Effect of P. gingivalis supernatant and Kavain on bone biology
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P. gingivalis, a red complex bacterium, has been associated with periodontitis. It has been studied extensively trying to understand the mechanism behind its virulence against the periodontium. Several investigations have studied the different virulence factors including Lipopolysaccharide (LPS), gingipain and fembriea. However, bone resorption mechanism that is caused by periodontitis is not fully understood. It is hypothesized that P. gingivalis virulence factors specifically LPS are behind bone resorption, not the bacterial cell itself. Therefore, we have tested this hypothesis and then further expanded on the results by adding Kavain that inhibit LPS-induced TNF-α in an attempt to rule out other virulence factor from bone resorption mechanism. Live neonatal mouse calvarial bone was utilized to carry out experiments in this project. We had five groups which included negative and positive control with parathyroid hormone (PTH) and PTH with Kavain and test groups with P. gingivalis supernatant with or without Kavain. These model systems were tested under resorption condition and evaluated by chemical, biochemical and histological analyses of the used media and calvarial bone. At the 8th day, calvaria from each experiments were analyzed by histology. TRAP and calcium release assays were also performed to further evaluate bone resorption and osteoclastic activity. We have found that when Kavain was added to the PTH, the calcium release and TRAP activity has reduced to half of the positive control without Kavain. P gingivalis supernatant alone showed uptake of calcium rather than release and adding Kavain increased the calcium uptake even more. However, TRAP activity were much higher than PTH group which does not coincide with the calcium release assay results. It seems that P. gingivalis LPS stimulated osteoclastic activity however it was not enough to result in bone resorption. It is thought that resorption and formation might be balanced and thus resorption was not observed. Further investigation is needed to study different doses of P. gingivalis supernatant on bone.