BackgroundNovel biological therapies have revolutionised the management of Rheumatoid Arthritis (RA) but no cure currently exists. Mesenchymal stem cells (MSCs) immunomodulate inflammatory responses through paracrine signalling via growth factors, cytokines, chemokines and extracellular vesicles (EVs) in the cell secretome; however, MSCs are still not available in the clinic. We evaluated the therapeutic potential of MSCs-derived EVs in an antigen-induced model of arthritis (AIA). MethodsEVs

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... lated from MSCs in normal (21% O2, 5% CO2) or hypoxic (2% O2, 5% CO2) culture or from MSCs pre-conditioned with a pro-inflammatory cytokine cocktail were applied into the AIA model. Disease pathology was assessed 3 days post arthritis induction through histopathological analysis of knee joints. Spleens and lymph nodes were collected and assessed for T cell polarisation within the immune response to AIA. Activated naïve CD4+ T cells from spleens of healthy mice were cultured with EVs or MSCs to assess deactivation capabilities. ResultsAll EV treatments significantly reduced knee-joint swelling and histopathological signs of AIA with enhanced responses to normoxic and pro-inflammatory primed EVs. Polarisation of T cells towards CD4+ helper cells expressing IL17a (Th17) was reduced when EV treatments from MSCs cultured in hypoxia or pro-inflammatory priming conditions were applied. ConclusionsHypoxically cultured EVs present a priming methodology that is as effective in reducing swelling, IL-17a expression, Th17 polarisation and T cell proliferation as pro-inflammatory priming. EVs present an effective novel technology for cell-free therapeutic translation in treating inflammatory arthritis and autoimmune disorders such as RA.