Dental follicle cells (DFCs) are a group of mesenchymal progenitor cells surrounding the tooth germ, responsible for cementum, periodontal ligament, and alveolar bone formation in tooth development. Cascades of signaling pathways and transcriptional factors in DFCs are involved in directing tooth eruption and tooth root morphogenesis. Substantial researches have been made to decipher multiple aspects of DFCs, including multilineage differentiation, senescence, and immunomodulatory ability. DFCs were proved to be multipotent progenitors with decent amplification, immunosuppressed and acquisition ability. They are able to differentiate into osteoblasts/cementoblasts, adipocytes, neuron-like cells, and so forth. The excellent properties of DFCs facilitated clinical application, as exemplified by bone tissue engineering, tooth root regeneration, and periodontium regeneration. Except for the oral and maxillofacial regeneration, DFCs were also expected to be applied in other tissues such as spinal cord defects (SCD), cardiomyocyte destruction. This article reviewed roles of DFCs in tooth development, their properties, and clinical application potentials, thus providing a novel guidance for tissue engineering.

The prognosis for successful treatment of periodontal diseases is generally poor. Current therapeutic strategies often fail to regenerate infected periodontium. Recently an alternative strategy has been developed that combines conventional treatment with the application of recombinant human growth factors (rhGFs). But ambiguities in existed studies on the clinical efficacy of rhGFs do not permit either the identification of the specific growth factors effective for therapeutic interventions or the optimal concentration of them. Neither is it known whether the same rhGF can stimulate regeneration of both soft tissue and bone, or whether different patient populations call for differential use of the growth factors. In order to explore these issues, a meta-analysis was carried out. Particular attention was given to the therapeutic impact of fibroblast growth factor 2(FGF-2) and platelet derived growth factor BB (PDGF-BB). Our findings indicate that 0.3% rhFGF-2 and 0.3 mg/ml rhPDGF-BB show a greater capacity for periodontal regeneration than other concentrations and superiority to control groups with statistical significance. In the case of patients suffering only from gingival recession, however, the application of rhPDGF-BB produces no significant regenerative advantage. The findings of this study can potentially endow clinicians with guidelines for the appropriate application of these two rhGFs.

The pulpotomy with pulp capping is aimed at retaining vital pulp with reparative dentin formation. Vascular endothelial growth factor (VEGF) plays a crucial role in dentin regeneration; however, its constant administrations in the human body is still problematic. Chitosan was widely studied as an effective carrier to deliver bioactive molecules in regenerative medicine. In this study, we conducted a chitosan/β-glycerophosphate (CS/β-GP) hydrogel as a VEGF-sustained release system and explored its effects on dental pulp stem cells (DPSCs). CS/β-GP hydrogel was manufactured using a sol-gel method. SEM assay showed the spongy and porous microstructure of the lyophilized hydrogels. DPSCs cultured in the CS/β-GP hydrogel kept adhesion and vitality. CCK-8 assay tested the promoted proliferation activity of DPSCs on the hydrogel. Besides, the added VEGF protein could continually release from VEGF/CS/β-GP hydrogel. The VEGF/CS/β-GP hydrogel could promote the odontogenic differentiation of DPSCs better than VEGF treatment without hydrogel. Our results suggested that CS/β-GP hydrogel could continually release VEGF and contribute to odontogenic differentiation of DPSCs, thus may become a potential carrier of bioactive molecules in pulp capping therapy.

Stem cells from the apical papilla (SCAPs) are important for the formation and regeneration of root dentin. Here, we examined the expression of Notch signaling components in SCAPs and investigated crosstalk between microRNA miR-34aand Notch signaling during cell differentiation. We found that human SCAPs express NOTCH2, NOTCH3, JAG2, DLL3, and HES1, and we tested the relationship between Notch signaling and both cell differentiation and miR-34a expression. NOTCH activation in SCAPs inhibited cell differentiation and up-regulated the expression of miR-34a, whereas miR-34a inhibited Notch signaling in SCAPs by directly targeting the 3′UTR of NOTCH2 and HES1 mRNA and suppressing the expression of NOTCH2, N2ICD, and HES1. DSPP, RUNX2, OSX, and OCN expression was consequently up-regulated. Thus, Notch signaling in human SCAPs plays a vital role in maintenance of these cells. miR-34a interacts with Notch signaling and promotes both odontogenic and osteogenic differentiation of SCAPs.

Objectives: The odontoblastic differentiation of dental pulp stem cells (DPSCs) contributes to tertiary dentin formation. Our previous study indicated that epiregulin (EREG) enhanced odontogenesis potential of dental pulp. Here, we explored the effects of EREG during DPSC odontoblastic differentiation.Methods: The changes in EREG were detected during tertiary dentin formation. DPSCs were treated with recombinant human EREG (rhEREG), EREG receptor inhibitor gefitinib and short hairpin RNAs. The odontoblastic differentiation was assessed with ALP staining, ALP activity assay, alizarin red S staining and real‐time RT‐PCR of DSPP, OCN, RUNX2 and OSX. Western blot was conducted to examine the levels of p38 mitogen‐activated protein kinase (p38 MAPK), c‐Jun N‐terminal kinase (JNK) and extracellular signal‐regulated kinase 1/2 (Erk1/2). The expression of EREG and odontoblastic differentiation‐related markers was investigated in human dental pulp from teeth with deep caries and healthy teeth.Results: Epiregulin was upregulated during tertiary dentin formation. rhEREG enhanced the odontoblastic differentiation of DPSCs following upregulated p38 MAPK and Erk1/2 phosphorylation, but not JNK, whereas depletion of EREG suppressed DPSC differentiation. Gefitinib decreased odontoblastic differentiation with decreased phosphorylation of p38 MAPK and Erk1/2. And suppression of p38 MAPK and Erk1/2 pathways attenuated DPSC differentiation. In human dental pulp tissue, EREG upregulation in deep caries correlates with odontoblastic differentiation enhancement.Conclusion: Epiregulin is released during tertiary dentin formation. And EREG enhanced DPSC odontoblastic differentiation via MAPK pathways.

Wnt/β-catenin signaling plays an important role in bone biology. The present study investigated the involvement of Wnt/β-catenin signaling in rat periapical bone destruction and whether lithium chloride (LiCl), a glycogen synthase kinase-3β (GSK-3β) inhibitor, promotes bone restoration. Rat bone marrow mesenchymal cells (BMMSCs) treated with Porphyromonas gingivalis lipopolysaccharide ( Pg LPS) showed decreased osteogenic potential through inhibited Wnt/β-catenin signaling as quantified by Western blot, immunofluorescence, and luciferase reporter assay. Transient Wnt3a treatment in vitro partially restored mineralization and Runx2/Osx and osteocalcin expression in cultures with Pg LPS-induced osteogenic arrest. Prolonged Wnt3a treatment impaired osteogenic commitment. X-ray microtomography showed dramatically enhanced periapical bone formation in rats gavage-fed with LiCl for 2 wks, while continuous LiCl treatment for 4 wks impaired periapical bone healing. LiCl treatment also increased GSK-3β phosphorylation and osteocalcin expression in periapical tissue. Collectively, these results indicate that Wnt/β-catenin has dichotomous functions in bone homeostasis. Modulation of this signaling pathway by LiCl may be a potential therapeutic option for bone destruction in endodontic disease.