The behavior of stem cells and progenitor cells in the periodontal ligament during wound healing as observed using immunohistochemical methods

The aim of this study was to identify stem cells or progenitor cells in the periodontal ligament and to investigate their behavior during wound healing of bone defects created experimentally in the alveolar process. Intradentinal cavities were created in the mesial root of the first molar of 25 adult male rats that were killed 1, 3, 5, 7 and 14 d after surgery. At each time-point, sections were stained immunohistochemically for CD44s (standard), CD34, c-KIT, PCNA, Cbfa-1 and 5-bromo-2-deoxyuridine using primary antibodies. For morphometric analysis, the ratios of Cbfa-1 and PCNA-positive cells were calculated from the total number of positive cells/10(4) mu m(2) in the cavities. 5-Bromo-2-deoxyuridine-positive cells were observed in the periodontal ligament and had migrated into the wound areas. A small number of CD44s-, CD34- and c-KIT-positive cells were observed in the bone marrow, but none were observed in the periodontal ligament. CD44s-positive cells were only observed in the alveolar bone cavity at 5 d after surgery. CD34- and c-KIT-positive cells were only observed in the dentin cavity at 7 d after surgery. Cbfa-1 and PCNA scores tended to show an increase 7 d after surgery. Mesenchymal stem cells and hematopoietic stem cells in the bone marrow are not involved in the regeneration of the periodontium. Cells that migrated from the residual periodontal ligament regenerated new alveolar bone at the early stage, and the regeneration around the dentin in the cavity was later than in other parts.