Figure 4.

NPC apoptosis model. (A) To exclude the effect of increased CO₂ solubility on the pH of the medium due to increased air pressure, NPCs were incubated in an air-free environment for 0 h, 24 h, and 48 h, and cell viability was detected using a CCK-8 kit. The results are expressed as the mean ± standard deviation, n=5 for each group. The data showed no significant change in cell proliferation viability in the 24 h and 48 h groups compared to the CTR group (P > 0.05). (B and C) Flow cytometric detection of the NPC apoptosis rate; NPCs were placed in a pressure chamber and cultured in a pressure environment of 1.0 MPa for 0 h, 12 h, 24 h, and 48 h, before detecting the apoptosis rate using an Annexin V-FITC/PI Apoptosis Detection Kit. The results are expressed as the mean ± standard deviation, n=5 for each group. The apoptosis increased significantly when the pressurization time was ≥ to 24 h (P < 0.05, compared to the CTR group), and increased continuously with the increase in pressurization time. *P < 0.05.

Abbreviations: NPC, nucleus pulposus cell; CTR, control; NS, non-significant.