Isolation and characterization of embryonic ameloblast lineage cells derived from tooth buds of fetal miniature swine.

Dental enamel formation, known as "amelogenesis," is initiated by cytodifferentiation of the ectodermally derived dental epithelium. Enamel cannot regenerate itself because once it is completely formed, ameloblasts are lost as the tooth erupts. Rodent teeth have been useful for studying the mechanisms of amelogenesis because ameloblast cell lines can be derived from the ever-growing incisors. However, higher mammals such as humans have no growing teeth, and cell lines derived from larger animals that are more similar to humans are required for higher fidelity studies. Here, we isolated embryonic enamel epithelium-derived epithelial cells from fetal swine. The explant culture of the developing deciduous molars that had been removed from the dental papilla-derived mesenchymal tissue and cells inside the tooth buds provided the epithelial cell population for the primary culture. To isolate the cell population, we performed a unique cell isolation technique called cell fishing. The isolated cells showed clear embryonic-stage ameloblast characteristics with appropriate gene/protein expressions of enamel matrix and proteinases, abundant glycogen pools, and secretory granular materials. They could be continuously subcultured several times and are presently being maintained. This cell population will facilitate the establishment of a stable cell line and allow us to characterize the definitive phenotype and functional behavior of porcine ameloblasts, which, in turn, promises to yield useful and practical findings that are more relevant than those provided by rodent studies. Finally, analysis of in vitro enamel formation will be important for engineering "bio-enamel" as a new dental therapy to restore enamel defects.