Conclusions
The present study demonstrated that PTN could protect DPSCs from senescence by improving the proliferation and osteo/dentinogenic differentiation ability, probably through the p38 MAPK pathway.
Methods
Dental pulp stem cells were isolated from human third molars. PTN was knocked down using short hairpin RNAs to study the role of PTN on the senescence of DPSCs. DPSCs with aging performance were obtained by a replicative senescence cell model was obtained by the long-term culture of DPSCs to the 15th passage in vitro (P15). We then investigated the effect of PTN on senescent DPSCs (P15 DPSCs). Real-time RT-PCR, western blotting, alizarin red staining, quantitative calcium analysis, SA-β-Gal staining, CFSE, and cell-counting kit-8 (CCK8) assays were used to study cellular senescence and function.
Results
The depletion of PTN increased the ratio of SA-β-gal-positive cells, upregulated the expression of p16, and down-regulated the expression of TERT and p-p38. Furthermore, 50 pg/ml of PTN recombinant protein rescued these changes the altered ratio of SA-β-gal-positive cells, decreased the expression of p16, enhanced TERT and p-p38 expression, as well as telomere activity, caused by PTN depletion and long-term culture. The15th passage cells displayed typical aging characteristic, including high ratio of SA-β-gal-positive cells, increased aging-related gene expression, decreased proliferation rate, high level of Cyclin D expression, and impaired osteo/dentinogenic differentiation potential. However, 50 pg/ml of PTN recombinant protein could partially reverse these alteration rescue these changes. Conclusions: The present study demonstrated that PTN could protect DPSCs from senescence by improving the proliferation and osteo/dentinogenic differentiation ability, probably through the p38 MAPK pathway.