Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA.
Autophagy. 2021 Nov;17(11):3338-3360. doi: 10.1080/15548627.2021.1872227. Epub 2021 Jan 18.
Intervertebral disc degeneration (IDD) is the primary pathological mechanism that underlies low back pain. Overloading-induced cell death, especially endogenous stem cell death, is the leading factor that undermines intrinsic repair and aggravates IDD. Previous research has separately studied the effect of oxygen concentration and mechanical loading in IDD. However, how these two factors synergistically influence endogenous repair remains unclear. Therefore, we established and models to study the mechanisms by which hypoxia interacted with overloading-induced cell death of the nucleus pulposus derived stem cells (NPSCs). We found the content of HIF1A (hypoxia inducible factor 1 subunit alpha) and the number of NPSCs decreased with disc degeneration in both rats and human discs. Hence, we isolated this subpopulation from rat discs and treated them simultaneously with hypoxia and excessive mechanical stress. Our results demonstrated that hypoxia exerted protective effect on NPSCs under compression, partially through elevating macroautophagy/autophagy. Proteomics and knockdown experiments further revealed HIF1A-BNIP3-ATG7 axis mediated the increase in autophagy flux, in which HMOX1 and SLC2A1 were also involved. Moreover, HIF1A-overexpressing NPSCs exhibited stronger resistance to over-loading induced apoptosis . They also showed higher survival rates, along with elevated autophagy after being intra-disc transplanted into over-loaded discs. Jointly, both and experiments proved the anti-apoptotic effect of HIF1A on NPSCs under the excessive mechanical loading, suggesting that restoring hypoxia and manipulating autophagy is crucial to maintain the intrinsic repair and to retard disc degeneration. 3-MA: 3-methyladenine; ACAN: aggrecan; ATG7: autophagy related 7; BafA1: bafilomycin A; BAX: BCL2 associated X, apoptosis regulator; BECN1: beclin 1; BNIP3: BCL2 interacting protein 3; BNIP3L: BCL2 interacting protein 3 like; CASP3: caspase 3; CCK8: cell counting kit-8; CHT: chetomin; CMP: compression; CoCl: cobalt chloride; COL2A1: collagen type II alpha 1 chain; Ctrl: control; DAPI: 4,6-diamidino-2-phenylindole; DEP: differentially expressed protein; DiR: 1,1-dioctadecyl-3,3,3,3-tetramethyl indotricarbocyanine; ECM: extracellular matrix; FCM: flow cytometry; GD2: disialoganglioside GD 2; GFP: green fluorescent protein; GO: gene ontology; GSEA: gene set enrichment analysis; H&E: hematoxylin-eosin; HIF1A: hypoxia inducible factor 1 subunit alpha; HK2: hexokinase 2; HMOX1: heme oxygenase 1; HX: hypoxia mimicry; IDD: intervertebral disc degeneration; IF: immunofluorescence; IHC: immunohistochemistry; IVD: intervertebral disc; KEGG: kyoto encyclopedia of genes and genomes; LBP: low back pain; Lv: lentivirus; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MMP: mitochondrial membrane potential; NC: negative control; NIR: near-infrared; NP: nucleus pulposus; NPC: nucleus pulposus cell; NPSC: nucleus pulposus derived stem cell; NX: normoxia; PPI: protein-protein interactions; RFP: red fluorescent protein; SLC2A1/GLUT1: solute carrier family 2 member 1; SQSTM1/p62: sequestosome 1; TEK/TIE2: TEK receptor tyrosine kinase; TEM: transmission electron microscopy; TUBB: tubulin beta class I.
椎间盘退变(IDD)是导致下腰痛的主要病理机制。细胞死亡,尤其是内源性干细胞死亡,是破坏内在修复并加重 IDD 的主要因素。先前的研究分别研究了氧浓度和机械加载对 IDD 的影响。然而,这两个因素如何协同影响内源性修复仍不清楚。因此,我们建立了 和 模型来研究缺氧与核髓核衍生干细胞(NPSCs)的超载诱导细胞死亡相互作用的机制。我们发现,在大鼠和人椎间盘,HIF1A(缺氧诱导因子 1 亚单位 alpha)的含量和 NPSCs 的数量随着椎间盘退变而减少。因此,我们从大鼠椎间盘分离出这一小群细胞,并同时对其进行缺氧和过度机械应激处理。我们的结果表明,在受压下,缺氧对 NPSCs 具有保护作用,部分是通过增加巨自噬/自噬来实现的。蛋白质组学和敲低实验进一步揭示了 HIF1A-BNIP3-ATG7 轴介导自噬通量的增加,其中 HMOX1 和 SLC2A1 也参与其中。此外,过表达 HIF1A 的 NPSCs 在过度加载诱导的细胞凋亡下表现出更强的抗性。在过载的椎间盘内移植后,它们还显示出更高的存活率和自噬增加。总之, 和 实验均证明了 HIF1A 在过度机械加载下对 NPSCs 的抗凋亡作用,提示恢复缺氧和操纵自噬对于维持内在修复和延缓椎间盘退变至关重要。3-MA:3-甲基腺嘌呤;ACAN:聚集蛋白聚糖;ATG7:自噬相关 7;BafA1:巴弗霉素 A;BAX:BCL2 相关 X,凋亡调节因子;BECN1:自噬相关蛋白 1;BNIP3:BCL2 相互作用蛋白 3;BNIP3L:BCL2 相互作用蛋白 3 样;CASP3:半胱天冬酶 3;CCK8:细胞计数试剂盒-8;CHT:chetomin;CMP:压缩;CoCl:氯化钴;COL2A1:胶原类型 II alpha 1 链;Ctrl:对照;DAPI:4,6-二脒基-2-苯基吲哚;DEP:差异表达蛋白;DiR:1,1-二辛基-3,3,3,3-四甲基吲哚三碳氰化物;ECM:细胞外基质;FCM:流式细胞术;GD2:二唾液酸神经节苷脂 GD2;GFP:绿色荧光蛋白;GO:基因本体论;GSEA:基因集富集分析;H&E:苏木精-伊红染色;HIF1A:缺氧诱导因子 1 亚单位 alpha;HK2:己糖激酶 2;HMOX1:血红素加氧酶 1;HX:缺氧模拟;IDD:椎间盘退变;IF:免疫荧光;IHC:免疫组织化学;IVD:椎间盘;KEGG:京都基因与基因组百科全书;LBP:下腰痛;Lv:慢病毒;MAP1LC3B/LC3B:微管相关蛋白 1 轻链 3B;MMP:线粒体膜电位;NC:阴性对照;NIR:近红外;NP:核髓;NPC:核髓细胞;NPSC:核髓衍生干细胞;NX:常氧;PPI:蛋白质-蛋白质相互作用;RFP:红色荧光蛋白;SLC2A1/GLUT1:溶质载体家族 2 成员 1;SQSTM1/p62:自噬体 1;TEK/TIE2:TEK 受体酪氨酸激酶;TEM:透射电子显微镜;TUBB:微管蛋白 beta 类 I。
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