CHARACTERIZATION OF INHIBITORY EFFECTS OF SUSPECTED PERIODONTOPATHOGENS ON OSTEOGENESIS IN-VITRO

By using an in vitro bone-forming culture system, the chick periosteal osteogenesis (CPO) model, the direct effects on osteogenesis of sonic ated extracts derived from oral bacteria were examined. Both extracts from bacterial species having strong associations with periodontal dis eases (Polphyromonas gingivalis, Actinobacillus actinomycetemcomitans, and Prevotella intermedia, hereinafter referred to as suspected perio dontopathogens) and extracts from species not correlated with periodon tal disease (Streptococcus sanguis, Veillonella atypica, and Prevotell a denticola, hereinafter referred to as nonpathogenic bacteria) were t ested. All bacterial cultures were grown under standard anaerobic cult ure conditions. Sonicated bacterial extracts were prepared from the ba cterial pellet. These were added in various proportions to the CPO cul tures, Parameters of osteogenesis, including alkaline phosphatase acti vity, calcium and P-i accumulation, and collagen synthesis, were measu red in 6-day-old cultures. Compared with controls grown in the absence of bacterial products, osteogenesis was inhibited significantly in cu ltures treated with extracts derived from the suspected periodontopath ogens. No osteogenic inhibition was observed in cultures treated with extracts from the nonpathogenic bacteria, These results suggest that t he ability to inhibit osteogenesis in vitro may be a pathogenic proper ty shared by a limited group of species. Further characterization of t he P. gingivalis extracts revealed that both proteinaceous and nonprot einaceous products, including lipopolysaccharide, were able to inhibit osteogenesis, P. gingivalis extract-mediated inhibition of osteogenes is in CPO cultures was blocked by indomethacin, implicating prostaglan dins in the regulation of the bacterial effects, The bacterial extract s had either reversible or irreversible inhibitory effects on osteogen esis when added after differentiation or before/during differentiation of bone cells, respectively.