting TGF-β1 expression in the early stage, followed by its inhibition in the later stages. Translational Relevance: PAE modulates TGF-β1 to balance corneal healing and fibrosis as a novel topical corticosteroid alternative, warranting human trials for its dual-phase healing/scarring action.