N-cadherin表达下调在高负荷压应力促进髓核细胞凋亡中的作用及机制研究

High compressive stress plays a crucial role in advancing the pathological process of intervertebral disc degeneration. Previous studies including our previous study demonstrated that the rate of nucleus pulposus (NP) cell apoptosis is significantly elevated by the high compressive stress. However, the potential mechanism is not fully understood. Previous study demonstrated that N-cadherin down-regulation could promote apoptosis of various types of cells. Moreover, our further experiments found that high compressive stress could increase apoptotic NP cells, and simultaneously decrease expression of N-cadherin and activity of PI3K/Akt signaling pathway. Therefore, we deduce that high compressive stress may promote NP cell apoptosis through down-regulating expression of N-cadherin and decreasing activity of PI3K/Akt signaling pathway. To verify this speculation, this study will investigate the role of N-cadherin down-regulation in the promotive effects of high compressive stress on NP cell apoptosis both in the nucleus pulposus cell three-dimensional culture system and the intervertebral disc organ culture system. The potential molecular mechanism will also be explored by inhibiting PI3K/Akt signaling pathway, enhancing N-cadherin expression and silencing N-cadherin expression. We hope this study will be helpful to further understand pathogenesis of compressive stress-related disc degeneration and provide novel theoretical evidence for the prevention and therapy of disc degeneration.

高负荷压应力在加速椎间盘退变进程中发挥重要作用。国内外和我们的前期研究表明高负荷压应力下椎间盘髓核细胞凋亡率显著升高，但其机制仍不完全清楚。以往有文献报道N-cadherin表达下调可促进多种细胞发生凋亡。进一步预实验发现高负荷压应力促进髓核细胞凋亡的同时，可诱导髓核细胞N-cadherin表达下调和PI3K/Akt通路活性下降。因此，我们推测高负荷压应力可通过下调N-cadherin表达继而降低PI3K/Akt通路活性来促进髓核细胞凋亡。为证实这一推测，本项目拟在髓核细胞三维培养体系和椎间盘器官培养体系中探讨N-cadherin表达下调在高负荷压应力促进髓核细胞凋亡中的作用，并通过阻断PI3K/Akt通路、条件性沉默或增强N-cadherin表达等技术深入研究其具体分子机制。期望通过本研究，进一步认识压应力相关椎间盘退行性疾病的病理机制，为椎间盘退变的防治策略提供新的理论依据。

高负荷压应力在加速椎间盘退变进程中发挥重要作用，国内外和我们的前期研究表明高负荷压应力下椎间盘髓核细胞凋亡率显著升高，但机制不完全清楚。文献报道N-cadherin(N-CDH)表达下调可促进多种细胞发生凋亡。本研究展开前我们预实验发现高负荷压应力促进髓核细胞凋亡的同时，可诱导髓核细胞N-CDH表达下调和PI3K/Akt通路活性下降，因此，我们推测高负荷压应力可通过下调N-CDH表达继而降低PI3K/Akt通路活性来促进髓核细胞凋亡。为证实这一推测，一方面，本项目探讨了N-CDH表达下调在高负荷压应力促进髓核细胞凋亡中的作用；另一方面，本研究通过阻断PI3K/Akt通路、条件性增强N-CDH表达等技术深入研究其具体分子机制。我们的研究结果表明：高负压压应力下(20%压缩性变)，髓核细胞N-CDH基因和蛋白表达明显降低，同时髓核细胞凋亡增强（细胞凋亡率增加、caspase-3活性增强、促凋亡分子表达升高、抗凋亡分子表达降低），此外髓核细胞PI3K/Akt-GSK-3β信号通路活性也显著降低；然而，高负荷压应力下，当过表达髓核细胞N-CDH后，髓核细胞凋亡减弱（细胞凋亡率降低、caspase-3活性减少、促凋亡分子表达降低、抗凋亡分子表达升高），髓核细胞PI3K/Akt-GSK-3β信号通路活性也相应增加；最后，高负荷压应力下，抑制过表达N-CDH的髓核细胞中PI3K/Akt通路活性后，髓核细胞N-CDH基因和蛋白表达无变化，髓核细胞凋亡增强（细胞凋亡率增加、caspase-3活性增强、促凋亡分子表达升高、抗凋亡分子表达降低）。通过本研究，有助于进一步认识压应力相关椎间盘退行性疾病的病理机制，为椎间盘退变的防治策略提供新的干预靶点及其理论依据。