TDP-43 ameliorates aging-related cartilage degradation through preventing chondrocyte senescence

Senescent chondrocytes or signaling mechanisms leading to senescence are promising new therapeutic approaches for ameliorating cartilage degradation. Herein, we show that the transactive response DNA/RNA-binding protein (TDP-43) regulates chondrocyte senescence and ameliorates cartilage degradation. First, a significant decrease in TDP-43 was observed in 16-month-old mice compared with younger mice. Immunohistochemistry (IHC) analysis of mouse articular cartilage showed that p21, p16, p53, and matrix metalloprotein-13 (MMP13) were increased, but laminB1 and Collagen type II alpha1 1 chain (Col2a1) were decreased in 16-month-old mice. Furthermore, TDP-43 levels were decreased in vivo following D-galactose (D-gal) induction. Therefore, we investigated the role of TDP-43 in the senescent chondrocytes. ATDC5 cells were induced to overexpress TDP-43. Western blot analysis showed increased expression of laminB1, Ki67, and PCNA but decreased expression of p21, p16, p53, and MMP13. Senescence-associated-β-galactosidase (SA-β-Gal) assay, γH2AX staining, and EdU were performed to assess changes in chondrocytes, showing weaker SA-β-Gal and γH2AX staining but stronger EdU and Alican Blue staining. However, TDP-43 deficiency had opposing effects, and similar to D-gal stimulation results. Taken together, our data verified that TDP-43 negatively correlated with senescence markers, positively correlated with cell proliferation markers, and could alleviate cartilage degradation induced by D-gal. This may be an essential mechanism of cellular senescence and cartilage degradation.