Single-cell RNA-seq analysis reveals the progression of human osteoarthritis

Understanding the molecular mechanisms underlying human cartilage degeneration and regeneration is helpful for improving therapeutic strategies for treating osteoarthritis (OA). Here, we report the molecular programmes and lineage progression patterns controlling human OA pathogenesis using single-cell RNA sequencing (scRNA-seq). We performed unbiased transcriptome-wide scRNA-seq analysis, computational analysis and histological assays on 1464 chondrocytes from 10 patients with OA undergoing knee arthroplasty surgery. We investigated the relationship between transcriptional programmes of the OA landscape and clinical outcome using severity index analysis and correspondence analysis. We identified seven molecularly defined populations of chondrocytes in human OA cartilage, including three novel phenotypes with distinct functions. We presented gene expression profiles and transcriptional networks among chondrocytes at different OA stages at single-cell resolution. We found a potential transition among proliferative chondrocytes, prehypertrophic chondrocytes and hypertrophic chondrocytes (HTCs) and defined a new subdivision within HTCs. We revealed novel markers for cartilage progenitor cells (CPCs) and demonstrated a relationship between CPCs and fibrocartilage chondrocytes using computational analysis. Notably, we derived predictive targets with respect to clinical outcomes and clarified the role of different cell types for the early diagnosis and treatment of OA.

解析人类软骨退变与再生的潜在分子机制，有助于优化骨关节炎（Osteoarthritis, OA）的治疗策略。本研究利用单细胞RNA测序（single-cell RNA sequencing, scRNA-seq）技术，解析了调控人类骨关节炎发病进程的分子程序与谱系发育模式。本研究对10例行膝关节置换术的骨关节炎患者的1464个软骨细胞（chondrocytes）开展了无偏倚的全转录组单细胞RNA测序分析、生物信息学计算分析及组织学检测。本研究通过严重程度指数分析与对应分析，探究了骨关节炎转录图谱中的转录调控程序与临床结局之间的关联。本研究在人类骨关节炎软骨中鉴定出7个经分子定义的软骨细胞亚群，其中包含3个功能独特的新型细胞表型。本研究以单细胞分辨率，绘制了不同骨关节炎病程阶段软骨细胞的基因表达谱与转录调控网络。本研究发现增殖性软骨细胞、前肥大软骨细胞与肥大软骨细胞（hypertrophic chondrocytes, HTCs）之间存在潜在的转化关系，并明确了肥大软骨细胞亚群内的一个新的细分类型。本研究揭示了软骨祖细胞（cartilage progenitor cells, CPCs）的新型标志物，并通过生物信息学分析阐明了软骨祖细胞与纤维软骨软骨细胞之间的关联。尤为重要的是，本研究筛选出了与临床结局相关的预测靶点，并厘清了不同细胞亚群在骨关节炎早期诊断与治疗中的作用。