Stimulatory effect of Aggregatibacter actinomycetemcomitans DNA on proinflammatory cytokine expression by human gingival fibroblasts

The Role of Gingival Fibroblasts in the Pathogenesis of Periodontitis

Gingival fibroblasts (GFs) are essential components of the periodontium, which are responsible for the maintenance of tissue structure and integrity. However, the physiological role of GFs is not restricted to the production and remodeling of the extracellular matrix. GFs also act as sentinel cells that modulate the immune response to oral pathogens invading the gingival tissue. As an important "nonclassical" component of the innate immune system, GFs respond to bacteria and damage-related signals by producing cytokines, chemokines, and other inflammatory mediators. Although the activation of GFs supports the elimination of invading bacteria and the resolution of inflammation, their uncontrolled or excessive activation may promote inflammation and bone destruction. This occurs in periodontitis, a chronic inflammatory disease of the periodontium initiated and sustained by dysbiosis. In the inflamed gingival tissue, GFs acquire imprinted proinflammatory phenotypes that promote the growth of inflammophilic pathogens, stimulate osteoclastogenesis, and contribute to the chronicity of inflammation. In this review, we discuss the biological functions of GFs in healthy and inflamed gingival tissue, highlighting recent studies that provide insight into their role in the pathogenesis of periodontal diseases. We also draw parallels with the recently discovered fibroblast populations identified in other tissues and their roles in health and disease. This knowledge should be used in future studies to discover more about the role of GFs in periodontal diseases, especially chronic periodontitis, and to identify therapeutic strategies targeting their pathological interactions with oral pathogens and the immune system.

Stable reconstructed human gingiva–microbe interaction model: Differential response to commensals and pathogens

Background

To investigate human oral health and disease, models are required which represent the interactions between the oral mucosa and microbiome. Our aim was to develop an organotypic model which maintains viability of both host and microbes for an extended period of time.

Methods

Reconstructed Human Gingiva (RHG) were cultured air-lifted with or without penicillin-streptomycin (PS) and topically exposed to Streptococcus gordonii (commensal) or Aggregatibacter actinomycetemcomitans (pathogen) for 72 hours in agar. RHG histology, viability and cytokines (ELISA), and bacterial viability (colony forming units) and location (FISH) were assessed.

Results

The low concentration of topically applied agar did not influence RHG viability. Topically applied bacteria in agar remained localized and viable for 72 hours and did not spill over to infect RHG culture medium. PS in RHG culture medium killed topically applied bacteria. Co-culture with living bacteria did not influence RHG viability (Ki67 expression, MTT assay) or histology (epithelium differentiation, Keratin10 expression). RHG exposed to S. gordonii (with or without PS) did not influence low level of IL-6, IL-8, CCL2, CCL5, CCL20 or CXCL1 secretion. However, all cytokines increased (except CCL2) when RHG were co-cultured with A. actinomycetemcomitans. The effect was significantly more in the presence of living, rather than dead, A. actinomycetemcomitans. Both bacteria resulted in increased expression of RHG antimicrobial peptides (AMPs) Elafin and HBD-2, with S. gordonii exposure resulting in the most Elafin secretion.

Conclusion

This technical advance enables living human oral host–microbe interactions to be investigated during a 72-hour period and shows differences in innate immunology triggered by S. gordonii and A. actinomycetemcomitans.

Cytocompatibility of 3D printed dental materials for temporary restorations on fibroblasts

Background

Three-dimensional (3D) printing is widely used in the fabrication of dental prostheses; however, the influence of dental materials used for 3D printing on temporary restoration of fibroblasts in tissues is unclear. Thus, the influence of different dental materials on fibroblasts were investigated.

Methods

Digital light processing (DLP) type 3D printing was used. Specimens in the control group were fabricated by mixing liquid and powder self-curing resin restoration materials. The temporary resin materials used were Model, Castable, Clear-SG, Tray, and Temporary, and the self-curing resin materials used were Lang dental, Alike, Milky blue, TOKVSO CUREFAST, and UniFast III. Fibroblast cells were cultured on each specimen and subsequently post-treated for analysis. Morphology of the adhered cells were observed using a confocal laser scanning microscope (CLSM) and a scanning electron microscope (SEM).

Results

CLSM and SEM cell imaging revealed that the 3D printed material group presented better cell adhesion with well-distributed filopodia compared to that in the conventional resin material group. Cell proliferation was significantly higher in the 3D printing materials.

Conclusion

Superior cytocompatibility of the specimens fabricated through 3D printing and polishing process was demonstrated with the proof of better cell adhesion and higher cell proliferation.

The impact of Aggregatibacter actinomycetemcomitans biofilm-derived effectors following antimicrobial photodynamic therapy on cytokine production in human gingival fibroblasts

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) is an effective adjunctive therapeutic modality for the treatment of local infections, including periodontitis and peri-implantitis. After receiving aPDT, microbial cells in the biofilm structure may produce and/ or release soluble biofilm-derived effectors (BDEs), which may affect the biology of the host cells in the community context of their surrounding microenvironment. Given the fact that no study has investigated the role of BDEs following aPDT in the pathogenesis of infectious diseases, the aim of the current study was to determine the effect of BDEs of Aggregatibacter actinomycetemcomitans following exposure to sub-lethal doses of indocyanine green (ICG)-aPDT on human gingival fibroblasts (HGFs) in terms of cytokines produced.

MATERIALS AND METHODS

In this study, we evaluated the effect of biofilm-conditioned medium (BCM) resulting from the treatment of A. actinomycetemcomitans biofilm with a sub-lethal dose of aPDT on cytokines production, including IL-6, IL-8, CXCL10, TGF-β, and bFGF of HGFs using enzyme-linked immunoassays (ELISA). The sensitivity of cytokines to BDEs was determined by micro-titer plates.

RESULTS

The maximal sub-lethal dose of ICG-PDT was 20.15 μM/mL ICG at a fluence of 31.2 J/cm². The BCM of ICG-PDT-treated viable A. actinomycetemcomitans significantly reduced IL-6, IL-8, and CXCL10 levels compared to the BCM of untreated viable A. actinomycetemcomitans (78-, 93-, and 61.6-fold reduction, respectively; all P < 0.01). TGF-β and bFGF were strongly induced by BCM of ICG-PDT treated viable A. actinomycetemcomitans (by 57.7 and 36.1 folds, respectively; both P < 0.05). The BCM of untreated viable A. actinomycetemcomitans degraded most of the CxCL10, TGF-β and bFGF (58.8, 61.5, and 71.6%, respectively) in 24 h, while it degraded 9.3% of IL-6 and 15.1% of IL-8 after 24 h.

CONCLUSION

The results of the current study revealed that a sub-lethal dose of ICG-aPDT through the effect of BCM on HGFs could not only significantly reduce the production of pro-inflammatory cytokines but also promoted their role in periodontal regeneration due to increasing the bFGF level. Altogether, ICG-aPDT, with it's antimicrobial effects reduces inflammation and induces of tissue regeneration resulting from BCM, can be considered an efficient adjunctive therapeutic method for the treatment of local infections.