RESUMEN
BACKGROUND AND OBJECTIVE: Human beta-defensins have been identified in the oral cavity and are predicted to play a role in the defense against pathogenic bacteria. Homologous rat beta-defensins (RBDs) have been identified, but their expression in the oral cavity has not been examined. Therefore, the aim of this study was to investigate the expression of innate immune mediators in the rat gingival epithelium. MATERIAL AND METHODS: Rats were pretreated with antibiotics to depress the normal oral flora, followed by the introduction of Actinobacillus actinomycetemcomitans in their food to allow colonization and the development of periodontal disease. At various time points, animals were killed and the gingival epithelium was extracted. Semiquantitative reverse transcription-polymerase chain reaction was performed to measure RBD and Toll-like receptor (TLR) mRNA levels. RESULTS: Three beta-defensins (RBD-1, -2 and -5) and two TLRs (TLR-3 and -4) are expressed in normal rat gingival epithelium. After the introduction of A. actinomycetemcomitans, RBD-1 and RBD-2 mRNA levels increased for the first week followed by a return to basal levels. No change in TLR mRNA levels was observed. CONCLUSION: The rat model provides a good system for experimental analysis of the innate immune response to periopathogenic bacteria in the oral cavity, as well as the potential role of beta-defensins in the host response to colonization.