Detection, identification and in vivo treatment responsiveness of bone morphogenetic protein (BMP)-activated cell populations in the synovium of patients with rheumatoid arthritis.

OBJECTIVE: To characterise the bone morphogenetic protein (BMP) target cells positive for phosphorylated (P)-SMAD1/5, in rheumatoid arthritis (RA) synovium. METHODS: Synovial biopsies were obtained by needle arthroscopy. Anti-P-SMAD1/5 antibodies were used for Western blot (WB) on protein extracts from RA and normal synovium and for immunostaining of synovial biopsy sections. Positive cells were further identified by double staining for CD3, CD20, CD68, CD138, CD90, alpha smooth muscle actin (SMA), endoglin (CD105) and von Willebrand factor (VWF). In sections from early patients with RA taken before and under antirheumatic treatment, the degree of inflammation and activation of the BMP pathway were quantified. RESULTS: P-SMAD1/5 protein was detected by WB in RA and to a lesser extent in normal synovium. Different P-SMAD1/5 positive cell populations were identified in RA synovium, mainly in perivascular and sublining cells. P-SMAD1/5 positive perivascular cells were alphaSMA positive and located around VWF positive endothelial cells. Some CD90 positive synovial fibroblasts were P-SMAD1/5 positive, as was part of the CD68 positive synovial cells but other cells of the haematopoietic lineage showed no SMAD1/5 phosphorylation. Treatment resulted in an absolute but not relative decrease in BMP activation in the synovium. CONCLUSION: BMP-activated cells belong to distinct stromal compartments in RA synovium and some of them express markers associated with the mesenchymal progenitor cell lineage. Antirheumatic treatment effectively downregulates synovial inflammation, but BMP activation in the synovium does persist albeit reduced.

Increased cellularity and expression of adhesion molecules in muscle biopsy specimens from patients with rheumatoid arthritis with clinical suspicion of vasculitis, but negative routine histology.

OBJECTIVE: Histological analysis of random quadriceps muscle biopsy specimens can be used to detect vasculitis in patients with rheumatoid arthritis (RA). This study aimed at determining the immunohistological features in patients with clinical suspicion of rheumatoid vasculitis, but without a transmural infiltrate or fibrinoid necrosis of the vessel wall on routine histology. METHODS: Three groups of patients with RA were studied: (a) without clinical signs of vasculitis (n=6); (b) with recent onset of extra-articular features and a clinical suspicion of vasculitis but normal routine histology (n=11); and (c) with recent onset of extra-articular features and vasculitis, histologically proved either in muscle or other biopsy specimens (n=14). A control group of patients with osteoarthritis was also included (n=5). Frozen sections from quadriceps muscle biopsy specimens were analysed with monoclonal antibodies to detect CD3, CD4, CD8, CD68, ICAM-1, VCAM-1, and HLA-DR. The slides were evaluated using a semiquantitative scoring system (0-4). RESULTS: The mean scores gradually increased from group 1 to 3, leading to significant differences between groups 1 and 2, but not between groups 2 and 3 for most markers (p< 0.05). Thus the pathological changes were similar for the two groups with clinical signs of vasculitis, even when the conventional histological evaluation was negative. Higher immunohistological scores were associated with perivascular infiltrates on routine histology. CONCLUSION: The pathophysiological events leading to vasculitis are reflected by the changes in the quadriceps muscle biopsy specimens. The data indicate that the sensitivity of examination of muscle biopsy specimens for the diagnosis of rheumatoid vasculitis can be increased by the use of new criteria.