Use of in vitro and in vivo zebrafish infection models to investigate the role of oral microorganisms in cardiovascular disease

Increasing evidence links periodontal pathogens with several systemic diseases, including cardiovascular disease, atherosclerosis, diabetes and Alzheimer’s disease. A well-established example is the association between periodontal disease that affects over 300 million people worldwide, and cardiovascular disease. Several periodontal pathogens have been detected in atherosclerotic plaques and patient vascular samples. These pathogens can enter the bloodstream through recurrent bleeding, disseminating systemically resulting in transient bacteraemia. However, little is known about how periodontal pathogens interact with the vasculature and which molecular mechanisms and virulence factors are responsible for initiation or potentiation of cardiovascular disease. Most research has focused on the oral pathogen Porphyromonas gingivalis (Pg), at the exclusion of other oral microorganisms identified in the circulation and atherosclerotic plaques, including Fusobacterium nucleatum (Fn) and Tanerella forsythia (Tf). Pg has been termed a ‘keystone pathogen’ and produces several virulence factors including cysteine proteases, gingipains and outer membrane vesicles (OMV). This study investigated the role of Pg gingipains in whole cell bacteria, as well as from OMV, in mediating endothelial damage assessed through cell adhesion molecule degradation and endothelial permeability in vitro and in vivo using a zebrafish larvae systemic infection model. In addition, since periodontitis is a polymicrobial infection, effects of Fn and Tf single species as well as multispecies endothelial infections with Pg were also assessed.