In this study, we established an experimental human corneal stroma model of simulated cornea tissue composed of thin anterior cornea strips layers obtained from small incision lenticular extraction (SMILE) surgery. We investigated the biomechanical effect of ultraviolet-A- riboflavin cross-linking at different depths of corneal stroma model and correlated it with stromal microstructural changes examined by transmission electron microscopy (TEM). Corneal strips were harvested from fresh human corneal lenticules obtained after SMILE surgery. Experimental models (n = 34) were established by superimposing the corneal lenticule strips until their thickness reached close to 500 μm. Corneal cross-linking (CXL) was performed subsequently using standard or accelerated protocol. Elasticity and viscosity were quantified using stress-strain extensometer. TEM was used to visualize the collagen fiber diameter and interfibrillar spacing. The relative change in Young's modulus (rel. ΔE) decreased nonlinearly with increasing stromal depth both in the standard and accelerated groups. Compared to the sham controls, the rel. ΔE in standard and accelerated CXL groups increased significantly in the anterior 400 μm and 275 μm depth, respectively. Also, the relative change in stress (rel. ΔS) was significantly lower after standard and accelerated CXL compared to sham controls. Depth analysis showed similar results for the elastic effect. TEM images showed a small, non-significant increase in fibril diameter. The interfibrillar spacing decreased significantly after standard and accelerated CXL in the anterior-mid stromal region. We noted that the increase of corneal stiffness correlated with decrease in interfibrillar spacing after CXL. The stiffening effect was depth dependent. The effect of accelerated CXL was less in the deep corneal stromal regions compared to standard CXL.

译文

在这项研究中,我们建立了由小切口透镜状提取 (SMILE) 手术获得的薄的前角膜条层组成的模拟角膜组织的实验性人角膜基质模型。我们研究了紫外线-A-核黄素交联在角膜基质模型不同深度处的生物力学作用,并将其与通过透射电子显微镜 (TEM) 检查的基质微结构变化相关联。从SMILE手术后获得的新鲜人类角膜透镜中收获角膜条。通过叠加角膜透镜条直到其厚度达到接近500 μ m建立实验模型 (n = 34)。随后使用标准或加速方案进行角膜交联 (CXL)。使用应力应变引伸计对弹性和粘度进行定量。TEM用于可视化胶原纤维直径和纤维间间距。在标准组和加速组中,杨氏模量 (rel。Δ e) 的相对变化均随基质深度的增加而非线性降低。与假对照相比,rel。标准和加速CXL组的 Δ e分别在前400 μ m和275 μ m深度显着增加。此外,与假对照组相比,标准和加速CXL后压力的相对变化 (rel. Δ s) 明显更低。深度分析显示弹性效应的结果相似。TEM图像显示原纤维直径的少量,非显着增加。在前中层基质区域标准和加速CXL后,纤维间间距显着降低。我们注意到,CXL后角膜硬度的增加与纤维间间距的减小有关。硬化效果与深度有关。与标准CXL相比,加速CXL在深角膜基质区域的作用较小。

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