Antidepressant effects of focused ultrasound induced blood-brain-barrier opening

Patient-derived induced pluripotent stem cells: Tools to advance the understanding and drug discovery in Major Depressive Disorder

Major Depressive Disorder (MDD) is a pleomorphic disease with substantial patterns of symptoms and severity with mensurable deficits in several associated domains. The broad spectrum of phenotypes observed in patients diagnosed with depressive disorders is the reflection of a very complex disease where clusters of biological and external factors (e.g., response/processing of life events, intrapsychic factors) converge and mediate pathogenesis, clinical presentation/phenotypes and trajectory. Patient-derived induced pluripotent stem cells (iPSCs) enable their differentiation into specialised cell types in the central nervous system to explore the pathophysiological substrates of MDD. These models may complement animal models to advance drug discovery and identify therapeutic approaches, such as cell therapy, drug repurposing, and elucidation of drug metabolism, toxicity, and mechanisms of action at the molecular/cellular level, to pave the way for precision psychiatry. Despite the remarkable scientific and clinical progress made over the last few decades, the disease is still poorly understood, the incidence and prevalence continue to increase, and more research is needed to meet clinical demands. This review aims to summarise and provide a critical overview of the research conducted thus far using patient-derived iPSCs for the modelling of psychiatric disorders, with a particular emphasis on MDD.

Characterization of the responses of brain macrophages to focused ultrasound-mediated blood-brain barrier opening

The opening of the blood-brain barrier (BBB) by focused ultrasound (FUS) coupled with intravenously injected microbubbles can be leveraged as a form of immunotherapy for the treatment of neurodegenerative disorders. However, how FUS BBB opening affects brain macrophages is not well understood. Here by using single-cell sequencing to characterize the distinct responses of microglia and central nervous system-associated macrophages (CAMs) to FUS-mediated BBB opening in mice, we show that the treatment remodels the immune landscape via the recruitment of CAMs and the proliferation of microglia and via population size increases in disease-associated microglia. Both microglia and CAMs showed early and late increases in population sizes, yet only the proliferation of microglia increased at both timepoints. The population of disease-associated microglia also increased, accompanied by the upregulation of genes associated with gliogenesis and phagocytosis, with the depletion of brain macrophages significantly decreasing the duration of BBB opening.

High-Accuracy Neuro-Navigation with Computer Vision for Frameless Registration and Real-Time Tracking

For the past three decades, neurosurgeons have utilized cranial neuro-navigation systems, bringing millimetric accuracy to operating rooms worldwide. These systems require an operating room team, anesthesia, and, most critically, cranial fixation. As a result, treatments for acute neurosurgical conditions, performed urgently in emergency rooms or intensive care units on awake and non-immobilized patients, have not benefited from traditional neuro-navigation. These emergent procedures are performed freehand, guided only by anatomical landmarks with no navigation, resulting in inaccurate catheter placement and neurological deficits. A rapidly deployable image-guidance technology that offers highly accurate, real-time registration and is capable of tracking awake, moving patients is needed to improve patient safety. The Zeta Cranial Navigation System is currently the only non-fiducial-based, FDA-approved neuro-navigation device that performs real-time registration and continuous patient tracking. To assess this system's performance, we performed registration and tracking of phantoms and human cadaver heads during controlled motions and various adverse surgical test conditions. As a result, we obtained millimetric or sub-millimetric target and surface registration accuracy. This rapid and accurate frameless neuro-navigation system for mobile subjects can enhance bedside procedure safety and expand the range of interventions performed with high levels of accuracy outside of an operating room.

Immunomodulation and targeted drug delivery with high intensity focused ultrasound (HIFU): Principles and mechanisms

High intensity focused ultrasound (HIFU) is a non-invasive and non-ionizing sonic energy-based therapeutic technology for inducing thermal and non-thermal effects in tissues. Depending on the parameters, HIFU can ablate tissues by heating them to >55 °C to induce denaturation and coagulative necrosis, improve radio- and chemo-sensitizations and local drug delivery from nanoparticles at moderate hyperthermia (~41-43 °C), and mechanically fragment cells using acoustic cavitation (also known as histotripsy). HIFU has already emerged as an attractive modality for treating human prostate cancer, veterinary cancers, and neuromodulation. Herein, we comprehensively review the role of HIFU in enhancing drug delivery and immunotherapy in soft and calcified tissues. Specifically, the ability of HIFU to improve adjuvant treatments from various classes of drugs is described. These crucial insights highlight the opportunities and challenges of HIFU technology and its potential to support new clinical trials and translation to patients.

Preclinical Research on Focused Ultrasound-Mediated Blood-Brain Barrier Opening for Neurological Disorders: A Review

Several therapeutic agents for neurological disorders are usually not delivered to the brain owing to the presence of the blood-brain barrier (BBB), a special structure present in the central nervous system (CNS). Focused ultrasound (FUS) combined with microbubbles can reversibly and temporarily open the BBB, enabling the application of various therapeutic agents in patients with neurological disorders. In the past 20 years, many preclinical studies on drug delivery through FUS-mediated BBB opening have been conducted, and the use of this method in clinical applications has recently gained popularity. As the clinical application of FUS-mediated BBB opening expands, it is crucial to understand the molecular and cellular effects of FUS-induced microenvironmental changes in the brain so that the efficacy of treatment can be ensured, and new treatment strategies established. This review describes the latest research trends in FUS-mediated BBB opening, including the biological effects and applications in representative neurological disorders, and suggests future directions.

Early Detection and Reversal of Cell Apoptosis Induced by Focused Ultrasound-Mediated Blood-Brain Barrier Opening

Focused ultrasound (FUS) combined with microbubbles (MBs) has recently emerged as a potential approach to open the blood-brain barrier (BBB) for delivering drugs into the brain. However, appropriate approaches are still lacking to monitor the sublethal damage during FUS-mediated BBB opening in vivo, especially the early stage cell apoptotic events. Here, we developed a kind of nanoprobe-loaded MBs (AV-ICG-NPs@MBs) which can monitor the apoptotic cells that occur during FUS-mediated BBB opening through encapsulating the annexin V-targeted nanoprobes AV-ICG-NPs into the cavity of lipid-PLGA hybrid MBs. When irradiated by FUS, AV-ICG-NPs@MBs in the cerebral blood vessels would produce cavitation, favoring the BBB opening. Meanwhile, AV-ICG-NPs@MBs would be destroyed and release their AV-ICG-NPs payload. These released AV-ICG-NPs can be further delivered into the brain via the destructed BBB and bind with the phosphatidylserine externalized on the membrane of apoptotic cells if this occurs, leading to the prolonged detention of fluorescent signals in the brain. Furthermore, we also provided an effective strategy to inhibit or reverse the possible damage to the brain from a FUS-mediated BBB opening technology, through developing AV-ICG-NPs/GAS@MBs that encapsulate the antioxidant gastrodin (GAS) into AV-ICG-NPs@MBs. Accompanied by FUS irradiation and bubble cavitation, GAS was released and delivered into the brain, where they scavenged the oxygen free radicals produced from cavitation, leading to significantly lower fluorescence signals in the brain due to the absence of externalized phosphatidylserine. In conclusion, our study provides an approach to monitor and inhibit cell apoptotic events during FUS-mediated BBB opening.

Therapeutic oxygen delivery by perfluorocarbon-based colloids

After the protocol-related indecisive clinical trial of Oxygent, a perfluorooctylbromide/phospholipid nanoemulsion, in cardiac surgery, that often unduly assigned the observed untoward effects to the product, the development of perfluorocarbon (PFC)-based O₂ nanoemulsions ("blood substitutes") has come to a low. Yet, significant further demonstrations of PFC O₂-delivery efficacy have continuously been reported, such as relief of hypoxia after myocardial infarction or stroke; protection of vital organs during surgery; potentiation of O₂-dependent cancer therapies, including radio-, photodynamic-, chemo- and immunotherapies; regeneration of damaged nerve, bone or cartilage; preservation of organ grafts destined for transplantation; and control of gas supply in tissue engineering and biotechnological productions. PFC colloids capable of augmenting O₂ delivery include primarily injectable PFC nanoemulsions, microbubbles and phase-shift nanoemulsions. Careful selection of PFC and other colloid components is critical. The basics of O₂ delivery by PFC nanoemulsions will be briefly reminded. Improved knowledge of O₂ delivery mechanisms has been acquired. Advanced, size-adjustable O₂-delivering nanoemulsions have been designed that have extended room-temperature shelf-stability. Alternate O₂ delivery options are being investigated that rely on injectable PFC-stabilized microbubbles or phase-shift PFC nanoemulsions. The latter combine prolonged circulation in the vasculature, capacity for penetrating tumor tissues, and acute responsiveness to ultrasound and other external stimuli. Progress in microbubble and phase-shift emulsion engineering, control of phase-shift activation (vaporization), understanding and control of bubble/ultrasound/tissue interactions is discussed. Control of the phase-shift event and of microbubble size require utmost attention. Further PFC-based colloidal systems, including polymeric micelles, PFC-loaded organic or inorganic nanoparticles and scaffolds, have been devised that also carry substantial amounts of O₂. Local, on-demand O₂ delivery can be triggered by external stimuli, including focused ultrasound irradiation or tumor microenvironment. PFC colloid functionalization and targeting can help adjust their properties for specific indications, augment their efficacy, improve safety profiles, and expand the range of their indications. Many new medical and biotechnological applications involving fluorinated colloids are being assessed, including in the clinic. Further uses of PFC-based colloidal nanotherapeutics will be briefly mentioned that concern contrast diagnostic imaging, including molecular imaging and immune cell tracking; controlled delivery of therapeutic energy, as for noninvasive surgical ablation and sonothrombolysis; and delivery of drugs and genes, including across the blood-brain barrier. Even when the fluorinated colloids investigated are designed for other purposes than O₂ supply, they will inevitably also carry and deliver a certain amount of O₂, and may thus be considered for O₂ delivery or co-delivery applications. Conversely, O₂-carrying PFC nanoemulsions possess by nature a unique aptitude for ¹⁹F MR imaging, and hence, cell tracking, while PFC-stabilized microbubbles are ideal resonators for ultrasound contrast imaging and can undergo precise manipulation and on-demand destruction by ultrasound waves, thereby opening multiple theranostic opportunities.

Repetitive Transcranial Magnetic Stimulation for Treatment-Resistant Depression: Recent Critical Advances in Patient Care

PURPOSE

Transcranial magnetic stimulation (TMS) is an evidence-based treatment for pharmacoresistant major depressive disorder (MDD). In the last decade, the field has seen significant advances in the understanding and use of this new technology. This review aims to describe the large, randomized controlled studies leading to the modern use of rTMS for MDD. It also includes a special section briefly discussing the use of these technologies during the COVID-19 pandemic.

RECENT FINDINGS

Several new approaches and technologies are emerging in this field, including novel approaches to reduce treatment time and potentially yield new approaches to optimize and maximize clinical outcomes. Of these, theta burst TMS now has evidence indicating it is non-inferior to standard TMS and provides significant advantages in administration. Recent studies also indicate that neuroimaging and related approaches may be able to improve TMS targeting methods and potentially identify those patients most likely to respond to stimulation.

SUMMARY

While new data is promising, significant research remains to be done to individualize and optimize TMS procedures. Emerging new approaches, such as accelerated TMS and advanced targeting methods, require additional replication and demonstration of real-world clinical utility. Cautious administration of TMS during the pandemic is possible with careful attention to safety procedures.

Therapeutic Potentials of Localized Blood-Brain Barrier Disruption by Noninvasive Transcranial Focused Ultrasound: A Technical Review

The demands for region-specific, noninvasive therapies for neurologic/psychiatric conditions are growing. The rise of transcranial focused ultrasound technology has witnessed temporary and reversible disruptions of the blood-brain barrier in the brain with exceptional control over the spatial precisions and depth, all in a noninvasive manner. Starting with small animal studies about a decade ago, the technique is now being explored in nonhuman primates and humans for the assessment of its efficacy and safety. The ability to transfer exogenous/endogenous therapeutic agents, cells, and biomolecules across the blood-brain barrier opens up new therapeutic avenues for various neurologic conditions, with a possibility to modulate the excitability of regional brain function. This review addresses the technical fundamentals, sonication parameters, experimental protocols, and monitoring techniques to examine the efficacy/safety in focused ultrasound-mediated blood-brain barrier disruption and discuss its potential translations to clinical use.

New neuromodulation techniques for treatment resistant depression

In the treatment of depression, when pharmacotherapy, psychotherapy and the oldest brain stimulation techniques are deadlocked, the emergence of new therapies is a necessary development. The field of neuromodulation is very broad and controversial. This article provides an overview of current progress in the technological advances in neuromodulation and neurostimulation treatments for treatment-resistant depression: magnetic seizure therapy; focal electrically administered seizure therapy; low field magnetic stimulation; transcranial pulsed electromagnetic fields; transcranial direct current stimulation; epidural cortical stimulation; trigeminal nerve stimulation; transcutaneous vagus nerve stimulation; transcranial focussed ultrasound; near infra-red transcranial radiation; closed loop stimulation. The role of new interventions is expanding, probably with more efficacy. Nowadays, still under experimentation, neuromodulation will probably revolutionise the field of neuroscience. At present, major efforts are still necessary before that these therapies are likely to become widespread.Key pointsThere is a critical need for new therapies for treatment resistant depression.Newer therapies are expanding. In the future, these therapies, as an evidence-based adjunctive treatments, could offer a good therapeutic choice for the patients with a TRD.The current trend in the new neuromodulation therapies is to apply a personalised treatment.These news therapies can be complementary.That treatment approaches can provide clinically significant benefits.

Investigating the effects of dexamethasone on blood-brain barrier permeability and inflammatory response following focused ultrasound and microbubble exposure

Rationale: Clinical trials are currently underway to test the safety and efficacy of delivering therapeutic agents across the blood-brain barrier (BBB) using focused ultrasound and microbubbles (FUS+MBs). While acoustic feedback control strategies have largely minimized the risk of overt tissue damage, transient induction of inflammatory processes have been observed following sonication in preclinical studies. The goal of this work was to explore the potential of post-sonication dexamethasone (DEX) administration as a means to mitigate treatment risk. Vascular permeability, inflammatory protein expression, blood vessel growth, and astrocyte activation were assessed. Methods: A single-element focused transducer (transmit frequency = 580 kHz) and Definity^TM microbubbles were used to increase BBB permeability unilaterally in the dorsal hippocampi of adult male rats. Sonicating pressure was calibrated based on ultraharmonic emissions. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was used to quantitatively assess BBB permeability at 15 min (baseline) and 2 hrs following sonication. DEX was administered following baseline imaging and at 24 hrs post-FUS+MB exposure. Expression of key inflammatory proteins were assessed at 2 days, and astrocyte activation and blood vessel growth were assessed at 10 days post-FUS+MB exposure. Results: Compared to saline-treated control animals, DEX administration expedited the restoration of BBB integrity at 2 hrs, and significantly limited the production of key inflammation-related proteins at 2 days, following sonication. Indications of FUS+MB-induced astrocyte activation and vascular growth were diminished at 10 days in DEX-treated animals, compared to controls. Conclusions: These results suggest that DEX provides a means of modulating the duration of BBB permeability enhancement and may reduce the risk of inflammation-induced tissue damage, increasing the safety profile of this drug-delivery strategy. This effect may be especially relevant in scenarios for which the goal of treatment is to restore or preserve neural function and multiple sonications are required.

Transcranial Focused Ultrasound (tFUS) and Transcranial Unfocused Ultrasound (tUS) Neuromodulation: From Theoretical Principles to Stimulation Practices

Transcranial focused ultrasound is an emerging technique for non-invasive neurostimulation. Compared to magnetic or electric non-invasive brain stimulation, this technique has a higher spatial resolution and can reach deep structures. In addition, both animal and human studies suggest that, potentially, different sites of the central and peripheral nervous system can be targeted by this technique. Depending on stimulation parameters, transcranial focused ultrasound is able to determine a wide spectrum of effects, ranging from suppression or facilitation of neural activity to tissue ablation. The aim is to review the state of the art of the human transcranial focused ultrasound neuromodulation literature, including the theoretical principles which underlie the explanation of the bioeffects on neural tissues, and showing the stimulation techniques and parameters used and their outcomes in terms of clinical, neurophysiological or neuroimaging results and safety.

Low-intensity focused ultrasound for the treatment of brain diseases: safety and feasibility

The use of focused ultrasound (FUS) as a tool for blood-brain barrier (BBB) permeabilization is opening new ways for the treatment of several pathologies, in particular brain tumors and neurodegenerative diseases. However, even if there are promising results in these fields, the efficacy and safety of this technique is unknown in long-term follow-up. The study of Blackmore et al. [Theranostics 2018; 8(22):6233-6247. doi:10.7150/thno.27941] evaluated the long-term effects of FUS on brain parenchyma in aged mice with Alzheimer's disease. This is the first study which applied a multimodal analysis to demonstrate the safety of FUS in aged brain in view of a potential introduction of this technique in common clinical practice in the future.

Angiogenic response of rat hippocampal vasculature to focused ultrasound-mediated increases in blood-brain barrier permeability

Focused ultrasound (FUS) and circulating microbubbles can induce a targeted and transient increase in blood-brain barrier permeability. While preclinical research has demonstrated the utility of FUS for efficacious drug deliver to the brain, there remain gaps in our knowledge regarding the long-term response of brain vasculature to this intervention. Previous work has demonstrated transcriptional changes in hippocampal microvessels following sonication that are indicative of the initiation of angiogenic processes. Moreover, blood vessel growth has been reported in skeletal muscle following application of FUS and microbubbles. The current study demonstrates that blood vessel density in the rat hippocampus is modestly elevated at 7 and 14 d post-FUS compared to the contralateral hemisphere (7 d: 10.9 ± 6.0%, p = 0.02; 14 d: 12.1 ± 3.2%, p < 0.01), but returns to baseline by 21 d (5.9 ± 2.6%, p = 0.12). Concurrently, relative newborn endothelial cell density and frequency of small blood vessel segments were both elevated in the sonicated hippocampus. While further work is required to determine the mechanisms driving these changes, the findings presented here may have relevance to the optimal frequency of repeated treatments.