, to target cells. Neutrophil EVs are remarkable in their antiinflammatory properties and were found to be abundant within the joints of RA patients. In addition, depletion of neutrophils within the joints of mice undergoing experimental arthritis, resulted in a reduced proteoglycan synthesis. We therefore investigated the role of Neutrophil EVs in RA and their effect on cartilage breakdown. Methods: Neutrophils were isolated from healthy volunteers and RA patient blood. EVs were isolated from these cells and tested in the K/ BxN serum transfer model of inflammatory arthritis in mice. EVs were administered intra-articularly, and joints were assessed for inflammatory outcomes and cartilage breakdown. Results: EVs were able to successfully enter the cartilage and deliver their cargo to the chondrocytes within. In murine inflammatory arthritis, neutrophil EVs displayed cartilage protective effects, resulting in a reduced loss of sulphated glycosaminoglycans in the treated joints compared to control paired joints. In vitro, neutrophil EVs were able to protect from IL-1 induced cartilage breakdown in 3D chondrocyte cultures and restored basal expression of cartilage specific genes, Sox9 and Collagen2a1. This protective effect occurred in part through the EV mediator Annexin A1 and its receptor Fpr2/3 on the chondrocyte. In addition, neutrophil EVs modulated the macrophage profile, polarizing the cells towards a more anti-inflammatory phenotype, characterized by a lower expression of MHCII and CD86 and higher levels of CD206 compared to contralateral controls. This was true for both healthy and RA derived vesicles. In vitro, co-culture of fibroblast like synoviocytes with classically activated macrophages resulted in upregulation of inflammatory markers in the fibroblasts, whereas pre-treatment of the macrophages with neutrophil EVs attenuated this effect. Conclusions: Neutrophil EVs exert powerful protective bioactions in inflammatory arthritis, displaying not only a modulation of the ongoing joint inflammation but also affording protection from cartilage breakdown. We propose these EVs provide a unique opportunity to target both the inflammatory component of RA and the resulting osteoarthritis with a single therapy.