Stem cells from human exfoliated deciduous teeth as an alternative cell source in bio-root regeneration

A stem cell-mediated bioengineered tooth root (bio-root) has proven to be a prospective tool for the treatment of tooth loss. As shown in our previous studies, dental follicle cells (DFCs) are suitable seeding cells for the construction of bio-roots. However, the DFCs which can only be obtained from unerupted tooth germ are restricted. Stem cells from human exfoliated deciduous teeth (SHEDs), which are harvested much more easily through a minimally invasive procedure, may be used as an alternative seeding cell. In this case, we compared the odontogenic characteristics of DFCs and SHEDs in bio-root regeneration. Methods: The biological characteristics of SHEDs and DFCs were determined in vitro. The cells were then induced to secrete abundant extracellular matrix (ECM) and form macroscopic cell sheets. We combined the cell sheets with treated dentin matrix (TDM) for subcutaneous transplantation into nude mice and orthotopic jaw bone implantation in Sprague-Dawley rats to further verify their regenerative potential. Results: DFCs exhibited a higher proliferation rate and stronger osteogenesis and adipogenesis capacities, while SHEDs displayed increased migration ability and excellent neurogenic potential. Both dental follicle cell sheets (DFCSs) and sheets of stem cells from human exfoliated deciduous teeth (SHEDSs) expressed not only ECM proteins but also osteogenic and odontogenic proteins. Importantly, similar to DFCSs/TDM, SHEDSs/TDM also successfully achieved the in vivo regeneration of the periodontal tissues, which consist of periodontal ligament fibers, blood vessels and new born alveolar bone. Conclusions: Both SHEDs and DFCs possessed a similar odontogenic differentiation capacity in vivo, and SHEDs were regarded as a prospective seeding cell for use in bio-root regeneration in the future.

[The key factors which affect the bio-root regeneration]

The morbidity of tooth missing is the highest one among all the human organ diseases. The present restorations used in clinic, including fixed bridges, removable dentures and implant prosthetics, all exhibit their own defects, and hardly to restore the whole tooth structure and function. With the development of stem cells and tissue engineering, as an alternative, tooth regeneration, aiming at the generation of a structure like nature tooth, will be the therapeutic orientation to restore the lost tooth. The dental root, which supports the crown and occlusal force, is the fundamental part for tooth function. Based on the theory of tissue engineering, bio-roots were successfully generated by using mesenchymal stem cells (MSC) in miniature pigs. But the success rate of bio-root is not too high, is urgent to be improved for future clinic application. MSC mediated bio-root regeneration is depended on the dentinogenic differentiation regulation of MSC. Up to now, many factors affect the directed differentiation of MSC and further for the success rate of bio-root, including seeding cells, scaffold, growth factors and microenvironmental niche, etc. Microenvironmental niche is the key factor for affecting the MSC characteristics and special tissue regeneration. Basically, the bio-root is regenerated in jaw, while the jaw microenvironmental niche is prone to induce MSC for osteogenic differentiation, instead of dentinogenic differentiation. How to improve the dentinogenic differentiation of MSC in jaw microenvironmental niche is the key issue for increasing the success rate of bio-root.