Zhou Lu-Ping, Kang Liang, Zhang Zhi-Gang, Jia Chong-Yu, Zhao Chen-Hao, Zhang Xian-Liang, Zhang Hua-Qing, Zhang Ren-Jie, Shen Cai-Liang
Department of Orthopedics and Spine Surgery, The First Affiliated Hospital of Anhui Medical University, 218 Jixi Road, Hefei, 230022, Anhui, China.
Laboratory of Spinal and Spinal Cord Injury Regeneration and Repair, The First Affiliated Hospital of Anhui Medical University, Hefei, 230022, Anhui, China.
J Transl Med. 2025 May 7;23(1):514. doi: 10.1186/s12967-025-06412-7.
Loss of nucleus pulposus (NP) cells is as one of the primary factors initiating intervertebral disc (IVD) degeneration (IVDD); however, the intrinsic physiological mechanisms of endogenous NP-derived stem cell (NPSC)-based therapy in IVDD remain poorly understood. Disturbed iron homeostasis is commonly observed in degenerative diseases, and an acidic microenvironment has been considered a crucial factor in IVDD. The molecular mechanism of ferroptosis in acidic microenvironments during IVDD has not been reported. Herein, we intended to investigate whether acidic conditions can induce ferroptosis in NPSCs and explore the mechanism of IVDD progression through NCOA4-mediated ferritinophagy, which is a type of selective autophagy mediating ferroptosis. The role of ring-box 1 (RBX1) in NCOA4-mediated ferritinophagy in NPSC ferroptosis and IVDD pathogenesis was also explored. First, clinical epidemiology research revealed that a reduction in serum ferritin level was an independent risk factor for IVDD. We then demonstrated that ferroptosis progressively increased in human NP tissues as IVDD advanced and the acidic conditions induced ferroptosis-associated decline in cell viability, reactive oxygen species accumulation, and extracellular matrix degradation in human NPSCs. In an acidic microenvironment, ferroptosis is promoted due to enhanced NCOA4-mediated ferritinophagy in NPSCs. A mechanistic study demonstrated that RBX1-mediated ubiquitination modulated NCOA4 expression and the inhibition of RBX1 promoted ferroptosis through NCOA4-mediated ferritinophagy in the human NPSCs. Our in vivo study further illustrated that RBX1 overexpression ameliorated ferroptotic effects on IVDD progression by suppressing NCOA4-mediated ferritinophagy. Results demonstrated the modulating role of RBX1 in NCOA4-mediated ferritinophagy and NPSC ferroptosis, providing valuable insights into the potential application of endogenous stem cell-based IVD self-repair and self-regeneration for IVDD treatment.
髓核（NP）细胞的丢失是引发椎间盘（IVD）退变（IVDD）的主要因素之一；然而，基于内源性NP衍生干细胞（NPSC）治疗IVDD的内在生理机制仍知之甚少。铁稳态紊乱在退行性疾病中普遍存在，酸性微环境被认为是IVDD的关键因素。IVDD期间酸性微环境中细胞铁死亡的分子机制尚未见报道。在此，我们旨在研究酸性条件是否能诱导NPSCs发生铁死亡，并通过NCOA4介导的铁蛋白自噬探索IVDD进展的机制，NCOA4介导的铁蛋白自噬是一种介导铁死亡的选择性自噬。还探讨了环盒1（RBX1）在NCOA4介导的NPSC铁死亡和IVDD发病机制中的铁蛋白自噬中的作用。首先，临床流行病学研究表明，血清铁蛋白水平降低是IVDD的独立危险因素。然后我们证明，随着IVDD进展，人NP组织中的铁死亡逐渐增加，酸性条件诱导人NPSCs中与铁死亡相关的细胞活力下降、活性氧积累和细胞外基质降解。在酸性微环境中，由于NPSCs中NCOA4介导的铁蛋白自噬增强，铁死亡得以促进。机制研究表明，RBX1介导的泛素化调节NCOA4表达，抑制RBX1通过NCOA4介导的铁蛋白自噬促进人NPSCs中的铁死亡。我们的体内研究进一步表明，RBX1过表达通过抑制NCOA4介导的铁蛋白自噬改善了铁死亡对IVDD进展的影响。结果证明了RBX1在NCOA4介导的铁蛋白自噬和NPSC铁死亡中的调节作用，为基于内源性干细胞的IVD自我修复和自我再生在IVDD治疗中的潜在应用提供了有价值的见解。
