Abstract
BACKGROUND: Mesenchymal stromal cells (MSCs) are widely used to treat osteoarthritis (OA). Optimising dose, timing, and safety while comparing efficacy with standard therapies like hyaluronic acid (HA) is essential for their standardisation. OBJECTIVES: To assess the safety and efficacy of equine umbilical cord-derived (eCB) MSCs in client-owned horses with fetlock or carpus OA. STUDY DESIGN: Prospective single-blinded randomised clinical study. METHODS: Horses diagnosed with fetlock or carpus OA via intra-articular (IA) anaesthesia were randomly assigned to receive either 10 or 20 million eCB-MSCs in HA or 3 mL of HA alone (control). Subjective lameness examinations were performed at baseline, 3 weeks, and 6 weeks post-treatment. Adverse reactions were evaluated 24-72 h post-injection. Follow-up surveys were sent to owners at 18 weeks. RESULTS: Twenty-seven client-owned horses were enrolled. No significant adverse reactions occurred. Lameness outcomes did not differ significantly between treatment groups at 3 or 6 weeks (p > 0.05), though all groups showed improvement over time (p < 0.05). Median lameness change at 6 weeks was -1.5 (0.5) grades for HA, -2.0 (1.0) for 10-MSC + HA, and -2.0 (1.0) for 20-MSC + HA. Although return-to-work rates were not significantly different (p > 0.05), both MSC + HA groups had higher return rates to the same or higher work levels than HA-only (8 out of 9, 7 out of 9, and 5 out of 9, respectively). MAIN LIMITATIONS: Small sample size. CONCLUSIONS: The study aimed to assess MSC treatment safety and efficacy. Higher return-to-exercise rates were expected in the MSC groups at 18 weeks, but unexpectedly high rates in the HA group may have led to underpowering. A post hoc calculation suggests 30 horses per group would be needed to detect significant differences.