VESSEL-LIKE STRUCTURES IN THE CALLUS CARTILAGE

The recent claim that the callus cartilage contained vessel-like struc tures has been investigated by new immunocytochemical methods. The fra cture callus was exposed to monoclonal antibodies which recognized dam aged or regenerating endothelial cells, The proteolytic enzyme urokina se which is expressed by migrating endothelium was also studied. No va scular structures were identified by these methods which suggests that the callus cartilage is truly avascular.