POS0042 NOTCH 1 INHIBITION INCREASES OSTEOCLAST PROGENITOR ACTIVITY IN THE MOUSE MODEL OF RHEUMATOID ARTHRITIS

Background: Osteoclasts mediate periarticular and systemic bone loss in rheumatoid arthritis (RA). Osteoclast progenitor cells (OCPs) derived from the myeloid lineage are susceptible to regulation through Notch signaling. Murine marrow splenic OCPs, identified as CD45 + Ly6G - CD3 B220 NK1.1 CD11b lo/+ CD115 CCR2 cells, specifically increased arthritis. We previously an frequency of OCPs expressing receptors arthritic mice. Objectives: Several studies suggested that signaling modulation affects course experimental aimed determine effects receptor inhibition on OCP activity severity murine collagen-induced (CIA). Methods: Male C57/Bl6 DBA mice were immunized with chicken type II collagen treated i.p. injections anti-Notch 1 neutralizing antibodies (1mg/kg). 4 expression was analyzed by flow cytometry (PBM) spleen (SPL). Gene receptors, ligands transcription targets well osteoclast differentiation genes RANK, cFos cFms determined qPCR tissues sorted OCPs. FACS stimulated osteoclastogenic factors (M-CSF RANKL), control, IgG, Jagged (Jag)1 or Delta-like (DLL)1 coated wells, without antibodies. Research approved Ethics Committee. Results: confirmed 2 being most abundantly expressed (around 25% 40% positive PBM 35% 20% SPL respectively), a significant increase Seeding DLL1 wells significantly while seeding Jag1 decreased osteoclastogenesis reflected number TRAP+ osteoclasts genes. The addition ligand-stimulated resulted osteoclasts, partially reversing inhibition. In vivo treatment did not affect total frequency, but both seen qPCR. Additionally, HES HEY. Both cultured produced higher large doubling area covered latter compared untreated Increased vitro further group. Conclusion: Our results confirm may represent important therapeutic target for enhanced CIA model, implying inhibitory role differentiation. As is mice, we next plan neutralization severity. References: [1]Ikić Matijašević M, Flegar D, Kovačić N, Katavić V, Kelava T, Šućur A, et al. chemotaxis circulatory contribute C57BL/6 mouse model Clin Exp Immunol. 2016;186(3):321–35. [2]Šućur Filipović Šisl Lukač inflammatory – systematic review. Immunology Letters 2020 Vol. 223, p. 106–14. Acknowledgements: work has been supported Croatian Science Foundation projects IP-2018-01-2414, UIP-2017-05-1965 DOK-2018-09-4276. Disclosure Interests: None declared.