Sensory pulpal nerve fibres and trigeminal ganglion neurons express IL-1RI: a potential mechanism for development of inflammatory hyperalgesia

Neuronal-immune axis alters pain and sensory afferent damage during dental pulp injury

ABSTRACT

Dental pulp tissue is densely innervated by afferent fibers of the trigeminal ganglion. When bacteria cause dental decay near the pulpal tissue, a strong neuronal and immune response occurs, creating pulpitis, which is associated with severe pain and pulp tissue damage. Neuroimmune interactions have the potential to modulate both the pain and pathological outcome of pulpitis. We first investigated the role of the neuropeptide calcitonin gene-related peptide (CGRP), released from peptidergic sensory afferents, in dental pain and immune responses by using Calca knockout (Calca -/- ) and wild-type (Calca +/+ ) mice, in a model of pulpitis by creating a mechanical exposure of the dental pulp horn. We found that the neuropeptide CGRP, facilitated the recruitment of myeloid cells into the pulp while also increasing spontaneous pain-like behavior 20% to 25% at an early time point. Moreover, when we depleted neutrophils and monocytes, we found that there was 20% to 30% more sensory afferent loss and increased presence of bacteria in deeper parts of the tissue, whereas there was a significant reduction in mechanical pain response scores compared with the control group at a later time point. Overall, we showed that there is a crosstalk between peptidergic neurons and neutrophils in the pulp, modulating the pain and inflammatory outcomes of the disease.

Effects of Low-Level Laser Therapy on Dentin Hypersensitivity in Periodontally Compromised Patients Undergoing Orthodontic Treatment: A Randomised Controlled Trial

OBJECTIVES

This study aimed to assess the effects of low-level laser therapy (LLLT) on dentin hypersensitivity (DH) in periodontally compromised patients undergoing orthodontic treatment.

METHODS

This triple-blinded randomised controlled trial included 143 teeth with DH from 23 periodontally compromised patients. Teeth on one side of the dental arch were randomly assigned to the LLLT group (LG), while those on the contralateral side were allocated to the non-LLLT group (NG). After orthodontic treatment commenced, patients' orthodontic pain (OP) perceptions were documented in pain diaries. DH was assessed chairside by a visual analogue scale (VASDH) at fifteen timepoints across the orthodontic treatment and retention. VASDH scores were compared among timepoints by the Friedman test, among patients with varying OP perceptions using the Kruskal-Wallis tests, and between the LG and NG with the Mann-Whitney U test.

RESULTS

DH generally decreased over the observation (p < 0.001). The VASDH scores differed among patients with varying OP perceptions at multiple timepoints (p < 0.05). The generalized estimating equation model showed teeth in the LG had a significantly lower VASDH score than the NG at the 3rd month of treatment (p = 0.011).

CONCLUSION

LLLT could be potentially beneficial in managing DH in periodontally compromised patients undergoing orthodontic treatment.

Present status and future directions - Mechanisms and management of local anaesthetic failures

Pain control during root canal treatment is of utmost importance for both the patient and the dental practitioner and many studies have investigated ways of overcoming problems with gaining adequate anaesthesia during treatment. The PubMed and Cochrane databases were searched for evidence-based studies regarding local anaesthesia for root canal treatment. Many variables, including premedication, pain during needle insertion, pain on injection, premedication with various types of drugs, volume of anaesthetic solutions, supplemental anaesthetic techniques, and additives to the anaesthetic solutions, may influence pain perception during root canal treatment. Differences between teeth with healthy pulps versus those with irreversible pulpitis should be considered when the effects of variables are interpreted. There are several concerns regarding the methodologies used in studies that have evaluated anaesthesia success rates. There are some conditions that may help to predict a patient's pain during root canal treatment and these conditions could be overcome either by employing methods such as premedication with a non-steroidal anti-inflammatory drug prior to the treatment visit or by using supplementary anaesthetic techniques before or during the treatment. However, authors need to be more careful when reporting details of their studies to reduce concerns regarding their study bias.

Effect of premedication on postoperative pain after root canal therapy in patients with irreversible pulpitis: a systematic review and meta-analysis

This systematic review aimed to assess the effect of premedication on postoperative pain after root canal treatment in vital teeth. Five electronic databases were searched for randomized clinical trials, and two independent reviewers selected eligible studies, extracted data, and assessed the quality of studies using the Cochrane Risk of Bias tool. Meta-analysis was conducted using the random-effects model, and the pooled effect estimate of the standardized mean difference (SMD) between premedication and placebo was calculated. Subgroup analysis was conducted based on the class and route of the drug. Studies with a high risk of bias were excluded from the sensitivity analysis. Ten trials satisfied the inclusion criteria, of which eight were included in the meta-analysis. Premedication was more effective in reducing postoperative pain than placebo at 6 hours (SMD = −1.00; 95% confidence interval [CI] = −1.33 to −0.66), 12 hours (SMD = −0.80; 95% CI = −1.05 to −0.56), and 24 hours (SMD = −0.72; 95% CI = −1.02 to −0.43). The results of the sensitivity analysis confirmed the findings of the primary analysis. Based on these results, it can be concluded that premedication is effective in reducing postoperative pain in teeth with irreversible pulpitis. However, additional quality studies are required for further validation.

Molecular mechanism in trigeminal nerve and treatment methods related to orthodontic pain

BACKGROUND

Orthodontic treatment is the main treatment approach for malocclusion. Orthodontic pain is an inevitable undesirable adverse reaction during orthodontic treatment. It is reported orthodontic pain has become one of the most common reason that patients withdraw from orthodontic treatment. Therefore, understanding the underlying mechanism and finding treatment of orthodontic pain are in urgent need.

AIMS

This article aims to sort out the mechanisms and treatments of orthodontic pain, hoping to provide some ideas for future orthodontic pain relief.

MATERIALS

Tooth movement will cause local inflammation. Certain inflammatory factors and cytokines stimulating the trigeminal nerve and further generating pain perception, as well as drugs and molecular targeted therapy blocking nerve conduction pathways, will be reviewed in this article.

METHOD

We review and summaries current studies related to molecular mechanisms and treatment approaches in orthodontic pain control.

RESULTS

Orthodontics pain related influencing factors and molecular mechanisms has been introduced. Commonly used clinical methods in orthodontic pain control has been evaluated.

DISCUSSION

With the clarification of more molecular mechanisms, the direction of orthodontic pain treatment will shift to targeted drugs.

Trigeminal sensory nerve patterns in dentine and their responses to attrition in rat molars

OBJECTIVE

Our goal was to define trigeminal nerve ending quantities and patterns in rat molar dentine, their responses to attrition (tooth wear), and their associated odontoblasts and connections with pulpal plexuses.

DESIGN

Trigeminal ganglia were labeled for axonal transport of ³H-proteins to dentinal nerve endings in male rats (3-13 months old). Autoradiography detected radio-labeled dentinal tubules as indicators of nerve ending locations. Quantitative morphometry was done (ANOVA, t-tests), and littermates were compared for attrition and innervation.

RESULTS

There were six dentinal patterns, only two of which had an associated neural plexus of Raschkow and cell-free zone (Den-1, Den-2). Other nerves entered dentin from bush-like endings near elongated odontoblasts (Den-B), as single fibers (Den-X), as networks in predentine (PdN), or as single fibers in tertiary dentine at cusp tips (Den-S). There were at least 186,600 innervated dentinal tubules within the set of three right maxillary molars of the best-labeled rat, and similar densities were found in other rats. Attrition levels differed among cusps and in littermates (t-test p < 0.02-0.0001), but the matched right/left cusps per rat were similar. Innervations of tertiary and enamel-free dentine (Den-S, Den-X) were preserved in all rats. Den-B and Den-2 coronal patterns were unchanged unless displaced by dentinogenesis. Den-1 losses occurred in older cusps, while Den-2 patterns increased near cervical and intercuspal odontoblasts.

CONCLUSIONS

The extensive molar dentinal innervation had unique distributions per rat per cusp that depended on region (buccal, middle, palatal) and attrition, but only two of six patterns connected to a plexus of Raschkow.

Dental nerves: a neglected mediator of pulpitis

As one of the most densely innervated tissues, the dental pulp contains abundant nerve fibres, including sensory, sympathetic and parasympathetic nerve fibres. Studies in animal models and human patients with pulpitis have revealed distinct alterations in protein expression and histological appearance in all types of dental nerve fibres. Various molecules secreted by neurons, such as classical neurotransmitters, neuropeptides and amino acids, not only contribute to the induction, sensitization and maintenance of tooth pain, but also regulate non-neuronal cells, including fibroblasts, odontoblasts, immune cells and vascular endothelial cells. Dental nerves are particularly important for the microcirculatory and immune responses in pulpitis via their release of a variety of functional substances. Further, nerve fibres are found to be involved in dental soft and hard tissue repair. Thus, understanding how dental nerves participate in pulpitis could have important clinical ramifications for endodontic treatment. In this review, the roles of dental nerves in regulating pulpal inflammatory processes are highlighted and their implications for future research on this topic are discussed.

Role(s) of cytokines in pulpitis: Latest evidence and therapeutic approaches

Pulpitis is known as a typical inflammation of dental pulp tissue, and microorganisms of the oral microbiome are involved in this opportunistic infection. Studies indicated that several factors related to host response have a crucial role in pulpitis. Among these factors, inflammatory mediators of the immune system such as cytokines and chemokines contribute to pulpal defense mechanisms. A wide range of cytokines have been observed in dental pulp and these small molecules are able to trigger inflammation and participate in immune cell trafficking, cell proliferation, inflammation, and tissue damage in pulp space. Therefore, the aim of this review was to describe the role of cytokines in the pathogenesis of pulpitis.

Chewing causes rapid changes in immunoreactive nerve patterns in rat molar teeth: Implications for dental proprioception and pain

OBJECTIVE

This study tests the hypothesis that normal use of teeth (chewing) causes changes in immunoreactive-(IR) patterns for endings of large Aβ and CGRP axons in rat molar cusps.

DESIGN

First, a new paradigm to test chewing in adult male rats was developed. Then IR patterns for large dental axons were analysed for a calcium-binding protein, parvalbumin (PV), heavy neurofilament protein-200 (NFP), and vesicle-release molecule synaptophysin (SYN) that all typify large dental axons and proprioceptors for comparison with endings of CGRP-IR neuropeptide axons. The behavior groups were: (1) daytime sleeping/fasting (Group:SF); (2) brief feeding after 8-11 h of daytime sleeping/fasting (Group:SF-C); (3) normal nocturnal feeding (Group:N); (4) nocturnal fasting (Group:NF); (5) brief feeding/chewing after nocturnal fasting (Group:NF-C).

RESULTS

Nerve endings with NFP-, PV-, or SYN-IR were lost or altered in pulp and dentin in all chewing groups. Other endings with CGRP-IR were near those with PV-, NFP- and SYN-IR at the pulp-dentin border and in dentin, and they also lost immunoreactivity in all chewing groups. The special beaded regions along the crown pulp/dentin borders lost neural labeling in all chewing groups. Nerves of molar roots and periodontal ligament were not changed.

CONCLUSIONS

Rapid neural reactions to chewing show extensive, reversible, non-nociceptive depletions of crown innervation. Those changes were rapid enough to occur during normal feeding followed by recovery during rest. The new dental paradigm related to chewing and fasting allows dissection of intradental proprioceptive-like mechanisms during normal tooth functions for comparison with nociceptive and mechanosensitive reactions after injury or inflammation.

IL-1β induced IL-8 and uPA expression/production of dental pulp cells: Role of TAK1 and MEK/ERK signaling

BACKGROUND/PURPOSE

Interleukin 1 beta (IL-1β) is a pro-inflammatory cytokine involved in the inflammatory processes of dental pulp. IL-8 and urokinase plasminogen activator (uPA) are two inflammatory mediators. However, the role of transforming growth factor beta-activated kinase-1 (TAK1) and mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathways in responsible for the effects of IL-1β on IL-8 and uPA expression/secretion of dental pulp cells are not clear.

METHODS

Human dental pulp cells were exposed to IL-1β with/without pretreatment with 5z-7-oxozeaneaeol (a TAK1 inhibitor) or U0126 (a MEK/ERK inhibitor). TAK1 activation was determined by immunofluorescent staining. The protein expression of IL-8 was tested by western blot. The expression of IL-8 and uPA mRNA was studied by reverse transcriptase-polymerase chain reaction (RT-PCR). The secretion of IL-8 and uPA was measured by enzyme-linked immunosorbent assay.

RESULTS

Exposure of dental pulp cells to IL-1β (0.1-10 ng/ml) stimulated IL-8 and uPA expression. IL-1β also induced IL-8 and uPA secretion of dental pulp cells. IL-1β stimulated p-TAK1 activation of pulp cells. Pretreatment and co-incubation of pulp cells by 5z-7oxozeaenol (1 and 2.5 μM) and U0126 (10 and 20 μM) prevented the IL-1β-induced IL-8 and uPA expression. 5z-7oxozeaenol and U0126 also attenuated the IL-1β-induced IL-8 and uPA secretion.

CONCLUSION

IL-1β is important in the pathogenesis of pulpal inflammatory diseases and repair via stimulation of IL-8 and uPA expression and secretion. These events are associated with TAK1 and MEK/ERK signaling. Blocking of TAK1 and MEK/ERK signaling has potential to control inflammation of dental pulp.

Multicenter Study of a Novel Topical Interleukin-1 Receptor Inhibitor, Isunakinra, in Subjects With Moderate to Severe Dry Eye Disease

OBJECTIVES

Isunakinra, formerly known as EBI-005, is a novel interleukin (IL)-1 receptor inhibitor developed for topical treatment of patients with dry eye disease (DED). This phase 1b/2a multicenter, double-masked, randomized, vehicle controlled environmental trial assessed the safety and biological activity of isunakinra in patients with moderate to severe DED.

METHODS

Subjects (N=74) were randomized to vehicle (placebo) or isunakinra (5 or 20 mg/mL) 3×/daily for 6 weeks. Evaluations included safety, tolerability, biological activity for signs (corneal fluorescein staining [CFS]), symptoms (pain or sore eyes and total Ocular Surface Disease Index [OSDI]), and reduction in rescue artificial tear use.

RESULTS

Topical administration of isunakinra (5 and 20 mg/mL) was safe and well tolerated and resulted in clinically relevant improvements in symptoms (OSDI score, painful/sore eye component of OSDI) and signs (total CFS) compared with baseline with no dose response. OSDI scores improved from baseline by 38% (18.9 points) at 6 weeks and CFS scores improved by 33% (3 points) in the isunakinra groups. These changes were not statistically significant compared with the vehicle. Use of artificial rescue tears was significantly reduced in the isunakinra treatment groups (mean=9 vials) compared with vehicle (mean=31 vials). The differences between isunakinra and vehicle treatments were more pronounced in subjects with OSDI scores less than 50 at baseline.

CONCLUSIONS

Isunakinra was safe, well tolerated and showed clinically meaningful improvements in signs and symptoms of DED. These results encouraged the design of an adequately powered study to characterize the safety and efficacy of isunakinra in ocular surface diseases.

Multiple complex somatosensory systems in mature rat molars defined by immunohistochemistry

OBJECTIVE

Intradental sensory receptors trigger painful sensations and unperceived mechanosensitivity, but the receptor bases for those functions are only partly defined. We present new evidence here concerning complex endings of myelinated axons in rat molars.

DESIGN

We sectioned mature rat jaws in sagittal and transverse planes to analyze neural immunoreactivity (IR) for parvalbumin, peripherin, neurofilament protein, neurotrophin receptors, synaptophysin, calcitonin gene-related peptide (CGRP), or mas-related g-protein-receptor-d (Mrgprd).

RESULTS

We found two complex sensory systems in mature rat molar dentin that labeled with neurofilament protein-IR, plus either parvalbumin-IR or peripherin-IR. The parvalbumin-IR system made extensively branched, beaded endings focused into dentin throughout each pulp horn. The peripherin-IR system primarily made unbeaded, fork-shaped dentinal endings scattered throughout crown including cervical regions. Both of these systems differed from neuropeptide CGRP-IR. In molar pulp we found peripherin- and parvalbumin-IR layered endings, either near special horizontal plexus arrays or in small coiled endings near tangled plexus, each with specific foci for specific pulp horns. Parvalbumin-IR nerve fibers had Aβ axons (5-7μm diameter), while peripherin-IR axons were thinner Aδ size (2-5μm). Mechano-nociceptive Mrgprd-IR was only found in peripherin-IR axons.

CONCLUSIONS

Complex somatosensory receptors in rat molars include two types of dentinal endings that both differ from CGRP-IR endings, and at least two newly defined types of pulpal endings. The PV-IR neurons with their widely branched, synaptophysin-rich, intradentinal beaded endings are good candidates for endodontic non-nociceptive, low threshold, unperceived mechanoreceptors. The complex molar dentinal and pulpal sensory systems were not found in rat incisors.

Vascular endothelial growth factors signalling in normal human dental pulp: a study of gene and protein expression

In the well-vascularized dental pulp vascular endothelial growth factor A (VEGF-A) is expressed. Vascular endothelial growth factor A is a member of the VEGF family, which includes VEGFs-B, -C, and -D. The latter three have not been investigated in the pulp. Vascular endothelial growth factors C and D are the only ligands for vascular endothelial growth factor receptor (VEGFR)-3, which is usually expressed in lymphatic endothelium. They can also activate VEGFR-2, the main angiogenic receptor. We aimed to study VEGFs signalling in human dental pulp at the gene level and to identify the cellular source for protein expression using immunolabelling. All VEGFs (-A, -B, -C, and -D) were expressed in the pulp and may exert both autocrine and paracrine effects in blood vessels and immune cells found to be equipped with VEGFRs-2 and -3. Lymphatic vessel endothelial hyaluronan receptor-positive macrophages, known to be involved in angiogenesis, were found in the pulp, whereas lymphatic vessels were not detected. Twenty-six of 84 VEGF signalling genes, including VEGFR-3, were expressed at a significantly higher level in the pulp than in the control periodontal ligament. In conclusion, the normal human pulp represents a tissue with relatively high VEGF signalling involving both immune responses and vascular activity.

Dental pulp and gingivomucosa in rats are innervated by two morphologically and neurochemically different populations of nociceptors

OBJECTIVES

Difference in phenotypes of sensory neurons innervating dental pulp or gingivomucosa may be responsible for intense pain sensations in pulpitis in contrast to relatively painless chronic periodontitis. Therefore, we classified these neurons according to their size and two neurochemical characteristics of nociceptors, their TrkA expression and isolectin IB4 binding.

DESIGN

In rats (n=6) fluorescent tracers Fluorogold and TrueBlue were simultaneously applied into the standard-sized tooth cavity and nearby gingival sulcus, respectively. After the fluorescence on paraffin trigeminal ganglia (TG) sections was identified and photographed, immunohistochemistry for TrkA expression and IB4 binding was performed on the same sections.

RESULTS

The average sizes of TG neurons projecting to the gingivomucosa and dental pulp were 894±441μm(2) and 1012±381μm(2), respectively. The proportions of small-sized gingival and pulpal neurons were 14% and 5%, respectively (p<0.05). The proportions of TrkA-positive neurons among all gingival or pulpal neurons were 76% and 86%, respectively (p<0.05). Among all gingival or pulpal neurons the proportions of IB4-positive neurons were 46% and 3% (p<0.001), respectively, and the majority of them were small-medium sized.

CONCLUSIONS

Dental pulp and gingivomucosa are richly innervated by nociceptive TrkA-expressing neurons. However, while great majority of pulpal neurons are larger NGF-dependent A-fibre nociceptors without affinity to bind IB4, almost half of the gingival neurons are smaller IB4 binding C-fibre nociceptors. The difference in phenotype of sensory neurons might partially explain the different sensitivity of both tissues during normal and pathological conditions.

Localization and signaling patterns of vascular endothelial growth factors and receptors in human periapical lesions

INTRODUCTION

Vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) are key players in vasculogenesis and are also involved in pathologic conditions with bone destruction. Vasculogenesis is critical for disease progression, and bone resorption is a hallmark of apical periodontitis. However, the localization of VEGFs and VEGFRs and their gene signaling pathways in human apical periodontitis have not been thoroughly investigated. The aim of this study was to localize VEGFs and VEGFRs and analyze their gene expression as well as signaling pathways in human periapical lesions.

METHODS

Tissue was collected after endodontic surgery from patients diagnosed with chronic apical periodontitis. Periodontal ligament samples from extracted healthy wisdom teeth was also collected and used as control tissue. In lesion cryosections, VEGFs/VEGFRs were identified by immunohistochemistry/double immunofluorescence by using specific antibodies. A human VEGF signaling polymerase chain reaction array system was used for gene expression analysis comparing lesions with periodontal ligament samples.

RESULTS

The histologic evaluation revealed heterogeneous morphology of the periapical lesions with various degrees of inflammatory infiltrates. In the lesions, all investigated factors and receptors were identified in blood vessels and various immune cells. No lymphatic vessels were detected. Gene expression analysis revealed up-regulation of VEGF-A and VEGFR-3, although not significant. Phosphatidylinositol-3-kinases, protein kinase C, mitogen-activated protein kinases, and phospholipases, all known to be involved in VEGF-mediated angiogenic activity, were significantly up-regulated.

CONCLUSIONS

The cellular and vascular expressions of VEGFs and VEGFRs in chronic apical periodontitis, along with significant alterations of genes mediating VEGF-induced angiogenic responses, suggest ongoing vascular remodeling in established chronic periapical lesions.

Interstitial Fluid and Lymph Formation and Transport: Physiological Regulation and Roles in Inflammation and Cancer

The interstitium describes the fluid, proteins, solutes, and the extracellular matrix (ECM) that comprise the cellular microenvironment in tissues. Its alterations are fundamental to changes in cell function in inflammation, pathogenesis, and cancer. Interstitial fluid (IF) is created by transcapillary filtration and cleared by lymphatic vessels. Herein we discuss the biophysical, biomechanical, and functional implications of IF in normal and pathological tissue states from both fluid balance and cell function perspectives. We also discuss analysis methods to access IF, which enables quantification of the cellular microenvironment; such methods have demonstrated, for example, that there can be dramatic gradients from tissue to plasma during inflammation and that tumor IF is hypoxic and acidic compared with subcutaneous IF and plasma. Accumulated recent data show that IF and its convection through the interstitium and delivery to the lymph nodes have many and diverse biological effects, including in ECM reorganization, cell migration, and capillary morphogenesis as well as in immunity and peripheral tolerance. This review integrates the biophysical, biomechanical, and biological aspects of interstitial and lymph fluid and its transport in tissue physiology, pathophysiology, and immune regulation.

Functional role for interleukin-1 in the injured peripheral taste system

The peripheral taste system presents an excellent model for studying the consequences of neural injury, for the damaged nerve and sensory cells and the neighboring, intact neural cells. Sectioning a primary afferent nerve, the chorda tympani (CT), rapidly recruits neutrophils to both sides of the tongue. The bilateral neutrophil response induces transient functional deficits in the intact CT. Normal function is subsequently restored as macrophages respond to injury. We hypothesized that macrophages produce the proinflammatory cytokine interleukin (IL)-1, which contributes to the maintenance of normal taste function after nearby injury. We demonstrate that IL-1β protein levels are significantly increased on the injured side of the tongue at day 2 after injury. Dietary sodium deficiency, a manipulation that prevents macrophage recruitment, inhibits the elevation in IL-1β. IL-1β was expressed in several cell populations, including taste receptor cells and infiltrating neutrophils and macrophages. To test whether IL-1 modulates taste function after injury, we blocked signaling with an IL-1 receptor antagonist (IL-1 RA) and recorded taste responses from the intact CT. This treatment inhibited the bilateral macrophage response to injury and impaired taste responses in the intact CT. Cytokine actions in the taste system are largely unstudied. These results demonstrate that IL-1 has a beneficial effect on taste function after nearby injury, in contrast to its detrimental role in the injured central nervous system.

Vascular endothelial growth factors and receptors are up-regulated during development of apical periodontitis

INTRODUCTION

Apical periodontitis is a common inflammatory disease caused by persistent root canal infection and is characterized by bone resorption. Vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) have been described in many pathologic and inflammatory conditions, but their involvement in the development of apical periodontitis has not been thoroughly investigated. The aim of this study was to quantify gene expression and localize VEGF-A, VEGF-C, and VEGF-D and VEGFR-2 and VEGFR-3 in a rat model of apical periodontitis.

METHODS

Molar pulps were unilaterally exposed to the oral cavity for 10 or 21 days. Jaw sections were used for localization of VEGFs and VEGFRs with immunohistochemistry and identification of cells with double immunofluorescence. Gene expression analysis for VEGF-A, VEGF-C, and VEGFR-3 of periapical tissues was performed with quantitative real-time polymerase chain reaction.

RESULTS

All investigated factors and receptors were expressed immunohistochemically in blood vessels at the periodontal ligament of control teeth and were up-regulated during lesion development. In apical lesions, macrophages and neutrophils expressed all studied factors and receptors, with macrophages being an important source of VEGF-C and VEGF-D. Osteoclasts expressed VEGFR-2 and VEGFR-3, and the latter was also identified in fibroblast-like cells in the lesions. VEGF-A and VEGFR-3 gene expression was up-regulated at days 10 and 21 (P < .05).

CONCLUSIONS

The current findings indicate that the VEGF family and receptors are involved in vascular remodeling and immune functions during disease development. The presence of VEGFR-2 and VEGFR-3 on osteoclasts indicates that bone resorbing activity is influenced by VEGFs.

Importance of lymph vessels in the transcapillary fluid balance in the gingiva studied in a transgenic mouse model

The gingiva is frequently challenged by oral bacterial products leading to inflammatory responses such as increased fluid filtration and edema formation. The role of initial lymphatics for transcapillary fluid balance in the gingiva is unknown and was therefore investigated in genetically engineered K14-VEGF receptor 3-Ig (K14) lymphedema mice. The mutant mice demonstrated a total lack of lymphatics in the gingiva, whereas lymphatics were found in the submucosal parts of the alveolar mucosa, although they were almost completely absent in the mucosa. In wild-type (WT) mice, lymphatic vessels were detected in mucosal and submucosal parts of the alveolar mucosa. Interstitial fluid pressure (Pif) measured with micropipettes was increased in the gingiva of K14 mice in the normal situation ( P < 0.001) and after inflammation ( P < 0.01) induced by lipopolysaccharide from the oral bacteria Porphyromonas gingivalis compared with WT littermates. Fluid volume expansion caused a >75% increase in interstitial fluid volume followed by a drop in Pif after recovery in both strains. Continuous measurements during the expansion showed an increase in Pif followed by a decline, suggesting that compliance is increased after the disruption of the extracellular matrix during edema formation. In the alveolar mucosa, no strain differences were observed in Pif in the normal situation or after fluid volume expansion, suggesting that lymph vessels in the mucosa are not critical for tissue fluid regulation in any situation. Our study demonstrates an important role of gingival lymphatics in transcapillary fluid balance in the steady-state condition and during acute perturbations.