Figure 6. The induction of cellular senescence in human NP-MSCs exposed to acidic conditions can be reversed by ASICs inhibition. (A) Representative images (left) and the calculated percentage (right) of cultured Pfirrmann grade IV NP-MSCs undergoing senescence determined using SA-β-gal staining after exposure to acidic pH 6.6 conditions for 0, 24, 72 and 120 hours. n=3; data are mean ± SD, * P≤0.05 compared to 0 h group. (B) Comparative rates of senescence determined as per (A) in NP-MSCs derived from patients with Pfirrmann III and IV grades IVDD cultured under control or acidic pH conditions (pH 6.6) for 72 h. n=3; data are mean ± SD, * P≤0.05 compared to corresponding control group. (C) Effects of ASIC inhibitors on senescence induction in Pfirrmann grade II NP-MSCs cultured in control versus pH 6.6 for 120 h with or without treatment using Amiloride, PcTx1, APETx2 as indicated. The samples in (A) were from case 10, that in (B) of Pfirrmann III and IV group from case 7 and 11, respectively, and that in (C) from case 6. n=3; data are mean ±SD, * indicates P≤0.05 compared to control group; # indicates P≤0.05 compared to pH 6.6 group.