Imaging of Retinal Hydroxyapatite as an Early Screen for AMD

老年性黄斑变性(AMD)是发达国家老年人最常见的致盲原因 影响了1000多万美国人。该病的发病是渐进性的，症状很少，大多数 直到眼睛检查发现不可逆转的视力丧失，患者才会意识到这一点。人们普遍认为， 脂肪和蛋白质在视网膜中的沉积，其中最著名的被称为玻璃体，导致 那里的光敏细胞。而不太常见的“湿性”AMD(CNV)可以被称为 血管内皮生长因子抑制剂，更常见的“干性”形式(GA)，目前无法治疗，尽管有几种治疗方法在... 发展。最近，我们发现软骨膜中含有微小的羟基磷灰石球体(HAP)，一种 骨骼和牙齿中丰富的磷酸钙形式，并有证据表明球体 使视网膜中的玻璃体生长成核。我们发现，荧光染色是用来研究骨骼生长的。 还会对球体进行染色，使其能够通过视网膜的荧光成像进行研究。我们 推测通过体内使用的这种成像方法早期检测HAP球体可能会预测 出现玻璃体，从而发展为AMD；至少在一些病例中得到了证实。 因此，这项生物工程研究拨款的主旨是开发和验证视网膜成像方法 用于AMD的筛查和早期检测，以提示治疗，并跟踪疾病的进程 评估治疗情况。在动物模型的骨骼研究中合成的一些染料在体外表现良好，但 它们在动物身上的行为和安全性鲜为人知，而且根本没有人体研究。然而，一些人 四环素类抗生素与骨矿物质结合时也会发出明亮的荧光，我们发现它们具有 在这些条件下的独特的荧光寿命，可以从背景中分辨 通过荧光寿命成像对视网膜进行荧光成像。四环素类具有众所周知的行为，可以 可能是口服的，对人类来说非常安全。用四环素对球体进行成像 我们必须构建一种荧光寿命成像检眼镜(Flio)，可用于人类或 唯一适合AMD的动物模型，猕猴(猴子)。我们将在现有的基础上构建Flio 仪器，改进我们在供体身体上的程序，然后在老年人身上测试Flio和染色程序 猕猴(发育球体)和日本猕猴，它们早期和迅速地发育成玻璃体。 高脂肪饮食的结果。需要回答的关键问题是球体的出现预测的可靠性有多高 玻璃疣的发展和发展为AMD，以及成像程序对猴子的安全性； 令人满意的结果可能会导致在人体上进行试验。

Age-related macular degeneration (AMD) is the most common cause of blindness in the elderly in developed countries, affecting over ten million Americans. The disease onset is gradual, with few symptoms and most patients unaware until irreversible vision loss is detected by eye examination. It is accepted that the buildup of deposits of fats and protein in the retina, the best known of which are called drusen, causes the death of the light-sensitive cells there. While the less common, “wet” form of AMD (CNV) can be arrested by drugs called VEGF inhibitors, the more common, “dry” form (GA) is currently untreatable, although several treatments are in development. Recently, we discovered that drusen contain microscopic spherules of hydroxyapatite (HAP), a form of calcium phosphate abundant in bones and teeth, and developed evidence indicating that the spherules nucleate the growth of drusen in the retina. We found that fluorescent stains developed to study bone growth would also stain the spherules, permitting them to be studied by fluorescence imaging of the retina. We inferred that detecting the HAP spherules early by such an imaging approach used in vivo might predict the appearance of the drusen and thus AMD development; this was confirmed in at least some cases. Thus, the thrust of this Bioengineering Research Grant is to develop and validate a retinal imaging approach for screening and early detection of AMD, both to cue treatment, and to follow the course of the disease to assess treatment. Some of the stains synthesized for bone studies in animal models perform well in vitro, but their behavior and safety is little known in animals, and there are no human studies at all. However, some tetracycline antibiotics also give bright fluorescence when bound to bone mineral, and we found that they have a distinct fluorescence lifetime under these conditions, which can be resolved from the background fluorescence of the retina by fluorescence lifetime imaging. The tetracyclines have well known behavior, can probably be administered orally, and are very safe in humans. To image the spherules with tetracycline staining we must construct a fluorescence lifetime imaging ophthalmoscope (FLIO), usable on humans or the only good animal model for AMD, macaques (monkeys). We will construct a FLIO based on an existing instrument, refine our procedures on donor cadavers, then test the FLIO and staining procedures on aged macaques (which develop spherules) and a Japanese macaque which develops drusen early and rapidly as a result of a high fat diet. Key questions to be answered are how reliably the appearance of spherules predicts the development of drusen and progression to AMD, and how safe the imaging procedure is for the monkeys; satisfactory results will likely lead to trials in humans.