Park Seungman
Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, USA.
Comput Methods Programs Biomed. 2017 Sep;148:91-98. doi: 10.1016/j.cmpb.2017.06.019. Epub 2017 Jun 29.
BACKGROUND AND OBJECTIVE: Interstitial flow (IF) is a creeping flow through the interstitial space of the extracellular matrix (ECM). IF plays a key role in diverse biological functions, such as tissue homeostasis, cell function and behavior. Currently, most studies that have characterized IF have focused on the permeability of ECM or shear stress distribution on the cells, but less is known about the prediction of shear stress on the individual fibers or fiber networks despite its significance in the alignment of matrix fibers and cells observed in fibrotic or wound tissues. In this study, I developed a computational model to predict shear stress for different structured fibrous networks. METHODS: To generate isotropic models, a random growth algorithm and a second-order orientation tensor were employed. Then, a three-dimensional (3D) solid model was created using computer-aided design (CAD) software for the aligned models (i.e., parallel, perpendicular and cubic models). Subsequently, a tetrahedral unstructured mesh was generated and flow solutions were calculated by solving equations for mass and momentum conservation for all models. Through the flow solutions, I estimated permeability using Darcy's law. Average shear stress (ASS) on the fibers was calculated by averaging the wall shear stress of the fibers. By using nonlinear surface fitting of permeability, viscosity, velocity, porosity and ASS, I devised new computational models. RESULTS: Overall, the developed models showed that higher porosity induced higher permeability, as previous empirical and theoretical models have shown. For comparison of the permeability, the present computational models were matched well with previous models, which justify our computational approach. ASS tended to increase linearly with respect to inlet velocity and dynamic viscosity, whereas permeability was almost the same. Finally, the developed model nicely predicted the ASS values that had been directly estimated from computational fluid dynamics (CFD). CONCLUSIONS: The present computational models will provide new tools for predicting accurate functional properties and designing fibrous porous materials, thereby significantly advancing tissue engineering.
背景与目的:间质流(IF)是一种通过细胞外基质(ECM)间质空间的蠕动流。IF在多种生物学功能中起关键作用,如组织稳态、细胞功能和行为。目前,大多数表征IF的研究都集中在ECM的渗透性或细胞上的剪切应力分布,但尽管其在纤维化或伤口组织中观察到的基质纤维和细胞排列中具有重要意义,关于单个纤维或纤维网络上剪切应力的预测却知之甚少。在本研究中,我开发了一种计算模型来预测不同结构纤维网络的剪切应力。 方法:为生成各向同性模型,采用了随机生长算法和二阶取向张量。然后,使用计算机辅助设计(CAD)软件为排列模型(即平行、垂直和立方模型)创建三维(3D)实体模型。随后,生成四面体非结构化网格,并通过求解所有模型的质量和动量守恒方程来计算流动解。通过流动解,我使用达西定律估算渗透率。通过平均纤维的壁面剪切应力来计算纤维上的平均剪切应力(ASS)。通过对渗透率、粘度、速度、孔隙率和ASS进行非线性表面拟合,我设计了新的计算模型。 结果:总体而言,如先前的经验和理论模型所示,所开发的模型表明较高的孔隙率会导致较高的渗透率。为了比较渗透率,本计算模型与先前的模型匹配良好,这证明了我们的计算方法的合理性。ASS倾向于随入口速度和动态粘度线性增加,而渗透率几乎相同。最后,所开发的模型很好地预测了从计算流体动力学(CFD)直接估算的ASS值。 结论:本计算模型将为预测准确的功能特性和设计纤维多孔材料提供新工具,从而显著推动组织工程的发展。
Comput Methods Programs Biomed. 2017-9
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