RIP1 perturbation induces chondrocyte necroptosis and promotes osteoarthritis pathogenesis

Receptor-interacting protein kinase 1 (RIP1)-mediated necroptosis plays a vital role in various diseases, but the involvement of RIP1 and its functional mechanism in osteoarthritis pathogenesis remains largely unknown. To identify molecular targets of RIP1 in chondrocytes, RNA sequencing was performed in chondrocytes treated with adenovirus expressing RIP1 or vector control. We found that 9857 genes were differentially expressed in chondrocytes after RIP1 overexpression. GO analysis indicated that DNA replication, chromosome segregation and regulation of cell cycle process were upregulated, while terms including cartilage development, skeletal system development, extracellular matrix organization, skeletal system morphogenesis, chondrocyte differentiation, collagen fibril organization and limb development were downregulated. Pathway analysis revealed that IL-17 signaling pathway, cell cycle, DNA replication, proteasome, TNF signaling pathway, cellular senescence and p53 signaling pathway were significantly upregulated by RIP1, meanwhile, ECM-receptor interaction, other glycan degradation and glycosaminoglycan degradation were downregulated. These results underscore the importance of RIP1 in OA by perturbing a series of essential events during disease progression such like cell cycle regulation, chondrocyte differentiation, inflammation and ECM remodeling.受体相互作用蛋白激酶1（Receptor-interacting protein kinase 1, RIP1）介导的坏死性凋亡（necroptosis）在多种疾病中发挥关键作用，但RIP1在骨关节炎（Osteoarthritis, OA）发病机制中的参与情况及其功能机制仍尚未完全阐明。为鉴定软骨细胞中RIP1的分子靶标，本研究对转染过表达RIP1的腺病毒或空载体对照的软骨细胞进行了RNA测序（RNA sequencing）。研究发现，RIP1过表达后软骨细胞中有9857个基因存在差异表达。基因本体（Gene Ontology, GO）分析显示，DNA复制、染色体分离及细胞周期进程调控相关基因表达上调；而软骨发育、骨骼系统发育、细胞外基质（extracellular matrix, ECM）组织、骨骼系统形态发生、软骨细胞分化、胶原纤维组织及肢体发育相关基因表达下调。通路富集分析表明，RIP1可显著上调IL-17信号通路、细胞周期、DNA复制、蛋白酶体（proteasome）、TNF信号通路、细胞衰老及p53信号通路相关基因的表达；同时下调细胞外基质-受体相互作用、其他聚糖降解及糖胺聚糖降解相关通路的基因表达。上述研究结果表明，RIP1通过扰动疾病进展过程中一系列关键事件，包括细胞周期调控、软骨细胞分化、炎症反应及细胞外基质重塑，在骨关节炎的发生发展中发挥重要作用。