Apoptosis in human and rat dental pulp

Apoptotic cells were visualized in human premolar and rat molar pulps using either the TUNEL method, which stains DNA strand breaks by ill situ nick end labeling, or labeling sections with an anti-transglutaminase antibody. Apoptotic cells were evident at the periphery of the pulp, mostly in a sub-odontoblastic location, and were more numerous in the crown than in the root region of the pulp. Most odontoblasts were unlabeled. A few apoptotic nuclei in the pulp of rat molars displayed the characteristics of chromatin condensation, as observed by electron microscopy. Many cell debris resembling apoptotic bodies were also observed. The 3 methods support the occurrence of apoptosis in the dental pulp. As this phenomenon was observed in healthy teeth, apoptosis is probably involved in the regulation of the pulp cell population.