Modulation of epithelial cell fate of the root in vitro.
Mouse molars are normally not capable of continuous growth. We hypothesized that the mouse molar has intrinsic potential to maintain the epithelial stem cell niche and assessed this potential by growth in vitro. Although the tooth germs flattened considerably, they developed a mineralized crown and a root. However, histologically, the root surface was composed of 3 structurally different regions affecting the fate of the dental epithelium. The anterior and posterior aspects maintained the morphological and molecular characteristics of the cervical loop of a continuously growing incisor, with a continuous layer of ameloblasts. The epithelium making contact with the supporting filter resembled Hertwig's epithelial root sheath. The top of the cultured molar exposed to air lacked epithelium altogether. We conclude that the fate of the epithelium is regulated by external cues influenced by culture conditions, and that the molar has the intrinsic capacity to grow continuously.
Tummers
M
M
Developmental Biology Program, Institute of Biotechnology, Viikki Biocenter, PO Box 56, FIN-00014, Helsinki, Finland. mark.tummers@helsinki.fi
Yamashiro
T
T
Thesleff
I
I
D000818:Animals; D002454:Cell Differentiation; D049109:Cell Proliferation; D004658:Enamel Organ / Q000166:cytology; D004847:Epithelial Cells / Q000166:cytology*; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D008822:Mice, Transgenic; D008963:Molar / Q000254:growth & development; D010513:Periodontal Ligament / Q000166:cytology / Q000254:growth & development*; D051880:Receptors, Notch / Q000378:metabolism; D046509:Tissue Culture Techniques; D014083:Tooth Germ / Q000166:cytology; D014092:Tooth Root / Q000166:cytology / Q000254:growth & development*
D051880:Receptors, Notch