Toward functional molecular neuroimaging using vasoactive probes in human subjects

我们建议开发一种用于分子精确监测人脑功能的探针技术； 与磁共振成像(MRI)或其他成像方式相结合，这些探针将提供 灵敏度和分辨率的结合，可以实现前所未有的动态神经元非侵入性研究 人的生理过程。我们的战略是基于一种全新类型的化学成像 旨在通过有目的地操纵内源性血流动力学来产生神经成像读数的探测器 大脑中的对比-重新调整血氧水平依赖(BOLD)效应，这是传统的 功能磁共振成像(FMRI)。这一新的“血管探头”概念提供了三个关键优势：第一，通过提供时间延迟， 由于对神经递质等稀释分子物种的敏感性悬而未决，这些探针可以使明确定义 神经生物学现象将在整个大脑中动态映射，大大超过现有的 非特异性功能磁共振成像方法。第二，由于它们影响的内源性造影源，探头 可通过与fMRI互补的非侵入性成像方式在各种时空尺度上检测到， 例如漫射光学或基于超声的方法。第三，通过绕过现有光学技术的限制， 磁性和放射性探头设计，血管探头结合了接近正电子的精致灵敏度 发射断层扫描(PET)具有MRI的分辨率和多功能性。在这个项目中，我们将在最近的基础上 概念验证使用血管探头建立非侵入性全脑给药策略并开发 在灵长类动物身上起作用的强大的神经化学感应器。我们建立的技术将满足多个目标 在基础神经科学和应用神经科学方面，我们希望它能产生适合临床的分子探针 在项目期结束时对人体受试者进行评估。 在目标1中，我们将创造血管探针变体，可以通过静脉注射和 自发透过血脑屏障(BBB)。我们将形成以血管探针为基础的结合物 带有“脑穿梭”抗体的传感器，此前已被证明可以通过受体- 介导性的细胞穿透。脑透性血管探针的展示将建立一条临床可行的途径 血管探头在整个大脑中的简便、非侵入性应用。在目标2中，我们将优化血管探头以 感知关键的神经递质多巴胺和谷氨酸；然后我们将在全脑范围内应用它们来 啮齿类动物大脑的分子水平功能磁共振成像。这些实验，结合目标1的结果，将设定 神经递质敏感型血管探针及相关感应器在灵长类动物大脑中的应用阶段。一致同意- 同样，在目标3中，我们将把神经递质敏感的血管探针技术应用于功能分子神经成像-- 绒猴的衰老，这是一种我们以前有过经验的易驯服的灵长类物种。成功完成 因此，在绒猴身上的验证实验将建立适用于转导的突破性显像剂。 对人类的影响，以及对许多进一步的神经生理靶点的适应。

We propose to develop a probe technology for monitoring human brain function with molecular precision; in conjunction with magnetic resonance imaging (MRI) or other imaging modalities, the probes will provide a combination of sensitivity and resolution that could permit unprecedented noninvasive studies of dynamic neu- rophysiological processes in people. Our strategy is based on a fundamentally new type of chemical imaging probe designed to produce neuroimaging readouts by purposefully manipulating endogenous hemodynamic contrast in the brain—repurposing the blood oxygen level dependent (BOLD) effect that underlies conventional functional MRI (fMRI). This new “vasoprobe” concept offers three key advantages: First, by providing time-de- pendent sensitivity to dilute molecular species such as neurotransmitters, the probes can enable well-defined neurobiological phenomena to be mapped dynamically across the entire brain, dramatically surpassing existing nonspecific fMRI approaches. Second, because of the endogenous contrast source they influence, the probes are detectable on a variety of spatiotemporal scales by noninvasive imaging modalities complementary to fMRI, such as diffuse optical or ultrasound-based methods. Third, by circumventing limitations of established optical, magnetic, and radioactive probe designs, vasoprobes combine exquisite sensitivity approaching that of positron emission tomography (PET) with the resolution and versatility of MRI. In this project, we will build on our recent proof-of-concept work with vasoprobes to establish noninvasive brain-wide delivery strategies and to develop robust neurochemical sensors that function in primates. The technology we establish will address multiple goals in basic and applied neuroscience, and we expect it to yield molecular probes that will be appropriate for clinical evaluation in human subjects by the end of the project period. In Aim 1, we will create vasoprobe variants that can be delivered to the brain via intravenous injection and spontaneous permeation through the blood-brain barrier (BBB). We will form conjugates of vasoprobe-based sensors with “brain shuttle” antibodies that have previously been shown to enable brain import via receptor- mediated transcytosis. Demonstration of brain-permeable vasoprobes will establish a clinically viable path for facile, noninvasive applications of vasoprobes throughout the brain. In Aim 2, we will optimize vasoprobes to sense the key neurotransmitters dopamine and glutamate; we will then apply them on a brain-wide scale for molecular-level fMRI in rodent brains. These experiments, in conjunction with outcome of Aim 1, will set the stage for applications of neurotransmitter-sensitive vasoprobes and related sensors in primate brains. Accord- ingly, in Aim 3, we will adapt neurotransmitter-sensitive vasoprobe technology for functional molecular neuroim- aging in marmosets, a tractable primate species with which we have previous experience. Successful completion of validation experiments in marmosets will therefore establish groundbreaking imaging agents suitable for trans- lation to humans, as well as for adaptation to many further neurophysiological targets.