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

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.

Advances in the application of low-intensity pulsed ultrasound to mesenchymal stem cells

Mesenchymal stem cells (MSCs) are stem cells that exhibit self-renewal capacity and multi-directional differentiation potential. They can be extracted from the bone marrow and umbilical cord, as well as adipose, amnion, and other tissues. They are widely used in tissue engineering and are currently considered an important source of cells in the field of regenerative medicine. Since certain limitations, such as an insufficient cell source, mature differentiation, and low transplantation efficiency, are still associated with MSCs, researchers have currently focused on improving the efficacy of MSCs. Low-intensity pulsed ultrasound (LIPUS) has mechanical, cavitation, and thermal effects that can produce different biological effects on organs, tissues, and cells. It can be used for fracture treatment, cartilage repair, and stem cell applications. An in-depth study of the role and mechanism of action of LIPUS in MSC treatment would promote our understanding of LIPUS and promote research in this field. In this article, we have reviewed the progress in research on the use of LIPUS with various MSCs and comprehensively discussed the progress in the use of LIPUS for promoting the proliferation, differentiation, and migration of MSCs, as well as its future prospects.

MECHANOBIOLOGICAL APPROACHES FOR STIMULATING CHONDROGENESIS OF STEM CELLS

Chondrogenesis is the process of differentiation of stem cells into mature chondrocytes. Such a process consists of chemical, functional, and structural changes which are initiated and mediated by the host environment of the cells. To date, the mechanobiology of chondrogenesis has not been fully elucidated. Hence, experimental activity is focused on recreating specific environmental conditions for stimulating chondrogenesis, and to look for a mechanistic interpretation of the mechanobiological response of cells in the cartilaginous tissues. There are a large number of studies on the topic that vary considerably in their experimental protocols used for providing environmental cues to cells for differentiation, making generalizable conclusions difficult to ascertain. The main objective of this contribution is to review the mechanobiological stimulation of stem cell chondrogenesis and methodological approaches utilized to date to promote chondrogenesis of stem cells in-vitro. In-vivo models will also be explored, but this area is currently limited. An overview of the experimental approaches used by different research groups may help the development of unified testing methods that could be used to overcome existing knowledge gaps, leading to an accelerated translation of experimental findings to clinical practice.

Induced Pluripotent Stem Cells and Hormesis

This paper represents the first assessment of agent-induced hormetic dose responses in induced pluripotent stem cells and their derived cells. The hormetic dose responses were induced by a broad range of chemicals, including pharmaceuticals (eg, metformin), dietary supplements/extracts from medicinal plants (eg, curcumin), and endogenous agents (eg, melatonin). The paper assesses the mechanistic foundations of these induced hormetic dose responses, their therapeutic implications and comparison with hormetic responses in multiple adult and embryonic stem cells.

Application of Alginate Hydrogels for Next-Generation Articular Cartilage Regeneration

The articular cartilage has insufficient intrinsic healing abilities, and articular cartilage injuries often progress to osteoarthritis. Alginate-based scaffolds are attractive biomaterials for cartilage repair and regeneration, allowing for the delivery of cells and therapeutic drugs and gene sequences. In light of the heterogeneity of findings reporting the benefits of using alginate for cartilage regeneration, a better understanding of alginate-based systems is needed in order to improve the approaches aiming to enhance cartilage regeneration with this compound. This review provides an in-depth evaluation of the literature, focusing on the manipulation of alginate as a tool to support the processes involved in cartilage healing in order to demonstrate how such a material, used as a direct compound or combined with cell and gene therapy and with scaffold-guided gene transfer procedures, may assist cartilage regeneration in an optimal manner for future applications in patients.

Cell-derived decellularized extracellular matrix scaffolds for articular cartilage repair

Articular cartilage repair remains a great clinical challenge. Tissue engineering approaches based on decellularized extracellular matrix (dECM) scaffolds show promise for facilitating articular cartilage repair. Traditional regenerative approaches currently used in clinical practice, such as microfracture, mosaicplasty, and autologous chondrocyte implantation, can improve cartilage repair and show therapeutic effect to some degree; however, the long-term curative effect is suboptimal. As dECM prepared by proper decellularization procedures is a biodegradable material, which provides space for regeneration tissue growth, possesses low immunogenicity, and retains most of its bioactive molecules that maintain tissue homeostasis and facilitate tissue repair, dECM scaffolds may provide a biomimetic microenvironment promoting cell attachment, proliferation, and chondrogenic differentiation. Currently, cell-derived dECM scaffolds have become a research hotspot in the field of cartilage tissue engineering, as ECM derived from cells cultured in vitro has many advantages compared with native cartilage ECM. This review describes cell types used to secrete ECM, methods of inducing cells to secrete cartilage-like ECM and decellularization methods to prepare cell-derived dECM. The potential mechanism of dECM scaffolds on cartilage repair, methods for improving the mechanical strength of cell-derived dECM scaffolds, and future perspectives on cell-derived dECM scaffolds are also discussed in this review.

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.

Preconditioning of mesenchymal stromal cells with low-intensity ultrasound: influence on chondrogenesis and directed SOX9 signaling pathways

Background

Continuous low-intensity ultrasound (cLIUS) facilitates the chondrogenic differentiation of human mesenchymal stromal cells (MSCs) in the absence of exogenously added transforming growth factor-beta (TGFβ) by upregulating the expression of transcription factor SOX9, a master regulator of chondrogenesis. The present study evaluated the molecular events associated with the signaling pathways impacting SOX9 gene and protein expression under cLIUS.

Methods

Human bone marrow-derived MSCs were exposed to cLIUS stimulation at 14 kPa (5 MHz, 2.5 Vpp) for 5 min. The gene and protein expression of SOX9 was evaluated. The specificity of SOX9 upregulation under cLIUS was determined by treating the MSCs with small molecule inhibitors of select signaling molecules, followed by cLIUS treatment. Signaling events regulating SOX9 expression under cLIUS were analyzed by gene expression, immunofluorescence staining, and western blotting.

Results

cLIUS upregulated the gene expression of SOX9 and enhanced the nuclear localization of SOX9 protein when compared to non-cLIUS-stimulated control. cLIUS was noted to enhance the phosphorylation of the signaling molecule ERK1/2. Inhibition of MEK/ERK1/2 by PD98059 resulted in the effective abrogation of cLIUS-induced SOX9 expression, indicating that cLIUS-induced SOX9 upregulation was dependent on the phosphorylation of ERK1/2. Inhibition of integrin and TRPV4, the upstream cell-surface effectors of ERK1/2, did not inhibit the phosphorylation of ERK1/2 and therefore did not abrogate cLIUS-induced SOX9 expression, thereby suggesting the involvement of other mechanoreceptors. Consequently, the effect of cLIUS on the actin cytoskeleton, a mechanosensitive receptor regulating SOX9, was evaluated. Diffused and disrupted actin fibers observed in MSCs under cLIUS closely resembled actin disruption by treatment with cytoskeletal drug Y27632, which is known to increase the gene expression of SOX9. The upregulation of SOX9 under cLIUS was, therefore, related to cLIUS-induced actin reorganization. SOX9 upregulation induced by actin reorganization was also found to be dependent on the phosphorylation of ERK1/2.

Conclusions

Collectively, preconditioning of MSCs by cLIUS resulted in the nuclear localization of SOX9, phosphorylation of ERK1/2 and disruption of actin filaments, and the expression of SOX9 was dependent on the phosphorylation of ERK1/2 under cLIUS.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1532-2) contains supplementary material, which is available to authorized users.

Low intensity pulsed ultrasound increases mandibular height and Col-II and VEGF expression in arthritic mice

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic inflammatory disease involving persistent inflammation resulting in cartilage and bone damage. RA can affect the temporomandibular joint (TMJ), and damage to the TMJ condyle can lead to craniofacial developmental disturbances, causing micrognathia, malocclusion, retrognathia, and increased overjet. Current treatments of TMJ arthritis are unsatisfactory. This pilot study aimed to investigate the effect of low intensity pulsed ultrasound (LIPUS) on the mandible and TMJ condyles in an RA mouse model using micro-computed tomography (Micro-CT), histologic, and immunohistochemical analyses.

METHODS

MRL-lpr/lpr mice received LIPUS application to their TMJs for 20 min/day for 2 and 4 weeks. Micro-CT analysis measured condylar length and width, posterior mandibular height (P.M.H), mandibular ramus length (M.R.L), effective mandibular length (Ef.M.L), angular process length (A.P.L), mandibular plane (M.P), mandibular axis (M.Ax), and lower incisor height (L.I.H). Condylar cartilage thickness was histologically measured, and type II collagen (Col-II), vascular endothelial growth factor (VEGF), nuclear factor kappa-B ligand (RANKL), and osteoprotegerin (OPG) expression was analyzed using immunohistochemistry.

RESULTS

Comparing the LIPUS-treated group with the control, P.M.H, M.R.L, and M.P were significantly greater in the LIPUS-treated group. Immunostaining for Col-II and VEGF was stronger in the LIPUS-treated group after 4 weeks. OPG showed slightly more expression in the LIPUS group.

CONCLUSIONS

LIPUS may enhance mandibular and TMJ condylar bone formation in this RA mouse model by preventing any growth disturbances involved in inflammation. Further studies are recommended to analyze the effect of LIPUS on TMJ of RA in other animal models.

Direct Control of Stem Cell Behavior Using Biomaterials and Genetic Factors

Stem cells have recently emerged as an important candidate for cell therapy. However, some major limitations still exist such as a small quantity of cell supply, senescence, and insufficient differentiation efficiency. Therefore, there is an unmet need to control stem cell behavior for better clinical performance. Since native microenvironment factors including stem cell niche, genetic factors, and growth factors direct stem cell fate cooperatively, user-specified in vitro settings are required to understand the regulatory roles and effects of each factor, thereby applying the factors for improved cell therapy. Among others, various types of biomaterials and transfection method have been employed as key tools for development of the in vitro settings. This review focuses on the current strategies to improve stemness maintenance, direct differentiation, and reprogramming using biomaterials and genetic factors without any aids from additional biochemicals and growth factors.

Enhancement of Cardiomyogenesis in Murine Stem Cells by Low-Intensity Ultrasound

OBJECTIVES

Low-intensity ultrasound (LIUS) has been shown to enhance bone and cartilage regeneration from stem cells. The ease of its incorporation makes it an attractive mechanical stimulus for not only osteogenesis and chondrogenesis, but also cardiomyogenesis. However, to date, no study has investigated its effects on cardiomyogenesis from embryonic stem cells.

METHODS

In this study, murine embryonic stem cells were differentiated via embryoid body formation and plating, and after 3 days they were subjected to daily 10 minutes of LIUS treatment with various conditions: (1) low-pulsed (21 mW/cm² , 20% duty cycle), (2) low-continuous, (3) high-pulsed (147 mW/cm² , 20% duty cycle), and (4) high-continuous LIUS.

RESULTS

Low-pulsed and high-continuous LIUS had improved beating rates of contractile areas as well as increased late cardiac gene expressions, such as α- and β-myosin heavy chain and cardiac troponin T, showing its benefits on cardiomyocyte differentiation. Meanwhile, an early endodermal marker, α-fetoprotein, was significantly attenuated after LIUS treatments.

CONCLUSIONS

With these observations, it is demonstrated that LIUS simulation could enhance cardiomyogenesis from embryonic stem cells and increase its selectivity toward cardiomyocytes by reducing spontaneous differentiation.

Laser-ultrasonic delivery of agents into articular cartilage

Research is ongoing to develop drug therapies to manage osteoarthritis (OA) and articular cartilage (AC) injuries. However, means to deliver drug to localized AC lesions are highly limited and not clinically available. This study investigates the capability of laser ultrasound (laser-induced plasma sound source) to deliver agents (methylene blue, MB, in PBS) into bovine AC. Treatment samples (n = 10) were immersed in MB solution simultaneously with LU exposure, while adjacent control 1 tissue (n = 10) was pre-treated with LU followed by immersion in MB and adjacent control 2 tissue (n = 10) was only immersed in MB. AC exposed (n = 22) or not exposed (n = 27) to LU were characterized for anomalies in structure, composition, viability or RNA expression. Optically detected MB content was significantly (p < 0.01) higher in treatment samples up to a depth of 500 µm from AC surface as compared to controls. No major unwanted short-term effects on AC structure, proteoglycan or collagen contents, chondrocyte viability or RNA expression levels were detected. In conclusion, LU can deliver agents into AC without major short-term concerns on safety. LU could reveal new strategies for the development of localized drug therapies in AC.

The Effect of Therapeutic Ultrasound on Pain and Physical Function in Patients with Knee Osteoarthritis

Osteoartritis (OA) is one of the most frequent causes of pain, loss of function and disability in adults. The prevalence of OA is expected to increase substantially in the future. Knee OA is the most common subset of OA. Therapeutic ultrasound (US) is one of several physical therapy modalities suggested for the management of pain and loss of function due to OA. The purpose of our study was to investigate the efficacy of US therapy in reducing pain and functional loss and improving the quality of life in patients with knee OA in comparison to sham US therapy. The study involved 62 patients. The patients were randomly divided into two groups. The patients in group 1 (n = 30) were administered 1 W/cm², 1 MHz continuous US, and the patients in group 2 (n = 32) were administered sham US. The US treatment was applied for 8 min to each knee, 16 min in total, 5 d a wk, for a total of 10 sessions during 2 wk. The patients were evaluated immediately after treatment and 1 mo after therapy according to the visual analog scale (VAS), night pain, range of motion, morning stiffness, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Lequesne and Short Form-36 (SF-36) scales and 6 min walking distance. Improvement in pain and joint functions was observed in both groups according to the evaluation immediately after treatment and at 1 mo after the therapy. According to the evaluation results immediately after treatment, there was significant improvement in all pain scales (VAS, WOMAC, Lequesne, SF-36), morning stiffness and 6 min walking distance in patients receiving real US treatment (p < 0.05), but only in some pain scales (VAS, WOMAC) and functions in the group receiving sham US (p < 0.05). Significantly better improvement was observed in some pain scales (SF-36), functions (WOMAC, SF-36) and 6 min walking distance in the real US group. At 1 mo after therapy, no significant difference was observed between groups except for improvement in night pain in the real US group. In conclusion, US therapy has been found to be effective in reducing pain and improving physical function in the short term, but this positive effect was not persistent in the long term. However, we believe that the results of our study may contribute to ongoing research for the treatment of patients with knee OA, and further systematic investigation on larger patient populations may delineate the role of US in knee OA treatment.

Combined effect of pulsed electromagnetic field and sound wave on In vitro and In vivo neural differentiation of human mesenchymal stem cells

Biophysical wave stimulus has been used as an effective tool to promote cellular maturation and differentiation in the construction of engineered tissue. Pulsed electromagnetic fields (PEMFs) and sound waves have been selected as effective stimuli that can promote neural differentiation. The aim of this study was to investigate the synergistic effect of PEMFs and sound waves on the neural differentiation potential in vitro and in vivo using human bone marrow mesenchymal stem cells (hBM-MSCs). In vitro, neural-related genes in hBM-MSCs were accelerated by the combined exposure to both waves more than by individual exposure to PEMFs or sound waves. The combined wave also up-regulated the expression of neural and synaptic-related proteins in a three-dimensional (3-D) culture system through the phosphorylation of extracellular signal-related kinase. In a mouse model of photochemically induced ischemia, exposure to the combined wave reduced the infarction volume and improved post-injury behavioral activity. These results indicate that a combined stimulus of biophysical waves, PEMFs and sound can enhance and possibly affect the differentiation of MSCs into neural cells. Our study is meaningful for highlighting the potential of combined wave for neurogenic effects and providing new therapeutic approaches for neural cell therapy. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:201-211, 2017.

The Application of Ultrasound in 3D Bio-Printing

Three-dimensional (3D) bioprinting is an emerging and promising technology in tissue engineering to construct tissues and organs for implantation. Alignment of self-assembly cell spheroids that are used as bioink could be very accurate after droplet ejection from bioprinter. Complex and heterogeneous tissue structures could be built using rapid additive manufacture technology and multiple cell lines. Effective vascularization in the engineered tissue samples is critical in any clinical application. In this review paper, the current technologies and processing steps (such as printing, preparation of bioink, cross-linking, tissue fusion and maturation) in 3D bio-printing are introduced, and their specifications are compared with each other. In addition, the application of ultrasound in this novel field is also introduced. Cells experience acoustic radiation force in ultrasound standing wave field (USWF) and then accumulate at the pressure node at low acoustic pressure. Formation of cell spheroids by this method is within minutes with uniform size and homogeneous cell distribution. Neovessel formation from USWF-induced endothelial cell spheroids is significant. Low-intensity ultrasound could enhance the proliferation and differentiation of stem cells. Its use is at low cost and compatible with current bioreactor. In summary, ultrasound application in 3D bio-printing may solve some challenges and enhance the outcomes.

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.

Effects of low-intensity ultrasound on oxidative damage in retinal pigment epithelial cells in vitro

Oxidative stress in retinal pigment epithelium (RPE) is one of the key causative factors of RPE injury in age-related macular degeneration (AMD). Low-intensity ultrasound (LIUS) less than 1 W/cm(2) in intensity has been found to have cytoprotective and anti-inflammatory effects in many cell types and diseases. In this study, we investigated for the first time the feasibility of using LIUS to protect RPE cells from oxidative damage. ARPE-19 cells were treated with H2O2 (an exogenous source of reactive oxygen species) or L-buthionine-(S,R)-sulfoximine (BSO), a glutathione synthase inhibitor, and exposed immediately to LIUS at intensities of 50, 100 and 200 mW/cm(2) and a frequency of 1 MHz for 20 min. Both H2O2 and BSO increased the percentage of cells positive for mitochondrial reactive oxygen species at 1 h, but not at 24 h. Co-treatment with LIUS clearly repressed these cells similarly at all intensities by approximately 34%-43% for H2O2 and 24%-25% for BSO (p < 0.05). The percentage of cells with mitochondrial membrane depolarization also increased with H2O2 and BSO treatment, particularly at 1 h, and decreased by approximately 60% with LIUS at 100 mW/cm(2) (p < 0.05). The amount of intracellular calcium ion ([Ca(2+)]i) was elevated only by BSO at 24 h and was also significantly diminished, by approximately 45%, by LIUS at 100 mW/cm(2) (p < 0.05). Both H2O2 and BSO significantly hampered cell viability at 24 h, but LIUS at 100 mW/cm(2) restored only BSO-induced cell viability by approximately 2.7-fold (p < 0.05). This study illustrated that LIUS has a protective effect on RPE cells against oxidative damage caused by BSO, an endogenous mitochondrial reactive oxygen species generator. We speculate that LIUS has the potential to treat oxidative damage and related pathologic changes in RPE.

Differentiation of neural stem/progenitor cells using low-intensity ultrasound

Herein, we report the evaluation of apoptosis, cell differentiation, neurite outgrowth and differentiation of neural stem/progenitor cells (NSPCs) in response to low-intensity ultrasound (LIUS) exposure. NSPCs were cultured under different conditions, with and without LIUS exposure, to evaluate the single and complex effects of LIUS. A lactic dehydrogenase assay revealed that the cell viability of NSPCs was maintained with LIUS exposure at an intensity range from 100 to 500 mW/cm(2). Additionally, in comparison with no LIUS exposure, the cell survival rate was improved with the combination of medium supplemented with nerve growth factor and LIUS exposure. Our results indicate that LIUS exposure promoted NSPC attachment and differentiation on a glass substrate. Neurite outgrowth assays revealed the generation of longer, thicker neurites after LIUS exposure. Furthermore, LIUS stimulation substantially increased the percentage of differentiating neural cells in NSPCs treated with nerve growth factor in comparison with the unstimulated group. The high percentage of differentiated neural cells indicated that LIUS induced neuronal networks denser than those observed in the unstimulated groups. Furthermore, the release of nitric oxide, an important small-molecule neurotransmitter, was significantly upregulated after LIUS exposure. It is therefore reasonable to suggest that LIUS promotes the differentiation of NSPCs into neural cells, induces neurite outgrowth and regulates nitric oxide production; thus, LIUS may be a potential candidate for NSPC induction and neural cell therapy.

Effects of low-intensity pulsed ultrasound on cell viability, proliferation and neural differentiation of induced pluripotent stem cells-derived neural crest stem cells

Low-intensity pulsed ultrasound (LIPUS) acting on induced pluripotent stem cells-derived neural crest stem cells (iPSCs-NCSCs) is considered a promising therapy to improve the efficacy of injured peripheral nerve regeneration. Effects of LIPUS on cell viability, proliferation and neural differentiation of iPSCs-NCSCs were examined respectively in this study. LIPUS at 500 mW cm(-2) enhanced the viability and proliferation of iPSCs-NCSCs after 2 days and, after 4 days, up-regulated gene and protein expressions of NF-M, Tuj1, S100β and GFAP in iPSCs-NCSCs whereas after 7 days expression of only NF-M, S100β and GFAP were up-regulated. LIPUS treatment at an appropriate intensity can, therefore, be an efficient and cost-effective method to enhance cell viability, proliferation and neural differentiation of iPSCs-NCSCs in vitro for peripheral nerve tissue engineering.

Clinical translation of stem cells: insight for cartilage therapies

The limited regenerative capacity of articular cartilage and deficiencies of current treatments have motivated the investigation of new repair technologies. In vitro cartilage generation using primary cell sources is limited by cell availability and expansion potential. Pluripotent stem cells possess the capacity for chondrocytic differentiation and extended expansion, providing a potential future solution to cell-based cartilage regeneration. However, despite successes in producing cartilage using adult and embryonic stem cells, the translation of these technologies to the clinic has been severely limited. This review discusses recent advances in stem cell-based cartilage tissue engineering and the major current limitations to clinical translation of these products. Concerns regarding appropriate animal models and studies, stem cell manufacturing, and relevant regulatory processes and guidelines will be addressed. Understanding the significant hurdles limiting the clinical use of stem cell-based cartilage may guide future developments in the fields of tissue engineering and regenerative medicine.

Cryopreservation of alginate encapsulated mesenchymal stromal cells

Human mesenchymal stromal cells (MSCs) can differentiate into various cell types, which makes them attractive for regenerative medicine and tissue engineering. Encapsulation of MSCs in alginate microspheres (AMS) is a novel and promising approach of tissue engineering. Application and research of such cell-hydrogel systems require selection of adequate cryopreservation protocols. In this study we investigated the response of MSCs encapsulated in AMS to different cryopreservation protocols. Bone marrow MSCs either encapsulated in AMS and or as cells in suspension, were cryopreserved with 5% and 10% of dimethyl sulfoxide (ME₂SO) using conventional 2-step slow cooling (protocol 1). The viability and metabolism of MSCs in AMS following cryopreservation with 5% Me₂SO were lower than in the group cryopreserved with 10% Me₂SO. MSCs in suspension were more resistant to cryopreservation than cells in AMS when cryopreserved with 5% Me₂SO, although when using a concentration of 10% Me₂SO, no differences were detected. Comparisons of the viability and metabolic activity of MSC cryopreserved either in AMS or as cell suspensions with 10% ME₂SO using protocol 1 (2-step cooling), protocol 2 (3-step slow cooling with induced ice nucleation) or protocol 3 (rapid 1-step freezing), showed that the highest viabilities and metabolic rates were obtained following cryopreservation of MSCs in AMS by protocol 2 (with controlled ice nucleation). Cryopreservation with protocol 3 resulted in critical damage of the encapsulated MSCs. After cryopreservation by protocol 2, AMS encapsulated MSCs were capable of achieving multilineage differentiation directed towards osteogenic, adipogenic and chondrogenic lineages. The data obtained indicate that cryo-banking of AMS encapsulated MSCs is feasible for future regenerative medicine projects.

The effects of low-intensity pulsed ultrasound on tendon-bone healing in a transosseous-equivalent sheep rotator cuff model

PURPOSE

The purpose of this study was to examine the effects Low-intensity Pulsed Ultrasound has on initial tendon-bone healing in a clinically relevant extra-articular transosseous-equivalent ovine rotator cuff model.

METHODS

Eight skeletally mature wethers, randomly allocated to either control group (n = 4) or treatment group (n = 4), underwent rotator cuff surgery following injury to the infraspinatus tendon. All animals were killed 28 days post surgery to allow examination of early effects of Low-intensity Pulsed Ultrasound treatment.

RESULTS

General improvement in histological appearance of tendon-bone integration was noted in the treatment group. Newly formed woven bone with increased osteoblast activity along the bone surface was evident. A continuum was observed between the tendon and bone in an interdigitated fashion with Sharpey's fibres noted in the treatment group. Low-intensity Pulsed Ultrasound treatment also increased bone mineral density at the tendon-bone interface (p < 0.01), while immunohistochemistry results revealed an increase in the protein expression patterns of VEGF (p = 0.038), RUNX2 (p = 0.02) and Smad4 (p = 0.05).

CONCLUSIONS

The results of this study indicate that Low-intensity Pulsed Ultrasound may aid in the initial phase of tendon-bone healing process in patients who have undergone rotator cuff repair. This treatment may also be beneficial following other types of reconstructive surgeries involving the tendon-bone interface.

Effect of low-intensity pulsed ultrasound on the cartilage repair in people with mild to moderate knee osteoarthritis: a double-blinded, randomized, placebo-controlled pilot study

OBJECTIVE

To determine the feasibility of conducting a randomized controlled trial assessing the effect of low-intensity pulsed ultrasound (US) therapy on cartilage repair in patients with mild to moderate knee osteoarthritis (OA).

DESIGN

Pilot, double-blinded, randomized placebo-controlled trial with 2-months follow-up.

SETTING

Rehabilitation research facility.

PARTICIPANTS

Adults (N=27; ≥45y) with grades 1 or 2 of medial joint space narrowing (Osteoarthritis Research Society International atlas) due to knee OA were randomly allocated to receive active (n=14) or sham (n=13) US therapy. Four participants withdrew for personal reasons.

INTERVENTIONS

Twenty-four sessions of active (20% duty cycle, 1MHz, average temporal intensity: 0.2W/cm(2), therapeutic dose: 112.5J/cm(2)) or sham (no sound-head crystal) US therapy.

MAIN OUTCOME MEASURES

Success of recruitment and adherence rates were established by a priori criteria. Effect on cartilage repair was assessed by measuring cartilage volume and thickness and scoring cartilage injury, subchondral cyst formation, and bone marrow lesions on magnetic resonance images.

RESULTS

Patient recruitment and adherence rates were successful. No significant age-adjusted differences were seen between groups in the cartilage repair outcomes. Age-adjusted analyses, including only subjects who attended 20 sessions or more, showed an increase in medial tibia cartilage thickness in the active US therapy group (90μm; 95% confidence interval, 1-200; P=.05).

CONCLUSIONS

Conducting a randomized controlled trial to assess the effects of US therapy on the cartilage repair in people with mild to moderate knee OA is feasible. However, further pilot studies are needed to determine the optimal US dose and application parameters before designing a full trial.

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

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

Advancing nasal reconstructive surgery: the application of tissue engineering technology

Cartilage tissue engineering is a rapidly progressing area of regenerative medicine with advances in cell biology and scaffold engineering constantly being investigated. Many groups are now capable of making neocartilage constructs with some level of morphological, biochemical, and histological likeness to native human cartilage tissues. The application of this useful technology in articular cartilage repair is well described in the literature; however, few studies have evaluated its application in head and neck reconstruction. Although there are many studies on auricular cartilage tissue engineering, there are few studies regarding cartilage tissue engineering for complex nasal reconstruction. This study therefore highlighted the challenges involved with nasal reconstruction, with special focus on nasal cartilage tissue, and examined how advancements made in cartilage tissue engineering research could be applied to improve the clinical outcomes of total nasal reconstructive surgery.

Induction of bone marrow mesenchymal stem cell chondrogenesis following short-term suspension culture

The objective of this study was to evaluate mesenchymal stem cell (MSC) chondrogenesis following incubation in chondrogenic suspension cultures from which single cells were obtained. MSCs were maintained in suspension over a nonadherent surface for 3 days, dissociated into a suspension, and then evaluated for chondrogenesis in agarose in the presence or absence of transforming growth factor beta (TGFβ). In a second experiment, MSCs from suspension culture were returned to monolayer expansion for 2 days prior to testing for chondrogenesis. In both cases, undifferentiated MSCs were evaluated as controls. Suspension culture alone did not stimulate chondrogenesis. Suspension followed by expansion stimulated a four- to ninefold increase in extracellular matrix (ECM) synthesis in TGFβ-free cultures, a finding that was attributed to an increase in viable MSCs that secreted a proteoglycan-rich ECM. Gene expression of aggrecan and type II collagen increased with suspension culture, but decreased with postsuspension expansion. Therefore, stimulation of ECM synthesis without additional TGFβ exposure could not be attributed to an enhancement of chondrogenesis with monolayer culture. ECM synthesis of suspension/expansion-conditioned MSCs without additional TGFβ exposure was less than samples maintained in TGFβ throughout the differentiation culture. Based on these findings, a better understanding of factors associated with early-stage chondrogenesis and MSC differentiation to a highly active phenotype may lead to improved methods for stimulating chondrogenesis during short-term culture.

Low-intensity pulsed ultrasound increases cellular uptake of superparamagnetic iron oxide nanomaterial: results from human osteosarcoma cell line U2OS

PURPOSE

To determine whether low-intensity pulsed ultrasound (LIPUS) is able to facilitate the uptake of a superparamagnetic iron oxide (SPIO) nanomaterial by cells that do not express high endocytosis capacity.

MATERIALS AND METHODS

The human osteosarcoma cell line U2OS and a silica-coated SPIO functionalized peripherally with amines groups (overall diameter 8 nm) were used in this study. Adherent U2OS cells were labeled with SPIO by incubating with culture media containing the SPIO at 4.5 microg[Fe]/mL. LIPUS with the same parameters as those used in clinical application to accelerate bone fracture healing (1.5 MHz, duty cycle 1:4, spatial-average temporal-average intensity 30 mW/cm(2)) was applied to the cells at the beginning of the labeling process for 0, 0.5, 1, or 3 hours. The total incubation time with SPIO was 12 hours. SPIO labeling efficiency was evaluated with Prussian blue staining and a blueness measurement method, and magnetic resonance imaging (MRI) of cell pellets via measuring areas of SPIO-induced signal void.

RESULTS

Both Prussian blue staining and in vitro MRI demonstrated that LIPUS application increased the SPIO nanomaterial labeling efficiency for U2OS cells in an exposure-duration-dependent manner.

CONCLUSION

This study is a "proof of concept" that LIPUS can facilitate the cellular take-up of SPIO nanomaterial.

Strategies for articular cartilage lesion repair and functional restoration

Injury of articular cartilage due to trauma or pathological conditions is the major cause of disability worldwide, especially in North America. The increasing number of patients suffering from joint-related conditions leads to a concomitant increase in the economic burden. In this review article, we focus on strategies to repair and replace knee joint cartilage, since knee-associated disabilities are more prevalent than any other joint. Because of inadequacies associated with widely used approaches, the orthopedic community has an increasing tendency to develop biological strategies, which include transplantation of autologous (i.e., mosaicplasty) or allogeneic osteochondral grafts, autologous chondrocytes (autologous chondrocyte transplantation), or tissue-engineered cartilage substitutes. Tissue-engineered cartilage constructs represent a highly promising treatment option for knee injury as they mimic the biomechanical environment of the native cartilage and have superior integration capabilities. Currently, a wide range of tissue-engineering-based strategies are established and investigated clinically as an alternative to the routinely used techniques (i.e., knee replacement and autologous chondrocyte transplantation). Tissue-engineering-based strategies include implantation of autologous chondrocytes in combination with collagen I, collagen I/III (matrix-induced autologous chondrocyte implantation), HYAFF 11 (Hyalograft C), and fibrin glue (Tissucol) or implantation of minced cartilage in combination with copolymers of polyglycolic acid along with polycaprolactone (cartilage autograft implantation system), and fibrin glue (DeNovo NT graft). Tissue-engineered cartilage replacements show better clinical outcomes in the short term, and with advances that have been made in orthopedics they can be introduced arthroscopically in a minimally invasive fashion. Thus, the future is bright for this innovative approach to restore function.

Effects of low-intensity pulsed ultrasound, dexamethasone/TGF-beta1 and/or BMP-2 on the transcriptional expression of genes in human mesenchymal stem cells: chondrogenic vs. osteogenic differentiation

The effects of low-intensity pulsed ultrasound (LIPUS) on the differentiation of human mesenchymal stem cells (hMSCs) were investigated in this study. hMSCs were subjected to LIPUS with or without dexamethasone/transforming growth factor-beta1 (TD) or bone morphogenetic protein-2 (BMP-2) and the effects of this treatment were assessed. TD-treated hMSCs exhibited characteristic chondrogenic morphology and increased messenger RNA (mRNA) expression of chondrogenic markers and LIPUS enhanced the chondrogenic differentiation of hMSCs treated with TD. The expression of Runx2, an osteogenic transcription factor was not altered in either TD treatment group; however, a significant increase was detected in the LIPUS only group. The osteogenic appearance exhibited 3 days after LIPUS and/or BMP-2 treatment. Increases in the mRNA expression levels of osteogenic markers, Runx2 and ALP were also detected. There was no additive or altered effect with combined LIPUS and BMP-2 treatment. LIPUS alone can increase osteogenic differentiation of hMSCs and LIPUS enhances TD-mediated chondrogenic differentiation of hMSCs. Clinically, LIPUS may differentially influence bone vs. cartilage repair.

Cartilage repair: past and future--lessons for regenerative medicine

Since the first cell therapeutic study to repair articular cartilage defects in the knee in 1994, several clinical studies have been reported. An overview of the results of clinical studies did not conclusively show improvement over conventional methods, mainly because few studies reach level I of evidence for effects on middle or long term. However, these explorative trials have provided valuable information about study design, mechanisms of repair and clinical outcome and have revealed that much is still unknown and further improvements are required. Furthermore, cellular and molecular studies using new technologies such as cell tracking, gene arrays and proteomics have provided more insight in the cell biology and mechanisms of joint surface regeneration. Besides articular cartilage, cartilage of other anatomical locations as well as progenitor cells are now considered as alternative cell sources. Growth Factor research has revealed some information on optimal conditions to support cartilage repair. Thus, there is hope for improvement. In order to obtain more robust and reproducible results, more detailed information is needed on many aspects including the fate of the cells, choice of cell type and culture parameters. As for the clinical aspects, it becomes clear that careful selection of patient groups is an important input parameter that should be optimized for each application. In addition, the study outcome parameters should be improved. Although reduced pain and improved function are, from the patient's perspective, the most important outcomes, there is a need for more structure/tissue-related outcome measures. Ideally, criteria and/or markers to identify patients at risk and responders to treatment are the ultimate goal for these more sophisticated regenerative approaches in joint surface repair in particular, and regenerative medicine in general.

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.