Increased Gene Expression of Toll-like Receptors and Antigen-Presenting Cell–related Molecules in the Onset of Experimentally Induced Furcation Lesions of Endodontic Origin in Rat Molars

IntroductionEarly immunopathogenic mechanisms behind pulp infection–induced furcal inflammation have not been well understood. To address the immunopathology of the pulp infection–induced furcal region of the periodontal ligament (PDL), we performed immunohistochemical and quantitative gene expression analyses for toll-like receptors (TLRs) in the furcal PDL of rat molars subjected to unsealed or sealed pulpotomy.MethodsFurcal inflammation in rat molars was generated by making unsealed pulpotomies that were exposed to the oral environment for 24 hours. Pulpotomized teeth sealed with a temporary filling material and untreated normal teeth served as controls. Gene expression was analyzed with laser capture real-time polymerase chain reaction for TLR-2, TLR-4, and antigen presenting cell (APC)-related molecules (class II MHC, CD83, and CD86). Immunohistochemistry for TLR-2 and TLR-4 was also performed.ResultsMessenger RNA expression levels of TLRs and the APC-related molecules in the furcal periodontal ligament were significantly up-regulated in teeth with unsealed pulpotomy. Immunohistochemistry for unsealed pulpotomized teeth revealed that TLRs-expressing cells were predominantly distributed within the PDL beneath the furcal dentin.ConclusionsThese results suggested the involvement of innate immune mechanisms involving TLRs and resulting activation of APCs in the early pathogenesis of pulp infection-induced furcal inflammation.