Effects of amniotic membrane suspension in the rat alkali burn model

Purpose: The main objective of this study is to determine the anti-inflammatory effect of topical amniotic membrane (AM) suspension on corneal alkali burn compared to topical serum eyedrops. Methods: Thirty eyes from 30 Sprague-Dawley male rats were used. After alkali injuries using 1 N NaOH, the control group (n=10) received topical PBS four times a day for 2 days. The first study group received topical 30% AM suspension, and the second study group (n=10) received topical 30% rat serum. Using slit lamp biomicroscopy, injured corneas were evaluated and scored in terms of re-epithelialization, corneal opacity, and neovascularization (NV). Tissue sections were analyzed histologically for cellular infiltration, and immunohistochemical staining was conducted using rat anti-mouse F4/80 antibody for the detection of macrophages. Results: In the inflammatory wound healing model, the epithelial healing ratios of the control group, the AM suspension group, and the serum eyedrop group were 1.8±15.1%, 34.1±17.7%, and 41.5±16.1%, respectively (p<0.0001). The opacity scores for the control group, the AM suspension group, and the serum eyedrop group 48 h after the insult were 4.8±0.5, 3.4±0.5, and 3.0±0.8, respectively, showing a significant difference (p<0.0001). Moreover, the NV scores for the control group, AM suspension group, and serum eyedrop group 48 h after the insult were 5.8±0.9, 4.0±1.3, and 4.3±0.9 (p=0.006). Upon immunohistochemical evaluation using F4/80, significantly fewer F4/80+ cells were recruited in the AM suspension and serum eyedrop groups than the control group (p=0.027). Conclusions: The suspension form of the amniotic membrane promoted epithelial healing and reduced corneal opacity and NV in alkali burn. It also suppressed F4/80 expression in the corneal stroma, indicating that the AM suspension maintains its beneficial biochemical effect on inflammatory corneal wound healing in vivo.