Single-pulsed electromagnetic field therapy increases osteogenic differentiation through Wnt signaling pathway and sclerostin downregulation: SPEMF Enhance Bone Growth by Wnt/Sost Control

CTGF Promotes the Osteoblast Differentiation of Human Periodontal Ligament Stem Cells by Positively Regulating BMP2/Smad Signal Transduction

Objective

This work is aimed at revealing the role and the molecular mechanism of connective tissue growth factor 2 (CTGF) in the osteoblast differentiation of periodontal ligament stem cells (PDLSCs).

Methods

The osteogenic differentiation of PDLSCs was induced by osteogenic induction medium (OM), and the expression level of osteogenic related proteins ALP, RUNX2, OCN, and CTGF was estimated using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting analysis. We constructed cell lines with CTGF overexpression or knockdown to verify the role of CTGF in the osteoblast differentiation of PDLSCs. Alkaline phosphatase (ALP) staining was introduced to measure the osteoblasts activity, and alizarin red S (ARS) staining was employed to test matrix mineralization. The interaction between CTGF and bone morphogenetic protein-2 (BMP-2) was determined by endogenous coimmunoprecipitation (Co-IP).

Results

The expression level of CTGF was increased during the osteogenic induction of PDLSCs. Additionally, CTGF overexpression effectively maintained the stemness and facilitated the osteoblast differentiation in PDLSCs, and CTGF knockdown exerted opposite effects. Moreover, at molecular mechanism, CTGF increased the activity of BMP-2/Smad signaling pathway.

Conclusion

This investigation verified that CTGF promotes the osteoblast differentiation in PDLSCs at least partly by activating BMP-2/Smad cascade signal.

Pulsed electromagnetic fields inhibit mandibular bone deterioration depending on the Wnt3a/β-catenin signaling activation in type 2 diabetic db/db mice

Type 2 diabetes mellitus (T2DM) patients have compromised mandibular bone architecture/quality, which markedly increase the risks of tooth loosening, tooth loss, and failure of dental implantation. However, it remains lacks effective and safe countermeasures against T2DM-related mandibular bone deterioration. Herein, we studied the effects of pulsed electromagnetic fields (PEMF) on mandibular bone microstructure/quality and relevant regulatory mechanisms in T2DM db/db mice. PEMF exposure (20 Gs, 15 Hz) for 12 weeks preserved trabecular bone architecture, increased cortical bone thickness, improved material properties and stimulated bone anabolism in mandibles of db/db mice. PEMF also upregulated the expression of canonical Wnt3a ligand (but not Wnt1 or Wnt5a) and its downstream β-catenin. PEMF improved the viability and differentiation of primary osteoblasts isolated from the db/db mouse mandible, and stimulated the specific activation of Wnt3a/β-catenin signaling. These positive effects of PEMF on mandibular osteoblasts of db/db mice were almost totally abolished after Wnt3a silencing in vitro, which were equivalent to the effects following blockade of canonical Wnt signaling using the broad-spectrum antagonist DKK1. Injection with Wnt3a siRNA abrogated the therapeutic effects of PEMF on mandibular bone quantity/quality and bone anabolism in db/db mice. Our study indicates that PEMF might become a non-invasive and safe treatment alternative resisting mandibular bone deterioration in T2DM patients, which is helpful for protecting teeth from loosening/loss and securing the dental implant stability.

Pulsed Electromagnetic Field Stimulation in Osteogenesis and Chondrogenesis: Signaling Pathways and Therapeutic Implications

Mesenchymal stem cells (MSCs) are the main cell players in tissue repair and thanks to their self-renewal and multi-lineage differentiation capabilities, they gained significant attention as cell source for tissue engineering (TE) approaches aimed at restoring bone and cartilage defects. Despite significant progress, their therapeutic application remains debated: the TE construct often fails to completely restore the biomechanical properties of the native tissue, leading to poor clinical outcomes in the long term. Pulsed electromagnetic fields (PEMFs) are currently used as a safe and non-invasive treatment to enhance bone healing and to provide joint protection. PEMFs enhance both osteogenic and chondrogenic differentiation of MSCs. Here, we provide extensive review of the signaling pathways modulated by PEMFs during MSCs osteogenic and chondrogenic differentiation. Particular attention has been given to the PEMF-mediated activation of the adenosine signaling and their regulation of the inflammatory response as key player in TE approaches. Overall, the application of PEMFs in tissue repair is foreseen: (1) in vitro: to improve the functional and mechanical properties of the engineered construct; (2) in vivo: (i) to favor graft integration, (ii) to control the local inflammatory response, and (iii) to foster tissue repair from both implanted and resident MSCs cells.

Electromagnetic radiation: a new charming actor in hematopoiesis?

INTRODUCTION

Electromagnetic waves play indispensable roles in life. Many studies addressed the outcomes of Electromagnetic field (EMF) on various biological functions such as cell proliferation, gene expression, epigenetic alterations, genotoxic, and carcinogenic effects, and its therapeutic applications in medicine. The impact of EMF on bone marrow (BM) is of high importance; however, EMF effects on BM hematopoiesis are not well understood.

AREAS COVERED

Publications in English were searched in ISI Web of Knowledge and Google Scholar with no restriction on publication date. A literature review has been conducted on the consequences of EMF exposure on BM non-hematopoietic stem cells, mesenchymal stem cells, and the application of these waves in regenerative medicine. Human blood cells such as lymphocytes, red blood cells and their precursors are altered qualitatively and quantitatively following electromagnetic radiation. Therefore, studying the impact of EMF on related signaling pathways in hematopoiesis and hematopoietic stem cell (HSC) differentiation could give a better insight into its efficacy on hematopoiesis and its potential therapeutic usage.

EXPERT OPINION

In this review, authors evaluated the possible biologic consequences of EMF on the hematopoiesis process in addition to its probable application in the treatment of hematologic disorders.

Pulsed Electromagnetic Field Stimulation of Bone Healing and Joint Preservation: Cellular Mechanisms of Skeletal Response

The US FDA has approved pulsed electromagnetic fields (PEMFs) as a safe and effective treatment for nonunions of bone. Despite its clinical use, the mechanisms of action of electromagnetic stimulation of the skeleton have been elusive. Recently, cell membrane receptors have been identified as the site of action of PEMF and provide a mechanistic rationale for clinical use. This review highlights key processes in cell responses to PEMF as follows: (1) signal transduction through A_2A and A₃ adenosine cell membrane receptors and (2) dose-response effects on the synthesis of structural and signaling extracellular matrix (ECM) components. Through these actions, PEMF can increase the structural integrity of bone and cartilage ECM, enhancing repair, and alter the homeostatic balance of signaling cytokines, producing anti-inflammatory effects. PEMFs exert a proanabolic effect on the bone and cartilage matrix and a chondroprotective effect counteracting the catabolic effects of inflammation in the joint environment. Understanding of PEMF membrane targets, and of the specific intracellular pathways involved, culminating in the synthesis of ECM proteins and reduction in inflammatory cytokines, should enhance confidence in the clinical use of PEMF and the identification of clinical conditions likely to be affected by PEMF exposure.

Pulsed electromagnetic fields modify the adverse effects of glucocorticoids on bone architecture, bone strength and porous implant osseointegration by rescuing bone-anabolic actions

Long-term glucocorticoid therapy is known to induce increased bone fragility and impaired skeletal regeneration potential. Growing evidence suggests that pulsed electromagnetic fields (PEMF) can accelerate fracture healing and increase bone mass both experimentally and clinically. However, how glucocorticoid-treated bone and bone cells respond to PEMF stimulation remains poorly understood. Here we tested the effects of PEMF on bone quantity/quality, bone metabolism, and porous implant osseointegration in rabbits treated with dexamethasone (0.5 mg/kg/day, 6 weeks). The micro-CT, histologic and nanoindentation results showed that PEMF ameliorated the glucocorticoid-mediated deterioration of cancellous and cortical bone architecture and intrinsic material properties. Utilizing the new porous titanium implant (Ti2448) with low toxicity and low elastic modulus, we found that PEMF stimulated bone ingrowth into the pores of implants and enhanced peri-implant bone material quality during osseous defect repair in glucocorticoid-treated rabbits. Dynamic histomorphometric results revealed that PEMF reversed the adverse effects of glucocorticoids on bone formation, which was confirmed by increased circulating osteocalcin and P1NP. PEMF also significantly attenuated osteocyte apoptosis, promoted osteoblast-related osteocalcin, Runx2 and Osx expression, and inhibited osteocyte-specific DKK1 and Sost expression (negative regulators of osteoblasts) in glucocorticoid-treated skeletons, revealing improved functional activities of osteoblasts and osteocytes. Nevertheless, PEMF exerted no effect on circulating bone-resorbing cytokines (serum TRAcP5b and CTX-1) or skeletal gene expression of osteoclast-specific markers (TRAP and cathepsin K). PEMF also significantly upregulated skeletal gene expression of canonical Wnt ligands (Wnt1, Wnt3a and Wnt10b), whereas PEMF did not alter non-canonical Wnt5a expression. This study demonstrates that PEMF treatment improves bone mass, strength and porous implant osseointegration in glucocorticoid-treated rabbits by promoting potent bone-anabolic action, which is associated with canonical Wnt-mediated improvement in osteoblast and osteocyte functions. This study provides a new treatment alternative for glucocorticoid-related bone disorders in a convenient and non-invasive manner.

Bone Morphogenetic Protein-2 Signaling in the Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells Induced by Pulsed Electromagnetic Fields

Pulsed electromagnetic fields (PEMFs) are clinically used with beneficial effects in the treatment of bone fracture healing. This is due to PEMF ability to favor the osteogenic differentiation of mesenchymal stem cells (MSCs). Previous studies suggest that PEMFs enhance the osteogenic activity of bone morphogenetic protein-2 (BMP2) which is used in various therapeutic interventions. This study investigated the molecular events associated to the synergistic activity of PEMFs and BMP2 on osteogenic differentiation. To this aim, human MSCs (hMSCs) were exposed to PEMFs (75 Hz, 1.5 mT) in combination with BMP2, upon detection of the minimal dose able to induce differentiation. Changes in the expression of BMP signaling pathway genes including receptors and ligands, as well as in the phosphorylation of BMP downstream signaling proteins, such as SMAD1/5/8 and MAPK, were analyzed. Results showed the synergistic activity of PEMFs and BMP2 on osteogenic differentiation transcription factors and markers. The PEMF effects were associated to the increase in BMP2, BMP6, and BMP type I receptor gene expression, as well as SMAD1/5/8 and p38 MAPK activation. These results increase knowledge concerning the molecular events involved in PEMF stimulation showing that PEMFs favor hMSCs osteogenic differentiation by the modulation of BMP signaling components.

A single-pulsed electromagnetic field enhances collagen synthesis in tendon cells

Tendinopathy is a progressive pathology of tendon that is characteristic of imbalance between matrix synthesis and degeneration and is often caused by failure to adapt to mechanical loading. Non-steroidal anti-inflammatory medications (NSAIDS) are used as a conventional treatment to alleviate pain and swelling in the short term, but the ideal treatment for tendinopathy remains unclear. Here, we show a single pulsed electromagnetic field (SPEMF, 0.2 Hz) that up-regulated tenogenic gene expression (Col1a1, Col3a1, Scx, Dcn) and down-regulated inflammatory gene expression (Mmp1) in vitro. After five days of SPEMF stimulation (3 min/day), the collagen type I and total collagen synthesis protein levels were significantly increased. Under pro-inflammatory cytokine (IL-1β) irritation, the decreased expression of Col1a1/Col3a1 was up-regulated by SPEMF treatment, and the increased expression of Mmp1 was also reversed. From the above, it can be inferred that SPEMF that enhances matrix synthesis and reduces matrix degeneration may counteract the imbalance in tendinopathy. SPEMF application may be developed as a potential future strategy for therapeutic intervention in tendon disorders.

Translational Insights into Extremely Low Frequency Pulsed Electromagnetic Fields (ELF-PEMFs) for Bone Regeneration after Trauma and Orthopedic Surgery

The finding that alterations in electrical potential play an important role in the mechanical stimulation of the bone provoked hype that noninvasive extremely low frequency pulsed electromagnetic fields (ELF-PEMF) can be used to support healing of bone and osteochondral defects. This resulted in the development of many ELF-PEMF devices for clinical use. Due to the resulting diversity of the ELF-PEMF characteristics regarding treatment regimen, and reported results, exposure to ELF-PEMFs is generally not among the guidelines to treat bone and osteochondral defects. Notwithstanding, here we show that there is strong evidence for ELF-PEMF treatment. We give a short, confined overview of in vitro studies investigating effects of ELF-PEMF treatment on bone cells, highlighting likely mechanisms. Subsequently, we summarize prospective and blinded studies, investigating the effect of ELF-PEMF treatment on acute bone fractures and bone fracture non-unions, osteotomies, spinal fusion, osteoporosis, and osteoarthritis. Although these studies favor the use of ELF-PEMF treatment, they likewise demonstrate the need for more defined and better controlled/monitored treatment modalities. However, to establish indication-oriented treatment regimen, profound knowledge of the underlying mechanisms in the sense of cellular pathways/events triggered is required, highlighting the need for more systematic studies to unravel optimal treatment conditions.

SHED-derived conditioned exosomes enhance the osteogenic differentiation of PDLSCs via Wnt and BMP signaling in vitro

The exosomes from human exfoliated deciduous teeth (SHED-Exos) have exhibited potential therapeutic role in dental and oral disorders. The biological effects of exosomes largely depend on cellular origin and physiological status of donor cell. In the present study, we explored the influence of conditioned exosomes from SHED with osteogenic induction on periodontal ligament stem cells (PDLSCs) in vitro. Conditioned SHED-Exos from a 3-day osteogenic supernatant were applied during PDLSCs osteogenic differentiation. We found that conditioned SHED-Exos had no cytotoxicity on PDLSCs viability assessed by CCK-8 assay. These SHED-Exos promoted PDLSCs osteogenic differentiation with deep Alizarin red staining, high alkaline phosphatase (ALP) activity and upregulated osteogenic gene expression (RUNX2, OPN and OCN). We further found BMP/Smad signaling and Wnt/β-catenin were activated by enhanced Smad1/5/8 phosphorylation and increased nuclear β-catenin protein expression. Inhibiting these two signaling pathways with specific inhibitors (cardamonin and LDN193189) remarkably weakened the enhanced osteogenic differentiation. Furthermore, Wnt3a and BMP2 were upregulated in SHED and SHED-Exos. Silencing Wnt3a and BMP2 in SHED-Exos partially counteracts the enhanced osteogenic differentiation. Our findings indicate that conditioned SHED-Exos-enhanced PDLSCs osteogenic differentiation was partly due to its carrying Wnt3a and BMP2. These data provide new insights into the use of SHED-Exos in periodontitis-induced bone defects therapy.

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.

Enhanced osteogenesis of bone marrow stem cells cultured on hydroxyapatite/collagen I scaffold in the presence of low-frequency magnetic field

As a non-invasive biophysical therapy, electromagnetic fields (EMF) have been widely used to promote the healing of fractures. In the present study, hydroxyapatite/collagen I (HAC) loaded with rabbit bone marrow mesenchymal stem cells (MSCs) were cultured in a dynamic perfusion bioreactor and exposed to EMF of 15 Hz/1mT. Osteogenic differentiation of the seeded cells was analyzed through the evaluation of ALP activity and osteogenesis-related genes expression in vitro. The in vivo osteogenesis efficacy of the cell laden HAC constructs treated with/without EMF was evaluated through a rabbit femur condyle defect model. The results showed that EMF of 15 Hz/1mT could enhance the osteogenic differentiation of the cells seeded on HAC scaffold. Furthermore, the in vivo experiments demonstrated that EMF exposure could promote bone regeneration within the defect and bone integration between the graft and host bone. Taking together, the MSCs seeded HAC scaffold combined with EMF exposure could be a promising approach for bone tissue engineering.

Sinusoidal Electromagnetic Fields Increase Peak Bone Mass in Rats by Activating Wnt10b/β-Catenin in Primary Cilia of Osteoblasts

Extremely low-frequency electromagnetic fields have been considered a potential candidate for the prevention and treatment of osteoporosis; however, their action mechanism and optimal magnetic flux density (intensity) parameter are still elusive. The present study found that 50-Hz sinusoidal electromagnetic fields (SEMFs) at 1.8 mT increased the peak bone mass of young rats by increasing bone formation. Gene array expression studies with femoral bone samples showed that SEMFs increased the expression levels of collagen-1α1 and Wnt10b, a critical ligand of the osteogenic Wnt/β-catenin pathway. Consistently, SEMFs promoted osteogenic differentiation and maturation of rat calvarial osteoblasts (ROBs) in vitro through activating the Wnt10b/β-catenin pathway. This osteogenesis-promoting effect of SEMFs via Wnt10b/β-catenin signaling was found to depend on the functional integrity of primary cilia in osteoblasts. When the primary cilia were abrogated by small interfering RNA (siRNA) targeting IFT88, the ability of SEMFs to promote the osteogenic differentiation of ROBs through activating Wnt10b/β-catenin signaling was blocked. Although the knockdown of Wnt10b expression with RNA interference had no effect on primary cilia, it significantly suppressed the promoting effect of SEMFs on osteoblastic differentiation/maturation. Wnt10b was normally localized at the bases of primary cilia, but it disappeared (or was released) from the cilia upon SEMF treatment. Interestingly, primary cilia were elongated to different degrees by different intensities of 50-Hz SEMFs, with the window effect observed at 1.8 mT, and the expression level of Wnt10b increased in accord with the lengths of primary cilia. These results indicate that 50-Hz 1.8-mT SEMFs increase the peak bone mass of growing rats by promoting osteogenic differentiation/maturation of osteoblasts, which is mediated, at least in part, by Wnt10b at the primary cilia and the subsequent activation of Wnt/β-catenin signaling. © 2019 American Society for Bone and Mineral Research.

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.

Pulsed electromagnetic fields modulate bone metabolism via RANKL/OPG and Wnt/β-catenin pathways in women with postmenopausal osteoporosis: A pilot study

Pulsed electromagnetic fields (PEMFs) have been proven to enhance in vitro and in vivo osteogenesis with unknown mechanism. Aim of our study was to explore whether RANKL/OPG and Wnt/β-Catenin pathways could be involved in bone response to PEMFs in a setting of postmenopausal osteoporotic women. Forty-three women (mean age 62.8 ± 4.5 yr.) were randomized into two groups. The PEMFs group received PEMFs treatment (50 min treatment session/day, 6 treatment sessions/week, for a total of 25 times), by wearing a specific gilet applied to the trunk and connected to the electromagnetic device (Biosalus, by HSD Srl, Serravalle RSM), while women assigned to control group received sham PEMFs with the same device. BSAP as bone formation and CTX as bone resorption markers, RANKL, OPG, β-Catenin, DKK-1 and sclerostin were obtained at baseline, after 30 and 60 days. In PEMFs group, BSAP levels significantly increased after 30 and 60 days while CTX concentrations decreased at day 60. RANKL levels significantly decreased after 60 days. OPG was not significantly changed, but the RANKL/OPG ratio significantly decreased at day 30. DKK-1 levels decreased, while β-catenin concentrations increased after 30 and 60 days (P < 0.05). No significant changes of calcium, phosphorus, creatinine and sclerostin were detected. In the PEMFs group, at day 30, Δsclerostin was associated with ΔRANKL/OPG ratio (r = -0.5, P = 0.03) and ΔDKK-1 was associated with Δβ-Catenin (r = -0.47, P = 0.02). In women with postmenopausal osteoporosis, our data provide evidence of a PEMFs modulation of RANKL/OPG and Wnt/β-Catenin signaling pathways able to explain the metabolic effects of PEMFs on bone.

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.

Emerging Strategies for Stem Cell Lineage Commitment in Tissue Engineering and Regenerative Medicine

Stem cells have transformed the fields of tissue engineering and regenerative medicine, and their potential to further advance these fields cannot be overstated. The stem cell niche is a dynamic microenvironment that determines cell fate during development and tissue repair following an injury. Classically, stem cells were studied in isolation of their microenvironment; however, contemporary research has produced a myriad of evidence that shows the importance of multiple aspects of the stem cell niche in regulating their processes. In the context of tissue engineering and regenerative medicine studies, the niche is an artificial environment provided by culture conditions. In vitro culture conditions may involve coculturing with other cell types, developing specific biomaterials, and applying relevant forces to promote the desired lineage commitment. Considerable advance has been made over the past few years toward directed stem cell differentiation; however, the unspecific differentiation of stem cells yielding a mixed population of cells has been a challenge. In this review, we provide a systematic review of the emerging strategies used for lineage commitment within the context of tissue engineering and regenerative medicine. These strategies include scaffold pore-size and pore-shape gradients, stress relaxation, sonic and electromagnetic effects, and magnetic forces. Finally, we provide insights and perspectives into future directions focusing on signaling pathways activated during lineage commitment using external stimuli.

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.

Physical stimulation and scaffold composition efficiently support osteogenic differentiation of mesenchymal stem cells

BACKGROUND

Despite significant achievements in the field of tissue engineering, simplification and improvement of the existing protocols are of great importance. The use of complex differentiation media, due to the presence of multiple factors, may have some undesired effects on cell health and functions. Thus, minimizing the number of involved factors, while maintaining the differentiation efficiency, provides less costly and controllable conditions. Adipose-derived Mesenchymal stem cells (ASCs), the adult stem cells present in adipose tissue, can be a suitable source of stem cells due to abundant and ease of access. The aim of this study is to optimize the osteogenic differentiation of ASCs by chemical composition of scaffold, in the first step, and then by electromagnetic treatments.

METHODS

ASCs were cultured on PVA/PES scaffold and tissue culture polystyrene surfaces (TCPS) and osteogenic differentiation was performed with either osteogenic medium, or electromagnetic field or both. The impact of each treatment on ASCs growth and proliferation was measured by MTT assay. Changes in gene expression levels of osteogenic-specific markers including ALP and RUNX2 were determined by Real Time PCR. Furthermore, alkaline phosphatase activity and calcium deposition were measured.

RESULTS

The MTT assay showed the significant effects on cell growth and respiration in scaffold-seeded ASCs treated with electromagnetic field, compared to control TCPS plate. Also, the electromagnetic treatment, increased alkaline phosphatase activity and calcium deposition. Finally, Real Time PCR showed higher expression of ALP and RUNX2 genes in electromagnetic field groups compared to control groups.

CONCLUSION

It can be concluded that PVA/PES scaffold used in this study improved the osteogenic capacity of ASCs. Moreover, the osteogenic potential of ASCs seeded on PVA/PES scaffold could be augmented by electromagnetic field without any chemical stimulation.

Notch pathway is active during osteogenic differentiation of human bone marrow mesenchymal stem cells induced by pulsed electromagnetic fields

Pulsed electromagnetic fields (PEMFs) have been used to treat bone diseases, particularly nonunion healing. Although it is known that PEMFs promote the osteogenic differentiation of human mesenchymal stem cells (hMSCs), to date PEMF molecular mechanisms remain not clearly elucidated. The Notch signalling is a highly conserved pathway that regulates cell fate decisions and skeletal development. The aim of this study was to investigate if the known PEMF-induced osteogenic effects may involve the modulation of the Notch pathway. To this purpose, during in vitro osteogenic differentiation of bone marrow hMSCs in the absence and in the presence of PEMFs, osteogenic markers (alkaline phosphatase activity, osteocalcin and matrix mineralization), the messenger ribonucleic acid expression of osteogenic transcription factors (Runx2, Dlx5, Osterix) as well as of Notch receptors (Notch1-4), their ligands (Jagged1, Dll1 and Dll4) and nuclear target genes (Hes1, Hes5, Hey1, Hey2) were investigated. PEMFs stimulated all osteogenic markers and increased the expression of Notch4, Dll4, Hey1, Hes1 and Hes5 in osteogenic medium compared to control. In the presence of DAPT and SAHM1, used as Notch pathway inhibitors, the expression of the osteogenic markers, including Runx2, Dlx5, Osterix, as well as Hes1 and Hes5 were significantly inhibited, both in unexposed and PEMF-exposed hMSCs. These results suggest that activation of Notch pathway is required for PEMFs-stimulated osteogenic differentiation. These new findings may be useful to improve autologous cell-based regeneration of bone defects in orthopaedics.

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.

Electromagnetic Fields and Stem Cell Fate: When Physics Meets Biology

Controlling stem cell (SC) fate is an extremely important topic in the realm of SC research. A variety of different external cues mainly mechanical, chemical, or electrical stimulations individually or in combination have been incorporated to control SC fate. Here, we will deconstruct the probable relationship between the functioning of electromagnetic (EMF) and SC fate of a variety of different SCs. The electromagnetic (EM) nature of the cells is discussed with the emphasis on the effects of EMF on the determinant factors that directly and/or indirectly influence cell fate. Based on the EM effects on a variety of cellular processes, it is believed that EMFs can be engineered to provide a controlled signal with the highest impact on the SC fate decision. Considering the novelty and broad applications of applying EMFs to change SC fate, it is necessary to shed light on many unclear mechanisms underlying this phenomenon.