Effects of electromagnetic fields in experimental fracture repair

Electromagnetic Modulation of Cell Behavior: Unraveling the Positive Impacts in a Comprehensive Review

There are numerous effective procedures for cell signaling, in which humans directly transmit detectable signals to cells to govern their essential behaviors. From a biomedical perspective, the cellular response to the combined influence of electrical and magnetic fields holds significant promise in various domains, such as cancer treatment, targeted drug delivery, gene therapy, and wound healing. Among these modern cell signaling methods, electromagnetic fields (EMFs) play a pivotal role; however, there remains a paucity of knowledge concerning the effects of EMFs across all wavelengths. It's worth noting that most wavelengths are incompatible with human cells, and as such, this study excludes them from consideration. In this review, we aim to comprehensively explore the most effective and current EMFs, along with their therapeutic impacts on various cell types. Specifically, we delve into the influence of alternating electromagnetic fields (AEMFs) on diverse cell behaviors, encompassing proliferation, differentiation, biomineralization, cell death, and cell migration. Our findings underscore the substantial potential of these pivotal cellular behaviors in advancing the treatment of numerous diseases. Moreover, AEMFs wield a significant role in the realms of biomaterials and tissue engineering, given their capacity to decisively influence biomaterials, facilitate non-invasive procedures, ensure biocompatibility, and exhibit substantial efficacy. It is worth mentioning that AEMFs often serve as a last-resort treatment option for various diseases. Much about electromagnetic fields remains a mystery to the scientific community, and we have yet to unravel the precise mechanisms through which wavelengths control cellular fate. Consequently, our understanding and knowledge in this domain predominantly stem from repeated experiments yielding similar effects. In the ensuing sections of this article, we delve deeper into our extended experiments and research.

The Cellular Response Is Determined by a Combination of Different ELF-EMF Exposure Parameters: A Scope Review

Since the establishment of regulations for exposure to extremely low-frequency (0-300) Hz electromagnetic fields, scientific opinion has prioritised the hypothesis that the most important parameter determining cellular behaviour has been intensity, ignoring the other exposure parameters (frequency, time, mode, waveform). This has been reflected in the methodologies of the in vitro articles published and the reviews in which they are included. A scope review was carried out, grouping a total of 79 articles that met the proposed inclusion criteria and studying the effects of the different experiments on viability, proliferation, apoptosis, oxidative stress and the cell cycle. These results have been divided and classified by frequency, intensity, exposure time and exposure mode (continuous/intermittent). The results obtained for each of the processes according to the exposure parameter used are shown graphically to highlight the importance of a good methodology in experimental development and the search for mechanisms of action that explain the experimental results, considering not only the criterion of intensity. The consequence of this is a more than necessary revision of current exposure protection regulations for the general population based on the reductionist criterion of intensity.

Enhancing bone tissue engineering using iron nanoparticles and magnetic fields: A focus on cytomechanics and angiogenesis in the chicken egg chorioallantoic membrane model

AIM

To evaluate the potential of iron nanoparticles (FeNPs) in conjunction with magnetic fields (MFs) to enhance osteoblast cytomechanics, promote cell homing, bone development activity, and antibacterial capabilities, and to assess their in vivo angiogenic viability using the chicken egg chorioallantoic membrane (CAM) model.

SETTINGS AND DESIGN

Experimental study conducted in a laboratory setting to investigate the effects of FeNPs and MFs on osteoblast cells and angiogenesis using a custom titanium (Ti) substrate coated with FeNPs.

MATERIALS AND METHODS

A custom titanium (Ti) was coated with FeNPs. Evaluations were conducted to analyze the antibacterial properties, cell adhesion, durability, physical characteristics, and nanoparticle absorption associated with FeNPs. Cell physical characteristics were assessed using protein markers, and microscopy, CAM model, was used to quantify blood vessel formation and morphology to assess the FeNP-coated Ti's angiogenic potential. This in vivo study provided critical insights into tissue response and regenerative properties for biomedical applications.

STATISTICAL ANALYSIS

Statistical analysis was performed using appropriate tests to compare experimental groups and controls. Significance was determined at P < 0.05.

RESULTS

FeNPs and MFs notably improved osteoblast cell mechanical properties facilitated the growth and formation of new blood vessels and bone tissue and promoted cell migration to targeted sites. In the group treated with FeNPs and exposed to MFs, there was a significant increase in vessel percentage area (76.03%) compared to control groups (58.11%), along with enhanced mineralization and robust antibacterial effects (P < 0.05).

CONCLUSION

The study highlights the promising potential of FeNPs in fostering the growth of new blood vessels, promoting the formation of bone tissue, and facilitating targeted cell migration. These findings underscore the importance of further investigating the mechanical traits of FeNPs, as they could significantly advance the development of effective bone tissue engineering techniques, ultimately enhancing clinical outcomes in the field.

Impact of Dopants on the Electrical and Optical Properties of Hydroxyapatite

This chapter deals with the effect of alternating electrical current on hydroxyapatite [HAp, Ca10(PO4)6(OH)2] and doped HAp along with their optical response and the processes involved. The dielectric constant, permittivity and ac conductivity were analyzed to have an insight into the surface charge polarization phenomenon. Further, the magnitude and the polarity of the surface charges, microstructure, and phases also play significant role in the cell proliferation and growth on the implants. Besides, the mechanism behind the electrical properties and the healing of bone fracture are discussed. The influence of various dopants on the optical properties of HAp viz., absorbance, transmission, band gaps and defects energy levels are analyzed along with the photoluminescence and excitation independent emission. In the future outlook, the analysis of effect of doping is summarized and its impact on the next generation biomaterials are elucidated.

Assessment of the effect of pulsed electromagnetic field application on the healing of bone defects in rats with heparin-induced osteoporosis

Osteoporosis is a systemic skeletal disease characterized by an increase in bone fragility and fracture risk due to low bone mass and deterioration of bone tissue. Application of pulsed electromagnetic fields (PEMF), a non-invasive method with a low complication risk, is known to stimulate bone formation. The present study examines the histomorphometric and biochemical effects of PEMF application on the healing of bone defects in rats with heparin-induced secondary osteoporosis. Briefly, 12-month-old male Sprague-Dawley rats were examined in a prospective, randomized, single-blind study. Osteoporosis was induced by administering a daily dose of 2 IU/g heparin for 33 days. Bone defects were created on the right femur on Day 35. PEMF of an average intensity of 0.8 ± 0.2 mT and a frequency of 7.3 Hz, was applied for 1 h/day, for 28 days following surgery. Bone healing was evaluated by histomorphometric and biochemical analyses. The heparin + PEMF group displayed the largest amount of new bone area (P = .002) and the lowest mean CTx on Day 63 (P = .05). This study demonstrates that heparin administration leads to bone loss and osteoporosis, whereas the application of PEMF decreases this effect.

Pulsed electromagnetic fields promote repair of focal articular cartilage defects with engineered osteochondral constructs

Articular cartilage injuries are a common source of joint pain and dysfunction. We hypothesized that pulsed electromagnetic fields (PEMFs) would improve growth and healing of tissue-engineered cartilage grafts in a direction-dependent manner. PEMF stimulation of engineered cartilage constructs was first evaluated in vitro using passaged adult canine chondrocytes embedded in an agarose hydrogel scaffold. PEMF coils oriented parallel to the articular surface induced superior repair stiffness compared to both perpendicular PEMF (p = .026) and control (p = .012). This was correlated with increased glycosaminoglycan deposition in both parallel and perpendicular PEMF orientations compared to control (p = .010 and .028, respectively). Following in vitro optimization, the potential clinical translation of PEMF was evaluated in a preliminary in vivo preclinical adult canine model. Engineered osteochondral constructs (∅ 6 mm × 6 mm thick, devitalized bone base) were cultured to maturity and implanted into focal defects created in the stifle (knee) joint. To assess expedited early repair, animals were assessed after a 3-month recovery period, with microfracture repairs serving as an additional clinical control. In vivo, PEMF led to a greater likelihood of normal chondrocyte (odds ratio [OR]: 2.5, p = .051) and proteoglycan (OR: 5.0, p = .013) histological scores in engineered constructs. Interestingly, engineered constructs outperformed microfracture in clinical scoring, regardless of PEMF treatment (p < .05). Overall, the studies provided evidence that PEMF stimulation enhanced engineered cartilage growth and repair, demonstrating a potential low-cost, low-risk, noninvasive treatment modality for expediting early cartilage repair.

Electrical stimulation in bone tissue engineering treatments

Electrical stimulation (EStim) has been shown to promote bone healing and regeneration both in animal experiments and clinical treatments. Therefore, incorporating EStim into promising new bone tissue engineering (BTE) therapies is a logical next step. The goal of current BTE research is to develop combinations of cells, scaffolds, and chemical and physical stimuli that optimize treatment outcomes. Recent studies demonstrating EStim's positive osteogenic effects at the cellular and molecular level provide intriguing clues to the underlying mechanisms by which it promotes bone healing. In this review, we discuss results of recent in vitro and in vivo research focused on using EStim to promote bone healing and regeneration and consider possible strategies for its application to improve outcomes in BTE treatments. Technical aspects of exposing cells and tissues to EStim in in vitro and in vivo model systems are also discussed.

The effects of electromagnetic fields on cultured human retinal pigment epithelial cells

A great deal of evidence has confirmed that electromagnetic fields (EMFs) can affect the central nervous system. In this study, cultured neonatal human retinal pigment epithelial (hRPE) cells were exposed to pulsed EMF of 1 mT intensity and 50 Hz frequency 8 h daily for 3 days. In addition to cell proliferation and cell death assays, immunocytochemistry for RPE65, PAX6, nestin, and cytokeratin 8/18 proteins were performed. Real-time reverse transcriptase polymerase chain reaction (RT-PCR) was performed for NES, PAX6, RPE65, and ACTA2 gene expression. Exposed hRPE cells did not demonstrate significant change in terms of cytomorphology, cell proliferation, or cell death. Protein expression of PAX6 was decreased in treated cells compared to controls and remained unchanged for RPE65, cytokeratin 8/18, and nestin. Gene expressions of NES, RPE65, and PAX6 were decreased in treated cells as compared to controls. Gene expression of ACTA2 did not significantly change. In conclusion, viability of cultivated neonatal hRPE cells did not change after short exposure to a safe dose of pulsed EMF albeit that both gene and protein expressions of retinal progenitor cell markers were reduced. Whether longer exposure durations that are being constantly produced by widely-used electronic devices may induce significant changes in these cells, needs further investigation. Bioelectromagnetics. 39:585-594, 2018. © 2018 Wiley Periodicals, Inc.

Physical stimulations and their osteogenesis-inducing mechanisms

Physical stimulations such as magnetic, electric and mechanical stimulation could enhance cell activity and promote bone formation in bone repair process via activating signal pathways, modulating ion channels, regulating bonerelated gene expressions, etc. In this paper, bioeffects of physical stimulations on cell activity, tissue growth and bone healing were systematically summarized, which especially focused on their osteogenesis-inducing mechanisms. Detailedly, magnetic stimulation could produce Hall effect which improved the permeability of cell membrane and promoted the migration of ions, especially accelerating the extracellular calcium ions to pass through cell membrane. Electric stimulation could induce inverse piezoelectric effect which generated electric signals, accordingly up-regulating intracellular calcium levels and growth factor synthesis. And mechanical stimulation could produce mechanical signals which were converted into corresponding biochemical signals, thus activating various signaling pathways on cell membrane and inducing a series of gene expressions. Besides, bioeffects of physical stimulations combined with bone scaffolds which fabricated using 3D printing technology on bone cells were discussed. The equipments of physical stimulation system were described. The opportunities and challenges of physical stimulations were also presented from the perspective of bone repair.

Short Exposures to an Extremely Low-Frequency Magnetic Field (ELF MF) Enhance Protein but not mRNA Alkaline Phosphatase Expression in Human Osteosarcoma Cells

Background

Among electromagnetic fields treatments used in orthopedics, extremely low-frequency magnetic fields (ELF MF) need more detailed information about the molecular mechanisms of their effects and exposure conditions.

Objective

Evaluation of the effects of an ELF MF exposure system, recently introduced among current clinical treatments for fracture healing and other bone diseases, on Alkaline Phosphatase (ALP) activity and expression in a human osteosarcoma cell line (SaOS-2), as marker typically associated to osteogenesis and bone tissue regeneration.

Method

Cells were exposed to the ELF MF physical stimulus (75 Hz, 1.5 mT) for 1h. Cell viability, enzymatic activity, protein and mRNA expression of alkaline phosphatase were then measured at different times after exposure (0, 4 and 24 h).

Results

Data demonstrate that this signal is active on an osteogenic process already one hour after exposure. Treatment was, in fact, capable, even after an exposure shorter than those commonly used in clinical applications, to significantly up-regulate alkaline phosphatase enzymatic activity. This regulation is produced essentially through an increase of ALP protein level, without changes of its mRNA concentration, while assessed magnetic field did not affect cell growth and viability and did not produce temperature variations.

Conclusion

Tested low-frequency magnetic field affects cellular ALP expression with a posttranslational mechanism, without the involvement of regulations at gene transcription and mRNA level. This molecular effect is likely produced even within treated tissues during therapies with this signal and may be implicated in the induction of observed effects in treated patients.

Osteoblast migration in vertebrate bone

Bone formation, for example during bone remodelling or fracture repair, requires mature osteoblasts to deposit bone with remarkable spatial precision. As osteoblast precursors derive either from circulation or resident stem cell pools, they and their progeny are required to migrate within the three-dimensional bone space and to navigate to their destination, i.e. to the site of bone formation. An understanding of this process is emerging based on in vitro and in vivo studies of several vertebrate species. Receptors on the osteoblast surface mediate cell adhesion and polarization, which induces osteoblast migration. Osteoblast migration is then facilitated along gradients of chemoattractants. The latter are secreted or released proteolytically by several cell types interacting with osteoblasts, including osteoclasts and vascular endothelial cells. The positions of these cellular sources of chemoattractants in relation to the position of the osteoblasts provide the migrating osteoblasts with tracks to their destination, and osteoblasts possess the means to follow a track marked by multiple chemoattractant gradients. In addition to chemotactic cues, osteoblasts sense other classes of signals and utilize them as landmarks for navigation. The composition of the osseous surface guides adhesion and hence migration efficiency and can also provide steering through haptotaxis. Further, it is likely that signals received from surface interactions modulate chemotaxis. Besides the nature of the surface, mechanical signals such as fluid flow may also serve as navigation signals for osteoblasts. Alterations in osteoblast migration and navigation might play a role in metabolic bone diseases such as osteoporosis.

Characterization of human cancellous and subchondral bone with respect to electro physical properties and bone mineral density by means of impedance spectroscopy

Computational simulation of electrical bone stimulation of the electrical and dielectric parameters of osteoarthritic bone tissue is useful for an exact patient-individual adaptation of the bone models. Therefore, we investigated electrical and dielectric parameters at a frequency of 20Hz of cancellous and subchondral human femoral head bone samples. Furthermore, the mechanical properties and the bone mineral density (BMD) were determined. Finally, these data were compared with the electrical and dielectric parameters. The bone samples were taken from patients with hip osteoarthritis. Electrical conductivity and dielectric permittivity of cancellous bone amounted to 0.043S/m and 8.1⋅10⁶. BMD of the bone samples determined by dual-x-ray-absorptiometry (DXA) and ashing resulted in 193 ± 70mg/cm² and 286 ± 59mg/cm³ respectively. Structural modulus (E_S) and ultimate compression strength (σ_max) were measured with 227 ± 94N/mm² and 6.5 ± 3.4N/mm². No linear correlation of the electrical and dielectric parameters compared with BMD and mechanical properties of cancellous bone samples was found. Electrical conductivity and dielectric permittivity of subchondral bone resulted in 0.029S/m and 8.97×10⁶.

Effects of four kinds of electromagnetic fields (EMF) with different frequency spectrum bands on ovariectomized osteoporosis in mice

Electromagnetic fields (EMF) was considered as a non-invasive modality for treatment of osteoporosis while the effects were diverse with EMF parameters in time domain. In present study, we extended analysis of EMF characteristics from time domain to frequency domain, aiming to investigate effects of four kinds of EMF (LP (1–100 Hz), BP (100–3,000 Hz), HP (3,000–50,000 Hz) and AP (1–50,000 Hz)) on ovariectomized (OVX) osteoporosis (OP) in mice. Forty-eight 3-month-old female BALB/c mice were equally assigned to Sham, OVX, OVX + LP, OVX + BP, OVX + HP and OVX + AP groups (n = 8). After 8-week exposure (3 h/day), LP and BP significantly increased serum bone formation markers and osteogenesis-related gene expressions compared with OVX. Bedsides, LP and BP also slightly increased bone resorption activity compared with OVX, evidenced by increased RANKL/OPG ratio. HP sharply decreased serum bone formation and resporption markers and osteogenesis and osteoclastogenesis related gene expressions compared with OVX. AP had accumulative effects of LP, BP and HP, which significantly increased bone formation and decreased bone resporption activity compared with OVX. As a result, LP, BP and HP exposure did not later deterioration of bone mass, microarchitecture and mechanical strength in OVX mice with OP. However, AP stimulation attenuated OVX-induced bone loss.

Effect of Magnetic Field on Bone Healing around Endosseous Implants - An In-vivo Study

INTRODUCTION

After implant placement, a stress-free healing period of 3-6 months is a pre-requisite to achieve good osseointegration. If this duration could be reduced, the patients would feel happier. Eventhough, immediate loading of implants is a clinically feasible concept; it is not possible in certain situations. Few studies have shown that Static magnetic field is useful to promote bone formation faster after the bone is wounded.

AIM

This pilot study was intended to evaluate the tissue response after implant placement under the influence of magnetic field.

MATERIALS AND METHODS

Twenty Tidal Spiral implants were used for this study. Two implants were placed in each patient in the anterior mandible corresponding to the B and D regions and the implant on the D region was exposed to magnetic field using safer magnet (Neodymium Boron Iron) and the implant on the B region served as a control. Both the implants were compared for stability using Resonance Frequency Analyzer (RFA) at Days 0, 30, 60 and 90. Mean Implant Stability Quotient (ISQ) values were compared on both sides using student's paired t-test and repeated measures ANOVA (analysis of variance). There was a significant difference in the mean ISQ values, hence, a post-hoc test was done to evaluate whether there is any difference between the follow-ups.

RESULTS

The average ISQ value for implants at 0 day in the B and D regions was 68.6 and 68.7 respectively. The average ISQ value at 30^th day, 60^th day and 90^th day was 73.25, 76.05 and 78.95 respectively on the magnetic side (D region). Whereas on the non-magnetic side (B region) at 30^th day, 60^th day and 90^th day was 68.45, 72.05 and 74.45 respectively.

CONCLUSION

The implant stability quotient values obtained on the magnetic side were significantly greater than on the non-magnetic side. Positive correlation exists between the magnetic field and osseointegration.

The effect of prenatal exposure to 1800 MHz electromagnetic field on calcineurin and bone development in rats

PURPOSE

To investigated the effects of exposure to an 1800 MHz electromagnetic field (EMF) on bone development during the prenatal period in rats.

METHODS

Pregnant rats in the experimental group were exposed to radiation for six, 12, and 24 hours daily for 20 days. No radiation was given to the pregnant rats in the control group. We distributed the newborn rats into four groups according to prenatal EMF exposure as follows: Group 1 was not exposed to EMF; groups 2, 3, and 4 were exposed to EMF for six, 12, and 24 hours a day, respectively. The rats were evaluated at the end of the 60th day following birth.

RESULTS

Increasing the duration of EMF exposure during the prenatal period resulted in a significant reduction of resting cartilage levels and a significant increase in the number of apoptotic chondrocytes and myocytes. There was also a reduction in calcineurin activities in both bone and muscle tissues. We observed that the development of the femur, tibia, and ulna were negatively affected, especially with a daily EMF exposure of 24 hours.

CONCLUSION

Bone and muscle tissue development was negatively affected due to prenatal exposure to 1800 MHz radiofrequency electromagnetic field.

An automatic approach for calibrating dielectric bone properties by combining finite-element and optimization software tools

The dielectric properties of human bone are one of the most essential inputs required by electromagnetic stimulation for improved bone regeneration. Measuring the electric properties of bone is a difficult task because of the complexity of the bone structure. Therefore, an automatic approach is presented to calibrate the electric properties of bone. The numerical method consists of three steps: generating input from experimental data, performing the numerical simulation, and calibrating the bone dielectric properties. As an example, the dielectric properties at 20 Hz of a rabbit distal femur were calibrated. The calibration process was considered as an optimization process with the aim of finding the optimum dielectric bone properties that match most of the numerically calculated simulation and experimentally measured data sets. The optimization was carried out automatically by the optimization software tool iSIGHT in combination with the finite-element solver COMSOL Multiphysics. As a result, the optimum conductivity and relative permittivity of the rabbit distal femur at 20 Hz were found to be 0.09615 S/m and 19522 for cortical bone and 0.14913 S/m and 1561507 for cancellous bone, respectively. The proposed method is a potential tool for the identification of realistic dielectric properties of the entire bone volume. The presented approach combining iSIGHT with COMSOL is applicable to, amongst others, designing implantable electro-stimulative devices or the optimization of electrical stimulation parameters for improved bone regeneration.

Conversion of titania (TiO2) into conductive titanium (Ti) nanotube arrays for combined drug-delivery and electrical stimulation therapy

The conversion of titania (TiO₂) nanotubes into titanium (Ti), while preserving their nanotubular structures is demonstrated for proposed application as bone implants and electrodes for combined local drug delivery and electrical stimulation therapy.

The effect of low-frequency electromagnetic field on human bone marrow stem/progenitor cell differentiation

Human bone marrow stromal cells (hBMSCs, also known as bone marrow-derived mesenchymal stem cells) are a population of progenitor cells that contain a subset of skeletal stem cells (hSSCs), able to recreate cartilage, bone, stroma that supports hematopoiesis and marrow adipocytes. As such, they have become an important resource in developing strategies for regenerative medicine and tissue engineering due to their self-renewal and differentiation capabilities. The differentiation of SSCs/BMSCs is dependent on exposure to biophysical and biochemical stimuli that favor early and rapid activation of the in vivo tissue repair process. Exposure to exogenous stimuli such as an electromagnetic field (EMF) can promote differentiation of SSCs/BMSCs via ion dynamics and small signaling molecules. The plasma membrane is often considered to be the main target for EMF signals and most results point to an effect on the rate of ion or ligand binding due to a receptor site acting as a modulator of signaling cascades. Ion fluxes are closely involved in differentiation control as stem cells move and grow in specific directions to form tissues and organs. EMF affects numerous biological functions such as gene expression, cell fate, and cell differentiation, but will only induce these effects within a certain range of low frequencies as well as low amplitudes. EMF has been reported to be effective in the enhancement of osteogenesis and chondrogenesis of hSSCs/BMSCs with no documented negative effects. Studies show specific EMF frequencies enhance hSSC/BMSC adherence, proliferation, differentiation, and viability, all of which play a key role in the use of hSSCs/BMSCs for tissue engineering. While many EMF studies report significant enhancement of the differentiation process, results differ depending on the experimental and environmental conditions. Here we review how specific EMF parameters (frequency, intensity, and time of exposure) significantly regulate hSSC/BMSC differentiation in vitro. We discuss optimal conditions and parameters for effective hSSC/BMSC differentiation using EMF treatment in an in vivo setting, and how these can be translated to clinical trials.

Functional outcome and cost-effectiveness of pulsed electromagnetic fields in the treatment of acute scaphoid fractures: a cost-utility analysis

Background

Physical forces have been widely used to stimulate bone growth in fracture repair. Addition of bone growth stimulation to the conservative treatment regime is more costly than standard health care. However, it might lead to cost-savings due to a reduction of the total amount of working days lost. This economic evaluation was performed to assess the cost-effectiveness of Pulsed Electromagnetic Fields (PEMF) compared to standard health care in the treatment of acute scaphoid fractures.

Methods

An economic evaluation was carried out from a societal perspective, alongside a double-blind, randomized, placebo-controlled, multicenter trial involving five centres in the Netherlands. One hundred and two patients with a clinically and radiographically proven fracture of the scaphoid were included in the study and randomly allocated to either active bone growth stimulation or standard health care, using a placebo. All costs (medical costs and costs due to productivity loss) were measured during one year follow up. Functional outcome and general health related quality of life were assessed by the EuroQol-5D and PRWHE (patient rated wrist and hand evaluation) questionnaires. Utility scores were derived from the EuroQol-5D.

Results

The average total number of working days lost was lower in the active PEMF group (9.82 days) compared to the placebo group (12.91 days) (p = 0.651). Total medical costs of the intervention group (€1594) were significantly higher compared to the standard health care (€875). The total amount of mean QALY’s (quality-adjusted life year) for the active PEMF group was 0.84 and 0.85 for the control group. The cost-effectiveness plane shows that the majority of all cost-effectiveness ratios fall into the quadrant where PEMF is not only less effective in terms of QALY’s but also more costly.

Conclusion

This study demonstrates that the desired effects in terms of cost-effectiveness are not met. When comparing the effects of PEMF to standard health care in terms of QALY’s, PEMF cannot be considered a cost-effective treatment for acute fractures of the scaphoid bone.

Trial registration

Netherlands Trial Register (NTR): NTR2064

A comparative analysis of the in vitro effects of pulsed electromagnetic field treatment on osteogenic differentiation of two different mesenchymal cell lineages

Human mesenchymal stem cells (MSCs) are a promising candidate cell type for regenerative medicine and tissue engineering applications. Exposure of MSCs to physical stimuli favors early and rapid activation of the tissue repair process. In this study we investigated the in vitro effects of pulsed electromagnetic field (PEMF) treatment on the proliferation and osteogenic differentiation of bone marrow MSCs (BM-MSCs) and adipose-tissue MSCs (ASCs), to assess if both types of MSCs could be indifferently used in combination with PEMF exposure for bone tissue healing. We compared the cell viability, cell matrix distribution, and calcified matrix production in unstimulated and PEMF-stimulated (magnetic field: 2 mT, amplitude: 5 mV) mesenchymal cell lineages. After PEMF exposure, in comparison with ASCs, BM-MSCs showed an increase in cell proliferation (p<0.05) and an enhanced deposition of extracellular matrix components such as decorin, fibronectin, osteocalcin, osteonectin, osteopontin, and type-I and -III collagens (p<0.05). Calcium deposition was 1.5-fold greater in BM-MSC-derived osteoblasts (p<0.05). The immunofluorescence related to the deposition of bone matrix proteins and calcium showed their colocalization to the cell-rich areas for both types of MSC-derived osteoblast. Alkaline phosphatase activity increased nearly 2-fold (p<0.001) and its protein content was 1.2-fold higher in osteoblasts derived from BM-MSCs. The quantitative reverse-transcription polymerase chain reaction (qRT-PCR) analysis revealed up-regulated transcription specific for bone sialoprotein, osteopontin, osteonectin, and Runx2, but at a higher level for cells differentiated from BM-MSCs. All together these results suggest that PEMF promotion of bone extracellular matrix deposition is more efficient in osteoblasts differentiated from BM-MSCs.

The clinical and radiological outcome of pulsed electromagnetic field treatment for acute scaphoid fractures

The use of pulsed electromagnetic fields (PEMF) to stimulate bone growth has been recommended as an alternative to the surgical treatment of ununited scaphoid fractures, but has never been examined in acute fractures. We hypothesised that the use of PEMF in acute scaphoid fractures would accelerate the time to union by 30% in a randomised, double-blind, placebo-controlled, multicentre trial. A total of 53 patients in three different medical centres with a unilateral undisplaced acute scaphoid fracture were randomly assigned to receive either treatment with PEMF (n = 24) or a placebo (n = 29). The clinical and radiological outcomes were assessed at four, six, nine, 12, 24 and 52 weeks.

A log-rank analysis showed that neither time to clinical and radiological union nor the functional outcome differed significantly between the groups. The clinical assessment of union indicated that at six weeks tenderness in the anatomic snuffbox (p = 0.03) as well as tenderness on longitudinal compression of the scaphoid (p = 0.008) differed significantly in favour of the placebo group.

We conclude that stimulation of bone growth by PEMF has no additional value in the conservative treatment of acute scaphoid fractures.

Migration responses of outer and inner meniscus cells to applied direct current electric fields

Injuries to the inner regions of the knee meniscus do not heal and can result in degenerative changes to the articular surface, ultimately leading to osteoarthritis. A possible stimulus to enhance meniscus healing is to use electric fields that induce galvanotaxis. In this study, a novel characterization of the effects of direct current electric fields on migration characteristics of meniscus cells was performed. Primary and passaged inner and outer meniscus cells were exposed to varying electric field strengths from 0 to 6 V/cm. Cell migration was tracked using time lapse digital photography, and cell displacement and cathodal direct velocity were quantified. Cytoskeletal staining was performed to examine actin distribution and nuclear content. Cell adhesion strength was quantified as a function of wall shear stress. Meniscus cells exhibited cathodal migration and cell elongation perpendicular to the applied electric field accompanied by actin reorganization. Outer meniscus cells migrated quicker and exhibited lower adhesion strengths when compared to inner meniscus cells. Passaged cells exhibited higher migration characteristics when compared to primary cells. Overall, this study demonstrated that electric fields can significantly enhance and direct meniscus cell migration and suggests the potential for their incorporation in strategies of meniscus repair and tissue engineering.

Effect of the Ca/P ratio on the dielectric properties of nanoscaled substoichiometric hydroxyapatite

Nanoscaled hydroxyapatite (n-HAp) was prepared by a wet chemical precipitation method, pressed to pellets and sintered at various temperatures between 900 and 1200 degrees C. With input stoichiometries of Ca/P ratios between 1.4 and 2.0, compositions in the substoichiometric range of Ca/P between 1.45(1) and 1.62(3) were determined after preparation. After sintering, final values of the Ca/P ratio between 1.45(8) and 1.66(4) were found. Capacitances and dielectric losses were determined in the frequency range between 20 Hz and 1 MHz and dielectric constants calculated from the capacitances. Dependencies of the dielectric properties on the composition, as well as on sintering temperature and frequencies were investigated. The dielectric constants generally tend to increase with increasing Ca-content. Different behaviour was observed for low frequencies (below 10(3) Hz) and for compositions far from the stoichiometric point of hydroxyapatite (Ca/P: 1.67). Comparable results were found for dielectric losses.

Noninvasive electromagnetic fields on keratinocyte growth and migration

BACKGROUND

Although evidence has shown that very small electrical currents produce a beneficial therapeutic result for wounds, noninvasive electromagnetic field (EMF) therapy has consisted mostly of anecdotal clinical reports, with very few well-controlled laboratory mechanistic studies. In this study, we evaluate the effects and potential mechanisms of a noninvasive EMF device on skin wound repair.

MATERIALS AND METHODS

The effects of noninvasive EMF on keratinocytes and fibroblasts were assessed via proliferation and incisional wound model migration assays. cDNA microarray and RT-PCR were utilized to assess genetic expression changes in keratinocytes after noninvasive EMF treatment.

RESULTS

In vitro analyses with human skin keratinocyte cultures demonstrated that noninvasive EMFs have a strong effect on accelerating keratinocyte migration and a relatively weaker effect on promoting keratinocyte proliferation. The positive effects of noninvasive EMFs on cell migration and proliferation seem keratinocyte-specific without such effects seen on dermal fibroblasts. cDNA microarray and RT-PCR performed revealed increased expression of CRK7 and HOXC8 genes in treated keratinocytes.

CONCLUSIONS

This study suggests that a noninvasive EMF accelerates wound re-epithelialization through a mechanism of promoting keratinocyte migration and proliferation, possibly due to upregulation of CRK7 and HOXC8 genes.

Electromagnetic enhancement of a culture of human SAOS-2 osteoblasts seeded onto titanium fiber-mesh scaffolds

The surface properties of a biomaterial are fundamental to determine the response of the host tissue. In the present study, we have followed a particular biomimetic strategy where electromagnetically stimulated SAOS-2 human osteoblasts proliferated and built a calcified extracellular matrix on a titanium fiber-mesh surface. In comparison with control conditions, the electromagnetic stimulation (magnetic field intensity, 2 mT; frequency, 75 Hz) caused higher cell proliferation and increased surface coating with type-I collagen, decorin, and osteopontin (9.8-fold, 11.3-fold, and 9.5-fold, respectively). Reverse transcriptase-polymerase analysis revealed the electromagnetically upregulated transcription specific for the foregoing matrix proteins and for the growth factor TGF-beta1. The immunofluorescence of type-I collagen, decorin, and osteopontin showed their colocalization in the cell-rich areas. The use of an electromagnetic bioreactor aimed at obtaining the surface modification of the biocompatible metallic scaffold in terms of cell colonization and coating with calcified extracellular matrix. The superficially modified biomaterial could be used, in clinical applications, as an implant for bone repair.

Electromagnetic effects - From cell biology to medicine

In this review we compile and discuss the published plethora of cell biological effects which are ascribed to electric fields (EF), magnetic fields (MF) and electromagnetic fields (EMF). In recent years, a change in paradigm took place concerning the endogenously produced static EF of cells and tissues. Here, modern molecular biology could link the action of ion transporters and ion channels to the "electric" action of cells and tissues. Also, sensing of these mainly EF could be demonstrated in studies of cell migration and wound healing. The triggers exerted by ion concentrations and concomitant electric field gradients have been traced along signaling cascades till gene expression changes in the nucleus. Far more enigmatic is the way of action of static MF which come in most cases from outside (e.g. earth magnetic field). All systems in an organism from the molecular to the organ level are more or less in motion. Thus, in living tissue we mostly find alternating fields as well as combination of EF and MF normally in the range of extremely low-frequency EMF. Because a bewildering array of model systems and clinical devices exits in the EMF field we concentrate on cell biological findings and look for basic principles in the EF, MF and EMF action. As an outlook for future research topics, this review tries to link areas of EF, MF and EMF research to thermodynamics and quantum physics, approaches that will produce novel insights into cell biology.

Ultrasound mimics the effect of mechanical loading on bone formation in vivo on rat ulnae

While the effect of ultrasound as an extreme example of low-magnitude high-frequency stimulation has been explored in the response of bone to injury, little is known about its effect on normal bone. This experiment was designed to test the hypothesis that ultrasound exerts a similar influence on bone as mechanical stimulation at a physiological level. Three groups of female Wistar rats were anaesthetised (6 per group). In one group, the left ulna was loaded cyclically in vivo 40 times, repeated on a further 5 occasions on alternate days. In a second group, transcutaneous low-intensity pulsed ultrasound stimulation was applied to the left ulnae for the same duration as the period of loading. In a third group, loading and ultrasound stimulation were applied concurrently. The right ulna served as non-loaded control in each animal. At the end of the experiment after 14 days, both ulnae were removed. Induced bone formation was assessed by measuring the proportion of medial periosteal bone surface with double label (dLS/BS, %) and by calculation of mineral apposition rate (MAR) from the inter-label distance. All three treatments induced a significant periosteal response, increasing dLS/BS values from <10% in control limbs to >80% in treated limbs. Increases in MAR of experimental ulnae versus contralateral control ulnae were 2.9 (+/-0.9), 8.6 (+/-2.4) and 8.7 microm (+/-3.2) for the ultrasound only, ultrasound and load, and load only groups, respectively. The effects of loading plus ultrasound were not significantly different from ultrasound alone. These data suggest that ultrasound is able to induce changes in bone that share at least some features with mechanical loading.

Effects of electromagnetic stimulation on calcified matrix production by SAOS-2 cells over a polyurethane porous scaffold

There is increasing interest in designing new biomaterials that could potentially be used in the form of scaffolds as bone substitutes. In this study we used a hydrophobic crosslinked polyurethane in a typical tissue-engineering approach, that is, the seeding and in vitro culturing of cells using a porous scaffold. Using an electromagnetic bioreactor (magnetic field intensity, 2 mT; frequency, 75 Hz), we investigated the effect of the electromagnetic stimulation on SAOS-2 human osteoblast proliferation and calcified matrix production. Cell proliferation was twice as high; expression of decorin, osteocalcin, osteopontin, type I collagen, and type III collagen was greater (1.3, 12.2, 12.1, 10.0, and 10.5 times as great, respectively); and calcium deposition was 5 times as great as under static conditions without electromagnetic stimulation. RT-PCR analysis revealed the electromagnetically upregulated transcription specific for decorin, fibronectin, osteocalcin, osteopontin, transforming growth factor-beta, type I collagen, and type III collagen. The immunolocalization of the extracellular matrix constituents showed their colocalization in the cell-rich areas. The bioreactor and the polyurethane foam were designed to obtain cell colonization and calcified matrix deposition. This cultured biomaterial could be used, in clinical applications, as an osteoinductive implant for bone repair.

Effects of electromagnetic fields on cells: physiological and therapeutical approaches and molecular mechanisms of interaction. A review

This review concentrates on findings described in the recent literature on the response of cells and tissues to electromagnetic fields (EMF). Models of the causal interaction between different forms of EMF and ions or biomolecules of the cell will be presented together with our own results in cell surface recognition. Naturally occurring electric fields are not only important for cell-surface interactions but are also pivotal for the normal development of the organism and its physiological functions. A further goal of this review is to bridge the gap between recent cell biological studies (which, indeed, show new data of EMF actions) and aspects of EMF-based therapy, e.g., in wounds and bone fractures.

Exposure of mouse preosteoblasts to pulsed electromagnetic fields reduces the amount of mature, type I collagen in the extracellular matrix

We tested the hypothesis that exposure of a mouse preosteoblast cell line to pulsed electromagnetic fields (PEMF) would affect components of the extracellular matrix. We report that exposure of MC3T3-E1 cells to a single PEMF waveform significantly reduced the amount of mature, alpha1(I) collagen in the extracellular matrix (ECM) and the conditioned medium, without affecting the amount of total ECM protein. This decrease was not due to changes in the steady-state level of Col1A1 mRNA or to degradation of mature collagen. We then tested the effect of three distinct PEMF waveforms, two orthogonal coil orientations, and two waveform amplitude levels on the amount of alpha1(I) collagen in the conditioned medium. A sequence of factorial ANOVAs and stepwise regression modeling revealed that the period (duration) of the individual pulses accounted for a significant proportion of the variance associated with the amount of alpha1(I) collagen in the conditioned medium. The total variance accounted for, however, was small (R(2)=0.155, p<0.001 and R(2)=0.172, p<0.001, in the horizontal and vertical orientations, respectively). The positive and negative regression coefficients for the coil orientations revealed that the influence of pulse period was significantly different for the orthogonal coil orientations (p<0.001). The findings imply that the dominant influence of PEMF on the amount of mature, alpha1(I) collagen in the ECM is related to variables other than those expressed in the time-amplitude domain. The results provide objective direction toward identifying waveform characteristics that contribute to the observed between-waveform differences with regard to collagen. Advances in this area may lead toward improving waveforms and waveform delivery protocols.

Exposure of murine cells to pulsed electromagnetic fields rapidly activates the mTOR signaling pathway

Murine pre-osteoblasts and fibroblast cell lines were used to determine the effect of pulsed electromagnetic field (PEMF) exposure on the production of autocrine growth factors and the activation of early signal transduction pathways. Exposure of pre-osteoblast cells to PEMF minimally increased the amount of secreted TGF-beta after 1 day, but had no significant effects thereafter. PEMF exposure of pre-osteoblast cells also had no effect on the amount of prostaglandin E(2) in the conditioned medium. Exposure of both pre-osteoblasts and fibroblasts to PEMF rapidly activated the mTOR signaling pathway, as evidenced by increased phosphorylation of mTOR, p70 S6 kinase, and the ribosomal protein S6. Inhibition of PI3-kinase activity with the chemical inhibitor LY294002 blocked PEMF-dependent activation of mTOR in both the pre-osteoblast and fibroblast cell lines. These findings suggest that PEMF exposure might function in a manner analogous to soluble growth factors by activating a unique set of signaling pathways, inclusive of the PI-3 kinase/mTOR pathway.

Effect of pulsed electromagnetic fields on maturation of regenerate bone in a rabbit limb lengthening model

To study the effect of applying pulsed electromagnetic fields (PEMF) during the consolidation phase of limb lengthening, a mid-tibial osteotomy was performed in 18 adult New Zealand White rabbits and an external fixator was applied anteromedially. Animals were randomly assigned to treatment and control groups. After a 7-day latency period, the tibiae were distracted 0.5 mm every 12 h for 10 days. The treatment group received a 20-day course of PEMF for 60 min daily, coinciding with initiation of the consolidation phase. The control group received sham PEMF. Radiographs were performed weekly after distraction. Animals were euthanized 3 weeks after the end of distraction. Radiographic analysis revealed no significant difference in regenerate callus area between treatment and control tibiae immediately after distraction, at 1 week, 2 weeks, or 3 weeks after distraction ( p = 0.71, 0.22, 0.44, and 0.50, respectively). There was also no significant difference in percent callus mineralization ( p = 0.96, 0.69, 0.99, and 0.99, respectively). There was no significant difference between groups with respect to structural stiffness ( p = 0.80) or maximal torque to failure ( p = 0.62). However, there was a significant positive difference in mineral apposition rate between groups during the interval 1-2 weeks post-distraction ( p < 0.05). This difference was no longer evident by the interval 2-3 weeks post-distraction. While PEMF applied during the consolidation phase of limb lengthening did not appear to have a positive effect on bone regenerate, it increased osteoblastic activity in the cortical bone adjacent to the distraction site. Since the same PEMF signal was reported to be beneficial in the rabbit distraction osteogenesis when applied during distraction phase and consolidation phase, application of PEMF in the early phase may be more effective. Further work is necessary to determine optimal timing of the PEMF stimulation during distraction osteogenesis.

The effect of induced biphasic pulsed currents on re-epithelialization of a novel wound healing model

The coordinated migration of keratinocytes is crucial to cutaneous wound healing; failure of keratinocytes to migrate into a wound can lead to chronic non-healing wounds. Keratinocyte migration can be influenced by applied electrical fields. Our aim was to investigate whether keratinocyte migration could be accelerated by applying an induced biphasic pulsed electrical field. We developed two in vitro biological systems models for this purpose: a keratinocyte colony-forming model and a reconstituted skin wound healing model with biphasic pulsed currents. Our in vitro skin models were capable of generating trans-epithelial potentials (TEP) similar to in vivo mammalian skin. Histological examination of the wound healing model also indicated that re-epithelialization occurred in a similar manner to that seen in vivo, although no evidence of a reconstitution of a basement membrane was seen during the 14 days in vitro experimental period. We found that growth of keratinocyte colonies and keratinocyte migration in an in vitro wound bed were not significantly affected by induced short duration biphasic pulsed currents at a frequency of 0.5 Hz of 100 and 200 mV/mm.

Engineering approaches for the detection and control of orthopaedic biofilm infections

Artificial joints are subject to chronic infections associated with bacterial biofilms, which only can be eradicated by the traumatic removal of the implant followed by sustained intravenous antibiotic therapy. We have adopted an engineering approach to develop electrical-current-based approaches to bacterial eradication and microelectromechanical systems that could be embedded within the implanted joint to detect the presence of bacteria and to provide in situ treatment of the infection before a biofilm can form. In the former case we will examine the combined bactericidal effects of direct and indirect electrical fields in combination with antibiotic therapy. In the latter case, bacterial detection will occur by developing a microelectromechanical-systems-based biosensor that can "eavesdrop" on bacterial quorum-sensing-based communication systems. Treatment will be effected by the release of a cocktail of pharmaceutical reagents contained within integral reservoirs associated with the implant, including a molecular jamming signal that competitively binds to the bacteria's quorum sensing receptors (which will "blind" the bacteria, preventing the production of toxins) and multiple high dose antibiotics to eradicate the planktonic bacteria. This approach is designed to take advantage of the relatively high susceptibility to antibiotics that planktonic bacteria display compared with biofilm envirovars. Here we report the development of a generic microelectromechanical systems biosensor that measures changes in internal viscosity in a base fluid triggered by a change in the external environment.

Redox control of angiogenic factors and CD31-positive vessel-like structures in mouse embryonic stem cells after direct current electrical field stimulation

The molecular mechanisms driving angiogenesis in tissues derived from embryonic stem (ES) cells are currently unknown. Herein we investigated the effects of direct current (DC) electrical field treatment on endothelial cell differentiation and angiogenesis of mouse ES cells. Treatment of ES cell-derived embryoid bodies with field strengths ranging from 250 V/m to 750 V/m, applied for 60 s, dose-dependently increased the capillary area staining positive for the endothelial-specific marker platelet endothelial cell adhesion molecule-1 (PECAM-1), indicating stimulation of endothelial cell differentiation and angiogenesis. Consequently, increased expression of hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) within 24 h was observed. Electric field treatment raised reactive oxygen species (ROS) generation for at least 48 h, which was blunted by NADPH-oxidase inhibitors diphenylen iodonium chloride (DPI) as well as 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF), and increased the expression of NADPH-oxidase subunits p22-phox, p47-phox, p67-phox, and gp91-phox within 24 h. Electrical field treatment resulted in activation of extracellular regulated kinase 1,2 (ERK1,2), p38, as well as c-Jun NH2-terminal kinase (JNK). Pretreatment with the JNK inhibitor SP600125 resulted in a significant decrease in capillary areas under control conditions as well as under conditions of electrical field treatment, whereas the p38 inhibitor SB203580 was without effects. By contrast, the ERK1,2 antagonist UO126 inhibited electrical field-induced angiogenesis, whereas angiogenesis under control conditions was unimpaired. The increase in capillary areas and VEGF expression as well as activation of JNK and ERK1,2 was significantly inhibited in the presence of the free radical scavenger vitamin E underscoring the role of ROS in electrical field-induced angiogenesis of ES cells.

Real-time control of neutrophil metabolism by very weak ultra-low frequency pulsed magnetic fields

In adherent and motile neutrophils NAD(P)H concentration, flavoprotein redox potential, and production of reactive oxygen species and nitric oxide, are all periodic and exhibit defined phase relationships to an underlying metabolic oscillation of approximately 20 s. Utilizing fluorescence microscopy, we have shown in real-time, on the single cell level, that the system is sensitive to externally applied periodically pulsed weak magnetic fields matched in frequency to the metabolic oscillation. Depending upon the phase relationship of the magnetic pulses to the metabolic oscillation, the magnetic pulses serve to either increase the amplitude of the NAD(P)H and flavoprotein oscillations, and the rate of production of reactive oxygen species and nitric oxide or, alternatively, collapse the metabolic oscillations and curtail production of reactive oxygen species and nitric oxide. Significantly, we demonstrate that the cells do not directly respond to the magnetic fields, but instead are sensitive to the electric fields which the pulsed magnetic fields induce. These weak electric fields likely tap into an endogenous signaling pathway involving calcium channels in the plasma membrane. We estimate that the threshold which induced electric fields must attain to influence cell metabolism is of the order of 10(-4) V/m.

Mechanism for action of electromagnetic fields on cells

A biophysical model for the action of oscillating electric fields on cells, presented by us before [Biochem. Biophys. Res. Commun. 272(3) (2000) 634-640], is extended now to include oscillating magnetic fields as well, extended to include the most active biological conditions, and also to explain why pulsed electromagnetic fields can be more active biologically than continuous ones. According to the present theory, the low frequency fields are the most bioactive ones. The basic mechanism is the forced-vibration of all the free ions on the surface of a cell's plasma membrane, caused by an external oscillating field. We have shown that this coherent vibration of electric charge is able to irregularly gate electrosensitive channels on the plasma membrane and thus cause disruption of the cell's electrochemical balance and function [Biochem. Biophys. Res. Commun. 272(3) (2000) 634-640]. It seems that this simple idea can be easily extended now and looks very likely to be able to give a realistic basis for the explanation of a wide range of electromagnetic field bioeffects.

Strong static magnetic field stimulates bone formation to a definite orientation in vitro and in vivo

The induction of bone formation to an intentional orientation is a potentially viable clinical treatment for bone disorders. Among the many chemical and physical factors, a static magnetic field (SMF) of tesla order can regulate the shapes of blood cells and matrix fibers. This study investigated the effects of a strong SMF (8 T) on bone formation in both in vivo and in vitro systems. After 60 h of exposure to the SMF, cultured mouse osteoblastic MC3T3-E1 cells were transformed to rodlike shapes and were orientated in the direction parallel to the magnetic field. Although this strong SMF exposure did not affect cell proliferation, it up-regulated cell differentiation and matrix synthesis as determined by ALP and alizarin red stainings, respectively. The SMF also stimulated ectopic bone formation in and around subcutaneously implanted bone morphogenetic protein (BMP) 2-containing pellets in mice, in which the orientation of bone formation was parallel to the magnetic field. It is concluded that a strong SMF has the potency not only to stimulate bone formation, but also to regulate its orientation in both in vitro and in vivo models. This is the first study to show the regulation of the orientation of adherent cells by a magnetic field. We propose that the combination of a strong SMF and a potent osteogenic agent such as BMP possibly may lead to an effective treatment of bone fractures and defects.

Effect of pulsed electromagnetic fields (PEMF) on late-phase osteotomy gap healing in a canine tibial model

The effects of a pulsed electromagnetic field (PEMF) on late bone healing phases using an osteotomy gap model in the canine mid-tibia were investigated. A transverse mid-diaphyseal tibial osteotomy with a 2-mm gap was performed unilaterally in 12 adult mixed-breed dogs and stabilized with external fixation. Animals in the variable group (n = 6) were treated with PEMF for 1 h daily starting 4 weeks after surgery for a total of 8 weeks, whereas no stimulation signal was generated in the control group (n = 6). Functional load-bearing and radiographic assessments were conducted time-sequentially until euthanasia 12 weeks after surgery. Torsional tests and an analysis of undecalcified histology were performed on the retrieved mid-tibial diaphysis containing the osteotomy site. In the PEMF group, load-bearing of the operated limb recovered earlier when compared to the control group (p < 0.05). Load-bearing in the PEMF group at 8 weeks was greater than in the control group (p < 0.02). The periosteal callus area increased following surgery at 6 weeks (p < 0.05) and thereafter (p < 0.01) in the PEMF group, while a significant increase was observed at 8 and 10 weeks after surgery (p < 0.05) in the control group. Both the normalized maximum torque and torsional stiffness of the PEMF group were significantly greater than those of the control group (p < 0.04 and p < 0.007, respectively). Histomorphometric analyses revealed greater new-bone formation (p < 0.05) in the osteotomy gap tissue and increased mineral apposition rate (p < 0.04) and decreased porosity in the cortex adjacent to the osteotomy line (p < 0.02) in the PEMF group. PEMF stimulation of 1 h per day for 8 weeks provided faster recovery of load-bearing, a significant increase in new bone formation, and a higher mechanical strength of the healing mid-tibial osteotomy. This study revealed enhancing effects of PEMF on callus formation and maturation in the late-phase of bone healing.

Transcriptional profiling of bone regeneration. Insight into the molecular complexity of wound repair

The healing of skeletal fractures is essentially a replay of bone development, involving the closely regulated, interdependent processes of chondrogenesis and osteogenesis. Using a rat femur model of bone healing to determine the degree of transcriptional complexity of these processes, suppressive subtractive hybridization (SSH) was performed between RNA isolated from intact bone to that of callus from post-fracture (PF) days 3, 5, 7, and 10 as a means of identifying up-regulated genes in the regenerative process. Analysis of 3,635 cDNA clones revealed 588 known genes (65.8%, 2392 clones) and 821 expressed sequence tags (ESTs) (31%, 1,127). The remaining 116 cDNAs (3.2%) yielded no homology and presumably represent novel genes. Microarrays were then constructed to confirm induction of expression and determine the temporal profile of all isolated cDNAs during fracture healing. These experiments confirmed that approximately 90 and approximately 80% of the subtracted known genes and ESTs are up-regulated (> or = 2.5-fold) during the repair process, respectively. Clustering analysis revealed subsets of genes, both known and unknown, that exhibited distinct expression patterns over 21 days (PF), indicating distinct roles in the healing process. Additionally, this transcriptional profiling of bone repair revealed a host of activated signaling molecules and even pathways (i.e. Wnt). In summary, the data demonstrate, for the fist time, that the healing process is exceedingly complex, involves thousands of activated genes, and indicates that groups of genes rather than individual molecules should be considered if the regeneration of bone is to be accelerated exogenously.

The porosity dependence of the dielectric constant for sintered hydroxyapatite

Hydroxyapatite (HAp) is the major mineral constituent of bone, and as such, the dielectric properties of HAp are of interest because electromagnetic fields have been shown to accelerate healing in bone fractures. In addition, an interest in the dielectric properties of HAp stems from the suggestion that electrically insulating HAp coatings might be used on implantable devices. In this study, the dielectric constant of polycrystalline hexagonal HAp was measured at nine different frequencies, from 45 kHz to 7.3 MHz for relative porosities ranging from 0.05 to 0.42. At a fixed frequency, the decrease in k as a function of increasing porosity is described well by an exponential function of porosity such that k = k(0)exp(-bP), where k(0) is the dielectric constant at zero porosity and b is a constant. In addition, the entire data set of 108 data points (representing the 12 specimens of differing porosity measured at each of the nine frequencies) was fit to a candidate function formed from the product k(0)exp(-bP) and a simple expression relating frequency to the dielectric constant. The candidate function fit the data relatively well, with a coefficient of determination of 0.91.