SIRT7 promotes dental pulp stem cells replicative senescence through desuccinylation of ROCK1

The therapeutic effectiveness of dental pulp stem cells (DPSCs) is limited. Sirtuin 7 (SIRT7) has been reported to be associated with a variety of age-related diseases. We aimed to identify the regulatory role of SIRT7 in DPSC senescence and investigate the underlying mechanism. DPSCs were isolated from healthy adults, the stem markers were verified by flow cytomerty analysis. Replicative senescence was induced in DPSCs by serial passage and cells were analyzed at PD16 and 54. DPSC senescence was evaluated by observing senescence-associated β-galactosidase (SA-β-gal) and telomerase reverse transcriptase (TERT) activity. Meanwhile, the markers of senescence levels were monitored by western blotting assay. SIRT7 protein was pulled-down, and the binding relationship between SIRT7 and ROCK1 was verified by immunoprecipitation and western blotting methods. Replicative senescence was induced in DPSCs at PD54. The number of SA-β-gal stained DPSCs significantly increased in the PD54 group while the level of TERT activity was decreased. The cyclin-dependent kinase inhibitors p53, p21, and p16, which are markers of senescence, were markedly up-regulated at PD54. SIRT7 was also found to be lowly expressed at PD54. Inhibition of SIRT7 significantly accelerated the senescence of DPSCs. Moreover, SIRT7 can bind with ROCK1, and SIRT7 could lead to ROCK1 desuccinylation at K520. Inhibited ROCK1 significantly reversed the effects of SIRT7 knockdown on regulating DPSCs senescence. Our results demonstrate that the SIRT7/ROCK1 axis plays a key role in the regulation of DPSC senescence and provide a candidate target to improve the functional and therapeutic potential of DPSCs.