Phenotypic Analysis Of The Caveolin-1 Knockout Mouse Mandibular First Molar Tooth

Tooth development is a long-term and complex biological process,including epithelial-mesenchymal interactions,cell proliferation and differentiation,tooth morphogenesis,dental hard tissue mineralization and tooth eruption etc.This process not only occurs in the embryo stage,but also continues after the birth.During the development,a variety of signaling molecules consist of a network by cascade reaction,which goes through the whole process of tooth development.Caveolin-1 is a marker protein of Caveolae,which can recruit many signaling molecules to Caveolae and regulate their activities.Our previous studies showed that Caveolin-1、CD147 and MMP-2 expressed in mouse mandibular first molar germ at different developmental stages.In cultured ameloblasts blocking the expression of Caveolin-1 gene can decrease MMP-2 m RNA and protein levels and the expression of high glucose CD147,which suggests Caveolin-1 might affect the expression of MMP-2 by regulating the level of glycosylation of CD147.Other researchers’ s studies also found that Caveolin-1 was involved in the development of tooth germ and biological activities of ameloblast.However,whether the absence of Caveolin-1gene will cause any morphological or structural abnormal in tooth development is largely unknown.Objective To observe the histological morphology of mandibular first molar tooth germ and analysis dental phenotype in Caveolin-1 knockout mice,which provides the histological basis for the further study on the role of Caveolin-1 in tooth development.Method 1.In both Caveolin-1 knockout mouse and wild-type homologous mouse,mandibular first molar germs or teeth of embryonic(E)13.5,E14.5,E16.5,E18.5 days and postnatal(PN)3days,2 weeks,and 1month were collected and stained with hematein eosin to observe the histological morphology under optical microscope.2.In both Caveolin-1 knockout and wild-type homologous mouse,mandibular first molar teeth of 1month were collected and scaned by Micro-CT to observe the morphology and structure of tooth hard tissue.Result 1.HE staining results showed: compared with WT mice,no obvious difference were observed in KO mice tooth germ at E13.5 days.At E14.5,the tooth germ of WT mice was at the cap stage.The enamel organ cells differentiated into inner enamel epithelium,outer enamel epithelium and stellate reticulum.However,the tooth germ of KO mice was still at the bud stage,and no obvious stratification and primary enamel knot formation were found.At E16.5,the enamel organ cells stratifications were similar to that of WT mice.While,KO mice enamel organ had smaller volume,less deeping of cervical loop into epithelial mesenchymal.At E18.5,KO mice enamel organ was at the bell stage,in which the shape of tooth crown was settled,but the columnar morphologies of the inner enamel epithelium cells were not obvious.At PN3 days,in KO mice,the inner enamel epithelium of enamel organ differentiated into ameloblasts with high columnar shapes,while the cell polarity of ameloblasts were not obvious.At 2 weeks,ameloblasts were granular morphologies and irregularly arrenged in KO mice tooth germ.At PN3,2weeks and 1month,the odontoblasts were granular morphologies,lacking of high columnar shapes and typical cell processes,and the cell polarities was not obvious in KO mice tooth.2.The results of Micro-CT and 3D reconstruction showed: compared with WT mice,KO mice had sharper tooth tips,thinner enamel layer.Parts of the crown surface of KO mice were absence of enamel.The root of KO mice had larger size root canals with an open apex.Conclusion 1.The deficiency of Caveolin-1 gene led to temporal arrest for the bud-to-cap transition in the development of molar tooth germs.2.The deficiency of Caveolin-1 gene had a negative effect on the morphology and cell polarity of ameloblasts and odontoblasts.3.The deficiency of Caveolin-1 gene caused the defect of enamel development and blocked the closing of apical foramen.