2D spatiotemporal passive cavitation imaging and evaluation during ultrasound thrombolysis based on diagnostic ultrasound platform.

Acoustic cavitation plays a critical role in various biomedical applications. However, uncontrolled cavitation can lead to undesired damage to healthy tissues. Therefore, real-time monitoring and quantitative evaluation of cavitation dynamics is essential for understanding underlying mechanisms and optimizing ultrasound treatment efficiency and safety. The current research addressed the limitations of traditionally used cavitation detection methods by developing introduced an adaptive time-division multiplexing passive cavitation imaging (PCI) system integrated into a commercial diagnostic ultrasound platform. This new method combined real-time cavitation monitoring with B-mode imaging, allowing for simultaneous visualization of treatment progress and 2D quantitative evaluation of cavitation dosage within targeted area. An improved delay-and-sum (DAS) algorithm, optimized with a minimum variance (MV) beamformer, is utilized to minimize the side lobe effect and improve the axial resolution typically associated with PCI. In additional to visualize and quantitatively assess the cavitation activities generated under varied acoustic pressures and microbubble concentrations, this system was specifically applied to perform 2D cavitation evaluation for ultrasound thrombolysis mediated by different solutions, e.g., saline, nanodiamond (ND) and nitrogen-annealed nanodiamond (N-AND). This research aims to bridge the gap between laboratory-based research systems and real-time spatiotemporal cavitation evaluation demands in practical uses. Results indicate that this improved 2D cavitation monitoring and evaluation system could offer a useful tool for comprehensive evaluating cavitation-mediated effects (e.g., ultrasound thrombolysis), providing valuable insights into in-depth understanding of cavitation mechanisms and optimization of cavitation applications.

Erratum to: Low-intensity pulsed ultrasound ameliorates angiotensin II-induced cardiac fibrosis by alleviating inflammation via a caveolin-1-dependent pathway.

The original version of this article (Zhao et al., 2021) unfortunately contained two mistakes.

Real-time passive cavitation mapping and B-mode fusion imaging via hybrid adaptive beamformer with modified diagnostic ultrasound platform.

The implementation of real-time, convenient and high-resolution passive cavitation imaging (PCM) is crucial for ensuring the safety and effectiveness of ultrasound applications related to cavitation effects. However, the current B-mode ultrasound imaging system cannot achieve these functions. By developing a hybrid adaptive beamforming algorithm, the current work presented a real-time PCM and B-mode fusion imaging technique, using a modified diagnostic ultrasound platform enabling time-division multiplexing external triggering function. The proposed hybrid adaptive beamformer combined the advantages of delay-multiply-and-sum (DMAS) and minimum variance (MV) methods to effectively suppress the side lobe and tail-like artifacts, improving the resolution of PCM images. A high-pass filter was applied to selectively detect cavitation-specific signals while removing the interference from the tissue scatters. The system enabled synchronous visualization of tissue structure and cavitation activity under ultrasound exposure. Both numerical and experimental studies demonstrated that, compared with DAS, MV-DAS and DMAS methods, the proposed MV-DMAS algorithm performed better in both axial and lateral resolutions. This work represented a significant advancement in achieving high-quality real-time B-mode and PCM fusion imaging utilizing commercial medical ultrasound system, providing a powerful tool for synchronous monitoring and manipulating cavitation activity, which would enhance the safety and efficacy of cavitation-based applications.

A lung disease diagnosis algorithm based on 2D spectral features of ultrasound RF signals.

Lung diseases are commonly diagnosed based on clinical pathological indications criteria and radiological imaging tools (e.g., X-rays and CT). During a pandemic like COVID-19, the use of ultrasound imaging devices has broadened for emergency examinations by taking their unique advantages such as portability, real-time detection, easy operation and no radiation. This provides a rapid, safe, and cost-effective imaging modality for screening lung diseases. However, the current pulmonary ultrasound diagnosis mainly relies on the subjective assessments of sonographers, which has high requirements for the operator's professional ability and clinical experience. In this study, we proposed an objective and quantifiable algorithm for the diagnosis of lung diseases that utilizes two-dimensional (2D) spectral features of ultrasound radiofrequency (RF) signals. The ultrasound data samples consisted of a set of RF signal frames, which were collected by professional sonographers. In each case, a region of interest of uniform size was delineated along the pleural line. The standard deviation curve of the 2D spatial spectrum was calculated and smoothed. A linear fit was applied to the high-frequency segment of the processed data curve, and the slope of the fitted line was defined as the frequency spectrum standard deviation slope (FSSDS). Based on the current data, the method exhibited a superior diagnostic sensitivity of 98% and an accuracy of 91% for the identification of lung diseases. The area under the curve obtained by the current method exceeded the results obtained that interpreted by professional sonographers, which indicated that the current method could provide strong support for the clinical ultrasound diagnosis of lung diseases.

Improved assessment sensitivity of time-varying cavitation events based on wavelet analysis.

Ultrasonic cavitation, characterized by the oscillation or abrupt collapse of cavitation nuclei in response to ultrasound stimulation, plays a significant role in various applications within both industrial and biomedical sectors. In particular, inertial cavitation (IC) has garnered considerable attention due to the resulting mechanical, chemical, and thermal effects. Passive cavitation detection (PCD) has emerged as a valuable technique for monitoring this procedure. While the fast Fourier transform (FFT) is a widely used algorithm to analyze IC-induced broadband noise detected by PCD system, it may not adequately capture the time-varying instability of cavitation due to potential nuclei collapse during ultrasound irradiation. In contrast, the continuous wavelet transform offers a more flexible approach, enabling more sensitive analysis of signals with varying frequencies over time. In this study, nanodiamond (ND) and its derivative, nitro-doped nanodiamond (N-AND), known to possess cavitation potential from previous research, were chosen as the source of cavitation nuclei. The cavitation signals detected by PCD were subjected to both FFT and wavelet analyses, with their results comprehensively compared. This research showcased the feasibility of employing wavelet analysis for effective inertial cavitation evaluation. It provided the advantage of monitoring the temporal evolution of cavitation events in real-time, enhancing sensitivity to weak and unstable cavitation signals, especially those in higher order components (3rd and 4th order). Additionally, it yielded a higher level of precision in determining IC thresholds and doses. Furthermore, the inclusion of time information through wavelet analysis offered insights into the limitations of low-cycle ultrasound in inducing IC. This study introduces a novel perspective for more sensitive and precise cavitation assessment, leveraging time and frequency data from wavelet analysis, and holds promise for effective utilization of cavitation effects while minimizing losses and damages resulting from unintended cavitation events.

Enhanced thrombolytic effect induced by acoustic cavitation generated from nitrogen-doped annealed nanodiamond particles.

In biomedical research, ultrasonic cavitation, especially inertial cavitation (IC) has attracted extensive attentions due to its ability to induce mechanical, chemical and thermal effects. Like ultrasound contrast agent (UCA) microbubbles or droplets, acoustic cavitation can be effectively triggered beyond a certain pressure threshold through the interaction between ultrasound and nucleation particles, leading to an enhanced thrombolytic effect. As a newly developed nanocarbon material, nitrogen-doped annealed nanodiamond (N-AND) has shown promising catalytic performance. To further explore its effects on ultrasonic cavitation, N-AND was synthesized at the temperature of 1000 °C. After systematic material characterization, the potential of N-AND to induce enhanced IC activity was assessed for the first time by using passive cavitation detection (PCD). Based on experiments performed at varied material suspension concentration and cycle number, N-AND demonstrated a strong capability to generate significant cavitation characteristics, indicating the formation of stable bubbles from the surface of the materials. Furthermore, N-AND was applied in the in vitro thrombolysis experiments to verify its contribution to ultrasound thrombolysis. The influence of surface hydrophobicity on the cavitation potentials of ND and N-AND was innovatively discussed in combination with the theory of mote-induced nucleation. It is found that the cavitation stability of N-AND was better than that of the commercial UCA microbubbles. This study would provide better understanding of the potential of novel carbonous nanomaterials as cavitation nuclei and is expected to provide guidance for their future biomedical and industrial applications.

Ultrasonic Imaging Based on Pulsed Airy Beams.

In ultrasonic imaging, high impedance obstacles in tissues may lead to artifacts behind them, making the examination of the target area difficult. Acoustical Airy beams possess the characteristics of self-bending and self-healing within a specific range. They are limited-diffracting when generated from finite aperture sources and are expected to have great potential in medical imaging and therapy. In this article, pulsed Airy (pAiry) beams are employed for ultrasonic imaging at megahertz frequency, and the protocol is demonstrated via both simulations and experiments. First, the generation of pAiry beams using a linear array is simulated, and the pulsed beams inherit some characteristics of continuous wave Airy beams, such as propagating along curved paths and self-healing. In experiments where obstacles are present at the beam paths, the image quality in pAiry-based imaging is superior to that in classical iso-depth imaging. The results demonstrate the feasibility and benefits of ultrasonic imaging based on pAiry beams and provide an important basis for developing imaging techniques employing nondiffracting acoustic beams.

In Vivo Multithread Ultrasound Thermal Strain Imaging.

While thermal therapy is increasingly applied in clinics, real-time temperature monitoring in the target tissue can facilitate improvements in the planning, controlling, and evaluating of therapeutic procedures. Thermal strain imaging (TSI), based on tracking the echo shifts in ultrasound images, has great potential for temperature estimation as is demonstrated in vitro. However, due to physiological motion-induced artifacts and estimation errors, employing TSI for in vivo thermometry is still challenging. Building on our earlier development of respiration-separated TSI (RS-TSI), a multithread TSI (MT-TSI) approach is proposed as the first part of a bigger plan. A flag image frame is first identified by analyzing the correlation between ultrasound images. Then, the quasi-periodic phase profile of respiration is determined and split into multiple parallelly distributed periodical subranges. Multiple threads of independent TSI calculations are thus established, with image matching, motion compensation, and thermal strain estimation performed in each thread. Finally, after applying temporal extrapolation, spatial alignment, and interthread noise suppression, the TSI results obtained in different threads are averaged to obtain the merged output. In microwave (MW) heating experiments targeting porcine perirenal fat, the thermometry accuracy of MT-TSI is comparable to that of RS-TSI, while the former exhibits lower noise and higher temporal density.

Intensified and controllable vaporization of phase-changeable nanodroplets induced by simultaneous exposure of laser and ultrasound.

Phase-changeable contrast agents have been proposed as a next-generation ultrasound contrast agent over conventional microbubbles given its stability, longer circulation time and ability to extravasate. Safe vaporization of nanodroplets (NDs) plays an essential role in the practical translation of ND applications in industry and medical therapy. In particular, the exposure parameters for initializing phase change as well as the site of phase change are concerned to be controlled. Compared to the traditional optical vaporization or acoustic droplet vaporization, this study exhibited the potential of using simultaneous, single burst laser and ultrasound incidence as a means of activating phase change of NDs to generate cavitation nuclei with reduced fluence and sound pressure. A theoretical model considering the laser heating, vapor cavity nucleation and growth was established, where qualitative agreement with experiment findings were found in terms of the trend of combined exposure parameters in order to achieve the same level of vaporization outcome. The results indicate that using single burst laser pulse and 10-cycle ultrasound might be sufficient to lower the exposure levels under FDA limit for laser skin exposure and ultrasound imaging. The combination of laser and ultrasound also provides temporal and spatial control of ND vaporization and cavitation nucleation without altering the sound field, which is beneficial for further safe and effective applications of phase-changeable NDs in medical, environmental, food processing and other industrial areas.

Ultrasound-driven exercise training ameliorates degeneration of ultrasonic responses in Caenorhabditis elegans.

The inevitability of age-related degeneration makes research on degradation mitigation attractive to humans, while exercise is considered an effective means due to its powerful impact on life and health. Caenorhabditis elegans is a model animal with a short life cycle and is widely used in health and aging studies. In this work, ultrasonic stimuli in the form of surface acoustic waves (SAWs) were used to induce behavioral activities in worms. As the worms grew, ultrasound-elicited behavioral responses started to decrease in the early adulthood stage. However, this situation was significantly ameliorated when ultrasonic training sessions at an effective acoustic pressure of 1.1 MPa were performed four times per day for 5 or 7 days, while ultrasonic responses in trained nematodes were stronger than those in untrained ones. These results suggest that long-term ultrasonic training might positively intervene in aging-related degeneration. Besides, it was found that exercise driven by long-term ultrasonic training had insignificant effects on the lifespan of worms. A preliminary exploration of the neural mechanisms underlying the sensation of SAWs was also conducted. The results show that, apart from touch receptor neurons (TRNs), polymodal nociceptors FLP and PVD neurons may also be involved in the perception of ultrasound in C. elegans. The results of this study may inspire related studies on other animals or humans.

C. elegans: Sensing the low-frequency profile of amplitude-modulated ultrasound.

Several research groups have demonstrated that C. elegans can respond to pulsed ultrasound stimuli, and elucidating the underlying mechanisms is necessary to develop ultrasound neuromodulation. Here, amplitude-modulated (AM) ultrasound is applied to C. elegans, and its behavioral responses are investigated in detail. By loading surface acoustic waves (SAWs) onto free-moving worms on an agar surface, a carrier wave with a frequency of 8.80 MHz is selected. The signal is modulated by a rectangular or sinusoidal profile. It is demonstrated that sinusoidal modulation can produce similar responses in worms to rectangular modulation, with the strongest responses occurring at modulation frequencies of around 1.00 kHz. Meanwhile, the behavioral response is relatively weak when the ultrasonic signal is unmodulated, that is, when only the carrier wave is applied. At modulation frequencies other than 100.00 Hz to 10.00 kHz, the worms respond weakly, but when a second modulation frequency of 1.00 kHz is introduced, an improvement in response can be observed. These results suggest that C. elegans may sense the low-frequency envelope and respond to amplitude-modulated ultrasonic stimuli like an amplitude demodulator. MEC-4, an ion channel for touch sensing, is involved in the behavioral response of C. elegans to ultrasound in the present setup.

Optimized acoustic streaming generated at oblique incident angles to improve ultrasound thrombolysis effect.

BACKGROUND: Combined with thrombolytic drugs and/or microbubbles, ultrasound (US) has been regarded as a useful tool for thrombolysis treatment by taking its advantages of noninvasive, non-ionization, low cost, and accurate targeting of tissues deep in body. Recently, low-intensity pulsed US, which can cause fewer complications by stable cavitation and acoustic streaming other than more violent effects, has attracted broad attention. PURPOSE: However, the thrombolysis effect in practice might not achieve expectation because there is not an ideal parallel multilayered structure between the skin and the targeted vessel. Therefore, the current work aims to better elucidate the influence of US incident angle on the generation of acoustic streaming and thrombolysis effect. METHODS: Systemic numerical and experimental studies, namely, finite element modeling (FEM), particle image velocimetry (PIV), and in vitro thrombolysis measurements, were performed to estimate the acoustical/streaming field pattern, maximum flow velocity, and shear stress on the surface of thrombus, as well as the lysis rate generated at different conditions. These methods aim at verifying the hypothesis that streaming-induced vortices can further accelerate the dissolution of the thrombus and optimized thrombolysis effected can be achieved by adjusting US incident angles. RESULTS: The pool data results showed that the variation trends of the flow velocity and shear stress obtained from FEM simulation and PIV experiments are qualitatively consistent with each other. There exists an optimal incident angle that can maximize the flow velocity and shear stress on the surface of thrombus, so that superior stirring and mixing effect can be generated. Furthermore, as the flow velocity and shear stress on thrombus surface are both highly correlated with the thrombolysis effect (the correlation coefficient R1 = 0.988, R2 = 0.958, respectively), the peak value of lysis rate (increase by at least 5.02%) also occurred at 10°. CONCLUSIONS: The current results demonstrated that, with appropriately determined incident angle, higher thrombolysis rate could be achieved without increasing the driving pressure. It may shed the light on future US thrombolysis planning strategy that, if combined with other advanced technologies (e.g., machine-learning-based image analysis and image-guided adaptive US emission modulation), more efficient thrombolytic effect could be realized while minimizing undesired side-effects caused by excessively high pressure.

Optimization of a random linear ultrasonic therapeutic array based on a genetic algorithm.

Given their advantage of suppressing grating lobes, randomly arranged linear arrays have potential for use in ultrasonic treatment. The current work proposes a method based on genetic algorithm to optimize the random arrangement of array elements, so that the suppression effect of grating lobes can be significantly improved with reduced calculating time. The maximum and average kerfs of array elements are used as genes, and the ratio of the maximum to the secondary maximum sound pressure at the focal plane is used as the optimized target. Typically, the calculation requirements of the current method can be reduced to ∼ 25% of the traversing method. We further discuss how the kerf width, the effective ratio of element areas and the ratio of focal distance to array aperture affect the suppression of grating lobes. For a typical linear array with 32 elements (1-MHz operating frequency, 1.5-mm element width and 150-mm focal distance), the results suggest that the grating lobes are suppressed well when (1) the ratio of maximum width to average width of the element is between 5 and 8, (2) the ratio of the effective element area to the area of the whole array is between 0.5 and 0.9, and (3) the ratio of the effective emission aperture to the actual emission aperture of the array is as large as possible. Based on optimized parameters, an experimental array was fabricated and the measured results of corresponding sound field were entirely consistent with the simulated results (Given her role as an Associate Editor of this journal, Juan Tu had no involvement in the peer-review of articles for which she was an author and had no access to information regarding the peer-review. Full responsibility for the peer-review process for this article was delegated to another Editor of this journal.).

Separated Respiratory Phases for In Vivo Ultrasonic Thermal Strain Imaging.

Thermal strain imaging (TSI) uses echo shifts in ultrasonic B-scan images to estimate changes in temperature which is of great values for thermotherapies. However, for in vivo applications, it is difficult to overcome the artifacts and errors arising from physiological motions. Here, a respiration separated TSI (RS-TSI) method is proposed, which can be considered as carrying out TSI in each of the exhalation and inhalation phases and then combining the results. Normalized cross correlation (NXcorr) coefficient between RF images along the timeline are used to extract the respiratory frequency, after which reference frames are selected to identify the exhalation and inhalation phases, and the two phases are divided quasi-periodically. RF images belonging to both phases are selected by applying NXcorr thresholds, and motion compensation together with a second frame selection helps to obtain two finely matched image sequences. After TSI calculations for each phase, the two processes are merged into one through extrapolation and interphase averaging. Compared to TSI based on dynamic frame selection (DFS), RS-TSI ensures that frames are selected during both the exhalation and inhalation phases while setting the frame selection range according to the respiratory frequency helps to improve motion compensation. The temporal intervals of TSI output are approximately half that employing DFS.

Non-Invasive Local Acoustic Therapy Ameliorates Diabetic Heart Fibrosis by Suppressing ACE-Mediated Oxidative Stress and Inflammation in Cardiac Fibroblasts.

PURPOSE: The extent of myocardial fibrosis is closely related to the prognosis of diabetic cardiomyopathy (DCM). Low-intensity pulsed ultrasound (LIPUS) has been reported to have multiple biological effects. However, the effect of LIPUS on diabetic heart fibrosis remains unclear. The present study aimed to investigate the effect of LIPUS on diabetic heart fibrosis and explore its underlying mechanisms. METHODS AND RESULTS: High glucose (HG) was applied to cultured neonatal rat cardiac fibroblasts (NRCFs) to mimic the in vivo hyperglycemia microenvironment. LIPUS (19.30 mW/cm2 to 77.20 mW/cm2) dose-dependently inhibited HG-induced fibrotic response in NRCFs. Also, LIPUS downregulated NADPH oxidase 4 (NOX4)-associated oxidative stress and nod-like receptor protein-3 (NLRP3) inflammasome activation in NRCFs. In vivo, diabetes in mice was induced with streptozotocin (STZ). Mice in the LIPUS group and STZ + LIPUS group were treated with LIPUS (77.20 mW/cm2) twice a week for 12 weeks and then euthanized at 12 weeks or 24 weeks post-diabetes. Treatment with LIPUS significantly ameliorated the progression of cardiac fibrosis (Masson staining 6.5 ± 2.3% vs. 2.8 ± 1.5%, P < 0.001) and dysfunction (E/A ratio 1.35 ± 0.14 vs. 1.59 ± 0.11, P < 0.05), as well as NOX4-associated oxidative stress (relative expression fold of NOX4 1.43 ± 0.12 vs. 1.07 ± 0.10, P < 0.01; relative DHE fluorescence 1.51 ± 0.13 vs. 1.28 ± 0.06, P < 0.05) and NLRP3 inflammasome activation (relative expression fold of NLRP3 1.57 ± 0.12 vs. 1.05 ± 0.16, P < 0.01), at 12 weeks post-diabetes. At 24 weeks post-diabetes, the heart function in diabetic mice treated with LIPUS was still significantly better than untreated diabetic mice (E/A ratio 1.08 ± 0.12 vs. 1.49 ± 0.14, P < 0.001). Further exploration revealed that LIPUS significantly attenuated the upregulated angiotensin-converting enzyme (ACE) and angiotensin II (AngII), in both HG-induced NRCFs and diabetic hearts (relative expression of ACE in myocardium 3.77 ± 0.55 vs. 1.07 ± 0.13, P < 0.001; AngII in myocardium 115.5 ± 21.77 ng/ml vs. 84.28 ± 9.03 ng/ml, P < 0.01). Captopril, an ACE inhibitor, inhibited NOX4-associated oxidative stress and NLRP3 inflammasome activation in both HG-induced NRCFs and diabetic hearts. CONCLUSION: Our results indicate that non-invasive local LIPUS therapy attenuated heart fibrosis and dysfunction in diabetic mice and the effect could be largely preserved at least 12 weeks after suspending LIPUS stimulation. LIPUS ameliorated diabetic heart fibrosis by inhibiting ACE-mediated NOX4-associated oxidative stress and NLRP3 inflammasome activation in cardiac fibroblasts. Our study may provide a novel therapeutic approach to hamper the progression of diabetic heart fibrosis.

Low-intensity pulsed ultrasound ameliorates angiotensin II-induced cardiac fibrosis by alleviating inflammation via a caveolin-1-dependent pathway.

OBJECTIVES: Cardiac hypertrophy and fibrosis are major pathological manifestations observed in left ventricular remodeling induced by angiotensin II (AngII). Low-intensity pulsed ultrasound (LIPUS) has been reported to ameliorate cardiac dysfunction and myocardial fibrosis in myocardial infarction (MI) through mechano-transduction and its downstream pathways. In this study, we aimed to investigate whether LIPUS could exert a protective effect by ameliorating AngII-induced cardiac hypertrophy and fibrosis and if so, to further elucidate the underlying molecular mechanisms. METHODS: We used AngII to mimic animal and cell culture models of cardiac hypertrophy and fibrosis. LIPUS irradiation was applied in vivo for 20 min every 2 d from one week before mini-pump implantation to four weeks after mini-pump implantation, and in vitro for 20 min on each of two occasions 6 h apart. Cardiac hypertrophy and fibrosis levels were then evaluated by echocardiographic, histopathological, and molecular biological methods. RESULTS: Our results showed that LIPUS could ameliorate left ventricular remodeling in vivo and cardiac fibrosis in vitro by reducing AngII-induced release of inflammatory cytokines, but the protective effects on cardiac hypertrophy were limited in vitro. Given that LIPUS increased the expression of caveolin-1 in response to mechanical stimulation, we inhibited caveolin-1 activity with pyrazolopyrimidine 2 (pp2) in vivo and in vitro. LIPUS-induced downregulation of inflammation was reversed and the anti-fibrotic effects of LIPUS were absent. CONCLUSIONS: These results indicated that LIPUS could ameliorate AngII-induced cardiac fibrosis by alleviating inflammation via a caveolin-1-dependent pathway, providing new insights for the development of novel therapeutic apparatus in clinical practice.

Cavitation-facilitated transmembrane permeability enhancement induced by acoustically vaporized nanodroplets.

Ultrasound-facilitated transmembrane permeability enhancement has attracted broad attention in the treatment of central nervous system (CNS) diseases, by delivering gene/drugs into the deep site of brain tissues with a safer and more effective way. Although the feasibility of using acoustically vaporized nanodroplets to open the blood-brain-barrier (BBB) has previously been reported, the relevant physical mechanisms and impact factors are not well known. In the current study, a nitrocellulose (NC) membrane was used to mimic the multi-layered pore structure of BBB. The cavitation activity and the penetration ability of phase-changed nanodroplets were systemically evaluated at different concentration levels, and compared with the results obtained for SonoVue microbubbles. Passive cavitation detection showed that less intensified but more sustained inertial cavitation (IC) activity would be generated by vaporized nanodroplets than microbubbles. As the results, with a sufficiently high concentration (∼5 × 108/mL), phase-changed nanodroplets were more effective than microbubbles in enabling a fluorescent tracer agent (FITC, 150 kDa) to penetrate deeper and more homogeneously through the NC membrane, and a positive correlation was observed between accumulated IC dose and the amount of penetrated FITC. In vivo studies further confirmed acoustically vaporized nanodroplets performed better than microbubbles by opening the BBB in rats' brains. These results indicated that phase-changed nanodroplets can be used as a safe, efficient and durable agent to achieve satisfactory cavitation-mediated permeability enhancement effect in biomedical applications.

Low-intensity pulsed ultrasound prevents angiotensin II-induced aortic smooth muscle cell phenotypic switch via hampering miR-17-5p and enhancing PPAR-γ.

Vascular events can trigger a pathological phenotypic switch in vascular smooth muscle cells (VSMCs), decreasing and disrupting the plasticity and diversity of vascular networks. The development of novel therapeutic approaches is necessary to prevent these changes. We aimed to investigate the effects and associated mechanisms of low-intensity pulsed ultrasound (LIPUS) irradiation on the angiotensin II (AngII)-induced phenotypic switch in VSMCs. In vivo, AngII was infused subcutaneously for 4 weeks to stimulate vascular remodeling in mice, and LIPUS irradiation was applied for 20 min every 2 days for 4 weeks. In vitro, cultured rat aortic VSMCs (RAVSMCs) were pretreated once with LIPUS irradiation for 20 min before 48-h AngII stimulation. Our results showed that LIPUS irradiation prevents AngII-induced vascular remodeling of the whole wall artery without discriminating between adventitia and media in vivo and RAVSMC phenotypic switching in vitro. LIPUS irradiation downregulated miR-17-5p expression and upregulated peroxisome proliferator-activated receptor gamma (PPAR-γ) expression. The PPAR-γ activator rosiglitazone could mimic the favorable effects of LIPUS irradiation on AngII-treated RAVSMCs. In contrast, GW9662 could impede the LIPUS-mediated downregulation of RAVSMC proliferation and inflammation under AngII stimulation conditions in vivo and in vitro. Also, the miR-17-5p agomir has the same effects as GW9662 in vitro. Besides, the inhibitory effects of GW9662 against the anti-remodeling effects of LIPUS irradiation in AngII-induced RAVSMCs could be blocked by pretreatment with the miR-17-5p antagomir. Overall, LIPUS irradiation prevents AngII-induced RAVSMCs phenotypic switching through hampering miR-17-5p and enhancing PPAR-γ, suggesting a new approach for the treatment of vascular disorders.

Low-intensity pulsed ultrasound prevents prolonged hypoxia-induced cardiac fibrosis through HIF-1α/DNMT3a pathway via a TRAAK-dependent manner.

Hypoxia-induced cardiac fibrosis is an important pathological process in cardiovascular disorders. This study aimed to determine whether low-intensity pulsed ultrasound (LIPUS), a novel and safe apparatus, could alleviate hypoxia-induced cardiac fibrosis, and to elucidate the underlying mechanisms. Hypoxia (1% O2 ) and transverse aortic constriction (TAC) were performed on neonatal rat cardiac fibroblasts and mice to induce cardiac fibrosis, respectively. LIPUS irradiation was applied for 20 minutes every 6 hours for a total of 2 times in vitro, and every 2 days from 1 week before surgery to 4 weeks after surgery in vivo. We found that LIPUS dose-dependently attenuated hypoxia-induced cardiac fibroblast phenotypic conversion in vitro, and ameliorated TAC-induced cardiac fibrosis in vivo. Hypoxia significantly upregulated the nuclear protein expression of hypoxia-inducible factor-1α (HIF-1α) and DNA methyltransferase 3a (DNMT3a). LIPUS pre-treatment reversed the elevated expression of HIF-1α, and DNMT3a. Further experiments revealed that HIF-1α stabilizer dimethyloxalylglycine (DMOG) hindered the anti-fibrotic effect of LIPUS, and hampered LIPUS-mediated downregulation of DNMT3a. DNMT3a small interfering RNA (siRNA) prevented hypoxia-induced cardiac fibrosis. Results also showed that the mechanosensitive protein-TWIK-related arachidonic acid-activated K+ channel (TRAAK) messenger RNA (mRNA) expression was downregulated in hypoxia-induced cardiac fibroblasts, and TAC-induced hearts. TRAAK siRNA impeded LIPUS-mediated anti-fibrotic effect and downregulation of HIF-1α and DNMT3a. Above results indicated that LIPUS could prevent prolonged hypoxia-induced cardiac fibrosis through TRAAK-mediated HIF-1α/DNMT3a signalling pathway.