IM01 - Identification of Extracellular Vesicles in Synovial Fluid and Blood of Immune-mediated Polyarthritis and Osteoarthritis Dogs

Abstract: Background – Immune-mediated polyarthritis (IMPA) presents a clinical challenge, requiring arthrocentesis for diagnosis and adequate monitoring. Relapses are common during therapy. Measurement of C-reactive protein can be useful, but lacks specificity for IMPA. Extracellular vesicles (EVs) show promising clinical impact, but have yet to be characterized in canine synovial fluid (SF). EVs may contain IMPA-specific biomarkers, helping guide clinical decisions.

Hypothesis – Dogs with IMPA have unique SF and plasma EV characteristics compared to dogs with OA.

Animals – Client-owned dogs: 10 IMPA, 10 OA, 10 healthy controls

Methods – Prospective pilot study: EVs are enriched from SF and plasma using precipitation-based methods and characterized by nanoparticle tracking analysis (NTA). Wilcoxon tests compare groups. RNA sequencing (ongoing) will assess differential gene expression between groups.

Results – NTA of plasma and SF EVs from 5 IMPA and 5 OA patients are available. In plasma, median EV size (IQR) was 93.2nm (22.2) for IMPA and 92.6nm (7.7) for OA (p = 0.69); median EV concentration (IQR) was 1.32×10¹¹particles/mL (1.80×10¹¹) for IMPA and 3.80×10¹¹particles/mL (2.75×10¹¹) for OA (p = 0.31). In synovial fluid, median EV size (IQR) was 117.0nm (26.6) for IMPA and 127.8nm (2.0) for OA (p = 0.42); median EV concentration (IQR) was 6.25×10¹⁰particles/mL (9.50×10¹⁰) for IMPA and 9.11×10¹⁰particles/mL (3.66×10¹⁰) for OA (p = 0.84).

Conclusions and Clinical Importance – Physical characteristics of canine SF and plasma EVs are not sufficient to differentiate IMPA and OA. Molecular analysis of EV contents with RNA sequencing will improve differentiation, advancing clinical diagnostic developments.