建立人眼传统房水流出通路微观结构的生物力学模型。
Modeling the biomechanics of the conventional aqueous outflow pathway microstructure in the human eye.
机构信息
Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, 1670 University Boulevard, VH 372B, Birmingham, AL 35294, USA.
Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, 1670 University Boulevard, VH 372B, Birmingham, AL 35294, USA.
出版信息
Comput Methods Programs Biomed. 2022 Jun;221:106922. doi: 10.1016/j.cmpb.2022.106922. Epub 2022 May 29.
BACKGROUND AND OBJECTIVE
Intraocular pressure (IOP) is determined by aqueous humor outflow resistance, which is a function of the combined resistance of Schlemm's canal (SC) endothelium and the trabecular meshwork (TM) and their interactions in the juxtacanalicular connective tissue (JCT) region. Aqueous outflow in the conventional outflow pathway results in pressure gradient across the TM, JCT, and SC inner wall, and induces mechanical stresses and strains that influence the geometry and homeostasis of the outflow system. The outflow resistance is affected by alteration in tissues' geometry, so there is potential for active, two-way, fluid-structure interaction (FSI) coupling between the aqueous humor (fluid) and the TM, JCT, and SC inner wall (structure). However, our understanding of the biomechanical interactions of the aqueous humor with the outflow connective tissues and its contribution to the outflow resistance regulation is incomplete.
METHODS
In this study, a microstructural finite element (FE) model of a human eye TM, JCT, and SC inner wall was constructed from a segmented, high-resolution histologic 3D reconstruction of the human outflow system. Three different elastic moduli (0.004, 0.128, and 51.5 MPa based on prior reports) were assigned to the TM/JCT complex while the elastic modulus of the SC inner wall was kept constant at 0.00748 MPa. The hydraulic conductivity was programmed separately for the TM, JCT, and SC inner wall using a custom subroutine. Cable elements were embedded into the TM and JCT extracellular matrix to represent the directional stiffness imparted by anisotropic collagen fibril orientation. The resultant stresses and strains in the outflow system were calculated using fluid-structure interaction method.
RESULTS
The higher TM/JCT stiffness resulted in larger stresses, but smaller strains in the outflow connective tissues, and resulted in a 4- and 5-fold larger pressure drop across the SC inner wall, respectively, compared to the most compliant model. Funneling through µm-sized SC endothelial pores was evident in the models at lower tissue stiffness, but aqueous flow was more turbulent in models with higher TM/JCT stiffness.
CONCLUSIONS
The mechanical properties of the outflow tissues play a crucial role in the hydrodynamics of the aqueous humor in the conventional outflow system.
背景和目的
眼内压（IOP）由房水流出阻力决定，而房水流出阻力是施莱姆氏管（SC）内皮和小梁网（TM）共同阻力及其在近管腔连接组织（JCT）区域相互作用的函数。在传统流出途径中，房水流出会导致 TM、JCT 和 SC 内表面之间产生压力梯度，并引起机械应力和应变，从而影响流出系统的几何形状和稳态。流出阻力受组织几何形状变化的影响，因此房水（流体）与 TM、JCT 和 SC 内表面（结构）之间可能存在主动、双向、流固相互作用（FSI）耦合。然而，我们对流体与流出连接组织的生物力学相互作用及其对流出阻力调节的理解并不完整。
方法
在这项研究中，从人类流出系统的高分辨率组织学 3D 重建中构建了人类 TM、JCT 和 SC 内表面的微观结构有限元（FE）模型。根据先前的报道，TM/JCT 复合体被赋予了三个不同的弹性模量（0.004、0.128 和 51.5 MPa），而 SC 内表面的弹性模量保持在 0.00748 MPa 不变。TM、JCT 和 SC 内表面的液压传导率分别通过定制子例程编程。电缆元件被嵌入 TM 和 JCT 细胞外基质中，以表示各向异性胶原纤维取向赋予的定向刚度。使用流固相互作用方法计算流出系统中的应力和应变。
结果
较高的 TM/JCT 刚度导致流出连接组织中的应力更大，但应变更小，与最柔顺的模型相比，SC 内表面的压力降分别增加了 4 倍和 5 倍。在较低组织刚度的模型中，明显存在通过 µm 大小的 SC 内皮孔的集束，但在 TM/JCT 刚度较高的模型中，房水流动更为湍流。
结论
流出组织的力学特性在传统流出系统中房水的流体动力学中起着至关重要的作用。
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