Histochemical localization of Dickkopf-1 in induced rat periapical lesions.

INTRODUCTION: The purpose of this study was to evaluate the expression of Dickkopf-1 (DKK-1), a secreted antagonist of the Wnt (wingless)/beta-catenin signaling pathway, during the development of periapical lesions in rats.

METHODS: Periapical lesions were induced in Wistar rats by occlusal exposure of the pulp of their mandibular first molars. The animals were sacrificed randomly at 0, 7, 14, 21, and 28 day after pulpal exposure. Jaws containing the first molar were obtained and routinely prepared for histologic, immunohistochemical, and enzyme histochemical double immunofluorescence analyses. Data were analyzed using 1-way analysis of variance and Pearson correlation test.

RESULTS: The expansion of the area of periapical lesions was visible from days 7-21 and slowed down thereafter. A few DKK-1- and receptor activator of nuclear factor kappa B ligand (RANKL)-positive cells and osteoclasts were observed on day 7. All positive samples peaked in number on day 14. The expression levels of DKK-1 and RANKL and the number of osteoclasts decreased on days 21 and 28. DKK-1 expression was positively correlated with RANKL expression and osteoclast number from days 7-28.

CONCLUSIONS: DKK-1 expression was up-regulated during periapical lesion development. DKK-1 may be associated with the inflammatory response and bone resorption in periapical lesions.