Platelet-derived mitochondrial preparation did not alter early inflammatory markers in a bilateral lipopolysaccharide-induced model of equine synovitis.

Objective: To evaluate IA autologous platelet-derived mitochondrial preparation versus vehicle control in a bilateral lipopolysaccharide (LPS)-induced model of equine synovitis.

Methods: 2 ng of LPS was injected into bilateral intercarpal joints of 6 horses over 3 months. Autologous mitochondria, isolated with a commercial kit, were injected into one joint, while the contralateral joint received a vehicle control, a within-subject controlled experimental design. Mitochondrial organelle appearance was visualized on transmission electron microscopy. Outcome measures included synovial fluid and whole-blood cytology, synovial fluid and serum multiplex cytokine assays, and synovial fluid leukocyte gene expression via quantitative real-time PCR from 0, 4, 8, 24, and 48 hours. Data were analyzed using linear mixed-effects models with nonparametric tests when normality assumptions failed.

Results: No significant differences were observed between treated and control joints in synovial fluid cytology, cytokine expression, or gene expression. Following LPS, increased total nucleated cells were observed in synovial fluid. Systemic changes included elevation in IL-12 and reduction in IL-10. In synovial fluid, FGF-2 decreased and interferon-γ, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-18, and tumor necrosis factor-α (TNF-α) increased compared to baseline. Gene expression of C-X-C motif chemokine ligand 1, IL-1β, IL-5, IL-6, IL-18, matrix metallopeptidase 13, and PTEN-induced kinase 1 were upregulated whereas OPA1 mitochondrial dynamin-like GTPase and TNF-α were downregulated over time.

Conclusions: The bilateral LPS-induced synovitis model produced minimal systemic inflammation and moderate local joint inflammation. No benefit of this mitochondrial preparation was identified.

Clinical relevance: While in concept there is potential for mitotherapy, our study design was unable to demonstrate benefits from this preparation in ameliorating the inflammatory effects of LPS-induced synovitis.