Department of Rehabilitation Sciences, School of Public Health and Health Professions, College of Arts and Sciences, University at Buffalo, Buffalo, New York, USA.
Neuroscience Program, College of Arts and Sciences, University at Buffalo, Buffalo, New York, USA.
J Neurotrauma. 2021 Dec;38(23):3248-3259. doi: 10.1089/neu.2020.7556.
In the present study, we have evaluated the blast-induced auditory neurodegeneration in chinchilla by correlating the histomorphometric changes with diffusion tensor imaging. The chinchillas were exposed to single unilateral blast-overpressure (BOP) at ∼172dB peak sound pressure level (SPL) and the pathological changes were compared at 1 week and 1 month after BOP. The functional integrity of the auditory system was assessed by auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE). The axonal integrity was assessed using diffusion tensor imaging at regions of interests (ROIs) of the central auditory neuraxis (CAN) including the cochlear nucleus (CN), inferior colliculus (IC), and auditory cortex (AC). Post-BOP, cyto-architecture metrics such as viable cells, degenerating neurons, and apoptotic cells were quantified at the CAN ROIs using light microscopic studies using cresyl fast violet, hematoxylin and eosin, and modified Crossmon's trichrome stains. We observed mean ABR threshold shifts of 30- and 10-dB SPL at 1 week and 1 month after BOP, respectively. A similar pattern was observed in DPAOE amplitudes shift. In the CAN ROIs, diffusion tensor imaging studies showed a decreased axial diffusivity in CN 1 month after BOP and a decreased mean diffusivity and radial diffusivity at 1 week after BOP. However, morphometric measures such as decreased viable cells and increased degenerating neurons and apoptotic cells were observed at CN, IC, and AC. Specifically, increased degenerating neurons and reduced viable cells were high on the ipsilateral side when compared with the contralateral side. These results indicate that a single blast significantly damages structural and functional integrity at all levels of CAN ROIs.
在本研究中,我们通过将组织形态计量学变化与扩散张量成像相关联,评估了单次单侧爆炸超压(BOP)对南美栗鼠的听觉神经退行性变的影响。南美栗鼠在约 172dB 峰值声压级(SPL)下暴露于单次单侧 BOP,在 BOP 后 1 周和 1 个月比较病理学变化。通过听觉脑干反应(ABR)和畸变产物耳声发射(DPOAE)评估听觉系统的功能完整性。使用弥散张量成像在包括耳蜗核(CN)、下丘(IC)和听觉皮层(AC)在内的中枢听觉神经轴(CAN)的感兴趣区(ROI)评估轴突完整性。在 BOP 后,使用 Cresyl 快速紫罗兰、苏木精和伊红以及改良的 Crossmon 三色染色的光镜研究在 CAN ROI 量化细胞存活、变性神经元和凋亡细胞等细胞结构测量值。我们观察到,BOP 后 1 周和 1 个月,ABR 阈值分别平均偏移 30dB 和 10dB SPL。DPAOE 幅度偏移也观察到类似的模式。在 CAN ROI 中,弥散张量成像研究显示,BOP 后 1 个月 CN 的轴向弥散度降低,BOP 后 1 周平均弥散度和径向弥散度降低。然而,在 CN、IC 和 AC 中观察到形态计量学测量值,如存活细胞减少和变性神经元和凋亡细胞增加。具体来说,与对侧相比,同侧的变性神经元增加,存活细胞减少。这些结果表明,单次爆炸显著损害了 CAN ROI 各级别的结构和功能完整性。