Low-intensity pulsed ultrasound (LIPUS) and cell-to-cell communication in bone marrow stromal cells

Higher-intensity ultrasound accelerates fracture healing via mechanosensitive ion channel Piezo1

Osteoporosis-related fractures are a major public health problem. Mechanobiological stimulation utilizing low-intensity pulsed ultrasound (LIPUS) is the most widely accepted modality for accelerating fracture healing. However, recent evidence has demonstrated the ineffectiveness of LIPUS, and the biophysical mechanisms of ultrasound-induced bone formation also remain elusive. Here, we demonstrate that ultrasound at a higher intensity than LIPUS effectively accelerates fracture healing in a mouse osteoporotic fracture model. Higher-intensity ultrasound promoted chondrogenesis and hypertrophic differentiation of chondrocytes in the fracture callus. Higher-intensity ultrasound also increased osteoblasts and newly formed bone in the callus, resulting in accelerated endochondral ossification during fracture healing. In addition, we found that accelerated fracture healing by ultrasound exposure was attenuated when the mechanosensitive ion channel Piezo1 was inhibited by GsMTx4. Ultrasound-induced new bone formation in the callus was attenuated in fractured mice treated with GsMTx4. Similar results were also confirmed in a 3D osteocyte-osteoblast co-culture system, where osteocytic Piezo1 knockdown attenuated the expression of osteoblastic genes after ultrasound exposure. Together these results demonstrate that higher-intensity ultrasound than clinically used LIPUS can accelerate endochondral ossification after fractures. Furthermore, our results suggest that mechanotransduction via Piezo1 mediates ultrasound-stimulated fracture healing and bone formation.

Microenvironment-targeted strategy steers advanced bone regeneration

Treatment of large bone defects represents a great challenge in orthopedic and craniomaxillofacial surgery. Traditional strategies in bone tissue engineering have focused primarily on mimicking the extracellular matrix (ECM) of bone in terms of structure and composition. However, the synergistic effects of other cues from the microenvironment during bone regeneration are often neglected. The bone microenvironment is a sophisticated system that includes physiological (e.g., neighboring cells such as macrophages), chemical (e.g., oxygen, pH), and physical factors (e.g., mechanics, acoustics) that dynamically interact with each other. Microenvironment-targeted strategies are increasingly recognized as crucial for successful bone regeneration and offer promising solutions for advancing bone tissue engineering. This review provides a comprehensive overview of current microenvironment-targeted strategies and challenges for bone regeneration and further outlines prospective directions of the approaches in construction of bone organoids.

Application of low-intensity pulsed ultrasound on tissue resident stem cells: Potential for ophthalmic diseases

INTRODUCTION

Tissue-resident stem cells (TRSCs) have the ability to self-renew and differentiate throughout an individual's lifespan, and they utilize both mechanisms to maintain homeostasis and regenerate damaged tissues. Several studies suggest that these stem cells can serve as a potential source for cell-replacement-based therapy by promoting differentiation or expansion. In recent years, low-intensity pulsed ultrasound (LIPUS) has been demonstrated to effectively stimulate stem cell proliferation and differentiation, promote tissue regeneration, and inhibit inflammatory responses.

AIMS

To present a comprehensive overview of current application and mechanism of LIPUS on tissue resident stem cells.

METHODS

We searched PubMed, Web of Science for articles on the effects of LIPUS on tissue resident stem cells and its application.

RESULTS

The LIPUS could modulate cellular activities such as cell viability, proliferation and differentiation of tissue resident stem cells and related cells through various cellular signaling pathways. Currently, LIPUS, as the main therapeutic ultrasound, is being widely used in the treatment of preclinical and clinical diseases.

CONCLUSION

The stem cell research is the hot topic in the biological science, while in recent years, increasing evidence has shown that TRSCs are good targets for LIPUS-regulated regenerative medicine. LIPUS may be a novel and valuable therapeutic approach for the treatment of ophthalmic diseases. How to further improve its efficiency and accuracy, as well as the biological mechanism therein, will be the focus of future research.

Traditional Multiwell Plates and Petri Dishes Limit the Evaluation of the Effects of Ultrasound on Cells In Vitro

Ultrasound accelerates healing in fractured bone; however, the mechanisms responsible are poorly understood. Experimental setups and ultrasound exposures vary or are not adequately characterized across studies, resulting in inter-study variation and difficulty in concluding biological effects. This study investigated experimental variability introduced through the cell culture platform used. Continuous wave ultrasound (45 kHz; 10, 25 or 75 mW/cm², 5 min/d) was applied, using a Duoson device, to Saos-2 cells seeded in multiwell plates or Petri dishes. Pressure field and vibration quantification and finite-element modelling suggested formation of complex interference patterns, resulting in localized displacement and velocity gradients, more pronounced in multiwell plates. Cell experiments revealed lower metabolic activities in both culture platforms at higher ultrasound intensities and absence of mineralization in certain regions of multiwell plates but not in Petri dishes. Thus, the same transducer produced variable results in different cell culture platforms. Analysis on Petri dishes further revealed that higher intensities reduced vinculin expression and distorted cell morphology, while causing mitochondrial and endoplasmic reticulum damage and accumulation of cells in sub-G1 phase, leading to cell death. More defined experimental setups and reproducible ultrasound exposure systems are required to study the real effect of ultrasound on cells for development of effective ultrasound-based therapies not just limited to bone repair and regeneration.

A transparent low intensity pulsed ultrasound (LIPUS) chip for high-throughput cell stimulation

We report an on-chip platform for low-intensity pulsed ultrasound (LIPUS) stimulation of cells directly cultured on a biocompatible surface of a transparent ultrasound transducer (TUT) fabricated using lithium niobate. The high light transmittance (>80%) and compact size (3 mm × 3 mm × 2 mm) of TUTs allowed easy integration with powerful optical microscopy techniques with no additional acoustic coupling and risk for contamination. TUTs were excited with varying acoustic excitation parameters (voltage amplitude and duty cycle) and resulting live cell calcium signaling was simultaneously imaged using time-lapse confocal microscopy, while the temperature change was measured by a thermocouple. Quantitative single-cell fluorescence analysis revealed the dynamic calcium signaling responses and together with the temperature measurements elucidated the optimal stimulation parameters for non-thermal and thermal effects. The fluorescence change profile was distinct from the recorded temperature change (<1 degree Celsius) profile under LIPUS treatment conditions. Cell dead assay results confirmed cells remain viable after the LIPUS treatment. These results confirmed that the TUT platform enables controllable, safe, high-throughput, and uniform mechanical stimulation of all plated cells. The on-chip LIPUS stimulation using TUTs has the potential to attract several in vitro and in vivo biomedical applications such as controlling stem cell differentiation and proliferation, studying biomechanical properties of cancer cells, and gaining fundamental insights into mechanotransduction pathways when integrated with state-of-the-art high-speed and high-resolution microscopy techniques.

Low Intensity Pulsed Ultrasound for Bone Tissue Engineering

As explained by Wolff's law and the mechanostat hypothesis, mechanical stimulation can be used to promote bone formation. Low intensity pulsed ultrasound (LIPUS) is a source of mechanical stimulation that can activate the integrin/phosphatidylinositol 3-OH kinase/Akt pathway and upregulate osteogenic proteins through the production of cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2). This paper analyzes the results of in vitro and in vivo studies that have evaluated the effects of LIPUS on cell behavior within three-dimensional (3D) titanium, ceramic, and hydrogel scaffolds. We focus specifically on cell morphology and attachment, cell proliferation and viability, osteogenic differentiation, mineralization, bone volume, and osseointegration. As shown by upregulated levels of alkaline phosphatase and osteocalcin, increased mineral deposition, improved cell ingrowth, greater scaffold pore occupancy by bone tissue, and superior vascularization, LIPUS generally has a positive effect and promotes bone formation within engineered scaffolds. Additionally, LIPUS can have synergistic effects by producing the piezoelectric effect and enhancing the benefits of 3D hydrogel encapsulation, growth factor delivery, and scaffold modification. Additional research should be conducted to optimize the ultrasound parameters and evaluate the effects of LIPUS with other types of scaffold materials and cell types.

In Vitro Study on the Piezodynamic Therapy with a BaTiO3-Coating Titanium Scaffold under Low-Intensity Pulsed Ultrasound Stimulation

To solve the poor sustainability of electroactive stimulation in clinical therapy, a strategy of combining a piezoelectric BaTiO3-coated Ti6Al4V scaffold and low-intensity pulsed ultrasound (LIPUS) was unveiled and named here as piezodynamic therapy. Thus, cell behavior could be regulated phenomenally by force and electricity simultaneously. First, BaTiO3 was deposited uniformly on the surface of the three-dimensional (3D) printed porous Ti6Al4V scaffold, which endowed the scaffold with excellent force-electricity responsiveness under pulsed ultrasound exposure. The results of live/dead staining, cell scanning electron microscopy, and F-actin staining showed that cells had better viability, better pseudo-foot adhesion, and more muscular actin bundles when they underwent the piezodynamic effect of ultrasound and piezoelectric coating. This piezodynamic therapy activated more mitochondria at the initial stage that intervened in the cell cycle by promoting cells' proliferation and weakened the apoptotic damage. The quantitative real-time polymerase chain reaction data further confirmed that the costimulation of the ultrasound and the piezoelectric scaffolds could trigger adequate current to upregulated the expression of osteogenic-related genes. The continuous electric cues could be generated by the BaTiO3-coated scaffold and intermittent LIPUS stimulation; thereon, more efficient bone healing would be promoted by piezodynamic therapy in future treatment.

The Roles of Different Stem Cells in Premature Ovarian Failure

Premature ovarian failure (POF) is characterized by amenorrhea, hypergonadotropism and hypoestrogenism before the age of 40, which affects 1% of women in the general population. POF is complex and heterogeneous due to its pathogenetic mechanisms. It is one of the significant causes of female infertility. Although many treatments are available for POF, these therapies are less efficient and trigger many side effects. Therefore, to find effective therapeutics for POF is urgently required. Due to stem cells having self-renewal and regeneration potential, they may be effective for the treatment of ovarian failure and consequently infertility. Recent studies have found that stem cells therapy may be able to restore the ovarian structure and function in animal models of POF and provide an effective treatment method. The present review summarizes the biological roles and the possible signaling mechanisms of the different stem cells in POF ovary. Further study on the precise mechanisms of stem cells on POF may provide novel insights into the female reproduction, which not only enhances the understanding of the physiological roles but also supports effective therapy for recovering ovarian functions against infertility.

[A review of mechanisms by which low-intensity pulsed ultrasound affects bone regeneration]

Low-intensity pulsed ultrasound (LIPUS) is a common physical therapy to accelerate the healing of bone fracture and treat delayed union of bone fracture. Vessels, nerves, and bone tissue are essential constituents of bone system. Recently, increasing evidence has been revealed that LIPUS can not only promote bone regeneration by directly regulating osteoblasts, osteoblasts, mesenchymal stem cells, but also have a positive impact on the repair of bone healing through vessels and nerves. Thus, we reviewed and summarized the latest published literature about the molecular mechanism for the effects of LIPUS on bone regeneration, which might offer a promising therapy for bone-related diseases.

Impact of low-intensity pulsed ultrasound on transcription and metabolite compositions in proliferation and functionalization of human adipose-derived mesenchymal stromal cells

To investigate the effect of low-intensity pulsed ultrasound (LIPUS) on the proliferation of human adipose-derived mesenchymal stromal cells (hASCs) and uncovered its stimulation mechanism. LIPUS at 30 mW/cm² was applied for 5 min/day to promote the proliferation of hASCs. Flow cytometry was used to study the cell surface markers, cell cycle, and apoptosis of hASCs. The proliferation of hASCs was detected by cell counting kit-8, cell cycle assay, and RT-PCR. The expression of hASCs cytokines was determined by ELISA. The differences between transcriptional genes and metabolites were analyzed by transcript analysis and metabolomic profiling experiments. The number of cells increased after LIPUS stimulation, but there was no significant difference in cell surface markers. The results of flow cytometry, RT-PCR, and ELISA after LIPUS was administered showed that the G₁ and S phases of the cell cycle were prolonged. The expression of cell proliferation related genes (CyclinD1 and c-myc) and the paracrine function related gene (SDF-1α) were up-regulated. The expression of cytokines was increased, while the apoptosis rate was decreased. The results of transcriptome experiments showed that there were significant differences in 27 genes;15 genes were up-regulated, while 12 genes were down-regulated. The results of metabolomics experiments showed significant differences in 30 metabolites; 7 metabolites were up-regulated, and 23 metabolites were down-regulated. LIPUS at 30 mW/cm² intensity can promote the proliferation of hASCs cells in an undifferentiating state, and the stem-cell property of hASCs was maintained. CyclinD1 gene, c-myc gene, and various genes of transcription and products of metabolism play an essential role in cell proliferation. This study provides an important experimental and theoretical basis for the clinical application of LIPUS in promoting the proliferation of hASCs cells.

Impact of Ultrasound Therapy on Stem Cell Differentiation - A Systematic Review

OBJECTIVE

This is a systematic review of the effects of low-intensity pulsed ultrasound (LIPUS) on stem cell differentiation.

BACKGROUND DATA

Recent studies have investigated several types of stem cells from different sources in the body. These stem cells should strictly be certified and promoted for cell therapies before being used in medical applications. LIPUS has been used extensively in treatment centers and in research to promote stem cell differentiation, function, and proliferation.

MATERIALS AND METHODS

The databases of PubMed, Google Scholar, and Scopus were searched for abstracts and full-text scientific papers published from 1989-2019 that reported the application of LIPUS on stem cell differentiation. Related English language articles were found using the following defined keywords: low-intensity pulsed ultrasound, stem cell, differentiation. Criteria for inclusion in the review were: LIPUS with frequencies of 1-3 MHz and pulsed ultrasound intensity of <500 mW/cm2. Duration, exposure time, and cell sources were taken into consideration.

RESULTS

Fifty-two articles were selected based on the inclusion criteria. Most articles demonstrated that the application of LIPUS had positive effects on stem cell differentiation. However, some authors recommended that LIPUS combined with other physical therapy aides was more effective in stem cell differentiation.

CONCLUSION

LIPUS significantly increases the level of stem cell differentiation in cells derived mainly from bone marrow mesenchymal stem cells. There is a need for further studies to analyze the effect of LIPUS on cells derived from other sources, particularly adipose tissue-derived mesenchymal stem cells, for treating hard diseases, such as osteoporosis and diabetic foot ulcer. Due to a lack of reporting on standard LIPUS parameters in the field, more experiments comparing the protocols for standardization of LIPUS parameters are needed to establish the best protocol, which would allow for the best results.

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.

Low-intensity pulsed ultrasound promotes the proliferation of human bone mesenchymal stem cells by activating PI3K/AKt signaling pathways

Low-intensity pulsed ultrasound (LIPUS) is a promising therapy that is widely used in clinical applications and fundamental research. Previous research has shown that LIPUS exposure has a positive effect on stem cell proliferation. However, the impact of LIPUS exposure on human bone marrow mesenchymal stem cells (hBMSCs) remains unknown. In our study, the effect and mechanism of LIPUS exposure on the proliferation of hBMSCs were investigated, and the optimal parameters of LIPUS were determined. hBMSCs were obtained and identified by flow cytometry, and the proliferation of hBMSCs was measured using the Cell Counting Kit-8 assay to determine cell cycle and cell count. Expression levels of the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKt) pathway proteins and cyclin D1 were determined by western blot analysis. Next, hBMSCs were successfully cultured and identified as multipotent mesenchymal stem cells. We found that LIPUS could promote the proliferation of hBMSCs when the exposure time was 5 or 10 minutes per day. Furthermore, 50 or 60 mW/cm² LIPUS had a more significant effect on cell proliferation, but if cells were irradiated by LIPUS for 20 minutes once a day, an intensity of at least 50 mW/cm² could markedly inhibit cell growth. Cell cycle analysis demonstrated that LIPUS treatment drives cells to enter S and G2/M phases from the G0/G1 phase. LIPUS exposure increased phosphorylation of PI3K/AKt and significantly upregulated expression of cyclin D1. However, these effects were inhibited when cells were treated with PI3K inhibitor (LY294002), which in turn reduced LIPUS-mediated proliferation of hBMSCs. These results suggest that LIPUS exposure may be involved in the proliferation of hBMSCs via activation of the PI3K/AKt signaling pathway and high expression of cyclin D1, and the intensity of 50 or 60 mW/cm² and exposure time of 5 minutes were determined to be the optimal parameters for LIPUS exposure.

Physical Stimulations for Bone and Cartilage Regeneration

A wide range of techniques and methods are actively invented by clinicians and scientists who are dedicated to the field of musculoskeletal tissue regeneration. Biological, chemical, and physiological factors, which play key roles in musculoskeletal tissue development, have been extensively explored. However, physical stimulation is increasingly showing extreme importance in the processes of osteogenic and chondrogenic differentiation, proliferation and maturation through defined dose parameters including mode, frequency, magnitude, and duration of stimuli. Studies have shown manipulation of physical microenvironment is an indispensable strategy for the repair and regeneration of bone and cartilage, and biophysical cues could profoundly promote their regeneration. In this article, we review recent literature on utilization of physical stimulation, such as mechanical forces (cyclic strain, fluid shear stress, etc.), electrical and magnetic fields, ultrasound, shock waves, substrate stimuli, etc., to promote the repair and regeneration of bone and cartilage tissue. Emphasis is placed on the mechanism of cellular response and the potential clinical usage of these stimulations for bone and cartilage regeneration.

Enhanced Osteogenic Differentiation of Human Mesenchymal Stem Cells Using Microbubbles and Low Intensity Pulsed Ultrasound on 3D Printed Scaffolds

Lipid-coated microbubbles, clinically approved as contrast enhancing agents for ultrasound imaging, are investigated for the first time for their possible applications in bone tissue engineering. Effects of microbubbles (average diameter 1.1 µm) coated by a mixture of lipids (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000], and 1,2-dipalmitoyl-3-trimethylmmonium-propane) in the presence of low intensity pulsed ultrasound (LIPUS) on human mesenchymal stem cells seeded on 3D printed poly(lactic acid) porous scaffolds are investigated. LIPUS stimulation (30 mW cm^-2 , 1.5 MHz, 20% duty cycle) for 3 min a day with 0.5% v/v microbubbles results in a significant increase in proliferation (up to 19.3%) when compared to control after 1, 3, and 5 d. A 3-week osteogenic differentiation study shows a significant increase in total protein content (up to 27.5%), calcium deposition (up to 4.3%), and alkaline phosphatase activity (up to 43.1%) initiated by LIPUS with and without the presence of microbubbles. The microbubbles are found to remain stable during exposure, and their sustained oscillations demonstrably help focus the LIPUS energy toward enhanced cellular response. Integrating LIPUS and microbubbles promises to be a novel and effective strategy for bone tissue engineering and regeneration therapies.

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.

Ultrasound Irradiation Combined with Hepatocyte Growth Factor Accelerate the Hepatic Differentiation of Human Bone Marrow Mesenchymal Stem Cells

This study investigated the impact of ultrasound (US) irradiation on the hepatic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) induced by hepatocyte growth factor (HGF) and the possible mechanisms. We treated hBMSCs, using HGF with and without US irradiation. Cell viability and stem cell surface markers were analyzed. Hepatocyte-like cell markers and functional markers including α-fetoprotein (αFP/AFP), cytokeratin 18 (CK18), albumin (ALB) and glycogen content were analyzed at the time point of day 1, 3 and 5 after treatment. The involvement of Wnt/β-catenin signaling pathway was evaluated as well. The results showed that the US treatment at 1.0 W/cm² or 1.5 W/cm² for 30 s or 60 s conditions yielded favorable cell viability and engendered stem cell differentiation. At day 5, the expressions of AFP, CK18, ALB and the glycogen content were significantly elevated in the US-treated group at both messenger ribonucleic acid and protein levels (all p <0.05), in comparison with HGF and control groups. Among all the US treated groups, the expression levels of specific hepatic markers in the (1.5 W/cm² for 60 s) group were the highest. Furthermore, Wnt1, β-Catenin, c-Myc and Cyclin D1 were significantly increased after US irradiation (all p <0.05), and the enhancements of c-Myc and Cyclin D1 could be obviously impaired by the inhibitor ICG-001 (p <0.05, p <0.05), in accordance with decreased ALB and CK18 expression and glycogen content (all p <0.05). In conclusion, US irradiation was able to promote the hBMSCs' differentiation mediated by HGF in vitro safely, easily and controllably. The activation of Wnt/β-catenin signaling pathway was involved in this process. US irradiation could serve as a potentially beneficial tool for the research and application of stem cell differentiation.

Low-intensity pulsed ultrasound promotes Schwann cell viability and proliferation via the GSK-3β/β-catenin signaling pathway

Background: It has been reported that ultrasound enhances peripheral nerve regeneration, but the mechanism remains elusive. Low-intensity pulsed ultrasound (LIPUS) has been reported to enhance proliferation and alter protein production in various types of cells. In this study, we detected the effects of LIPUS on Schwann cells. Material and methods: Schwann cells were separated from new natal Sprague-Dawley rat sciatic nerves and were cultured and purified. The Schwann cells were treated by LIPUS for 10 minutes every day, with an intensity of 27.37 mW/cm2. After treatment for 5 days, MTT, EdU staining, and flow cytometry were performed to examine cell viability and proliferation. Neurotrophic factors, including FGF, NGF, BDNF, and GDNF, were measured by western blot and real-time PCR. GSK-3β, p-GSK-3β, β-catenin and Cyclin D1 protein levels were detected using a western blot analysis. The expression of Cyclin D1 was also detected by immunofluorescence. Results: MTT and EdU staining showed that LIPUS increased the Schwann cells viability and proliferation. Compared to the control group, LIPUS increased the expression of growth factors and neurotrophic factors, including FGF, NGF, BDNF, GDNF, and Cyclin D1. Meanwhile, GSK-3β activity was inhibited in the LIPUS group as demonstrated by the increased level of p-GSK-3β and the ratio of the p-GSK-3β/GSK-3β level. The mRNA and protein expressions of β-catenin were increased in the LIPUS group. However, SB216763, a GSK-3β inhibitor, reversed the effects of LIPUS on Schwann cells. Conclusion: LIPUS promotes Schwann cell viability and proliferation by increasing Cyclin D1 expression via enhancing the GSK-3β/β-catenin signaling pathway.

Effects of low-intensity pulsed ultrasound (LIPUS)-pretreated human amnion-derived mesenchymal stem cell (hAD-MSC) transplantation on primary ovarian insufficiency in rats

BACKGROUND

Human amnion-derived mesenchymal stem cells (hAD-MSCs) have the features of mesenchymal stem cells (MSCs). Low-intensity pulsed ultrasound (LIPUS) can promote the expression of various growth factors and anti-inflammatory molecules that are necessary to keep the follicle growing and to reduce granulosa cell (GC) apoptosis in the ovary. This study aims to explore the effects of LIPUS-pretreated hAD-MSC transplantation on chemotherapy-induced primary ovarian insufficiency (POI) in rats.

METHODS

The animals were divided into control, POI, hAD-MSC treatment, and LIPUS-pretreated hAD-MSC treatment groups. POI rat models were established by intraperitoneal injection of cyclophosphamide (CTX). The hAD-MSCs isolated from the amnion were exposed to LIPUS or sham irradiation for 5 consecutive days and injected into the tail vein of POI rats. Expression and secretion of growth factors promoted by LIPUS in hAD-MSCs were detected by real-time quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA) in vitro. Estrous cycle, serum sex hormone levels, follicle counts, ovarian pathological changes, GC apoptosis, Bcl2 and Bax expression, and pro-inflammatory cytokine levels in ovaries were examined.

RESULTS

Primary hAD-MSCs were successfully isolated from the amnion. LIPUS promoted the expression and secretion of growth factors in hAD-MSCs in vitro. Both hAD-MSC and LIPUS-pretreated hAD-MSC transplantation increased the body and reproductive organ weights, improved ovarian function, and reduced reproductive organ injuries in POI rats. Transplantation of hAD-MSCs increased the Bcl-2/Bax ratio and reduced GC apoptosis and ovarian inflammation induced by chemotherapy in ovaries. These effects could be improved by pretreatment with LIPUS on hAD-MSCs.

CONCLUSION

Both hAD-MSC transplantation and LIPUS-pretreated hAD-MSC transplantation can repair ovarian injury and improve ovarian function in rats with chemotherapy-induced POI. LIPUS-pretreated hAD-MSC transplantation is more advantageous for reducing inflammation, improving the local microenvironment, and inhibiting GC apoptosis induced by chemotherapy in ovarian tissue of POI rats.

Comparison of the in vitro effects of low-level laser therapy and low-intensity pulsed ultrasound therapy on bony cells and stem cells

To compare the in vitro effectiveness of Low-Level Laser Therapy (LLLT) and Low Intensity Pulsed Ultrasound (LIPUS) on bony cells and related stem cells. In this study, we aim to systematically review the published scientific literature which explores the use of LLLT and LIPUS to biostimulate the activity or the proliferation of bony cells or stem cells in vitro. We searched the database PubMed for LLLT or LIPUS, with/without bone, osteoblast, osteocyte, stem cells, the human osteosarcoma cell line (MG63), bone-forming cells, and cell culture (or in vitro). These studies were subdivided into categories exploring the effect of LLLT or LIPUS on bony cells, stem cells, and other related cells. 75 articles were found between 1987 and 2016; these included: 50 full paper articles on LLLT and 25 full papers on LIPUS. These articles met the eligibility criteria and were included in our review. A detailed and concise description of the LLLT and the LIPUS protocols and their individual effects on bony cells or stem cells and their results are presented in five tables. Based on the main results and the conclusions of the reviewed articles in the current work, both, LLLT and LIPUS, apply a biostimulatory effect on osteoblasts, osteocytes, and enhance osteoblast proliferation and differentiation on different bony cell lines used in in vitro studies, and therefore, these may be useful tools for bone regeneration therapy. Moreover, in consideration of future cell therapy protocols, both, LLLT and LIPUS (especially LLLT), enhnce a significant increase in the initial number of SCs before differentiation, thus increasing the number of differentiated cells for tissue engineering, regenerative medicine, and healing. Further studies are necessary to determine the LLLT or the LIPUS parameters, which are optimal for biostimsulating bony cells and SCs for bone healing and regenerative medicine.

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.

Forced acoustic oscillations of biological cell

This article considers the possibility of excitation of acoustic oscillations in a cell by electromagnetic waves. In this process, not only the frequency but also the length of a wave is of great importance. It is also reported that the pulse signal can be more effective than harmonic signal, and the pulse length is not essential. In accordance with this fact, it is possible to explain the biological effects of electromagnetic waves and to develop new medical electronic devices. Bioelectromagnetics. 38:613-617, 2017. © 2017 Wiley Periodicals, Inc.

Effect of Low-Intensity Pulsed Ultrasound after Mesenchymal Stromal Cell Injection to Treat Osteochondral Defects: An In Vivo Study

We investigated the effect of low-intensity pulsed ultrasound (LIPUS) treatment combined with mesenchymal stromal cell (MSC) injection for cartilage repair and subchondral bone reconstitution for treatment of osteochondral defects. An osteochondral defect was created on both femur grooves of Wistar rats. Four weeks later, bone marrow MSCs were injected into the right knee joint. The rats were divided into two intervention groups: without or with LIPUS irradiation. Cartilage repair was evaluated histologically based on the Wakitani cartilage repair score. Subchondral bone reconstitution was evaluated as bone volume (BV)/tissue volume (TV) by micro-computed tomography analysis. MSC injection improved the cartilage repair score, and LIPUS irradiation improved BV/TV. Combination treatment promoted both cartilage repair and BV/TV improvement. Thus, MSC injection combined with LIPUS irradiation is more effective than either treatment alone in promoting concurrent cartilage repair and subchondral reconstitution.

Stimulation of Bone Repair with Ultrasound

This chapter reviews the different options available for the use of ultrasound in the enhancement of fracture healing or in the reactivation of a failed healing process: LIPUS, shock waves and ultrasound-mediated delivery of bioactive molecules, such as growth factors or plasmids. The main emphasis is on LIPUS, or Low Intensity Pulsed Ultrasound, the most widespread and studied technique. LIPUS has pronounced bioeffects on tissue regeneration, while employing intensities within a diagnostic range. The biological response to LIPUS is complex as the response of numerous cell types to this stimulus involves 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 and iNOS/NO pathways, and activation of the ATI mechanoreceptor. Mechanisms at the origin of LIPUS biological effects remain intriguing, and analysis is hampered by the diversity of experimental systems used in-vitro. Data point to clear evidence that bioeffects can be modulated by direct and indirect mechanical effects, like acoustic radiation force, acoustic streaming, propagation of surface waves, heat, fluid-flow induced circulation and redistribution of nutrients, oxygen and signaling molecules. One of the future engineering challenge is therefore the design of dedicated experimental set-ups allowing control of these different mechanical phenomena, and to relate them to biological responses. Then, the derivation of an 'acoustic dose' and the cross-calibration of the different experimental systems will be possible. Despite this imperfect knowledge of LIPUS biophysics, the clinical evidence, although most often of low quality, speaks in favor of the clinical use of LIPUS, when the economics of nonunion and the absence of toxicity of this ultrasound technology are taken into account.

Low-Intensity Pulsed Ultrasound Stimulation Enhances Heat-Shock Protein 90 and Mineralized Nodule Formation in Mouse Calvaria-Derived Osteoblasts

Low-intensity pulsed ultrasound (LIPUS) has demonstrated its positive effects on osteogenic differentiation of mesenchymal stem cells and the proliferation and differentiation of osteoblasts, negative effects on osteoclast growth, and promotion of angiogenesis, leading to improvement of the tissue perfusion. Heat-shock proteins (HSPs) are initially identified as molecules encouraged and expressed by heat stress or chemical stress to cells and involved in the balance between differentiation and apoptosis of osteoblasts. However, it remains unclear if the effect of LIPUS on osteoblast differentiation could involve HSP expression and contribution. In this study, mouse calvarial osteoblasts were exposed to LIPUS at a frequency of 3.0 MHz by 30 mW/cm(2) for 15 min or to 42°C heat shock for 20 min at day 3 of cell culture and examined for osteogenesis with pursuing induction of HSP27, HSP70, and HSP90. LIPUS as well as heat shock initially upregulated HSP90 and phosphorylation of Smad1 and Smad5, encouraging cell viability and proliferation at 24 h, enhancing mineralized nodule formation stronger by LIPUS after 10 days. However, HSP27, associated with BMP2-stimulated p38 mitogen-activated protein kinase during osteoblast differentiation, was downregulated by both stimulations at this early time point. Notably, these two stimuli maintained Smad1 phosphorylation with mineralized nodule formation even under BMP2 signal blockage. Therefore, LIPUS might be a novel inducer of osteoblastic differentiation through a noncanonical signal pathway. In conclusion, LIPUS stimulation enhanced cell viability and proliferation as early as 24 h after treatment, and HSP90 was upregulated, leading to dense mineralization in the osteoblast cell culture after 10 days.

Effect of sound on gap-junction-based intercellular signaling: Calcium waves under acoustic irradiation

We present a previously unrecognized effect of sound waves on gap-junction-based intercellular signaling such as in biological tissues composed of endothelial cells. We suggest that sound irradiation may, through temporal and spatial modulation of cell-to-cell conductance, create intercellular calcium waves with unidirectional signal propagation associated with nonconventional topologies. Nonreciprocity in calcium wave propagation induced by sound wave irradiation is demonstrated in the case of a linear and a nonlinear reaction-diffusion model. This demonstration should be applicable to other types of gap-junction-based intercellular signals, and it is thought that it should be of help in interpreting a broad range of biological phenomena associated with the beneficial therapeutic effects of sound irradiation and possibly the harmful effects of sound waves on health.

Low intensity pulsed ultrasound enhanced mesenchymal stem cell recruitment through stromal derived factor-1 signaling in fracture healing

Low intensity pulsed ultrasound (LIPUS) has been proven effective in promoting fracture healing but the underlying mechanisms are not fully depicted. We examined the effect of LIPUS on the recruitment of mesenchymal stem cells (MSCs) and the pivotal role of stromal cell-derived factor-1/C-X-C chemokine receptor type 4 (SDF-1/CXCR4) pathway in response to LIPUS stimulation, which are essential factors in bone fracture healing. For in vitro study, isolated rat MSCs were divided into control or LIPUS group. LIPUS treatment was given 20 minutes/day at 37 °C for 3 days. Control group received sham LIPUS treatment. After treatment, intracellular CXCR4 mRNA, SDF-1 mRNA and secreted SDF-1 protein levels were quantified, and MSCs migration was evaluated with or without blocking SDF-1/CXCR4 pathway by AMD3100. For in vivo study, fractured 8-week-old young rats received intracardiac administration of MSCs were assigned to LIPUS treatment, LIPUS+AMD3100 treatment or vehicle control group. The migration of transplanted MSC to the fracture site was investigated by ex vivo fluorescent imaging. SDF-1 protein levels at fracture site and in serum were examined. Fracture healing parameters, including callus morphology, micro-architecture of the callus and biomechanical properties of the healing bone were investigated. The in vitro results showed that LIPUS upregulated SDF-1 and CXCR4 expressions in MSCs, and elevated SDF-1 protein level in the conditioned medium. MSCs migration was promoted by LIPUS and partially inhibited by AMD3100. In vivo study demonstrated that LIPUS promoted MSCs migration to the fracture site, which was associated with an increase of local and serum SDF-1 level, the changes in callus formation, and the improvement of callus microarchitecture and mechanical properties; whereas the blockade of SDF-1/CXCR4 signaling attenuated the LIPUS effects on the fractured bones. These results suggested SDF-1 mediated MSCs migration might be one of the crucial mechanisms through which LIPUS exerted influence on fracture healing.

Influence of low-intensity pulsed ultrasound on osteogenic tissue regeneration in a periodontal injury model: X-ray image alterations assessed by micro-computed tomography

OBJECTIVE

This study was conducted to evaluate, with micro-computed tomography, the influence of low-intensity pulsed ultrasound on wound-healing in periodontal tissues.

METHODS

Periodontal disease with Class II furcation involvement was surgically produced at the bilateral mandibular premolars in 8 adult male beagle dogs. Twenty-four teeth were randomly assigned among 4 groups (G): G1, periodontal flap surgery; G2, periodontal flap surgery+low-intensity pulsed ultrasound (LIPUS); G3, guided tissue regeneration (GTR) surgery; G4, GTR surgery plus LIPUS. The affected area in the experimental group was exposed to LIPUS. At 6 and 8weeks, the X-ray images of regenerated teeth were referred to micro-CT scanning for 3-D measurement.

RESULTS

Bone volume (BV), bone surface (BS), and number of trabeculae (Tb) in G2 and G4 were higher than in G1 and G3 (p<0.05). BV, BS, and Tb.N of the GTR+LIPUS group were higher than in the GTR group. BV, BS, and Tb.N of the LIPUS group were higher than in the periodontal flap surgery group.

CONCLUSION

LIPUS irradiation increased the number, volume, and area of new alveolar bone trabeculae. LIPUS has the potential to promote the repair of periodontal tissue, and may work effectively if combined with GTR.

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.

Genes responsive to low-intensity pulsed ultrasound in MC3T3-E1 preosteoblast cells

Although low-intensity pulsed ultrasound (LIPUS) has been shown to enhance bone fracture healing, the underlying mechanism of LIPUS remains to be fully elucidated. Here, to better understand the molecular mechanism underlying cellular responses to LIPUS, we investigated gene expression profiles in mouse MC3T3-E1 preosteoblast cells exposed to LIPUS using high-density oligonucleotide microarrays and computational gene expression analysis tools. Although treatment of the cells with a single 20-min LIPUS (1.5 MHz, 30 mW/cm(2)) did not affect the cell growth or alkaline phosphatase activity, the treatment significantly increased the mRNA level of Bglap. Microarray analysis demonstrated that 38 genes were upregulated and 37 genes were downregulated by 1.5-fold or more in the cells at 24-h post-treatment. Ingenuity pathway analysis demonstrated that the gene network U (up) contained many upregulated genes that were mainly associated with bone morphology in the category of biological functions of skeletal and muscular system development and function. Moreover, the biological function of the gene network D (down), which contained downregulated genes, was associated with gene expression, the cell cycle and connective tissue development and function. These results should help to further clarify the molecular basis of the mechanisms of the LIPUS response in osteoblast cells.

Lipopolysaccharide effects on the proliferation of NRK52E cells via alternations in gap-junction function

BACKGROUND

Gap junctions regulate proper kidney function by facilitating intercellular communication, vascular conduction, and tubular purinergic signaling. However, no clear relationship has been described between gap-junction function and acute kidney injury induced by the endotoxin lipopolysaccharide (LPS).

METHODS

Normal rat kidney epithelial cells (NRK52E cells) were seeded at high and low densities to promote or impede gap-junction formation, respectively, and establish distinctive levels of intercellular communication in culture. Cells were then challenged with LPS at various concentrations (10-1,000 ng/mL). LPS-induced formation and function of gap junctions were assessed by measuring changes in cell proliferation and colony-forming rates, fluorescent dye transmission to adjacent cells, expression levels of connexin43, and repositioning of confluent cells in response to the gap junction inhibitor oleamide or agonist retinoic acid.

RESULTS

The cell proliferation rate and colony-forming rate of high- and low-density NRK52E cells were decreased upon LPS challenge, in a dose-dependent manner. The colony-forming rate of confluent high-density cells was significantly lower than that of low-density cells. Oleamide treatment raised the LPS-induced colony-forming rate of high-density cells, whereas retinoic acid decreased the rate. Neither oleamide nor retinoic acid significantly affected the LPS-induced colony-forming rate of low-density cells. Fluorescence transmission of high-density cells was reduced by LPS challenge, in a dose-dependent manner, but inclusion of retinoic acid increased the LPS-induced transmission of fluorescence. LPS challenge of either high- or low-density NRK52E cells resulted in down-regulated connexin43 expression.

CONCLUSION

Gap-junction function plays an important role in concentration-dependent cytotoxic effect of LPS on normal rat kidney cells in vitro.

Osteogenic effect of low intensity pulsed ultrasound on rat adipose-derived stem cells in vitro

The osteogenic in vitro effect of low intensity pulsed ultrasound (LIPUS) on SD rat adipose-derived stem cells (ADSCs) was investigated. Rat ADSCs underwent LIPUS (intensity=100 mW/cm(2)) or sham exposure for 8 min per treatment once everyday in vitro, and then the alkaline phosphatase (ALP) activity and mineralized nodule formation were assessed to evaluate the osteogenic effect of LIPUS on ADSCs. To further explore the underlying mechanism, the osteogenic-related gene mRNA expression was determined by using reverse transcriptase-polymerase chain reaction (RT-PCR) at 1st, 3rd, 5th, 7th day after exposure repectively. Westen blot was used to evaluate the protein expression levels of two osteogenic differentiation associated genes at 7th and 14th day repectively. It was found that ALP activity was increased after LIPUS exposure and LIPUS resulted in mineralized nodule formation of ADSCs in vitro. LIPUS-treated ADSCs displayed higher mRNA expression levels of runt-related transcription factor 2 (Runx2), osteocalcin (OCN), ALP and bone sialoprotein (BSP) genes than controls, and the protein levels of Runx2 and BSP were also increased. The results suggested that LIPUS may induce the osteogenic differentiation of ADSCs in vitro.