Identification of Disease-stage Therapeutic Responses of Mesenchymal Stromal Cells Retrieved from Murine Osteoarthritic Joints

Ana Ivanovska ¹ Patrizio Mancuso ¹ Amy Burke ¹ Conor Hennesy ¹ Swarna Raman ¹ Claire Dooley ¹ Steven Mcloughlin ¹ Georgina Shaw ¹ Eka Mukeria ¹ Jamie Reilly ¹ Aisling O'brien ¹ Thomas Ritter ¹ Aideen Edele Ryan ¹ Raj Kamath ² Marc C Levesque ² Deborah Van Riet ² Karen English ³ Ian Hawthorne ³ Brian Johnstone ⁴ Derek W Morris ¹ Frank Barry ¹ J Mary Murphy ^1*

• ¹ University of Galway, Galway, County Galway, Ireland
• ² Abbvie Bioresearch Center, Worcester, United States
• ³ Maynooth University, Maynooth, County Kildare, Ireland
• ⁴ Oregon Health and Science University, Portland, Oregon, United States

Objective: Osteoarthritis (OA) is a widespread and debilitating joint disease characterized by synovial inflammation, cartilage degeneration and chronic joint pain. Mesenchymal stromal cells (MSCs) have shown therapeutic efficacy for many diseases with a strong inflammatory profile including OA, but disease-specific mechanisms of action underpinning effects post-local MSC delivery remain unaddressed. Here, we sought to characterize the disease-induced profile of MSCs following exposure to the in vivo osteoarthritis environment.Methods: Murine syngeneic GFP+ bone marrow-derived-MSCs (BM-MSCs) were delivered via intraarticular injection in a mouse collagenase-induced osteoarthritis (CIOA) model (n=8). BM-MSCs were retrieved by cell sorting at day 14 and day 56 following whole mouse knee digestions. The retrieved cells were expanded in culture and characterised based on their phenotype, immunomodulatory effect on lymphocytes and macrophages, and transcriptomic profile.Results: Retrieved BM-MSCs (1.33%) had minimal effects on lymphocyte proliferation but induced macrophage anti-inflammatory activity. Surviving retrieved BM-MSCs activated various pathways with their secretome impacting immune system regulation and extracellular matrix organization correlating to disease stage. Data comparing the transcriptomic profiles of retrieved and in vitro licensed BM-MSCs suggested a chondroprogenitor profile and identified BRINP3 as a novel factor in MSC function for potential OA modulation.Beneficial effects of BM-MSCs in OA post-local delivery could be attributed to a specific subset of cells able to resist the micro-inflammatory milieu and contribute to cartilage healing and suppression of associated synovial inflammation. Furthermore, data suggests a paradigm of environmentally-guided plasticity associated with MSC upon local delivery in early and late OA.