Abstract: Objective： To investigate the effect of aging on the multi-directional differentiation ability of human periodontal ligament stem cells (PDLSCs). Methods： 14 healthy third molars were collected with complete roots in clinic and divided into two groups according to the donors’ ages: the younger group (donor age at 16-19 years) and the older group (donor age at 38-50 years). The periodontal ligament tissues were obtained and PDLSCs were isolated and cultured. Flow cytometry analysis was used to identify the phenotypes of PDLSCs. To compare the multi-directional differentiation ability of PDLSCs, cells were subjected to osteogenic and adipogenic induction in vitro respectively. Results： Flow cytometry analysis revealed that PDLSCs in both groups had the characteristics of mesenchymal stem cells. And the multi-directional differentiation ability of PDLSCs in the older group was significantly decreased compared with that in the younger group(P＜0.05). Conclusions： The multi-directional differentiation ability of PDLSCs decreased with age.

Key words: periodontal ligament stem cells , aging, multi-directional differentiation ability