Tannerella forsythia scavenges Fusobacterium nucleatum secreted NOD2 stimulatory molecules to dampen oral epithelial cell inflammatory response

The oral organism Tannerella forsythia is auxotrophic for peptidoglycan amino sugar N-acetylmuramic acid (MurNAc). It survives in the oral cavity by scavenging MurNAc- and MurNAc-linked peptidoglycan fragments (muropeptides) secreted by co-habiting bacteria such as Fusobacterium nucleatum with which it forms synergistic biofilms. Muropeptides, MurNAc-l-Ala-d-isoGln (MDP, muramyl dipeptide) and d-γ-glutamyl-meso-DAP (iE-DAP dipeptide), are strong immunostimulatory molecules that activate nucleotide oligomerization domain (NOD)-like innate immune receptors and induce the expression of inflammatory cytokines and antimicrobial peptides. In this study, we utilized an in vitro T. forsythia-F. nucleatum co-culture model to determine if T. forsythia can selectively scavenge NOD ligands from the environment and impact NOD-mediated inflammation. The results showed that NOD-stimulatory molecules were secreted by F. nucleatum in the spent culture broth, which subsequently induced cytokine and antimicrobial peptide expression in oral epithelial cells. In the spent broth from T. forsythia-F. nucleatum co-cultures, the NOD-stimulatory activity was significantly reduced. These data indicated that F. nucleatum releases NOD2-stimulatory muropeptides in the environment, and T. forsythia can effectively scavenge the muropeptides released by co-habiting bacteria to dampen NOD-mediated host responses. This proof-of-principle study demonstrated that peptidoglycan scavenging by T. forsythia can impact the innate immunity of oral epithelium by dampening NOD activation.

Bulk RNA-seq analyses of mandibular condylar cartilage in a post-traumatic TMJ osteoarthritis rabbit model

OBJECTIVE

The temporomandibular joint (TMJ) is anatomically comprised of the mandibular condylar cartilage (CC) lined with fibrocartilaginous superficial zone and is crucial for eating and dental occlusion. TMJ osteoarthritis (OA) leads to pain, joint dysfunction and permanent loss of cartilage tissue. However, there are no drugs clinically available that ameliorate OA and little is known about global profiles of genes that contribute to TMJ OA. Furthermore, animal models that recapitulate the complexity of signalling pathways contributing to OA pathogenesis are crucial for designing novel biologics that thwart OA progression. We have previously developed a New Zealand white rabbit TMJ injury model that demonstrates CC degeneration. Here, we performed genome-wide profiling to identify new signalling pathways critical for cellular functions during OA pathology.

MATERIALS AND METHODS

Temporomandibular joint OA was surgically induced in New Zealand white rabbits. Three months following injury, we performed global gene expression profiling of the TMJ condyle. RNA samples from TMJ condyles were subjected to sequencing. After raw RNA-seq data were mapped to relevant genomes, differential expression was analysed with DESeq2. Gene ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis were conducted.

RESULTS/CONCLUSIONS

Our study revealed multiple pathways altered during TMJ OA induction including the Wnt, Notch and PI3K-Akt signalling pathways. We demonstrate an animal model that recapitulates the complexity of the cues and signals underlying TMJ OA pathogenesis, which is essential for developing and testing novel pharmacologic agents to treat OA.

Lgr5-expressing secretory cells form a Wnt inhibitory niche in cartilage critical for chondrocyte identity

Osteoarthritis is a degenerative joint disease that causes pain, degradation, and dysfunction. Excessive canonical Wnt signaling in osteoarthritis contributes to chondrocyte phenotypic instability and loss of cartilage homeostasis; however, the regulatory niche is unknown. Using the temporomandibular joint as a model in multiple species, we identify Lgr5-expressing secretory cells as forming a Wnt inhibitory niche that instruct Wnt-inactive chondroprogenitors to form the nascent synovial joint and regulate chondrocyte lineage and identity. Lgr5 ablation or suppression during joint development, aging, or osteoarthritis results in depletion of Wnt-inactive chondroprogenitors and a surge of Wnt-activated, phenotypically unstable chondrocytes with osteoblast-like properties. We recapitulate the cartilage niche and create StemJEL, an injectable hydrogel therapy combining hyaluronic acid and sclerostin. Local delivery of StemJEL to post-traumatic osteoarthritic jaw and knee joints in rabbit, rat, and mini-pig models restores cartilage homeostasis, chondrocyte identity, and joint function. We provide proof of principal that StemJEL preserves the chondrocyte niche and alleviates osteoarthritis.

Notch Regulates Fibrocartilage Stem Cell Fate and Is Upregulated in Inflammatory TMJ Arthritis

The Notch pathway is critical for the development of the extracellular matrix in cartilage by regulating both anabolic and catabolic cellular activities. Similarly, Notch signaling plays a biphasic role in adult cartilage health and osteoarthritis by maintaining homeostasis and contributing to degeneration, respectively. The temporomandibular joint (TMJ) is the synovial joint of the craniofacial complex and is subject to injury and osteoarthritis. While Notch has been studied in axial skeletal joints, little is known about the role of Notch in TMJ development and disease. We identified fibrocartilage stem cells (FCSCs) localized within the TMJ condyle superficial zone niche that regenerate cartilage and repair joint injury. Here we investigate the role of Notch in regulating TMJ development and FCSC fate. Using a Notch reporter mouse, we discovered FCSCs localized within the TMJ superficial niche exhibit Notch activity during TMJ morphogenesis. We further showed that constitutively activating Notch promotes FCSC differentiation toward both cartilage and bone lineages, but inhibits adipogenesis. Using a TNF-α-induced TMJ inflammatory arthritis mouse model, we found that the expression of Notch receptors and ligands are upregulated and coupled with cells undergoing cartilage to bone transdifferentiation, which may contribute to TMJ pathogenesis. We also discovered that global Notch inhibition reduces osteogenic and chondrogenic differentiation of FCSCs. Together, these findings suggest that Notch is critical for FCSC fate specification and TMJ homeostasis, and reveal that inhibition of the Notch pathway may be a new therapeutic target for treating TMJ osteoarthritis.

Evidence of vasculature and chondrocyte to osteoblast transdifferentiation in craniofacial synovial joints: Implications for osteoarthritis diagnosis and therapy

Temporomandibular joint osteoarthritis (TMJ OA) leads to permanent cartilage destruction, jaw dysfunction, and compromises the quality of life. However, the pathological mechanisms governing TMJ OA are poorly understood. Unlike appendicular articular cartilage, the TMJ has two distinct functions as the synovial joint of the craniofacial complex and also as the site for endochondral jaw bone growth. The established dogma of endochondral bone ossification is that hypertrophic chondrocytes undergo apoptosis, while invading vasculature with osteoprogenitors replace cartilage with bone. However, contemporary murine genetic studies support the direct differentiation of chondrocytes into osteoblasts and osteocytes in the TMJ. Here we sought to characterize putative vasculature and cartilage to bone transdifferentiation using healthy and diseased TMJ tissues from miniature pigs and humans. During endochondral ossification, the presence of fully formed vasculature expressing CD31⁺ endothelial cells and α-SMA⁺ vascular smooth muscle cells were detected within all cellular zones in growing miniature pigs. Arterial, endothelial, venous, angiogenic, and mural cell markers were significantly upregulated in miniature pig TMJ tissues relative to donor matched knee meniscus fibrocartilage tissue. Upon surgically creating TMJ OA in miniature pigs, we discovered increased vasculature and putative chondrocyte to osteoblast transformation dually marked by COL2 and BSP or RUNX2 within the vascular bundles. Pathological human TMJ tissues also exhibited increased vasculature, while isolated diseased human TMJ cells exhibited marked increased in vasculature markers relative to control 293T cells. Our study provides evidence to suggest that the TMJ in higher order species are in fact vascularized. There have been no reports of cartilage to bone transdifferentiation or vasculature in human-relevant TMJ OA large animal models or in human TMJ tissues and cells. Therefore, these findings may potentially alter the clinical management of TMJ OA by defining new drugs that target angiogenesis or block the cartilage to bone transformation.

Extracellular matrix turnover and inflammation in chemically-induced TMJ arthritis mouse models

The temporomandibular joint (TMJ) is a fibrocartilaginous tissue critical for chewing and speaking. In patients with temporomandibular disorders (TMDs), permanent tissue loss can occur. Recapitulating the complexity of TMDs in animal models is difficult, yet critical for the advent of new therapies. Synovial fluid from diseased human samples revealed elevated levels of tumor necrosis factor alpha (TNF-alpha). Here, we propose to recapitulate these findings in mice by subjecting murine TMJs with TNF-alpha or CFA (Complete Freund’s Adjuvant) in mandibular condyle explant cultures and by local delivery in vivo using TMJ intra-articular injections. Both TNF-alpha and CFA delivery to whole mandibular explants and in vivo increased extracellular matrix deposition and increased cartilage thickness, while TNF-alpha treated explants had increased expression of inflammatory cytokines and degradative enzymes. Moreover, the application of TNF-alpha or CFA in both models reduced cell number. CFA delivery in vivo caused soft tissue inflammation, including pannus formation. Our work provides two methods of chemically induced TMJ inflammatory arthritis through a condyle explant model and intra-articular injection model that replicate findings seen in synovial fluid of human patients, which can be used for further studies delineating the mechanisms underlying TMJ pathology.

Peptidoglycan synthesis in Tannerella forsythia: Scavenging is the modus operandi

Tannerella forsythia is a Gram-negative oral pathogen strongly associated with periodontitis. This bacterium has an absolute requirement for exogenous N-acetylmuramic acid (MurNAc), an amino sugar that forms the repeating disaccharide unit with amino sugar N-acetylglucosamine (GlcNAc) of the peptidoglycan backbone. In silico genome analysis indicates that T. forsythia lacks the key biosynthetic enzymes needed for the de novo synthesis of MurNAc, and so relies on alternative ways to meet its requirement for peptidoglycan biosynthesis. In the subgingival niche, the bacterium can acquire MurNAc and peptidoglycan fragments (muropeptides) released by the cohabiting bacteria during their cell wall breakdown associated with cell division. Tannerella forsythia is able to also use host sialic acid (Neu5Ac) in lieu of MurNAc or muropeptides for its survival during the biofilm growth. Evidence suggests that the bacterium might be able to shunt sialic acid into a metabolic pathway leading to peptidoglycan synthesis. In this review, we explore the mechanisms by which T. forsythia is able to scavenge MurNAc, muropeptide and sialic acid for its peptidoglycan synthesis, and the impact of these scavenging activities on pathogenesis.

Fibrocartilage Stem Cells Engraft and Self-Organize into Vascularized Bone

Angiogenesis is a complex, multicellular process that is critical for bone development and generation. Endochondral ossification depends on an avascular cartilage template that completely remodels into vascularized bone and involves a dynamic interplay among chondrocytes, osteoblasts, and endothelial cells. We have discovered fibrocartilage stem cells (FCSCs) derived from the temporomandibular joint (TMJ) mandibular condyle that generates cartilage anlagen, which is subsequently remodeled into vascularized bone using an ectopic transplantation model. Here we explore FCSC and endothelial cell interactions during vascularized bone formation. We found that a single FCSC colony formed transient cartilage and host endothelial cells may participate in bone angiogenesis upon subcutaneous transplantation in a nude mouse. FCSCs produced an abundance of the proangiogenic growth factor vascular endothelial growth factor A and promoted the proliferation of human umbilical vein endothelial cells (HUVECs). Using a fibrinogen gel bead angiogenesis assay experiment, FCSC cell feeder layer induced HUVECs to form significantly shorter and less sprouts than D551 fibroblast controls, suggesting that FCSCs may initially inhibit angiogenesis to allow for avascular cartilage formation. Conversely, direct FCSC-HUVEC contact significantly enhanced the osteogenic differentiation of FCSCs. To corroborate this idea, upon transplantation of FCSCs into a bone defect microenvironment, FCSCs engrafted and regenerated intramembranous bone. Taken together, we demonstrate that the interactions between FCSCs and endothelial cells are essential for FCSC-derived vascularized bone formation. A comprehensive understanding of the environmental cues that regulate FCSC fate decisions may contribute to deciphering the mechanisms underlying the role of FCSCs in regulating bone formation.

Regulation and Molecular Basis of Environmental Muropeptide Uptake and Utilization in Fastidious Oral Anaerobe Tannerella forsythia

Tannerella forsythia is a Gram-negative oral anaerobe associated with periodontitis. This bacterium is auxotrophic for the peptidoglycan amino sugar N-acetylmuramic (MurNAc) and likely relies on scavenging peptidoglycan fragments (muropeptides) released by cohabiting bacteria during their cell wall recycling. Many Gram-negative bacteria utilize an inner membrane permease, AmpG, to transport peptidoglycan fragments into their cytoplasm. In the T. forsythia genome, the Tanf_08365 ORF has been identified as a homolog of AmpG permease. In order to confirm the functionality of Tanf_08365, a reporter system in an Escherichia coli host was generated that could detect AmpG-dependent accumulation of cytosolic muropeptides via a muropeptide-inducible β-lactamase reporter gene. In trans complementation of this reporter strain with a Tanf_08365 containing plasmid caused significant induction of β-lactamase activity compared to that with an empty plasmid control. These data indicated that Tanf_08365 acted as a functional muropeptide permease causing accumulation of muropeptides in E. coli and thus suggested that it is a permease involved in muropeptide scavenging in T. forsythia. Furthermore, we showed that the promoter regulating the expression of Tanf_08365 was activated significantly by a hybrid two-component system regulatory protein, GppX. We also showed that compared to the parental T. forsythia strain a mutant lacking GppX in which the expression of AmpG was reduced significantly attenuated in utilizing free muropeptides. In summary, we have uncovered the mechanism by which this nutritionally fastidious microbe accesses released muropeptides in its environment, opening up the possibility of targeting this activity to reduce its numbers in periodontitis patients with potential benefits in the treatment of disease.

An accurate and efficient experimental approach for characterization of the complex oral microbiota

BACKGROUND

Currently, taxonomic interrogation of microbiota is based on amplification of 16S rRNA gene sequences in clinical and scientific settings. Accurate evaluation of the microbiota depends heavily on the primers used, and genus/species resolution bias can arise with amplification of non-representative genomic regions. The latest Illumina MiSeq sequencing chemistry has extended the read length to 300 bp, enabling deep profiling of large number of samples in a single paired-end reaction at a fraction of the cost. An increasingly large number of researchers have adopted this technology for various microbiome studies targeting the 16S rRNA V3-V4 hypervariable region.

RESULTS

To expand the applicability of this powerful platform for further descriptive and functional microbiome studies, we standardized and tested an efficient, reliable, and straightforward workflow for the amplification, library construction, and sequencing of the 16S V1-V3 hypervariable region using the new 2 × 300 MiSeq platform. Our analysis involved 11 subgingival plaque samples from diabetic and non-diabetic human subjects suffering from periodontitis. The efficiency and reliability of our experimental protocol was compared to 16S V3-V4 sequencing data from the same samples. Comparisons were based on measures of observed taxonomic richness and species evenness, along with Procrustes analyses using beta(β)-diversity distance metrics. As an experimental control, we also analyzed a total of eight technical replicates for the V1-V3 and V3-V4 regions from a synthetic community with known bacterial species operon counts. We show that our experimental protocol accurately measures true bacterial community composition. Procrustes analyses based on unweighted UniFrac β-diversity metrics depicted significant correlation between oral bacterial composition for the V1-V3 and V3-V4 regions. However, measures of phylotype richness were higher for the V1-V3 region, suggesting that V1-V3 offers a deeper assessment of population diversity and community ecology for the complex oral microbiota.

CONCLUSION

This study provides researchers with valuable experimental evidence for the selection of appropriate 16S amplicons for future human oral microbiome studies. We expect that the tested 16S V1-V3 framework will be widely applicable to other types of microbiota, allowing robust, time-efficient, and inexpensive examination of thousands of samples for population, phylogenetic, and functional crossectional and longitutidal studies.

Sialic acid transporter NanT participates in Tannerella forsythia biofilm formation and survival on epithelial cells

Tannerella forsythia is a periodontal pathogen implicated in periodontitis. This gram-negative pathogen depends on exogenous peptidoglycan amino sugar N-acetylmuramic acid (NAM) for growth. In the biofilm state the bacterium can utilize sialic acid (Neu5Ac) instead of NAM to sustain its growth. Thus, the sialic acid utilization system of the bacterium plays a critical role in the growth and survival of the organism in the absence of NAM. We sought the function of a T. forsythia gene annotated as nanT coding for an inner-membrane sugar transporter located on a sialic acid utilization genetic cluster. To determine the function of this putative sialic acid transporter, an isogenic nanT-deletion mutant generated by allelic replacement strategy was evaluated for biofilm formation on NAM or Neu5Ac, and survival on KB epithelial cells. Moreover, since T. forsythia forms synergistic biofilms with Fusobacterium nucleatum, co-biofilm formation activity in mixed culture and sialic acid uptake in culture were also assessed. The data showed that the nanT-inactivated mutant of T. forsythia was attenuated in its ability to uptake sialic acid. The mutant formed weaker biofilms compared to the wild-type strain in the presence of sialic acid and as co-biofilms with F. nucleatum. Moreover, compared to the wild-type T. forsythia nanT-inactivated mutant showed reduced survival when incubated on KB epithelial cells. Taken together, the data presented here demonstrate that NanT-mediated sialic transportation is essential for sialic acid utilization during biofilm growth and survival of the organism on epithelial cells and implies sialic acid might be key for its survival both in subgingival biofilms and during infection of human epithelial cells in vivo.

Changes in opioid and other analgesic use 1995-2010: repeated cross-sectional analysis of dispensed prescribing for a large geographical population in Scotland

BACKGROUND

Despite recent concerns about increasing rates of analgesic prescribing, detailed epidemiological studies are lacking. We identified and described changes in the pattern of community-dispensed prescriptions to the Tayside population, Scotland, between 31st March 1995 (n = 301,020) and 31st March 2010 (n = 311,881).

METHODS

Repeated cross-sectional analysis of patient-level population data on dispensed analgesics, stratified by sociodemographic variables; logistic regression to identify factors associated with strong opioid dispensing in 2010.

RESULTS

The proportion of people currently dispensed any analgesic increased in 2010 (17.9%) compared with 1995 (15.7%). This increase was not equal across drug classes, with paracetamol, opioids and gabapentin/pregabalin showing an increase, but others showing a decrease. Weak opioids were less commonly dispensed in 2010 (8.2% vs. 8.4%) but dispensing of strong opioids increased 18-fold (3.6% vs. 0.2%), including a five-fold increase of morphine, fentanyl or oxycodone (0.75% vs. 0.15%). People receiving more non-analgesic drugs (odds ratio 20.7 if dispensed >14 non-analgesic medications vs. those dispensed <4) and those living in more deprived areas (OR 1.63 most deprived vs. most affluent) were more likely to receive a strong opioid in 2010.

CONCLUSIONS

Analgesic use rose modestly between 1995 and 2010, but with larger changes within individual classes, only partly reflecting evidence-based guidance. Dispensing of strong opioids increased dramatically, largely driven by tramadol, although other strong opioids tripled. Polypharmacy and socio-economic deprivation were strongly associated with strong opioid use. Research is needed to establish the causes, benefits and harms of the increase in analgesic, and especially strong opioid use.

[Cytomegalovirus-induced protein-losing gastropathy: a case report]

Protein-losing gastropathy is an uncommon disease of uncertain etiology, known also as Menetrier's disease. In medical literature only 50 pediatric cases have been described. These childhood forms, in contrast to classic adult Menetrier's disease, have a typical benign and transient course, and require only supportive therapy. The role of Cytomegalovirus (CMV) in the pathogenesis has been demonstrated by gastric biopsy in one third of the cases. Also other infectious, allergic and immunological factors have been hypothesized. We describe a case of hypertrophic gastropathy with important protein-loss, admitted to our Pediatric Department for evaluation because of vomit, weight loss, abdominal pain and hypoalbuminemia. Gastric mucosal biopsy revealed a morphological evidence of CMV infection.

[Immunological development in asymptomatic HIV infected children]

In HIV infected children, CD45+CD4+ T lymph. reconstitution has been related to efficient thymopoiesis. Because human thymus undergoes spontaneous involution at a relatively young age, institution of antiretroviral therapy early in the course of infection has been recommended. 12 HIV vertically infected children aged 4-8 years were investigated T-cell subsets for four years. 7 children were naive for therapy (group NT); 5 experienced nucleoside analogues only (group T). CD45RA+ and CD45RO+ CD4+ values were compared to predicted values of healthy children. The two groups showed similar clinical and immunological baseline characteristics (CDC class N-A). Mean VL at t0 was 4.26 log10 (SD 0.71) in gr. NT and 4.01 log10 (SD 0.57) in gr. T; median CD4 T lymph values were 27% in gr. NT and 23.5% in gr. T. Median CD45RA+ values were 62.8% in gr. NT and 71.3% in gr. T. No differences in VL, CD4+ T lymph., CD45RA+, CD45RO+ were found in between groups or within each group at each time evaluation. Median CD45RA+ values were not different from predicted values of healthy children. None of the children changed CDC class during the study period. Although the number of subjects was small, our study evidenced the possibility of a normal immunological development in HIV-1 vertically infected asymptomatic children naive for HAART during the first decade, even in the presence of significant viremia.