Abstract
BackgroundInformative serum biomarkers for monitoring inflammatory activity and treatment responses in axial spondyloarthritis (axSpA) are lacking. We assessed whether Lipocalin 2 (LCN2) and Oncostatin M (OSM), both having roles in inflammation and bone remodeling, may accurately reflect chronic joint inflammation and treatment response in axSpA. Previous reports in animal models showed involvement of LCN2 and OSM in joint/gut inflammation. We asked whether they also play a role in human axSpA.MethodsWe analyzed a longitudinal observational axSpA cohort (286 patients) with yearly clinical assessments and concurrent measurements of serum LCN2 and OSM (1204 serum samples) for a mean of 4 years. Biomarker levels were correlated with MRI scoring and treatment response.ResultsPersistent and transient elevation of LCN2 and OSM were observed in axSpA patients. Persistent elevation of LCN2 or OSM, but not CRP, correlated with sacroiliac joint (SIJ) MRI SPARCC scores (Pearson’s correlation p = 0.0005 and 0.005 for LCN2 and OSM respectively), suggesting that LCN2/OSM outperforms CRP as reflective of SIJ inflammation. We observed both concordant and discordant patterns of LCN2 and OSM in relationship to back pain, the cardinal clinical symptom in axSpA. Twenty-six percent (73/286) of the patients remained both clinically and serologically active (CASA). Sixty percent (173/286) of the patients became clinically quiescent, with back pain resolved, but 53% (92/173) of them were serologically active (CQSA), indicating that pain control may not indicate control of joint inflammation, as reflected by positive MRI imaging of SIJ. With respect to treatment responses, transient elevation of LCN2 or OSM over time was predictive of better response to all treatments.ConclusionIn axSpA, persistent LCN2 and/or OSM elevation reflects chronic SIJ inflammation and suboptimal treatment response. In our cohort, half of the currently deemed clinically quiescent patients with back pain resolved continued to demonstrate chronic joint inflammation. LCN2 and OSM profiling outperforms CRP as a predictive measure and provides an objective assessment of chronic local inflammation in axSpA patients.
Highlights
Informative serum biomarkers for monitoring inflammatory activity and treatment responses in axial spondyloarthritis are lacking
We explored the role of Lipocalin 2 (LCN2) and Oncostatin M (OSM) in local inflammation of axial spondyloarthritis (axSpA) patients for the following reasons: First, LCN2 is an acute-phase protein released in response to microbial triggers [1] and has both pro- and anti-inflammatory properties which are context-dependent [2,3,4,5]
Since both LCN2 and OSM have known functions in local inflammation and bone remodeling [2, 5, 11, 12], the pathological hallmark of axSpA, we propose that both LCN2- and OSM-associated pathways are involved in axSpA pathogenesis
Summary
Informative serum biomarkers for monitoring inflammatory activity and treatment responses in axial spondyloarthritis (axSpA) are lacking. Previous reports in animal models showed involvement of LCN2 and OSM in joint/gut inflammation We asked whether they play a role in human axSpA. Serological biomarkers which accurately reflect local joint inflammation and treatment response are lacking in axial spondyloarthritis (axSpA), a progressively debilitating disease. Both genetic and environmental effects such as microbial factors contribute to the pathogenesis of axSpA. There is a mechanistic basis to support this perspective: ank/ank mice show higher serum LCN2 in mutant mice with gut involvement [8] and gut inflammation in mice is driven by OSM [10] To address whether these inflammation mechanisms play a similar role in human axSpA pathogenesis, we conducted an observational study
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