Enterococcus faecalis affects the proliferation and differentiation of ovine osteoblast-like cells

Single-cell atlas of dental pulp stem cells exposed to the oral bacteria Porphyromonas gingivalis and Enterococcus faecalis

Introduction: Porphyromonas gingivalis and Enterococcus faecalis promote the development of pulpitis and periapical periodontitis. These bacteria are difficult to eliminate from the root canal systems, leading to persistent infection and poor treatment outcomes. We explored the response of human dental pulp stem cells (hDPSCs) to bacterial invasion and the mechanisms underlying the impact of residual bacteria on dental pulp regeneration. Methods: Single-cell sequencing was used to categorize the hDPSCs into clusters based on their response to P. gingivalis and E. faecalis. We depicted a single-cell transcriptome atlas of hDPSCs stimulated by P. gingivalis or E. faecalis. Results: The most differentially expressed genes in the Pg samples were THBS1, COL1A2, CRIM1, and STC1, which are related to matrix formation and mineralization, and HILPDA and PLIN2, which are related to the cellular response to hypoxia. A cell cluster characterized by high expression levels of THBS1 and PTGS2 was increased after P. gingivalis stimulation. Further signaling pathway analysis showed that hDPSCs prevented P. gingivalis infection by regulating the TGF-β/SMAD, NF-κB, and MAPK/ERK signaling pathways. Differentiation potency and pseudotime trajectory analyses showed that hDPSCs infected by P. gingivalis undergo multidirectional differentiation, particularly to the mineralization-related cell lineage. Furthermore, P. gingivalis can create a hypoxia environment to effect cell differentiation. The Ef samples were characterized by the expression of CCL2, which is related to leukocyte chemotaxis, and ACTA2, which is related to actin. There was an increased proportion of a cell cluster that was similar to myofibroblasts and exhibited significant ACTA2 expression. The presence of E. faecalis promoted the differentiation of hDPSCs into fibroblast-like cells, which highlights the role of fibroblast-like cells and myofibroblasts in tissue repair. Discussion: hDPSCs do not maintain their stem cell status in the presence of P. gingivalis and E. faecalis. They differentiate into mineralization-related cells in the presence of P. gingivalis and into fibroblast-like cells in the presence of E. faecalis. We identified the mechanism underlying the infection of hDPSCs by P. gingivalis and E. faecalis. Our results will improve understanding of the pathogenesis of pulpitis and periapical periodontitis. Furthermore, the presence of residual bacteria can have adverse effects on the outcomes of regenerative endodontic treatment.

Role of Enterococcus faecalis in refractory apical periodontitis: from pathogenicity to host cell response

BACKGROUND

Refractory apical periodontitis (RAP) is an oral infectious disease characterised by persistent inflammation, progressive alveolar bone destruction, and delayed bone healing. RAP has received increasing attention, because it cannot be cured after repeated root canal therapies. The aetiology of RAP is related to the complex interplay between the pathogen and its host. However, the exact pathogenesis of RAP remains unclarified and includes several factors, such as microorganism immunogenicity, host immunity and inflammation, and tissue destruction and repair. Enterococcus faecalis is the dominant pathogen involved in RAP, and has evolved multiple strategies to ensure survival, which cause persistent intraradicular and extraradicular infections.

OBJECTIVE

To review the crucial role of E. faecalis in the pathogenesis of RAP, and open new avenues for prevention and treatment of RAP.

METHODS

The PubMed and Web of Science databases were searched for pertinent publications, employing the search terms "Enterococcus faecalis", "refractory apical periodontitis", "persistent periapical periodontitis", "pathogenicity", "virulence", "biofilm formation", "dentine tubule", "immune cell", "macrophage", and "osteoblast".

RESULTS AND CONCLUSION

Besides its high pathogenicity due to various virulence mechanisms, E. faecalis modulates the macrophage and osteoblast responses, including regulated cell death, cell polarisation, cell differentiation, and inflammatory response. An in-depth understanding of the multifaceted host cell responses modulated by E. faecalis will help to design potential future therapeutic strategies and overcome the challenges of sustained infection and delayed tissue healing in RAP.

Effect of Enterococcus faecalis OG1RF on human calvarial osteoblast apoptosis

Background

Enterococcus faecalis is a dominant pathogen in the root canals of teeth with persistent apical periodontitis (PAP), and osteoblast apoptosis contributes to imbalanced bone remodelling in PAP. Here, we investigated the effect of E. faecalis OG1RF on apoptosis in primary human calvarial osteoblasts. Specifically, the expression of apoptosis-related genes and the role of anti-apoptotic and pro-apoptotic members of the BCL-2 family were examined.

Methods

Primary human calvarial osteoblasts were incubated with E. faecalis OG1RF at multiplicities of infection corresponding to infection time points. Flow cytometry, terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay, caspase-3/-8/-9 activity assay, polymerase chain reaction (PCR) array, and quantitative real-time PCR were used to assess osteoblast apoptosis.

Results

E. faecalis infection increased the number of early- and late-phase apoptotic cells and TUNEL-positive cells, decreased the mitochondrial membrane potential (ΔΨm), and activated the caspase-3/-8/-9 pathway. Moreover, of all 84 apoptosis-related genes in the PCR array, the expression of 16 genes was upregulated and that of four genes was downregulated in the infected osteoblasts. Notably, the mRNA expression of anti-apoptotic BCL2 was downregulated, whereas that of the pro-apoptotic BCL2L11, HRK, BIK, BMF, NOXA, and BECN1 and anti-apoptotic BCL2A1 was upregulated.

Conclusions

E. faecalis OG1RF infection triggered apoptosis in human calvarial osteoblasts, and BCL-2 family members acted as regulators of osteoblast apoptosis. Therefore, BCL-2 family members may act as potential therapeutic targets for persistent apical periodontitis.

Quantification of Multiple Bacteria in Calcified Structural Valvular Heart Disease

Genome studies of heart valve tissue (HVT) in patients with structural valvular heart disease (sVHD) and acute infective endocarditis (aIE) showed polymicrobial infections. Subject of this study is the quantification of bacterial DNA in HVT of sVHD in comparison to aIE. It will be examined whether the bacterial DNA concentration can be used as surrogate marker to differentiate chronic and acute infections. DNA was isolated from HVT of 100 patients with sVHD and 23 microbiologically positively tested patients with aIE. Selected pathogens (Cutibacterium acnes, Enterococcus faecalis, Enterococcus faecium, Staphylococcus aureus, Streptococcus pyogenes, Streptococcus agalactiae, Clostridium difficile, and Klebsiella pneumoniae) were quantified using TaqMan-qPCR. Polymicrobial infiltration of HVT was investigated by immunohistologic methods. Of 100 sVHD patients, 94 tested positive for bacteria by 16S-rDNA and 72 by TaqMan-qPCR. In 29% of the sVHD cohort and in 70% of the aIE cohort, a coinfection with more than 2 bacteria was observed as indication of a polymicrobial infection. The most common pathogens in the sVHD patients were C. acnes (59%; 5-4074 pg/mL), E. faecalis (16%, 174-2781 pg/mL), and S. aureus (15%, 8-105 pg/mL). The DNA concentration of E. faecalis (P = 0.0285) and S. aureus (P = 0.0149) is significantly lower in the sVHD cohort than in the aIE cohort. sVHD is associated with bacterial infection and infiltration of the HVT in a majority of cases. TaqMan-qPCR is a valid instrument for the specific detection of bacteria in HVT and allows discrimination between sVHD and aIE for E. faecalis and S. aureus.

Enterococcus faecalis attenuates osteogenesis through activation of p38 and ERK1/2 pathways in MC3T3-E1 cells

AIM

To explore the role of Enterococcus faecalis in the proliferation, apoptosis and differentiation of osteoblasts.

METHODOLOGY

Pre-osteoblastic MC3T3-E1 cells were treated with heat-killed E. faecalis ATCC 29212 and clinical E. faecalis P25RC strains, respectively. Cell proliferation, mineralized calcium deposition, alkaline phosphatase (ALP) activity and apoptosis were assessed at various time-points. The expression levels of osteogenic-related genes including ALP, osteocalcin (OC), runt-related protein 2 (Runx2) and collagen type 1 (COL1) were also analysed throughout the duration of the experiment. Additionally, the involvement of mitogen-activated protein kinases (MAPKs) signalling pathways was analysed by Western blotting. In the presence of culture supernatant from E. faecalis-treated murine macrophages, apoptosis of MC3T3-E1 cells was detected with flow cytometry. Data were analysed using analysis of variance (anova), and P < 0.05 was considered significantly different.

RESULTS

E. faecalis significantly inhibited proliferation (P < 0.05) and also significantly induced apoptosis of MC3T3-E1 cells (P < 0.05), whilst differentiation seemed to be unaffected after 7 days of E. faecalis treatment. However, osteogenic differentiation was significantly inhibited with 21-day E. faecalis treatment (P < 0.05). The p38 and ERK1/2 phosphorylation pathways associated with mineral deposition and apoptosis were significantly activated in MC3T3-E1 cells. The culture supernatants from E. faecalis-treated macrophages induced osteoblast apoptosis.

CONCLUSIONS

E. faecalis exerted an inhibitory effect on osteogenesis in pre-osteoblastic MC3T3-E1 cells via phosphorylation of p38 and ERK1/2.

An artificial fusion protein between bone morphogenetic protein 2 and titanium-binding peptide is functional in vivo

The purpose of this study was to investigate osteogenesis using an artificial fusion protein (AFP) composed of modified bone morphogenetic protein 2 (BMP-2) with a titanium (Ti)-binding peptide (TBP) motif on a Ti surface in vivo. In the in vivostudy, 5-μm thick Ti was coated with electron cyclotron resonance sputtering on a porous carbon scaffold which was then dipped in one of three different mixtures of collagen gel: (1) collagen gel only, (2) collagen gel with TBP, and (3) collagen gel with the AFP between BMP-2 and the TBP motif (AFP-TBP-BMP-2). These scaffolds were then implanted into rat abdominal muscles and were studied histologically at various times and the expression of several bone-related protein messenger RNAs (mRNAs) was also analyzed. The Ti-coated scaffold of the collagen gel with AFP-TBP-BMP-2 produced cartilage in the muscle and the expression of alkaline phosphatase, bone sialoprotein, and runt-related gene 2 mRNAs was significantly increased. These results suggest that the scaffold of the collagen gel with AFP-TBP-BMP-2 accelerates osteogenesis in vivo.