Expression Of Dmp1 Research Articles

Ginsenoside RB1 Influences Macrophage–DPSC Interactions in Inflammatory Conditions

Unresolved inflammation and tissue destruction are supposed to underlie the failure of dental pulp repair. As crucial regulators of the injury response, dental pulp stem cells (DPSCs) play a key role in pulp tissue repair and regeneration. M2 macrophages have been demonstrated to induce osteogenic/odontogenic differentiation of DPSCs. Ginsenoside Rb1 (GRb1) is the major component of ginseng and manifested an anti-inflammatory role by promoting M1 macrophage polarised into M2 macrophage in inflammatory disease. However, whether GRb1 facilitates odontogenic differentiation of DPSCs via promoting M2 macrophage polarisation under inflammatory conditions has yet to be established. Human monocyte leukemic cells (THP-1) differentiated macrophages were induced into M1 subsets and then treated with GRb1. After that, the conditioned medium was added to DPSCs. The cell co-cultured system was then subjected to odontogenic differentiation in osteogenic media. Effects of GRb1 on human dental pulp stem cells' (hDPSCs') osteogenic/odontogenic differentiation under inflammatory conditions were assessed by alkaline phosphatase (ALP) staining, Alizarin Red S (ARS) staining, and quantitative polymerase chain reaction testing. Results demonstrated that GRb1 could facilitate the polarisation of macrophages from the M1 subtype to the M2 subtype. Conditioned medium from GRb1 + M1 macrophages, in comparison with M1 macrophages, may markedly increase the gene expression of ALP, DSPP, and DMP1. Moreover, ALP and ARS staining uncovered that the osteogenic/odontogenic differentiation ability of hDPSCs was strengthened in the M1 + GRb1 co-culture group. GRb1 plays a crucial role in the inflammatory response and reparative dentine formation after dental pulp injury. Findings show that GRb1 modulates the interaction between macrophages and DPSCs during inflammation. The current study discusses modifications of deep caries therapy.

BRF1 promotes the odontogenic differentiation of dental pulp stem cells in pulpitis by inducing autophagy

ObjectiveWhile post-transcriptional modifications play a pivotal role in the autophagy regulation, studies on dental pulp disease are limited. This study investigated the effect of BRF1 on autophagy in inflamed pulp tissue and human dental pulp stem cells (hDPSCs). MethodsImmunohistochemical analysis was used to examine BRF1 expression, autophagy levels, and dentinogenic markers in normal and inflamed pulp. The presence of autophagosomes was observed by transmission electron microscopy. Primary hDPSCs were treated with 1 μg/mL lipopolysaccharide (LPS) for different lengths of time. The expression of BRF1 and autophagy makers was determined by Western blotting. BRF1 knockdown and 3 MA treatment were employed to assess changes in autophagy and dentinogenic differentiation. Double immunofluorescence staining was performed to co-localize BRF1 with LC3B in pulp tissue. ResultsThe expressions of BRF1, LC3, DMP1, and DSP were significantly elevated in the inflamed pulp. LPS enhanced the protein production of IL-6, BRF1, LC3, and Beclin-1 from 6 h to 24 h after the treatment. BRF1 knockdown reduced the ratio of LC3-II/LC3-I and the differentiation ability of hDPSCs, while 3 MA inhibited LPS-mediated dentinogenic differentiation. Double-labeling revealed that BRF1 co-localized with LC3B in inflamed pulp. ConclusionThis study demonstrated that BRF1 promoted autophagy activation and odontogenic differentiation in pulpitis.

NRP1 promotes osteo/odontogenic differentiation via shroom3 in dental pulp stem cells

Neuropilin-1 (NRP1) is a single transmembrane glycoprotein involved in a variety of physiological events. However, the exact mechanisms by which NRP1 regulates dental pulp stem cells (DPSCs) to differentiate toward an osteo/odontogenic phenotype are poorly understood. Here, we determined the significantly increased expression of full-length NRP1 and glycosaminoglycan (GAG)-modified NRP1 during osteo/odontogenesis in DPSCs. NRP1 was confirmed to promote alkaline phosphatase (ALP) activity, mineralized nodule deposition, protein and mRNA expression of Runx2, DSPP and DMP1 in DPSCs via the loss-of-function and gain-of-function approaches. Further, a non-GAG-modified NRP1 mutant (NRP1 S612A) was generated and the suppression of osteo/odontogenic differentiation was observed in the NRP1 S612A overexpression cells. Knockdown of the adaptor protein shroom3 resulted in the inhibition of osteo/odontogenesis. The protein-protein interaction network, the protein-protein docking and confocal analyses indicated the interactions between NRP1 and shroom3. Furthermore, immunoprecipitation followed by western analysis confirmed the binding of NRP1 to shroom3, but overexpression of NRP1 S612A greatly influenced the recruitment of shroom3 by NRP1. These results provide strong evidence that NRP1 is a critical regulator for osteo/odontogenesis through interacting with shroom3. Moreover, our results indicate that NRP1 S612A attenuates osteo/odontogenesis, suggesting that GAG modification is essential for NRP1 in DPSCs.

Weighted Gene Co-expression Network Analysis (WGCNA) of Wnt Signaling Related to Periodontal Ligament Formation: A Bioinformatics-Based Analysis.

Introduction The Wnt signaling pathway is crucial for tooth development, odontoblast differentiation, and dentin formation. It interacts with epithelial cadherin (E-cadherin) and beta-catenin in tooth development and periodontal ligament (PDL) formation. Dysregulation of Wnt signaling is linked to periodontal diseases, requiring an understanding of therapeutic interventions. Weighted gene co-expression network analysis (WGCNA) can identify co-expressed gene modules. Our study aims to identify hub genes in WGCNA analysis of Wnt signaling-based PDL formation. Methods The study used a microarray datasetGSE201313 from the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus to analyze the impact of DMP1 expression on XLH dental pulp cell differentiation and PDL formation. The standardized dataset was used for WGCNA analysis, which generated a co-expression network by calculating pairwise correlations between genes and constructing an adjacency matrix. The topological overlap matrix (TOM) was transformed into a hierarchical clustering tree and then cut into modules or clusters of highly interconnected genes. The module eigengene (ME) was calculated for each module, and the genes within this module were identified as hub genes. Gene ontology (GO) and KEGG pathway enrichment analysis were performed to gain insights into the biological functions of the hub genes. The integrated Differential Expression and Pathway analysis (iDEP) tool (http://bioinformatics.sdstate.edu/idep/; South Dakota State University, Brookings, USA) was used for WGCNA analysis. Results The study used the WGCNA package to analyze 1,000 differentially expressed genes, constructing a gene co-expression network and generating a hierarchical clustering tree and TOM. The analysis reveals a scale-free topology fitting index R2 and mean connectivity for various soft threshold powers, with an R2 value of 5. COL6A1, MMP3, BGN, COL1A2, and FBN2 are hub genes implicated in PDL development. Conclusion The study identified key hub genes, including COL6A1, MMP3, BGN, and FBN2, crucial for PDL formation, tissue remodeling, and cell-matrix interactions, guiding future therapeutic strategies.

PIEZO1 Promotes Odontoblast-Mediated Reactionary Dentinogenesis via SEMA3A

Located at the interface of the dentin–pulp complex, the odontoblasts are specialized cells responsible for dentin synthesis and nociceptive signal detection in response to external stimuli. Recent studies have shown that the mechanosensitive ion channel PIEZO1 is involved in bone formation and remodeling through the influx of calcium ions, and it is abundantly expressed in odontoblasts. However, the specific role of PIEZO1 in reactionary dentinogenesis and the underlying mechanisms remain elusive. In this study, we found intense PIEZO1 expression in the plasma membrane and cytoplasm of odontoblasts in healthy human third molars, mouse mandibular molars, and human odontoblast-like cells (hOBLCs). In hOBLCs, PIEZO1 positively regulated DSPP, DMP1, and COL1A1 expression through the Ca2+/PI3K-Akt/SEMA3A signaling pathway. In addition, exogenous SEMA3A supplementation effectively reversed reduced mineralization capacity in PIEZO1-knockdown hOBLCs. In vivo, Piezo1 expression peaked at day 7 and returned to baseline at day 21 in a wild-type mice dentin injury model, with Sema3a presenting a similar expression pattern. To investigate the specific role of PIEZO1 in odontoblast-mediated reactionary dentinogenesis, mice with a conditional knockout of Piezo1 in odontoblasts were generated, and no significant differences in teeth phenotypes were observed between the control and conditional knockout (cKO) mice. Nevertheless, cKO mice exhibited reduced reactionary dentin formation and decreased Sema3a and Dsp positive staining after dentin injury, indicating impaired dental pulp repair by odontoblasts. In summary, these findings suggest that PIEZO1 enhances the mineralization capacity of hOBLCs in vitro via the Ca2+/PI3K-Akt/SEMA3A signaling pathway and contributes to reactionary dentinogenesis in vivo.

Biological evaluation of novel phosphorylated pullulan-based calcium hydroxide formulations as direct pulp capping materials: An invivo study on a rat model.

Calcium hydroxide (CH) has been considered as a direct pulp capping materials (DPC) for the last decades despite having some limitations. Phosphorylate pullulan (PPL) incorporated with CH (CHPPL) is a novel biomaterial that was introduced as a promising DPC material. Thus, the aim of the study was to evaluate the inflammatory response and mineralized tissue formation (MTF) ability of PPL-based CH formulations on rat molars after DPC. This study consisted of six groups: CH with 1% PPL (CHPPL-1); 3% PPL (CHPPL-3); 5% PPL (CHPPL-5); Dycal and NEX MTA Cement (N-MTA) as the positive control, and no capping materials (NC). One hundred twenty maxillary first molar cavities were prepared on Wistar rats. After capping, all the cavities were restored with 4-META/MMA-TBB resin and pulpal responses were evaluated at days 1, 7, and 28. Kruskal-Wallis followed by Mann-Whitney U-test was performed with a significance level of 0.05. Immunohistochemical expression of IL-6, Nestin, and DMP-1 was observed. At day 1, CHPPL-1, N-MTA, and Dycal exhibited no to mild inflammation, whilst CHPPL-3, CHPPL-5, and NC showed mild to moderate inflammation, and the results were significantly different (p < .05). At day 7, mild to moderate inflammation was observed in CHPPL-1, N-MTA, and Dycal, whereas CHPPL-3, CHPPL-5, and NC exhibited moderate to severe inflammation. Significant differences were observed between CHPPL-1 and N-MTA with NC (p < .05), CHPPL-1 and CHPPL-3 with CHPPL-5 and Dycal (p < .05), and CHPPL-3 with N-MTA (p < .05). A thin layer of mineralized tissue formation (MTF) was observed in all groups. At day 28, CHPPL-1, Dycal, and N-MTA showed no to mild inflammation, whilst CHPPL-3, CHPPL-5, and NC exhibited mild to severe inflammation, and statistically significant difference was detected (p < .05). CHPPL-1, Dycal, and N-MTA exhibited continuous MTF, whilst CHPPL-3, CHPPL-5, and NC had thicker and interrupted MTF. Significant differences were observed between CHPPL-1, CHPPL-3, and N-MTA with NC group (p < .05). Variable expressions of IL-6, Nestin, and DMP-1 indicated differences in the materials' impact on odontoblast-like cell formation and tissue mineralization. These findings suggest that CHPPL-1 has the potential to minimize pulpal inflammation and promote MTF and had similar efficacy as MTA cement.

Creating 3D constructs with cranial neural crest-derived cell lines using a bio-3D printer

ObjectivesThe development of bio-three-dimensional (bio-3D) printers has led to significant advances in regenerative medicine. Three-dimensional constructs, including spheroids, are maintained by extracellular matrix proteins secreted by cells so that the cells can be cultured in conditions closer to the physiological environment. This study aimed to create a useful 3D construct as a model of the dentin-pulp complex. MethodsWe examined the expression patterns of extracellular matrix proteins and cell proliferation areas in a 3D construct created using O9-1 cells derived from cranial neural crest cells of mice. The 3D construct was created by sticking the spheroid cultures onto a needle array using a bio-3D printer. ResultsCell proliferation areas along with characteristic expression of tenascin C and DMP1 were evaluated. The expression of tenascin C and DMP1 was significantly enhanced in the spheroids compared to that in two-dimensional cultures. Moreover, cell proliferation regions and tenascin C expression were confirmed in the outer layer of spheroids in the embryonic stem cell medium, with insignificant DMP1 expression being observed. Interestingly, in a 3D construct cultured in calcification-induction medium, DMP1 expression was promoted, and DMP1-positive cells existed in the outermost layer without overlapping with tenascin C expression. ConclusionsThe extracellular matrix proteins, tenascin C and DMP1, were expressed in a polarized manner in spheroids and 3D constructs, similar to the findings in the dental papilla. Therefore, these 3D constructs show potential as artificial models for studying odontogenesis.

Functionalization of PCL-Based Fiber Scaffolds with Different Sources of Calcium and Phosphate and Odontogenic Potential on Human Dental Pulp Cells.

This study investigated the incorporation of sources of calcium, phosphate, or both into electrospun scaffolds and evaluated their bioactivity on human dental pulp cells (HDPCs). Additionally, scaffolds incorporated with calcium hydroxide (CH) were characterized for degradation, calcium release, and odontogenic differentiation by HDPCs. Polycaprolactone (PCL) was electrospun with or without 0.5% w/v of calcium hydroxide (PCL + CH), nano-hydroxyapatite (PCL + nHA), or β-glycerophosphate (PCL + βGP). SEM/EDS analysis confirmed fibrillar morphology and particle incorporation. HDPCs were cultured on the scaffolds to assess cell viability, adhesion, spreading, and mineralized matrix formation. PCL + CH was also evaluated for gene expression of odontogenic markers (RT-qPCR). Data were submitted to ANOVA and Student's t-test (α = 5%). Added CH increased fiber diameter and interfibrillar spacing, whereas βGP decreased both. PCL + CH and PCL + nHA improved HDPC viability, adhesion, and proliferation. Mineralization was increased eightfold with PCL + CH. Scaffolds containing CH gradually degraded over six months, with calcium release within the first 140 days. CH incorporation upregulated DSPP and DMP1 expression after 7 and 14 days. In conclusion, CH- and nHA-laden PCL fiber scaffolds were cytocompatible and promoted HDPC adhesion, proliferation, and mineralized matrix deposition. PCL + CH scaffolds exhibit a slow degradation profile, providing sustained calcium release and stimulating HDPCs to upregulate odontogenesis marker genes.

Effects of exosomes derived from platelet-rich plasma on osteogenic differentiation of dental pulp stem cells.

Platelet-rich plasma (PRP) can cause osteogenic differentiation of dental pulp stem cells (DPSCs). However, the effect of exosomes derived from PRP (PRP-Exos) on osteogenic differentiation of DPSCs remains unclear. Herein, we evaluated the impact of PRP-Exos on osteogenic differentiation of DPSCs. PRP-Exos were isolated and identified by transmission electron microscopy (TEM) and western blotting (WB). Immunofluorescence staining was performed to evaluate endocytosis of PRP-Exos by DPSCs. Alkaline phosphatase staining, alizarin red staining, western blot and qRT-PCR were carried out to evaluate the DPSCs osteogenic differentiation. The sequencing microRNA (miRNA) was conducted to determine the microRNA profile of PRP-Exos treated and untreated DPSCs. The results showed that endocytosis of PRP-Exos stimulated DPSCs odontogenic differentiation by elevated expression of ALP, DMP-1, OCN, and RUNX2. ALP activity and calcified nodules formation of PRP-Exos treated DPSCs were considerably elevated relative to that of the control group. MicroRNA sequencing revealed that 112 microRNAs considerably varied in PRP-Exos treated DPSCs, of which 84 were elevated and 28 were reduced. Pathway analysis suggested that genes targeted by differentially expressed (DE) miRNAs were contributed to many signaling cascades, such as the Wnt cascade. 65 genes targeted by 30 DE miRNA were contributed to Wnt signaling. Thus, it can be infered that PRP-Exos could enhance osteogenic differentiation and alter the miRNA expression profile of DPSCs.

Periostin Is a Candidate Regulator of the Host Microenvironment in Regeneration of Pulp and Dentin Complex and Periodontal Ligament in Transplantation with Stem Cell-Conditioned Medium.

The microenvironment is required for tissues to maintain their properties in vivo. This microenvironment encompasses the types and three-dimensional arrangement of cells forming the tissues, and their interactions with neighboring cells and extracellular matrices, as represented by the stem cell niche. Tissue regeneration depends not on the original tissue source of the transplanted cells, but on the microenvironment in which they are transplanted. We have previously reported pulp regeneration in a heterotopic root graft model by transplantation of conditioned medium alone, which suggests that host-derived cells expressing receptors for migration factors in conditioned medium migrate into the root canal and cause pulp regeneration. Regenerative medicine is needed to restore the original function of complex tissues. To achieve this, it is necessary to reproduce the changes in the microenvironment of the host tissue that accompany the regenerative response. Therefore, it is important to reproduce the microenvironment in vivo for further development of tissue regeneration therapy. Periostin is also found in the epithelial-mesenchymal junction, with expression sites that differ depending on the mineralized matrix stage, and is involved in regulation of calcification. We investigate whether periostin contributes to microenvironmental changes in regenerated pulp tissue. Dental pulp stem cells were induced into dentin, and gene expression of DSPP, nestin, DMP1, Runx2, and periostin was analyzed by qPCR and protein expression by IHC. Similarly, gene expression was analyzed using qPCR and protein expression using IHC in regenerated dental pulp obtained by ectopic transplantation. Since these regenerated tissues were observable on the same slice, it was possible to understand changes in the microenvironment within the tissues. Periostin promoted proliferation of pulp stem cells, migration in type I collagen, and calcification in regenerated pulp, which strongly suggests that periostin is a promising candidate as a factor that contributes to the microenvironment of regenerated pulp.

TFEB regulates the odontoblastic differentiation of dental pulp stem cells by promoting a positive feedback loop between mitophagy and glycolysis

ObjectiveTo evaluate the regulatory effect of transcription factor EB (TFEB) on the odontoblastic differentiation of dental pulp stem cells(DPSCs) in vivo and in vitro. DesignsRNA-seq was used to detect differentially expressed genes in differentiated DPSCs. Lysosomes and the expression of the related gene TFEB were examined in DPSCs. DPSCs were then transfected with lentivirus for TFEB-overexpression. Cell proliferation was detected using CCK-8 and EdU assays, while cell differentiation was detected using ALP and ARS detection kits. Subsequently, mitophagy and cell metabolism were examined using TEM and Seahorse. An odontoblastic differentiation model was constructed subcutaneously in nude mice. Finally, the effects of glycolysis and mitophagy inhibitors were evaluated on odontoblastic differentiation and the associated mechanisms were explored. ResultsTFEB overexpression promoted a significant increase in ALP activity and the expression of differentiation-related genes in DPSCs, while it inhibited cell proliferation. In vivo, TFEB overexpression caused higher bone volume/trabecular volume(BV/TV), and an increase in collagen formation and heightened DMP-1 expression. Furthermore, Seahorse flux analysis demonstrated that TFEB promoted metabolic reprogramming. Transmission electron microscope(TEM) results indicated an increase in mitochondrial autophagosomes after TFEB overexpression, and the expression of mitophagy-related genes was also elevated. The odontoblastic differentiation of DPSCs promoted by TFEB overexpression was suppressed after the addition of 2-DG and Midiv-1. Addition of Midiv-1 reduced the glycolytic rate of DPSCs, while addition of 2-DG also decreased the mitophagy level of the cells. ConclusionsOur results showed that TFEB promoted the odontoblastic differentiation of DPSCs and identified mitophagy and metabolic reprogramming as a positive feedback loop.

The regenerative potential of Tideglusib and CHIR99021 small molecules as potent odontogenic differentiation enhancers of human dental pulp stem cells.

To assess the effect of Tideglusib and CHIR99021 small molecules on the odontogenic differentiation potential of human dental pulp stem cells (hDPSCs) via Wnt/β-catenin pathway activation. hDPSCs were isolated from impacted third molars indicated for extraction and were characterized by flow cytometry. hDPSCs were then induced to differentiate into odontogenic lineage in the presence of Tideglusib and CHIR99021. Odontogenic differentiation was evaluated using Alizarin Red stain and RT-PCR for expression of odontogenic specific differentiation markers: DSPP, DMP1, ALP, OPN, and RUNX2 in relation to undifferentiated cells. RT-PCR was also conducted to assess the expression of Wnt/β-catenin pathway activation marker (AXIN2). One-way ANOVA Kruskal-Wallis test was used for statistical analysis. Wnt/β-catenin pathway was successfully activated by Tideglusib and CHIR99021 in hDPSCs where AXIN2 was significantly upregulated. Successful odontogenic differentiation was confirmed by Alizarin Red staining of calcified nodules. RT-PCR for odontogenic differentiation markers DSPP, DMP1, and RUNX expression by hDPSCs induced by CHIR99021 was higher than that expressed by hDPSCs induced by Tideglusib, whereas expression of OPN and ALP was higher in Tideglusib-induced cells than in CHIR99021-induced cells. Both small molecules successfully induced odontogenic differentiation of hDPSCs through Wnt/β-catenin pathway activation. These findings suggest that Tideglusib and CHIR99021 can be applied clinically in pulp regeneration to improve strategies for vital pulp regeneration and to promote dentine repair.

Extracellular Fe2+ and Fe3+ modulate osteocytic viability, expression of SOST, RANKL and FGF23, and fluid flow-induced YAP1 nuclear translocation

Iron overload negatively affects bone mass and strength. However, the impact of iron excess on osteocytes—important bone cells for mechanotransduction and remodeling—is poorly understood. Herein, we examined the effects of iron exposure on osteocytes during their maturation process. We discovered that iron overload caused apoptosis of osteocytes in early and late stages of differentiation. Notably, the expression of key proteins for iron entry was downregulated during differentiation, suggesting that mature osteocytes were less susceptible to iron toxicity due to limited iron uptake. Furthermore, iron overload also enriched a subpopulation of mature osteocytes, as indicated by increased expression of Dmp1, a gene encoding protein for bone mineralization. These iron-exposed osteocytes expressed high levels of Sost, Tnfsf11 and Fgf23 transcripts. Consistently, we demonstrated that exogenous FGF23 stimulated the formation and survival of osteoclasts, suggesting its regulatory role in bone resorption. In addition, iron overload downregulated the expression of Cx43, a gene encoding gap junction protein in the dendritic processes, and impaired YAP1 nuclear translocation in response to fluid flow in differentiated osteocytes. It can be concluded that iron overload induces cellular adaptation in differentiating osteocytes, resulting in insensitivity to mechanical stimulation and potential disruption of the balance in bone remodeling.

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.

Phosphorylated pullulan promotes calcification during bone regeneration in the bone defects of rat tibiae.

The current study aimed to evaluate bone tissue regeneration using a combination of β-tricalcium phosphate (βTCP) and phosphorylated pullulan (PPL, a phosphate-rich polysaccharide polymer consisting of maltotriose units). Round defects of 2mm diameter were created in the arterial center of rat tibiae, which were further treated with vehicle (control group), βTCP (βTCP group), or βTCP + PPL (βTCP + PPL group) grafts. The control specimens without bone grafts exhibited rapid bone formation after 1week; however, the regenerated bone was not resorbed until 4weeks. In contrast, βTCP-grafted specimens exhibited fewer but thicker trabeculae, whereas the βTCP + PPL group displayed many fine trabeculae at 4weeks. In the βTCP + PPL group, new bone was associated with the βTCP granules and PPL. Similarly, PHOSPHO1-positive osteoblasts were localized on the βTCP granules as well as the PPL. On the other hand, TRAP-reactive osteoclasts predominantly localized on newly-formed bone and βTCP granules rather than on the PPL. No significant differences were observed in the expression of Alp, Integrin αv, Osteopontin, Osteocalcin, and Dmp-1 in PPL-treated MC3T3-E1 osteoblastic cells, suggesting that PPL did not facilitate osteoblastic differentiation. However, von Kossa staining identified abundant needle-like calcified structures extending inside the PPL. Furthermore, transmission electron microscopy (TEM) revealed many globular structures identical to calcified nodules. In addition, calcified collagen fibrils were observed in the superficial layer of the PPL. Thus, PPL may serve as a scaffold for osteoblastic bone formation and promotes calcification on its surface. In conclusion, we speculated that βTCP and PPL might promote bone regeneration and could be integrated into promising osteoconductive materials.

Absence of melatonin during development impairs craniofacial and dental onset in rats.

Herein, we evaluated pinealectomy-induced melatonin absence to determine its effects on craniofacial and dental development in the offspring. Female Wistar rats in three groups, i.e., intact pregnant rats, pinealectomized pregnant rats (PINX), and pinealectomized pregnant rats subjected to oral melatonin replacement therapy, were crossed 30days after surgery. The heads of 7-day-old pups were harvested for cephalometric and histological analyses, and maxillae and incisors were collected for mRNA expression analysis. The PINX pups exhibited a reduction in neurocranial and facial parameters such as a decrease in alveolar bone area, incisor size and proliferation, and an increase in odontoblasts and the dentin layer. Based on incisor mRNA expression analysis, we found that Dmp1 expression was upregulated, whereas Col1a1 expression was downregulated. Maxillary mRNA expression revealed that Rankl expression was upregulated, whereas that of Opn and Osx was downregulated. Our results demonstrated that the absence of maternal melatonin during early life could affect dental and maxillary development in offspring, as well as delay odontogenesis and osteogenesis in maxillary tissues. Our findings suggest that disruptions or a lack of melatonin during pregnancy may cause changes in craniofacial and dental development, at least in animal experiments; however, in humans, these feedings are still poorly understood, and thus careful evaluations of melatonin levels in humans need to be investigated in craniofacial alterations.

BDNF/TrkB Is a Crucial Regulator in the Inflammation-Mediated Odontoblastic Differentiation of Dental Pulp Stem Cells.

The odontoblastic differentiation of dental pulp stem cells (DPSCs) associated with caries injury happens in an inflammatory context. We recently demonstrated that there is a link between inflammation and dental tissue regeneration, identified via enhanced DPSC-mediated dentinogenesis in vitro. Brain-derived neurotrophic factor (BDNF) is a nerve growth factor-related gene family molecule which functions through tropomyosin receptor kinase B (TrkB). While the roles of BDNF in neural tissue repair and other regeneration processes are well identified, its role in dentinogenesis has not been explored. Furthermore, the role of BDNF receptor-TrkB in inflammation-induced dentinogenesis remains unknown. The role of BDNF/TrkB was examined during a 17-day odontogenic differentiation of DPSCs. Human DPSCs were subjected to odontogenic differentiation in dentinogenic media treated with inflammation inducers (LTA or TNFα), BDNF, and a TrkB agonist (LM22A-4) and/or antagonist (CTX-B). Our data show that BDNF and TrkB receptors affect the early and late stages of the odontogenic differentiation of DPSCs. Immunofluorescent data confirmed the expression of BDNF and TrkB in DPSCs. Our ELISA and qPCR data demonstrate that TrkB agonist treatment increased the expression of dentin matrix protein-1 (DMP-1) during early DPSC odontoblastic differentiation. Coherently, the expression levels of runt-related transcription factor 2 (RUNX-2) and osteocalcin (OCN) were increased. TNFα, which is responsible for a diverse range of inflammation signaling, increased the levels of expression of dentin sialophosphoprotein (DSPP) and DMP1. Furthermore, BDNF significantly potentiated its effect. The application of CTX-B reversed this effect, suggesting TrkB`s critical role in TNFα-mediated dentinogenesis. Our studies provide novel findings on the role of BDNF-TrkB in the inflammation-induced odontoblastic differentiation of DPSCs. This finding will address a novel regulatory pathway and a therapeutic approach in dentin tissue engineering using DPSCs.

PER2 Promotes Odontoblastic/Osteogenic Differentiation of Dental Pulp Stem Cells by Modulating Mitochondrial Metabolism.

Human dental pulp stem cells (hDPSCs) possess remarkable self-renewal and multilineage differentiation ability. PER2, an essential circadian molecule, regulates various physiological processes. Evidence suggests that circadian rhythm and PER2 participate in physiological functions of DPSCs. However, the influence of PER2 on DPSCs' differentiation remains largely unknown. This study aimed to explore the effect and potential mechanism of PER2 on hDPSCs' differentiation. Dental pulp tissues were extracted, and hDPSCs were cultured for in vitro and in vivo experiments. Dorsal subcutaneous transplantation was performed in 6-week-old male BALB/c mice. The hDPSCs' odontoblastic/osteogenic differentiation was assessed, and mitochondrial metabolism was evaluated. The results indicated PER2 expression increasing during hDPSCs' odontoblastic/osteogenic differentiation. Gain- and loss-of function studies confirmed that PER2 promoted alkaline phosphatase (ALP) activity, mineralized nodules deposition, mRNA expression of DSPP, DMP1, COL1A1 and protein expression of DSPP and DMP1 in hDPSCs. Furthermore, PER2 enhanced collagen deposition, osteodentine-like tissue formation and DSPP expression in vivo. Mitochondrial metabolic evaluation aimed to investigate the mechanism of PER2-mediated hDPSC odontoblastic/osteogenic differentiation, which showed that PER2 increased ATP synthesis, elevated mitochondrial membrane potential and changed expression of proteins regulating mitochondrial dynamics. This study demonstrated that PER2 promoted hDPSCs' odontoblastic/osteogenic differentiation, which involved mitochondrial metabolic change.

Notch1 is a marker for in situ resting osteocytes in a 3-dimensional gel culture model

ABSTRACT Purpose Osteocytes in vivo exhibit different functional states, but no specific marker to distinguish these is currently available. Materials and methods To simulate the differentiation process of pre-osteoblasts to osteocytes in vitro, MC3T3-E1 cells were cultured on type I collagen gel and a three-dimensional (3D) culture system was established. The Notch expression of osteocyte-like cells in 3D culture system was compared with that of in situ osteocytes in bone tissues. Results Immunohistochemistry demonstrated that Notch1 was not detected in “resting” in situ osteocytes, but was detected in normal cultured osteocyte-like cell line MLO-Y4. Osteocytes obtained from conventional osteogenic-induced osteoblasts and long-term cultured MLO-Y4 cells could not replicate the Notch1 expression pattern from in situ osteocytes. From day 14–35 of osteogenic induction, osteoblasts in 3D culture system gradually migrated into the gel to form canaliculus-like structures similar to bone canaliculus. On day 35, stellate-shaped osteocyte-like cells were observed, and expression of DMP1 and SOST, but not Runx2, was detected. Notch1 was not detected by immunohistochemistry, and Notch1 mRNA level was not significantly different from that of in situ osteocytes. In MC3T3-E1 cells, down-regulation of Notch2 increased Notch1, Notch downstream genes (β-catenin and Nfatc1), and Dmp1. In MLO-Y4 cells, Notch2 decreased after Notch1 siRNA transfection. Downregulation of Notch1 or Notch2 decreased Nfatc1, β-catenin, and Dmp1, and increased Sost. Conclusions We established “resting state” osteocytes using an in vitro 3D model. Notch1 can be a useful marker to help differentiate the functional states of osteocytes (activated vs. resting state).

FGF4 and FGF9 have synergistic effects on odontoblast differentiation.

The purpose of this study was to investigate whether fibroblast growth factor 4 (FGF4) and FGF9 are active in dentin differentiation. Dentin matrix protein 1 (Dmp1) -2A-Cre transgenic mice, which express the Cre-recombinase in Dmp1-expressing cells, were crossed with CAG-tdTomato mice as reporter mouse. The cell proliferation and tdTomato expressions were observed. The mesenchymal cell separated from neonatal molar tooth germ were cultured with or without FGF4, FGF9, and with or without their inhibitors ferulic acid and infigratinib (BGJ398) for 21days. Their phenotypes were evaluated by cell count, flow cytometry, and real-time PCR. Immunohistochemistry for FGFR1, 2, and 3 expression and the expression of DMP1 were performed. FGF4 treatment of mesenchymal cells obtained promoted the expression of all odontoblast markers. FGF9 failed to enhance dentin sialophosphoprotein (Dspp) expression levels. Runt-related transcription factor 2 (Runx2) was upregulated until day 14 but was downregulated on day 21. Compared to Dmp1-negative cells, Dmp1-positive cells expressed higher levels of all odontoblast markers, except for Runx2. Simultaneous treatment with FGF4 and FGF9 had a synergistic effect on odontoblast differentiation, suggesting that they may play a role in odontoblast maturation.