外周神经髓鞘再生在高原缺氧环境听觉习服中的作用及分子调控

Studies show that low oxygen is the main cause of delayed hearing impairment in the plateau region.In our previous work, we found that there are an phenomenon of sound acclimatization in the migrated population from the plain to the plateau. Animal experiments have confirmed that sound acclimatizationis associated with the regeneration of the peripheral auditory nerve myelin.However, the mechanism to regulate the regeneration of the snowman in low oxygen environment has not been clarified. This project work schwann cells from auditory area of peripheral nerve as cellular model which is treated with different oxygen content mimicked the plateau low oxygen conditions. The characteristicsof schwann cell reprogramming is determined through observed the schwann cellular polarity, change of proliferation capacity and epithelial-mesenchymal transition. The regulation mechanism of Hippo/Yap, PI3K/Akt/mTORC1 signaling pathway and EMT correlation transcription factors on phenotype transformation of the schwann cell are determined. Based on the model of the rat plain moving to the plateau, the characteristics of sound acclimatization are observed dynamicallyby auditory function detection. The correlation between the polarity change of the schwann cells andremyelination in the process of sound acclimatization are evaluated through analyzed the changes of the sub-population of schwann cells in the cochlea axis and osseous spiral lamina of the cochlea. The aim of this study is focused on discovering novel regulatory factor which can lead to hypoxic adaptation in auditory system, which provides theoretical basis for preventing the hypoxia-induced hearing impairment and treating the disorders of peripheral myelin.

研究表明低氧是造成高原地区迟发性听力障碍的主要原因。我们在前期工作中发现，平原移居高原人群有听力习服现象；高原听力习服与外周听觉神经髓鞘雪旺细胞损伤再生有关。但低氧环境下影响髓鞘再生的雪旺细胞表型转换机制目前尚未阐明。课题采用体外分离耳蜗神经组织块和原代雪旺细胞，以不同氧含量预处理细胞模拟高原生态，通过观察细胞表型、增殖特征和间质化能力改变，确定低氧条件下雪旺细胞重编程规律；确定Hippo/Yap、PI3K/Akt/mTORC1信号通路和EMT相关转录因子对雪旺细胞表型转换的调控机制。以大鼠平原移居高原为模型，动态观察高原听力习服规律。观察分析耳蜗外周神经组织区域雪旺细胞亚群的改变，确定雪旺细胞的极性变化和髓鞘再生与听觉习服能力的相关性。探讨低氧髓鞘再生不同阶段关键基因的表达及调控方式。期望发现能够促进听觉系统低氧适应性调控因子，为预防低氧所致的听觉损伤和外周髓鞘病变的治疗提供理论依据。

听觉系统持续低氧刺激能促使机体产生获得性适应性反应，提高机体缺氧环境下声习服能力，减轻持续低氧导致的听觉损害。目前关于听觉低氧适应相关基因及其诱导调控机制尚未明确。课题采用多层次转录组学对移居高原不同阶段大鼠的耳蜗神经组织进行RNA-seq转录组测序，筛选出低氧听觉习服过程不同阶段的mRNA、lncRNA、circRNA和miRNA差异表达基因，同时构建雪旺细胞重编程相关差异基因时序表达谱。通过功能和通路分析，发现Aqp1、Rbp4、Six2、Bglap、Gabrb2、Slc1a2、Grm5、Msx1、Sox10和Grm3具有最丰富的GO功能，被富集在Hippo/YAP、PI3K/AKT和GAB-Aergic synapse信号传导通路中。通过整合mRNA和lncRNA数据，发现LincRNA TCONS_00042166正调控SLC1a2基因，促进神经纤维修复；采用透射电子显微镜技术观察移居高原不同时间点大鼠听觉外周神经系统亚细胞结构改变，结合电生理指标，发现低氧能够导致大鼠部分耳蜗神经元变性和髓鞘结构破坏，长期低氧可激活GAP-43，促进损伤的神经元轴突及髓鞘的再生；体外模拟缺氧环境，发现低氧可增强原代雪旺细胞（RSCs）的增殖能力和迁移能力，改变RSCs细胞形态、极性和生长排列方向，低氧环境下更有利雪旺细胞趋向于修复功能表型；以耳蜗器官离体培养建立缺氧模型，发现耳蜗缺氧可导致耳蜗毛细胞和神经元死亡，红景天苷（SAL）可通过调控耳蜗组织的抗氧化屏障系统抵抗缺氧诱导的耳毒性，激活NRF2/HO-1信号抑制NF-kB激活，同时SAL激活AKT活性，增加抑制性GSK-3磷酸化，导致GSK-3β活性降低，发挥抗氧化作用。本研究阐明了低氧诱导的声习服与外周神经髓鞘再生的关联性，筛选出与高原低氧听觉习服相关基因。为预防和干预移居高原人群可能出现的听觉损伤提供了理论依据。