Method: 25 patients with active RA diagnosed according to the ACR criteria and willing to sign an informed consent were recruited from the outpatient clinics at the Centre Hospitalier Universitaire de Sherbrooke. Adalimumab 40 mg sub-cutaneous was administered every two weeks. Primary outcomes were 1) the number of OC precursor (CD14+) cells in the peripheral blood, 2) the number of OCs generated in vitro, and 3) the amount of bone resorption in vitro before administration of Adalimumab and 3 and 6 months into the treatment. Secondary outcomes were disease activity defined as a DAS28 scoreand change in functional status by the M-HAQ. PBMCs were isolated from 50 ml of blood by Ficoll-Hypaque gradient and the number of CD14+ cells was determined by FACS. The whole population of PBMCs was plated in 48-well tissue culture plates and the cells were allowed to differentiate for 21 days in the presence of recombinant RANKL (75 ng/ml) and M-CSF (10 ng/ml). The cells were then stained for TRAP activity. The number of TRAP+ cells containing 3 or more nuclei was counted in each well. For bone resorption assays, cells differentiated for 30 days on bone slices were stained for 0.2 % toluidine blue. Resorption surface was quantified using the image analysis program Simple PCI.
Results: Treatment with Adalimumab had no impact on the number of OC precursors in peripheral blood in any of the points studied. For the number of OCs generated in vitro, the medians with (25th centile, 75th centile) at first, 3 months and 6 months visits were 220.0 (109.5, 396.5), 201.0 (38.0, 387.0) and 58.0 (19.0, 386.5) OCs/well; these differences were not statistically significant. For the resorption assays, the medians with (25th centile, 75th centile) at first, 3 months and 6 months visits were 21466.0 (0.0, 855844.1), 0.0 (0.0, 411915.0) and 0.0 (0.0, 0.0) μm2. Although there was a strong trend towards a decrease in the resorption area in visits 3 and 6 months, none of these results reached statistically significant difference when compared to the first visit (p = 0,057). Adalimumab induced a significant decrease in the DAS28 score and in the M-HAQ. For the DAS28 score, the difference between the medians was statistically significant for the first and 3 months visits (p = 0.0008) and for the first and 6 months visits (p = 0.0017). For the M-HAQ, the difference was statistically significant for the first and 6 months visits (p = 0,006).
Conclusion: Treatment with Adalimumab up to 6 months had no statistically significant impact on the number of OC precursors, osteoclastogenesis and resorption in vitro even if we can observe a trend toward a decrease in the number of OCs and bone resorption with treatment. For the clinical results, Adalimumab had a statistically significant impact in DAS28 and M-HAQ, decreasing both.
Disclosure: S. Guay-Belanger, None; A. J. Fernandes, None.