Pulsed electromagnetic fields preserve bone architecture and mechanical properties and stimulate porous implant osseointegration by promoting bone anabolism in type 1 diabetic rabbits

Insulin-like growth factor 1 and sex hormones for assessment of anthropometric and pubertal growth of Egyptian children and adolescents with type 1 diabetes mellitus (single center study)

BACKGROUND

This study aimed to assess the anthropometric measures and pubertal growth of children and adolescents with Type 1 diabetes mellitus (T1DM) and to detect risk determinants affecting these measures and their link to glycemic control.

PATIENTS AND METHODS

Two hundred children and adolescents were assessed using anthropometric measurements. Those with short stature were further evaluated using insulin-like growth factor 1 (IGF-1), bone age, and thyroid profile, while those with delayed puberty were evaluated using sex hormones and pituitary gonadotropins assay.

RESULTS

We found that 12.5% of our patients were short (height SDS < -2) and IGF-1 was less than -2 SD in 72% of them. Patients with short stature had earlier age of onset of diabetes, longer duration of diabetes, higher HbA1C and urinary albumin/creatinine ratio compared to those with normal stature (p < 0.05). Additionally, patients with delayed puberty had higher HbA1c and dyslipidemia compared to those with normal puberty (p < 0.05). The regression analysis revealed that factors associated with short stature were; age at diagnosis, HbA1C > 8.2, and albumin/creatinine ratio > 8 (p < 0.05).

CONCLUSION

Children with uncontrolled T1DM are at risk of short stature and delayed puberty. Diabetes duration and control seem to be independent risk factors for short stature.

Recent progress in bone-repair strategies in diabetic conditions

Bone regeneration following trauma, tumor resection, infection, or congenital disease is challenging. Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia. It can result in complications affecting multiple systems including the musculoskeletal system. The increased number of diabetes-related fractures poses a great challenge to clinical specialties, particularly orthopedics and dentistry. Various pathological factors underlying DM may directly impair the process of bone regeneration, leading to delayed or even non-union of fractures. This review summarizes the mechanisms by which DM hampers bone regeneration, including immune abnormalities, inflammation, reactive oxygen species (ROS) accumulation, vascular system damage, insulin/insulin-like growth factor (IGF) deficiency, hyperglycemia, and the production of advanced glycation end products (AGEs). Based on published data, it also summarizes bone repair strategies in diabetic conditions, which include immune regulation, inhibition of inflammation, reduction of oxidative stress, promotion of angiogenesis, restoration of stem cell mobilization, and promotion of osteogenic differentiation, in addition to the challenges and future prospects of such approaches.

A novel nonsurgical therapy for peri-implantitis using focused pulsed electromagnetic field: A pilot randomized double-blind controlled clinical trial

Pulsed electromagnetic field (PEMF) therapy modulates the immune response and is successfully used in orthopedics to treat osteoarthritis and improve bone regeneration. This may suggest that this treatment may consequently reduce peri-implant soft tissue inflammation and marginal bone loss. To compare clinical, radiographic, and immunological results following nonsurgical treatment for peri-implantitis with or without PEMF therapy. Patients with peri-implantitis were included: pocket probing depth (PPD) between 6 and 8 mm with bleeding on probing (BOP); crestal bone loss between 3 and 5 mm. A novel healing abutment that contained active (test) or inactive (control) PEMF was connected. PEMF was administered via the abutment at exposure ratio of 1/500-1/5000, intensity: 0.05-0.5 mT, frequency: 10-50 kHz for 30 days. Nonsurgical mechanical implant surface debridement was performed. Patients were examined at baseline, 1 and 3 months. Clinical assessment included: plaque index, BOP, PPD, recession, and bone crest level which was radiography measured. Samples of peri-implant crevicular fluid were taken to analyze interleukin-1β (IL-1β). Twenty-three patients (34 implants; 19 control, 15 test) were included. At the follow-up, mean crestal bone loss was lower in the test group at 1 and 3 months (2.48 mm vs. 3.73 mm, p < 0.05 and 2.39 vs. 3.37, p < 0.01). IL-1β levels were also lower in the test group at 2 weeks (72.86 pg/mL vs. 111.7, p < 0.05). Within all the limitation of this preliminary study, the test group improved clinical parameters after a short-term period compared to the control group.

Advanced surface engineering of titanium materials for biomedical applications: From static modification to dynamic responsive regulation

Titanium (Ti) and its alloys have been widely used as orthopedic implants, because of their favorable mechanical properties, corrosion resistance and biocompatibility. Despite their significant success in various clinical applications, the probability of failure, degradation and revision is undesirably high, especially for the patients with low bone density, insufficient quantity of bone or osteoporosis, which renders the studies on surface modification of Ti still active to further improve clinical results. It is discerned that surface physicochemical properties directly influence and even control the dynamic interaction that subsequently determines the success or rejection of orthopedic implants. Therefore, it is crucial to endow bulk materials with specific surface properties of high bioactivity that can be performed by surface modification to realize the osseointegration. This article first reviews surface characteristics of Ti materials and various conventional surface modification techniques involving mechanical, physical and chemical treatments based on the formation mechanism of the modified coatings. Such conventional methods are able to improve bioactivity of Ti implants, but the surfaces with static state cannot respond to the dynamic biological cascades from the living cells and tissues. Hence, beyond traditional static design, dynamic responsive avenues are then emerging. The dynamic stimuli sources for surface functionalization can originate from environmental triggers or physiological triggers. In short, this review surveys recent developments in the surface engineering of Ti materials, with a specific emphasis on advances in static to dynamic functionality, which provides perspectives for improving bioactivity and biocompatibility of Ti implants.

The role of wnt signaling in diabetes-induced osteoporosis

Osteoporosis, a chronic complication of diabetes mellitus, is characterized by a reduction in bone mass, destruction of bone microarchitecture, decreased bone strength, and increased bone fragility. Because of its insidious onset, osteoporosis renders patients highly susceptible to pathological fractures, leading to increased disability and mortality rates. However, the specific pathogenesis of osteoporosis induced by chronic hyperglycemia has not yet been fully elucidated. But it is currently known that the disruption of Wnt signaling triggered by chronic hyperglycemia is involved in the pathogenesis of diabetic osteoporosis. There are two main types of Wnt signaling pathways, the canonical Wnt signaling pathway (β-catenin-dependent) and the non-canonical Wnt signaling pathway (non-β-catenin-dependent), both of which play an important role in regulating the balance between bone formation and bone resorption. Therefore, this review systematically describes the effects of abnormal Wnt pathway signaling on bone homeostasis under hyperglycemia, hoping to reveal the relationship between Wnt signaling and diabetic osteoporosis to further improve understanding of this disease.

Electric/Magnetic Intervention for Bone Regeneration: A Systematic Review and Network Meta-Analysis

Electric/magnetic material or field is a promising strategy for bone regeneration. The aim of this systematic review and network meta-analysis was to analyze the evidence regarding the efficacy of electric and magnetic intervention for bone regeneration and provide directions for further research. A comprehensive search was performed to identify the rats/rabbits/mice research that involved the electric/magnetic treatment with quantitative radiographic assessment of bone formation. Network meta-analyses were also conducted to assess different interventions and outcomes for osteogenesis. In total, there were 51 articles included in the systematic review and 19 articles in the network meta-analyses. The majority used microcomputerized tomography bone volume/tissue volume (BV/TV) to evaluate outcomes in rats. Results showed that placing electric/magnetic materials in situ had more prominent effects than the electric/magnetic field on bone regeneration. For all species, electrical materials with zeta potential of -53 mV proved to be the most effective in increasing BV (mean difference [MD]: 4.20 mm³, 95% confidence interval [CI]: [1.72-6.68]) and bone mineral density (MD: 312 mg/cm³, 95% CI: [172.43-451.57]). Magnetic materials with external magnetic fields topped in BV/TV (MD: 43%, 95% CI: [36.04-49.96]). It also led in trabecular number (MD: 2.00 mm^-1, 95% CI: [1.45-2.55]), trabecular thickness (MD: 61.00 μm, 95% CI: [44.31- 77.69]), and trabecular separation (MD: -0.40 mm, 95% CI: [-0.56 to -0.24]) on the condition of lacking electric materials. Biomaterials implantation is the most effective method for stimulating osteogenesis in rats, especially in electrical materials with negative charge. The combination of diverse interventions shows promising effects but needs further research, so does the underlying mechanism. Impact Statement Bone defect, especially for the large defect from aging, trauma, or pathology, which cannot be completely healed, remains a clinical challenge. Mimicking physical microenvironment has emerged as a new strategy for tissue regeneration. Electric and magnetic material and field used as the physical stimulation for bone regeneration have attracted interest due to their potential and facile application in clinic. This article reviewed related animal studies and carried out a network meta-analysis to thoroughly understand how electric and magnetic interventions impacted on tissues and created an osteogenic microenvironment.

Bone Deterioration in Response to Chronic High-Altitude Hypoxia Is Attenuated by a Pulsed Electromagnetic Field Via the Primary Cilium/HIF-1α Axis

Chronic high-altitude hypoxia induces irreversible abnormalities in various organisms. Emerging evidence indicates that hypobaric hypoxia markedly suppresses bone mass and bone strength. However, few effective means have been identified to prevent such bone deficits. Here, we assessed the potential of pulsed electromagnetic fields (PEMFs) to noninvasively resist bone deterioration induced by hypobaric hypoxia. We observed that exogenous PEMF treatment at 15 Hz and 20 Gauss (Gs) improved the cancellous and cortical bone mass, bone microstructure, and skeletal mechano-properties in rats subjected to chronic exposure of hypobaric hypoxia simulating an altitude of 4500 m for 6 weeks by primarily modulating osteoblasts and osteoblast-mediated bone-forming activity. Moreover, our results showed that whereas PEMF stimulated the functional activity of primary osteoblasts in hypoxic culture in vitro, it had negligible effects on osteoclasts and osteocytes exposed to hypoxia. Mechanistically, the primary cilium was found to function as the major electromagnetic sensor in osteoblasts exposed to hypoxia. The polycystins PC-1/PC-2 complex was identified as the primary calcium channel in the primary cilium of hypoxia-exposed osteoblastic cells responsible for the detection of external PEMF signals, and thereby translated these biophysical signals into intracellular biochemical events involving significant increase in the intracellular soluble adenylyl cyclase (sAC) expression and subsequent elevation of cyclic adenosine monophosphate (cAMP) concentration. The second messenger cAMP inhibited the transcription of oxygen homeostasis-related hypoxia-inducible factor 1-alpha (HIF-1α), and thus enhanced osteoblast differentiation and improved bone phenotype. Overall, the present study not only advances our understanding of bone physiology at high altitudes, but more importantly, proposes effective means to ameliorate high altitude-induced bone loss in a noninvasive and cost-effective manner. © 2023 American Society for Bone and Mineral Research (ASBMR).

Harnessing electromagnetic fields to assist bone tissue engineering

Bone tissue engineering (BTE) emerged as one of the exceptional means for bone defects owing to it providing mechanical supports to guide bone tissue regeneration. Great advances have been made to facilitate the success of BTE in regenerating bone within defects. The use of externally applied fields has been regarded as an alternative strategy for BTE. Electromagnetic fields (EMFs), known as a simple and non-invasive therapy, can remotely provide electric and magnetic stimulation to cells and biomaterials, thus applying EMFs to assist BTE would be a promising strategy for bone regeneration. When combined with BTE, EMFs improve cell adhesion to the material surface by promoting protein adsorption. Additionally, EMFs have positive effects on mesenchymal stem cells and show capabilities of pro-angiogenesis and macrophage polarization manipulation. These advantages of EMFs indicate that it is perfectly suitable for representing the adjuvant treatment of BTE. We also summarize studies concerning combinations of EMFs and diverse biomaterial types. The strategy of combining EMFs and BTE receives encouraging outcomes and holds a promising future for effectively treating bone defects.

Low frequency pulsed electromagnetic fields exposure alleviate the abnormal subchondral bone remodeling at the early stage of temporomandibular joint osteoarthritis

BACKGROUND

Temporomandibular joint osteoarthritis (TMJOA) is characterized by abnormal subchondral bone remodeling and cartilage degeneration. As a non-invasive biophysical technology, pulsed electromagnetic field (PEMF) treatment has been proven to be efficient in promoting osteogenesis. However, the potential bone protective effect and mechanism of PEMF on abnormal subchondral bone remodeling in TMJOA are unknown.

METHODS

Unilateral anterior crossbite (UAC) was used to create TMJOA model in rats, and 17β-estradiol (E₂) were injected daily to mimic patients with high-physiological levels of estrogen. Mouse osteoblast-like MC3T3-E1 cells treated with recombinant murine IL-1β was used to establish inflammatory environment in vitro. The treatment group were subjected to PEMF (2.0mT, 15 Hz, 2 h/d). Micro-CT scanning, histological staining, real-time PCR and western blotting assays were preformed to observe the changes in the subchondral bone.

RESULTS

Abnormal resorption of subchondral bone induced by UAC, characterized by decreased bone mineral density, increased osteoclast activity and expression of osteoclast-related factors (RANKL) and down-regulated expression of osteogenesis-related factors (OPG, ALP, Runx2 and OCN) at the early stage, could be reversed by PEMF exposure, which was similar to the effect of estrogen. In addition, PEMF exposure and E₂ supplement may have a synergistic effect to some extent. Moreover, PEMF exposure could promote the ALP activity and osteogenic mineralization ability of MC3T3-E1 cells. PEMF promoted the expression of factors related to Wnt/β-Catenin signal pathway both in vivo and in vitro.

CONCLUSIONS

Appropriate PEMF exposure have a protective effect on subchondral bone in TMJOA at early stage, in which canonical Wnt/β-Catenin pathway may be involved. PEMF may be a promising biophysical approach for early intervention of TMJOA in clinic.

Effect of transcutaneous electrical acupoint stimulation on bone metabolism in patients with immobilisation after foot and ankle fracture surgery: a randomised controlled trial study protocol

INTRODUCTION

Fracture is a disease with a high incidence worldwide. Foot and ankle fractures are common among fractures of the lower extremities. Foot and ankle fractures usually require surgical fixation and a period of fixed treatment, which can lead to decreased bone density. Although transcutaneous electrical acupoint stimulation (TEAS) is widely used for movement system diseases, there is minimal evidence to show the effectiveness of TEAS on patients after surgical fixation of ankle and foot fractures. This trial aims to evaluate whether TEAS can reduce bone loss in patients with immobilisation after ankle and foot fractures.

METHODS AND ANALYSIS

A randomised controlled trial will be conducted in which 60 patients will be randomly divided into two groups: (a) the control group will be treated according to the routine procedures of basic orthopaedics treatment; (b) in the treatment group, bilateral SP36, BL23 and ST36 will be performed on the basis of the control group, and the test will be performed for 30 min every other day for a total of 8 weeks. Bone turnover markers will be used as primary outcome. Secondary outcomes are composed of blood phosphorus, blood calcium and bone mineral density. Treatment safety will be monitored and recorded.

ETHICS AND DISSEMINATION

This trial is approved by the Ethics Committee of Beijing University of Chinese Medicine (2020BZYLL0611) and the Ethics Committee of Beijing Luhe Hospital (2020-LHKY-055-02), and inpatients who meet the following diagnostic and inclusion criteria are eligible to participate in this study.

TRIAL REGISTRATION NUMBER

ChiCTR 2000039944.

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.

Effects of Magnetic Stimulation on Dental Implant Osseointegration: A Scoping Review

This PRISMA-ScR driven scoping review aims to evaluate the influence of magnetic field stimulation on dental implant osseointegration. Seven databases were screened adopting ad-hoc strings. All clinical and preclinical studies analyzing the effects of magnetic fields on dental implant osseointegration were included. From 3124 initial items, on the basis of the eligibility criteria, 33 articles, regarding both Pulsed ElectroMagnetic Fields (PEMF) and Static magnetic Fields from permanent Magnets (SFM) were finally included and critically analyzed. In vitro studies showed a positive effect of PEMF, but contrasting effects of SFM on bone cell proliferation, whereas cell adhesion and osteogenic differentiation were induced by both types of stimulation. In vivo studies showed an increased bone-to-implant contact rate in different animal models and clinical studies revealed positive effects on implant stability, under magnetic stimulation. In conclusion, although positive effects of magnetic exposure on osteogenesis activity and osseointegration emerged, this scoping review highlighted the need for further preclinical and clinical studies. More standardized designs, accurate choice of stimulation parameters, adequate methods of evaluation of the outcomes, greater sample size and longer follow-ups are needed to clearly assess the effect of magnetic fields on dental implant osseointegration.

Challenges to Improve Bone Healing Under Diabetic Conditions

Diabetes mellitus (DM) can affect bone metabolism and the bone microenvironment, resulting in impaired bone healing. The mechanisms include oxidative stress, inflammation, the production of advanced glycation end products (AGEs), etc. Improving bone healing in diabetic patients has important clinical significance in promoting fracture healing and improving bone integration. In this paper, we reviewed the methods of improving bone healing under diabetic conditions, including drug therapy, biochemical cues, hyperbaric oxygen, ultrasound, laser and pulsed electromagnetic fields, although most studies are in preclinical stages. Meanwhile, we also pointed out some shortcomings and challenges, hoping to provide a potential therapeutic strategy for accelerating bone healing in patients with diabetes.

Systemically impaired fracture healing in small animal research: A review of fracture repair models

Fracture healing is a complex process requiring mechanical stability, an osteoconductive matrix, and osteoinductive and osteogenic biology. This intricate process is easily disrupted by various patient factors such as chronic disease and lifestyle. As the medical complexity and age of patients with fractures continue to increase, the importance of developing relevant experimental models is becoming paramount in preclinical research. The objective of this review is to describe the most common small animal models of systemically impaired fracture healing used in the orthopedic literature including osteoporosis, diabetes mellitus, smoking, alcohol use, obesity, and ageing. This review will provide orthopedic researchers with a summary of current models of systemically impaired fracture healing used in small animals and present an overview of the methods of induction for each condition.

Amelioration of bone fragility by pulsed electromagnetic fields in type 2 diabetic KK-Ay mice involving Wnt/β-catenin signaling

Type 2 diabetes mellitus (T2DM) results in compromised bone microstructure and quality, and subsequently increased risks of fractures. However, it still lacks safe and effective approaches resisting T2DM bone fragility. Pulsed electromagnetic fields (PEMFs) exposure has proven to be effective in accelerating fracture healing and attenuating osteopenia/osteoporosis induced by estrogen deficiency. Nevertheless, whether and how PEMFs resist T2DM-associated bone deterioration remain not fully identified. The KK-Ay mouse was used as the T2DM model. We found that PEMF stimulation with 2 h/day for 8 wk remarkably improved trabecular bone microarchitecture, decreased cortical bone porosity, and promoted trabecular and cortical bone material properties in KK-Ay mice. PEMF stimulated bone formation in KK-Ay mice, as evidenced by increased serum levels of bone formation (osteocalcin and P1NP), enhanced bone formation rate, and increased osteoblast number. PEMF significantly suppressed osteocytic apoptosis and sclerostin expression in KK-Ay mice. PEMF exerted beneficial effects on osteoblast- and osteocyte-related gene expression in the skeleton of KK-Ay mice. Nevertheless, PEMF exerted no effect on serum biomarkers of bone resorption (TRAcP5b and CTX-1), osteoclast number, or osteoclast-specific gene expression (TRAP and cathepsin K). PEMF upregulated gene expression of canonical Wnt ligands (including Wnt1, Wnt3a, and Wnt10b), but not noncanonical Wnt5a. PEMF also upregulated skeletal protein expression of downstream p-GSK-3β and β-catenin in KK-Ay mice. Moreover, PEMF-induced improvement in bone microstructure, mechanical strength, and bone formation in KK-Ay mice was abolished after intragastric administration with the Wnt antagonist ETC-159. Together, our results suggest that PEMF can improve bone microarchitecture and quality by enhancing the biological activities of osteoblasts and osteocytes, which are associated with the activation of the Wnt/β-catenin signaling pathway. PEMF might become an effective countermeasure against T2DM-induced bone deterioration.NEW & NOTEWORTHY PEMF improved trabecular bone microarchitecture and suppressed cortical bone porosity in T2DM KK-Ay mice. It attenuated T2DM-induced detrimental consequence on trabecular and cortical bone material properties. PEMF resisted bone deterioration in KK-Ay mice by enhancing osteoblast-mediated bone formation. PEMF also significantly suppressed osteocytic apoptosis and sclerostin expression in KK-Ay mice. The therapeutic potential of PEMF on T2DM-induced bone deterioration was associated with the activation of Wnt/ß-catenin signaling.

Neurokinin-1-tachykinin receptor agonist promotes diabetic fracture healing in rats with type 1 diabetes via modulation of Wnt/β-catenin signalling axis

Diabetes mellitus is an ill-famed metabolic disorder with varied repercussions including delayed fracture healing. Wnt/β-catenin axis is known to play a tight pivotal role in the bone healing process. Substance P (SubP) is a neuropeptide with established positive modulatory functions in fracture healing and associated neuronal milieu. In this study, we performed local delivery of recombinant adenovirus of Dickkopf-1 (DKK1) into the fracture site to understand the antagonizing the role of DKK1 against substance P. Rats were segregated into 4 groups: (i) Fractured non-diabetic rats; (ii) Fractured T1D rats; T1D was provoked by using STZ 50 mg/kg for 5 consecutive days; (iii) Fractured T1D + SubP (50 mg/ml/Kg; i.p.; 30 min prior to fracture procedure); (iv) Fractured T1D + SubP + Ad-DKK1. Bone radiographs were taken using a Faxitron X-ray machine and the residual gap size was measured using an electric caliper. Western blotting was also performed to determine the protein expression levels of osteogenic markers (RUNX2, OSTX and OSTC) bone resorption markers (OPG, RANKL and RANK) and also Wnt-signalling markers (β-catenin, LRP5 and GSK-3β). We observed that SubP promoted osteogenesis (as indicated by RUNX2, OSTX and OSTC upregulation) and mitigated the bone resorption (as indicated by optimized OPG/RANKL/RANK axis) via activated Wnt signalling (manifested by upmodulated β-catenin and LRP5, with downmodulated GSK-3β levels. Activation of endogenous SubP or administration of exogenous mimics might counter-protect the fractured bone against the deforming effects of T1D.

Pulsed Electromagnetic Fields Ameliorate Skeletal Deterioration in Bone Mass, Microarchitecture, and Strength by Enhancing Canonical Wnt Signaling-Mediated Bone Formation in Rats with Spinal Cord Injury

Spinal cord injury (SCI) leads to extensive bone loss and high incidence of low-energy fractures. Pulsed electromagnetic fields (PEMF) treatment, as a non-invasive biophysical technique, has proven to be efficient in promoting osteogenesis. The potential osteoprotective effect and mechanism of PEMF on SCI-related bone deterioration, however, remain unknown. The spinal cord of rats was transected at vertebral level T12 to induce SCI. Thirty rats were assigned to the control, SCI, and SCI+PEMF groups (n = 10). One week after surgery, the SCI+PEMF rats were subjected to PEMF (2.0 mT, 15 Hz, 2 h/day) for eight weeks. Micro-computed tomography results showed that PEMF significantly ameliorated trabecular and cortical bone microarchitecture deterioration induced by SCI. Three-point bending and nanoindentation assays revealed that PEMF significantly improved bone mechanical properties in SCI rats. Serum biomarker and bone histomorphometric analyses demonstrated that PEMF enhanced bone formation, as evidenced by significant increase in serum osteocalcin and P1NP, mineral apposition rate, and osteoblast number on bone surface. The PEMF had no impact, however, on serum bone-resorbing cytokines (TRACP 5b and CTX-1) or osteoclast number on bone surface. The PEMF also attenuated SCI-induced negative changes in osteocyte morphology and osteocyte survival. Moreover, PEMF significantly increased skeletal expression of canonical Wnt ligands (Wnt1 and Wnt10b) and stimulated their downstream p-GSK3β and β-catenin expression in SCI rats. This study demonstrates that PEMF can mitigate the detrimental consequence of SCI on bone quantity/quality, which might be associated with canonical Wnt signaling-mediated bone formation, and reveals that PEMF may be a promising biophysical approach for resisting osteopenia/osteoporosis after SCI in clinics.

In Vitro Production of Calcified Bone Matrix onto Wool Keratin Scaffolds via Osteogenic Factors and Electromagnetic Stimulus

Pulsed electromagnetic field (PEMF) has drawn attention as a potential tool to improve the ability of bone biomaterials to integrate into the surrounding tissue. We investigated the effects of PEMF (frequency, 75 Hz; magnetic induction amplitude, 2 mT; pulse duration, 1.3 ms) on human osteoblast-like cells (SAOS-2) seeded onto wool keratin scaffolds in terms of proliferation, differentiation, and production of the calcified bone extracellular matrix. The wool keratin scaffold offered a 3D porous architecture for cell guesting and nutrient diffusion, suggesting its possible use as a filler to repair bone defects. Here, the combined approach of applying a daily PEMF exposure with additional osteogenic factors stimulated the cells to increase both the deposition of bone-related proteins and calcified matrix onto the wool keratin scaffolds. Also, the presence of SAOS-2 cells, or PEMF, or osteogenic factors did not influence the compression behavior or the resilience of keratin scaffolds in wet conditions. Besides, ageing tests revealed that wool keratin scaffolds were very stable and showed a lower degradation rate compared to commercial collagen sponges. It is for these reasons that this tissue engineering strategy, which improves the osteointegration properties of the wool keratin scaffold, may have a promising application for long term support of bone formation in vivo.

Specific low-frequency electromagnetic fields induce expression of active KDM6B associated with functional changes in U937 cells

In this study, we investigated the effects of specific low-frequency electromagnetic field sequences on U937 cells, an in vitro model of human monocyte/macrophage differentiation. U937 cells were exposed to electromagnetic stimulation by means of the SynthéXer system using two similar sequences, XR-BC31 and XR-BC31/F. Each sequence was a time series of 29 wave segments, equal to a total duration of 77 min. Here, we report that exposure (4 d, once a day) of U937 cells to the XR-BC31 setting, but not to the XR-BC31/F, resulted in increased expression of the histone demethylase KDM6B along with a global reduction in histone H3 lysine 27 tri-methylation (H3K27me3). Furthermore, exposure to the XR-BC31 sequence induced differentiation of U937 cells towards a macrophage-like phenotype displaying a KDM6B dependent increase in expression and secretion of the anti-inflammatory interleukins (ILs), IL-10 and IL-4. Importantly, all the observed changes were highly dependent on the nature of the sequence. Our results open a new way of interpretation for the effects of low-frequency electromagnetic fields observed in vivo. Indeed, it is conceivable that a specific low-frequency electromagnetic fields treatment may cause the reprogramming of H3K27me3 and cell differentiation.

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.

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.

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.

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.