Table_2_Single-cell RNA sequencing reveals distinct chondrocyte states in femoral cartilage under weight-bearing load in Rheumatoid arthritis.xlsx

IntroductionRheumatoid arthritis (RA) is a common autoimmune joint disease, the pathogenesis of which is still unclear. Cartilage damage is one of the main manifestations of the disease. Chondrocytes are the main functional component of articular cartilage, which is relevant to disease progression. Mechanical loading affects the structure and function of articular cartilage and chondrocytes, but the effect of weight bearing on chondrocytes in rheumatoid arthritis is still unclear.
MethodsIn this paper, single-cell RNA sequencing (scRNA-seq) was performed on collected cartilage from the weight-bearing region (Fb group) and non-weight-bearing region (Fnb group) of the femur, and the differences between the Fb and Fnb groups were analyzed by cell type annotation, pseudotime analysis, enrichment analysis, cell interactions, single-cell regulatory network inference and clustering (SCENIC) for each cell type.
ResultsA total of 87,542 cells were analyzed and divided into 9 clusters. Six chondrocyte subpopulations were finally identified by cellular annotation, and two new chondrocyte subtypes were annotated as immune-associated chondrocytes. The presence of each chondrocyte subpopulation and its distribution were verified using immunohistochemical staining (IHC). In this study, the atlas of femoral cartilage in knee rheumatoid arthritis and 2 new immune-related chondrocytes were validated using scRNA-seq and IHC, and chondrocytes in the weight-bearing and non-weight-bearing regions of the femur were compared. There might be a process of macrophage polarization transition in MCs in response to mechanical loading, as in macrophages.
ConclusionTwo new immune-associated chondrocytes were identified. MCs have contrasting functions in different regions, which might provide insight into the role of immune and mechanical loading on chondrocytes in the development of knee rheumatoid osteoarthritis.

引言
类风湿关节炎（RA）是一种常见的自身免疫性关节疾病，其具体发病机制尚未完全阐明。软骨损伤是该疾病的核心临床表现之一。软骨细胞（chondrocytes）作为关节软骨的核心功能组成单元，与疾病进展密切相关。机械负荷可调控关节软骨及软骨细胞的结构与功能，但负重状态对类风湿关节炎患者软骨细胞的具体影响仍有待明确。
方法
本研究针对收集的股骨负重区（Fb组）与非负重区（Fnb组）软骨组织开展单细胞RNA测序（scRNA-seq），并通过细胞类型注释、拟时分析、富集分析、细胞互作分析、单细胞调控网络推断与聚类（SCENIC）等方法，对两组间的细胞差异进行系统性分析。
结果
本研究共纳入87542个细胞进行分析，将其划分为9个细胞簇。通过细胞注释最终鉴定出6个软骨细胞亚群，其中2个新的软骨细胞亚型被注释为免疫相关软骨细胞。研究通过免疫组化染色（IHC）验证了各软骨细胞亚群的存在及其组织分布特征。
本研究通过单细胞RNA测序与免疫组化染色，构建了膝关节类风湿关节炎患者股骨软骨细胞图谱，鉴定出2种新型免疫相关软骨细胞，并对比了股骨负重区与非负重区软骨细胞的转录组差异。研究发现，髓系细胞（MCs）在响应机械负荷时，可能存在类似巨噬细胞的极化转化过程。
结论
本研究成功鉴定出2种新型免疫相关软骨细胞。髓系细胞（MCs）在不同解剖区域呈现出显著的功能异质性，该发现可为阐明免疫与机械负荷在膝关节类风湿性骨关节炎发病进程中对软骨细胞的调控作用提供全新的研究视角。