Elucidation of the capacity of dental pulp differentiation as demonstrated by autogenic and allogenic tooth transplantation

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1. Pulpal regeneration following allogenic tooth transplantation into mouse maxillaThe upper right first molar (M1) of 2-wk-old mice was extracted and allo-grafted in the original socket in both the littermate and non-littermate after the extraction of Ml. Tooth transplantation weakened the nestin-positive reactions in the pulp tissue that had shown immunoreactivity for nestin before operation. On postoperative Days 5-7, tertiary dentin formation commenced next to the pre-existing dentin where nestin-positive odontoblast-like cells were arranged in all cases of the littermate group until Day 14, except for the unusual occurrence of immunological rejection in the pulp chamber (10%). In the non-littermate group, bone-like tissue formation occurred in the pulp chamber in addition to tertiary dentin formation until Day 14. The rate of tertiary dentin was 38%, and the rate of the mixed form of dentin and bone-like tissue formation was 23% (the remainder was immunological rejection). Interes … More tingly, the periodontal tissue recovered even in the case of immunological rejection in which the pulp chamber was replaced by bone marrow-like tissue. These results suggest that the selection of littermate or non-littermate is decisive for the survival of odontoblast-lineage cells and that the immunological rejection does not influence the periodontal regeneration.2. Capacity of dental pulp differentiation in mouse molars as demonstrated by allogenic tooth transplantationFollowing the extraction of the molars of 3-wk-old mice, the roots and pulp floor were resected and immediately allo-grafted into the sublingual region in the littermate. In addition, we investigated the contribution of donor and host cells to the regenerated pulp tissue using the combination of allogenic tooth transplantation and lacZ transgenic ROSA26 mice. On Days 5-7, tubular dentin formation commenced next to the pre-existing dentin at the pulp horn where nestin-positive odontoblast-like cells were arranged. Until Day 14, bone-like tissue formation occurred in the pulp chamber, where intense TRAP-positive cells appeared. Furthermore, allogenic transplantation using ROSA26 mice clearly demonstrated that both donor and host cells differentiated into the osteoblast-like cells with the assistance of osteoclast-lineage cells, whereas newly-differentiated odontoblasts were exclusively derived from the donor cells. These results suggest that both donor and host cells contribute to the bone-like tissue formation in the regenerated pulp tissue. Less