This paper investigates pathogenic mechanisms of the Streptococcus anginosus group (SAG) of bacteria which influence the biological activity of periodontal ligament (PDL) cells, endothelial cells and also how matrix proteins produced by these host cells influence bacterial virulence factors. Isolates of SAG species, designated S. anginosus, S. constellatus and S. intermedius, were derived from healthy commensal and clinical pathogenic infection sites. SAG culture supernatants contained multiple protein components which differed between isolates. All SAG supernatants increased cellular proliferation and decreased decorin synthesis and collagen assembly by PDL cells and reduced endothelial cell migration. SAG isolates responded differently to extracellular matrix (ECM) components synthesised by PDL cells, but there was an overall notable increase in hydrolytic enzyme activity and in the production of the cytotoxin intermedilysin by S. intermedius. Collectively, the results indicate that both commensal and pathogenic SAG isolates were capable of impairing the ability of PDL cells and endothelial cells to make functional vascularised tissue. Reduced decorin synthesis is likely to have a major impact on cell signalling, angiogenesis and matrix assembly. Furthermore, ECM components produced by PDL cells were differentially capable of moderately increasing SAG enzymic activity, leading to subtle ECM modifications. The impact this bidirectional effect has on the tissue remodelling process is discussed.
Keywords: Streptococcus anginosus group, periodontal ligament, mesenchymal cells, endothelial cells, decorin