Clinical Outcomes Following Intra-Articular Administration of Autologous Muscle-Derived Mesenchymal Stem Cells in Horses with Chronic Osteoarthritis: A Prospective Open-Label Study

Mesenchymal stromal/stem cells (MSCs) are increasingly investigated as intra-articular therapies for equine osteoarthritis (OA), although most studies have focused on allogeneic or combination-based approaches. Evidence supporting the use of autologous MSCs as a stand-alone treatment remains limited. The present study evaluated the safety and clinical evolution following intra-articular administration of autologous muscle-derived MSCs (mdMSCs) in horses with naturally occurring chronic OA. Thirteen horses with confirmed clinical disease were included. Each affected joint received a single injection, with the administered cell dose adapted to joint size (1 × 107 or 2 × 107 cells). Clinical assessments were conducted at baseline and at 6 and 12 weeks post-treatment using the American Association of Equine Practitioners (AAEP) lameness scale, together with a joint inflammation score and a composite total clinical score (TCS). Clinical scores decreased over time, with statistically significant improvements observed at both follow-up time points. Seven of thirteen horses met the predefined responder criteria based on AAEP improvement, including complete resolution of lameness in several cases. The treatment was well tolerated, with only mild and transient local reactions that resolved without intervention. These results indicate that intra-articular administration of autologous mdMSCs is associated with clinically relevant improvement in horses with chronic OA.