This study aims to explore the potential role of circulating Dickkopf-1 (Dkk-1) and osteoprotegerin (OPG) in evaluating erosive arthritis in systemic lupus erythematosus (SLE).
Serum Dkk-1 and OPG levels were examined in 130 SLE patients including eight with erosive arthritis, 100 rheumatoid arthritis (RA) patients and 50 healthy individuals by ELISA. Comparison of serum Dkk-1 levels with presence of anti-cyclic citrullinated peptides (CCP) antibodies in evaluating erosive arthritis in SLE was carried out. Associations of Dkk-1 and OPG levels with results of clinical examination were also noted.
Dkk-1 levels were significantly increased in eight SLE patients with erosive arthritis, compared to 58 SLE patients with non-erosive arthritis, 64 SLE patients without arthritis, and healthy controls, while similar with RA. In contrast, no significant changes of OPG levels were found except for higher levels in RA. No differences were found in Dkk-1 levels of SLE patients with erosive arthritis subdivided according to presence or absence of anti-CCP antibodies. Moreover, higher levels of Dkk-1 were identified in anti-CCP positive SLE patients with erosive arthritis compared to those with non-erosive arthritis or without arthritis. However, no significant correlations between Dkk-1 and OPG levels or between Dkk-1 levels and other laboratory and clinical manifestations were observed.
High levels of circulating Dkk-1 were associated with bone erosion in patients with SLE, even when anti-CCP antibodies were absent.