Richard Darveau

University of Washington | UW · Department of Periodontics

Background Stannous fluoride dentifrice is well established for its beneficial clinical effects. In this study, we evaluated the effects of stannous fluoride on inflammation and oral microbiome. Methods In this randomized, parallel‐arm, double‐blind, controlled clinical trial, we compared clinical resolution of experimental gingivitis by evaluatin...

Variation in human immune response to the same bacterial or viral pathogen is well established in the literature. Variation in immune response to microbial challenge has also been observed within the human oral cavity. Our recent study focused on characterizing observed variations in microbially induced gingival inflammation—resulting in three dist...

The oral microbiome, with a unique emphasis on Porphyromonas gingivalis has been associated with a constellation of inflammatory diseases such as cardiovascular disease, rheumatoid arthritis, Alzheimer's disease, type II diabetes, and non-alcoholic associated fatty liver disease. Periodontal disease has also been shown to induce “leaky gut” leading...

Background: The gingival epithelium protects periodontal tissues and the alveolar bone by maintaining a steady state of regulated inflammatory surveillance, also known as healthy homeostasis. Accordingly, the repertoire of receptors present within the gingival epithelium showcases its ability to recognize microbial colonization and contribute to b...

Commensal microbes critically regulate skeletal homeostasis, yet the impact of specific microbiota communities on osteoimmune response mechanisms is unknown. To discern osteoimmunomodulatory effects imparted by the commensal oral microbiota that are distinct from the systemic microbiota, osteoimmunology studies were performed in both alveolar bone...

Colorectal cancer is a major health concern worldwide. Growing evidence for the role of the gut microbiota in the initiation of CRC has sparked interest in approaches that target these microorganisms. However, little is known about the composition and role of the microbiota associated with precancerous polyps. Here, we found distinct microbial sign...

Significance Experimental gingivitis studies where dental hygiene is withheld from select teeth, allowing natural bacterial accumulation, provide a unique opportunity to study the reversible transition from health to inflammatory disease in humans. Longitudinal analysis of both the microbial and host changes during human experimental gingivitis rev...

Aim: Clinically healthy gingival tissue is maintained through controlled regulation of host defense mechanisms against plaque biofilm overgrowth. One key component is the transit of neutrophils from the vasculature into gingival tissue where the expression of different neutrophil chemokines are tightly regulated. This cross-sectional study examines...

Introduction We verified the association between selected bacterial profiles and levels of cytokines, chemokines and the expression of signs and symptoms of primary endodontic infection with apical periodontitis (PEIAP). Methods Samples were collected from 21 root canals, and macrophages stimulated for 24 h. TNF-α, IL-6, IL-10, IL-12p70, INF-γ, an...

The central theme of this volume of Periodontology 2000 is that the microbial dental plaque biofilm, specifically the subgingival dental plaque biofilm, mimics a human tissue in both structure and function. As a basis for this assertion we use the definition of a tissue as an aggregate of similar cells and cell products forming a defined structure...

Years of coevolution with resident microbes has made them an essential component of health. Yet, little is known about oral commensal bacteria’s contribution to and role in the maintenance of oral health and homeostasis. Commensal bacteria are speculated to play a host protective role in the maintenance of health. In this review, we describe and pr...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Colorectal cancer is a major health concern worldwide. Growing evidence for the role of the gut microbiota in the initiation of CRC has sparked interest in approaches that target these microorganisms. However, little is known about the composition and role of the microbiota associated with precancerous polyps. Here, we found distinct microbial sign...

The majority of Gram-negative bacteria elicit a potent immune response via recognition of lipid A expressed on the outer bacterial membrane by the host immune receptor TLR4. However, some Gram-negative bacteria evade detection by TLR4 or alter the outcome of TLR4 signaling by modification of lipid A species. Although the role of lipid A modificatio...

Epidemiological studies reveal significant associations between periodontitis and oral cancer. However, knowledge about the contribution of periodontal pathogens to oral cancer and potential regulatory mechanisms involved is limited. Previously, we showed that nisin, a bacteriocin and commonly used food preservative, reduced oral cancer tumorigenes...

Objective: Sudantha® (SUD), a natural proprietary mixture of herbal extracts that has been incorporated into toothpaste, has been shown in two separate placebo controlled human clinical studies to promote gingival health; and reduce gingival bleeding and plaque formation. However, the herbal based anti-gingivitis mechanisms of Sudantha are not ful...

Background: Natural products constitute a promising class of therapeutics for the treatment of gingivitis and periodontitis as well as the maintenance of oral health. However, the limited understanding behind their potential mechanisms and modes of action have hampered their incorporation into popular western therapeutics. This in vitro study char...

Background: The oral microbiota has been implicated in the pathogenesis of rheumatoid arthritis through activation of mucosal immunity. This study tested for associations between oral health, microbial communities and juvenile idiopathic arthritis (JIA). Methods: A cross-sectional exploratory study of subjects aged 10-18 years with oligoarticula...

Gingival epithelium plays a pivotal role in protecting the underlying periodontium from the microbial colonization found in the gingival sulcus. Having an appropriate phenotype displayed by gingival epithelial cells is a critical host component required for protection against bacterial invasion into gingival tissues. In the present study, gingival...

The P. gingivalis ATCC 33277 (33277) and 381 genomes are nearly identical. However, strain 33277 displays a significantly diminished capacity to stimulate host cell TLR2-dependent signaling and IL-1β production relative to 381, suggesting that there are strain-specific differences in one or more bacterial immune-modulatory factors. Genomic sequenci...

Purpose Successful endodontic therapy relies on chemomechanical debridement. Laser-assisted irrigation techniques are available for debridement. However, there are limited studies demonstrating the effectiveness of dual lasers for root canal disinfection. Hence, the aim of the present study is to determine if laser activation irrigation using the E...

Background: Oral gingival tissue, especially the junctional epithelium (JE), is constantly exposed to sub-gingival plaque. A key component of gingival health is the regulation of the number of neutrophils that migrate into the gingival crevice to counteract its harmful effects. This report investigates the contribution of innate defense receptors,...

Removal of one acyl chain from bacterial lipid A by deacylase activity is a mechanism used by many pathogenic bacteria to evade the host's Toll-like receptor 4 (TLR4)-mediated innate immune response. In Porphyromonas gingivalis , a periodontal pathogen, lipid A deacylase activity converts a majority of the initially synthesized penta-acylated lipid...

Aim: To investigate the influence of auxiliary chemical substances (ACS) and calcium hydroxide [Ca(OH)2] dressings on LPS/lipid A detection and its functional ability in activating Toll-like receptor 4 (TLR4). Methodology: Fusobacterium nucleatum pellets were exposed to antimicrobial agents as following: 1) ACS: 5.25%, 2.5% and 1% sodium hypochl...

Age is the single greatest risk factor for many diseases, including oral diseases. Despite this, a majority of preclinical oral health research has not adequately considered the importance of aging in research aimed at the mechanistic understanding of oral disease. Here, we have attempted to provide insights from animal studies in the geroscience f...

Background Recently, we reported that toll-like receptor (TLR)2 and TLR4 localized on the glomerular endothelium in the glomeruli of streptozotocin (STZ)-induced type 1 diabetic mice and high fat diet feed-induced type 2 diabetic mice, and that periodontal pathogen Porphyromonas gingivalis LPS (Pg-LPS) administration lowered the survival rate of di...

Lipopolysaccharide (LPS)-binding protein (LBP) as an acute-phase protein plays a crucial role in innate host response to bacterial challenge. Our previous study shows that LBP expression in human gingiva is associated with periodontal status. Porphyromonas gingivalis is a keystone periodontopathogen, and its LPS with lipid A structural heterogeneit...

Background: The sino-nasal disease chronic rhinosinusitis (CRS) is primarily an inflammatory condition that manifests in several ways. However, the aetiology of this complex disease is poorly understood. The aim of this study was to explore the association between toll-like receptor (TLR) activation, host immune response and sino-nasal mucus in hea...

Background: The sino-nasal disease chronic rhinosinusitis (CRS) is primarily an inflammatory condition that manifests in several ways. However, the aetiology of this complex disease is poorly understood. The aim of this study was to explore the association between toll-like receptor (TLR) activation, host immune response and sino-nasal mucus in he...

Periodontal (gum) disease is a highly prevalent infection and inflammation accounting for the majority of tooth loss in adult population worldwide. Porphyromonas gingivalis is a keystone periodontal pathogen and its lipopolysaccharide (PgLPS) acts as a major virulence attribute to the disease. Herein, we deciphered the overall host response of huma...

Background and objective: It is commonly believed that pigmented pathogens are selectively targeted by dental lasers. To test this notion optical diffuse reflection spectroscopy (DRS) was used to obtain absorption spectra for the periodontal pathogens, Porphyromonas gingivalis (Pg) and Prevotella intermedia (Pi). Materials and methods: Spectra f...

Importance: The guts of animals harbor a variety of Gram-negative bacteria associated with both states of intestinal health or disease. Environmental factors, such as dietary habits, can drive the microbial composition of the host animal's intestinal bacterial community towards a more pathogenic state. Both beneficial and harmful Gram-negative bac...

We present the draft genome of Porphyromonas gingivalis MP4-504, a low-passage clinical isolate obtained from a periodontitis patient. The genome is composed of 92 contigs for a length of 2,373,453 bp and a G+C of 48.3%. The traA-Q conjugative transfer locus is genetically distinct from W83 but highly similar to ATCC 33277.

The aim of this study was to compare the biological activity of lipopolysaccharides (LPS) purified from Fusobacterium nucleatum and Porphyromonas gingivalis strains, both isolated from primary endodontic infection (PEI) in the levels of IL-1β and TNF-α released by macrophage cells. Moreover, LPS was purified from F. nucleatum and P. gingivalis Amer...

Background: The role of bacteria in the etiology of chronic rhinosinusitis (CRS) is not fully understood. Commensal bacteria may have a significant impact on the development of normal paranasal sinus anatomy and mucosal immunity, as they do in the gut. Studying the paranasal sinuses of germ-free (GF) mice may provide some insight into the effect o...

The oral microbial community is the best-characterized bacterial ecosystem in the human host. It has been shown in the mouse that oral commensal bacteria significantly contribute to clinically healthy periodontal homeostasis by influencing the number of neutrophils that migrate from the vasculature to the junctional epithelium. Furthermore, in clin...

The ability of the subgingival microbial community to induce an inappropriate inflammatory response ultimately results in the destruction of bone and gingival tissue. In this study, subgingival plaque samples from both healthy and diseased sites in the same individual were obtained from adults with chronic periodontitis and screened for their abili...

SELECTIVE DESTRUCTION OF PERIODONTOPATHOGENS WITH DENTAL LASERS David M. Harris, Lou Reinisch, Steve Jacques and Richard Darveau INTRODUCTION Current treatment options for periodontal infections include debridement of root surfaces with a surgical, mechanical and chemical armamentarium and disinfection of the periodontal sulcus with systemic and l...

This review discusses polymicrobial interactions with the host in both health and disease. As our ability to identify specific bacterial clonal types, with respect to their abundance and location in the oral biofilm, improves, we will learn more concerning their contribution to both oral health and disease. Recent studies examining host- bacteria i...

Innate and adaptive immunosurveillance mechanisms in response to the normal commensal bacteria can affect periodontal innate defense status. However, it is still unclear how commensal bacteria contribute to the inflammatory responses of junctional epithelium (JE) and periodontal connective tissue (PCT). The aim of the present study was to investiga...

Toll-like receptor (TLR)-mediated inflammatory response could negatively affect bone metabolism. In this study, we determined how osteogenesis is regulated during inflammatory responses that are downstream of TLR signaling. Human primary osteoblasts were cultured in collagen gels. Pam3CSK4 (P3C) and Escherichia coli lipopolysaccharide (EcLPS) were...

Defining the contribution of individual members of dysbiotic host-associated bacterial communities has been difficult. The recent paper by Maekawa et al. in Cell Host & Microbe describes bacterial manipulation of neutrophil responses by Porphyromonas gingivalis as a mechanism that contributes to forming a dysbiotic community.

Several successful pathogens have evolved mechanisms to evade host defense, resulting in the establishment of persistent and chronic infections. One such pathogen, Porphyromonas gingivalis, induces chronic low-grade inflammation associated with local inflammatory bone loss and systemic inflammation manifested as atherosclerosis. P. gingivalis expre...

Objective: Environmental factors could play important roles in modulating bacteria-host crosstalk and interaction in the current paradigm of periodontal pathogenesis. Given that in different oral inflammatory conditions, the temperature in periodontal niches varies as well. This study aimed to examine the effect of bacterial growth temperature on t...

Toll-like receptor (TLR) mediated inflammatory response could negatively affect bone metabolism. Bone homeostasis is regulated by orchestrating osteogenesis and osteoclastogenesis. Osteoclast mediated bone resorption is well explored but, little is known how osteogenesis is regulated during inflammatory conditions. Objectives: Determine how osteoge...

Homeostasis of healthy periodontal tissues is affected by innate and adaptive immunosurveillance mechanisms in response to the normal oral flora. Recent comparisons of germ-free (GF) and normal specific-pathogen-free (SPF) mice have revealed the impact of host immunosurveillance mechanisms in response to the normal oral flora on alveolar bone heigh...

Background: There is little consensus on the most appropriate cement to use when restoring a cement-retained, implant-supported restoration. One consideration should be the interaction of pathogenic oral bacteria with restorative cements. Purpose: To determine how oral bacteria associated with peri-implant disease grow in the presence of implant...

Periodontitis is a disease of polymicrobial etiology characterized by inflammation, degradation of host tissue, and bone that irreversibly destroys the supporting apparatus of teeth. Porphyromonas gingivalis contains lipid A with structural heterogeneity that has been postulated to contribute to the initiation of dysbiosis in oral communities by mo...

Antimicrobial peptides represent an important aspect of the innate defense system that contributes to the control of bacterial colonization and infection. As studies have progressed it has become clear that antimicrobial peptides manifest other functions in addition to their antimicrobial effects. These functions include chemotaxis of numerous type...

Background: Porphyromonas gingivalis lipid A heterogeneity modulates cytokine expression in human cells. This study investigates the effects of two lipid A isoforms of P. gingivalis, lipopolysaccharide (LPS)1435/1449 and LPS1690, on the secretion of proinflammatory and regulatory cytokines in total blood cultures from patients with and without chr...

Cell death and removal of cell corpses in a timely manner is a key event in both physiological and pathological situations including tissue homeostasis and the resolution of inflammation. Phagocytic clearance of cells dying by apoptosis is a complex sequential process comprising attraction, recognition, tethering, signalling and ultimately phagocyt...

Morphological characterisation of THP cells and their differentiated counterparts. (A) THP-1 monocytes (THP-1) cells were stimulated to differentiate in the presence of dihydroxyvitamin D3 (VD3), phorbol ester (PMA) or both (VD3/PMA) for 48 hours. Resultant cells were detached into 5mM EDTA in PBS by incubation at 37°C for 15 min prior to flow cyto...

Assessment of LPS required to activate NFκB inflammatory signalling. HeLa cells were transfected with both the luciferase NFκB reporter plasmid and a CD14WT expression plasmid or ICAM-3 expression plasmid as a control using TransIT LT-1. Expression was allowed to proceed for 24 hours prior to further analyses. Cells were treated with the indicated...

Characterisation of HeLa cells transfected with membrane associated CD14 constructs (WT and point mutant). (A) Monoclonal Ab 63D3 was tested for reactivity against wild-type CD14 and a panel of point mutants. Anti-human Fc immobilised soluble CD14-Fc fusion proteins were probed by ELISA with mAb 63D3 and binding detected with anti-mouse-HRP prior t...

Monoclonal Ab MEM18 competes with 61D3 for binding to CD14. Anti-human Fc immobilised soluble WT CD14-Fc fusion protein was probed by ELISA with mAb 61D3-biotin and binding of the biotinylated mAb detected with streptavidin-HRP prior to developing with OPD substrate and reading OD492nm. The ability of unlabelled 61D3 (red bar) or unlabelled MEM18 (...

Natural heterogeneity in the structure of the lipid A portion of LPS structure results in differential effects on the innate immune response. Gram-negative bacterial species produce LPS structures that vary from the classic endotoxic LPS structures. These variations include hypo-acylation and hypo-phosphorylation of the diglucosamine backbone, both...

Background Porphyromonas gingivalis lipopolysaccharide (LPS) is a crucial virulence factor strongly associated with chronic periodontitis which is the primary cause of tooth loss in adults. It exhibits remarkable heterogeneity containing tetra-(LPS1435/1449) and penta-(LPS1690) acylated lipid A structures. Human gingival fibroblasts (HGFs) as the m...

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...

P. gingivalis (Pg) LPS -induced gene expression of inflammatory mediators in HGFs. The cells were treated with PgLPS at 1 µg/mL or culture medium alone for 24 h. Total RNA was extracted and reverse transcribed into cDNA templates. The templates used in PCR array were pooled equally from triplicate samples. Representative heat maps showing the fold-...

Kinetics of protein kinase B (PKB) or AKT phosphorylation in HGFs. The cells were stimulated with P. gingivalis (Pg) LPS1435/1449 (PgLPS1435/1449) (A), PgLPS1690 (B) and E. coli LPS (C) at 1 µg/mL for the indicated periods of time. Cell extracts were prepared and the sample aliquots containing 40 µg of protein were separated by SDS-polyacrylamide g...

P. gingivalis (Pg) LPS1690 induced the mRNA expression of inflammatory mediators in HGFs. The cells were stimulated with PgLPS and E. coli LPS (1 µg/mL) for 24 h. The harvested RNA was subjected to real-time quantitative PCR analysis. Fold increase of genes were analyzed relative to the internal control β-Actin, including GM-CSF (A), CXCL10 (B), IL...

Genes included in the TLR signaling pathway RT-PCR array kit (SA Biosciences). A total of 84 genes related to TLR signaling family were analyzed, including adaptor and effector proteins, members of the NF-κB, JNK/p38, IRF and JAK/STAT signaling pathways as well as downstream pathway genes. (DOCX)

Confocal images of TLR2 (S1.1) and TLR4 (S1.2) expression in HGFs following LPS stimulation for 24 h. HGFs were left untreated (A) or stimulated with 1 µg/ml of P. gingivalis (Pg) LPS1435/1449 (PgLPS1435/1449) (B) PgLPS1690 (C) and E. coli LPS (D). Negative control: E. Cells were then permeabilized with 0.1% Triton X-100 and subsequently stained wi...

Differential expression profile of genes associated with TLR signal transduction in HGF. The cells were treated with P. gingivalis (Pg) LPS1435/1449 (PgLPS1435/1449) and PgLPS1690 (1 µg/mL) for 24 h. After the stimulation, mRNA was extracted from cellular fraction and reverse transcribed to cDNA. Pathway-focused PCR gene array was adopted to analys...

Nucleotide sequence of primers for real-time PCR. Quantitative real time (QRT) PCR was performed using custom-designed primers for the cell surface receptors, adaptor molecules and pro-inflammatory cytokines using purified RNA from HGFs stimulated with P. gingivalis LPS and E. coli LPS. (DOCX)

Commensal bacteria have been shown to be active participants in the development of the structure and function of host tissues (Gordon and Pesti, 1971; Hooper et al., 2001; Macpherson and Harris, 2004; Umesaki and Setoyama, 2000; Xu and Gordon, 2003). For example, commensal bacteria are required for the complete development of Peyer's patches, the l...

Infection by the chronic periodontitis-associated pathogen Porphyromonas gingivalis activates a Toll-like receptor 2 (TLR2) response that triggers inflammation in the host but also promotes bacterial persistence. Our aim was to define ligands on the surfaces of intact P. gingivalis cells that determine its ability to activate TLR2. Molecules previo...

Lipopolysaccharide (LPS) -binding protein (LBP) plays a crucial role in innate host response to bacterial challenge. Porphyromonas gingivalis is a keystone pathogen in periodontal disease and the shift of P. gingivalis LPS lipid A structure from penta-acylated (LPS(1690) ) to tetra-acylated (LPS(1435/1449) ) isoform may significantly contribute to...

Recent studies have highlighted the importance of the human microbiome in health and disease. However, for the most part the mechanisms by which the microbiome mediates disease, or protection from it, remain poorly understood. The keystone-pathogen hypothesis holds that certain low-abundance microbial pathogens can orchestrate inflammatory disease...

Objective: To microbiologically evaluate the efficacy of cotton and polytetrafluoroethylene (PTFE) tape used as spacer materials. Method and materials: Twenty-six extracted human molars were restored using either cotton or PTFE tape as spacers under a standardized provisional restorative material (Cavit). The teeth were incubated for 7 days in a...