Differences in Bone Cell Activity Between Rheumatoid Arthritis and Ankylosing Spondylitis

Rheumatoid arthritis (RA) and ankylosing spondylitis (AS) are characterized by chronic systemic inflammation and share common pathogenic pathways. In both diseases, cytokines like TNF and IL-17, known for their pro-inflammatory and osteoclastogenic effects, are relevant players, however, while RA is characterized by bone erosions, AS favors bone overgrowth. Understanding this paradox may hold the key for a better management of both diseases. Our hypothesis is that there are differences in the cellular environment and intracellular signaling between AS and RA. To test this hypothesis we will evaluate the cytokine milieu, the kinetics of bone cells differentiation and their activity in untreated and immunossuppressed RA and AS patients. We will also perform the same observations in patients exposed to targeted treatments.