MMP13 and periodontitis: Expression of cytokeratin 19 (CK19) was markedly increased in the basement membranes of the oral epithelium and in all layers of the pocket epithelium where it caused evident cell proliferation and migration of sulcular epithelial cells into the lamina propria of periodontitis tissue. TLR4 and the cytoplasmic NLRP3 were expressed in all sections examined regardless of disease state. However, expression of TLR9-,CK19-and collagenolytic matrix metalloproteinase-13 and activated NF-kB subunit p65 was more commonly found in periodontitis tissues than in gingivitis tissues.