Dental Apical Papilla stem/Progenitor Cells enriched by Flow Cytometry

Objective: A novel potential source of Mesenchymal stem cells (MSCs) for dental tissue engineering has been recently identified in the apical papilla of adult teeth (Stem Cells from the Apical Papilla-SCAP). However, neither MSCs nor more committed, papilla-specific progenitors have been well-characterized. In this study, we used flow cytometry to isolate and characterize SCAP cells with respect to immunophenotyic profiles, growth characteristics, self-renewal efficiency and multipotentiality.

Method: SCAP cultures were established from apical papilla biopsies of wisdom teeth at the stage of root development. Cell cultures were analyzed with flow cytometry for stem-cell markers, including STRO-1, CD146, CD34, CD45 and nestin, as well as the embryonic markers Nanog, Oct3/4 and TRA-1-60. SCAP cultures were also analyzed for growth characteristics, colony-forming units-fibroblastic (CFU-F) efficiency (clonogenicity) and ability for multipotential differentiation towards osteo/odontogenic, adipogenic and neurogenic lineages. Subsequently, a population STRO1+/CD146+ cells was sorted and reanalyzed with respect to the same stem cell properties.

Result: SCAP mixed cultures were positive for STRO-1, CD146, CD34, nestin, Nanog and Oct3/4 in different percentages according to cell donor. These cultures were negative for the hematopoietic marker CD45 and the embryonic stage-specific antigen TRA-1-60. Furthermore, SCAP cells displayed a high proliferation rate, CFU-F efficiency and potential for multipotential differentiation towards osteo/odontogenic, adipogenic and neurogenic phenotypes. CFU-efficiency and multipotentiality of SCAP mixed cultures was positively correlated with the percentage of STRO-1+ cells contained in these cultures. On the other hand, in enriched STRO1+/CD146+ sorted cultures, a clear population of TRA-1-60 (0.5-2%) embryonic stem cells could be newly identified. Sorted STRO1+/CD146+ cells also showed an enhanced CFU-F potential and ability for multilneage differentiation

Conclusion: These results show that viable odontogenic precursor cells with enhanced stem cell characteristics can be enriched from heterogeneous apical papilla MSCs populations with simple flow cytometric methods. These cells may be a valuable source for dental-tissue regeneration.