Synovial and Adipose Tissue Composition in Overweight/Obese Patients With Active Rheumatoid Arthritis Under JAK/STAT Inhibition

Rheumatoid Arthritis (RA) is a chronic autoimmune disease that affects nearly 1% of the general population worldwide leading to joint inflammation, disability and increate mortality. Several factors are associated with disease activity and treatment outcomes. Among them, overweight/obesity status was demonstrated to be associated with higher risk of RA development and most importantly to different treatment response to biological DMARDs. Moreover, overweight/obese RA patients do show higher degree of synovial inflammation compared to lean RA patients. In this context, adipose tissue accumulation is associated with higher inflammatory burden through the secretion by activated mature adipocytes of adipokines with pro-inflammatory properties on innate and adaptive immune cells. Among them, Leptin is an important adipokine, released by mature adipocytes with multiple activating properties on immune cells as monocytes, macrophages, dendritic cells, T and B lymphocytes acting through the activation of its receptor LEPR via JAK/STAT pathway. In particular, leptin exerts its effects on macrophages populations through the promotion of M1 differentiation with pro-inflammatory phenotype. In our research hypothesis we expect that leptin levels does correlate with immunohistochemical scores of synovial inflammatory cells (CD68+, CD21+, CD20+ and CD3+) and CD31+ synovial vessels. Moreover, we expect that the inhibition of JAK/STAT signal using Tofacitinib may interfere with leptin activation action on resident synovial inflammatory cells expressing LEPR (as CD68+, CD20+ and CD3+) in particular restoring the M1/M2 phenotype ratio within resident macrophages populations. Finally, we expect that the inhibition of JAK/STAT signaling pathway by Tofacitinib will result in a significant reduction of synovitis degree in patients with higher leptin expression due to adipose tissue activation.