Focused ultrasound mitigates pathology and improves spatial memory in Alzheimer's mice and patients

Potential mechanism and efficacy evaluation of transcranial focused ultrasound therapy for Alzheimer's disease

BACKGROUND

Transcranial focused ultrasound (TFU) is emerging as a promising non-invasive therapy capable of blood-brain barrier (BBB) opening. TFU potentially allows the transfer of therapeutic agents to targeted brain areas for patients affected with Alzheimer's disease (AD).

NEW METHOD

The efficacy and mechanism of TFU in modulating BBB permeability in key brain regions, including the hippocampus and frontal lobe, are investigated in this research. A total of 20 participants aged 60-85 years were involved with AD. The treatment protocol involved three TFU sessions, spaced three weeks apart. The research encompasses pre-assessment and post-assessment of treatment with follow-up ranging from 5 to 12 months.

RESULTS

Statistical analysis involved paired t-tests to compare pre- and post-treatment cognitive scores, and ANOVA to predict significant differences in amyloid reduction across different brain regions, with the high decrease observed in the hippocampus. Multivariate Analysis (MANOVA) to explore the combined effect of cognitive and amyloid data. Linear Regression Analysis to predict cognitive improvement from amyloid plaque reduction. Longitudinal analysis for time-to-event analysis assessing the durability of effects over time.

COMPARISON WITH EXISTING METHODS

Florbetaben Positron Emission Tomography (PET) scans demonstrated a reduction in β-amyloid plaque burden, with a 15 % average decrease in the treated brain regions. No adverse effects on disease progression were observed up to 1 year after treatment.

CONCLUSION

This analysis presents the largest cohort of AD patients treated with TFU, with the longest follow-up to date. The treatment demonstrated safety and feasibility, with reversible BBB opening in multiple brain regions.

Effects of blood-brain barrier opening using ultrasound on tauopathies: A systematic review

Blood-brain barrier opening with ultrasound can potentiate drug efficacy in the treatment of brain pathologies and also provides therapeutic effects on its own. It is an innovative tool to transiently, repeatedly and safely open the barrier, with studies showing beneficial effects in both preclinical models for Alzheimer's disease and recent clinical studies. The first preclinical and clinical work has mainly shown a decrease in amyloid burden in mice models and in patients. However, Alzheimer's disease pathology also encompasses tauopathy, which is closely related to cognitive decline, making it a crucial therapeutic target. The effects of blood-brain barrier opening with ultrasound have been rarely assessed on tau and are still unclear.

METHODS

This systematic review, conducted through searches using Pubmed, Embase, Web of Science and Cochrane Central databases, extracted results of 15 studies reporting effects of blood-brain barrier opening using ultrasound on tau proteins.

RESULTS

This review of the literature indicates that blood-brain barrier opening using ultrasound can decrease the extent of the tau pathology or potentialize the effect of a therapeutic drug. However, selected studies report paradoxically that blood-brain barrier opening can increase tau pathology burden and induce brain damage.

DISCUSSION

Apparent discrepancies between reports could originate from the variability in protocols or analytical methods that may impact the effects of blood-brain barrier opening with ultrasound on tauopathies, glial populations, tissue integrity and functional outcomes.

CONCLUSION

This calls for a better standardization effort combined with improved methodologies allowing between-studies comparisons, and for further understanding of the effects of blood-brain barrier opening on tau pathology as an essential prerequisite before translation to clinic.

Non-pharmacological treatment of Alzheimer's disease: an update

Alzheimer's disease (AD) is a neurodegenerative disorder that significantly impairs memory, cognitive function, and the ability to perform daily tasks. The pathological features of AD include β-amyloid plaques, neurofibrillary tangles, and neuronal loss. Current AD treatments target pathological changes but often fail to noticeably slow disease progression and can cause severe complications, limiting their effectiveness. In addition to therapies targeting the core pathology of AD, a more comprehensive approach may be needed for its treatment. In recent years, non-pharmacological treatments such as physical therapy, exercise therapy, cell therapy, and nanoparticles have shown great potential in mitigating disease progression and alleviating clinical symptoms. This article reviews recent advances in non-pharmacological treatment approaches for AD, highlighting their contributions to AD management and facilitating the exploration of novel therapeutic strategies.

Multimodal imaging of murine cerebrovascular dynamics induced by transcranial pulse stimulation

INTRODUCTION

Transcranial pulse stimulation (TPS) is increasingly being investigated as a promising potential treatment for Alzheimer's disease (AD). Although the safety and preliminary clinical efficacy of TPS short pulses have been supported by neuropsychological scores in treated AD patients, its fundamental mechanisms are uncharted.

METHODS

Herein, we used a multi-modal preclinical imaging platform combining real-time volumetric optoacoustic tomography, contrast-enhanced magnetic resonance imaging, and ex vivo immunofluorescence to comprehensively analyze structural and hemodynamic effects induced by TPS. Cohorts of healthy and AD transgenic mice were imaged during and after TPS exposure at various per-pulse energy levels.

RESULTS

TPS enhanced the microvascular network, whereas the blood-brain barrier remained intact following the procedure. Notably, higher pulse energies were necessary to induce hemodynamic changes in AD mice, arguably due to their impacted vessels.

DISCUSSION

These findings shed light on cerebrovascular dynamics induced by TPS treatment, and hence are expected to assist improving safety and therapeutic outcomes.

HIGHLIGHTS

·Transcranial pulse stimulation (TPS) facilitates transcranial wave propagation using short pulses to avoid tissue heating. ·Preclinical multi-modal imaging combines real-time volumetric optoacoustic (OA) tomography, contrast-enhanced magnetic resonance imaging (CE-MRI), and ex vivo immunofluorescence to comprehensively analyze structural and hemodynamic effects induced by TPS. ·Blood volume enhancement in microvascular networks was reproducibly observed with real-time OA imaging during TPS stimulation. ·CE-MRI and gross pathology further confirmed that the brain architecture was maintained intact without blood-brain barrier (BBB) opening after TPS exposure, thus validating the safety of the procedure. ·Higher pulse energies were necessary to induce hemodynamic changes in AD compared to wild-type animals, arguably due to their pathological vessels.

Clinical Applications of Micro/Nanobubble Technology in Neurological Diseases

Nanomedicine, leveraging the unique properties of nanoparticles, has revolutionized the diagnosis and treatment of neurological diseases. Among various nanotechnological advancements, ultrasound-mediated drug delivery using micro- and nanobubbles offers promising solutions to overcome the blood-brain barrier (BBB), enhancing the precision and efficacy of therapeutic interventions. This review explores the principles, current clinical applications, challenges, and future directions of ultrasound-mediated drug delivery systems in treating stroke, brain tumors, neurodegenerative diseases, and neuroinflammatory disorders. Additionally, ongoing clinical trials and potential advancements in this field are discussed, providing a comprehensive overview of the impact of nanomedicine on neurological diseases.

Exploiting the mechanical effects of ultrasound for noninvasive therapy

Focused ultrasound is a platform technology capable of eliciting a wide range of biological responses with high spatial precision deep within the body. Although focused ultrasound is already in clinical use for focal thermal ablation of tissue, there has been a recent growth in development and translation of ultrasound-mediated nonthermal therapies. These approaches exploit the physical forces of ultrasound to produce a range of biological responses dependent on exposure conditions. This review discusses recent advances in four application areas that have seen particular growth and have immense clinical potential: brain drug delivery, neuromodulation, focal tissue destruction, and endogenous immune system activation. Owing to the maturation of transcranial ultrasound technology, the brain is a major target organ; however, clinical indications outside the brain are also discussed.

The road ahead to successful BBB opening and drug-delivery with focused ultrasound

This review delves into the innovative technology of Blood-Brain Barrier (BBB) opening with low-intensity focused ultrasound in combination with microbubbles (LIFU-MB), a promising therapeutic modality aimed at enhancing drug delivery to the central nervous system (CNS). The BBB's selective permeability, while crucial for neuroprotection, significantly hampers the efficacy of pharmacological treatments for CNS disorders. LIFU-MB emerges as a non-invasive and localized method to transiently increase BBB permeability, facilitating the delivery of therapeutic molecules. Here, we review the procedural stages of LIFU-MB interventions, including planning and preparation, sonication, evaluation, and delivery, highlighting the technological diversity and methodological challenges encountered in current clinical applications. With an emphasis on safety and efficacy, we discuss the crucial aspects of ultrasound delivery, microbubble administration, acoustic feedback monitoring and assessment of BBB permeability. Finally, we explore the critical choices for effective BBB opening with LIFU-MB, focusing on selecting therapeutic agents, optimizing delivery methods, and timing for delivery. Overcoming existing barriers to integrate this technology into clinical practice could potentially revolutionize CNS drug delivery and treatment paradigms in the near future.

Transcranial blood-brain barrier opening in Alzheimer's disease patients using a portable focused ultrasound system with real-time 2-D cavitation mapping

Background : Focused ultrasound (FUS) in combination with microbubbles has recently shown great promise in facilitating blood-brain barrier (BBB) opening for drug delivery and immunotherapy in Alzheimer's disease (AD). However, it is currently limited to systems integrated within the MRI suites or requiring post-surgical implants, thus restricting its widespread clinical adoption. In this pilot study, we investigate the clinical safety and feasibility of a portable, non-invasive neuronavigation-guided FUS (NgFUS) system with integrated real-time 2-D microbubble cavitation mapping. Methods : A phase 1 clinical study with mild to moderate AD patients (N = 6) underwent a single session of microbubble-mediated NgFUS to induce transient BBB opening (BBBO). Microbubble activity under FUS was monitored with real-time 2-D cavitation maps and dosing to ensure the efficacy and safety of the NgFUS treatment. Post-operative MRI was used for BBB opening and closure confirmation as well as safety assessment. Changes in AD biomarker levels in both blood serum and extracellular vesicles (EVs) were evaluated, while changes in amyloid-beta (Aβ) load in the brain were assessed through 18F-florbetapir PET. Results : BBBO was achieved in 5 out of 6 subjects with an average volume of 983 ± 626 mm3 following FUS at the right frontal lobe both in white and gray matter regions. The outpatient treatment was completed within 34.8 ± 10.7 min. Cavitation dose significantly correlated with the BBBO volume (R 2 > 0.9, N = 4), demonstrating the portable NgFUS system's capability of predicting opening volumes. The cavitation maps co-localized closely with the BBBO location, representing the first report of real-time transcranial 2-D cavitation mapping in the human brain. Larger opening volumes correlated with increased levels of AD biomarkers, including Aβ42 (R 2 = 0.74), Tau (R 2 = 0.95), and P-Tau181 (R 2 = 0.86), assayed in serum-derived EVs sampled 3 days after FUS (N = 5). From PET scans, subjects showed a lower Aβ load increase in the treated frontal lobe region compared to the contralateral region. Reduction in asymmetry standardized uptake value ratios (SUVR) correlated with the cavitation dose (R 2 > 0.9, N = 3). Clinical changes in the mini-mental state examination over 6 months were within the expected range of cognitive decline with no additional changes observed as a result of FUS. Conclusion : We showed the safety and feasibility of this cost-effective and time-efficient portable NgFUS treatment for BBBO in AD patients with the first demonstration of real-time 2-D cavitation mapping. The cavitation dose correlated with BBBO volume, a slowed increase in pathology, and serum detection of AD proteins. Our study highlights the potential for accessible FUS treatment in AD, with or without drug delivery.

Transcranial Blood-Brain Barrier Opening in Alzheimer's Disease Patients Using a Portable Focused Ultrasound System with Real-Time 2-D Cavitation Mapping

Background

Focused ultrasound (FUS) in combination with microbubbles has recently shown great promise in facilitating blood-brain barrier (BBB) opening for drug delivery and immunotherapy in Alzheimer's disease (AD). However, it is currently limited to systems integrated within the MRI suites or requiring post-surgical implants, thus restricting its widespread clinical adoption. In this pilot study, we investigate the clinical safety and feasibility of a portable, non-invasive neuronavigation-guided FUS (NgFUS) system with integrated real-time 2-D microbubble cavitation mapping.

Methods

A phase 1 clinical study with mild to moderate AD patients (N=6) underwent a single session of microbubble-mediated NgFUS to induce transient BBB opening (BBBO). Microbubble activity under FUS was monitored with real-time 2-D cavitation maps and dosing to ensure the efficacy and safety of the NgFUS treatment. Post-operative MRI was used for BBB opening and closure confirmation as well as safety assessment. Changes in AD biomarker levels in both blood serum and extracellular vesicles (EVs) were evaluated, while changes in amyloid-beta (Aβ) load in the brain were assessed through 18F-Florbetapir PET.

Results

BBBO was achieved in 5 out of 6 subjects with an average volume of 983±626 mm3 following FUS at the right frontal lobe both in white and gray matter regions. The outpatient treatment was completed within 34.8±10.7 min. Cavitation dose significantly correlated with the BBBO volume (R 2>0.9, N=4), demonstrating the portable NgFUS system's capability of predicting opening volumes. The cavitation maps co-localized closely with the BBBO location, representing the first report of real-time transcranial 2-D cavitation mapping in the human brain. Larger opening volumes correlated with increased levels of AD biomarkers, including Aβ42 (R 2=0.74), Tau (R 2=0.95), and P-Tau181 (R 2=0.86), assayed in serum-derived EVs sampled 3 days after FUS (N=5). From PET scans, subjects showed a lower Aβ load increase in the treated frontal lobe region compared to the contralateral region. Reduction in asymmetry standardized uptake value ratios (SUVR) correlated with the cavitation dose (R 2>0.9, N=3). Clinical changes in the mini-mental state examination over 6 months were within the expected range of cognitive decline with no additional changes observed as a result of FUS.

Conclusion

We showed the safety and feasibility of this cost-effective and time-efficient portable NgFUS treatment for BBBO in AD patients with the first demonstration of real-time 2-D cavitation mapping. The cavitation dose correlated with BBBO volume, a slowed increase in pathology, and serum detection of AD proteins. Our study highlights the potential for accessible FUS treatment in AD, with or without drug delivery.

Translating ultrasound-mediated drug delivery technologies for CNS applications

Ultrasound enhances drug delivery into the central nervous system (CNS) by opening barriers between the blood and CNS and by triggering release of drugs from carriers. A key challenge in translating setups from in vitro to in vivo settings is achieving equivalent acoustic energy delivery. Multiple devices have now been demonstrated to focus ultrasound to the brain, with concepts emerging to also target the spinal cord. Clinical trials to date have used ultrasound to facilitate the opening of the blood-brain barrier. While most have focused on feasibility and safety considerations, therapeutic benefits are beginning to emerge. To advance translation of these technologies for CNS applications, researchers should standardise exposure protocol and fine-tune ultrasound parameters. Computational modelling should be increasingly used as a core component to develop both in vitro and in vivo setups for delivering accurate and reproducible ultrasound to the CNS. This field holds promise for transformative advancements in the management and pharmacological treatment of complex and challenging CNS disorders.

Light on Alzheimer's disease: from basic insights to preclinical studies

Alzheimer's disease (AD), referring to a gradual deterioration in cognitive function, including memory loss and impaired thinking skills, has emerged as a substantial worldwide challenge with profound social and economic implications. As the prevalence of AD continues to rise and the population ages, there is an imperative demand for innovative imaging techniques to help improve our understanding of these complex conditions. Photoacoustic (PA) imaging forms a hybrid imaging modality by integrating the high-contrast of optical imaging and deep-penetration of ultrasound imaging. PA imaging enables the visualization and characterization of tissue structures and multifunctional information at high resolution and, has demonstrated promising preliminary results in the study and diagnosis of AD. This review endeavors to offer a thorough overview of the current applications and potential of PA imaging on AD diagnosis and treatment. Firstly, the structural, functional, molecular parameter changes associated with AD-related brain imaging captured by PA imaging will be summarized, shaping the diagnostic standpoint of this review. Then, the therapeutic methods aimed at AD is discussed further. Lastly, the potential solutions and clinical applications to expand the extent of PA imaging into deeper AD scenarios is proposed. While certain aspects might not be fully covered, this mini-review provides valuable insights into AD diagnosis and treatment through the utilization of innovative tissue photothermal effects. We hope that it will spark further exploration in this field, fostering improved and earlier theranostics for AD.

Shedding light on ultrasound in action: Optical and optoacoustic monitoring of ultrasound brain interventions

Monitoring brain responses to ultrasonic interventions is becoming an important pillar of a growing number of applications employing acoustic waves to actuate and cure the brain. Optical interrogation of living tissues provides a unique means for retrieving functional and molecular information related to brain activity and disease-specific biomarkers. The hybrid optoacoustic imaging methods have further enabled deep-tissue imaging with optical contrast at high spatial and temporal resolution. The marriage between light and sound thus brings together the highly complementary advantages of both modalities toward high precision interrogation, stimulation, and therapy of the brain with strong impact in the fields of ultrasound neuromodulation, gene and drug delivery, or noninvasive treatments of neurological and neurodegenerative disorders. In this review, we elaborate on current advances in optical and optoacoustic monitoring of ultrasound interventions. We describe the main principles and mechanisms underlying each method before diving into the corresponding biomedical applications. We identify areas of improvement as well as promising approaches with clinical translation potential.

Treating the Brain With Focused Ultrasound

Focused ultrasound is an early stage, noninvasive therapy with the potential to treat a range of medical conditions. Like diagnostic ultrasound, it uses sound waves above the range of human hearing. But its purpose is to interact with tissues in the body, rather than just produce images of them. In focused ultrasound, multiple, intersecting beams of high frequency sound are aimed to converge on specific targets deep within the body. There, the ultrasound energy can act in multiple ways to either modify or destroy tissue.