Epigenetic regulation of dental pulp stem cells and its potential in regenerative endodontics

Regenerative endodontics(RE)therapy means physiologically replacing damaged pulp tissue and regaining functional dentin–pulp complex.Current clinical RE procedures recruit endogenous stem cells from the apical papilla,periodontal tissue,bone marrow and peripheral blood,with or without application of scaffolds and growth factors in the root canal space,resulting in cementum-like and bone-like tissue formation.Without the involvement of dental pulp stem cells(DPSCs),it is unlikely that functional pulp regeneration can be achieved,even though acceptable repair can be acquired.DPSCs,due to their specific odontogenic potential,high proliferation,neurovascular property,and easy accessibility,are considered as the most eligible cell source for dentin–pulp regeneration.The regenerative potential of DPSCs has been demonstrated by recent clinical progress.DPSC transplantation following pulpectomy has successfully reconstructed neurovascularized pulp that simulates the physiological structure of natural pulp.The self-renewal,proliferation,and odontogenic differentiation of DPSCs are under the control of a cascade of transcription factors.Over recent decades,epigenetic modulations implicating histone modifications,DNA methylation,and noncoding(nc)RNAs have manifested as a new layer of gene regulation.These modulations exhibit a profound effect on the cellular activities of DPSCs.In this review,we offer an overview about epigenetic regulation of the fate of DPSCs;in particular,on the proliferation,odontogenic differentiation,angiogenesis,and neurogenesis.We emphasize recent discoveries of epigenetic molecules that can alter DPSC status and promote pulp regeneration through manipulation over epigenetic profiles.

Experts consensus on the procedure of dental operative microscope in endodontics and operative dentistry

The dental operative microscope has been widely employed in the field of dentistry,particularly in endodontics and operative dentistry,resulting in significant advancements in the effectiveness of root canal therapy,endodontic surgery,and dental restoration.However,the improper use of this microscope continues to be common in clinical settings,primarily due to operators’insufficient understanding and proficiency in both the features and established operating procedures of this equipment.In October 2019,Professor Jingping Liang,Vice Chairman of the Society of Cariology and Endodontology,Chinese Stomatological Association,organized a consensus meeting with Chinese experts in endodontics and operative dentistry.The objective of this meeting was to establish a standard operation procedure for the dental operative microscope.Subsequently,a consensus was reached and officially issued.Over the span of about four years,the content of this consensus has been further developed and improved through practical experience.

Meeting report: a close look at oral biofilms and microbiomes

The "Biofilms, Microbiomes and Oral Diseases: Challenges and Future Perspectives" symposium jointly organized by Penn Dental Medicine and West China School of Stomatology was held on 30 September 2017 at Penn Wharton China Center(PWCC) in Beijing,China. The topics included the pathogenicity of oral biofilms, novel strategies for the control of biofilm-related diseases, oral microbiome and single-cell approaches, and the link between oral diseases and overall health. Researchers from a number of disciplines, representing institutions from China and Penn Dental Medicine, gathered to discuss advances in our understanding of biofilms, as well as future directions for the control of biofilm-related oral and systemic diseases.

Network Modelling and Visualisation Analysis of the Undergraduate Dental Curriculum System in China

Objectives: This study aims to present the characteristics of the undergraduate dental curriculum system using network modelling and visualisation analysis based on complex network theory, thus providing a theoretical foundation for the course development and curriculum reform. Methods: The correlation coefficient was used to quantify the intensity of the correlation between courses, and a visualisation complex network of the dental curriculum was built to explore the curriculum pattern from a dynamic perspective. Further, the statistical measurements of curriculum network were adopted to express the most relevant topological features. Subsequently, the minimum spanning tree and parallel coordinates plot were drawn to explore the curriculum community structure, quantify the key courses, and present different courses in time and space relationships. Results: The correlation analysis results show that the courses are closely related to each other. The main courses focus on pathology, pathophysiology, oral anatomy and physiology, closely connecting almost all medicine-related courses. The whole course network has an average degree value of 41.53, and a clustering coefficient of 0.78, indicating an obvious small-world characteristic. From the perspective of curriculum attributes, the number of public and theoretical courses was more than that of skills and practical courses. Moreover, the academic performance of skills and practical courses was lower than that of public and theoretical courses. Conclusion: The undergraduate dental courses have a progressive structure from basic professional knowledge to professional skills, which is reasonable for the dental education in China. However, some efforts towards curriculum reform based on this study are needed.

Expert consensus on difficulty assessment of endodontic therapy

Endodontic diseases are a kind of chronic infectious oral disease. Common endodontic treatment concepts are based on the removal of inflamed or necrotic pulp tissue and the replacement by gutta-percha. However, it is very essential for endodontic treatment to debride the root canal system and prevent the root canal system from bacterial reinfection after root canal therapy(RCT). Recent research, encompassing bacterial etiology and advanced imaging techniques, contributes to our understanding of the root canal system’s anatomy intricacies and the technique sensitivity of RCT. Success in RCT hinges on factors like patients, infection severity, root canal anatomy, and treatment techniques. Therefore, improving disease management is a key issue to combat endodontic diseases and cure periapical lesions. The clinical difficulty assessment system of RCT is established based on patient conditions, tooth conditions, root canal configuration, and root canal needing retreatment, and emphasizes pre-treatment risk assessment for optimal outcomes. The findings suggest that the presence of risk factors may correlate with the challenge of achieving the high standard required for RCT. These insights contribute not only to improve education but also aid practitioners in treatment planning and referral decision-making within the field of endodontics.

Transforming growth factor-β in stem cells and tissue homeostasis

TGF-β 1–3 are unique multi-functional growth factors that are only expressed in mammals, and mainly secreted and stored as a latent complex in the extracellular matrix(ECM). The biological functions of TGF-β in adults can only be delivered after ligand activation, mostly in response to environmental perturbations. Although involved in multiple biological and pathological processes of the human body, the exact roles of TGF-β in maintaining stem cells and tissue homeostasis have not been well-documented until recent advances, which delineate their functions in a given context. Our recent findings, along with data reported by others, have clearly shown that temporal and spatial activation of TGF-β is involved in the recruitment of stem/progenitor cell participation in tissue regeneration/remodeling process, whereas sustained abnormalities in TGF-β ligand activation, regardless of genetic or environmental origin, will inevitably disrupt the normal physiology and lead to pathobiology of major diseases. Modulation of TGF-β signaling with different approaches has proven effective pre-clinically in the treatment of multiple pathologies such as sclerosis/fibrosis, tumor metastasis, osteoarthritis, and immune disorders. Thus, further elucidation of the mechanisms by which TGF-β is activated in different tissues/organs and how targeted cells respond in a context-dependent way can likely be translated with clinical benefits in the management of a broad range of diseases with the involvement of TGF-β.

Oral bacteria colonize and compete with gut microbiota in gnotobiotic mice

The oral microbiota is associated with oral diseases and digestive systemic diseases.Nevertheless,the causal relationship between them has not been completely elucidated,and colonisation of the gut by oral bacteria is not clear due to the limitations of existing research models.The aim of this study was to develop a human oral microbiota-associated (HOMA) mouse model and to investigate the ecological invasion into the gut.By transplanting human saliva into germ-free (GF) mice,a HOMA mouse model was first constructed.16S rRNA gene sequencing was used to reveal the biogeography of oral bacteria along the cephalocaudal axis of the digestive tract.In the HOMA mice,84.78% of the detected genus-level taxa were specific to the donor.Principal component analysis (PCA) revealed that the donor oral microbiota clustered with those of the HOMA mice and were distinct from those of specific pathogen-free (SPF) mice.In HOMA mice,OTU counts decreased from the stomach and small intestine to the distal gut.The distal gut was dominated by Streptococcus,Veillonella,Haemophilus,Fusobacterium,Trichococcus and Actinomyces.HOMA mice and human microbiota-associated (HMA) mice along with the GF mice were then cohoused.Microbial communities of cohoused mice clustered together and were significantly separated from those of HOMA mice and HMA mice.The Source Tracker analysis and network analysis revealed more significant ecological invasion from oral bacteria in the small intestines,compared to the distal gut,of cohoused mice.In conclusion,a HOMA mouse model was successfully established.By overcoming the physical and microbial barrier,oral bacteria colonised the gut and profiled the gut microbiota,especially in the small intestine.

The Oral Microbiome Bank of China

The human microbiome project（HMP） promoted further understanding of human oral microbes. However, research on the human oral microbiota has not made as much progress as research on the gut microbiota. Currently, the causal relationship between the oral microbiota and oral diseases remains unclear, and little is known about the link between the oral microbiota and human systemic diseases. To further understand the contribution of the oral microbiota in oral diseases and systemic diseases, a Human Oral Microbiome Database（HOMD） was established in the US. The HOMD includes 619 taxa in 13 phyla, and most of the microorganisms are from American populations. Due to individual differences in the microbiome, the HOMD does not reflect the Chinese oral microbial status. Herein, we established a new oral microbiome database—the Oral Microbiome Bank of China（OMBC,http：//www.sklod.org/ombc）. Currently, the OMBC includes information on 289 bacterial strains and 720 clinical samples from the Chinese population, along with lab and clinical information. The OMBC is the first curated description of a Chinese-associated microbiome; it provides tools for use in investigating the role of the oral microbiome in health and diseases, and will give the community abundant data and strain information for future oral microbial studies.

Dental remineralization via poly(amido amine) and restorative materials containing calcium phosphate nanoparticles

Tooth decay is prevalent,and secondary caries causes restoration failures,both of which are related to demineralization.There is an urgent need to develop new therapeutic materials with remineralization functions.This article represents the first review on the cutting edge research of poly(amido amine)(PAMAM) in combination with nanoparticles of amorphous calcium phosphate (NACP).PAMAM was excellent nucleation template,and could absorb calcium (Ca) and phosphate (P) ions via its functional groups to activate remineralization.NACP composite and adhesive showed acid-neutralization and Ca and P ion release capabilities.PAMAM +NACP together showed synergistic effects and produced triple benefits: excellent nucleation templates,superior acidneutralization,and ions release.Therefore,the PAMAM+NACP strategy possessed much greater remineralization capacity than using PAMAM or NACP alone.PAMAM+NACP achieved dentin remineralization even in an acidic solution without any initial Ca and P ions.Besides,the long-term remineralization capability of PAMAM+NACP was established.After prolonged fluid challenge,the immersed PAMAM with the recharged NACP still induced effective dentin mineral regeneration.Furthermore,the hardness of predemineralized dentin was increased back to that of healthy dentin,indicating a complete remineralization.Therefore,the novel PAMAM+NACP approach is promising to provide long-term therapeutic effects including tooth remineralization,hardness increase,and caries-inhibition capabilities.

Metabolic-epigenetic nexus in regulation of stem cell fate

Stem cell fate determination is one of the central questions in stem cell biology,and although its regulation has been studied at genomic and proteomic levels,a variety of biological activities in cells occur at the metabolic level.Metabolomics studies have established the metabolome during stem cell differentiation and have revealed the role of metabolites in stem cell fate determination.While metabolism is considered to play a biological regulatory role as an energy source,recent studies have suggested the nexus between metabolism and epigenetics because several metabolites function as cofactors and substrates in epigenetic mechanisms,including histone modification,DNA methylation,and microRNAs.Additionally,the epigenetic modification is sensitive to the dynamic metabolites and consequently leads to changes in transcription.The nexus between metabolism and epigenetics proposes a novel stem cell-based therapeutic strategy through manipulating metabolites.In the present review,we summarize the possible nexus between metabolic and epigenetic regulation in stem cell fate determination,and discuss the potential preventive and therapeutic strategies via targeting metabolites.

Intestinal microbiota: a potential target for the treatment of postmenopausal osteoporosis

Postmenopausal osteoporosis （PMO） is a prevalent metabolic bone disease characterized by bone loss and structural destruction, which increases the risk of fracture in postmenopausal women. Owing to the high morbidity and serious complications of PMO, many efforts have been devoted to its prophylaxis and treatment. The intestinal microbiota is the complex community of microorganisms colonizing the gastrointestinal tract. Probiotics, which are dietary or medical supplements consisting of beneficial intestinal bacteria, work in concert with endogenous intestinal microorganisms to maintain host health. Recent studies have revealed that bone loss in PMO is closely related to host immunity, which is influenced by the intestinal microbiota. The curative effects of probiotics on metabolic bone diseases have also been demonstrated. The effects of the intestinal microbiota on bone metabolism suggest a promising target for PMO management. This review seeks to summarize the critical effects of the intestinal microbiota and probiotics on PMO, with a focus on the molecular mechanisms underlying the pathogenic relationship between bacteria and host, and to define the possible treatment options.

Dysbiosis of oral and gut microbiota and its association with metabolites in patients with different degrees of coronary artery stenosis

To the Editor:Coronary atherosclerotic heart disease(CAD)arises from coronary atherosclerosis(CAS)plaque buildup,resulting in coronary stenosis(CS)and occlusion,ultimately causing myocardial ischemia,hypoxia,or necrosis.Studies showed that the high-grade CS may be an important predictor of ST segment elevation myocardial infarction in subsequent months.

Oral microbiota in human systematic diseases

Oral bacteria directly affect the disease status of dental caries and periodontal diseases. The dynamic oral microbiota cooperates with the host to reflect the information and status of immunity and metabolism through two-way communication along the oral cavity and the systemic organs. The oral cavity is one of the most important interaction windows between the human body and the environment.The microenvironment at different sites in the oral cavity has different microbial compositions and is regulated by complex signaling,hosts, and external environmental factors. These processes may affect or reflect human health because certain health states seem to be related to the composition of oral bacteria, and the destruction of the microbial community is related to systemic diseases. In this review, we discussed emerging and exciting evidence of complex and important connections between the oral microbes and multiple human systemic diseases, and the possible contribution of the oral microorganisms to systemic diseases. This review aims to enhance the interest to oral microbes on the whole human body, and also improve clinician’s understanding of the role of oral microbes in systemic diseases. Microbial research in dentistry potentially enhances our knowledge of the pathogenic mechanisms of oral diseases,and at the same time, continuous advances in this frontier field may lead to a tangible impact on human health.

Remineralization of enamel caries by an amelogenin-derived peptide and fluoride in vitro

Dental caries is one of the most common oral diseases in the world.This study was tantamount to investigate the combinatory effects of an amelogenin-derived peptide(called QP5)and fluoride on the remineralization of artificial enamel caries.The peptide QP5 was synthesized and characterized,and the binding capability of the peptide on hydroxyapatite(HA)and demineralized tooth enamel surface was analysed.Then,the mineralization function of the peptide and fluoride was studied through the spontaneous mineralization testing and remineralization on enamel caries in vitro.First,the novel peptide QP5 could bind on the hydroxyapatite and demineralized tooth enamel surfaces.Second,QP5 can transitorily stabilize the formation of amorphous calcium phosphate and direct the transformation into hydroxyapatite crystals alone and in combination with fluoride.In addition,compared to blocks treated by peptide QP5 alone or fluoride,the sample blocks showed significantly higher surface microhardness,lower mineral loss and shallower lesion depth after treatment with a combination of QP5 and fluoride at high or low concentrations.The peptide QP5 could control the crystallization of hydroxyapatite,and combinatory application of peptide QP5 and fluoride had a potential synergistic effect on the remineralization of enamel caries.

Microenvironmental stiffness mediates cytoskeleton re-organization in chondrocytes through laminin-FAK mechanotransduction

Microenvironmental biophysical factors play a fundamental role in controlling cell behaviors including cell morphology,proliferation,adhesion and differentiation,and even determining the cell fate.Cells are able to actively sense the surrounding mechanical microenvironment and change their cellular morphology to adapt to it.Although cell morphological changes have been considered to be the first and most important step in the interaction between cells and their mechanical microenvironment,their regulatory network is not completely clear.In the current study,we generated silicon-based elastomer polydimethylsiloxane(PDMS)substrates with stiff(15:1,PDMS elastomer vs.curing agent)and soft(45:1)stiffnesses,which showed the Young’s moduli of~450 k Pa and 46 kPa,respectively,and elucidated a new path in cytoskeleton re-organization in chondrocytes in response to changed substrate stiffnesses by characterizing the axis shift from the secreted extracellular protein lamininβ1,focal adhesion complex protein FAK to microfilament bundling.We first showed the cellular cytoskeleton changes in chondrocytes by characterizing the cell spreading area and cellular synapses.We then found the changes of secreted extracellular linkage protein,lamininβ1,and focal adhesion complex protein,FAK,in chondrocytes in response to different substrate stiffnesses.These two proteins were shown to be directly interacted by Co-IP and colocalization.We next showed that impact of FAK on the cytoskeleton organization by showing the changes of microfilament bundles and found the potential intermediate regulators.Taking together,this modulation axis of lamininβ1-FAK-microfilament could enlarge our understanding about the interdependence among mechanosensing,mechanotransduction,and cytoskeleton re-organization.

Expert consensus on digital guided therapy for endodontic diseases

Digital guided therapy(DGT)has been advocated as a contemporary computer-aided technique for treating endodontic diseases in recent decades.The concept of DGT for endodontic diseases is categorized into static guided endodontics(SGE),necessitating a meticulously designed template,and dynamic guided endodontics(DGE),which utilizes an optical triangulation tracking system.Based on cone-beam computed tomography(CBCT)images superimposed with or without oral scan(OS)data,a virtual template is crafted through software and subsequently translated into a 3-dimensional(3D)printing for SGE,while the system guides the drilling path with a real-time navigation in DGE.DGT was reported to resolve a series of challenging endodontic cases,including teeth with pulp obliteration,teeth with anatomical abnormalities,teeth requiring retreatment,posterior teeth needing endodontic microsurgery,and tooth autotransplantation.Case reports and basic researches all demonstrate that DGT stand as a precise,time-saving,and minimally invasive approach in contrast to conventional freehand method.This expert consensus mainly introduces the case selection,general workflow,evaluation,and impact factor of DGT,which could provide an alternative working strategy in endodontic treatment.

Cell-scaffold interactions in tissue engineering for oral and craniofacial reconstruction

Tissue engineering(TE)is critical in oral and craniofacial reconstruction.One of the most popular topics on the biomaterial-based tissue regeneration process may be the interaction between cells and scaffolds.An increasing number of studies have identified the variables affecting cell-scaffold interaction.The creation and investigation of new scaffolds for TE and regenerative medicine based on specific interactions have become possible owing to these findings.This review discusses the effects of various types of scaffold materials on cells in TE.Because the intrinsic properties of scaffolds are essential,the influence of the physical,chemical,mechanical,and biological characteristics of scaffold materials on cell-scaffold interaction that has been discovered in recent research is elaborated in this review.The components carried by scaffolds,the degradation process,and the role of degraded products in cell-scaffold interactions are examined.Further,the roles of cells,including cell types,functions,and adhesion mechanisms,and extracellular matrix are discussed.Finally,the latest research progress on cell-scaffold interactions among various engineered tissues or organs in the oral and craniofacial region is summarized.A deeper understanding of cell-scaffold interactions is anticipated to benefit the development of TE and regenerative medicine.

Hedgehog signaling in tissue homeostasis, cancers, and targeted therapies

The past decade has seen significant advances in our understanding of Hedgehog(HH)signaling pathway in various biological events.HH signaling pathway exerts its biological effects through a complex signaling cascade involved with primary cilium.HH signaling pathway has important functions in embryonic development and tissue homeostasis.It plays a central role in the regulation of the proliferation and differentiation of adult stem cells.Importantly,it has become increasingly clear that HH signaling pathway is associated with increased cancer prevalence,malignant progression,poor prognosis and even increased mortality.Understanding the integrative nature of HH signaling pathway has opened up the potential for new therapeutic targets for cancer.A variety of drugs have been developed,including small molecule inhibitors,natural compounds,and long non-coding RNA(LncRNA),some of which are approved for clinical use.This review outlines recent discoveries of HH signaling in tissue homeostasis and cancer and discusses how these advances are paving the way for the development of new biologically based therapies for cancer.Furthermore,we address status quo and limitations of targeted therapies of HH signaling pathway.Insights from this review will help readers understand the function of HH signaling in homeostasis and cancer,as well as opportunities and challenges of therapeutic targets for cancer.

The potential regulatory role of BMP9 in inflammatory responses

Inflammation is a protective response of the body to pathogens and injury.Hence,it is particularly important to explore the pathogenesis and key regulatory factors of inflammation.BMP9 is a unique member of the BMP family,which is widely known for its strong osteogenic potential and insensitivity to the inhibition of BMP3.Recently,several studies have reported an underlying pivotal link between BMP9 and inflammation.What is clear,though not well understood,is that BMP9 plays a role in inflammation in a carefully choreographed manner in different contexts.In this review,we have summarized current studies focusing on BMP9 and inflammation in various tissues and the latest advances in BMP9 expression,signal transduction,and crystal structure to better understand the relationship between BMP9 and inflammation.In addition,we also briefly summarized the inflammatory characteristics of some TGF-b superfamily members to provide better insights and ideas for the study of BMP9 and inflammation.

Klotho in Osx+-mesenchymal progenitors exerts pro-osteogenic and anti-inflammatory effects during mandibular alveolar bone formation and repair

Maxillofacial bone defects are commonly seen in clinical practice.A clearer understanding of the regulatory network directing maxillofacial bone formation will promote the development of novel therapeutic approaches for bone regeneration.The fibroblast growth factor(FGF)signalling pathway is critical for the development of maxillofacial bone.Klotho,a type I transmembrane protein,is an important components of FGF receptor complexes.Recent studies have reported the presence of Klotho expression in bone.However,the role of Klotho in cranioskeletal development and repair remains unknown.Here,we use a genetic strategy to report that deletion of Klotho in Osx-positive mesenchymal progenitors leads to a significant reduction in osteogenesis under physiological and pathological conditions.Klotho-deficient mensenchymal progenitors also suppress osteoclastogenesis in vitro and in vivo.Under conditions of inflammation and trauma-induced bone loss,we find that Klotho exerts an inhibitory function on inflammation-induced TNFR signaling by attenuating Rankl expression.More importantly,we show for the first time that Klotho is present in human alveolar bone,with a distinct expression pattern under both normal and pathological conditions.In summary,our results identify the mechanism whereby Klotho expressed in Osx+-mensenchymal progenitors controls osteoblast differentiation and osteoclastogenesis during mandibular alveolar bone formation and repair.Klotho-mediated signaling is an important component of alveolar bone remodeling and regeneration.It may also be a target for future therapeutics.