Figure 4. MT retarded the senescence of NPCs in lumbar IVDs. (A) SA-β-Gal staining showed the cellular senescence in discs (bar = 100μm). The blue cells indicated by the black arrow are senescence-related positive cells. (B) The percentage of SA-β-Gal positive cells was calculated. (C) Telomerase activity of the NPCs was indirectly reflected by the relative mRNA expression of telomerase reverse transcriptase detected by PCR. (D–G) Western blot analysis showed the relative expressions of senescence-related p53, p21 and p16 proteins in NPCs. Values are expressed as the mean ± SD (N = 8). Compared with the YCG, ##P < 0.01; compared with the AG, ** P < 0.01. NPC: nucleus pulposus cell, SA-β-Gal: senescence-associated β-galactosidase, YCG: young control group, AG: aging group, MTG: manual therapy group.