Organoids from mouse molar and incisor as new tools to study tooth-specific biology and development

Organoid models provide powerful tools to study tissue biology and development in a dish. Presently, organoids have not yet been developed from mouse tooth. Here, we established tooth organoids (TOs) from early-postnatal mouse molar and incisor, which are long-term expandable, express dental epithelium stem cell (DESC) markers, and recapitulate key properties of the dental epithelium in a tooth-type-specific manner. TOs display in vitro differentiation capacity toward ameloblast-resembling cells, even more pronounced in assembloids in which dental mesenchymal (pulp) stem cells are combined with the organoid DESCs. Single-cell transcriptomics supports this developmental potential and reveals co-differentiation into junctional epithelium- and odontoblast-/cementoblast-like cells in the assembloids. Finally, TOs survive and show ameloblast-resembling differentiation also in vivo. The developed organoid models provide new tools to study mouse tooth-type-specific biology and development and gain deeper molecular and functional insights that may eventually help to achieve future human biological tooth repair and replacement.