College of Applied Medical Science, Inaya Medical College, Riyadh, Saudi Arabia; Cornea Research Chair, College of Applied Medical Science, King Saud University, Riyadh, Saudi Arabia.
Department of Physiology, Faculty of Medical Sciences in Katowice, Medical University of Silesia, Katowice, Poland.
Exp Eye Res. 2022 Jun;219:109064. doi: 10.1016/j.exer.2022.109064. Epub 2022 Apr 3.
Corneal collagen cross-linking (CXL) is a treatment that is widely applied to halt the progression of ectatic diseases such as keratoconus by creating biomechanical strength in the cornea. Most of the studies assessed the effect of the CXL on the cornea without any differentiation of its effect between periphery and the center of the untreated control cornea especially after the 7 days of CXL application. We investigate the ultrastructural changes in the architecture of the center and periphery of rat corneas, 7 days after standard CXL application. Five Wistar rats (10 corneas) were used in the present study. The left eye corneas (5 mm area) were de-epithelialized and irradiated with standard CXL application using riboflavin and Ultraviolet-A (UVA) (3 mW/cm for 30 min). The right eye corneas were used as a control. The sclera-cornea button was removed and processed for electron microscopy. Digital images were captured with a bottom mounted Quemesa camera and analyzed using the iTEM software. The ultrastructure of epithelium, hemi-desmosomes, Bowman's layer and stroma were organized in both untreated control and CXL rat cornea in both untreated control and CXL rat cornea. Within the same CXL cornea, both the collagen fibril (CF) diameter and interfibrillar spacing at the center were significantly smaller compared to the peripheral diameter and spacing of the cornea. When comparing the untreated control and CXL cornea, the central interfibrillar spacing of the CXL cornea was significantly smaller than the central spacing the untreated control cornea. In the CXL cornea the peripheral spacing was significantly higher compared to the peripheral interfibrillar spacing of the untreated control cornea. Within the CXL cornea, the proteoglycans (PGs) area and density of the periphery was significantly higher compared to the area and density of the center of the cornea. It suggests that CXL was more effective at the periphery of the cornea. This could be due to the higher amount of leucine rich PG lumican and higher diffusion of oxygen and riboflavin at the periphery cornea.
角膜胶原交联 (CXL) 是一种广泛应用于治疗扩张性疾病（如圆锥角膜）的治疗方法，通过在角膜中产生生物力学强度来阻止疾病的进展。大多数研究评估了 CXL 对角膜的影响，而没有对未经处理的对照角膜的中心和周边之间的影响进行任何区分，特别是在 CXL 应用后的 7 天。我们研究了标准 CXL 应用后 7 天大鼠角膜中心和周边结构的超微结构变化。本研究使用了 5 只 Wistar 大鼠（10 只眼角膜）。左眼（5mm 面积）去上皮化，并用核黄素和紫外线-A（UVA）（3mW/cm2 照射 30 分钟）进行标准 CXL 应用照射。右眼作为对照。取下巩膜 - 角膜按钮，进行电子显微镜处理。使用底部安装的 Quemesa 相机拍摄数字图像，并使用 iTEM 软件进行分析。上皮、半桥粒、Bowman 层和基质的超微结构在未经处理的对照和 CXL 大鼠角膜中均有组织排列。在同一 CXL 角膜中，与角膜的周边直径和间隔相比，中心的胶原纤维（CF）直径和纤维间间隔明显更小。在比较未经处理的对照和 CXL 角膜时，CXL 角膜的中央纤维间间隔明显小于未经处理的对照角膜的中央间隔。在 CXL 角膜中，周边间隔明显高于未经处理的对照角膜的周边纤维间间隔。在 CXL 角膜中，周边的蛋白聚糖（PG）面积和密度明显高于角膜中心的面积和密度。这表明 CXL 在角膜周边更为有效。这可能是由于周边角膜中富含亮氨酸的 PG 蛋白聚糖和氧以及核黄素的扩散较高。
