Department of Rheumatology and Immunology, Peking University People's Hospital, 11 Xizhimen South Street, Beijing, 100044, China.
Beijing Key Laboratory for Rheumatism Mechanism and Immune Diagnosis (BZ0135), Beijing, China.
Arthritis Res Ther. 2020 Sep 21;22(1):221. doi: 10.1186/s13075-020-02308-7.
Monocytes as precursors of osteoclasts in rheumatoid arthritis (RA) are well demonstrated, while monocyte subsets in osteoclast formation are still controversial. Tyro3 tyrosine kinase (Tyro3TK) is a member of the receptor tyrosine kinase family involved in immune homeostasis, the role of which in osteoclast differentiation was reported recently. This study aimed to compare the osteoclastic capacity of CD14CD16 and CD14CD16 monocytes in RA and determine the potential involvement of Tyro3TK in their osteoclastogenesis.
Osteoclasts were induced from CD14CD16 and CD14CD16 monocyte subsets isolated from healthy control (HC) and RA patients in vitro and evaluated by tartrate-resistant acid phosphatase (TRAP) staining. Then, the expression of Tyro3TK on CD14CD16 and CD14CD16 monocyte subsets in the peripheral blood of RA, osteoarthritis (OA) patients, and HC were evaluated by flow cytometry and qPCR, and their correlation with RA patient clinical and immunological features was analyzed. The role of Tyro3TK in CD14CD16 monocyte-mediated osteoclastogenesis was further investigated by osteoclast differentiation assay with Tyro3TK blockade.
The results revealed that CD14CD16 monocytes were the primary source of osteoclasts. Compared with HC and OA patients, the expression of Tyro3TK on CD14CD16 monocytes in RA patients was significantly upregulated and positively correlated with the disease manifestations, such as IgM level, tender joint count, and the disease activity score. Moreover, anti-Tyro3TK antibody could inhibit Gas6-mediated osteoclast differentiation from CD14CD16 monocytes in a dose-dependent manner.
These findings indicate that elevated Tyro3TK on CD14CD16 monocytes serves as a critical signal for osteoclast differentiation in RA.
单核细胞作为类风湿关节炎（RA）破骨细胞的前体细胞已得到充分证实，而破骨细胞形成中的单核细胞亚群仍存在争议。酪氨酸激酶 3（Tyro3TK）是受体酪氨酸激酶家族的一员，参与免疫稳态，其在破骨细胞分化中的作用最近有报道。本研究旨在比较 RA 患者中 CD14CD16 和 CD14CD16 单核细胞的破骨细胞能力，并确定 Tyro3TK 在其破骨细胞生成中的潜在作用。
体外从健康对照（HC）和 RA 患者中分离 CD14CD16 和 CD14CD16 单核细胞亚群诱导破骨细胞，并通过抗酒石酸酸性磷酸酶（TRAP）染色进行评估。然后，通过流式细胞术和 qPCR 评估 RA、骨关节炎（OA）患者和 HC 外周血中 CD14CD16 和 CD14CD16 单核细胞亚群上 Tyro3TK 的表达，并分析其与 RA 患者临床和免疫特征的相关性。通过 Tyro3TK 阻断的破骨细胞分化测定进一步研究 Tyro3TK 在 CD14CD16 单核细胞介导的破骨细胞生成中的作用。
结果表明，CD14CD16 单核细胞是破骨细胞的主要来源。与 HC 和 OA 患者相比，RA 患者 CD14CD16 单核细胞上 Tyro3TK 的表达明显上调，并与疾病表现呈正相关，如 IgM 水平、压痛关节数和疾病活动评分。此外，抗 Tyro3TK 抗体可呈剂量依赖性抑制 Gas6 介导的 CD14CD16 单核细胞向破骨细胞的分化。
这些发现表明，CD14CD16 单核细胞上升高的 Tyro3TK 可作为 RA 中破骨细胞分化的关键信号。
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