Biological Sciences, Hurvitz Brain Sciences Research Program, Sunnybrook Research Institute, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
Biological Sciences, Hurvitz Brain Sciences Research Program, Sunnybrook Research Institute, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
J Control Release. 2022 Nov;351:667-680. doi: 10.1016/j.jconrel.2022.09.048. Epub 2022 Oct 6.
Focused ultrasound combined with intravenously injected microbubbles (FUS) is known to non-invasively, locally, and transiently increase the permeability of the blood-brain barrier (BBB). A promising approach for non-invasive gene delivery to the brain is to administer recombinant adeno-associated viruses (AAVs) intravenously and allow them to cross the BBB at precise FUS-targeted brain regions. FUS-AAV delivery has been achieved in animal models; however, the key elements influencing, guiding, and monitoring the success of FUS-AAV delivery to the brain remain largely unknown. We systematically compared the ability of AAV1, AAV2, AAV5, AAV8, AAV9, and AAVrg to enter four specific brain regions and transduce two main cell types: neurons and astrocytes. Our results demonstrate that the AAV serotype, the extent of FUS-induced BBB permeability, and the intrinsic properties of the targeted brain tissue influence the observed biodistribution, diffusion and transduction of AAV to cells of the cerebrovasculature and brain parenchyma. Non-invasive contrast-enhanced MR imaging was found to predict the efficacy of FUS-AAV delivery. Notably, we also found that AAVs with high biodistribution to peripheral organs result in low gene delivery to the brain when combined with FUS. Gene delivery by AAV1, AAV2, AAV5, AAV8 and AAV9 was highly and selectively localized to FUS-targeted brain areas. To obtain non-invasive gene delivery to multiple brain regions with one area of FUS-BBB modulation, we combined a modified AAV2 vector harboring enhanced retrograde transport properties (AAVrg) with FUS-mediated brain delivery. This allowed for gene delivery from the FUS-targeted site to multiple connected brain regions. This study demonstrates that MR imaging can be used as a non-invasive indication of AAV delivery to the brain, and that the properties of AAV serotypes influence the efficacy of gene delivery to the brain with FUS. AAVs that have minimal peripheral biodistribution are ideal candidates for enhanced, and perhaps exclusive with future serotypes, delivery to the brain with FUS. The characterization of parameters influencing FUS-AAV delivery to the brain are critical to the design of safe and efficient gene therapies, from preclinical studies to future clinical applications.
聚焦超声联合静脉内注射微泡（FUS）已被证实可无创、局部且短暂地增加血脑屏障（BBB）的通透性。一种有前途的非侵入性脑内基因传递方法是静脉内给予重组腺相关病毒（AAV），并允许它们在精确的 FUS 靶向脑区穿过 BBB。FUS-AAV 传递已在动物模型中实现；然而，影响、指导和监测 FUS-AAV 传递到大脑成功的关键因素在很大程度上仍然未知。我们系统地比较了 AAV1、AAV2、AAV5、AAV8、AAV9 和 AAVrg 进入四个特定脑区并转导两种主要细胞类型：神经元和星形胶质细胞的能力。我们的结果表明，AAV 血清型、FUS 诱导的 BBB 通透性程度以及靶向脑组织的固有特性影响观察到的 AAV 向脑血管和脑实质细胞的分布、扩散和转导。非侵入性对比增强磁共振成像被发现可预测 FUS-AAV 传递的效果。值得注意的是，我们还发现，当与 FUS 结合时，具有高外周器官分布的 AAV 会导致向大脑的基因传递效率降低。AAV1、AAV2、AAV5、AAV8 和 AAV9 的基因传递高度且选择性地定位于 FUS 靶向的脑区。为了通过一次 FUS-BBB 调制区域获得对多个脑区的非侵入性基因传递，我们将具有增强逆行转运特性的改良 AAV2 载体（AAVrg）与 FUS 介导的脑传递相结合。这允许从 FUS 靶向部位向多个连接的脑区进行基因传递。这项研究表明，磁共振成像可用作脑内 AAV 传递的非侵入性指标，并且 AAV 血清型的特性影响 FUS 增强基因传递到大脑的效果。具有最小外周分布的 AAV 是增强（也许是未来血清型的唯一选择）与 FUS 一起向大脑传递的理想候选物。影响 FUS-AAV 向大脑传递的参数的特性对于从临床前研究到未来临床应用的安全有效的基因治疗的设计至关重要。
