Cyclic di-adenosine monophosphate regulates the osteogenic and adipogenic differentiation of hPDLSCs via MAPK and NF-κB signaling.

Cyclic di-adenosine monophosphate (c-di-AMP) is a bacterial second messenger that can be recognized by infected host cells and activate the immunoinflammatory response. The purpose of this study is to demonstrate the effect of c-di-AMP on the differentiation of human periodontal ligament stem cells (hPDLSCs) and its underlying mechanisms. In the present study, we find that the gingival crevicular fluid (GCF) of patients with chronic periodontitis has a higher expression level of c-di-AMP than that of healthy people. In vitro, c-di-AMP influences the differentiation of hPDLSCs by upregulating Toll-like receptors (TLRs); specifically, it inhibits osteogenic differentiation by activating NF-κB and ERK/MAPK and promotes adipogenic differentiation through the NF-κB and p38/MAPK signaling pathways. Inhibitors of TLRs or activated pathways reduce the changes induced by c-di-AMP. Our results establish the potential correlation among bacterial c-di-AMP, periodontal tissue homeostasis and chronic periodontitis pathogenesis.

Dentin remineralization in acidic solution without initial calcium phosphate ions via poly(amido amine) and calcium phosphate nanocomposites after fluid challenges.

OBJECTIVES: A previous study showed that the combination of poly(amido amine) (PAMAM) and rechargeable composites with nanoparticles of amorphous calcium phosphate (NACP) induced dentin remineralization in an acidic solution with no initial calcium (Ca) and phosphate (P) ions, mimicking the oral condition of individuals with dry mouths. However, the frequent fluid challenge in the oral cavity may decrease the remineralization capacity. Therefore, the objective of the present study was to investigate the remineralization efficacy on dentin in an acid solution via PAMAM + NACP after fluid challenges for the first time. METHODS: The NACP nanocomposite was stored in a pH 4 solution for 77 days to exhaust its Ca and P ions and then recharged. Demineralized dentin samples were divided into four groups: (1) control dentin, (2) dentin coated with PAMAM, (3) dentin with recharged NACP composite, and (4) dentin with PAMAM + recharged NACP. PAMAM-coated dentin was shaken in phosphate-buffered saline for 77 days to desorb PAMAM from dentin. Samples were treated in pH 4 lactic acid with no initial Ca and P ions for 42 days. RESULTS: After 77 days of fluid challenge, PAMAM failed to prevent dentin demineralization in lactic acid. The recharged NACP nanocomposite raised the pH to above 6.5 and re-released more than 6.0 and 4.0 mmol/L Ca and P ions daily, respectively, which inhibited further demineralization. In contrast, the PAMAM + NACP combined method induced great dentin remineralization and restored the dentin microhardness to 0.54 ± 0.04 GPa, which approached that of sound dentin (P = 0.426, P > 0.05). CONCLUSIONS: The PAMAM + NACP combination achieved dentin remineralization in an acid solution with no initial Ca and P ions, even after severe fluid challenges. CLINICAL RELEVANCE: The novel PAMAM + NACP has a strong and sustained remineralization capability to inhibit secondary caries, even for individuals with dry mouths.

Intermittent parathyroid hormone improves orthodontic retention via insulin-like growth factor-1.

OBJECTIVES: This study aimed to investigate the effects of intermittent parathyroid hormone (iPTH) on the stability of orthodontic retention and to explore the possible regulatory role of insulin-like growth factor-1 (IGF-1) in this process. METHODS: Forty-eight 6-week-old male Wistar rats were adopted in this study. An orthodontic relapsing model was established to investigate the effects of iPTH on orthodontic retention. In vitro, an immortalized mouse cementoblast cell line OCCM-30 was detected by flow cytometry to study the effects of iPTH on cell proliferation and apoptosis. By application of a specific IGF-1 receptor inhibitor, the role of IGF-1 was also explored. RESULTS: In vivo study found that daily injection of PTH significantly reduced the relapsing distance. Histological staining and ELISA assay showed faster periodontal regeneration during retention period in PTH group with increased RANKL/OPG ratio and greater amount of OCN, ALP, and IGF-1 in gingival cervical fluid (GCF). Cell experiment revealed that iPTH promoted proliferation and suppressed apoptosis of cementoblast. IGF-1 receptor inhibitor significantly restrained the anabolic effect of iPTH on OCCM-30 cells. CONCLUSIONS: These findings suggest that iPTH could improve the stability of tooth movement by promoting periodontal regeneration. IGF-1 is essential in mediating the anabolic effects of iPTH.

AFF4 enhances odontogenic differentiation of human dental pulp cells.

AFF4 is a component of super elongation complex (SECs) and functions as a scaffold protein to bridge the transcription elongation factors. It is associated with leukemia, HIV transcription, and head neck cancer. However, its role in odontogenic differentiation of dental pulp cells (DPCs) is unclear. Here, we show the expression of AFF4 is increased during odontogenesis. Depletion of AFF4 in human DPCs leads to a decrease of alkaline phosphatase (ALP) activity, calcium mineralization and odontogenic-related genes expression. On the contrary, Lentivirus-mediated overexpression of AFF4 induces the odontogenic potential of DPCs. Mechanistically, we found AFF4 regulates the transcription of NFIC, a key factor for tooth root formation. Overexpression of NFIC successfully rescues the restricted differentiation of AFF4-depleted cells. Our data demonstrate that AFF4 serves as a previously unknown regulator of odontogenesis.

[Oral Health Management of Children during the Epidemic Period of Coronavirus Disease 2019].

Coronavirus disease 2019 (COVID-19) is becoming a major public health event affecting China and even the whole world. During the epidemic period of corona virus disease, appropriate oral health management and disease prevention of children is very important for children's oral and general health. In order to prevent the occurrence of cross-infection and epidemic spreading of COVID-19 during dental practice, the recommendations to parents include: not only training children to maintain hand hygiene at home, exercise appropriately, strengthen physical resistance, but also helping children develop good oral and diet habit such as effective brushing and flossing to avoid oral diseases and emergency. If non-emergency oral situation occur, parents could assist their child to take home based care such as rinsing to relieve the symptoms. When oral emergencies such as acute pulpitis, periapical periodontitis, dental trauma, oral and maxillofacial infections happen, parents and children should visit dental clinic in time with correct personal protection. During the epidemic period, children's oral emergencies should be treated in accordance with current guidelines and control of COVID-19.

[Screen and Function Study of the Key Regulative Odontogenic Genes in Mice].

OBJECTIVE: To screen the key odontogenic genes in mice and verify the odontogenic inducing effect on amniotic epithelial cells (WISH). METHODS: The spatially and temporally different expression of bone morphogenetic proteins 4 (BMP4), fibroblast growth factor 8 (FGF8), sonic hedgehog (SHH), lymphoid enhancer factor 1 (LEF1) proteins and their genes expression in the early odontogenesis stage (embryo day 10.5 (E10.5)、E11.5、E14.5) in fetal mice were detected by immunohistochemistry staining and quantitative real-time PCR (RT-qPCR). According to the results, we screened the probable key odontogenic genes. Then adding osteogenic inducing solution to induce non-odontogenic epithelium cells, WISH. After 3 weeks culture of non-odontogenic epithelial WISH for osteogenic induction, the epithelial-mesenchymal transformation cap ability was evaluated by using Alizarin (ALZ) red staining and RT-qPCR on the alkaline phosphatase ( ALP) mRNA expression level. Using germ layer recombination experiment to observe and verify whether the screened genes can induce non-odontogenic epithelium cells acquire odontogenesis ability. The recombined tissue grafts containing key genes were transplanted beneath the renal capsule of mice. RESULTS: The results of immunohistochemistry staining and RT-qPCR showed that on E10.5 BMP4 protein and gene were differently expressed in the first and second branchial arch epithelium, which synchronized the odontogenic capability transferring from epithelium to mesenchyme from E10.5-E14.5. Though the expression of FGF8 protein and gene existed such difference in the first and second branchial arch epithelium, there was no synchronization in transfer. The expression of LEF1 and SHH proteins and genes had neither difference nor synchronization. So far, we considered the BMP4 was the probable key odontogenic gene. Through 3 weeks' osteogenic induction, ALZ red stained positively and calcium nodules were observed in WISH, and the expression level of ALP mRNA increased. In the germ layer recombination experiment, exogenous BMP4 protein enabled the second branchial arch mesenchyme forming tooth-like structures after recombined with the second branchial arch epithelium or WISH. CONCLUSIONS: The proteins and genes of BMP4, FGF8, SHH and LEF1 are spatially and temporally differently expressed in the early tooth development stage in mice. The protein and gene of BMP4 are differently expressed between the first and second branchial arch epithelium and enables the non-odontogenic epithelium acquiring odontogenic ability. BMP4 is the possible key odontogenic gene.

Intermittent parathyroid hormone (PTH) promotes cementogenesis and alleviates the catabolic effects of mechanical strain in cementoblasts.

BACKGROUND: External root resorption, commonly starting from cementum, is a severe side effect of orthodontic treatment. In this pathological process and repairing course followed, cementoblasts play a significant role. Previous studies implicated that parathyroid hormone (PTH) could act on committed osteoblast precursors to promote differentiation, and inhibit apoptosis. But little was known about the role of PTH in cementoblasts. The purpose of this study was to investigate the effects of intermittent PTH on cementoblasts and its influence after mechanical strain treatment. RESULTS: Higher levels of cementogenesis- and differentiation-related biomarkers (bone sialoprotein (BSP), osteocalcin (OCN), Collagen type I (COL1) and Osterix (Osx)) were shown in 1-3 cycles of intermittent PTH treated groups than the control group. Additionally, intermittent PTH increased alkaline phosphatase (ALP) activity and mineralized nodules formation, as measured by ALP staining, quantitative ALP assay, Alizarin red S staining and quantitative calcium assay. The morphology of OCCM-30 cells changed after mechanical strain exertion. Expression of BSP, ALP, OCN, osteopontin (OPN) and Osx was restrained after 18 h mechanical strain. Furthermore, intermittent PTH significantly increased the expression of cementogenesis- and differentiation-related biomarkers in mechanical strain treated OCCM-30 cells. CONCLUSIONS: Taken together, these data suggested that intermittent PTH promoted cementum formation through activating cementogenesis- and differentiation-related biomarkers, and attenuated the catabolic effects of mechanical strain in immortalized cementoblasts OCCM-30.

Formation of persisters in Streptococcus mutans biofilms induced by antibacterial dental monomer.

Antibacterial monomers can combat oral biofilm acids and caries; however, little is known on whether quaternary ammonium monomers (QAMs) would induce drug persistence in oral bacteria. The objectives of this study were to investigate the interactions of Streptococcus mutans (S. mutans) with dimethylaminohexadecyl methacrylate (DMAHDM), and determine for the first time whether DMAHDM could induce persisters in S. mutans. DMAHDM was synthesized using a modified Menschutkin reaction. Dose-dependent killing curves and time-dependent killing curves of planktonic S. mutans and biofilms were determined to evaluate drug persistence, using chlorhexidine (CHX) as control. The inheritability assay, minimum inhibitory concentration (MIC) and live/dead biofilm assay were determined to investigate persister characteristics. DMAHDM matched the killing potency of the gold standard CHX against S. mutans biofilms. DMAHDM and CHX induced drug persistence in S. mutans biofilms but not in planktonic bacteria. S. mutans biofilm persistence was not inheritable in that the tolerance to DMAHDM or CHX of the surviving persisters in the initial population was not transferred to subsequent generations, as displayed by the inheritability assay. The MIC of S. mutans parental strain and induced persisters remained the same. The induced persisters in S. mutans biofilms could be eliminated via higher doses of 300 µg/mL of DMAHDM and CHX. In conclusion, this study showed for the first time that (1) DMAHDM induced persisters only in biofilms, but not in planktonic bacteria; and (2) both DMAHDM-induced and CHX-induced S. mutans persister biofilms could be completely eradicated by even higher concentrations of DMAHDM and CHX. More studies are needed on the induction of persisters in oral biofilms for the development and use of a new generation of antibacterial dental monomers and resins.

The effect of teeth extraction for orthodontic treatment on the upper airway: a systematic review.

PURPOSE: The purpose of this study was to evaluate the effect of teeth extraction for orthodontic treatment on the upper airway. METHODS: Relevant trials assessing the effect of orthodontic extractions on the upper airway were retrieved electronically through PubMed, Embase, Medline, Web of Knowledge, and the Cochrane Library. The processes of literature search, selection, quality assessment, and data extraction were performed by two authors independently. RESULTS: Seven articles were included in this systematic review. They were categorized into three groups according to their indications for extractions, namely anteroposterior discrepancy (group 1), crowding (group 2), and unspecified indications (group 3). In group 1, enrolled patients were diagnosed with class I bimaxillary protrusion and had four first premolars extracted, with a significant decrease in upper airway dimension. In group 2, increase in the upper airway dimension was reported in patients who were diagnosed with class I crowding and four first premolars extracted. In group 3, all patients were adolescents and no significant change in the upper airway dimension was observed. CONCLUSIONS: Currently, it is difficult to draw evidence-based conclusions because of the exceeding heterogeneity among included studies, and more qualified trials are required to provide reliable evidence. Extractions followed by large retraction of the anterior teeth in adult bimaxillary protrusion cases could possibly lead to narrowing of the upper airway. Mesial movement of the molars appeared to increase the posterior space for the tongue and enlarge the upper airway dimensions. Although the effect of teeth extraction on upper airway dimension seems to be related to indications for extraction, accepted scientific evidence is still insufficient owing to the limited number of included studies. The relationship between the upper airway size and the respiratory function has not been demonstrated. While there may be a decrease in the upper airway volume, there is no evidence that this would turn an airway more collapsible. None of the studies assessed in this review had actual functional assessment of breathing. Additional qualified trials are necessary to verify reliability.

Expert consensus on pediatric orthodontic therapies of malocclusions in children.

Malocclusion, identified by the World Health Organization (WHO) as one of three major oral diseases, profoundly impacts the dental-maxillofacial functions, facial esthetics, and long-term development of ~260 million children in China. Beyond its physical manifestations, malocclusion also significantly influences the psycho-social well-being of these children. Timely intervention in malocclusion can foster an environment conducive to dental-maxillofacial development and substantially decrease the incidence of malocclusion or reduce the severity and complexity of malocclusion in the permanent dentition, by mitigating the negative impact of abnormal environmental influences on the growth. Early orthodontic treatment encompasses accurate identification and treatment of dental and maxillofacial morphological and functional abnormalities during various stages of dental-maxillofacial development, ranging from fetal stages to the early permanent dentition phase. From an economic and societal standpoint, the urgency for effective early orthodontic treatments for malocclusions in childhood cannot be overstated, underlining its profound practical and social importance. This consensus paper discusses the characteristics and the detrimental effects of malocclusion in children, emphasizing critical need for early treatment. It elaborates on corresponding core principles and fundamental approaches in early orthodontics, proposing comprehensive guidance for preventive and interceptive orthodontic treatment, serving as a reference for clinicians engaged in early orthodontic treatment.

Spatiotemporal cellular dynamics and molecular regulation of tooth root ontogeny.

Tooth root development involves intricate spatiotemporal cellular dynamics and molecular regulation. The initiation of Hertwig's epithelial root sheath (HERS) induces odontoblast differentiation and the subsequent radicular dentin deposition. Precisely controlled signaling pathways modulate the behaviors of HERS and the fates of dental mesenchymal stem cells (DMSCs). Disruptions in these pathways lead to defects in root development, such as shortened roots and furcation abnormalities. Advances in dental stem cells, biomaterials, and bioprinting show immense promise for bioengineered tooth root regeneration. However, replicating the developmental intricacies of odontogenesis has not been resolved in clinical treatment and remains a major challenge in this field. Ongoing research focusing on the mechanisms of root development, advanced biomaterials, and manufacturing techniques will enable next-generation biological root regeneration that restores the physiological structure and function of the tooth root. This review summarizes recent discoveries in the underlying mechanisms governing root ontogeny and discusses some recent key findings in developing of new biologically based dental therapies.

LITTIP/Lgr6/HnRNPK complex regulates cementogenesis via Wnt signaling.

Orthodontically induced tooth root resorption (OIRR) is a serious complication during orthodontic treatment. Stimulating cementum repair is the fundamental approach for the treatment of OIRR. Parathyroid hormone (PTH) might be a potential therapeutic agent for OIRR, but its effects still lack direct evidence, and the underlying mechanisms remain unclear. This study aims to explore the potential involvement of long noncoding RNAs (lncRNAs) in mediating the anabolic effects of intermittent PTH and contributing to cementum repair, as identifying lncRNA-disease associations can provide valuable insights for disease diagnosis and treatment. Here, we showed that intermittent PTH regulates cell proliferation and mineralization in immortalized murine cementoblast OCCM-30 via the regulation of the Wnt pathway. In vivo, daily administration of PTH is sufficient to accelerate root regeneration by locally inhibiting Wnt/ß-catenin signaling. Through RNA microarray analysis, lncRNA LITTIP (LGR6 intergenic transcript under intermittent PTH) is identified as a key regulator of cementogenesis under intermittent PTH. Chromatin isolation by RNA purification (ChIRP) and RNA immunoprecipitation (RIP) assays revealed that LITTIP binds to mRNA of leucine-rich repeat-containing G-protein coupled receptor 6 (LGR6) and heterogeneous nuclear ribonucleoprotein K (HnRNPK) protein. Further co-transfection experiments confirmed that LITTIP plays a structural role in the formation of the LITTIP/Lgr6/HnRNPK complex. Moreover, LITTIP is able to promote the expression of LGR6 via the RNA-binding protein HnRNPK. Collectively, our results indicate that the intermittent PTH administration accelerates root regeneration via inhibiting Wnt pathway. The lncRNA LITTIP is identified to negatively regulate cementogenesis, which activates Wnt/ß-catenin signaling via high expression of LGR6 promoted by HnRNPK.

Creating an atlas of the bone microenvironment during oral inflammatory-related bone disease using single-cell profiling.

Oral inflammatory diseases such as apical periodontitis are common bacterial infectious diseases that may affect the periapical alveolar bone tissues. A protective process occurs simultaneously with the inflammatory tissue destruction, in which mesenchymal stem cells (MSCs) play a primary role. However, a systematic and precise description of the cellular and molecular composition of the microenvironment of bone affected by inflammation is lacking. In this study, we created a single-cell atlas of cell populations that compose alveolar bone in healthy and inflammatory disease states. We investigated changes in expression frequency and patterns related to apical periodontitis, as well as the interactions between MSCs and immunocytes. Our results highlight an enhanced self-supporting network and osteogenic potential within MSCs during apical periodontitis-associated inflammation. MSCs not only differentiated toward osteoblast lineage cells but also expressed higher levels of osteogenic-related markers, including Sparc and Col1a1. This was confirmed by lineage tracing in transgenic mouse models and human samples from oral inflammatory-related alveolar bone lesions. In summary, the current study provides an in-depth description of the microenvironment of MSCs and immunocytes in both healthy and disease states. We also identified key apical periodontitis-associated MSC subclusters and their biomarkers, which could further our understanding of the protective process and the underlying mechanisms of oral inflammatory-related bone disease. Taken together, these results enhance our understanding of heterogeneity and cellular interactions of alveolar bone cells under pathogenic and inflammatory conditions. We provide these data as a tool for investigators not only to better appreciate the repertoire of progenitors that are stress responsive but importantly to help design new therapeutic targets to restore bone lesions caused by apical periodontitis and other inflammatory-related bone diseases.

Substrate stiffness regulates the differentiation profile and functions of osteoclasts via cytoskeletal arrangement.

OBJECTIVES: Aging and common diseases alter the stiffness of bone tissue, causing changes to the microenvironment of the mechanosensitive bone cells. Osteoclasts, the sole bone-resorbing cells, play a vital role in bone remodeling. This study was performed to elucidate the mechanism through which osteoclasts sense and react to substrate stiffness signals. MATERIALS AND METHODS: We fabricated polydimethylsiloxane (PDMS) substrates of different stiffness degrees for osteoclast formation progressed from osteoclast precursors including bone marrow-derived macrophages (BMMs) and RAW264.7 monocytes. Osteoclast differentiation in response to the stiffness signals was determined by examining the cell morphology, fusion/fission activities, transcriptional profile, and resorption function. Cytoskeletal changes and mechanosensitive adhesion molecules were also assessed. RESULTS: Stiffer PDMS substrates accelerated osteoclast differentiation, firstly observed by variations in their morphology and fusion/fission activities. Upregulation of canonical osteoclast markers (Nfatc1, Acp5, Ctsk, Camk2a, Mmp9, Rela, and Traf6) and the fusion master regulator DC-stamp were detected on stiffer substrates, with similar increases in their bone resorption functions. Additionally, the activation of cytoskeleton-associated adhesion molecules, including fibronectin and integrin αvß3, followed by biochemical signaling cascades of paxillin, FAK, PKC, and RhoA, was detected on the stiffer substrates. CONCLUSIONS: This is the first study to provide evidence proving that extracellular substrate stiffness is a strong determinant of osteoclast differentiation and functions. Higher stiffness upregulated the differentiation profile and activity of osteoclasts, revealing the mechanical regulation of osteoclast activity in bone homeostasis and diseases.

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 kPa 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 laminin ß1, 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, laminin ß1, 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 laminin ß1-FAK-microfilament could enlarge our understanding about the interdependence among mechanosensing, mechanotransduction, and cytoskeleton re-organization.

Activation of the pattern recognition receptor NOD1 in periodontitis impairs the osteogenic capacity of human periodontal ligament stem cells via p38/MAPK signalling.

OBJECTIVES: Nucleotide oligomerization domain receptor 1 (NOD1) mediates host recognition of pathogenic bacteria in periodontium. However, the specific role of NOD1 in regulating osteogenesis is unclear. Therefore, this study focused on the activation status of NOD1 in periodontitis and its effect on the osteogenic capacity of human periodontal ligament stem cells (hPDLSCs) as well as the underlying mechanism. METHODS: Histological staining and Western blot were utilized to assess NOD1 expression in the periodontium of people with or without periodontitis. HPDLSCs were cultured under NOD1 agonist or antagonist treatment. Q-PCR and Western blot were employed to assess the expression of osteogenic marker genes and proteins. Alizarin red staining and alkaline phosphatase staining were used to determine the osteogenic capability of hPDLSCs. The activation of downstream signalling was determined and specific inhibitors were utilized to confirm the signalling pathway in NOD1-regulated osteogenesis. RESULTS: NOD1 expression is significantly elevated in periodontitis. With NOD1 activated by particular agonist tri-DAP, the osteogenic potential of hPDLSCs was impaired. NOD1 antagonist co-incubation partially restored the decreased osteogenesis in hPDLSCs. P38/MAPK was phosphorylated in tri-DAP-induced NOD1 activation. The inhibitor of p38 rescued the suppression of osteogenesis induced by tri-DAP in hPDLSCs. CONCLUSIONS: Our study revealed the expression status of NOD1 in periodontitis. Its activation greatly decreased the osteogenic capacity of hPDLSCs which was mediated by the phosphorylation of p38 downstream signalling.

Osteoporosis and Alveolar Bone Health in Periodontitis Niche: A Predisposing Factors-Centered Review.

Periodontitis is a periodontal inflammatory condition that results from disrupted periodontal host-microbe homeostasis, manifested by the destruction of tooth-supporting structures, especially inflammatory alveolar bone loss. Osteoporosis is characterized by systemic deterioration of bone mass and microarchitecture. The roles of many systemic factors have been identified in the pathogenesis of osteoporosis, including endocrine change, metabolic disorders, health-impaired behaviors and mental stress. The prevalence rate of osteoporotic fracture is in sustained elevation in the past decades. Recent studies suggest that individuals with concomitant osteoporosis are more vulnerable to periodontal impairment. Current reviews of worse periodontal status in the context of osteoporosis are limited, mainly centering on the impacts of menopausal and diabetic osteoporosis on periodontitis. Herein, this review article makes an effort to provide a comprehensive view of the relationship between osteoporosis and periodontitis, with a focus on clarifying how those risk factors in osteoporotic populations modify the alveolar bone homeostasis in the periodontitis niche.

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.

Connective tissue growth factor promotes cementogenesis and cementum repair via Cx43/ß-catenin axis.

BACKGROUND: Orthodontic tooth movement inevitably induces cementum resorption, which is an urgent problem for orthodontists to confront. Human periodontal ligament stem cells (hPDLSCs) exert an important role in the orthodontic tooth movement and exhibit multidirectional differentiation ability in cementum regeneration. Connective tissue growth factor (CTGF) is an important extracellular matrix protein for bone homeostasis and cell differentiation. The purpose of our study was to explore the role of CTGF in cementum repair and cementogenesis and to elucidate its underlying mechanism. METHODS: A cementum defect model was established by tooth movement with heavy forces, and the cementum repair effect of CTGF was observed via micro-CT, HE staining and immunohistochemical staining. RT‒qPCR, western blotting (WB), alizarin red staining and ALP activity experiments verified the mineralization ability of hPDLSCs stimulated with CTGF. The expression of Cx43 in periodontal ligament cells was detected by WB and immunofluorescence (IF) experiments after CTGF stimulation in vivo and in vitro. Subsequently, the mineralization ability of hPDLSCs was observed after application of CTGF and the small interfering RNA Si-Cx43. Additionally, co-intervention via application of the small interfering RNA Si-CTGF and the Cx43 agonist ATRA in hPDLSCs was performed to deepen the mechanistic study. Next, WB, IF experiments and co-immunoprecipitation were conducted to confirm whether CTGF triggers the Cx43/ß-catenin axis to regulate cementoblast differentiation of hPDLSCs. RESULTS: Local oral administration of CTGF to the cementum defects in vivo facilitated cementum repair. CTGF facilitated the cementogenesis of hPDLSCs in a concentration-dependent manner. Cx43 acted as a downstream effector of CTGF to regulate cementoblast differentiation. Si-Cx43 reduced CTGF-induced cementoblast differentiation. The Cx43 agonist ATRA restored the low differentiation capacity induced by Si-CTGF. Further mechanistic studies showed that CTGF triggered the activation of ß-catenin in a dose-dependent manner. In addition, co-localization IF analysis and co-immunoprecipitation demonstrated that Cx43 interacted with ß-catenin at cell‒cell connections. Si-Cx43 attenuated the substantial expression of ß-catenin induced by CTGF. The Cx43 agonist reversed the inhibition of ß-catenin induced by Si-CTGF. IF demonstrated that the nuclear importation of ß-catenin was related to the immense expression of Cx43 at cell‒cell junctions. CONCLUSIONS: Taken together, these data demonstrate that CTGF promotes cementum repair and cementogenesis through activation of the Cx43/ß-catenin signalling axis.

Experts' consensus on space management of mixed dentition.

The mixed dentition stage is the period between primary and permanent dentition. The following biological processes are complicated and variable: jaw growth, development of inherited permanent teeth embryo, physiological absorption of primary teeth, restoration of surrounding alveolar bones, and growth and function establishment of soft tissues. For the normal development of the jaw, the establishment of the good occlusion relationship, development, and function of soft tissue is very important, whether or not the primary teeth are normally replaced by the permanent teeth in the mixed dentition stage. The eruption space is linked to the normal replacement of primary and permanent teeth. The presence of a mixed dentition space results in the incidence and progression of malocclusion and impacts the normal growth and development of the occlusion, jaw, and face. Space management in the mixed dentition stage is a crucial means to prevent and reduce malocclusion. The following were discussed and analyzed: the possible space problems, why the size of the space was affected, the content that needs to be assessed, and the methods of space management in the mixed dentition that can be used to unify and standardize the management of mixed dentition. This paper was developed to serve as a guide for regulated space management during the mixed dentition period.