Exposure to low-intensity ultrasound increases aggrecan gene expression in a rat femur fracture model

Transcutaneous CO2 application combined with low-intensity pulsed ultrasound accelerates bone fracture healing in rats

BACKGROUND

Low-intensity pulsed ultrasound (LIPUS) is a non-invasive therapy that accelerates fracture healing. As a new treatment method for fracture, we recently reported that the transcutaneous application of CO2 accelerated fracture healing in association with promoting angiogenesis, blood flow, and endochondral ossification. We hypothesized that transcutaneous CO2 application, combined with LIPUS, would promote bone fracture healing more than the single treatment with either of them.

METHODS

Femoral shaft fractures were produced in 12-week-old rats. Animals were randomly divided into four groups: the combination of CO2 and LIPUS, CO2, LIPUS, and control groups. As the transcutaneous CO2 application, the limb was sealed in a CO2-filled bag after applying hydrogel that promotes CO2 absorption. Transcutaneous CO2 application and LIPUS irradiation were performed for 20 min/day, 5 days/week. At weeks 1, 2, 3, and 4 after the fractures, we assessed the fracture healing process using radiography, histology, immunohistochemistry, real-time PCR, and biomechanical assessment.

RESULTS

The fracture healing score using radiographs in the combination group was significantly higher than that in the control group at all time points and those in both the LIPUS and CO2 groups at weeks 1, 2, and 4. The degree of bone fracture healing in the histological assessment was significantly higher in the combination group than that in the control group at weeks 2, 3, and 4. In the immunohistochemical assessment, the vascular densities of CD31- and endomucin-positive microvessels in the combination group were significantly higher than those in the control and LIPUS groups at week 2. In the gene expression assessment, significant upregulation of runt-related transcription factor 2 (Runx2) and vascular endothelial growth factor (VEGF) was detected in the combination group compared to the LIPUS and CO2 monotherapy groups. In the biomechanical assessment, the ultimate stress was significantly higher in the combination group than in the LIPUS and CO2 groups.

CONCLUSION

The combination therapy of transcutaneous CO2 application and LIPUS had a superior effect in promoting fracture healing through the promotion of angiogenesis and osteoblast differentiation compared to monotherapy.

A Bibliometric Analysis for Low-Intensity Ultrasound Study Over the Past Three Decades

Low-intensity ultrasound (LI-US) is a non-invasive stimulation technique that has emerged in recent years and has been shown to have positive effects on neuromodulation, fracture healing, inflammation improvement, and metabolic regulation. This study reports the conclusions of a bibliometric analysis of LI-US. Input data for the period between 1995 and 2022, including 7209 related articles in the field of LI-US, were collected from the core library of the Web of Science (WOS) database. Using these data, a set of bibliometric indicators was obtained to gain knowledge on different aspects: global production, research areas, and sources analysis, contributions of countries and institutions, author analysis, citation analysis, and keyword analysis. This study combined the data analysis capabilities provided by the WOS database, making use of two bibliometric software tools: R software and VOS viewer to achieve analysis and data exploration visualization, and predicted the further development trends of LI-US. It turns out that the United States and China are co-leaders while Zhang ZG is the most significant author in LI-US. In the future, the hot spots of LI-US will continue to focus on parameter research, mechanism discussion, safety regulations, and neuromodulation applications.

Ultrasound-derived mechanical stimulation of cell-laden collagen hydrogels for bone repair

Cell therapy is emerging as an effective treatment strategy for many diseases. Here we describe a novel approach to bone tissue repair that combines hydrogel-based cell therapy with low intensity pulsed ultrasound (LIPUS), an FDA approved treatment for fracture repair. Bone marrow-derived stromal cells (BMSCs) have been encapsulated in type I collagen hydrogels and mechanically stimulated using LIPUS-derived acoustic radiation force (ARF). We observed the expression and upward trend of load-sensitive, osteoblast-specific markers and determined that the extent of cell response is dependent on an optimal combination of both hydrogel stiffness and ARF intensity. Specifically, cells encapsulated in hydrogels of optimal stiffness respond at the onset of ultrasound by upregulating early bone-sensitive markers such as calcium, cyclooxygenase-2, and prostaglandin E2 , and later by supporting mineralized tissue formation after 21 days of culture. In vivo evaluation of a critical size calvarial defect in NOD scid gamma (NSG) mice indicated that the implantation of BMSC-laden hydrogels of optimal stiffness improved healing of calvarial defects after daily administration of ARF over 4 weeks. Collectively, these findings validate the efficacy of our system of localized cell delivery for treating bone defects where undifferentiated BMSCs are induced to the osteoblastic lineage. Further, in vivo healing may be enhanced via non-invasive transdermal mechanical stimulation of implanted cells using ARF.

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.

Application of Ultrasound to Enhancing Stem Cells Associated Therapies

Pluripotent stem cell therapy exhibits self-renewal capacity and multi-directional differentiation potential and is considered an important regenerative approach for the treatment of several diseases. However, insufficient cell transplantation efficiency, uncontrollable differentiation, low cell viability, and difficult tracing limit its clinical applications and treatment outcome. Ultrasound (US) has mechanical, cavitation, and thermal effects that can produce different biological effects on organs, tissues, and cells. US can be combined with different US-responsive particles for enhanced physical-chemical stimulation and drug delivery. In the meantime, US also can provide a noninvasive and harmless imaging modality for deep tissue in vivo. An in-depth evaluation of the role and mechanism of action of US in stem cell therapy would enhance understanding of US and encourage research in this field. In this article, we comprehensively review progress in the application of US alone and combined with US-responsive particles for the promotion of proliferation, differentiation, migration, and in vivo detection of stem cells and the potential clinical applications.

Biochemical and Physiological Events Involved in Responses to the Ultrasound Used in Physiotherapy: A Review

Therapeutic ultrasound (TUS) is the ultrasound modality widely used in physical therapy for the treatment of acute and chronic injuries of various biological tissues. Its thermal and mechanical effects modify the permeability of the plasma membrane, the flow of ions and molecules and cell signaling and, in this way, promote the cascade of physiological events that culminate in the repair of injuries. This article is a review of the biochemical and physiological effects of TUS with parameters commonly used by physical therapists. Integrins can translate the mechanical signal of the TUS into a cellular biochemical signal for protein synthesis and modification of the active site of enzymes, so cell function and metabolism are modified. TUS also alters the permeability of the plasma membrane, allowing the influx of ions and molecules that modulate the cellular electrochemical signaling pathways. With biochemical and electrochemical signals tampered with, the cellular response to damage is then modified or enhanced. Greater release of pro-inflammatory factors, cytokines and growth factors, increased blood flow and activation of protein kinases also seem to be involved in the therapeutic response of TUS. Although a vast number of publications describe the mechanisms by which TUS can interact with the biological system, little is known about the metabolic possibilities of TUS because of the lack of standardization in its application.

MRI Bone Abnormality of the Knee following Ultrasound Therapy: Case Report and Short Review

Ultrasound (US) therapy in sports and medical pathologies is widely used by many physiotherapists and sports medicine clinicians; however, data regarding their potential side effects remain rare. We report a case of a 21-year-old woman with iliotibial band (ITB) syndrome treated with a physiotherapy session combined with US therapy. She had twenty 7 min US sessions on the knee, for 3 months (US at 1 Mhz with an intensity between 1 and 2 W/cm²). Due to persistence of the ITB syndrome's symptomatology after the 3 months of physiotherapy sessions, an MRI (magnetic resonance imaging) was carried out and revealed osteonecrosis-like bone abnormalities on the external femoral condyle, the external tibial plateau, and the proximal fibula. In view of these lesions, the ultrasonic therapy was stopped, and a repeat MRI demonstrated the progressive disappearance of these imaging abnormalities one year after the last US (ultrasound) treatment. In light of this case, we propose here a short review of reported osseous "osteonecrosis" abnormalities associated with US therapies.

Enhanced Bone Regeneration by Bone Morphogenetic Protein-2 after Pretreatment with Low-Intensity Pulsed Ultrasound in Distraction Osteogenesis

BACKGROUND

Bone morphogenetic protein 2 (BMP-2) and low-intensity pulsed ultrasound (LIPUS) have been used to enhance bone healing in distraction osteogenesis (DO). The aim of this study was to assess the synergistic effect of BMP-2 and LIPUS on bone regeneration in DO and to determine the optimal treatment strategy for enhanced bone regeneration.

METHODS

Rat mesenchymal stromal cells were treated with various application protocols of BMP-2 and LIPUS, and cell proliferation, alkaline phosphatase activity, and osteogenesis-related marker expression were evaluated. In vivo experiments were performed in a rabbit DO model according to the application protocols with different timings of BMP-2 and LIPUS application.

RESULTS

Application of BMP-2 after LIPUS pretreatment (BMP-2 after LIPUS) showed greater cell proliferation than LIPUS treatment alone, and higher ALP activity than all other treatment protocols. BMP-2 after LIPUS also exhibited increased gene expression levels of ALP, Cbfa1, and Osterix compared with LIPUS treatment alone. In vivo experiments revealed no significant differences in bone healing based on the timing of LIPUS treatment in DO. The combination of BMP-2 and LIPUS resulted in increased bone volume and bone mineral density compared with BMP-2 or LIPUS. Regarding the timing of BMP-2 application, the application of BMP-2 after LIPUS pretreatment led to greater bone volume than the application of BMP-2 before LIPUS.

CONCLUSION

The results of this study suggest that the combined treatment of BMP-2 and LIPUS can lead to enhanced bone healing in DO and that effective bone healing can be achieved through the application of LIPUS before BMP-2.

Growth Modulation by Stimulating the Growth Plate: A Pilot Study

This study investigates the ability of low-intensity pulsed ultrasound (LIPUS) or direct injection of recombinant growth hormone (rGH) to stimulate local growth of long bones. In a randomized controlled animal trial, healthy immature rabbits were allocated to 1 of the following 4 conditions: epiphyseal rGH periosteal injection, transdermal LIPUS, saline periosteal injection, or no treatment. New bone deposition was labeled with calcein at days 1 and 18, and microscopic measurements of growth were conducted by blinded observers. Statistically significant differences in growth were observed between the LIPUS and rGH stimulated legs compared with contralateral control legs (35% p = 0.04 and 41% p = 0.04, respectively); whereas no difference was observed between the 4 control groups (p = 0.37). There was no evidence of physeal bar formation, suggesting that direct injection of rGH and application of LIPUS around the distal femoral physis in rabbits may have a positive effect on microscopic growth without short-term adverse sequelae.

Effect of low-intensity pulsed ultrasound on orofacial sensory disturbance following inferior alveolar nerve injury: Role of neurotrophin-3 signaling

Percutaneous treatment of low-intensity pulsed ultrasound (LIPUS) to the site of inferior alveolar nerve (IAN) transection promotes functional regeneration, but the detailed mechanism is unknown. We examined the involvement of neurotrophin-3 (NT-3), which primarily binds with tropomyosin receptor kinase C (TrkC), in functional transected IAN regeneration following LIPUS treatment in rats. Daily LIPUS treatment to the transected IAN was performed, and the mechanical sensitivity of the facial skin was measured for 14 d. On day 5 after IAN transection, the expression of NT-3 in the transected IAN and TrkC-positive trigeminal ganglion neurons were immunohistochemically examined. Further, the effect of TrkC neutralization on the acceleration of facial mechanosensory disturbance restoration due to LIPUS treatment was analyzed. LIPUS treatment to the site of IAN transection significantly facilitated functional recovery from sensory disturbance on facial skin. Schwann cells in the transected IAN expressed NT-3, and LIPUS treatment increased the amount of NT-3. The facilitated recovery from the mechanosensory disturbance by continuous LIPUS treatment was inhibited by the ongoing TrkC neutralization at the IAN transection site. These results suggest that LIPUS treatment accelerates the recovery of orofacial mechanosensory function following IAN transection through the enhancement of NT-3 signaling in the transected IAN.

Osteocytes as main responders to low-intensity pulsed ultrasound treatment during fracture healing

Ultrasound stimulation is a type of mechanical stress, and low-intensity pulsed ultrasound (LIPUS) devices have been used clinically to promote fracture healing. However, it remains unclear which skeletal cells, in particular osteocytes or osteoblasts, primarily respond to LIPUS stimulation and how they contribute to fracture healing. To examine this, we utilized medaka, whose bone lacks osteocytes, and zebrafish, whose bone has osteocytes, as in vivo models. Fracture healing was accelerated by ultrasound stimulation in zebrafish, but not in medaka. To examine the molecular events induced by LIPUS stimulation in osteocytes, we performed RNA sequencing of a murine osteocytic cell line exposed to LIPUS. 179 genes reacted to LIPUS stimulation, and functional cluster analysis identified among them several molecular signatures related to immunity, secretion, and transcription. Notably, most of the isolated transcription-related genes were also modulated by LIPUS in vivo in zebrafish. However, expression levels of early growth response protein 1 and 2 (Egr1, 2), JunB, forkhead box Q1 (FoxQ1), and nuclear factor of activated T cells c1 (NFATc1) were not altered by LIPUS in medaka, suggesting that these genes are key transcriptional regulators of LIPUS-dependent fracture healing via osteocytes. We therefore show that bone-embedded osteocytes are necessary for LIPUS-induced promotion of fracture healing via transcriptional control of target genes, which presumably activates neighboring cells involved in fracture healing processes.

Fracture Nonunion Treated with Low-Intensity Pulsed Ultrasound and Monitored with Ultrasonography: A Feasibility Study

The positive effect of low-intensity pulsed ultrasound (LIPUS) on bone fracture healing has been proved. However, during the period of LIPUS therapy, it is undetermined whether LIPUS promotes the formation of heterotopic ossification (HO), which usually occurs in muscle tissues after trauma such as bone fracture and spinal cord injury. Here, we used 6-week LIPUS therapy in a 42-year-old Chinese male patient with a fracture nonunion in combination with ultrasonography for monitoring fracture healing and HO formation. After the LIPUS therapy, the mineralized bone formation in the area of defect of the distal tibia was presented in an ultrasound image, which was consistent with the outcome of plain radiography showing callus formation and the blurred fracture line in the area exposed to LIPUS. In addition, ultrasound images revealed no evidence of HO development within soft tissues during the period of LIPUS therapy. This study suggests that ultrasonography is a potential tool to guarantee the performance of LIPUS therapy with monitoring HO formation. Easy to use, the integration of the handheld ultrasound scanner and the ultrasonic therapeutic apparatus is entirely dedicated to help orthopedists make high-quality care and diagnosis.

Can low intensity pulsed ultrasound (LIPUS) be used as an alternative to revision surgery for patients with non-unions following fracture fixation?

BACKGROUND

Non-union is a significant complication of fracture fixation surgery, and can negatively impact a patient's quality of life. Low intensity pulsed ultrasound (LIPUS) has been used to treat delayed or non-unions previously in the literature. The aim of this study was to determine the success rate of LIPUS treatment in patients with chronic fracture non-unions, and to establish the effect of systemic or local factors on its success.

METHODS

This was a retrospective, observational study which included all patients undergoing LIPUS treatment in a single institution. Patients deemed suitable for LIPUS underwent treatment for a period of 6 months from initiation. They were followed up with sequential radiographs to assess union at intervals of 6 weeks, 3 months, 6 months and 1 year. LIPUS treatment was considered to be successful when patients achieved clinical and radiological union, without the need for revision surgery.

RESULTS

A total of 46 patients were included in the study; 8 were lost to follow - up, leaving 38 patients for the final analysis. The mean age of patients was 47.03 ± 19.7 with a male to female ratio of 1.2:1. Union was achieved in 57.89%; the rest underwent revision surgery. There was no significant association between outcomes after LIPUS treatment and patients' age, gender, smoking status or type of non-union. Patients with a small inter-fragment bone gap were more likely to have a successful outcome after LIPUS (p = 0.041). Time to treatment did not have a statistically significant impact on outcomes after LIPUS. Interestingly, all 6 patients with diabetes in the study managed to achieve union after LIPUS.

CONCLUSIONS

This study demonstrates that LIPUS is not successful in a large proportion of patients with established fracture non-unions. However, it does represent a low risk treatment modality as an alternative to revision surgery, especially for patients with diabetes who have a small inter - fragment bone gap. More research in the form of large randomised controlled trials needs to be carried out to further assess the role of LIPUS in the treatment of non-unions.

Ultrasound Therapy: Experiences and Perspectives for Regenerative Medicine

Ultrasound has emerged as a novel tool for clinical applications, particularly in the context of regenerative medicine. Due to its unique physico-mechanical properties, low-intensity ultrasound (LIUS) has been approved for accelerated fracture healing and for the treatment of established non-union, but its utility has extended beyond tissue engineering to other fields, including cell regeneration. Cells and tissues respond to acoustic ultrasound by switching on genetic repair circuits, triggering a cascade of molecular signals that promote cell proliferation, adhesion, migration, differentiation, and extracellular matrix production. LIUS also induces angiogenesis and tissue regeneration and has anti-inflammatory and anti-degenerative effects. Accordingly, the potential application of ultrasound for tissue repair/regeneration has been tested in several studies as a stand-alone treatment and, more recently, as an adjunct to cell-based therapies. For example, ultrasound has been proposed to improve stem cell homing to target tissues due to its ability to create a transitional and local gradient of cytokines and chemokines. In this review, we provide an overview of the many applications of ultrasound in clinical medicine, with a focus on its value as an adjunct to cell-based interventions. Finally, we discuss the various preclinical and clinical studies that have investigated the potential of ultrasound for regenerative medicine.

Clinical and patient-reported outcomes following Low Intensity Pulsed Ultrasound (LIPUS, Exogen) for established post-traumatic and post-surgical nonunion in the foot and ankle

BACKGROUND

Biophysical methods including Low Intensity Pulsed Ultrasound (LIPUS) are emerging as potential alternatives to revision surgery for treating established nonunions. We aim to prospectively review the clinical and patient-reported outcomes of patients treated with LIPUS following post-traumatic and post-surgical nonunions in the foot and ankle.

METHODS

Forty-seven consecutive patients underwent Exogen treatment. Patient-reported outcome scores included MOXFQ, EQ-5D and VAS. Patients were divided in to 3 groups: fractures (A), hindfoot procedures (B) and midfoot/forefoot procedures (C).

RESULTS

Thirty-seven patients (78.7%) clinically united, 4 patients (8.5%) noticed no significant improvement but did not want further intervention and 6 patients (12.8%) underwent revision surgery. The mean duration of Exogen treatment was 6 months. Union rates of 93%, 67% and 78% were noted in the three groups. Significant improvement in functional outcomes and potential cost savings were observed.

CONCLUSIONS

Exogen for established nonunion in the foot and ankle is a safe, valuable and economically viable clinical option as an alternative to revision surgery. We observed better results in the fracture and midfoot/forefoot groups and relatively poorer results in the hindfoot fusion group.

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.

Low-intensity pulsed ultrasound enhances callus consolidation in distraction osteogenesis of the tibia by the technique of lengthening over the nail procedure

BACKGROUND

Low-intensity pulsed ultrasound (LIPUS) has been widely accepted in promoting the fracture healing process. However, there have been limited clinical trials focused on the efficacy of LIPUS during distraction osteogenesis (DO) by the technique of lengthening over the nail procedure. The purpose of the current study was to evaluate the efficacy of LIPUS during DO.

METHODS

We retrospectively evaluated 30 patients (60 segments) who underwent simultaneous bilateral tibial lengthening over the nail. The patients were grouped into the LIPUS group and the control group based on LIPUS stimulation. The two patient groups were compared for demographic data (sex, age at operation, preoperative height, BMI, and smoking history), qualitative assessments of the callus (callus shape and type), external fixation index, and four cortical healing indexes.

RESULTS

Fifteen patients (30 segments) were classified as the LIPUS group, and another 15 patients (30 segments) were classified as the control group. No significant differences were found in the assessed demographic data between the groups. LIPUS stimulated a more cylindrical, more homogenous, and denser type of callus formation at the end of the distraction phase. The two groups exhibited equivalent outcomes in terms of external fixation index (p = 0.579). However, significant differences were found in healing indexes of the anterior and medial cortices (p <  0.001 and p = 0.002, respectively). The healing indexes of those cortices in the LIPUS group (mean of 36.6 days/cm and 32.5 days/cm, respectively) reflected their significantly faster healing compared to the control group (mean HI of 57.5 days/cm and 44.2 days/cm, respectively). There were no LIPUS-related complications.

CONCLUSIONS

LIPUS is a noninvasive and effective adjuvant therapy to enhance callus maturation during DO. It enhances callus consolidation and may have a positive effect on the appropriate callus shape and type.

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.

Low-intensity pulsed ultrasound promotes alveolar bone regeneration in a periodontal injury model

Periodontitis is a common oral disease characterized by progressive destruction of periodontal tissue and loss of teeth. However, regeneration of periodontal tissue is a time-consuming process. Low-intensity pulsed ultrasound (LIPUS) is a widely used non-invasive intervention for enhancing bone healing in fractures and non-unions. With the hypothesis that LIPUS may accelerate periodontal regeneration, the effects of LIPUS on periodontal tissue regeneration were investigated both in vitro and in vivo. LIPUS (90 mw/cm², 20 min/d, 1.5 MHz) was applied to stimulate dog periodontal ligament cells (dPDLCS). The mRNA expression of BSP (P < 0.05), OPN (P < 0.05) and COL3 (P < 0.05) was increased significantly in the LIPUS group. The positive stained mineralized nodules by alizarin red in the LIPUS group were greater than in the control group (P < 0.05). Eight male beagle dogs were divided into 4 groups: guided tissue regeneration (GTR) group (G1), LIPUS + GTR group (G2), LIPUS group (G3), and control group (G4, no treatment). A 4 × 5 mm² defect was created in the buccal alveolar bone. The modeling areas in the G2 and G3 groups were then exposed to LIPUS. Eight weeks after surgery, histological assessment indicated increased periodontal tissue in the LIPUS + GTR group. Micro computed tomography (micro-CT) showed that the regenerated bone volume (BV) in the G2 was significantly higher than that in the G1, G3 and G4 groups (P < 0.05). The bone surface (BS) trabecular number (Tb.N) and trabecular thickness (Tb.Th) in G2 were markedly higher than in G4 (P < 0.05). It is concluded that LIPUS + GTR can accelerate new alveolar bone formation, with a prospective for promoting periodontal tissue repair.

Low-Intensity Pulsed Ultrasound for Nonoperative Treatment of Scaphoid Nonunions: A Meta-Analysis

Background: Scaphoid fractures progress to nonunion rates of up to 15% when non-displaced, and are even more frequent when the fracture is displaced. Standard treatment in these cases is surgery; however, individuals unable to undergo this operation, or for those who wish to try more conservative measures, there may be benefit from nonoperative options. Of these, low-intensity pulsed ultrasound (LIPUS) has been shown to improve fracture nonunion healing. The purpose of this study was to perform a comprehensive meta-analysis of relevant literature to determine success of the use of LIPUS for treatment of scaphoid nonunion. Methods: Utilizing PubMed, Embase, and Ovid databases, we performed a literature search using key terms for scaphoid nonunions. A total of 686 studies met initial search criteria. Studies reporting fewer than 5 cases, those not published in English, those not related to LIPUS nonoperative scaphoid nonunion treatment, and those without sufficient data were excluded. Five studies met these criteria, and statistical analysis was performed to determine overall union rates. Results: The use of LIPUS on 166 nonunions reported a mean healing index of 78.6%. The average time to union following LIPUS treatment was 4.2 months. Conclusions: While surgical intervention is still the standard, our results show that LIPUS may serve as a nonoperative alternative to scaphoid nonunion in certain cases. The results are encouraging in which these challenging fracture a nonunions can heal without further surgical intervention in the majority of patients.

Cell type-specific suppression of mechanosensitive genes by audible sound stimulation

Audible sound is a ubiquitous environmental factor in nature that transmits oscillatory compressional pressure through the substances. To investigate the property of the sound as a mechanical stimulus for cells, an experimental system was set up using 94.0 dB sound which transmits approximately 10 mPa pressure to the cultured cells. Based on research on mechanotransduction and ultrasound effects on cells, gene responses to the audible sound stimulation were analyzed by varying several sound parameters: frequency, wave form, composition, and exposure time. Real-time quantitative PCR analyses revealed a distinct suppressive effect for several mechanosensitive and ultrasound-sensitive genes that were triggered by sounds. The effect was clearly observed in a wave form- and pressure level-specific manner, rather than the frequency, and persisted for several hours. At least two mechanisms are likely to be involved in this sound response: transcriptional control and RNA degradation. ST2 stromal cells and C2C12 myoblasts exhibited a robust response, whereas NIH3T3 cells were partially and NB2a neuroblastoma cells were completely insensitive, suggesting a cell type-specific response to sound. These findings reveal a cell-level systematic response to audible sound and uncover novel relationships between life and sound.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The efficacy and safety of combination therapy of low-intensity pulsed ultrasound stimulation in the treatment of unstable both radius and ulna fractures in children

BACKGROUND

There are few reports of Low-intensity pulsed ultrasound (LIPUS) treatment for fresh forearm fractures in children.

OBJECTIVES

LIPUS stimulation was applied after surgery of forearm fractures in children and the efficacy and safety of combination therapy of LIPUS treatment were evaluated.

PATIENTS AND METHODS

Children with both radius and ulna fracture, twenty-five diaphysis (mid-R&U) and nineteen metaphysis (dist-R&U) fractures, were treated with intramedullary nailing followed by cast and splint mobilization. Thirteen patients in the mid-R&U fracture group and eight patients in the dist-R&U fracture group were combined with LIPUS stimulation postoperatively.

RESULTS

Periosteal callus appeared significantly earlier after surgery in the LIPUS-treated groups than in the groups without LIPUS treatment. The duration of external fixation was significantly shorter in the dist-R&U fracture group treated with LIPUS stimulation compared with that in the mid-R&U fracture group without LIPUS treatment. Furthermore, the time span needed for bone union in the groups with LIPUS stimulation was significantly shorter than in the groups without LIPUS stimulation.

CONCLUSIONS

It is suggested that LIPUS stimulation can lead to a reduction of treatment periods of unstable forearm fractures safely after operation even in children.

Effect of low-intensity pulsed ultrasound on the biological behavior of osteoblasts on porous titanium alloy scaffolds: An in vitro and in vivo study

Low-intensity pulsed ultrasound (LIPUS) has been used in patients with fresh fractures, delayed union and non-union to enhance bone healing and improve functional outcome. However, there were few studies concerning the effects of LIPUS on the biological behavior of osteoblasts on porous scaffolds. This study aimed to evaluate the effects of LIPUS on the biological behavior of osteoblasts on porous titanium-6aluminum-4vanadium (Ti6Al4V) alloy scaffolds in vitro and in vivo. Scaffolds were randomly divided into an ultrasound group and a control group. Mouse pre-osteoblast cells were cultured with porous Ti6Al4V scaffolds in vitro. The effects of LIPUS on the biological behavior of osteoblasts were evaluated by observing the adhesion, proliferation, differentiation and ingrowth depth on porous Ti6Al4V scaffolds. In addition, scaffolds were implanted into rabbit mandibular defects in vivo. The effects of LIPUS on bone regeneration were evaluated via micro-CT, fluorescent staining and toluidine blue staining. The results revealed that osteoblast adhered well to the scaffolds, and there was no significant difference in the methyl thiazolyl tetrazolium value between the ultrasound group and the control group (p>0.05). Compared with the control group, ultrasound promoted the alkaline phosphatase activity, osteocalcin levels and ingrowth depth of the cells on the scaffolds (p<0.05). In addition, micro-CT and histomorphological analysis showed that the volume and amount of new bone formation were increased and that bone maturity was improved in the ultrasound group compared to the control group. These results indicate that LIPUS promotes osteoblast differentiation as well as enhances bone ingrowth in porous Ti6Al4V scaffolds, and promotes bone formation and maturity in porous Ti6Al4V scaffolds.

A study to compare the efficacy of polyether ether ketone rod device with titanium devices in posterior spinal fusion in a canine model

BACKGROUND

The benefits of posterior lumbar fusion surgery with orthotopic paraspinal muscle-pediculated bone flaps are well established. However, the problem of non-union due to mechanical support is not completely resolved. The aim of the study was to compare the efficacy of polyether ether ketone (PEEK) rod device with conventional titanium devices in the posterior lumbar fusion surgery with orthotopic paraspinal muscle-pediculated bone flaps.

METHODS

This was a randomized controlled study with an experimental animal model. Thirty-two mongrel dogs were randomly divided into two groups-control group (n = 16), which received the titanium device and the treatment group (n = 16), which received PEEK rods. The animals were sacrificed 8 or 16 weeks after surgery. Lumbar spines of dogs in both groups were removed, harvested, and assessed for radiographic, biomechanical, and histological changes.

RESULTS

Results in the current study indicated that there was no significant difference in the lumbar spine of the control and treatment groups in terms of radiographic, manual palpation, and gross examination. However, certain parameters of biomechanical testing showed significant differences (p < 0.05) in stiffness and displacement, revealing a better fusion (treatment group showed decreased stiffness with decreased displacement) of the bone graft. Similarly, the histological analysis also revealed a significant fusion mass in both treatment and control groups (p < 0.05).

CONCLUSIONS

These findings revealed that fixation using PEEK connecting rod could improve the union of the bone graft in the posterior lumbar spine fusion surgery compared with that of the titanium rod fixation.

Synergistic effect of exogeneous and endogeneous electrostimulation on osteogenic differentiation of human mesenchymal stem cells seeded on silk scaffolds

Bioelectrical regulation of bone fracture healing is important for many cellular events such as proliferation, migration, and differentiation. The aim of this study was to investigate the osteogenic differentiation potential of human mesenchymal stem cells (hMSCs) cultivated on silk scaffolds in response to different modes of electrostimulation (e.g., exogeneous and/or endogeneous). Endogeneous electrophysiology was altered through the use of monensin (10 nM) and glibenclamide (10 μM), along with external electrostimulation (60 kHz; 100-500 mV). Monensin enhanced the expression of early osteogenic markers such as alkaline phosphatase (ALP) and runt-related transcription factor 2 (RUNX-2). When exogeneous electrostimulation was combined with glibenclamide, more mature osteogenic marker upregulation based on bone sialoprotein expression (BSP) and mineralization was found. These results suggest the potential to exploit both exogeneous and endogeneous biophysical control of cell functions towards tissue-specific goals.

Modulation of the Effect of Transforming Growth Factor-β3 by Low-Intensity Pulsed Ultrasound on Scaffold-Free Dedifferentiated Articular Bovine Chondrocyte Tissues

The aim of this study was to evaluate how low-intensity pulsed ultrasound (LIPUS) modulates the effect of transforming growth factor-β3 (TGF-β3) on the differentiation of scaffold-free dedifferentiated bovine articular chondrocyte tissues toward a cartilage-like phenotype. Specifically, the effect of these stimuli on the expression of hypertrophic markers collagen type I, collagen type X, and cartilage-degrading collagenase gene expression for a scaffold-free model was analyzed. A bioreactor that applied LIPUS directly from the transducer through a silicone gel to a six-well plate containing the tissues allowed simple, sterile, and large-scale experiments. Tissues were subjected to LIPUS of 55 mW/cm(2) in a 200 μs burst sine wave of 1 MHz over a 10-day period with or without TGF-β3 (10 ng/mL). Tissues exposed to TGF-β3 had significantly increased glycosaminoglycan and total collagen protein production along with upregulated cartilage-specific gene expression, resulting in tissues with a higher Young's Modulus. However, these tissues had also upregulated gene expression for hypertrophic markers collagen type I, collagen type X, MMP-1, MMP-13, MMP-2, and also an increase in the phosphorylation of p38. The expression of these matrix-degrading enzymes was remediated by hypertrophic development and differentiate dedifferentiated bovine articular chondrocytes towards a chondrogenic lineage allowing it to be a valuable tool in cartilage tissue engineering.

Effects of low-intensity pulsed ultrasound on spinal pseudarthrosis created by nicotine administration: a model of lumbar posterolateral pseudarthrosis in rabbits

OBJECTIVES

Low-intensity pulsed ultrasound (US) can enhance spinal fusion and fracture healing; however, its effect on spinal pseudarthrosis has not been reported in the literature. We hypothesized that low-intensity pulsed US could overcome spinal pseudarthrosis created by nicotine administration.

METHODS

Thirty-two rabbits underwent posterolateral fusion with an iliac bone graft and nicotine administration. At 5 weeks, the spines were examined by computed tomography (CT) to determine the presence of pseudarthrosis. All rabbits with pseudarthrosis were randomly divided into groups A, B, C, and D according to treatment: no second graft, iliac autograft only, low-intensity pulsed US only, and iliac autograft and low-intensity pulsed US, respectively. At 10 weeks, the rabbits were euthanized, and the specimens were assessed with radiography, CT, manual palpation, and histologic analysis.

RESULTS

One rabbit was lost because of severe infection. Twenty-seven (87%) had pseudarthrosis on CT at 5 weeks. On manual palpation at 10 weeks, the fusion rates were 0%, 29%, 0%, and 57% in groups A, B, C, and D, respectively. Group D had highest radiographic scores (mean ± SD, 2.87 ± 0.92), and the difference was statistically significant compared to the other groups (P < .001). Computed tomography confirmed that group D had the most fused segments at 10 weeks. Histologic specimens from group D also showed the most mature bone formation inside the fusion mass.

CONCLUSIONS

Low-intensity pulsed US can enhance spinal fusion but cannot overcome spinal pseudarthrosis created by nicotine administration. Stopping nicotine consumption or administering a more powerful bone substitute might be an alternative method for overcoming spinal pseudarthrosis.

Low-intensity pulsed ultrasound treatment for scaphoid fracture nonunions in adolescents

Background Treatment of scaphoid nonunion is challenging, leading clinicians to pursue innovation in surgical technique and adjunctive therapies to improve union rates. Purpose The purpose of this study was to investigate the use of low-intensity pulsed ultrasound as an adjunctive treatment modality following surgical treatment of scaphoid nonunion in adolescent patients, for whom this therapy has not yet been FDA-approved. Patients and Methods We performed a retrospective review of adolescent patients with scaphoid nonunion treated surgically followed by adjunctive low-intensity pulsed ultrasound therapy. All patients underwent 20 minutes of daily ultrasound therapy postoperatively until there was evidence of bony healing, based on both clinical and radiographic criteria. Final healing was confirmed by > 50% bone bridging on CT scan. Results Thirteen of fourteen (93%) patients healed at a mean interval of 113 days (range 61-217 days). There were no surgical or postoperative complications. One patient developed heterotopic bone formation about the scaphoid. Conclusions Our study suggests that low-intensity pulsed ultrasound therapy can safely be utilized as an adjunctive modality in adolescents to augment scaphoid healing following surgical intervention. Level of Evidence Level IV, Case series.

Effects of low-intensity pulsed ultrasound on new trabecular bone during bone-tendon junction healing in a rabbit model: a synchrotron radiation micro-CT study

This study was designed to evaluate the effects of low-intensity pulsed ultrasound on bone regeneration during the bone-tendon junction healing process and to explore the application of synchrotron radiation micro computed tomography in three dimensional visualization of the bone-tendon junction to evaluate the microarchitecture of new trabecular bone. Twenty four mature New Zealand rabbits underwent partial patellectomy to establish a bone-tendon junction injury model at the patella-patellar tendon complex. Animals were then divided into low-intensity pulsed ultrasound treatment (20 min/day, 7 times/week) and placebo control groups, and were euthanized at week 8 and 16 postoperatively (n = 6 for each group and time point). The patella-patellar tendon specimens were harvested for radiographic, histological and synchrotron radiation micro computed tomography detection. The area of the newly formed bone in the ultrasound group was significantly greater than that of control group at postoperative week 8 and 16. The high resolution three dimensional visualization images of the bone-tendon junction were acquired by synchrotron radiation micro computed tomography. Low-intensity pulsed ultrasound treatment promoted dense and irregular woven bone formation at week 8 with greater bone volume fraction, number and thickness of new trabecular bone but with lower separation. At week 16, ultrasound group specimens contained mature lamellar bone with higher bone volume fraction and thicker trabeculae than that of control group; however, there was no significant difference in separation and number of the new trabecular bone. This study confirms that low-intensity pulsed ultrasound treatment is able to promote bone formation and remodeling of new trabecular bone during the bone-tendon junction healing process in a rabbit model, and the synchrotron radiation micro computed tomography could be applied for three dimensional visualization to quantitatively evaluate the microarchitecture of new bone in bone-tendon junction.

Focused low-intensity pulsed ultrasound enhances bone regeneration in rat calvarial bone defect through enhancement of cell proliferation

A number of studies have reported the therapeutic potential of low-intensity pulsed ultrasound (LIPUS) for induction of bone repair. This study investigated whether bone regeneration might be enhanced by application of focused LIPUS to selectively stimulate fractured calvarial bone. To accomplish this, bone defects were surgically created in the middle of the skull of rats that were subsequently exposed to focused LIPUS. Bone regeneration was assessed by repeated computed tomography imaging after the operation, as well as histologic analysis with calcein, hematoxylin and eosin and proliferating cell nuclear antigen assay. At 6 wk after surgery, bone formation in the focused LIPUS-treated group improved significantly relative to the control. Interestingly, new bone tissue sprouted from focused LIPUS target points. Histologic analysis after exposure to focused LIPUS revealed that proliferating cells were significantly increased relative to the control. Taken together, these results suggest that focused LIPUS can improve re-ossification through enhancement of cell proliferation in calvarial defect sites.

Low-intensity pulsed ultrasound enhances bone formation around miniscrew implants

Miniscrew implants (MSIs) are currently used to provide absolute anchorage in orthodontics; however, their initial stability is an issue of concern. Application of low-intensity pulsed ultrasound (LIPUS) can promote bone healing. Therefore, LIPUS application may stimulate bone formation around MSIs and enhance their initial stability.

AIM

To investigate the effect of LIPUS exposure on bone formation after implantation of titanium (Ti) and stainless steel (SS) MSIs.

METHODS

MSIs made of Ti-6Al-4V and 316L SS were placed on rat tibiae and treated with LIPUS. The bone morphology around MSIs was evaluated by scanning electron microscopy and three-dimensional micro-computed tomography. MC3T3-E1 cells cultured on Ti and SS discs were treated with LIPUS, and the temporary expression of alkaline phosphatase (ALP) was examined.

RESULTS

Bone-implant contact increased gradually from day 3 to day 14 after MSI insertion. LIPUS application increased the cortical bone density, cortical bone thickness, and cortical bone rate after implantation of Ti and SS MSIs (P<0.05). LIPUS exposure induced ALP upregulation in MC3T3-E1 cells at day 3 (P<0.05).

CONCLUSION

LIPUS enhanced bone formation around Ti and SS MSIs, enhancing the initial stability of MSIs.

Application of an acoustofluidic perfusion bioreactor for cartilage tissue engineering

Cartilage grafts generated using conventional static tissue engineering strategies are characterised by low cell viability, suboptimal hyaline cartilage formation and, critically, inferior mechanical competency, which limit their application for resurfacing articular cartilage defects. To address the limitations of conventional static cartilage bioengineering strategies and generate robust, scaffold-free neocartilage grafts of human articular chondrocytes, the present study utilised custom-built microfluidic perfusion bioreactors with integrated ultrasound standing wave traps. The system employed sweeping acoustic drive frequencies over the range of 890 to 910 kHz and continuous perfusion of the chondrogenic culture medium at a low-shear flow rate to promote the generation of three-dimensional agglomerates of human articular chondrocytes, and enhance cartilage formation by cells of the agglomerates via improved mechanical stimulation and mass transfer rates. Histological examination and assessment of micromechanical properties using indentation-type atomic force microscopy confirmed that the neocartilage grafts were analogous to native hyaline cartilage. Furthermore, in the ex vivo organ culture partial thickness cartilage defect model, implantation of the neocartilage grafts into defects for 16 weeks resulted in the formation of hyaline cartilage-like repair tissue that adhered to the host cartilage and contributed to significant improvements to the tissue architecture within the defects, compared to the empty defects. The study has demonstrated the first successful application of the acoustofluidic perfusion bioreactors to bioengineer scaffold-free neocartilage grafts of human articular chondrocytes that have the potential for subsequent use in second generation autologous chondrocyte implantation procedures for the repair of partial thickness cartilage defects.

Effects of therapeutic ultrasound on the nucleus and genomic DNA

In recent years, data have been accumulating on the ability of ultrasound to affect at a distance inside the cell. Previous conceptions about therapeutic ultrasound were mainly based on compromising membrane permeability and triggering some biochemical reactions. However, it was shown that ultrasound can access deep to the nuclear territory resulting in enhanced macromolecular localization as well as alterations in gene and protein expression. Recently, we have reported on the occurrence of DNA double-strand breaks in different human cell lines exposed to ultrasound in vitro with some insight into the subsequent DNA damage response and repair pathways. The impact of these observed effects again sways between extremes. It could be advantageous if employed in gene therapy, wound and bone fracture-accelerated healing to promote cellular proliferation, or in cancer eradication if the DNA lesions would culminate in cell death. However, it could be a worrying sign if they were penultimate to further cellular adaptations to stresses and thus shaking the safety of ultrasound application in diagnosis and therapy. In this review, an overview of the rationale of therapeutic ultrasound and the salient knowledge on ultrasound-induced effects on the nucleus and genomic DNA will be presented. The implications of the findings will be discussed hopefully to provide guidance to future ultrasound research.

Combined use of low-intensity pulsed ultrasound and rhBMP-2 to enhance bone formation in a rat model of critical size defect

BACKGROUND

Bone repair is regulated by biological factors and the local mechanical environment. We hypothesize that the combined use of low-intensity pulsed ultrasound (LIPUS) and recombinant human bone morphogenetic protein-2 (rhBMP-2) will synergistically or additively enhance bone regeneration in a model simulating the more difficult scenarios in orthopaedic traumatology.

METHODS

Femoral defects in rats were replaced with absorbable collagen sponges carrying rhBMP-2 (0, 1.2, 6, or 12 μg; n = 30). Each group was divided equally to receive daily treatment of either LIPUS or sham stimulation. At 4 weeks, new bone formation was assessed using quantitative (radiography and microcomputed tomography), qualitative (histology), and functional (biomechanical) end points.

RESULTS

LIPUS with 1.2 μg of rhBMP-2 significantly improved the radiographic healing as compared with its sham control starting as early as 2 weeks. Quantitatively, the use of LIPUS with 6 μg of rhBMP-2 significantly increased the bone volume. However, using LIPUS with 12 μg of rhBMP-2 indicated a reduction in callus size, without compromising the bone volume, which was also observable histologically, showing organized lamellar bone and repopulated marrow in the original defect region. Histologically, 1.2 μg of rhBMP-2 alone showed the presence of uncalcified cartilage in the defect, which was reduced with LIPUS treatment. Biomechanically, LIPUS treatment significantly increased the peak torsion and stiffness in the 6- and 12 μg rhBMP-2 groups.

CONCLUSIONS

LIPUS enhances rhBMP-2-induced bone formation at lower doses (1.2 and 6 μg) and callus maturation at 12-μg dose delivered on absorbable collagen sponge for bone repair in a rat critical-sized femoral segmental defect.

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.

Effects of low-intensity pulsed ultrasound on integrin-FAK-PI3K/Akt mechanochemical transduction in rabbit osteoarthritis chondrocytes

The effect of low-intensity pulsed ultrasound (LIPUS) on extracellular matrix (ECM) production via modulation of the integrin/focal adhesion kinase (FAK)/phosphatidylinositol 3-kinase (PI3K)/Akt pathway has been investigated in previous studies in normal chondrocytes, but not in osteoarthritis (OA). Therefore, we investigated the LIPUS-induced integrin β1/FAK/PI3K/Akt mechanochemical transduction pathway in a single study in rabbit OA chondrocytes. Normal and OA chondrocytes were exposed to LIPUS, and mRNA and protein expression of cartilage, metalloproteinases and integrin-FAK-PI3K/Akt signal pathway-related genes was determined by quantitative reverse transcription polymerase chain reaction and Western blotting, respectively. Compared with levels in normal chondrocytes, expression levels of ECM-related genes were significantly lower in OA chondrocytes and those of metalloproteinase-related genes were significantly higher. In addition, integrin β1 gene expression and the phosphorylation of FAK, PI3K and Akt were significantly higher in OA chondrocytes. The expression of all tested genes was significantly increased except for that of metalloproteinase, which was significantly decreased in the LIPUS-treated OA group compared to the untreated OA group. LIPUS may affect the integrin-FAK-PI3K/Akt mechanochemical transduction pathway and alter ECM production by OA chondrocytes. Our findings will aid the future development of a treatment or even cure for OA.

Effect of therapeutic ultrasound on folliculogenesis, angiogenesis and apoptosis after heterotopic mouse ovarian transplantation

One of the challenges in ovarian transplantation is ischemia-reperfusion damage. When transitional tissue faces an acute and critical condition in terms of blood supply (immediately after organ transplantation), treatment with low-intensity pulsed ultrasound (LIPUS) seems to be very beneficial. The aim of this study was to evaluate the effects of ultrasound therapy on heterotopic transplanted mouse ovarian tissue. Adult female Naval Medical Research Institute mice were divided into three groups. In the experimental groups, the transplanted ovary was exposed 5 min daily to ultrasound with an intensity of 0.3 W/cm(2), frequency of 3 MHz and pulse mode of 1:4. The grafted ovaries were assessed with the usual histology and immunohistochemistry techniques. Results indicate that more CD31 angiogenic factor was expressed in irradiated animals than in control animals, and ultrasound therapy resulted in better follicular preservation, especially after 14 d. In conclusion, therapeutic ultrasound may accelerate and increase re-angiogenesis and can help to promote ovarian follicular growth.