The aim of this study was to assess the response of dental pulp associated with donor or host cells in the pulp chamber and root canal after extra-oral transplantation. Methods: Wild type or green fluorescent protein (GFP) transgenic first molars from 3-week, 6-week, and 12-week mice were transplanted into the subcutaneous layer of GFP mice or wild type mice. The teeth were histologically and immunohistochemically examined at 5 weeks after transplantation. Results: Blood vessels present in the original coronal pulp had anastomosed with those from the recipient tissue that had invaded the root canal. Two distinct eosin-stained extracellular matrices were observed in the pulp chamber and root canal. Acellular matrix composed of nestin-positive, odontoblast-like cells invaded from the outside and was seen in the root canal of 3-week teeth. Cellular matrix comprising alkaline phosphatase (ALP)-positive fibroblast-like cells appeared in the original coronal pulp. In the root canal of the 6-week and 12-week teeth, cellular extracellular matrix consisting of ALP-positive fibroblast-like cells had invaded the recipient tissue. Conclusion: Dental pulp from immature teeth might be able to regenerate dentin-like tissue. This model could be useful in the development of an optimized vitalization treatment.
The aim of regenerative medicine is to restore the original functions of tissues and organs damaged by disease or impairment. Stem cell transfusion has been used clinically as regenerative therapy in a wide range of fields. This therapy promotes regeneration of partially damaged tissues or organs by transfer of tissue stem cells. Teeth are produced from dental germ, which is induced by interactions between epithelial and mesenchymal stem cells. Wnt signals are heavily involved in this process. Furthermore, it has been shown that β-catenin is expressed in the nucleus of odontoblasts and dentinal cells located immediately under repaired dentine after pulpotomy, and that macrophages in dental pulp express Wnt10a, suggesting involvement of Wnt10a in odontoblasts in generation and repair processes. However, little is known about the involvement of Wnt10a in odontoblasts in regenerated pulp tissues. Hayashi et al. transplanted dental pulp, bone marrow, adipose stem cells, or culture supernatants derived from each of them in the ectopic tooth transplantation. As a result, we have succeeded in regenerating dental pulp tissue that expresses the dental pulp marker TRH-DE, regardless of the transplantation. In this study, we used this model to examine morphologically how Wnt10a and odontoblasts change with time in regenerated dental pulp. We then analyzed the dynamics of Wnt10a in dentinal induction in dental pulp stem cells. The results of this study showed an increase in odontoblasts with increased regeneration of dental pulp, and these odontoblasts expressed Wn-t10a. Expression of DSPP increases upon inhibition of expression of DKK1, and induction of dentinal differentiation occurs via expression of Wnt10a in dental pulp regeneration. Therefore, Wnt10a is a candidate as a non-cellular agent for induction of dental pulp regeneration with dentine-inducing capacity.
Abstruct: In organs, multiple functionally differentiated cells and stem cells are organized to express specific functions through a series of complex interactions. The Wnt signaling pathway is deeply involved in these processes throughout life. The dependence of Wnt signaling on spatiotemporal specificity and the changes in vivo interactions caused by the balance and distribution of Wnt ligands and antagonists. Regeneration is thought to involve reconstitution of the growth mechanism, and thus control of stem cells and tissue regeneration has been attempted by mimicking canonical Wnt signals. Wnt10a has been reported to be involved in tooth development and regeneration. These findings indicate the importance of understanding and reproducing involvement of Wnt10a in dental pulp regeneration for development of regenerative dental treatment. Accordingly, we examined the spatiotemporal specificity of Wnt signals involved in dental pulp regeneration by morphologically examining changes in Wnt signals over time in regenerated dental pulp using ectopic tooth root implantation. Expression levels of Wnt10a and DKK1 in regenerated dental pulp suggest that Wnt expression does not increase continuously with time as regeneration increases, which reflects the spatiotemporal specificity of Wnt. In addition, the Dkk1 expression kinetics had a phase shift relative to those of Wnt10a: Dkk1 expression was low when that of Wnt10a was high, and Wnt10a expression decreased when Dkk1 expression increased. These results suggest that canonical Wnt signals have an elaborate control mechanism in regenerated pulp, as suggested in previous reports. Moreover, Wnt reflects the percentage of regenerated pulp. Therefore Wnt is a potential biomarker of pulp regeneration.
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