Department of Orthopaedic Surgery, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
Department of Orthopaedic Surgery, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan; Global Station for Soft Matter, Global Institution for Collaborative Research and Education (GSS, GI-CoRE), Hokkaido University, Sapporo, Japan.
J Biomech. 2019 Sep 20;94:22-30. doi: 10.1016/j.jbiomech.2019.07.006. Epub 2019 Jul 10.
Glycosphingolipids (GSLs) are ubiquitous membrane components that play an indispensable role in maintaining chondrocyte homeostasis. To gain better insight into roles of GSLs, we studied the effects of GSL-deletion on the physiological responses of chondrocytes to mechanical stress. Mice lacking Ugcg gene (Ugcg) were genetically generated to obtain GSL-deficient mice, and their chondrocytes from the joints were used for functional analyses in vitro culture experiments. The cells were seeded in a three-dimensional collagen gel and subjected to 5%, 10% or 16% cyclic tensile strain for either 3 or 24 h. The gene expressions of chondrocyte anabolic and catabolic factors, and the induction of Ca signaling were analyzed. Our results revealed that chondrocytes derived from GSL-deficient mice exhibited an elevation in the expression of catabolic factors (ADAMTS-5, MMP-13) following the exposure to strain with amplitudes of 10%. Likewise, applying cyclic tensile strain with these amplitudes resulted in an increased Ca oscillation ratio in chondrocytes from GSL-deficient as compared to the ratio from control mice. These results demonstrated that deletion of GSL stimulated the catabolic responses of chondrocytes to mechanical stress via the augmentation of the sensitivity to mechanical stress that may lead to the cartilage deterioration. These findings suggest that the regulation of the physiological responses of chondrocytes by GSLs could be a potential target in a therapeutic intervention in osteoarthritis.
糖鞘脂 (Glycosphingolipids, GSLs) 是普遍存在于细胞膜的成分，在维持软骨细胞的内环境稳定中发挥着不可或缺的作用。为了更深入地了解 GSLs 的作用，我们研究了 GSL 缺失对软骨细胞对机械应激生理反应的影响。通过基因敲除 Ugcg 基因（Ugcg）的方法，我们成功获得了 GSL 缺陷型小鼠，并在体外培养实验中使用其关节软骨细胞进行功能分析。将细胞接种于三维胶原凝胶中，并施加 5%、10%或 16%的周期性拉伸应变，持续 3 或 24 小时。分析软骨细胞合成代谢和分解代谢因子的基因表达情况，以及钙信号的诱导情况。结果表明，与对照组相比，GSL 缺陷型小鼠软骨细胞在受到 10%幅度的应变刺激后，分解代谢因子（ADAMTS-5、MMP-13）的表达水平升高。同样，施加这些幅度的周期性拉伸应变会导致 GSL 缺陷型软骨细胞中的钙振荡比率增加。这些结果表明，GSL 的缺失通过增强对机械应激的敏感性，刺激软骨细胞对机械应激的分解代谢反应，可能导致软骨恶化。这些发现表明，GSL 对软骨细胞生理反应的调节可能成为骨关节炎治疗干预的一个潜在靶点。
