An ultrastructural and immunohistochemical study of human dental pulp: identification of Weibel-Palade bodies and von Willebrand factor in pulp endothelial cells

Special and specific immunohistochemical techniques as well as routine transmission electron microscopy were used to identify the presence of von Willebrand factor (vWF), a blood clotting factor essential to normal hemostasis, and Weibel-Palade bodies (WPB's), respectively, in the endothelial cells lining the blood vessels from both normal and inflamed human pulpal tissues. In human endothelial cells, WPB's are peculiar and specialized organelles which store vWF. All classes of blood vessels (capillaries, arterioles, arteries, venules, and veins) were vWF positive. The fine structural studies showed similar results with regard to the presence of WPB's. Interestingly, morphometric analyses conducted on the same tissues using either light or transmission electron microscopy showed that significantly more vWF-positive blood vessels were seen in the inflamed tissues. In agreement with the latter observation, transmission electron microscopy showed that more vascular endothelial cells contained WPB's in the inflamed tissues when compared with the normal tissues. From this it appears that during pulpal inflammation, the cascade of events associated with hemostasis may be activated with the increased synthesis and release of vWF by endothelial cells.