BMP signaling in the development and regeneration of tooth roots: from mechanisms to applications.

Short root anomaly (SRA), along with caries, periodontitis, and trauma, can cause tooth loss, affecting the physical and mental health of patients. Dental implants have become widely utilized for tooth restoration; however, they exhibit certain limitations compared to natural tooth roots. Tissue engineering-mediated root regeneration offers a strategy to sustain a tooth with a physiologically more natural function by regenerating the bioengineered tooth root (bio-root) based on the bionic principle. While the process of tooth root development has been reported in previous studies, the specific molecular mechanisms remain unclear. The Bone Morphogenetic Proteins (BMPs) family is an essential factor regulating cellular activities and is involved in almost all tissue development. Recent studies have focused on exploring the mechanism of BMP signaling in tooth root development by using transgenic animal models and developing better tissue engineering strategies for bio-root regeneration. This article reviews the unique roles of BMP signaling in tooth root development and regeneration.

DLP 3D printing of high-resolution root scaffold with bionic bioactivity and biomechanics for personalized bio-root regeneration.

Digital light projection (DLP) printing of hydroxyapatite (HAp) bioceramic provides a promising strategy for fabrication of complex personalized bio-tooth root scaffold with high-resolution. However, it is still a challenge to fabricate bionic bio-tooth root with satisfied bioactivity and biomechanics. This research studied the HAp-based bioceramic scaffold with bionic bioactivity and biomechanics for personalized bio-root regeneration. Compared to natural decellularized dentine (NDD) scaffolds with unitary shape and restricted mechanical properties, those DLP printing bio-tooth roots with natural size, high precision appearance, excellent structure, and a smooth surface were successfully manufactured, which met various shape and structure requirements for personalized bio-tooth regeneration. Moreover, the bioceramic sintering at 1250 °C enhanced the physicochemical properties of HAp and exhibited good elastic modulus (11.72 ± 0.53 GPa), which was almost twice of early NDD (4.76 ± 0.75 GPa). To further improve the surface activity of sintered biomimetic, the nano-HAw (nano-hydroxyapatite whiskers) coating deposited by hydrothermal treatment increased the mechanical properties and surface hydrophilicity, which indicated positive effects on dental follicle stem cells (DFSCs)' proliferation and enhanced the DFSCs osteoblastic differentiation in vitro. Subcutaneous transplantation in nude mice and in-situ transplantation in rat alveolar fossa proved that the nano-HAw-containing scaffold could promote the DFSCs differentiate into periodontal ligament-like enthesis formation. In conclusion, by combining the optimized sintering temperature and modified nano-HAw interface through hydrothermal treatment, the DLP-printing of HAp-based bioceramic with favorable bioactivity and biomechanics is a promising candidate for personalized bio-root regeneration.

Adipose-derived stromal/stem cells are verified to be potential seed candidates for bio-root regeneration in three-dimensional culture.

BACKGROUND: Bio-root regeneration is a promising treatment for tooth loss. It has been reported that dental-derived stem cells are effective seed cells for bio-root construction, but further applications are limited by their few sources. Human adipose tissues have a wide range of sources and numerous studies have confirmed the ability of adipose-derived stromal/stem cells (ASCs) in regenerative medicine. In the current study, the odontogenic capacities of ASCs were compared with dental-derived stem cells including dental follicle cells (DFCs), and stem cells from human exfoliated deciduous teeth (SHEDs). METHODS: The biological characteristics of ASCs, DFCs, and SHEDs were explored in vitro. Two-dimensional (2D) and three-dimensional (3D) cultures were compared in vitro. Odontogenic characteristics of porcine-treated dentin matrix (pTDM) induced cells under a 3D microenvironment in vitro were compared. The complexes (cell/pTDM) were transplanted subcutaneously into nude mice to verify regenerative potential. RNA sequencing (RNA-seq) was used to explore molecular mechanisms of different seed cells in bio-root regeneration. RESULTS: 3D culture was more efficient in constructing bio-root complexes. ASCs exhibited good biological characteristics similar to dental-derived stem cells in vitro. Besides, pTDM induced ASCs presented odontogenic ability similar to dental-derived stem cells. Furthermore, 3D cultured ASCs/pTDM complex promoted regeneration of dentin-like, pulp-like, and periodontal fiber-like tissues in vivo. Analysis indicated that PI3K-Akt, VEGF signaling pathways may play key roles in the process of inducing ASCs odontogenic differentiation by pTDM. CONCLUSIONS: ASCs are potential seed cells for pTDM-induced bio-root regeneration, providing a basis for further research and application.

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.

Elaboración de un biodiente: enfoque actual y desafíos / Making a Bio-tooth: Current Approaches and Challenges

Antecedentes: El edentulismo es uno de los mayores problemas de salud oral que cause alteraciones fisiológicas, sociales, estéticas, fonéticas y nutricionales. Las terapias actuales para el remplazo dental son artificiales y no satisfacen los requisitos básicos de un diente natural. La bioingeniería de tejidos constituye una alternativa para la sustitución de dientes perdidos. Objetivo: Identificar los enfoques/técnicas disponibles actualmente para obtener un diente completo por bioingeniería (biodiente), así como puntualizar sus desafíos y perspectivas futuras. Métodos: Se realizó una revisión integrativa de la literatura, por medio de las siguientes palabras clave: biodiente, bioingeniería de tejidos, diente entero y células madre. Los años de la búsqueda fueron 2000-2018, en las bases de datos: PubMed, Scopus, EBSCO, Science Direct, Wiley Online Library, Lilacs y Google Académico/Scholar, en inglés y español. Se seleccionaron únicamente artículos y libros de mayor relevancia y pertinencia. Resultados: Se obtuvieron 53 artículos y 10 libros. Para la elaboración de un biodiente se emplean los siguientes métodos: andamios, sin andamios, células madre pluripotentes inducidas, germen de órganos, diente quimérico y estimulación de la formación de la tercera dentición. El tamaño y forma normales del diente, así como la obtención de células epiteliales, son los principales desafíos. Conclusiones: La posibilidad de crear y desarrollar un biodiente en un ambiente oral adulto es cada vez más real gracias a los avances biotecnológicos que ocurren diariamente. Es posible que estos conceptos sean la base de la odontología restauradora en un futuro próximo.

Background: Edentulism is one of the major oral health problems that cause physiological, social, aesthetic, phonetic, and nutritional issues. Current therapies for dental replacement are artificial and do not satisfy the basic requirements of a natural tooth. Tissue bioengineering could be a viable alternative to substitute lost teeth. Objective: To identify current available approaches/techniques to obtain a complete bioengineered tooth (bio-tooth) and to point out future challenges and perspectives. Methods: This was an integrative literature review. Search keywords used were: bio-tooth, tissue bioengineering, whole tooth, stem cells. The search included the years 2000 through 2018, using the databases PubMed, Scopus, EBSCO, Science Direct, Wiley Online Library, Lilacs and Google Scholar, both in English and Spanish. Only relevant and pertinent articles and books were selected. Results: 53 articles and 10 books were obtained. Methods for bio-tooth generation found were: scaffolds, scaffold-free, induced pluripotent stem cells, tooth organ germ, chimeric tooth, and stimulation of third dentition formation. Achieving normal tooth size and shape and obtaining epithelial cells are the main challenges. Conclusions: The possibility of creating and developing a whole bioengineered tooth (bio-tooth) in an adult oral environment is becoming more realistic, considering the daily biotechnological advances. It is possible that these concepts will be the basis of restorative dentistry in a near future.

Xenogeneic Bio-Root Prompts the Constructive Process Characterized by Macrophage Phenotype Polarization in Rodents and Nonhuman Primates.

Tissue or organ regeneration using xenogeneic matrices is a promising approach to address the shortage of donor matrices for allotransplantation. Success of such approach has been demonstrated to correlate with macrophage-mediated fibrotic homeostasis and tissue remodeling. The previous studies have demonstrated that treated dentin matrix (TDM) could be a suitable bioactive substrate for allogeneic tooth root regeneration. This study constructed xenogeneic bioengineered tooth root (bio-root) via a combination of porcine TDM (pTDM) with allogeneic dental follicle cells (DFCs). Macrophage phenotypes are used to evaluate the remodeling process of xenogeneic bio-roots in vitro and in vivo. pTDM can facilitate odontoblast differentiation of human derived DFCs. Xenogeneic bio-roots in rat subcutaneous tissue prompt constructive response via M1 macrophage infiltration during early postimplantation stages and increase restorative M2 phenotype at later stages. After implantation of bio-roots into jaws of rhesus monkeys for six months, periodontal ligament-like fibers accompanied by macrophage polarization are observed, which are positive for COL-1, Periostin, ßIII-tubulin and display such structures as fibroblasts and blood vessels. The reconstructed bio-root possesses biomechanical properties for the dissipation of masticatory forces. These results support that xenogeneic bio-root could maintain fibrotic homeostasis during remodeling process and highlight the potential application of xenogeneic matrices in regenerative medicine.

[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.

The key factors which affect the bio-root regeneration / 中华口腔医学杂志

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.