Effects of extracts from Bacteroides gingivalis, Bacteroides intermedius, and Bacteroides asaccharolyticus on the growth of fibroblast lines obtained from healthy and inflamed human gingiva

Oral bacterial extracts facilitate early osteogenic/dentinogenic differentiation in human dental pulp-derived cells

OBJECTIVES

Bacterial metabolites demineralize dental hard tissues, and soluble factors lead to tertiary dentinogenesis in the area of the dentin-pulp complex. However, it is unclear whether the oral bacteria are directly involved in the differentiation of dental pulp cells. In this study, we evaluated the effect of oral bacterial extracts on cellular differentiation in human dental pulp-derived cells (hDPC).

STUDY DESIGN

The hDPC were obtained from third molar teeth, and the cells were subcultured. The sonicated extracts were obtained from Porphyromonas gingivalis (gram-negative) and Streptococcus mutans (gram-positive). The effect of bacterial extracts on cellular growth and differentiation in hDPC were tested.

RESULTS

Alkaline phosphatase activity and bone sialoprotein (BSP) gene expression were increased in hDPC exposed to low concentrations of both sonicated extracts, whereas the activity was decreased upon exposure to high concentrations of sonicated extracts from P. gingivalis.

CONCLUSION

This is the first evidence that oral bacteria have a positive effect on cellular differentiation in hPDC.

Cellular microbiology: cycling into the millennium

Cellular microbiology is a newly developing science born from the realization that many different aspects of eukaryotic cell biology are targeted by microbial virulence mechanisms. One example of this is the emerging evidence that several bacteria can interfere, directly or indirectly, with the eukaryotic cell cycle. This article discusses the cell-cycle effects of bacterially generated molecules, their role in virulence and their possible therapeutic potential.

Cytotoxic effect of endodontic bacteria on periapical fibroblasts

This study was conducted to investigate the effects of sonicated bacterial extracts (SBEs) from anaerobic Gram-negative bacteria on periapical fibroblast obtained from the apical portion of human periodontal ligaments. Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, and Fusobacterium nucleatum were chosen from among the endodontic bacteria isolated from root canals having a periapical lesion and compared in terms of their cytotoxicity. The purpose of this study was to examine which bacteria are involved in the development of periapical inflammation. The anaerobes were cultured under strict anaerobic conditions, and the bacterial cells were then harvested by centrifugation after incubation. The concentrated cell suspensions were sonicated and subsequently centrifuged. An SBE was made of each of the filtered supernatants. Each SBE was added to cultures of periapical fibroblasts. The cell growth and proliferation were measured by the MTT method after 3, 5, and 7 days. The SBEs from P. endodontalis, P. gingivalis, and F. nucleatum inhibited the growth of the fibroblasts, whereas the SBE from P. intermedia did not inhibit it. The SBEs from P. gingivalis and F. nucleatum inhibited the fibroblast growth more strongly than did the P. endodontalis, P. gingivalis, and F. nucleatum may participate in the development of periapical lesions.

Effect of sonicated material from Fusobacterium nucleatum on the functional capacity of accessory cells derived from dental pulp

Fusobacterium nucleatum-derived components were studied for their effect on the ability of accessory pulpal cells to induce T-lymphocyte proliferation. In initial experiments, spleen cells were used to establish concentration ranges at which testing of the effect of the bacterial components would be suitable. At low concentrations, bacterial substances induced a stimulatory effect on the proliferation rate of spleen cells, but not when purified T-lymphocytes were incubated in the presence of concanavalin A and pulpal accessory cells. At increasing concentrations, a dose-dependent reduction was observed. Pretreatment with the bacterial products for 4 h gave a stimulatory effect in the absence of concanavalin A for both spleen cells and T-lymphocytes. Removal of low-molecular weight components (<3.5 kDa) did not influence the inhibitory effect, whereas preheating the bacterial substances to 100 degrees C eliminated the observed inhibition. Findings show that heat-sensitive, high-molecular-weight components of F. nucleatum can evoke a concentration-dependent stimulatory or suppressive effect on the proliferation rate of T-lymphocytes in the presence of accessory cells derived from the dental pulp.

Stimulation of plasmin activity in cultured human fibroblast cells by Porphyromonas endodontalis

1. Plasmin activity in the conditioned medium of Gin-1 cells, a human gingival fibroblast cell line, was stimulated by Porphyromonas endodontalis, a putative pathogen of oral submucous abscesses, in a time- and dose-dependent manner. 2. P. endodontalis stimulated the activity of plasminogen activator in both the conditioned medium and the cell lysate. The plasminogen activator in Gin-1 cells was approx. 50 kDa by zymography. 3. The conditioned medium of Gin-1 cells exposed to P. endodontalis stimulated the conversion of human serum prekallikrein to kallikrein. 4. These results suggested that P. endodontalis stimulates the plasminogen activator-plasmin system in Gin-1 cells, and that activated plasmin plays a role in the progress of periodontal tissue inflammation.

Toxicity of sonicated extracts of Bacteroides gingivalis on human pulpal cells and L929 cells in vitro

Human pulpal fibroblasts and L929 cells were treated with sonicated extracts of two strains of Bacteroides gingivalis (W83 and ATCC 33277). The cell reaction was evaluated by monitoring cell growth and DNA synthesis. Light and scanning electron microscopic analysis were used to evaluate morphological changes of the cells. Extracts from both bacterial strains exerted a growth inhibitory effect on the cells. The pulpal cells were more sensitive than L929 cells. The ATCC 33277 strain of B. gingivalis was more cytotoxic than the W83 strain. Pulpal cells appeared to be markedly affected on the microscopic level. The diffusion of these toxic bacterial by-products, through dentin to the pulp, may account for pulpal cell damage that contributes to the initiation of pulpal pathosis.

Extracellular matrix molecules and their receptors: an overview with special emphasis on periodontal tissues

Knowledge of extracellular matrix molecules and their cell receptors has increased exponentially during the last 2 decades. It is now known that the structure and function of each tissue is based on specific combinations of matrix molecules. The major constituents of the extracellular matrix are collagens, proteoglycans, and adhesive glycoproteins. The rapid development of biochemical, molecular biological, and immunological research has revealed a lot of interesting details pertaining to these molecules. Several new collagen types have been discovered. In addition to being responsible for the strength and form of tissues, each collagen type has specific sequences providing them with special features such as flexibility and the ability to interact with other matrix molecules and cells. Proteoglycans are another large group of matrix molecules with a variety of functions. Proteoglycans play an important role in tissue resilience and filtering. Some proteoglycans have a capacity to specifically bind other matrix molecules and growth factors, while others act as matrix receptors on the cell surface. An important part of regulation of the cell behavior is played by adhesive glycoproteins belonging to the fibronectin and laminin families. Several isoforms of fibronectin and laminin that result from alternative RNA splicing serve specific functions such as controlling the attachment, migration, and synthetic activity of cells. A major group of cell receptors for cell-matrix and cell-cell interactions is termed integrins. The integrins are cell surface proteins composed of two polypeptides whose structure dictates the specificity of each receptor. The cytoplasmic domain of the integrins interacts with cytoskeletal elements within the cell, and thereby relays the information from the extracellular space into the protein synthesis machinery. The expression of the integrins is controlled by the extracellular matrix and growth factors, most notably TGF beta. During periodontal diseases several aspects of the cell-matrix interactions may be disturbed. Therefore, an understanding of the special features of the extracellular matrix and their receptors in periodontal tissues is a prerequisite for developing new approaches to the prevention and treatment of periodontal diseases.

Immunoadjuvant effects of periodontitis-associated bacteria

Sonic extract (SE) from periodontopathic bacteria were studied for their effects on the immune response and adjuvanticity. The preparations of SE from A. actinomycetemcomitans, B. intermedius and B. gingivalis were found to have strong immunomodulating activity against the antigen itself and also sheep erythrocytes (SRBC) in in vivo experiments using C3H/HeN mice. All the SE enhanced the immune response to antigen and SRBC at low concentration. A strong immuno suppressive effect, however, was found at high concentrations of A. actinomycetemcomitans and B. intermedius but not of B. gingivalis. Moreover, these immunosuppressive effects were enhanced by the 3-day-prior injection to SRBC even at low concentrations, including that of B. gingivalis. The suppressive effect of SE from A. actinomycetemcomitans was dependent on the protein fraction in the SE tested, because suppressed anti-SRBC immune response was restored by pronase treatment or heating. Failure to recover immune response, found in a similar experiment using Bacteroides intermedius, indicated that its suppressive effect was due to a heat-stable and pronase-resistant substance. These findings, along with the data presented in this paper, support the hypothesis that patients who harbor these bacteria could suffer systemic immune suppression not only from the initial periodontopathic bacteria but also from secondary infecting bacteria. These suppressive effects may also enhance the pathogenicity of other opportunistic organisms in the gingival crevice.