滑膜液中分化的肥大细胞和骨赘中的固有肥大细胞增强骨关节炎的炎症病理。

INTRODUCTION: Osteophytes are a prominent feature of osteoarthritis (OA) joints and one of the clinical hallmarks of the disease progression. Research on osteophytes is fragmentary and modes of its contribution to OA pathology are obscure. AIM: To elucidate the role of osteophytes in OA pathology from a perspective of molecular and cellular events. METHODS: RNA-seq of fully grown osteophytes, collected from tibial plateau of six OA patients revealed patterns corresponding to active extracellular matrix re-modulation and prominent participation of mast cells. Presence of mast cells was further confirmed by immunohistochemistry, performed on the sections of the osteophytes using anti-tryptase alpha/beta-1 and anti-FC epsilon RI antibodies and the related key up-regulated genes were validated by qRT-PCR. To test the role of OA synovial fluid (SF) in mast cell maturation as proposed by the authors, hematopoietic stem cells (HSCs) and ThP1 cells were cultured in a media supplemented with 10% SF samples, obtained from various grades of OA patients and were monitored using specific cell surface markers by flow cytometry. Proteomics analysis of SF samples was performed to detect additional markers specific to mast cells and inflammation that drive the cell differentiation and maturation. RESULTS: Transcriptomics of osteophytes revealed a significant upregulation of mast cells specific genes such as chymase 1 (CMA1; 5-fold) carboxypeptidase A3 (CPA3; 4-fold), MS4A2/FCERI (FCERI; 4.2-fold) and interleukin 1 receptor-like 1 (IL1RL1; 2.5-fold) indicating their prominent involvement. (In IHC, anti-tryptase alpha/beta-1 and anti- FC epsilon RI-stained active mast cells were seen populated in cartilage, subchondral bone, and trabecular bone.) Based on these outcomes and previous learnings, the authors claim a possibility of mast cells invasion into osteophytes is mediated by SF and present in vitro cell differentiation assay results, wherein ThP1 and HSCs showed differentiation into HLA-DR+/CD206+ and FCERI+ phenotype, respectively, after exposing them to medium containing 10% SF for 9 days. Proteomics analysis of these SF samples showed an accumulation of mast cell-specific inflammatory proteins. CONCLUSIONS: RNA-seq analysis followed by IHC study on osteophyte samples showed a population of mast cells resident in them and may further accentuate inflammatory pathology of OA. Besides subchondral bone, the authors propose an alternative passage of mast cells invasion in osteophytes, wherein OA SF was found to be necessary and sufficient for maturation of mast cell precursor into effector cells.

简介：骨赘是骨关节炎（OA）关节的一个显著特征，也是疾病进展的临床标志之一。骨赘的研究是零散的，其对 OA 病理学的贡献模式尚不清楚。

目的：从分子和细胞事件的角度阐明骨赘在 OA 病理学中的作用。

方法：对来自 6 名 OA 患者胫骨平台的完全生长的骨赘进行 RNA-seq 分析，揭示了与细胞外基质的活跃再调节和肥大细胞的显著参与相对应的模式。肥大细胞的存在通过免疫组织化学进一步得到证实，使用抗胰蛋白酶 alpha/beta-1 和抗 FC epsilon RI 抗体对骨赘切片进行了免疫组织化学染色，并通过 qRT-PCR 验证了相关的关键上调基因。为了验证作者提出的 OA 滑液（SF）在肥大细胞成熟中的作用，将造血干细胞（HSCs）和 ThP1 细胞在补充有 10%SF 样本的培养基中培养，这些 SF 样本来自不同等级的 OA 患者，并通过流式细胞术使用特定的细胞表面标志物进行监测。对 SF 样本进行蛋白质组学分析，以检测驱动细胞分化和成熟的特定于肥大细胞和炎症的其他标记物。

结果：骨赘的转录组学分析显示，肥大细胞特异性基因如糜蛋白酶 1（CMA1；5 倍）、羧肽酶 A3（CPA3；4 倍）、MS4A2/FCERI（FCERI；4.2 倍）和白细胞介素 1 受体样 1（IL1RL1；2.5 倍）的显著上调表明它们的显著参与。（在 IHC 中，可见抗胰蛋白酶 alpha/beta-1 和抗 FCepsilon RI 染色的活性肥大细胞存在于软骨、软骨下骨和小梁骨中。）基于这些结果和以前的研究，作者提出肥大细胞侵入骨赘可能是由 SF 介导的，并提供了体外细胞分化实验结果，其中 ThP1 和 HSCs 在暴露于含有 10%SF 的培养基 9 天后分别显示出向 HLA-DR+/CD206+和 FCERI+表型的分化。对这些 SF 样本的蛋白质组学分析显示，肥大细胞特异性炎症蛋白的积累。

结论：对骨赘样本进行 RNA-seq 分析后进行 IHC 研究显示，其中存在一群驻留的肥大细胞，可能进一步加重 OA 的炎症病理。除了软骨下骨，作者提出了肥大细胞侵入骨赘的另一种途径，其中 OA SF 被发现是肥大细胞前体成熟为效应细胞的必要和充分条件。