Localization of vascular endothelial growth factor in synovial membrane mast cells: examination with "multi-labelling subtraction immunostaining"

Mast cells are believed to play a novel part in the development of destruct ive synovial pannus in rheumatoid arthritis (RA). This study was undertaken to investigate the localization of vascular endothelial growth factor (VEG F) in the synovial membrane using a unique immunostaining technique. Synovi al specimens of RA patients were examined immunohistochemically and were co mpared with specimens from non-RA controls. Multi-labelling subtraction imm unostaining, a modification of double- and triple-labelling immunostaining, revealed that the VEGF-positive cells were identical to tryptase-positive cells (mast cells). No other cell types were found to be positive for VEGF. The synovium of RA patients showed a larger number of VEGF-positive mast c ells than that of non-RA controls (P<0.001). The study suggests that mast c ell-derived VEGF may contribute to the development of synovial pannus in RA .