Electro-magnetic field promotes osteogenic differentiation of BM-hMSCs through a selective action on Ca(2+)-related mechanisms

Hierarchically designed bone scaffolds: From internal cues to external stimuli

Bone tissue engineering utilizes three critical elements - cells, scaffolds, and bioactive factors - to recapitulate the bone tissue microenvironment, inducing the formation of new bone. Recent advances in materials development have enabled the production of scaffolds that more effectively mimic the hierarchical features of bone matrix, ranging from molecular composition to nano/micro-scale biochemical and physical features. This review summarizes recent advances within the field in utilizing these features of native bone to guide the hierarchical design of materials and scaffolds. Biomimetic strategies discussed in this review cover several levels of hierarchical design, including the development of element-doped compositions of bioceramics, the usage of molecular templates for in vitro biomineralization at the nanoscale, the fabrication of biomimetic scaffold architecture at the micro- and nanoscale, and the application of external physical stimuli at the macroscale to regulate bone growth. Developments at each level are discussed with an emphasis on their in vitro and in vivo outcomes in promoting osteogenic tissue development. Ultimately, these hierarchically designed scaffolds can complement or even replace the usage of cells and biological elements, which present clinical and regulatory barriers to translation. As the field progresses ever closer to clinical translation, the creation of viable therapies will thus benefit from further development of hierarchically designed materials and scaffolds.

Novel magnetic stimulation methodology for low-current implantable medical devices

Recent studies highlight the ability of inductive architectures to deliver therapeutic magnetic stimuli to target tissues and to be embedded into small-scale intracorporeal medical devices. However, to date, current micro-scale biomagnetic devices require very high electric current excitations (usually exceeding 1 A) to ensure the delivery of efficient magnetic flux densities. This is a critical problem as advanced implantable devices demand self-powering, stand-alone and long-term operation. This work provides, for the first time, a novel small-scale magnetic stimulation system that requires up to 50-fold lower electric current excitations than required by relevant biomagnetic technology recently proposed. Computational models were developed to analyse the magnetic stimuli distributions and densities delivered to cellular tissues during in vitro experiments, such that the feasibility of this novel stimulator can be firstly evaluated on cell culture tests. The results demonstrate that this new stimulative technology is able to deliver osteogenic stimuli (0.1-7 mT range) by current excitations in the 0.06-4.3 mA range. Moreover, it allows coil designs with heights lower than 1 mm without significant loss of magnetic stimuli capability. Finally, suitable core diameters and stimulator-stimulator distances allow to define heterogeneity or quasi-homogeneity stimuli distributions. These results support the design of high-sophisticated biomagnetic devices for a wide range of therapeutic applications.

The Response of Osteoblasts and Bone to Sinusoidal Electromagnetic Fields: Insights from the Literature

Electromagnetic fields (EMFs) have been proposed as a tool to ameliorate bone formation and healing. Despite their promising results, however, they have failed to enter routine clinical protocols to treat bone conditions where higher bone mass has to be achieved. This is no doubt also due to a fundamental lack of knowledge and understanding on their effects and the optimal settings for attaining the desired therapeutic effects. This review analysed the available in vitro and in vivo studies that assessed the effects of sinusoidal EMFs (SEMFs) on bone and bone cells, comparing the results and investigating possible mechanisms of action by which SEMFs interact with tissues and cells. The effects of SEMFs on bone have not been as thoroughly investigated as pulsed EMFs; however, abundant evidence shows that SEMFs affect the proliferation and differentiation of osteoblastic cells, acting on multiple cellular mechanisms. SEMFs have also proven to increase bone mass in rodents under normal conditions and in osteoporotic animals.

Involvement of calcium in 50-Hz magnetic field-induced activation of sphingosine kinase 1 signaling pathway

Previously, we found that exposure to a 50-Hz magnetic field (MF) could induce human amniotic epithelial (FL) cell proliferation and sphingosine kinase 1 (SK1) activation, but the mechanism was not clearly understood. In the present study, the possible signaling pathways which were involved in SK1 activation induced by 50-Hz MF exposure were investigated. Results showed that MF exposure increased intracellular Ca²⁺ which was dependent on the L-type calcium channel, and induced Ca²⁺ -dependent phosphorylation of extracellular regulated protein kinase (ERK), SK1, and protein kinase C α (PKCα). Also, treatment with U0126, an inhibitor of ERK, could block MF-induced SK1 phosphorylation, but had no effect on PKCα phosphorylation. Also, the inhibitor of PKCα, Gö6976, had no effect on MF-induced SK1 activation in FL cells. In addition, the activation of ERK and PKCα could be abolished by SKI II, the inhibitor of SK1. In conclusion, the intracellular Ca²⁺ mediated the 50-Hz MF-induced SK1 activation which enhanced PKCα phosphorylation, and there might be a feedback mechanism between SK1 and ERK activation in responding to MF exposure in FL cells. Bioelectromagnetics. 9999:XX-XX, 2019. © 2019 Bioelectromagnetics Society.

Ca2+ and CACNA1H mediate targeted suppression of breast cancer brain metastasis by AM RF EMF

BACKGROUND

Brain metastases are a major cause of death in patients with metastatic breast cancer. While surgical resection and radiation therapy are effective treatment modalities, the majority of patients will succumb from disease progression. We have developed a novel therapy for brain metastases that delivers athermal radiofrequency electromagnetic fields that are amplitude-modulated at breast cancer specific frequencies (BCF).

METHODS

27.12 MHz amplitude-modulated BCF were administered to a patient with a breast cancer brain metastasis by placing a spoon-shaped antenna on the anterior part of the tongue for three one-hour treatments every day. In preclinical models, a BCF dose, equivalent to that delivered to the patient's brain, was administered to animals implanted with either brain metastasis patient derived xenografts (PDXs) or brain-tropic cell lines. We also examined the efficacy of combining radiation therapy with BCF treatment. Additionally, the mechanistic underpinnings associated with cancer inhibition was identified using an agnostic approach.

FINDINGS

Animal studies demonstrated a significant decrease in growth and metastases of brain-tropic cell lines. Moreover, BCF treatment of PDXs established from patients with brain metastases showed strong suppression of their growth ability. Importantly, BCF treatment led to significant and durable regression of brain metastasis of a patient with triple negative breast cancer. The tumour inhibitory effect was mediated by Ca²⁺ influx in cancer cells through CACNA1H T-type voltage-gated calcium channels, which, acting as the cellular antenna for BCF, activated CAMKII/p38 MAPK signalling and inhibited cancer stem cells through suppression of β-catenin/HMGA2 signalling. Furthermore, BCF treatment downregulated exosomal miR-1246 level, which in turn decreased angiogenesis in brain environment. Therefore, targeted growth inhibition of breast cancer metastases was achieved through CACNA1H.

INTERPRETATION

We demonstrate that BCF, as a single agent or in combination with radiation, is a novel treatment approach to the treatment of brain metastases. This paradigm shifting modality warrants further clinical trials for this unmet medical need.

The cellular effects of Pulsed Electromagnetic Fields on osteoblasts: A review

Electromagnetic fields (EMFs) have long been known to interact with living organisms and their cells and to bear the potential for therapeutic use. Among the most extensively investigated applications, the use of Pulsed EMFs (PEMFs) has proven effective to ameliorate bone healing in several studies, although the evidence is still inconclusive. This is due in part to our still-poor understanding of the mechanisms by which PEMFs act on cells and affect their functions and to an ongoing lack of consensus on the most effective parameters for specific clinical applications. The present review has compared in vitro studies on PEMFs on different osteoblast models, which elucidate potential mechanisms of action for PEMFs, up to the most recent insights into the role of primary cilia, and highlight the critical issues underlying at least some of the inconsistent results in the available literature. Bioelectromagnetics. 2019;9999:XX-XX. © 2019 Bioelectromagnetics Society.

Magnetic Resonance Spectroscopy for Evaluating the Effect of Pulsed Electromagnetic Fields on Marrow Adiposity in Postmenopausal Women With Osteopenia

OBJECTIVE

Pulsed electromagnetic fields (PEMFs) could promote osteogenic differentiation and suppress adipogenic differentiation in bone mesenchymal stem cells ex vivo. However, data on the effect of PEMF on marrow adiposity in humans remain elusive. We aimed to determine the in vivo effect of PEMF on marrow adiposity in postmenopausal women using magnetic resonance spectroscopy.

METHODS

Sixty-one postmenopausal women with osteopenia, aged 53 to 85 years, were randomly assigned to receive either PEMF treatment or placebo. The session was performed 3 times per week for 6 months. All women received adequate dietary calcium and vitamin D. Bone mineral density (BMD) by dual-energy x-ray absorptiometry, vertebral marrow fat content by magnetic resonance spectroscopy, and serum biomarkers were evaluated before and after 6 months of treatment.

RESULTS

A total of 27 (87.1%) and 25 (83.3%) women completed the treatment schedule in the PEMF and placebo groups, respectively. After the 6-month treatment, lumbar spine and hip BMD increased by 1.46% to 2.04%, serum bone-specific alkaline phosphatase increased by 3.23%, and C-terminal telopeptides of type 1 collagen decreased by 9.12% in the PEMF group (P < 0.05), whereas the mean percentage changes in BMD and serum biomarkers were not significant in the placebo group. Pulsed electromagnetic field treatment significantly reduced marrow fat fraction by 4.81%. The treatment difference between the 2 groups was -4.43% (95% confidence interval, -3.70% to -5.65%; P = 0.009).

CONCLUSIONS

Pulsed electromagnetic field is an effective physiotherapy in postmenopausal women, and this effect may, at least in part, regulate the amount of fat within the bone marrow. Magnetic resonance spectroscopy may serve as a complementary imaging biomarker for monitoring response to therapy in osteoporosis.

The Use of Pulsed Electromagnetic Fields to Promote Bone Responses to Biomaterials In Vitro and In Vivo

Implantable biomaterials are extensively used to promote bone regeneration or support endosseous prosthesis in orthopedics and dentistry. Their use, however, would benefit from additional strategies to improve bone responses. Pulsed Electromagnetic Fields (PEMFs) have long been known to act on osteoblasts and bone, affecting their metabolism, in spite of our poor understanding of the underlying mechanisms. Hence, we have the hypothesis that PEMFs may also ameliorate cell responses to biomaterials, improving their growth, differentiation, and the expression of a mature phenotype and therefore increasing the tissue integration of the implanted devices and their clinical success. A broad range of settings used for PEMFs stimulation still represents a hurdle to better define treatment protocols and extensive research is needed to overcome this issue. The present review includes studies that investigated the effects of PEMFs on the response of bone cells to different classes of biomaterials and the reports that focused on in vivo investigations of biomaterials implanted in bone.

Magnetic field and nano-scaffolds with stem cells to enhance bone regeneration

Novel strategies utilizing magnetic nanoparticles (MNPs) and magnetic fields are being developed to enhance bone tissue engineering efficacy. This article first reviewed cutting-edge research on the osteogenic enhancements via magnetic fields and MNPs. Then the current developments in magnetic strategies to improve the cells, scaffolds and growth factor deliveries were described. The magnetic-cell strategies included cell labeling, targeting, patterning, and gene modifications. MNPs were incorporated to fabricate magnetic composite scaffolds, as well as to construct delivery systems for growth factors, drugs and gene transfections. The novel methods using magnetic nanoparticles and scaffolds with magnetic fields and stem cells increased the osteogenic differentiation, angiogenesis and bone regeneration by 2-3 folds over those of the controls. The mechanisms of magnetic nanoparticles and scaffolds with magnetic fields and stem cells to enhance bone regeneration were identified as involving the activation of signaling pathways including MAPK, integrin, BMP and NF-κB. Potential clinical applications of magnetic nanoparticles and scaffolds with magnetic fields and stem cells include dental, craniofacial and orthopedic treatments with substantially increased bone repair and regeneration efficacy.

In vitro response of mesenchymal stem cells to biomimetic hydroxyapatite substrates: A new strategy to assess the effect of ion exchange

Biomaterials can interact with cells directly, that is, by direct contact of the cells with the material surface, or indirectly, through soluble species that can be released to or uptaken from the surrounding fluids. However, it is difficult to characterise the relevance of this fluid-mediated interaction separately from the topography and composition of the substrate, because they are coupled variables. These fluid-mediated interactions are amplified in the case of highly reactive calcium phosphates (CaPs) such as biomimetic calcium deficient hydroxyapatite (CDHA), particularly in static in vitro cultures. The present work proposes a strategy to decouple the effect of ion exchange from topographical features by adjusting the volume ratio between the cell culture medium and biomaterial (V_CM/V_B). Increasing this ratio allowed mitigating the drastic ionic exchanges associated to the compositional changes experienced by the material exposed to the cell culture medium. This strategy was validated using rat mesenchymal stem cells (rMSCs) cultured on CDHA and beta-tricalcium phosphate (β-TCP) discs using different V_CM/V_B ratios. Whereas in the case of β-TCP the cell response was not affected by this ratio, a significant effect on cell adhesion and proliferation was found for the more reactive CDHA. The ionic exchange, produced by CDHA at low V_CM/V_B, altered cell adhesion due to the reduced number of focal adhesions, caused cell shrinkage and further rMCSs apoptosis. This was mitigated when using a high V_CM/V_B, which attenuated the changes of calcium and phosphate concentrations in the cell culture medium, resulting in rMSCs spreading and a viability over time. Moreover, rMSCs showed an earlier expression of osteogenic genes on CDHA compared to sintered β-TCP when extracellular calcium fluctuations were reduced.

STATEMENT OF SIGNIFICANCE

Fluid mediated interactions play a significant role in the bioactivity of calcium phosphates. Ionic exchange is amplified in the case of biomimetic hydroxyapatite, which makes the in vitro characterisation of cell-material interactions especially challenging. The present work proposes a novel and simple strategy to explore the mechanisms of interaction of biomimetic and sintered calcium phosphates with mesenchymal stem cells. The effects of topography and ion exchange are analysed separately by modifying the volume ratio between cell culture medium and biomaterial. High ionic fluctuations interfered in the maturation of focal adhesions, hampering cell adhesion and leading to increased apoptosis and reduced proliferation rate.

The effect of pulsed electromagnetic field exposure on osteoinduction of human mesenchymal stem cells cultured on nano-TiO2 surfaces

Human bone marrow-derived mesenchymal stem cells (hBM-MSCs) are considered a great promise in the repair and regeneration of bone. Considerable efforts have been oriented towards uncovering the best strategy to promote stem cells osteogenic differentiation. In previous studies, hBM-MSCs exposed to physical stimuli such as pulsed electromagnetic fields (PEMFs) or directly seeded on nanostructured titanium surfaces (TiO₂) were shown to improve their differentiation to osteoblasts in osteogenic condition. In the present study, the effect of a daily PEMF-exposure on osteogenic differentiation of hBM-MSCs seeded onto nanostructured TiO₂ (with clusters under 100 nm of dimension) was investigated. TiO₂-seeded cells were exposed to PEMF (magnetic field intensity: 2 mT; intensity of induced electric field: 5 mV; frequency: 75 Hz) and examined in terms of cell physiology modifications and osteogenic differentiation. Results showed that PEMF exposure affected TiO₂-seeded cells osteogenesis by interfering with selective calcium-related osteogenic pathways, and greatly enhanced hBM-MSCs osteogenic features such as the expression of early/late osteogenic genes and protein production (e.g., ALP, COL-I, osteocalcin and osteopontin) and ALP activity. Finally, PEMF-treated cells resulted to secrete into conditioned media higher amounts of BMP-2, DCN and COL-I than untreated cell cultures. These findings confirm once more the osteoinductive potential of PEMF, suggesting that its combination with TiO₂ nanostructured surface might be a great option in bone tissue engineering applications.

Hydroxyapatite nanobelt/polylactic acid Janus membrane with osteoinduction/barrier dual functions for precise bone defect repair

Controllable osteoinduction maintained in the original defect area is the key to precise bone repair. To meet the requirement of precise bone regeneration, a hydroxyapatite (HAp) nanobelt/polylactic acid (PLA) (HAp/PLA) Janus membrane has been successfully prepared in this study by coating PLA on a paper-like HAp nanobelt film by a casting-pervaporation method. The Janus membrane possesses dual functions: excellent osteoinduction from the hydrophilic HAp nanobelt side and barrier function originating from the hydrophobic PLA film. The cell viability and osteogenic differentiation ability of human adipose-derived stem cells (hADSCs) on the Janus membrane were assessed. The in vitro experimental results prove that the HAp nanobelt side presents high cell viability and efficient osteoinduction without any growth factor and that the PLA side can prohibit cell attachment. The in vivo repair experiments on a rat mandible defect model prove that the PLA side can prevent postoperative adhesion between bone and adjacent soft tissues. Most importantly, the HAp side has a strong ability to promote defect repair and bone regeneration. Therefore, the HAp/PLA Janus membrane will have wide applications as a kind of tissue engineering material in precise bone repair because of its unique dual osteoinduction/barrier functions, biocompatibility, low cost, and its ability to be mass-produced.

STATE OF SIGNIFICANCE

Precise bone defect repair to keeping tissue integrity and original outline shape is a very important issue for tissue engineering. Here, we have designed and prepared a novel HAp/PLA Janus membrane using a casting-pervaporation method to form a layer of PLA film on paper-like HAp nanobelt film. HAp nanobelt side of the Janus membrane can successfully promote osteogenic differentiation. PLA side of the Janus membrane exhibits good properties as a barrier for preventing the adhesion of cells in vitro. Mandible repair experiments in vivo have shown that the HAp/PLA Janus membrane can promote rat mandible repair on the HAp side and can successfully prevent postoperative adhesion on the PLA side at the same time. Therefore, the HAp/PLA Janus membrane with its osteoinduction/barrier dual functions can be applied to repair bone defect precisely.

Pulsed electromagnetic fields increase osteogenetic commitment of MSCs via the mTOR pathway in TNF-α mediated inflammatory conditions: an in-vitro study

Pulsed electromagnetic fields (PEMFs) have been considered a potential treatment modality for fracture healing, however, the mechanism of their action remains unclear. Mammalian target of rapamycin (mTOR) signaling may affect osteoblast proliferation and differentiation. This study aimed to assess the osteogenic differentiation of mesenchymal stem cells (MSCs) under PEMF stimulation and the potential involvement of mTOR signaling pathway in this process. PEMFs were generated by a novel miniaturized electromagnetic device. Potential changes in the expression of mTOR pathway components, including receptors, ligands and nuclear target genes, and their correlation with osteogenic markers and transcription factors were analyzed. Involvement of the mTOR pathway in osteogenesis was also studied in the presence of proinflammatory mediators. PEMF exposure increased cell proliferation and adhesion and the osteogenic commitment of MSCs even in inflammatory conditions. Osteogenic-related genes were over-expressed following PEMF treatment. Our results confirm that PEMFs contribute to activation of the mTOR pathway via upregulation of the proteins AKT, MAPP kinase, and RRAGA, suggesting that activation of the mTOR pathway is required for PEMF-stimulated osteogenic differentiation. Our findings provide insights into how PEMFs influence osteogenic differentiation in normal and inflammatory environments.

Stem cells: their source, potency and use in regenerative therapies with focus on adipose-derived stem cells - a review

Stem cells can be defined as units of biological organization that are responsible for the development and the regeneration of organ and tissue systems. They are able to renew their populations and to differentiate into multiple cell lineages. Therefore, these cells have great potential in advanced tissue engineering and cell therapies. When seeded on synthetic or nature-derived scaffolds in vitro, stem cells can be differentiated towards the desired phenotype by an appropriate composition, by an appropriate architecture, and by appropriate physicochemical and mechanical properties of the scaffolds, particularly if the scaffold properties are combined with a suitable composition of cell culture media, and with suitable mechanical, electrical or magnetic stimulation. For cell therapy, stem cells can be injected directly into damaged tissues and organs in vivo. Since the regenerative effect of stem cells is based mainly on the autocrine production of growth factors, immunomodulators and other bioactive molecules stored in extracellular vesicles, these structures can be isolated and used instead of cells for a novel therapeutic approach called "stem cell-based cell-free therapy". There are four main sources of stem cells, i.e. embryonic tissues, fetal tissues, adult tissues and differentiated somatic cells after they have been genetically reprogrammed, which are referred to as induced pluripotent stem cells (iPSCs). Although adult stem cells have lower potency than the other three stem cell types, i.e. they are capable of differentiating into only a limited quantity of specific cell types, these cells are able to overcome the ethical and legal issues accompanying the application of embryonic and fetal stem cells and the mutational effects associated with iPSCs. Moreover, adult stem cells can be used in autogenous form. These cells are present in practically all tissues in the organism. However, adipose tissue seems to be the most advantageous tissue from which to isolate them, because of its abundancy, its subcutaneous location, and the need for less invasive techniques. Adipose tissue-derived stem cells (ASCs) are therefore considered highly promising in present-day regenerative medicine.

Effects of PEMFs on Osx, Ocn, TRAP, and CTSK gene expression in postmenopausal osteoporosis model mice

Objective: Ovariectomized mice were used to simulate the symptoms of postmenopausal women with osteoporosis, and observe the effects of PEMF treatment on expression of Osx, Ocn, TRAP, and CTSK in ovariectomized mice. Methods: Thirty-week-old wild-type C57BL/6 mice were randomly divided into three groups (n=10, each group): sham operation group, ovariectomy (OVX) group, and PEMF group. Mice in the sham group underwent sham ovariectomy, while mice in the remaining two groups were ovariectomized. On postoperative day two, mice in the PEMF treatment group received PEMF treatment at a frequency of 8 Hz and an intensity of 3.8 mT for one hour daily for four weeks. At the same time, mice in the remaining two groups were placed in the PEMF treatment area under power-down state daily, similar to that in the PEMF group. After four weeks, all relevant indicators were tested. Results: (1) Compared with mice in the sham group, the number of trabecular bones significantly decreased, the thickness of the trabecular bone became thinner, the number of osteoclasts significantly increased, the gene expression of Osx and Ocn significantly decreased, and the gene expression of TRAP and CTSK significantly increased in the OVX group (P<0.01). (2) Compared with the blank controls without operation, the number of osteoblasts increased in the PEMF group. (3) Compared with the OVX group, the number of osteoclasts significantly decreased, the expression of Osx and Ocn significantly increased, and the gene expression of TRAP and CTSK significantly decreased in the PEMF group (P<0.01). Conclusion: PEMF treatment can significantly promote bone formation, which may be realized through inhibition of osteoclast formation, achieving bone morphological protection. PEMFs can significantly upregulate Osx and Ocn osteogenesis-related genes, which affect bone formation, and downregulate TRAP and CTSK osteoclast-related genes, which affect bone resorption. PEMFs may be used to treat postmenopausal osteoporosis by regulating Osx, Ocn, TRAP, and CTSK gene expression.

Mesenchymal stem cell differentiation: Control by calcium-activated potassium channels

Mesenchymal stem cells (MSCs) are widely used in modern medicine for which understanding the mechanisms controlling their differentiation is fundamental. Ion channels offer novel insights to this process because of their role in modulating membrane potential and intracellular milieu. Here, we evaluate the contribution of calcium-activated potassium (K_Ca ) channels to the three main components of MSC differentiation: initiation, proliferation, and migration. First, we demonstrate the importance of the membrane potential (V_m ) and the apparent association of hyperpolarization with differentiation. Of K_Ca subtypes, most evidence points to activity of big-conductance channels in inducing initiation. On the other hand, intermediate-conductance currents have been shown to promote progression through the cell cycle. While there is no information on the role of K_Ca channels in migration of MSCs, work from other stem cells and cancer cells suggest that intermediate-conductance and to a lesser extent big-conductance channels drive migration. In all cases, these effects depend on species, tissue origin and lineage. Finally, we present a conceptual model that demonstrates how K_Ca activity could influence differentiation by regulating V_m and intracellular Ca²⁺ oscillations. We conclude that K_Ca channels have significant involvement in MSC differentiation and could potentially enable novel tissue engineering approaches and therapies.

Effects of pulsed electromagnetic fields and platelet rich plasma in preventing osteoclastogenesis in an in vitro model of osteolysis

Osteolysis is the main limiting cause for the survival of an orthopedic prosthesis and is accompanied by an enhancement in osteoclastogenesis and inflammation, due by wear debris formation. Unfortunately therapeutic treatments, besides revision surgery, are not available. The aim of the present study was to evaluate the effects of Pulsed Electro Magnetic Fields (PEMFs) and platelet rich plasma (PRP), alone or in combination, in an in vitro model of osteolysis. Rats peripheral blood mononuclear cells were cultured on Ultra High Molecular Weight Polyethylene particles and divided into four groups of treatments: (1) PEMF stimulation (12 hr/day, 2.5 mT, 75 Hz, 1.3 ms pulse duration); (2) 10% PRP; (3) combination of PEMFs, and PRP; (4) no treatment. Treatments were performed for 3 days and cell viability, osteoclast number, expression of genes related to osteoclastogenesis and inflammation and production of pro-inflammatory cytokines were assessed up to 14 days. PEMF stimulation exerted best results because it increased cell viability at early time points and counteracted osteoclastogenesis at 14 days. On the contrary, PRP increased osteoclastogenesis and reduced cell viability in comparison to PEMFs alone. The combination of PEMFs and PRP increased cell viability over time and reduced osteoclastogenesis in comparison to PRP alone. However, these positive results did not exceed the level achieved by PEMF alone. At longer time points PEMF could not counteract osteoclastogenesis increased by PRP. Regarding inflammation, all treatments maintained the production of pro-inflammatory cytokines at low level, although PRP increased the level of interleukin 1 beta.

Enhancement of mesenchymal stem cell chondrogenesis with short-term low intensity pulsed electromagnetic fields

Pulse electromagnetic fields (PEMFs) have been shown to recruit calcium-signaling cascades common to chondrogenesis. Here we document the effects of specified PEMF parameters over mesenchymal stem cells (MSC) chondrogenic differentiation. MSCs undergoing chondrogenesis are preferentially responsive to an electromagnetic efficacy window defined by field amplitude, duration and frequency of exposure. Contrary to conventional practice of administering prolonged and repetitive exposures to PEMFs, optimal chondrogenic outcome is achieved in response to brief (10 minutes), low intensity (2 mT) exposure to 6 ms bursts of magnetic pulses, at 15 Hz, administered only once at the onset of chondrogenic induction. By contrast, repeated exposures diminished chondrogenic outcome and could be attributed to calcium entry after the initial induction. Transient receptor potential (TRP) channels appear to mediate these aspects of PEMF stimulation, serving as a conduit for extracellular calcium. Preventing calcium entry during the repeated PEMF exposure with the co-administration of EGTA or TRP channel antagonists precluded the inhibition of differentiation. This study highlights the intricacies of calcium homeostasis during early chondrogenesis and the constraints that are placed on PEMF-based therapeutic strategies aimed at promoting MSC chondrogenesis. The demonstrated efficacy of our optimized PEMF regimens has clear clinical implications for future regenerative strategies for cartilage.

Effects of pulsed electromagnetic fields on postmenopausal osteoporosis

Postmenopausal osteoporosis (PMOP) is considered to be a well-defined subject that has caused high morbidity and mortality. In elderly women diagnosed with PMOP, low bone mass and fragile bone strength have been proven to significantly increase risk of fragility fractures. Currently, various anabolic and anti-resorptive therapies have been employed in an attempt to retain healthy bone mass and strength. Pulsed electromagnetic fields (PEMFs), first applied in treating patients with delayed fracture healing and nonunions, may turn out to be another potential and effective therapy for PMOP. PEMFs can enhance osteoblastogenesis and inhibit osteoclastogenesis, thus contributing to an increase in bone mass and strength. However, accurate mechanisms of the positive effects of PEMFs on PMOP remain to be further elucidated. This review attempts to summarize recent advances of PEMFs in treating PMOP based on clinical trials, and animal and cellular studies. Possible mechanisms are also introduced, and the future possibility of application of PEMFs on PMOP are further explored and discussed. Bioelectromagnetics. 38:406-424, 2017. © 2017 Wiley Periodicals, Inc.

Biophysical characterization of nanostructured TiO2 as a good substrate for hBM-MSC adhesion, growth and differentiation

Mesenchymal stem cells from human bone marrow (hBM-MSC) are widely utilized for clinical applications involving bone healing. In this context, their use has been often optimized in association to variously designed titanium substrates, being this material of great use in orthopaedic implants. According to recent findings, the ability of hBM-MSC to differentiate towards a specific lineage is not only driven by biochemical signals, but physical stimuli, such as rigidity or roughness of the substrate, can also support a commitment towards osteogenic differentiation. Moreover, the presence of features with defined dimensional scales, in particular nanometer-size, also proved to elicit specific biological effects. Here we evaluated the effectiveness of a nano-patterned titanium surface in sustaining hBM-MSC adhesion, growth and differentiation by means of a panel of biophysical tools: morphometry, electrophysiology, intracellular calcium measurements and immunocytochemistry. The results substantiate the idea that this micro-textured titanium dioxide is a good surface for growth and differentiation of hBM-MSC and it exhibits a stimulating action mainly in the initial period of differentiation. Moreover, the basal concentration of free cytosolic Calcium [Ca²⁺]_i is confirmed to be a good hallmark of the hBM-MSC maturation stage. The study could provide relevant hints to help improving the biocompatibility and osteointegration potential of clinical titanium implants.

Establishing the Basis for Mechanobiology-Based Physical Therapy Protocols to Potentiate Cellular Healing and Tissue Regeneration

Life is mechanobiological: mechanical stimuli play a pivotal role in the formation of structurally and functionally appropriate body templates through mechanobiologically-driven cellular and tissue re/modeling. The body responds to mechanical stimuli engendered through physical movement in an integrated fashion, internalizing and transferring forces from organ, through tissue and cellular length scales. In the context of rehabilitation and therapeutic outcomes, such mechanical stimuli are referred to as mechanotherapy. Physical therapists use mechanotherapy and mechanical interventions, e.g., exercise therapy and manual mobilizations, to restore function and treat disease and/or injury. While the effect of directed movement, such as in physical therapy, is well documented at the length scale of the body and its organs, a number of recent studies implicate its integral effect in modulating cellular behavior and subsequent tissue adaptation. Yet the link between movement biomechanics, physical therapy, and subsequent cellular and tissue mechanoadaptation is not well established in the literature. Here we review mechanoadaptation in the context of physical therapy, from organ to cell scale mechanotransduction and cell to organ scale extracellular matrix genesis and re/modeling. We suggest that physical therapy can be developed to harness the mechanosensitivity of cells and tissues, enabling prescriptive definition of physical and mechanical interventions to enhance tissue genesis, healing, and rehabilitation.

Piezoelectric Effects of Materials on Bio-Interfaces

Electrical stimulation of cells and tissues is an important approach of interaction with living matter, which has been traditionally exploited in the clinical practice for a wide range of pathological conditions, in particular, related to excitable tissues. Standard methods of stimulation are, however, often invasive, being based on electrodes and wires used to carry current to the intended site. The possibility to achieve an indirect electrical stimulation, by means of piezoelectric materials, is therefore of outstanding interest for all the biomedical research, and it emerged in the latest decade as a most promising tool in many bioapplications. In this paper, we summarize the most recent achievements obtained by our group and by others in the exploitation of piezoelectric nanoparticles and nanocomposites for cell stimulation, describing the important implications that these studies present in nanomedicine and tissue engineering. A particular attention will be also dedicated to the physical modeling, which can be extremely useful in the description of the complex mechanisms involved in the mechanical/electrical transduction, yet also to gain new insights at the base of the observed phenomena.

Pulsed Electromagnetic Field Stimulation Promotes Anti-cell Proliferative Activity in Doxorubicin-treated Mouse Osteosarcoma Cells

AIM

We aimed to investigate the synergistic effects of pulsed electromagnetic field (PEMF) and doxorubicin therapy in a mouse osteosarcoma cell line (LM8 cells) in vitro.

MATERIALS AND METHODS

The effects of PEMF (5 mT, 200 Hz) of different durations and doxorubicin on the proliferative activity of LM8 cells were measured by the MTT assay. Apoptotic-related factors such as cell-cycle phase, mitochondrial membrane potential, and caspase 3/7 activity were investigated using 4',6-diamidino-2-phenylindole staining and apoptosis kits. Identification of intracellular signaling molecules induced by the combination was comprehensively explored using a stress and apoptosis-related protein array kit.

RESULTS

PEMF enhanced the inhibition of cell proliferation mediated by doxorubicin but did not affect the cell cycle, mitochondrial membrane potential, or doxorubicin-induced G₂/M arrest. The combination of PEMF and doxorubicin altered a few signaling molecules. PEMF tended to reduce the doxorubicin-induced decrease of phosphorylated BAD, while reducing the increased expression of total IĸB and phosphorylated-CHK1 induced by doxorubicin.

CONCLUSION

Our results indicate that combination of PEMF and doxorubicin could be a novel chemotherapeutic strategy.

Pulsed Electromagnetic Field Regulates MicroRNA 21 Expression to Activate TGF-β Signaling in Human Bone Marrow Stromal Cells to Enhance Osteoblast Differentiation

Pulsed electromagnetic fields (PEMFs) have been documented to promote bone fracture healing in nonunions and increase lumbar spinal fusion rates. However, the molecular mechanisms by which PEMF stimulates differentiation of human bone marrow stromal cells (hBMSCs) into osteoblasts are not well understood. In this study the PEMF effects on hBMSCs were studied by microarray analysis. PEMF stimulation of hBMSCs' cell numbers mainly affected genes of cell cycle regulation, cell structure, and growth receptors or kinase pathways. In the differentiation and mineralization stages, PEMF regulated preosteoblast gene expression and notably, the transforming growth factor-beta (TGF-β) signaling pathway and microRNA 21 (miR21) were most highly regulated. PEMF stimulated activation of Smad2 and miR21-5p expression in differentiated osteoblasts, and TGF-β signaling was essential for PEMF stimulation of alkaline phosphatase mRNA expression. Smad7, an antagonist of the TGF-β signaling pathway, was found to be miR21-5p's putative target gene and PEMF caused a decrease in Smad7 expression. Expression of Runx2 was increased by PEMF treatment and the miR21-5p inhibitor prevented the PEMF stimulation of Runx2 expression in differentiating cells. Thus, PEMF could mediate its effects on bone metabolism by activation of the TGF-β signaling pathway and stimulation of expression of miR21-5p in hBMSCs.

Electrical control of calcium oscillations in mesenchymal stem cells using microsecond pulsed electric fields

BACKGROUND

Human mesenchymal stem cells are promising tools for regenerative medicine due to their ability to differentiate into many cellular types such as osteocytes, chondrocytes and adipocytes amongst many other cell types. These cells present spontaneous calcium oscillations implicating calcium channels and pumps of the plasma membrane and the endoplasmic reticulum. These oscillations regulate many basic functions in the cell such as proliferation and differentiation. Therefore, the possibility to mimic or regulate these oscillations might be useful to regulate mesenchymal stem cells biological functions.

METHODS

One or several electric pulses of 100 μs were used to induce Ca2+ spikes caused by the penetration of Ca2+ from the extracellular medium, through the transiently electropermeabilized plasma membrane, in human adipose mesenchymal stem cells from several donors. Attached cells were preloaded with Fluo-4 AM and exposed to the electric pulse(s) under the fluorescence microscope. Viability was also checked.

RESULTS

According to the pulse(s) electric field amplitude, it is possible to generate a supplementary calcium spike with properties close to those of calcium spontaneous oscillations, or, on the contrary, to inhibit the spontaneous calcium oscillations for a very long time compared to the pulse duration. Through that inhibition of the oscillations, Ca2+ oscillations of desired amplitude and frequency could then be imposed on the cells using subsequent electric pulses. None of the pulses used here, even those with the highest amplitude, caused a loss of cell viability.

CONCLUSIONS

An easy way to control Ca2+ oscillations in mesenchymal stem cells, through their cancellation or the addition of supplementary Ca2+ spikes, is reported here. Indeed, the direct link between the microsecond electric pulse(s) delivery and the occurrence/cancellation of cytosolic Ca2+ spikes allowed us to mimic and regulate the Ca2+ oscillations in these cells. Since microsecond electric pulse delivery constitutes a simple technology available in many laboratories, this new tool might be useful to further investigate the role of Ca2+ in human mesenchymal stem cells biological processes such as proliferation and differentiation.

Accelerated Bone Regeneration by Two-Photon Photoactivated Carbon Nitride Nanosheets

Human bone marrow-derived mesenchymal stem cells (hBMSCs) present promising opportunities for therapeutic medicine. Carbon derivatives showed only marginal enhancement in stem cell differentiation toward bone formation. Here we report that red-light absorbing carbon nitride (C₃N₄) sheets lead to remarkable proliferation and osteogenic differentiation by runt-related transcription factor 2 (Runx2) activation, a key transcription factor associated with osteoblast differentiation. Accordingly, highly effective hBMSCs-driven mice bone regeneration under red light is achieved (91% recovery after 4 weeks compared to 36% recovery in the standard control group in phosphate-buffered saline without red light). This fast bone regeneration is attributed to the deep penetration strength of red light into cellular membranes via tissue and the resulting efficient cell stimulation by enhanced photocurrent upon two-photon excitation of C₃N₄ sheets near cells. Given that the photoinduced charge transfer can increase cytosolic Ca²⁺ accumulation, this increase would promote nucleotide synthesis and cellular proliferation/differentiation. The cell stimulation enhances hBMSC differentiation toward bone formation, demonstrating the therapeutic potential of near-infrared two-photon absorption of C₃N₄ sheets in bone regeneration and fracture healing.

Mesenchymal stem cells as therapeutic target of biophysical stimulation for the treatment of musculoskeletal disorders

BACKGROUND

Musculoskeletal disorders are regarded as a major cause of worldwide morbidity and disability, and they result in huge costs for national health care systems. Traditional therapies frequently turned out to be poorly effective in treating bone, cartilage, and tendon disorders or joint degeneration. As a consequence, the development of novel biological therapies that can treat more effectively these conditions should be the highest priority in regenerative medicine. Mesenchymal stem cells (MSCs) represent one of the most promising tools in musculoskeletal tissue regenerative medicine, thanks to their proliferation and differentiation potential and their immunomodulatory and trophic ability. Indeed, MSC-based approaches have been proposed for the treatment of almost all orthopedic conditions, starting from different cell sources, alone or in combination with scaffolds and growth factors, and in one-step or two-step procedures. While all these approaches would require cell harvesting and transplantation, the possibility to stimulate the endogenous MSCs to enhance their tissue homeostasis activity represents a less-invasive and cost-effective therapeutic strategy. Nowadays, the role of tissue-specific resident stem cells as possible therapeutic target in degenerative pathologies is underinvestigated. Biophysical stimulations, and in particular extracorporeal shock waves treatment and pulsed electromagnetic fields, are able to induce proliferation and support differentiation of MSCs from different origins and affect their paracrine production of growth factors and cytokines.

SHORT CONCLUSIONS

The present review reports the attempts to exploit the resident stem cell potential in musculoskeletal pathologies, highlighting the role of MSCs as therapeutic target of currently applied biophysical treatments.

Electric pulses: a flexible tool to manipulate cytosolic calcium concentrations and generate spontaneous-like calcium oscillations in mesenchymal stem cells

Human adipose mesenchymal stem cells (haMSCs) are multipotent adult stem cells of great interest in regenerative medicine or oncology. They present spontaneous calcium oscillations related to cell cycle progression or differentiation but the correlation between these events is still unclear. Indeed, it is difficult to mimic haMSCs spontaneous calcium oscillations with chemical means. Pulsed electric fields (PEFs) can permeabilise plasma and/or organelles membranes depending on the applied pulses and therefore generate cytosolic calcium peaks by recruiting calcium from the external medium or from internal stores. We show that it is possible to mimic haMSCs spontaneous calcium oscillations (same amplitude, duration and shape) using 100 μs PEFs or 10 ns PEFs. We propose a model that explains the experimental situations reported. PEFs can therefore be a flexible tool to manipulate cytosolic calcium concentrations. This tool, that can be switched on and off instantaneously, contrary to chemicals agents, can be very useful to investigate the role of calcium oscillations in cell physiology and/or to manipulate cell fate.

Weak electromagnetic fields alter Ca(2+) handling and protect against hypoxia-mediated damage in primary newborn rat myotube cultures

Weak electromagnetic fields (WEF) enhance Ca(2+) entry into cells via voltage-gated Ca(2+) channels and affect various aspects of metabolism, structure, and function. However, little information is available on the effect of WEF on skeletal muscle, which depends primarily on intracellular Ca(2+) stores for function and metabolism. Here, we examine the effects of 30 min exposure of rat primary myotube cultures to WEF (1.75 μT, 16 Hz) on Ca(2+) handling and creatine kinase (CK) release. Free myoplasmic Ca(2+) concentration ([Ca(2+) i]) was measured with the ratiometric dye indo-1. WEF did not affect basal [Ca(2+)]i but decreased the twitch [Ca(2+)]i transient in a time-dependent manner, and the twitch amplitude was decreased to ∼30 % after 30 min. WEF completely abolished the increase in [Ca(2+)]i induced by potassium chloride (∼60 mM) but had no effect on the increase induced by caffeine (∼6 mM). Hypoxia (2 h exposure to 100 % argon) resulted in a marked loss of CK into the medium (400 % of normoxic value), as well as a rapid (within 20 min) and sustained increase in basal [Ca(2+)]i (∼20 % above baseline). However, during exposure to WEF, basal [Ca(2+)]i remained constant during the initial 60 min of hypoxia and, thereafter, increased to levels similar to those observed in the absence of WEF. Finally, WEF blocked about 80 % of hypoxia-mediated CK release (P < 0.05). These data demonstrate that WEF inhibits increases in [Ca(2+)]i by interfering with muscle excitation and protects against muscle damage induced by hypoxia. Thus, WEF may have therapeutic/protective effects on skeletal muscle.