The effect of sonication on simulated osteoarthritis. Part II: alleviation of osteoarthritis pathogenesis by 1 MHz ultrasound with simultaneous hyaluronate injection

Exosomes derived from bone marrow mesenchymal stem cell preconditioned by low-intensity pulsed ultrasound stimulation promote bone-tendon interface fibrocartilage regeneration and ameliorate rotator cuff fatty infiltration

Background

Fibrovascular scar healing of bone-tendon interface (BTI) instead of functional fibrocartilage regeneration is the main concern associated with unsatisfactory prognosis in rotator cuff repair. Mesenchymal stem cells (MSCs) exosomes have been reported to be a new promising cell-free approach for rotator cuff healing. Whereas, controversies abound in whether exosomes of native MSCs alone can effectively induce chondrogenesis.

Purpose

To explore the effect of exosomes derived from low-intensity pulsed ultrasound stimulation (LIPUS)-preconditioned bone marrow mesenchymal stem cells (LIPUS-BMSC-Exos) or un-preconditioned BMSCs (BMSC-Exos) on rotator cuff healing and the underlying mechanism.

Methods

C57BL/6 mice underwent unilateral supraspinatus tendon detachment and repair were randomly assigned to saline, BMSCs-Exos or LIPUS-BMSC-Exos injection therapy. Histological, immunofluorescent and biomechanical tests were detected to investigate the effect of exosomes injection on BTI healing and muscle fatty infiltration of the repaired rotator cuff. In vitro, native BMSCs were incubated with BMSC-Exos or LIPUS-BMSC-Exos and then chondrogenic/adipogenic differentiation were observed. Further, quantitative real-time polymerase chain reaction (qRT-PCR) was performed to detect the chondrogenesis/adipogenesis-related miRNA profiles of LIPUS-BMSC-Exos and BMSC-Exos. The chondrogenic/adipogenic potential of the key miRNA was verified through function recover test with its mimic and inhibitor.

Results

The results indicated that the biomechanical properties of the supraspinatus tendon-humeral junction were significantly improved in the LIPUS-BMSC-Exos group than that of the BMSCs-Exos group. The LIPUS-BMSC-Exos group also exhibited a higher histological score and more newly regenerated fibrocartilage at the repair site at postoperative 2 and 4 weeks and less fatty infiltration at 4 weeks than the BMSCs-Exos group. In vitro, co-culture of BMSCs with LIPUS-BMSC-Exos could significantly promote BMSCs chondrogenic differentiation and inhibit adipogenic differentiation. Subsequently, qRT-PCR revealed significantly higher enrichment of chondrogenic miRNAs and less enrichment of adipogenic miRNAs in LIPUS-BMSC-Exos compared with BMSC-Exos. Moreover, we demonstrated that this chondrogenesis-inducing potential was primarily attributed to miR-140, one of the most abundant miRNAs in LIPUS-BMSC-Exos.

Conclusion

LIPUS-preconditioned BMSC-Exos can effectively promote BTI fibrocartilage regeneration and ameliorate supraspinatus fatty infiltration by positive regulation of pro-chondrogenesis and anti-adipogenesis, which was primarily through delivering miR-140.

The translational potential of this article

These findings propose an innovative "LIPUS combined Exosomes strategy" for rotator cuff healing which combines both physiotherapeutic and biotherapeutic advantages. This strategy possesses a good translational potential as a local injection of LIPUS preconditioned BMSC-derived Exos during operation can be not only efficient for promoting fibrocartilage regeneration and ameliorating rotator cuff fatty infiltration, but also time-saving, simple and convenient for patients.

Low-Intensity Continuous Ultrasound Therapies—A Systematic Review of Current State-of-the-Art and Future Perspectives

Therapeutic ultrasound has been studied for over seven decades for different medical applications. The versatility of ultrasound applications are highly dependent on the frequency, intensity, duration, duty cycle, power, wavelength, and form. In this review article, we will focus on low-intensity continuous ultrasound (LICUS). LICUS has been well-studied for numerous clinical disorders, including tissue regeneration, pain management, neuromodulation, thrombosis, and cancer treatment. PubMed and Google Scholar databases were used to conduct a comprehensive review of all research studying the application of LICUS in pre-clinical and clinical studies. The review includes articles that specify intensity and duty cycle (continuous). Any studies that did not identify these parameters or used high-intensity and pulsed ultrasound were not included in the review. The literature review shows the vast implication of LICUS in many medical fields at the pre-clinical and clinical levels. Its applications depend on variables such as frequency, intensity, duration, and type of medical disorder. Overall, these studies show that LICUS has significant promise, but conflicting data remain regarding the parameters used, and further studies are required to fully realize the potential benefits of LICUS.

Sustained Acoustic Medicine Combined with A Diclofenac Ultrasound Coupling Patch for the Rapid Symptomatic Relief of Knee Osteoarthritis: Multi-Site Clinical Efficacy Study

BACKGROUND

Sustained Acoustic Medicine (SAM) is an emerging, non-invasive, non-narcotic, home-use ultrasound therapy for the daily treatment of joint pain. The aim of this multi-site clinical study was to examine the efficacy of long-duration continuous ultrasound combined with a 1% diclofenac ultrasound gel patch in treating pain and improving function in patients with knee osteoarthritis.

METHODS

The Consolidated Standards of Reporting Trials (CONSORT) were followed. Thirty-two (32) patients (18-males, 14-females) 54 years of average age with moderate to severe knee pain and radiographically confirmed knee osteoarthritis (Kellgren-Lawrence (KL) grade II/III) were enrolled for treatment with the SAM device and diclofenac patch applied daily to the treated knee. SAM ultrasound (3 MHz, 0.132 W/cm2, 1.3 W) and 6 grams of 1% diclofenac were applied with a wearable device for 4 hours daily for 1 week, delivering 18,720 Joules of ultrasound energy per treatment. The primary outcome was the daily change in pain intensity using a numeric rating scale (NRS 0-10), which was assessed prior to intervention (baseline, day 1), before and after each daily treatment, and after 1 week of daily treatment (day 7). Rapid responders were classified as those patients exhibiting greater than a 1-point reduction in pain following the first treatment. Change in Western Ontario McMaster Osteoarthritis Questionnaire (WOMAC) score from baseline to day 7 was the secondary functional outcome measure. Additionally, a series of daily usability and user experience questions related to devising ease of use, functionality, safety, and effectiveness, were collected. Data were analyzed using t-tests and repeated measure ANOVAs.

RESULTS

The study had a 94% retention rate, and there were no adverse events or study-related complaints across 224 unique treatment sessions. Rapid responders included 75% of the study population. Patients exhibited a significant mean NRS pain reduction over the 7-day study of 2.06-points (50%) for all subjects (n=32, p<0.001) and 2.96-points (70%) for rapid responders (n=24, p<0.001). The WOMAC functional score significantly improved by 351 points for all subjects (n=32, p<0.001), and 510 points for rapid responders (n=24, p<0.001). Over 95% of patients found the device safe, effective and easy to use, and would continue treatment for their knee OA symptoms.

CONCLUSION

Sustained Acoustic Medicine combined with 1% topical diclofenac rapidly reduced pain and improved function in patients with moderate to severe osteoarthritis-related knee pain. The clinical findings suggest that this treatment approach may be used as a conservative, non-invasive treatment option for patients with knee osteoarthritis. Additional research is warranted on non-weight bearing joints of the musculoskeletal system as well as different topical drugs that could benefit from improved localized delivery.Clinical Trial Registry Number: (NCT04391842).

Sustained acoustic medicine; sonophoresis for nonsteroidal anti-inflammatory drug delivery in arthritis

Background: Arthritis pain is primarily managed by nonsteroidal anti-inflammatory drugs (NSAIDs), such as diclofenac. Topical diclofenac gel is limited in efficacy due to its limited penetration through the skin. This study investigates the use of a multihour, wearable, localized, sonophoresis transdermal drug delivery device for the penetration enhancement of diclofenac through the skin. Materials & methods: A commercially available, sustained acoustic medicine (sam®) ultrasound device providing 4 h, 1.3 W, 132 mW/cm2, 3 MHz ultrasound treatment was evaluated for increasing the drug delivery of diclofenac gel through a human skin model and was compared with standard of care topical control diclofenac gel. Results: Sonophoresis of the diclofenac gel for 4 h increases diclofenac delivery by 3.8× (p < 0.01), and penetration by 32% (p < 0.01). Conclusion: Sustained acoustic medicine can be used as a transdermal drug-delivery device for nonsteroidal anti-inflammatory drugs.

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 ultrasound inhibits brain oedema formation in rats: potential action on AQP4 membrane localization

AIMS

Brain oedema is a major contributing factor to the morbidity and mortality of a variety of brain disorders. Although there has been considerable progress in our understanding of pathophysiological and molecular mechanisms associated with brain oedema so far, more effective treatment is required and is still awaited. Here we intended to study the effects of low intensity ultrasound (LIUS) on brain oedema.

METHODS

We prepared the rat hippocampal slice in vitro and acute water intoxication in vivo models of brain oedema. We applied LIUS stimulation in these models and studied the molecular mechanisms of LIUS action on brain oedema.

RESULTS

We found that LIUS stimulation markedly inhibited the oedema formation in both of these models. LIUS stimulation significantly reduced brain water content and intracranial pressure resulting in increased survival of the rats. Here, we showed that the AQP4 localization was increased in the astrocytic foot processes in the oedematous hippocampal slices, while it was significantly reduced in the LIUS-stimulated hippocampal slices. In the in vivo model too, AQP4 expression was markedly increased in the microvessels of the cerebral cortex and hippocampus after water intoxication but was reduced in the LIUS-stimulated rats.

CONCLUSIONS

These data show that LIUS has an inhibitory effect on cytotoxic brain oedema and suggest its therapeutic potential to treat brain oedema. We propose that LIUS reduces the AQP4 localization around the astrocytic foot processes thereby decreasing water permeability into the brain tissue.

Focused Low-intensity Pulsed Ultrasound Affects Extracellular Matrix Degradation via Decreasing Chondrocyte Apoptosis and Inflammatory Mediators in a Surgically Induced Osteoarthritic Rabbit Model

We investigated whether focused low-intensity pulsed ultrasound (FLIPUS) affects extracellular matrix (ECM) production in osteoarthritic (OA) rabbits by decreasing chondrocyte apoptosis and pro-inflammatory mediators. An OA model using New Zealand White rabbits (N = 30) and 30 normal rabbits were randomized into three groups (2-, 4- and 8-wk groups; n = 10 knees each). A knee from each rabbit was randomly selected to receive FLIPUS and the other knee received a sham treatment as a control. Another 30 normal rabbits were blank controls. We measured ECM degradation, joint effusion volume and levels of prostaglandin E2 and nitric oxide. Also, ratios of chondrocyte proliferation and apoptosis were calculated. Compared with sham stimulation, FLIPUS attenuated release of type II collagen and proteoglycans and reduced chondrocyte apoptosis as well as total joint effusion volume and significantly alleviated OA-induced accretion of prostaglandin E2 and nitric oxide in the synovial fluid. FLIPUS application promoted ECM production in OA through down regulation inflammatory mediators, joint effusion volume and chondrocyte apoptosis.

Effects of low-intensity ultrasound on gramicidin D-induced erythrocyte edema

OBJECTIVES

To determine whether low-intensity ultrasound (US) can reduce red blood cell (RBC) edema and, if so, whether the US activity is associated with aquaporin 1 (AQP-1), a water channel in the cell membrane.

METHODS

Red blood cell edema was induced by gramicidin D treatment at 40 ng/mL for 20 minutes and evaluated by a hematocrit assay. Low-intensity continuous wave US at 1 MHz was applied to RBCs for the last 10 minutes of gramicidin D treatment. To determine whether US activity was associated with AQP-1, RBCs were treated with 40 μM mercuric chloride (HgCl(2)), an AQP-1 inhibitor, for 20 minutes at the time of gramicidin D treatment. Posttreatment morphologic changes in RBCs were observed by actin staining with phalloidin.

RESULTS

Red blood cell edema increased significantly with gramicidin D at 20 (1.8%), 40 (6.7%), 60 (16.7%), and 80 (11.3%) ng/mL, reaching a peak at 60 ng/mL, compared to the control group (20 ng/mL, P = .019; 40, 60, and 80 ng/mL, P < .001). No significant RBC hemolysis was observed in any group. Edema induced by gramicidin D at 40 ng/mL was significantly reduced by US at 30 (3.4%; P = .003), 70 (4.4%; P = .001), and 100 (2.9%; P = .001) mW/cm(2). Subsequent experiments showed that edema reduction by US ranged from 7% to 10%. Cotreatment with HgCl(2) partially reversed the US effect and showed a significantly different level of edema compared to gramicidin D-alone and US-cotreated groups (P = .001). These results were confirmed by microscopic observation of RBC morphologic changes.

CONCLUSIONS

Low-intensity US could reduce gramicidin D-induced RBC edema, and its effect appeared to at least partly involve regulation of AQP-1 activity. These results suggest that low-intensity US can be used as an alternative treatment to control edema and related disorders.

Prostaglandin E2 receptor type 2-selective agonist prevents the degeneration of articular cartilage in rabbit knees with traumatic instability

Introduction

Osteoarthritis (OA) is a common cause of disability in older adults. We have previously reported that an agonist for subtypes EP2 of the prostaglandin E2 receptor (an EP2 agonist) promotes the regeneration of chondral and osteochondral defects. The purpose of the current study is to analyze the effect of this agonist on articular cartilage in a model of traumatic degeneration.

Methods

The model of traumatic degeneration was established through transection of the anterior cruciate ligament and partial resection of the medial meniscus of the rabbits. Rabbits were divided into 5 groups; G-S (sham operation), G-C (no further treatment), G-0, G-80, and G-400 (single intra-articular administration of gelatin hydrogel containing 0, 80, and 400 μg of the specific EP2 agonist, ONO-8815Ly, respectively). Degeneration of the articular cartilage was evaluated at 2 or 12 weeks after the operation.

Results

ONO-8815Ly prevented cartilage degeneration at 2 weeks, which was associated with the inhibition of matrix metalloproteinase-13 (MMP-13) expression. The effect of ONO-8815Ly failed to last, and no effects were observed at 12 weeks after the operation.

Conclusions

Stimulation of prostaglandin E2 (PGE2) via EP2 prevents degeneration of the articular cartilage during the early stages. With a system to deliver it long term, the EP2 agonist could be a new therapeutic tool for OA.

Quantitative assessment of mobile protein levels in human knee synovial fluid: feasibility of chemical exchange saturation transfer (proteinCEST) MRI of osteoarthritis

PURPOSE

To establish the feasibility of chemical exchange saturation transfer (proteinCEST) MRI in the differentiation of osteoarthritis (OA) knee joints from non-OA joints by detecting mobile protein and peptide levels in synovial fluid by determining their relative distribution.

MATERIALS AND METHODS

A total of 25 knees in 11 men and 12 women with knee injuries were imaged using whole knee joint proteinCEST MRI sequence at 3 T. The joint synovial fluid was segmented and the asymmetric magnetization transfer ratio at 3.5 ppm MTR(asym) (3.5 ppm) was calculated to assess protein content in the synovial fluid. The 85th percentile of synovial fluid MTR(asym) (3.5 ppm) distribution profile was compared using the independent Student's t test. The diagnostic performance of the 85th percentile of synovial fluid MTR(asym) (3.5 ppm) in differentiating OA and non-OA knee joints was evaluated.

RESULTS

The 85th percentile of synovial fluid MTR(asym) (3.5 ppm) in knee joints with OA was 8.6%±3.4% and significantly higher than that in the knee joints without OA (6.3%±1.4%, P<.05). A knee joint with an 85th percentile of synovial fluid MTR(asym) (3.5 ppm) greater than 7.7% was considered to be an OA knee joint. With the threshold, the sensitivity, specificity and overall accuracy for differentiating knee joints with OA from the joints without OA were 54% (7/13), 92% (11/12) and 72% (18/25), respectively.

CONCLUSION

proteinCEST MRI appears feasible as a quantitative methodology to determine mobile protein levels in synovial fluid and identify patterns characteristic for OA disease.

Modification of osteoarthritis in the guinea pig with pulsed low-intensity ultrasound treatment

OBJECTIVE

The Hartley guinea pig develops articular cartilage degeneration similar to that seen in idiopathic human osteoarthritis (OA). We investigated whether the application of pulsed low-intensity ultrasound (PLIUS) to the Hartley guinea pig joint would prevent or attenuate the progression of this degenerative process.

METHODS

Treatment of male Hartley guinea pigs was initiated at the onset of degeneration (8 weeks of age) to assess the ability of PLIUS to prevent OA, or at a later age (12 months) to assess the degree to which PLIUS acted to attenuate the progression of established disease. PLIUS (30 mW/cm(2)) was applied to stifle joints for 20 min/day over periods ranging from 3 to 10 months, with contralateral limbs serving as controls. Joint cartilage histology was graded according to a modified Mankin scale to evaluate treatment effect. Immunohistochemical staining for interleukin-1 receptor antagonist (IL-1ra), matrix metalloproteinase (MMP)-3, MMP-13, and transforming growth factor (TGF)-beta1 was performed on the cartilage to evaluate patterns of expression of these proteins.

RESULTS

PLIUS did not fully prevent cartilage degeneration in the prevention groups, but diminished the severity of the disease, with the treated joints showing markedly decreased surface irregularities and a much smaller degree of loss of matrix staining as compared to controls. PLIUS also attenuated disease progression in the groups with established disease, although to a somewhat lesser extent as compared to the prevention groups. Immunohistochemical staining demonstrated a markedly decreased degree of TGF-beta1 production in the PLIUS-treated joints. This indicates less active endogenous repair, consistent with the marked reduction in cartilage degradation.

CONCLUSIONS

PLIUS exhibits the ability to attenuate the progression of cartilage degeneration in an animal model of idiopathic human OA. The effect was greater in the treatment of early, rather than established, degeneration.

Low-Intensity Ultrasound (LIUS) as an Innovative Tool for Chondrogenesis of Mesenchymal Stem Cells (MSCs)

Mesenchymal stem cells (MSCs) have a capacity to differentiate into the chondrogenic lineage and are a valuable allogenic source for cartilage tissue engineering. However, they still have critical limitations of relatively inefficient chondrogenic differentiation in vitro and of dedifferentiation and/or hypertrophic changes at late stages of differentiation. Numerous approaches using biochemical and mechanical factors have been tried but have so far failed to overcome these problems. Recent studies by other groups and ours have shown that low-intensity ultrasound (LIUS) is an efficient tool for promoting the chondrogenic differentiation of MSCs both in vitro and in vivo. A series of our experiments suggests that LIUS not only induces chondrogenic differentiation of MSCs but also has diverse additional activities that enhance the viability of MSCs, increase possibly the integrity of the differentiated tissues and delays hypertrophic changes during differentiation. Therefore, LIUS could be an innovative and versatile tool for chondrogenic differentiation of MSCs and for cartilage tissue engineering.

Alleviation of osteoarthritis by calycosin-7-O-beta-D-glucopyranoside (CG) isolated from Astragali radix (AR) in rabbit osteoarthritis (OA) model

OBJECTIVE

This work was undertaken to assess the protective effect of an isoflavonoid, calycosin-7-O-beta-D-glucopyranoside (CG), isolated from Astragali radix (AR) on the pathogenesis of osteoarthritis (OA)-like lesion in a rabbit model.

METHODS

Nine rabbits underwent an anterior cruciate ligament and menisectomy transection (ACLMT) of the rear knee joints to induce OA-like lesion. They were randomly divided into three groups (n=6/group): a negative control group treated with 200 microl of 0.5% (v/v) dimethyl sulfoxide (DMSO), a positive control group treated with 200 microl of 100 microM piroxicam, and a test group treated with 100 microg/500 microl of CG, where the test agents were administered by injection once a week for 4 weeks starting from the third week. Rabbits were then sacrificed to observe the progression of OA-like lesion. The synovial fluid was analyzed for the amounts of total proteins, glycosaminoglycans (GAG) and prostaglandin E(2) (PGE(2)). In addition, histopathologic analyses were performed on the OA-like articular cartilage with or without therapeutic treatments.

RESULTS

The total synovial fluid volume (P<0.05) was most strikingly reduced by the treatment with CG. Moreover, the CG treatment also significantly alleviated the OA-induced accumulation of prostaglandin (PG) (P<0.001) and total proteins (P<0.001) in the synovial fluid. The histopathologic analyses revealed that the CG treatment reduced the severity of the OA-like structural damages in the cartilage. However, the level of PGE(2), a pathologic inflammatory molecule, was not diminished by CG or piroxicam.

CONCLUSION

These results indicate that the isoflavonoid CG isolated from AR significantly alleviated the pathologic changes in the OA-like rabbit knee joints. This suggests that CG from AR could be a promising treatment for the therapy of OA.

Mechanotransduction pathways of low-intensity ultrasound in C-28/I2 human chondrocyte cell line

Low-intensity ultrasound (LIUS) has recently been considered to be an effective method to induce cartilage repair and/or regeneration after injury. Nevertheless, there is no study to provide a cellular mechanism or signal pathways of LIUS stimulation. The current study is designed to investigate the effects of LIUS on the mechanotransduction pathways in C-28/I2, an immortalized human chondrocyte cell line. C-28/I2 cells were treated with LIUS at an intensity of 200 mW/cm2 using Noblelife™ from Duplogen. The role of stretch-activated channels (SAC) and integrins that are most well-known mechanoreceptors on the chondrocyte cell surface was first examined in mediating the LIUS effects on the expression of type II collagen and aggrecan. When analysed by reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry, gadolinium (a specific inhibitor of SACs) or GRGDSP (a peptide inhibitor of integrins) specifically reduced the LIUS-induced elevation of type II collagen and aggrecan expressions depending on the incubation time. In addition, the LIUS treatment of C-28/I2 cells induced the phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) but not p38 kinase among the members of the mitogen-activated protein kinases (MAPKs). The phosphorylation of ERK by LIUS was repressed by a specific inhibitor of the ERK pathway and integrin function. These results suggest that the LIUS signal might be mediated via canonical mechanoreceptors of SACs and integrins and subsequently through JNK and ERK pathways. The present study provides the first evidence for the activation of the mechanotransduction pathways by LIUS in human chondrocytes.

Low-intensity ultrasound inhibits apoptosis and enhances viability of human mesenchymal stem cells in three-dimensional alginate culture during chondrogenic differentiation

Many studies have investigated optimal chondrogenic conditions, but only a few of them have addressed their effects on cell viability or the methods to enhance it. This study investigated the effect of low-intensity ultrasound (LIUS), a well-known chondrogenic inducer, on the viability of human mesenchymal stem cells (hMSCs) during chondrogenic differentiation in three-dimensional (3-D) alginate culture. The hMSCs/alginate layer was cultured in a chondrogenic defined medium and treated with transforming growth factor-beta1 (TGF-beta1) and/or LIUS for 2 weeks. Along with chondrogenic differentiation for 2 weeks, the 3-D alginate culture and TGF-beta1 treatment resulted in the decrease of cell viability, which appeared to be mediated by apoptosis. In contrast, co-treatment with LIUS clearly enhanced cell viability and inhibited apoptosis under the same conditions. The effect of LIUS on the apoptotic event was further demonstrated by changes in the expression of apoptosis/viability related genes of p53, bax, bcl-2, and PCNA. These results suggest that the LIUS treatment could be a valuable tool in cartilage tissue engineering using MSCs as it enhances cell viability and directs the chondrogenic differentiation process, its well-known activity.

Preconditioning of mesenchymal stem cells with low-intensity ultrasound for cartilage formation in vivo

The purpose of this study was to evaluate the benefits of in vitro preconditioning of mesenchymal stem cells (MSCs) using low-intensity ultrasound (US) in the induction of chondrogenic differentiation of MSCs in vivo. After rabbit bone marrow-derived MSCs were seeded onto a polyglycolic acid (PGA) scaffold, the PGA-MSCs constructs were divided into 4 subgroups: untreated control, low-intensity US group, transforming growth factor-beta [TGF]-treated group and low-intensity US/TGF group. The chondrocyte-seeded PGA construct served as a positive control. For 1 week before implantation, the low-intensity US groups were subjected to ultrasound treatment for 20 min daily at an intensity of 200 mW/cm(2). The TGF groups were treated with 10 ng/mL TGF-beta1. The cells were then implanted into the nude mouse subcutaneously. Retrieved 1, 2, 4, and 6 weeks after implantation, each construct underwent gross examination, histology, biochemical assays, mechanical testing, and reverse transcriptase polymerase chain reaction (RT-PCR). Substantial size reduction and blood invasion were found much earlier in the groups that did not undergo low-intensity US than in those that did. Safranin O/Fast green staining revealed that the chondrogenic differentiation of MSCs was more widespread throughout the constructs in the low-intensity US groups. In the biochemical and mechanical analyses, the low-intensity US and low-intensity US/TGF groups were significantly better in forming hyaline cartilage-like tissue by 4 weeks than the non-low-intensity US groups. Presented by von Kossa staining, the development of osteogenic phenotypes was highly suppressed until 4 weeks in the low-intensity US groups, along with compressive strength comparable to the positive control. In the RT-PCR analysis before implantation, the messenger RNA levels of Sox-9, aggrecan, and tissue inhibitors of metalloproteinase-2 were higher in the low-intensity US groups, while those of type I and type X collagens and matrix metalloproteinase-13 were higher in the non-low-intensity US groups. Blood invasion into the constructs was also considerably hindered in the low-intensity US groups. These results strongly indicate that low-intensity US preconditioning in vitro could be an effective cue to upregulate chondrogenic differentiation of MSCs in vivo.

Therapeutic ultrasound effects on interleukin-1beta stimulated cartilage construct in vitro

A low-intensity ultrasound (LIUS) was examined for its possible therapeutic effects on degenerative osteoarthritic cartilage. Along with the daily treatment of 5 ng interleukin-1beta (IL-1beta) for 5 d, an engineered 3D neocartilage construct was used as an in vitro OA model. Followed by 24 h preincubation with the first dose of IL-1beta, the constructs were then given ultrasonic stimulation (frequency 1.5 MHz and SATA 30 mW/cm(2)) once a day up to 5 d for the predetermined time. Fresh IL-1beta was added before the stimulation. The difference in the cell number and viability was insignificant between control (US-/IL+) and LIUS-stimulated groups. As the daily stimulation time was extended, the GAG contents in the constructs themselves significantly increased with 50 min stimulation but those released into the culture medium remained unaffected by LIUS. While the gene expression level of aggrecan was similar between control and LIUS (50 min) group, the ratio of collagen type II to type I was found to be higher in the control. The mRNA level of matrix metalloproteinase (MMP)-1 was substantially downregulated in the stimulated construct and that of MMP-13 was indifferent between control and stimulated one. The endogenous expression of transforming growth factor (TGF)-beta1 and beta3 was barely responsive to the LIUS stimulation. From histologic analysis, more intense GAG deposition was clearly identified with the LIUS-stimulated constructs. This study indicates that LIUS may have a significant potential to be a chondroprotective stimulant for osteoarthritic cartilage.

Low-intensity ultrasound stimulates the viability and matrix gene expression of human articular chondrocytes in alginate bead culture

We investigated the effects of low-intensity ultrasound (LIUS) on the activity of human articular chondrocytes isolated from osteoarthritis patients and cultured in the three-dimensional alginate beads. LIUS was treated at 0, 100, 200, and 300 mW/cm(2) for 10 min everyday for 2, 7, or 15 days. LIUS induced the viability of cells only at day 15 but not until day 7 after treatment, when examined by trypan blue exclusion and LIVE/DEAD(R) assay kit. When examined at day 7, the proliferation of cells was not changed by LIUS in the (3)H-thymine incorporation. The expression of matrix producing proteins (type II collagen and proteoglycan) was clearly induced by 200-300 mW/cm(2) LIUS in the incorporation of radioactivity and Northern blot analysis. Although the expression of MMP-1, a matrix degrading protein, was decreased, that of TIMP-1, an inhibitor of MMPs, was not affected by LIUS. Histological analysis revealed an increase in the number and size of glycosaminoglycan-positive lacunae and cellular organelles, appearing as rough endoplasmic reticulum and mitochondria by LIUS. These results showed that the viability and metabolism of human articular chondrocytes in alginate culture was induced by LIUS treatment, suggesting that they could be a promising autologous source for cartilage tissue engineering.

Low-intensity Ultrasound Stimulation Enhances Chondrogenic Differentiation in Alginate Culture of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are regarded as a potential autologous source for cartilage repair, because they can differentiate into chondrocytes by transforming growth factor-beta (TGF-beta) treatment under the 3-dimensional (3-D) culture condition. However, more efficient and versatile methods for chondrogenic differentiation of MSCs are still in demand for its clinical application. Recently, low-intensity ultrasound (LIUS) was shown to enhance fracture healing in vitro and induce chondrogenesis of MSCs in vitro. In this study, we investigated the effects of LIUS on the chondrogenesis of rabbit MSCs (rMSCs) in a 3-D alginate culture and on the maintenance of chondrogenic phenotypes after replating them on a monolayer culture. The LIUS treatment of rMSCs increased: (i) the matrix formation; (ii) the expression of chondrogenic markers such as collagen type II, aggrecan, and Sox-9; (iii) the expression of tissue inhibitor of metalloprotease-2 implicated in the integrity of cartilage matrix; and (iv) the capacity to maintain the chondrogenic phenotypes in a monolayer culture. Notably, LIUS effects were clearly shown even without TGF-beta treatment. These results suggest that LIUS treatment could be an efficient and cost-effective method to induce chondrogenic differentiation of MSCs in vitro for cartilage tissue engineering.