MSC exosome as a cell-free MSC therapy for cartilage regeneration: Implications for osteoarthritis treatment

Mesenchymal stem cell (MSC) therapies have demonstrated efficacy in cartilage repair in animal and clinical studies. The efficacy of MSC-based therapies which was previously predicated on the chondrogenic potential of MSC is increasingly attributed to the paracrine secretion, particularly exosomes. Exosomes are thought to function primarily as intercellular communication vehicles to transfer bioactive lipids, nucleic acids (mRNAs and microRNAs) and proteins between cells to elicit biological responses in recipient cells. For MSC exosomes, many of these biological responses translated to a therapeutic outcome in injured or diseased cells. Here, we review the current understanding of MSC exosomes, discuss the possible mechanisms of action in cartilage repair within the context of the widely reported immunomodulatory and regenerative potency of MSC exosomes, and provide new perspectives for development of an off-the-shelf and cell-free MSC therapy for treatment of cartilage injuries and osteoarthritis.