Modified cell proliferation due to electrical currents

Long-term changes in transmembrane voltage after electroporation are governed by the interplay between nonselective leak current and ion channel activation

Electroporation causes a temporal increase in cell membrane permeability and leads to prolonged changes in transmembrane voltage (TMV) in both excitable and non-excitable cells. However, the mechanisms of these TMV changes remain to be fully elucidated. To this end, we monitored TMV over 30 min after exposing two different cell lines to a single 100 µs electroporation pulse using the FLIPR Membrane Potential dye. In CHO-K1 cells, which express very low levels of endogenous ion channels, membrane depolarization following pulse exposure could be explained by nonselective leak current, which persists until the membrane reseals, enabling the cells to recover their resting TMV. In U-87 MG cells, which express many different ion channels, we unexpectedly observed membrane hyperpolarization following the initial depolarization phase, but only at 33 °C and not at 25 °C. We developed a theoretical model, supported by experiments with ion channel inhibitors, which indicated that hyperpolarization could largely be attributed to the activation of calcium-activated potassium channels. Ion channel activation, coupled with changes in TMV and intracellular calcium, participates in various physiological processes, including cell proliferation, differentiation, migration, and apoptosis. Therefore, our study suggests that ion channels could present a potential target for influencing the biological response after electroporation.

Modifying membrane potential synchronously controls the somite's formation periodicity and growth

Coordination between periodicity of somite formation and somite growth is crucial for regular body pattern formation during somitogenesis. Yet, the specific mechanism that links the two processes remains unclear. Using chick embryos, we demonstrate that both temporal and spatial features can be simultaneously controlled by membrane potential (Vm) of somite-forming cells. Our findings show that somites hyperpolarize as they mature, displaying step-like changes in Vm observed between specific groups of somites, reflecting the reported onset of biochemical and structural changes within them. We modify Vm by changing chemical compositions of the microenvironment of the embryo. Alteration of Vm sets a new pace of somite formation (cell migration and self-assembly) and its concurrent growth (cell proliferation) without disturbing the somite's regular aspect ratio. Our results therefore suggest that Vm has the ability to orchestrate cell proliferation, migration and self-assembly - processes that are hallmarks of embryogenesis, tumorigenesis and tissue regeneration.

Conductive Cellulose Bio‐Nanosheets Assembled Biostable Hydrogel for Reliable Bioelectronics

Biostable electronic materials that can maintain their super mechanical and conductive properties, even when exposed to biofluids, are the fundamental basis for designing reliable bioelectronic devices. Herein, cellulose‐derived conductive 2D bio‐nanosheets as electronic base materials are developed and assembled into a conductive hydrogel with ultra‐high biostability, capable of surviving in harsh physiological environments. The bio‐nanosheets are synthesized by guiding the in situ regeneration of cellulose crystal into a 2D planar structure using the polydopamine‐reduced‐graphene oxide as supporting templates. The nanosheet‐assembled hydrogel exhibits stable electrical and mechanical performances after undergoing aqueous immersion and in vivo implantation. Thus, the hydrogel‐based bioelectronic devices are able to conformally integrate with the human body and stably record electrophysiological signals. Owing to its tissue affinity, the hydrogel further serves as an “E‐skin,” which employs electrotherapy to aid in the faster healing of chronic wounds in diabetic mice through transcutaneous electrical stimulation. The nanosheet‐assembled biostable, conductive, flexible, and cell/tissue affinitive hydrogel lays a foundation for designing electronically and mechanically reliable bioelectronic devices.

Direct Current Electric Stimulation Alters the Frequency and the Distribution of Mitotic Cells in Planarians

Background: The use of direct current electric stimulation (DCS) is an effective strategy to treat disease and enhance body functionality. Thus, treatment with DCS is an attractive biomedical alternative, but the molecular underpinnings remain mostly unknown. The lack of experimental models to dissect the effects of DCS from molecular to organismal levels is an important caveat. Here, we introduce the planarian flatworm Schmidtea mediterranea as a tractable organism for in vivo studies of DCS. We developed an experimental method that facilitates the application of direct current electrical stimulation to the whole planarian body (pDCS). Materials and Methods: Planarian immobilization was achieved by combining treatment with anesthesia, agar embedding, and low temperature via a dedicated thermoelectric cooling unit. Electric currents for pDCS were delivered using pulled glass microelectrodes. The electric potential was supplied through a constant voltage power supply. pDCS was administered up to six hours, and behavioral and molecular effects were measured by using video recordings, immunohistochemistry, and gene expression analysis. Results: The behavioral immobilization effects are reversible, and pDCS resulted in a redistribution of mitotic cells along the mediolateral axis of the planarian body. The pDCS effects were dependent on the polarity of the electric field, which led to either increase in reductions in mitotic densities associated with the time of pDCS. The changes in mitotic cells were consistent with apparent redistribution in gene expression of the stem cell marker smedwi-1. Conclusion: The immobilization technique presented in this work facilitates studies aimed at dissecting the effects of exogenous electric stimulation in the adult body. Treatment with DCS can be administered for varying times, and the consequences evaluated at different levels, including animal behavior, cellular and transcriptional changes. Indeed, treatment with pDCS can alter cellular and transcriptional parameters depending on the polarity of the electric field and duration of the exposure.

Advances in Engineering Human Tissue Models

Research in cell biology greatly relies on cell-based in vitro assays and models that facilitate the investigation and understanding of specific biological events and processes under different conditions. The quality of such experimental models and particularly the level at which they represent cell behavior in the native tissue, is of critical importance for our understanding of cell interactions within tissues and organs. Conventionally, in vitro models are based on experimental manipulation of mammalian cells, grown as monolayers on flat, two-dimensional (2D) substrates. Despite the amazing progress and discoveries achieved with flat biology models, our ability to translate biological insights has been limited, since the 2D environment does not reflect the physiological behavior of cells in real tissues. Advances in 3D cell biology and engineering have led to the development of a new generation of cell culture formats that can better recapitulate the in vivo microenvironment, allowing us to examine cells and their interactions in a more biomimetic context. Modern biomedical research has at its disposal novel technological approaches that promote development of more sophisticated and robust tissue engineering in vitro models, including scaffold- or hydrogel-based formats, organotypic cultures, and organs-on-chips. Even though such systems are necessarily simplified to capture a particular range of physiology, their ability to model specific processes of human biology is greatly valued for their potential to close the gap between conventional animal studies and human (patho-) physiology. Here, we review recent advances in 3D biomimetic cultures, focusing on the technological bricks available to develop more physiologically relevant in vitro models of human tissues. By highlighting applications and examples of several physiological and disease models, we identify the limitations and challenges which the field needs to address in order to more effectively incorporate synthetic biomimetic culture platforms into biomedical research.

Assessment of recombinant tissue plasminogen activator (rtPA) toxicity in cultured neural cells and subsequent treatment with poly-arginine peptide R18D

Thrombolytic therapy with recombinant tissue plasminogen activator (rtPA) in ischaemic stroke has been associated with neurotoxicity, blood brain barrier (BBB) disruption and intra-cerebral hemorrhage. To examine rtPA cellular toxicity we investigated the effects of rtPA on cell viability in neuronal, astrocyte and brain endothelial cell (bEnd.3) cultures with and without prior exposure to oxygen-glucose deprivation (OGD). In addition, the neuroprotective peptide poly-arginine-18 (R18D; 18-mer of D-arginine) was examined for its ability to reduce rtPA toxicity. Studies demonstrated that a 4- or 24-h exposure of rtPA was toxic, affecting neuronal cell viability at ≥ 2 µM, and astrocyte and bEnd.3 cells viability at ≥ 5 μM. In addition, a 4-h exposure to rtPA after a period of OGD (OGD/rtPA) exacerbated toxicity, affecting neuronal, astrocyte and bEnd.3 cell viability at rtPA concentrations as low as 0.1 µM. Treatment of cells with low concentrations of R18D (0.5 and 1 µM) reduced the toxic effects of rtPA and OGD/rtPA, while on some occasions a higher 2 µM R18D concentrations exacerbated neuronal and bEnd.3 cell toxicity in OGD/rtPA exposed cultures. In exploratory studies we also demonstrated that OGD activates matrix metalloproteinase-9 (MMP-9) release into the supernatant of astrocyte and bEnd.3 cell cultures, but not neuronal cultures, and that OGD/rtPA increases MMP-9 activation. Furthermore, R18D decreased MMP-9 activation in OGD/rtPA treated astrocyte and bEnd.3 cell cultures. In summary, the findings show that rtPA can be toxic to neural cells and that OGD exacerbates toxicity, while R18D has the capacity to reduce rtPA neural cellular toxicity and reduce MMP-9 activation in astrocytes and bEnd.3. Poly-arginine-18 peptides, which are being developed as neuroprotective therapeutics for ischaemic stroke, therefore have the additional potential of reducing cytotoxic effects associated with rtPA thrombolysis in the treatment of ischaemic stroke.

Electric field-responsive nanoparticles and electric fields: physical, chemical, biological mechanisms and therapeutic prospects

Electric fields are among physical stimuli that have revolutionized therapy. Occurring endogenously or exogenously, the electric field can be used as a trigger for controlled drug release from electroresponsive drug delivery systems, can stimulate wound healing and cell proliferation, may enhance endocytosis or guide stem cell differentiation. Electric field pulses may be applied to induce cell fusion, can increase the penetration of therapeutic agents into cells, or can be applied as a standalone therapy to ablate tumors. This review describes the main therapeutic trends and overviews the main physical, chemical and biological mechanisms underlying the actions of electric fields. Overall, the electric field can be used in therapeutic approaches in several ways. The electric field can act on drug carriers, cells and tissues. Understanding the multiple effects of this powerful tool will help harnessing its full therapeutic potential in an efficient and safe way.

Clinical and economic evaluation of modulated electrohyperthermia concurrent to dose-dense temozolomide 21/28 days regimen in the treatment of recurrent glioblastoma: a retrospective analysis of a two-centre German cohort trial with systematic comparison and effect-to-treatment analysis

OBJECTIVE

To assess the efficacy and cost-effectiveness of modulated electrohyperthermia (mEHT) concurrent to dose-dense temozolomide (ddTMZ) 21/28 days regimen versus ddTMZ 21/28 days alone in patients with recurrent glioblastoma (GBM).

DESIGN

A cohort of 54 patients with recurrent GBM treated with ddTMZ+mEHT in 2000-2005 was systematically retrospectively compared with five pooled ddTMZ 21/28 days cohorts (114 patients) enrolled in 2008-2013.

RESULTS

The ddTMZ+mEHT cohort had a not significantly improved mean survival time (mST) versus the comparator (p=0.531) after a significantly less mean number of cycles (1.56 vs 3.98, p<0.001). Effect-to-treatment analysis (ETA) suggests that mEHT significantly enhances the efficacy of the ddTMZ 21/28 days regimen (p=0.011), with significantly less toxicity (no grade III-IV toxicity vs 45%-92%, p<0.0001). An estimated maximal attainable median survival time is 10.10 months (9.10-11.10). Cost-effectiveness analysis suggests that, unlike ddTMZ 21/28 days alone, ddTMZ+mEHT is cost-effective versus the applicable cost-effectiveness thresholds €US$25 000-50 000/quality-adjusted life year (QALY). Budget impact analysis suggests a significant saving of €8 577 947/$11 201 761 with 29.1-38.5 QALY gained per 1000 patients per year. Cost-benefit analysis suggests that mEHT is profitable and will generate revenues between €3 124 574 and $6 458 400, with a total economic effect (saving+revenues) of €5 700 034 to $8 237 432 per mEHT device over an 8-year period.

CONCLUSIONS

Our ETA suggests that mEHT significantly improves survival of patients receiving the ddTMZ 21/28 days regimen. Economic evaluation suggests that ddTMZ+mEHT is cost-effective, budget-saving and profitable. After confirmation of the results, mEHT could be recommended for the treatment of recurrent GBM as a cost-effective enhancer of ddTMZ regimens, and, probably, of the regular 5/28 days regimen. mEHT is applicable also as a single treatment if chemotherapy is impossible, and as a salvage treatment after the failure of chemotherapy.

Unraveling the mechanistic effects of electric field stimulation towards directing stem cell fate and function: A tissue engineering perspective

Electric field (EF) stimulation can play a vital role in eliciting appropriate stem cell response. Such an approach is recently being established to guide stem cell differentiation through osteogenesis/neurogenesis/cardiomyogenesis. Despite significant recent efforts, the biophysical mechanisms by which stem cells sense, interpret and transform electrical cues into biochemical and biological signals still remain unclear. The present review critically analyses the variety of EF stimulation approaches that can be employed to evoke appropriate stem cell response and also makes an attempt to summarize the underlying concepts of this notion, placing special emphasis on stem cell based tissue engineering and regenerative medicine. This review also discusses the major signaling pathways and cellular responses that are elicited by electric stimulation, including the participation of reactive oxygen species and heat shock proteins, modulation of intracellular calcium ion concentration, ATP production and numerous other events involving the clustering or reassembling of cell surface receptors, cytoskeletal remodeling and so on. The specific advantages of using external electric stimulation in different modalities to regulate stem cell fate processes are highlighted with explicit examples, in vitro and in vivo.

Understanding the response of pulsed electric field on osteoblast functions in three-dimensional mesh structures

The endogenous electric field plays a determining role in impacting biological functions including communication with the physiological system, brain, and bone regeneration by influencing cellular functions. From this perspective, the objective of the study described here is to elucidate the effect of external electric field under dynamic conditions, in providing a guiding cue to osteoblasts in terms of cell-cell interactions and synthesis of prominent adhesion and cytoskeleton proteins. This was accomplished using pulsed direct current electric field of strength 0.1-1 V/cm. The electric field provided guided cue to the cells to migrate toward cathode. Membrane blebbing or necrosis was nearly absent in the vicinity of cathode at 0.1 and 0.5 V/cm electric field strength. Moreover, a higher cell proliferation as well as higher expression of vinculin and densely packed actin stress fibers was observed. At anode, the cells though healthy but expression of actin and vinculin was less. We underscore for the first time that the biological functionality can be favorably modulated on 3D printed scaffolds in the presence of electric field and under dynamic conditions with consequent positive effect on cell proliferation, growth, and expression level of prominent proteins.

Aligned Nanofibers from Polypyrrole/Graphene as Electrodes for Regeneration of Optic Nerve via Electrical Stimulation

The damage of optic nerve will cause permanent visual field loss and irreversible ocular diseases, such as glaucoma. The damage of optic nerve is mainly derived from the atrophy, apoptosis or death of retinal ganglion cells (RGCs). Though some progress has been achieved on electronic retinal implants that can electrically stimulate undamaged parts of RGCs or retina to transfer signals, stimulated self-repair/regeneration of RGCs has not been realized yet. The key challenge for development of electrically stimulated regeneration of RGCs is the selection of stimulation electrodes with a sufficient safe charge injection limit (Q(inj), i.e., electrochemical capacitance). Most traditional electrodes tend to have low Q(inj) values. Herein, we synthesized polypyrrole functionalized graphene (PPy-G) via a facile but efficient polymerization-enhanced ball milling method for the first time. This technique could not only efficiently introduce electron-acceptor nitrogen to enhance capacitance, but also remain a conductive platform-the π-π conjugated carbon plane for charge transportation. PPy-G based aligned nanofibers were subsequently fabricated for guided growth and electrical stimulation (ES) of RGCs. Significantly enhanced viability, neurite outgrowth and antiaging ability of RGCs were observed after ES, suggesting possibilities for regeneration of optic nerve via ES on the suitable nanoelectrodes.

The effect of sinusoidal AC electric stimulation of 3D PCL/CNT and PCL/β-TCP based bio-composites on cellular activities for bone tissue regeneration

Various physical stimulations have been widely applied to tissue regenerative applications. In particular, for bone tissue regeneration, several experimental studies have reported that electric stimulation can enhance the mineral formation in cultured osteoblasts and even alter the pattern of gene expression, promoting bone tissue formation. However, to date, for rapid-prototyped polycaprolactone (PCL)-based composites of pure PCL and dispersed materials including carbon nanotubes and β-tricalcium phosphate (TCP), the effect of electric stimulation on various cellular activities has not been analyzed. Here, a sinusoidal AC electric field (55 ± 8 mV cm^-1 and 60 Hz) between parallel electrodes was applied to three-dimensional scaffolds (pure PCL, PCL/CNT-0.2 wt%, and PCL/β-TCP-20 wt%) cultured with osteoblast-like cells (MG63) 30 min per day for 14 days. When exposed to electric stimulation, alkaline phosphatase and calcium mineralization were enhanced in all scaffolds, and the PCL/β-TCP scaffold in particular showed the highest improvement in bone mineralization compared with other scaffolds. In this work, we surmised that the improvement may have been due to chemical precipitation of the calcium ions from the PCL/β-TCP scaffolds. To evaluate the effect of the released calcium ions from the composite scaffold, we observed the cellular behavior (cellular contraction) of proliferated cells under electric stimulation. The results indicate that in addition to the applied electric field conditions, the scaffold materials are also an important parameter for successful electric stimulation.

Murine model of neuromuscular electrical stimulation on squamous cell carcinoma: potential implications for dysphagia therapy

BACKGROUND

Dysphagia is a potential consequence of treatment for head and neck cancer. Neuromuscular electrical stimulation (NMES) has evolved as a treatment option, with the goal of improved swallow function in patients with chronic dysphagia. However, the effects of NMES on tumorigenicity are unknown and often confound the initiation of this therapy, potentially limiting its efficacy in treating patients with head and neck cancer.

METHODS

Squamous cell carcinoma was grown in the flank of athymic, nude mice. Mice were randomized into treatment and control groups; the experimental group received daily NMES directly to the flank for 8 days.

RESULTS

Tumor volumes, recorded on days 0, 3, 7, and 10, demonstrated no significant differences between groups on each day of measurement. Immunohistochemical analysis of apoptosis, proliferation, and vascularization also failed to demonstrate statistically significant differences between treated and untreated groups.

CONCLUSIONS

NMES does not promote the growth of underlying tumor in our model. These data may provide preliminary evidence that applying electrical stimulation over the muscles of the anterior neck does not increase the risk of tumorigenicity. Early initiation of NMES in this challenging population may be feasible from an oncologic standpoint.

Decubitus direct current treatment (DDCT) of pressure ulcers: results of a randomized double-blinded placebo controlled study

Electrostimulation for the treatment of pressure sores remains problematic and controversial. We studied the decubitus direct current treatment (DDCT) electrostimulation treatment of pressure sores stage 3 degree, with respect to rates of ulcer closure and wound area reduction. This was a multicenter, double-blind, randomized, placebo-controlled study involving 11 departments of geriatric and rehabilitation medicine including 63 patients. We compared a placebo treated group (PG) with an active treatment group (TG). Treatment lasted for 8 consecutive weeks, followed by a 12-week-period of follow-up. At day 57 (end of treatment) and at day 147 (end of follow-up), there was no difference between the groups with regards to rates of complete closure of ulcers (p=0.28 and 0.39, respectively), as well as for the mean time needed to achieve complete wound closure (p=0.16). Absolute ulcer area reduction and speed rate of wound area reduction (reflected by change from baseline ulcer area, percentage) were better in participants allocated in the treatment group only until day 45 (standardized estimate for trend of healing speed -0.44 and -0.14 for TG and PG, respectively). Afterwards, there were no differences between the two groups. A logistic regression analysis favored complete healing in TG, compared with PG (odds ratio 1.6, CI 0.4-4.73). Analysis of per protocol patients revealed that time needed for wound closure was 52% longer in PG (p=0.03, compared with TG). The results suggest that DDCT treatment for pressure ulcers grade 3 degree, in addition to the conservative wound care, may be useful in accelerating the healing process during the first period of care.

Cell proliferation and apoptosis in rat mammary cancer after electrochemical treatment (EChT)

Background: Several authors have recently reported encouraging results from Electrochemical treatment (EChT) in malignant tumours. However, EChT is not established and mechanisms are not completely understood. In vivo studies were conducted to evaluate the toxic changes and effectiveness of EChT on an animal tumour model. Methods: Tumours were induced by injecting cells from the R3230AC rat mammary tumour cell line clone D subcutaneously, in 28 female Fischer 344 rats. EChT was conducted by inserting a platinum electrode into the tumours. The positive and negative control groups were subjected to the same conditions but without current. The rats were kept for 0, 7 or 14 days post-treatment. Three hours prior to euthanasia an i.p. injection of Bromodioxyuridine (BrdU) was given. The rats were euthanized, the lesions extirpated and samples were collected for histopathological, and immunohistochemical examination. Results: Significant changes in cell proliferation rate were seen both in the cathode and anode regions. Apoptosis were induced in the anodic treated area outside the primary necrosis, detected with the TUNEL method. Discussion: The results suggest that secondary cell destruction was caused by necrosis with cathodic EChT and apoptosis or necrosis with anodic EChT.

Animal models for treatment of unresectable liver tumours: a histopathologic and ultra-structural study of cellular toxic changes after electrochemical treatment in rat and dog liver

INTRODUCTION

Electrochemical treatment (EChT) has been taken under serious consideration as being one of several techniques for local treatment of malignancies. The advantage of EChT is the minimal invasive approach and the absence of serious side effects. Macroscopic, histopathological and ultra-structural findings in liver following a four-electrode configuration (dog) and a two-electrode EChT design (dog and rat) were studied.

MATERIALS AND METHODS

30 female Sprague-Dawley rats and four female beagle dogs were studied with EChT using Platinum:Iridium electrodes and the delivered dose was 5, 10 or 90 C (As). After EChT, the animals were euthanized.

RESULTS

The distribution of the lesions was predictable, irrespective of dose and electrode configuration. Destruction volumes were found to fit into a logarithmic curve (dose-response). Histopathological examination confirmed a spherical (rat) and cylindrical/ellipsoidal (dog) lesion. The type of necrosis differed due to electrode polarity. Ultra-structural analysis showed distinct features of cell damage depending on the distance from the electrode. Histopathological and ultra-structural examination demonstrated that the liver tissue close to the border of the lesion displayed a normal morphology.

CONCLUSIONS

The in vivo dose-planning model is reliable, even in species with larger tissue mass such as dogs. A multi-electrode EChT-design could obtain predictable lesions. The cellular toxicity following EChT is clearly identified and varies with the distance from the electrode and polarity. The distinct border between the lesion and normal tissue suggests that EChT in a clinical setting for the treatment of liver tumours can give a reliable destruction margin.

[Non-pharmacological treatments in the stimulation of osteogenesis]

Mechanical loads cause bone deformation leading to bone resorption and an increase in local bone formation. However, the stimulus for bone formation depends on the amount and frequency of bone deformation. High calcium intake is required to increase bone formation. There are also non-pharmacological treatments, such as electrical stimulation, low-intensity ultrasound, and laser, which revealed to promote osteogenesis. The article intends to evaluate non-pharmacological, alternative methods which assist in the increase of bone formation or in the osteogenic stimulus. A literature review was carried out for the period between 1982 to 2001.

Electrochemical treatment of mouse Ehrlich tumor with direct electric current

Electrochemical treatment of cancer utilizes direct electric current (DEC) to produce direct alterations and chemical changes in tumors. However, the DEC treatment is not established and mechanisms are not well understood. In vivo studies were conducted to evaluate the effectiveness of DEC on animal tumor models. Ehrlich tumors were implanted subcutaneously in sixty male BALB/c mice. When the tumor volumes reached 850 mm(3), four platinum electrodes were inserted into the tumors. DEC of 4 mA was applied for 21 min to the treated group; the total charge was 5 C. The healthy and sick control groups were subjected to the same conditions but without DEC. Hematological and chemical parameters as well as histopathological and peritumoral findings were studied. After the electrochemical therapy it was observed that both tumor volume decrease and necrosis percentage increase were significant in the treated group. Moreover, 24 h after treatment an acute inflammatory response, as well as sodium ion decrease, and potassium ion and spleen weight increase were observed in this group. It was concluded that both electrochemical reactions (fundamentally those in which reactive oxygen species are involved), and immune system stimulation induced by cytotoxic action of the DEC could constitute the most important antitumor mechanisms.

Potentiation of bleomycin antitumor effectiveness by electrotherapy

Electrotherapy was investigated for its ability to increase the responsiveness of murine tumors to bleomycin treatment. Mice bearing fibrosarcoma were treated with 250 micrograms bleomycin and then with 0.6 mA direct current (DC) for 60 min. Antitumor effects of single treatments were moderate with bleomycin, but significant with electrotherapy. Combined treatment with bleomycin followed by electrotherapy was more effective than either treatment alone. Tumor growth delay of the animals after combined treatment was greater than the summation of tumor growth delays after single treatments. The results of our study indicate that bleomycin and electrotherapy treatments interact, with electrotherapy potentiating the effectiveness of bleomycin treatment.