Objectives To assess glycosaminoglycan (GAG) content of lumbar intervertebral discs (IVD) in patients with spondyloarthritis (SpA) using glycosaminoglycan chemical exchange saturation transfer (gagCEST) in high-field magnetic resonance imaging (MRI).
Methods Ninety lumbar intervertebral discs of nine patients with predominantly axial SpA (eight patients with ankylosing spondylitis; one patient with spondylitis related to inflammatory bowel disease; mean age: 44.1±14.0 years; range: 27 - 72 years) and 18 age-matched healthy controls were examined at a 3T MRI scanner in this prospective study. The MRI protocol included standard morphological, sagittal T2 weighted (T2w) images to assess Pfirrmann MRI-score of the five lumbar inter vertebral discs (IVD, L1 to S1) and biochemical imaging with gagCEST to calculate the local GAG content of nucleus pulposus (NP) and annulus fibrosus (AF). Prior to statistical testing of gagCEST effects in patients and controls, IVDs were classified according to the Pfirrmann score.
Results Pooled non-degenerative IVDs (Pfirrmann 1 and 2) had significantly lower gagCEST effects in patients suffering from SpA compared to healthy controls in NP (1.76±1.47; p<0.001) and AF (1.31±1.16; p<0.001) by comparing the differences of the means. No significant difference of GAG values was found in degenerative IVDs between patients and controls in NP and AF.
Conclusions GagCEST analysis of morphologically non-degenerative IVDs demonstrated significantly lower GAG values in patients with axial SpA possibly representing a depletion of GAG in SpA in the absence of morphologic degeneration. GagCEST may be a powerful research tool to access IVD composition in early SpA and to investigate therapy effects on GAG content in advanced studies.
Disclosure of Interest None declared