Systematic Evaluation Of The Teratogenic Effect Of 2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD) On Craniofacial And Palatal Bone Development In Mice

Objective: The aim of this study was to comprehensively characterize the teratogenic effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD)on craniofacial and palatine bone development via three-dimensional volumetric imaging and gene signal detection of osteogenesis.Then find out the susceptibility genes that regulate the occurrence of the palatal plate,and provide etiological support for the clinical molecular treatment of cleft lip and palate.Methods: Pregnant mice were treated with TCDD at embryonic day 12.5(E 12.5)by oral gavage.Skulls of embryos at day 18.5 were collected for three-dimensional microcomputed tomography(Micro-CT)scanning and imported into the Mimics19.0software for reconstruction and measurements.Reconstruction of skulls and isolated palatine bones from TCDD and control embryos were analyzed three-dimensionally in size and shape.Heads of embryos at day 13.5 and day 14.5 were collected for histological immunohistochemistry and in situ hybridization to identify the alteration of master transcriptional effectors of osteogenesis and upstream regulators under TCDD exposure during palatogenesis.Results: TCDD exposure at day 12.5 induced a variety of craniofacial malformations,including premature fusion of metopic and coronal sutures,truncated palatal processes of maxillary and palatine bones,opening oriented pterygoid process,as well as reduced mandibular descent,while the shape and size of main craniofacial bone components were indistinctly changed.Except for the length,not only the width and volume of palatine bone were decreased significantly,but the horizontal growth of palatal process was impaired dramatically under TCDD exposure,resulting in excessive vertical extension and large middle gap.In palatal mesenchymal cells,apparent decrease in the expression of genes responsible for osteogenic differentiation were detected,including Run X2,Osterix,Col1a1,Bmp2,and Bmp4,except for Sox9 and Col2a1.Ah R and ER-α,the upstream regulators of osteogenic transcription factors,were repressed in the TCDD-treated palate.Conclusion: TCDD was teratogenic in mouse skull development,causing a variety of craniofacial deformations,including craniosynostosis and osteogenic inhibition,especially the severe truncation of palatal processes of maxillary and palatine bones.TCDD may inhibited the osteogenic differentiation of palatal mesenchymal cells via altering multiple transcriptional effectors of osteogenesis.