Role of oral flora in chemotherapy-induced oral mucositis in vivo.

Abstract

OBJECTIVE\nTo determine if commensal oral microflora impacts the severity of chemotherapy-induced oral mucositis (OM).\n\n\nDESIGN\nSpecific-pathogen-free (SPF) and germ-free Swiss Webster mice in the experimental groups were dosed with 5-fluorouracil (5-FU) to induce OM. Mice in the control group received phosphate buffered saline. Comparative analyses of the epithelial thickness and cell proliferation/turnover rates, as well as the expression levels of metalloproteinases and pro-inflammatory mediators in the oral mucosa between the control and experimental groups were determined by histopathological and immunohistochemical analyses.\n\n\nRESULTS\n5-FU-treated SPF and germ-free mice showed characteristic features of OM with reduced oral epithelial thickness, presence of inflammatory cells in the connective tissues, and increased levels of expression of metalloproteinases and pro-inflammatory cytokines compared to the respective control groups. When 5-FU-treated SPF and germ-free mice were compared, 5-FU-treated germ-free mice exhibited less severe epithelial destruction with higher expression of the cell proliferation marker Ki67, coupled with lower expression levels of metalloproteinases and pro-inflammatory cytokine in the oral mucosa.\n\n\nCONCLUSION\nThis study provides the first histopathological evidence that oral flora has a detrimental effect on chemotherapy-induced OM in vivo.