Upregulation of S100 calcium-binding protein A9 is required for induction of smooth muscle cell proliferation by a periodontal pathogen.

We investigated the effect of a periodontal pathogen, Porphyromonas gingivalis, on human aortic smooth muscle cell (hAOSMC) proliferation as mechanisms of atherosclerosis. Cultured hAOSMCs exposed to the supernatant of plasma incubated with P. gingivalis showed a marked transformation from a contractile to proliferative phenotype, resulting in enhancement of cell growth. DNA microarray analysis revealed a P. gingivalis-dependent upregulation of S100A9 in hAOSMCs. Small interference-RNA for S100A9 dramatically attenuated the effect of P. gingivalis on transformation and proliferation of hAOSMCs. Our data suggested that upregulation of S100A9 mediated by P. gingivalis is an important event in the development of aortic intimal hyperplasia.