Background: Platelet-rich plasma (PRP) and mesenchymal stromal or stem cells (MSCs) have been investigated as treatments for equine tendon and ligament injuries, but little consensus exists on the efficacy of these treatments. The study sought to evaluate the efficacy of PRP and MSC treatments by systematic review and meta-analysis.

Methods: A systematic review was performed using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines. Inclusion criteria required an original, peer-reviewed study where horses were administered MSCs or PRP (or both), and a comparator group was described. Studies were assessed for risk of bias and study quality. Random effects meta-analysis with inverse variance weighting was used to calculate pooled estimates of the ORs for the primary outcomes of return to performance and reinjury.

Results: The search criteria identified 764 unique studies, and 21 studies met the inclusion criteria for the systematic review. Seventeen studies were further assessed for the primary outcomes of return to performance and reinjury rate within a meta-analysis. Meta-analyses revealed no increase in the likelihood of a return to performance with any of the biologic treatments. However, MSCs and MSCs administered concurrently with PRP provide a reduced risk of reinjury.

Clinical relevance: The current study identified a decrease in reinjury rate in horses administered MSCs or a combination of MSCs and PRP for tendinopathy and desmopathy. However, results should be interpreted with consideration of the heterogeneity of findings, poor study quality, and high risk of bias in the majority of studies.