RESUMO
We investigated the role of Sonic hedgehog (SHH) in osteoblast differentiation and bone formation. The numbers of ALP-positive cells in the mouse fibroblastic cell line C3H10T1/2 and the mouse osteoblastic cell line MC3T3-E1 were increased by co-culture with chicken fibroblasts transfected with chicken Shh cDNA encoding amino-terminal peptide (Shh-N). The conditioned medium of Shh-N-RCAS-transfected chicken fibroblast cultures also significantly increased ALP activity in both C3H10T1/2 and MC3T3-E1 cells. Intramuscular transplantation of Shh-N-RCAS-transfected chicken fibroblasts into athymic mice induced ectopic bone formation. These results indicate that SHH induces osteoblast differentiation and ectopic bone formation.
Assuntos
Desenvolvimento Ósseo , Osteoblastos/citologia , Biossíntese de Proteínas , Transativadores , Células 3T3 , Animais , Diferenciação Celular , Linhagem Celular , Embrião de Galinha , Técnicas de Cocultura , Indução Embrionária , Fibroblastos/citologia , Fibroblastos/metabolismo , Fibroblastos/transplante , Proteínas Hedgehog , Cinética , Camundongos , Camundongos Endogâmicos C3H , Camundongos Nus , Osteoblastos/transplante , Fragmentos de Peptídeos/biossíntese , Proteínas Recombinantes/biossíntese , Fatores de Tempo , TransfecçãoRESUMO
Differentiation of odontoblasts is important for dentin formation in tooth germs and mature teeth. Although previous reports have indicated that there may be a kind of inductive agent that could induce mesenchymal cells in dental pulps to differentiate into odontoblasts, and secrete dentin matrix, the primary inductive factor of odontoblasts has not been found. Bone morphogenetic protein (BMP), which induces the formation of cartilage and bone when implanted in muscle tissue, is found in dentin matrix. The relationship between the differentiation of odontoblasts and BMP was observed by means of immunohistochemical staining with monoclonal antibody (MAb) against BMP in dental pulp tissue and cell culture; [3H]thymidine incorporation; and measurement of alkaline phosphatase activity. The conclusions are: (1) BMP exists in odontoblasts, ameloblasts, and dentin matrix (the positive reaction in ameloblasts appeared earlier and remained stronger); (2) BMP promotes incorporation of [3H]thymidine and increases the activity of alkaline phosphatase in cultured dental pulp cells; (3) BMP-induced dental pulp cells in dental pulp tissue cultures differentiate from mesenchymal to odontoblast-like cells; and (4) BMP induces formation of osteodentin and tubular dentin when used as a dental capping agent of dogs' teeth. Bone morphogenetic protein plays an important role in differentiation of odontoblasts and might be one of the inductive agents of odontoblasts. Further investigations of BMP as a biologic dental capping agent are warranted.
