Immunolocalization of receptor activator of NF kappa B ligand in rat periapical lesions.

The purpose of this study is to observe the immunohistochemical localization of Receptor Activator of NF Kappa B Ligand (RANKL) in the rat periapical lesions. Periapical lesions were induced in Sprague-Dawley (SD) rats by occlusal exposure of the pulp of their mandibular first molars. Animals were sacrificed randomly at 0, 7, 14, 21, and 28 days after the exposure and their mandibles were removed, demineralized, and embedded in paraffin. Frontal sections in the region of the first molar were prepared for enzyme histochemistry and immunohistochemistry. Tartrate-resistant acid phosphatase (TRAP)-positive cells and RANKL-positive cells could be observed on day 7. From day 7 to day 14, increasing amounts of inflammatory infiltration and alveolar bone resorption were observed in the periapical region. The expression and number of TRAP-positive cells and RANKL-positive cells were climaxed on day 14. In the 21- and 28-day samples, the expression of RANKL decreased and fewer TRAP-positive cells could be observed. These findings demonstrated that RANKL could be observed, which may be associated with the pathogenesis of periapical lesions.