LBX1表达增高通过影响椎旁肌发育导致青少年特发性脊柱侧凸的机制研究

Adolescent idiopathic scoliosis (AIS) is the most common spinal deformity in teenagers, and one of its pathogenesis is dysplasia of paraspinal muscle. Recently, it was found that LBX1 gene, which involves in regulating of muscle development, is a predisposing gene for AIS. The variation of LBX1 gene leads to overexpression of LBX1, but its pathogenesis is unknown. Our previous study confirmed that patients with LBX1 mutations had significant alternations in paravertebral muscle structure, and overexpression of LBX1 inhibited myogenic differentiation. It can be speculated that the AIS spinal deformity which caused by LBX1 variation is likely to be mediated by paraspinal muscle dysplasia. However, the specific mechanism of aberrant paraspinal muscle caused by LBX1 mutation, as well as its relationship with spinal deformity, remains to be explored. This project intends: to carry out case-control studies, for verifying the correlation between LBX1 mutation and paraspinal muscle abnormalities in AIS patients; to investigate the development of paraspinal muscles in LBX1-overexpressing mice, for exploring the specific mechanism of LBX1-induced paraspinal muscle dysplasia; to investigate the spinal deformities in LBX1-overexpressing mice, for clarifying its relationship with paraspinal muscle dysplasia. This study will elucidate the specific mechanism of aberrant paraspinal muscle caused by LBX1 gene mutation, will clarify the relationship between paraspinal muscle dysplasia and the pathogenesis of AIS, and will finally interpret the pathogenesis of AIS and provide new ideas for the prevention and treatment of AIS.

青少年特发性脊柱侧凸（AIS）是青少年最常见的脊柱畸形，椎旁肌发育异常是潜在病因之一。最近研究证实，参与调控肌肉发育的LBX1基因是该病的易感基因，其变异导致LBX1表达增高，但其致病机制未明。我们前期也发现，LBX1变异的患者椎旁肌结构改变明显，且LBX1高表达抑制细胞成肌分化。由此可推测，LBX1变异所致的AIS脊柱畸形可能通过椎旁肌发育异常介导。然而，LBX1变异引起椎旁肌异常的具体机制、其与脊柱畸形的关系仍待探讨。本项目拟：开展病例对照研究，验证LBX1变异与AIS椎旁肌异常的相关性；考察LBX1高表达小鼠的椎旁肌发育，探究LBX1高表达引起椎旁肌发育异常的具体机制；考察LBX1高表达小鼠的脊柱畸形，明确其与椎旁肌发育异常的关系。本研究将阐明LBX1基因变异引起椎旁肌发育异常的具体机制，厘清椎旁肌发育异常与脊柱畸形之间的关系，最终完善AIS的发病机制学说，为AIS的防治提供新思路。

Ladybird Homeobox 1（LBX1）基因是青少年特发性脊柱侧凸（AIS）的易感基因，研究提示其参与调控肌肉发育，推测其异常表达可能通过影响椎旁肌结果异常而引起脊柱畸形的发生。然而LBX1异常表达如何引起椎旁肌及肌腱发育异常仍然未知。本研究主要围绕LBX1基因的功能角色，考察了：LBX1 变异与AIS椎旁肌肌腱发育异常的关系、LBX1高表达引起肌腱发育异常的具体机制、髓核脊索细胞的特征及LBX1的表达、以及LBX1及炎性因子在椎间盘退变过程的角色。通过本研究，我们首次发现并证实LBX1基因可抑制肌腱干细胞分化功能，并且提出了一个全新的LBX1基因调控肌腱干细胞功能的机制——LBX1通过影响细胞线粒体功能、进而影响肌腱干细胞的分化能力。我们结果提示，在AIS患者中LBX1变异可导致LBX1表达上调，通过影响线粒体代谢，进一步导致肌腱干细胞分化异常，并进一步导致肌肉-骨骼交界的肌腱存在病变。上述异常可能是AIS发病的机制之一。此外，我们探索了椎间盘发育早期髓核中脊索细胞的亚群分类，首次鉴定出髓核中“发育相关脊索细胞（Developmental Notochord Cell）”和“稳态相关脊索细胞（Homeostatic Notochord Cell）”。我们发现LBX1在各亚群细胞中均无显著表达，进一步排除LBX1通过椎间盘脊索细胞异常导致AIS的可能，也不参与椎间盘退变的过程。此外，我们首次详细描绘了II型胶原的信号分子功能，进一步证实II型胶原并非单纯结构蛋白，还通过ITGB1-SMAD通路发挥维持软骨细胞形状、抑制肥大、延缓退变的生物学效应。依托本项目，课题组发表高质量SCI共6篇（合计IF=33分）。本项目阐明了LBX1基因影响肌腱发育的机制，提出AIS发生发展的新学说，并证实了LBX1在脊柱系统疾病中具有重要的角色，为进一步深入研究相关机制奠定了基础。