The Regenerative Potential of Stem Cells From Apical Papilla (SCAP) in Comparison to Dental Pulp Stem Cells (DPSC)

Objectives: This study aims at investigating stemness and differentiation potential of stem cells from apical papilla (SCAP) in comparison to dental pulp stem cells (DPSC).
Methods: The apical and coronal pulp tissues were obtained from 13, and they were primarily cultured by outgrowth method. Stemness of SCAP and DPSC were evaluated by proliferation assay, colony forming unit-fibroblast (CFU-F) assay, and flow cytometry analysis using Stro-1, CD146, CD90, CD105, CD31 markers. In vitro adipogenic and osteogenic differentiation potential was investigated using Oil Red O staining, Alizarin Red S staining, and quantitative realtime-PCR (qPCR). For in vivo study, each of SCAP and DPSC were mixed with macroporous biphasic calcium phosphate (MBCP) and subcutaneously transplanted into immunocompromised mice. The characteristics and quantity of the newly formed hard tissue were examined by qPCR, ALP activity analysis, HE staining, and immunohistochemistry.
Results: Similar proliferation rate and CFU-F colonies were similar between SCAP and DPSC. In flow cytometry analysis, SCAP and DPSC were both positive for Stro-1, CD146, CD90, CD150, and negative for CD 31. In histologic sections, CD146 and Stro1 were stained in the surrounding tissue around the apical papilla. Regarding in vitro study, SCAP and DPSC showed similar differentiation potential. The amount of newly generated hard tissue in vivo was similar between SCAP and DPSC, but they presented different histologic features. In histologic analysis and qPCR, the hard tissue formed by SCAP presented PDL-like tissue and significantly high expression level of Collagen XII and Postin.
Conclusions: This study confirmed the potential of SCAP and DPSC to be applied in stem cell engineering. Unlike DPSC, the regenerated hard tissue by SCAP contained PDL-like tissue surrounding hard tissue, which indicates the potential of SCAP as a source of stem cell in tooth engineering as well as in dental regeneration.