Background:Age is the most important risk factor in degenerative osteoarthritis (OA) and is associated with the accumulation of senescent cells that contribute to functional decline of joint. We previously demonstrated that extracellular vesicles (EVs) from mesenchymal stromal cells (MSCs) largely mediate the therapeutic effect of parental cells in OA.Objectives:Here, we assessed the impact of senescence on the characteristics of EVs from adipose tissue-derived MSCs (ASC-EVs) and their properties in an in vitro model of OAMethods:ASCs were induced to senescence using 25µM etoposide for 24 hours. Senescence was assessed by quantifying proliferation rate, SA-βGal activity, nuclear γH2AX foci number, phalloidin staining and expression of cyclin dependent kinase inhibitors (CDKI) (RT-qPCR). ASC-EVs were isolated by differential ultracentrifugation and characterized by size, concentration, total protein content, structure (cryo-TEM) and immunophenotype. In vitro OA model used chondrocytes isolated from OA patients, which were stimulated with IL1β for 48h before culture with ASCs or ASC-EVs for 7 days. Expression of chondrocytic and inflammatory markers was quantified by RT-qPCR and SASP factors were quantified by ELISA in supernatants.Results:Senescence-induced ASCs experienced growth arrest and increase of SA-βGal staining, of p21 CDKI expression, of nuclear γH2AX foci, of stress fibers and of several SASP factors (IL6, IL8, MMP3) confirming the expression of main senescence features. Senescent ASCs produced 4-fold more EVs than healthy ASCs and senescent ASC-EVs were larger. In vitro, both healthy and senescent ASCs decreased fibrotic markers (type III COLLAGEN), catabolic and hypertrophic markers (MMP3, MMP13, AP) and increased COX2 expression in OA chondrocytes. By contrast, healthy ASCs decreased the expression of IL6 while senescent ASCs highly increased IL6. Looking at the role of ASC-EVs on OA chondrocytes, we found out that both healthy and senescent ASC-EVs were able to increase the expression of AGG and type II COLLAGEN while they decreased the expression of MMP13, AP, type X COLLAGEN, HMOX1 and IL6. Finally, healthy and senescent ASC-EVs decreased the number of SA-βGal positive chondrocytes but did not impact the expression of p21 in IL1β-induced chondrocytes.Conclusion:Our results indicated a chondroprotective effect of ASC-EVs, independently of the senescent state of parental cells and suggested that EVs might act through different mechanisms than ASCs, which warrants further investigationDisclosure of Interests:Jérémy Boulestreau: None declared, Marie Maumus Employee of: Bauerfeind France, Pauline Rozier: None declared, Christian Jorgensen Shareholder of: Medxcell sciences, Consultant of: Medxcell sciences, Daniele Noel Shareholder of: Medxcell sciences, Consultant of: Medxcell sciences