118 SYSTEMIC INFLAMMATION AND ANTIBODIES TO CITRULLINATED PEPTIDES IN HAND OSTEOARTHRITIS

Abstract

ABSTRACTObjective. To investigate systemic in-flammation and autoimmune response to citrullinated peptides in patients with erosive and non erosive “lone” hand osteoarthritis (HOA) with no hip/knee involvement and their relationship with radiographic structural damage. Methods. Sera were obtained from a total of 99 patients with HOA (52 pa-tients with erosive HOA and 47 pa-tients with non-erosive HOA) and from 50 control subjects (NC). Hand radio-graphs were obtained from all patients and scored for joint damage according to the Kellgren-Lawrence and the Kall-man scores. Serum levels of high-sen-sitivity CRP (hsCRP), IL-6, pentraxin-3 (PTX-3), anti-CCP and anti-modified citrullinated vimentin (MCV) antibodies were evaluated by a sandwich ELISA.Results. Circulating levels of inflam-matory biomarkers hsCRP, IL-6 and PTX3 were not significantly different in the two groups of patients with erosive and non-erosive HOA compared to NC and no significant difference was seen between non-erosive and erosive HOA.Anti-CCP positivity was detected re-spectively in 1 patient (2.1%) with non-erosive HOA and 1 patient (1.9%) with erosive HOA. Anti-MCV antibod-ies were present in 4 patients (8.5%) with non-erosive HOA, and 4 patients (7.7%) with erosive HOA. In the con-trol group, one subject (2%) was posi-tive for anti-CCP and 2 subjects (4%) had anti-MCV antibodies.Significant correlation was obtained only between body mass index and hsCRP concentration (r=0.4071; p<0.0001). No correlation between inflammation markers/autoantibodies and disease duration and radiological scores was found. Conclusions. Our study underlines the lack of systemic inflammation and autoimmunity in “lone” HOA and con-firms the association between BMI and CRP levels.IntroductionLocal inflammation is increasingly rec-ognised as a contributing factor to the symptoms and progression of osteoar-thritis (OA) (1). Several studies have shown that the acute-phase response may take place in OA; indeed CRP may be slightly elevated in OA patients (1). Levels of high-sensitivity-C reac-tive protein have been reported to be associated with local inflammation in hip and knee OA patients (2) and high circulating levels of IL-6 are associated with the development of radiographic knee OA (3).Inflammatory mediators, such as TNF-α and IL-1, have been shown to induce CRP (albeit to a lesser extent com-pared to IL-6), an acute-phase protein belonging to the pentraxin family, as well as pentraxin-3 (PTX3). Evidence suggests that PTX3 is a useful new serological marker, rapidly reflecting tissue inflammation and damage under different clinical conditions (4). OA synoviocytes produce PTX3 (5), but no data on PTX3 systemic expression in OA patients are yet available.Inflammatory changes in joint tissue are triggered by innate and adaptive immu-nological mechanisms (1). Even though much remains to know about the trigger antigens in OA, autoantigens have been suggested as putative candidates. In inflamed rheumatoid joints, autoim-mune reactions lead to the production of antibodies against citrullinated pro-teins; recently antibodies against these proteins have also been found in the sera of other arthritides such as OA(6).In rheumatoid arthritis (RA), anti-CCP positivity showed the strongest asso-ciation with erosive arthritis (7) and the combined detection of antibodies against mutated citrullinated vimentin (anti-MCV), another type of citrullinat-ed protein, might improve the diagnos-tic and prognostic value of these tests in clinical practice (7). A subset of HOA is characterised by an inflammatory and erosive pattern, more severe symptoms, perimenopausal on-set and destructive changes involving the proximal and distal interphalangeal joints (8, 9). Therefore, erosive HOA is unique, sharing features typical of OA and inflammatory arthritis.Most studies addressing circulating bio-markers of inflammatory and autoim-mune response have focused on knee and hip OA, whereas data on HOA are scarce and the applicability of most results ob-tained in knee and hip OA is unknown.