Molecular mechanisms underlying antiproliferative and differentiating responses of hepatocarcinoma cells to subthermal electric stimulation

Electric currents of 448 kHz upregulate anti-senescence pathways in human dermal fibroblasts

BACKGROUND

Currently, finding new therapeutic strategies that reduce skin aging is a challenge for dermatologists and aesthetic doctors. In recent years, physical therapies have been included in the options for antiaging treatments; however, the biological bases of such treatments have scarcely been studied. One of these physical therapies is capacitive-resistive electric transfer (CRET) therapy. Previous studies have shown that subthermal treatment with CRET promotes the proliferation and migration of various cell types involved in skin regeneration, such as human ADSC (stem cells), fibroblasts, or keratinocytes.

OBJECTIVE

This study investigates the effects of in vitro treatment with CRET-Std (standard, non-modulated signal) or CRET-Mod (modulated signal) on cell proliferation and migration, markers of aging, and extracellular matrix production.

METHODS

Three types of human dermal fibroblasts were used: neonatal fibroblasts (HFn), replicative senescent fibroblasts (HFs), and adult fibroblasts (HFa). The effects of electric stimulation on cell proliferation and migration were studied through XTT and wound closure assays, respectively. The expression of the aging marker β-galactosidase was assessed using a colorimetric assay, whereas immunoblot, immunofluorescence, and ELISAs were carried out to analyze the expression levels of migration, aging, and extracellular matrix proteins.

RESULTS

The treatment with CRET-Std increased HFn and HFa proliferation, as well as migration in the three types of fibroblasts studied compared to those of the controls. Conversely, CRET-Mod did not modify either of these two processes with respect to the controls. Additionally, CRET-Std also reduced the cellular senescence markers β-gal, vimentin, p53, and p21 in all three types of human skin fibroblasts. In addition, the application of CRET-Std also induced fibronectin production in HFn and was able to stimulate ECM neocollagenesis.

CONCLUSION

CRET treatment improves a number of functions related to migration and proliferation, and it reduces age-related cellular changes in human dermal fibroblasts. Therefore, the use of this CRET therapy to reduce the signs of dermal aging and to promote tissue regeneration could be of interest.

Anti-Fibrotic Effects of RF Electric Currents

Hypertrophic scars and keloids are two different manifestations of excessive dermal fibrosis and are caused by an alteration in the normal wound-healing process. Treatment with radiofrequency (RF)-based therapies has proven to be useful in reducing hypertrophic scars. In this study, the effect of one of these radiofrequency therapies, Capacitive Resistive Electrical Transfer Therapy (CRET) on biomarkers of skin fibrosis was investigated. For this, in cultures of human myofibroblasts treated with CRET therapy or sham-treated, proliferation (XTT Assay), apoptosis (TUNEL Assay), and cell migration (Wound Closure Assay) were analyzed. Furthermore, in these cultures the expression and/or localization of extracellular matrix proteins such as α-SMA, Col I, Col III (immunofluorescence), metalloproteinases MMP1 and MMP9, MAP kinase ERK1/2, and the transcription factor NFκB were also investigated (immunoblot). The results have revealed that CRET decreases the expression of extracellular matrix proteins, modifies the expression of the metalloproteinase MMP9, and reduces the activation of NFκB with respect to controls, suggesting that this therapy could be useful for the treatment of fibrotic pathologies.

A tissue-engineered neural interface with photothermal functionality

Neural interfaces are well-established as a tool to understand the behaviour of the nervous system via recording and stimulation of living neurons, as well as serving as neural prostheses. Conventional neural interfaces based on metals and carbon-based materials are generally optimised for high conductivity; however, a mechanical mismatch between the interface and the neural environment can significantly reduce long-term neuromodulation efficacy by causing an inflammatory response. This paper presents a soft composite material made of gelatin methacryloyl (GelMA) containing graphene oxide (GO) conjugated with gold nanorods (AuNRs). The soft hydrogel presents stiffness within the neural environment range of modulus below 5 kPa, while the AuNRs, when exposed to light in the near infrared range, provide a photothermal response that can be used to improve the spatial and temporal precision of neuromodulation. These favourable properties can be maintained at safer optical power levels when combined with electrical stimulation. In this paper we provide mechanical and biological characterization of the optical activity of the GO-AuNR composite hydrogel. The optical functionality of the material has been evaluated via photothermal stimulation of explanted rat retinal tissue. The outcomes achieved with this study encourage further investigation into optical and electrical costimulation parameters for a range of biomedical applications.

Effects of Electrical Stimulation of the Cell: Wound Healing, Cell Proliferation, Apoptosis, and Signal Transduction

Electrical stimulation of the cell can have a number of different effects depending on the type of cell being stimulated. In general, electrical stimulation can cause the cell to become more active, increase its metabolism, and change its gene expression. For example, if the electrical stimulation is of low intensity and short duration, it may simply cause the cell to depolarize. However, if the electrical stimulation is of high intensity or long duration, it may cause the cell to become hyperpolarized. The electrical stimulation of cells is a process by which an electrical current is applied to cells in order to change their function or behavior. This process can be used to treat various medical conditions and has been shown to be effective in a number of studies. In this perspective, the effects of electrical stimulation on the cell are summarized.

Electroporation in Head-and-Neck Cancer: An Innovative Approach with Immunotherapy and Nanotechnology Combination

Squamous cell carcinoma is the most common malignancy that arises in the head-and-neck district. Traditional treatment could be insufficient in case of recurrent and/or metastatic cancers; for this reason, more selective and enhanced treatments are in evaluation in preclinical and clinical trials to increase in situ concentration of chemotherapy drugs promoting a selectively antineoplastic activity. Among all cancer treatment types (i.e., surgery, chemotherapy, radiotherapy), electroporation (EP) has emerged as a safe, less invasive, and effective approach for cancer treatment. Reversible EP, using an intensive electric stimulus (i.e., 1000 V/cm) applied for a short time (i.e., 100 μs), determines a localized electric field that temporarily permealizes the tumor cell membranes while maintaining high cell viability, promoting cytoplasm cell uptake of antineoplastic agents such as bleomycin and cisplatin (electrochemotherapy), calcium (Ca²⁺ electroporation), siRNA and plasmid DNA (gene electroporation). The higher intracellular concentration of antineoplastic agents enhances the antineoplastic activity and promotes controlled tumor cell death (apoptosis). As secondary effects, localized EP (i) reduces the capillary blood flow in tumor tissue ("vascular lock"), lowering drug washout, and (ii) stimulates the immune system acting against cancer cells. After years of preclinical development, electrochemotherapy (ECT), in combination with bleomycin or cisplatin, is currently one of the most effective treatments used for cutaneous metastases and primary skin and mucosal cancers that are not amenable to surgery. To reach this clinical evidence, in vitro and in vivo models were preclinically developed for evaluating the efficacy and safety of ECT on different tumor cell lines and animal models to optimize dose and administration routes of drugs, duration, and intensity of the electric field. Improvements in reversible EP efficacy are under evaluation for HNSCC treatment, where the focus is on the development of a combination treatment between EP-enhanced nanotechnology and immunotherapy strategies.

TECAR Therapy Associated with High-Intensity Laser Therapy (Hilt) and Manual Therapy in the Treatment of Muscle Disorders: A Literature Review on the Theorised Effects Supporting Their Use

Background: It has been estimated that between 30 and 50 per cent of all injuries that take place throughout participation in a sport are the consequence of soft tissue injuries, and muscle injuries are the primary cause of physical disability. Methods: The current literature review was designed between October 2021 and April 2022, according to the PRISMA standards, using the PubMed, Scopus, and Web of Science databases. At the screening stage, we eliminated articles that did not fit into the themes developed in all subchapters of the study (n = 70), articles that dealt exclusively with orthopaedics (n = 34), 29 articles because the articles had only the abstract visible, and 17 articles that dealt exclusively with other techniques for the treatment of musculoskeletal disorders. The initial search revealed 343 titles in the databases, from which 56 duplicate articles were automatically removed, and 2 were added from other sources. Results: The combination of these three techniques results in the following advantages: It increases joint mobility, especially in stiff joints, it increases the range of motion, accelerates tissue repair, improves tissue stability, and extensibility, and it reduces soft tissue inflammation (manual therapy). In addition, it decreases the concentration of pro-inflammatory mediators and improves capillary permeability, resulting in the total eradication of inflammation (HILT). It warms the deep tissues, stimulates vascularity, promotes the repose of tissues (particularly muscle tissue), and stimulates drainage (TECAR). Conclusions: TECAR therapy, combined with manual therapy and High-Intensity Laser therapy in treating muscle diseases, presented optimal collaboration in the recovery process of all muscle diseases.

Comparison of resistive capacitive energy transfer therapy on cadaveric molars and incisors with and without implants

Capacitive–resistive energy transfer therapy (CRet) is used to improve the rehabilitation of different injuries. This study aimed to evaluate and compare the changes in temperature and current flow during different CRet applications on upper and lower molars and incisors, with and without implants, on ten cryopreserved corpses. Temperatures were taken on molars and incisors with invasive devices and skin temperature was taken with a digital thermometer at the beginning and after treatments. Four interventions: 15 VA capacitive hypothermic (CAPH), 8 watts resistive (RES8), 20 watts resistive (RES20) and 75 VA capacitive (CAP75) were performed for 5 min each. All treatments in this study generated current flow (more than 0.00005 A/m²) and did not generate a significant temperature increase (p > 0.05). However, RES20 application slightly increased surface temperature on incisors without implants (p = 0.010), and molar with (p = 0.001) and without implant (p = 0.008). Also, CAP75 application increased surface temperature on molars with implant (p = 0.002) and upper incisor with implant (p = 0.001). In conclusion, RES8 and CAPH applications seem to be the best options to achieve current flow without an increase in temperature on molars and incisors with and without implants.

Is Tecar Therapy Effective on Biceps Femoris and Quadriceps Rehabilitation? A Cadaveric Study

BACKGROUND

Capacitive-resistive electric transfer therapy is an interesting rehabilitation treatment to use in musculoskeletal injuries. The purpose is to analyze the temperature change and current flow in superficial and deep biceps femoris and quadriceps tissues when applying different protocols of capacitive-resistive electric transfer therapy.

METHODS

Five cryopreserved cadavers (10 legs) were included in this study. Four interventions (high/low power) were performed for 5 minutes. Dynamic movements were performed to the biceps femoris and quadriceps. Superficial, middle, and deep temperature were recorded at 1-minute intervals and 5 minutes after the treatment using invasive temperature meters placed with ultrasound guidance.

RESULTS

Low-power applications have generated a very low thermal effect and an important current flow. The high-power capacitive application achieves a greater increase in superficial temperature compared with low power (P < .001). The high-power resistive application recorded a greater increase in superficial, middle, and deep temperatures with a greater current flow compared with the other applications (P < .001).

CONCLUSION

This study could serve as basic science data to justify the acceleration of the processes of muscle recovery, improving cell proliferation without increasing the temperature in acute muscle injuries and increasing the temperature and viscoelasticity of the tissues in chronic processes with this therapy.

Silver nanowire loaded poly(ε-caprolactone) nanocomposite fibers as electroactive scaffolds for skeletal muscle regeneration

Volumetric muscle loss (VML) due to trauma and tumor removal operations affects millions of people every year. Although skeletal muscle has a natural repair mechanism, it cannot provide self-healing above a critical level of VML. In this study, nanocomposite aligned fiber scaffolds as support materials were developed for volumetric skeletal muscle regeneration. For this purpose, silver nanowire (Ag NW) loaded poly(ε-caprolactone) (PCL) nanocomposite fiber scaffolds (PCL-Ag NW) were prepared to mimic the aligned electroactive structure of skeletal muscle and provide topographic and conductive environment to modulate cellular behavior and orientation. A computer-aided rotational wet spinning (RWS) system was designed to produce high-yield fiber scaffolds. Nanocomposite fiber bundles with lengths of 50 cm were fabricated via this computer-aided RWS system. The morphological, chemical, thermal properties and biodegradation profiles of PCL and PCL-Ag NW nanocomposite fibers were characterized in detail. The proliferation behavior and morphology of C2C12 mouse myoblasts were investigated on PCL and PCL-Ag NW nanocomposite fibrous scaffolds with and without electrical stimulation. Significantly enhanced cell proliferation was observed on PCL-Ag NW nanocomposite fibers compared to neat PCL fibers with electrical stimulations of 1.5 V, 3 V and without electrical stimulation.

Application of Capacitive-Resistive Electric Transfer in Physiotherapeutic Clinical Practice and Sports

Diathermy techniques embody an oscillating electrical current passaging through the body tissues generating therapeutic heat; use of this technique in the physiotherapy field has been introduced recently, and because there is scarce information, the following review is proposed, aiming to explore the available evidence on applying CRET in physiotherapy clinical practice and sports. A systematic search was led through a keyword search on PubMed, MedLine, DialNet, Scopus, PEDro, Web of Science and Clinicaltrials databases. Including randomised controlled trials and quasi-experimental studies, which applied radiofrequency diathermy in sports and physiotherapy fields, without any restrictions on dates, published in Spanish, English, Portuguese or Italian. Data extraction was conducted through the Cochrane data extraction form and presented in tabular format; 30 articles were included for analysis, and assessment of methodological quality was made through the PEDro scale with a "Good/Fair" general quality score. The nature of existing articles does not allow a quantitative analysis. Conclusion: identified fields of applications were musculoskeletal physiotherapy, treatment of pelvic floor and sexual dysfunctions, as well as dermato-functional physiotherapy and sports, evidencing an increase of skin temperature, enhanced skin and muscle blood perfusion, as well as reporting an increase in oxyhaemoglobin. Further research is needed. Prospero registration number: CRD42020215592.

Research Progress of Electrical Stimulation in Ischemic Heart Disease

Ischemic heart disease (IHD) is a considerable health burden worldwide with high mortality and morbidity. Treatments for IHD are mainly focused on decreasing oxygen demand or increasing myocardial oxygen supply, including pharmacological, interventional, and surgical treatment, but there are also some limitations. Therefore, it is important to find a simple, effective, and economical treatment. As non-invasive and safe physiotherapy, electrical stimulation (ES) has a promising application in the treatment of IHD. Current studies suggest that ES can affect the occurrence and development of IHD by promoting angiogenesis, regulating autophagy and apoptosis, inhibiting the inflammatory response and oxidative stress. In this review, we focus predominantly on the mechanism of ES and the current progress of ES therapy in IHD, furthermore, give a brief introduction to the forms of ES in clinical application.

Effect of Electrical Stimulation on Ocular Cells: A Means for Improving Ocular Tissue Engineering and Treatments of Eye Diseases

Tissue engineering is biomedical engineering that uses suitable biochemical and physicochemical factors to assemble functional constructs that restore or improve damaged tissues. Recently, cell therapies as a subset of tissue engineering have been very promising in the treatment of ocular diseases. One of the most important biophysical factors to make this happen is noninvasive electrical stimulation (ES) to target ocular cells that may preserve vision in multiple retinal and optic nerve diseases. The science of cellular and biophysical interactions is very exciting in regenerative medicine now. Although the exact effect of ES on cells is unknown, multiple mechanisms are considered to underlie the effects of ES, including increased production of neurotrophic agents, improved cell migration, and inhibition of proinflammatory cytokines and cellular apoptosis. In this review, we highlighted the effects of ES on ocular cells, especially on the corneal, retinal, and optic nerve cells. Initially, we summarized the current literature on the in vitro and in vivo effects of ES on ocular cells and then we provided the clinical studies describing the effect of ES on ocular complications. For each area, we used some of the most impactful articles to show the important concepts and results that advanced the state of these interactions. We conclude with reflections on emerging new areas and perspectives for future development in this field.

Response of human cancer cells to simultaneous treatment with sorafenib and radiofrequency current

Due to their alleged analgesic, anti-inflammatory and tissue regenerative effects, capacitive-resistive electrothermal therapy (CRET), which is based on non-invasive exposure to radiofrequency (RF) currents, is often applied to chemotherapeutically treated patients with cancer. Our previous studies have demonstrated that subthermal CRET currents can elicit a number of cell responses, including anti-proliferative effects, in the human liver cancer cell line HepG2. Such effects involve significant changes in the regulation of proteins involved in MAPK signaling pathways, which are also implicated in the cancer cell response to standard anticancer drugs such as sorafenib. This overlap in response pathways may lead to competitive, neutralizing or blocking interactions between the electrical and chemical treatments, thus raising questions on the advisability of CRET treatment for their analgesic, anti-inflammatory or other purposes in patients undergoing chemotherapy. The present study analyzed the effects of simultaneous treatment with sorafenib and 448-kHz, subthermal CRET current on the proliferation and viability of HepG2 cell cultures. Cell viability was assessed through Trypan blue or XTT assays, while flow cytometry was applied for cell cycle and apoptosis analysis. The expression of proteins involved in cell proliferation were assessed by immunoblotting and immunofluorescence. The results revealed no evidence to suggest that the electrical treatment counteracted or neutralized the cellular response to sorafenib at the different conditions evaluated. Furthermore, at the standard pharmacological sorafenib concentration, 5 µM, the combined treatment elicited an anti-proliferative response significantly stronger than that induced by each of the treatments when applied separately in HepG2 cells. These data do not support the hypothesis that CRET exposure may inhibit or diminish the effects of a chemotherapeutic drug used in cancer treatment, and highlights the requirement for further investigation into the cell response to the combined action of electrical and chemical treatments.

Temperature and current flow effects of different electrode placement in shoulder capacitive-resistive electric transfer applications: a cadaveric study

BACKGROUND

Impingement syndrome is currently estimated to represent 60% of all shoulder pain disorders. Capacitive-Resistive electric transfer therapy is aimed to provoke temperature and current flow changes in superficial and deep tissues. This in vitro study has evaluated the variation of temperature and current flow in the shoulder tissues during two different areas of application of the movable capacitive-resistive electric transfer electrode.

METHODS

A cross-sectional study designed, five fresh cryopreserved cadavers (10 shoulders) were included in this study. Four interventions (capacitive and resistive modes; low- and high-power) were performed for 5 min each by a diathermy "T-Plus" device in two shoulder regions: postero-superior and antero-lateral. Supraspinatus tendon, glenohumeral capsule and superficial temperatures were recorded at 1-min intervals and 5 min after treatment.

RESULTS

A statistically significant difference was found only for the superficial area and time interaction, with high power-resistive application at the postero-superior shoulder area (P< 0.035). All the applications showed a 5 min after treatment temperature increase compared with the basal data, in all the application points. Superficial temperature in the high power-resistive application showed the greatest percent increase (42.93% ± 22.58), followed by the temperature in the tendon area with the same high power-resistive application (22.97% ± 14.70). The high power-resistive application showed the greatest percent of temperature increase in the applications, reaching 65.9% ± 22.96 at 5-min at the superficial level, and 32% ± 24.25 at 4-min at the level of the supraspinatus tendon. At the capsule level, high power-resistive was also the application that showed the greatest percent of increase, with 21.52% ± 16.16. The application with the lowest percent of temperature increase was the low power-capacitive, with a mean value of 4.86% at supraspinatus tendon level and 7.47% at capsular level.

CONCLUSION

The shoulder postero-superior or antero-lateral areas of application of capacitive-resistive electric transfer did not cause statistically significant differences in the temperature changes in either supraspinatus tendon or glenohumeral capsule tissues in cadaveric samples. The high power-resistive application in the postero-superior area significantly increased superficial temperature compared with the same application in the antero-lateral position area.

Thermal and Current Flow Effects of a Capacitive-Resistive Electric Transfer Application Protocol on Chronic Elbow Tendinopathy. A Cadaveric Study

Lateral elbow tendinopathy, or "tennis elbow," is a pathology that affects around 1.3% of the general population. Capacitive-resistive electric transfer therapy aims to provoke temperature and current flow changes in superficial and deep tissues. The aim of this in vitro study was to analyze the thermal behavior and transmission of electric current on the superficial and deep tissues of the elbow during the application of different modalities of a capacitive-resistive electric transfer treatment protocol for chronic elbow tendinopathy. A cross-sectional study was designed; five fresh cryopreserved cadavers (10 elbows) were included in this study. A 30 min intervention was performed based on a protocol commonly used in clinics for the treatment of chronic lateral elbow tendinopathy by diathermy using the "T-Plus." Common extensor tendon, radiohumeral capsule, and superficial temperatures were registered after each application for the duration of the 30 min treatment protocol. During all applications, we observed a current flow of over 0.03 A. The protocol showed a statistically significant increase in superficial temperature by 24% (5.02°) (p < 0.005), the common extensor tendon by 19.7% (4.36°) (p < 0.007), and the radiohumeral joint capsule by 17.5% (3.41°) (p < 0.005) at the end of the 30 min protocol compared with the baseline temperature. The different applications of the protocol showed specific effects on the temperature and current flow in the common extensor tendon and radiohumeral capsule. All applications of the protocol produced a current flow that is associated with the generation of cell proliferation. These results strengthen the hypothesis of cell proliferation and thermal changes in deep and distal structures. More studies are needed to confirm these results.

Thermal and non-thermal effects of capacitive-resistive electric transfer application on different structures of the knee: a cadaveric study

Capacitive-resistive electric transfer therapy is used in physical rehabilitation and sports medicine to treat muscle, bone, ligament and tendon injuries. The purpose is to analyze the temperature change and transmission of electric current in superficial and deep knee tissues when applying different protocols of capacitive-resistive electric transfer therapy. Five fresh frozen cadavers (10 legs) were included in this study. Four interventions (high/low power) were performed for 5 min by a physiotherapist with experience. Dynamic movements were performed to the posterior region of the knee. Capsular, intra-articular and superficial temperature were recorded at 1-min intervals and 5 min after the treatment, using thermocouples placed with ultrasound guidance. The low-power protocols had only slight capsular and intra-capsular thermal effects, but electric current flow was observed. The high-power protocols achieved a greater increase in capsular and intra-articular temperature and a greater current flow than the low-power protocols. The information obtained in this in vitro study could serve as basic science data to hypothesize capsular and intra-articular knee recovery in living subjects. The current flow without increasing the temperature in inflammatory processes and increasing the temperature of the tissues in chronic processes with capacitive-resistive electric transfer therapy could be useful for real patients.

Thermal and non-thermal effects off capacitive-resistive electric transfer application on the Achilles tendon and musculotendinous junction of the gastrocnemius muscle: a cadaveric study

Background

Calf muscle strain and Achilles tendon injuries are common in many sports. For the treatment of muscular and tendinous injuries, one of the newer approaches in sports medicine is capacitive-resistive electric transfer therapy. Our objective was to analyze this in vitro, using invasive temperature measurements in cadaveric specimens.

Methods

A cross-sectional study designed with five fresh frozen cadavers (10 legs) were included in this study. Four interventions (capacitive and resistive modes; low- and high-power) was performed for 5 min each by a diathermy “T-Plus” device. Achilles tendon, musculotendinous junction and superficial temperatures were recorded at 1-min intervals and 5 min after treatment.

Results

With the low-power capacitive protocol, at 5 min, there was a 25.21% increase in superficial temperature, a 17.50% increase in Achilles tendon temperature and an 11.27% increase in musculotendinous junction temperature, with a current flow of 0.039 A ± 0.02.

With the low-power resistive protocol, there was a 1.14% increase in superficial temperature, a 28.13% increase in Achilles tendon temperature and an 11.67% increase in musculotendinous junction temperature at 5 min, with a current flow of 0.063 A ± 0.02. With the high-power capacitive protocol there was an 88.52% increase in superficial temperature, a 53.35% increase in Achilles tendon temperature and a 39.30% increase in musculotendinous junction temperature at 5 min, with a current flow of 0.095 A ± 0.03. With the high-power resistive protocol, there was a 21.34% increase in superficial temperature, a 109.70% increase in Achilles tendon temperature and an 81.49% increase in musculotendinous junction temperature at 5 min, with a current flow of 0.120 A ± 0.03.

Conclusion

The low-power protocols resulted in only a very slight thermal effect at the Achilles tendon and musculotendinous junction, but current flow was observed. The high-power protocols resulted in a greater temperature increase at the Achilles tendon and musculotendinous junction and a greater current flow than the low-power protocols. The high-power resistive protocol gave the greatest increase in Achilles tendon and musculotendinous junction temperature. Capacitive treatments (low- and high-power) achieved a greater increase in superficial temperature.

Electrical stimulation as a novel tool for regulating cell behavior in tissue engineering

Recently, electrical stimulation as a physical stimulus draws lots of attention. It shows great potential in disease treatment, wound healing, and mechanism study because of significant experimental performance. Electrical stimulation can activate many intracellular signaling pathways, and influence intracellular microenvironment, as a result, affect cell migration, cell proliferation, and cell differentiation. Electrical stimulation is using in tissue engineering as a novel type of tool in regeneration medicine. Besides, with the advantages of biocompatible conductive materials coming into view, the combination of electrical stimulation with suitable tissue engineered scaffolds can well combine the benefits of both and is ideal for the field of regenerative medicine. In this review, we summarize the various materials and latest technologies to deliver electrical stimulation. The influences of electrical stimulation on cell alignment, migration and its underlying mechanisms are discussed. Then the effect of electrical stimulation on cell proliferation and differentiation are also discussed.

Response of neuroblastoma cells to RF currents as a function of the signal frequency

BACKGROUND

Capacitive-resistive electric transfer (CRET) is a non-invasive therapeutic strategy that applies radiofrequency electric currents within the 400-600 kHz range to tissue repair and regeneration. Previous studies by our group have shown that 48 h of intermittent exposure to a 570 kHz CRET signal at a subthermal density of 50 μA/mm² causes significant changes in the expression and activation of cell cycle control proteins, leading to cycle arrest in human cancer cell cultures. The present study investigates the relevance of the signal frequency in the response of the human neuroblastoma cell line NB69 to subthermal electric treatment with four different signal frequency currents within the 350-650 kHz range.

METHODS

Trypan blue assay, flow cytometry, immunofluorescence and immunoblot were used to study the effects of subthermal CRET currents on cell viability, cell cycle progression and the expression of several marker proteins involved in NB69 cell death and proliferation.

RESULTS

The results reveal that among the frequencies tested, only a 448 kHz signal elicited both proapoptotic and antiproliferative, statistically significant responses. The apoptotic effect would be due, at least in part, to significant changes induced by the 448 kHz signal in the expression of p53, Bax and caspase-3. The cytostatic response was preceded by alterations in the kinetics of the cell cycle and in the expression of proteins p-ERK1/2, cyclin D1 and p27, which is consistent with a potential involvement of the EGF receptor in electrically induced changes in the ERK1/2 pathway. This receives additional support from results indicating that the proapototic and antiproliferative responses to CRET can be transiently blocked when the electric stimulus is applied in the presence of PD98059, a chemical inhibitor of the ERK1/2 pathway.

CONCLUSION

The understanding of the mechanisms underlying the ability of slowing down cancer cell growth through electrically-induced changes in the expression of proteins involved in the control of cell proliferation and apoptosis might afford new insights in the field of oncology.

Liquid Metal Enabled Electrobiology: A New Frontier to Tackle Disease Challenges

In this article, a new conceptual biomedical engineering strategy to tackle modern disease challenges, called liquid metal (LM) enabled electrobiology, is proposed. This generalized and simple method is based on the physiological fact that specially administrated electricity induces a series of subsequent desired biological effects, either shortly, transitionally, or permanently. Due to high compliance within biological tissues, LM would help mold a pervasive method for treating physiological or psychological diseases. As highly conductive and non-toxic multifunctional flexible materials, such LMs can generate any requested electric treating fields (ETFields), which can adapt to various sites inside the human body. The basic mechanisms of electrobiology in delivering electricity to the target tissues and then inducing expected outputs for disease treatment are interpreted. The methods for realizing soft and conformable electronics based on LM are illustrated. Furthermore, a group of typical disease challenges are observed to illustrate the basic strategies for performing LM electrobiology therapy, which include but are not limited to: tissue electronics, brain disorder, immunotherapy, neural functional recovery, muscle stimulation, skin rejuvenation, cosmetology and dieting, artificial organs, cardiac pacing, cancer therapy, etc. Some practical issues regarding electrobiology for future disease therapy are discussed. Perspectives in this direction for incubating a simple biomedical tool for health care are pointed out.

Effects of electrical stimulation on cell proliferation and apoptosis

The application of exogenous electrical stimulation (ES) to cells in order to manipulate cell apoptosis and proliferation has been widely investigated as a possible method of treatment in a number of diseases. Alteration of the transmembrane potential of cells via ES can affect various intracellular signaling pathways which are involved in the regulation of cellular function. Controversially, several types of ES have proved to be effective in both inhibiting or inducing apoptosis, as well as increasing proliferation. However, the mechanisms through which ES achieves this remain fairly unclear. The aim of this review was to comprehensively summarize current findings from in vitro and in vivo studies on the effects of different types of ES on cell apoptosis and proliferation, highlighting the possible mechanisms through which ES induced these effects and define the optimum parameters at which ES can be used. Through this we hope to provide a greater insight into how future studies can most effectively use ES at the clinical trial stage.

Antiadipogenic effects of subthermal electric stimulation at 448 kHz on differentiating human mesenchymal stem cells

The 448 kHz capacitive‑resistive electric transfer (CRET) is an electrothermal therapy currently applied in anticellulite and antiobesity treatments. The aim of the present study was to determine whether exposure to the CRET electric signal at subthermal doses affected early adipogenic processes in adipose‑derived stem cells (ADSC) from human donors. ADSC were incubated for 2 or 9 days in the presence of adipogenic medium, and exposed or sham‑exposed to 5 min pulses of 448 kHz electric signal at 50 µA/mm2 during the last 48 h of the incubation. Colorimetric, immunofluorescence, western blotting and reverse transcription‑quantitative polymerase chain reaction assays were performed to assess adipogenic differentiation of the ADSC. Electric stimulation significantly decreased cytoplasmic lipid content, after both 2 and 9 days of differentiation. The antiadipogenic response in the 9 day samples was accompanied by activation of mitogen‑activated protein kinase kinase 1/2, decreased expression and partial inactivation of peroxisome proliferator‑activated receptor (PPAR) γ, which was translocated from the nucleus to the cytoplasm, together with a significant decrease in the expression levels of the PPARG1 gene, perilipin, angiopoietin‑like protein 4 and fatty acid synthase. These results demonstrated that subthermal stimulation with CRET interferes with the early adipogenic differentiation in ADSC, indicating that the electric stimulus itself can modulate processes controlling the synthesis and mobilization of fat, even in the absence of the concomitant thermal and mechanical components of the thermoelectric therapy CRET.