The Expression Of BMP-2 And BFGF In Tooth Development Of Postnatal Mice

Bone morphogenic protein-2(BMP-2),which belongs to transforming growth factor-β(TGF-β)superfamily,is a small-molecule polypeptide with high bone induction activity.It is located in the cells with osteoblast-characteristics and involved in the formation of osseous and dental tissues.Basic fibroblast growth factor(bFGF),which belongs to fibroblast growth factor family,is a multifunctional factor.It can widespreadly enhance cell proliferation which from mesoblast and neural ectoderm.bGFF is also an important factor for traumato-henosis,playing important role in bone induction.These factors both involve in tooth development,play important role in periodontal tissues regeneration.But there are few researches about the expression of BMP-2 and bFGF in the whole tooth development,especially the comparison of their expression in periodontal tissues development.So we adopted immunohistochemical technique to study and compare the expression of BMP-2 and bFGF in developing dental tissues of postnatal mice.Objectives:(1)To establish a postnatal mice tooth developing model.(2)To study the expression of BMP-2 and bFGF in postnatal mice tooth development.Methods:For tissues preparation,mandibles including the first molars were removed form the postnatal BALB/c mice at various stages of tooth development and fixed with 4%paroformaldehyde overnight at 4℃.Then decalcidied with formic acid-sodium formate compound solution for 1～28 days.Decalcified specimens were dehydrated with increasing concentrations of ethanol,embedded in paraffin and 5um sections were made.The sections were subjected to build postnatal mice tooth developing model histologically and determine the expression of BMP-2 and bFGF in the tooth development by immunohistochemical technique.Results:(1)Tooth development of postnatal mice:At 5th day,tooth germ was at later bell stage,the epithelial root sheath had already innerly folded,but the root still could not be seen.This was the symbol of initiation for root development.With the development of the germ,at 9th day,dental follicle cells at root region differentiated into periodontal tissues,the outline of tooth root was formed.The root kept on extending,when to 27th day,the apical foramen was becoming narrowed;there was much cellular cementum around the apical zone.The tooth development was completed.(2)Expression of BMP-2 in developing dental tissues of postnatal mice: BMP-2 stainings was observed in the newly formed alveolar bone,dental sac, the pulp and predentin,periodontal ligament,while not in odontoblast and ameloblast.During the development of root formation,the expression of BMP-2 in predentin,alveolar bone and pulp was declined with time,even disappeared at last,while in periodontal ligament,BMP-2 staining was always apparent.During the whole development,BMP-2 was not observed in dentin and cementum.(3)Expression of bFGF in developing dental tissues of postnatal mice: The expression of bFGF was similar to that of BMP-2,bFGF was also expressed in the newly formed alveolar bone,dental sac,the pulp and predentin,periodontal ligament.But in periodontal ligament,the expression of bFGF was weaker than that of BMP-2.In predentin,the expression of BMP-2 was obviously stronger than that of bFGF at day 5,9,13,then they both disappeared.Although the expression of bFGF in the pulp decreased with time, it was still stronger than that of BMP-2.Conclusions:(1)The span of the developing periodontal tissue of the first molar in mandible is from 5th day to 27th day.(2)BMP-2 may play an important role in the deposition of tooth dentin,the differentiation of pulp cells,the formation of periodontal tissues and and maintain function of dental tissues during tooth development,but BMP-2 seems more important in the early stage than in the late stage.(3)bFGF also involves in the development of pulp-dentin complex and the periodontal tissue,but it may play a different role in the whole process. bFGF means more important for pulp,but weaker for predentin and periodontal tissues.