Bone Biomechanics Engineering Laboratory of Shandong Province, Neck-Shoulder and Lumbocrural Pain Hospital of Shandong First Medical University, Shandong Medicinal Biotechnology Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan 250062, China.
Shandong University of Traditional Chinese Medicine, Jinan 250014, China.
Oxid Med Cell Longev. 2021 Mar 16;2021:6699326. doi: 10.1155/2021/6699326. eCollection 2021.
Intervertebral disc degeneration (IVDD) is one of the major causes of low back pain and motor deficiency. Nucleus pulposus (NP) degeneration plays a key role in the process of IVDD. The mechanical and biological interactions involved in NP degeneration have not been elucidated. The present study is aimed at investigating the effect and mechanism of cyclic mechanical stretch in regulating the function and degeneration of NP cells.
NP cells were subjected to cyclic tensile stress (10% deformation) of 0.1 Hz for 8640 cycles. Cell proliferation was conducted through the MTT assay. The cell cycle and apoptosis were detected by flow cytometry. A gene expression profile chip was used to analyze the differentially expressed genes between the tensile stress group and the control group. Enrichment analysis of Gene Ontology (GO) annotation and signaling pathways were analyzed. Western blot and RNA interference were carried out to investigate the role of the ITGA2/PI3K/AKT pathway in the effect of cyclic mechanical stretch on NP cells.
NP cells exhibited a greater ( < 0.05) growth rate in the tensile stress group compared to the control group. Cyclic mechanical stress significantly promoted the cell cycle transition of NP cells from the S phase to the G2/M phase. A fewer proportion of apoptotic cells were found in the tensile stress group ( < 0.05), indicating that cyclic mechanical stretch inhibits NP cell apoptosis. Microarray analysis revealed 689 significant differentially expressed genes between the two groups ( < 0.05), of which 333 genes were upregulated and another 356 genes were downregulated. Cyclic mechanical stretch altered the expression of 31 genes involved in the ITGA2/PI3K/AKT pathway and remarkably promoted this pathway in NP cells. Downregulation of ITGA2 and AKT further demonstrated that the PI3K/AKT pathway was responsible for the proliferation and COL2A1 expression of NP cells upon cyclic mechanical stretch.
Cyclic mechanical stretch promoted the proliferation and cell cycle and reversely inhibited the apoptosis of NP cells. Cyclic mechanical stretch promoted COL2A1 expression and ameliorated the degeneration of NP cells via regulation of the ITGA2/PI3K/AKT signaling pathway. Our results may provide a potential target and a possibility of IVDD disease treatment by ameliorating the degenerative changes.
椎间盘退变（IVDD）是腰痛和运动功能障碍的主要原因之一。 髓核（NP）退变在 IVDD 过程中起关键作用。 NP 退变涉及的力学和生物学相互作用尚未阐明。 本研究旨在探讨循环机械拉伸对 NP 细胞功能和退变的调节作用及机制。
对 NP 细胞施加 10%变形的 0.1 Hz 循环拉伸应力 8640 个循环。 通过 MTT 测定法进行细胞增殖。 通过流式细胞术检测细胞周期和细胞凋亡。 使用基因表达谱芯片分析拉伸应力组与对照组之间差异表达的基因。 对基因本体论（GO）注释和信号通路进行富集分析。 进行 Western blot 和 RNA 干扰实验，以研究 ITGA2/PI3K/AKT 通路在循环机械拉伸对 NP 细胞的影响中的作用。
NP 细胞在拉伸组的生长速度更快（ < 0.05）。 循环机械力显著促进 NP 细胞从 S 期向 G2/M 期的细胞周期过渡。 拉伸组凋亡细胞比例较低（ < 0.05），表明循环机械拉伸抑制 NP 细胞凋亡。 微阵列分析显示两组之间有 689 个显著差异表达的基因（ < 0.05），其中 333 个基因上调，另外 356 个基因下调。 循环机械拉伸改变了 ITGA2/PI3K/AKT 通路中 31 个基因的表达，并显著促进了 NP 细胞中的该通路。 ITGA2 和 AKT 的下调进一步表明，PI3K/AKT 通路负责 NP 细胞在循环机械拉伸下的增殖和 COL2A1 表达。
循环机械拉伸促进 NP 细胞增殖和细胞周期，并反向抑制 NP 细胞凋亡。 循环机械拉伸通过调节 ITGA2/PI3K/AKT 信号通路促进 COL2A1 表达并改善 NP 细胞退变。 我们的研究结果可能为通过改善退行性变化治疗 IVDD 疾病提供潜在的靶点和可能性。
