Efficacy and Safety of Transitioning to Lemborexant from Z-drug, Suvorexant, and Ramelteon in Japanese Insomnia Patients: An Open-label, Multicenter Study

INTRODUCTION

For patients with chronic insomnia, conventional therapy may not always provide satisfactory efficacy and safety. Thus, switching to an alternative therapeutic agent can be explored. However, there is a lack of prospective studies evaluating the effectiveness of such changes. This prospective, non-randomized, open-label, interventional, multicenter study assessed whether Japanese patients with chronic insomnia dissatisfied with treatment could transition directly to lemborexant (LEM) from four cohorts-non-benzodiazepine sedative-hypnotic (zolpidem, zopiclone, or eszopiclone) monotherapy, dual orexin receptor antagonist (suvorexant) monotherapy, suvorexant + benzodiazepine receptor agonists (BZRAs), and melatonin receptor agonist (ramelteon) combination. We evaluated whether transitioning to LEM improved patient satisfaction based on efficacy and safety.

METHODS

The primary endpoint was the proportion of successful transitions to LEM at 2 weeks (titration phase end), defined as the proportion of patients on LEM by the end of the 2-week titration phase who were willing to continue on LEM during the maintenance phase (Weeks 2-14). Patient satisfaction and safety (the incidence of treatment-emergent adverse events [TEAEs]) were assessed at 14 weeks (end of titration and maintenance phases).

RESULTS

Among the 90 patients enrolled, 95.6% (95% confidence interval: 89.0-98.8%) successfully transitioned to LEM at 2 weeks. The proportions of patients who successfully continued on LEM were 97.8% and 82.2% at the end of the titration and maintenance phases (Weeks 2 and 14), respectively. The overall incidence of TEAEs was 47.8%; no serious TEAEs occurred. In all cohorts, the proportions of patients with positive responses were higher than the proportions with negative responses on the three scales of the Patient Global Impression-Insomnia version. During the maintenance phase, Insomnia Severity Index scores generally improved at Weeks 2, 6, and 14 of LEM transition.

CONCLUSIONS

Direct transition to LEM may be a valid treatment option for patients with insomnia who are dissatisfied with current treatment.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT04742699.

Electrohydrodynamics of diffuse porous colloids

The present article deals with the electrohydrodynamic motion of diffuse porous particles governed by an applied DC electric field. The spatial distribution of monomers as well as the charge distribution across the particle are considered to follow sigmoidal distribution involving decay length. Such a parameter measures the degree of inhomogeneity of the monomer distribution across the particle. The diffuse porous particles resemble several colloidal entities which are often seen in the environment as well as in biological and pharmaceutical industries. Considering the impact of bulk pH and ion steric effects, we modelled the electrohydrodynamics of such porous particulates based on the modified Boltzmann distribution for the spatial distribution of electrolyte ions and the Poisson equation for electric potential as well as the conservation of mass and momentum principles. We adopt regular perturbation analysis with weak field assumption and the perturbed equations are solved numerically to calculate the electrophoretic mobility and neutralization fraction of the particle charge during its motion as well as fluid collection efficiency. We further deduced the closed form relation between the drag force experienced by the charged porous particle and the fluid collection efficiency. In addition to the numerical results, we further derived the closed form analytical results for all the intrinsic parameters indicated above derived within the Debye-Hückel electrostatic framework and homogeneous distribution of monomers within the particle for which the decay length vanishes. The deduced mathematical results as indicated above will be useful to analyze several electrostatic and hydrodynamic features of a wide class of porous particulate and environmental entities.

Influence of IgA nephropathy on the progression of pulpitis and apical periodontitis in HIGA mice

OBJECTIVES

Immunoglobulin (Ig)A nephropathy has been associated with oral infections such as periodontitis, but its pathogenesis is not fully understood; no treatments exist. This study analyzes the influence of IgA nephropathy, an autoimmune disease, on the pathogenesis of pulpitis and apical periodontitis.

METHODS

Two groups of mice were used in pulp infection experiments: high serum IgA nephropathy model mice (HIGA) and control mice (BALB/c). Histologic analyses of the pulp and apical periodontal tissues were performed on days 3, 5, 7, 14, and 28 following oral bacterial infection. The dynamics of odontoblasts, apoptotic cells, and IgA expression were analyzed using anti-Nestin, TUNEL, and anti-IgA staining, respectively.

RESULTS

Inflammatory cells infiltrated the exposed pulp at day three in both groups and by 14 days, these cells had infiltrated from the pulp to the apical periodontal tissue. The area of necrotic pulp tissue increased significantly in the control group at seven days. Odontoblasts decreased from day three onwards and disappeared by 28 days in both groups. The number of apoptotic cells in the pulp and apical periodontal tissues was significantly higher in the experimental group at day 28. The experimental group exhibited a significant increase in IgA production in the pulp after 14 days. Bone resorption in the apical periodontal tissue was significantly decreased in the experimental group at day 28.

CONCLUSIONS

The results of this study suggest that IgA nephropathy may modulate the inflammatory response and sustain long-term biological defense responses in pulpitis and apical periodontitis in HIGA mice.

Oral biosciences: The annual review 2023

BACKGROUND

The Journal of Oral Biosciences is dedicated to advancing and disseminating fundamental knowledge with regard to every aspect of oral biosciences. This review features review articles in the fields of "bone regeneration," "periodontitis," "periodontal diseases," "salivary glands," "sleep bruxism," and "Sjögren's syndrome."

HIGHLIGHT

This review focuses on human demineralized dentin and cementum matrices for bone regeneration, oxidized low-density lipoprotein in periodontal disease and systemic conditions, the relationship between inflammatory mediators in migraine and periodontitis, phosphoinositide signaling molecules in the salivary glands, and the pathophysiologies of sleep bruxism and Sjögren's syndrome.

CONCLUSION

The review articles featured in the Journal of Oral Biosciences have broadened the knowledge of readers regarding various aspects of oral biosciences. The current editorial review discusses the findings and significance of these review articles.

Trends in the multiple prescriptions of hypnotic drugs in a university outpatient in Japan

AIMS

In Japan, the daily dosage of hypnotic drugs for insomnia treatment is increasing year by year, and over-dependence on treatment with hypnotic drugs is a major problem. This study aimed to examine the factors related to the elimination of prescriptions of three or more hypnotic drugs within 1 year in our clinic.

METHODS

We conducted two surveys. Survey ① assessed the frequency of prescriptions of three or more hypnotic drugs by retrospectively reviewing the medical records of all patients who visited general and psychiatric outpatient clinics from January 2013 to March 2019. Survey ② assessed changes in prescriptions of hypnotic and psychotropic drugs within the subsequent year by retrospectively reviewing the medical records of all patients prescribed three or more hypnotic drugs who visited neuropsychiatric outpatient clinics multiple times between April 2013 and March 2019.

RESULTS

The frequency of prescribing three or more hypnotic drugs was six to nine times higher in psychiatry than in other departments. Flunitrazepam and brotizolam were the most common drugs prescribed and had the second lowest discontinuation rate after zolpidem. Conversely, eszopiclone, zopiclone, and suvorexant had the highest discontinuation rates. The success factors for drug reduction were age (odds ratio [OR]: 0.97, p < 0.0037), trazodone addition (OR: 12.86, p < 0.0194) and number of years of psychiatric experience.

CONCLUSIONS

The characteristics and success factors in relation to drug reduction in patients with multiple prescriptions of hypnotic drugs identified in this study may contribute to solving the problem of multiple prescriptions of hypnotic drugs.

Loss of Autophagy Disrupts Stemness of Ameloblast-Lineage Cells in Aging

Autophagy is one of the intracellular degradation pathways and maintains cellular homeostasis, regulating the stress response, cell proliferation, and signal transduction. To elucidate the role of autophagy in the maintenance of dental epithelial stem cells and the subsequent enamel formation, we analyzed autophagy-deficient mice in epithelial cells (Atg7f/f;KRT14-Cre mice), focusing on the influence of aging and stress environments. We also performed in vitro cell and organ culture experiments with an autophagy inhibitor. In young Atg7f/f;KRT14-Cre mice, morphological change was not obvious in maxillary incisors, except for the remarkable cell death in the stratum intermedium of the transitional stage. However, under stress conditions of hyperglycemia, the incisor color changed to white in diabetes Atg7f/f;KRT14-Cre mice. Regarding dental epithelial stem cells, the shape of the apical bud region of the incisor became irregular with age, and odontoma was formed in aged Atg7f/f;KRT14-Cre mice. In addition, the shape of apical bud culture cells of Atg7f/f;KRT14-Cre mice became irregular and enlarged atypically, with epigenetic changes during culture, suggesting that autophagy deficiency may induce tumorigenesis in dental epithelial cells. The epigenetic change and upregulation of p21 expression were induced by autophagy inhibition in vivo and in vitro. These findings suggest that autophagy is important for the regulation of stem cell maintenance, proliferation, and differentiation of ameloblast-lineage cells, and an autophagy disorder may induce tumorigenesis in odontogenic epithelial cells.

Early revascularization activates quiescent dental pulp stem cells following tooth replantation in mice

Introduction

The intentional perforation of the pulp chamber floor before tooth replantation promotes pulpal healing by facilitating the revascularization of the pulp cavity. This study aimed to elucidate the effects of this method on the dynamics of quiescent dental pulp stem cells (DPSCs).

Methods

The right and left maxillary first molars of Crlj:CD1 mice and TetOP-histone 2B (H2B)-green fluorescent protein (GFP) mice were extracted. The left molars were immediately replanted as the control group (CG), whereas the pulp chamber floor of the right molars were perforated before the tooth was replanted as the experimental group (EG). Immunohistochemistry for Nestin and GFP, and quantitative RT-PCR for Nestin, Opn, CD11c, and Oct3/4 mRNA were performed.

Results

The rate of Nestin-positive perimeter along the pulp-dentin border in the EG tended to be higher than that of the CG at days 5 and 7 and was significantly increased between days 3 and 7. The rate of GFP-positive cells in the EG was significantly higher than that of the CG at days 5 and/or 7 in the mesial and middle coronal pulp. CD11c mRNA in the EG at day 5 was significantly higher than that of the CG and tended to be higher than that of the CG during the observation period. Oct3/4 mRNA expression in the EG was significantly higher than that of the CG at day 7.

Conclusions

The current experimental model demonstrated the promotion of the survival of DPSCs and their differentiation into odontoblast-like cells (OBLCs). Thus, the use of this model is expected to clarify the crosstalk mechanism between immune cells, including macrophages and dendritic cells, and DPSCs with regards to pulpal healing after tooth replantation. It also provides insight into the differentiation process of DPSCs into OBLCs.

Establishing protein expression profiles involved in tooth development using a proteomic approach

Various growth and transcription factors are involved in tooth development and developmental abnormalities; however, the protein dynamics do not always match the mRNA expression level. Using a proteomic approach, this study comprehensively analyzed protein expression in epithelial and mesenchymal tissues of the tooth germ during development. First molar tooth germs from embryonic day 14 and 16 Crlj:CD1 (ICR) mouse embryos were collected and separated into epithelial and mesenchymal tissues by laser microdissection. Mass spectrometry of the resulting proteins was carried out, and three types of highly expressed proteins [ATP synthase subunit beta (ATP5B), receptor of activated protein C kinase 1 (RACK1), and calreticulin (CALR)] were selected for immunohistochemical analysis. The expression profiles of these proteins were subsequently evaluated during all stages of amelogenesis using the continuously growing incisors of 3-week-old male ICR mice. Interestingly, these three proteins were specifically expressed depending on the stage of amelogenesis. RACK1 was highly expressed in dental epithelial and mesenchymal tissues during the proliferation and differentiation stages of odontogenesis, except for the pigmentation stage, whereas ATP5B and CALR immunoreactivity was weak in the enamel organ during the early stages, but became intense during the maturation and pigmentation stages, although the timing of the increased protein expression was different between the two. Overall, RACK1 plays an important role in maintaining the cell proliferation and differentiation in the apical end of incisors. In contrast, ATP5B and CALR are involved in the transport of minerals and the removal of organic materials as well as matrix deposition for CALR.

Distribution patterns of infraorbital nerve branches and risk for injury

BACKGROUND

During oral and head and neck surgery, oral vestibular incisions may require a transverse incision on the upper lip mucosa, resulting in possible sensory disturbances in the area innervated by infraorbital nerve (ION) branches. Although sensory disturbances are attributed to nerve injuries, anatomy textbooks have not showed the precise distribution patterns of the ION branches in the upper lip. Furthermore, no detailed study has been available on this issue. This study aimed to reveal the precise distribution patterns of ION branches in the upper lip by dissecting the detached upper lip and cheek area using a stereomicroscope.

METHODS

During a gross anatomy course at Niigata University (2021-2022), nine human cadavers were examined with special focus on the relationship between ION branches in the upper lip and the layered structure of facial muscles.

RESULTS

The ION branched to the inferior palpebral (IP), external and internal nasal, and superior labial (lateral and medial) nerves. The ION branches in the upper lip did not run in a horizontal pattern from outside to inside but showed a predominantly vertical pattern. Considering their course, incising the upper lip mucosa transversely may cause paresthesia of the ION branches. The internal nasal (IN) and medial superior labial (SLm) branches tended to penetrate the orbicularis oris and descend between this muscle and labial glands, whereas the lateral superior labial (SLl) branches tended to innervate the skin.

CONCLUSIONS

These findings suggest that a lateral mucosal incision is recommended for oral vestibular incisions of the upper lip and that deeper incisions to the labial glands should be avoided when incising the medial side to preserve the ION during surgery from an anatomical point of view.

Diffusiophoresis of Weakly Charged Fluid Droplets in a General Electrolyte Solution: An Analytical Theory

Owing to the importance of analytical results for electrokinetics of colloidal entities, we performed a mathematical analysis to determine the closed form analytical results for the diffusiophoretic velocity of a hydrophobic and polarizable fluid droplet. A comprehensive mathematical model is developed for diffusiophoresis, considering the background aqueous medium as general electrolytes (e.g., binary valence-symmetric/asymmetric electrolytes and a mixed solution of binary electrolytes). We performed our analysis under a weak concentration gradient, and the analytical results for diffusiophoretic velocity are calculated within the Debye-Hückel electrostatic framework. The exact form of the diffusiophoretic velocity is further approximated with negligible error, and the approximate form is found to be free from any of the cumbersome exponential integrals and thus very convenient for practical use. The present theory also covers the diffusiophoresis of perfectly dielectric as well as perfectly conducting droplets as its limiting case. In addition, we have further derived a number of closed form expressions for diffusiophoretic velocity pertaining to several particular cases, and we observed that the derived limit correctly recovers the available existing analytical results for diffusiophoretic velocity. Thus, the present analytical theory for diffusiophoresis can be applied to a wide class of fluidic droplets, e.g., hydrophobic and dielectric oil/conducting mercury droplets, air bubbles, nanoemulsions, as well as any polarizable and hydrophobic fluidic droplet suspended in a solution of general electrolytes.

The accuracy of quantifying the degree of hard tissue calcification using an electron probe micro analyzer, micro-focus X-ray computed tomography, and tissue sectioning methods

OBJECTIVES

Micro-focus X-ray computed tomography (μCT) helps evaluate specimens without destroying it. However, its accuracy of quantifying bone mineral density remains to be fully elucidated. We aimed to verify the accuracy of calcification assessed by μCT, by comparing the images of identical specimens obtained via different methods such as μCT and electron probe micro analyzer (EPMA) analyses.

METHODS

The maxillae, mandibles, and tibiae of five-week-old male mice were analyzed. Calcification density was analyzed using μCT. The right sides of the specimens were decalcified and processed for Azan staining. The left side of the specimens underwent elemental mapping for Ca, Mg, and P using EPMA.

RESULTS

μCT revealed a significant increase in calcification levels in the following order: enamel, dentin, cortical bone, and trabecular bone. These results reflected the Ca and P levels observed in the EPMA analyses. μCT demonstrated significant differences in the degree of calcification among the enamel tissues or dentin tissues, except for dentin in the maxillary incisors and molars. However, EPMA analysis did not demonstrate significant differences in the Ca and P levels among the same tissue samples.

CONCLUSIONS

EPMA elemental analysis can be used to measure Ca and P levels for evaluating the calcification rate of hard tissues. Additionally, the study results validate the evaluation of calcification density via μCT. Furthermore, μCT can evaluate even minute differences in calcification rates compared with EPMA analysis.

Effects of Rheumatoid Arthritis on the Progression of Pulpitis and Apical Periodontitis in SKG Mice

INTRODUCTION

Rheumatoid arthritis (RA) is an autoimmune disease that involves joint inflammation. Although periodontal disease reportedly contributes to RA onset, the associations of RA with pulpitis and apical periodontitis have not been described. The purpose of this study was to examine the effects of immune response disruption of RA for pulpitis and apical periodontitis with SKG mice.

METHODS

SKG and BALB/c (control) mice were used to establish models of pulp infection. Histologic studies of pulp and apical periodontal tissue were performed at 3, 5, 7, 14, and 28 days; odontoblast dynamics were analyzed by antinestin staining, and apoptotic cells were examined by TdT-mediated digoxygenin (biotin)-dUTP nick end labeling staining.

RESULTS

Inflammatory cell infiltration into the exposed pulp was observed at 3 days in the SKG and control group groups; the infiltration extended to the apical pulp area at 14 days after surgery. Inflammatory cell infiltration and bone resorption in the apical pulp area were observed from 14-28 days in the SKG and control groups; there were significant increases in inflammatory cell infiltration and bone resorption in the control group at 28 days. The numbers of apoptotic cells in pulp and apical periodontal tissue were higher in the SKG group than in the control group at 14 and 28 days. The number of odontoblasts decreased in the SKG and control groups until 14 days and then disappeared in the SKG and control groups at 28 days.

CONCLUSIONS

This study suggested that immune response disruption in RA is involved in prolonging the inflammatory state of pulpitis and apical periodontitis.

Cuspal Shape Alterations by Bmp4 Directing Cell Proliferation and Apoptosis

The enamel knot (EK), located at the center of cap stage tooth germs, is a transitory cluster of nondividing epithelial cells. The EK acts as a signaling center that provides positional information for tooth morphogenesis and regulates the growth of tooth cusps. To identify species-specific cuspal patterns, this study analyzed the cellular mechanisms in the EK that were related to bone morphogenetic protein (Bmp), which plays a crucial role in cell proliferation and apoptosis. To understand the cellular mechanisms in the EK, the differences between 2 species showing different cuspal patterning, mouse (pointy bunodont cusp) and gerbil (flat lophodont cusp), were analyzed with quantitative reverse transcriptase polymerase chain reaction and immunofluorescent staining. Based on these, we performed protein-soaked bead implantation on tooth germs of the 2 different EK regions and compared the cellular behavior in the EKs of the 2 species. Many genes related with cell cycle, cell apoptosis, and cell proliferation were involved in BMP signaling in the EK during tooth development. A comparison of the cell proliferation and apoptosis associated with Bmp revealed distinctive patterns of the cellular mechanisms. Our findings indicate that the cellular mechanisms, such as cell proliferation and apoptosis, in the EK are related to Bmp4 and play an important role in tooth morphogenesis.

Conditional knockout of transient receptor potential melastatin 7 in the enamel epithelium: Effects on enamel formation

Transient receptor potential melastatin 7 (TRPM7) is a unique ion channel connected to a kinase domain. We previously demonstrated that Trpm7 expression is high in mouse ameloblasts and odontoblasts, and that amelogenesis is impaired in TRPM7 kinase-dead mice. Here, we analyzed TRPM7 function during amelogenesis in Keratin 14-Cre;Trpm7^fl/fl conditional knockout (cKO) mice and Trpm7 knockdown cell lines. cKO mice showed lesser tooth pigmentation than control mice and broken incisor tips. Enamel calcification and microhardness were lower in cKO mice. Electron probe microanalysis (EPMA) showed that the calcium and phosphorus contents in the enamel were lower in cKO mouse than in control mice. The ameloblast layer in cKO mice showed ameloblast dysplasia at the maturation stage. The morphological defects were observed in rat SF2 cells with Trpm7 knockdown. Compared with mock transfectants, the Trpm7 knockdown cell lines showed lower levels of calcification with Alizarin Red-positive staining and an impaired intercellular adhesion structures. These findings suggest that TRPM7 is a critical ion channel in enamel calcification for the effective morphogenesis of ameloblasts during amelogenesis.

Sleep Structure in Untreated Adults With ADHD: A Retrospective Study

OBJECTIVE

Polysomnographic findings in neurodevelopmental disorders have been reported, but previous studies have had several limitations. The purpose of this study was to characterize sleep structure in untreated adults diagnosed with ADHD, excluding ADHD-related sleep disorders as determined by polysomnography and multiple sleep latency testing.

METHODS

This study included 55 patients aged 18 years or older who visited the Kurume University Hospital Sleep Clinic between April 2015 and March 2020. The diagnosis of ADHD was determined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (ADHD group, n = 28; non-ADHD, n = 27).

RESULTS

The ADHD group had significantly longer slow wave sleep (SWS) duration than the non-ADHD group (ADHD: 68.3 ± 31.0 minutes vs. non-ADHD: 43.4 ± 36.6 minutes; p = .0127).

CONCLUSIONS

The increased SWS volume observed in drug-naïve adult patients with ADHD may be related to the pathogenesis of this disorder.

Oral biosciences: The annual review 2022

BACKGROUND

The Journal of Oral Biosciences is devoted to advancing and disseminating fundamental knowledge concerning every aspect of oral biosciences.

HIGHLIGHT

This review features review articles in the fields of "Bone Cell Biology," "Tooth Development & Regeneration," "Tooth Bleaching," "Adipokines," "Milk Thistle," "Epithelial-Mesenchymal Transition," "Periodontitis," "Diagnosis," "Salivary Glands," "Tooth Root," "Exosome," "New Perspectives of Tooth Identification," "Dental Pulp," and "Saliva" in addition to the review articles by the winner of the "Lion Dental Research Award" ("Plastic changes in nociceptive pathways contributing to persistent orofacial pain") presented by the Japanese Association for Oral Biology.

CONCLUSION

The review articles in the Journal of Oral Biosciences have inspired its readers to broaden their knowledge about various aspects of oral biosciences. The current editorial review introduces these exciting review articles.

The effect of intentionally perforating the floor of the pulp chamber on pulpal healing after tooth replantation in mice

OBJECTIVES

Shortening the root of a mouse molar prior to tooth replantation results in early revascularization in the pulp cavity and activation of the dental pulp quiescent stem cells. This study aimed to validate the effects of pulp chamber floor perforation on pulpal healing after tooth replantation as a strategy to promote early revascularization into the pulp.

METHODS

The maxillary first molars of three-week-old Crlj:CD1 mice were extracted and repositioned into the original socket: the left teeth were immediately replanted (control group: CG), whereas the floor of the pulp chamber of the right teeth was perforated with a tungsten carbide bur before tooth replantation (experimental group: EG). The samples were collected from three days to eight weeks postoperatively. In addition to the TUNEL assay, immunohistochemistry for Nestin, CK14, and Ki-67 was conducted.

RESULTS

In the EG, early revascularization occurred with a decrease in apoptosis and an increase in cell proliferation, facilitating pulpal healing, compared with the CG. The rate of Nestin-positive perimeter in the distal root significantly increased on days 5 and 14 and the amount of Nestin-positive hard tissue increased on day 14. However, on day 7, the number of epithelial cell rests of Malassez in the EG significantly decreased, making the EG susceptible to ankylosis at the floor.

CONCLUSIONS

Intentionally perforating the floor of the pulp chamber provides a route for early revascularization, resulting in better pulpal healing after tooth replantation.

SVCT2-GLUT1-mediated ascorbic acid transport pathway in rat dental pulp and its effects during wound healing

Ascorbic acid (AA; vitamin C) plays a crucial role in the biosynthesis and secretion of collagen to produce the organic matrix of hard tissues. Nevertheless, the detailed mechanism by which AA induces reparative dentinogenesis is still unknown. This study aimed to investigate the pathway and function of AA during wound healing in a rat pulpotomy model. Sodium-dependent vitamin C transporter (SVCT) 2 and glucose transporter (GLUT) 1 were detected in odontoblasts, endothelial cells, and nerve fibers in normal pulp tissues. SVCT2 and GLUT1 were also expressed in odontoblast-like cells in pulpotomized tissues of Wistar rats, and immunopositive cells of SVCT2 were significantly increased at 5 days after pulpotomy (p < 0.05). By contrast, osteogenic disorder Shionogi (ODS) rats, which cannot generate AA, also expressed SVCT2 and GLUT1 in normal and wound healing conditions. However, in ODS rats, when compared with the AA-addition group, the formation of dentin bridges in the AA-loss group was not evident, a layer of osteopontin was significantly increased beneath the wound surface (p < 0.05), and alpha smooth muscle actin at the odontoblast-like cells observed along this layer was significantly increased (p < 0.05), but not Nestin. Moreover, the amounts of type 1 collagen generated in the reparative dentin and beneath the wound healing site were significantly diminished (p < 0.05). Macrophages expressing CD68 and CD206 increased beneath the wound site. Hence, AA may be involved in odontoblast-like cell differentiation and anti-inflammatory response during dental pulp wound healing. Our results provide new insights into the function of AA through SVCT2 and GLUT1 in reparative dentinogenesis and may help in developing new therapeutic targets for dental pulpal disease.

Energy metabolic shift contributes to the phenotype modulation of maturation stage ameloblasts

Maturation stage ameloblasts (M-ABs) are responsible for terminal enamel mineralization in teeth and undergo characteristic cyclic changes in both morphology and function between ruffle-ended ameloblasts (RA) and smooth-ended ameloblasts (SA). Energy metabolism has recently emerged as a potential regulator of cell differentiation and fate decisions; however, its implication in M-ABs remains unclear. To elucidate the relationship between M-ABs and energy metabolism, we examined the expression pattern of energy metabolic enzymes in M-ABs of mouse incisors. Further, using the HAT7 cell line with M-AB characteristics, we designed experiments to induce an energy metabolic shift by changes in oxygen concentration. We revealed that RA preferentially utilizes oxidative phosphorylation, whereas SA depends on glycolysis-dominant energy metabolism in mouse incisors. In HAT7 cells, hypoxia induced an energy metabolic shift toward a more glycolytic-dominant state, and the energy metabolic shift reduced alkaline phosphatase (ALP) activity and calcium transport and deposition with a change in calcium-related gene expression, implying a phenotype shift from RA to SA. Taken together, these results indicate that the energy metabolic state is an important determinant of the RA/SA phenotype in M-ABs. This study sheds light on the biological significance of energy metabolism in governing M-ABs, providing a novel molecular basis for understanding enamel mineralization and elucidating the pathogenesis of enamel hypomineralization.

Role of osteopontin in the process of pulpal healing following tooth replantation in mice

Introduction

The role of osteopontin (OPN) following severe injury remains to be elucidated, especially its relationship with type I collagen (encoded by the Col1a1 gene) secretion by newly-differentiated odontoblast-like cells (OBLCs). In this study, we examined the role of OPN in the process of reparative dentin formation with a focus on reinnervation and revascularization after tooth replantation in Opn knockout (KO) and wild-type (WT) mice.

Methods

Maxillary first molars of 2- and 3-week-old-Opn KO and WT mice (Opn KO 2W, Opn KO 3W, WT 2W, and WT 3W groups) were replanted, followed by fixation 3–56 days after operation. Following micro-computed tomography analysis, the decalcified samples were processed for immunohistochemistry for Ki67, Nestin, PGP 9.5, and CD31 and in situ hybridization for Col1a1.

Results

An intense inflammatory reaction occurred to disrupt pulpal healing in the replanted teeth of the Opn KO 3W group, whereas dental pulp achieved healing in the Opn KO 2W and WT groups. The tertiary dentin in the Opn KO 3W group was significantly decreased in area compared with the Opn KO 2W and WT groups, with a significantly low percentage of Nestin-positive, newly-differentiated OBLCs during postoperative days 7–14. In the Opn KO 3W group, the blood vessels were significantly decreased in area and pulp healing was disturbed with a failure of pulpal revascularization and reinnervation.

Conclusions

OPN is necessary for proper reinnervation and revascularization to deposit reparative dentin following severe injury within the dental pulp of erupted teeth with advanced root development.

•

Osteopontin deficiency inhibits hard tissue formation in advanced erupted teeth.

•

Odontoblast-like cells may be different origins between mild and severe injuries.

•

Osteopontin has an important role for proper reinnervation and revascularization.

•

Osteopontin is necessary to deposit reparative dentin in advanced erupted teeth.

Electrophoresis of Dielectric and Hydrophobic Spherical Fluid Droplets Possessing Uniform Surface Charge Density

The present article deals with the theoretical study on electrophoresis of hydrophobic and dielectric spherical fluid droplets possessing uniform surface charge density. Unlike the ideally polarizable liquid droplet bearing constant surface ζ-potential, the tangential component of the Maxwell stress is nonzero for dielectric fluid droplets with uniform surface charge density. We consider the continuity of the tangential component of total stress (sum of the hydrodynamic and Maxwell stresses) and jump in dielectric displacement along the droplet-to-electrolyte interface. The typical situation is considered here for which the interfacial tension of the fluid droplet is sufficiently high so that the droplet retains its spherical shape during its motion. The present theory can be applied to nanoemulsions, hydrophobic oil droplets, gas bubbles, droplets of immiscible liquid suspended in aqueous medium, etc. Based on weak field and low charge assumptions and neglecting the Marangoni effect, the resultant electrokinetic equations are solved using linear perturbation analysis to derive the closed form expression for electrophoretic mobility applicable for the entire range of Debye-Hückel parameter. We further deduced an alternate approximate expression for electrophoretic mobility without involving exponential integrals. Besides, we have derived analytical results for mobility pertaining to various limiting cases. The results are further illustrated to show the impact of pertinent parameters on the overall electrophoretic mobility.

Gel Electrophoresis of a Hydrophobic Liquid Droplet with an Equipotential Slip Surface

A theoretical study has been carried out on the electrophoresis of charged dielectric liquid droplets with an equipotential and hydrodynamically slipping surface moving in a quenched polymeric charged hydrogel medium. The liquid inside the droplet is electrically neutral. The Brinkman-Debye-Bueche model is employed to study the gel electrophoresis of such a hydrophobic and equipotential liquid droplet considering the long-range hydrodynamic interaction between a migrating droplet and the gel skeleton. Within the weak field and Debye-Hückel electrostatic framework, we derive an original closed-form expression for electrophoretic mobility, which further recovers the existing mobility expressions derived under several limiting conditions. The derived expressions for electrophoretic mobility explicitly involve exponential integrals, which are not so convenient for practical applications. Thus, the exact forms of the electrophoretic mobility under various electrohydrodynamic conditions are further approximated to make them free from exponential integrals. The approximate forms are found to be in excellent agreement with the exact results with maximum relative errors of about 1.5%.

Mast4 determines the cell fate of MSCs for bone and cartilage development

Mesenchymal stromal cells (MSCs) differentiation into different lineages is precisely controlled by signaling pathways. Given that protein kinases play a crucial role in signal transduction, here we show that Microtubule Associated Serine/Threonine Kinase Family Member 4 (Mast4) serves as an important mediator of TGF-β and Wnt signal transduction in regulating chondro-osteogenic differentiation of MSCs. Suppression of Mast4 by TGF-β1 led to increased Sox9 stability by blocking Mast4-induced Sox9 serine 494 phosphorylation and subsequent proteasomal degradation, ultimately enhancing chondrogenesis of MSCs. On the other hand, Mast4 protein, which stability was enhanced by Wnt-mediated inhibition of GSK-3β and subsequent Smurf1 recruitment, promoted β-catenin nuclear localization and Runx2 activity, increasing osteogenesis of MSCs. Consistently, Mast4-/- mice demonstrated excessive cartilage synthesis, while exhibiting osteoporotic phenotype. Interestingly, Mast4 depletion in MSCs facilitated cartilage formation and regeneration in vivo. Altogether, our findings uncover essential roles of Mast4 in determining the fate of MSC development into cartilage or bone.

Oral biosciences: The annual review 2021

BACKGROUND

The Journal of Oral Biosciences is devoted to advancing and disseminating fundamental knowledge concerning every aspect of oral biosciences.

HIGHLIGHT

This review features review articles in the fields of "Extracellular Vesicles," "Propolis," "Odontogenic Tumors," "Periodontitis," "Periodontium," "Flavonoids," "Lactoferrin," "Dental Plaque," "Anatomy," "Induced Pluripotent Stem Cells," "Bone Cell Biology," "Dysgeusia," "Dental Caries," and "Dental Pulp Cavity," in addition to the review article by the winners of the "Lion Award" ("Sox9 function in salivary gland development") presented by the Japanese Association for Oral Biology.

CONCLUSION

These reviews in the Journal of Oral Biosciences have inspired its readers to broaden their knowledge regarding various aspects of oral biosciences. The current editorial review introduces these exciting review articles.

Osteopontin on the Dental Implant Surface Promotes Direct Osteogenesis in Osseointegration

After dental implantation, osteopontin (OPN) is deposited on the hydroxyapatite (HA) blasted implant surface followed by direct osteogenesis, which is significantly disturbed in Opn-knockout (KO) mice. However, whether applying OPN on the implant surface promotes direct osteogenesis remains unclarified. This study analyzed the effects of various OPN modified protein/peptides coatings on the healing patterns of the bone-implant interface after immediately placed implantation in the maxilla of four-week-old Opn-KO and wild-type (WT) mice (n = 96). The decalcified samples were processed for immunohistochemistry for OPN and Ki67 and tartrate-resistant acid phosphatase histochemistry. In the WT mice, the proliferative activity in the HA binding peptide-OPN mimic peptide fusion coated group was significantly higher than that in the control group from day 3 to week 1, and the rates of OPN deposition and direct osteogenesis around the implant surface significantly increased in the recombinant-mouse-OPN (rOPN) group compared to the Gly-Arg-Gly-Asp-Ser peptide group in week 2. The rOPN group achieved the same rates of direct osteogenesis and osseointegration as those in the control group in a half period (week 2). None of the implant surfaces could rescue the direct osteogenesis in the healing process in the Opn-KO mice. These results suggest that the rOPN coated implant enhances direct osteogenesis during osseointegration following implantation.

Exploration of the role of the subodontoblastic layer in odontoblast-like cell differentiation after tooth drilling using Nestin-enhanced green fluorescent protein transgenic mice

OBJECTIVES

Original odontoblasts and regenerated odontoblast-like cells (OBLCs) may differently regulate Nestin expression. This study aimed to investigate the role of the subodontoblastic layer (SOBL) using green fluorescent protein (GFP) reactivity in the process of OBLC differentiation after tooth drilling in Nestin-enhanced GFP transgenic mice.

METHODS

A groove-shaped cavity was prepared on the mesial surface of the maxillary first molars of 5- or 6-week-old mice under deep anesthesia. Immunohistochemical staining for Nestin and GFP and Nestin in situ hybridization were conducted on the sections obtained at 1-14 days postoperative.

RESULTS

Odontoblasts showed intense endogenous Nestin protein and mRNA expression, whereas the coronal SOBL cells showed a Nestin-GFP-positive reaction in the control groups. The injured odontoblasts had significantly decreased Nestin immunoreactivity as well as decreased expression of Nestin mRNA 1-2 days after the injury; subsequently, newly differentiated OBLCs were arranged along the pulp-dentin border, with significantly increased Nestin expression as well as increased expression of Nestin mRNA on days 3-5 to form reparative dentin. Nestin-GFP-positive cells at the pulp-dentin border significantly increased in number on days 1 and 2. GFP(+)/Nestin(+) and GFP(-)/Nestin(+) cells were intermingled in the newly differentiated OBLCs.

CONCLUSIONS

The commitment of Nestin-GFP-positive cells into Nestin-positive OBLCs suggests that the restriction of endogenous Nestin protein and mRNA expression in the static SOBL cells was removed by exogenous stimuli, resulting in their migration along the pulp-dentin border and their differentiation into OBLCs.

Deletion of epithelial cell-specific p130Cas impairs the maturation stage of amelogenesis

Amelogenesis consists of secretory, transition, maturation, and post-maturation stages, and the morphological changes of ameloblasts at each stage are closely related to their function. p130 Crk-associated substrate (Cas) is a scaffold protein that modulates essential cellular processes, including cell adhesion, cytoskeletal changes, and polarization. The expression of p130Cas was observed from the secretory stage to the maturation stage in ameloblasts. Epithelial cell-specific p130Cas-deficient (p130Cas^Δepi-) mice exhibited enamel hypomineralization with chalk-like white mandibular incisors in young mice and attrition in aged mouse molars. A micro-computed tomography analysis and Vickers micro-hardness testing showed thinner enamel, lower enamel mineral density and hardness in p130Cas^Δepi- mice in comparison to p130Cas^flox/flox mice. Scanning electron microscopy, and an energy dispersive X-ray spectroscopy analysis indicated the disturbance of the enamel rod structure and lower Ca and P contents in p130Cas^Δepi- mice, respectively. The disorganized arrangement of ameloblasts, especially in the maturation stage, was observed in p130Cas^Δepi- mice. Furthermore, expression levels of enamel matrix proteins, such as amelogenin and ameloblastin in the secretory stage, and functional markers, such as alkaline phosphatase and iron accumulation, and Na⁺/Ca²⁺+K⁺-exchanger in the maturation stage were reduced in p130Cas^Δepi- mice. These findings suggest that p130Cas plays important roles in amelogenesis (197 words).

Electrophoresis of Liquid-Layer Coated Particles: Impact of Ion Partitioning and Ion Steric Effects

The biomimetic core-shell nanoparticles coated with membranes of various biological cells have attracted significant research interest, because of their extensive applications in targeted drug delivery systems. The cell membrane consists of a lipid bilayer, which can be regarded as a two-dimensional oriented viscous liquid with low dielectric permittivity, compared to a bulk aqueous medium. Such a liquid layer comprised of cell membrane may bear additional mobile charges, because of the presence of free lipid molecules or charged surfactant molecules, which further results in nonzero charge along the surface of the peripheral layer. In this article, we present an analytical theory for electrophoresis of such cell membrane coated functionalized nanoparticles in the extent of electrolyte solution, considering the combined effects of finite ion size and of ion partitioning. Going beyond the Debye-Huckel approximations, we propose an analytical theory for Donnan potential and electrophoretic mobility. The derived expressions are applicable for moderate to highly charged undertaken core-shell particles when the thickness of the peripheral liquid layer greatly exceeds the electric double layer thickness. The impact of pertinent parameters on the electrophoretic response of such a particle is further discussed.

Fluoride Alters Signaling Pathways Associated with the Initiation of Dentin Mineralization in Enamel Fluorosis Susceptible Mice

Fluoride can alter the formation of mineralized tissues, including enamel, dentin, and bone. Dentin fluorosis occurs in tandem with enamel fluorosis. However, the pathogenesis of dentin fluorosis and its mechanisms are poorly understood. In this study, we report the effects of fluoride on the initiation of dentin matrix formation and odontoblast function. Mice from two enamel fluorosis susceptible strains (A/J and C57BL/6J) were given either 0 or 50 ppm fluoride in drinking water for 4 weeks. In both mouse strains, there was no overall change in dentin thickness, but fluoride treatment resulted in a significant increase in the thickness of the predentin layer. The lightly mineralized layer (LL), which lies at the border between predentin and fully mineralized dentin and is associated with dentin phosphoprotein (DPP), was absent in fluoride exposed mice. Consistent with a possible reduction of DPP, fluoride-treated mice showed reduced immunostaining for dentin sialoprotein (DSP). Fluoride reduced RUNX2, the transcription regulator of dentin sialophosphoprotein (DSPP), that is cleaved to form both DPP and DSP. In fluoride-treated mouse odontoblasts, the effect of fluoride was further seen in the upstream of RUNX2 as the reduced nuclear translocation of β-catenin and phosphorylated p65/NFκB. In vitro, MD10-F2 pre-odontoblast cells showed inhibition of the Dspp mRNA level in the presence of 10 μM fluoride, and qPCR analysis showed a significantly downregulated level of mRNAs for RUNX2, β-catenin, and Wnt10b. These findings indicate that in mice, systemic exposure to excess fluoride resulted in reduced Wnt/β-catenin signaling in differentiating odontoblasts to downregulate DSPP production via RUNX2.

The effect of mineral trioxide aggregate on dental pulp healing in the infected pulp by direct pulp capping

This study aimed to clarify the effect of mineral trioxide aggregate (MTA) on pulp healing in the infected pulp by direct pulp capping (DPC). Thirty-six male ICR mice were divided into infected and uninfected groups. The pulp tissue was exposed to the oral flora for 24 h after pulp exposure in the infected group, or not exposed in the uninfected group, followed by sealing with MTA, calcium hydroxide cement (CH), or no DPC. Pulpal healing process was analyzed by hematoxylin-eosin staining and immunohistochemistry for nestin and Ki67. The active cell proliferation occurred on 1 week in the both MTA and CH groups, followed by the differentiation of odontoblast-like cells on 2 weeks in the MTA group, whereas their differentiation were not facilitated in the CH group. MTA is suggested to be a useful material for DPC with the infected and uninfected pulp tissue.

A simplified model for gel electrophoresis of a hydrophobic rigid colloid

Electrophoresis of a charged dielectric hydrophobic colloid embedded in a charged hydrogel medium is addressed. A slip velocity condition at the particle surface is considered. The characteristic of the gel electrophoresis is different compared with the free-solution electrophoresis due to the presence of immobile charges of the gel medium, which induces a strong background electroosmotic flow and modifies the Debye layer of the colloid. The gel electrophoresis of the dielectric hydrophobic charged colloid is made based on first-order perturbation analysis. A closed form solution involving simple exponential integrals for the mobility is derived, which reduces to several existing mobility expressions under limiting conditions such as for the gel electrophoresis of hydrophilic particles and a hydrophobic colloid in free-solution electrophoresis. We find that the mobility reversal is achieved by varying the Debye length or gel permeability. For the present first-order perturbation analysis, unlike free-solution electrophoresis, the particle dielectric permittivity is found to influence the mobility. One of the intriguing features of the present study is the derivation of the simplified mobility expression, which can be easily computed for a given set of parameter values.

Posterior superior alveolar nerves contribute to sensation in the anterior teeth

BACKGROUND

There is no available data on the occurrence rate of a converged alveolar canal, the detailed three-dimensional (3D) courses of alveolar canals/grooves (ACGs), or the contribution of each superior alveolar nerve to each area in the maxilla. This study aimed to clarify the 3D courses of ACGs, the relationship between ACGs and superior alveolar nerves, and the contribution of posterior superior alveolar nerves (PSANs) using computed tomography (CT) with histological analysis.

METHODS

During the gross anatomy course at Niigata University, we investigated nine human cadavers.

RESULTS

All anterior and posterior ACGs converged into the common alveolar canal, which contained blood vessels and several nerve bundles surrounded by perineurium, located at the nasal floor near the pyriform aperture. Histometrical analysis clarified that 16.3% of the nerve bundles in this canal were derived from PSANs, and 67% of the bundles were dispersed while they coursed down to the nasal floor. There seems to be no relationship between the density of nerve bundles in the canal and the number of remaining anterior teeth.

CONCLUSIONS

Data obtained from observing the detailed 3D courses of anterior and posterior ACGs, and their relationship with superior alveolar nerves, suggest that PSANs partially contribute to the nociception of the anterior teeth.

Variations in the venous supply of the floor of the oral cavity: Assessment of relative hemorrhage risk during surgery

There is little anatomical evidence about the venous plexus in the floor of the oral cavity, although venous injury can elicit late postoperative bleeding after oral surgery and it is difficult to identify the exact location of such an injury. The aim of this study was to assess the relative risk for venous injury during surgery. We investigated the course patterns of the venous plexus in the floor of the oral cavity and analyzed their relationships to those of the arteries using 23 human cadavers (41 halves) in the anatomy course at Niigata University during 2016-2018. The venous plexus in the floor of the oral cavity comprised the perforating submental vein, the vena comitans of the hypoglossal nerve, the vena comitans of the submandibular duct, the vena comitans of the lingual nerve, the sublingual vein, and the deep lingual vein. Individual variations of this plexus include duplications or absences of some veins. There is a high incidence of a submental branch running above the mylohyoid or perforating submental artery in the sublingual fossa among individuals with the perforating submental vein piercing the mylohyoid muscle, whereas the sublingual artery has a high incidence there when there is no perforating submental vein. The course patterns of arteries in the floor of the oral cavity can be predicted by estimating the course patterns of the submental veins. The course patterns of the submental veins or veins associated with the nerves and submandibular duct need to be carefully considered during surgery.

The effects of reducing the root length by apicoectomy on dental pulp revascularization following tooth replantation in mice

BACKGROUND/AIM

Root length is a critical factor for dental pulp regeneration following tooth replantation. The aim of this study was to analyze the effects of reducing the root length by apicoectomy on the pulp healing process using a model for tooth replantation.

MATERIAL AND METHODS

After extraction of the upper first molars (M1) of 3-week-old mice, the roots from the experimental group (EG) were shortened to half to two-thirds of their length before replantation, whereas in the control group (CG) the extracted teeth were immediately repositioned into their alveolar sockets. To determine the effects of root resection on the survival of inherent pulp cells, this study included tooth transplantation with root resection using wild-type (WT) and green fluorescent protein (GFP) transgenic mice. The M1 of GFP transgenic mice were transplanted into the alveolar socket of the M1 of WT mice. The roots of the right M1 were shortened (EG), whereas the left M1 remained untreated (CG).

RESULTS

Apoptotic cells in the EG significantly decreased in number compared with the CG at day 3. Cell proliferative activity in the EG was significantly higher than that in the CG in the root pulp during days 3-5, and nestin-positive odontoblast-like cells began to arrange themselves along the pulp-dentin border in the cusp area at day 5 in the EG but not in the CG. At week 2, tertiary dentin had formed throughout the pulp in the EG, whereas the combined tissue of dentin and bone occupied the pulp space in 60% of the CG. Root resection also positively affected the survival of inherent pulp cells to differentiate into odontoblast-like cells as demonstrated by transplantation using GFP transgenic mice.

CONCLUSIONS

Reducing the root length accelerated pulp regeneration following tooth replantation due to the better environment for revascularization.

The Sonic Hedgehog–Patched–Gli Signaling Pathway Maintains Dental Epithelial and Pulp Stem/Progenitor Cells and Regulates the Function of Odontoblasts

This study aimed to elucidate the role of the Sonic hedgehog (Shh)–Patched (Ptch)–Gli signaling pathway in maintaining dental epithelial and pulp stem/progenitor cells and regulating the function of odontoblasts. Doxycycline (dox)-inducible histone 2B (H2B)–green fluorescent protein (GFP) transgenic mice ingested dox at prenatal embryonic days 14.5 or 15.5 and their offspring were collected from postnatal day 1 (P1) to week 3 (P3W). Immunohistochemistry for Gli1, Ptch1, and Ptch2 andin situhybridization forShhandPtch1were conducted. Mandibular incisors of postnatal day 2 H2B-GFP transgenic and wild-type mice were cultivated in a nutrient medium with Shh antibody for 4 days and subsequently processed for immunohistochemistry for Sox2. In molars, dense H2B-GFP-label-retaining cells (H2B-GFP-LRCs) were densely distributed throughout the dental pulp during P1 to postnatal week 2 (P2W) and decreased in number by postnatal P3W, whereas the number of dense H2B-GFP-LRCs in the subodontoblastic layer increased in number at P2W. Gli1+and Pthc1+cells were distributed throughout the enamel organ and dental pulp, including the odontoblast and subodontoblastic layers.ShhmRNA was expressed in the inner enamel epithelium and shifted into odontoblasts after dentin deposition.Ptch1mRNA was expressed in the inner enamel epithelium and cuspal pulpal tissue on P1 and decreased in intensity from postnatal week 1 to P3W. In incisors, the apical bud contained H2B-GFP-LRCs, Gli1+cells, and Ptch1+cells. The addition of Shh antibody to explants induced a decrease in the number of Sox2+cells due to the increase in apoptotic cells in the apical bud. Thus, the Shh–Ptch–Gli signaling pathway plays a role in maintaining quiescent adult stem cells and regulating the function of odontoblasts.

The role of angiogenesis and pulpal healing in tooth replantation and allograft transplantation

Tooth transplantation is one of the treatment options for extracted teeth that can be considered before dental implantation. Although the success rate of tooth transplantation is lower than that of implantation, tooth replantation and transplantation have the great advantage of using natural teeth. Tooth replantation might be considered a promising option in some cases. In present study, the expression patterns of revascularization and pulpal healing, which are the most important for the pulp viability, were analyzed after tooth replantation and allograft in mice. The inflammatory response and root dentin resorption were observed and not different between replantation and allograft in initiation of healing process. However, bonelike tissue formation, pulp revascularization and pulp healing were faster in replantation. The difference of healing patterns between tooth replantation and allograft found in present study will be helpful to select the treatment option and to understand healing mechanism.

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The expression of healing markers begins in root canal and moves to pulp cavity.

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Pulp healing response becomes normal in 7 days after tooth replantation.

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Overall healing process in tooth replantation is faster than allograft.

Oral biosciences: The annual review 2020

BACKGROUND

The Journal of Oral Biosciences is devoted to the advancement and dissemination of fundamental knowledge concerning every aspect of oral biosciences.

HIGHLIGHT

This review featured the review articles in the fields of "Microbiology," "Palate," "Stem Cells," "Mucosal Diseases," "Bone Cell Biology," "MicroRNAs," "TRPV1 Cation Channels," and "Interleukins" in addition to the review article by prize-winners of the "Rising Members Award" ("DKK3 expression and function in head and neck squamous cell carcinoma and other cancers"), presented by the Japanese Association for Oral Biology.

CONCLUSION

These reviews in the Journal of Oral Biosciences have inspired the readers of the journal to broaden their knowledge regarding the various aspects of oral biosciences. The current editorial review introduces these exciting review articles.

Effect of core hydrophobicity on the electrophoresis of pH-regulated soft particles

We propose a theoretical study on the electrophoresis of core-shell composite soft particles considering the effect of hydrodynamic slip length of the hydrophobic inner core. The surface of the inner core as well as the soft polymeric shell bear zwitterionic functional groups and the charged conditions depend on the nearby micro-environment. Within a low potential and weak electric field framework, the mathematical equations of the generalized electrokinetic theory for soft surfaces are solved analytically subject to appropriate boundary conditions, and a general electrophoretic mobility expression in an integral form involving the pH-dependent electrostatic potential is derived. With the help of suitable numerical schemes, electrophoretic mobility can easily be obtained. The effect of hydrophobicity of the inner core on the electrophoretic mobility of pH-regulated soft particles is illustrated for a wide range of pertinent parameters.

Oxygen regulates epithelial stem cell proliferation via RhoA-actomyosin-YAP/TAZ signal in mouse incisor

Stem cells are maintained in specific niches that strictly regulate their proliferation and differentiation for proper tissue regeneration and renewal. Molecular oxygen (O₂) is an important component of the niche microenvironment, but little is known about how O₂ governs epithelial stem cell (ESC) behavior. Here, we demonstrate that O₂ plays a crucial role in regulating the proliferation of ESCs using the continuously growing mouse incisors. We have revealed that slow-cycling cells in the niche are maintained under relatively hypoxic conditions compared with actively proliferating cells, based on the blood vessel distribution and metabolic status. Mechanistically, we have demonstrated that, during hypoxia, HIF1α upregulation activates the RhoA signal, thereby promoting cortical actomyosin and stabilizing the adherens junction complex, including merlin. This leads to the cytoplasmic retention of YAP/TAZ to attenuate cell proliferation. These results shed light on the biological significance of blood-vessel geometry and the signaling mechanism through microenvironmental O₂ to orchestrate ESC behavior, providing a novel molecular basis for the microenvironmental O₂-mediated stem cell regulation during tissue development and renewal.

Electrokinetics of Concentrated Suspension of Soft Particles with pH-Regulated Volumetric Charges

This article presents a theoretical study on the electrokinetics of concentrated suspension of charge-regulated soft particles under a weak electric field and low potential assumptions. The inner core of the undertaken particle is "semisoft" in nature, which allows ion penetration while the fluid cannot flow within it, and the outer soft polymeric shell allows the flow of the ionized fluid. In addition, the inner core and the outer polyelectrolyte layer (PEL) bear pH-regulated basic and acidic functional groups, respectively. The Poisson-Boltzmann equation-based mathematical model was adopted here for electric potential. The fluid flow across the electrolyte medium and PEL is governed by the Stokes equation and the Darcy-Brinkman equation, respectively. The Kuwabara's unit cell model (J. Phys. Soc. Japan, 1959, 14, 522-527) was invoked to observe the effect of the interaction between the neighboring particles in a concentrated suspension. A first order perturbation technique was used to determine the mean electrophoretic mobility of the undertaken soft particles in a concentrated suspension. The effect of pH and concentration of bulk electrolyte, electrohydrodynamic properties of both the inner core and PEL, on the mean electrophoretic mobility has been studied extensively. In addition, the results have been presented for the neutralization factor that measures the fraction of fixed charges neutralized by the mobile counterions.

Sulfated vizantin causes detachment of biofilms composed mainly of the genus Streptococcus without affecting bacterial growth and viability

BACKGROUND

Sulfated vizantin, a recently developed immunostimulant, has also been found to exert antibiofilm properties. It acts not as a bactericide, but as a detachment-promoting agent by reducing the biofilm structural stability. This study aimed to investigate the mechanism underlying this activity and its species specificity using two distinct ex vivo oral biofilm models derived from human saliva.

RESULTS

The biofilm, composed mainly of the genus Streptococcus and containing 50 μM of sulfated vizantin, detached significantly from its basal surface with rotation at 500 rpm for only 15 s, even when 0.2% sucrose was supplied. Expression analyses for genes associated with biofilm formation and bacterial adhesion following identification of the Streptococcus species, revealed that a variety of Streptococcus species in a cariogenic biofilm showed downregulation of genes encoding glucosyltransferases involved in the biosynthesis of water-soluble glucan. The expression of some genes encoding surface proteins was also downregulated. Of the two quorum sensing systems involved in the genus Streptococcus, the expression of luxS in three species, Streptococcus oralis, Streptococcus gordonii, and Streptococcus mutans, was significantly downregulated in the presence of 50 μM sulfated vizantin. Biofilm detachment may be facilitated by the reduced structural stability due to these modulations. As a non-specific reaction, 50 μM sulfated vizantin decreased cell surface hydrophobicity by binding to the cell surface, resulting in reduced bacterial adherence.

CONCLUSION

Sulfated vizantin may be a candidate for a new antibiofilm strategy targeting the biofilm matrix while preserving the resident microflora.

Electrophoresis of dielectric and immiscible-liquid-layer-encapsulated colloids in aqueous media

In this paper we consider the electrophoresis of a functionalized nanoparticle in electrolyte solution. The undertaken particle is comprised of a rigid inner core encapsulated with a layer of dielectric liquid (e.g., oil or lipid layer), which is immiscible to the bulk aqueous medium. The peripheral liquid layer of the undertaken nanoparticle contains mobile charges due to presence of solubilized surfactants. The mobile electrolyte ions can penetrate across the peripheral layer depending on the difference in the Born energy of the both phases. Such types of nanoparticles have received substantial attention due to their widespread applications in biomedical research. The electric double layer (EDL) is governed by the linearized Poisson-Boltzmann equation under a low potential limit and the electroosmotic flow field is governed by modified Stokes equation. We adopt the flat-plate formalism to obtain the closed analytical expression for the electrophoretic mobility of the undertaken particle under a thin EDL approximation. The dependence of electrophoretic mobility on the pertinent parameters is also illustrated.

Impact of ion-steric and ion-partitioning effects on electrophoresis of soft particles

A theoretical study on the electrophoresis of a soft particle is made by taking into account the ion steric interactions and ion partitioning effects under a thin Debye layer consideration with negligible surface conduction. Objective of this study is to provide a simple expression for the mobility of a soft particle which accounts for the finite-ion-size effect and the ion partitioning arise due to the Born energy difference between two media. The Donnan potential in the soft layer is determined by considering the ion steric interactions and the ion partitioning effect. The volume exclusion due to the finite ion size is considered by the Carnahan-Starling equation and the ion partitioning is accounted through the difference in Born energy. The modified Poisson-Boltzmann equation coupled with Stokes-Darcy-Brinkman equations are considered to determine the mobility. A closed-form expression for the electrophoretic mobility is obtained, which reduces to several existing expressions for mobility under various limiting cases.

Electrokinetic ion transport and fluid flow in a pH-regulated polymer-grafted nanochannel filled with power-law fluid

In this article, we have discussed extensively electrokinetic ion transport and fluid flow through a slit polymer-grafted nanochannel filled with power-law fluid. The rigid walls of the channel are coated with the ion and fluid penetrable polymer layer containing a pH-regulated zwitterionic functional group (e.g., succinoglycan). The mathematical model is based on the non-linear Poisson-Boltzmann equation for electric double layer potential and the flow field within the polymer layer is governed by a modified Darcy-Brinkman equation; the Cauchy momentum equation governs the fluid flow outside of the polymer layer along with the equation of continuity for incompressible fluid. In order to consider a wide range of pertinent parameters, we adopt a finite difference based numerical tool to solve the coupled set of governing equations. We have analyzed several interesting features of electrokinetic transport phenomena through such a polymer-grafted nanochannel for a wide range of electrostatic and hydrodynamic properties of the polymer layer, parameters describing the non-Newtonian rheology of the background fluid, and the pH and concentration of the bulk electrolyte. In addition, we have also illustrated the ionic current across the undertaken nanochannel and observed that it can be either cation selective, anion selective or non-selective, depending on the critical choice of the pertinent parameters.

Msx1 deficiency interacts with hypoxia and induces a morphogenetic regulation during mouse lip development

Nonsyndromic clefts of the lip and palate are common birth defects resulting from gene-gene and gene-environment interactions. Mutations in human MSX1 have been linked to orofacial clefting and we show here that Msx1 deficiency causes a growth defect of the medial nasal process (Mnp) in mouse embryos. Although this defect alone does not disrupt lip formation, Msx1-deficient embryos develop a cleft lip when the mother is transiently exposed to reduced oxygen levels or to phenytoin, a drug known to cause embryonic hypoxia. In the absence of interacting environmental factors, the Mnp growth defect caused by Msx1 deficiency is modified by a Pax9-dependent 'morphogenetic regulation', which modulates Mnp shape, rescues lip formation and involves a localized abrogation of Bmp4-mediated repression of Pax9 Analyses of GWAS data revealed a genome-wide significant association of a Gene Ontology morphogenesis term (including assigned roles for MSX1, MSX2, PAX9, BMP4 and GREM1) specifically for nonsyndromic cleft lip with cleft palate. Our data indicate that MSX1 mutations could increase the risk for cleft lip formation by interacting with an impaired morphogenetic regulation that adjusts Mnp shape, or through interactions that inhibit Mnp growth.

Adjunct use of mouth rinses with a sonic toothbrush accelerates the detachment of a Streptococcus mutans biofilm: an in vitro study

BACKGROUND

The aim of this in vitro study was to examine the possible enhancement of the biofilm peeling effect of a sonic toothbrush following the use of an antimicrobial mouth rinse.

METHODS

The biofilm at a noncontact site in the interdental area was treated by sound wave convection with the test solution or by immersion in the solution. The biofilm peeling effect was evaluated by determining the bacterial counts and performing morphological observations. A Streptococcus mutans biofilm was allowed to develop on composite resin discs by cultivation with stirring at 50 rpm for 72 h. The specimens were then placed in recesses located between plastic teeth and divided into an immersion group and a combination group. The immersion group was treated with phosphate buffer, chlorhexidine digluconate Peridex™ (CHX) mouth rinse or Listerine® Fresh Mint (EO) mouth rinse. The combination group was treated with CHX or EO and a sonic toothbrush.

RESULTS

The biofilm thickness was reduced by approximately one-half compared with the control group. The combination treatment produced a 1 log reduction in the number of bacteria compared to the EO immersion treatment. No significant difference was observed in the biofilm peeling effect of the immersion group compared to the control group.

CONCLUSIONS

The combined use of a sonic toothbrush and a mouth rinse enhanced the peeling of the biofilm that proliferates in places that are difficult to reach using mechanical stress.

Functional Expression of Sodium-Dependent Glucose Transporter in Amelogenesis

Glucose is an essential source of energy for mammalian cells and is transported into the cells by glucose transporters. There are 2 types of glucose transporters: one is a passive glucose transporter, GLUT (SLC2A), and the other is a sodium-dependent active glucose transporter, SGLT (SLC5A). We previously reported that the expression of GLUTs during tooth development is precisely and spatiotemporally controlled and that the glucose uptake mediated by GLUT1 plays a crucial role in early tooth morphogenesis and tooth size determination. This study aimed to clarify the localization and roles of SGLT1 and SGLT2 in murine ameloblast differentiation by using immunohistochemistry, immunoelectron microscopy, an in vitro tooth organ culture experiment, and in vivo administration of an inhibitor of SGLT1/2, phloridzin. SGLT1, which has high affinity with glucose, was immunolocalized in the early secretory ameloblasts and the ruffle-ended ameloblasts in the maturation stage. However, SGLT2, which has high glucose transport capacity, was observed in the stratum intermedium, papillary layer, and ameloblasts at the maturation stage and colocalized with Na⁺-K⁺-ATPase. The inhibition of SGLT1/2 by phloridzin in the tooth germs induced the disturbance of ameloblast differentiation and enamel matrix formation both in vitro (organ culture) and in vivo (mouse model). The expression of SGLT1 and SGLT2 was significantly upregulated in hypoxic conditions in the ameloblast-lineage cells. These findings suggest that the active glucose uptake mediated by SGLT1 and SGLT2 is strictly regulated and dependent on the intra- and extracellular microenvironments during tooth morphogenesis and that the appropriate passive and active glucose transport is an essential event in amelogenesis.