miR-146b负调控NF-κB信号通路抑制异常应力下椎间盘退变的机制

Inflammation, which could be induced by abnormal loading, is one of the main cause of intervertebral disc degeneration(IVDD). It has been demonstrated that miR-146b played an important role in immunoregulation, which could repress inflammation and endothelial activity by inhibiting NF-κB pathway, however, it is still unclear whether it can inhibit intervertebral disc degeneration through above-mentioned way. According to microRNA array analysis of rats and mice respectively, we found that there was significant difference of miR-146b expression between normal and degenerative intervertebral discs. Our preliminary work also demonstrated that miR-146b expression decreased significantly in nucleus pulposus(NP) and was negatively correlated with IL-1β expression. So, we hypothesize that miR-146b inhibit IVDD following abnormal loading through down-regulating IL-1β signaling to NF-κB pathway. In order to verify this hypothesis, we will investigate the mechanism of miR-146b in inhibiting intervertebral disc degeneration following abnormal loading trough down-regulating NF-κB signaling pathway and its influence on vascular inflammation around the intervertebral disc by designing multi-level experiments using human intervertebral disc tissues, IVDD models of SD rats, miR-146b knock-out mice, through polymerase chain reaction (PCR),Western blot, small interference RNA(siRNA), lentivirus transfection, and tissue staining techniques et al. Our purpose is to determine the effects and mechanism of miR-146b on intervertebral disc degeneration and provide new clues of targeted therapy for primary IVDD.

异常应力可诱发椎间盘炎性反应，导致其退变。研究表明miR-146在免疫调节中发挥重要作用，可通过下调NF-κB通路抑制炎性反应及血管内皮细胞活性。但能否通过上述途径抑制异常应力下椎间盘退变，尚不清楚。预实验结果显示，退变髓核中miR-146b表达明显降低，且与IL-1β表达呈负相关。故我们提出假说，miR-146b通过下调髓核细胞IL-1β介导的NF-κB通路，抑制异常应力下椎间盘退变。为验证该假说，我们将通过人椎间盘组织、SD大鼠应力诱导椎间盘退变模型、miR-146b基因敲除小鼠，采用PCR、Western blot、RNA干扰、病毒转染、组织学染色等手段，从分子、细胞、组织以及动物体内多层次探讨miR-146b调控NF-κB通路在异常应力下椎间盘退变中的作用及可能机制，并阐明其对椎间盘退变周围微血管炎性反应的影响，为椎间盘退变早期阶段靶向干预治疗提供新的思路。

异常应力诱发的椎间盘炎性反应是目前认为导致退变的主要因素之一。传统的各种保守和手术治疗方案，难以从根本上阻止或逆转已发生的椎间盘退变，临床效果难以令人满意。基因治疗是目前研究热点之一。微小RNA (miRNA)是基因治疗领域的研究热点之一，其广泛参与蛋白表达的调控，在机体的多种生理和病理过程中发挥重要作用。研究表明，miR-146在免疫调节中发挥重要作用，可通过下调NF-κB通路抑制炎性反应以及血管内皮细胞活性，并可明显抑制骨性关节炎炎性因子的表达和软骨细胞退变。然而，在以髓核软骨样细胞为主的椎间盘组织中，其作用方式以及具体机制尚不清楚。我们采用基因芯片技术，检测显示椎间盘退变髓核miR146b较正常组显著降低。本项目进一步通过收集60例椎间盘突出症患者手术摘除的标本，检测miR-146b、IL-1β和基质降解酶（MMPS）、聚蛋白多糖酶（ADAMTS）等基因的表达水平（de real-time PCR和Western blot检测），证实miR-146b在椎间盘退变髓核中呈显著低表达，且与炎性因子IL-1β表达呈显著负相关。我们通过构建异常应力下椎间盘退变动物模型，提取髓核细胞，进而应用pri-miR-146b过表达慢病毒载体（Lenti-miR-146b）以及miR-146b抑制剂HDAC1慢病毒载体（Lenti-HDAC1）感染退变髓核细胞。采用real-time PCR及Western blot方法等方法检测miR-146b、髓核细胞IL-1β、NF-κB p65/p50以及IRAK1、TRAF6等变化，发现过表达miR-146b后，IRAK1、TRAF6表达明显降低。我们进而采用荧光素酶报告基因系统，证实IRAK1以及TRAF6为miR-146b的直接靶基因。阐明了miR-146b通过靶向IRAK1以及TRAF6下调IL-1β介导的NF-κB信号通路抑制椎间盘炎性反应，从而延缓其退变。本研究从临床病例、动物模型、细胞学以及动物体内多层次探讨了IL-1β相关miRNA-146b调控NF-KB通路在椎间盘退变中的作用及机制，证实miR-146b通过下调髓核细胞IL-1β介导的NF-κB通路抑制退变椎间盘的炎性反应，从而延缓椎间盘退变。为其用于椎间盘退变生物治疗提供了科学依据和理论支持。

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