Background: TNF-α inhibitors are potent anti-inflammatory drugs that have revolutionized the treatment of rheumatoid arthritis (RA). Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) is a non-invasive method to study cartilage quality, in particular the glycosaminoglycan (GAG) content.
Purpose: To evaluate knee cartilage quality before and after treatment with a TNF-α inhibitor (infliximab) in patients with RA using dGEMRIC and to study clinical parameters and serum cartilage oligomeric protein (COMP) after the same treatment.
Material and methods: Seven patients with chronic RA received infusions of 3 mg/kg infliximab at weeks 0, 2, 6, 14, and 22. Clinical examination, serum COMP level, and dGEMRIC scans (1.5 T) were performed at baseline and after 7 months. The dGEMRIC index (ms), reflecting cartilage GAG content, was calculated using an inversion recovery sequence in the femoral weight-bearing cartilage. Seven years after treatment, charts were reviewed regarding joint replacement surgery (TKA).
Results: Clinical parameters showed an improvement for all patients after the 7-month treatment period. Serum COMP decreased from 13±4.5 to 11±3.4 (μg, mean ± SD) μg/ml (P<0.05). The dGEMRIC index was lower at follow-up than at baseline, 332±85 and 382±69 (ms, mean ± SD), respectively (P<0.05), indicating loss of GAG. The two patients with the lowest dGEMRIC index had received a TKA 7 years after treatment.
Conclusion: This longitudinal study indicates a substantial GAG loss from the knee cartilage matrix in patients with chronic RA. Treatment with infliximab does not seem to protect the cartilage from further deterioration despite improvements in clinical parameters and decreased serum COMP.