Enhanced angiogenesis induced by diffusible angiogenic growth factors released from human dental pulp explants of orthodontically moved teeth

The aim of this study was to determine if diffusible angiogenic growth factors were released in human dental pulp during orthodontic tooth movement. These factors, if diffusible, could induce angiogenesis in other tissues, and may then be isolated and identified. The pulps from 14 premolar teeth treated with straight wire fixed orthodontic appliances for 2 weeks were compared with those of 14 untreated control premolar teeth from the same subjects. Following tooth extraction and sectioning, 1-mm horizontal sections of pulp tissue were embedded in collagen with 1-mm sections of rat aorta and co-cultured in growth media for up to 4 weeks. Sections of rat aorta alone were also cultured. Angiogenic changes in the form of microvessel growth were observed by light microscopy. Microvessel identification was confirmed by electron microscopy and by immunohistochemistry using staining for factor VIII-related antigen marker for endothelial cells. When compared at days 5, 10, and 14 of co-culture, the number of microvessels was significantly greater in the pulps from orthodontically moved teeth than in those from the control teeth. The number of rat aorta microvessels was also significantly greater when co-cultured with pulp from orthodontically moved teeth than with pulp from control teeth and when compared with control cultures of rat aorta alone. There were no significant differences in microvessel numbers between the rat aorta co-cultured with pulp from control teeth and control cultures of rat aorta alone. These results indicate an increase in angiogenic growth factors in the pulp of orthodontically moved teeth, and the enhanced response of the rat aorta when co-cultured with this pulp shows that these factors appear to be diffusible.