The effects of LIPUS on soft-tissue healing: a review of literature

Highly controlled and usable system for Low-Intensity Pulsed Ultrasound Stimulation of Cells

This work aims to describe the design and development of an in vitro highly controlled ultrasonic stimulation system able to guarantee, at the same time, high usability and full sterility of the tested samples. After creating the first prototype of an ultrasound-transparent three-chambers culture well, sealing tests were conducted to prove its impermeability to external contaminants and in vitro tests were carried out to verify the usability of this system for ultrasonic stimulation of cells in vitro. No statistically significant differences were found between control and tested samples during sealing tests, thus demonstrating optimal sealing ability towards external contaminants. Furthermore, the thin polystyrene membrane used to guarantee US-transparency guaranteed a good adhesion and viability of both human fibroblasts and induced pluripotent stem cells.

Low-Intensity Pulsed Ultrasound Prevents Development of Bisphosphonate-Related Osteonecrosis of the Jaw-Like Pathophysiology in a Rat Model

We developed a rat model of bisphosphonate-related osteonecrosis of the jaw (BRONJ) by removing a maxillary molar tooth (M1) from ovariectomized rats after treatment with alendronate. To mimic periodontitis, some of the rats were administered Porphyromonas gingivalis (p. gingivalis) at the M1 site every 2 to 3 d for 2 wk. Rats pretreated with alendronate plus p. gingivalis showed delayed healing of socket epithelia, periosteal reaction of alveolar bone formation and lower bone mineral density in the alveolus above adjacent M2 teeth. These abnormalities were prevented by tooth socket exposure to 20 min/d low-intensity pulsed ultrasound (LIPUS), which restored diminished expression of RANKL, Bcl-2, IL-6, Hsp70, NF-κB and TNF-α messenger ribonucleic acids in remote bone marrow, suggesting LIPUS prevented development of BRONJ-like pathophysiology in rat by inducing systemic responses for regeneration, in addition to accelerating local healing. Non-invasive treatment by LIPUS, as well as low-level laser therapy, may be useful for medication-related osteonecrosis of the jaw patients.

Regulation of exosomes secretion by low-intensity pulsed ultrasound in lung cancer cells

Low-intensity pulsed ultrasound (LIPUS) is a noninvasive therapeutic method which gradually being used in clinic including cancers. Exosomes mediate intercellular communication functions in disease development and the potential clinical applications in diagnosis and therapy. However, few studies have discussed the relationship between LIPUS and exosomes. Herein, we show that low intensity (0.6-2.1 W/cm² or 0.6-3.4 W/cm²) LIPUS promoted exosomes secretion whereas higher intensity (3.4-5.0 W/cm² or 5.0 W/cm²) LIPUS inhibited exosomes secretion, and this phenomenon is associated with autophagy. Pretreatment with 3-MA or down-regulation of LC3 potentiated low intensity LIPUS's promotion of exosomes secretion and conferred resistance to higher intensity LIPUS's effects on exosomes secretion. Furthermore, pretreatment with PP242 attenuated LIPUS-influenced exosomes secretion while expression of constitutively active Akt (Ad-myr-Akt) elevated LIPUS-influenced exosomes secretion, implying mTOR-dependent mechanism involved. The findings indicate that LIPUS influences exosomes secretion by targeting mTOR-mediated LC3 signaling in SPC-A1 and SPC-A1-BM cells. Our data provided initial evidence to connect LIPUS and secretion of exosomes, and highlight that LIPUS may be exploited in exosome-related diseases.

Action of Ultrasound Therapy in Altering Motor Nerve Conduction Velocity of Ulnar Nerve

Ultrasound therapy is one of the commonest and most popular modality used for tissue healing, pain reduction, tissue extensibility and in inflammation by physiotherapists all around the globe. Various sensitivity tests on peripheral nerves are done with ultrasound therapy, yet conclusions are still skeptical, which makes it inconclusive in progressing the modality further into management of nerve disorders. This study aimed to analyze efficiency of therapeutic ultrasound in influencing ulnar nerve conduction velocity. To Analyze the effect of ultrasound therapy in altering motor nerve conduction velocity of ulnar nerve with two therapeutic frequencies. 40 healthy individuals were included according to the selection criteria and they were explained about safety and simplicity of procedure and informed consent was obtained. All the participants were randomly assigned into two groups as 20 in each group. Group-A was given ultrasound therapy at specific site of elbow to target the ulnar nerve with 1MHz frequency and Group–B followed the same procedure with 3MHz frequency. Pre and Post to ultrasound therapy application Motor Nerve Conduction Velocity (MNCV) of ulnar nerve were recorded for both the groups. The posttest mean of MNCV for forearm segment and arm segment for Group A and Group B showed statistically significant difference (P Value <0.001).The analysis done by the statistical data also revealed that the MNCV at forearm segment showed an increase in velocity compared to its pretest values, whereas the post MNCV values at arm component showed a decrease in velocity when compared to its pretest values. Among comparison the data within the groups it is evident that group A with 1 MHz of ultrasound sonification is more capable of altering the MNCV values in comparison with the 3MHz. frequency. Findings of this study conclude that ultrasound therapy can be used effectively in altering conduction velocity of a nerve and it has a potential ability to facilitate or inhibit a nerve physiological function.

Ultrasound therapy: Dose-dependent effects in LBP treatment

BACKGROUND

Low back pain (LBP) affects most people at least once in their lives.

OBJECTIVE

To evaluate the efficacy of ultrasound therapy (UD) in patients with LBP receiving two different treatment dosages.

METHODS

The study design was a randomized prospective study. Patients were subjected to UD for two weeks. All persons in the study were evaluated at the Outpatient Rehabilitation Clinic at the Antoni Jurasz University Hospital in Bydgoszcz, Poland. Inclusion criteria were lumbosacral pain lasting more than 8 weeks, signs of osteoarthritis on imaging studies, and ages30-65 years. Exclusion criteria were radicular pain, nonmechanical causes of pain, contraindications for UD, or the patient received other LBP therapy during the study. The Oswestry Disability Index (ODI), Roland-Morris Disability Questionnaire (RM), and Visual Analog Scale (VAS) were used to evaluate the results.

RESULTS

For both groups, the ODI scores were significantly reduced by 13.7% and 8.84%, the RM scores decreased by 3.37 points and 3.59 points, and pain remissions on the VAS scale were 20.28 mm and 16.31 mm (p< 0.05).

CONCLUSION

UD decreased patients' disability levels and pain intensity. However, effective ultrasound parameters must be determined because of the wide dosage variations.

Therapeutic Systems and Technologies: State-of-the-Art Applications, Opportunities, and Challenges

In this review, we present current state-of-the-art developments and challenges in the areas of thermal therapy, ultrasound tomography, image-guided therapies, ocular drug delivery, and robotic devices in neurorehabilitation. Additionally, intellectual property and regulatory aspects pertaining to therapeutic systems and technologies are addressed.

Four-dimensional optoacoustic monitoring of tissue heating with medium intensity focused ultrasound

Medium-intensity focused ultrasound (MIFU) concerns therapeutic ultrasound interventions aimed at stimulating physiological mechanisms to reinforce healing responses without reaching temperatures that can cause permanent tissue damage. The therapeutic outcome is strongly affected by the temperature distribution in the treated region and its accurate monitoring represents an unmet clinical need. In this work, we investigate on the capacities of four-dimensional optoacoustic tomography to monitor tissue heating with MIFU. Calibration experiments in a tissue-mimicking phantom have confirmed that the optoacoustically-estimated temperature variations accurately match the simultaneously acquired thermocouple readings. The performance of the suggested approach in real tissues was further shown with bovine muscle samples. Volumetric temperature maps were rendered in real time, allowing for dynamic monitoring of the ultrasound focal region, estimation of the peak temperature and the size of the heat-affected volume.

Mitigation of Articular Cartilage Degeneration and Subchondral Bone Sclerosis in Osteoarthritis Progression Using Low-Intensity Ultrasound Stimulation

The purpose of this study was to evaluate the effect of low-intensity ultrasound on articular cartilage and subchondral bone alterations in joints under normal and functional disuse conditions during osteoarthritis (OA) progression. Total of thirty 5-mo-old female Sprague-Dawley rats were randomly assigned to six groups (n = 5/group): age-matched group, OA group, OA + ultrasound (US) group, hindlimb suspension (HLS) group, HLS + OA group and HLS + OA + US group. The surgical anterior cruciate ligament was used to induce OA in the right knee joints. After 2 wk of OA induction, low-intensity ultrasound generated with a 3-MHz transducer with 20% pulse duty cycle and 30 mW/cm² acoustic intensity was delivered to the right knee joints for 20 min a day, 5 d a week for a total of 6 wk. Then, the right tibias were harvested for micro-computed tomography, histologic and mechanical analysis. Micro-computed tomography results indicated that the thickness and sulfated glycosaminoglycan content of cartilage decreased, but the thickness of the subchondral cortical bone plate and the formation of subchondral trabecular bone increased in the OA group under the normal joint use condition. Furthermore, histologic results revealed that chondrocyte density and arrangement in cartilage corrupted and the underlying subchondral bone increased during OA progression. These changes were accompanied by reductions in mechanical parameters in OA cartilage. However, fewer OA symptoms were observed in the HLS + OA group under the joint disuse condition. The cartilage degeneration and subchondral bone sclerosis were alleviated in the US treatment group, especially under normal joint use condition. In conclusion, low-intensity ultrasound could improve cartilage degeneration and subchondral sclerosis during OA progression. Also, it could provide a promising strategy for future clinical treatment for OA patients.

Design of A Novel Wearable LIPUS Treatment Device for Mental Health Treatment

Low-intensity pulsed ultrasound (LIPUS) has been proven to be an effective treatment modality to improve bone fractures, soft tissue regeneration and neuromodulation. Recently, it has been shown for treating mental health diseases. In this paper, a novel wearable LIPUS treatment device, including a wearable headband and a LIPUS generator, is designed. The circuit in the LIPUS generator is specially built to generate LIPUS for stimulating the brain via temples. Considering comfortableness and safety, we designed a flexible cap to cover ultrasound transducer. The custommade replaceable transducer cap can be refilled by different ultrasound coupling agents. We demonstrated how polyurethane rubber caps filled with different ultrasound coupling agents affect the ultrasound transmission intensity. Milli-Q water is identified to be the best ultrasound coupling agent for the polyurethane rubber cap with about 39.76% LIPUS intensity transmission.

Functional regulation of YAP mechanosensitive transcriptional coactivator by Focused Low-Intensity Pulsed Ultrasound (FLIPUS) enhances proliferation of murine mesenchymal precursors

Yes-associated protein (YAP) acts as a mechanotransducer in determining the cell fate of murine C2C12 mesenchymal precursors as investigated after stimulation with ultrasound. We applied Focused Low-Intensity Pulsed Ultrasound (FLIPUS) at a sound frequency of 3.6 MHz, 100 Hz pulse repetition frequency (PRF), 27.8% duty cycle (DC), and 44.5 mW/cm² acoustic intensity I_SATA for 5 minutes and evaluated early cellular responses. FLIPUS decreased the level of phosphorylated YAP on Serine 127, leading to higher levels of active YAP in the nucleus. This in turn enhanced the expression of YAP-target genes associated with actin nucleation and stabilization, cytokinesis, and cell cycle progression. FLIPUS enhanced proliferation of C2C12 cells, whereas silencing of YAP expression abolished the beneficial effects of ultrasound. The expression of the transcription factor MyoD, defining cellular myogenic differentiation, was inhibited by mechanical stimulation. This study shows that ultrasound exposure regulates YAP functioning, which in turn improves the cell proliferative potential, critical for tissue regeneration process.

Effect of low-intensity pulsed ultrasound on distraction osteogenesis: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Low-intensity pulsed ultrasound (LIPUS) is a common adjunct used to promote bone healing for fresh fractures and non-unions, but its efficacy for bone distraction osteogenesis remains uncertain. This study aims to determine whether LIPUS can effectively and safely reduce the associated treatment time for patients undergoing distraction osteogenesis.

METHODS

MEDLINE, EMBASE, and the Cochrane Library were searched until May 1, 2018, without language restriction. Studies should be randomized controlled trials (RCTs) or quasi-RCTs of LIPUS compared with sham devices or no devices in patients who undergo distraction osteogenesis. The primary outcome was the treatment time. The secondary outcome was the risk of complications. Treatment effects were assessed using mean differences, standardized mean differences, or risk ratios using a random-effects model. The Cochrane risk-of-bias tool was used to assess the risk of bias. The I² statistic was used to assess the heterogeneity. The GRADE system was used to evaluate the evidence quality.

RESULTS

A total of 7 trials with 172 patients were included. The pooled results suggested that during the process of distraction osteogenesis, LIPUS therapy did not show a statistically significant reduction in the treatment time (mean difference, - 8.75 days/cm; 95% CI, - 20.68 to 3.18 days/cm; P = 0.15; I² = 72%) or in the risk of complications (risk ratio, 0.90 in favor of LIPUS; 95% CI, 0.65 to 1.24; I² = 0%). Also, LIPUS therapy did not show a significant effect on the radiological gap fill area (standardized mean difference, 0.48 in favor of control; 95%CI, - 1.49 to 0.52; I² = 0%), the histological gap fill length (standardized mean difference, 0.76 in favor of control; 95%CI, - 1.78 to 0.27; I² = 0%), or the bone density increase (standardized mean difference, 0.43 in favor of LIPUS; 95%CI, - 0.02 to 0.88; I² = 0%).

CONCLUSIONS

Among patients undergoing distraction osteogenesis, neither the treatment time nor the risk of complications could be reduced by LIPUS therapy. The currently available evidence is insufficient to support the routine use of this intervention in clinical practice.

TRIAL REGISTRATION

CRD 42017073596.

A preliminary study of effects of low-intensity pulsed ultrasound (LIPUS) irradiation on dentoalveolar ankylosis

The purpose of this experiment was to investigate whether low-intensity pulsed ultrasound (LIPUS) irradiation can inhibit dentoalveolar ankylosis in transplanted rat teeth. LIPUS irradiation (the pulsed ultrasound signal had a frequency of 3.0 MHz, a spatial average intensity of 30 mW/cm², and a pulse ratio of 1:4) was performed on the face over the re-planted teeth of rats for 4 weeks. After the rats were euthanized, we measured mobility (Periotest value [PTV]) of the transplanted and control teeth using a Periotest. Finally, we performed histological evaluation to detect ankylosis. PTVs tended to be significantly lower for re-planted teeth than for control teeth. Histological evaluation revealed that the roots of all re-planted teeth were coalescent with alveolar bone. Furthermore, no ankylosis was observed in three-fifths of the re-planted teeth following LIPUS irradiation. These results indicate the potential efficacy of LIPUS to inhibit dentoalveolar ankylosis.

Therapy Concepts for the Proximal Interphalangeal Joint

The principles of hand therapy for proximal interphalangeal joint disorders include protecting injured structures, minimizing patient discomfort, and optimizing patient recovery. Comprehension of hand anatomy, the nature of the injury being treated, and the phases of healing are critical when designing a safe and effective hand therapy program. Hand therapists use a combination of orthoses, guided exercises, and modalities to improve edema, sensitivity, range of motion, and function.

Low-intensity pulsed ultrasound (LIPUS) stimulates mineralization of MC3T3-E1 cells through calcium and phosphate uptake

The present study aimed to evaluate the effect of low-intensity pulsed ultrasound (LIPUS) on pre-osteoblast mineralization using in vitro bioassays. Pre-osteoblastic MC3T3-E1 cells were exposed to LIPUS at 1 MHz frequency, 0.2 W/cm² intensity and 20% duty cycle for 30 min. The analyses were carried out up to 336 h (14 days) after exposure. The concentration of collagen, phosphate, alkaline phosphatase, calcium and transforming growth factor beta 1 (TGF-β1) in cell supernatant and the presence of calcium deposits in the cells were analyzed. Our results showed that LIPUS promotes mineralized nodules formation. Collagen, phosphate, and calcium levels were decreased in cell supernatant at 192 h after LIPUS exposure. However, alkaline phosphatase and TGF-β1 concentrations remained unchanged. Therapeutic pulsed ultrasound is capable of stimulating differentiation and mineralization of pre-osteoblastic MC3T3-E1 cells by calcium and phosphate uptake with consequent hydroxyapatite formation.

Effect of low-intensity pulsed ultrasound therapy on a rat knee joint contracture model

[Purpose] Histopathological investigation of the effects of low-intensity pulsed ultrasound (LIPUS) on joint components using a rat knee joint contracture model. [Subjects and Methods] Nineteen, 9-week-old Wistar male rats were divided into a control group (n=6) and an experimental group. Rats in the experimental group underwent cast immobilization of the right rear limb for 8 weeks. They were then randomly divided into a non-treatment group (n=6), which was raised under normal conditions for 4 weeks, and a treatment group (n=7), which underwent LIPUS for 4 weeks. LIPUS irradiation was performed at a frequency of 3 MHz, an intensity of 30 mW/cm², and a pulse rate of 20% duty cycle. Irradiation was performed once daily for 10 min, 5 days per week. At the end of this period, tissue specimens in which the knee sagittal plane could be observed were prepared and observed using an optical microscope. [Results] The extension-limiting angle of the knee joint was significantly less in the treatment group compared with the non-treatment group. The posterior joint capsule was significantly thicker only in the non-treatment group, and the density was 53.5 ± 7.5% for the control group, 77.2 ± 5.7% for the non-treatment group, and 69.2 ± 2.9% for the treatment group, with significant differences existing across all groups. [Conclusion] LIPUS may widen the space between collagen fiber bundles of the joint capsule, thereby improving the range of motion.

The effects of low-intensity pulsed ultrasound on fresh fracture: A meta-analysis

BACKGROUND

Low-intensity pulsed ultrasonography (LIPUS) is a form of mechanical stimulation that is delivered via a special device to the fracture site for the acceleration of fracture healing. We conducted a meta-analysis to assess the effect of LIPUS for fresh fractures in adults.

METHODS

MEDLINE, EMBASE and the Cochrane Library searched between Jan 1980 and Nov 2016. Studies should be quasi-randomized and randomized controlled trials (RCTs) comparing treatment with LIPUS to placebo or no treatment in adults with fresh fractures, reporting outcomes such as function; time to union; delayed union or non-union. Summary standard mean difference (SMD) and the risk ratio (RR) with their 95% confidence interval (CI) calculated with a random effects model. I statistic was used to assess the heterogeneity. Risk of bias was assessed by the Cochrane risk-of-bias tool. The GRADE system was used to evaluate the evidence quality.

RESULTS

A total of 12 trials with 1099 patients were included. The pooled results showed that LIPUS significantly reduced the time to fracture union (SMD: 0.65, 95% CI: 1.13 to 0.17), improved the quality of life (SMD: 0.20, 95% CI: 0.03-0.37) without affecting the time to full weight bearing (SMD: 0.76, 95% CI: 1.92 to 0.4), the time to return to work (SMD: 0.06, 95% CI: 0.14 to 0.27), or the incidence rate of delayed union and nonunion (RR: 1.02, 95% CI: 0.60-1.74).

CONCLUSIONS

Moderate-to-high quality evidence shows that LIPUS treatment reduces the time to fracture union and improves the quality of life without affecting functional recovery and incident rate of delayed union and nonunion, suggesting that LIPUS treatment may be a good treatment modality for adults with fresh fractures. However, there are some methodological limitations in the eligible trials, further studies are needed to determine the clinical circumstances under which LIPUS is truly valid and to examine the optimal approach for the use of this adjunctive therapy.

Neuroprotective Effect of Low-Intensity Pulsed Ultrasound Against MPP+-Induced Neurotoxicity in PC12 Cells: Involvement of K2P Channels and Stretch-Activated Ion Channels

Parkinson's disease is the second most common neurodegenerative disease. It is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta. 1-Methyl-4-phenylpyridinium (MPP⁺) is a dopaminergic neuronal toxin that is widely used in constructing Parkinson's disease models in vitro. Low-intensity pulsed ultrasound (LIPUS) is a non-invasive therapeutic approach that has neuromodulation and neuroprotective effects in the central neural system; however, whether LIPUS can provide protection for dopaminergic neurons against MPP⁺-induced neurocytotoxicity remains unknown. In this study, we found that pre-treatment with LIPUS (1 MHz, 50 mW/cm², 20% duty cycle and 100-Hz pulse repetition frequency, 10 min) inhibited MPP⁺-induced neurotoxicity and mitochondrial dysfunction in PC12 cells. LIPUS decreased MPP⁺-induced oxidative stress by modulating antioxidant proteins, including thioredoxin-1 and heme oxygenase-1, and prevented neurocytotoxicity via the phosphoinositide 3-kinase (PI3K)-Akt and ERK1/2 pathways. Furthermore, these beneficial effects were attributed to the activation of K2P channels and stretch-activated ion channels by LIPUS. These data indicate that LIPUS protects neuronal cells from MPP⁺-induced cell death through the K2P channel- and stretch-activated ion channel-mediated downstream pathways. The data also suggest that LIPUS could be a promising therapeutic method in halting or retarding the degeneration of dopaminergic neurons in Parkinson's disease in a non-invasive manner.

Optimal Ultrasound Exposure Conditions for Maximizing C2C12 Muscle Cell Proliferation and Differentiation

Described here is an in vitro systematic investigation of the effects on C2C12 myoblasts of exposure to finely controlled and repeatable low-intensity pulsed ultrasound of different frequencies (500 kHz, 1 MHz, 3 MHz and 5 MHz) and different intensities (250, 500 and 1000 mW/cm²). An in-house stimulation system and an ultrasound-transparent cell culture well minimized reflections and attenuations, allowing precise control of ultrasound delivery. Results indicated that a 3 MHz stimulation at 1 W/cm² intensity maximized cell proliferation in comparison with the other exposure conditions and untreated controls. In contrast, cell differentiation and the consequent formation of multinucleated myotubes were maximized by 1 MHz stimulation at 500 mW/cm² intensity. The highly controlled exposure conditions employed allowed precise correlation of the ultrasound delivery to the bio-effects produced, thus overcoming the inconsistency of some results available in the literature and contributing to the potential of ultrasound treatment for muscle therapy and regeneration.

Ultrasound as a stimulus for musculoskeletal disorders

Ultrasound is an inaudible form of acoustic sound wave at 20 kHz or above that is widely used in the medical field with applications including medical imaging and therapeutic stimulation. In therapeutic ultrasound, low-intensity pulsed ultrasound (LIPUS) is the most widely used and studied form that generally uses acoustic waves at an intensity of 30 mW/cm², with 200 ms pulses and 1.5 MHz. In orthopaedic applications, it is used as a biophysical stimulus for musculoskeletal tissue repair to enhance tissue regeneration. LIPUS has been shown to enhance fracture healing by shortening the time to heal and reestablishment of mechanical properties through enhancing different phases of the healing process, including the inflammatory phase, callus formation, and callus remodelling phase. Reports from in vitro studies reveal insights in the mechanism through which acoustic stimulations activate cell surface integrins that, in turn, activate various mechanical transduction pathways including FAK (focal adhesion kinase), ERK (extracellular signal-regulated kinase), PI3K, and Akt. It is then followed by the production of cyclooxygenase 2 and prostaglandin E2 to stimulate further downstream angiogenic, osteogenic, and chondrogenic cytokines, explaining the different enhancements observed in animal and clinical studies. Furthermore, LIPUS has also been shown to have remarkable effects on mesenchymal stem cells (MSCs) in musculoskeletal injuries and tissue regeneration. The recruitment of MSCs to injury sites by LIPUS requires the SDF-1 (stromal cell derived factor-1)/CXCR-4 signalling axis. MSCs would then differentiate differently, and this is regulated by the presence of different cytokines, which determines their fates. Other musculoskeletal applications including bone–tendon junction healing, and distraction osteogenesis are also explored, and the results are promising. However, the use of LIPUS is controversial in treating osteoporosis, with negative findings in clinical settings, which may be attributable to the absence of an injury entry point for the acoustic signal to propagate, strong attenuation effect of cortical bone and the insufficient intensity for penetration, whereas in some animal studies it has proven effective.

The Effect of Low-Intensity Ultrasound on Brain-Derived Neurotropic Factor Expression in a Rat Sciatic Nerve Crushed Injury Model

Low-intensity ultrasound (LIU) can improve nerve regeneration and functional recovery after peripheral nerve crush injury, but the underlying mechanism is not clear. The objective of this study was to examine the effects of LIU on rat sciatic crush injury and to investigate a possible molecular mechanism. Adult male Sprague-Dawley rats underwent left sciatic nerve crush surgery and were then randomized into two groups: a treatment group that received LIU every other d, and a control group that received sham exposure. Compared with rats in the control group, rats in the treatment group had higher sciatic nerve function indexes, compound muscle action potentials, wet weight ratios of the target muscle and mRNA expression of brain-derived neurotropic factor (BDNF) in the crushed nerve and ipsilateral dorsal root ganglia. Our findings suggest that LIU might promote injured nerve regeneration by stimulating BDNF release.

Effect of Low-Intensity Pulsed Ultrasound on a Rat Model of Dentin-Dental Pulp Injury and Repair

This study investigated histopathologic changes in dental pulp after treatment with low-intensity pulsed ultrasound (LIPUS). Fifty rats were randomly divided into an experimental group (n = 25) and a blank control group (n = 25). In the experimental group, a cavity was prepared in the bilateral maxillary first molars. The upper right first molars were stimulated with LIPUS (30 mW/cm², 1.5 MHz) for 20 min/d. The cavities prepared in the left teeth were used as experimental controls (i.e., no LIPUS). Five rats in each group were sacrificed at days 1, 3, 5, 7 and 14. Inflammatory response was visible at different time points after cavity preparation, peaking at day 3, after which it gradually weakened. More reparative dentin was found on the LIPUS treatment side. transforming growth factor-β1 expression increased after treatment, peaking at day 5 and returning to normal at day 14 on both sides, but was stronger with LIPUS treatment. SMAD2 and SMAD3 expressions in the dental pulp gradually increased after cavity preparation, especially in the experimental group. LIPUS promoted the repair of dentin-pulp complex injury, to a certain extent and should be investigated further as a potential therapy.

Low-Intensity Pulsed Ultrasound Enhances Nerve Growth Factor-Induced Neurite Outgrowth through Mechanotransduction-Mediated ERK1/2-CREB-Trx-1 Signaling

Enhancing the action of nerve growth factor (NGF) is a potential therapeutic approach to neural regeneration. To facilitate neural regeneration, we investigated whether combining low-intensity pulsed ultrasound (LIPUS) and NGF could promote neurite outgrowth, an essential process in neural regeneration. In the present study, PC12 cells were subjected to a combination of LIPUS (1 MHz, 30 or 50 mW/cm², 20% duty cycle and 100-Hz pulse repetition frequency, 10 min every other day) and NGF (50 ng/mL) treatment, and then neurite outgrowth was compared. Our findings indicated that the combined treatment with LIPUS (50 mW/cm²) and NGF (50 ng/mL) promotes neurite outgrowth that is comparable to that achieved by NGF (100 ng/mL) treatment alone. LIPUS significantly increased NGF-induced neurite length, but not neurite branching. These effects were attributed to the enhancing effects of LIPUS on NGF-induced phosphorylation of ERK1/2 and CREB and the expression of thioredoxin (Trx-1). Furthermore, blockage of stretch-activated ion channels with Gd³⁺ suppressed the stimulating effects of LIPUS on NGF-induced neurite outgrowth and the downstream signaling activation. Taken together, our findings suggest that LIPUS enhances NGF-induced neurite outgrowth through mechanotransduction-mediated signaling of the ERK1/2-CREB-Trx-1 pathway. The combination of LIPUS and NGF could potentially be used for the treatment of nerve injury and neurodegenerative diseases.

Activation of Mechanosensitive Transcription Factors in Murine C2C12 Mesenchymal Precursors by Focused Low-Intensity Pulsed Ultrasound (FLIPUS)

In this paper, we investigated the mechanoresponse of C2C12 mesenchymal precursor cells to focused low-intensity pulsed ultrasound (FLIPUS). The setup has been developed for in vitro stimulation of adherent cells in the defocused far field of the ultrasound propagating through the bottom of the well plate. Twenty-four-well tissue culture plates, carrying the cell monolayers, were incubated in a temperature-controlled water tank. The ultrasound was applied at 3.6-MHz frequency, pulsed at 100-Hz repetition frequency with a 27.8% duty cycle, and calibrated at an output intensity of I_SATA = 44.5 ±7.1 mW/cm². Numerical sound propagation simulations showed no generation of standing waves in the well plate. The response of murine C2C12 cells to FLIPUS was evaluated by measuring activation of mechanosensitive transcription factors, i.e., activator protein-1 (AP-1), specificity protein 1 (Sp1), and transcriptional enhancer factor (TEAD), and expression of mechanosensitive genes, i.e., c-fos, c-jun, heparin binding growth associated molecule (HB-GAM), and Cyr-61. FLIPUS induced 50% ( p ≤ 0.05 ) and 70% ( p ≤ 0.05 ) increases in AP-1 and TEAD promoter activities, respectively, when stimulated for 5 min. The Sp1 activity was enhanced by about 20% ( p ≤ 0.05 ) after 5-min FLIPUS exposure and the trend persisted for 30-min ( p ≤ 0.05 ) and 1-h ( p ≤ 0.05 ) stimulation times. Expressions of mechanosensitive genes c-fos ( p ≤ 0.05 ), c-jun ( p ≤ 0.05 ), HB-GAM ( p ≤ 0.05 ), and cystein-rich protein 61 ( p ≤ 0.05 ) were enhanced in response to 5-min FLIPUS stimulation. The increase in proliferation of C2C12s occurred after the FLIPUS stimulation ( p ≤ 0.05 ), with AP-1, Sp1, and TEAD possibly regulating the observed cellular activities.

Effects and Mechanisms of Low-Intensity Pulsed Ultrasound for Chronic Prostatitis and Chronic Pelvic Pain Syndrome

Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS) is one of the most common urologic diseases, and no curative treatments have been identified. Low-intensity pulsed ultrasound (LIPUS) has been successfully used in promoting tissue healing, inhibiting inflammation and pain, differentiating stem cells, and stimulating nerve regeneration/muscle regeneration, as well as enhancing angiogenesis. Very recently, LIPUS has been proven an effective approach for CP/CPPS. This review summarizes the possible mechanisms responsible for the therapeutic effect of LIPUS for CP/CPPS. To search publications relevant to the topics of this review, the search engine for life sciences of Entrez was used. We reviewed the available evidence from 1954 through 2015 concerning LIPUS for CP/CPPS. According to the literature, both transrectal and transperineal approaches of LIPUS are effective for CP/CPPS.

Clinical applications of low-intensity pulsed ultrasound and its potential role in urology

Low-intensity pulsed ultrasound (LIPUS) is a form of ultrasound that delivered at a much lower intensity (<3 W/cm²) than traditional ultrasound energy and output in the mode of pulse wave, and it is typically used for therapeutic purpose in rehabilitation medicine. LIPUS has minimal thermal effects due to its low intensity and pulsed output mode, and its non-thermal effects which is normally claimed to induce therapeutic changes in tissues attract most researchers’ attentions. LIPUS have been demonstrated to have a rage of biological effects on tissues, including promoting bone-fracture healing, accelerating soft-tissue regeneration, inhibiting inflammatory responses and so on. Recent studies showed that biological effects of LIPUS in healing morbid body tissues may be mainly associated with the upregulation of cell proliferation through activation of integrin receptors and Rho/ROCK/Src/ERK signaling pathway, and with promoting multilineage differentiation of mesenchyme stem/progenitor cell lines through ROCK-Cot/Tpl2-MEK-ERK signaling pathway. Hopefully, LIPUS may become an effective clinical procedure for the treatment of urological diseases, such as chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS), erectile dysfunction (ED), and stress urinary incontinence (SUI) in the field of urology. It still needs an intense effort for basic-science and clinical investigators to explore the biomedical applications of ultrasound.

Low-intensity pulsed ultrasound treatment improved the rate of autograft peripheral nerve regeneration in rat

Low intensity pulsed ultrasound (LIPUS) has been widely used in clinic for the treatment of repairing pseudarthrosis, bone fractures and of healing in various soft tissues. Some reports indicated that LIPUS accelerated peripheral nerve regeneration including Schwann cells (SCs) and injured nerves. But little is known about its appropriate intensities on autograft nerves. This study was to investigate which intensity of LIPUS improved the regeneration of gold standard postsurgical nerves in experimental rat model. Sprague-Dawley rats were made into 10 mm right side sciatic nerve reversed autologous nerve transplantation and randomly treated with 250 mW/cm², 500 mW/cm² or 750 mW/cm² LIPUS for 2–12 weeks after operation. Functional and pathological results showed that LIPUS of 250 mW/cm² significantly induced faster rate of axonal regeneration. This suggested that autograft nerve regeneration was improved.

Low Intensity Pulsed Ultrasound Promotes the Extracellular Matrix Synthesis of Degenerative Human Nucleus Pulposus Cells Through FAK/PI3K/Akt Pathway

STUDY DESIGN

In vitro experimental study.

OBJECTIVE

To investigate the effect of low-intensity pulsed ultrasound (LIPUS) on the extracellular matrix (ECM) synthesis of degenerative human nucleus pulposus cells and explore the molecular mechanism.

SUMMARY OF BACKGROUND DATA

LIPUS has been used successfully for bone fracture healing and been proved to be effective in stimulating ECM metabolism in animal intervertebral disc cells. However, whether LIPUS also exerts an anabolic effect on degenerative human nucleus pulposus cells and the possible molecular mechanism is still unclear.

METHODS

The degenerative human nucleus pulposus cells were cultured in calcium alginate beads. In the LIPUS group, cells were exposed to an average temporal intensity of 30  mW/cm2 and a frequency of 1.5  MHz of LIPUS 20 minutes daily for 1 week. The control group was cultured in the same way but without LIPUS stimulation. The LY294002 group was stimulated by LIPUS and treated with LY294002 simultaneously. The expression of aggrecan, collagen-II, Sox9, tissue inhibitor of metalloproteinase-,1 and matrix metalloproteinase-3 were evaluated by Enzyme-Linked Immunosorbent Assay, Western blot or RT-PCR. Expression of signaling proteins involved in FAK/PI3K/Akt pathway was studied by Western blot analysis.

RESULTS

LIPUS significantly upregulated expression of aggrecan, collagen-II, Sox9, and tissue inhibitor of metalloproteinase-1 compared with control group, but inhibited secretion of matrix metalloproteinase-3. The study further demonstrated that the upregulation of aggrecan, collagen-II, and Sox9 was related to the activation of focal adhesion kinase (FAK)//PI3K/Akt pathway caused by LIPUS. Moreover, inhibition of PI3K/Akt significantly suppressed the special biological effect activated by LIPUS.

CONCLUSION

LIPUS promotes the ECM synthesis of degenerative human nucleus pulposus cells through activation of FAK/PI3K/Akt pathway.

LEVEL OF EVIDENCE

N/A.

A Focused Low-Intensity Pulsed Ultrasound (FLIPUS) System for Cell Stimulation: Physical and Biological Proof of Principle

Quantitative ultrasound (QUS) is a promising technique for bone tissue evaluation. Highly focused transducers used for QUS also have the capability to be applied for tissue-regenerative purposes and can provide spatially limited deposition of acoustic energy. We describe a focused low-intensity pulsed ultrasound (FLIPUS) system, which has been developed for the stimulation of cell monolayers in the defocused far field of the transducer through the bottom of the well plate. Tissue culture well plates, carrying the cells, were incubated in a special chamber, immersed in a temperature-controlled water tank. A stimulation frequency of 3.6 MHz provided an optimal sound transmission through the polystyrene well plate. The ultrasound was pulsed for 20 min daily at 100-Hz repetition frequency with 27.8% duty cycle. The calibrated output intensity corresponded to I(SATA) = 44.5 ± 7.1 mW/cm2, which is comparable to the most frequently reported nominal output levels in LIPUS studies. No temperature change by the ultrasound exposure was observed in the well plate. The system was used to stimulate rat mesenchymal stem cells (rMSCs). The applied intensity had no apoptotic effect and enhanced the expression of osteogenic markers, i.e., osteopontin (OPN), collagen 1 (Col-1), the osteoblast-specific transcription factor-Runx-2 and E11 protein, an early osteocyte marker, in stimulated cells on day 5. The proposed FLIPUS setup opens new perspectives for the evaluation of the mechanistic effects of LIPUS.

Low-intensity Pulsed Ultrasound Improves Erectile Function in Streptozotocin-induced Type I Diabetic Rats

OBJECTIVE

To investigate the effect of low-intensity pulsed ultrasound (LIPUS) as a treatment for erectile dysfunction (ED) in a rat model of type I diabetes mellitus (DM) induced by streptozotocin (STZ).

MATERIALS AND METHODS

Seventy male Sprague-Dawley rats were randomly assigned to 2 cohorts: a normal control (NC) group and an STZ-induced DM group, which was further subdivided into DM, DM+LIPUS 100, DM+LIPUS 200, and DM+LIPUS 300 groups and a DM+LESWT (low-energy shock wave therapy) 300 positive control group. Animals in the LIPUS subgroups were treated at different energy levels (100, 200, and 300 mW/cm(2)) for 3 minutes, and animals in the LESWT group received 300 shocks at 0.09 mJ/mm(2). All procedures were repeated 3 times per week for 2 weeks. After a 2-week wash-out period, intracavernous pressure (ICP) was measured; the midpenile region was examined histologically; and VEGF, αSMA, eNOS, and nNOS expression, and activity of the TGF-β1/Smad/CTGF signaling pathway were examined in penile tissue by Western blot analysis.

RESULTS

LIPUS therapy significantly improved erectile function in diabetic rats, as evidenced by enhanced ICP levels, increased endothelial and smooth muscle content, a higher collagen I/collagen III ratio, increased quantity of elastic fibers, and elevated eNOS and nNOS expression. Interestingly, LIPUS was also associated with downregulation of the TGF-β1/Smad/CTGF signaling pathway in penile tissue, whose activation is correlated with ED pathology.

CONCLUSION

LIPUS therapy improved erectile function and reversed pathologic changes in penile tissue of STZ-induced diabetic rats. LIPUS therapy has potential as a noninvasive therapy for diabetic ED in the clinic.

Design of a Thermoacoustic Sensor for Low Intensity Ultrasound Measurements Based on an Artificial Neural Network

In therapeutic ultrasound applications, accurate ultrasound output intensities are crucial because the physiological effects of therapeutic ultrasound are very sensitive to the intensity and duration of these applications. Although radiation force balance is a benchmark technique for measuring ultrasound intensity and power, it is costly, difficult to operate, and compromised by noise vibration. To overcome these limitations, the development of a low-cost, easy to operate, and vibration-resistant alternative device is necessary for rapid ultrasound intensity measurement. Therefore, we proposed and validated a novel two-layer thermoacoustic sensor using an artificial neural network technique to accurately measure low ultrasound intensities between 30 and 120 mW/cm². The first layer of the sensor design is a cylindrical absorber made of plexiglass, followed by a second layer composed of polyurethane rubber with a high attenuation coefficient to absorb extra ultrasound energy. The sensor determined ultrasound intensities according to a temperature elevation induced by heat converted from incident acoustic energy. Compared with our previous one-layer sensor design, the new two-layer sensor enhanced the ultrasound absorption efficiency to provide more rapid and reliable measurements. Using a three-dimensional model in the K-wave toolbox, our simulation of the ultrasound propagation process demonstrated that the two-layer design is more efficient than the single layer design. We also integrated an artificial neural network algorithm to compensate for the large measurement offset. After obtaining multiple parameters of the sensor characteristics through calibration, the artificial neural network is built to correct temperature drifts and increase the reliability of our thermoacoustic measurements through iterative training about ten seconds. The performance of the artificial neural network method was validated through a series of experiments. Compared to our previous design, the new design reduced sensing time from 20 s to 12 s, and the sensor’s average error from 3.97 mW/cm² to 1.31 mW/cm² respectively.

Mechanical high-intensity focused ultrasound destruction of soft tissue: working mechanisms and physiologic effects

The best known method of high-intensity focused ultrasound is thermal ablation, but interest in non-thermal, mechanical destruction is increasing. The advantages of mechanical ablation are that thermal protein denaturation remains limited and less damage is created to the surrounding tissue by thermal diffusion. The two main techniques for mechanical fragmentation of tissue are histotripsy and boiling histotripsy. These techniques can be used for complete liquefaction of tumor tissue into submicron fragments, after which the fragmented tissue can be easily removed by natural (immunologic) responses. Interestingly it seems that there is a correlation between the degree of destruction and tissue specific characteristics based on the treatment settings used. In this review article, the technical aspects of these two techniques are described, and an overview of the in vivo pathologic and immunologic responses is provided.

Clinical results after ultrasound-guided intratissue percutaneous electrolysis (EPI®) and eccentric exercise in the treatment of patellar tendinopathy

PURPOSE

To investigate the outcome of ultrasound (US)-guided intratissue percutaneous electrolysis (EPI(®)) and eccentric exercise in the treatment of patellar tendinopathy during a long-term follow-up.

METHODS

Forty patients with patellar tendinopathy were prospectively evaluated over a 10-year follow-up period. Pain and function were evaluated before treatment, at 3 months and at 2, 5 and 10 years using the Victorian Institute of Sport Assessment-Patella (VISA-P) score, the Tegner score and Blazina's classification. According to VISA-P score at baseline, patients were also dichotomized into Group 1 (<50 points) and Group 2 (≥50 points). There were 21 patients in Group 1 and 19 in Group 2. Patient satisfaction was measured according to the Roles and Maudsley score.

RESULTS

The VISA-P score improved globally by 41.2 points (p < 0.01) after a mean 4.1 procedures. In Group 1, VISA-P score improved from 33.1 ± 13 to 78.9 ± 14.4 at 3-month and to 88.8 ± 10.1 at 10-year follow-up (p < 0.001). In Group 2, VISA-P score improved from 69.3 ± 10.5 to 84.9 ± 9 at 3-month and to 96.0 ± 4.3 at 10-year follow-up (p < 0.001). After 10 years, 91.2 % of the patients had a VISA-P score >80 points. The same level (80 % of patients) or the Tegner score at no more than one level lower (20 % of patients) was restored, and 97.5 % of the patients were satisfied with the procedure.

CONCLUSION

Treatment with the US-guided EPI(®) technique and eccentric exercises in patellar tendinopathy resulted in a great improvement in knee function and a rapid return to the previous level of activity after few sessions. The procedure has proved to be safe with no recurrences on a long-term basis.

LEVEL OF EVIDENCE

Therapeutic study, Level IV.

Stimulation of bone repair with ultrasound: a review of the possible mechanic effects

In vivo and in vitro studies have demonstrated the positive role that ultrasound can play in the enhancement of fracture healing or in the reactivation of a failed healing process. We review the several options available for the use of ultrasound in this context, either to induce a direct physical effect (LIPUS, shock waves), to deliver bioactive molecules such as growth factors, or to transfect cells with osteogenic plasmids; with a main focus on LIPUS (or Low Intensity Pulsed Ultrasound) as it is the most widespread and studied technique. The biological response to LIPUS is complex as numerous cell types respond to this stimulus involving several pathways. Known to-date mechanotransduction pathways involved in cell responses include MAPK and other kinases signaling pathways, gap-junctional intercellular communication, up-regulation and clustering of integrins, involvement of the COX-2/PGE2, iNOS/NO pathways and activation of ATI mechanoreceptor. The mechanisms by which ultrasound can trigger these effects remain intriguing. Possible mechanisms include direct and indirect mechanical effects like acoustic radiation force, acoustic streaming, and propagation of surface waves, fluid-flow induced circulation and redistribution of nutrients, oxygen and signaling molecules. Effects caused by the transformation of acoustic wave energy into heat can usually be neglected, but heating of the transducer may have a potential impact on the stimulation in some in-vitro systems, depending on the coupling conditions. Cavitation cannot occur at the pressure levels delivered by LIPUS. In-vitro studies, although not appropriate to identify the overall biological effects, are of great interest to study specific mechanisms of action. The diversity of current experimental set-ups however renders this analysis very complex, as phenomena such as transducer heating, inhomogeneities of the sound intensity in the near field, resonances in the transmission and reflection through the culture dish walls and the formation of standing waves will greatly affect the local type and amplitude of the stimulus exerted on the cells. A future engineering challenge is therefore the design of dedicated experimental set-ups, in which the different mechanical phenomena induced by ultrasound can be controlled. This is a prerequisite to evaluate the biological effects of the different phenomena with respect to particular parameters, like intensity, frequency, or duty cycle. By relating the variations of these parameters to the induced physical effects and to the biological responses, it will become possible to derive an 'acoustic dose' and propose a quantification and cross-calibration of the different experimental systems. Improvements in bone healing management will probably also come from a combination of ultrasound with a 'biologic' components, e.g. growth factors, scaffolds, gene therapies, or drug delivery vehicles, the effects of which being potentiated by the ultrasound.

Low-intensity pulsed ultrasound promotes chondrogenic progenitor cell migration via focal adhesion kinase pathway

Low-intensity pulsed ultrasound (LIPUS) has been studied frequently for its beneficial effects on the repair of injured articular cartilage. We hypothesized that these effects are due to stimulation of chondrogenic progenitor cell (CPC) migration toward injured areas of cartilage through focal adhesion kinase (FAK) activation. CPC chemotaxis in bluntly injured osteochondral explants was examined by confocal microscopy, and migratory activity of cultured CPCs was measured in transwell and monolayer scratch assays. FAK activation by LIPUS was analyzed in cultured CPCs by Western blot. LIPUS effects were compared with the effects of two known chemotactic factors: N-formyl-methionyl-leucyl-phenylalanine (fMLF) and high-mobility group box 1 (HMGB1) protein. LIPUS significantly enhanced CPC migration on explants and in cell culture assays. Phosphorylation of FAK at the kinase domain (Tyr 576/577) was maximized by 5 min of exposure to LIPUS at a dose of 27.5 mW/cm(2) and frequency of 3.5 MHz. Treatment with fMLF, but not HMBG1, enhanced FAK activation to a degree similar to that of LIPUS, but neither fMLF nor HMGB1 enhanced the LIPUS effect. LIPUS-induced CPC migration was blocked by suppressing FAK phosphorylation with a Src family kinase inhibitor that blocks FAK phosphorylation. Our results imply that LIPUS might be used to promote cartilage healing by inducing the migration of CPCs to injured sites, which could delay or prevent the onset of post-traumatic osteoarthritis.

Histomorphometrical analysis on the effects of two therapeutic ultrasound intensities on fracture healing in aged rats

Introduction Experimental studies conducted in young animals show that therapeutic ultrasound (TUS) has been successfully used to shorten the healing time of bone fractures. However, they were not found in the literature, studies comparing the effect of different intensities of UST in aged animals. Objective To test the efficacy of intensity 1.0 W/cm2 and of 0.5 W/cm2 in the consolidation of experimental fracture of the tibia from aged Wistar rats. Materials and methods Three groups of 15 month old rats were submitted to a midshaft osteotomy of the tibia and then, the hind member was immobilized with a metal splint and plaster of Paris, wrapping the knee and ankle joint. One group (L), received ultrasound at 0.5 W/cm2; the other group (I), were exposed to ultrasound at 1.0 W/cm2. One control group (C), did not receive the ultrasound. Fifteen animals (five from each group) were euthanatized at the end of the first week and fifteen (five from each group) at the end of the third week. The progress of the fracture healing was performed for each group by morphometric analysis of histological sections of the fracture region. Results and conclusion The results showed that fractures treated with ultrasound at 1.0 W/cm2 healed significantly faster than did the fractures treated with ultrasound at 0.5 W/cm2 and the control.

Effects of low-intensity pulsed ultrasound on cell viability, proliferation and neural differentiation of induced pluripotent stem cells-derived neural crest stem cells

Low-intensity pulsed ultrasound (LIPUS) acting on induced pluripotent stem cells-derived neural crest stem cells (iPSCs-NCSCs) is considered a promising therapy to improve the efficacy of injured peripheral nerve regeneration. Effects of LIPUS on cell viability, proliferation and neural differentiation of iPSCs-NCSCs were examined respectively in this study. LIPUS at 500 mW cm(-2) enhanced the viability and proliferation of iPSCs-NCSCs after 2 days and, after 4 days, up-regulated gene and protein expressions of NF-M, Tuj1, S100β and GFAP in iPSCs-NCSCs whereas after 7 days expression of only NF-M, S100β and GFAP were up-regulated. LIPUS treatment at an appropriate intensity can, therefore, be an efficient and cost-effective method to enhance cell viability, proliferation and neural differentiation of iPSCs-NCSCs in vitro for peripheral nerve tissue engineering.

Low-intensity pulsed ultrasound stimulation facilitates osteogenic differentiation of human periodontal ligament cells

Human periodontal ligament cells (hPDLCs) possess stem cell properties, which play a key role in periodontal regeneration. Physical stimulation at appropriate intensities such as low-intensity pulsed ultrasound (LIPUS) enhances cell proliferation and osteogenic differentiation of mesechymal stem cells. However, the impacts of LIPUS on osteogenic differentiation of hPDLCs in vitro and its molecular mechanism are unknown. This study was undertaken to investigate the effects of LIPUS on osteogenic differentiation of hPDLCs. HPDLCs were isolated from premolars of adolescents for orthodontic reasons, and exposed to LIPUS at different intensities to determine an optimal LIPUS treatment dosage. Dynamic changes of alkaline phosphatase (ALP) activities in the cultured cells and supernatants, and osteocalcin production in the supernatants after treatment were analyzed. Runx2 and integrin β1 mRNA levels were assessed by reverse transcription polymerase chain reaction analysis after LIPUS stimulation. Blocking antibody against integrinβ1 was used to assess the effects of integrinβ1 inhibitor on LIPUS-induced ALP activity, osteocalcin production as well as calcium deposition. Our data showed that LIPUS at the intensity of 90 mW/cm2 with 20 min/day was more effective. The ALP activities in lysates and supernatants of LIPUS-treated cells started to increase at days 3 and 7, respectively, and peaked at day 11. LIPUS treatment significantly augmented the production of osteocalcin after day 5. LIPUS caused a significant increase in the mRNA expression of Runx2 and integrin β1, while a significant decline when the integrinβ1 inhibitor was used. Moreover, ALP activity, osteocalcin production as well as calcium nodules of cells treated with both daily LIPUS stimulation and integrinβ1 antibody were less than those in the LIPUS-treated group. In conclusion, LIPUS promotes osteogenic differentiation of hPDLCs, which is associated with upregulation of Runx2 and integrin β1, which may thus provide therapeutic benefits in periodontal tissue regeneration.

Induction of skeletal muscle differentiation in vitro by therapeutic ultrasound

Therapeutic ultrasound (TU) has been used for the last 50 y in rehabilitation, including treatment of soft tissues. Ultrasound waves can be employed in two different modes of operation, continuous and pulsed, which produce both thermal and non-thermal effects. Despite the large-scale use of TU, there are few scientific studies on its biologic effects during skeletal muscle differentiation. To better analyze the cellular effects of TU, we decided to follow cells in vitro. The main purpose of this study was to evaluate the effects of TU in primary chick myogenic cell cultures using phase contrast optical microscopy and immunofluorescence microscopy, followed by image analysis and quantification. Our results indicate that TU can stimulate the differentiation of skeletal muscle cells in vitro, as measured by the thickness of multinucleated myotubes, the ratio of mononucleated cells to multinucleated cells and expression of the muscle-specific protein desmin. This study is a first step toward a metrologic and science-based protocol for cell treatment under different ultrasound field exposures.

In vitro effects of low-intensity pulsed ultrasound stimulation on the osteogenic differentiation of human alveolar bone-derived mesenchymal stem cells for tooth tissue engineering

Ultrasound stimulation produces significant multifunctional effects that are directly relevant to alveolar bone formation, which is necessary for periodontal healing and regeneration. We focused to find out effects of specific duty cycles and the percentage of time that ultrasound is being generated over one on/off pulse period, under ultrasound stimulation. Low-intensity pulsed ultrasound ((LIPUS) 1 MHz) with duty cycles of 20% and 50% was used in this study, and human alveolar bone-derived mesenchymal stem cells (hABMSCs) were treated with an intensity of 50 mW/cm(2) and exposure time of 10 min/day. hABMSCs exposed at duty cycles of 20% and 50% had similar cell viability (O.D.), which was higher (*P < 0.05) than that of control cells. The alkaline phosphatase (ALP) was significantly enhanced at 1 week with LIPUS treatment in osteogenic cultures as compared to control. Gene expressions showed significantly higher expression levels of CD29, CD44, COL1, and OCN in the hABMSCs under LIPUS treatment when compared to control after two weeks of treatment. The effects were partially controlled by LIPUS treatment, indicating that modulation of osteogenesis in hABMSCs was related to the specific stimulation. Furthermore, mineralized nodule formation was markedly increased after LIPUS treatment than that seen in untreated cells. Through simple staining methods such as Alizarin red and von Kossa staining, calcium deposits generated their highest levels at about 3 weeks. These results suggest that LIPUS could enhance the cell viability and osteogenic differentiation of hABMSCs, and could be part of effective treatment methods for clinical applications.

Low-intensity pulsed ultrasound accelerates tooth movement via activation of the BMP-2 signaling pathway

The present study was designed to determine the underlying mechanism of low-intensity pulsed ultrasound (LIPUS) induced alveolar bone remodeling and the role of BMP-2 expression in a rat orthodontic tooth movement model. Orthodontic appliances were placed between the homonymy upper first molars and the upper central incisors in rats under general anesthesia, followed by daily 20-min LIPUS or sham LIPUS treatment beginning at day 0. Tooth movement distances and molecular changes were evaluated at each observation point. In vitro and in vivo studies were conducted to detect HGF (Hepatocyte growth factor)/Runx2/BMP-2 signaling pathways and receptor activator of NFκB ligand (RANKL) expression by quantitative real time PCR (qRT-PCR), Western blot and immunohistochemistry. At day 3, LIPUS had no effect on the rat orthodontic tooth movement distance and BMP-2-induced alveolar bone remodeling. However, beginning at day 5 and for the following time points, LIPUS significantly increased orthodontic tooth movement distance and BMP-2 signaling pathway and RANKL expression compared with the control group. The qRT-PCR and Western blot data in vitro and in vivo to study BMP-2 expression were consistent with the immunohistochemistry observations. The present study demonstrates that LIPUS promotes alveolar bone remodeling by stimulating the HGF/Runx2/BMP-2 signaling pathway and RANKL expression in a rat orthodontic tooth movement model, and LIPUS increased BMP-2 expression via Runx2 regulation.

Multimodal noninvasive monitoring of soft tissue wound healing

Here we report results of non-invasive measurements of indirect markers of soft tissue healing of traumatic wounds in an observational swine study and describe the quantification of analog physiological signals. The primary purpose of the study was to measure bone healing of fractures with four different wound treatments. A second purpose was to quantify soft tissue wound healing by measuring the following indirect markers: (1) tissue oxygenation, (2) fluid content, and (3) blood flow, which were all measured by non-invasive modalities, measured with available devices. Tissue oxygenation was measured by near infrared spectroscopy; fluid content was measured by bipolar bio-impedance; and blood flow was measured by Doppler ultrasound. Immediately after comminuted femur fractures were produced in the right hind legs of thirty anesthetized female Yorkshire swine, one of four wound treatments was instilled into each wound. The four wound treatments were as follows: salmon fibrinogen/thrombin-n = 8; commercial bone filler matrix-n = 7; bovine collagen-n = 8; porcine fibrinogen/thrombin-n = 7. Fractures were stabilized with an external fixation device. Immediately following wound treatments, measurements were made of tissue oxygenation, fluid content and blood flow; these measurements were repeated weekly for 3 weeks after surgery. Analog signals of each modality were recorded on both the wounded (right) hind leg and the healthy (left) hind leg, for comparison purposes. Data were processed off-line. The mean values of 10-s periods were calculated for right-left leg comparison. ANOVA was applied for statistical analysis. Results of the bone healing studies are published separately (Rothwell et al. in J Spec Oper Med 13:7-18, 2013). For soft tissue wounds, healing did not differ significantly among the four wound treatments; however, regional oxygenation of wounds treated with salmon fibrinogen/thrombin showed slightly different time trends. Further studies are needed to establish standards for healthy wound healing and for detection of pathological alterations such as infection. Non-invasive measurement and quantification of indirect markers of soft tissue wound healing support the goals and principles of evidence-based medicine and show potential as easy to administer tools for clinicians and battlefield medical personnel to apply when procedures such as the PET scan are not available or affordable. The method we developed for storing analog physiological signals could be used for maintaining electronic health records, by incorporating vital signs such as ECG and EEG, etc.

Acoustic droplet-hydrogel composites for spatial and temporal control of growth factor delivery and scaffold stiffness

Wound healing is regulated by temporally and spatially restricted patterns of growth factor signaling, but there are few delivery vehicles capable of the "on-demand" release necessary for recapitulating these patterns. Recently we described a perfluorocarbon double emulsion that selectively releases a protein payload upon exposure to ultrasound through a process known as acoustic droplet vaporization (ADV). In this study, we describe a delivery system composed of fibrin hydrogels doped with growth factor-loaded double emulsion for applications in tissue regeneration. Release of immunoreactive basic fibroblast growth factor (bFGF) from the composites increased up to 5-fold following ADV and delayed release was achieved by delaying exposure to ultrasound. Releasates of ultrasound-treated materials significantly increased the proliferation of endothelial cells compared to sham controls, indicating that the released bFGF was bioactive. ADV also triggered changes in the ultrastructure and mechanical properties of the fibrin as bubble formation and consolidation of the fibrin in ultrasound-treated composites were accompanied by up to a 22-fold increase in shear stiffness. ADV did not reduce the viability of cells suspended in composite scaffolds. These results demonstrate that an acoustic droplet-hydrogel composite could have broad utility in promoting wound healing through on-demand control of growth factor release and/or scaffold architecture.

Clinical and immunohistopathological aspects of venous ulcers treatment by Low-Intensity Pulsed Ultrasound (LIPUS)

The immunological mechanisms that are triggered by Low-Intensity Pulsed Ultrasound (LIPUS) in wound healing are unknown. In the present study, experimental groups were used to assess the treatment of chronic venous ulcers with 30mW/cm(2) SATA peripheral LIPUS three times per week compared to a daily treatment of 1% silver sulfadiazine (SDZ). The ulcers of the SDZ group (n=7) (G1) and LIPUS group (n=9) (G2) were photographed five times three months, and the images were analyzed using ImageJ software to quantify the total area (S), fibrin/sphacel area (yellow) and granulation area (red). The healing process was evaluated by the wound healing rate (WHR), granulation tissue rate (GTR) and fibrin/sphacel tissue rate (FTR). The ulcers were biopsied on days 1 and 45 and stained for collagen fiber quantification (picrosirius) and CD68(+) protein and VEGF (vascular endothelial growth factor) expression using HRP-streptavidin (horseradish peroxidase-streptavidin). On day 90, G2 had a mean 41% decrease in the ulcer area, while no decrease was observed in G1 (p<0.05). An increased tendency toward positive labeling of collagen fibers and VEGF (p>0.05) was observed in G2 compared to G1, and the number of CD68(+) cells was greater in G2 than in G1 (p<0.05). LIPUS presents superior activity compared to SDZ in stimulating the inflammatory and proliferative (angiogenesis and collagenesis, respectively) phases of chronic venous wound healing.

The effect of low-intensity therapeutic ultrasound in induced fracture of rat tibiae

OBJECTIVE:

To analyze the possible effects of low-intensity ultrasound on induced tibia fracture of rats in a dose commonly used in physical therapy treatments.

METHODS:

Twenty male Wistar rats were divided into two groups with 10 animals each. In the ultrasound group (USG), the animals were submitted to bone fracture and treatment with therapeutic ultrasound (TUS). Ultrasonic parameters are: frequency of 1.0 MHz, intensity of 0.2 W/cm2, pulsed mode at 20%, applied in stationary form during 10 minutes on the fracture region, for five weeks. The control group (CG) was submitted to bone fracture but not treated with ultrasound.

RESULTS:

The radiographies showed better consolidation in USG compared to CG. The statistical tests for alkaline phosphatase and serum calcium did not show significant difference between groups.

CONCLUSION:

According to this study, TUS, applied with these parameters (not commonly used for bone therapy) accelerates bone healing, confirmed by radiography, yet the biochemical analysis was not conclusive. One reason for this inconsistency may have been some inadequacy of the biochemical protocol, currently under investigation. Level of Evidence II, Prospective comparative study.

Low-intensity pulsed ultrasound inhibits messenger RNA expression of matrix metalloproteinase-13 induced by interleukin-1β in chondrocytes in an intensity-dependent manner

The effect of low-intensity pulsed ultrasound (LIPUS) on articular cartilage metabolism has been characterized. However, the effect of LIPUS intensity on articular cartilage degradation factors remains unknown. This study aimed to investigate the immediate effect of LIPUS at several intensities on cultured chondrocytes treated with interleukin-1β (IL-1β) to induce an inflammatory response and on articular cartilage explants. Cultured chondrocytes and articular cartilage explants were treated by LIPUS at intensities of 0, 7.5, 30 and 120 mW/cm(2) or 0, 27 and 67 mW/cm(2), respectively. mRNA analysis revealed that LIPUS inhibited induction of MMP13 mRNA expression by 100 pg/mL IL-1β in cultured chondrocytes in an intensity-dependent manner. LIPUS also inhibited MMP13 and MMP1 mRNA expression in articular cartilage explants. Our results indicate that LIPUS may potentially protect articular cartilage by inhibiting MMP mRNA expression in an intensity-dependent manner and should thus be considered a useful candidate for daily treatment of OA.