UCSF

Periodontal disease is characterized by destruction of the hard and soft tissues that comprise the periodontium. This destruction translates to a degradation of the extracellular matrices (ECM), which is mediated by bacterial proteases, host-derived matrix metalloproteinases (MMPs), and other proteases released by host tissues and immune cells. Bacterial pathogens interact with host tissue and thereby trigger adverse cellular functions, including a heightened immune response, tissue destruction, and tissue migration. Oral spirochete, Treponema denticola (Td), is highly associated with periodontal disease. A Td outer membrane protein complex called dentilisin, contributes to the chronic activation of pro-MMP-2 in periodontal ligament (PDL) cells and triggers increased expression levels of activators and effectors of active MMP-2 in PDL cells. Despite these advances, there is no mechanism known for dentilisin-induced MMP-2 activation, PDL cytopathic behaviors leading to disease, or potential treatment. This thesis demonstrated that Td through dentilisin influences PDL cellular functions such as metabolism, contractility, migration, actin cytoskeletal reorganization, and mechanotransduction. Furthermore, we show dentilisin through an actin-RASA4-MMP-2 axis influences depolymerization and over expression and activity of MMP-2. Therapeutically, one possible avenue to combat these interactions is through the use of bacteriocin nisin. This thesis demonstrated that nisin delivered in a solid lipid nanoparticle (SLN-Nisin) is an effective anti-microbial against Td, with the potential to bacterial clearance inside and outside of the PDL cells. Proper clearance of Td may provide a more symbiotic microbiome and “reset” homeostatic conditions needed for repair, remodeling, or regeneration of the periodontium. Thus, the main hypotheses of this proposal are that T. denticola interactions with PDL cells mediate adverse effects on homeostasis and cellular functions leading to a compromised cellular phenotype. Additionally, nisin is a potential therapeutic for abrogating these effects. This hypothesis was tested using various functional assays, live imaging dyes and immunofluorescent staining via confocal microscopy, RNA sequencing and real-time quantitative polymerase chain reaction, western blotting, bacterial mutants, and functional gene knockdown approaches. The following dissertation provides molecular evidence for a mechanism of Td-mediated adverse cytopathic effects leading to cellular characteristics consistent with severe periodontitis; and evidence for nisin as a potential therapeutic for reducing or reversing Td-mediated periodontopathic processes in vitro.