Recent reports have described that NCSCs (neural crest derived stem cells) are not only present in the embryonic neural crest, but also in the adult tissues. Dental pulp is one of mesenchymal soft tissues origin from cranial neural crest cells, and thought to be a source of adult stem cells.

Scientists investigated the existence of NCSCs-like cells in apical pulp of human developing tooth. Human impacted third molars with immature apex freshly extracted were obtained. The cells derived from the apical pulp tissue not framed by dentin or the coronal pulp tissues were cultured by primary explant culture.

APDCs (apical pulp derived cells) and CPCs (coronal pulp cells) formed spheres under neurosphere culture condition. The number of spheres from APDCs was larger than that from CPCs.

The sphere-forming cells derived from APDCs had self-renewal capacity, and expressed neural crest-associated markers (p75, Snail, Slug) and neural stem cell markers (Nestin, Musashi1). The expression pattern of mesenchymal stem cell markers, CD105 and CD166, on the surface of sphere forming cells derived APDCs was different from that of APDCs. These sphere-forming cells could differentiate into multiple mesenchymal lineages (osteoblasts, adipocytes, chondrocytes, smooth muscle cells) and neural lineage (neurons) in vitro, and generated ectopic bone tissues on the border of hydroxyapatite scaffold in vivo.

The results of this study suggest that APDCs contain cells with characteristics of neural crest stem cells reported previously in mice. Human developing tooth with immature apex is an effective source of cells for neural crest lineage tissue regeneration.