Kim Min Kyu M, Burns Marissa J, Serjeant Meaghan E, Séguin Cheryle A
Department of Physiology and Pharmacology Schulich School of Medicine & Dentistry, The University of Western Ontario London Ontario Canada.
Bone and Joint Institute, The University of Western Ontario London Ontario Canada.
JOR Spine. 2020 Jul 20;3(4):e21114. doi: 10.1002/jsp2.1114. eCollection 2020 Dec.
The intervertebral disk (IVD) is a composite structure essential for spine stabilization, load bearing, and movement. Biomechanical factors are important contributors to the IVD microenvironment regulating joint homeostasis; however, the cell type-specific effectors of mechanotransduction in the IVD are not fully understood. The current study aimed to determine the effects of cyclic tensile strain (CTS) on annulus fibrosus (AF) cells and identify mechano-sensitive pathways. Using a cell-type specific reporter mouse to differentiation NP and AF cells from the murine IVD, we characterized AF cells in dynamic culture exposed to CTS (6% strain) at specific frequencies (0.1 Hz, 1.0 Hz, or 2.0 Hz). We demonstrate that our culture model maintains the phenotype of primary AF cells and that the bioreactor system delivers uniform biaxial strain across the cell culture surface. We show that exposure of AF cells to CTS induces cytoskeleton reorganization resulting in stress fiber formation, with acute exposure to CTS at 2.0 Hz inducing a significant yet transient increase ERK1/2 pathway activation. Using SYBPR-based qPCR to assess the expression of extracellular matrix (ECM) genes, ECM-remodeling genes, candidate mechano-sensitive genes, inflammatory cytokines and cell surface receptors, we demonstrated that exposure of AF cells to CTS at 0.1 Hz increased , , and expression. AF cells exposed to CTS at 1.0 Hz showed a significant increase in the expression of , , and . Exposure of AF cells to CTS at 2.0 Hz induced a significant increase in , , , , , and expression. Among the cell surface receptors assessed, AF cells exposed to CTS at 2.0 Hz showed a significant increase in , , and expression Our findings demonstrate that the response of AF cells to CTS is frequency dependent and suggest that mechanical loading may directly contribute to matrix remodeling and the onset of local tissue inflammation in the murine IVD.
椎间盘（IVD）是一种对脊柱稳定、承重和运动至关重要的复合结构。生物力学因素是调节关节稳态的IVD微环境的重要促成因素；然而，IVD中机械转导的细胞类型特异性效应器尚未完全了解。当前的研究旨在确定循环拉伸应变（CTS）对纤维环（AF）细胞的影响，并识别机械敏感通路。使用细胞类型特异性报告小鼠从鼠IVD中分化出髓核（NP）和AF细胞，我们对在特定频率（0.1 Hz、1.0 Hz或2.0 Hz）下暴露于CTS（6%应变）的动态培养中的AF细胞进行了表征。我们证明我们的培养模型维持了原代AF细胞的表型，并且生物反应器系统在细胞培养表面提供均匀的双轴应变。我们表明，AF细胞暴露于CTS会诱导细胞骨架重组，导致应力纤维形成，在2.0 Hz下急性暴露于CTS会诱导ERK1/2通路激活显著但短暂增加。使用基于SYBPR的qPCR评估细胞外基质（ECM）基因、ECM重塑基因、候选机械敏感基因、炎性细胞因子和细胞表面受体的表达，我们证明AF细胞在0.1 Hz下暴露于CTS会增加 、 、 和 的表达。在1.0 Hz下暴露于CTS的AF细胞显示 、 和 的表达显著增加。AF细胞在2.0 Hz下暴露于CTS会诱导 、 、 、 、 和 的表达显著增加。在所评估的细胞表面受体中，在2.0 Hz下暴露于CTS的AF细胞显示 、 和 的表达显著增加。我们的研究结果表明，AF细胞对CTS的反应是频率依赖性的，并表明机械负荷可能直接促进鼠IVD中的基质重塑和局部组织炎症的发生。
