INDUCIBLE NITRIC-OXIDE SYNTHASE IS EXPRESSED IN GRANULOMA PYOGENICUM

It is known that granuloma pyogenicum (GP) grows rapidly but cherry an gioma (CA) does not, although they show the same histological features of hyperplasia of the capillary vessels. Although some cytokines have been thought to be angiogenic factors, a nitric oxide (NO) synthase-d ependent effector mechanism is reported to be involved in macrophage-d erived angiogenesis in humans. Under the hypothesis that this mechanis m is also involved in the more rapid growth of GP, we examined the exp ression of inducible NO synthase (iNOS) in GP as compared with that in CA. The expression of iNOS mRNA was detected in GP, but not in CA, by reverse transcription-polymerase chain reaction (RT-PCR) analysis. In situ hybridization (ISH) demonstrated iNOS mRNA expression in endothe lial cells and to a lesser extent round cells and spindle cells in the myxomatous stroma in GP, Immunohistochemical study showed that iNOS p rotein was expressed in endothelial cells, infiltrating round cells an d spindle cells in the stroma in GP. These results suggested that a NO S-dependent mechanism may be involved in angiogenesis and the rapid gr owth of GP.