Objective: To investigate the role of Wnt/β-catenin signaling in aging of mesenchymal stem cells (MSCs) of rats.
Methods: Serum samples were collected from young (8 ≈ 12 w) and aged (64 ≈ 72 w) SD rat. Four experiment groups were assigned: young rat serum (YRS), YRS+Wnt 3a, old rat serum (ORS) and ORS+DKK1 groups. Immunofluorescence and Western blotting were used to detect the expression of intracellular β-catenin. The senescence-associated changes were examined with SA-β-galactosidase staining. The proliferation ability was tested by MTT assays. The survived and apoptotic cells were determined by AO/EB staining. The expressions of γ-H2A. X and p53 protein were detected by immunofluorescence and Western blotting. RT-PCR was used to detect the expression of p53 and p21 mRNA.
Results: Compared with the YRS group, the intracellular expression of β-catenin in the ORS group was significantly increased,especially in the nuclei of MSCs. After treatment of DKK1 in ORS, the γ-catenin expression was reduced. The number of SA-β-galactosidase positive MSCs was significantly higher in the YRS+Wnt 3a group than that in the YRS group (P<0.01), and the proliferative and survival ability of MSCs was significantly decreased in the YRS+Wnt 3a group. The number of SA-β-galactosidase positive MSCs in the ORS+DKK1 group was significantly decreased compared with that in ORS group (P <0.01), and the proliferative and survival ability of MSCs was significantly increased in the ORS+DKK1 group. The expression of γ-H2A.X, p53 and p21 was markedly increased in the ORS group than that in YRS group, however, after treatment with Wnt/β-catenin signaling inhibitor DKK1, the expression of γ-H2A.X, p53 and p21 was significantly decreased compared with that in the ORS group.
Conclusion: Results suggest that the Wnt/β-catenin signaling is activated in the MSCs cultured with ORS and excessive activation of Wnt/β-catenin signaling can promote MSCs aging. The DNA damage response and p53/p21 pathway may be main mediators of MSC aging induced by excessive activation of Wnt/β-catenin signaling.