Table_6_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（Rheumatoid arthritis, RA）是一种常见的自身免疫性关节疾病，其发病机制尚未完全阐明。软骨损伤是该疾病的主要临床表现之一。软骨细胞（Chondrocytes）是关节软骨（articular cartilage）的核心功能组分，与疾病进展密切相关。机械负荷（Mechanical loading）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影响仍有待阐明。
方法
本研究对采集的股骨负重区（Fb组）与非负重区（Fnb组）软骨组织开展了单细胞RNA测序（single-cell RNA sequencing, scRNA-seq），并针对各细胞类型，通过细胞类型注释、拟时分析、富集分析、细胞互作分析以及单细胞调控网络推断与聚类（single-cell regulatory network inference and clustering, SCENIC）对两组间的差异进行了系统分析。
结果
本研究共纳入87542个细胞进行分析，并将其划分为9个细胞聚类簇。通过细胞注释最终鉴定出6个软骨细胞亚群，其中两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（immunohistochemical staining, 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的股骨软骨细胞图谱，鉴定出两种新的免疫相关软骨细胞，并对股骨负重区与非负重区的软骨细胞进行了比较分析。研究发现，巨噬细胞（MCs）在响应机械负荷时，可能存在与常规巨噬细胞类似的极化转换过程。
结论
本研究成功鉴定出两种新的免疫相关软骨细胞。巨噬细胞在不同区域的功能存在显著差异，该发现可为揭示免疫与机械负荷在膝关节类风湿性骨关节炎发生发展过程中对软骨细胞的调控作用提供新的研究思路。