Effect of lipopolysaccharides on vascular endothelial growth factor expression in mouse pulp cells and macrophages

Photobiomodulation therapy does not depend on the differentiation of dental pulp cells to enhance functional activity associated with angiogenesis and mineralization

The purpose of this study is to analyze the influence of InGaAlP diode laser (660 nm) with or without an odontogenic medium (OM) in the functional activity of OD-21 cells. Undifferentiated OD-21 pulp cells were cultivated with or without OM and divided into four groups (n = 5): nonirradiated control (C -), nonirradiated + OM (C +), irradiated (L -), and irradiated + OM (L +). Laser application was performed in two sessions of a 24-h interval with an irradiance of 11.3 mW/cm2, energy density of 1 J/cm², and total cumulative energy/well of 4.6 J. Cell proliferation, VEGF-164 expression, mineralization, and expression of Alp, Runx2, and Dmp1 genes, as well as immunolocalization of RUNX2 and MEPE proteins, were evaluated. Data were analyzed by statistical tests (α = 0.05). All studied groups showed a similar increase in cell proliferation with or without OM. After 7 and 10 days, a significatively higher concentration of VEGF-164 in L - group when compared to C - group was observed. A significant increase in mineralized nodules in the L + was noted when compared to C + in the same conditions. Photobiomodulation upregulated significantly Runx2 and Dmp1 expression after 10 days in L - and after 7 days in L + , with downregulation of Dmp1 after 10 days in L + group. Immunolocalization of RUNX2 and MEPE was expressive after 7 days of culture in the cytoplasm adjacent to the nucleus with a decrease after 10 days, regardless of the presence of OM. Photobiomodulation enhances metabolism associated with angiogenesis, gene expression, and mineralization regardless of the odontogenic medium in OD-21 cells.

The effect of different irrigation solutions and activation techniques on the expression of growth factors from dentine of extracted premolar teeth

AIM

To evaluate in a laboratory study, the effect of different canal irrigant solutions and activation techniques on transforming growth factor (TGF-β1), insulin growth factor-1 (IGF-1), bone morphogenetic protein-7 (BMP-7) and vascular endothelial growth factor-A (VEGF-A) release levels from the dentine of extracted premolar teeth.

METHODOLOGY

Seventy premolar teeth with single root and canal were used. The lengths of the root segments were standardized to 12 mm, and the root canals were prepared up to size 100 with hand files. All surfaces of the teeth were covered with nail polish except the inner root canal surface. The root canals were irrigated with 1.5% NaOCl. Ten teeth were allocated to the control group. The remaining sixty teeth were divided into 2 main groups according to the chelating agent used (17% EDTA, 10% Citric acid; CA) and 3 subgroups (n = 10) according to irrigation activation technique (conventional syringe irrigation (CSI), passive ultrasonic irrigation (PUI) and Er:YAG laser activation). After the activation procedure, the root segments were placed into eppendorf tubes containing 1 mL of phosphate-buffered saline solution and kept at 37℃. TGF-β1, IGF-1, BMP-7 and VEGF-A release levels from dentine were measured using the enzyme-linked immunosorbent assay (ELISA) method at 24 h and at day 7. The volume of root canals was calculated using cone-beam computed tomography. The growth factor levels were calculated in ng/mL except VEGF-A (pg/ml). Normality analysis of the data was evaluated with the Kolmogorov-Smirnov test. Statistical analysis was performed using the Mann-Whitney-U and Wilcoxon tests.

RESULTS

Regardless of the activation type and sampling time, EDTA caused significantly more IGF release than did CA, whereas EDTA and CA were equally effective for the release of the other growth factors. For either EDTA or CA, the lowest and highest growth factor release levels were observed in the CSI and Er:YAG laser groups, respectively (p < .05). All of the growth factors were released significantly more at 24 h than on day 7 (p < .05).

CONCLUSIONS

Irrigation activation techniques with EDTA or CA increased the release levels of all growth factors from the dentine of canal walls in extracted premolar teeth.

Effects of different pulp-capping materials on cell death signaling pathways of lipoteichoic acid-stimulated human dental pulp stem cells

PURPOSE

This study aimed to evaluate the response of dental pulp stem cells (DPSCs) cultured with and without lipoteichoic acid (LTA) to different pulp-capping materials.

METHODS

The cells were cultured and seeded in 6-well plates and exposed to 1% LTA solution. Dycal, ProRoot MTA and Biodentine materials were applied on cells and all groups were evaluated by cell proliferation, viability, cell cycle and cell death signaling pathways for 24 and 72 h.

RESULTS

LTA + Dycal treatment significantly inhibited the proliferation of DPSCs and increased the apoptosis rate of cells more than the other groups at 72 h. Compared to other groups, LTA + Dycal treatment significantly increased the levels of Caspase-3 and AKT and decreased the levels of p-AKT.

CONCLUSIONS

The results of this study revealed that all tested materials caused apoptosis in DPSCs via an extrinsic apoptotic pathway. The DPSCs showed an early apoptosis response to the Dycal and a late apoptosis response to the ProRoot MTA and Biodentine treatments. LTA led autophagy and inhibited the proliferation of DPSCs. ProRoot MTA and Biodentin eliminated the LTA's bioactivity with higher efficiency than Dycal.

Human closed and open apex premolar teeth express different toll-like receptor

Background

The innate immune activation which promotes inflammation responses in the dental pulp tissue leads to the progression of dentin caries. Accordingly, toll‐like receptors (TLRs) are key molecules of the innate immune system that identify pathogen‐associated molecular patterns (PAMPs) on microorganisms and may have a critical role in a dental injury. Therefore, this study aimed to investigate the expression of TLR2, TLR3, and TLR4 in the human dental pulp of opened and closed apex teeth.

Methods

Human dental pulps were derived from the healthy opened and closed apex premolar, in which extraction was indicated for orthodontic reasons. The extraction of RNA was performed and the gene expression determined by real‐time polymerase chain reaction (RT‐PCR). The result from real‐time PCR was confirmed using western blot analysis.

Results

Real‐time PCR data analysis showed that the expression TLR2 and TLR4 were significantly increased in closed apex premolar teeth compared to open apex teeth, whereas TLR3 expression was not significantly different in these two groups (p < .05).

Conclusion

The results of the present study suggested increased expression of TLR2 and TLR4 by the maturation of the apex, which may be due to the presence of microorganisms in the normal or destructed dental pulp tissue. Thus, identifying the expression of TLRs molecules in dental pulp tissue helps to develop a deeper knowledge of the immune responses in the oral cavity.

The Neurovascular Properties of Dental Stem Cells and Their Importance in Dental Tissue Engineering

Within the field of tissue engineering, natural tissues are reconstructed by combining growth factors, stem cells, and different biomaterials to serve as a scaffold for novel tissue growth. As adequate vascularization and innervation are essential components for the viability of regenerated tissues, there is a high need for easily accessible stem cells that are capable of supporting these functions. Within the human tooth and its surrounding tissues, different stem cell populations can be distinguished, such as dental pulp stem cells, stem cells from human deciduous teeth, stem cells from the apical papilla, dental follicle stem cells, and periodontal ligament stem cells. Given their straightforward and relatively easy isolation from extracted third molars, dental stem cells (DSCs) have become an attractive source of mesenchymal-like stem cells. Over the past decade, there have been numerous studies supporting the angiogenic, neuroprotective, and neurotrophic effects of the DSC secretome. Together with their ability to differentiate into endothelial cells and neural cell types, this makes DSCs suitable candidates for dental tissue engineering and nerve injury repair.

MicroRNA 665 Regulates Dentinogenesis through MicroRNA-Mediated Silencing and Epigenetic Mechanisms

Studies of proteins involved in microRNA (miRNA) processing, maturation, and silencing have indicated the importance of miRNAs in skeletogenesis, but the specific miRNAs involved in this process are incompletely defined. Here, we identified miRNA 665 (miR-665) as a potential repressor of odontoblast maturation. Studies with cultured cell lines and primary embryonic cells showed that miR-665 represses the expression of early and late odontoblast marker genes and stage-specific proteases involved in dentin maturation. Notably, miR-665 directly targeted Dlx3 mRNA and decreased Dlx3 expression. Furthermore, RNA-induced silencing complex (RISC) immunoprecipitation and biotin-labeled miR-665 pulldown studies identified Kat6a as another potential target of miR-665. KAT6A interacted physically and functionally with RUNX2, activating tissue-specific promoter activity and prompting odontoblast differentiation. Overexpression of miR-665 reduced the recruitment of KAT6A to Dspp and Dmp1 promoters and prevented KAT6A-induced chromatin remodeling, repressing gene transcription. Taken together, our results provide novel molecular evidence that miR-665 functions in an miRNA-epigenetic regulatory network to control dentinogenesis.

TNF-α and LPS activate angiogenesis via VEGF and SIRT1 signalling in human dental pulp cells

AIM

To assess whether SIRT1 and VEGF are responsible for tumour necrosis factor-α (TNF-α) and lipopolysaccharide (LPS)-induced angiogenesis and to examine the molecular mechanism(s) of action in human dental pulp cells (HDPCs).

METHODOLOGY

Immortalized HDPCs obtained from Prof. Takashi Takata (Hiroshima University, Japan) were treated with LPS (1 μg mL(-1) ) and TNF-α (10 ng mL(-1) ) for 24 h. mRNA and protein levels were examined by RT-PCR and Western blotting, respectively. Migration and tube formation were examined in human umbilical vein endothelial cells (HUVECs). The data were analysed by one-way anova. Statistical analysis was performed at α = 0.05.

RESULTS

LPS and TNF-α upregulated VEGF and SIRT1 mRNA and protein levels. Inhibition of SIRT1 activity by sirtinol and SIRT1 siRNA or inhibition of the VEGF receptor by CBO-P11 significantly attenuated LPS + TNF-α-stimulated MMPs production in HDPCs, as well as migration and tube formation in HUVECs (P < 0.05). Furthermore, sirtinol, SIRT1 siRNA and CBO-P11 attenuated phosphorylation of Akt, extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinase (JNK) and the nuclear translocation of NF-κB p65. Pre-treatment with inhibitors of p38, ERK, JNK, PI3K and NF-κB decreased LPS + TNF-α-induced VEGF and SIRT1 expression, MMPs activity in HDPCs and angiogenesis (P < 0.05) in HUVECs.

CONCLUSIONS

TNF-α and LPS led to upregulation of VEGF and SIRT1, and subsequent upregulation of MMP-2 and MMP-9 production, and promote angiogenesis via pathways involving PI3K, p38, ERK, JNK and NF-κB. The results suggest that inhibition of SIRT1 and VEGF might attenuate pro-inflammatory mediator-induced pulpal disease.

Propolis decreases lipopolysaccharide-induced inflammatory mediators in pulp cells and osteoclasts

BACKGROUND

Intracanal medicaments are used to disinfect the root canal system, reduce interappointment pain and inflammation, and prevent resorption. Bacterial components such as lipopolysaccharide (LPS) are implicated in the development of pulpal and periapical inflammation and inducing osteoclastogenesis. Propolis is a natural, non-toxic substance collected from bee's wax that has been used for many years in folk medicine. Propolis has been demonstrated to have antibacterial and anti-inflammatory properties. Our previous studies have shown that propolis inhibits osteoclast maturation. However, the effect of propolis on the inflammatory response of pulp cells and osteoclasts has not been explored.

AIM

The purpose of this study was to evaluate whether propolis alters the inflammatory response of three endodontically relevant cell lines: mouse odontoblast-like cells (MDPC-23), macrophages (RAW264.7), and osteoclasts.

MATERIAL AND METHODS

Cells were exposed to 0-20 ug ml(-1) LPS to induce an inflammatory response, in the presence of propolis or vehicle control. Culture supernatants were collected after 6 and 24 h, and expression of multiple soluble mediators was determined using Luminex(®) multiplex technology.

RESULTS

Propolis was effective in reducing secretion of the LPS-induced inflammatory cyto/chemokines: IL-1α, IL-6, IL-12(p70), IL-15, G-CSF, TNF-α, MIP-1α, MCP-1, and IP-10.

CONCLUSION

Our results demonstrate that propolis suppresses the LPS-induced inflammatory response of key cells within the root canal system.

Inhibitory effect of Zingiber cassumunar extracts on lipopolysaccharide-induced cyclooxygenase-2 and matrix metalloproteinase expression in human gingival fibroblasts

BACKGROUND AND OBJECTIVE

Lipopolysaccharides (LPS) induce the production of proinflammatory mediators such as prostaglandins and matrix metalloproteinases (MMPs) in human gingival fibroblasts (HGFs). Zingiber cassumunar is a medicinal plant that possesses anti-inflammatory properties. The aim of this study was to determine the effects of the Z. cassumunar extract on the expression of cyclooxygenase (COX)-1, COX-2 and MMP-2 in HGFs challenged with LPS.

MATERIAL AND METHODS

HGFs were treated with LPS in the presence or absence of Z. cassumunar extracts. The levels of expression of COX-1, COX-2 and MMP-2 mRNAs and of COX-1, COX-2 and MMP-2 proteins were detected by reverse transcription-polymerase chain reaction and western blotting, respectively. MMP-2 activities in cell-culture supernatants were determined using gelatin zymography. MAPK activation was evaluated by western blotting.

RESULTS

LPS treatment of HGFs resulted in the activation of ERK1/2, p38 and JNK. Z. cassumunar extracts significantly inhibited the phosphorylation of ERK1/2 and JNK in HGFs stimulated with LPS. A lesser inhibitory effect was observed for the phosphorylation of p38. RT-PCR and western blot analyses showed that Z. cassumunar extracts inhibited the LPS-induced expression of COX-2 mRNA and COX-2 protein, respectively, but not of COX-1 mRNA or COX-1 protein. Pretreatment of HGFs with Z. cassumunar also attenuated the induction of MMP-2 with LPS.

CONCLUSION

Our results indicate that Z. cassumunar extracts inhibit COX-2 and MMP-2 production by LPS-activated human gingival fibroblasts through blocking the proinflammatory signaling pathway involving ERK1/2, JNK and p38.

Prolyl hydroxylase inhibitors increase the production of vascular endothelial growth factor in dental pulp-derived cells

INTRODUCTION

Prolyl hydroxylase (PHD) inhibitors can induce a proangiogenic response that stimulates regeneration in soft and hard tissues. However, the effect of PHD inhibitors on the dental pulp is unclear. The purpose of this study was to evaluate the effects of PHD inhibitors on the proangiogenic capacity of human dental pulp-derived cells.

METHODS

To test the response of dental pulp-derived cells to PHD inhibitors, the cells were exposed to dimethyloxalylglycine, desferrioxamine, L-mimosine, and cobalt chloride. To assess the response of dental pulp cells to a capping material supplemented with PHD inhibitors, the cells were treated with supernatants from calcium hydroxide. Viability, proliferation, and protein synthesis were assessed by formazan formation, (3)[H]thymidine, and (3)[H]leucine incorporation assays. The effect on the proangiogenic capacity was measured by immunoassays for vascular endothelial growth factor (VEGF).

RESULTS

We found that all 4 PHD inhibitors can reduce viability, proliferation, and protein synthesis at high concentrations. At nontoxic concentrations and in the presence of supernatants from calcium hydroxide, PHD inhibitors stimulated the production of VEGF in dental pulp-derived cells. When calcium hydroxide was supplemented with the PHD inhibitors, the supernatants from these preparations did not significantly elevate VEGF levels.

CONCLUSIONS

These results show that PHD inhibitors can stimulate VEGF production of dental pulp-derived cells, suggesting a corresponding increase in their proangiogenic capacity. Further studies will be required to understand the impact that this might have on pulp regeneration.

Semaphorin 4A exerts a proangiogenic effect by enhancing vascular endothelial growth factor-A expression in macrophages

The axon guidance cues semaphorins (Semas) and their receptors plexins have been shown to regulate both physiological and pathological angiogenesis. Sema4A plays an important role in the immune system by inducing T cell activation, but to date, the role of Sema4A in regulating the function of macrophages during the angiogenic and inflammatory processes remains unclear. In this study, we show that macrophage activation by TLR ligands LPS and polyinosinic-polycytidylic acid induced a time-dependent increase of Sema4A and its receptors PlexinB2 and PlexinD1. Moreover, in a thioglycollate-induced peritonitis mouse model, Sema4A was detected in circulating Ly6C(high) inflammatory monocytes and peritoneal macrophages. Acting via PlexinD1, exogenous Sema4A strongly increased macrophage migration. Of note, Sema4A-activated PlexinD1 enhanced the expression of vascular endothelial growth factor-A, but not of inflammatory chemokines. Sema4A-stimulated macrophages were able to activate vascular endothelial growth factor receptor-2 and the PI3K/serine/threonine kinase Akt pathway in endothelial cells and to sustain their migration and in vivo angiogenesis. Remarkably, in an in vivo cardiac ischemia/reperfusion mouse model, Sema4A was highly expressed in macrophages recruited at the injured area. We conclude that Sema4A activates a specialized and restricted genetic program in macrophages able to sustain angiogenesis and participates in their recruitment and activation in inflammatory injuries.

In vitro evaluation of the odontogenic potential of mouse undifferentiated pulp cells

The aim of this study was to evaluate the odontogenic potential of undifferentiated pulp cells (OD-21 cell line) through chemical stimuli in vitro. Cells were divided into uninduced cells (OD-21), induced cells (OD-21 cultured in supplemented medium/OD-21+OM) and odontoblast-like cells (MDPC-23 cell line). After 3, 7, 10 and 14 days of culture, it was evaluated: proliferation and cell viability, alkaline phosphatase activity, total protein content, mineralization, immunolocalization of dentin matrix acidic phosphoprotein 1 (DMP1), alkaline phosphatase (ALP) and osteopontin (OPN) and quantification of genes ALP, OSTERIX (Osx), DMP1 and runt-related transcription factor 2 (RUNX2) through real-time polymerase chain reaction (PCR). Data were analyzed by Kruskal-Wallis and Mann-Whitney U tests (p<0.05). There was a decrease in cell proliferation in OD-21 + OM, whereas cell viability was similar in all groups, except at 7 days. The amount of total protein was higher in group OD-21 + OM in all periods; the same occurred with ALP activity after 10 days when compared with OD-21, with no significant differences from the MDPC-23 group. Mineralization was higher in OD-21+OM when compared with the negative control. Immunolocalization demonstrated that DMP1 and ALP were highly expressed in MDPC-23 cells and OD-21 + OM cells, whereas OPN was high in all groups. Real-time PCR revealed that DMP1 and ALP expression was higher in MDPC-23 cell cultures, whereas RUNX2 was lower for these cells and higher for OD-21 negative control. Osx expression was lower for OD-21 + OM. These results suggest that OD-21 undifferentiated pulp cells have odontogenic potential and could be used in dental tissue engineering.

Regenerative endodontics in light of the stem cell paradigm

Stem cells play a critical role in development and in tissue regeneration. The dental pulp contains a small sub-population of stem cells that are involved in the response of the pulp to caries progression. Specifically, stem cells replace odontoblasts that have undergone cell death as a consequence of the cariogenic challenge. Stem cells also secrete factors that have the potential to enhance pulp vascularisation and provide the oxygen and nutrients required for the dentinogenic response that is typically observed in teeth with deep caries. However, the same angiogenic factors that are required for dentine regeneration may ultimately contribute to the demise of the pulp by enhancing vascular permeability and interstitial pressure. Recent studies focused on the biology of dental pulp stem cells revealed that the multipotency and angiogenic capacity of these cells could be exploited therapeutically in dental pulp tissue engineering. Collectively, these findings suggest new treatment paradigms in the field of endodontics. The goal of this review is to discuss the potential impact of dental pulp stem cells to regenerative endodontics.

LPS Sensitizes TRPV1 via Activation of TLR4 in Trigeminal Sensory Neurons

Recent studies have demonstrated that the lipopolysaccharide (LPS) receptor (TLR4) is expressed in TRPV1 containing trigeminal sensory neurons. In this study, we evaluated whether LPS activates trigeminal neurons, and sensitizes TRPV1 responses via TLR4. To test this novel hypothesis, we first demonstrated that LPS binds to receptors in trigeminal neurons using competitive binding. Second, we demonstrated that LPS evoked aconcentration-dependent increase in intracellular calcium accumulation (Ca2+)i and inward currents. Third, LPS significantly sensitized TRPV1 to capsaicin measured by (Ca2+)i, release of calcitonin gene-related peptide, and inward currents. Importantly, a selective TLR4 antagonist blocked these effects. Analysis of these data, collectively, demonstrates that LPS is capable of directly activating trigeminal neurons, and sensitizing TRPV1 via a TLR4-mediated mechanism. These findings are consistent with the hypothesis that trigeminal neurons are capable of detecting pathogenic bacterial components leading to sensitization of TRPV1, possibly contributing to the inflammatory pain often observed in bacterial infections.

MAPK Signaling Is Required for LPS-induced VEGF in Pulp Stem Cells

Caries-induced pulpitis is typically accompanied by an increase in dental pulp microvascular density. However, the mechanisms by which dental pulp cells recognize lipopolysaccharides (LPSs) remain unclear. We hypothesized that Porphyromonas endodontalis and Escherichia coli LPSs induce vascular endothelial growth factor (VEGF) expression in dental pulp stem cells (DPSC) and human dental pulp fibroblasts (HDPF) through mitogen-activated protein kinase (MAPK) signaling. ELISA, semi-quantitative RT-PCR, immunofluorescence, and Western blots were used. Here, we observed that LPSs induced VEGF expression in DPSC and HDPF cells, and both cell types express Toll-like receptor 4 (TLR- 4). Notably, LPS-induced VEGF is associated with phosphorylation of protein kinase C (PKC ζ) and extracellular signal-regulator kinase (ERK1/2) and is dependent upon MAPK activation. Analysis of these data, collectively, unveils a signaling pathway responsible for synthesis of VEGF by pulp cells and suggests a novel therapeutic target for the management of vascular responses in teeth with pulpitis.

Angiogenic signaling triggered by cariogenic bacteria in pulp cells

The inflammation observed in the dental pulp of teeth with deep caries lesions is characterized by a significant increase in blood vessel density. It is known that lipoteichoic acid (LTA) from Gram-positive cariogenic bacteria induces expression of vascular endothelial growth factor (VEGF) in dental pulp cells. The hypothesis underlying this study was that LTA induces VEGF expression in dental pulp cells through TLR2 and PI3k/Akt signaling. Odontoblast-like cells (MDPC-23) and undifferentiated pulp cells (OD-21) were exposed to LTA from Streptococcus sanguis, and the role of TLR2, PI3K/Akt, and IKK signaling in LTA-induced VEGF expression was evaluated. These studies demonstrated that TLR2 signaling through the PI3K-Akt pathway is necessary for LTA-induced VEGF expression in pulp cells. In contrast, inhibition of IKK signaling did not prevent VEGF up-regulation in response to LTA. Understanding signaling pathways triggered by cariogenic bacteria may reveal novel therapeutic targets for the clinical management of pulpitis.

Temporal induction of secretory leukocyte protease inhibitor (SLPI) in odontoblasts by lipopolysaccharide and wound infection

INTRODUCTION

The secretory leukocyte protease inhibitor (SLPI) is a bacterial lipopolysaccharide (LPS)-induced product of macrophages that antagonizes the LPS-induced activation of a number of proinflammatory signaling factors. From our previous experiments, it was found that SLPI was expressed slightly in odontoblast-like cells (MDPC-23). Therefore, these experiments were designed to determine the function of SLPI in MDPC-23 and odontoblasts during the inflammatory response caused by infections and wounds.

METHODS

MDPC-23 cells were exposed to 100 ng/mL Escherichia coli LPS, and artificial wounds were induced in the right first molar of the maxillary of rats. In addition, a morphological change in the MDPC-23 cells was observed after LPS treatment. MDPC-23 cells were transfected transiently with the nuclear factor kappa-B (NF-kappaB) promoter binding vector.

RESULTS

The level of SLPI expression increased strongly 30 minutes after the LPS treatment. Scanning electron microscopy revealed many extensions of the cytoplasmic processes after LPS stimulation. SLPI was expressed along the dentinal tubules and odontoblasts layer in rat teeth after an artificial wound. SLPI also inhibited the LPS-induced activation of NF-kappaB in MDPC-23.

CONCLUSIONS

We report for the first time that SLPI is expressed temporally in infected odontoblasts and may participate in the anti-inflammatory response through NF-kappaB signaling in odontoblast-like cells.

VEGF and odontoblast-like cells: stimulation by low frequency ultrasound

OBJECTIVE

Vascular endothelial growth factor (VEGF) has been implicated in the regulation of dental pulp and dentine repair. Therapeutic ultrasound was shown to be effective for fracture repair. We investigated whether low frequency ultrasound influences the production of VEGF by odontoblast-like cells. Moreover, we examined the direct effects of VEGF on odontoblast-like cell proliferation.

DESIGN

MDPC-23, an established odontoblast-like cell line, was exposed to increasing intensities of 30kHz ultrasound using an ultrasonic tip probe.

RESULTS

After 24h cell culture, WST-1 analysis of cell viability and number showed a dose-dependent decrease in the number of viable cells with increasing ultrasound power. However, the relative concentration of VEGF as analysed by ELISA and normalised to cell number was significantly increased in the culture supernatants indicating an ultrasound-induced stimulation of odontoblastic VEGF secretion. Analysis of VEGF gene expression by sqRT-PCR revealed the expression of the main VEGF isoforms in the MDPC-23 cells, i.e. VEGF(120) and VEGF(164) as well as to a minor extent VEGF(188). Low power ultrasound increased gene expression of all VEGF isoforms. Addition of recombinant VEGF to the cell cultures significantly stimulated cell proliferation. Gene expression of the VEGF receptors Flt1/VEGFR1 and KDR/VEGFR2 was detected in the MDPC-23, suggesting the possibility that VEGF may act on the odontoblast-like cells in an autocrine manner.

CONCLUSIONS

Our results indicate that ultrasound promoted VEGF expression and production by odontoblast-like cells and that VEGF may have autocrine effects on these cells. It is proposed that ultrasound may influence odontoblast activity and dentine repair by modulating production of endogenous growth factors in the dentine-pulp complex.

Soluble vascular endothelial growth factor receptor-1 protects mice in sepsis

OBJECTIVE

To determine the putative role in the modulation of inflammation of a soluble form of Flt-1 (sFlt), a potent vascular endothelial growth factor antagonist, in experimental endotoxemia and sepsis.

DESIGN

Randomized prospective experimental study.

SETTING

University medical laboratory.

SUBJECTS

Male C56BL/6 strain mice.

INTERVENTIONS

We investigated the expression patterns and the effects of vascular endothelial growth factor and soluble Flt-1 in experimental endotoxic shock and sepsis. The possible anti-inflammatory mechanism of soluble Flt-1 was also evaluated.

MEASUREMENTS AND MAIN RESULTS

Both vascular endothelial growth factor and sFlt-1 were rapidly released from macrophages activated in vitro by lipopolysaccharide and in the plasma of endotoxemic mice. Administration of vascular endothelial growth factor enhanced proinflammatory cytokine production and mediated a dramatic increase in mortality in endotoxemic mice. Treatment with sFlt-1 attenuated inflammatory responses, inhibited recruitment of inflammatory cells into the peritoneal cavity, and improved survival in a lethal endotoxemia and cecal ligation and puncture-induced sepsis model, even when administered as late as 24 hrs after the onset of sepsis.

CONCLUSIONS

These findings support a critical protective role of sFlt-1 in endotoxic shock and sepsis. sFlt-1 may therefore have utility as an adjunctive agent for the treatment of sepsis syndrome.

Vascular endothelial growth factor receptor-2 expression in the pulp of human primary and young permanent teeth

The purpose of this study was to evaluate the expression of vascular endothelial growth factor receptor-2 (VEGFR-2) in endothelial cells within the dental pulp of human primary and young permanent teeth and the spatial distribution of VEGFR-2-positive cells. Nine sound primary teeth and 4 sound young permanent teeth were evaluated by immunohistochemistry with a human anti-VEGFR-2 antibody. Stained tissue sections were analyzed qualitatively under light microscopy. Here we observed that endothelial cells of both primary and permanent teeth showed positive immunostaining for VEGFR-2. Notably, VEGFR-2-positive cells in the primary teeth tended to be found close to the subodontoblastic layer, whereas the spatial distribution of VEGFR-2 immunostaining in the permanent teeth was more uniform. In conclusion, VEGFR-2 was expressed in the microvascular endothelial cells of both primary and young permanent teeth, which suggests that these cells are capable of responding to the morphogenetic and survival signals mediated by VEGF.

Tooth Slice–Based Models for the Study of Human Dental Pulp Angiogenesis

Treatment of avulsed young permanent teeth aims to revascularize the dental pulp. The study of therapeutic strategies for avulsed teeth has been hindered by the scarcity of experimental models. The purpose of this work is to characterize two model systems to study dental pulp revascularization. Tooth slices from human third molars were prepared with a sterile diamond saw. The tooth slices were cultured in vitro for up to 7 days. Immunohistochemical staining with Factor VIII showed an increase in microvascular density in pulps treated with 50 ng/mL rhVEGF(165) as compared with untreated controls (p < 0.05). Alternatively, tooth slices were prepared and immediately implanted subcutaneously in immunodeficient mice. Pulp vitality and vascularization were confirmed by histological analysis and terminal deoxynucleotide transferase dUTP nick end labeling assays 7 days after implantation. The models presented here may be valuable in the assessment of angiogenesis-based therapeutic strategies for the dental pulp.

Vascular endothelial growth factor and its relationship with the dental pulp

The dental pulp is a loose connective tissue located within rigid dentinal walls. Therefore, when subjected to a stimulus, the pulpal tissue has little expansion capacity. The defense mechanisms of this tissue include the formation of tertiary dentin as well as the production of signaling molecules that help in the repair. The dentin matrix is rich in growth factors (GFs) that, when diluted and diffused into the pulp tissue, aid the healing process of the dentinopulpar complex. The angiogenic GFs participate in this event. Vascular endothelial growth factor (VEGF), a potent mitogen for endothelial cells, promotes endothelial cell survival and angiogenesis. Among its receptors, VEGFR-2 seems to be the most intimately associated with mitogenic activities, cell migration, vascular permeability, and survival of endothelial cells. This literature review addresses the cell-signaling process that occurs in response to a pulp stimulus up to its transduction in the target cell, describing the VEGF, as well as its characteristics and receptors. The reported studies have correlated the expression of VEGF and its potential functions that may have an impact on several dental specialties, thus indicating that further clinical investigations should be conducted in order to translate the results obtained until this moment primarily in laboratory experiments.

TLR4 Mediates LPS-Induced VEGF Expression in Odontoblasts

Lipopolysaccharide (LPS) from gram-negative bacteria cell walls such as Prevotella intermedia and Escherichia coli induce vascular endothelial growth factor (VEGF) expression in odontoblasts, but not in undifferentiated dental pulp cells. CD14 and TLR4 are responsible for LPS signaling in macrophages, but their expression levels and function in dental pulp cells are unknown. We showed here that murine odontoblast-like cells (MDPC-23) express CD14 and TLR4 by immunohistochemistry and flow cytometry. In contrast, undifferentiated dental pulp cells (OD-21) presented low or no expression of these two receptors. MDPC-23 cells showed CD14 and TLR4 up-regulation upon exposure to LPS, as determined by real time PCR. Dominant negative murine TLR4 (DN-mTLR4) transfected MDPC-23 cells did not show upregulated VEGF expression in response to LPS stimulation. These results demonstrate that odontoblast-like cells express CD14 and TLR4, and that LPS-induced VEGF expression is mediated, at least in part, by TLR4 signaling.

Adhesive resin and the hydrophilic monomer HEMA induce VEGF expression on dental pulp cells and macrophages

Vascular endothelial growth factor (VEGF) plays an important role in angiogenesis by inducing endothelial cell proliferation, migration and survival. Direct pulp capping with an adhesive resin system was shown to induce local increase in blood vessel density and lack of dentin bridging. However, the mechanisms involved in the increase in blood vessel density observed near the pulp exposures capped with an adhesive resin are largely unknown. OBJECTIVES.: To investigate the effect of an adhesive resin or one of its hydrophilic monomers (HEMA), in the expression of VEGF by pulp cells. METHODS.: Mouse odontoblast-like cells (MDPC-23), undifferentiated pulp cells (OD-21), gingival fibroblasts, and macrophages were exposed to SingleBond (3M) or to 0-1000nM HEMA. VEGF expression was evaluated by ELISA and semi-quantitative RT-PCR. RESULTS AND SIGNIFICANCE.: VEGF expression was upregulated in MDPC-23 cells exposed to HEMA (p<0.001) or to SingleBond (p<0.018), and in macrophages exposed to HEMA (p<0.001) or SingleBond (p=0.001). In contrast, VEGF expression remained unchanged in undifferentiated pulp cells (OD-21), or fibroblasts exposed to either HEMA or Single Bond (p>0.05). Treatment with SingleBond or HEMA did not affect VEGF expression at the mRNA level of any cell type evaluated here, suggesting that the induction of VEGF expression in these cells is regulated primarily at the post-transcriptional level. These findings suggest that VEGF is involved in the regulation of pulp neovascularization observed in response to the application of adhesive resins at site of pulp exposure.

Induction of vascular endothelial growth factor expression in human pulp fibroblasts stimulated with black-pigmented Bacteroides

AIM

To investigate the effect of black-pigmented Bacteroides on the expression of vascular endothelial growth factor (VEGF) gene in human pulp fibroblasts.

METHODOLOGY

The supernatants of Porphyromonas endodontalis, Porphyromonas gingivalis and Prevotella intermedia were used to evaluate VEGF gene expression in human pulp fibroblasts. The levels of mRNAs were measured by the quantitative reverse-transcriptase polymerase chain reaction analysis.

RESULTS

Black-pigmented Bacteroides induced significantly high levels of VEGF mRNA gene expression in human pulp fibroblasts (P < 0.05). In addition, the expression of VEGF depended on the bacteria tested.

CONCLUSIONS

Black-pigmented Bacteroides may be involved in developing pulpal disease through the stimulation of VEGF production that would lead to the expansion of the vascular network coincident to progression of the inflammation.