Compartment-Resolved Immunofluorescence Analysis of NF-κB p65, IL-1β, MMP-3, and CD68 in the Synovium of Patients with Hip Osteoarthritis

Hip osteoarthritis (HOA) has shown the largest relative increase in prevalent cases of any osteoarthritis site, yet compartment-resolved data on the NF-κB-driven inflammatory–catabolic axis of synovitis derive mainly from the knee. We quantified nuclear factor-κB p65 (NF-κB p65), interleukin-1β (IL-1β), matrix metalloproteinase-3 (MMP-3), and the macrophage marker cluster of differentiation 68 (CD68) in the synovial intima and subintima of 19 patients undergoing hip arthroplasty for HOA and 10 controls (CTRL) without histological synovitis who underwent arthroplasty for femoral neck fracture. Immunofluorescence was quantified after blinded three-observer compartment delineation, and groups were compared by two-way analysis of variance with Tukey’s test. All four markers were increased in the HOA intima (2.6- to 3.6-fold vs. CTRL; p < 0.0001) and were higher in the intima than in the subintima of HOA synovium (p < 0.0001). In the subintima, NF-κB p65 (p < 0.0001), MMP-3 (p < 0.01), and CD68 (p < 0.05) were also increased, whereas IL-1β was not significantly increased (1.12-fold). These hypothesis-generating data show that NF-κB p65, IL-1β, MMP-3, and CD68 immunoreactivity is concentrated in the intimal lining of HOA synovium; the IL-1β increase was detected only in the intima, a distinction that bulk analysis cannot resolve.