Dental pulp tissue engineering of pulpotomized rat molars with bone marrow mesenchymal stem cells

The major goal of dental pulp tissue engineering is to enable the healing of inflamed tissue or to replace necrotic pulp tissue with newly formed dental pulp tissue. Here, we report a protocol for pulp tissue engineering in vivo in pulpotomized rat teeth using constructs of rat bone marrow mesenchymal stem cells, preformed biodegradable scaffolds, and hydrogel. The constructs were implanted into pulpotomized pulp chambers for 3, 7, or 14 days. At 3 days, cells were located mainly along the preformed scaffolds. At 7 days, pulp tissue regeneration was observed in almost the entire implanted region. At 14 days, pulp tissue regeneration further progressed throughout the implanted region. In immunohistochemistry, at 3 days, a number of small and round macrophages immunoreactive to CD68 were predominantly distributed around the scaffolds. The density of CD68+ macrophages decreased until 14 days. On the other hand, nestin-expressing odontoblast-like cells beneath the dentin at the border of implanted region increased until 14 days. Quantitative gene expression analysis revealed that odontoblast differentiation marker dentin sialophosphoprotein mRNA in the implanted region gradually increased until 14 days. Together, the results suggested that regeneration of dental pulp tissue had occurred. Thus, our study provides a novel experimental rat model of dental pulp regeneration.