Focused ultrasound-mediated opening of the blood brain barrier for non-invasive drug delivery to the murine cerebellum.

Abstract

Background: The blood brain barrier (BBB) limits effective treatment for cerebellar diseases. Region-specific parameterization and safety data for MRI-guided focused ultrasound (MRgFUS) BBB opening (BBBO) in the cerebellum are scarce. The goal of this study is to establish safety and feasibility of cerebellar BBBO for antibody delivery.

Methods: Mice received i.v. AF680 IgG and microbubbles immediately prior to sonication at 0.30 or 0.45 MPa peak negative pressure (1.15 MHz, 10 ms bursts, 2 s burst period, 60 bursts). BBBO was quantified by contrast-enhanced T1-weighted MRI (9.4T) and assessed for recovery at 12 h. Radiologic safety was evaluated by T2-weighted MRI. Acoustic emissions were analyzed via real-time passive cavitation detection, and acoustic simulations estimated the derated pressure caused by skull incidence angle. IgG delivery was quantified by ex vivo IVIS epifluorescence imaging and immunofluorescence analysis. Safety assessments included cardio-respiratory monitoring, body weight, motor function, and neuropathology assessment of endpoint H&E.

Results: Both regimens yielded cerebellar BBBO without radiologic evidence of injury. BBB integrity was restored by 12 h. While the higher pressure increased MRI and cavitation signals, IgG delivery was similarly enhanced (> 2-fold vs. sham) by FUS, irrespective of peak negative pressure. Heart rate, respiratory rate, body weight, and motor function were unchanged by FUS, and neuropathologic evaluation revealed no hemorrhage, inflammation, vacuolation, or architectural abnormalities.

Conclusions: FUS enables safe, transient BBBO in the cerebellum and significantly enhances antibody delivery without measurable physiologic, functional, radiologic, or histologic injury. These findings establish a foundation for expansion of pharmacologic and theranostic delivery strategies directed to the cerebellum.