Extracellular vesicles from equine mesenchymal stem cells decrease inflammation markers in chondrocytes in vitro

Background: Mesenchymal stem cells (MSCs) have been used therapeutically in equine medicine. MSCs release extracellular vesicles (EVs), which affect cell processes by inhibiting cell apoptosis and regulating inflammation. To date, little is known about equine EVs and their regenerative properties. Objectives: To characterise equine MSC-derived extracellular vesicles (EVs) and evaluate their effect on equine chondrocytes treated with pro-inflammatory cytokines in vitro. Study design: In vitro experiments with randomised complete block design.Methods: Mesenchymal stem cells from bone marrow, adipose tissue, and synovial fluid were cultured in vitro. The MSC culture medium was centrifuged and filtered. Isolated particles were analysed for size and concentration (total number of particles per mL). Transmission electron microscopy analysis was performed to evaluate the morphology and CD9 expression of the particles. Chondrocytes from healthy equines were treated with the inflammatory cytokines interleukin (IL)-1β and tumour necrosis factor-alpha. MSC-derived EVs from bone marrow and synovial fluid cells were added as co-treatments in vitro. Gene expression analysis by real-time PCR was performed to evaluate the effects of EVs. Results: The particles isolated from MSCs derived from different tissues did not differ significantly in size and concentration. The particles had a round-like shape and positively expressed CD9. EVs from bone marrow cells displayed reduced expression of metalloproteinase-13. Main limitations: Sample size and characterisation of the content of EVs Conclusions: EVs isolated from equine bone marrow MSCs reduced metalloproteinase 13 gene expression; this gene encodes an enzyme related to cartilage degradation in inflamed chondrocytes in vitro. EVs derived from MSCs can reduce inflammation and could potentially be used as an adjuvant treatment to improve tissue and cartilage repair in the articular pathologies.