Machado Camilla R L, Choi Eunice, Perumal Narayanan B, Benschop Robert J, Dressler Gregory R, Wang Wei, Boyle David L, Firestein Gary S
Division of Rheumatology, Autoimmunity and Inflammation, UC San Diego School of Medicine, San Diego, CA, 92093, USA.
Department of Chemistry and Biochemistry, UC San Diego, San Diego, CA, 92093, USA.
Arthritis Res Ther. 2025 Aug 29;27(1):172. doi: 10.1186/s13075-025-03637-1.
Cadherins (CDH), such as CDH11, are glycoprotein adhesion molecules contributing to cell-cell interactions in health and disease. CDH11 has demonstrated important functions in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS). In transcriptome expression studies, we observed that Cadherin 6 (CDH6) expression was higher in RA compared to osteoarthritis (OA). CDH6 is associated with cancer progression, but little information is known on the role of CDH6 in RA. The present study investigates CDH6 expression, regulation, function in FLS, and distribution in RA synovia.
Synovial tissue and FLS were obtained from RA or OA patients undergoing joint replacement. CDH6 epigenetic marks and expression in RA and OA FLS were evaluated using public databases. CDH6 expression was determined by RT-PCR, Western blot, and immunostaining. RA and OA FLS were stimulated with cytokines and growth factors, and CDH6 mRNA expression was determined. CDH6 was silenced using siRNA, and the effect on migration, cell growth, apoptosis, autophagy, cell cycle, and signaling was studied.
In our analysis of cadherin family expression, CDH6 expression was higher in RA than OA FLS. This was associated with differential chromatin accessibility and histone marks in the CDH6 promoter of RA FLS. H3K27ac was identified as an important regulator of CDH6 expression in RA FLS based on experiments using histone deacetylase inhibitors. TGFß, but not IL-1β, TNF, IL-17A, IFNγ, IL-6, or PDGF, increased CDH6 expression of cultured RA FLS. CDH6 knockdown significantly decreased RA FLS migration and cell growth. The latter was associated with increased apoptosis in CDH6 deficient FLS. Immunofluorescence showed CDH6 protein distribution in the membrane, perinuclear, and nuclear regions of cultured FLS. In RA synovial tissue, CDH6 expression was noted in FLS and macrophages within the lining and sublining regions.
CDH6 expression is elevated in RA FLS due to epigenetic and local conditions of synovitis promoting migration, survival and cell growth, which are characteristic features of aggressive RA FLS. The intracellular distribution suggests additional functions beyond adhesion and homotypic aggregation, such as signaling and gene regulation. These data suggest CDH6 contributes to RA pathogenesis by influencing pathologic FLS behavior and could be a therapeutic target.
钙黏蛋白（CDH），如CDH11，是糖蛋白黏附分子，在健康和疾病状态下参与细胞间相互作用。CDH11在类风湿关节炎（RA）成纤维样滑膜细胞（FLS）中已显示出重要功能。在转录组表达研究中，我们观察到与骨关节炎（OA）相比，RA中钙黏蛋白6（CDH6）的表达更高。CDH6与癌症进展相关，但关于CDH6在RA中的作用知之甚少。本研究调查CDH6在RA FLS中的表达、调控、功能以及在RA滑膜中的分布。
从接受关节置换的RA或OA患者获取滑膜组织和FLS。使用公共数据库评估RA和OA FLS中CDH6的表观遗传标记和表达。通过逆转录聚合酶链反应（RT-PCR）、蛋白质印迹法和免疫染色测定CDH6表达。用细胞因子和生长因子刺激RA和OA FLS，并测定CDH6信使核糖核酸（mRNA）表达。使用小干扰RNA（siRNA）使CDH6沉默，并研究其对迁移、细胞生长、凋亡、自噬、细胞周期和信号传导的影响。
在我们对钙黏蛋白家族表达的分析中，RA中CDH6的表达高于OA FLS。这与RA FLS的CDH6启动子中染色质可及性和组蛋白标记的差异有关。基于使用组蛋白脱乙酰酶抑制剂的实验，H3K27ac被确定为RA FLS中CDH6表达的重要调节因子。转化生长因子β（TGFβ），而非白细胞介素-1β（IL-1β）、肿瘤坏死因子（TNF）、白细胞介素-17A（IL-17A）、干扰素γ（IFNγ）、白细胞介素-6（IL-6）或血小板衍生生长因子（PDGF），增加培养的RA FLS中CDH6的表达。CDH6敲低显著降低RA FLS的迁移和细胞生长。后者与CDH6缺陷的FLS中凋亡增加有关。免疫荧光显示CDH6蛋白分布于培养的FLS的膜、核周和核区域。在RA滑膜组织中，在衬里和衬里下层区域的FLS和巨噬细胞中观察到CDH6表达。
由于滑膜炎的表观遗传和局部条件促进迁移、存活和细胞生长，RA FLS中CDH6表达升高，这些是侵袭性RA FLS的特征。细胞内分布提示除黏附和同型聚集之外的其他功能，如信号传导和基因调控。这些数据表明CDH6通过影响病理性FLS行为而促成RA发病机制，并且可能是一个治疗靶点。
