P090 Pro-inflammatory cytokines and cell interactions between PBMC and synoviocytes induce retraction and formation of pseudopodia

Career situation of first and presenting author Student for a master or a PhD. Introduction Rheumatoid synovitis is infiltrated by immune cells, which interact with synoviocytes inducing abnormal proliferation and massive production of pro-inflammatory cytokines. Objectives The aim was to evaluate the effect of inflammatory environment and cell interactions on morphological parameters of synoviocytes alone or in co-culture with peripheral blood mononuclear cells (PBMC). Methods Synoviocytes from different donors: healthy (HE) or rheumatoid arthritis (RA) were exposed or not to inflammatory conditions (IL-17 alone, TNF alone and their combination) during 48 hours and observed with different microscopes (optical, digital holographic and holographic-tomographic). Quantification of morphological parameters included cell confluence, area, motility speed and number of pseudopodia/cell. Co-cultures between normal PBMC and synoviocytes with or without phytohemagglutinin (PHA) or cytokines (IL-17/TNF) were used to mimic the in vivo situation. Results Inflammatory cytokines induced a change in synoviocyte morphology, inducing a retracted cell with a higher number of pseudopodia. Several parameters decreased in inflammatory conditions: cell confluence (Ctrl:31.7%±2.5%, IL-17:21.8%±2.0%, TNF:19.2%±1.5%, IL-17/TNF:19.8%±1.6%, p Conclusions The inflammatory environment or cell interactions induced massive changes in synoviocytes, with cell retraction and increase of pseudopodia number, leading to better interactions with other cells. Except in the case of RA, the inflammatory environment was absolutely required for such changes. Disclosure of Interest None declared.