Arbabi Vahid, Pouran Behdad, Weinans Harrie, Zadpoor Amir A
Department of Biomechanical Engineering, Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628CD Delft, The Netherlands.
Department of Biomechanical Engineering, Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628CD Delft, The Netherlands; Department of Orthopedics, UMC Utrecht, Heidelberglaan100, 3584CX Utrecht, The Netherlands.
J Biomech. 2016 Jun 14;49(9):1510-1517. doi: 10.1016/j.jbiomech.2016.03.024. Epub 2016 Mar 21.
Charged and uncharged solutes penetrate through cartilage to maintain the metabolic function of chondrocytes and to possibly restore or further breakdown the cartilage tissue in different stages of osteoarthritis. In this study the transport of charged solutes across the various zones of cartilage was quantified, taken into account the physicochemical interactions between the solute and the cartilage constituents. A multiphasic finite-bath finite element (FE) model was developed to simulate equine cartilage diffusion experiments that used a negatively charged contrast agent (ioxaglate) in combination with serial micro-computed tomography (micro-CT) to measure the diffusion. By comparing the FE model with the experimental data both the diffusion coefficient of ioxaglate and the fixed charge density (FCD) were obtained. In the multiphasic model, cartilage was divided into multiple (three) zones to help understand how diffusion coefficient and FCD vary across cartilage thickness. The direct effects of charged solute-FCD interaction on diffusion were investigated by comparing the diffusion coefficients derived from the multiphasic and biphasic-solute models. We found a relationship between the FCD obtained by the multiphasic model and ioxaglate partitioning obtained from micro-CT experiments. Using our multi-zone multiphasic model, diffusion coefficient of the superficial zone was up to ten-fold higher than that of the middle zone, while the FCD of the middle zone was up to almost two-fold higher than that of the superficial zone. In conclusion, the developed finite-bath multiphasic model provides us with a non-destructive method by which we could obtain both diffusion coefficient and FCD of different cartilage zones. The outcomes of the current work will also help understand how charge of the bath affects the diffusion of a charged molecule and also predict the diffusion behavior of a charged solute across articular cartilage.
带电和不带电的溶质穿透软骨，以维持软骨细胞的代谢功能，并可能在骨关节炎的不同阶段恢复或进一步破坏软骨组织。在本研究中，考虑到溶质与软骨成分之间的物理化学相互作用，对带电溶质在软骨各区域的转运进行了量化。开发了一种多相有限浴有限元（FE）模型，以模拟马软骨扩散实验，该实验使用带负电荷的造影剂（碘克沙醇）结合串行微计算机断层扫描（micro-CT）来测量扩散。通过将FE模型与实验数据进行比较，获得了碘克沙醇的扩散系数和固定电荷密度（FCD）。在多相模型中，软骨被分为多个（三个）区域，以帮助理解扩散系数和FCD如何随软骨厚度变化。通过比较多相和双相溶质模型得出的扩散系数，研究了带电溶质-FCD相互作用对扩散的直接影响。我们发现多相模型获得的FCD与micro-CT实验获得的碘克沙醇分配之间存在关系。使用我们的多区域多相模型，表层区域的扩散系数比中间区域高多达十倍，而中间区域的FCD比表层区域高多达近两倍。总之，所开发的有限浴多相模型为我们提供了一种非破坏性方法，通过该方法我们可以获得不同软骨区域的扩散系数和FCD。当前工作的结果也将有助于理解浴液电荷如何影响带电分子的扩散，并预测带电溶质在关节软骨上的扩散行为。
