Aims: In order to investigate the histological change in effect attenuation cases of etanercept compared with methotrexate (MTX), we performed immunohistochemical examination by seven different molecules.
Methods: We histologically assessed synovial tissue from five MTX-treated rheumatoid arthritis (RA) patients as control and six etanercept and MTX-treated RA patients after synovectomy by arthroscopy. The synovium of both groups were assessed by hematoxylin and eosin (HE) and we also analysed the expression of tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), matrix metalloproteinase-3 (MMP-3), B-cell precursors and mature B-cell transmembrane protein, CD20, macrophage marker, CD68, bromodeoxyuridine (BrdU) and vascular endothelial growth factor (VEGF) by immunohistochemistry.
Results: HE staining showed vascular and cell proliferations of the synovium of the RA patients who received etanercept compared with the control MTX group. TNF-α and IL-6 were expressed in both groups.MMP-3 and CD68 expressed less significantly in the etanercept group compared with the control (P < 0.05). CD20 strongly expressed in the etanercept group significantly (P < 0.05). BrdU expressed in the synovium in the etanercept group significantly (P < 0.05). VEGF was not found overall in both group.
Conclusion: Based on the histological change of synovium, treatment by etanercept may be involved in vascular and cell proliferations with inhibition of the expression of CD68 and MMP-3 in synovium of RA patients. These findings indicate immunohistochemical change of synovium with etanercept is one of the mechanism of efficacy of etanercept.