Polymicrobial periodontal disease triggers a wide radius of effect and unique virome.

Periodontal disease is a microbially-mediated inflammatory disease of tooth-supporting tissues that leads to bone and tissue loss around teeth. Although bacterially-mediated mechanisms of alveolar bone destruction have been widely studied, the effects of a polymicrobial infection on the periodontal ligament and microbiome/virome have not been well explored. Therefore, the current investigation introduced a new mouse model of periodontal disease to examine the effects of a polymicrobial infection on periodontal ligament (PDL) properties, changes in bone loss, the host immune response, and the microbiome/virome using shotgun sequencing. Periodontal pathogens, namely Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, and Fusobacterium nucleatum were used as the polymicrobial oral inoculum in BALB/cByJ mice. The polymicrobial infection triggered significant alveolar bone loss, a heightened antibody response, an elevated cytokine immune response, a significant shift in viral diversity and virome composition, and a widening of the PDL space; the latter two findings have not been previously reported in periodontal disease models. Changes in the PDL space were present at sites far away from the site of insult, indicating that the polymicrobial radius of effect extends beyond the bone loss areas and site of initial infection and wider than previously appreciated. Associations were found between bone loss, specific viral and bacterial species, immune genes, and PDL space changes. These findings may have significant implications for the pathogenesis of periodontal disease and biomechanical properties of the periodontium. This new polymicrobial mouse model of periodontal disease in a common mouse strain is useful for evaluating the features of periodontal disease.

Retroviral transduction of human periodontal cells with a temperature-sensitive SV40 large T antigen.

The periodontal ligament (PDL) is considered to contain subpopulations of cells responsible for the development, repair and regeneration of the periodontium. Cell cultures have been used as model systems in order to understand the complex cellular and biochemical events underlying these processes. In order to obtain long-term cultures of these cells that can be cloned and characterized, primary cultures of PDL and gingival cells were infected with an amphotropic retroviral construct encoding a temperature-sensitive SV40 large T antigen (tsT). After selection for drug resistance, the cells expressed the T antigen and proliferated at 34 degrees C for more than 40 passages. However, when the T antigen was inactivated by incubation at 39 degrees C, the cultures became growth-arrested and the granularity of the cells increased, possibly as a result of differentiation. Reverse transcribed-polymerase chain reaction and flow cytometry showed that the tsT-transduced cells expressed a number of soft and hard connective-tissue antigens, including osteocalcin, osteonectin, osteopontin, collagen type I and alkaline phosphatase. Moreover, incubation of the transduced PDL cells at 39 degrees C was found to upregulate the expression of osteocalcin, osteopontin and collagen type I, but downregulate osteonectin. At this temperature, the presence of the dexamethasone downregulated type I collagen, while vitamin D3 had no effect on the expression of any of the antigens examined. Under all culture conditions, antigen expression was far higher in the transduced PDL cells than the gingival cells. The findings thus show that growth of the tsT-transduced PDL and gingival cells is temperature-dependent and that the presence of the T antigen increases their lifespan but does not ablate the expression of certain of their characteristic phenotypic and functional features.