Notch Signaling Participates in TGF-β-Induced SOST Expression Under Intermittent Compressive Stress

MicroRNA expression in JAG1/Notch-activated periodontal ligament stem cells

OBJECTIVES

The study explored the expression profile of miRNAs in Notch-activated periodontal ligament stem cells (PDLSCs) and examined their potential cellular targets.

METHODS

PDLSCs were cultured and treated with indirect immobilized Jagged1. The miRNA expression profile was examined using NanoString analysis. Bioinformatic analysis was performed together with enrichment, and miRNA expression was evaluated and validated using a quantitative polymerase chain reaction (qPCR).

RESULTS

A total of 26 miRNAs were differentially expressed in Jagged1 treated PDLSCs compared with the controls. Pathway analysis revealed that altered miRNAs were significantly associated with the transforming growth factor β (TGF-β) signaling pathway. Target prediction analysis demonstrated that 11,170 genes as predictable targets of these altered miRNAs. Enrichment of predicted target genes revealed that they were related to ErbB, Ras and MAPK signaling pathways and small GTPase transduction.

CONCLUSIONS

The research concludes that several miRNAs are differentially expressed in jagged-1 treated PDLSCs. In translational terms the differential functionality of these miRNAs offer promise for the development of targeted regenerative materials that are necessary for managing lost tissue replacement in periodontal diseases.

Effects of continuous and released compressive force on osteoclastogenesis invitro

Objective

Compressive force has been found to be catabolic to alveolar bone during orthodontic tooth movement. This study quantified the fusion of mononuclear RAW 264.7 cells (a murine osteoclastic-like cell line) into multinucleated osteoclasts under a hydrostatic pressure-generated mechanical compression-the new model of various magnitudes and durations.

Methods

RAW 264.7 cells were subjected to 0.3, 0.6 or 0.9 g/cm2 of compressive force by an acrylic cylinder custom-made by laser cutting or no compressive force for 4 days during osteoclastogenic induction. TRAP-positive multinucleated cells were quantified. For the release from force experiment, osteoclastogenesis was induced by 0.6 g/cm2 mechanical stimuli for 0, 1, 2, 3 or 4 days. Cell viability, TRAP-positive multinucleated cells, DCSTAMP and Cathepsin K (CTSK) gene expression were evaluated 4 days after release from force.

Results

Compressive force at 0.6 and 0.9 g/cm2 significantly increase the number of TRAP-positive multinucleated cells (P < 0.05). Release from continuous mechanical compression after 4 days significantly elevated the number of TRAP-positive multinucleated cells and DCSTAMP and CTSK mRNA expression, with no adverse effects on cell viability (P < 0.05).

Conclusions

Continuous stimulation with compressive force induced osteoclastogenesis in RAW 264.7 cells by enhancing DCSTAMP and CTSK expression, which provides new understanding of bone remodeling during orthodontic treatment.

Intermittent compressive force regulates dentin matrix protein 1 expression in human periodontal ligament stem cells

Background/purpose

Mechanical force differentially regulates periodontal ligament functions depending on types, magnitudes, and duration of stimulation. Intermittent compressive force (ICF) promotes an in vitro mineralization in human periodontal ligament cells. The present study investigated the effect of ICF on dentin matrix protein-1 (DMP1) expression in human periodontal ligament stem cells (hPDLSCs).

Materials and methods

Cells were treated with ICF in a serum-free culture medium for 24 h The mRNA and protein expression were examined using real-time polymerase chain reaction, immunofluorescence staining and Western blot analysis, respectively.

Results

The exposure to ICF in a serum-free condition significantly induced DMP1 expression in both mRNA and protein levels. The effect of ICF-induced DMP1 expression was inhibited by pretreatment with cycloheximide, indicating the requirement of the intermediated molecule(s). Pretreatment with transforming growth factor β (TGF-β) receptor inhibitor (SB431542) or neutralized antibody against TGF-β1 prior to ICF application abolished the effect of ICF-induced DMP1 expression. Further, recombinant TGF-β1 treatment stimulated DMP1 expression.

Conclusion

The present study illustrated that ICF induces DMP1 expression in hPDLSCs via the regulation of TGF-β signaling pathway.

Intermittent compressive force regulates human periodontal ligament cell behavior via yes-associated protein

Intermittent compressive force influences human periodontal ligament (PDL) cell behavior that facilitates periodontal tissue regeneration. In response to mechanical stimuli, Yes-associated protein (YAP) has been recognized as a mechanosensitive transcriptional activator that regulates cell proliferation and cell fate decisions. This study aimed to investigate whether compressive forces influence cell proliferation and cell fate decisions of human PDL cells via YAP signaling. YAP expression was silenced by shRNA. The effect of YAP on cell proliferation, adipogenesis and osteogenesis of PDL cells under ICF loading were determined. Adipogenic differentiation bias upon ICF loading was confirmed by fourier-transform infrared spectroscopy (FTIR). The results revealed that ICF-induced YAP promotes osteogenesis, but it inhibits adipogenesis in PDL cells. Depletion of YAP results in PDL cells that are irresponsive to ICF and, therefore, the failure of the PDL cells to undergo osteogenic differentiation. This was shown by a significant reduction in calcium deposited in the CF-derived osteoblasts of the YAP-knockdown (YAP-KD) PDL cells. As to control treatment, reduction of YAP promoted adipogenesis, whereas ICF-induced YAP inhibited this mechanism. However, the adipocyte differentiation in YAP-KD cells was not affected upon ICF treatment as the YAP-KD cells still exhibited a better adipogenic differentiation that was unrelated to the ICF. This study demonstrated that, in response to ICF treatment, YAP could be a crucial mechanosensitive transcriptional activator for the regulation of PDL cell behavior through a mechanobiological process. Our results may provide the possibility of facilitating PDL tissue regeneration by manipulation of the Hippo-YAP signaling pathway.

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YAP plays role as a mechanosensitive transcriptional activator of human PDL cells in response to ICF.

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ICF activates YAP and its target genes to promote cell proliferation and osteogenic differentiation of human PDL cells.

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Loss of YAP enhances adipogenic differentiation of human periodontal ligament cells.

Responses of canine periodontal ligament cells to bubaline blood derived platelet rich fibrin in vitro

Platelet-rich fibrin (PRF) promotes wound healing by providing the release of growth factors. Here, the influence of Thai and Murrah bubaline blood derived PRF on canine periodontal ligament cells (cPDLs) was investigated. PRF was prepared from Thai and Murrah buffaloes with single centrifugation. Results demonstrated that Thai bubaline blood derived PRF exhibited fiber-mesh like morphology and contained more platelet entrapment than Murrah bubaline blood derived PRF. Both bubaline PRFs were able to degrade in vitro under condition with trypsin. Thai but not Murrah bubaline blood derived PRF promoted cPDLs proliferation in serum free and 2% serum culture conditions. Correspondingly, the significant upregulation of KI67 mRNA expression was observed in those cells treated with Thai bubaline blood derived PRF. However, both Thai and Murrah bubaline blood derived PRF accelerated cell migration in an in vitro wound healing assay and facilitated cell spreading. Further, cPDLs cultured in osteogenic induction medium supplemented with Thai bubaline blood derived PRF exhibited the increased mineral deposition in vitro. Frozen Thai bubaline blood derived PRF also promoted cell proliferation, KI67 mRNA expression, cell migration, and cell spreading in cPDLs. Taken these evidence together, bubaline blood derived PRF could provide potential benefits for canine periodontal tissue healing.

Notch-ing up knowledge on molecular mechanisms of skin fibrosis: focus on the multifaceted Notch signalling pathway

Fibrosis can be defined as an excessive and deregulated deposition of extracellular matrix proteins, causing loss of physiological architecture and dysfunction of different tissues and organs. In the skin, fibrosis represents the hallmark of several acquired (e.g. systemic sclerosis and hypertrophic scars) and inherited (i.e. dystrophic epidermolysis bullosa) diseases. A complex series of interactions among a variety of cellular types and a wide range of molecular players drive the fibrogenic process, often in a context-dependent manner. However, the pathogenetic mechanisms leading to skin fibrosis are not completely elucidated. In this scenario, an increasing body of evidence has recently disclosed the involvement of Notch signalling cascade in fibrosis of the skin and other organs. Despite its apparent simplicity, Notch represents one of the most multifaceted, strictly regulated and intricate pathways with still unknown features both in health and disease conditions. Starting from the most recent advances in Notch activation and regulation, this review focuses on the pro-fibrotic function of Notch pathway in fibroproliferative skin disorders describing molecular networks, interplay with other pro-fibrotic molecules and pathways, including the transforming growth factor-β1, and therapeutic strategies under development.

Mechanical loading and the control of stem cell behavior

OBJECTIVE

Mechanical stimulation regulates many cell responses. The present study describes the effects of different in vitro mechanical stimulation approaches on stem cell behavior.

DESIGN

The narrative review approach was performed. The articles published in English language that addressed the effects of mechanical force on stem cells were searched on Pubmed and Scopus database. The effects of extrinsic mechanical force on stem cell response was reviewed and discussed.

RESULTS

Cells sense mechanical stimuli by the function of mechanoreceptors and further transduce force stimulation into intracellular signaling. Cell responses to mechanical stimuli depend on several factors including type, magnitude, and duration. Further, similar mechanical stimuli exhibit distinct cell responses based on numerous factors including cell type and differentiation stage. Various mechanical applications modulate stemness maintenance and cell differentiation toward specific lineages.

CONCLUSIONS

Mechanical force application modulates stemness maintenance and differentiation. Modification of force regimens could be utilized to precisely control appropriate stem cell behavior toward specific applications.

Designing Biomaterials to Modulate Notch Signaling in Tissue Engineering and Regenerative Medicine

The design of cell-instructive biomaterials for tissue engineering and regenerative medicine is at a crossroads. Although the conventional tissue engineering approach is top-down (cells seeded to macroporous scaffolds and mature to form tissues), bottom-up tissue engineering strategies are becoming appealing. With such developments, we can study cell signaling events, thus enabling functional tissue assembly in physiologic and diseased models. Among many important signaling pathways, the Notch signaling pathway is the most diverse in its influence during tissue morphogenesis and repair following injury. Although Notch signaling is extensively studied in developmental biology and cancer biology, our knowledge of designing biomaterial-based Notch signaling platforms and incorporating Notch signaling components into engineered tissue systems is limited. By incorporating Notch signaling to tissue engineering scaffolds, we can direct cell-specific responses and improve engineered tissue maturation. This review will discuss recent progress in the development of Notch signaling biomaterials as a promising target to control cellular fate decisions, including the influences of ligand identity, biophysical material cues, ligand presentation strategies, and mechanotransduction. Notch signaling is consequently of interest to direct, control, and reprogram cellular behavior on a biomaterial surface. We anticipate that discussions in this article will allow for enhanced knowledge and insight into designing Notch targeted biomaterials for various tissue engineering and cell fate determinations. Impact statement Notch signaling is recognized as an important pathway in tissue engineering and regenerative medicine; however, there is no systematic review on this topic. The comprehensive review and perspectives presented here provide an in-depth discussion on ligand presentation strategies both in 2D and in 3D cell culture environments involving biomaterials/scaffolds. In addition, this review article provides insight into the challenges in designing cell surrogate biomaterials capable of providing Notch signals. To the best of the authors' knowledge, this is the first review relevant to the fields of tissue engineering.

NOTCH2 participates in Jagged1-induced osteogenic differentiation in human periodontal ligament cells

Jagged1 activates Notch signaling and subsequently promotes osteogenic differentiation in human periodontal ligament cells (hPDLs). The present study investigated the participation of the Notch receptor, NOTCH2, in the Jagged1-induced osteogenic differentiation in hPDLs. NOTCH2 and NOTCH4 mRNA expression levels increased during hPDL osteogenic differentiation. However, the endogenous NOTCH2 expression levels were markedly higher compared with NOTCH4. NOTCH2 expression knockdown using shRNA in hPDLs did not dramatically alter their proliferation or osteogenic differentiation compared with the shRNA control. After seeding on Jagged1-immobilized surfaces and maintaining the hPDLs in osteogenic medium, HES1 and HEY1 mRNA levels were markedly reduced in the shNOTCH2-transduced cells compared with the shControl group. Further, shNOTCH2-transduced cells exhibited less alkaline phosphatase enzymatic activity and in vitro mineralization than the shControl cells when exposed to Jagged1. MSX2 and COL1A1 mRNA expression after Jagged1 activation were reduced in shNOTCH2-transduced cells. Endogenous Notch signaling inhibition using a γ-secretase inhibitor (DAPT) attenuated mineralization in hPDLs. DAPT treatment significantly promoted TWIST1, but decreased ALP, mRNA expression, compared with the control. In conclusion, Notch signaling is involved in hPDL osteogenic differentiation. Moreover, NOTCH2 participates in the mechanism by which Jagged1 induced osteogenic differentiation in hPDLs.

Intermittent compressive force promotes osteogenic differentiation in human periodontal ligament cells by regulating the transforming growth factor-β pathway

Mechanical force regulates periodontal ligament cell (PDL) behavior. However, different force types lead to distinct PDL responses. Here, we report that pretreatment with an intermittent compressive force (ICF), but not a continuous compressive force (CCF), promoted human PDL (hPDL) osteogenic differentiation as determined by osteogenic marker gene expression and mineral deposition in vitro. ICF-induced osterix (OSX) expression was inhibited by cycloheximide and monensin. Although CCF and ICF significantly increased extracellular adenosine triphosphate (ATP) levels, pretreatment with exogenous ATP did not affect hPDL osteogenic differentiation. Gene-expression profiling of hPDLs subjected to CCF or ICF revealed that extracellular matrix (ECM)-receptor interaction, focal adhesion, and transforming growth factor beta (TGF-β) signaling pathway genes were commonly upregulated, while calcium signaling pathway genes were downregulated in both CCF- and ICF-treated hPDLs. The TGFB1 mRNA level was significantly increased, while those of TGFB2 and TGFB3 were decreased by ICF treatment. In contrast, CCF did not modify TGFB1 expression. Inhibiting TGF-β receptor type I or adding a TGF-β1 neutralizing antibody attenuated the ICF-induced OSX expression. Exogenous TGF-β1 pretreatment promoted hPDL osteogenic marker gene expression and mineral deposition. Additionally, pretreatment with ICF in the presence of TGF-β receptor type I inhibitor attenuated the ICF-induced mineralization. In conclusion, this study reveals the effects of ICF on osteogenic differentiation in hPDLs and implicates TGF-β signaling as one of its regulatory mechanisms.

RNA sequencing data of human periodontal ligament cells treated with continuous and intermittent compressive force

Mechanical force regulates numerous biological functions. Application of different force types leads to different cell responses. This data article describes RNA sequencing data identifying gene expression of human periodontal ligament cells (hPDLs) treated with the continuous or intermittent compressive force. These data could be further utilized to investigate the controlling pathways that regulate hPDLs' behaviors by the different force types. Raw RNA sequencing data were deposited in the NCBI Sequence Read Archive (SRP136155) and NCBI Gene Expression Omnibus (GSE112122).

Cyclic Stretch Force Induces Periodontal Ligament Cells to Secrete Exosomes That Suppress IL-1β Production Through the Inhibition of the NF-κB Signaling Pathway in Macrophages

In the oral mechanical environment, periodontal ligament cells (PDL cells) contribute to maintaining periodontal tissue homeostasis. Recent studies showed that exosomes, which are small vesicles secreted by various types of cells, play a pivotal role in cell-to-cell communication in biological processes. We examined the secretion of exosomes from PDL cells stimulated with cyclic stretch and their role in the inflammatory response of macrophages using the human macrophage cell line THP-1 and human primary monocytes/macrophages. We prepared supernatants from human PDL cells (PDL-sup) stimulated with cyclic stretch. The treatment of macrophages with PDL-sup, but not PDL-sup from unstimulated PDL cells, inhibited the production of IL-1β in LPS/nigericin-stimulated macrophages. The pretreatment of PDL cells with GW4869, an inhibitor of exosome secretion, or siRNA for Rab27B, which controls exosome secretion, abrogated the inhibitory effects of PDL-sup. A transmission electron microscopy analysis demonstrated the existence of exosomes with diameters ranging between 30 and 100 nm in PDL-sup, suggesting that exosomes in PDL-sup contribute to this inhibition. An immunofluorescence microscopy analysis revealed that exosomes labeled with PKH67, a fluorescent dye, were incorporated by macrophages as early as 2 h after the addition of exosomes. Purified exosomes inhibited IL-1β production in LPS/nigericin-stimulated macrophages and the nuclear translocation of NF-κB as well as NF-κB p65 DNA-binding activity in LPS-stimulated macrophages, suggesting that exosomes suppress IL-1β production by inhibiting the NF-κB signaling pathway. Our results indicate that PDL cells in mechanical environments contribute to the maintenance of periodontal immune/inflammatory homeostasis by releasing exosomes.

Comparison of ultimate force revealed by compression tests on extracted first premolars and FEA with a true scale 3D multi-component tooth model based on a CBCT dataset

OBJECTIVE

The aim of this study was to develop a new method for creating a multi-component and true scale 3-dimensional (3D) model of a human tooth based on cone-beam computed tomography (CBCT) images.

MATERIALS AND METHODS

First maxillary premolar tooth model was reconstructed from a patient's CBCT images. The 2D serial sections were used to create the 3D model. This model was used for finite element analysis (FEA). Model validation was performed by comparing the ultimate compressive force (UF) obtained experimentally using a universal testing machine and from simulation. The simulations of three component-omitting models (silicone, cementum, and omitting both) were performed to analyze the maximum (max.) principal stress and stress distribution.

RESULTS

The simulation-based UF indicating tooth fracture was 637 N, while the average UF in the in vitro loading was 651 N. The discrepancy between the simulation-based UF and the experimental UF was 2.2%. From the simulation, the silicone-omitting models showed a significant change in max. principal stress, resulting in a UF error of 26%, whereas there was no notable change in the cementum-omitting model.

CONCLUSION

This study, for the first time, developed a true scale multi-component 3D model from CBCT for predicting stress distribution in a human tooth.

CLINICAL RELEVANCE

This study proposed a method to create 3D modeling from CBCT in a true scale and multi-component manner. The PDL-like component-omitting simulation led to a higher error value of UF, indicating the importance of multi-component tooth modeling in FEA. Tooth 3D modeling could help determine mechanical failure in dental treatments in a more precise manner.

Gene expression profiling of Jagged1-treated human periodontal ligament cells

OBJECTIVE

Jagged1 regulates several biological functions in human periodontal ligament cells (hPDLs). The present study aimed to evaluate mRNA expression profiling of Jagged1-treated hPDLs using microarray technique.

METHODS

Notch ligands, Jagged1, were indirectly immobilized on tissue culture surface. Subsequently, hPDLs were seeded on Jagged1 immobilized surface and maintained in growth medium for 48 hr. Total RNA was collected and processed. Gene expression profiling was examined using microarray technique. Real-time polymerase chain reaction and immunofluorescence staining were employed to determine mRNA and protein expression levels, respectively. Cell proliferation and colony-forming unit assay were performed. Cell cycle was evaluated using propidium iodide staining and flow cytometry analysis.

RESULTS

The isolated cells demonstrated fibroblast-like morphology and exhibited the co-expression of CD44, CD90, and CD105 surface markers. After stimulated with Jagged1, the total of 411 genes was differentially expressed, consisting both coding and non-coding genes. For coding genes, 165 and 160 coding genes were upregulated and downregulated, respectively. Pathway analysis revealed that the upregulated genes were mainly involved in cellular interactions, signal transduction, and collagen formation and degradation while the downregulated genes were in the events and phases in cell cycle. Jagged1 significantly decreased cell proliferation, reduced colony-forming unit ability, and induced G0/G1 cell cycle arrest in hPDLs.

CONCLUSION

Jagged1 regulates various biological pathways in hPDLs. This gene expression profiling could help to understand the mechanisms potentially involved in the Notch signaling regulation in periodontal homeostasis.

SphK1/S1P mediates TGF-β1-induced proliferation of pulmonary artery smooth muscle cells and its potential mechanisms

The upregulation of Sphingosine kinase 1 (SphK1) expression and accompanied sphingosine-1-phosphate (S1P) production have been reported to contribute to the proliferation of pulmonary artery smooth muscle cells (PASMC) and pulmonary arterial remodeling. However, the molecular mechanisms of SphK1/S1P upregulation in PASMC and the specific mechanisms of how SphK1/S1P pathway promotes PASMC proliferation remain largely unclear. This study aims to address these issues. Here, we demonstrated that TGF-β1 significantly upregulated SphK1 expression and S1P production by promoting the phosphorylation of Smad2/3 in PASMC. Further study indicated that SphK1/S1P pathway mediated TGF-β1-induced Notch3 activation in PASMC. In addition, we showed that TGF-β1 significantly induced proliferation of PASMC, while pre-inhibition of Smad2/3 phosphorylation with SB431542 or silencing SphK1 using small interfering RNA in advance, or pre-blocking Notch3 pathway with N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), attenuated TGF-β1-induced PASMC proliferation. Taken together, our study indicates that Smad2/3/SphK1/S1P/Notch3 pathway mediates TGF-β1-induced PASMC proliferation and suggests this pathway as a potential therapeutic target in the prevention and treatment of pulmonary hypertension.