Weibel-Palade bodies as a marker for neovascularization induced by tumor and rheumatoid angiogenesis factors.

An analysis was made of ultrastructural changes in capillary endothelial cells in experimentally induced angiogenesis and in a human pathological situation known to involve increased angiogenesis. Chick chorioalloantoic membrane (CAM) showing a positive angiogenic response to low-molecular weight angiogenesis factor isolated from rat Walker sarcoma or from human rheumatoid joint was compared with untreated CAM. Serotonin-treated CAM provided an additional control in that serotonin has the capacity to stimulate endothelial cell growth in vitro but did not induce angiogenesis on the CAM. Human rheumatoid joints were studied using normal healthy human joints as controls. The number of Weibel-Palade (W-P) bodies per unit of cytoplasmic area were higher in tumor angiogenesis factor-treated CAMs (not significant) and rheumatoid angiogenesis factor-treated CAMs (P less than 0.008) than in untreated controls. These differences were more pronounced if W-P body volumetric density was analyzed (P in both cases less than 0.008). Serotonin-treated control CAMs did not show higher numbers of W-P body or greater WPV than untreated controls. Numbers of W-P body and W-P body volumetric density were higher (P less than 0.008) in rheumatoid joints than normal joints. Median values for W-P body number were 16-fold higher and, for W-P body volumetric density, they were up to 30-fold higher in rheumatoid joints.