The growth and senescence of intervertebral disc (IVD) cells in alginate culture. (a) Compared with control cultures, the proportion of Ki-67-immunopositive cells was significantly decreased in serum-deprived cultures and increased in glucose-deprived cultures. Oxygen deprivation had no significant effect. Inset: representative images of glucose-deprived alginate cultures, showing a viable cell cluster, and Ki-67-immunopositive cells following harvest (arrow) (original magnification ×200). (b) The proportion of senescence-associated beta-galactosidase (SA-β-gal)-positive IVD cells was significantly increased in serum-deprived cultures compared with control cultures but was unaffected by glucose or oxygen deprivation. Data are presented as mean ± standard error of the mean (n = 4). *P < 0.05.