Different Secretory Activity of Articular and Subcutaneous Adipose Tissues from Rheumatoid Arthritis and Osteoarthritis Patients

Rheumatoid arthritis (RA) and osteoarthritis (OA) are characterized by joint and systemic high- or low-grade inflammation, respectively. Adipose tissue (AT) may contribute to the pathogenesis of these diseases. To address this issue, we investigated whether basal and pro-inflammatory cytokine (IL-1β)-triggered release of adipocytokines (TNF, IL-6, IL-10, IL-1Ra, TGFβ, CCL2/MCP-1, CCL5/RANTES, MMP-3) from subcutaneous (ScAT) and intraarticular (AAT) adipose tissues of RA and OA patients mirror differences between these diseases in an intensity of systemic and local inflammation. We found that in both diseases basal adipocytokine release was usually higher from AAT than ScAT, reflecting stronger local than systemic inflammation. However, ScAT secreted considerable amounts of pro- and anti-inflammatory factors as well. Spontaneous secretion of some adipocytokines (MMP-3 and/or TNF, CCL2/MCP-1, IL-1Ra) was higher in osteoarthritis than rheumatoid ATs and probably caused by weaker anti-inflammatory treatment of OA patients. By contrast, reactivity of ATs to IL-1β was significantly lower in OA than RA and IL-1β antagonist (IL-1Ra) could be responsible for this because we found its overproduction in OA ATs. Interestingly, higher reactivity of ScAT than AAT to IL-1β was a characteristic for OA while reactivity of rheumatoid ScAT and AAT to this stimulus was equal. We conclude that differences between OA and RA in reactivity of AAT and ScAT to pro-inflammatory stimulus mimicking in vivo condition reflect dissimilarity in an intensity of disease-specific inflammation and thus support contribution of ATs to these pathological processes. Moreover, we propose that more efficient anti-inflammatory mechanism(s) are preserved in ATs of OA than RA patients.