Low-intensity ultrasound increases FAK, ERK-1/2, and IRS-1 expression of intact rat bones in a noncumulative manner

Focal adhesion kinase (FAK): its structure, characteristics, and signaling in skeletal system

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase and distributes important regulatory functions in skeletal system. Mesenchymal stem cell (MSC) possesses significant migration and differentiation capacity, is an important source of distinctive bone cells production and a prominent bone development pathway. MSC has a wide range of applications in tissue bioengineering and regenerative medicine, and is frequently employed for hematopoietic support, immunological regulation, and defect repair, although current research is insufficient. FAK has been identified to cross-link with many other keys signaling pathways in bone biology and is considered as a fundamental "crossroad" on the signal transduction pathway and a "node" in the signal network to mediate MSC lineage development in skeletal system. In this review, we summarized the structure, characteristics, cellular signaling, and the interactions of FAK with other signaling pathways in the skeletal system. The discovery of FAK and its mediated molecules will lead to a new knowledge of bone development and bone construction as well as considerable potential for therapeutic use in the treatment of bone-related disorders such as osteoporosis, osteoarthritis, and osteosarcoma.

Sustained acoustic medicine for the treatment of musculoskeletal injuries: a systematic review and meta-analysis

BACKGROUND

Musculoskeletal injuries account for 10 million work-limited days per year and often lead to both acute and/or chronic pain, and increased chances of re-injury or permanent disability. Conservative treatment options include various modalities, nonsteroidal anti-inflammatory drugs, and physical rehabilitation programs. Sustained Acoustic Medicine is an emerging prescription home-use mechanotransductive device to stimulate cellular proliferation, increase microstreaming and cavitation in situ, and to increase tissue profusion and permeability. This research aims to summarize the clinical evidence on Sustained Acoustic Medicine and measurable outcomes in the literature.

METHODS

A systematic literature review was conducted using PubMed, EBSCOhost, Academic Search Complete, Google Scholar and ClinicalTrials.gov to identify studies evaluating the effects of Sustained Acoustic Medicine on the musculoskeletal system of humans. Articles identified were selected based on inclusion criteria and scored on the Downs and Black checklist. Study design, clinical outcomes and primary findings were extracted from included studies for synthesis and meta-analysis statistics.

RESULTS

A total of three hundred and seventy-two participants (372) were included in the thirteen clinical research studies reviewed including five (5) level I, four (4) level II and four (4) level IV studies. Sixty-seven (67) participants with neck and back myofascial pain and injury, one hundred and fifty-six (156) participants with moderate to severe knee pain and radiographically confirmed knee osteoarthritis (Kellgren-Lawrence grade II/III), and one hundred forty-nine (149) participants with generalized soft-tissue injury of the elbow, shoulder, back and ankle with limited function. Primary outcomes included daily change in pain intensity, change in Western Ontario McMaster Osteoarthritis Questionnaire, change in Global Rate of Change, and functional outcome measures including dynamometry, grip strength, range-of-motion, and diathermic heating (temperature measurement).

CONCLUSION

Sustained Acoustic Medicine treatment provides tissue heating and tissue recovery, improved patient function and reduction of pain. When patients failed to respond to physical therapy, Sustained Acoustic Medicine proved to be a useful adjunct to facilitate healing and return to work. As a non-invasive and non-narcotic treatment option with an excellent safety profile, Sustained Acoustic Medicine may be considered a good therapeutic option for practitioners.

Low Intensity Ultrasound Induces Epithelial Cell Adhesion Responses

In this study, we investigated the cellular mechanosensitive responses to a low intensity ultrasound (LIUS) stimulation (ISATA = 1 mW/cm2, pressure = 10 kPa). The dose and temporal effects at cell-substrate adhesion (CSA) at the basal level and cell-cell adhesion (CCA) at the apical level are reported in detail. A model of mouse mammary gland epithelial cells (EpH4) and the phosphorylation of mechanosensitive 130 kDa Crk-associated substrate (p130CAS) as an indicator for cellular responses were used. The intensity of phospho-p130CAS was found to be dependent on LIUS stress level, and the p130CAS was phosphorylated after 1 min stimulation at CSA. The phospho-p130CAS was also found to increase significantly at CCA upon LIUS stimulation. We confirmed that the cellular responses to ultrasound are immediate and dose dependent. Ultrasound affects not only CSA but also CCA. An E-cadherin knockout (EpH4ECad-/-) model also confirmed that phosphorylation of p130CAS at CCA is related to E-cadherins.

Shortening of Overall Orthodontic Treatment Duration with Low-Intensity Pulsed Ultrasound (LIPUS)

The aim of this retrospective clinical study was to determine if there is a reduction in the overall treatment duration in orthodontic patients using low-intensity pulsed ultrasound (LIPUS) and Invisalign SmartTrack® clear aligners. Data were collected from the first thirty-four patients (9 males, 25 females; average age 41.37 ± 15.02) who finished their orthodontic treatment using an intraoral LIPUS device and Invisalign clear aligners in a private clinic. The LIPUS parameters used by patients at home for 20 min/day were: ultrasonic frequency 1.5 MHz, pulse duration 200µs, pulse repetition rate 1 kHz, and spatial average-temporal average intensity 30mW/cm². A control group (11 males, 23 females; average age 31.36 ± 14.41) matching for the same malocclusions was randomly selected from finished treatment cases of the same clinician. The date of first Invisalign attachment placement and first use of LIPUS application was recorded as T0, and the date of retainer delivery was recorded as T1. The treatment duration (T1–T0) and treatment reduction percentage with LIPUS device were collected and analyzed using two-sample t-test in Microsoft Excel. Treatment duration was significantly reduced in the LIPUS group (541.44 ± 192.23 days) compared to control group (1061.05 ± 455.64 days) (p < 0.05). The LIPUS group showed on average 49% reduction in the overall treatment time as compared to the control group. The average compliance of the patients using LIPUS was 66.02%. Patients who used LIPUS showed a clinically significant reduction in the overall orthodontic treatment duration compared to the control group who used Invisalign clear aligners only.

Effect of Low-Intensity Pulsed Ultrasound Stimulation, Extracorporeal Shockwaves and Radial Pressure Waves on Akt, BMP-2, ERK-2, FAK and TGF-β1 During Bone Healing in Rat Tibial Defects

An experimental study was conducted to determine whether low-intensity pulsed ultrasound stimulation (LIPUS), extracorporeal shockwave treatment (ESWT) and radial pressure wave treatment (RPWT) modulate Akt, bone morphogenetic protein-2 (BMP-2), extracellular signal-regulated kinase-2 (ERK-2), focal adhesion kinase (FAK) and transforming growth factor-β1 (TGF-β1) during bone healing in rat tibial defects. Rat tibial defects were exposed to 500 shots of ESWT delivered at 0.12 mJ/mm², 500 impulses of RPWT operated at 2.0 bar or to daily 20-min 30 mW/cm² LIPUS. Following 1, 3 and 6 wk, bones were harvested to determine the expression and activity of Akt, BMP-2, ERK-2, FAK and TGF-β1. Animals exposed to ultrasound were followed up to 3 wk. Protein expression and activity were unchanged following LIPUS treatment. ESWT increased Akt activity 2.11-fold (p = 0.043) and TGF-β1 expression 9.11-fold (p = 0.016) at 1 wk and increased FAK activity 2.16-fold (p = 0.047) at 3 wk. RPWT increased FAK activity 2.6-fold (p = 0.028) at 3 wk and decreased Akt expression 0.52-fold (p = 0.05) at 6 wk. In conclusion, the protocols employed for ESWT and RPWT modulated distinct signaling pathways during fracture healing, while LIPUS standard protocol did not change the usual signaling pathways of the proteins investigated. Future studies are required to monitor osteogenesis so that the biologic meaning of our results can be clarified.

Design of an ultrasound chamber for cellular excitation and observation

In this work, a design of integrating ultrasonic transduction with live cell imaging chamber is introduced. The principle of a metal-incident-glass-output acoustic path was used to deliver a uniform energy profile into the imaging/incubation chamber in the form of leaky Lamb waves. The design was applied to examine living mouse mammary gland epithelial cells (EpH4). Significant changes in intracellular activities were observed even at a very low energy intensity level (1 MHz, I_SATA = 1 mW/cm², continuous wave). Live imaging with ultrasonic stimulation provides a different paradigm to interrogate cellular mechanosensitive responses in real time.

Low Intensity Pulsed Ultrasound Influences the Myogenic Differentiation of Muscle Satellite Cells in a Stress Urinary Incontinence Rat Model

OBJECTIVE

To investigate the therapeutic effect of low intensity pulsed ultrasound (LIPUS) in a stress urinary incontinence (SUI) rat model and its influence on myogenic satellite cells.

METHODS

Fifty Sprague-Dawley rats underwent vaginal distension and bilateral ovariectomy mimicking partum injury and menopause to construct SUI models, which were further randomized into 100 mW/cm² LIPUS, 200 mW/cm² LIPUS, 300 mW/cm² LIPUS, and none-treatment control subgroups with 10 rats per subgroup. Ten rats served as mock operation control. Leak point pressure and bladder capacity were recorded 1 week after LIPUS treatment. Immunofluorescence staining and Western blot were performed to examine histological changes, myodifferentiation, and signaling pathway.

RESULTS

Here,we found the leak point pressure and bladder capacity were restored in 200 mW/cm² LIPUS and 300 mW/cm² LIPUS groups, but not in 100 mW/cm² LIPUS group. More robust striated muscle regeneration was observed in 200 mW/cm² LIPUS group comparing with the SUI none-treatment group. Moreover, we found LIPUS activated the myodifferentiation of muscle satellite cells, which is correlated to p38 phosphorylation level.

CONCLUSION

LIPUS restored the leak point pressure and bladder capacity, and activated satellite cell myodifferentiation in SUI rat model.

Role of Reactive Oxygen Species during Low-Intensity Pulsed Ultrasound Application in MC-3 T3 E1 Pre-osteoblast Cell Culture

We evaluated the activation of mitogen-activated protein kinase (MAPK) activation through reactive oxygen species (ROS) by application of low-intensity ultrasound (LIPUS) to MC-3 T3 E1 pre-osteoblasts. The cells were subjected to one LIPUS application for either 10 or 20 min, and the control group was exposed to a sham transducer. For ROS inhibition, 10 μM diphenylene iodonium (DPI) was added to the cells an hour before LIPUS application. Samples were collected 1, 3, 6, 12 and 24 h after LIPUS application, and cells were evaluated for ROS generation, cell viability, gene expression and MAPK activation by immunoblot analyses. LIPUS caused a significant increase in ROS and cell viability in the non-DPI-treated group. Expression of RUNX2, OCN and OPN mRNA was higher in the LIPUS-treated groups at 1 h in both the DPI-treated and non-DPI-treated groups; RUNX2 and OCN mRNA levels increased at 6 h. ERK1/2 activation was increased in the LIPUS-treated groups. These results indicate that LIPUS activates MAPK by ROS generation in MC-3 T3 E1 pre-osteoblasts.

Low-intensity pulsed ultrasound activates ERK1/2 and PI3K-Akt signalling pathways and promotes the proliferation of human amnion-derived mesenchymal stem cells

OBJECTIVES

This study was to investigate the effect and mechanism of low-intensity pulsed ultrasound (LIPUS) on the proliferation of human amnion-derived mesenchymal stem cells (hAD-MSCs).

METHODS

Human amnion-derived mesenchymal stem cells were isolated from the amnion of term placentas and identified by flow cytometry and differentiation culture. Proliferation of hAD-MSCs was investigated by Cell Counting Kit-8, cell cycle and EdU assays. Western blotting was used to determine the protein expression levels.

RESULTS

Human amnion-derived mesenchymal stem cells were successfully isolated from the amnion and identified as multipotent mesenchymal stem cells. Low-intensity pulsed ultrasound promoted the proliferation of hAD-MSCs. Cell cycle analysis showed that LIPUS promoted cells to enter S and G2/M phases from G0/G1 phase. Western blot results showed that LIPUS promoted the phosphorylation and activation of ERK1/2 and Akt and significantly upregulated expression of cyclin D1, cyclin E1, cyclin A2 and cyclin B1. ERK1/2 inhibitor (U0126) and PI3K inhibitor (LY294002) significantly reduced LIPUS-induced phosphorylation of ERK1/2 and Akt, respectively, which in turn reduced the LIPUS-induced proliferation of hAD-MSCs.

CONCLUSIONS

Low-intensity pulsed ultrasound can promote the proliferation of hAD-MSCs, and ERK1/2 and PI3K-Akt signalling pathways may play important roles in this process.

Chondro-protective effects of low intensity pulsed ultrasound

OBJECTIVES

Cartilage is a highly mechano-responsive tissue. Chondrocytes undergo a series of complex changes, including proliferation and metabolic alteration as the target of external biomechanical and biochemical stimuli. IL-1β is known to regulate chondrocyte metabolism and plays an important role in the pathogenesis of osteoarthritis (OA). The objective of this study was to employ low-intensity pulsed ultrasound (LIPUS) as a localized mechanical stimulus and assess its effects on chondrocyte migration, proliferation, metabolism, and differentiation, as well as its ability to suppress IL-1β mediated catabolism in cartilage.

METHODS

Human cartilage explants and chondrocytes were stimulated by LIPUS in the presence and absence of IL-1β to asses cartilage degradation, chondrocytes metabolism, migration, and proliferation. Western blot analyses were conducted to study IL-1β the associated NFκB pathway in chondrocytes.

RESULTS

LIPUS stimulation increased the proteoglycan content in human cartilage explants and inhibited IL-1β induced loss of proteoglycans. LIPUS stimulation increased rates of chondrocyte migration and proliferation, and promoted chondrogenesis in mesenchymal stem cells (MSC). Further, LIPUS suppressed IL-1β induced activation of phosphorylation of NFκB-p65 and IĸBα leading to reduced expression of MMP13 and ADAMT5 in chondrocytes.

CONCLUSIONS

Collectively, these data demonstrate the potential therapeutic effects of LIPUS in preventing cartilage degradation and treating OA via a mechanical stimulation that inhibits the catabolic action of IL-1β and stimulates chondrocyte migration, proliferation, and differentiation.

Application of ultrasound stimulation in bone tissue engineering

Many studies have been investigated on the effects of the low-intensity pulsed ultrasound (LIPUS) on bone healing, acceleration of bone mineralization and regeneration. Many researchers have focused on a more comprehensive understanding of the biological mechanism of the osteoblast by LIPUS because the osteoblast is an important cell in bone formation. The effects of LIPUS on the proliferation, gene expression of Runx2, Msx2, Dlx5, and AJ18, and the second messenger signaling of osteoblast were reported. Various parameters of LIPUS, such as intensity, frequency, duration and topology, were investigated to find appropriate conditions in osteoblast. Less than 120 mW/cm(2) of intensity and 1-3 MHz of frequency were considered good condition for regeneration of bone tissue. Increased osteoblast cells and higher mineralized nodule formation explain the enhancement of proliferation by LIPUS. In addition, LIPUS affects on differentiation of osteoblast cells, which is shown by increased ALPase, and transcriptional factors, Runx2. Ultrasound stimulates PEG2 and COX-2 in osteoblast, and the signals accelerates the bone regeneration in tissue engineering.

Low-intensity pulsed ultrasound induces osteogenic differentiation of human periodontal ligament cells through activation of bone morphogenetic protein-smad signaling

OBJECTIVES

Low-intensity pulsed ultrasound (US) can accelerate fracture healing and osteogenic differentiation. The aim of this study was to investigate the osteogenic effect of low-intensity pulsed US on human periodontal ligament cells and to determine whether bone morphogenetic protein (BMP)-Smad signaling was involved.

METHODS

Human periodontal ligament cells were exposed to low-intensity pulsed US at a frequency of 1.5 MHz and intensity of 90 mW/cm(2) for 20 min/d. Osteogenic differentiation was determined by assaying alkaline phosphatase (ALP) and calcium deposition. Expression of BMP-2, BMP-6, and BMP-9 was detected by real-time polymerase chain reaction analysis. Phosphorylated Smad was detected by western blotting; Smad in the cells was labeled by an immunofluorescent antibody and observed by laser-scanning confocal microscopy.

RESULTS

The optical density of ALP stimulated by US at 1.5 MHz and 90 mW/cm(2) for 20 min/d was significantly higher than in other groups (P < .01); therefore, this dosage was considered optimal for promoting osteogenic differentiation. After 13 days of US exposure, ALP increased gradually after 5 days, peaked at 11 days, and decreased at 13 days, with a significant difference compared with the control group (P < .05). Osteocalcin production increased from 9 to 13 days and peaked at 15 days, with a significant difference compared with the control group (P < .05). BMP-2 and BMP-6 increased dynamically after exposure for 13 days. BMP-2 increased 6.07-fold at 3 days, 6.39-fold at 11 days, and 5.97-fold at 13 days. BMP-6 expression increased 6.82-fold at 1 day and 51.5-fold at 3 days and decreased thereafter. BMP-9 was not expressed. Phospho-Smad1/5/8 expression was significantly increased after exposure (P< .05) and transferred from the cytoplasm into the nuclei.

CONCLUSIONS

Low-intensity pulsed US effectively induced osteogenic differentiation of human periodontal ligament cells, and the BMP-Smad signaling pathway was involved in the mechanism.

Low intensity pulsed ultrasound (LIPUS) influences the multilineage differentiation of mesenchymal stem and progenitor cell lines through ROCK-Cot/Tpl2-MEK-ERK signaling pathway

Mesenchymal stem cells (MSCs) are pluripotent cells that can differentiate into multilineage cell types, including adipocytes and osteoblasts. Mechanical stimulus is one of the crucial factors in regulating MSC differentiation. However, it remains unknown how mechanical stimulus affects the balance between adipogenesis and osteogenesis. Low intensity pulsed ultrasound (LIPUS) therapy is a clinical application of mechanical stimulus and facilitates bone fracture healing. Here, we applied LIPUS to adipogenic progenitor cell and MSC lines to analyze how multilineage cell differentiation was affected. We found that LIPUS suppressed adipogenic differentiation of both cell types, represented by impaired lipid droplet appearance and decreased gene expression of peroxisome proliferator-activated receptor γ2 (Pparg2) and fatty acid-binding protein 4 (Fabp4). LIPUS also down-regulated the phosphorylation level of peroxisome proliferator-activated receptor γ2 protein, inhibiting its transcriptional activity. In contrast, LIPUS promoted osteogenic differentiation of the MSC line, characterized by increased cell calcification as well as inductions of runt-related transcription factor 2 (Runx2) and Osteocalcin mRNAs. LIPUS induced phosphorylation of cancer Osaka thyroid oncogene/tumor progression locus 2 (Cot/Tpl2) kinase, which was essential for the phosphorylation of mitogen-activated kinase kinase 1 (MEK1) and p44/p42 extracellular signal-regulated kinases (ERKs). Notably, effects of LIPUS on both adipogenesis and osteogenesis were prevented by a Cot/Tpl2-specific inhibitor. Furthermore, effects of LIPUS on MSC differentiation as well as Cot/Tpl2 phosphorylation were attenuated by the inhibition of Rho-associated kinase. Taken together, these results indicate that mechanical stimulus with LIPUS suppresses adipogenesis and promotes osteogenesis of MSCs through Rho-associated kinase-Cot/Tpl2-MEK-ERK signaling pathway.

Ultrasound stimulation increases proliferation of MC3T3-E1 preosteoblast-like cells

Background

Mechanical stimulation of bone increases bone mass and fracture healing, at least in part, through increases in proliferation of osteoblasts and osteoprogenitor cells. Researchers have previously performed in vitro studies of ultrasound-induced osteoblast proliferation but mostly used fixed ultrasound settings and have reported widely varying and inconclusive results. Here we critically investigated the effects of the excitation parameters of low-intensity pulsed ultrasound (LIPUS) stimulation on proliferation of MC3T3-E1 preosteoblastic cells in monolayer cultures.

Methods

We used a custom-designed ultrasound exposure system to vary the key ultrasound parameters—intensity, frequency and excitation duration. MC3T3-E1 cells were seeded in 12-well cell culture plates. Unless otherwise specified, treated cells, in groups of three, were excited twice for 10 min with an interval of 24 h in between after cell seeding. Proliferation rates of these cells were determined using BrdU and MTS assays 24 h after the last LIPUS excitation. All data are presented as the mean ± standard error. The statistical significance was determined using Student's two-sample two-tailed t tests.

Results

Using discrete LIPUS intensities ranging from 1 to 500 mW/cm² (SATA, spatial average-temporal average), we found that approximately 75 mW/cm² produced the greatest increase in osteoblast proliferation. Ultrasound exposures at higher intensity (approximately 465 mW/cm²) significantly reduced proliferation in MC3T3-E1 cells, suggesting that high-intensity pulsed ultrasound may increase apoptosis or loss of adhesion in these cells. Variation in LIPUS frequency from 0.5 MHz to 5 MHz indicated that osteoblast proliferation rate was not frequency dependent. We found no difference in the increase in proliferation rate if LIPUS was applied for 30 min/day or 10 min/day, indicating a habituation response.

Conclusion

This study concludes that a short-term stimulation with optimum intensity can enhance proliferation of preosteoblast-like bone cells that plays an important role in bone formation and accelerated fracture healing, also suggesting a possible therapeutic treatment for reduced bone mass.

Reversal of the detrimental effects of simulated microgravity on human osteoblasts by modified low intensity pulsed ultrasound

Microgravity (MG) is known to induce bone loss in astronauts during long-duration space mission because of a lack of sufficient mechanical stimulation under MG. It has been demonstrated that mechanical signals are essential for maintaining cell viability and motility, and they possibly serve as a countermeasure to the catabolic effects of MG. The objective of this study was to examine the effects of high-frequency acoustic wave signals on osteoblasts in a simulated microgravity (SMG) environment (created using 1-D clinostat bioreactor) using a modified low-intensity pulsed ultrasound (mLIPUS). Specifically, we evaluated the hypothesis that osteoblasts (human fetal osteoblastic cell line) exposure to mLIPUS for 20 min/d at 30 mW/cm(2) will significantly reduce the detrimental effects of SMG. Effects of SMG with mLIPUS were analyzed using the MTS proliferation assay for proliferation, phalloidin for F-actin staining, Sirius red stain for collagen, and Alizarin red for mineralization. Our data showed that osteoblast exposure to SMG results in significant decreases in proliferation (∼ -38% and ∼ -44% on days 4 and 6, respectively; p < 0.01), collagen content (∼ -22%; p < 0.05) and mineralization (∼ -37%; p < 0.05) and actin stress fibers. In contrast, mLIPUS stimulation in SMG condition significantly increases the rate of proliferation (∼24% by day 6; p < 0.05), collagen content (∼52%; p < 0.05) and matrix mineralization (∼25%; p < 0.001) along with restoring formation of actin stress fibers in the SMG-exposed osteoblasts. These data suggest that the acoustic wave can potentially be used as a countermeasure for disuse osteopenia.