Development of a mouse model for dental pulp disease and biodistribution of human dental pulp stem cells transplanted intra-pulpally in the mouse

Abstract

The aims of this study were (1) to establish the mouse model for pulp-dentin complex regeneration research and (2) to test in vivo fate of intra-pulpal transplanted dental pulp stem cells in comparison with those of intravenously trasnplanted DPSCs using the developed the mouse model. In order to establish the mouse model, a total of 45 mice had their pulp exposed, and five mice each were sacrificed at 1, 2, 4, 7, 9, 12, and 14 days after pulp exposure. As a control group to check normal pulp status, unprepared teeth were used. In order to verify the pulp necrosis and formation of apical lesions, five mice were sacrificed 28 and 35 days after pulp exposure. Histologic changes over time were observed by light microscope. In order to test in vivo biodistribution of intra-pulpal and intravenously transplanted human DPSCs, normal impacted third molars were collected from volunteer and hDPSCs were isolated and cultured using the method, as described by Gronthos et al. Under deep anesthesia, 1 x 105 hDPSCs were transplanted a mouse through the tail vein for intravenous transplantation or pulp chamber for intra-pulpal transplantation. After transplantation of hDPSCs, mice were sacrificed at various time periods, and the number of hDPSCs in the organs were analyzed quantitatively. Also, qualitative analysis was performed to detect intra-pulpally transplanted hDPSCs in the pulp chamber. Up to seven days after exposure of the dental pulp in mice, inflammation and necrosis was limited to the area superior to the orifice level. By 14 days after pulp exposure, necrosis had progressed as far as the root apices, and all the cells and tissues in the root canals had undergone necrosis. Intravenously injected hDPSCs were mostly distributed to the lungs. The number of hDPSCs in the lungs continued to decrease at 15 minutes, 30 minutes, and up to 12 hour after hDPSCs transplantation. hDPSCs were rarely detected in other organs except the lungs throughout all time periods. The hDPSCs transplanted into the pulp chamber rarely migrate to other organs across all time periods. Even after 12 hours had passed, the viable cells were found within the pulp chamber. The results suggest that there seems to be no safety problem in cell based approach which transplants hDPSCs into pulp chamber for pulp-dentin complex regeneration.