HIF-1α drives the transcription of NOG to inhibit osteogenic differentiation of periodontal ligament stem cells in response to hypoxia.

Osteogenic differentiation of periodontal ligament stem cells (PDLSCs) is limited in hypoxia, and HIF-1α is key to the response to hypoxia. However, its mechanisms remain largely unknown. This study discovered an osteogenesis-related gene sensitive to hypoxia in PDLSCs, and investigated the molecular mechanisms between HIF-1α and the gene. NOG, a gene that negatively regulates osteogenesis, was discovered by RNA-seq. Under normoxic conditions, HIF-1α overexpression led to enhanced expression of NOG/Noggin and inhibited the expression of osteogenesis-related genes, while inhibition of HIF-1α reversed this effect. The expression of HIF-1α, NOG/Noggin and the osteogenesis-related genes were detected by qRT-PCR or Western blot. Mechanistically, we verified that HIF-1α binds to the hypoxia response element (-1505 to -1502) in the promotor of NOG to enhance secretion of Noggin by chromatin immunoprecipitation and a dual-luciferase reporter assay. IHC staining findings in an animal model verified that Noggin-associated osteogenic differentiation was inhibited in hypoxia. NOG displayed a concordant relationship with HIF-1α, and secreted more with increasing of HIF-1α. Hypoxia stabilized HIF-1α, which bound to the HRE (-1505 to -1502) of the NOG promotor to enhance NOG transcription resulted in inhibiting osteogenic differentiation of PDLSCs. This study offers a promising therapy for periodontitis.

Efficacy of a four-curvature auxiliary arch at preventing maxillary central incisor linguoclination during orthodontic treatment: a finite element analysis.

BACKGROUND: Correct torque of the incisors is beneficial in the assessment of the effects of orthodontic treatment. However, evaluating this process effectively remains a challenge. Improper anterior teeth torque angle can cause bone fenestrations and exposure of the root surface. METHODS: A three-dimensional finite element model of the maxillary incisor torque controlled by a homemade four-curvature auxiliary arch was established. The four-curvature auxiliary arch placed on the maxillary incisors was divided into four different state groups, among which 2 groups had tooth extraction space retracted traction force set to 1.15 N. Initial displacements and pressure stresses of the periodontal tissue in the maxillary incisors and molars were calculated after torque forces (0.5, 1, 1.5, and 2 N) were applied to the teeth at different stable states. RESULTS: The effect of using the four-curvature auxiliary arch on the incisors was significant but did not affect the position of the molars. Given the absence of tooth extraction space, when the four-curvature auxiliary arch was used in conjunction with absolute anchorage, the recommended force value was < 1.5 N. In the other 3 groups (i.e., molar ligation, molar retraction, and microimplant retraction groups), the recommended force value was < 1 N. The application of a four-curvature auxiliary arch did not influence the molar periodontal and displacement. CONCLUSION: A four-curvature auxiliary arch may treat severely upright anterior teeth and correct cortical fenestrations of the bone and root surface exposure.

p75NTR optimizes the osteogenic potential of human periodontal ligament stem cells by up-regulating α1 integrin expression.

Human periodontal ligament stem cells (hPDLSCs) are a promising source in regenerative medicine. Due to the complexity and heterogeneity of hPDLSCs, it is critical to isolate homogeneous hPDLSCs with high regenerative potential. In this study, p75 neurotrophin receptor (p75NTR) was used to isolate p75NTR+ and p75NTR- hPDLSCs by fluorescence-activated cell sorting. Differences in osteogenic differentiation among p75NTR+ , p75NTR- and unsorted hPDLSCs were observed. Differential gene expression profiles between p75NTR+ and p75NTR- hPDLSCs were analysed by RNA sequencing. α1 Integrin (ITGA1) small interfering RNA and ITGA1-overexpressing adenovirus were used to transfect p75NTR+ and p75NTR- hPDLSCs. The results showed that p75NTR+ hPDLSCs demonstrated superior osteogenic capacity than p75NTR- and unsorted hPDLSCs. Differentially expressed genes between p75NTR+ and p75NTR- hPDLSCs were highly involved in the extracellular matrix-receptor interaction signalling pathway, and p75NTR+ hPDLSCs expressed higher ITGA1 levels than p75NTR- hPDLSCs. ITGA1 silencing inhibited the osteogenic differentiation of p75NTR+ hPDLSCs, while ITGA1 overexpression enhanced the osteogenic differentiation of p75NTR- hPDLSCs. These findings indicate that p75NTR optimizes the osteogenic potential of hPDLSCs by up-regulating ITGA1 expression, suggesting that p75NTR can be used as a novel cell surface marker to identify and purify hPDLSCs to promote their applications in regenerative medicine.

Oxysophocarpine Retards the Growth and Metastasis of Oral Squamous Cell Carcinoma by Targeting the Nrf2/HO-1 Axis.

BACKGROUND/AIMS: Nuclear factor erythroid 2-related factor 2 (Nrf2) is an oncogene in various types of cancers, including oral squamous cell carcinoma (OSCC). Oxysophocarpine (OSC) is a natural alkaloid that has multiple pharmacological activities. However, the biological functions and molecular mechanism underlying the effects of OSC on the growth and metastasis of OSCC are unclear. METHODS: Nrf2 levels were determined in OSCC tissues and non-cancerous specimens by quantitative real-time PCR, western blotting, and immunohistochemistry (IHC) assays. The effects of OSC on OSCC cell growth and metastasis were explored (1) using 5-ethynyl-20-deoxyuridine staining and Cell Counting Kit-8, colony formation, flow cytometry, wound-healing, Transwell, and tube formation assays in vitro; and (2) by establishing a xenograft nude mouse model in vivo. The molecular mechanisms underlying the effects of OSC on the growth and metastasis of OSCC were investigated in vitro by western blotting, caspase-3 activity, and enzyme-linked immunosorbent assays, and in vivo by western blotting and IHC assays. RESULTS: The expression levels of Nrf2 in OSCC tissues and in cell lines were much higher than in non-cancerous tissues and normal oral keratinocytes. The upregulation of Nrf2 was positively correlated with a high incidence of lymph node metastasis and advanced histological grade and TNM stage, but inversely associated with differentiation and survival of OSCC patients. OSC reduced the expression of Nrf2 and heme oxygenase 1 (HO-1) in OSCC cells. OSC also inhibited proliferation, migration, invasion, and pro-angiogenesis of OSCC cells. Moreover, OSC induced cell cycle arrest, enhanced apoptosis of OSCC cells in vitro, and decreased OSCC tumor growth in vivo. Mechanically, OSC reduced the aggressive behavior of OSCC cells by inactivation of the Nrf2/HO-1 signaling pathway. CONCLUSION: Our findings provide evidence that OSC inhibits the growth and metastasis of OSCC by targeting the Nrf2/ HO-1 axis, suggesting that OSC may be a potential therapeutic agent for OSCC.

The root canal morphology in mandibular first premolars: a comparative evaluation of cone-beam computed tomography and micro-computed tomography.

OBJECTIVES: This study evaluated the accuracy of cone-beam computed tomography (CBCT) in detecting the root canal morphology of mandibular first premolars using micro-computed tomography (micro-CT) as a reference standard. MATERIALS AND METHODS: In total, 143 extracted human mandibular first premolars were selected and scanned using micro-CT and CBCT. The acquired images were used to evaluate the root canal morphology in each tooth, and evaluations were repeated after 2 weeks. The root canal configurations observed on the three-dimensional images were recorded, and the findings from both modalities were compared using chi-square tests. The actual agreement between the two modalities was assessed using kappa statistics. RESULTS: In total, the root morphologies in 136 mandibular first premolars were consistently identified by both CBCT and micro-CT: type I in 104, type III in five, type V in 20, and type IX in seven. Of the remaining seven teeth, the morphology in two, one, and four teeth was identified as type I, type VII, and type IX (type 1-3 in two and type 1-2-3 in two), respectively, by micro-CT and misdiagnosed as type III, type V, and type V, respectively, by CBCT. There were no significant differences between the two modalities with regard to the accurate detection of root canal configurations, with a kappa value of 0.886 for the actual agreement. CONCLUSIONS: Although CBCT may be accurate in detecting the root canal configuration in mandibular first premolars, it produces poorer image details compared with micro-CT. CLINICAL RELEVANCE: CBCT is a reliable radiological technique, but its accuracy in detecting details of the root canal morphology in mandibular first premolars, especially in some complex root canal configurations, needs to be improved.

COX-2 rs689466, rs5275, and rs20417 polymorphisms and risk of head and neck squamous cell carcinoma: a meta-analysis of adjusted and unadjusted data.

BACKGROUND: Numerous case-control studies have been performed to investigate the association between three cyclooxygenase-2 (COX-2) polymorphisms (rs20417 (-765G > C), rs689466 (-1195G > A), and rs5275 (8473 T > C)) and the risk of head and neck squamous cell carcinoma (HNSCC). However, the results were inconsistent. Therefore, we conducted this meta-analysis to investigate the association. METHODS: We searched in PubMed, Embase, and Web of Science up to January 20, 2015 (last updated on May 12, 2016). Two independent reviewers extracted the data. Odds ratios (ORs) with their 95 % confidence intervals (CIs) were used to assess the association. All statistical analyses were performed using the Review Manager (RevMan) 5.2 software. RESULTS: Finally 8 case-control studies were included in this meta-analysis. For unadjusted data, an association with increased risk was observed in three genetic models in COX-2 rs689466 polymorphism; however, COX-2 rs5275 and rs20417 polymorphisms were not related to HNSCC risk in this study. The pooled results from adjusted data all revealed non-significant association between these three polymorphisms and risk of HNSCC. We also found a similar result in the subgroup analyses, based on both unadjusted data and adjusted data. CONCLUSION: Current results suggest that COX-2 rs689466, rs5275, and rs20417 polymorphisms are not associated with HNSCC. Further large and well-designed studies are necessary to validate this association.

In vitro cementoblast-like differentiation of postmigratory neural crest-derived p75(+) stem cells with dental follicle cell conditioned medium.

Cranial neural crest-derived cells (CNCCs) play important role in epithelial-mesenchymal interactions during tooth morphogenesis. However, the heterogeneity of CNCCs and their tendency to spontaneously differentiate along smooth muscle or osteoblast lineages in vitro limit further understanding of their biological properties. We studied the differentiation properties of isolated rat embryonic postmigratory CNCCs, expressing p75 neurotrophin receptor (p75NTR). These p75NTR positive (p75(+)) CNCCs, isolated using fluorescence activated cell sorter, exhibited fibroblast-like morphology and characteristics of mesenchymal stem cells. Incubation of p75(+) CNCCs in dental follicle cell conditioned medium (DFCCM) combined with dentin non-collagenous proteins (dNCPs), altered their morphological features to cementoblast-like appearance. These cells also showed low proliferative activity, high ALP activity and significantly increased calcified nodule formation. Markers related to mineralization or specific to cementoblast lineage were highly expressed in dNCPs/DFCCM-treated p75(+) cells, suggesting their differentiation along cementoblast-like lineage. p75(+) stem cells selected from postmigratory CNCCs represent a pure stem cell population and could be used as a stem cell model for in vitro studies due to their intrinsic ability to differentiate to neuronal cells and transform from neuroectoderm to ectomesenchyme. They can provide a potential stem cell resource for tooth engineering studies and help to further investigate mechanisms of epithelial-mesenchymal interactions in tooth morphogenesis.

A micro-computed tomography study of the relationship between radicular grooves and root canal morphology in mandibular first premolars.

OBJECTIVES: This study aims to explore the correlation between radicular grooves and root canal types by quantitatively detecting the radicular groove of mandibular first premolars using micro-computed tomography. MATERIALS AND METHODS: A total of 127 mandibular first premolars were scanned by micro-computed tomography, and 52 teeth with radicular grooves were identified. Details of root canal type and groove length, depth, and location were analyzed from three-dimensional images. RESULTS: A total of 40.9 % (52/127) of teeth had radicular grooves. Most of the grooves (69.5 %) were located on the mesial surface of the root. The prevalence of radicular grooves in single canals (17.4 %; 15/86) was lower than that in multiple and complex canals (90.2 %; 37/41); this difference was statistically significant (P < 0.001). The mean length and depth of radicular groove in type V (7.7 ± 2.16 and 0.87 ± 0.39 mm, respectively) and other types of canals (6.91 ± 2.67 and 0.63 ± 0.27 mm, respectively) were significantly longer and deeper than type I canals (6.06 ± 2.12 and 0.43 ± 0.14 mm, respectively). CONCLUSIONS: Multiple and complex canals had a higher incidence of radicular grooves and more complicated root morphology than single and simple canals. Therefore, the anatomy of radicular grooves may influence root canal morphology. CLINICAL RELEVANCE: The existence of a radicular groove is closely related to root anatomy and root canal morphology. Anatomical complexity increases the difficulty of root canal treatment and periodontal therapy; therefore, the current data may provide clinicians with a more thorough understanding of the relationship between radicular grooves and root canal morphology.

Artificial intelligence in dentistry: A bibliometric analysis from 2000 to 2023.

Background/purpose: Artificial intelligence (AI) is reshaping clinical practice in dentistry. This study aims to provide a comprehensive overview of global trends and research hotspots on the application of AI to dentistry. Materials and methods: Studies on AI in dentistry published between 2000 and 2023 were retrieved from the Web of Science Core Collection. Bibliometric parameters were extracted and bibliometric analysis was conducted using VOSviewer, Pajek, and CiteSpace software. Results: A total of 651 publications were identified, 88.7 % of which were published after 2019. Publications originating from the United States and China accounted for 34.5 % of the total. The Charité Medical University of Berlin was the institution with the highest number of publications, and Schwendicke and Krois were the most active authors in the field. The Journal of Dentistry had the highest citation count. The focus of AI in dentistry primarily centered on the analysis of imaging data and the dental diseases most frequently associated with AI were periodontitis, bone fractures, and dental caries. The dental AI applications most frequently discussed since 2019 included neural networks, medical devices, clinical decision support systems, head and neck cancer, support vector machine, geometric deep learning, and precision medicine. Conclusion: Research on AI in dentistry is experiencing explosive growth. The prevailing research emphasis and anticipated future development involve the establishment of medical devices and clinical decision support systems based on innovative AI algorithms to advance precision dentistry. This study provides dentists with valuable insights into this field.

p75NTR antibody-conjugated microspheres: an approach to guided tissue regeneration by selective recruitment of endogenous periodontal ligament cells.

Repairing defects in alveolar bone is essential for regenerating periodontal tissue, but it is a formidable challenge. One promising therapeutic approach involves using a strategy that specifically recruits periodontal ligament cells (PDLCs) with high regenerative potential to achieve in situ regeneration of alveolar bone. In this study, we have created a new type of microsphere conjugated with an antibody to target p75 neurotrophin receptor (p75NTR), which is made of nano-hydroxyapatite (nHA) and chitosan (CS). The goal of this design is to attract p75NTR+hPDLCs selectively and promote osteogenesis. In vitro experiments demonstrated that the antibody-conjugated microspheres attracted significantly more PDLCs compared to non-conjugated microspheres. Incorporating nHA not only enhances cell adhesion and proliferation on the surface of the microsphere but also augments its osteoinductive properties. Microspheres effectively recruited p75NTR+ cells at bone defect sites in SD rats, as observed through immunofluorescent staining of p75NTR antibodies. This p75NTR antibody-conjugated nHA/CS microsphere presents a promising approach for selectively recruiting cells and repairing bone defects.

The Fgfr2(S252W/+) mutation in mice retards mandible formation and reduces bone mass as in human Apert syndrome.

Apert syndrome is a common craniosynostosis caused by gain-of-function missense mutations of fibroblast growth factor receptor 2 (FGFR2). Mice with the FGFR2 S252W mutation can elucidate the mechanism by which the human Apert syndrome phenotypes arise. However, many studies have focused on mutant skull and long bone malformation, only few studies have focused on mandible changes. Bone formation and micro-architecture between 28- and 56-day-old mutant mice and controls were compared to investigate the changes in the mandibular micro-architecture caused by the Fgfr2(S252W/+) mutation to provide a basis for exploring the pathogenesis and therapeutic measures of human Apert syndrome. Fgfr2(S252W/+) mutant mice were established, and their general characteristics, including weight, naso-anal length, and calcium and phosphate content in serum and bone were tested. Calcein labeling, tartrate-resistant acid phosphatase staining and toluidine blue staining were used to detect osteoblast and osteoclast activities. H&E staining and micro-CT detection were used to test micro-architecture changes. The changes in mineral apposition rate and micro-architecture of the Fgfr2(S252W/+) mice were statistically significant; however, the magnitude of the micro-architecture became less with age. The Fgfr2(S252W/+) mutation may retard mandibular bone formation, decreased bone volume, and compromised skeletal architecture by regulating both osteoblastogenesis and osteoclastogenesis.

Global Trends and Hotspots in Research on Tooth Agenesis: A 20-Year Bibliometric Analysis.

Tooth agenesis, one of the most common developmental defects in humans, not only impairs oral function but can also lead to craniofacial deformities. Bibliometric analysis can reveal significant shifts in research and publishing trends within specific fields. This study aims to provide a comprehensive overview of the research hotspots in tooth agenesis and predict future trends through bibliometric analysis. We searched for English-language publications related to tooth agenesis from 2001 to 2021 on the Web of Science. The publications were limited to original and review articles, and bibliometric parameters such as publication year, country, institution, author, journal, citations, and keywords were extracted and analyzed using VOSviewer, Microsoft Excel 2010, and CiteSpace. A total of 2,287 papers were ultimately selected. The results show that the USA holds a leading position in the field of tooth agenesis research. A total of 9,803 authors participated in these studies, with Alexandre R Vieira from the USA being the most prolific and most cited author. This study indicates that multidisciplinary management has become the consensus first choice for treating dental agenesis. Gene mutations related to tooth agenesis continue to be a research hotspot attracting scholarly attention. Exploring the relationship between tooth agenesis and cancer may be a future research direction. These findings contribute to potential collaborations among experts in future research on the genetic causes of tooth agenesis and tumor development and to assist the scientific community by identifying research gaps in this field.

[Measurement of cortical bone thickness of zygomatic alveolar ridge in adolescents by Cone-beam CT and its correlation with cervical vertebral bone age].

PURPOSE: To measure the cortical bone thickness of zygomatic alveolar ridge in adolescents and explore the correlation between cortical bone thickness and cervical vertebral bone age. METHODS: Cone-beam CT data of 80 adolescents were collected, including 20 adolescents with cervical vertebral bone ages of Cvs3, Cvs4, Cvs5 and Cvs6, respectively. CBCT images were reconstructed with the maxillary occlusal plane as the reference plane. Cortical bone thickness of different slices in the left maxillary zygomatic alveolar ridge area was measured in the direction parallel to and 60° from the reference plane, and the measured data were statistically analyzed by SPSS 21.0 software package. RESULTS: When the measurement direction was parallel to the reference plane and at 60°, the cortical bone thickness in the zygomatic alveolar ridge area of Cvs3-Cvs6 adolescents was (0.90±0.09) -(1.72±0.21) mm and (1.35±0.44)-(3.98±1.48) mm, respectively. There was significant difference in cortical bone thickness between Cvs4 and Cvs5 group(P＜0.05). Spearman correlation analysis showed a strong positive correlation(P＜0.01) between cortical bone thickness of zygomatic alveolar ridge and cervical vertebral bone age in adolescents. CONCLUSIONS: The cortical bone thickness of zygomatic alveolar ridge in adolescents increases with the increase of cervical vertebral bone age, and the cortical bone thickness may increase significantly during Cvs4-Cvs5. In terms of cortical bone thickness, all slices of zygomatic alveolar ridge of CVS3-CVS6 adolescents are suitable for implanting miniscrews, and the anterior slices should be selected for implantation as far as possible for Cvs3 and Cvs4 adolescents.

p75NTR promotes tooth rhythmic mineralization via upregulation of BMAL1/CLOCK.

The circadian clock plays a critical role in dentomaxillofacial development. Tooth biomineralization is characterized by the circadian clock; however, the mechanisms underlying the coordination of circadian rhythms with tooth development and biomineralization remain unclear. The p75 neurotrophin receptor (p75NTR) is a clock factor that regulates the oscillatory components of the circadian rhythm. This study aims to investigate the impact of p75NTR on the rhythmic mineralization of teeth and elucidate its underlying molecular mechanisms. We generated p75NTR knockout mice to examine the effects of p75NTR deficiency on tooth mineralization. Ectomesenchymal stem cells (EMSCs), derived from mouse tooth germs, were used for in vitro experiments. Results showed a reduction in tooth mineral density and daily mineralization rate in p75NTR knockout mice. Deletion of p75NTR decreased the expression of DMP1, DSPP, RUNX2, and ALP in tooth germ. Odontogenic differentiation and mineralization of EMSCs were activated by p75NTR. Histological results demonstrated predominant detection of p75NTR protein in odontoblasts and stratum intermedium cells during rapid formation phases of dental hard tissue. The mRNA expression of p75NTR exhibited circadian variations in tooth germs and EMSCs, consistent with the expression patterns of the core clock genes Bmal1 and Clock. The upregulation of BMAL1/CLOCK expression by p75NTR positively regulated the mineralization ability of EMSCs, whereas BMAL1 and CLOCK exerted a negative feedback regulation on p75NTR by inhibiting its promoter activity. Our findings suggest that p75NTR is necessary to maintain normal tooth biomineralization. Odontogenic differentiation and mineralization of EMSCs is regulated by the p75NTR-BMAL1/CLOCK signaling axis. These findings offer valuable insights into the associations between circadian rhythms, tooth development, and biomineralization.

Characterization of p75(+) ectomesenchymal stem cells from rat embryonic facial process tissue.

Several populations of stem cells, including those from the dental pulp and periodontal ligament, have been isolated from different parts of the tooth and periodontium. The characteristics of such stem cells have been reported as well. However, as a common progenitor of these cells, ectomesenchymal stem cells (EMSCs), derived from the cranial neural crest have yet to be fully characterized. The aim of this study was to better understand the characteristics of EMSCs isolated from rat embryonic facial processes. Immunohistochemical staining showed that EMSCs had migrated to rat facial processes at E11.5, while the absence of epithelial invagination or tooth-like epithelium suggested that any epithelial-mesenchymal interactions were limited at this stage. The p75 neurotrophin receptor (p75NTR), a typical neural crest marker, was used to select p75NTR-positive EMSCs (p75(+) EMSCs), which were found to show a homogeneous fibroblast-like morphology and little change in the growth curve, proliferation capacity, and cell phenotype during cell passage. They also displayed the capacity to differentiate into diverse cell types under chemically defined conditions in vitro. p75(+) EMSCs proved to be homogeneous, stable in vitro and potentially capable of multiple lineages, suggesting their potential for application in dental or orofacial tissue engineering.

Effects of systemic ornidazole, systemic and local compound ornidazole and pefloxacin mesylate on experimental periodontitis in rats.

BACKGROUND: The purpose of the current study is to evaluate the effects of systemic ornidazole (SO) and systemic and local compound ornidazole and pefloxacin mesylate (SCOPM/LCOMP) on the inflammatory response associated with rat experimental chronic periodontitis (ECP) in sites with subgingival debridement. MATERIAL/METHODS: Periodontitis was induced in male Sprague-Dawley rats by placing a thin steel ligature around the upper first molars and inoculating them with Porphyromonas gingivalis 381. After the successful induction of the rat ECP, the periodontitis rats were randomly divided into 3 different combined treatment groups: (A) SO with scaling and root planing (SRP); (B) SCOMP with SRP; and (C) LCOMP with SRP. After 2 weeks the effects of the treatments were evaluated based on gingivitis, plaque index, probing pocket depth, aspartate aminotransferase, alveolar bone loss, and hematoxylin-eosin staining of the region around the first molars. RESULTS: After treatment, comparison with ECP was performed. The mean percentage reductions of SBI in SO, SCOPM, and LCOPM were 27.73%, 33.61%, and 58.82%, respectively. Those of PI were 33.20%, 42.80%, and 60.00%; those of PPD were 48.66%, 55.70%, and 72.48%; those of GCF-AST were 41.64%, 49.03%, and 66.42%; and those of ABL were 41.19%, 43.63%, and 54.47%, respectively. The inflammatory score of H&E showed median scores of 2.5, 1.75, 1.63, and 0.95 for ECP, SO, SCOMP, and LCOMP, respectively. All 3 treatment groups exhibited significantly reduced inflammation indicators (P<0.05). Of the 3, group C was the most effective (P<0.05). CONCLUSIONS: Although all the combined treatment groups responded to therapy with significant resolution of the infection, adjunctive LCOMP therapy is more effective for periodontitis.

Dynamic expression of Mage-D1 in rat dental germs and potential role in mineralization of ectomesenchymal stem cells.

Mage-D1 (MAGE family member D1) is involved in a variety of cell biological effects. Recent studies have shown that Mage-D1 is closely related to tooth development, but its specific regulatory mechanism is unclear. The purpose of this study was to investigate the expression pattern of Mage-D1 in rat dental germ development and its differential mineralization ability to ectomesenchymal stem cells (EMSCs), and to explore its potential mechanism. Results showed that the expression of Mage-D1 during rat dental germ development was temporally and spatially specific. Mage-D1 promotes the proliferation ability of EMSCs but inhibits their migration ability. Under induction by mineralized culture medium, Mage-D1 promotes osteogenesis and tooth-forming ability. Furthermore, the expression pattern of Mage-D1 at E19.5 d rat dental germ is similar to p75 neurotrophin receptor (p75NTR), distal-less homeobox 1 (Dlx1) and msh homeobox 1 (Msx1). In addition, Mage-D1 is binding to p75NTR, Dlx1, and Msx1 in vitro. These findings indicate that Mage-D1 is play an important regulatory role in normal mineralization of teeth. p75NTR, Dlx1, and Msx1 seem to be closely related to the underlying mechanism of Mage-D1 action.

A potential role of p75NTR in the regulation of circadian rhythm and incremental growth lines during tooth development.

Objective: Tooth morphogenesis and the formation of hard tissues have been reported to be closely related to circadian rhythms. This study investigates the spatiotemporal expression and relationship of p75NTR with core clock genes, mineralization-related or odontogenesis-related genes, and aims to derive the potential role of p75NTR in regulating circadian rhythm and incrementality growth line formation during tooth development. Materials and methods: The dynamic morphology of the rat dental germ was observed at seven stages (E14.5 d, E16.5 d, E18.5 d, P.N. 4 d, P.N. 7 d, P.N. 10 d, and P.N. 15 d). Next, the expressions of p75NTR and other target factors were traced. The ectomesenchymal stem cells (EMSCs) were isolated from the E18.5d rat dental germs and synchronized using 50% of fetal bovine serum. Then, they were cultured in light/light (L.L.), dark/dark (D.D.), and light/dark (L.D.) conditions for 48 h. The total RNA was collected every 4 h, and the circadian rhythm dynamics of target factors were observed. To reveal the mechanism further, p75NTR was down-regulated in p75NTR ExIII-/- mice and up-regulated in immortalized mouse dental apical papilla progenitor cells. The change tendencies of other target factors were also detected. Results: The clock genes Bmal1, Clock, Per1, and Per2 were all expressed in tooth germs before the formation of dental hard tissues and demonstrated a regular oscillating expression pattern in EMSCs from dental germs. Their expression was affected by the L.D. stimulus, and most of them were promoted by D.D. conditions. p75NTR presented a similar expression pattern and a positive or negative relationship with most clock genes, mineralization-related and odontogenesis-related factors, such as brain and muscle ARNT-like protein-1 (Bmal1), runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), MSH-like 1 (MSX1), dentin matrix acidic phosphoprotein 1 (Dmp1), and dentin sialophosphoprotein (Dspp). Moreover, the arrangement, morphology, and even boundary in pre-odontoblast/pre-ameloblast layers were disordered in the p75NTR ExIII-/- mice. Conclusion: Circadian rhythm was found to affect tooth development. p75NTR might play a crucial role in regulating clock genes in the mineralization and formation of the dental hard tissues. p75NTR is actively involved in the odontoblast-ameloblast junction and cell polarity establishment during tooth morphogenesis.

Adipose tissue-deprived stem cells acquire cementoblast features treated with dental follicle cell conditioned medium containing dentin non-collagenous proteins in vitro.

Adipose tissue-derived stem cells (ADSCs), which are easily harvested and show excellent pluripotency potential, have generated considerable interest in regenerative medicine. In this study, the differentiation of ADSCs was assessed after treatment with dental follicle cell conditioned medium (DFCCM) containing dentin non-collagenous proteins (dNCPs). ADSCs exhibited a fibroblast-like morphology and high proliferative capacity. However, after treatment with dNCPs/DFCCM, ADSCs changed from a fibroblast-like to cementoblast-like morphology and significantly lost their proliferative capacity. Alkaline phosphatase activity and in vitro mineralization behaviour of ADSCs were significantly enhanced. Mineralization-related markers including cementum attachment protein, bone sialoprotein, osteocalcin, osteopontin and osteonectin were detected at mRNA or protein levels, whereas dentin sialophosphoprotein and dentin sialoprotein were not detected, implying a cementoblast-like phenotype. These results demonstrate that ADSCs acquired cementoblast features in vitro with dNCPs/DFCCM treatment and could be a potential source of cementogenic cells for periodontal regeneration.