In vivo reduction or blockade of interleukin-1β in primary osteoarthritis influences expression of mediators implicated in pathogenesis.

OBJECTIVE: Diminish interleukin-1β (IL-1β) signaling in a model of primary osteoarthritis by RNA interference-based transcript reduction or receptor blockade, and quantify changes incurred on transcript expression of additional mediators. METHODS: Knees of Hartley guinea pigs were collected at 120 and 180 days of age following injection with viral vectors (N = 4/treatment group/date) at 60 days. Two groups received either adeno-associated viral serotype 5 vector containing a knockdown sequence (TV), or adenoviral vector encoding for IL-1 receptor antagonist protein (Ad-IRAP); treatments were contrasted with opposite knees administered corresponding vector controls. A third group evaluated TV relative to saline-only injected knees. Chondropathy and immunohistochemistry findings were compared to untreated guinea pigs. Transcript expression levels in cartilage were calculated using the comparative CT (2(-ΔΔCT)) method and analyzed by one-way analysis of variance (ANOVA) with pairwise comparisons using Tukey 95% confidence intervals. RESULTS: Vector transduction was confirmed at both harvest dates. TV and Ad-IRAP, relative to vector controls, significantly decreased IL-1β. Inflammatory mediators [tumor necrosis factor-α (TNF-α), IL-8, interferon-γ (IFN-γ)], and catabolic matrix metalloproteinase 13 (MMP13) were also decreased, while anabolic transforming growth factor-β1 (TGF-β1) was increased. IL-1β was also decreased by TV vs saline, with a decrease in MMP13 and increase TGF-β1; TNF-α, IL-8, and IFN-γ were transiently increased. CONCLUSIONS: This work confirmed that a reduction in IL-1β signaling was accomplished by either method, resulting in decreased expression of three inflammatory mediators and one catabolic agent, and increased expression of an anabolic molecule. Thus, evidence is provided that IL-1β serves a role in vivo in spontaneous osteoarthritis and that these translational tools may provide beneficial disease modification.