A Novel Mixed-Type Stem Cell Pellet for Cementum/Periodontal Ligament-Like Complex

Background: Functional tissue regeneration underscores the construction of favorable extracellular matrix environment and neovascularization. In this study, we propose a mixed-type stem cell-pellet cultivation system for human periodontal ligament stem cells (hPDLSCs) to recreate a favorable regeneration microenvironment. Methods: The hPDLSCs were cocultured with human bone marrow mesenchymal stem cells (hBMMSCs) and mixed by osteoinduced ceramic bovine bone (CBB) powder as a mixed-type stem cell sheet. The influence of osteoinduced CBB on hPDLSCs was analyzed by alkaline phosphatase (ALP) and osteogenic differentiation assays. The effects of hBMMSCs on hPDLSCs were estimated by proliferating cell nuclear antigen, ALP, real-time reverse transcription polymerase chain reaction, and Western blot assays. The mixed-cell sheet was the preliminary observations in vitro that laid the foundation for additional implantation. After the cells were detached, the mixed-type sheet spontaneously contracted to produce a mixed-type stem cell pellet, which was transplanted into immunocompromised mice. Results: In vitro, the results showed that osteoinduced CBB could upregulate ALP activity and accelerate mineralization of hPDLSCs. When the hPDLSCs were cocultured with hBMMSCs, the ALP activity and proliferation kinetics were upregulated and also indicated in the expression of collagen I, osteocalcin, and vascular endothelial growth factor. It was found that, in vivo, the mixed-type hPDLSC pellets support cementum/periodontal ligament (PDL)-like tissue regeneration with neovascularization. Conclusions: These results suggest that the mixed-type hPDLSC pellet could mimic the microenvironment of PDL and enhance the reconstruction of physiologic architecture of a dental cementum/PDL-like complex. This tissue mimicking may also be a promising alternative to promote periodontal defect repair for additional clinical applications. J Periodontol 2012;83:805-815.