Stem Cells

 

Postnatal orofacial tissues harbor rare cells that exhibit stem cell properties

 

Diagrams of Human and Mouse Orofacial Tissues from which Stem/Progenitor Cells Have Been Studied. (A) Epithelial stem cells reside in the developing tooth germ, oral epithelium, and salivary gland. Connective tissue stem/progenitor cells (of mesenchyme/mesoderm origin) have been isolated from calvarial bone, tooth pulp, dental papilla, the periodontal ligament, and marrow of alveolar bone. (B) The developing rodent incisors have been the most prevalent model for studying orofacial epithelium stem cells. Rodent incisors undergo continuous growth and eruption throughout life. The cervical loop of the developing incisor harbors both epithelial and mesenchyme stem cells. Epithelial stem cells are known to give rise to transient amplifying cells that propagate and migrate anteriorly and differentiate into ameloblasts that produce enamel matrix. Strikingly, enamel is produced only on the labial side in rodents (red). In contrast, mesenchyme stem cells migrate anteriorly to differentiate into odontoblasts that produce dentin (green), in addition to giving rise to interstitial fibroblast-like cells in dental pulp. (Source)