The secretion of TNF-α and IL-1 β by HGFs favor the recruitment of macrophages and neutrophils to the site of infection, as well as the expression of MMP-1, MMP-13, MMP-8, and MMP-9, which contribute to the degradation of the extracellular matrix of the periodontal tissue as well as the reabsorption of bone tissue (Ara et al., 2009; Song et al., 2021; Cheng et al., 2020; Franco et al., 2017). This evidence concerns the gene MMP9 and infection.