A Single-cell Interactome of Human Tooth Germ Elucidates Signaling Networks Regulating Dental Development

Abstract

Background: Development of dental tissue is regulated by extensive cell crosstalk based on various signaling molecules, such as BMP, FGF and SHH pathways. However, an intact network of the intercellular regulation is still lacking.Result: To gain an unbiased and comprehensive view of this dental cell interactome, we applied single-cell RNA-seq on immature human tooth germ of the third molar, discovered refined cell subtypes, and applied multiple network analysis to identify the central signaling pathways. We found that immune cells made up over 80% of all tooth germ cells, which exhibited profound regulation on dental cells via TGF-β, TNF and IL-1. During osteoblast differentiation, expression of genes related to extracellular matrix and mineralization was continuously elevated by signals from BMP and FGF family. As for the self-renewal of apical papilla stem cell, BMP-FGFR1-MSX1 pathway directly regulated the G0-to-S cell cycle transition. We also confirmed that CSF1 secreted from pericyte and TNFSF11 secreted from osteoblast regulated a large proportion of genes related to osteoclast transformation from macrophage and monocyte. Conclusion: We constructed the intercellular signaling networks that regulated the essential developmental process of human tooth, which served as a foundation for future dental regeneration engineering and the understanding of oral pathology.