The YTHDC1-m⁶A-GADD45B axis promotes chondrogenesis of hPDLSCs via suppressing senescence through p53/p21 signalling...

Temporomandibular joint osteoarthritis (TMJOA) is a degenerative disease with limited therapeutic options. Stem cell-based tissue engineering, particularly utilizing human periodontal ligament stem cells (hPDLSCs), represents a promising approach for cartilage regeneration. However, we have previously demonstrated that chronic inflammation and hypoxic stress in the TMJOA microenvironment markedly accelerate cellular senescence in hPDLSCs, severely impairing their regenerative potential. Here, we identify the YTHDC1-m⁶A-GADD45B axis as a critical regulator of senescence and chondrogenic differentiation in hPDLSCs. We show that YTHDC1, an m⁶A reader protein, is downregulated under inflammatory and senescent conditions. Functional studies reveal that YTHDC1 overexpression attenuates senescence and enhances chondrogenesis, whereas its knockdown exacerbates senescence and suppresses differentiation. Mechanistically, YTHDC1 recognizes m⁶A modifications on GADD45B mRNA and promotes its decay, leading to inhibition of the p53/p21 signaling pathway. Mutation of the m⁶A site in GADD45B abolishes the regulatory effects of YTHDC1. In rats with TMJOA, transplantation of YTHDC1-overexpressing hPDLSCs ameliorated disease phenotypes, an effect reversed by co-expression of wild-type GADD45B. Our findings reveal a novel epitranscriptomic mechanism that regulates hPDLSCs senescence and subsequently affects chondrogenic differentiation, and highlight the therapeutic potential of targeting the YTHDC1-GADD45B-p53/p21 axis.