Non-invasive Low-Intensity Pulsed Ultrasound Modulates Primary Cilia of Rat Hippocampal Neurons

Advances in transcranial focused ultrasound neuromodulation for mental disorders

Mental disorders are a major public health concern, affecting millions worldwide. Current treatments have limitations, highlighting the need for novel, effective, and safe interventions. Transcranial focused ultrasound (tFUS), a non-invasive neuromodulation technology, has emerged as a promising tool for treating mental disorders due to its high controllability, precision, and safety. This review summarizes the research progress of tFUS in several major mental disorders, including depression, anxiety, schizophrenia, and substance use disorders (SUDs). Animal studies have demonstrated the efficacy of tFUS in improving psychiatric symptoms and modulating neural circuits through various mechanisms, such as enhancing neuronal activity, synaptic plasticity, and neurotransmitter release. Preliminary clinical trials have also shown the potential of tFUS in alleviating symptoms in patients with treatment-resistant mental disorders. Safety evaluation studies across in vitro, animal, and human levels have supported the overall safety of tFUS under commonly used parameters. tFUS has shown broad application prospects in treating mental disorders, supported by its efficacy in animal models and preliminary clinical trials. By modulating neuronal activity, synaptic plasticity, neurotransmitters, and brain networks, tFUS could improve psychiatric symptoms and regulate neural circuits. However, current research on tFUS in mental disorders is still in its early stages, and further studies are needed to elucidate its mechanisms of action, expand its applications, and conduct large-sample, long-term clinical trials to systematically evaluate its efficacy, protocol optimization, and safety. As an innovative neuromodulation technology, tFUS has the potential to complement conventional therapies and provide new hope for addressing the global challenge of mental disorders.

LIPUS regulates the progression of knee osteoarthritis in mice through primary cilia-mediated TRPV4 channels

Osteoarthritis (OA) is a common disease in middle-aged and elderly people. An imbalance in calcium ion homeostasis will contribute to chondrocyte apoptosis and ultimately lead to the progression of OA. Transient receptor potential channel 4 (TRPV4) is involved in the regulation of intracellular calcium homeostasis. TRPV4 is expressed in primary cilia, which can sense mechanical stimuli from outside the cell, and its abnormal expression is closely related to the development of OA. Low-intensity pulsed ultrasound (LIPUS) can alleviate chondrocyte apoptosis while the exact mechanism is unclear. In this project, with the aim of revealing the mechanism of action of LIPUS, we proposed to use OA chondrocytes and animal models, LIPUS intervention, inhibition of primary cilia, use TRPV4 inhibitors or TRPV4 agonist, and use Immunofluorescence (IF), Immunohistochemistry (IHC), Western Blot (WB), Quantitative Real-time PCR (QP) to detect the expression of cartilage synthetic matrix and endoplasmic reticulum stress markers. The results revealed that LIPUS altered primary cilia expression, promoted synthetic matrix metabolism in articular chondrocytes and was associated with primary cilia. In addition, LIPUS exerted a active effect on OA by activating TRPV4, inducing calcium inward flow, and facilitating the entry of NF-κB into the nucleus to regulate synthetic matrix gene transcription. Inhibition of TRPV4 altered primary cilia expression in response to LIPUS stimulation, and knockdown of primary cilia similarly inhibited TRPV4 function. These results suggest that LIPUS mediates TRPV4 channels through primary cilia to regulate the process of knee osteoarthritis in mice.

A Bibliometric Analysis for Low-Intensity Ultrasound Study Over the Past Three Decades

Low-intensity ultrasound (LI-US) is a non-invasive stimulation technique that has emerged in recent years and has been shown to have positive effects on neuromodulation, fracture healing, inflammation improvement, and metabolic regulation. This study reports the conclusions of a bibliometric analysis of LI-US. Input data for the period between 1995 and 2022, including 7209 related articles in the field of LI-US, were collected from the core library of the Web of Science (WOS) database. Using these data, a set of bibliometric indicators was obtained to gain knowledge on different aspects: global production, research areas, and sources analysis, contributions of countries and institutions, author analysis, citation analysis, and keyword analysis. This study combined the data analysis capabilities provided by the WOS database, making use of two bibliometric software tools: R software and VOS viewer to achieve analysis and data exploration visualization, and predicted the further development trends of LI-US. It turns out that the United States and China are co-leaders while Zhang ZG is the most significant author in LI-US. In the future, the hot spots of LI-US will continue to focus on parameter research, mechanism discussion, safety regulations, and neuromodulation applications.

Development of a wireless ultrasonic brain stimulation system for concurrent bilateral neuromodulation in freely moving rodents

Bilateral brain stimulation is an important modality used to investigate brain circuits and treat neurological conditions. Recently, low-intensity pulsed ultrasound (LIPUS) received significant attention as a novel non-invasive neurostimulation technique with high spatial specificity. Despite the growing interest, the typical ultrasound brain stimulation study, especially for small animals, is limited to a single target of sonication. The constraint is associated with the complexity and the cost of the hardware system required to achieve multi-regional sonication. This work presented the development of a low-cost LIPUS system with a pair of single-element ultrasound transducers to address the above problem. The system was built with a multicore processor with an RF amplifier circuit. In addition, LIPUS device was incorporated with a wireless module (bluetooth low energy) and powered by a single 3.7 V battery. As a result, we achieved an ultrasound transmission with a central frequency of 380 kHz and a peak-to-peak pressure of 480 kPa from each ultrasound transducer. The developed system was further applied to anesthetized rats to investigate the difference between uni- and bilateral stimulation. A significant difference in cortical power density extracted from electroencephalogram signals was observed between uni- and bilateral LIPUS stimulation. The developed device provides an affordable solution to investigate the effects of LIPUS on functional interhemispheric connection.

A review of functional brain differences predicting relapse in substance use disorder: Actionable targets for new methods of noninvasive brain stimulation

Neuroimaging studies have identified a variety of brain regions whose activity predicts substance use (i.e., relapse) in patients with substance use disorder (SUD), suggesting that malfunctioning brain networks may exacerbate relapse. However, this knowledge has not yet led to a marked improvement in treatment outcomes. Noninvasive brain stimulation (NIBS) has shown some potential for treating SUDs, and a new generation of NIBS technologies offers the possibility of selectively altering activity in both superficial and deep brain structures implicated in SUDs. The goal of the current review was to identify deeper brain structures involved in relapse to SUD and give an account of innovative methods of NIBS that might be used to target them. Included studies measured fMRI in currently abstinent SUD patients and tracked treatment outcomes, and fMRI results were organized with the framework of the Addictions Neuroclinical Assessment (ANA). Four brain structures were consistently implicated: the anterior and posterior cingulate cortices, ventral striatum and insula. These four deeper brain structures may be appropriate future targets for the treatment of SUD using these innovative NIBS technologies.

Ultrasound Used for Diagnostic Imaging Facilitates Dendritic Branching of Developing Neurons in the Mouse Cortex

Neuronal differentiation and synaptogenesis are regulated by precise orchestration of intrinsic and extrinsic chemical and mechanical factors throughout all developmental steps critical for the assembly of neurons into functional circuits. While ultrasound is known to alter neuronal migration and activity acutely, its chronic effect on neuronal behavior or morphology is not well characterized. Furthermore, higher-frequency (3–5 MHz) ultrasound (HFU) is extensively used in gynecological practice for imaging, and while it has not been shown harmful for the developing brain, it might be associated with mild alterations that may have functional consequences. To shed light on the neurobiological effects of HFU on the developing brain, we examined cortical pyramidal cell morphology in a transgenic mouse model, following a single and short dose of high-frequency ultrasound. Layer V neurons in the retrosplenial cortex of mouse embryos were labeled with green and red fluorescent proteins by in utero electroporation at the time of their appearance (E14.5). At the time of their presumptive arrival to layer V (E18.5), HFU stimulation was performed with parameters matched to those used in human prenatal examinations. On the third postnatal day (P3), basic morphometric analyses were performed on labeled neurons reconstructed with Neurolucida. Low-intensity HFU-treated cells showed significantly increased dendritic branching compared to control (non-stimulated) neurons and showed elevated c-fos immunoreactivity. Labeled neurons were immunopositive for the mechanosensitive receptor TRPC4 at E18.5, suggesting the role of this receptor and the associated signaling pathways in the effects of HFU stimulation.

Transcranial Focused Ultrasound Neuromodulation: A Review of the Excitatory and Inhibitory Effects on Brain Activity in Human and Animals

Non-invasive neuromodulation technology is important for the treatment of brain diseases. The effects of focused ultrasound on neuronal activity have been investigated since the 1920s. Low intensity transcranial focused ultrasound (tFUS) can exert non-destructive mechanical pressure effects on cellular membranes and ion channels and has been shown to modulate the activity of peripheral nerves, spinal reflexes, the cortex, and even deep brain nuclei, such as the thalamus. It has obvious advantages in terms of security and spatial selectivity. This technology is considered to have broad application prospects in the treatment of neurodegenerative disorders and neuropsychiatric disorders. This review synthesizes animal and human research outcomes and offers an integrated description of the excitatory and inhibitory effects of tFUS in varying experimental and disease conditions.

Therapeutic Potential of Ultrasound Neuromodulation in Decreasing Neuropathic Pain: Clinical and Experimental Evidence

Background

For more than seven decades, ultrasound has been used as an imaging and diagnostic tool. Today, new technologies, such as focused ultrasound (FUS) neuromodulation, have revealed some innovative, potential applications. However, those applications have been barely studied to deal with neuropathic pain (NP), a cluster of chronic pain syndromes with a restricted response to conventional pharmaceuticals.

Objective

To analyze the therapeutic potential of low-intensity (LIFUS) and high-intensity (HIFUS) FUS for managing NP.

Methods

We performed a narrative review, including clinical and experimental ultrasound neuromodulation studies published in three main database repositories.

Discussion

Evidence shows that FUS may influence several mechanisms relevant for neuropathic pain management such as modulation of ion channels, glutamatergic neurotransmission, cerebral blood flow, inflammation and neurotoxicity, neuronal morphology and survival, nerve regeneration, and remyelination. Some experimental models have shown that LIFUS may reduce allodynia after peripheral nerve damage. At the same time, a few clinical studies support its beneficial effect on reducing pain in nerve compression syndromes. In turn, Thalamic HIFUS ablation can reduce NP from several etiologies with minor side-effects, but some neurological sequelae might be permanent. HIFUS is also useful in lowering non-neuropathic pain in several disorders.

Conclusion

Although an emerging set of studies brings new evidence on the therapeutic potential of both LIFUS and HIFUS for managing NP with minor side-effects, we need more controlled clinical trials to conclude about its safety and efficacy.

Noninvasive Ultrasound Stimulation of Ventral Tegmental Area Induces Reanimation from General Anaesthesia in Mice

Evidence in animals suggests that deep brain stimulation or optogenetics can be used for recovery from disorders of consciousness (DOC). However, these treatments require invasive procedures. This report presents a noninvasive strategy to stimulate central nervous system neurons selectively for recovery from DOC in mice. Through the delivery of ultrasound energy to the ventral tegmental area, mice were aroused from an unconscious, anaesthetized state in this study, and this process was controlled by adjusting the ultrasound parameters. The mice in the sham group under isoflurane-induced, continuous, steady-state general anaesthesia did not regain their righting reflex. On insonation, the emergence time from inhaled isoflurane anaesthesia decreased (sham: 13.63 ± 0.53 min, ultrasound: 1.5 ± 0.19 min, p < 0.001). Further, the induction time (sham: 12.0 ± 0.6 min, ultrasound: 17.88 ± 0.64 min, p < 0.001) and the concentration for 50% of the maximal effect (EC50) of isoflurane (sham: 0.6%, ultrasound: 0.7%) increased. In addition, ultrasound stimulation reduced the recovery time in mice with traumatic brain injury (sham: 30.38 ± 1.9 min, ultrasound: 7.38 ± 1.02 min, p < 0.01). This noninvasive strategy could be used on demand to promote emergence from DOC and may be a potential treatment for such disorders.

Transcranial Low-Intensity Pulsed Ultrasound Stimulation Induces Neuronal Autophagy

Autophagy, or cellular self-digestion, is an essential process for eliminating abnormal protein in mammalian cells. Accumulating evidence indicates that increased neuronal autophagy has a protective effect on neurodegenerative disorders. It has been reported that low-intensity pulsed ultrasound (LIPUS) can noninvasively modulate neural activity in the brain. Yet, the effect of LIPUS on neuronal autophagy is still unclear. The objective of this study was to examine whether LIPUS stimulation could induce neuronal autophagy. Primary neurons were treated by LIPUS with a frequency of 0.68 MHz, a pulse repetition frequency (PRF) of 500 Hz, a spatial peak temporal-average intensities ( [Formula: see text]) of 70 and 165 mW/cm². Then, the immunofluorescent analysis of LC3B was carried out for evaluating neuronal autophagy. Furthermore, 0.5-MHz LIPUS was noninvasively delivered to the cortex and hippocampus of adult mice ( n = 16 ) with PRF of 500 Hz and [Formula: see text] of 235 mW/cm². The LC3BII/LC3BI ratio and p62 (autophagic markers) were measured by western blot analysis. In the in vitro study, the expression of LC3B in primary neurons was statistically improved after LIPUS stimulation was implemented for 4 h ( ). With the increase in the irradiation duration or acoustic intensity of LIPUS stimulation, the expression of LC3B in primary neurons was increased. Furthermore, transcranial LIPUS stimulation increased the LC3BII/LC3BI ratio ( ) and decreased the expression of p62 ( ) in the cortex and hippocampus. We concluded that LIPUS provides a safe and capable tool for activating neuronal autophagy in vitro and in vivo.

Ultrasound Stimulation of Periaqueductal Gray Induces Defensive Behaviors

Low-intensity focused ultrasound stimulation (LIFUS) has the potential to noninvasively penetrate the intact skull and to modulate neural activity in the cortex and deep brain nuclei. The midbrain periaqueductal gray (PAG) is associated with the generation of defensive behaviors. The aim of this study was to examine whether LIFUS of the PAG induced defensive behaviors in mice. A 3.8-MHz head-mounted ultrasound transducer with a small focus size (0.5 mm × 0.5 mm) was fabricated in house to precisely stimulate the free-moving mice. The corresponding behaviors were recorded in real time. Avoidance, flight, and freezing were used to assess ultrasound-induced defensive responses. The safety of LIFUS was examined via hematoxylin and eosin (H&E) staining and Nissl staining. Ultrasound stimulation of the PAG induced multiple defensive behaviors, including location-specific passive avoidance behavior, flight, and freezing. In addition, H&E and Nissl staining verified that LIFUS did not cause any injury to the brain tissue. These findings demonstrate that LIFUS may have neuromodulatory effects on the innate defensive behaviors in mice. LIFUS may be used as a novel neuromodulatory tool for the treatment of psychological diseases associated with defensive behaviors.

Noninvasive Ultrasound Deep Brain Stimulation for the Treatment of Parkinson's Disease Model Mouse

Modulating basal ganglia circuitry is of great significance in the improvement of motor function in Parkinson's disease (PD). Here, for the first time, we demonstrate that noninvasive ultrasound deep brain stimulation (UDBS) of the subthalamic nucleus (STN) or the globus pallidus (GP) improves motor behavior in a subacute mouse model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Immunohistochemical c-Fos protein expression confirms that there is a relatively high level of c-Fos expression in the STN-UDBS and GP-UDBS group compared with sham group (both p < 0.05). Furthermore, STN-UDBS or GP-UDBS significantly increases the latency to fall in the rotarod test on day 9 (p < 0.05) and decreases the time spent climbing down a vertical rod in the pole test on day 12 (p < 0.05). Moreover, our results reveal that STN-UDBS or GP-UDBS protects the dopamine (DA) neurons from MPTP neurotoxicity by downregulating Bax (p < 0.001), upregulating Bcl-2 (p < 0.01), blocking cytochrome c (Cyt C) release from mitochondria (p < 0.05), and reducing cleaved-caspase 3 activity (p < 0.01) in the ipsilateral substantia nigra (SN). Additionally, the safety of ultrasound stimulation is characterized by hematoxylin and eosin (HE) and Nissl staining; no hemorrhage or tissue damage is detected. These data demonstrate that UDBS enables modulation of STN or GP neural activity and leads to neuroprotection in PD mice, potentially serving as a noninvasive strategy for the clinical treatment of PD.