University of Rochester Medical Center, Rochester, New York.
Arthritis Rheumatol. 2016 Apr;68(4):805-16. doi: 10.1002/art.39489.
Rheumatoid arthritis (RA) is a systemic autoimmune disease that often leads to joint damage. The mechanisms of bone damage in RA are complex, involving activation of bone-resorbing osteoclasts (OCs) by synoviocytes and Th17 cells. This study was undertaken to investigate whether B cells play a direct role in osteoclastogenesis through the production of RANKL, the essential cytokine for OC development.
RANKL production by total B cells or sorted B cell subpopulations in the peripheral blood and synovial tissue from healthy donors or anti-cyclic citrullinated peptide-positive patients with RA was examined by flow cytometry, real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemical analysis. To define direct effects on osteoclastogenesis, B cells were cocultured with CD14+ monocytes, and OCs were enumerated by tartrate-resistant acid phosphatase staining.
Healthy donor peripheral blood B cells were capable of expressing RANKL upon stimulation, with switched memory B cells (CD27+IgD-) having the highest propensity for RANKL production. Notably, switched memory B cells in the peripheral blood from RA patients expressed significantly more RANKL compared to healthy controls. In RA synovial fluid and tissue, memory B cells were enriched and spontaneously expressed RANKL, with some of these cells visualized adjacent to RANK+ OC precursors. Critically, B cells supported OC differentiation in vitro in a RANKL-dependent manner, and the number of OCs was higher in cultures with RA B cells than in those derived from healthy controls.
These findings reveal the critical importance of B cells in bone homeostasis and their likely contribution to joint destruction in RA.
类风湿关节炎（RA）是一种系统性自身免疫性疾病，常导致关节损伤。RA 中骨破坏的机制很复杂，涉及滑膜细胞和 Th17 细胞激活破骨细胞（OC）。本研究旨在探讨 B 细胞是否通过产生 OC 发育所必需的细胞因子 RANKL 直接参与破骨细胞生成。
通过流式细胞术、实时聚合酶链反应、酶联免疫吸附试验和免疫组织化学分析，检测来自健康供体或抗环瓜氨酸肽阳性 RA 患者的外周血和滑膜组织中总 B 细胞或分选 B 细胞亚群产生的 RANKL。为了明确对破骨细胞生成的直接影响，将 B 细胞与 CD14+单核细胞共培养，并通过抗酒石酸酸性磷酸酶染色计数 OC。
健康供体外周血 B 细胞在刺激后能够表达 RANKL，其中转换型记忆 B 细胞（CD27+IgD-）最易产生 RANKL。值得注意的是，与健康对照组相比，RA 患者外周血中的转换型记忆 B 细胞表达的 RANKL 明显更多。在 RA 滑液和组织中，记忆 B 细胞丰富并自发表达 RANKL，其中一些细胞与 RANK+OC 前体相邻。关键的是，B 细胞以 RANKL 依赖的方式在体外支持 OC 分化，并且来自 RA 患者的 B 细胞培养物中的 OC 数量高于来自健康对照组的培养物。
这些发现揭示了 B 细胞在骨稳态中的重要性及其在 RA 中导致关节破坏的可能贡献。
