Apoptosis of Dental Pulp Cells and Their Elimination by Macrophages and MHC Class II-expressing Dendritic Cells

Abstract

Apoptosis of dental pulp cells of rat incisors was investigated by the TUNEL method and electron microscopy. The results showed that a considerable amount of apoptosis occurred in the pulp, increasing in extent with incisal direction. OX6, ED1, and ED2 antibodies were used to detect macrophages and dendritic cells in combination with immunoelectron microscopy. Apoptotic fragments were eliminated mainly by MHC Class II-expressing cells, including dendritic cells positive for the OX6 antibody, and by MHC Class II-negative macrophages. Macrophages and dendritic cells positive for OX6, ED1, or ED2 increased from the apical to incisal direction of the incisor. These results indicate that apoptosis contributes to normal pulp formation and maintenance.