OBJECTIVETo investigate the expression of wingless-type MMTV integration site family, member 3 (Wnt3) in rat dental follicles and its protein level in dental follicle cells (DFC) undergoing osteogenic induction and to discuss the effects of Wnt3 on the differentiation of DFC.

METHODSRats at postnatal days 1, 3, 5, 7, 9, 11 and 13 were executed, then the mandibles were immediately removed and immunohistochemistry was performed to detect the expression of Wnt3 in dental follicles of postnatal rats. The expression and distribution of Wnt3 in DFC were determined by immunofluorescence. Alizarin red-S staining was performed to assess the mineralization of DFC. Western blotting was used to evaluate Wnt3 and β-catenin protein levels after stimulated by osteogenic medium for 1, 2 and 3 weeks, respectively.

RESULTSImmunohistochemistry revealed that the expression of Wnt3 in rat dental follicles began at day 5 and sustained to day 13. On day 1 and 3, the expression of Wnt3 in dental follicles was negative.Wnt3 was expressed in the cytoplasm of DFC. Alizarin red-S staining indicated that the osteogenic medium stimulated the differentiation of DFC into osteoblastic lineage.Western blotting demonstrated that the Wnt3 protein levels were significantly up-regulated after stimulated with osteogenic medium for 1 weeks compared with the control (2.60 ± 0.04 vs.1.00 ± 0.00, P < 0.05). Then the levels of Wnt3 protein were declined, and at the 3rd week, no significant difference was observed between osteo-induced group and the control (1.00 ± 0.05 vs.1.00 ± 0.00, P > 0.05). The levels of β-catenin were increased in osteo-induced groups compared with the control (1.95 ± 0.05 vs.1.00 ± 0.00, P < 0.05; 9.77 ± 0.65 vs.1.00 ± 0.00, P < 0.05;1.75 ± 0.21 vs.1.00 ± 0.00, P < 0.05). Furthermore, the expression of β-catenin reached to a peak on the 2nd week (9.77 ± 0.65), and then declined.

CONCLUSIONSWnt3 was expressed in the rat dental follicles both in vivo and in vitro and up-regulated during early phase of osteoblast differentiation in DFC.Wnt3 may be involved in early phase of osteoblast differentiation.