Chondrocyte-Derived Extracellular Vesicles Promote Progenitor Cell Homing and Chondrogenesis

Chondrogenesis by chondrogenic progenitor cells (CPCs) has emerged as a promising avenue for articular cartilage regeneration and early-stage treatment of posttraumatic osteoarthritis. The mechanism of chondrogenesis involves the differentiation of CPCs residing in the cartilage extracellular matrix (ECM). CPC chemotaxis to damaged or degenerated cartilage, followed by in situ proliferation, is an essential first step in restoring tissue integrity. Extracellular vesicles (EVs) have gained significant attention in regenerative medicine due to their several advantages, such as intercellular communication, minimally invasive administration, and reduced immune rejection. In particular, chondrocyte-derived small extracellular vesicles (CC-sEVs) contain highly and differentially expressed microRNAs that enhanced chondrogenesis in our previous studies. In this study, we aimed to evaluate the effects of CC-sEV on CPC homing and chondrogenic differentiation in both monolayer and three-dimensional (3D) hydrogel culture systems. Treatment with 1 × 10 10 /mL CC-sEV (CC-sEV-H) significantly enhanced CPC chemotaxis and proliferation compared with untreated control. Moreover, reactive oxygen species production involved in cartilage degradation was reduced in CC-sEV. Gene expression analysis revealed that CC-sEV upregulated chondrogenic markers, including SRY-box transcription factor 9, collagen type 2 alpha 1, and aggrecan and downregulated catabolic markers, including a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5), matrix metalloproteinases 3 (MMP3), and MMP13. In a fibrin/hyaluronate hydrogel culture system, CC-sEV-H was effective in promoting ECM formation via glycosaminoglycan and collagen depositions. Thus, our findings from in vitro experiments revealed that CC-sEVs could significantly attract CPCs and induce chondrogenesis. Impact Statement This study presents a promising, minimally invasive, and nonsurgical approach to cartilage regeneration. It is based on the ability of chondrogenic progenitor cells (CPCs) to migrate toward injury sites and initiate the repair of cartilage. Small extracellular vesicles (sEVs) derived from chondrocytes significantly enhance cell homing and the process of chondrogenic differentiation when targeting CPCs. These findings highlight the potential of an sEV-based strategy for regenerating damaged and diseased cartilage, offering an innovative approach to prevent posttraumatic osteoarthritis.