LncRNA-BNR介导BMP2/NOG表达失衡在强直性脊柱炎MSCs成骨分化增强中的机制研究

Ankylosing spondylitis (AS) is a type of autoimmune disease characterized by pathological osteogenesis and chronic inflammation. We previously demonstrated that imbalance between bone morphogenetic protein 2 (BMP2) and noggin (NOG) led to enhanced osteogenic differentiation of mesenchymal stem cells (MSCs) in AS, which is an important mechanism of pathological osteogenesis. However, the mechanism of imbalance between BMP2 and NOG expression remain unclear. Further study found that long non-coding RNA-BNR (LncRNA-BNR) was down-regulated in MSCs from AS patients during osteogenic differentiation. Besides, LncRNA-BNR regulated the expression of BMP2 and NOG and the subsequent osteogenic differentiation of MSCs through binding to hnRNPL. Therefore, we suggest that down-regulation of LncRNA-BNR is the key reason for the imbalance between BMP2 and NOG and the subsequent enhanced osteogenic differentiation of MSCs in AS. In this study, we aim to investigate the concrete mechanism of the expression balance between BMP2 and NOG regulated by LncRNA-BNR binding to hnRNPL, and the role of these factors play in the enhanced osteogenic differentiation of MSCs from AS patients. Moreover, we estimate the value of LncRNA-BNR in forecasting, assessing and treating the pathological osteogenesis in AS, which will provide brand-new ideas for early diagnosis and treatment in AS.

强直性脊柱炎（AS）是一种以病理性成骨和慢性炎症为特征的自身免疫性疾病。我们前期已证实BMP2/NOG表达失衡导致AS患者间充质干细胞（MSCs）成骨分化能力增强，是AS病理性成骨重要机制，但BMP2/NOG表达失衡机制不清。进一步预实验结果提示AS患者MSCs成骨分化过程中长链非编码RNA-BNR（LncRNA-BNR）表达下调；LncRNA-BNR可能通过结合hnRNPL以调控BMP2/NOG表达平衡、引导MSCs成骨分化。据此，我们推测LncRNA-BNR下调是介导BMP2/NOG表达失衡、导致AS患者MSCs成骨分化增强的重要机制。本研究拟以此为切入点，通过体内外实验研究LncRNA-BNR结合hnRNPL调控BMP2/NOG表达平衡的机制及其在AS患者MSCs成骨分化增强中的作用，探讨LncRNA-BNR在预测、评估和治疗AS病理性成骨中的价值，为AS早期诊断和治疗提供新的思路。

强直性脊柱炎 (Ankylosing spondylitis, AS) 是一种常见的自身免疫性疾病，临床主要表现为炎症性背痛和脊柱强直。慢性炎症与病理性成骨是 AS 的两大核心病理特征。AS 病理性成骨发病机制仍未阐明，前期研究发现AS 患者 MSCs 在成骨分化过程中表达 BMP2 增多而 Noggin （NOG） 减少，BMP2/NOG 表达失衡导致AS患者 MSCs 成骨分化能力增强。本项目就 MSCs 成骨分化机制、AS 患者 MSCs 功能异常、AS 中病理性成骨与炎症之间的关系等问题进行了深入研究。.通过本项目，我们主要取得以下进展：（1）我们发现了一条新型lncRNA，并且命名为 lncRNA-OG，它通过调控BMP家族蛋白的表达在 MSCs 成骨分化中发挥着重要的正向作用。H3K27 乙酰化激活的lncRNA-OG与 heterogeneous nuclear ribonucleoprotein K (hnRNPK) 相关联，hnRNPK促进 lncRNA-OG 的转录活性。（2）TNF receptor-associated factor 4 (TRAF4) 通过促进 Smad ubiquitination-related factor 2（Smurf2）泛素化降解进而促进 MSCs 成骨分化。（3）我们发现了另一条新型 lncRNA ，并命名为GAS5，它通过UPF1/SMAD7轴促进 MSCs 成骨分化。（4）AS 患者 MSCs在成骨过程中比正常人 MSCs 分泌更多的monocyte chemoattractant protein 1 （MCP1），进而促进单核细胞的迁移、巨噬细胞的极化和TNF -α 的分泌。（5）TRAF4 表达升高促使Lipopolysaccharide (LPS) 介导的 MSCs 自噬在AS病人中比正常人弱。