Objective To investigate the role and mechanism of developmental endothelial locus-1 (Del-1) in collagen-induced arthritis (CIA).

Methods CIA mouse model was constructed, and the mice were divided into control group, CIA group, and Del-1 group (Del-1 for intervention of CIA). In the Del-1 group, each mouse was injected with Del-1 for 2 μg each time through caudal vein for 2 times in total. Arthritis index (AI) was used to assess the progression of arthritis; hematoxylin-eosin (HE) staining was used to observe the arthritic lesions in mice; enzyme-linked immunosorbent assay (ELISA) was used to detect the expression of serum interleukin-6 (IL-6) and matrix metalloproteinases-9 (MMP-9) in mice.

Results On the 34th, 36th, 38th and 40th days after the primary immunization, the AI scores in the Del-1 group were (3.80±1.17), (3.80±1.17), (4.20±1.17) and (4.20±1.17) respectively, which were significantly lower than (6.80±1.94), (8.80±3.19), (9.60±3.61) and (9.40±3.61) in the CIA group (P < 0.05). On the 42nd day after the primary immunization, when compared to the CIA group, the HE staining showed that the local inflammatory infiltration and synovial hyperplasia of the joints in the Del-1 group were obviously alleviated, and the cartilage destruction was obviously reduced. On the 42nd day after the initial immunization, ELISA result showed that the expression levels of serum IL-6 and MMP-9 in the CIA group were significantly higher than that in the normal control group (P < 0.05), while those in the Del-1 group were significantly lower than the CIA group (P < 0.05).

Conclusion Del-1 can improve the joint symptoms of CIA mouse model, reduce inflammation and bone destruction, inhibit the expression of key cytokines such as IL-6 and MMP-9, and these actions may play certain roles in the treatment of RA.