Wu Yongren, Cisewski Sarah, Sachs Barton L, Yao Hai
Department of Bioengineering, Clemson University, Clemson-MUSC Bioengineering Program, 173 Ashley Avenue, Charleston, SC 29425, USA.
Mol Cell Biomech. 2013 Jun;10(2):159-82.
This study examines the effects of cartilage endplate (CEP) calcification and the injection of intervertebral disc (IVD) cells on the nutrition distributions inside the human IVD under physiological loading conditions using multiphasic finite element modeling. The human disc was modeled as an inhomogeneous mixture consisting of a charged elastic solid, water, ions (Na+ and Cl-), and nutrient solute (oxygen, glucose and lactate) phases. The effect of the endplate calcification was simulated by a reduction of the tissue porosity (i.e., water volume faction) from 0.60 to 0.48. The effect of cell injection was simulated by increasing the cell density in the nucleus pulposus (NP) region by 50%, 100%, and 150%. Strain-dependent transport properties (e.g., hydraulic permeability and solute diffusivities) were considered to couple the solute transport and the mechanical loading. The simulation results showed that nutrient solute distribution inside the disc is maintained at a stable state during the day and night. The physiological diurnal cyclic loading does not change the nutrient environment in the human IVD. The cartilage endplate plays a significant role in the nutrient supply to human IVD. Calcification of the cartilage endplate significantly reduces the nutrient levels in human IVD. Therefore, in cell based therapy for IVD regeneration, the increased nutrient demand as a result of cell injection needs to be addressed. Excessive numbers of injected cells may cause further deterioration of the nutrient environment in the degenerated disc. This study is important for understanding the pathology of IVD degeneration and providing new insights into cell based therapies for low back pain.
本研究使用多相有限元模型，在生理负荷条件下，研究软骨终板（CEP）钙化和椎间盘（IVD）细胞注射对人IVD内部营养物质分布的影响。将人体椎间盘建模为一种非均匀混合物，由带电弹性固体、水、离子（Na+和Cl-）和营养溶质（氧气、葡萄糖和乳酸）相组成。通过将组织孔隙率（即水体积分数）从0.60降低到0.48来模拟终板钙化的影响。通过将髓核（NP）区域的细胞密度分别增加50%、100%和150%来模拟细胞注射的影响。考虑应变相关的传输特性（如水力渗透率和溶质扩散率）来耦合溶质传输和机械负荷。模拟结果表明，椎间盘内营养溶质分布在白天和夜间保持稳定状态。生理昼夜循环负荷不会改变人IVD中的营养环境。软骨终板在为人IVD提供营养方面起着重要作用。软骨终板钙化显著降低人IVD中的营养水平。因此，在基于细胞的IVD再生治疗中，需要解决因细胞注射导致的营养需求增加的问题。注射过多的细胞可能会导致退变椎间盘中营养环境的进一步恶化。本研究对于理解IVD退变的病理以及为腰痛的基于细胞的治疗提供新见解具有重要意义。
