PET Probes for Senescence Detection in Brain

项目摘要 全世界约有5000万人患有阿尔茨海默病（AD）和相关痴呆症， AD主要见于老年人。目前AD的诊断主要依赖于对 当发生不可逆的脑损伤时，精神和认知功能下降。正电子发射 用于AD早期诊断的断层摄影（PET）示踪剂已经通过评估Aβ或tau水平而被开发， 然而，聚集体靶向示踪剂经常遭受高非特异性结合。因此迫切 需要开发新的靶向分子水平的工具，以提高AD早期诊断的特异性。 细胞衰老已被证明是破坏体内平衡和细胞功能的关键因素。 老化的大脑在老年大脑中，衰老细胞积累并对大脑产生慢性炎症压力。 周围的细胞。在小鼠中观察到不同类型脑细胞的更高水平的衰老， AD患者和选择性去除衰老细胞可减少小鼠脑中Aβ斑块的形成， 改善认知功能。这些发现表明，衰老可能作为一个早期指标， 和AD的治疗靶点。然而，用于实时体内衰老检测的工具极其有限。 最近，佛罗里达大学（UF）的崔小组开发了一系列可激活的分子探针， 首次在动物模型中成功实现衰老的实时成像。这些探测器 - 由安装在探针上的自固定部分产生的高检测灵敏度， 探针可以在激活位点共价连接到周围的蛋白质。 基于这一战略，SenoTrac，与UF和莫菲特癌症中心合作，旨在开发第一个- 用于衰老的PET探针。简而言之，新型PET探针将由β-半乳糖苷组成，其可以是 由衰老相关的β-半乳糖苷酶（SA-β-gal）、18F和自固定的 在活化时可以将探针锚在周围蛋白质上的部分。我们希望可激活的PET 探头具有高脑摄取、最小弥散和高信号/背景对比度， 分辨率我们将在体外表征这些探针（SenoTrac和UF），我们还将评估它们的能力 在动物中穿过血脑屏障（UF）。PET成像前的放射化学将在Moffitt进行。 AD小鼠模型（5xFAD）将用于动态PET/CT扫描，以观察AD小鼠中的衰老水平。 不同的年龄组。此外，我们将使用senolytics清除衰老细胞，进行PET成像， 衰老并评估这些小鼠中的AD表型。脑组织的离体分析将提供 其他AD和衰老生物标志物（UF）的信息。我们希望得出衰老水平的相关性 和各种AD表型。在第一阶段，我们将开发用于AD动物衰老跟踪的PET探针 模型在第二阶段，我们将在不同的动物模型和小规模的人体试验中评估探针。我们 将引导监管要求，并致力于这些探针的商业化。

PROJECT SUMMARY Around 50 million people worldwide are suffering from Alzheimer’s disease (AD) and related dementias, and AD is observed primarily in aged people. Current diagnosis of AD relies primarily on observations of declines in mental and cognitive functions, when irreversible brain damage occurs. Positron emission tomography (PET) tracers for early diagnosis of AD have been developed via assessing Aβ or tau levels, however aggregate-targeting tracers often suffer from high nonspecific binding. Therefore, there is an urgent need for developing novel tools targeting molecular level to improve the specificity of early diagnosis of AD. Cellular senescence has been shown to be a critical contributor disrupting the homeostasis and functions of aging brains. In aged brains, senescent cells accumulate and exert chronic inflammatory pressure on surrounding cells. Higher levels of senescence in different types of brain cells have been observed in mice and human with AD and selective removal of senescent cells reduces Aβ plaque formation in mouse brain and improves cognitive functions. These findings indicate that senescence can potentially serve as an early indicator and therapeutic target for AD. However, tools for real-time in vivo senescence detection are extremely limited. Recently, the Cui group at the University of Florida (UF) has developed a series of activatable molecular probes, enabling the successful real-time imaging of senescence in animal models for the first time. These probes have high detection sensitivity produced by a self-immobilizing moiety installed on the probe so that upon activation, the probe can be covalently linked to surrounding proteins at the site of activation. Based on this strategy, SenoTrac, partnering with UF and Moffitt Cancer Center, aims to develop the first- in-class PET probes for senescence. Briefly, the novel PET probe will consist of a β-galactoside that can be specifically cleaved by senescence-associated β-galactosidase (SA-β-gal), a 18F, and a self-immobilizing moiety that can anchor the probe onto surrounding proteins upon activation. We expect the activatable PET probe to have high brain uptake, minimal diffusion and high signal/background contrast with excellent spatial resolution. We will characterize these probes in vitro (SenoTrac and UF), and we will also evaluate their ability to cross the blood brain barrier in animals (UF). Radiochemistry before PET imaging will be carried at Moffitt. AD mouse model (5xFAD) will be used in the dynamic PET/CT scan to see the levels of senescence in different age groups. Additionally, we will clear senescent cells using senolytics, perform PET imaging of senescence and evaluate AD phenotypes in these mice. Ex vivo analysis of the brain tissues will provide information of other AD and senescence biomarkers (UF). We expect to draw correlation of senescence levels and various AD phenotypes. In Phase 1, we will develop the PET probes for senescence tracking in AD animal models. In Phase 2, we will evaluate the probes in different animal models, and a small-scale human trial. We will navigate the regulatory requirements, and work towards commercialization of these probes.