Identification Of Human Cranio-Maxillofacial Skeletal Stem Cells

Compared with long bone that arises from the mesoderm, the major portion of the maxillofacial bones are derived from cranial neural crest cells and undergo intramembranous ossification. Human skeletal stem cells have been identified in embryonic and fetal long bones. But whether specific skeletal stem cells exist in maxillofacial bones remains elusive. Single-cell RNA sequencing (scRNA-seq) was applied to analyze the transcriptomes of individual cells from human embryonic mandibles isolated at different gestational periods. Cells from all samples were integrated and divided into subpopulations using unsupervised clustering and marker analysis. Laser capture microdissection sequencing (LCM-seq) was performed to provide the original spatial location information of the subpopulations identified by scRNA-seq. The characteristics of IFITM5+ cells were identified through a series of in vitro and in vivo functional assays. We describe a single-cell atlas of the human embryonic mandible and identify a population of cranio-maxillofacial skeletal stem cells (CMSSCs). These CMSSCs are marked by Interferon Induced Transmembrane Protein 5 (IFITM5) and are specifically located around the periosteum of the jawbone and frontal bone. Additionally, These CMSSCs exhibit strong self-renewal and osteogenic differentiation capacities but lower chondrogenic differentiation potency, mediating intramembranous bone formation without cartilage formation. IFITM5+ cells are also observed in the adult jawbone and exhibit functions similar to those of embryonic CMSSCs. Thus, this study identifies CMSSCs that orchestrate the intramembranous ossification of cranio-maxillofacial bones, providing a deeper understanding of cranio-maxillofacial skeletal development and promising seed cells for bone repair.