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

Scaffold Adhering to Peptide-Based Biomimetic Extracellular Matrix Composite Nanobioglass Promotes the Proliferation and Migration of Skin Fibroblasts Through the GSK-3β/β-Catenin Signaling Axis

Introduction

Nano-mesoporous bioactive glass and RGD peptide-coated collagen membranes have great potential in wound healing. However, the application of their compound has not been further studied. Our purpose is to prepare a novel bioactive collagen scaffold containing both NMBG stent and adhesion peptides (BM), which then proves its promising prospect the assessment of physical properties, biocompatibility, GSK-3β/β-catenin signaling axis and toxicological effects.

Methods

The structural and morphological changes of BM were analyzed using scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). In vivo, wound healing of BM was assessed in SD rats through dynamic monitoring and calculation of wound healing rate. Immunohistofluorescence (IHF), H&E, and Masson staining were utilized; in vitro, primary cell culture, and a variety of assays including CCK-8, Transwell, Scratch, Immunocytofluorescence (ICF), and Western blot (WB) were performed, both for morphology and molecular analysis.

Results and Discussion

Preparation of BM involved attaching NMBG to RGD-exposed collagen while avoiding the use of toxic chemical reagents. BM exhibited a distinctive superficial morphology with increased Si content, indicating successful NMBG attachment. In vivo studies on SD rats demonstrated the superior wound healing capability of BM, as evidenced by accelerated wound closure, thicker epithelial layers, and enhanced collagen deposition compared to the NC group. Additionally, BM promoted skin fibroblast migration and proliferation, possibly through activation of the GSK-3β/β-catenin signaling axis, which was crucial for tissue regeneration. This study underscored the potential of BM as an effective wound-healing dressing.

Conclusion

A new method for synthesizing ECM-like membranes has been developed using nano-mesoporous bioactive glass and collagen-derived peptides. This approach enhances the bioactivity of biomaterials through surface functionalization and growth factor-free therapy.

Emerging role of extracellular vesicles and exogenous stimuli in molecular mechanisms of peripheral nerve regeneration

Peripheral nerve injuries lead to significant morbidity and adversely affect quality of life. The peripheral nervous system harbors the unique trait of autonomous regeneration; however, achieving successful regeneration remains uncertain. Research continues to augment and expedite successful peripheral nerve recovery, offering promising strategies for promoting peripheral nerve regeneration (PNR). These include leveraging extracellular vesicle (EV) communication and harnessing cellular activation through electrical and mechanical stimulation. Small extracellular vesicles (sEVs), 30-150 nm in diameter, play a pivotal role in regulating intercellular communication within the regenerative cascade, specifically among nerve cells, Schwann cells, macrophages, and fibroblasts. Furthermore, the utilization of exogenous stimuli, including electrical stimulation (ES), ultrasound stimulation (US), and extracorporeal shock wave therapy (ESWT), offers remarkable advantages in accelerating and augmenting PNR. Moreover, the application of mechanical and electrical stimuli can potentially affect the biogenesis and secretion of sEVs, consequently leading to potential improvements in PNR. In this review article, we comprehensively delve into the intricacies of cell-to-cell communication facilitated by sEVs and the key regulatory signaling pathways governing PNR. Additionally, we investigated the broad-ranging impacts of ES, US, and ESWT on PNR.

LIPUS-SCs-Exo promotes peripheral nerve regeneration in cavernous nerve crush injury-induced ED rats via PI3K/Akt/FoxO signaling pathway

OBJECTIVE

Clinical treatment of erectile dysfunction (ED) caused by cavernous nerve (CN) injury during pelvic surgery is difficult. Low-intensity pulsed ultrasound (LIPUS) can be a potential strategy for neurogenic ED (NED). However, whether Schwann cells (SCs) can respond to LIPUS stimulation signals is unclear. This study aims to elucidate the signal transmission between SCs paracrine exosome (Exo) and neurons stimulated by LIPUS, as well as to analyze the role and potential mechanisms of exosomes in CN repair after injury.

METHODS

The major pelvic ganglion (MPG) neurons and MPG/CN explants were stimulated with LIPUS of different energy intensities to explore the appropriate LIPUS energy intensity. The exosomes were isolated and purified from LIPUS-stimulated SCs (LIPUS-SCs-Exo) and non-stimulated SCs (SCs-Exo). The effects of LIPUS-SCs-Exo on neurite outgrowth, erectile function, and cavernous penis histology were identified in bilateral cavernous nerve crush injury (BCNI)-induced ED rats.

RESULTS

LIPUS-SCs-Exo group can enhance the axon elongation of MPG/CN and MPG neurons compared to SCs-Exo group in vitro. Then, the LIPUS-SCs-Exo group showed a stronger ability to promote the injured CN regeneration and SCs proliferation compared to the SCs-Exo group in vivo. Furthermore, the LIPUS-SCs-Exo group increased the Max intracavernous pressure (ICP)/mean arterial pressure (MAP), lumen to parenchyma and smooth muscle to collagen ratios compared to the SCs-Exo group in vivo. Additionally, high-throughput sequencing combined with bioinformatics analysis revealed the differential expression of 1689 miRNAs between the SCs-Exo group and the LIPUS-SCs-Exo group. After LIPUS-SCs-Exo treatment, the phosphorylated levels of Phosphatidylinositol 3-kinase (PI3K), protein kinase B (Akt) and forkhead box O (FoxO) in MPG neurons increased significantly compared to negative control (NC) and SCs-Exo groups.

CONCLUSION

Our study revealed that LIPUS stimulation could regulate the gene of MPG neurons by changing miRNAs derived from SCs-Exo, then activating the PI3K-Akt-FoxO signal pathway to enhance nerve regeneration and restore erectile function. This study had important theoretical and practical significance for improving the NED treatment.

Functional material-mediated wireless physical stimulation for neuro-modulation and regeneration

Nerve injuries and neurological diseases remain intractable clinical challenges. Despite the advantages of stem cell therapy in treating neurological disorders, uncontrollable cell fates and loss of cell function in vivo are still challenging. Recently, increasing attention has been given to the roles of external physical signals, such as electricity and ultrasound, in regulating stem cell fate as well as activating or inhibiting neuronal activity, which provides new insights for the treatment of neurological disorders. However, direct physical stimulations in vivo are short in accuracy and safety. Functional materials that can absorb energy from a specific physical field exerted in a wireless way and then release another localized physical signal hold great advantages in mediating noninvasive or minimally invasive accurate indirect physical stimulations to promote the therapeutic effect on neurological disorders. In this review, the mechanism by which various physical signals regulate stem cell fate and neuronal activity is summarized. Based on these concepts, the approaches of using functional materials to mediate indirect wireless physical stimulation for neuro-modulation and regeneration are systematically reviewed. We expect that this review will contribute to developing wireless platforms for neural stimulation as an assistance for the treatment of neurological diseases and injuries.

Low-intensity pulsed ultrasound enhances the positive effects of high-intensity treadmill exercise on bone in rats

INTRODUCTION

Moderate exercise benefits bone health, but excessive loading leads to bone fatigue and a decline in mechanical properties. Low-intensity pulsed ultrasound (LIPUS) can stimulate bone formation. The purpose of this study was to explore whether LIPUS could augment the skeletal benefits of high-intensity exercise.

MATERIALS AND METHODS

MC3T3-E1 osteoblasts were treated with LIPUS at 80 mW/cm2 or 30 mW/cm2 for 20 min/day. Forty rats were divided into sham treatment normal control (Sham-NC), sham treatment high-intensity exercise (Sham-HIE), 80 mW/cm2 LIPUS (LIPUS80), and high-intensity exercise combined with 80 mW/cm2 LIPUS (LIPUS80-HIE). The rats in HIE group were subjected to 30 m/min slope treadmill exercise for 90 min/day, 6 days/week for 12 weeks. The LIPUS80-HIE rats were irradiated with LIPUS (1 MHz, 80 mW/cm2) for 20 min/day at bilateral hind limb after exercise.

RESULTS

LIPUS significantly accelerated the proliferation, differentiation, mineralization, and migration of MC3T3-E1 cells. Compared to 30 mW/cm2 LIPUS, 80 mW/cm2 LIPUS got better promotion effect. 12 weeks of high-intensity exercise significantly reduced the muscle force, which was significantly reversed by LIPUS. Compared with the Sham-NC group, Sham-HIE group significantly optimized bone microstructure and enhanced mechanical properties of femur, and LIPUS80-HIE further enhanced the improvement effect on bone. The mechanisms may be related to activate Wnt/β-catenin signal pathway and then up-regulate the protein expression of Runx2 and VEGF, the key factors of osteogenesis and angiogenesis.

CONCLUSION

LIPUS could augment the skeletal benefits of high-intensity exercise through Wnt/β-catenin signal pathway.

Research Progress of Low-Intensity Pulsed Ultrasound in the Repair of Peripheral Nerve Injury

Peripheral nerve injury (PNI) is a common disease that has profound impact on the health of patients, but has poor prognosis. The gold standard for the treatment of peripheral nerve defects is autologous nerve grafting; notwithstanding, due to the extremely high requirement for surgeons and medical facilities, there is great interest in developing better treatment strategies for PNI. Low-intensity pulsed ultrasound (LIPUS) is a noninterventional stimulation method characterized by low-intensity pulsed waves. It has good therapeutic effect on fractures, inflammation, soft tissue regeneration, and nerve regulation, and can participate in PNI repair from multiple perspectives. This review concentrates on the effects and mechanisms of LIPUS in the repair of PNI from the perspective of LIPUS stimulation of neural cells and stem cells, modulation of neurotrophic factors, signaling pathways, proinflammatory cytokines, and nerve-related molecules. In addition, the effects of LIPUS on nerve conduits are reviewed, as nerve conduits are expected to be a successful alternative treatment for PNI with the development of tissue engineering. Overall, the application advantages and prospects of LIPUS in the repair of PNI are highlighted by summarizing the effects of LIPUS on seed cells, neurotrophic factors, and nerve conduits for neural tissue engineering.

Sonomechanobiology: Vibrational stimulation of cells and its therapeutic implications

All cells possess an innate ability to respond to a range of mechanical stimuli through their complex internal machinery. This comprises various mechanosensory elements that detect these mechanical cues and diverse cytoskeletal structures that transmit the force to different parts of the cell, where they are transcribed into complex transcriptomic and signaling events that determine their response and fate. In contrast to static (or steady) mechanostimuli primarily involving constant-force loading such as compression, tension, and shear (or forces applied at very low oscillatory frequencies (≤ 1 Hz) that essentially render their effects quasi-static), dynamic mechanostimuli comprising more complex vibrational forms (e.g., time-dependent, i.e., periodic, forcing) at higher frequencies are less well understood in comparison. We review the mechanotransductive processes associated with such acoustic forcing, typically at ultrasonic frequencies (> 20 kHz), and discuss the various applications that arise from the cellular responses that are generated, particularly for regenerative therapeutics, such as exosome biogenesis, stem cell differentiation, and endothelial barrier modulation. Finally, we offer perspectives on the possible existence of a universal mechanism that is common across all forms of acoustically driven mechanostimuli that underscores the central role of the cell membrane as the key effector, and calcium as the dominant second messenger, in the mechanotransduction process.

Hippo Pathway in Schwann Cells and Regeneration of Peripheral Nervous System

Hippo pathway is an evolutionarily conserved signaling pathway comprising a series of MST/LATS kinase complexes. Its key transcriptional coactivators YAP and TAZ regulate transcription factors such as TEAD family to direct gene expression. The regulation of Hippo pathway, especially the nuclear level change of YAP and TAZ, significantly influences the cell fate switching from proliferation to differentiation, regeneration, and postinjury repair. This review outlines the main findings of Hippo pathway in peripheral nerve development, regeneration, and tumorigenesis, especially the studies in Schwann cells. We also summarize other roles of Hippo pathway in damage repair of the peripheral nerve system and discuss the potential future research which probably contributes to novel therapeutic strategies.

Low-intensity pulsed ultrasound promotes proliferation and myelinating genes expression of Schwann cells through NRG1/ErbB signaling pathway

Schwann cells (SCs) are the major component of myelin sheath in the peripheral nervous system, which are necessary in the development, function maintenance, and repair of peripheral nerves. This study aimed to investigate the potential mechanism of low-intensity pulsed ultrasound (LIPUS) affecting the proliferation and myelinating activity of SCs. Rat Schwann cell line RSC96 were cultured and exposed to LIPUS of different duty ratios (control, 20 %, 50 %, 80 %). Results demonstrated that LIPUS with a duty ratio of 50 % showing the maximal effect in facilitating proliferation of SCs. The expressions of Krox20 and myelin basic protein (MBP), the key molecules of SC myelination, and the potent inducer of myelination neuregulin 1 (NRG1) and its receptors ErbB2 and ErbB3 increased significantly by LIPUS. The reaction of these factors to LIPUS were both time- and duty ratio-dependent: namely LIPUS with higher duty ratios took effects when applied repeatedly over more consecutive days. These observations indicated that NRG1/ErbB signaling pathway might contribute to the effects of LIPUS on the proliferation and myelinating status of SCs, which could be one of the mechanisms in the protective role of LIPUS in nerve repair and regeneration. Our work provided novel insights for promising strategies of nerve repair therapy.

Low-intensity pulsed ultrasound promotes skeletal muscle regeneration via modulating the inflammatory immune microenvironment

Background: Low-intensity pulsed ultrasound (LIPUS, a form of mechanical stimulation) can promote skeletal muscle functional repair, but a lack of mechanistic understanding of its relationship and tissue regeneration limits progress in this field. We investigated the hypothesis that specific energy levels of LIPUS mediates skeletal muscle regeneration by modulating the inflammatory microenvironment. Methods: To address these gaps, LIPUS irritation was applied in vivo for 5 min at two different intensities (30mW/cm² and 60mW/cm²) in next 7 consecutive days, and the treatment begun at 24h after air drop-induced contusion injury. In vitro experiments, LIPUS irritation was applied at three different intensities (30mW/cm², 45mW/cm², and 60mW/cm²) for 2 times 24h after introduction of LPS in RAW264.7. Then, we comprehensively assessed the functional and histological parameters of skeletal muscle injury in mice and the phenotype shifting in macrophages through molecular biological methods and immunofluorescence analysis both in vivo and in vitro. Results: We reported that LIPUS therapy at intensity of 60mW/cm² exhibited the most significant differences in functional recovery of contusion-injured muscle in mice. The comprehensive functional tests and histological analysis in vivo indirectly and directly proved the effectiveness of LIPUS for muscle recovery. Through biological methods and immunofluorescence analysis both in vivo and in vitro, we found that this improvement was attributable in part to the clearance of M1 macrophages populations and the increase in M2 subtypes with the change of macrophage-mediated factors. Depletion of macrophages in vivo eliminated the therapeutic effects of LIPUS, indicating that improvement in muscle function was the result of M2-shifted macrophage polarization. Moreover, the M2-inducing effects of LIPUS were proved partially through the WNT pathway by upregulating FZD5 expression and enhancing β-catenin nuclear translocation in macrophages both in vitro and in vivo. The inhibition and augment of WNT pathway in vitro further verified our results. Conclusion: LIPUS at intensity of 60mW/cm² could significantly promoted skeletal muscle regeneration through shifting macrophage phenotype from M1 to M2. The ability of LIPUS to direct macrophage polarization may be a beneficial target in the clinical treatment of many injuries and inflammatory diseases.

The impact of physical, biochemical, and electrical signaling on Schwann cell plasticity

Peripheral nervous system (PNS) injuries are an ongoing health care concern. While autografts and allografts are regarded as the current clinical standard for traumatic injury, there are inherent limitations that suggest alternative remedies should be considered for therapeutic purposes. In recent years, nerve guidance conduits (NGCs) have become increasingly popular as surgical repair devices, with a multitude of various natural and synthetic biomaterials offering potential to enhance the design of conduits or supplant existing technologies entirely. From a cellular perspective, it has become increasingly evident that Schwann cells (SCs), the primary glia of the PNS, are a predominant factor mediating nerve regeneration. Thus, the development of severe nerve trauma therapies requires a deep understanding of how SCs interact with their environment, and how SC microenvironmental cues may be engineered to enhance regeneration. Here we review the most recent advancements in biomaterials development and cell stimulation strategies, with a specific focus on how the microenvironment influences the behavior of SCs and can potentially lead to functional repair. We focus on microenvironmental cues that modulate SC morphology, proliferation, migration, and differentiation to alternative phenotypes. Promotion of regenerative phenotypic responses in SCs and other non-neuronal cells that can augment the regenerative capacity of multiple biomaterials is considered along with innovations and technologies for traumatic injury.

Ca2+ signaling-mediated low-intensity pulsed ultrasound-induced proliferation and activation of motor neuron cells

Motor neuron diseases (MND) including amyotrophic lateral sclerosis and Parkinson disease are commonly neurodegenerative, causing a gradual loss of nerve cells and affecting the mechanisms underlying changes in calcium (Ca²⁺)-regulated dendritic growth. In this study, the NSC-34 cell line, a population of hybridomas generated using mouse spinal cord cells with neuroblastoma, was used to investigate the effect of low-intensity pulsed ultrasound (LIPUS) as part of an MND treatment model. After NSC-34 cells were seeded for 24 h, LIPUS stimulation was performed on the cells at days 1 and 3 using a non-focused transducer at 1.15 MHz for 8 min. NSC-34 cell proliferation and morphological changes were observed at various LIPUS intensities and different combinations of Ca²⁺ channel blockers. The nuclear translocation of Ca²⁺-dependent transcription factors was also examined. We observed that the neurite outgrowth and cell number of NSC-34 significantly increased with LIPUS stimulation at days 2 and 4, which may be associated with the treatment's positive effect on the activation of Ca²⁺-dependent transcription factors, such as nuclear factor of activated T cells and nuclear factor-kappa B. Our findings suggest that the LIPUS-induced Ca²⁺ signaling and transcription factor activation facilitate the morphological maturation and proliferation of NSC-34 cells, presenting a promising noninvasive method to improve stimulation therapy for MNDs in the future.

Low-Intensity Pulsed Ultrasound Enhanced Adipose-Derived Stem Cell-Mediated Angiogenesis in the Treatment of Diabetic Erectile Dysfunction through the Piezo-ERK-VEGF Axis

Objectives

Erectile dysfunction is a major comorbidity of diabetes. Stem cell transplantation is a promising method to treat diabetic erectile dysfunction. In this study, we evaluated whether low-intensity pulsed ultrasound (LIPUS) could enhance the efficacy of adipose-derived stem cells (ADSCs) and investigated the underlying molecular mechanism. Materials and methods. Sixty 8-week-old male Sprague–Dawley rats were randomly divided into the normal control (NC) cohort or the streptozocin-induced diabetic ED cohort, which was further subdivided into DM, ADSC, LIPUS, and ADSC+LIPUS groups. Rats in the ADSC or ADSC+LIPUS group received ADSC intracavernosal injection. Rats in the LIPUS or ADSC+LIPUS group were treated with LIPUS. The intracavernous pressure (ICP) and mean arterial pressure (MAP) were recorded at Day 28 after injection. The corpus cavernosum tissues were harvested and subjected to histologic analysis and ELISA. The effects of LIPUS on proliferation and cytokine secretion capacity of ADSCs were assessed in vitro. RNA sequencing and bioinformatic analysis were applied to predict the mechanism involved, and western blotting and ELISA were used for verification.

Results

Rats in the ADSC+LIPUS group achieved significantly higher ICP and ICP/MAP ratios than those in the DM, ADSC, and LIPUS groups. In addition, the amount of cavernous endothelium and cGMP level also increased significantly in the ADSC+LIPUS group. In vitro experiments demonstrated that LIPUS promoted proliferation and cell cycle progression in ADSCs. The excretion of cytokines such as CXCL12, FGF2, and VEGF was also enhanced by LIPUS. Bioinformatic analysis based on RNA sequencing indicated that LIPUS stimulation might activate the MAPK pathway. We confirmed that LIPUS enhanced ADSC VEGF secretion through the Piezo-ERK pathway.

Conclusion

LIPUS enhanced the curative effects of ADSCs on diabetic erectile dysfunction through the activation of the Piezo-ERK-VEGF pathway. ADSC transplantation combined with LIPUS could be applied as a synergistic treatment for diabetic ED.

Investigating the Optimal Initiation Time of Ultrasound Therapy for Peripheral Nerve Regeneration after Axonotmesis in Rats

This study was aimed at identifying the optimal initiation time of ultrasound (US) therapy for peripheral nerve regeneration after axonotmesis. Thirty-six rats with sciatic nerve crush injury were divided into four groups that received US irradiation initiated 1, 7 or 14 d after injury, or sham stimulation for 4 wk. Motor function analysis was conducted weekly; however, there was no significant improvement attributed to US treatment. Four weeks after injury, compound muscle action potential amplitude values of the group in which US irradiation was initiated 1 d after the injury exhibited significant improvement compared with the sham stimulation group. In addition, myelin sheath thickness was significantly greater in the 1-d group than in other groups. These results indicate that US treatment initiated 1 d after peripheral nerve injury promotes maximum regeneration.

Therapeutic Low-Intensity Ultrasound for Peripheral Nerve Regeneration – A Schwann Cell Perspective

Peripheral nerve injuries are common conditions that can arise from trauma (e.g., compression, severance) and can lead to neuropathic pain as well as motor and sensory deficits. Although much knowledge exists on the mechanisms of injury and nerve regeneration, treatments that ensure functional recovery following peripheral nerve injury are limited. Schwann cells, the supporting glial cells in peripheral nerves, orchestrate the response to nerve injury, by converting to a “repair” phenotype. However, nerve regeneration is often suboptimal in humans as the repair Schwann cells do not sustain their repair phenotype long enough to support the prolonged regeneration times required for successful nerve regrowth. Thus, numerous strategies are currently focused on promoting and extending the Schwann cells repair phenotype. Low-intensity ultrasound (LIU) is a non-destructive therapeutic approach which has been shown to facilitate peripheral nerve regeneration following nerve injury in rodents. Still, clinical trials in humans are scarce and limited to small population sizes. The benefit of LIU on nerve regeneration could possibly be mediated through the repair Schwann cells. In this review, we discuss the known and possible molecular mechanisms activated in response to LIU in repair Schwann cells to draw support and attention to LIU as a compelling regenerative treatment for peripheral nerve injury.

Ultrasound Stimulation Inhibits Morphological Degeneration of Motor Endplates in the Denervated Skeletal Muscle of Rats

Recovery of motor function after peripheral nerve injury requires treatment of the neuromuscular junction (NMJ), as well as the injured nerve and skeletal muscle. The purpose of this study was to examine the effects of ultrasound (US) stimulation on NMJ degeneration after denervation using a rat model of peroneal nerve transection. Twelve-week-old male Wistar rats were randomly assigned to 3 groups: US stimulation, sham stimulation, and intact. US or sham stimulation was performed on the left tibialis anterior (TA) muscle starting the day after peroneal nerve transection for 5 minutes daily under anesthesia. Four weeks later, the number and morphology of the motor endplates were analyzed to assess NMJ in the TA muscle. The endplates were classified as normal, partially fragmented, or fully fragmented for morphometric analysis. In addition, the number of terminal Schwann cells (tSCs) per endplate and percentage of endplates with tSCs (tSC retention percentage) were calculated to evaluate the effect of tSCs on NMJs. Our results showed that endplates degenerated 4 weeks after transection, with a decrease in the normal type and an increase in the fully fragmented type in both the US and sham groups compared to the intact group. Furthermore, the US group showed significant suppression of the normal type decrease and a fully fragmented type increase compared to the sham group. These results suggest that US stimulation inhibits endplate degeneration in denervated TA muscles. In contrast, the number of endplates and tSC and tSC retention percentages were not significantly different between the US and sham groups. Further investigations are required to determine the molecular mechanisms by which US stimulation suppresses degeneration.

Low-intensity pulsed ultrasound inhibits fibroblast-like synoviocyte proliferation and reduces synovial fibrosis by regulating Wnt/β-catenin signaling

OBJECTIVE

Synovial fibrosis is a characteristic symptom of osteoarthritis (OA), which is closely associated with joint pain and stiffness. Previous studies have reported that low-intensity pulsed ultrasound (LIPUS) can alleviate cartilage degradation in OA. However, the functions and mechanisms of LIPUS in OA synovial fibrosis are still unknown.

METHODS

The destabilization of the medial meniscus (DMM) mouse model of OA was established in C57 male mice and fibroblast-like synoviocytes (FLS) were isolated from synovial tissue of OA patients. The knee joint diameter, Masson's trichrome (MT) and Hematoxylin-eosin (HE) staining were used to evaluate synovial fibrosis and hyperplasia. The Immunohistochemistry (IHC) staining was performed to detected the expression of synovial fibrosis makers and the activation of Wnt/β-catenin signaling in vivo. FLS were treated with TGF-β1 to serve as an in vitro model of synovial fibrosis, Wnt3a was used to activate the Wnt/β-catenin signaling in cells. Cell proliferation was detected by using EdU assay, cell viability was performed by CCK8 assay. The protein levels of α-SMA, CTGF, Col Ⅰ, β-catenin, active β-catenin, c-Myc and cyclin D1 were examined by western blot and immunofluorescence staining.

RESULTS

Two weeks after the LIPUS treatment, the synovial fibrosis, synovial hyperplasia and synoviocyte proliferation in the DMM model were significantly decreased. In vitro, LIPUS directly inhibited the TGF-β1-induced fibrotic response and proliferation of FLS. Meanwhile, LIPUS suppressed Wnt/β-catenin signaling in the synovium of DMM mice and cultured FLS. More importantly, we found that the synovial fibrosis makers, Wnt/β-catenin pathway downstream proteins and FLS proliferation were significantly decreased in Wnt3a-stimulated FLS following LIPUS treatment.

CONCLUSIONS

Our results present a novel role of LIPUS in OA-related synovial fibrosis, which is associated with its ability to repress Wnt/β-catenin signaling in FLS.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

This study provides new insight into the clinical application of LIPUS as a therapeutic option to manage synovial fibrosis in OA.

Development and validation of low-intensity pulsed ultrasound systems for highly controlled in vitro cell stimulation

This work aims to describe the development and validation of two low-intensity pulsed ultrasound stimulation systems able to control the dose delivered to the biological target. Transducer characterization was performed in terms of pressure field shape and intensity, for a high-frequency range (500 kHz to 5 MHz) and for a low-frequency value (38 kHz). This allowed defining the distance, on the beam axis, at which biological samples should be placed during stimulation and to exactly know the intensity at the target. Carefully designed retaining systems were developed, for hosting biological samples. Sealing tests proved their impermeability to external contaminants. The assembly/de-assembly time of the systems resulted ~3 min. Time-domain acoustic simulations allowed to precisely estimate the ultrasound beam within the biological sample chamber, thus enabling the possibility to precisely control the pressure to be transmitted to the biological target, by modulating the transducer's input voltage. Biological in vitro tests were also carried out, demonstrating the sterility of the system and the absence of toxic and inflammatory effects on growing cells after multiple immersions in water, over seven days.

Low-intensity pulsed ultrasound for regenerating peripheral nerves: potential for penile nerve

Peripheral nerve damage, such as that found after surgery or trauma, is a substantial clinical challenge. Much research continues in attempts to improve outcomes after peripheral nerve damage and to promote nerve repair after injury. In recent years, low-intensity pulsed ultrasound (LIPUS) has been studied as a potential method of stimulating peripheral nerve regeneration. In this review, the physiology of peripheral nerve regeneration is reviewed, and the experiments employing LIPUS to improve peripheral nerve regeneration are discussed. Application of LIPUS following nerve surgery may promote nerve regeneration and improve functional outcomes through a variety of proposed mechanisms. These include an increase of neurotrophic factors, Schwann cell (SC) activation, cellular signaling activations, and induction of mitosis. We searched PubMed for articles related to these topics in both in vitro and in vivo animal research models. We found numerous studies, suggesting that LIPUS following nerve surgery promotes nerve regeneration and improves functional outcomes. Based on these findings, LIPUS could be a novel and valuable treatment for nerve injury-induced erectile dysfunction.

Low-Intensity Pulsed Ultrasound Prompts Both Functional and Histologic Improvements While Upregulating the Brain-Derived Neurotrophic Factor Expression after Sciatic Crush Injury in Rats

The aim of this study was to determine that low-intensity pulsed ultrasound (LIPUS) at an intensity of 140 mW/cm² promotes functional and histologic improvements in sciatic nerve crush injury in a rat model and to investigate changes over time in relevant growth factors and receptors, exploring the mechanism of LIPUS in the recovery process after injury. Toe angle in the toe-off phase, regenerative axonal length, myelinated nerve fiber density, diameter of myelinated nerve fiber, axon diameter and myelin sheath thickness were significantly higher in the LIPUS group than in the sham group. Gene and protein expression of brain-derived neurotrophic factor (BDNF) was upregulated in the LIPUS group. In conclusion, LIPUS contributed to rapid functional and histologic improvement and upregulated BDNF expression after sciatic nerve crush injury in rats.

The Hippo pathway: Horizons for innovative treatments of peripheral nerve diseases

Initially identified in Drosophila, the Hippo signaling pathway regulates how cells respond to their environment by controlling proliferation, migration and differentiation. Many recent studies have focused on characterizing Hippo pathway function and regulation in mammalian cells. Here, we present a brief overview of the major components of the Hippo pathway, as well as their regulation and function. We comprehensively review the studies that have contributed to our understanding of the Hippo pathway in the function of the peripheral nervous system and in peripheral nerve diseases. Finally, we discuss innovative approaches that aim to modulate Hippo pathway components in diseases of the peripheral nervous system.

The bone marrow-derived mesenchymal stem cells (BMSCs) alleviate diabetic peripheral neuropathy induced by STZ via activating GSK-3β/β-catenin signaling pathway

BACKGROUND

Diabetic peripheral neuropathy, a common complication of diabetic mellitus, has brought a threaten on patients' health. The bone marrow-derived mesenchymal stem cells (BMSCs) were reported to play an important role in diverse diseases. Nevertheless, the specific function of BMSCs in diabetic peripheral neuropathy remained uncharacterized.

METHODS

A wide range of experiments including RT-qPCR, western blot, H&E staining, oxidative stress assessment, measurement of thermal sensitivity, ELISA, urine protein and CCK-8 assays were implemented to explore the function and mechanism of BMSCs in vivo and vitro.

RESULTS

The experimental results displayed that BMSCs improve STZ-induced diabetes symptoms in rats by decreasing blood glucose and urinary protein. Functionally, BMSCs ameliorate oxidative stress, painful diabetic neuropathy, neurotrophic status and angiogenesis in STZ-induced rats. Moreover, BMSCs participate in the regulation of sciatic neuro morphology in diabetic neuropathy rat model. In mechanism, BMSCs alleviate diabetic peripheral neuropathy via activating GSK-3β/β-catenin signaling pathway in rats and improve Schwann's cells viability by activating GSK-3β/β-catenin signaling pathway under high glucose.

CONCLUSIONS

We verified that BMSCs alleviate diabetic peripheral neuropathy of rats induced by STZ via activating GSK-3β/β-catenin signaling pathway, which implied a novel biomarker for diabetic peripheral neuropathy treatment.

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.

The Regenerative Potential of Therapeutic Ultrasound on Neural Tissue: A Pragmatic Review

Objectives

Low-intensity ultrasound (LIU)/low-intensity pulsed ultrasound (LIPUS) may influence nerve tissue regeneration and axonal changes in the context of carpal tunnel syndrome (CTS) and in the animal model. The purpose of this pragmatic review is to understand the current knowledge for the effects of low-intensity therapeutic ultrasound in the animal and human model and determine the future directions of this novel field.

Design

Pragmatic review.

Methods

We performed a literature search of available material using OVID, EmBase, and PubMed for LIU/LIPUS, all of which were preclinical trials, case reports, and case series using animal models. For CTS, a literature search was performed on PubMed (1954 to 2019), CENTRAL (the Cochrane Library, 1970 to 2018), Web of Science (1954 to 2019), and SCOPUS (1954 to 2019) to retrieve randomized controlled trials.

Results

Eight articles were discussed showing the potential effects of LIU on nerve regeneration in the animal model. Each of these trials demonstrated evidence of nerve regeneration in the animal model using LIPUS or LIU. Seven randomized controlled trials were reviewed for ultrasound effects for the treatment of carpal tunnel syndrome, each showing clinical efficacy comparable to other treatment modalities.

Conclusions

LIU/LIPUS is a promising and noninvasive means of facilitating nerve regeneration in the animal model and in the treatment of carpal tunnel syndrome. Although many of the trials included in this review are preclinical, each demonstrates promising outcomes that could eventually be extrapolated into human studies.

Low-intensity pulsed ultrasound regulates proliferation and differentiation of neural stem cells through notch signaling pathway

Low-intensity pulsed ultrasound (LIPUS) is widely used to regulate stem cell proliferation and differentiation. However, the effect of LIPUS stimulation on neural stem cells (NSCs) is not well documented. In this study, we have identified the optimal parameters, and investigated the cellular mechanisms of LIPUS to regulate the proliferation and differentiation of NSCs in vitro. NSCs were obtained and identified by nestin immunostaining. The proliferation of NSCs were measured by using Cell Counting Kit-8 (CCK-8). The expressions of nutritional factors (NTFs) were detected with immunoassay (ELISA). NSCs differentiation were detected by immunofluorescence and immunoblotting analysis. The expression level of proteins involved in the Notch signaling pathway was also measured by immunoblotting assay. Our results showed the intensity of 69.3 mW/cm² (1 MHz, 8 V) was applicable for LIPUS stimulation. ELISA analysis demonstrated that LIPUS treatment promoted the expression of nutritional factors of NSCs in vitro. Immunofluorescence and immunoblotting analyses suggested that the LIPUS not only reduced the astrocyte differentiation, but also stimulated the differentiation to neurons. Additionally, LIPUS stimulation significantly upregulated expression level of Notch1 and Hes1. Results from our study suggest that LIPUS triggers NSCs proliferation and differentiation by modulating the Notch signaling pathway. This study implies LIPUS as a potential and promising therapeutic platform for the optimization of stem cells and enable noninvasive neuromodulation for central nervous system diseases.

Roles of transforming growth factor-β and phosphatidylinositol 3-kinase isoforms in integrin β1-mediated bio-behaviors of mouse lung telocytes

Background

Telocytes (TCs) have the capacity of cell–cell communication with adjacent cells within the tissue, contributing to tissue repair and recovery from injury. The present study aims at investigating the molecular mechanisms by which the TGFβ1-ITGB1-PI3K signal pathways regulate TC cycle and proliferation.

Methods

Gene expression of integrin (ITG) family were measured in mouse primary TCs to compare with other cells. TC proliferation, movement, cell cycle, and PI3K isoform protein genes were assayed in ITGB1-negative or positive mouse lung TCs treated with the inhibition of PI3Kp110α, PI3Kα/δ, PKCβ, or GSK3, followed by TGFβ1 treatment.

Results

We found the characters and interactions of ITG or PKC family member networks in primary mouse lung TCs, different from other cells in the lung tissue. The deletion of ITGB1 changed TCs sensitivity to treatment with multifunctional cytokines or signal pathway inhibitors. The compensatory mechanisms occur among TGFβ1-induced PI3Kp110α, PI3Kα/δ, PKCβ, or GSK3 when ITGB1 gene was deleted, leading to alterations of TC cell cycle and proliferation. Of those PI3K isoform protein genes, mRNA expression of PIK3CG altered with ITGB1-negative TC cycle and proliferation.

Conclusion

TCs have strong capacity of proliferation through the compensatory signaling mechanisms and contribute to the development of drug resistance due to alterations of TC sensitivity.

p38 MAPK signaling is a key mediator for low-intensity pulsed ultrasound (LIPUS) in cultured human omental adipose-derived mesenchymal stem cells

Visceral obesity is an independent risk factor for cardiovascular disorders and lacks effective, non-drug based clinical therapy. The use of low-intensity pulsed ultrasound (LIPUS) to treat chronic pain and bone fracture is well-known, but its application for visceral obesity treatment has not been studied. Here, we evaluated the therapeutic potential of LIPUS by studying its effects, at varying doses, on human omental adipose-derived mesenchymal stem cells (hAMSCs). LIPUS stimulation was applied for 1 min at intensities between 70 and 210 mW/cm². Cell viability was measured using the Cell Counting Kit-8 assay. Cell apoptosis was quantified by flow cytometry and immunoblotting of apoptosis marker proteins. We found that a high dose of LIPUS (210 mW/cm²) promoted apoptosis in hAMSCs, while a low dose (70 mW/cm²) increased hAMSC viability. Phosphorylation of p38, a mitogen-activated protein kinase (MAPK), increased with high dose LIPUS treatment, but markedly decreased with a low dose. Inhibition of p38 phosphorylation by SB203580, an inhibitor of p38 MAPK activity, rescued the apoptotic effects of high dose LIPUS. Our results showed the dose-dependent, opposing effects of LIPUS on hAMSCs and suggested that p38 plays a key role in mediating the effects of LIPUS on hAMSCs.