P5. Rescuing nucleus pulposus cells from senescence via dual-functional greigite nanozyme activated by ROS to alleviate intervertebral disc degeneration

High levels of reactive oxygen species (ROS) lead to progressive deterioration of mitochondrial function, resulting in tissue degeneration. In this study, we observed ROS accumulation induced nucleus pulposus cells senescence in degenerative human and rat intervertebral disc, suggesting senescence as a new therapeutic target to reverse intervertebral disc degeneration (IVDD). High levels of reactive oxygen species (ROS) lead to progressive deterioration of mitochondrial function, resulting in tissue degeneration. In this study, we observed ROS accumulation induced nucleus pulposus cells senescence in degenerative human and rat intervertebral disc, suggesting senescence as a new therapeutic target to reverse intervertebral disc degeneration (IVDD). To explore effective strategies for delaying IVDD from the perspective of materials science. Preparation of greigite nanozyme, detection of characterized and enzyme-like activity of greigite nanozyme. In vitro experiments were conducted to verify the toxicity of persulfide released by greigite nanozyme and its supernatant on rat nucleus pulposus cells, the scavenging ability of reactive oxygen species, the effect on mitochondrial membrane potential, and the rescue effect on aging, synthesis and catabolism. The mechanism of greigite nanozyme inhibiting nucleus pulposus cell senescence was screened by RNA sequencing. A rat model of coccygeal disc degeneration was established by coccygeal acupuncture, and greigite nanozyme nanoflower solution or its supernatant was injected locally after the model. The protective effect of greigite nanozyme on anti-oxidative stress and anti-aging disc injury in vivo was verified by intervertebral disc tissue H&E, saffranine solid green staining, and immunofluorescence staining. We successfully constructed greigite nanozyme, showing the ability to release abundant polysulfide and presenting strong superoxide dismutase and catalase activities, both of which can suppress ROS and maintain the tissue at physical redox level. The constructed greigite nanozyme appeared with the lamellar structure and formed nano-flowers, presenting well biocompatibility. Greigite nanozyme significantly lowered the ROS level and rescued the damaged mitochondrial function in IVDD model both in vitro and in vivo, which rescued the nucleus pulposus cells from senescence and alleviated the inflammatory response. Furthermore, RNA-sequencing revealed ROS-p53-p21 axis was responsible for cellular senescence induced IVDD. Hence, we activated p53-p21 signaling when greigite nanozyme was added into the in vitro IVDD model. As expected, the rescuing phenotype of nucleus pulposus cells senescence and the subsequently alleviated inflammatory response by greigite nanozyme were abolished, confirming the role of ROS-p53-p21 axis in facilitating IVDD. Our study demonstrates ROS induced nucleus pulposus cells senescence leads to IVDD and the bifunctional greigite nanozyme is a potential regent to effectively reverse this process, providing a new strategy for management of IVDD. This abstract does not discuss or include any applicable devices or drugs.