Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, HSC, Morgantown, 1 Medical Center Dr, Morgantown, WV, 26506, USA.
Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, 44106, USA.
Fluids Barriers CNS. 2022 Sep 8;19(1):72. doi: 10.1186/s12987-022-00369-1.
Systemic drug delivery to the central nervous system is limited by presence of the blood-brain barrier (BBB). Low intensity focused ultrasound (LiFUS) is a non-invasive technique to disrupt the BBB, though there is a lack of understanding of the relationship between LiFUS parameters, such as cavitation dose, time of sonication, microbubble dose, and the time course and magnitude of BBB disruption. Discrepancies in these data arise from experimentation with modified, clinically untranslatable transducers and inconsistent parameters for sonication. In this report, we characterize microbubble and cavitation doses as LiFUS variables as they pertain to the time course and size of BBB opening with a clinical Insightec FUS system.
Female Nu/Nu athymic mice were exposed to LiFUS using the ExAblate Neuro system (v7.4, Insightec, Haifa, Israel) following target verification with magnetic resonance imaging (MRI). Microbubble and cavitation doses ranged from 4-400 μL/kg, and 0.1-1.5 cavitation dose, respectively. The time course and magnitude of BBB opening was evaluated using fluorescent tracers, ranging in size from 105-10,000 Da, administered intravenously at different times pre- or post-LiFUS. Quantitative autoradiography and fluorescence microscopy were used to quantify tracer accumulation in brain.
We observed a microbubble and cavitation dose dependent increase in tracer uptake within brain after LiFUS. Tracer accumulation was size dependent, with C-AIB (100 Da) accumulating to a greater degree than larger markers (~ 625 Da-10 kDa). Our data suggest opening of the BBB via LiFUS is time dependent and biphasic. Accumulation of solutes was highest when administered prior to LiFUS mediated disruption (2-fivefold increases), but was also significantly elevated at 6 h post treatment for both C-AIB and Texas Red.
The magnitude of LiFUS mediated BBB opening correlates with concentration of microbubbles, cavitation dose as well as time of tracer administration post-sonication. These data help define the window of maximal BBB opening and applicable sonication parameters on a clinically translatable and commercially available FUS system that can be used to improve passive permeability and accumulation of therapeutics targeting the brain.
全身药物递送至中枢神经系统受到血脑屏障（BBB）的限制。低强度聚焦超声（LiFUS）是一种非侵入性技术，可以破坏 BBB，但对于 LiFUS 参数（例如空化剂量、超声时间、微泡剂量以及 BBB 破坏的时间过程和程度）之间的关系，人们了解甚少。这些数据的差异源于对经过修改的、临床上无法转化的换能器的实验以及超声参数的不一致。在本报告中，我们使用临床可用的 Insightec FUS 系统，将微泡和空化剂量作为与 BBB 开放的时间过程和大小有关的 LiFUS 变量进行了表征。
雌性 Nu/Nu 无胸腺小鼠在经过磁共振成像（MRI）验证靶点后，使用 ExAblateNeuro 系统（v7.4，Insightec，海法，以色列）接受 LiFUS 治疗。微泡和空化剂量范围分别为 4-400μL/kg 和 0.1-1.5 空化剂量。使用大小范围为 105-10000Da 的荧光示踪剂静脉内给药，在 LiFUS 之前或之后的不同时间点进行 BBB 开放的时间过程和程度的评估。定量放射自显影和荧光显微镜用于定量脑内示踪剂的积累。
我们观察到 LiFUS 后脑内示踪剂摄取量随微泡和空化剂量的增加而增加。示踪剂的积累具有尺寸依赖性，与较大的标记物（~625Da-10kDa）相比，C-AIB（100Da）的积累程度更高。我们的数据表明，通过 LiFUS 打开 BBB 是时间依赖性和双相性的。当在 LiFUS 介导的破坏之前给予时，溶质的积累最高（增加 2-5 倍），但在治疗后 6 小时，C-AIB 和 TexasRed 的积累也显著增加。
LiFUS 介导的 BBB 开放的程度与微泡浓度、空化剂量以及超声后示踪剂给药时间有关。这些数据有助于定义在可临床转化和商业上可用的 FUS 系统上打开 BBB 的最大窗口和适用的超声参数，可用于改善针对大脑的治疗药物的被动通透性和积累。
