Extracellular vesicles mediate improved functional outcomes in engineered cartilage produced from MSC/chondrocyte cocultures.

Several recent studies have demonstrated that coculture of chondrocytes (CHs) with bone marrow-derived mesenchymal stem cells (MSCs) improves their chondrogenesis. This implies that intercellular communication dictates fate decisions in recipient cells and/or reprograms their metabolic state to support a differentiated function. While this coculture phenomenon is compelling, the differential chondroinductivity of zonal CHs on MSC cocultures, the nature of the molecular cargo, and their transport mechanisms remains undetermined. Here, we demonstrate that juvenile CHs in coculture with adult MSCs promote functional differentiation and improved matrix production. We further demonstrate that close proximity between the two cell types is a prerequisite for this response and that the outcome of this interaction improves viability, chondrogenesis, matrix formation, and homeostasis in the recipient MSCs. Furthermore, we visualized the transfer of intracellular contents from CHs to nearby MSCs and showed that inhibition of extracellular vesicle (EV) transfer blocks the synergistic effect of coculture, identifying EVs as the primary mode of communication in these cocultures. These findings will forward the development of therapeutic agents and more effective delivery systems to promote cartilage repair.