Responses of BrdU label-retaining dental pulp cells to allogenic tooth transplantation into mouse maxilla

Abstract

Recently, we demonstrated that a pulse of BrdU given to prenatal animals reveals the existence of slow-cycling long-term label-retaining cells (LRCs), putative adult stem or progenitor cells, which reside in the dental pulp. This study aims to clarify responses of LRCs to allogenic tooth transplantation into mouse maxilla using prenatal BrdU-labeling, in situ hybridization for osteopontin and periostin, and immunohistochemistry for BrdU, nestin, and osteopontin. The upper-right first molars were allografted in the original socket between BrdU-labeled and non-labeled mice or between GFP transgenic and wild-type mice. Tooth transplantation caused degeneration of the odontoblast layer, resulting in the disappearance of nestin-positive reactions in the dental pulp. On postoperative days 5-7, tertiary dentin formation commenced next to the preexisting dentin where nestin-positive odontoblast-like cells were arranged in the successful cases. In BrdU-labeled transplanted teeth, dense LRCs were maintained in the center of the dental pulp beneath the odontoblast-like cells including LRCs, whereas LRCs disappeared in the area surrounding the bone-like tissue. In contrast, LRCs were not recognized in the pulp chamber of non-labeled transplants through the experimental period. Tooth transplantation using GFP mice demonstrated that the donor cells constituted the dental pulp of the transplant except for endothelial cells and some migrated cells, and the periodontal tissue was replaced by host-derived cells except for epithelial cell rests of Malassez. These results suggest that the maintenance of BrdU label-retaining dental pulp cells play a role in the regeneration of odontoblast-like cells in the process of pulpal healing following tooth transplantation.

The relationship between cell proliferation and differentiation and mapping of putative dental pulp stem/progenitor cells during mouse molar development by chasing BrdU-labeling

“…The differentiation capacity of LRCs in mice has been recently clarified after the exogenous stimuli such as allogenic tooth transplantation in our previous study: the LRCs in the transplant maintain Proliferating cells are shown in red, strong nestin-IR is shown in blue, weak nestin-IR is shown in light blue and dense LRCs are shown in green. Enamel knots in tooth germs are shown in yellow their proliferative and differentiation capacity for odontoblastlike cells (Mutoh et al 2011;Saito et al 2011). …”

Two Distinct Processes of Bone-like Tissue Formation by Dental Pulp Cells after Tooth Transplantation

“…Therefore, the formation of mineralized tissue within the pulp cavity has been widely examined in both clinical and animal studies. These studies ordinarily focused on the formation of reparative dentin and the dentin bridge, although several other reports described the induction of bone-like tissues in the pulp cavity following various stimulations such as tooth transplantation (Hosoya et al 2003) or replantation (Zhao et al 2007;Mutoh et al 2011), traumatic injury (Robertson et al 1997), and laser irradiation (Tate et al 2006). These bone-like tissues are quite similar to normal bone regarding their histological appearance and matrix properties; however, the origin of the osteoblast-like cells that appear in the dental pulp is still controversial.…”

Recent progress in histochemistry and cell biology

“…Similarly, the M1 of a GFP transgenic mice or wild-type mice was transplanted into the alveolar socket of wild-type or GFP transgenic mice, respectively. With respect to BrdU-labeling, repeated intraperitoneal injections (E17-21) into pregnant Wistar rats have been demonstrated to successful identify dense slow-cycling long-term labelretaining cells (LRCs), which are regarded to be putative adult stem or progenitor cells (Ishikawa et al 2011;Mutoh et al 2011). These cells can be found in the mature tissue of born animals in the center of the dental pulp, associating with blood vessels.…”

“…To analyze the processes occurring after allogenic tooth transplantation into mouse maxilla, Mutoh et al 2011) made use of prenatal bromodeoxyuridine (BrdU)-labeled and GFP transgenic mice. In the case of the BrdU-labeled mice, the BrdU-labeled extracted molar (M1) was allo-grafted into the original socket of non-labeled, M1-extracted mice and vice versa.…”