To test this hypothesis, we evaluated target gene expression following the infection of young and old hGFs with the oral bacterium, F. nucleatum. Compared to young hGFs, old hGFs showed a highly enhanced upregulation to mRNA expressions of MMP3, MMP9 (both at 6 h) and IL1B (at 2 h) after infection with F. nucleatum (Fig 4B). Here, MMP9 is linked to infection.