Atp6i deficient mouse model uncovers transforming growth factor-β1/Smad2/3 as a key signaling pathway regulating odontoblast differentiation and tooth root formation

摘要

The biomolecular mechanisms that regulate tooth root development and odontoblast differentiation are poorly understood.We found that Atp6i deficient mice(Atp6i−/−)arrested tooth root formation,indicated by truncated Hertwig’s epithelial root sheath(HERS)progression.Furthermore,Atp6i deficiency significantly reduced the proliferation and differentiation of radicular odontogenic cells responsible for root formation.Atp6i−/−mice had largely decreased expression of odontoblast differentiation marker gene expression profiles(Col1a1,Nfic,Dspp,and Osx)in the alveolar bone.Atp6i−/−mice sample RNA-seq analysis results showed decreased expression levels of odontoblast markers.Additionally,there was a significant reduction in Smad2/3 activation,inhibiting transforming growth factor-β(TGF-β)signaling in Atp6i−/−odontoblasts.Through treating pulp precursor cells with Atp6i−/−or wild-type OC bone resorption-conditioned medium,we found the latter medium to promote odontoblast differentiation,as shown by increased odontoblast differentiation marker genes expression(Nfic,Dspp,Osx,and Runx2).This increased expression was significantly blocked by anti-TGF-β1 antibody neutralization,whereas odontoblast differentiation and Smad2/3 activation were significantly attenuated by Atp6i−/−OC conditioned medium.Importantly,ectopic TGF-β1 partially rescued root development and root dentin deposition of Atp6i−/−mice tooth germs were transplanted under mouse kidney capsules.Collectively,our novel data shows that the prevention of TGF-β1 release from the alveolar bone matrix due to OC dysfunction may lead to osteopetrosis-associated root formation via impaired radicular odontoblast differentiation.As such,this study uncovers TGF-β1/Smad2/3 as a key signaling pathway regulating odontoblast differentiation and tooth root formation and may contribute to future therapeutic approaches to tooth root regeneration.