Fig. 4

Coculturing tumor necrosis factor (TNF)-α-treated nucleus pulposus mesenchymal stem cells (NPMSCs) with notochordal cell (NC)-rich nucleus pulposus (NP) explants attenuates cell senescence. Morphological changes in NPMSCs with different test compounds, as detected by inverted microscopy, scanning electron microscopy, and senescence-associated β-galactosidase (SA-β-gal) staining after 7 days of culture (a). Positive staining for SA-β-gal was compared in different groups (b). Meanwhile, real-time PCR analysis of p16 (c), p21 (d), and p53 (e) mRNA expression was performed. Furthermore, the expression of senescence-associated proinflammatory cytokines interleukin (IL)-6 (f) and extracellular proteases MMP-13 (g) and ADAMTS-5 (h) was tested. Data are expressed as mean ± SD values (n = 4). *p < 0.05