Figure 4.

CHOP deficiency weakens apoptosis and protects human NP cell degeneration. NP cells of G2 tissues without or with the CHOP-siRNA transfection were cultured with 100 µM of H₂O₂ for 24 h. (A and B) The protein expression level of collagen II and caspase-9 were determined by (A) IF (magnification, x400) and (B) quantification analysis. (C) The mRNA expression levels of collagen II, ATF4, CHOP and caspase-9 were assayed by RT-PCR. (D and E) The protein expression levels of collagen II, ATF4, CHOP, and caspase-9 were determined by (D) WB and (E) quantification analysis. (F and G) The ratio of apoptotic cells was analyzed by (F) flow cytometry and (G) quantification analysis. The values are mean ± SD of three independent experiments (n=3). (^*P<0.05, ^**P<0.01, ^***P<0.001, compared with 100 µM H₂O₂). ATF4, activating transcription factor 4; CHOP, C/EBP homologous protein; WB, western blot; NP, nucleus pulposus; RT-PCR, reverse transcription-polymerase chain reaction; IF, immunofluorescence.