Studies in Glaucomatous Optic Nerve Damage

描述（由申请人提供）：了解眼内压升高引起的轴突损伤的细胞机制对于开发保护视神经的青光眼治疗方法至关重要。我们已经确定，麻醉大鼠暴露于控制IOP升高（CEI） 8小时会重现视神经损伤和视神经头（ONH）内的基因表达变化，这是慢性IOP升高的特征。利用这一模型，通过控制全身血压（BP）和眼内压，我们现在建议识别ONH内激活的有害细胞通路，特别关注眼压诱导的生物力学应力/应变和缺血/缺氧特异性目标1将(a)利用轴突变性的组织学证据和视网膜电图暗位阈值反应（STR）对视网膜神经节细胞/内视网膜损伤的功能评估，确定视神经损伤的发展和时间，暴露于50和60 mmHg (CEI 50-8和CEI 60-8) 8小时。然后，我们将(b)使用微阵列聚类分析来确定CEI 60-8基因表达变化的时序级联，(c)通过qPCR确认并与CEI 50-8进行比较，我们预计CEI 50-8将产生更少的缺血/缺氧变化和更少的生物力学应力/应变动态变化。Specific Aim 2将通过(a)减少正常IOP眼的ONH灌注和(b)增加血压以改善IOP升高眼的灌注来确定特定的缺血/缺氧基因表达变化，使用qPCR确认前者出现缺血/缺氧反应，后者出现缺血/缺氧反应的减少和/或消除。这些将通过多普勒光学相干断层扫描对视网膜和ONH灌注的评估来指导，该断层扫描由华盛顿大学的王瑞康博士用于大鼠眼睛。特异性Aim 3将证明抑制Jak2/Stat3通路（IOP升高时ONH的初始应答者）可以抑制下游特异性ONH基因表达反应并改变急性IOP升高引起的轴突损伤，确定该通路在轴突存活或损伤中的关键作用，以及潜在的未来神经保护靶点。特异性目的4将证明老年动物更容易受到眼压升高引起的轴突损伤，这是由于年龄相关的基因表达改变对眼压升高的反应。这些研究将揭示ONH通路被io诱导的生物力学应力/应变和缺血/缺氧激活，从而产生轴索损伤，并将导致针对特定临床情况（如血管痉挛和衰老）的神经保护治疗。鼠类CEI模型的成功建立将简化和加速青光眼视神经损伤的研究和潜在神经保护剂的测试。

DESCRIPTION (provided by applicant): Understanding cellular mechanisms of axonal injury from elevated intraocular pressure (IOP) is essential for developing glaucoma treatments that will protect the optic nerve. We have determined that an 8- hour exposure to Controlled Elevation of IOP (CEI) in anesthetized rats will reproduce optic nerve injury and gene expression changes within the optic nerve head (ONH) that are characteristic of chronic IOP elevation. Working with this model, and manipulating systemic blood pressure (BP) as well as IOP, we now propose to identify injurious cellular pathways that are activated within the ONH, paying particular attention to IOP-induced biomechanical stress/strain and ischemia/hypoxia Specific Aim 1 will (a) define the development and timing of optic nerve injury to 8 hours' exposure to 50 and 60 mmHg (CEI 50-8 and CEI 60-8) using histologic evidence of axonal degeneration and functional assessment of retinal ganglion cell/inner retina injury with the scotopic threshold response (STR) by electroretinography. We will then (b) use a microarray cluster analysis to determine the chronological cascade of gene expression changes to CEI 60-8, with (c) confirmation by qPCR and comparison to CEI 50-8, which we anticipate will produce fewer ischemia/hypoxia changes and less dynamic changes from biomechanical stress/strain. Specific Aim 2 will identify specific ischemia/hypoxia gene expression changes by (a) reducing ONH perfusion in eyes with normal IOP and (b) increasing BP to improve perfusion in eyes with elevated IOP, using qPCR confirmation of the appearance of ischemia/hypoxia responses in the former and their reduction and/or elimination in the latter. These will be guided by assessment of retina and ONH perfusion with Doppler-Optical Coherence Tomography, adapted for rat eyes by Dr. Ruikang Wang at the University of Washington. Specific Aim 3 will demonstrate that inhibition of the Jak2/Stat3 pathway, an initial ONH responder to elevated IOP, can suppress downstream specific ONH gene expression responses and alter axonal injury from acute IOP elevation, identifying a key role for this pathway in axon survival or injury, and a potential futue neuroprotective target. Specific Aim 4 will demonstrate that elderly animals are more susceptible to IOP-induced axonal injury and that this results from age-related alterations in gene expression responses to IOP elevation. These studies will reveal ONH pathways activated by IOP-induced biomechanical stress/strain and ischemia/hypoxia to produce axonal injury and will lead to neuroprotective treatments "targeted" to specific clinical situations like vasospasm and aging. Successful development of the CEI model in rodents will simplify and accelerate the study of glaucomatous optic nerve damage and testing of potential neuroprotective agents.