A high-throughput microfluidic dental plaque biofilm system to visualize and quantify the effect of antimicrobials

OBJECTIVES

Few model systems are amenable to developing multi-species biofilms in parallel under environmentally germane conditions. This is a problem when evaluating the potential real-world effectiveness of antimicrobials in the laboratory. One such antimicrobial is cetylpyridinium chloride (CPC), which is used in numerous over-the-counter oral healthcare products. The aim of this work was to develop a high-throughput microfluidic system that is combined with a confocal laser scanning microscope (CLSM) to quantitatively evaluate the effectiveness of CPC against oral multi-species biofilms grown in human saliva.

METHODS

Twenty-four-channel BioFlux microfluidic plates were inoculated with pooled human saliva and fed filter-sterilized saliva for 20 h at 37°C. The bacterial diversity of the biofilms was evaluated by bacterial tag-encoded FLX amplicon pyrosequencing (bTEFAP). The antimicrobial/anti-biofilm effect of CPC (0.5%-0.001% w/v) was examined using Live/Dead stain, CLSM and 3D imaging software.

RESULTS

The analysis of biofilms by bTEFAP demonstrated that they contained genera typically found in human dental plaque. These included Aggregatibacter, Fusobacterium, Neisseria, Porphyromonas, Streptococcus and Veillonella. Using Live/Dead stain, clear gradations in killing were observed when the biofilms were treated with CPC between 0.5% and 0.001% w/v. At 0.5% (w/v) CPC, 90% of the total signal was from dead/damaged cells. Below this concentration range, less killing was observed. In the 0.5%-0.05% (w/v) range CPC penetration/killing was greatest and biofilm thickness was significantly reduced.

CONCLUSIONS

This work demonstrates the utility of a high-throughput microfluidic-CLSM system to grow multi-species oral biofilms, which are compositionally similar to naturally occurring biofilms, to assess the effectiveness of antimicrobials.

Spatial reorganization of Saccharomyces cerevisiae enolase to alter carbon metabolism under hypoxia

Hypoxia has critical effects on the physiology of organisms. In the yeast Saccharomyces cerevisiae, glycolytic enzymes, including enolase (Eno2p), formed cellular foci under hypoxia. Here, we investigated the regulation and biological functions of these foci. Focus formation by Eno2p was inhibited temperature independently by the addition of cycloheximide or rapamycin or by the single substitution of alanine for the Val22 residue. Using mitochondrial inhibitors and an antioxidant, mitochondrial reactive oxygen species (ROS) production was shown to participate in focus formation. Focus formation was also inhibited temperature dependently by an SNF1 knockout mutation. Interestingly, the foci were observed in the cell even after reoxygenation. The metabolic turnover analysis revealed that [U-(13)C]glucose conversion to pyruvate and oxaloacetate was accelerated in focus-forming cells. These results suggest that under hypoxia, S. cerevisiae cells sense mitochondrial ROS and, by the involvement of SNF1/AMPK, spatially reorganize metabolic enzymes in the cytosol via de novo protein synthesis, which subsequently increases carbon metabolism. The mechanism may be important for yeast cells under hypoxia, to quickly provide both energy and substrates for the biosynthesis of lipids and proteins independently of the tricarboxylic acid (TCA) cycle and also to fit changing environments.

Porphyromonas gingivalis fimbriae

Marginal periodontitis is not a homogeneous disease but is rather influenced by an intricate set of host susceptibility differences as well as diversities in virulence among the harbored organisms. It is likely that clonal heterogeneity of subpopulations with both high and low levels of pathogenicity exists among organisms harbored by individuals with negligible, slight, or even severe periodontal destruction. Therefore, specific virulent clones of periodontal pathogens may cause advanced and/or aggressive periodontitis. Porphyromonas gingivalis is a predominant periodontal pathogen that expresses a number of potential virulence factors involved in the pathogenesis of periodontitis, and accumulated evidence shows that its expression of heterogenic virulence properties is dependent on clonal diversity. Fimbriae are considered to be critical factors that mediate bacterial interactions with and invasion of host tissues, with P. gingivalis shown to express two distinct fimbria-molecules, long and short fimbriae, on the cell surface, both of which seem to be involved in development of periodontitis. Long fimbriae are classified into six types (I to V and Ib) based on the diversity of fimA genes encoding FimA (a subunit of long fimbriae). Studies of clones with type II fimA have revealed their significantly greater adhesive and invasive capabilities as compared to other fimA type clones. Long and short fimbriae induce various cytokine expressions such as IL-1α, IL-β, IL-6, and TNF-α, which result in alveolar bone resorption. Although the clonal diversity of short fimbriae is unclear, distinct short fimbria-molecules have been found in different strains. These fimbriae variations likely influence the development of periodontal disease.

The role of thymosin beta 4 on odontogenic differentiation in human dental pulp cells

We recently reported that overexpression of thymosin beta-4 (Tβ4) in transgenic mice promotes abnormal hair growth and tooth development, but the role of Tβ4 in dental pulp regeneration was not completely understood. The aim of this study was to investigate the role of Tβ4 on odontoblastic differentiation and the underlying mechanism regulating pulp regeneration in human dental pulp cells (HDPCs). Our results demonstrate that mRNA and protein expression of Tβ4 is upregulated during odontogenic differentiation in HDPCs. Transfection with Tβ4 siRNA decreases OM-induced odontoblastic differentiation by decreasing alkaline phosphatase (ALP) activity, mRNA expression of differentiation markers, and calcium nodule formation. In contrast, Tβ4 activation with a Tβ4 peptide promotes these processes by enhancing the phosphorylation of p38, JNK, and ERK mitogen-activated protein kinases (MAPKs), bone morphogenetic protein (BMP) 2, BMP4, phosphorylation of Smad1/5/8 and Smad2/3, and expression of transcriptional factors such as Runx2 and Osterix, which were blocked by the BMP inhibitor noggin. The expression of integrin receptors α1, α2, α3, and β1 and downstream signaling molecules including phosphorylated focal adhesion kinase (p-FAK), p-paxillin, and integrin-linked kinase (ILK) were increased by Tβ4 peptide in HDPCs. ILK siRNA blocked Tβ4-induced odontoblastic differentiation and activation of the BMP and MAPK transcription factor pathways in HDPCs. In conclusion, this study demonstrates for the first time that Tβ4 plays a key role in odontoblastic differentiation of HDPCs and activation of Tβ4 could provide a novel mechanism for regenerative endodontics.

Neutron reflectometry studies of the adsorbed structure of the amelogenin, LRAP

Amelogenins make up over 90% of the protein present during enamel formation and have been demonstrated to be critical in proper enamel development, but the mechanism governing this control is not well understood. Leucine-rich amelogenin peptide (LRAP) is a 59-residue splice variant of amelogenin and contains the charged regions from the full protein thought to control crystal regulation. In this work, we utilized neutron reflectivity (NR) to investigate the structure and orientation of LRAP adsorbed from solutions onto molecularly smooth COOH-terminated self-assembled monolayer (SAM) surfaces. Sedimentation velocity (SV) experiments revealed that LRAP is primarily a monomer in saturated calcium phosphate (SCP) solutions (0.15 M NaCl) at pH 7.4. LRAP adsorbed as ∼32 Å thick layers at ∼70% coverage as determined by NR. Rosetta simulations of the dimensions of LRAP in solution (37 Å diameter) indicate that the NR determined z dimension is consistent with an LRAP monomer. SV experiments and Rosetta simulations show that the LRAP monomer has an extended, asymmetric shape in solution. The NR data suggests that the protein is not completely extended on the surface, having some degree of structure away from the surface. A protein orientation with the C-terminal and inner N-terminal regions (residues ∼8-24) located near the surface is consistent with the higher scattering length density (SLD) found near the surface by NR. This work presents new information on the tertiary and quaternary structure of LRAP in solution and adsorbed onto surfaces. It also presents further evidence that the monomeric species may be an important functional form of amelogenin proteins.

The role of small molecules in musculoskeletal regeneration

The uses of bone morphogenetic proteins and parathyroid hormone therapeutics are fraught with several fundamental problems, such as cost, protein stability, immunogenicity, contamination and supraphysiological dosage. These downsides may effectively limit their more universal use. Therefore, there is a clear need for alternative forms of biofactors to obviate the drawbacks of protein-based inductive factors for bone repair and regeneration. Our group has studied small molecules with the capacity to regulate osteoblast differentiation and mineralization because their inherent physical properties minimize limitations observed in protein growth factors. For instance, in general, small molecule inducers are usually more stable, highly soluble, nonimmunogenic, more affordable and require lower dosages. Small molecules with the ability to induce osteoblastic differentiation may represent the next generation of bone regenerative medicine. This review describes efforts to develop small molecule-based biofactors for induction, paying specific attention to their novel roles in bone regeneration.

Tetra- and penta-acylated lipid A structures of Porphyromonas gingivalis LPS differentially activate TLR4-mediated NF-κB signal transduction cascade and immuno-inflammatory response in human gingival fibroblasts

Background

Porphyromonas gingivalis is a major pathogen of periodontal disease that affects a majority of adults worldwide. Increasing evidence shows that periodontal disease is linked to various systemic diseases like diabetes and cardiovascular disease, by contributing to increased systemic levels of inflammation. Lipopolysaccharides (LPS), as a key virulent attribute of P. gingivalis, possesses significant amount of lipid A heterogeneity containing tetra- (LPS_1435/1449) and penta-acylated (LPS₁₆₉₀) structures. Hitherto, the exact molecular mechanism of P. gingivalis LPS involved in periodontal pathogenesis remains unclear, due to limited understanding of the specific receptors and signaling pathways involved in LPS-host cell interactions.

Methodology/Principal Findings

This study systematically investigated the effects of P. gingivalis LPS_1435/1449 and LPS₁₆₉₀ on the expression of TLR2 and TLR4 signal transduction and the activation of pro-inflammatory cytokines IL-6 and IL-8 in human gingival fibroblasts (HGFs). We found that LPS_1435/1449 and LPS₁₆₉₀ differentially modulated TLR2 and TLR4 expression. NF-κB pathway was significantly activated by LPS₁₆₉₀ but not by LPS_1435/1449. In addition, LPS₁₆₉₀ induced significant expression of NF-κB and p38 MPAK pathways-related genes, such as NFKBIA, NFKB1, IKBKB, MAP2K4 and MAPK8. Notably, the pro-inflammatory genes including GM-CSF, CXCL10, G-CSF, IL-6, IL-8 and CCL2 were significantly upregulated by LPS₁₆₉₀ while down-regulated by LPS_1435/1449. Blocking assays confirmed that TLR4-mediated NF-κB signaling was vital in LPS₁₆₉₀-induced expression of IL-6 and IL-8 in HGFs.

Conclusions/Significance

The present study suggests that the tetra- and penta-acylated lipid A structures of P. gingivalis LPS differentially activate TLR4-mediated NF-κB signaling pathway, and significantly modulate the expression of IL-6 and IL-8 in HGFs. The ability to alter the lipid A structure of LPS could be one of the strategies carried-out by P. gingivalis to evade innate host defense in gingival tissues, thereby contributing to periodontal pathogenesis.

An approach to normalizing micro-CT depth profiles of mineral density for monitoring enamel remineralization progress

To indicate the possibility of a new approach to creating mineral density profiles, and to examine longitudinal changes in 'the rate of remineralization (RA)' and 'the mineral density (DAs) at 4 different depths' (surface zone: SZ, lesion body: LB, middle zone: MZ, deep zone near to sound area: DZ) in enamel subsurface lesions, eight demineralized bovine enamel-dentin blocks were remineralized for 1 to 4 week and investigated using Micro-focus X-ray CT (micro-CT). After CT scanning, mineral density profiles were created.Mineral densities at each depth after demineralization were SZ is approximately equal to LB<MZ<DZ. Increase in RA was the greatest in the first week of remineralization and it decreased over time. Increments of the mineral density were greater in the order of SZ is approximately equal to LB>MZ>DZ. This study indicated a new approach to create a mineral density profile and suggested the greater the value of the mineral density before the remineralization, the smaller the mineral density increments.

Unique features of pedicellate attachment of the upper jaw teeth in the adult gobiid fish Sicyopterus japonicus (Teleostei, Gobiidiae): morphological and structural characteristics and development

Sicyopterus japonicus (Teleostei, Gobiidae), a hill-stream herbivorous gobiid fish, possesses an unusual oral dentition among teleost fishes on account of its feeding habitat. By using scanning electron microscopy, light microscopy, and transmission electron microscopy, including vital staining with tetracycline, we examined the development of the attachment tissues of the upper jaw teeth in this fish. The functional teeth of S. japonicus had an asymmetrical dentine shaft. The dentine shaft attached to the underlying uniquely shaped pedicel by means of two different attachment mechanisms. At the lingual base, collagen fiber bundles connected the dentine shaft with the pedicel (hinged attachment), whereas the labial base articulated with an oval-shaped projection of the pedicel (articulate attachment). The pedicel bases were firmly ankylosed to the crest of the thin flange of porous spongy bone on the premaxillary bone, which afforded a flange-groove system on the labial surface of the premaxillary bone. Developmentally, the pedicel and thin flange of spongy bone were completely different mineralized attachment tissues. The pedicel had a dual origin, i.e., the dental papilla cells, which differentiated into odontoblasts that constructed the internal surface of the pedicel, and the mesenchymal cells, which differentiated into osteoblasts that formed the outer face of the pedicel. A thin flange of spongy bone was deposited on the superficial resorbed labial side of the premaxillary bone proper, and later rapid bone remodeling proceeded toward the pedicel base. These unique features of pedicellate tooth attachment for the upper jaw teeth in the adult S. japonicus are highly modified teeth for enhancing the ability of individual functional teeth to move closely over irregularities in the rock surfaces during the scraping of algae.

Zinc and human disease

The vast knowledge of the physiologic functions of zinc in at least 3000 proteins and the recent recognition of fundamental regulatory functions of zinc(II) ions released from cells or within cells links this nutritionally essential metal ion to numerous diseases. However, this knowledge so far has had remarkably limited impact on diagnosing, preventing, and treating human diseases. One major roadblock is a lack of suitable biomarkers that would detect changes in cellular zinc metabolism and relate them to specific disease outcomes. It is not only the right amount of zinc in the diet that maintains health. At least as important is the proper functioning of the dozens of proteins that control cellular zinc homeostasis, regulate intracellular traffic of zinc between the cytosol and vesicles/organelles, and determine the fluctuations of signaling zinc(II) ions. Cellular zinc deficiencies or overloads, a term referring to zinc concentrations exceeding the cellular zinc buffering capacity, compromise the redox balance. Zinc supplementation may not readily remedy zinc deficiency if other factors limit the capability of a cell to control zinc. The role of zinc in human diseases requires a general understanding of the wide spectrum of functions of zinc, how zinc is controlled, how it interacts with the metabolism of other metal ions, in particular copper and iron, and how perturbation of specific zinc-dependent molecular processes causes disease and influences the progression of disease.

Whole cigarette smoke increased the expression of TLRs, HBDs, and proinflammory cytokines by human gingival epithelial cells through different signaling pathways

The gingival epithelium is becoming known as a regulator of the oral innate immune responses to a variety of insults such as bacteria and chemicals, including those chemicals found in cigarette smoke. We investigated the effects of whole cigarette smoke on cell-surface-expressed Toll-like receptors (TLR)-2, -4 and -6, human β-defensin (HBD) and proinflammatory cytokine expression and production in primary human gingival epithelial cells. Whole cigarette smoke was shown to increase TLR2, TLR4 and TLR6 expression. Cigarette smoke led to ERK1/2, p38 and JNK phosphorylation in conjunction with nuclear factor-κB (NFκB) translocation into the nucleus. TLR expression following cigarette smoke exposure was down regulated by the use of ERK1/2, p38, JNK MAP kinases, and NFκB inhibitors, suggesting the involvement of these signaling pathways in the cellular response against cigarette smoke. Cigarette smoke also promoted HBD2, HBD3, IL-1β, and IL-6 expression through the ERK1/2 and NFκB pathways. Interestingly, the modulation of TLR, HBD, and cytokine expression was maintained long after the gingival epithelial cells were exposed to smoke. By promoting TLR, HBDs, and proinflammatory cytokine expression and production, cigarette smoke may contribute to innate immunity dysregulation, which may have a negative effect on human health.

VimA mediates multiple functions that control virulence in Porphyromonas gingivalis

Porphyromonas gingivalis, a black-pigmented, gram-negative anaerobe, is an important etiological agent of periodontal disease. Its ability to survive in the periodontal pocket and orchestrate the microbial/host activities that can lead to disease suggest that P. gingivalis possesses a complex regulatory network involving transcriptional and post-transcriptional mechanisms. The vimA (virulence modulating) gene is part of the 6.15-kb bcp-recA-vimA-vimE-vimF-aroG locus and plays a role in oxidative stress resistance. In addition to the glycosylation and anchorage of several surface proteins including the gingipains, VimA can also modulate sialylation, acetyl coenzyme A transfer, lipid A and its associated proteins and may be involved in protein sorting and transport. In this review, we examine the multifunctional role of VimA and discuss its possible involvement in a major regulatory network important for survival and virulence regulation in P. gingivalis. It is postulated that the multifunction of VimA is modulated via a post-translational mechanism involving acetylation.

Cancer cell micronucleus: an update on clinical and diagnostic applications

Micronucleus (MN) is the small nucleus that forms whenever a chromosome or its fragment is not incorporated into one of the daughter nuclei during cell division. Any form of genotoxic stress due to extraneous or internal factors leads to formation of a MN, which serves as an indicator of chromosomal instability. Chromosomal damage and formation of MN are believed to play a significant role in the pathogenesis of many malignancies. Studies have shown that MN assay can be used as a tool for risk prediction, screening, diagnosis, prognosis and as a treatment-response indicator in cancers. With the advancements in technology, greater details are becoming available regarding the molecular events in carcinogenesis. The micronuclei (MNi) in the cancer cells are now being used as tools to understand the pathogenetics of the malignancies. However, despite large number of studies on MNi in lymphocytes or exfoliated cells of cancer patients, the data regarding a cancer cell MN remain scarce. This review article tries to unleash some of the mysteries related to the formation of MN inside the cancer cell. Also, it discusses the possible effects and the events post MN formation in the cancer cell.

Mineralization induction effects of osteopontin, bone sialoprotein, and dentin phosphoprotein on a biomimetic collagen substrate

Native bone tissue is composed of a matrix of collagen, noncollagenous proteins, and calcium phosphate minerals, which are primarily hydroxyapatite. The SIBLING (small integrin-binding ligand, N-linked glycoprotein) family of proteins is the primary noncollagenous protein group found in mineralized tissues. In this work, the mineralization induction capabilities of three of the SIBLING members, bone sialoprotein (BSP), osteopontin (OPN), and the calcium-binding subdomain of dentin sialophosphoprotein, dentin phosphoprotein (DPP), are directly compared on a biomimetic collagen substrate. A self-assembled, loosely aligned collagen fibril substrate was prepared, and then (125) I-radiolabeled adsorption isotherms were developed for BSP, OPN, and DPP. The results showed that BSP exhibited the highest binding capacity for collagen at lower concentrations, followed by DPP and OPN. However, at the highest concentrations, all three proteins had similar adsorption levels. The adsorption isotherms were then used to identify conditions that resulted in identical amounts of adsorbed protein. These substrates were prepared and placed in simulated body fluid for 5, 10, and 24 h at 37°C. The resulting mineral morphology was assessed by atomic force microscopy, and the composition was determined using photochemical assays. Mineralization was seen in the presence of all the proteins. However, DPP was seen to be the only protein that formed individual mineral nodules similar to those seen in developing bone. This suggests that DPP plays a significant role in the biomineralization process and that the incorporation of DPP into tissue engineering constructs may facilitate the induction of biomimetic mineral formation.

Stem cells in dentistry--Part II: Clinical applications

New technologies that facilitate solid alveolar ridge augmentation are receiving considerable attention in the field of prosthodontics because of the growing requirement for esthetic and functional reconstruction by dental implant treatments. Recently, several studies have demonstrated potential advantages for stem-cell-based therapies in regenerative treatments. Mesenchymal stem/stromal cells (MSCs) are now an excellent candidate for tissue replacement therapies, and tissue engineering approaches and chair-side cellular grafting approaches using autologous MSCs represent the clinical state of the art for stem-cell-based alveolar bone regeneration. Basic studies have revealed that crosstalk between implanted donor cells and recipient immune cells plays a key role in determining clinical success that may involve the recently observed immunomodulatory properties of MSCs. Part II of this review first overviews progress in regenerative dentistry to consider the implications of the stem cell technology in dentistry and then highlights cutting-edge stem-cell-based alveolar bone regenerative therapies. Factors that affect stem-cell-based bone regeneration as related to the local immune response are then discussed. Additionally, pre-clinical stem cell studies for the regeneration of teeth and other oral organs as well as possible applications of MSC-based immunotherapy in dentistry are outlined. Finally, the marketing of stem cell technology in dental stem cell banks with a view toward future regenerative therapies is introduced.

Role of stress-related brain-derived neurotrophic factor (BDNF) in the rat submandibular gland

The nerve growth factor (NGF) family comprises NGF, brain-derived neurotrophic factor (BDNF) and neurotrophins (NTs)-3, -4/5, -6 and -7, all of which are collectively referred to as neurotrophins. However, the expression of neurotrophins other than NGF in the salivary gland has not been described in detail. Through interaction with the TrkB receptor, BDNF plays an important role in long-term potentiation. We found that BDNF expression increased within submandibular gland tissue in response to stress, suggesting that the salivary glands are sensitive to stress. In addition, stress caused increases in plasma BDNF derived from the submandibular gland and in TrkB receptor mRNA in the adrenal medulla. Plasma BDNF might activate TrkB receptors in the adrenal medulla during acute stress. The salivary glands are likely to influence not only oral health, but also systemic organs. This review addressed the relationship between hormone-like effects and stress-related BDNF expression in the rat submandibular gland.

Regional variation in IIM myosin heavy chain expression in the temporalis muscle of female and male baboons (Papio anubis)

OBJECTIVE

The purpose of this study was to determine whether high amounts of fast/type II myosin heavy chain (MyHC) in the superficial as compared to the deep temporalis muscle of adult female and male baboons (Papio anubis) correlates with published data on muscle function during chewing. Electromyographic (EMG) data show a regional specialization in activation from low to high amplitude activity during hard/tough object chewing cycles in the baboon superficial temporalis.(48,49) A positive correlation between fast/type II MyHC amount and EMG activity will support the high occlusal force hypothesis.

DESIGN

Deep anterior temporalis (DAT), superficial anterior temporalis (SAT), and superficial posterior temporalis (SPT) muscle samples were analyzed using SDS-PAGE gel electrophoresis to test the prediction that SAT and SPT will show high amounts of fast/type II MyHC compared to DAT. Serial muscle sections were incubated against NOQ7.5.4D and MY32 antibodies to determine the breadth of slow/type I versus fast/type II expression within each section.

RESULTS

Type I and type IIM MyHCs comprise nearly 100% of the MyHCs in the temporalis muscle. IIM MyHC was the overwhelmingly predominant fast MyHC, though there was a small amount of type IIA MyHC (≤5%) in DAT in two individuals. SAT and SPT exhibited a fast/type II phenotype and contained large amounts of IIM MyHC whereas DAT exhibited a type I/type II (hybrid) phenotype and contained a significantly greater proportion of MyHC-I. MyHC-I expression in DAT was sexually dimorphic as it was more abundant in females.

CONCLUSIONS

The link between the distribution of IIM MyHC and high relative EMG amplitudes in SAT and SPT during hard/tough object chewing cycles is evidence of regional specialization in fibre type to generate high occlusal forces during chewing. The high proportion of MyHC-I in DAT of females may be related to a high frequency of individual fibre recruitment in comparison to males.

A Novel Homozygous WDR72 Mutation in Two Siblings with Amelogenesis Imperfecta and Mild Short Stature

Amelogenesis imperfecta (AI) is a clinically and genetically heterogeneous group of inherited defects of enamel formation. In isolated AI (no additional segregating features), mutations in at least 7 genes are known so far, causing dominant, recessive or X-linked AI and allowing the identification of the molecular etiology in 40-50% of affected families. We report on 2 siblings (an 11-year-old female and a 7-year-old male) born to consanguineous Turkish parents, with AI and mild, proportionate short stature. Both parents have normal teeth, but mother, maternal grandmother and great-grandfather are/were also of short stature. A spine X-ray performed in the girl excluded brachyolmia. Affymetrix GenomeWide SNP6.0 Array analysis identified no pathogenic copy number changes, but showed sharing of large homozygous regions, including chromosome band 15q21.3 containing the WDR72 gene. WDR72 sequence analysis in both siblings revealed homozygosity for a novel stop mutation in exon 10 (c.997A>T, p.Lys333X) explaining the AI phenotype. Mutations in WDR72 are a very rare cause of autosomal-recessive hypomaturation type of isolated AI. The mutation described in our patients specifies the diagnosis AI IIA3 and represents only the sixth WDR72 mutation reported so far. The WDR72 protein is critical for dental enamel formation, but its exact function is still unknown.

Cell dynamics in cervical loop epithelium during transition from crown to root: implications for Hertwig's epithelial root sheath formation

BACKGROUND AND OBJECTIVE

Some clinical cases of hypoplastic tooth root are congenital. Because the formation of Hertwig's epithelial root sheath (HERS) is an important event for root development and growth, we have considered that understanding the HERS developmental mechanism contributes to elucidate the causal factors of the disease. To find integrant factors and phenomenon for HERS development and growth, we studied the proliferation and mobility of the cervical loop (CL).

MATERIAL AND METHODS

We observed the cell movement of CL by the DiI labeling and organ culture system. To examine cell proliferation, we carried out immunostaining of CL and HERS using anti-Ki67 antibody. Cell motility in CL was observed by tooth germ slice organ culture using green fluorescent protein mouse. We also examined the expression of paxillin associated with cell movement.

RESULTS

Imaging using DiI labeling showed that, at the apex of CL, the epithelium elongated in tandem with the growth of outer enamel epithelium (OEE). Cell proliferation assay using Ki67 immunostaining showed that OEE divided more actively than inner enamel epithelium (IEE) at the onset of HERS formation. Live imaging suggested that mobility of the OEE and cells in the apex of CL were more active than in IEE. The expression of paxillin was observed strongly in OEE and the apex of CL.

CONCLUSION

The more active growth and movement of OEE cells contributed to HERS formation after reduction of the growth of IEE. The expression pattern of paxillin was involved in the active movement of OEE and HERS. The results will contribute to understand the HERS formation mechanism and elucidate the cause of anomaly root.

Trichocyalides A and B, new inhibitors of alkaline phosphatase activity in bone morphogenetic protein-stimulated myoblasts, produced by Trichoderma sp. FKI-5513

Two new butenolides, designated trichocyalides A and B, were isolated along with the known compound harzianolide, from the culture broth of Trichoderma sp. FKI-5513 by solvent extraction, ODS column chromatography and HPLC. Their structures were elucidated by several spectral analyses, showing that they have the common skeleton of butenofuranone. Trichocyalides A and B inhibited alkaline phosphatase (ALP) activity, a typical marker enzyme of osteoblastic differentiation (IC(50): 83.0 and 187 μM, respectively), in bone morphogenetic protein (BMP)-stimulated C2C12 myoblasts mutant cells, which stably express BMP receptor activity, whereas harzianolide showed no inhibitory activity against ALP even at 500 μM.

Adhesion of MC3T3-E1 cells bound to dentin phosphoprotein specifically bound to collagen type I

Dentin sialophosphoprotein (DSPP) is a member of the SIBLING (small integrin binding N-linked glycoprotein) family of proteins commonly found in mineralized tissues. Dentin phosphoprotein (DPP) is a naturally occurring subdomain of DSPP that contains the cell binding RGD sequence. Previously, the orientation and conformation of other SIBLING family members specifically bound to collagen I have been investigated with respect to their cell adhesion properties. In this study, the orientation of DPP under similar circumstances is examined, and the results are discussed relative to the previous investigations. Radiolabeled adsorption isotherms were developed for DPP adsorbing to both tissue culture polystyrene (TCPS) and collagen coated TCPS. Then, a MC3T3-E1 cell adhesion assay was performed on TCPS and collagen coated TCPS in the presence of identical amounts of adsorbed DPP. It was discovered that there was a significant difference in the number of bound cells on the TCPS and collagen coated TCPS, with a preference for TCPS. Furthermore, a cell inhibition assay was conducted to confirm that the cell binding that occurred was due to specific integrin interactions with the RGD sequence of DPP. These results suggest that the orientation of DPP, rather than its conformation, dictates the accessibility of the cell binding RGD domains of DPP and that the RGD sequence in DPP is less accessible when DPP is specifically bound to collagen. The results obtained in this study are in stark contrast to previous studies with related SIBLING proteins, and suggest that DPP does not play a key role in cell binding to the collagen matrix of developing bone.

Peptide-based delivery to bone

Peptides are attractive as novel therapeutic reagents, since they are flexible in adopting and mimicking the local structural features of proteins. Versatile capabilities to perform organic synthetic manipulations are another unique feature of peptides compared to protein-based medicines, such as antibodies. On the other hand, a disadvantage of using a peptide for a therapeutic purpose is its low stability and/or high level of aggregation. During the past two decades, numerous peptides were developed for the treatment of bone diseases, and some peptides have already been used for local applications to repair bone defects in the clinic. However, very few peptides have the ability to form bone themselves. We herein summarize the effects of the therapeutic peptides on bone loss and/or local bone defects, including the results from basic studies. We also herein describe some possible methods for overcoming the obstacles associated with using therapeutic peptide candidates.

Relationships between the root-crown ratio and the loss of occlusal contact and high mandibular plane angle in patients with open bite

OBJECTIVE

To determine the root-crown (R/C) ratio and dental root length of teeth in patients with open bite and seek any relationships with occlusal contact (OC) and the mandibular plane (Mp) angle.

MATERIALS AND METHODS

Thirty-one patients with open bite with negative overbite of at least four anterior teeth and 31 control patients with clinically normal overjet and overbite were enrolled. R/C ratios, dental root length, OC, and Mp angle were measured using panoramic radiographs, dental casts, and cephalograms, respectively. Mean differences between the groups, and variations between the R/C ratio or root length and Mp angle in patients with open bite were statistically analyzed.

RESULTS

R/C and OC ratios from the incisors to premolars were significantly lower for patients with open bite than for controls, and some teeth had short dental roots. Relationships between low R/C ratio or root length and high Mp angle were significant in patients with open bite.

CONCLUSION

Patients with open bite, especially those with a high Mp angle, have an unfavorable R/C ratio and short dental roots in some teeth, which may be related to the loss of OC.

Two distinct processes of bone-like tissue formation by dental pulp cells after tooth transplantation

Dental pulp is involved in the formation of bone-like tissue in response to external stimuli. However, the origin of osteoblast-like cells constructing this tissue and the mechanism of their induction remain unknown. We therefore evaluated pulp mineralization induced by transplantation of a green fluorescent protein (GFP)-labeled tooth into a GFP-negative hypodermis of host rats. Five days after the transplantation, the upper pulp cavity became necrotic; however, cell-rich hard tissue was observed adjacent to dentin at the root apex. At 10 days, woven bone-like tissue was formed apart from the dentin in the upper pulp. After 20 days, these hard tissues expanded and became histologically similar to bone. GFP immunoreactivity was detected in the hard tissue-forming cells within the root apex as well as in the upper pulp. Furthermore, immunohistochemical observation of α-smooth muscle actin, a marker for undifferentiated cells, showed a positive reaction in cells surrounding this bone-like tissue within the upper pulp but not in those within the root apex. Immunoreactivities of Smad4, Runx2, and Osterix were detected in the hard tissue-forming cells within both areas. These results collectively suggest that the dental pulp contains various types of osteoblast progenitors and that these cells might thus induce bone-like tissue in severely injured pulp.

Evaluating the feasibility of utilizing the small molecule phenamil as a novel biofactor for bone regenerative engineering

Osteoblast cell adhesion and differentiation on biomaterials are important achievements necessary for implants to be useful in bone regenerative engineering. Recombinant bone morphogenetic proteins (BMPs) have been shown to be important for these processes; however, there are many challenges associated with the widespread use of these proteins. A recent report demonstrated that the small molecule phenamil, a diuretic derivative, was able to induce osteoblast differentiation and mineralization in vitro via the canonical BMP signalling cascade (Park et al., 2009). In this study, the feasibility of using phenamil as a novel biofactor in conjunction with a biodegradable poly(lactide-co-glycolide acid) (PLAGA) polymeric scaffold for engineering bone tissue was evaluated. The in vitro cellular behaviour of osteoblast-like MC3T3-E1 cells cultured on PLAGA scaffolds in the presence of phenamil at 10 μM were characterized with regard to initial cell adhesion, proliferation, alkaline phosphatase (ALP) activity and matrix mineralization. The results demonstrate that phenamil supported cell proliferation, promoted ALP activity and facilitated matrix mineralization of osteoblast-like MC3T3-E1 cells. Moreover, in this study, we found that phenamil promoted integrin-mediated cell adhesion on PLAGA scaffolds. It was also shown that phenamil encapsulated within porous, microsphere PLAGA scaffolds retained its osteogenic activity upon release. Based on these findings, the small molecule phenamil has the potential to serve as a novel biofactor for the repair and regeneration of bone tissues.

Stem cells in dentistry--part I: stem cell sources

Stem cells can self-renew and produce different cell types, thus providing new strategies to regenerate missing tissues and treat diseases. In the field of dentistry, adult mesenchymal stem/stromal cells (MSCs) have been identified in several oral and maxillofacial tissues, which suggests that the oral tissues are a rich source of stem cells, and oral stem and mucosal cells are expected to provide an ideal source for genetically reprogrammed cells such as induced pluripotent stem (iPS) cells. Furthermore, oral tissues are expected to be not only a source but also a therapeutic target for stem cells, as stem cell and tissue engineering therapies in dentistry continue to attract increasing clinical interest. Part I of this review outlines various types of intra- and extra-oral tissue-derived stem cells with regard to clinical availability and applications in dentistry. Additionally, appropriate sources of stem cells for regenerative dentistry are discussed with regard to differentiation capacity, accessibility and possible immunomodulatory properties.

gbpC gene repertoire variation among mutans Streptococci

The human dental caries pathogen Streptococcus mutans harbors one glucan-binding wall-anchored protein gene, gbpC, and another human pathogen, Streptococcus sobrinus, has 4 gbpC homologues. As no 4 gbpC homologues have so far been detected in other mutans streptococci, however, we cannot say whether those in S. sobrinus are paralogous or orthologous. Therefore, the purpose of this study was to identify and sequence the gbpC/dbl genes in Streptococcus downei and Streptococcus criceti. The findings revealed that the former harbored 5 gbpC/dbl homologues and the latter 4. In addition, another dbl homologue, the dblC gene, was found in some strains of S. sobrinus. We performed a phylogenetic analysis with the gbpC/dbl genes in these mutans streptococci. These results indicate that the gbpC and dbl genes have an orthologous relationship.

Probiotics as oral health biotherapeutics

INTRODUCTION

Oral health is affected by its resident microorganisms. Three prominent oral disorders are dental caries, gingivitis and periodontitis, with the oral microbiota playing a key role in the initiation/progression of all three. Understanding the microbiota and the diseases they may cause is critical to the development of new therapeutics. This review is focused on probiotics for the prevention and/or treatment of oral diseases.

AREAS COVERED

This review describes the oral ecosystem and its correlation with oral health/disease. The pathogenesis and current prevention/treatment strategies of periodontal diseases (PD) and dental caries (DC) are depicted. An introduction of probiotics is followed by an analysis of their role in PD and DC, and their potential role(s) in oral health. Finally, a discussion ensues on the future research directions and limitations of probiotics for oral health.

EXPERT OPINION

An effective oral probiotic formulation should contribute to the prevention/treatment of microbial diseases of the oral cavity. Understanding the oral microbiota's role in oral disease is important for the development of a therapeutic to prevent/treat dental diseases. However, investigations into clinical efficacy, delivery/dose optimization, mechanism(s) of action and other related parameters are yet to be fully explored. Keeping this in mind, investigations into oral probiotic therapies are proving promising.

Immunohistochemical localization of the NH(2)-terminal and COOH-terminal fragments of dentin sialoprotein in mouse teeth

Dentin sialoprotein (DSP) is a major non-collagenous protein in dentin. Mutation studies in human, along with gene knockout and transgenic experiments in mice, have confirmed the critical role of DSP for dentin formation. Our previous study reported that DSP is processed into fragments in mouse odontoblast-like cells. In order to gain insights into the function of DSP fragments, we further evaluated the expression pattern of DSP in the mouse odontoblast-like cells using immunohistochemistry and western blot assay with antibodies against the NH(2)-terminal and COOH-terminal regions of DSP. Then, the distribution profiles of the DSP NH(2)-terminal and COOH-terminal fragments and osteopontin (OPN) were investigated in mouse teeth at different ages by immunohistochemistry. In the odontoblast-like cells, multiple low molecular weight DSP fragments were detected, suggesting that part of the DSP protein was processed in the odontoblast-like cells. In mouse first lower molars, immunoreactions for anti-DSP-NH(2) antibody were intense in the predentin matrix but weak in mineralized dentin; in contrast, for anti-DSP-COOH antibody, strong immunoreactions were found in mineralized dentin, in particular dentinal tubules but weak in predentin. Therefore, DSP NH(2)-terminal and COOH-terminal fragments from odontoblasts were secreted to different parts of teeth, suggesting that they may play distinct roles in dentinogenesis. Meanwhile, both DSP antibodies showed weak staining in reactionary dentin (RD), whereas osteopontin (OPN) was clearly positive in RD. Therefore, DSP may be less crucial for RD formation than OPN.

Lysyl oxidase and the lysyl oxidase-like protein modulate odontoblastic differentiation of human dental pulp cells

INTRODUCTION

The lysyl oxidase (LOX) family is an emerging family of amine oxidases responsible for the formation of collagen fibrils in the extracellular matrix. To date, 5 LOX family genes have been identified in humans, encoding LOX and LOX-like proteins (LOXL, LOXL2, LOXL3, and LOXL4). The goal of this study was to evaluate the expression and function of the LOX family genes in odontoblastic differentiation of human dental pulp (HDP) cells.

METHODS

Expression of the LOX family genes was assessed by reverse transcriptase polymerase chain reaction analysis, and the amine oxidase activity of HDP cells was evaluated by peroxidase-coupled fluorometric assays. Mineral nodule formation and expression of odontoblastic marker genes were assessed in the presence and absence of specific small interfering RNAs (siRNAs) of the LOX family genes.

RESULTS

Among the LOX family genes, only LOX and LOXL showed prominent expression during odontoblastic differentiation of HDP cells. Suppression of LOX and LOXL expression by siRNA-induced interference substantially decreased the amine oxidase activity of the differentiating HDP cells. Furthermore, interference of LOX and LOXL expression inhibited mineral nodule formation and expression of odontoblastic marker genes during odontoblastic differentiation of HDP cells.

CONCLUSIONS

These findings show for the first time that the LOX- and LOXL-mediated organization of collagen fibrils in extracellular matrices of HDP cells might be an important regulator for odontoblastic differentiation of HDP cells.

Hereditary dentine diseases resulting from mutations in DSPP gene

OBJECTIVES

This review groups the newest results of molecular analyses of DSPP gene for patients diagnosed either with dentinogenesis imperfecta type II/III or dentine dysplasia and tries to link the phenotypes with specific mutations in the DSPP gene.

DATA

The review includes biochemical data introducing a specificity of DSPP protein which justifies it as a critical factor for dentine mineralization and maturation. The majority of the review analyzes mutations in the DSPP gene which result in phenotypes of dentinogenesis imperfecta types II or/and III or dentine dysplasia.

SOURCES

An electronic search was conducted in the databases of Pub Med and supplemented by manual study of relevant references.

STUDY SELECTION

52 out of 108 references were finally selected for the review based on the novelty and/or originality of data.

CONCLUSION

Hereditary dentine disorders dentinogenesis imperfecta type II/III and dentine dysplasia are currently proposed to be one disease with distinct clinical manifestations reflecting various mutations in the same DSPP gene. For years both disorders were linked exclusively to mutations in the DSP code but a growing number of papers describe mutations which manifest a similar phenotype but are localized in the strongly repetitive sequence of the 3' terminus of the DSPP which codes DPP protein. Our search suggests that the localization of mutation in the sequence of the DSPP gene might result in a different phenotype due to the diverse cellular fate of the mutated protein. Thus comprehensive research on the cellular fate and processing of both normal and mutated DSPP is still required.