FTO Protein Fights Stem Cell Aging by Silencing a Key Senescence Gene

Dental pulp stem cells (DPSCs) hold significant promise for regenerative medicine, but their therapeutic utility is hampered by replicative senescence during in vitro expansion. Understanding the molecular drivers of DPSC aging is therefore a high-priority research goal.

This study from Wuhan University investigated the role of FTO—an m6A RNA demethylase—in DPSC senescence. The team first confirmed that FTO expression progressively declines as DPSCs passage from early (P3) to late (P12) passages, correlating with rising β-galactosidase activity and declining mineralization capacity. This established FTO loss as a molecular signature of DPSC aging.

Gain- and loss-of-function experiments clarified FTO's functional role. FTO knockdown (via siRNA or the pharmacological inhibitor FB23-2) accelerated senescence, increased p16 and γH2AX protein levels, elevated reactive oxygen species (ROS), caused G0/G1 cell cycle arrest, and inhibited proliferation. Conversely, FTO overexpression reduced p16, decreased ROS, lowered γH2AX, and enhanced proliferative capacity—collectively demonstrating that FTO is a bona fide suppressor of DPSC senescence.

RNA sequencing of FTO-depleted versus control DPSCs revealed 341 differentially expressed genes. Gene set enrichment analysis (GSEA) identified the ribosomal pathway as the most significantly suppressed, with multiple ribosomal protein-coding genes (RPL13, RPL18, RPL35) downregulated. Among upregulated genes, NOLC1—a nucleolar phosphoprotein previously linked to senescence via inhibition of pre-ribosomal RNA (pre-rRNA) transcription—emerged as a key candidate. MeRIP-RT-PCR confirmed that FTO knockdown increases m6A methylation on NOLC1 mRNA, and actinomycin D chase experiments demonstrated that this hypermethylation stabilizes NOLC1 mRNA, prolonging its half-life. Reporter assays with wild-type versus m6A-mutant NOLC1 constructs validated these specific modification sites. The resulting NOLC1 protein accumulation suppressed pre-rRNA synthesis, induced nucleolar stress, and drove p53 accumulation—a classical senescence-activating cascade. Critically, NOLC1 knockdown partially rescued the senescent phenotype induced by FTO deficiency, confirming epistasis within the FTO/NOLC1/p53 axis.

The study positions this axis as a mechanistically coherent pathway: FTO normally erases m6A marks on NOLC1 mRNA, destabilizing it and keeping NOLC1 protein low; when FTO falls with age, NOLC1 rises, nucleolar function deteriorates, and p53-driven senescence ensues. These findings offer a novel molecular target for interventions aimed at preserving stem cell fitness during ex vivo expansion or in aged tissues.