A comparative study of the application of three digital imaging techniques to assess the thickness of the palatal mucosa of the maxillary anterior teeth.

BACKGROUND: This study highlights the need for precise and efficient methods to measure palatal mucosal thickness in the maxillary anterior teeth, particularly for soft tissue augmentation in the aesthetic zone. The research evaluates three digital imaging techniques, suggesting that Cone Beam Computed Tomography (CBCT) combined with intraoral scanners (IOS) is a promising approach for reliable clinical assessment. METHODS: Ten volunteers with healthy periodontium were selected, and three methods were employed: CBCT-based indirect gingival imaging, modified soft tissue CBCT (ST-CBCT), and CBCT combined with IOS. Measurements of palatal mucosal thickness were taken at multiple points along the palatal gingival margin. Statistical analysis included Bland-Altman plots for method agreement and intraclass Correlation Coefficient (ICC) analysis for reliability. All measurements were standardized, repeated for consistency, and accurate to 0.01 mm to ensure reliability. RESULTS: The Bland-Altman plots showed that less than 5% of the points for palatal mucosal thickness differences measured by the gingival indirect radiographic method, modified ST-CBCT, and CBCT combined with IOS were located outside the 95% limits of agreement (LoA). The mean value of the differences was within 0.2 mm, indicating good clinical agreement among the three methods. The inter- and intra-study ICC values for palatal mucosal thickness measurements of the maxillary anterior teeth using the three CBCT methods were greater than 0.75 (P < 0.001), demonstrating reproducibility. CONCLUSIONS: Based on the evaluation of three digital imaging techniques, this study indicates that the combination of CBCT with IOS is a feasible method for measuring palatal mucosal thickness in the maxillary anterior teeth and demonstrates good reproducibility.

TAZ reverses the inhibitory effects of LPS on the osteogenic differentiation of human periodontal ligament stem cells through the NF-κB signaling pathway.

BACKGROUND: Human periodontal ligament stem cells (hPDLSCs) are important candidate seed cells for periodontal tissue engineering, but the presence of lipopolysaccharide(LPS) in periodontal tissues inhibits the self-renewal and osteogenic differentiation of hPDLSCs. Our previous studies demonstrated that TAZ is a positive regulator of osteogenic differentiation of hPDLSCs, but whether TAZ can protect hPDLSCs from LPS is still unknown. The present study aimed to explore the regulatory effect of TAZ on the osteogenic differentiation of hPDLSCs in an LPS-induced inflammatory model, and to preliminarily reveal the molecular mechanisms related to the NF-κB signaling pathway. METHODS: LPS was added to the culture medium of hPDLSCs. The influence of LPS on hPDLSC proliferation was analyzed by CCK-8 assays. The effects of LPS on hPDLSC osteogenic differentiation were detected by Alizarin Red staining, ALP staining, Western Blot and qRT-PCR analysis of osteogenesis-related genes. The effects of LPS on the osteogenic differentiation of hPDLSCs with TAZ overexpressed or knocked down via lentivirus were analyzed. NF-κB signaling in hPDLSCs was analyzed by Western Blot and immunofluorescence. RESULTS: LPS inhibited the osteogenic differentiation of hPDLSCs, inhibited TAZ expression, and activated the NF-κB signaling pathway. Overexpressing TAZ in hPDLSCs partly reversed the negative effects of LPS on osteogenic differentiation and inhibited the activation of the NF-κB pathway by LPS. TAZ knockdown enhanced the inhibitory effects of LPS on osteogenesis. CONCLUSION: Overexpressing TAZ could partly reverse the inhibitory effects of LPS on the osteogenic differentiation of hPDLSCs, possibly through inhibiting the NF-κB signaling pathway. TAZ is a potential target for improving hPDLSC-based periodontal tissue regeneration in inflammatory environments.

PSAT1 positively regulates the osteogenic lineage differentiation of periodontal ligament stem cells through the ATF4/PSAT1/Akt/GSK3ß/ß-catenin axis.

BACKGROUND: Periodontal ligament stem cells (PDLSCs) are important seed cells for tissue engineering to realize the regeneration of alveolar bone. Understanding the gene regulatory mechanisms of osteogenic lineage differentiation in PDLSCs will facilitate PDLSC-based bone regeneration. However, these regulatory molecular signals have not been clarified. METHODS: To screen potential regulators of osteogenic differentiation, the gene expression profiles of undifferentiated and osteodifferentiated PDLSCs were compared by microarray and bioinformatics methods, and PSAT1 was speculated to be involved in the gene regulation network of osteogenesis in PDLSCs. Lentiviral vectors were used to overexpress or knock down PSAT1 in PDLSCs, and then the proliferation activity, migration ability, and osteogenic differentiation ability of PDLSCs in vitro were analysed. A rat mandibular defect model was built to analyse the regulatory effects of PSAT1 on PDLSC-mediated bone regeneration in vivo. The regulation of PSAT1 on the Akt/GSK3ß/ß-catenin signalling axis was analysed using the Akt phosphorylation inhibitor Ly294002 or agonist SC79. The potential sites on the promoter of PSAT1 that could bind to the transcription factor ATF4 were predicted and verified. RESULTS: The microarray assay showed that the expression levels of 499 genes in PDLSCs were altered significantly after osteogenic induction. Among these genes, the transcription level of PSAT1 in osteodifferentiated PDLSCs was much lower than that in undifferentiated PDLSCs. Overexpressing PSAT1 not only enhanced the proliferation and osteogenic differentiation abilities of PDLSCs in vitro, but also promoted PDLSC-based alveolar bone regeneration in vivo, while knocking down PSAT1 had the opposite effects in PDLSCs. Mechanistic experiments suggested that PSAT1 regulated the osteogenic lineage fate of PDLSCs through the Akt/GSK3ß/ß-catenin signalling axis. PSAT1 expression in PDLSCs during osteogenic differentiation was controlled by transcription factor ATF4, which is realized by the combination of ATF4 and the PSAT1 promoter. CONCLUSION: PSAT1 is a potential important regulator of the osteogenic lineage differentiation of PDLSCs through the ATF4/PSAT1/Akt/GSK3ß/ß-catenin signalling pathway. PSAT1 could be a candidate gene modification target for enhancing PDLSCs-based bone regeneration.

Dasatinib regulates the proliferation and osteogenic differentiation of PDLSCs through Erk and EID3 signals.

Periodontal ligament stem cells (PDLSCs) are important candidate seed cells for alveolar bone tissue engineering. Dasatinib is a tyrosine kinase inhibitor, and its influence on the osteogenic differentiation of mesenchymal stem cells is a controversial topic. The present study explored the effects of different concentrations of dasatinib on the proliferation and osteogenic differentiation of PDLSCs and tentatively revealed the related mechanism. The results of CCK8 showed that low concentrations of dasatinib (1 nM) did not affect proliferation, while high concentrations of dasatinib significantly inhibited the proliferative activity of PDLSCs. This could be related to the inhibiting effects of dasatinib on Erk signals. ALP staining, alizarin red staining, and western blot proved that low concentrations of dasatinib (1 nM) promoted the osteogenic differentiation of PDLSCs, while high concentrations of dasatinib inhibited it. The negative effects of dasatinib on osteogenic differentiation were reversed when EID3 was knocked down, suggesting that EID3 mediates the regulation of dasatinib on the osteo-differentiation of PDLSCs. Taken together, high concentrations of dasatinib inhibited the proliferation and osteogenic differentiation of PDLSCs through Erk and EID3 signals, while low concentrations of dasatinib could be a potential method to enhance the bone regeneration ability of PDLSCs.

Analyses of key mRNAs and lncRNAs for different osteo-differentiation potentials of periodontal ligament stem cell and gingival mesenchymal stem cell.

Both human periodontal ligament stem cells (hPDLSCs) and human gingival mesenchymal stem cells (hGMSCs) are candidate seed cells for bone tissue engineering, but the osteo-differentiation ability of the latter is weaker than the former, and the mechanisms are unknown. To explore the potential regulation of mRNAs and long non-coding RNAs (lncRNAs), this study obtained the gene expression profiles of hPDLSCs and hGMSCs in both undifferentiated and osteo-differentiated conditions by microarray assay and then analysed the common and specific differentially expressed mRNAs and lncRNAs in hPDLSCs and hGMSCs through bioinformatics method. The results showed that 275 mRNAs and 126 lncRNAs displayed similar changing patterns in hPDLSCs and hGMSCs after osteogenic induction, which may regulate the osteo-differentiation in both types of cells. In addition, the expression of 223 mRNAs and 238 lncRNAs altered only in hPDLSCs after osteogenic induction, and 177 mRNAs and 170 lncRNAs changed only in hGMSCs. These cell-specific differentially expressed mRNAs and lncRNAs could underlie the different osteo-differentiation potentials of hPDLSCs and hGMSCs. Finally, dickkopf Wnt signalling pathway inhibitor 1 (DKK1) was proved to be one regulator for the weaker osteo-differentiation ability of hGMSCs through validation experiments. We hope these results help to reveal new mRNAs-lncRNAs-based molecular mechanism for osteo-differentiation of hPDLSCs and hGMSCs and provide clues on strategies for improving stem cell-mediated bone regeneration.

Metformin promotes osteogenic differentiation and protects against oxidative stress-induced damage in periodontal ligament stem cells via activation of the Akt/Nrf2 signaling pathway.

Periodontal ligament stem cell (PDLSC)-based tissue engineering is an important method for regenerating lost bone in periodontitis. Maintaining or enhancing the osteogenic differentiation of PDLSCs, as well as enhancing the resistance of PDLSCs to oxidative stress, is necessary in this process. As a common hypoglycemic drug, metformin has been reported to have multiple effects on cell functions. This study found that low concentrations of metformin did not affect cell proliferation but did inhibit adipogenic differentiation and promote osteogenic differentiation of PDLSCs. This positive effect was associated with activation of Akt signaling by metformin. Moreover, applying metformin as either a pretreatment or co-treatment could reduce the amount of reactive oxygen species, enhance antioxidant capacity, and rescue the cell viability and osteogenic differentiation that were negatively affected by H2O2-induced oxidative stress in PDLSCs. In addition, metformin was found to activate the Nrf2 signaling pathway in PDLSCs, and knockdown of Nrf2 by siRNA impaired the protective effect of metformin. Taken together, these results indicate that metformin not only promotes osteogenic differentiation of PDLSCs, but also protects PDLSCs against oxidative stress-induced damage, suggesting that metformin could be potentially useful in promoting PDLSC-based bone regeneration in the treatment of periodontitis.

Downregulation of Prolactin-Induced Protein Promotes Osteogenic Differentiation of Periodontal Ligament Stem Cells.

BACKGROUND Periodontal ligament stem cells (PDLSCs) are promising seed cells for bone tissue engineering and periodontal regeneration applications. However, the mechanism underlying the osteogenic differentiation process remains largely unknown. Previous reports showed that prolactin-induced protein (PIP) was upregulated after PDLSCs osteogenic induction. However, few studies have reported on the function of PIP in osteogenic differentiation. The purpose of the present study was to investigate the effect of PIP on osteogenic differentiation of PDLSCs. MATERIAL AND METHODS The expression pattern of PIP during PDLSCs osteogenic differentiation was detected and the effect of each component in the osteogenic induction medium on PIP was also tested by qRT-PCR. Then, the PIP knockdown cells were established using lentivirus. The knockdown efficiency was measured and the proliferation, apoptosis, and osteogenic differentiation ability were examined to determine the functional role of PIP on PDLSCs. RESULTS QRT-PCR showed that PIP was sustainedly upregulated during the osteogenic induction process and the phenomenon was mainly caused by the stimulation of dexamethasone in the induction medium. CCK-8 and flow cytometer showed that knocking down PIP had no influence on proliferation and apoptosis of PDLSCs. ALP staining and activity, Alizarin Red staining, and western blot analysis demonstrated PIP knockdown enhanced the osteogenic differentiation and mineralization of PDLSCs. CONCLUSIONS PIP was upregulated after osteogenic induction; however, PIP knockdown promoted PDLSCs osteogenic differentiation. PIP might be a by-product of osteogenic induction, and downregulating of PIP might be a new target in bone tissue engineering applications.

YAP balances the osteogenic and adipogenic differentiation of hPDLSCs in vitro partly through the Wnt/ß-catenin signaling pathway.

Human periodontal ligament stem cells (hPDLSCs) are potential seed cells for bone tissue engineering, but the molecular regulatory mechanisms of their multi-differentiation remain unclear. Here, we found that Yes-associated protein (YAP), a transcriptional coactivator in Hippo signaling pathway, regulated the multi-differentiation ability of hPDLSCs: overexpressing YAP contributed to an enhancement of osteogenic differentiation and a decrease in adipogenic differentiation, while knocking down YAP inhibited the osteogenic differentiation and promoted the adipogenic differentiation of hPDLSCs. In addition, YAP promoted the stabilization and nuclear transfer of ß-catenin in hPDLSCs, probably through regulating several upstream proteins of the Wnt/ß-catenin signaling pathway, including LRP6 and DVL3. Treatment with DKK1 or Wnt3a reversed the effects of overexpressing or knocking down YAP on non-phospho ß-catenin (stabilized ß-catenin) and cell differentiation. Taken together, YAP promoted osteogenic and inhibited adipogenic differentiation of hPDLSCs in vitro, which was partly via LRP6 and DVL3 mediated Wnt/ß-catenin signaling pathway. YAP could be a candidate regulatory target for facilitating the application of hPDLSCs in bone regeneration.

Activated Yes-Associated Protein Accelerates Cell Cycle, Inhibits Apoptosis, and Delays Senescence in Human Periodontal Ligament Stem Cells.

Objectives: To provide insight into the biological effects of activated Yes-associated protein (YAP) on the proliferation, apoptosis, and senescence of human periodontal ligament stem cells (h-PDLSCs). Methods: h-PDLSCs were isolated by the limiting dilution method, and their surface markers were quantified by flow cytometry. Enhanced green fluorescence protein (EGFP)-labeled lentiviral vector was used to activate YAP in h-PDLSCs, then qRT-PCR and Western blotting were used to evaluate the expression level of YAP. Immunofluorescence was used to detect the location of YAP in h-PDLSCs. The proliferation activity was detected by cell counting kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU), and the cell cycle was determined by flow cytometry. Apoptosis was analyzed by Annexin V-APC staining. Cell senescence was detected by ß-galactosidase staining. Proteins in ERK, Bcl-2, and p53 signaling pathways were detected by Western blotting. Results: h-PDLSCs were isolated successfully and were positive for human mesenchymal stem cell surface markers. After YAP was activated by lentiviral vector, the mRNA and protein of YAP were highly expressed, and more YAP translocated into the nucleus. When YAP was overexpressed in h-PDLSCs, proliferation activity was improved; early and late apoptosis rates decreased (P<0.05); the proportion of cells in G2/M phases increased (P<0.05), while that in G0/G1 phase decreased (P<0.05); cellular senescence was delayed (P<0.01); the expression of P-MEK, P-ERK, P-P90RSK and P-Msk increased, while the expression of Bcl-2 family members (Bak, Bid and Bik) decreased. Conclusions: Activated YAP promotes proliferation, inhibits apoptosis, and delays senescence of h-PDLSCs. The Hippo-YAP signaling pathway can influence ERK and Bcl-2 signaling pathways.

The Crosstalk between HDPSCs and HUCMSCs on Proliferation and Osteogenic Genes Expression in Coculture System.

Objectives: The present study established a non-contact coculture system in vitro, aiming to investigate the crosstalk between human dental pulp stem cells (hDPSCs) and human umbilical cord mesenchymal stem cells (hUCMSCs) on proliferation activity and osteogenic genes expression through paracrine. Materials and methods: The stemness of hDPSCs and hUCMSCs were identified by flow cytometric analysis and multipotential differentiation assays. With the help of transwell inserts, the non-contact coculture system in vitro was established between hDPSCs and hUCMSCs. EdU labeling analysis and Western Blot were used to detect the proliferation activity. The mRNA and protein levels of osteogenic genes were evaluated by RT-PCR and Western Blot. The expression of elements in Akt/mTOR signaling pathway were detected by Western Blot. Results: Both hDPSCs and hUCMSCs were positive to MSCs specific surface markers and had multi-differentiation potential. The proportion of EdU-positive cells increased and the expression of CDK6 and CYCLIN A were up-regulated in cocultured hDPSCs. Both prior coculture and persistent coculture improved mRNA and protein levels of osteogenic genes in hDPSCs. While in cocultured hUCMSCs, no statistical differences were observed on proliferation and osteogenesis. The phosphorylation of Akt and mTOR was up-regulated in cocultured hDPSCs. Conclusions: The crosstalk between hDPSCs and hUCMSCs in coculture system increased the proliferation activity and enhanced osteogenic genes expression in hDPSCs. Akt/mTOR signaling pathway might take part in the enhancing effects in both cell proliferation and gene expression.

Knockdown of Yes-Associated Protein Induces the Apoptosis While Inhibits the Proliferation of Human Periodontal Ligament Stem Cells through Crosstalk between Erk and Bcl-2 Signaling Pathways.

Objective: The purpose of this study was to provide an insight into the biological effects of knockdown Yes-associated protein (YAP) on the proliferation and apoptosis of human periodontal ligament stem cells (h-PDLSCs). Methods: Immunofluorescence and Western blot were used to evaluate Hippo-YAP signaling expression level. Enhanced green fluorescence protein lentiviral vector was constructed to down-regulate YAP in h-PDLSCs. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot were used to detect the interfering efficiency of YAP expression. The proliferation activity was detected by EdU staining. Analysis of apoptosis in h-PDLSCs was done through Annexin V-APC staining, while cell cycle analysis was detected by flow cytometry. Cellular senescence was analyzed by ß-galactosidase activity detection. The expression of elements in signaling pathways related with proliferation and apoptosis was detected by Western blot. Results: YAP was located in nucleus and cytoplasm. After the lentivirus transfection, the expression of YAP mRNA and protein was significantly reduced (P<0.001). When YAP was knocked down, the proliferation activity of h-PDLSCs was inhibited; the early & late apoptosis rates increased; the proportion of cells in G1 phases increased (P<0.05), while that in G2 and S phase decreased (P<0.05); cellular senescence was accelerated (P<0.01); ERK and its target proteins P-P90RSK and P-MEK were reduced while Bcl-2 family members increased. Conclusion: Knockdown of YAP inhibits the proliferation activity and induces apoptosis of h-PDLSCs with the involvement of Hippo pathway and has a crosstalk between Erk and Bcl-2 signaling pathways.

EID3 inhibits the osteogenic differentiation of periodontal ligament stem cells and mediates the signal transduction of TAZ-EID3-AKT/MTOR/ERK.

Exploring the molecular mechanisms of cell behaviors is beneficial for promoting periodontal ligament stem cell (PDLSC)-mediated tissue regeneration. This study intends to explore the regulatory effects of EID3 on cell proliferation, apoptosis, and osteogenic differentiation and to preliminarily explore the regulatory mechanism of EID3. Here, EID3 was overexpressed or knocked down in PDLSCs by recombinant lentivirus. Then, cell proliferation activity was analyzed by colony-forming assay, EdU assay, and cell cycle assay. Cell apoptosis was detected by flow cytometry. The osteo-differentiation potential was analyzed using ALP activity assay, ALP staining, alizarin red staining, and mRNA and protein assay of osteo-differentiation related genes. The results showed that when EID3 was knocked down, the proliferation activity and osteogenic differentiation potential of PDLSCs decreased, while they increased when EID3 was overexpressed. The cell apoptosis rate decreased in PDLSCs with EID3 knockdown but increased in PDLSCs with EID3 overexpression. Moreover, EID3 inhibited the transduction of the AKT/MTOR and ERK signaling pathway. In addition, TAZ negatively regulated the expression of EID3, and the overexpression of EID3 partially reversed the promotive effects of TAZ on the osteogenic differentiation of PDLSCs. Taken together, EID3 inhibits the proliferation and osteogenic differentiation while promoting the apoptosis of PDLSCs. EID3 inhibits the transduction of the AKT/MTOR and ERK signaling pathways and mediates the regulatory effect of TAZ on PDLSC osteogenic differentiation.

Diabetic and nondiabetic BMSC-derived exosomes affect bone regeneration via regulating miR-17-5p/SMAD7 axis.

Diabetic bone disease (DBD) is a complication of diabetes mellitus (DM) and is characterized by impaired osteocyte function and delayed bone remodeling due to high blood glucose levels and sustained release of inflammatory factors. Recent studies show that the regulation of osteoblasts (OBs) by bone marrow stromal cells (BMSCs) is an important mechanism in alleviating DBD and that exosomes are recognized as the key medium. Mesenchymal stem cell-derived exosome (MSC-Exos) therapy is a promising approach to facilitate tissue repair. However, the influence of exosomes from diabetic conditioned BMSCs on OBs and bone regeneration, as well as the underlying mechanism, are still elusive. Here, we used high-glucose medium to mimic diabetic conditions and normal-glucose medium as control to mimic nondiabetic conditions in vitro and found that microRNA-17 (miR-17) was downregulated in diabetic-conditioned BMSC-derived exosomes (HG-Exos), HG-Exo-co-cultured osteoblasts, and the skull of rats with type 2 diabetes mellitus (T2DM). Further experiment concluded that nondiabetic conditioned BMSC-Exos (NG-Exos) promoted the osteogenesis of OBs and bone regeneration of rats with T2DM via upregulation of miR-17. Compare with NG-Exos, HG-Exos impeded osteogenesis of OBs in vitro and bone regeneration of rats in vivo by downregulation of miR-17. Moreover, miR-17 promoted bone regeneration by targeting SMAD7, which was further proved to have a negative effect on osteogenesis. Taken together, nondiabetic BMSC-derived exosomes greatly foster bone regeneration, whereas diabetic BMSC-derived exosomes undermine the promotion effect of MSC-Exos by regulating the miR-17/SMAD7 axis. These findings provide support for the miR-17-5p/SMAD7 axis as a promising therapeutic target to treat DBD.

Microarray analysis of long non-coding RNAs related to osteogenic differentiation of human dental pulp stem cells.

Background/purpose: Dental pulp stem cells (DPSCs) are candidate seed cells for bone tissue engineering, but the molecular regulation of osteogenic differentiation in DPSCs is not fully understood. Long non-coding RNAs (lncRNAs) are important regulators of gene expression, and whether they play roles in osteogenic differentiation of DPSCs requires more study. Materials and methods: DPSCs were isolated and cultured. The mRNA and lncRNA expression profiles were compared through microarray assay between osteo-differentiated DPSCs and non-differentiated DPSCs. Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, Gene ontology (GO) analyses, and the mRNA-lncRNA co-expression analyses were performed for functional annotation of differentially expressed RNAs. Small interfering RNA (siRNA) was used to interfere the expression of lncRNA ENST00000533992 (also named smooth muscle-induced lncRNA or SMILR), a candidate regulator, then the osteogenic differentiation potential of DPSCs was analyzed. Results: DPSCs were isolated and cultured successfully. The expression of 273 mRNAs and 184 lncRNAs changed significantly in DPSCs after osteogenic induction. KEGG analyses and GO analyses showed that the differentially expressed RNAs were enriched in several pathways and biological processes. The mRNA-lncRNA co-expression network was constructed to reveal the potential relationships between mRNAs and lncRNAs. The osteogenic differentiation potential of DPSCs decreased when SMILR was interfered. Conclusion: The present study provides clues for seeking for lncRNAs that participate in the regulation of osteogenic differentiation in DPSCs. LncRNA SMILR could play a role in regulating osteogenic differentiation of DPSCs.

Quercetin reverses TNF­α induced osteogenic damage to human periodontal ligament stem cells by suppressing the NF­κB/NLRP3 inflammasome pathway.

Quercetin (Quer) is a typical antioxidant flavonoid from plants that is involved in bone metabolism, as well as in the progression of inflammatory diseases. Elevated levels of tumor necrosis factor­α (TNF­α), a typical pro­inflammatory cytokine, can affect osteogenesis. In the present study, TNF­α was used to establish an in vitro model of periodontitis. The effects of Quer on, as well as its potential role in the osteogenic response of human periodontal ligament stem cells (hPDLSCs) under TNF­α­induced inflammatory conditions and the underlying mechanisms were then investigated. Within the appropriate concentration range, Quer did not exhibit any cytotoxicity. More importantly, Quer significantly attenuated the TNF­α induced the suppression of osteogenesis­related genes and proteins, alkaline phosphatase (ALP) activity and mineralized matrix in the hPDLSCs. These findings were associated with the fact that Quer inhibited the activation of the NF­κB signaling pathway, as well as the expression of NLRP3 inflammation­associated proteins in the inflammatory microenvironment. Moreover, the silencing of NLRP3 by small interfering RNA (siRNA) was found to protect the hPDLSCs against TNF­α­induced osteogenic damage, which was in accordance with the effects of Quer. On the whole, the present study demonstrates that Quer reduces the impaired osteogenesis of hPDLSCs under TNF­α­induced inflammatory conditions by inhibiting the NF­κB/NLRP3 inflammasome pathway. Thus, Quer may prove to be a potential remedy against periodontal bone defects.

Rutin protects human periodontal ligament stem cells from TNF-α induced damage to osteogenic differentiation through suppressing mTOR signaling pathway in inflammatory environment.

OBJECTIVES: To investigate whether rutin could protect human periodontal ligament stem cells (hPDLSCs) from TNF-α induced damage to osteogenic differentiation in inflammatory environment and detect the underlying mechanism. MATERIALS AND METHODS: hPDLSCs were identified by flow cytometery. TNF-α was used to stimulate hPDLSCs to establish an inflammation model in vitro. Alkaline phosphatase (ALP) staining, ALP activity test, and Alizarin Red staining were used to detect the changes of osteogenic differentiation ability. The mRNA and protein levels of osteogenic genes were evaluated by RT-PCR and Western Blot. The expression of mTOR was also detected by Western Blot. RESULTS: hPDLSCs were positive to MSCs specific surface markers. The inflammatory environment in vitro could be established by stimulating hPDLSCs with TNF-α (20 ng/mL). TNF-α (20 ng/mL) could decrease the ALP activity and mineralization ability of hPDLSCs and down-regulate the expression of osteogenic genes in inflammatory environment. Moreover, rutin could affect TNF-α (20 ng/mL) induced damage to osteogenic differentiation of hPDLSCs in a dose-dependent manner, 10 µmol/L rutin could significantly reverse the damage caused by TNF-α. In addition, rutin inhibited TNF-α-activated mTOR signal transduction by inhibiting the phosphorylation of mTOR, similar to the effects of rapamycin(a specific mTOR inhibitor). CONCLUSIONS: Rutin could protect hPDLSCs from TNF-α induced damage to osteogenic differentiation in inflammatory environment, and rutin is expected to become a new candidate drug for the treatment of bone defect of periodontitis.

Curcumin promotes osteogenic differentiation of periodontal ligament stem cells through the PI3K/AKT/Nrf2 signaling pathway.

OBJECTIVES: The aim of this study was to investigate the effect of curcumin on the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) and its underlying potential mechanism. MATERIALS AND METHODS: The tissue explant adherence method was used to isolate hPDLSCs. Flow cytometry, Alizarin Red staining and Oil Red O staining were applied to confirm the stemness of the stem cells. CCK8 assays were used to evaluate the effect of curcumin at different concentrations on cytotoxicity, and alkaline phosphate (ALP) activity assays, ALP staining and Alizarin Red staining were used to measure the osteogenic differentiation ability. In addition, hPDLSCs were treated with LY294002 (a phosphatidylinositol-3-kinase [PI3K] inhibitor) and erythroid transcription factor NF-E2 siRNA (siNrf2), respectively in the presence of curcumin. Western blotting was applied to evaluate the protein kinase B (AKT) phosphorylation levels and the Nrf2 levels. Besides, western blotting, RT-qPCR, ALP activity assays, ALP staining and Alizarin Red staining were used to detect the potential effects of curcumin on osteogenic differentiation. RESULTS: Curcumin at an appropriate concentration had no cytotoxicity and could promote osteogenic differentiation of the hPDLSCs. The results of western blotting and RT-qPCR revealed that the protein and mRNA levels of ALP, COL1 and RUNX2 were increased by curcumin, while the PI3K/AKT/Nrf2 signaling pathway was activated. In addition, LY294002 was added to inhibit the PI3K/AKT signaling pathway, or siNrf2 was used to block the Nrf2 pathway; then, the stimulatory effects of curcumin on osteogenic differentiation were reversed. CONCLUSION: Curcumin could promote the osteogenesis of hPDLSCs, and the effect is related to the PI3K/AKT/Nrf2 signaling pathway.

Lipopolysaccharide from Escherichia coli stimulates osteogenic differentiation of human periodontal ligament stem cells through Wnt/ß-catenin-induced TAZ elevation.

Human periodontal ligament stem cells (PDLSCs), a type of dental tissue-derived mesenchymal stem cells (MSCs), can be clinically applied in periodontal tissue regeneration to treat periodontitis, which is initiated and sustained by bacteria. Lipopolysaccharide (LPS), the major component of the outer membrane of gram-negative bacteria, is a pertinent deleterious factor in the oral microenvironment. The aim of this study was to investigate the effect of LPS on the proliferation and osteogenic differentiation of PDLSCs, as well as the mechanisms involved. Proliferation and osteogenic differentiation of PDLSCs were detected under the stimulation of Escherichia coli-derived LPS. The data showed that E. coli-derived LPS did not affect the proliferation, viability, and cell cycle of PDLSCs. Furthermore, it promoted osteogenic differentiation with the activation of TAZ. Lentivirus-mediated depletion of TAZ (transcriptional activator with a PDZ motif) was used to determine the role of TAZ on LPS-induced enhancement of osteogenesis. PDLSCs cultured in osteogenic media with or without LPS and DKK1 (Wnt/ß-catenin pathway inhibitor) were used to determine the regulatory effect of Wnt signaling. We found that TAZ depletion offset LPS-induced enhancement of osteogenesis. Moreover, treatment with DKK1 offset LPS-induced TAZ elevation and osteogenic promotion. In conclusion, E. coli-derived LPS promoted osteogenic differentiation of PDLSCs by fortifying TAZ activity. The elevation and activation of TAZ were mostly mediated by the Wnt/ß-catenin pathway. PDLSC-governed alveolar bone tissue regeneration was not necessarily reduced under bacterial conditions and could be modulated by Wnt and TAZ.

Comparative analysis of lncRNA and mRNA expression profiles between periodontal ligament stem cells and gingival mesenchymal stem cells.

Oral tissue-derived mesenchymal stem cells, such as periodontal ligament stem cells (PDLSCs) and gingival mesenchymal stem cells (GMSCs), possess different biological characteristics, but the molecular mechanism remains unclear, which restricts their application in tissue engineering. Long noncoding RNAs (lncRNAs) are known to be significant regulators of gene expression, but our knowledge about their roles in the regulation of stem cell biological properties is still limited. This study compared the lncRNA and mRNA expression profiles between PDLSCs and GMSCs through microarray analysis, and applied bioinformatics methods to analyze and predict the function and connection of differentially expressed genes, aiming to screen potential key regulators of diverse biological characteristics in PDLSCs and GMSCs. Microarray analysis showed that 2162 lncRNAs and 1347 mRNAs were significantly differentially expressed between PDLSCs and GMSCs. Gene ontology (GO) analysis and pathway analysis indicated that these differentially expressed genes were involved in diverse biological processes and signaling pathways. The gene signal network and pathway relation network predicted some potentially important regulators. The coding-noncoding gene coexpression network (CNC network) revealed many potential lncRNA-mRNA connection pairs that participated in the regulation of biological behaviors. These results stressed the roles of lncRNAs in controlling stem cell biological behaviors and provided guides for molecular mechanistic study of different biological characteristics in PDLSCs and GMSCs.

Effect of 1α, 25-dihydroxyvitamin D3 on the osteogenic differentiation of human periodontal ligament stem cells and the underlying regulatory mechanism.

1α, 25­dihydroxyvitamin D3 (1,25­D3), an active vitamin D metabolite, is a well­known regulator of osteogenic differentiation. However, how 1,25­D3 regulates osteogenic differentiation in human periodontal ligament stem cells (hPDLSCs) remains to be fully elucidated. The present study aimed to clarify this issue through well­controlled in vitro experiments. After hPDLSCs were treated with 1,25­D3, immunofluorescence and western blotting were used to detect the expression of vitamin D receptor; Cell Counting Kit­8 and western blotting were used to assay the cell proliferation ability. Alkaline phosphatase staining, Alizarin Red staining and western blotting were used to detect the osteogenic differentiation. It was found that treating hPDLSCs with 1,25­D3: i) Inhibited cell proliferation; ii) promoted osteogenic differentiation; iii) upregulated the expression of transcriptional coactivator with PDZ­binding motif (TAZ), an important downstream effector of Hippo signaling that has been demonstrated to be involved in the osteogenic differentiation of stem/progenitor cells; and iv) that co­treatment of TAZ­overexpressing hPDLSCs with 1,25­D3 synergistically stimulated the expression of osteogenic markers. These results suggested that the induction of osteogenic differentiation promoted by 1,25­D3 in hPDLSCs involves, at least in part, the action of TAZ.