Depletion of Macrophages during Early Postnatal Development Leads to Disrupted Tooth Root Development and Altered Gli1⁺ MSC Trajectory

ABSTRACT: Mammalian tooth development proceeds through two principal stages—crown formation and root development—driven by intricate interactions between the oral epithelium and neural crest–derived mesenchyme. After crown formation, root development is guided by Hertwig’s epithelial root sheath (HERS), during which Gli1⁺ mesenchymal stem cells (MSCs) give rise to dental pulp, dentin, cementum, and the periodontal ligament (PDL). The root anchors the tooth to alveolar bone via PDL fibers, forming a dynamic occlusal buffer that mediates mechanosensation and nutrient supply. While previous work has shown that macrophages are abundant in the dental pulp and follicle, the functional importance of macrophages in tooth development has not been well characterized. Here, we examined the dynamically changing macrophage populations, labelled by CD68, F4/80, CD206 and other markers, in molars and surrounding tissues during root development in early postnatal mice. We also tracked the dynamic distribution of osteoclasts during tooth development. Importantly, selective depletion of macrophages using clodronate liposomes led to shortened tooth root, impaired PDL elongation and retarded alveolar bone shooting surrounding the root. Gli1⁺ MSCs exhibited increased proliferation but delayed differentiation upon macrophage depletion. Single-cell RNA sequencing and in vitro co-culture experiments support a model in which macrophage-derived TGF-β acts on mesenchymal TGF-β receptors to direct MSC fate and thereby regulate root morphogenesis. Collectively, these findings establish macrophages as critical niche components that orchestrate tooth root development through immune–mesenchymal crosstalk.

ORGANISM(S): Mus musculus

PROVIDER: GSE320526 | GEO | 2026/06/18

REPOSITORIES: GEO