TYPE Original Research PUBLISHED 24 November 2022 DOI 10.3389/fvets.2022.1057667 OPEN ACCESS EDITED BY Scott J. Roberts, Royal Veterinary College (RVC), United Kingdom REVIEWED BY Jayesh Dudhia, Royal Veterinary College (RVC), United Kingdom Luca Melotti, University of Padua, Italy *CORRESPONDENCE Emily J. Clarke eclarke@liverpool.ac.uk SPECIALTY SECTION This article was submitted to Veterinary Regenerative Medicine, a section of the journal Frontiers in Veterinary Science RECEIVED 29 September 2022 ACCEPTED 10 November 2022 PUBLISHED 24 November 2022 CITATION Clarke EJ, Johnson E, Caamaño Gutierrez E, Andersen C, Berg LC, Jenkins RE, Lindegaard C, Uvebrant K, Lundgren-Åkerlund E, Turlo A, James V, Jacobsen S and Peffers MJ (2022) Temporal extracellular vesicle protein changes following intraarticular treatment with integrin α10β1-selected mesenchymal stem cells in equine osteoarthritis. Front. Vet. Sci. 9:1057667. doi: 10.3389/fvets.2022.1057667 COPYRIGHT © 2022 Clarke, Johnson, Caamaño Gutierrez, Andersen, Berg, Jenkins, Lindegaard, Uvebrant, Lundgren-Åkerlund, Turlo, James, Jacobsen and Peffers. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Temporal extracellular vesicle protein changes following intraarticular treatment with integrin α10β1-selected mesenchymal stem cells in equine osteoarthritis Emily J. Clarke 1 *, Emily Johnson 2 , Eva Caamaño Gutierrez 2 , Camilla Andersen 3 , Lise C. Berg 3 , Rosalind E. Jenkins 4 , Casper Lindegaard 3 , Kristina Uvebrant 5 , Evy Lundgren-Åkerlund 5 , Agnieszka Turlo 1 , Victoria James 6 , Stine Jacobsen 3 and Mandy J. Peffers 1 1 Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, United Kingdom, 2 Computational Biology Facility, Liverpool Shared Research Facilities, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, United Kingdom, 3 Department of Veterinary Clinical Sciences, University of Copenhagen, Copenhagen, Denmark, 4 Department of Pharmacology and Therapeutics, Institute of Systems, Molecular and Integrative Biology, Centre for Drug Safety Science Bioanalytical Facility, Liverpool Shared Research Facilities, University of Liverpool, Liverpool, United Kingdom, 5 Xintela AB, Lund, Sweden, 6 School of Veterinary Medicine and Science, University of Nottingham, Nottingham, United Kingdom Introduction: Equine osteoarthritis (OA) is a heterogeneous, degenerative disease of the musculoskeletal system with multifactorial causation, characterized by a joint metabolic imbalance. Extracellular vesicles are nanoparticles involved in intracellular communication. Mesenchymal stem cell (MSC) therapy is a form of regenerative medicine that utilizes their properties to repair damaged tissues. Despite its wide use in veterinary practice, the exact mechanism of action of MSCs is not fully understood. The aim of this study was to determine the synovial fluid extracellular vesicle protein cargo following integrin α10β1-selected mesenchymal stem cell (integrin α10-MSC) treatment in an experimental model of equine osteoarthritis with longitudinal sampling. Methods: Adipose tissue derived, integrin α10-MSCs were injected intraarticularly in six horses 18 days after experimental induction of OA. Synovial fluid samples were collected at day 0, 18, 21, 28, 35, and 70. Synovial fluid was processed and extracellular vesicles were isolated and characterized. Extracellular vesicle cargo was then analyzed using data independent acquisition mass spectrometry proteomics. Results: A total of 442 proteins were identified across all samples, with 48 proteins differentially expressed (FDR ≤ 0.05) between sham-operated control joint without MSC treatment and OA joint treated with MSCs. The most significant pathways following functional enrichment analysis of the differentially abundant protein dataset were serine endopeptidase activity (p = 0.023), complement activation (classical pathway) (p = 0.023), and collagen containing extracellular matrix (p = 0.034). Due to the lack of an OA group without MSC treatment, findings cannot be directly correlated to only MSCs. Frontiers in Veterinary Science 01 frontiersin.org