Abstract
BackgroundPsoriatic arthritis (PsA) and axial spondyloarthritis (axSpA) are chronic inflammatory rheumatic diseases with complex origins. Both are characterized by altered extracellular matrix remodeling in joints and entheses that results in destructive and osteochondral proliferative lesions. There is a need for biomarkers reflecting core disease pathways for diagnosis and disease mapping. Pro-C2 reflects mature cartilage collagen type IIB formation, while C-Col10 represents turnover of type X collagen, which is exclusively expressed by hypertrophic chondrocytes. The objectives of this study were to study cartilage metabolism in axSpA and PsA by assessing Pro-C2 and C-Col10 and to evaluate their diagnostic utility against a healthy reference population.MethodsPatients with PsA (n = 101) or axSpA (n = 110) were recruited consecutively from three rheumatology outpatient clinics. Demographic and clinical disease measures were recorded. Pro-C2 and C-Col10 were quantified in serum by using newly developed and specific competitive enzyme-linked immunosorbent assays based on monoclonal antibodies. One-way analysis of variance and Tukey’s multiple comparison tests were performed on log-transformed data. ROC curve analysis was carried out to evaluate their discriminative power.ResultsPro-C2 levels in serum were significantly increased in both axSpA (median concentration 1.11 ng/ml, 0.67–1.64) and PsA (median concentration 1.03 ng/ml, 0.53–1.47) compared with healthy controls (median concentration 0.30 ng/ml, 0.16–0.41) (p < 0.0001). Pro-C2 did not differ according to treatment. C-Col10 was slightly but equally elevated in the PsA and axSpA groups vs. the control group, but it was significantly lower in patients with axSpA undergoing tumor necrosis factor-α inhibitor (TNFi) treatment. ROC curve analysis revealed AUCs of 0.85 (95 % CI 0.79–0.89) for axSpA and 0.81 (95 % CI 0.75–0.86) for PsA.ConclusionsThese findings indicate that cartilage collagen metabolism was enhanced in the axSpA and PsA groups compared with the healthy control group. The lower C-Col10 level in patients with axSpA undergoing TNFi treatment may reflect that hypertrophic chondrocytes in axSpA are targeted by TNFi. ROC curve analysis showed a diagnostic potential for Pro-C2 in axSpA and PsA.
Highlights
Psoriatic arthritis (PsA) and axial spondyloarthritis are chronic inflammatory rheumatic diseases with complex origins
110 patients with axial spondyloarthritis (axSpA) classified according to the Assessment of SpondyloArthritis international Society (ASAS) criteria [21, 22] and 101 patients with PsA fulfilling the Classification of Psoriatic Arthritis (CASPAR) criteria [23] were enrolled in the study
Cartilage turnover is increased in axSpA and PsA Pro-C2 was significantly increased in the axSpA and PsA groups compared with the healthy control group (Fig. 1a)
Summary
Psoriatic arthritis (PsA) and axial spondyloarthritis (axSpA) are chronic inflammatory rheumatic diseases with complex origins. Both are characterized by altered extracellular matrix remodeling in joints and entheses that results in destructive and osteochondral proliferative lesions. The objectives of this study were to study cartilage metabolism in axSpA and PsA by assessing Pro-C2 and C-Col and to evaluate their diagnostic utility against a healthy reference population. In psoriatic arthritis (PsA), early diagnosis has been shown to significantly decrease morbidity and increase quality of life [9]. The utility of several cartilage and bone biochemical markers has been assessed, in osteoarthritis and rheumatoid arthritis, and less intensively, in axial spondyloarthritis (axSpA) and PsA [10]. C-Col is, to our knowledge, the first marker available for the assessment of type X collagen turnover, and so far it has been applied only to patients with osteoarthritis [19]
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