Zhao Zhongyang, Liang Minghui, He Huan, Wang Xuemei, Zhu Chengfang, Li Lan, Liu Bin, Zong Rongrong, Jin Qifang, Wu Huping, Li Wei, Lin Zhirong
Eye Institute and Affiliated Xiamen Eye Center of Xiamen University, School of Medicine, Xiamen University, Xiamen, China.
Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Xiamen, China.
Front Med (Lausanne). 2022 May 26;9:762730. doi: 10.3389/fmed.2022.762730. eCollection 2022.
Allergic conjunctivitis (AC) is one of the reported potential risk factors of progression in keratoconus patients after corneal cross-linking surgery; however, the causal relationship is still inconclusive. Recent studies have indicated that various inflammatory cytokines play a vital role in the development of primary keratoconus. It is still unclear whether these inflammatory mediators also trigger CXL failures. This study aimed to investigate the impact of AC on the rabbit corneas after epithelial corneal cross-linking (TCXL).
A total of six rabbits were kept untreated as the normal control (NC) group. A total of 18 rabbits were treated by TCXL and divided into three groups (six in each group), namely, no treatment (TCXL group); induction of AC (TCXL + AC group); and induction of AC plus topical prednisolone acetate (TCXL + AC + PA group), according to additional treatment. AC was induced by topical application of ovalbumin after intraperitoneal pre-sensitization with ovalbumin. Rabbits were evaluated by slit lamp, laser scanning confocal microscopy, anterior segment optical coherence tomography, and measurement of corneal biomechanics. The cornea specimens were collected for the transmission electron microscope, the collagenase I digestion test, and PCR assay for TNF-α, IL-6, IL-1β, matrix metalloproteinase 9 (MMP-9), lysyl oxidase (LOX), and tissue inhibitor of metalloproteinases 1 (TIMP-1) on the day (D) 28.
On D28, the TNF-α, IL-6, IL-1β, MMP-9, and LOX levels were significantly increased while the TIMP-1 was decreased in the TCXL + AC group when compared with the TCXL and TCXL + AC + PA groups. confocal microscopy revealed that at a depth of 150-210 μm, a trabecular patterned hyperdense structure surrounded by elongated needle-like processes could be observed in the TCXL and TCXL + AC + PA groups, but hardly seen in the TCXL + AC group. The demarcation lines were indistinct and blurred in the TCXL + AC group. An electron microscope demonstrated less interlacing fibril lamellae and higher interfibrillar spacing in the TCXL + AC group. The stability of corneal biomechanics and resistance to collagenase were decreased in the TCXL + AC group.
The corneal microstructures induced by TCXL and biomechanical stability were diminished in rabbits with AC but could be maintained by topical anti-inflammatory treatment. Our results supported the causal relationship between altered cytokine profiles and corneal microstructure after primary corneal cross-linking.
过敏性结膜炎（AC）是报道的圆锥角膜患者角膜交联手术后病情进展的潜在危险因素之一；然而，因果关系仍不明确。最近的研究表明，多种炎性细胞因子在原发性圆锥角膜的发展中起重要作用。这些炎性介质是否也会引发角膜交联失败仍不清楚。本研究旨在探讨上皮角膜交联（TCXL）后AC对兔角膜的影响。
共6只兔未接受治疗作为正常对照组（NC组）。共18只兔接受TCXL治疗，并根据额外治疗分为三组（每组6只），即未治疗组（TCXL组）；诱导AC组（TCXL + AC组）；诱导AC加局部应用醋酸泼尼松龙组（TCXL + AC + PA组）。通过卵清蛋白腹腔预致敏后局部应用卵清蛋白诱导AC。通过裂隙灯、激光扫描共聚焦显微镜、眼前节光学相干断层扫描和角膜生物力学测量对兔进行评估。在第28天收集角膜标本用于透射电子显微镜检查、胶原酶I消化试验以及TNF-α、IL-6、IL-1β、基质金属蛋白酶9（MMP-9）、赖氨酰氧化酶（LOX）和金属蛋白酶组织抑制剂1（TIMP-1）的PCR检测。
在第28天，与TCXL组和TCXL + AC + PA组相比，TCXL + AC组的TNF-α、IL-6、IL-1β、MMP-9和LOX水平显著升高，而TIMP-1水平降低。共聚焦显微镜显示，在150 - 210μm深度处，TCXL组和TCXL + AC + PA组可观察到由细长针状突起包围的小梁状高密度结构，而在TCXL + AC组中几乎未见。TCXL + AC组的分界线不清晰且模糊。电子显微镜显示TCXL + AC组的交织原纤维薄片较少且原纤维间距较大。TCXL + AC组角膜生物力学稳定性和对胶原酶的抵抗力降低。
AC兔中TCXL诱导的角膜微观结构和生物力学稳定性降低，但局部抗炎治疗可维持。我们的结果支持原发性角膜交联后细胞因子谱改变与角膜微观结构之间的因果关系。
