Background Ideally a disease modifying osteoarthritis drug (DMOAD) combines treatment for pain, tissue damage and inflammation, all in one molecule. Intra-articular application of a DMOAD brings additional value to treatment for two reasons, (i) lower risk of systemic side effects and (ii) higher drug concentration and potentially improved penetration of non-vascularized articular cartilage. Interleukin-4 (IL-4) and Interleukin-10 (IL-10) have been shown to prevent joint degeneration and can work synergistically1.
Objectives This study evaluates the DMOAD activity of repetitive intra-articular injections with a human fusion protein of IL-4 and IL-10 (hIL4–10FP) in the canine Groove model of osteoarthritis (OA).
Methods In 8 dogs joint degeneration was induced according to the Groove model. Six weeks after surgery dogs were treated with ten weekly intra-articular injections of either hIL4–10FP (n=4) or PBS (n=4). Subsequently, dogs were euthanized and cartilage and synovium were harvested. Cartilage damage and synovial inflammation were macroscopically evaluated. Proteoglycan release and content were determined ex vivo by staining of glycosaminoglycans (GAGs) with Alcian Blue. Proteoglycan synthesis was measured by 35SO42– incorporation and precipitation with cetylpyridium chloride and liquid scintillation analysis of 35SO42–-labeled GAGs. Potential antibody formation against hIL4–10FP was evaluated with ELISA and a cell based assay. Immunohistochemistry of CD79α and CD10 was used to evaluate the presence of B-cells in synovium.
Results Affected knees of PBS treated dogs showed enhanced macroscopic cartilage damage compared to their controls (0.31 vs 2.44, p=0.068). Also differences in proteoglycan release, content and synthesis indicated a degenerative state in the affected knees.
Unexpectedly, enhanced synovial inflammation was observed in hIL4–10FP treated joints compared to PBS treated joints, demonstrated by enhanced macroscopic (3.5 vs 2.3 out of 5) and histologic (2.5 vs 1.8 out of 6) scores. CD79α and CD10 showed enhanced expression in synovium of the hIL4–10FP group compared to the PBS group, although not statistically significant (fig 1). Additional analyzes showed that hIL4–10FP was immunogenic in dogs after multiple injections. Formation of neutralizing antibodies was shown in a cell based assay where the activity of hIL4–10FP was inhibited in the presence of serum of hIL4–10FP treated dogs (fig 2). Despite the enhanced inflammatory response in hIL4–10FP group there was no enhanced cartilage degeneration detected compared to the PBS group (fig 3).
Conclusions Repetitive intra-articular injection of human IL4–10FP led to antibody formation in a non-inflammatory canine model of OA. Despite the immune response, proteoglycan turnover parameters were comparable between the two treatment groups, suggesting a beneficial effect of hIL4–10FP. This study also shows that it is not evident to use a human protein in a (canine) animal model, although this is often done. Instead, a species specific protein is warranted. Therefore a canine version of IL4–10FP will be developed to study its DMOAD activity in this model.
van Roon JA, Lafeber FP, Bijlsma JW. Synergistic activity of interleukin-4 and interleukin-10 in suppression of inflammation and joint destruction in rheumatoid arthritis. Arthritis and rheumatism. 2001;44(1):3–12.
Disclosure of Interest None declared