Exosomes from the synovial microenvironment in joint homeostasis and osteoarthritis

<h2>ABSTRACT</h2><h3>Introduction</h3> Orthobiologics, such as mesenchymal stem cells (MSCs), known for their multipotency, are key players in stem cell therapy. One of the ways MSCs realize their therapeutic potential is through the release of extracellular vesicles (EVs), small lipid-membrane–bound structures that carry bioactive materials from their progenitor cells. <h3>Objectives</h3> This review aims to provide an overview of EVs in and from the synovial joint in both physiological and pathological context specifically in osteoarthritis. <h3>Methods</h3> This narrative review synthesizes findings from PubMed using keywords—orthobiologics, EVs, synovial joint EVs, osteoarthritis, and synovial fluid. This review focuses on the potential of EVs isolated from different sources of MSCs found in the synovial joint, evaluating their differentiation capacity and contributions to joint health and osteoarthritis. <h3>Results</h3> EVs from various MSC types show promising results for osteochondral regeneration. However, the differentiation potential and therapeutic efficacy vary among cell types. Understanding the dynamic nature of the biological function of these cell types that serve as sources of EVs is essential for predicting their therapeutic actions. The synovium itself is identified as a significant source of EVs, which may offer unique applications for treating osteoarthritis and cartilage defects. <h3>Conclusions</h3> EVs and exosomes play a critical role in cartilage and osteochondral defect repair. They exhibit preservative and restorative benefits for tissue injuries, highlighting their potential in treating osteoarthritis and cartilage defects. Additionally, the synovium, as a source of EVs and exosomes, presents unique therapeutic applications as orthobiologic.