Validation of a novel rodent Candida-associated denture stomatitis model for studying pathogenesis and therapeutic management

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Project Summary/Abstract Dentures are one of the most widely used appliances by our aging veterans. Unfortunately, veterans wearing dentures often develop Candida-associated denture stomatitis (CADS), a common recurring disease that affects up to 67% of denture wearers due to microbial colonization and biofilm formation of the denture surface. Further, other dental diseases, oral mucosal and systemic infections, and even death often result from this disease. The establishment of a small animal (i.e. rodent) model for studying CADS has been slowed by a number of challenges which include: (1) the design and fabrication of custom dentures in sufficient numbers for in vivo studies, and (2) the relative natural resistance of rodents to Candida infection. Previously described models have often used severely immunocompromised animals which do not adequately replicate the condition of patients in the clinic and fail to reproducibly form biofilms on oral tissues, a major aspect of CADS. Moreover, none of the prior models have been able to be used to evaluate the effectiveness of anticandidal medications over extended periods of time. Our lab recently developed a new approach for manufacturing rat dentures that uses Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) methods, so that large quantities of dentures with uniform properties/characteristics can be produced. After fabrication, a small hole is drilled into the denture so that reagents and/or microorganisms can be injected/inoculated into the space between the denture and palate. The denture is subsequently fitted and secured to the rat maxilla with dental cement. To initiate the development of CADS, rats are repeatedly injected with Candida (every 2-3 days; PBS was used as a control) through the hole in the denture and fed a liquid diet. Two Candida strains, SC5314 and tetO-UME6 have been used in pilot studies to create the infection. After 4 weeks, the palatal mucosa of animals infected with SC5314 display a slight red color, while animals infected with tetO-UME6 are densely colonized with fungus. In Candida inoculated rats, large amounts of Candida are recovered from the dentures and palatal tissues with lower amounts from tongue and buccal mucosa. No Candida has been recovered from the oral cavity of control groups and/or major organs in both the locally inoculated and control groups. Histological studies revealed the presence of hyphae in palatal mucosa, confirming that our model is able to replicate the palatal manifestations of Candida invasion, as seen in denture wearers with CADS. We have also demonstrated the feasibility of a new cell-binding anticandidal drug delivery system in vitro. This novel system will be used to validate the utility of the optimized rat CADS model. The proposed studies will build upon these preliminary data and further optimize and validate this novel rat CADS model. The specific aims are to: (1) optimize the rat CADS model, and (2) validate the optimized rat CADS model by testing antifungal treatment modalities. If successful, the new in vivo model will help increase our understanding of the pathogenesis of CADS and other oral fungal infections as well as our ability to test new antifungal drugs/devices for treating oral fungal infections, thereby enhancing the management of both oral and overall health of our veterans.