Cross-species vascular anatomy and sensitivity to intraocular pressure in glaucoma

总结 血管功能障碍，伴或不伴眼内压（IOP）升高，被认为是重要的风险 青光眼和其他神经病变的因素。然而，血管功能障碍和机制之间的联系 导致青光眼中特征性视野缺陷的原因还没有完全了解。部分原因是缺乏 对视神经乳头（ONH）血管系统的3D结构有了坚实的定量理解， 与承重结缔组织的解剖学关系，以及IOP如何影响它。我们的总体 假设是脉管系统特征及其与结缔组织的关系倾向于 某些ONH区域的灌注受损，并且这种易感性被升高的IOP放大。 为了验证这一假设，我们将依次收集体内、离体和组织学3D形态学和组织学数据。 正常眼和实验性眼ONH血管和结缔组织的生物力学数据 青光眼（EG）。我们将集中在三个物种的关键筛板（LC）区域：人，猴， （最接近人的模型，胶原性LC）和小鼠（最常用的模型，无胶原性LC）。在目标1中，我们 绘制人类、猴子和小鼠ONH的血管和结缔组织的3D图，并分析 这些地图定量包括流域分析。我们预测早期青光眼的视力丧失区域 将对应于具有最脆弱的血管供应的区域，例如，低连通性的稀疏毛细血管 和低灌注冗余。我们假设，在灵长类动物中，并非所有的LC光束都有毛细管，反之亦然， 一些毛细血管不在强大的富含胶原蛋白的光束内。我们还将讨论临床上重要的 体内OCT血管造影在多大程度上显示ONH内更小或更深的血管。在 目的2，我们将在猴和小鼠眼睛上进行离体膨胀试验，以量化急性IOP的影响 升高对血管灌注和生物力学的影响，以及LC梁支撑。我们的初步数据显示， “无保护”的血管可能特别容易受到机械扭曲的影响，这反过来会影响血液 流在目标3中，我们将描述慢性IOP升高对血管和光束的影响。我们特别 将比较慢性IOP升高（EG）前后的眼睛以及对侧对照。这将允许 我们可以辨别哪些特征是青光眼的诱因，哪些是青光眼的结果。 我们将检验这样的假设，即在小鼠中血管对升高的IOP的敏感性模式（仅具有神经胶质细胞）。 这些细胞与灵长类动物不同。在相同的ONH中组合多种成像模式， 三个物种将提供交叉验证的技术，并更深入地了解LC胶原的作用， 在正常和升高的IOP下支撑ONH脉管系统的梁。这些实验将有助于识别 ONH特征可预测神经损伤和视力丧失的易感性。

SUMMARY Vascular dysfunction, with or without elevated intraocular pressure (IOP), is believed to be an important risk factor in glaucoma and other neuropathies. However, the link between vascular dysfunction and the mechanisms leading to the characteristic visual field defects in glaucoma is not fully understood. This is partly due to the lack of a solid quantitative understanding of the 3D architecture of the vasculature of the optic nerve head (ONH), its anatomical relationship with the load-bearing connective tissues, and how it is affected by IOP. Our overarching hypothesis is that features of the vasculature and its relationship with the connective tissues predispose certain ONH regions to compromised perfusion and that this susceptibility is amplified by elevated IOP. To test this hypothesis, we will sequentially collect in vivo, ex vivo, and histological 3D morphological and biomechanical data on vascular and connective tissues of the ONH in normal eyes and in eyes with experimental glaucoma (EG). We will focus on the critical lamina cribrosa (LC) region in three species: human, monkey (closest model to human, collagenous LC), and mouse (most used model, no collagenous LC). In Aim 1, we will map in 3D the vasculature and connective tissues of the ONHs of humans, monkeys, and mice, and analyze these maps quantitatively including by watershed analysis. We predict that zones of visual loss in early glaucoma will correspond to regions with the most vulnerable vascular supply, e.g., sparse capillaries with low connectivity and low perfusion redundancy. We postulate that, in primates, not all LC beams have a capillary, and conversely, that some capillaries are not within a robust collagen-rich beam. We will also address the clinically important question to which extent in vivo OCT angiography visualizes the smaller or deeper vessels inside the ONH. In Aim 2, we will perform ex vivo inflation tests on monkey and mouse eyes to quantify the effects of acute IOP elevation on vessel perfusion and biomechanics, and the LC beams support. Our preliminary data suggests that “unprotected” vessels may be particularly vulnerable to mechanical distortion, which could, in turn, affect blood flow. In Aim 3, we will characterize the effects of chronic IOP elevation on vessels and beams. Specifically, we will compare eyes before and after chronic IOP elevation (EG), and with the contralateral control. This will allow us to discern characteristics that pre-dispose an eye to glaucoma from those that are the result of the disease. We will test the hypothesis that the patterns of vessel sensitivity to elevated IOP in mice (that have only a glial lamina) are different from those in primates. Combining multiple imaging modalities across the same ONHs in three species will provide cross-verification of the techniques, and deeper insights into the role of LC collagenous beams supporting the ONH vasculature under normal and elevated IOP. These experiments will help identifying ONH features that predict susceptibility to neural injury and vision loss.