IGF-1/SLC25A33通过抑制TGF-β/Smad2介导的血管周细胞活化维持年龄相关性听力损失中的血-迷路屏障完整性

文献信息

中文摘要

背景： 年龄相关性听力损失（ARHL）是老年人中常见的感觉障碍，但耳蜗老化的分子机制仍不完全清楚。尽管胰岛素样生长因子1（IGF-1）已被认为与ARHL有关，但其在血管纹中的作用，特别是在血管周细胞介导的血-迷路屏障（BLB）调控中的作用，仍鲜有明确。方法：我们对年轻和年老小鼠血管纹中FACS纯化的血管周细胞进行了转录组分析。功能研究采用原代血管周细胞培养、慢病毒基因调控和AAV介导的体内递送进行。听觉功能通过听性脑干反应（ABR）和畸变产物耳声发射（DPOAE）评估。分子变化通过qPCR、western blot、免疫荧光、流式细胞术和透射电子显微镜（TEM）评估。结果：转录组学显示，年老血管周细胞中Igf1和Slc25a33显著下调，并富集TGF-β信号通路。IGF-1缺乏在体外抑制SLC25A33表达，导致线粒体ROS（mtROS）积累、TGF-β/Smad2信号激活以及血管周细胞表型转换，其特征为α-SMA增加和E-钙黏蛋白减少。在体内，抑制IGF-1或SLC25A33会激活血管纹中的TGF-β/Smad2信号，破坏BLB超微结构，并加重听力损失。相反，外源性IGF-1或SLC25A33过表达可减弱这些效应并部分恢复听觉功能。结论：我们的发现确定了一条新的IGF-1/SLC25A33-TGF-β/Smad2轴，该轴调控衰老耳蜗中的血管周细胞活化和BLB完整性。该通路为ARHL发病机制提供了机制性见解，并突出了保护老年人听力的潜在治疗靶点。

英文摘要

Age-related hearing loss (ARHL) is a prevalent sensory disorder in the elderly, yet the molecular mechanisms underlying cochlear aging remain incompletely understood. While insulin-like growth factor 1 (IGF-1) has been implicated in ARHL, its role in the stria vascularis, particularly in pericyte-mediated blood-labyrinth barrier (BLB) regulation, is poorly defined. We performed transcriptomic analysis of FACS-purified pericytes from young and aged mouse stria vascularis. Functional studies were conducted using primary pericyte cultures, lentiviral gene modulation, and AAV-mediated in vivo delivery. Auditory function was assessed by auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE). Molecular changes were evaluated via qPCR, western blot, immunofluorescence, flow cytometry, and transmission electron microscopy (TEM). Transcriptomics revealed significant downregulation of Igf1 and Slc25a33 in aged pericytes, with enrichment of the TGF-β signaling pathway. IGF-1 deficiency suppressed SLC25A33 expression in vitro, leading to mitochondrial ROS (mtROS) accumulation, activation of TGF-β/Smad2 signaling, and pericyte phenotypic switching, characterized by increased α-SMA and decreased E-cadherin. In vivo, suppression of IGF-1 or SLC25A33 activated TGF-β/Smad2 signaling in the stria vascularis, disrupted BLB ultrastructure, and exacerbated hearing loss. Conversely, exogenous IGF-1 or SLC25A33 overexpression attenuated these effects and partially restored auditory function. Our findings identify a novel IGF-1/SLC25A33-TGF-β/Smad2 axis that regulates pericyte activation and BLB integrity in the aging cochlea. This pathway provides mechanistic insight into ARHL pathogenesis and highlights a potential therapeutic target for preserving hearing in older adults.