Expression of vascular permeability factor (VPF/VEGF) messenger RNA by plasma cells: possible involvement in the development of edema in chronic inflammation

Edema occurs in some types of chronic inflammation such as nasal polyps, uterine cervical polyps and gastric hyper-plastic polyps. However, the factors or cellular components involved in the development of edema in chronic inflammation remain to be clarified. Recently, the gene encoding vascular permeability factor (VPF) or vascular endothelial growth factor (VEGF) and the genes encoding its receptors (kinase insert domain-containing receptor (KDR) and fms-like tyrosine kinase-1 [fit-1]) have been cloned. VPF/VEGF induces vascular hyperpermeability and vascular endothe lial proliferation through KDR or fit-1 receptors. As there is a possibility that VPF/VEGF may play a role in the development of edema in chronic inflammation, we examined the messenger (m) RNA expression of VPF/VEGF and its recep tors in nasal polyp tissues, which is an example of chronic inflammation with remarkable edema. Using northern blotting, all nasal polyp tissues examined expressed mRNA of VPF/VEGF and KDR. In situ hybridization revealed that VPF/ VEGF mRNA-expressing cells were scattered in the edematous stroma of nasal polyps. In the adjacent sections, these cells showed the morphological features of plasma cells and expressed mRNA of immunoglobulin light chains. Human B cell leukemia and plasmacytoma cell lines expressed VPF/VEGF mRNA but human mast-cell leukemia and T cell leukemia cell lines did not. The alternatively spliced pattern of VPF/VEGF transcripts observed in nasal polyp tissues was consistent with that in plasmacytoma cell lines. Taken together, the VPF/VEGF mRNA-expressing cells in nasal polyps appeared to be plasma cells, suggesting that plasma cells may play an important role in the development of edema in chronic inflammation through the production of VPF/VEGF.