Mesenchymal stem cell-derived extracellular vesicles modulate Th1- and STAT1-Associated inflammatory responses in...

Osteoarthritis (OA) is increasingly recognized as a chronic inflammatory disease, with dysregulated immune responses contributing to cartilage degeneration and disease progression. Immune dysregulation, including alterations in Th1-associated responses, may contribute to the chronic inflammatory environment observed in osteoarthritis. MSC-derived exosomes have been highlighted as potential cell-free therapeutic agents due to their potent immunomodulatory properties; however, their effects on Th1-associated immune responses in OA remain poorly understood.

Extracellular vesicles produced from MSCs were extracted and analyzed by scanning electron microscopy (SEM), dynamic light scattering, and Western blotting for CD9, CD81, and CD63. Healthy controls and OA patients' PBMCs were grown with and without MSC-derived extracellular vesicles. Flow cytometry was used to quantify Th1 cells. STAT1, IL-1β, IL-6, and TNFα expression was assessed by quantitative real-time PCR. ELISA measured cytokine secretion in culture supernatants.

PBMCs were obtained from 10 patients with OA and 10 age- and sex-matched healthy controls. Treatment with the MSC-derived extracellular vesicle preparation (20 µg total protein-equivalent material per approximately 1 × 10⁶ PBMCs for 48 h) was associated with a significant reduction in CD4⁺IFN-γ⁺ Th1-cell frequency in both healthy controls and OA patients. In OA PBMCs, Th1-cell frequency decreased from 33.8% ± 7.7% at baseline to 26.9% ± 7.0% after treatment (P = 0.0080). STAT1 mRNA expression decreased from 2.21 ± 0.45 to 1.54 ± 0.27 relative expression units (P = 0.0028). Treatment was also associated with reduced IL-1β, IL-6, and TNF-α mRNA expression and decreased concentrations of these cytokines in culture supernatants.

MSC-derived extracellular vesicles were associated with reduced Th1-associated responses, decreased STAT1 mRNA expression, and reduced inflammatory cytokine production in PBMCs from patients with OA. These findings provide preliminary in vitro evidence of an immunomodulatory effect; however, they do not establish a causal role for STAT1 or demonstrate therapeutic efficacy. Further studies with comprehensive EV characterization and pathway-specific mechanistic analyses are warranted.