Studies in Glaucomatous Optic Nerve Damage

描述（由申请人提供）：了解眼内压（IOP）升高导致轴突损伤的细胞机制对于开发保护视神经的青光眼治疗至关重要。我们已经确定，在麻醉大鼠中暴露于控制性IOP升高（CEI）8小时将再现视神经损伤和视神经乳头（ONH）内的基因表达变化，这些变化是慢性IOP升高的特征。使用该模型，并操纵全身血压（BP）以及IOP，我们现在提出鉴定在ONH内激活的有害细胞通路，特别注意IOP诱导的生物力学应力/应变和缺血/缺氧，具体目标1将（a）确定视神经损伤的发展和时间，以8小时暴露于50和60 mmHg使用轴突变性的组织学证据和通过视网膜电描记术用暗视阈值反应（STR）对视网膜神经节细胞/内层视网膜损伤的功能评估（CEI 50-8和CEI 60-8）。然后，我们将（B）使用微阵列聚类分析来确定CEI 60-8的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将产生较少的缺血/缺氧变化和较少的来自生物力学应力/应变的动态变化。 具体目标2将通过（a）减少具有正常IOP的眼睛中的ONH灌注和（B）增加BP以改善具有升高的IOP的眼睛中的灌注来鉴定特异性缺血/缺氧基因表达变化，使用qPCR确认前者中缺血/缺氧反应的出现以及后者中缺血/缺氧反应的减少和/或消除。这些将由华盛顿大学的Ruikang Wang博士采用多普勒光学相干断层扫描技术对视网膜和ONH灌注进行评估来指导。 具体目标3将证明，抑制Jak 2/Stat 3通路（对IOP升高的初始ONH反应）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。 具体目标4将证明老年动物更容易受到IOP诱导的轴突损伤，并且这是由IOP升高的基因表达反应中的年龄相关改变引起的。 这些研究将揭示由IOP诱导的生物力学应力/应变和缺血/缺氧激活的ONH通路，以产生轴突损伤，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。在啮齿类动物中成功开发CEI模型将简化和加速对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.