Intervertebral disc degeneration (IVDD) is the pathological basis of a range of degenerative spinal diseases and is the primary cause of lower back pain. Mesenchymal stem cell (MSC) transplantation inhibits IVDD progression. However, the specific mechanisms that underlie these effects remain unclear. In this study, candidate microRNAs (miRNAs) are screened using bioinformatics and high-throughput sequencing. TNF-α is used to induce nucleus pulposus cell (NPC) degeneration. MSC-derived exosomes (MSC-exosomes) are obtained using high-speed centrifugation and identified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and western blot analysis. Cell viability is determined by CCK-8 assay. Flow cytometry and TUNEL assays are used to detect cell apoptosis. The expression levels of miR-125b-5p are detected by RT-qPCR, and a dual-luciferase gene reporter assay confirms the downstream target genes of miR-125b-5p. Protein expression is determined by western blot analysis. Rat models are used to validate the function of miR-125b-5p in MSC-exosomes. The results show that miR-125b-5p is expressed at low levels in degenerated disc tissues compared with that in normal disc tissues; however, it is highly expressed in MSC-exosomes. Furthermore, MSC-exosomes are efficiently taken up by NPCs while miR-125b-5p is delivered into NPCs; thus, MSC-exosomes act as inhibitors of apoptosis in NPCs. Overexpression of miR-125b-5p downregulates TRAF6 expression and inhibits NF-κB activation. However, TRAF6 overexpression reverses these effects of miR-125b-5p. We demonstrate that MSC-exosomes attenuate IVDD in vivo by delivering miR-125b-5p. MSC-exosomes can deliver miR-125b-5p to target TRAF6, inhibit NF-κB activation, and attenuate the progression of IVDD.

中文翻译：

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间充质干细胞外泌体通过 miR-125b-5p/TRAF6/NF-κB 通路轴抑制髓核细胞凋亡。

椎间盘退变（IVDD）是一系列退行性脊柱疾病的病理基础，也是腰痛的主要原因。间充质干细胞 (MSC) 移植可抑制 IVDD 进展。然而，这些影响的具体机制仍不清楚。在这项研究中，利用生物信息学和高通量测序筛选候选 microRNA (miRNA)。TNF-α 用于诱导髓核细胞 (NPC) 变性。MSC 衍生的外泌体 (MSC-exosomes) 通过高速离心获得，并通过透射电子显微镜 (TEM)、纳米颗粒跟踪分析 (NTA) 和蛋白质印迹分析进行鉴定。通过 CCK-8 测定法测定细胞活力。流式细胞术和TUNEL测定用于检测细胞凋亡。通过RT-qPCR检测miR-125b-5p的表达水平，并通过双荧光素酶基因报告基因测定证实miR-125b-5p的下游靶基因。通过蛋白质印迹分析确定蛋白质表达。大鼠模型用于验证 MSC 外泌体中 miR-125b-5p 的功能。结果表明，与正常椎间盘组织相比，退变椎间盘组织中miR-125b-5p的表达水平较低；然而，它在 MSC 外泌体中高度表达。此外，MSC-外泌体被 NPC 有效吸收，而 miR-125b-5p 被递送到 NPC 中；因此，MSC-外泌体充当 NPC 细胞凋亡的抑制剂。miR-125b-5p 的过表达会下调 TRAF6 表达并抑制 NF-κB 激活。然而，TRAF6 过表达可逆转 miR-125b-5p 的这些影响。我们证明 MSC-外泌体通过传递 miR-125b-5p 来减弱体内 IVDD。MSC-外泌体可以将 miR-125b-5p 递送至靶点 TRAF6，抑制 NF-κB 激活，并减弱 IVDD 的进展。