Lubberts Erik, Oppers-Walgreen Birgitte, Pettit Allison R, Van Den Bersselaar Liduine, Joosten Leo A B, Goldring Steven R, Gravallese Ellen M, Van Den Berg Wim B
University Medical Center Nijmegen, Nijmegen, The Netherlands.
Arthritis Rheum. 2002 Nov;46(11):3055-64. doi: 10.1002/art.10607.
The receptor activator of nuclear factor kappaB (RANK)/RANK ligand (RANKL) pathway is critical in osteoclastogenesis and bone resorption and has been implicated in the process of focal bone erosion in arthritis. This study was undertaken to identify in vivo the hitherto-unknown origin and localization of RANK-expressing osteoclast precursor cells at sites of bone erosion in arthritis.
DBA-1 mice were immunized with bovine type II collagen/Freund's complete adjuvant and were given an intraperitoneal booster injection of type II collagen on day 21. Arthritis was monitored visually, and joint pathology was examined histologically. RANK and RANKL expression were analyzed using specific immunohistochemistry, and tartrate-resistant acid phosphatase (TRAP) staining was performed. In addition, TRAP and cathepsin K messenger RNA expression were analyzed by in situ hybridization.
A marked increase in the number of cells expressing RANK correlated with the progression of synovial inflammation and clinical disease severity in evolving collagen-induced arthritis (CIA). Interestingly, RANK expression demonstrated a gradient pattern with increased numbers of RANK-positive cells within the synovial infiltrate in areas closer to periosteum and cortical bone. Cells expressing RANK included cells in synovial tissue, bone lining cells on the surface of trabecular bone at sites of erosion, and cells in periosteal areas adjacent to synovial inflammation. In areas where RANK-positive cells were abundant, TRAP-positive, multinucleated osteoclast-like cells were also present at sites of focal bone erosion, suggesting differentiation of synovially derived RANK-positive osteoclast precursor cells into osteoclasts. In addition, TRAP- and cathepsin K-double-positive osteoclast-like cells were detected on the synovial side of cortical bone at sites of early and advanced cortical bone erosion. Sites of RANK expression also correlated well with sites of RANKL expression, and there was a close correlation of the temporal expression of the receptor-ligand pair.
Cells expressing RANK increased in abundance with the progression of arthritis in evolving CIA, and sites of RANK-expressing cells correlated with sites of TRAP-positive, multinucleated osteoclast-like cells as well as with sites of RANKL expression. These data support the hypothesis that the RANK/RANKL pathway plays an important role in the process of bone erosion in CIA.
核因子κB受体激活剂（RANK）/RANK配体（RANKL）通路在破骨细胞生成和骨吸收过程中至关重要，并且与关节炎中局灶性骨侵蚀的进程有关。本研究旨在体内确定关节炎骨侵蚀部位表达RANK的破骨细胞前体细胞迄今未知的来源和定位。
用牛II型胶原/弗氏完全佐剂免疫DBA - 1小鼠，并在第21天腹腔注射II型胶原进行加强免疫。通过肉眼监测关节炎情况，并进行组织学检查关节病理。使用特异性免疫组织化学分析RANK和RANKL表达，并进行抗酒石酸酸性磷酸酶（TRAP）染色。此外，通过原位杂交分析TRAP和组织蛋白酶K信使核糖核酸表达。
在逐渐发展的胶原诱导性关节炎（CIA）中，表达RANK的细胞数量显著增加，这与滑膜炎症的进展和临床疾病严重程度相关。有趣的是，RANK表达呈现出一种梯度模式，在靠近骨膜和皮质骨的滑膜浸润区域内，RANK阳性细胞数量增加。表达RANK的细胞包括滑膜组织中的细胞、侵蚀部位小梁骨表面的骨衬细胞以及与滑膜炎症相邻的骨膜区域中的细胞。在RANK阳性细胞丰富的区域，局灶性骨侵蚀部位也存在TRAP阳性的多核破骨细胞样细胞，这表明滑膜来源的RANK阳性破骨细胞前体细胞分化为破骨细胞。此外，在早期和晚期皮质骨侵蚀部位的皮质骨滑膜侧检测到TRAP和组织蛋白酶K双阳性的破骨细胞样细胞。RANK表达部位也与RANKL表达部位密切相关，并且受体 - 配体对的时间表达密切相关。
在逐渐发展的CIA中，随着关节炎的进展，表达RANK的细胞数量增多，表达RANK的细胞部位与TRAP阳性的多核破骨细胞样细胞部位以及RANKL表达部位相关。这些数据支持RANK/RANKL通路在CIA骨侵蚀过程中起重要作用的假说。
