Objective  To evaluate the roles of embryonic oral epithelial cells derived from the mandibular process and enamel organ epithelial cells in the tooth-like structure forming by E12.5 ectomesenchymal cells from mandibular process. Methods  Mandibular process of E12.5 SD rats were minced and digested enzymatically to obtain single cell suspension. Ectomesenchymal cells were further isolated from the obtained cell mixture (containing epithelial cells and ectomesenchymal cells) by adherent method and identified with HNK-1 and Vimentin immunostainings. Enamel organ epithelial cells were isolated from the first molar of 4-day-old SD rats and identified with CK14 immunostaining. The obtianed cells were divided into 4 groups

group A (the cell mixture)

group B (purified ectomesenchymal cells)

group C (purified ectomesenchymal cells and enamel organ epithelial cells)

and group D (enamel organ epithelial cells). After combined with gelatin sponge

these cell groups were implanted into the renal capsule of adult rats. The implants were excised and evaluated by histological analysis in 4 weeks later. Results  In 4 weeks later

implants of group A were enlarged and dentin-pulp complex were observed. Implants of group C were enlarged too and tooth-like structures including enamel-like tissue and dentin-pulp complex were seen. No tooth-like structure was found but bone-like structure was seen in the implants of group D. No implant was found in the group B

and the cell mass was absorbed and disappeared soon. Conclusion  Dental epithelial cells including mandibular epithelial and enamel organ epithelial cells play critical roles in tooth-like structure forming from E12.5 ectomesenchymal cells. Enamel organ epithelial cells maybe still have tooth forming ability.