Making Sense of Electrical Stimulation: A Meta-analysis for Wound Healing

Electrical stimulation as a mode of external enhancement factor in wound healing has been explored widely. It has proven to have multidimensional effects in wound healing including antibacterial, galvanotaxis, growth factor secretion, proliferation, transdifferentiation, angiogenesis, etc. Despite such vast exploration, this modality has not yet been established as an accepted method for treatment. This article reviews and analyzes the approaches of using electrical stimulation to modulate wound healing and discusses the incoherence in approaches towards reporting the effect of stimulation on the healing process. The analysis starts by discussing various processes adapted in in vitro, in vivo, and clinical practices. Later it is focused on in vitro approaches directed to various stages of wound healing. Based on the analysis, a protocol is put forward for reporting in vitro works in such a way that the outcomes of the experiment are replicable and scalable in other setups. This work proposes a ground of unification for all the in vitro approaches in a more sensible manner, which can be further explored for translating in vitro approaches to complex tissue stimulation to establish electrical stimulation as a controlled clinical method for modulating wound healing.

Coupling cell shape and velocity leads to oscillation and circling in keratocyte galvanotaxis

During wound healing, fish keratocyte cells undergo galvanotaxis where they follow a wound-induced electric field. In addition to their stereotypical persistent motion, keratocytes can develop circular motion without a field or oscillate while crawling in the field direction. We developed a coarse-grained phenomenological model that captures these keratocyte behaviors. We fit this model to experimental data on keratocyte response to an electric field being turned on. A critical element of our model is a tendency for cells to turn toward their long axis, arising from a coupling between cell shape and velocity, which gives rise to oscillatory and circular motion. Galvanotaxis is influenced not only by the field-dependent responses, but also cell speed and cell shape relaxation rate. When the cell reacts to an electric field being turned on, our model predicts that stiff, slow cells react slowly but follow the signal reliably. Cells that polarize and align to the field at a faster rate react more quickly and follow the signal more reliably. When cells are exposed to a field that switches direction rapidly, cells follow the average of field directions, while if the field is switched more slowly, cells follow a "staircase" pattern. Our study indicated that a simple phenomenological model coupling cell speed and shape is sufficient to reproduce a broad variety of different keratocyte behaviors, ranging from circling to oscillation to galvanotactic response, by only varying a few parameters.

Microcurrent and Gold Nanoparticles Combined with Hyaluronic Acid Accelerates Wound Healing

This study aimed to investigate the effects of iontophoresis and hyaluronic acid (HA) combined with a gold nanoparticle (GNP) solution in an excisional wound model. Fifty Wistar rats (n = 10/group) were randomly assigned to the following groups: excisional wound (EW); EW + MC; EW + MC + HA; EW + MC + GNPs; and EW + MC + HA + GNPs. The animals were induced to a circular excision, and treatment started 24 h after injury with microcurrents (300 µA) containing gel with HA (0.9%) and/or GNPs (30 mg/L) in the electrodes (1 mL) for 7 days. The animals were euthanized 12 h after the last treatment application. The results demonstrate a reduction in the levels of pro-inflammatory cytokines (IFNϒ, IL-1β, TNFα, and IL-6) in the group in which the therapies were combined, and they show increased levels of anti-inflammatory cytokines (IL-4 and IL-10) and growth factors (FGF and TGF-β) in the EW + MC + HA and EW + MC + HA + GNPs groups. As for the levels of dichlorofluorescein (DCF) and nitrite, as well as oxidative damage (carbonyl and sulfhydryl), they decreased in the combined therapy group when compared to the control group. Regarding antioxidant defense, there was an increase in glutathione (GSH) and a decrease in superoxide dismutase (SOD) in the combined therapy group. A histological analysis showed reduced inflammatory infiltrate in the MC-treated groups and in the combination therapy group. There was an increase in the wound contraction rate in all treated groups when compared to the control group, proving that the proposed therapies are effective in the epithelial healing process. The results of this study demonstrate that the therapies in combination favor the tissue repair process more significantly than the therapies in isolation.

Novel Technologies in Chronic Wound Care

In Israel, 20% of wounds do not progress to full healing under treatment with conservative technologies of which 1 to 2% are eventually defined as chronic wounds. Chronic wounds are a complex health burden for patients and pose considerable therapeutic and budgetary burden on health systems. The causes of chronic wounds include systemic and local factors. Initial treatment involves the usual therapeutic means, but as healing does not progress, more advanced therapeutic technologies are used. Undoubtedly, advanced means, such as negative pressure systems, and advanced technologies, such as oxygen systems and micrografts, have vastly improved the treatment of chronic wounds. Our service specializes in treating ulcers and difficult-to-heal wounds while providing a multiprofessional medical response. Herein, we present our experience and protocols in treating chronic wounds using a variety of advanced dressings and technologies.

Efficacy of Low-frequency Monophasic Pulsed Microcurrent Stimulation Therapy in Undermining Pressure Injury: A Double-blind Crossover-controlled Study

Objectives:

This double-blind crossover-controlled trial aimed to verify the effect of electrical stimulation therapy on pressure injuries with undermining.

Methods

: In this trial, we compared the healing rates between a sham period and a treatment period using monophasic pulsed microcurrent therapy. The participants were randomly assigned to the sham or treatment group and received stimulation for 2 weeks. All the participants, physical therapists, and researchers were blinded to the allocation. For the main analysis, data on the effect of the intervention on changes in weekly healing and contraction rates of the wound areas, including undermining, were analyzed based on a two-period crossover study design. The intervention effect was estimated by examining the mean treatment difference for each period using Wilcoxon’s signed-rank test.

Results

: The reduction of the entire wound area, including the undermining area, resulted in significantly higher healing and contraction rates in the treatment group (overall wound area reduction rate: contraction rate, P=0.008; period healing rate, P=0.002).

Conclusions

: Electrical stimulation therapy for pressure injuries, using conditions based on the findings of an in vivo culture study, was effective in reducing the wound area.

Electrical microcurrent stimulation therapy for wound healing: A meta-analysis of randomized clinical trials

BACKGROUND

Electrical microcurrent therapy (EMT) consists of the application of low intensity (μA) currents that are similar to endogenous electric fields generated during wound healing.

AIMS

To examine the effectiveness and safety of EMT for improving wound healing and pain in people with acute or chronic wounds.

METHOD

Randomized clinical trials (RCTs) assessing the effectiveness of EMT in wound healing published up to August 1st, 2020 were included. The main outcomes were wound surface area, healing time, and number of wounds healed. Secondary outcomes were pain perception and adverse events. A quantitative analysis was conducted using the inverse variance and Mantel-Haenszel methods.

RESULTS

Eight RCTs were included in the qualitative summary and seven in the quantitative analysis (n = 337 participants). EMT plus standard wound care (SWC) produced a greater decrease in wound surface [mean difference (MD) = -8.3 cm²; CI 95%: -10.5 to -6.0] and healing time (MD = -7.0 days; CI 95%: -11.9 to -2.1) that SWC alone, showing moderate and low certainty in the evidence, respectively. However, no differences were observed in the number of healed wounds [risk ratio = 2.0; CI 95%: 0.5 to 9.1], with very low quality of evidence. EMT decreased perceived pain (MD = -1.4; CI 95%: -2.7 to -0.2), but no differences in adverse effects were noted between groups (risk difference = 0.05; CI 95%: -0.06 to 0.17).

CONCLUSIONS

EMT is an effective, safe treatment for improving wound area, healing time, and pain. Further clinical trials that include detailed intervention parameters and protocols should be designed to lower the risk of bias.

Wound Healing with Electrical Stimulation Technologies: A Review

Electrical stimulation (ES) is an attractive field among clinicians in the topic of wound healing, which is common yet complicated and requires multidisciplinary approaches. The conventional dressing and skin graft showed no promise on complete wound closure. These urge the need for the exploration of electrical stimulation to supplement current wound care management. This review aims to provide an overview of electrical stimulation in wound healing. The mechanism of galvanotaxis related to wound repair will be reviewed at the cellular and molecular levels. Meanwhile, different modalities of externally applied electricity mimicking a physiologic electric field will be discussed and compared in vitro, in vivo, and clinically. With the emerging of tissue engineering and regenerative medicine, the integration of electroconductive biomaterials into modern miniaturised dressing is of interest and has become possible with the advancing understanding of smart biomaterials.

Microcurrent stimulates cell proliferation and modulates cytokine release in fibroblast cells

AIMS

To analyse the effects of microcurrent on L929 fibroblast cell culture.

METHODS

Cells were cultivated in six-well plates at densities of 5×10⁴, 1×10⁵, 3×10⁵ and 5×10⁵ cells/well to determine the best plating density. Subsequently, two methods of current application were tested: with a paper cone coupled to the electrode (M1) and with the electrode directly inside the well (M2). Then, streams of 60µA (G60), 100µA (G100), 500µA (G500) and 900µA (G900) were applied to the cells (n=3) once a day for three minutes, for a period of one (T1), two (T2) and three days (T3). The MTT assay method was used to evaluate cell proliferation. For the quantification of the inflammatory markers by flow cytometry, the group and time that presented the best results were selected.

RESULTS

The ideal plating density was established as 1x10⁵ cells/well and M2 as the best application method. An increase in cell viability was observed at all intensities from T1 to T2, but with no significant differences. From T2 to T3, there was a decrease in viability in all groups, with a significant difference only in G500 (p<0.05). Flow cytometry was performed in the GC and G900 groups at T2. It was possible to observe an increase of 0.56pg/ml in Interleukin (IL)-17 and a decrease of 5.45pg/ml in IL-2.

CONCLUSION

This study showed that two applications of microcurrent increases cell proliferation and modulates the inflammatory response, aiding tissue regeneration and playing a key role in rehabilitation.

Accelerated Skin Wound Healing by Electrical Stimulation

When the integrity of the skin got damaged, an endogenous electric field will be generated in the wound and a series of physiological reactions will be initiated to close the wound. The existence of the endogenous electric field of the wound has a promoting effect on all stages of wound healing. For wounds that cannot heal on their own, the exogenous electric field can assist the treatment. In this review, the effects of exogenous electrical stimulation on wound healing, such as the inflammation phase, blood flow, cell proliferation and migration, and the wound scarring is overviewed. This article also reviews the new electrical stimulation methods that have emerged in recent years, such as small power supplies, nanogenerators (NGs), and other physical, chemical or biological strategies. These new electrical stimulation methods and devices are safe, low-cost, stable, and small in size. The challenge and perspective are discussed for the future trends of the electrical stimulation treatment in accelerating skin wound healing.

Influence of microcurrent on the modulation of remodelling genes in a wound healing assay

The literature has shown the beneficial effects of microcurrent (MC) therapy on tissue repair. We investigated if the application of MC at 10 μA/90 s could modulate the expression of remodeling genes transforming growth factor beta (Tgfb), connective tissue growth factor (Ctgf), insulin-like growth factor 1 (Igf1), tenascin C (Tnc), Fibronectin (Fn1), Scleraxis (Scx), Fibromodulin (Fmod) and tenomodulin in NIH/3T3 fibroblasts in a wound healing assay. The cell migration was analyzed between days 0 and 4 in both fibroblasts (F) and fibroblasts + MC (F+MC) groups. On the 4th day, cell viability and gene expression were also analyzed after daily MC application. Higher expression of Ctgf and lower expression of Tnc and Fmod, respectively, were observed in the F+MC group in relation to F group (p < 0.05), and no difference was observed between the groups for the genes Tgfb, Fn1 and Scx. In cell migration, a higher number of cells in the scratch region was observed in group F+MC (p < 0.05) compared to group F on the 4th day, and the cell viability assay showed no difference between the groups. In conclusion, MC therapy at an intensity/time of 10 μA/90 s with 4 daily applications did not affect cell viability, stimulated fibroblasts migration with the involvement of Ctgf, and reduced the Tnc and Fmod expression.

Electrical stimulation for treating pressure ulcers

BACKGROUND

Pressure ulcers (also known as pressure sores, decubitus ulcers or bedsores) are localised injuries to the skin or underlying tissue, or both. Pressure ulcers are a disabling consequence of immobility. Electrical stimulation (ES) is widely used for the treatment of pressure ulcers. However, it is not clear whether ES is effective.

OBJECTIVES

To determine the effects (benefits and harms) of electrical stimulation (ES) for treating pressure ulcers.

SEARCH METHODS

In July 2019 we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE (including In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also searched clinical trials registries for ongoing and unpublished studies, and scanned reference lists of relevant included studies as well as reviews, meta-analyses and health technology reports to identify additional studies. We did not impose any restrictions with respect to language, date of publication or study setting.

SELECTION CRITERIA

We included published and unpublished randomised controlled trials (RCTs) comparing ES (plus standard care) with sham/no ES (plus standard care) for treating pressure ulcers.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, extracted data, and assessed risk of bias. We assessed the certainty of evidence using GRADE.

MAIN RESULTS

We included 20 studies with 913 participants. The mean age of participants ranged from 26 to 83 years; 50% were male. ES was administered for a median (interquartile range (IQR)) duration of five (4 to 8) hours per week. The chronicity of the pressure ulcers was variable, ranging from a mean of four days to more than 12 months. Most of the pressure ulcers were on the sacral and coccygeal region (30%), and most were stage III (45%). Half the studies were at risk of performance and detection bias, and 25% were at risk of attrition and selective reporting bias. Overall, the GRADE assessment of the certainty of evidence for outcomes was moderate to very low. Nineteen studies were conducted in four different settings, including rehabilitation and geriatric hospitals, medical centres, a residential care centre, and a community-based centre. ES probably increases the proportion of pressure ulcers healed compared with no ES (risk ratio (RR) 1.99, 95% confidence interval (CI) 1.39 to 2.85; I² = 0%; 11 studies, 501 participants (512 pressure ulcers)). We downgraded the evidence to moderate certainty due to risk of bias. It is uncertain whether ES decreases pressure ulcer severity on a composite measure compared with no ES (mean difference (MD) -2.43, 95% CI -6.14 to 1.28; 1 study, 15 participants (15 pressure ulcers) and whether ES decreases the surface area of pressure ulcers when compared with no ES (12 studies; 494 participants (505 pressure ulcers)). Data for the surface area of pressure ulcers were not pooled because there was considerable statistical heterogeneity between studies (I² = 96%) but the point estimates for the MD of each study ranged from -0.90 cm² to 10.37 cm². We downgraded the evidence to very low certainty due to risk of bias, inconsistency and imprecision. It is uncertain whether ES decreases the time to complete healing of pressure ulcers compared with no ES (hazard ratio (HR) 1.06, 95% CI 0.47 to 2.41; I² = 0%; 2 studies, 55 participants (55 pressure ulcers)). We downgraded the evidence to very low certainty due to risk of bias, indirectness and imprecision. ES may be associated with an excess of, or difference in, adverse events (13 studies; 586 participants (602 pressure ulcers)). Data for adverse events were not pooled but the types of reported adverse events included skin redness, itchy skin, dizziness and delusions, deterioration of the pressure ulcer, limb amputation, and occasionally death. We downgraded the evidence to low certainty due to risk of selection and attrition bias and imprecision. ES probably increases the rate of pressure ulcer healing compared with no ES (MD 4.59% per week, 95% CI 3.49 to 5.69; I² = 25%; 12 studies, 561 participants (613 pressure ulcers)). We downgraded the evidence to moderate certainty due to risk of bias. We did not find any studies that looked at quality of life, depression, or consumers' perception of treatment effectiveness.

AUTHORS' CONCLUSIONS

ES probably increases the proportion of pressure ulcers healed and the rate of pressure ulcer healing (moderate certainty evidence), but its effect on time to complete healing is uncertain compared with no ES (very low certainty evidence). It is also uncertain whether ES decreases the surface area of pressure ulcers. The evidence to date is insufficient to support the widespread use of ES for pressure ulcers outside of research. Future research needs to focus on large-scale trials to determine the effect of ES on all key outcomes.

Mammalian fibroblast cells avoid residual stress zone caused by nanosecond laser pulses

This study investigates the effects of laser irradiation on crystalline silicon and its application in biomaterials. We used an analytical model to predict the ablation depth and pit size resulting from laser exposure of silicon samples. The temperatures generated are predicted correlate with laser power, and to result in the formation of a residual stress zone bordering the ablated groove. Different crystal orientations found in the substrate confirm that there was crystal distortion, which consequently induces these residual stress zones. Mouse embryonic fibroblasts avoid the stress areas and accumulate outside of these zones. Higher laser power results in broader residual stress zone and a larger zone of cellular exclusion. We argue that residual stress resulting from high-energy laser ablation of silicon may be a promising avenue to explore as a method for patterning cell growth on these materials.

Monophasic Pulsed Microcurrent of 1-8 Hz Increases the Number of Human Dermal Fibroblasts

Objective

Pressure injuries seriously impact the quality of life of patients and increase public and private healthcare costs. Electrical stimulation therapy is recommended for wound contraction, and some clinical studies have shown that the application of a monophasic pulsed microcurrent can help to reduce the treatment period. However, the optimal stimulus conditions are unclear. The purpose of this study was to investigate the effect of different frequencies of monophasic pulsed microcurrent stimulation on the number and viability of human dermal fibroblasts.

Methods

Human dermal fibroblasts were electrically stimulated in vitro (intensity: 200 μA; frequency: 1, 2, 4, 8, 16, 32, and 64 Hz; duty factor: 50%) for 1 h three times every 24 h. Controls were unstimulated. Cell numbers and cell viability were assessed after each electrical stimulation session.

Results

In the 1-, 2-, 4-, and 8-Hz groups, cell numbers were significantly higher than those in the control group, whereas electrical stimulation at 64 Hz resulted in a decrease in cell numbers at 24 h after the third treatment (p < 0.05). Cell viability was high in both the control and low-frequency stimulation groups, with no significant differences between groups.

Conclusion

Application of 1-8 Hz monophasic pulsed microcurrent stimulation increased the number of human dermal fibroblasts in vitro, and is proposed as the optimal condition for accelerating the healing of pressure injuries.

Electrical Stimulation Technologies for Wound Healing

Objective: To discuss the physiological bases for using exogenously applied electric field (EF) energy to enhance wound healing with conductive electrical stimulation (ES) devices. Approach: To describe the types of electrical currents that have been reported to enhance chronic wound-healing rate and closure. Results: Commercial ES devices that generate direct current (DC), and mono and biphasic pulsed current waveforms represent the principal ES technologies which are reported to enhance wound healing. Innovation: Wafer-thin, disposable ES technologies (wound dressings) that utilize mini or micro-batteries to deliver low-level DC for wound healing and antibacterial wound-treatment purposes are commercially available. Microfluidic wound-healing chips are currently being used with greater accuracy to investigate the EF effects on cellular electrotaxis. Conclusion: Numerous clinical trials described in subsequent sections of this issue have demonstrated that ES used adjunctively with standard wound care (SWC), enhances wound healing rate faster than SWC alone.

Effects and mechanisms of a microcurrent dressing on skin wound healing: a review

The variety of wound types has resulted in a wide range of wound dressings, with new products frequently being introduced to target different aspects of the wound healing process. The ideal wound dressing should achieve rapid healing at a reasonable cost, with minimal inconvenience to the patient. Microcurrent dressing, a novel wound dressing with inherent electric activity, can generate low-level microcurrents at the device-wound contact surface in the presence of moisture and can provide an advanced wound healing solution for managing wounds. This article offers a review of the effects and mechanisms of the microcurrent dressing on the healing of skin wounds.

Galvanic microparticles increase migration of human dermal fibroblasts in a wound-healing model via reactive oxygen species pathway

Electrical signals have been implied in many biological mechanisms, including wound healing, which has been associated with transient electrical currents not present in intact skin. One method to generate electrical signals similar to those naturally occurring in wounds is by supplementation of galvanic particles dispersed in a cream or gel. We constructed a three-layered model of skin consisting of human dermal fibroblasts in hydrogel (mimic of dermis), a hydrogel barrier layer (mimic of epidermis) and galvanic microparticles in hydrogel (mimic of a cream containing galvanic particles applied to skin). Using this model, we investigated the effects of the properties and amounts of Cu/Zn galvanic particles on adult human dermal fibroblasts in terms of the speed of wound closing and gene expression. The collected data suggest that the effects on wound closing are due to the ROS-mediated enhancement of fibroblast migration, which is in turn mediated by the BMP/SMAD signaling pathway. These results imply that topical low-grade electric currents via microparticles could enhance wound healing.

Laserterapia e microcorrente na cicatrização de queimadura em ratos: terapias associadas ou isoladas?

Este estudo teve o objetivo de investigar se há diferenças entre as terapias associadas e isoladas do laser e microcorrentes no reparo de lesão por queimadura em ratos. Um total de 40 animais foi dividido aleatoriamente em quatro grupos: grupo controle (GC); grupo microcorrente (GM), grupo laser (GL) e grupo laser/microcorrente (GLM), tratados com laser associado a microcorrentes. Após lesões térmicas induzidas no dorso do animal, foi realizado um total de dez dias de tratamento. Amostras do tecido foram coletadas para estudo histopatológico semiquantitativo com Hematoxilina Eosina e Tricrômico de Masson. Foram utilizados os testes de Kruskal-Wallis e post-hoc de Dunn. Houve diferença significativa entre os grupos para a produção de fibroblastos (p=0,0003), colágeno (p=0,0153), neoangiogênese (p=0,0031) e anexos cutâneos (p=0,0004). Na análise histológica semiquantitativa, o GLM apresentou valores menores nos parâmetros histológicos de presença de colágeno, número de fibroblastos e anexos cutâneos (p<0,05) em relação às terapias isoladas, exceto para a neoangiogênese, cujos valores da terapia associada foram semelhantes aos grupos de terapia com modalidade única. Apesar do laser e da microcorrente separadamente terem efeitos benéficos para a cicatrização tecidual, a associação das modalidades parece ter diminuído a ação de reparo. No entanto, sugere-se que a associação destes recursos parece diminuir os efeitos do tratamento quando se comparam os grupos de modalidade única.