Moderate temperature reduction is sufficient for prevention of 5-fluorouracil-induced oral mucositis: an experimental in vivo study in rats

PURPOSE: The current idea of how oral mucositis (OM) develops is primarily based on hypotheses and the early events which precede clinically established OM remain to be demonstrated. Cryotherapy (CT) continues to have considerable promise in clinical settings to reduce chemotherapy-induced OM. Although being effective, the knowledge is scarce regarding the ideal temperature for prevention of OM. Thus, the present study had two main objectives: (i) to develop an animal model to investigate the early events of OM; (ii) to study at what cooling temperature these early events could be abolished. METHODS: Male Sprague–Dawley rats were anaesthetized and given an intravenous bolus dose with the cytostatic drug fluorouracil (5-FU). During the first hour following injection with 5-FU, the oral cavity of the rats was cooled to a mucosal temperature at the range of 15–30 (○)C, or left uncooled (35 (○)C), serving as control. After 3–5 days, the rats were euthanized, and the buccal mucosa was excised. Subsequently, mucosal thickness and expression of IL-6 and TNF-α were analyzed with immunohistochemistry and enzyme-linked immunosorbent assay (ELISA). RESULTS: Five days following treatment with 5-FU, a statistically significant thickening of the oral mucosa occurred, and a distinct expression of both IL-6 and TNF-α were observed. The cryo-treated groups (15–30 °C) displayed statistically significantly thinner mucosa as compared to the control group (35 °C). The ELISA showed an increase in expression of the proinflammatory cytokines IL-6 and TNF-α in tissues exposed to 5-FU that were treated with increasing temperatures (15–30 °C). CONCLUSION: Bolus i.v. injection with 5-FU in rats can be used to create a functional animal model for chemotherapy-induced OM. Further, moderate temperature reduction is sufficient to reduce the early events which may precede clinically established OM.