Background: Human periodontal ligament stem cells (hPDLSCs) are readily accessible and represent a promising source of mesenchymal stem cells (MSCs) for therapies. For expected clinical applications of stem cell therapies, prolonged maintenance of stemness of hPDLSCs after storage is crucial. Likewise, optimization of cell quality and standardization of manufacturing protocols require evaluation of hPDLSC characteristics after storage. The aim of this study is to evaluate maintenance of stemness of hPDLSCs isolated after prolonged storage of the periodontal ligament (PDL), by studying: 1) growth and proliferation; 2) immunophenotypes; and 3) differentiation capabilities of hPDLSCs.
Methods: After extraction of premolars (N = 10), hPDLSCs were isolated immediately (n = 5) or after 1 week of tooth storage in growth medium (n = 5). Both groups were evaluated for: 1) colony formation; 2) proliferation; and 3) immunophenotypes. Osteogenic, adipogenic, and chondrogenic differentiation capabilities of hPDLSCs were evaluated at different times and by real-time polymerase chain reaction (PCR).
Results: Storing PDLs attached to teeth did not affect stemness of hPDLSCs. Colony formation and proliferation properties of hPDLSCs from PDLs harvested immediately after extraction or after storage for 1 week were comparable, and there were no significant differences in immunophenotypic markers between the two groups. Osteogenic, adipogenic, and chondrogenic differentiation capabilities of hPDLSCs were unaltered after PDL storage. Real-time PCR analyses indicated that the expression of: 1) osteogenic (runt-related transcription factor 2, alkaline phosphatase, and osteocalcin); 2) adipogenic (peroxisome proliferator-activated receptor-γ and lipoprotein lipase); and 3) chondrogenic (aggrecan, collagen Type 2, and collagen Type 10) differentiation markers were similar for both groups.
Conclusion: Within the limitations of the study, hPDLSCs stored for 1 week maintain the important characteristics of MSCs.
Keywords: Periodontal ligament; periodontium; regenerative medicine; stem cells; tissue banks; tissue engineering.