Protective effect of carboxymethylated chitosan on hydrogen peroxide-induced apoptosis in nucleus pulposus cells

Although the etiology of intervertebral disc degeneration is poorly understood, one approach to prevent this process may be to inhibit apoptosis. In the current study, the anti-apoptotic effects of carboxymethylated chitosan (CMCS) in nucleus pulposus (NP) cells were investigated with the aim to enhance disc cell survival. Rat NP cells were isolated and cultured in vitro, and hydrogen peroxide (H(2)O(2)) was used to build the NP cell apoptosis model. Cell viability was assessed with a cell counting kit-8 assay. The ratio of apoptotic cells was surveyed by annexin V-fluorescein isothiocyanate (FITC) and propidium iodide (PI) double staining analysis, and the morphology was observed by Hoechst 33342 staining. The mitochondrial membrane potential of NP cells was evaluated by rhodamine 123 fluorescence staining. Reverse transcription (RT)-quantitative polymerase chain reaction (qPCR) was performed to measure mRNA levels of inducible nitric oxide synthase (iNOS), caspase-3, B-cell lymphoma (Bcl)-2, type II collagen and aggrecan. Western blot analysis was performed to detect protein levels of iNOS and Bcl-2. The annexin V-FITC/PI and Hoechst 33342 staining results indicated that CMCS was able to prevent NP cells from apoptosis in a dose-dependent manner. Rhodamine 123 staining clarified that CMCS reduced the impairment of the mitochondrial membrane potential in H(2)O(2)-treated NP cells. Reduced caspase-3 and increased Bcl-2 activity were detected in CMCS-treated NP cells by RT-qPCR and western blot analysis. CMCS also promoted the proliferation and secretion of type II collagen and aggrecan in H(2)O(2)-treated NP cells. CMCS was indicated to be effective in preventing apoptotic cell death in vitro, demonstrating the potential advantages of this therapeutic approach in regulating disc degeneration.