Supernatant cytotoxicity and proteolytic activity of selected oral bacteria against human gingival fibroblasts in vitro

Evaluation of Cytotoxic Effect of Graphene Oxide Added to Mineral Trioxide Aggregate

Aim:

Recently, although studies have shown that biomaterials containing graphene oxide (GO) in biomedicine stand out for their positive effects, the effect of GO on dental tissues when used with dental materials is not well known. The aim of this study was an evaluation of the cytotoxic effects of GO on gingival fibroblasts when it is combined in two different ratios with Mineral Trioxide Aggregate (MTA).

Materials and Methods:

In this in-vitro study, a homogenous mixture of adding +0.1 weight (wt)% and +0.3 wt% GO to Angelus MTA was created (two experimental groups) and compared with pure Angelus MTA and negative control groups. The materials were mixed according to the manufacturer’s instructions, and Teflon molds were used to form 24 disc-shaped samples for each group. The samples were divided into groups according to the simple random sampling method. The cytotoxic effect of samples was determined on gingival fibroblast cells by using the MTT test, and total oxidant status (TOS) and total antioxidant capacity (TAC) kits in 24 and 72 hours. The data were statistically analyzed using one-way ANOVA and Tukey tests.

Results:

A significant difference was found between the material-applied groups and the control group at the TAC 24 and 72 hours and between the groups containing GO and the control group at the MTT 72 hours and TAC and TOS 24 and 72 hours ( p < .05).

Conclusion:

The addition of GO to MTA increased the dose and time-based toxicity and oxidant amount, and decreased antioxidant capacity.

Development of an oral mucosa model to study host-microbiome interactions during wound healing

Crosstalk between the human host and its microbiota is reported to influence various diseases such as mucositis. Fundamental research in this area is however complicated by the time frame restrictions during which host-microbe interactions can be studied in vitro. The model proposed in this paper, consisting of an oral epithelium and biofilm, can be used to study microbe-host crosstalk in vitro in non-infectious conditions up to 72 h. Microbiota derived from oral swabs were cultured on an agar/mucin layer and challenged with monolayers of keratinocytes grown on plastic or collagen type I layers embedded with fibroblasts. The overall microbial biofilm composition in terms of diversity remained representative for the oral microbiome, whilst the epithelial cell morphology and viability were unaffected. Applying the model to investigate wound healing revealed a reduced healing of 30 % in the presence of microbiota, which was not caused by a reduction of the proliferation index (52.1-61.5) or a significantly increased number of apoptotic (1-1.13) or necrotic (32-30.5 %) cells. Since the model allows the separate study of the microbial and cellular exometabolome, the biofilm and epithelial characteristics after co-culturing, it is applicable for investigations within fundamental research and for the discovery and development of agents that promote wound healing.

Cytotoxicity and biocompatibility of direct and indirect pulp capping materials

There are several studies about the cytotoxic effects of dental materials in contact with the pulp tissue, such as calcium hydroxide (CH), adhesive systems, resin composite and glass ionomer cements. The aim of this review article was to summarize and discuss the cytotoxicity and biocompatibility of materials used for protection of the dentin-pulp complex, some components of resin composites and adhesive systems when placed in direct or indirect contact with the pulp tissue. A large number of dental materials present cytotoxic effects when applied close or directly to the pulp, and the only material that seems to stimulate early pulp repair and dentin hard tissue barrier formation is CH.

Necrotizing fasciitis: a complication of percutaneous coronary revascularization

Percutaneous coronary revascularization is rarely complicated by infection. Necrotizing fasciitis (NF) is a severe, deep-seated, potentially life-threatening infection of fascia and subcutaneous tissues. We report herein 2 cases of NF in patients undergoing percutaneous transluminal coronary revascularization for treatment of acute coronary syndrome. These are the first 2 reported cases of NF associated with percutaneous coronary revascularization.

Anaerobic cocci populating the deep tissues of chronic wounds impair cellular wound healing responses in vitro

BACKGROUND

Anaerobic cocci are estimated to be present in the deep tissues of over 50% of chronic skin wounds. While the part they play in the chronicity of these wounds is uninvestigated, anaerobic cocci have previously been shown to be involved in other chronic inflammatory human conditions.

METHODS

In this study the anaerobic microflora of the deep tissues of 18 patients with refractory chronic venous leg ulcers (mean age 80.3 years; mean duration > 24 months) was characterized using strict anaerobic culture conditions. The effect of the anaerobic organisms isolated from these tissues on extracellular matrix (ECM) proteolysis and cellular wound healing responses was studied using in vitro models.

RESULTS

Anaerobic organisms were present in the deep tissues of 14 of 18 wounds and were principally Peptostreptococcus spp. The effects of three Peptostreptococcus spp. isolated from these wounds (P. magnus, P. vaginalis and P. asaccharolyticus) on cellular wound healing responses were compared with those of two pathogenic organisms also isolated from these wounds (Pseudomonas aeruginosa and Citrobacter diversus). While the direct ECM proteolytic activity exhibited by the Peptostreptococcus spp. was limited, they did significantly inhibit both fibroblast and keratinocyte proliferation, but only at high concentrations. However, at lower concentrations peptostreptococcal supernatants profoundly inhibited keratinocyte wound repopulation and endothelial tubule formation. The magnitude of these effects varied between strains and they were distinct from those demonstrated by Pseudomonas aeruginosa and Citrobacter diversus.

CONCLUSIONS

These studies confirm the importance of anaerobic organisms in chronic wounds and demonstrate an indirect, strain-specific mechanism by which these microorganisms may play a part in mediating the chronicity of these wounds.

Potential role of anaerobic cocci in impaired human wound healing

Although more than 80% of infected and 70% of noninfected leg ulcers have been shown to harbor anaerobic organisms, their role in mediating impaired wound healing in the skin is frequently overlooked. There is now increasing evidence that the gram-positive anaerobic cocci play a role (both directly and indirectly) in mediating impaired wound healing in vivo. This article discusses the mechanisms by which these microorganisms may interfere with the inflammation, repair, and remodeling phases of the wound healing process.

Virulence factors of Actinobacillus actinomycetemcomitans

A. actinomycetemcomitans has clearly adapted well to its environs; its armamentarium of virulence factors (Table 2) ensures its survival in the oral cavity and enables it to promote disease. Factors that promote A. actinomycetemcomitans colonization and persistence in the oral cavity include adhesins, bacteriocins, invasins and antibiotic resistance. It can interact with and adhere to all components of the oral cavity (the tooth surface, other oral bacteria, epithelial cells or the extracellular matrix). The adherence is mediated by a number of distinct adhesins that are elements of the cell surface (outer membrane proteins, vesicles, fimbriae or amorphous material). A. actinomycetemcomitans enhances its chance of colonization by producing actinobacillin, an antibiotic that is active against both streptococci and Actinomyces, primary colonizers of the tooth surface. The fact that A. actinomycetemcomitans resistance to tetracyclines, a drug often used in the treatment of periodontal disease, is on the rise is an added weapon. Periodontal pathogens or their pathogenic products must be able to pass through the epithelial cell barrier in order to reach and cause destruction to underlying tissues (the gingiva, cementum, periodontal ligament and alveolar bone). A. actinomycetemcomitans is able to elicit its own uptake into epithelial cells and its spread to adjacent cells by usurping normal epithelial cell function. A. actinomycetemcomitans may utilize these remarkable mechanisms for host cell infection and migration to deeper tissues. A. actinomycetemcomitans also orchestrates its own survival by elaborating factors that interfere with the host's defense system (such as factors that kill phagocytes and impair lymphocyte activity, inhibit phagocytosis and phagocyte chemotaxis or interfere with antibody production). Once the organisms are firmly established in the gingiva, the host responds to the bacterial onslaught, especially to the bacterial lipopolysaccharide, by a marked and continual inflammatory response, which results in the destruction of the periodontal tissues. A. actinomycetemcomitans has at least three individual factors that cause bone resorption (lipopolysaccharide, proteolysis-sensitive factor and GroEL), as well as a number of activities (collagenase, fibroblast cytotoxin, etc.) that elicit detrimental effects on connective tissue and the extracellular matrix. It is of considerable interest to know that A. actinomycetemcomitans possesses so many virulence factors but unfortunate that only a few have been extensively studied. If we hope to understand and eradicate this pathogen, it is critical that in-depth investigations into the biochemistry, genetic expression, regulation and mechanisms of action of these factors be initiated.