ABSTRACT

Purpose

Fibrillar collagen network and glycosaminoglycans (GAGs) are the primary components of extracellular matrix (ECM) of the sclera. The main goal of this study was to investigate the possible structural roles of GAGs in the scleral tensile properties as a function of preconditioning and displacement rate.

Methods

Four-step uniaxial stress-relaxation tests were used for characterizing the viscoelastic tensile response of the posterior porcine sclera with and without enzymatic GAG removal. The scleral strips were divided into different groups based on the displacement rate and the presence or absence of a preconditioning step in the loading protocol. The groups were (1) displacement rate of 0.2 mm/min without preconditioning, (2) displacement rate of 1 mm/min without preconditioning, (3) displacement rate of 0.2 mm/min with preconditioning, and (4) displacement rate of 1 mm/min with preconditioning. The peak stress, equilibrium stress, and the equilibrium elastic modulus were calculated for all specimens and compared against each other.

Results

Increasing the displacement rate from 0.2 mm/min to 1.0 mm/min was found to cause an insignificant change in the equilibrium stress and equilibrium elastic modulus of porcine scleral strips. Removal of GAGs resulted in an overall stiffer tensile behavior independent of the displacement rate in samples that were not preconditioned (P < .05). The behavior of preconditioned samples with and without GAG removal was not significantly different from each other.

Conclusions

The experimental measurements of the present study showed that GAGs play an important role in the mechanical properties of the posterior porcine sclera. Furthermore, using a preconditioning step in the uniaxial testing protocol resulted in not being able to identify any significant difference in the tensile behavior of GAG depleted and normal scleral strips.

中文翻译：

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糖胺聚糖耗尽后巩膜的拉伸粘弹性

摘要

目的

纤维状胶原网络和糖胺聚糖 (GAG) 是巩膜细胞外基质 (ECM) 的主要成分。本研究的主要目的是研究 GAG 在巩膜拉伸特性中可能的结构作用，作为预处理和位移速率的函数。

方法

四步单轴应力松弛试验用于表征猪后巩膜的粘弹性拉伸响应，有和没有酶促 GAG 去除。根据移位率和加载协议中是否存在预处理步骤，将巩膜条分成不同的组。各组为 (1) 0.2 mm/min 无预处理位移速率、(2) 1 mm/min 无预处理位移速率、(3) 0.2 mm/min 预处理位移速率和 (4) 位移速率 1毫米/分钟与预处理。计算所有试样的峰值应力、平衡应力和平衡弹性模量并相互比较。

结果

发现将位移速率从 0.2 mm/min 增加到 1.0 mm/min 会导致猪巩膜条的平衡应力和平衡弹性模量发生不显着的变化。去除 GAG 会导致整体更硬的拉伸行为，与未经预处理的样品的位移速率无关 ( P < .05)。去除和不去除 GAG 的预处理样品的行为彼此之间没有显着差异。

结论

本研究的实验测量表明，GAGs 在猪后巩膜的力学性能中起重要作用。此外，在单轴测试协议中使用预处理步骤导致无法识别 GAG 耗尽和正常巩膜条的拉伸行为的任何显着差异。