Junnan Shi

Odontogenic capability: bone marrow stromal stem cells versus dental pulp stem cells

Background information. Although adult bone‐marrow‐derived cell populations have been used to make teeth when recombined with embryonic oral epithelium, the differences between dental and non‐dental stem‐cell‐mediated odontogenesis remain an open question.

Differentiation potential of STRO-1+ dental pulp stem cells changes during cell passaging

BackgroundDental pulp stem cells (DPSCs) can be driven into odontoblast, osteoblast, and chondrocyte lineages in different inductive media. However, the differentiation potential of naive DPSCs after serial passaging in the routine culture system has not been fully elucidated.ResultsDPSCs were isolated from human/rat dental pulps by the magnetic activated cell sorting based on STRO-1 expression, cultured and passaged in the conventional culture media. The biological features of STRO-1+ DPSCs at the 1st and 9th passages were investigated. During the long-term passage, the proliferation ability of human STRO-1+ DPSCs was downregulated as indicated by the growth kinetics. When compared with STRO-1+ DPSCs at the 1st passage (DPSC-P1), the expression of mature osteoblast-specific genes/proteins (alkaline phosphatase, bone sialoprotein, osterix, and osteopontin), odontoblast-specific gene/protein (dentin sialophosphoprotein and dentin sialoprotein), and chondrocyte-specific gene/protein (type II collagen) was significantly upregulated in human STRO-1+ DPSCs at the 9th passage (DPSC-P9). Furthermore, human DPSC-P9 cells in the mineralization-inducing media presented higher levels of alkaline phosphatase at day 3 and day 7 respectively, and produced more mineralized matrix than DPSC-P9 cells at day 14. In vivo transplantation results showed that rat DPSC-P1 cell pellets developed into dentin, bone and cartilage structures respectively, while DPSC-P9 cells can only generate bone tissues.ConclusionsThese findings suggest that STRO-1+ DPSCs consist of several interrelated subpopulations which can spontaneously differentiate into odontoblasts, osteoblasts, and chondrocytes. The differentiation capacity of these DPSCs changes during cell passaging, and DPSCs at the 9th passage restrict their differentiation potential to the osteoblast lineage in vivo.

Effects of FGF2 and TGFβ1 on the differentiation of human dental pulp stem cells in vitro

Two crucial growth factors, FGF2 and TGFβ1, were investigated in this study to determine their inductive effects on the odontoblastic differentiation of human dental pulp stem cells (DPSCs) in vitro. DPSCs were isolated by immunomagnetic bead selection using the STRO‐1 antibody, and then co‐cultured respectively with FGF2, TGFβ1 and FGF2 + TGFβ1. The results showed that FGF2 can exert a significant effect on the cell proliferation, while TGFβ1 or FGF2 + TGFβ1 can initiate an odontoblast‐like differentiation of DPSCs. Moreover, FGF2 can synergistically upregulate the effects of TGFβ1 on the odontoblastic differentiation of DPSCs, as indicated by the increased alkaline phosphatase activity, the polarized cell appearance and secretary ultrastructural features, the formation of mineralized nodules and the gene/protein expression of dentin sialoprotein and dentin matrix protein‐1. Together, FGF2 acted primarily on the cell proliferation, while TGFβ1 and FGF2 + TGFβ1 mainly stimulated the odontoblastic differentiation of DPSCs. This study provides interesting progress in the odontoblastic differentiation of DPSCs induced by FGF2 and TGFβ1.

Current Approaches and Challenges in Making a Bio-Tooth

Tooth loss adversely affects not only mouth functions but also the esthetics of ones face. To repair these defects, current treatment methods mainly depend on nonbiological materials or artificial implants that also can, sometimes, reduce the quality of life because of their limited physiological function, or elicit an immunological rejection. Theoretically, a biological tooth (bio-tooth) that is made from the patients own cells and grows in its intended location should be the best choice for treating tooth loss, although such bioengineered teeth have been nothing more than a dream for many centuries. Recently, significant advances in the fields of tissue engineering, stem cell biology, developmental biology, molecular genetics, and bionics have brought us close to the realization of a bio-tooth. However, issues involving in the reconstruction of a bio-tooth regarding the shape determination, size control, availability of dental epithelium, directional growth and eruption, and graft rejection in the jaws remain to be resolved. Here, this review outlines the current approaches toward the tooth regeneration, and focuses on several key challenges that must be met in the making of a bio-tooth.

Epithelial-Mesenchymal Cell Ratios Can Determine the Crown Morphogenesis of Dental Pulp Stem Cells

Although dental pulp stem cells (DPSC) have been isolated from adult dental pulp tissues, knowledge on how to use them to make teeth lags behind. To date, little is known about the effects of epithelial-mesenchymal cell ratios on the bioengineered odontogenesis mediated by DPSCs. In this study, we investigated the effects of apical bud cells (ABC) from dental epithelial stem cell niche of rat incisors on the differentiation and morphogenesis of molar DPSCs at different proportions (DPSC/ABC cell ratios=1:10, 1:3, 1:1, 3:1, 10:1, respectively). In vitro mixed DPSCs/ABCs at 1:1, 1:3, and 3:1 ratios displayed several crucial characteristics of odontoblast/ameloblast lineages, as indicated by accelerated mineralization, upregulated alkaline phosphatase activity, protein/gene expression for dentin sialophosphoprotein and ameloblastin. In vivo transplantation of reassociated DPSC and ABC pellets at different ratios was also carried out. Histological analyses demonstrated that only DPSC/ABC recombinants at 1:1 ratio generated typical molar crown-shaped structures, whereas recombinations at other ratios presented an atypical crown morphogenesis with unbalanced distribution of amelogenesis and dentinogenesis. Together, these findings revealed that the proportions of dental epithelial and mesenchymal cell populations can determine the odontogenic differentiation of DPSCs/ABCs in vitro as well as the bioengineered tooth morphogenesis in vivo.

Cementum and Periodontal Ligament–like Tissue Formation Induced Using Bioengineered Dentin

Stem cell-mediated root regeneration offers opportunities to regenerate a bio-root and its associated periodontal tissues to restore tooth loss. Periodontal ligament (PDL) and cementum complex and dentin pulp complex have been tissue engineered using human dental pulp stem cells and PDL stem cells, respectively. The aim of this study was to explore whether dentin formation could be induced using an inductive substrate and whether bioengineered dentin could induce cementum and PDL formation. First, dentin was bioengineered from tooth papillae of Sprague-Dawley (SD) rats with an inductive substrate, and its phenotype was characterized; then primarily cultured human PDL cells were seeded on the surface of dentin and transplanted under the skin of immunocompromised mice. Histological, immunohistochemical, and scanning electronic microscopy examinations results showed that bioengineered dentin could induce cementogenesis and PDL formation, and condense PDL arranged perpendicularly on the dentin surface via a layer of cementum-like tissue. The results indicated that tissue-engineered dentin could be induced using an inductive substrate and could be used as a further substrate for cementum and PDL tissue engineering.