Enhanced Proliferation and Differentiation of Human Osteoblasts by Remotely Controlled Magnetic-Field-Induced Electric Stimulation Using Flexible Substrates

With the progressive aging of the population, bone fractures are an increasing major health concern. Diverse strategies are being studied to reduce the recovery times using nonaggressive treatments. Electrical stimulation (either endogenous or externally applied electric pulses) has been found to be effective in accelerating bone cell proliferation and differentiation. However, the direct insertion of electrodes into tissues can cause undesirable inflammation or infection reactions. As an alternative, magnetoelectric heterostructures (wherein magnetic fields are applied to induce electric polarization) could be used to achieve electric stimulation without the need for implanted electrodes. Here, we develop a magnetoelectric platform based on flexible kapton/FeGa/P(VDF-TrFE) (flexible substrate/magnetostrictive layer/ferroelectric layer) heterostructures for remote magnetic-field-induced electric field stimulation of human osteoblast cells. We show that the use of flexible supports overcomes the clamping effects that typically occur when analogous magnetoelectric structures are grown onto rigid substrates (which preclude strain transfer from the magnetostrictive to the ferroelectric layers). The study of the diverse proliferation and differentiation markers evidence that in all the stages of bone formation (cell proliferation, extracellular matrix maturation, and mineralization), the electrical stimulation of the cells results in a remarkably better performance. The results pave the way for novel strategies for remote cell stimulation based on flexible platforms not only in bone regeneration but also in many other applications where electrical cell stimulation may be beneficial (e.g., neurological diseases or skin regeneration).

Effects of electric charge on fracture healing

Fracture nonunion is a common and challenging complication. Although direct current stimulation has been suggested to promote fracture healing, differences in cell density near the positive and negative electrodes have been reported during direct current stimulation. This study aimed to explore the effects of these differences on osteoblast proliferation and fracture healing. MC3T3-E1 cells were stimulated by positive and negative charges to observe cell proliferation, apoptosis, and osteogenic factor expression in vitro, while positive and negative charges were connected to the Kirschner wires of the fractures in an in vivo double-toe fracture model in New Zealand white rabbits and fracture healing was assessed in digital radiography (DR) examinations performed on days 1, 15, 30. Bone tissue samples of all rabbits were analysed histologically after the last examination. The results showed that in comparison with the control group, after DC stimulation, the number of cells near the positive electrode decreased significantly (P < 0.05), apoptosis increased (P < 0.05), the expression of osteocalcin, osteoblast-specific genes, and osteonectin decreased significantly near the positive electrode (P < 0.05) and increased significantly at the negative electrode (P < 0.05). The fracture at the positive electrode junction of New Zealand white rabbits did not heal. Histomorphological analysis showed more bone trabeculae and calcified bone in the bone tissue sections of the control group and the negative electrode group than in the positive electrode group. The bone trabeculae were thick and showed good connections. However, positive charge inhibited osteoblast proliferation and a positive charge at fracture sites did not favour fracture healing. Thus, a positive charge near the fracture site may be a reason for fracture nonunion.

Pulse Electromagnetic Field for Treating Postmenopausal Osteoporosis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Postmenopausal osteoporosis is a type of chronic disease with high morbidity and high economic burden. Due to the adverse effects of long-term drug therapy, physical therapy, such as pulsed electromagnetic fields (PEMF), is widely implemented in clinical practice. Therefore, we first conducted the meta-analysis on the efficacy and safety of PEMF in the treatment of postmenopausal osteoporosis. We searched eight databases to acquire potentially eligible studies. Outcome indicators include bone mineral density (BMD), visual analogue scale (VAS), biochemical markers of alkaline phosphatase (ALP), osteocalcin, bone-specific alkaline phosphatase (BSAP), type I collagen carboxy-terminal peptide (CTX), and adverse events. The results showed that a total of 19 studies (1303 patients) were retrieved from eight databases. Compared with conventional medications, PEMF combined with conventional medications significantly increased BMD of lumbar vertebra, femoral, Ward's triangle, bone-specific biochemical indicators of ALP, BSAP, and osteocalcin, and relieved pain. However, The incidence of adverse events was not statistically significant between PEMF combined with conventional medications and conventional medications alone. Compared with conventional medications, PEMF significantly increased the BMD of the femur and reduced the degree of pain, but there was no statistical difference in the BMD of the lumbar spine between PEMF and placebo. Except osteocalcin, BSAP, CTX, and ALP showed no significant difference. In view of its efficacy and safety, PEMF intervention can be considered as a potentially effective complementary therapy for postmenopausal women with osteoporosis. © 2022 Bioelectromagnetics Society.

Osteogenesis Modulation: Induction of Mandibular Bone Growth in Adults by Electrical Field for Aesthetic Purposes

BACKGROUND

A new technique in plastic surgery termed Osteogenesis Modulation is described. This technique uses a surgically implanted, battery-operated medical device to deliver customized electrical pulses to produce mandibular bone growth. This device was designed to be a temporary, nonpermanent implant. The purpose of this study was to review both the safety and efficacy of Osteogenesis Modulation.

METHODS

This study comprises two phases. Phase I involved experimental technology development and animal experiments. Phase II included technology development for clinical use and a clinical trial. In Phase II, four patients with a diagnosis of mandibular hypoplasia and microgenia underwent surgical implantation of the novel medical device over the chin bone. Once a satisfactory change of contour of mandibular bone was achieved, the devices were removed. In all patients, the devices were left in place for 12 months, then surgically removed under local anesthesia. Preoperative and long-term postoperative cephalometric controls were done.

RESULTS

In all patients, symmetrical mandibular bone growth was observed with good-to-excellent aesthetic results. The overall follow-up period was 39 months. Cephalometric controls taken 3 to 6 months after the device removal showed an average increase in mandible length of 5.26mm (range, 2.83-7.60mm) CONCLUSIONS: Preliminary clinical results suggest that Osteogenesis Modulation is a safe, minimally invasive, and effective alternative treatment for the correction of mandibular hypoplasia in selected cases.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

EFFECTIVENESS OF VIBRATION (CYCLIC LOADING) IN ACCELERATING BONE REMODELING AND ORTHODONTIC TOOTH MOOVEMENT: A SHORT REVIEW

This paper assesses the effectiveness of vibration in accelerating bone remodeling and orthodontic tooth movement. Databases of PubMed, Web of Science, and ScienceDirect were searched from January 2017 to March 2019 for randomized or quasi-randomized controlled trials that evaluated the effectiveness of vibration in accelerating bone remodeling and orthodontic tooth movement. The inclusion criteria were as follows: (i) studies that assessed the efficacy of vibration (cyclic loading) in bone remodeling and orthodontic tooth movement and (ii) those that employed groupings (experimental vs. control/placebo groups) on the basis of the use of vibration (cyclic loading). Eight clinical trials were included in this short review. Five studies met the eligibility criteria for bone remodeling and orthodontic tooth movement. Four studies found that low-magnitude high-frequency vibration could accelerate bone remodeling. However, contradictory results were obtained with regard to the acceleration of orthodontic tooth movement by vibration in human participants. Low-magnitude high-frequency vibration can accelerate bone remodeling and orthodontic tooth movement. However, this acceleration is dependent on the magnitude and frequency. Further research is necessary to determine the most feasible protocols for investigating the effects of magnitude and frequency of vibration on the acceleration of orthodontic tooth movement in human participants.

Synergistic effect of electromagnetic fields and nanomagnetic particles on osteogenesis through calcium channels and p-ERK signaling

Electromagnetic fields (EMFs) are widely used in a number of cell therapies and bone disorder treatments, and nanomagnetic particles (NMPs) also promote cell activity. In this study, we investigated the synergistic effects of EMFs and NMPs on the osteogenesis of the human Saos-2 osteoblast cell line and in a rat calvarial defect model. The Saos-2 cells and critical-size calvarial defects of the rats were exposed to EMF (1 mT, 45 Hz, 8 h/day) with or without Fe₃ O₄ NMPs. Biocompatibility was evaluated with MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and LDH (lactate dehydrogenase) assays. This analysis showed that NMP and EMF did not induce cell toxicity. Quantitative reverse-transcription polymerase chain reaction indicated that the osteogenesis-related markers were highly expressed in the NMP-incorporated Saos-2 cells after exposure to EMF. Also, the expression of gene-encoding proteins involved in calcium channels was activated and the calcium concentration of the NMP-incorporated + EMF-exposed group was increased compared with the control group. In particular, in the NMP-incorporated + EMF-exposed group, all osteogenic proteins were more abundantly expressed than in the control group. This indicated that the NMP incorporation + EMF exposure induced a signaling pathway through activation of p-ERK and calcium channels. Also, in vivo evaluation revealed that rat calvarial defects treated with EMFs and NMPs had good regeneration results with new bone formation and increased mineral density after 6 weeks. Altogether, these results suggest that NMP treatment or EMF exposure of Saos-2 cells can increase osteogenic activity and NMP incorporation following EMF exposure which is synergistically efficient for osteogenesis.

Electrochemical methods to enhance osseointegrated prostheses

Osseointegrated (OI) prosthetic limbs have been shown to provide an advantageous treatment option for amputees. In order for the OI prosthesis to be successful, the titanium implant must rapidly achieve and maintain proper integration with the bone tissue and remain free of infection. Electrochemical methods can be utilized to control and/or monitor the interfacial microenvironment where the titanium implant interacts with the biological system (host bone tissue or bacteria). This review will summarize the current understanding of how electrochemical modalities can influence bone tissue and bacteria with specific emphasis on applications where the metallic prosthesis itself can be utilized directly as a stimulating electrode for enhanced osseointegration and infection control. In addition, a summary of electrochemical impedance sensing techniques that could be used to potentially assess osseointegration and infection status of the metallic prosthesis is presented.

Photobiomodulation in acceleration of orthodontic tooth movement: A systematic review and meta analysis

BACKGROUND

Photobiomodulation therapy, a non invasive method with no adverse effects, has been used to accelerate tooth movement in orthodontia. However, the specific characteristics of laser settings used in studies documented have reported varied inconsistent conflicting results.

OBJECTIVES

We decided to undertake a systematic review to eliminate this inconsistency by quantifying the literature studies that indicated the link between photobiomodulation and acceleration of tooth movement and to assess if there is any association of photobiomodulation therapy in accelerating tooth movement.

SEARCH STRATEGY

We systematically searched for articles of existing literatures on Photobiomodulation therapy and acceleration of tooth movement over Cochrane library, Pubmed central, EMBASE, Scopus and Web of sciences from 2000 to 2017. Mesh search terms using various descriptors were used to identify the studies.

SEARCH CRITERIA

We included randomized control trial and clinical control trail studies that used Ga-Al-As diode laser and Oseeopulse laser with specific characteristics and company specifications, addressing relevant efficiency and safety outcomes.

DATA COLLECTION AND ANALYSIS

Eligible studies were reviewed and data was extracted on a standard from. We used Cochrane review manager software (Revman version 5.3) to assess the qualities of each included trials. Data were analyzed using an inverse variance method with random effects model effect.

RESULTS

We observed a statistical significant difference between the photobiomodulation therapy compared to non laser group in the acceleration of tooth movement (Mean difference 0.59 (95%CI- 0.24 to 0.95) I² 95%). However, these results need caution while generalizing in clinical practice due to the large amount of heterogeneity across the studies.

CONCLUSION

Findings of the current systematic review suggest a possible benefit with photobiomodulation therapy and tooth movement in orthodontia. However these findings need to be further validated in larger trials using specific standardized characteristics of laser settings to uniform the methodological design that can be used in routine clinical practice.

Flexoelectricity in Bones

Bones generate electricity under pressure, and this electromechanical behavior is thought to be essential for bone's self-repair and remodeling properties. The origin of this response is attributed to the piezoelectricity of collagen, which is the main structural protein of bones. In theory, however, any material can also generate voltages in response to strain gradients, thanks to the property known as flexoelectricity. In this work, the flexoelectricity of bone and pure bone mineral (hydroxyapatite) are measured and found to be of the same order of magnitude; the quantitative similarity suggests that hydroxyapatite flexoelectricity is the main source of bending-induced polarization in cortical bone. In addition, the measured flexoelectric coefficients are used to calculate the (flexo)electric fields generated by cracks in bone mineral. The results indicate that crack-generated flexoelectricity is theoretically large enough to induce osteocyte apoptosis and thus initiate the crack-healing process, suggesting a central role of flexoelectricity in bone repair and remodeling.

Piezoelectric smart biomaterials for bone and cartilage tissue engineering

Tissues like bone and cartilage are remodeled dynamically for their functional requirements by signaling pathways. The signals are controlled by the cells and extracellular matrix and transmitted through an electrical and chemical synapse. Scaffold-based tissue engineering therapies largely disturb the natural signaling pathways, due to their rigidity towards signal conduction, despite their therapeutic advantages. Thus, there is a high need of smart biomaterials, which can conveniently generate and transfer the bioelectric signals analogous to native tissues for appropriate physiological functions. Piezoelectric materials can generate electrical signals in response to the applied stress. Furthermore, they can stimulate the signaling pathways and thereby enhance the tissue regeneration at the impaired site. The piezoelectric scaffolds can act as sensitive mechanoelectrical transduction systems. Hence, it is applicable to the regions, where mechanical loads are predominant. The present review is mainly concentrated on the mechanism related to the electrical stimulation in a biological system and the different piezoelectric materials suitable for bone and cartilage tissue engineering.

Piezoelectric material - A promising approach for bone and cartilage regeneration

Bone and cartilage are major weight-bearing connective tissues in human and possesses utmost vulnerability for degeneration. The potential causes are mechanical trauma, cancer and disease condition like osteoarthritis and osteoporosis, etc. The regeneration/repair is a challenging, since their complex structures and activities. Current treatment options comprise of auto graft, allograft, artificial bone substituent, autologous chondrocyte implantation, mosaicplasty, marrow stimulation and tissue engineering. Were incompetent to overcome the problem like abandoned growth factor degradation, indistinct growth factor dose and lack of integrity and mechanical properties in regenerated tissues. Present, paper focuses on the novel hypothesis for regeneration of bone and cartilage by using piezoelectric smart property of scaffold material.

Diamond-Graphite Nanoplatelet Surfaces as Conductive Substrates for the Electrical Stimulation of Cell Functions

The nanocarbon allotropes constitute valid alternatives when designing control and actuation devices for electrically assisted tissue regeneration purposes, gathering among them important characteristics such as chemical inertness, biocompatibility, extreme mechanical properties, and, importantly, low and tailorable electrical resistivity. In this work, coatings of thin (100 nm) vertically aligned nanoplatelets composed of diamond (5 nm) and graphite were produced via a microwave plasma chemical vapor deposition (MPCVD) technique and used as substrates for electrical stimulation of MC3T3-E1 preosteoblasts. Increasing the amount of N₂ up to 14.5 vol % during growth lowers the coatings' electrical resistivity by over 1 order of magnitude, triggers the nanoplatelet vertical growth, and leads to the higher crystalline quality of the nanographite phase. When preosteoblasts were cultured on these substrates and subjected to two consecutive daily cycles of 3 μA direct current stimulation, enhanced cell proliferation and metabolism were observed accompanied by high cell viability. Furthermore, in the absence of DC stimulation, alkaline phosphatase (ALP) activity is increased significantly, denoting an up-regulating effect of preosteoblastic maturation intrinsically exerted by the nanoplatelet substrates.

Multi and mixed 3D-printing of graphene-hydroxyapatite hybrid materials for complex tissue engineering

With the emergence of three-dimensional (3D)-printing (3DP) as a vital tool in tissue engineering and medicine, there is an ever growing need to develop new biomaterials that can be 3D-printed and also emulate the compositional, structural, and functional complexities of human tissues and organs. In this work, we probe the 3D-printable biomaterials spectrum by combining two recently established functional 3D-printable particle-laden biomaterial inks: one that contains hydroxyapatite microspheres (hyperelastic bone, HB) and another that contains graphene nanoflakes (3D-graphene, 3DG). We demonstrate that not only can these distinct, osteogenic, and neurogenic inks be co-3D-printed to create complex, multimaterial constructs, but that composite inks of HB and 3DG can also be synthesized. Specifically, the printability, microstructural, mechanical, electrical, and biological properties of a hybrid material comprised of 1:1 HA:graphene by volume is investigated. The resulting HB-3DG hybrid exhibits mixed characteristics of the two distinct systems, while maintaining 3D-printability, electrical conductivity, and flexibility. In vitro assessment of HB-3DG using mesenchymal stem cells demonstrates the hybrid material supports cell viability and proliferation, as well as significantly upregulates both osteogenic and neurogenic gene expression over 14 days. This work ultimately demonstrates a significant step forward towards being able to 3D-print graded, multicompositional, and multifunctional constructs from hybrid inks for complex composite tissue engineering. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 274-283, 2017.

[Interosseous electrostimulation in a model of lengthening with external fixation]

BACKGROUND

A fracture repair involves complex cellular processes. However, despite optimal treatment, some fractures heal slowly or do not repair. These complications support the need for innovative therapies. Electromagnetic stimulation is a non-invasive technology that could have a direct impact on many cellular pathways.

OBJECTIVE

To demonstrate the effectiveness of electro-stimulation by alternating current applied during bone elongation to accelerate the consolidation process for 30 days in an animal model.

MATERIALS AND METHODS

A device with closed circuit and graduated voltage was designed and kept in contact with the external fixator. Group A was elongated without electro-stimulation and group B was electro-stimulated since the beginning of the distraction. Radiographs were taken at 15 and 30 days post-surgical. Haematoxylin and eosin staining and Masson's trichrome stain were performed.

RESULTS

No significant difference were observed in bone density of group A (4.05±3.24, P=0.163). In group B there was a significant difference (61.06±20.17, P=0.03) in bone density. Group A maintained a fibrous tissue repair, with areas of cartilage and bone matrix. Group B had more organised tissue in the stages of bone repair.

CONCLUSION

Because there is a significant difference in the growth and callus formation at 15 and 30 days between groups, electro-stimulation could be considered as an adjuvant during bone elongation.

Review Management of nonunion in trauma

Treatment of nonunion has radically changed in recent years. We define nonunion as a fracture of bone induced either by trauma or surgery which does not show clinical or radiographic signs of progression to healing within a reasonable time span. The reparative processes are present but inadequate. Fracture healing may be considered to be a balance between repair and breakdown processes at the fracture site. When breakdown exceeds repair, nonunion is the result. Altering the conditions at the fracture site even marginally in favour of repair will eventually lead to bony continuity being restored. Nonunion treatment should follow three principles: a) realignment; b) stabilization; and c) stimulation. Any surgical proce dure should address one or all of these areas. In this article the principles of nonunion management are explained, together with different bone healing stimulation techniques and our clinical results.

Efficiency of low-level laser therapy within induced dental movement: A systematic review and meta-analysis

The low level laser is widely used in Dentistry, in particular, to decrease pain and increase the speed of tooth movement. This study was to perform a systematic literature search to investigate the effectiveness of low level laser and low energy density therapy of the induced tooth movement. This research was performed following the PRISMA instructions and was registered in the PROSPERO. The articles were searched in six electronic databases, with no date and language restriction. Only randomized clinical trials were selected. Articles that did not use the extraction of first premolars as orthodontic planning were excluded, as well as articles using high energy density laser therapy. The articles were assessed for risk of bias and individual quality. The results were analyzed using meta-analysis, using randomized effect. The initial sample consisted of 161 articles. Six articles remained eligible for qualitative analysis and five for quantitative analysis. According to the individual quality, most articles were classified as high quality. Three articles detected statistically significant differences in induced movement by comparing the orthodontic movement between the experimental and control groups. For the maxilla, there was a statistically significant influence of the laser in three months and, for the mandible, in one month. It may be concluded that there is no evidence that laser therapy can accelerate the induced tooth movement.

Effective parameters on conductivity of mineralized carbon nanofibers: an investigation using artificial neural networks

The aim of this study was to predict the effects of different parameters on the conductivity of mineralized PAN-based carbon nanofibers by the artificial neural network (ANN) method.

Enhanced patella-patellar tendon healing using combined magnetic fields in a rabbit model

BACKGROUND

A combined magnetic field (CMF) is a composite of a dynamic sinusoidal magnetic field and a magnetostatic field. Stimuli from CMFs has proved to be an effective tool for healing problem fractures and spinal fusion procedures.

HYPOTHESIS

Combined magnetic field technology will enhance healing of bone-tendon junction repair via endochondral ossification for regeneration of the fibrocartilage zone.

STUDY DESIGN

Controlled laboratory study.

METHODS

Forty-eight mature rabbits were randomly divided into CMF-treated and placebo-treated (control) groups. A partial patellectomy model was created. The CMF-treated group was subjected to CMF stimulation from the third postoperative day for 30 minutes per day up to weeks 8 or 16. At each time point, tissue samples were harvested and evaluated biomechanically and histomorphologically. The area of newly formed bone and the thickness of fibrocartilage were measured in hematoxylin and eosin-stained sections and toluidine blue-stained sections, respectively, while the density of fibrocartilage cells and the amount of proteoglycans were calculated using safranin O-stained sections. A biomechanical analysis was carried out to ascertain tensile strength.

RESULTS

Quantitative histological measurements showed that the newly formed bone and regenerated fibrocartilage zone in the CMF-treated group increased by a respective 99.2% and 41.9% compared with the control group at week 8 and a respective 97.8% and 22.8% at week 16. In the CMF-treated group at postoperative week 16, the amount of proteoglycans was 36.9% more than that of the control group, but the density of fibrocartilage cells was just 71.4% of the control group; there were no significant differences at week 8. Mechanical test results showed that energy to failure was not significantly different between the 2 groups at week 8. Yet, at week 16, load to failure, ultimate strength, and energy to failure in the CMF-treated group (311.0 ± 59.4 N, 8.46 ± 1.41 MPa, and 0.87 ± 0.17 J, respectively) were significantly higher than those in the control group (247.1 ± 65.6 N, 6.84 ± 1.12 MPa, and 0.52 ± 0.15 J, respectively).

CONCLUSION

Biophysical stimulation with CMFs enhances healing after bone-tendon junction injuries in a rabbit model.

CLINICAL RELEVANCE

These results demonstrate the feasibility of using CMFs for stimulating bone-tendon healing after repair.

Chitosan/nano-hydroxyapatite composite electret membranes enhance cell proliferation and osteoblastic expression in vitro

Chitosan/nano-hydroxyapatite membranes with negative charges were fabricated by grid-controlled constant voltage corona charging, and the charged membranes were investigated for cell biocompatibility and osteoinduction. The osteoblasts on the chitosan/nano-hydroxyapatite composite electret membranes significantly enhanced the adhesion, proliferation, and differentiation capacity compared to the uncharged group. This study not only provides evidence for the potential clinical application of our novel membranes but also could be used as a strategy for chitosan/nano-hydroxyapatite scaffolds.

Low-intensity pulsed ultrasound accelerates tooth movement via activation of the BMP-2 signaling pathway

The present study was designed to determine the underlying mechanism of low-intensity pulsed ultrasound (LIPUS) induced alveolar bone remodeling and the role of BMP-2 expression in a rat orthodontic tooth movement model. Orthodontic appliances were placed between the homonymy upper first molars and the upper central incisors in rats under general anesthesia, followed by daily 20-min LIPUS or sham LIPUS treatment beginning at day 0. Tooth movement distances and molecular changes were evaluated at each observation point. In vitro and in vivo studies were conducted to detect HGF (Hepatocyte growth factor)/Runx2/BMP-2 signaling pathways and receptor activator of NFκB ligand (RANKL) expression by quantitative real time PCR (qRT-PCR), Western blot and immunohistochemistry. At day 3, LIPUS had no effect on the rat orthodontic tooth movement distance and BMP-2-induced alveolar bone remodeling. However, beginning at day 5 and for the following time points, LIPUS significantly increased orthodontic tooth movement distance and BMP-2 signaling pathway and RANKL expression compared with the control group. The qRT-PCR and Western blot data in vitro and in vivo to study BMP-2 expression were consistent with the immunohistochemistry observations. The present study demonstrates that LIPUS promotes alveolar bone remodeling by stimulating the HGF/Runx2/BMP-2 signaling pathway and RANKL expression in a rat orthodontic tooth movement model, and LIPUS increased BMP-2 expression via Runx2 regulation.

Electrical stimuli to increase cell proliferation on carbon nanotubes/mesoporous silica composites for drug delivery

The development of smart materials as bone implants is nowadays a challenging task to optimize their fast osteointegration. Nevertheless, no attempts have been done in joining the possibility of using electrical stimulation and drug delivery together in a material intended for bone tissue engineering. Moreover, the use of this synergy to induce bone healing is still limited until novel drug reservoirs material formulations allow an efficient applicability of the electrical stimuli. Herein, we present the biological response of osteoblasts cells, cultured over carbon nanotubes-mesoporous silica composites while exposed to external electrical stimulus. Moreover, its ability to function as drug delivery systems is also demonstrated. Bone cell metabolism was stimulated and mitochondrial activity was increased up to seven times in the presence of these composites under electrical stimulus, suggesting their potential application in bone regeneration processes.

Low current electrical stimulation upregulates cytokine expression in the anal sphincter

AIM

Stem cells are an emerging treatment for regeneration of damaged anal sphincter tissues. Homing to the site of injury can be potentiated by stromal derived factor 1 (SDF-1) and monocyte chemotactic protein 3 (MCP-3) expression. The effects of electrical stimulation (ES) on upregulation of these cytokines were investigated.

METHODS

The anal sphincter complex of Sprague Dawley rats was stimulated with current of 0.25 mA, pulse duration of 40 pulses/s, pulse width of 100 μs, and frequency of 100 Hz for 1 or 4 h. Sham was created using the same needle which was inserted into the anal sphincter without electrical stimulation in different groups of animals. The rats were euthanized immediately or 24 h after stimulation. Cytokine analysis was performed using real-time polymerase chain reaction. Statistical analysis was performed.

RESULTS

Results are presented as a fold increase compared to sham that was normalized to 1. SDF-1 and MCP-3 immediately after 1 h were 2.5 ± 0.77 and 3.1± 0.93 vs. sham, respectively, showing significant increase. After 1-h stimulation and euthanasia 24 h after, SDF-1 and MCP-3 were 1.49 ± 0.16 and 1.51± 0.14 vs. sham, respectively, showing significant increase. Immediately and 24 h after 4-h stimulation, SDF-1 was 1.21 ± 0.16 and 0.54 ± 0.16 vs. sham, respectively, and was not significantly different. Immediately and 24 h after 4-h stimulation, MCP-3 was 1.29 ± 0.41 and 0.35 ±1.0 vs. sham, respectively, and was not significantly different. SDF-1 and MCP-3 after 1 h were significantly higher than after 4 h of stimulation at both time points.

CONCLUSION

Electrical stimulation for 1 h significantly upregulates SDF-1 and MCP-3 expression that persists for 24 h. Prolonged stimulation reduced chemokine expression, suggesting electrolysis of cells.

Possible role of calcium permselectivity in bone adaptation

According to the core activity of calcium in the bone cellular expression, a new hypothesis linking calcium transport with the mechanical loading is proposed to explain the mechano-adaptation of bone tissue. Due to the piezoelectric coupling, the tensile and compressive areas of bone produce different electrical environments for the osteocytic cells that are embedded in the lacuno-canalicular porosity. This electrical asymmetry engenders a calcium enrichment-exclusion effect that strongly changes the calcium concentration in the lacuno-canalicular fluid and thus modifies the remodelling process. A bibliographic body of evidence supporting this idea is given and its experimental validation is suggested.

Electric-field-enhanced nutrient consumption in dielectric biomaterials that contain anchorage-dependent cells

This research contribution addresses electric-field stimulation of intra-tissue mass transfer and cell proliferation in viscoelastic biomaterials. The unsteady state reaction-diffusion equation is solved according to the von Kármán-Pohlhausen integral method of boundary layer analysis when nutrient consumption and tissue regeneration occur in response to harmonic electric potential differences across a parallel-plate capacitor in a dielectric-sandwich configuration. The partial differential mass balance with diffusion and electro-kinetic consumption contains the Damköhler (Λ(2)) and Deborah (De) numbers. Zero-field and electric-field-sensitive Damköhler numbers affect nutrient boundary layer growth. Diagonal elements of the 2nd-rank diffusion tensor are enhanced in the presence of weak electric fields, in agreement with the formalism of equilibrium and nonequilibrium thermodynamics. Induced dipole polarization density within viscoelastic biomaterials is calculated via the real and imaginary components of the complex dielectric constant, according to the Debye equation, to quantify electro-kinetic stimulation. Rates of nutrient consumption under zero-field conditions are described by third-order kinetics that include local mass densities of nutrients, oxygen, and attached cells. Thinner nutrient boundary layers are stabilized at shorter dimensionless diffusion times when the zero-field intra-tissue Damköhler number increases above its initial-condition-sensitive critical value [i.e., {Λ(2)(zero-field)}(critical)≥53, see Eq. (23)], such that the biomaterial core is starved of essential ingredients required for successful proliferation. When tissue regeneration occurs above the critical electric-field-sensitive intra-tissue Damköhler number, the electro-kinetic contribution to nutrient consumption cannot be neglected. The critical electric-field-sensitive intra-tissue Damköhler number is proportional to the Deborah number.

Chemokine upregulation in response to anal sphincter and pudendal nerve injury: potential signals for stem cell homing

PURPOSE

Stromal derived factor-1 (SDF-1) and monocyte chemotactic protein-3 (MCP-3) are signals forcing the migration of bone marrow-derived stem cells to ischemic tissue. This study investigates SDF-1 and MCP-3 expression following direct injury to the anal sphincter and pudendal nerve and to determine if these same mechanisms have any role.

METHODS

Chemokine expression was studied after anal sphincter injury in female rats after either a sphincterotomy (n = 15), pudendal nerve crush (PNC; n = 15), sham pudendal nerve crush (n = 15), or acted as unmanipulated controls (n = 5). Analysis was done at 1 h and 10 and 21 days after injury.

RESULTS

After injury, SDF-1 expression increased 40.2 ± 6.42 (P = 0.01) at 1 h and 28.2 ± 2.37 (P = 0.01) at 10 days, respectively, compared to controls. Likewise, MCP-3 expression increased 40.8 ± 8.17 (P = 0.02) at the same intervals compared to controls. After PNC, SDF-1 expression increased 46.4 ± 6.01 (P = 0.02) and 50.6 ± 10.11 (P = 0.01), and MCP-3 expression increased 46.3 ± 7.76 (P = 0.03) and 190.8 ± 22.15 (P = 0.01), respectively, at the same time intervals compared to controls. However, when PNC was compared to sham injured, a significant increase was seen in SDF-1 and MCP-3 at 10 days. At 21 days, PNC compared to sham injured was significantly low in expression for both SDF-1 and MCP-3 (P < 0.05).

CONCLUSIONS

Direct anal sphincter injury results in higher levels of SDF-1 and MCP-3 expression soon after injury, whereas denervation via pudendal nerve crush results in greater SDF-1 and MCP-3 expression 10 days after injury. Chemokine overexpression suggests the potential for cell-based therapeutic strategies.

Application of low-frequency alternating current electric fields via interdigitated electrodes: effects on cellular viability, cytoplasmic calcium, and osteogenic differentiation of human adipose-derived stem cells

Electric stimulation is known to initiate signaling pathways and provides a technique to enhance osteogenic differentiation of stem and/or progenitor cells. There are a variety of in vitro stimulation devices to apply electric fields to such cells. Herein, we describe and highlight the use of interdigitated electrodes to characterize signaling pathways and the effect of electric fields on the proliferation and osteogenic differentiation of human adipose-derived stem cells (hASCs). The advantage of the interdigitated electrode configuration is that cells can be easily imaged during short-term (acute) stimulation, and this identical configuration can be utilized for long-term (chronic) studies. Acute exposure of hASCs to alternating current (AC) sinusoidal electric fields of 1 Hz induced a dose-dependent increase in cytoplasmic calcium in response to electric field magnitude, as observed by fluorescence microscopy. hASCs that were chronically exposed to AC electric field treatment of 1 V/cm (4 h/day for 14 days, cultured in the osteogenic differentiation medium containing dexamethasone, ascorbic acid, and β-glycerol phosphate) displayed a significant increase in mineral deposition relative to unstimulated controls. This is the first study to evaluate the effects of sinusoidal AC electric fields on hASCs and to demonstrate that acute and chronic electric field exposure can significantly increase intracellular calcium signaling and the deposition of accreted calcium under osteogenic stimulation, respectively.

Electrical stimulation for long-bone fracture-healing: a meta-analysis of randomized controlled trials

BACKGROUND

Bone stimulation represents a $500 million market in the United States. The use of electromagnetic stimulation in the treatment of fractures is common; however, the efficacy of this modality remains uncertain. We conducted a systematic review and meta-analysis of randomized controlled trials to evaluate the effect of electromagnetic stimulation on long-bone fracture-healing.

METHODS

We searched four electronic databases (MEDLINE, EMBASE, CINAHL, and all Evidence-Based Medicine Reviews) for trials of electromagnetic stimulation and bone repair, in any language, published from the inception of the database to April 2008. In addition, we searched by hand seven relevant journals published between 1980 and April 2008 and the bibliographies of eligible trials. Eligible trials enrolled patients with long-bone lesions, randomly assigned them to electromagnetic stimulation or a control group, and reported on bone-healing. Information on the methodological quality, stimulation device, duration of treatment, patient demographics, and all clinical outcomes were independently extracted by two reviewers.

RESULTS

Of 2546 citations obtained in the literature search, eleven articles met the inclusion criteria. Evidence from four trials reporting on 106 delayed or ununited fractures demonstrated an overall nonsignificant pooled relative risk of 1.76 (95% confidence interval, 0.8 to 3.8; p = 0.15; I(2) = 60.4%) in favor of electromagnetic stimulation. Single studies found a positive benefit of electromagnetic stimulation on callus formation in femoral intertrochanteric osteotomies, a limited benefit for conservatively managed Colles fracture or for lower limb-lengthening, and no benefit on limb-length imbalance and need for reoperation in surgically managed pseudarthroses or on time to clinical healing in tibial stress fractures. Pain was reduced in one of the four trials assessing this outcome.

CONCLUSIONS

While our pooled analysis does not show a significant impact of electromagnetic stimulation on delayed unions or ununited long-bone fractures, methodological limitations and high between-study heterogeneity leave the impact of electromagnetic stimulation on fracture-healing uncertain.

Low-energy laser stimulates tooth movement velocity via expression of RANK and RANKL

OBJECTIVE

Recent studies have demonstrated that low-energy laser irradiation stimulates bone formation in vitro and in vivo. However, very little is known about the effects of laser irradiation on osteoclastogenesis. The receptor activator of the nuclear factor-kB (RANK) / RANK ligand (RANKL) / osteoprotegerin (OPG) system is essential and sufficient for osteoclastogenesis. The present study was designed to examine the effects of low-energy laser irradiation on expressions of RANK, RANKL, and OPG during experimental tooth movement.

DESIGN

To induce experimental tooth movement in rats, 10 g of orthodontic force was applied to the molars. Next, a Ga-Al-As diode laser was used to irradiate the area around the moved tooth and the amount of tooth movement was measured for 7 days. Immunohistochemical staining with RANK, RANKL, and OPG was performed. Real time PCR was also performed to elucidate the expression of RANK in irradiated rat osteoclast precursor cells in vitro.

RESULTS

In the irradiation group, the amount of tooth movement was significantly greater than in the non-irradiation group by the end of the experimental period. Cells that showed positive immunoreactions to the primary antibodies of RANKL and RANK were significantly increased in the irradiation group on day 2 and 3, compared with the non-irradiation group. In contrast, the expression of OPG was not changed. Further, RANK expression in osteoclast precursor cells was detected at an early stage (day 2 and 3) in the irradiation group.

CONCLUSION

These findings suggest that low-energy laser irradiation stimulates the velocity of tooth movement via induction of RANK and RANKL.

The effects of pulsed electromagnetic fields on the cellular activity of SaOS-2 cells

Although pulsed electromagnetic fields (PEMFs) have been used for treatments of nonunion bone fracture healing for more than three decades, the underlying cellular mechanism of bone formation promoted by PEMFs is still unclear. It has been observed that a series of parameters such as pulse shape and frequency should be carefully controlled to achieve effective treatments. In this article, the effects of PEMFs with repetitive pulse burst waveform on the cellular activity of SaOS-2 osteoblast-like cells were investigated. In particular, cell proliferation and mineralization due to the imposed PEMFs were assessed through direct cell counts, the MTT assay, tissue nonspecific alkaline phosphatase (ALP) and Alizarin Red S (ARS) staining. PEMF stimulation with repetitive pulse burst waveform did not affect metabolic activity and cell number. However, the ALP activity of SaOS-2 cells and mineral nodule formation increased significantly after PEMF stimulation. These observations suggest that repetitive pulse burst PEMF does not affect cellular metabolism; however, it may play a role in the enhancement of SaOS-2 cell mineralization. We are currently investigating cellular responses under different PEMF waveforms and Western blots for protein expression of bone mineralization specific proteins.

Bioreactors for tissues of the musculoskeletal system

Muskuloskeletal tissue includes bone, cartilage, ligament, skeletal muscle and tendons. These tissues malfunction either due to a natural injury, trauma, or a disorder. In all cases natural regeneration needs to be enhanced by medication and, in many instances, by surgery. Surgical techniques are limited to suturing, autografts or allografts. Tissue engineering stems from the challenge presented by the limited resources for natural implants and the ineffectiveness of previous curing techniques. The challenge in tissue engineering resides in the design of a functional bioreactor that would: (1) house the engineered construct under sterile conditions; and (2) provide the appropriate stimuli that would result in a neotissue with biochemical and biomechanical properties comparable to in situ tissue. The various types and designs of bioreactors for the regeneration of musculoskeletal tissue, including spinner flask, rotating wall vessel, flow perfusion, and mechanical loading devices are presented in this paper.

Accelerated calcification in electrically conductive polymer composites comprised of poly(ɛ-caprolactone), polyaniline, and bioactive mesoporous silicon

In this study the fabrication and characterization of an electrically conductive composite material comprised of poly(epsilon-caprolactone) (PCL), polyaniline (PANi), and bioactive mesoporous silicon (BioSilicon) is discussed. The influence of PANi and silicon on calcium phosphate induction was assessed via ex vitro calcification analyses (by acellular simulated body fluid (SBF) exposure) both with and without electrical bias. Acceleration of calcium phosphate formation is one possible desirable feature of "smart" synthetic scaffolds for selected orthopedic-relevant applications. In addition, electrical stability assays were performed in growth medium (DMEM) to determine the stability of such structures to bias in an authentic electrolyte during a typical cell experiment. The cytocompatibility of the composites was evaluated in vitro using human kidney fibroblasts (HEK 293) cell proliferation assays, along with more orthopedically relevant mesenchymal stem cells from mouse stroma. Importantly, these composites demonstrate accelerated calcification in SBF when electrical bias is applied cathodically to the scaffold. Furthermore, these scaffolds exhibit noncytotoxic behavior in the presence of fibroblasts over an 8-day culture period, and attachment of stromal cells to the semiconducting scaffold was directly imaged via scanning electron microscopy. Overall, these results suggest that materials of this type of composition have potential merit as a biomaterial.

Carboxy-endcapped conductive polypyrrole: biomimetic conducting polymer for cell scaffolds and electrodes

Numerous regenerating tissues respond favorably to electrical stimulation, creating a need for a bioactive conducting platform for tissue engineering applications. The drive for biosensors and electrode coatings further requires control of the surface properties of promising conductive materials such as polypyrrole. Here we present carboxy-endcapped polypyrrole (PPy-alpha-COOH), a unique bioactive conducting polymer with a carboxylic acid layer, composed of a polypyrrole (PPy) surface modified with pyrrole-alpha-carboxylic acid (Py-alpha-COOH). This unique structure is simple to produce, provides a stable bioactive surface via covalent bonds, and preserves bulk properties such as electrical conductivity and mechanical integrity. The chemical structure of this polymer composite was characterized by angle-resolved X-ray photoelectron spectroscopy (XPS), which demonstrated the presence of carboxylic acid functionality on the top surface of conductive PPy. A four-point probe test was used to verify the similar conductivity of PPy-alpha-COOH compared to that of standard PPy. To demonstrate the potential to influence cellular activity, the carboxylic acid monolayer surface was grafted with the cell-adhesive Arg-Gly-Asp (RGD) motif. Human umbilical vein endothelial cells (HUVECs) cultured on RGD-modified PPy-alpha-COOH demonstrated significantly higher adhesion and spreading than on the negative controls PPy-alpha-COOH and unmodified PPy.