Expression Of β-catenin And DKK1 In Postnatal Mice In Different Periods Of Dental Development

Objective:1.To observe the morphological characteristics of dental development in postnatal mice at different time.2.To study the expression of β-catenin and Dickkopf1(DKK1)in different time and space during dental development of postnatal mice,and to clarify the mechanism of wnt signaling pathway in tooth development.Methods:Three postnatal mice of each group were killed by cervical dislocation respectively every other day noon from day 0.5 to day 30.5.Mandibular tissue containing first molar was carefully peeled off and fixed in 4% paraformaldehyde phosphate buffer for 1 night and soaked in 10% ethylene diamine tetraacetic acid(EDTA)disodium solution for decalcification.According to tissue’s different calcification,decalcification time ranging from 1 to 30 days were applied.Paraffin sections of mandibular bone including the first molar were prepared at the thickness of 5μm after the tissues were dehydrated and paraffin-embedded,which was followed by HE staining and immunohistochemical staining in order to detect the expression of β-catenin and DKK1.Results:1.We successfully produced tissue sections containing mandibular first molar of postnatal mice and observed the development of postnatal mice by HE staining at different time points.2.Immunohistochemical method was used to observe the expression of β-catenin and DKK1 in tooth and periodontal tissues of postnatal mice.(1)At 0.5d after birth,β-catenin was slightly expressed in odontoblasts,ameloblasts and glaze nodules,but there were no β-catenin expressed in pulp tissues.At 4.5d,the expression of β-catenin in odontoblast and ameloblasts are increasing,but there was no expression in epithelial root sheath.At 6.5d,there was slight expression of β-catenin in the pulp and it raised up from then on.At 12.5d,the expression of β-catenin in the pulp increased,showing positive expression.Meanwhile,β-catenin showed positive expression in the newly formed periodontal ligament.From 14.5d to 26.5d,β-catenin showed strong positive expression in the periodontal ligament and pulp.Alveolar bone also showed positive expression lately,but it began to decrease at 30.5d.(2)At 0.5d,there was no expression of DKK1 in dental germ.At 6.5d,DKK1 was weakly expressed in ameloblasts,odontoblasts and pre-dentin,and the epithelium root sheath showed pale yellow.At 12.5 days,DKK1 was positive in the ameloblasts,odontoblast,early dentin and periodontal ligament.From 14.5d to 18.5d,DKK1 was expressed stablely in odontoblast and pre-dentin,while the expression of DKK1 in Periodontal ligament was increased.From 20.5d to 24.5d,DKK1 in the periodontal ligament became strong positive expression.It is worth noting that DKK1-positive cells can be seen in the root cellular cementum and alveolar bone.This expression has continued to 30.5 day,yet there was no DKK1 in pulp in the whole stage.Conclusion:We observed the development of postnatal mice by HE staining which provides evidence for the research of tooth development.β-catenin and DKK1 showed regular expression at different tooth developmental stages after birth in tooth and periodontal tissues.The results provide evidence for clarifying the mechanism of wnt signaling pathway in dental development.