ABSTRACT
BACKGROUND: Our preliminary study has shown that methylene blue exerts toxic effect on human nucleus pulposus cells in a concentration-dependent manner, but the toxic range remains unclear. OBJECTIVE: To determine the critical range of the cytotoxicity of methylene blue to nucleus pulposus cells by cell counting-kit 8 (CCK-8) assay. METHODS: The nucleus pulposus was from a patient with intervertebral disc herniation. The nucleus pulposus cells were extracted and cultured. Passage 1 cells mere used to make cell suspensions. The cells were divided into nine groups for culture: blank control (only the medium, CCK-8 solution), control (only medium, cells and CCK-8 solution), and methylene blue groups (1%, 0.5%, 0.1%, 0.05%, 0.01% and 0.005% of methylene blue). The absorbance values were measured by CCK-8 assay at 24, 48, 72 and 96 hours after incubation. The cell viability was calculated, and the color was observed. RESULTS AND CONCLUSION: The color in the control group was the darkest, and the color in the methylene blue groups became lighter with the concentration of methylene blue increasing, and the 0.05%, 0.01%, 0.005% and 0.001% methylene blue groups showed darker color similar to the control group. The absorbance values in the 0.1% methylene blue group were significantly less than those in the control group (P＜ 0.05). There were no significant differences in the absorbance values and cell viability between 1% and 0.5% methylene blue groups (P ＞0.05). The absorbance values and cell viability in the 0.1% methylene blue group were significantly higher than those in the 0.5% methylene blue group, but were significantly less than those in the 0.05% methylene blue group (P ＜ 0.05). Thus, methylene blue exerts cytotoxicity to human nucleus pulposus cells, and the critical value of toxicity is between 0.1% and 0.05% and close to 0.05%. However, the exact value needs a further investigation.
ABSTRACT
BACKGROUND: Methylene blue is used as a developer to identify intervertebral disc degeneration in the transforaminal endoscopic surgery. However, many scholars have indicated that methylene blue can accelerate the degeneration process, whilst foreign researches have reported that it may play therapeutic effect on degenerative intervertebral discs under acidic conditions due to its acidophily. Therefore, whether methylene blue holds toxic effect on the disc remains controversial. OBJECTIVE: To determine whether methylene blue exerts toxic effect on nucleus pulposus cells by cell counting-kit 8 (CCK-8) assay. METHODS: The discarded nucleus pulposus from two patients with intervertebral disc herniation were selected. After digestion, nucleus pulposus cells were extracted and cultured until proliferated to 80% of the medium. Then, the cells were digested to make cell suspensions, divided into six groups and inoculated into the 96-well plates: blank control (only the medium, CCK-8 solution), control group (only medium, cells and CCK-8 solution), and the other groups were cultured with 1%, 2%, 3%, and 4% methylene blue, respectively. The absorbance values were measured by CCK-8 assay at 24, 48, 72 and 96 hours after incubation to calculate the cell viability, and the color change was observed. RESULTS AND CONCLUSION: The color in the control group was the deepest, and the color became lighter with the concentration of methylene blue increasing. The cell viability was the highest in the control group, and it was decreased with the concentration of methylene blue increasing. Thus, methylene blue may exert toxic effect on human nucleus pulposus cells.