Thy-1调控间充质干细胞成软骨化及其在青少年特发性脊柱侧凸软骨内成骨障碍中的作用和机制研究

青少年特发性脊柱侧凸(AIS)是青少年最常见的脊柱畸形。椎体软骨内成骨障碍被认为是AIS重要发病机制。充质干细胞（MSC）软骨分化能力减弱可能与软骨内成骨障碍密切相关。探索其分子机制有助于明确AIS椎体软骨内成骨障碍及其发病机制，但目前缺乏相关系统性研究。本课题组前期单细胞测序发现，AIS骨髓中以Thy-1缺失MSC为主，Thy-1缺失MSC向软骨分化完全停滞。Wnt通路关键蛋白表达降低。我们在动物和细胞水平上观察到，Thy-1缺失小鼠骨量明显减少。敲除/过表Thy-1，MSC成骨能力减弱/增强。基于前期研究我们推测，Thy-1可能通过Wnt通路促进MSC向软骨分化，其表达缺陷可能影响MSC软骨内成骨，参与AIS发病。本研究拟在前期研究基础上，探寻Thy-1在调控MSC软骨分化中的作用和分子机制，及其表达缺陷对AIS软骨内成骨的影响，为AIS提出新的发病机制和干预靶点。

Adolescent idiopathic scoliosis (AIS) is the most common spinal deformity of adolescents, leading to patients’ both ‘physical and psychological disability’. Dysfunctions of endochondral ossification in vertebra is regarded as an important etiology of AIS. The decreased ability of chondrocyte differentiation in MSC (Mesenchyma stem cell) is significantly with dysfunctions of endochondral ossification in AIS vertebra. Therefore, the exploration of molecular mechanisms of chondrocyte differentiation in AIS vertebra is the key point of understanding of dysfunctions of endochondral ossification and AIS etiology. However, no studies have been performed. Our group, for the first time, performed single-cell high-throughput sequencing analysis on AIS and healthy human vertebra, and the results showed that Thy-1-/- MSC is the most common sub-type of MSC in AIS and the disruption of chondrocyte differentiation of Thy-1-/- MSC was also observed in AIS. In addition, low expression of key proteins in the Wnt signal pathway were also observed in AIS patients. In Thy-1-/- mice, osteopenia was observed. Furthermore, we also found that the function of chondrocyte differentiation of MSC in Thy-1-/- mice significantly decreased compared with that in WT mice. When we knocked down the Thy-1 on WT MSC with siRNA, we found that the chondrocyte differentiation was inhibited. Conversely, the ability of chondrocyte differentiation of MSC was enhanced when the expression of Thy-1 was up-regulated. Based on our preliminary results, we speculate that Thy-1 may have positive impacts on chondrocyte differentiation of MSC through Wnt signal pathway, and the defective expression of Thy-1 in MSC may have adverse effects on endochondral ossification of vertebra in AIS, which might be an important etiology of AIS. Therefore, the objective of this project is to explore the role and mechanisms of the effects of Thy-1 on chondrocyte differentiation of MSC, and also to detect the effects of defective expression of Thy-1 on regulation of chondrocyte differentiation and endochondral ossification in AIS. Through this project, we hope to explore the mechanisms how Thy-1 affects chondrocyte differentiation and endochondral ossification in the pathogenesis of AIS, and to provide theoretical basis for the early diagnosis and prevention of AIS.