Establishment and evaluation of rabbit model for corneal ectasia by photorefractive keratectomy

The study aimed to compare the effects of different types of excimer laser keratectomy on rabbit corneas and to identify the optimal disease model for corneal ectasia. Additionally, investigating the structural and molecular alterations in the novel disease model helped explore the mechanisms underlying biomechanical cues in corneal ectasia. 2.0-2.5 kg New Zealand white rabbits were treated with different types of excimer laser keratectomy, including comparisons between photorefractive keratectomy (PRK) and phototherapeutic keratectomy (PTK) surgeries, as well as comparisons of different ablation depths of PRK. Detailed tests on post-surgery corneas included pentacam analyzer, H&E staining and optical coherence tomography (OCT), transmission electron microscopy (TEM), raman spectroscopy and uniaxial tensile tests. Later, tandem mass tag-labeled proteomics and multiply statistic analysis were performed on post-PRK75 corneas. Western blot was used to validate protein expression. Herein, we found that tapered corneal thinning in post-PRK corneas predisposed to corneal ectasia. Greater ablation depth increased ectasia risk. PRK75 (ablation of 75% of corneal thickness using PRK mode) emerged as the optimal modeling approach, evidenced by significant and sustained corneal ectasia for 4 weeks. The 4-week post-PRK75 corneas were evaluated by changes in stromal cell microstructure, basement membrane, collagen lamellae, collagen covalent bonds and decreased corneal biomechanical strength. Additionally, PRK75 surgery induced 109 differentially expressed proteins (DEPs), with 51 previously linked to human corneal ectasia. The statistic analysis demonstrated the dysregulation of immue response was involved in the post-PRK75 corneas, and identified nine core proteins involved in corneal ectasia, including SERPINH1, ALDH1A1, MMP10, A2M, GSTM3, CD44, CLU, C3, and ITGB2. Therefore, we concluded that PRK75 was a novel and reliable modeling method for corneal ectasia, resemble human corneal ectasia. The intrinsic structural remodeling and molecular alteration in post-PRK75 corneas could shed lights on understanding the mechanism of biomechanical cues in corneal ectasia in the future.