神经源性CGRP通过调控髓核细胞MAPK/ CHSY-1轴影响椎间盘退变机制研究

Low back pain is an important disease which significantly affect life quality of a number of elderly and middle-aged population. It is majorly resulted from the sensory nerve ending irritation which happened in intervertebral disc degeneration (IDD). The current treatments are aimed at interrupting the pain transduction which mediated by sensory nerve. However, sensory nerve not only functions as stimulation signal transduction, it also participants in regulation of organ metabolism homeostasis. We previously uncovered that denervation of sensory nerve in mice could result in IDD phenotype which includes loss of extracellular matrix (ECM) in nucleus pulposus (NP), lower synthesis of chondroitin sulfate (CS) and lower expression of CS synthetase CHSY-1 gene expression. These findings indicate sensory nerve could regulate ECM metabolism in intervertebral disc. Further experimental results demonstrate that sensory nerve neuropeptide calcitonin gene-related peptide (CGRP) could promote CHSY-1 expression and CS synthesis in NP cells. Based on these evidence, the project is aimed to investigate the detailed regulatory mechanism of CHSY-1 by sensory nerve secreted CGRP in vitro, in vivo and in clinical level. This project facilitates us to understand the communications between the sensory nerve and intervertebral disc, it is also beneficial for us to create a therapeutic strategy which targets this regulatory pathway for the matrix preservation of the intervertebral disc.

下腰痛为困扰广大中老年人重要疾患，其主要发病机理为感觉神经末梢在椎间盘退变（IDD）过程中被刺激。目前多种临床治疗手段针对阻断感觉神经对疼痛传导从而达到缓解腰痛的目的。但感觉神经除传递痛觉，其本身也参与器官稳态调节。我们预实验首次发现感觉神经缺失小鼠可自发IDD，表现为椎间盘细胞外基质（ECM）合成减少，保水分子硫酸软骨素（CS）含量以及CS合成酶CHSY-1基因表达降低，提示感觉神经可调节椎间盘ECM代谢。进一步实验发现髓核细胞CHSY-1表达接受感觉神经肽CGRP的正调控。以上证据提示感觉神经分泌CGRP可沟通髓核，上调髓核细胞CHSY-1基因表达，调节CS合成进而影响髓核ECM代谢。综上，本项目拟在体内、体外及临床样本层面阐明感觉神经分泌CGRP对椎间盘髓核CHSY-1及CS合成调控机制，揭示感觉神经与椎间盘ECM代谢调节关系，为在该调控通路中寻找IDD生物治疗靶点提供理论基础。

下腰痛为困扰广大中老年人重要疾患，其主要发病机理为感觉神经末梢在椎间盘退变（IDD）过程中被刺激。目前多种临床治疗手段针对阻断感觉神经对疼痛传导从而达到缓解腰痛的目的。但感觉神经除传递痛觉，其本身也参与器官稳态调节。本项目首次发现了感觉神经除参与椎间盘痛觉感知外，还可直接通过分泌感觉神经肽CGRP直接沟通椎间盘髓核细胞以调节椎间盘稳态并影响IDD进展。课题组利用感觉神经缺失小鼠发现在感觉神经缺失时，椎间盘内硫酸软骨素（CS）含量明显降低，其合成关键基因CHSY1表达明显下调，椎间盘退变加速进展。这表明位于椎间盘外侧的感觉神经能通过某种机制参与椎间盘内部细胞外基质稳态的维持。进一步深入研究发现感觉神经通过分泌神经肽CGRP活化RAMP1/CREB信号通路介导髓核细胞CHSY1表达影响髓核CS分子合成，进而调节椎间盘水稳态。当椎间盘退变时，髓核细胞RAMP1的表达降低，进而导致髓核细胞不能响应CGRP的调节，进而加速椎间盘退变进程。最后，我们通过使用细胞cAMP的激活剂毛喉素（Forskolin）直接活化细胞CREB信号通路后，椎间盘退变的进程得以延缓。本研究首次发现感觉神经参与维持椎间盘稳态的新机制，证实感觉神经能通过分泌神经肽CGRP活化RAMP1/CREB信号通路介导髓核细胞CHSY1表达影响髓核CS分子合成进而调节椎间盘水稳态，同时发现Forskolin对椎间盘退变有一定治疗效果，为今后IDD的生物治疗带来新的思路。