Pigment Regeneration Mechanisms in the Human Retina

摘要 在过去的2-30年里，人们在解决光和暗的机制方面做了重要的工作 以小鼠为模型系统，研究哺乳动物视杆细胞和视锥细胞感光细胞的适应和疾病。 然而，老鼠是一种夜间活动的动物，没有黄斑，黄斑是灵长类视网膜的一个专门的中心区域 这提供了对人类日常生存至关重要的高敏锐度色觉。因此，人类的机制 日间视力或破坏黄斑感光细胞的疾病，如老年性黄斑 变性(AMD)，在小鼠身上研究是具有挑战性的。例如，干燥症没有有效的治疗方法。 这是一种老年性黄斑变性，是老年人最常见的致盲原因。因此，迫切需要更好地 了解人类黄斑中光感受器在健康和疾病中的生物学。这一点尤其正确 与已被更广泛研究的杆状感光器相比，视锥感光器具有更大的优势。最近的研究表明 在小鼠视网膜内建立了光不依赖和光依赖的色素再生途径 分离自色素上皮(RPE)。这些途径通过锥体特异的Müler细胞再生色素 通路(光不依赖和依赖视网膜内的视觉周期)或光感受器细胞本身 通过一种细胞自主再生机制。然而，对这些机制在 人的黄斑或中心凹。本提案的目标是确定独立于RPE的 视锥细胞对黑暗的快速适应和在强光下保持敏感度的色素再生途径 尤其是在人类的斑疹中。我们的中心假设是，正则视觉周期通过 RPE速度太慢，不能在明亮的光线下保持视力，也不能在快速变化的 人类黄斑中的照明。这项工作被组织成两个具体的目标。这些是用来确定 光不依赖视网膜内视觉周期(AIM I)和光色素再生途径的贡献 (AIM II)人黄斑视锥细胞的暗适应和光敏感性的维持。这些实验将会 采用体外视网膜电描记术和单细胞吸引器电极记录。这些技术很好地 适用于评估黑暗中视觉周期和细胞自主色素再生途径的作用 光敏感度的适应和维持。我们将利用我们的经验和合作 我们在过去三年中建立了眼库，以制定捐赠者的标准和方案，以 记录器官或研究供体人眼黄斑视锥的光诱发反应1-5小时 死后死亡。这些研究的结果将确定不同的视觉周期路径对人类的贡献 视锥细胞调节的视觉穿过视网膜的地理区域，包括中心凹。此信息将 为阐明黄斑营养不良的发病机制和改进的潜在靶点提供了基础 视力或防止老化或患病的人眼的视力丧失。

ABSTRACT During the past 2-3 decades important work has been done to resolve the mechanisms of light and dark adaptation as well as disease in the mammalian rod and cone photoreceptors using mouse as a model system. However, the mouse is a nocturnal animal that lacks the macula, a specialized central region in primate retina that provides high-acuity color vision critical for human everyday survival. Consequently, mechanisms of human daytime vision or diseases that disrupt photoreceptors in the macula, such as Age-Related Macular Degeneration (AMD), are challenging to study in mice. For example, there is no effective treatment for the dry form of AMD, the most common cause of blindness among the elderly. Thus, there is a critical need to better understand the biology of the photoreceptors in the human macula in health and disease. This is particularly true of cone photoreceptors compared to rods that have been more extensively studied. Recent studies have established both light-independent and light-dependent pigment regeneration pathways within the mouse retina isolated from the pigment epithelium (RPE). These pathways regenerate pigment via Müller cells in cone-specific pathways (light-independent and -dependent intraretinal visual cycles) or in the photoreceptor cells themselves by a cell-autonomous regeneration mechanism. However, nothing is known about these mechanisms in the human macula or fovea. The goal of this proposal is to determine the contribution of the RPE-independent pigment regeneration pathways to the ability of cones to dark adapt quickly and maintain sensitivity in bright light specifically in the human macula. Our central hypothesis is that the canonical visual cycle that operates via the RPE is too slow to maintain vision in bright light or mediate dark adaptation during rapidly changing levels of illumination in the human macula. The work is organized into two specific aims. These are to determine the contribution of the light-independent intraretinal visual cycle (Aim I) and photic pigment regeneration pathways (Aim II) to dark adaptation and maintenance of light sensitivity of human macular cones. The experiments will employ ex vivo electroretinography and single cell suction electrode recordings. These techniques are well suited for assessing the role of visual cycles and cell-autonomous pigment regeneration pathways in dark adaptation and maintenance of light sensitivity, respectively. We will leverage our experience and collaborations with Eye Banks that we have established during the past three years to develop donor criteria and protocols to record light-evoked responses of macular cones from organ or research donor human eyes 1 – 5 hours postmortem. Results of these studies will determine the contribution of different visual cycle pathways to human vision mediated by the cones across geographical regions of the retina, including the fovea. This information will provide a basis for studies to elucidate pathogenesis of macular dystrophies and potential targets to improve vision or prevent vision loss in aging or diseased human eye.