Articular cartilage injury and degeneration causing pain and loss of quality-of-life has become a serious problem for increasingly aged populations. Given the poor self-renewal of adult human chondrocytes, alternative functional cell sources are needed. Direct reprogramming by small molecules potentially offers an oncogene-free and cost-effective approach to generate chondrocytes, but has yet to be investigated. Here, we directly reprogrammed mouse embryonic fibroblasts into PRG4+ chondrocytes using a 3D system with a chemical cocktail, VCRTc (valproic acid, CHIR98014, Repsox, TTNPB, and celecoxib). Using single-cell transcriptomics, we revealed the inhibition of fibroblast features and activation of chondrogenesis pathways in early reprograming, and the intermediate cellular process resembling cartilage development. The in vivo implantation of chemical-induced chondrocytes at defective articular surfaces promoted defect healing and rescued 63.4% of mechanical function loss. Our approach directly converts fibroblasts into functional cartilaginous cells, and also provides insights into potential pharmacological strategies for future cartilage regeneration.

对于日益老龄化的人口来说，导致疼痛和生活质量下降的关节软骨损伤和变性已经成为严重的问题。鉴于成人软骨细胞的自我更新能力较差，因此需要其他功能性细胞来源。小分子直接重编程可能会提供一种无致癌基因且具有成本效益的方法来生成软骨细胞，但尚未进行研究。在这里，我们使用带有化学混合物，VCRTc（丙戊酸，CHIR98014，Repsox，TTNPB和塞来昔布）的3D系统将小鼠胚胎成纤维细胞直接重编程为PRG4 +软骨细胞。使用单细胞转录组学，我们揭示了在早期重编程中，成纤维细胞特征的抑制和软骨生成途径的激活，以及类似于软骨发育的中间细胞过程。的在有缺陷的关节表面体内植入化学诱导的软骨细胞可促进缺陷的愈合并挽救63.4％的机械功能丧失。我们的方法将成纤维细胞直接转化为功能性软骨细胞，并且还为未来软骨再生的潜在药理策略提供了见识。