Hierarchical evaluation of electrical stimulation protocols for chronic wound healing: An effect size meta-analysis

Can Electrical Stimulation Prevent Recurrence of Keloid Scars: A Scoping Review

OBJECTIVE

Keloids represent a symptomatic, aberrant healing process that is difficult to treat with high recurrence rates spanning from 55-100% if treated via excision without adjuvant therapy. Electrical stimulation (ES) has demonstrated findings that suggest it could reduce the recurrence rate of keloids after resection. Therefore, the aim of this study is to conduct a scoping review to investigate ES as an adjuvant therapy for decreasing keloid recurrence after excision.

APPROACH

A scoping review was performed using PubMed and Web of Science databases. The search strategy encompassed terms linking keloids and various aspects of electrical stimulation.

RESULTS

Our search yielded 2229 articles. 115 articles were analyzed as full text. 1 article met inclusion criteria. Despite this, ES has demonstrated other evidence that suggests its utility. ES has been shown to counter keloidic features by reducing mast cell counts, shifting wound composition from M2 to M1 macrophages, promoting angiogenesis, and, controlling fibroblast orientation and location. An alternating current will orient fibroblasts perpendicular to the current without unintended migration.

INNOVATION

Our study indicates that, based on a compilation of clinical and preclinical in vitro data, the optimal scenario for ES in the role of keloid treatment is after excision with a biphasic pulsed application and square waveform.

CONCLUSIONS

ES could serve as a multifaceted, adjuvant treatment after keloid excision, steering the healing process away from keloid-associated characteristics. Its cost-effectiveness means it could be adopted globally, providing a strategy to mitigate the burden of keloids irrespective of other available treatments or economic conditions.

Piezoelectric dressings for advanced wound healing

The treatment of chronic refractory wounds poses significant challenges and threats to both human society and the economy. Existing research studies demonstrate that electrical stimulation fosters cell proliferation and migration and promotes the production of cytokines that expedites the wound healing process. Presently, clinical settings utilize electrical stimulation devices for wound treatment, but these devices often present issues such as limited portability and the necessity for frequent recharging. A cutting-edge wound dressing employing the piezoelectric effect could transform mechanical energy into electrical energy, thereby providing continuous electrical stimulation and accelerating wound healing, effectively addressing these concerns. This review primarily reviews the selection of piezoelectric materials and their application in wound dressing design, offering a succinct overview of these materials and their underlying mechanisms. This study also provides a perspective on the current limitations of piezoelectric wound dressings and the future development of multifunctional dressings harnessing the piezoelectric effect.

Electrical stimulation facilitates NADPH production in pentose phosphate pathway and exerts an anti-inflammatory effect in macrophages

Macrophages play an important role as effector cells in innate immune system. Meanwhile, macrophages activated in a pro-inflammatory direction alter intracellular metabolism and damage intact tissues by increasing reactive oxygen species (ROS). Electrical stimulation (ES), a predominant physical agent to control metabolism in cells and tissues, has been reported to exert anti-inflammatory effect on immune cells. However, the mechanism underlying the anti-inflammatory effects by ES is unknown. This study aimed to investigate the effect of ES on metabolism in glycolytic-tricarboxylic acid cycle (TCA) cycle and inflammatory responses in macrophages. ES was performed on bone marrow-derived macrophages and followed by a stimulation with LPS. The inflammatory cytokine expression levels were analyzed by real-time polymerase chain reaction and ELISA. ROS production was analyzed by CellRox Green Reagent and metabolites by capillary electrophoresis-mass spectrometry. As a result, ES significantly reduced proinflammatory cytokine expression levels and ROS generation compared to the LPS group and increased glucose-1-phosphate, a metabolite of glycogen. ES also increased intermediate metabolites of the pentose phosphate pathway (PPP); ribulose-5-phosphate, rebose-5 phosphate, and nicotinamide adenine dinucleotide phosphate, a key factor of cellular antioxidation systems, as well as α-Ketoglutarate, an anti-oxidative metabolite in the TCA cycle. Our findings imply that ES enhanced NADPH production with enhancement of PPP, and also decreased oxidative stress and inflammatory responses in macrophages.

On Putting an End to the Backlash Against Electrophysical Agents

Electrophysical agents (EPAs) are core therapeutic interventions in academic physical therapy curricula around the world. They are used concomitantly with several other therapeutic interventions such as exercise, manual therapy techniques, medications, and surgery for the management of a wide variety of soft tissue disorders. Over the past decade, the practice of EPAs has been the subject of intense scrutiny in the U.S. This has been colored by some physical therapists publicly engaging in bashing rhetoric that has yet to be officially and publicly addressed by the guiding organizations which, together, regulate the practice of physical therapy in this country. Published in world renowned public media are unsubstantiated mocking remarks against the practice of EPAs and unethical allegations against its stakeholders. This rhetoric suggests that EPA interventions are "magical" treatments and that those practitioners who include them in their plans of care may be committing fraud. Such bashing rhetoric is in striking contradiction to the APTA's Guide to Physical Therapist Practice 4.0, which lists EPAs as one of its categories of interventions, the CAPTE's program accreditation policy, and the FSBPT's national licensing exam. The purpose of this commentary is to expose the extent of this discourse and to call to action the APTA, CAPTE, and FSBPT organizations, as well as physical therapists, with the aim at putting an end to this rhetoric.

The effect of wound electrical stimulation in venous leg ulcer healing-a systematic review

OBJECTIVE

The benefit of using electric stimulation therapy (EST) to heal venous leg ulcers (VLUs) is not well established. The main aim of this systematic review was to evaluate the effects of ulcer EST in VLU healing.

METHODS

A systematic search of the literature was conducted using the databases PubMed, Scopus, and Web of Science and included original studies that reported VLU healing after EST. The inclusion criteria were at least two surface electrodes placed on or near the wound or a planar probe covering the ulcer area to be treated. The Cochrane risk of bias tool for randomized control trials (RCTs) and Joanna Briggs Institute critical appraisal checklist for case series were used to evaluate the risk of bias.

RESULTS

This review included eight RCTs and three case series involving a total of 724 limbs in 716 patients with VLUs. The mean patient age was 64.2 years (95% confidence interval, 62.3-66.2), and 46.2% (95% confidence interval, 41.2%-50.4%) were men. The active electrode was placed on the wound with the passive electrode placed on healthy skin (n = 6), the two electrodes were placed on either side of the wound edges (n = 4), or a planar probe was used (n = 1). The pulsed current was the most used waveform (n = 9). The change in the ulcer size was the main method used to determine ulcer healing (n = 8), followed by the ulcer healing rate (n = 6), exudate levels (n = 4), and the time to healing (n = 3). Five RCTs detected a statistically significant improvement in at least one VLU healing outcome, after EST compared with the control group. In two of these, EST was better than the control but only for patients who had not undergone surgical treatment of VLU.

CONCLUSIONS

The findings from the present systematic review support the use of EST to accelerate wound healing of VLUs, especially for patients who are not surgical candidates. However, the significant variation in electric stimulation protocols represents an important limitation to its use and should be addressed in future studies.

Literature review of transcutaneous electrical nerve stimulation in peripheral arterial occlusive disease of the lower limbs

The therapeutic challenge in peripheral arterial occlusive disease (PAD) is often to increase walking distance, improve pain or heal a wound when PAD is symptomatic. Walking rehabilitation or surgical revascularization techniques are limited. Others strategies as alternatives and/or complementary treatments are needed. Among alternative options, Transcutaneous Electrical Nerve Stimulations (TENS) could be of interest, both for improved walking distance or pain reduction. The Transcutaneous Electrical Nerve Stimulation (TENS) is a non-pharmacological, mini-invasive technique involving transcutaneous electrical stimulation. However, there are other transcutaneous electrical nerve stimulation techniques based on the principle of vagus nerve stimulation with different mechanistics. Trans-auricular Vagus nerve stimulation (Ta-VNS) is another TENS technique (electrode on the external ear) which relies on the anti-inflammatory pathways of efferent and afferent vagal fibers. We propose here to review the literature of mini-invasive electrical stimulations, whatever the anatomical zone concerned, in PAD.

METHOD

The aim was to evaluate the use of non-invasive transcutaneous electrical stimulation therapies (regardless of location) in PAD of the lower limbs, whatever the disease grade. A review of the literature was carried out via a search of the MEDLINE/PubMed database from 1975 to 2023. The articles were selected via abstracts by checking (1) medical indications: PAD patients with claudication were retained, excluding neurological or venous claudication, PAD whatever the disease grade (intermittent claudication or critical limb ischemia [CLI]) and (2) non invasive electrical stimulations were considered (neuromuscular electrical stimulation and spinal cord stimulation were excluded) whatever the anatomical site. Non-electrical stimuli such as acupuncture and reflexotherapy were excluded.

RESULTS

Only 9 items were selected, including 7 studies with TENS treatment on the calf, one with trans-auricular vagus nerve stimulation and one with electro-acupuncture points of stimulation.

CONCLUSION

Even if the mechanisms involved are different, TENS on the calves or in the external ears show an improvement of walking distance in PAD patients with intermittent claudication. The results of the studies show few positive effects in arteriopathy but we should keep vigilant in the technics used since mechanisms are different and not fully understood. Electro-stimulation of the calf and external ear appears to be an easy-to-use and accessible therapeutic option, especially since some PAD patients are still failing to be released from pain, despite the rise of endovascular interventional techniques.

Flexible, Breathable, and Self-Powered Patch Assembled of Electrospun Polymer Triboelectric Layers and Polypyrrole-Coated Electrode for Infected Chronic Wound Healing

Chronic wound healing is often impaired by bacterial infection and weak trans-epithelial potential. Patches with electrical stimulation and bactericidal activity may solve this problem. However, inconvenient power and resistant antibiotics limit their application. Here, we proposed a self-powered and intrinsic bactericidal patch based on a triboelectric nanogenerator (TENG). Electrospun polymer tribo-layers and a chemical vapor-deposited polypyrrole electrode are assembled as the TENG, offering the patch excellent flexibility, breathability, and wettability. Electrical stimulations by harvesting mechanical motions and positive charges on the polypyrrole surface kill over 96% of bacteria due to their synergistic effects on cell membrane disruption. Moreover, the TENG patch promotes infected diabetic rat skin wounds to heal within 2 weeks. Cell culture and animal tests suggest that electrical stimulation enhances gene expression of growth factors for accelerated wound healing. This work provides new insights into the design of wearable and multifunctional electrotherapy devices for chronic wound treatment.

The effect of high-voltage monophasic pulsed current on diabetic ulcers and their potential pathophysiologic factors: A systematic review and meta-analysis

The present review was conducted to determine the efficacy of high-voltage monophasic pulsed current (HVMPC) in treating diabetic ulcers, assess its effect on skin lesions with each of the pathophysiologic factors potentially contributing to diabetic ulcers, evaluate its safety, and identify treatment parameters. Electronic search of PubMed, Scopus, PEDro and Google Scholar databases was conducted. The revised tool for assessing risk of bias in randomised trials (RoB 2), the risk of bias in non-randomised studies-of interventions (ROBINS-I) and the Joanna Briggs Institute (JBI) critical appraisal tool were used to assess risk of bias and methodological quality. Overall quality of evidence was determined using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) principles. Thirty-two studies matched the eligibility criteria, and included 1061 patients with 1103 skin lesions of selected aetiologies; 12 randomised controlled trials were included in quantitative synthesis. HVMPC plus standard wound care (SWC) likely increased the probability of complete wound healing of pressure ulcers (PrUs) compared with sham/no stimulation plus SWC; relative risk (RR) 2.08; 95% CI: [1.42, 3.04], p = 0.0002; I²  = 0%, p = 0.61; eight studies, 358 ulcers. Although conclusive evidence regarding the effect of HVMPC on diabetic ulcers was not found, collateral evidence might suggest a potential benefit. Direct evidence, with moderate certainty, may support its efficacy in treating PrUs, albeit few adverse reactions were reported. Other observations, moreover, might indicate that this efficacy may not be limited to PrUs. Nonetheless, several aspects remain to be clarified for safe and effective application of electrical stimulation for wound healing.

Home-Based Electrical Stimulation to Accelerate Wound Healing-A Double-Blinded Randomized Control Trial

BACKGROUND

Electrical stimulation (E-Stim) may offer a unique adjunctive treatment to heal complicated diabetic foot ulcers (DFU). Our primary goal is to examine the effectiveness of daily home-based E-Stim therapy to speed-up wound healing.

METHODS

Patients with chronic DFUs and mild to severe peripheral arterial disease (PAD) were recruited and randomized to either control (CG) or intervention (IG) groups. The IG received 1-hour home-based E-Stim therapy on daily basis for 4 weeks (4W). E-Stim was delivered through electrical pads placed above the ankle joint using a bio-electric stimulation technology (BEST^®) platform (Tennant Biomodulator^® PRO). The CG was provided with an identical but non-functional device for the same period. The primary outcome included wound area reduction at 4W from baseline (BL).

RESULTS

Thirty-eight patients were recruited and 5 were removed due to non-compliance or infection, leaving 33 participants (IG, n = 16; CG, n =17). At 4W, the IG showed a significant wound area reduction of 22% (BL: 7.4 ± 8.5 cm² vs 4W: 5.8 ± 8.0 cm², P = 0.002). Average of wound area was unchanged in the CG (P = 0.982). The self-report adherence to daily home-therapy was 93.9%.

CONCLUSIONS

Daily home-based E-Stim provides early results on the feasibility, acceptability, and effectiveness of E-Stim as an adjunctive therapy to speed up wound healings in patients with chronic DFU and mild to severe PAD.

Iontophoresis of treprostinil promotes wound healing in a murine model of scleroderma-related ulcers

OBJECTIVE

Systemic Sclerosis (SSc) is a rare, chronic disease characterized by fibrosis, vascular alterations and digital ulcerations. Few drugs have shown efficacy to enhance wound healing of existing SSc-related ulcers. Local delivery of treprostinil, a prostacyclin analogue, may improve wound healing. The present work aimed first at developing a mouse model of SSc-related ulcerations and second at assessing the effect of iontophoresis of treprostinil on wound healing.

METHODS

We used two murine models of SSc: chemically-induced with HOCl, and Urokinase-type plasminogen activator receptor (uPAR)-deficient. Excisional wounding was performed on the dorsal midline with a biopsy punch. Animals were randomized into three groups: treated with electrostimulation alone, with treprostinil iontophoresis, or untreated. We assessed wound healing over time, as well as skin microvascular reactivity, inflammation, microvessel density, and collagen distribution, before wounding and after re-epithelialization.

RESULTS

uPAR-/- mice, but not HOCl-treated mice, showed impaired wound healing and decreased microvascular reactivity compared with their controls. Treprostinil iontophoresis improved wound healing and microvascular density and decreased inflammation in uPAR-/- mice, while electro-stimulation did not. However, treprostinil had no effect on microvascular reactivity and collagen distribution.

CONCLUSION

This study suggests that excisional wounds in uPAR-/- mice are a relevant model of SSc-related ulcers. In addition, treprostinil iontophoresis enhances wound healing in this model. Further work in now needed to show whether this effect translates in humans.

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.

Conductive Biomaterials as Bioactive Wound Dressing for Wound Healing and Skin Tissue Engineering

Conductive biomaterials based on conductive polymers, carbon nanomaterials, or conductive inorganic nanomaterials demonstrate great potential in wound healing and skin tissue engineering, owing to the similar conductivity to human skin, good antioxidant and antibacterial activities, electrically controlled drug delivery, and photothermal effect. However, a review highlights the design and application of conductive biomaterials for wound healing and skin tissue engineering is lacking. In this review, the design and fabrication methods of conductive biomaterials with various structural forms including film, nanofiber, membrane, hydrogel, sponge, foam, and acellular dermal matrix for applications in wound healing and skin tissue engineering and the corresponding mechanism in promoting the healing process were summarized. The approaches that conductive biomaterials realize their great value in healing wounds via three main strategies (electrotherapy, wound dressing, and wound assessment) were reviewed. The application of conductive biomaterials as wound dressing when facing different wounds including acute wound and chronic wound (infected wound and diabetic wound) and for wound monitoring is discussed in detail. The challenges and perspectives in designing and developing multifunctional conductive biomaterials are proposed as well.

Come together: On-chip bioelectric wound closure

There is a growing interest in bioelectric wound treatment and electrotaxis, the process by which cells detect an electric field and orient their migration along its direction, has emerged as a potential cornerstone of the endogenous wound healing response. Despite recognition of the importance of electrotaxis in wound healing, no experimental demonstration to date has shown that the actual closing of a wound can be accelerated solely by the electrotaxis response itself, and in vivo systems are too complex to resolve cell migration from other healing stages such as proliferation and inflammation. This uncertainty has led to a lack of standardization between stimulation methods, model systems, and electrode technology required for device development. In this paper, we present a 'healing-on-chip' approach that is a standardized, low-cost, model for investigating electrically accelerated wound healing. Our device provides a biomimetic convergent field geometry that more closely resembles actual wound fields. We validate this device by using electrical stimulation to close a 1.5 mm gap between two large (30 mm2) layers of primary skin keratinocyte to completely heal the gap twice as quickly as in an unstimulated tissue. This demonstration proves that convergent electrotaxis is both possible and can accelerate healing and offers an accessible 'healing-on-a-chip' platform to explore future bioelectric interfaces.

Wound healing: potential therapeutic options

This review highlights the range of therapeutic options available to clinicians treating difficult-to-heal wounds. While certain treatments are established in daily clinical practice, most therapeutic interventions lack robust and rigorous data regarding their efficacy, which would help to determine when, and for whom, they should be used. The purpose of this review is to give a broad overview of the available interventions, with a brief summary of the evidence base for each intervention.

Triboelectric Nanogenerators for Self-Powered Wound Healing

Wound healing, one of the most complex processes in the human body, involves the spatial and temporal synchronization of a variety of cell types with distinct roles. Slow or nonhealing skin wounds have potentially life-threatening consequences, ranging from infection to scar, clot, and hemorrhage. Recently, the advent of triboelectric nanogenerators (TENGs) has brought about a plethora of self-powered wound healing opportunities, owing to their pertinent features, including wide range choices of constitutive biocompatible materials, simple fabrication, portable size, high output power, and low cost. Herein, a comprehensive review of TENGs as an emerging biotechnology for wound healing applications is presented and covered from three unique aspects: electrical stimulation, antibacterial activity, and drug delivery. To provide a broader context of TENGs applicable to wound healing applications, state-of-the-art designs are presented and discussed in each section. Although some challenges remain, TENGs are proving to be a promising platform for human-centric therapeutics in the era of Internet of Things. Consequently, TENGs for wound healing are expected to provide a new solution in wound management and play an essential role in the future of point-of-care interventions.

Electrical stimulation for pain reduction in hard-to-heal wound healing

OBJECTIVE

Despite treatment advances over the past 30 years, the societal impact of hard-to-heal wounds is increasingly burdensome. An unresolved issue is wound pain, which can make many treatments, such as compression in venous leg ulcers, intolerable. The aim of this review is to present the evidence and stimulate thinking on the use of electrical stimulation devices as a treatment technology with the potential to reduce pain, improve adherence and thus hard-to-heal wound outcomes.

METHOD

A literature search was conducted for clinical studies up to August 2020 reporting the effects of electrical stimulation devices on wound pain. Devices evoking neuromuscular contraction or direct spinal cord stimulation were excluded.

RESULTS

A total of seven publications (three non-comparative and four randomised trials) were identified with four studies reporting a rapid (within 14 days) reduction in hard-to-heal wound pain. Electrical stimulation is more widely known for accelerated healing and is one of the most evidence-based technologies in wound management, supported by numerous in vitro molecular studies, five meta-analyses, six systematic reviews and 30 randomised controlled trials (RCTs). Despite this wealth of supportive evidence, electrical stimulation has not yet been adopted into everyday practice. Some features of electrical stimulation devices may have hampered adoption in the past.

CONCLUSION

As new, pocket-sized, portable devices allowing convenient patient treatment and better patient adherence become more widely available and studied in larger RCTs, the evidence to date suggests that electrical stimulation should be considered part of the treatment options to address the challenges of managing and treating painful hard-to-heal wounds.

Electrical Stimulation to Enhance Wound Healing

Electrical stimulation (ES) can serve as a therapeutic modality accelerating the healing of wounds, particularly chronic wounds which have impaired healing due to complications from underlying pathology. This review explores how ES affects the cellular mechanisms of wound healing, and its effectiveness in treating acute and chronic wounds. Literature searches with no publication date restrictions were conducted using the Cochrane Library, Medline, Web of Science, Google Scholar and PubMed databases, and 30 full-text articles met the inclusion criteria. In vitro and in vivo experiments investigating the effect of ES on the general mechanisms of healing demonstrated increased epithelialization, fibroblast migration, and vascularity around wounds. Six in vitro studies demonstrated bactericidal effects upon exposure to alternating and pulsed current. Twelve randomized controlled trials (RCTs) investigated the effect of pulsed current on chronic wound healing. All reviewed RCTs demonstrated a larger reduction in wound size and increased healing rate when compared to control groups. In conclusion, ES therapy can contribute to improved chronic wound healing and potentially reduce the financial burden associated with wound management. However, the variations in the wound characteristics, patient demographics, and ES parameters used across studies present opportunities for systematic RCT studies in the future.

Monophasic Pulsed Current Stimulation of Duty Cycle 10% Promotes Differentiation of Human Dermal Fibroblasts into Myofibroblasts

OBJECTIVE

Many clinical trials have shown the therapeutic effects of electrical stimulation (ES) in various conditions. Our previous studies showed that ES (200 μA and 2 Hz) promotes migration and proliferation of human dermal fibroblasts (HDFs). However, the effective duty cycle and the effect of ES on myofibroblast differentiation are unclear. This study aimed to investigate the relationship between duty cycle and myofibroblast differentiation.

METHODS

HDFs were subjected to ES (200 μA and 2 Hz) for 24 h with the duty cycle adapted at 0% (control), 10%, 50%, or 90%. α-smooth muscle actin (SMA) and transforming growth factor (TGF)-β1 mRNA and α-SMA protein expressions were assessed. Collagen gel contraction was observed for 48 h after ES initiation and the gel area was measured. Cell viability and pH of culture medium were analyzed for cytotoxicity of the ES.

RESULTS

Cell viabilities were decreased in the 50% and the 90% groups but ES did not influence on pH of culture media. ES with a duty cycle of 10% significantly promoted the mRNA expression of α-SMA and TGF-β1. α-SMA protein expression in the 10% group was also significantly higher than that of the control group. Collagen gel subjected to ES with a duty cycle of 10% was contracted.

CONCLUSION

Duty cycle can influence on myofibroblast differentiation and ES with a duty cycle 10% is the effective for wound healing.

Comparison of photobiomodulation in the treatment of skin injury with an open wound in mice

This study aimed to investigate the effects of photobiomodulation at a wavelength of 660 and 830 nm at different numbers of application points in the healing of open wounds in mice. In total, 120 mice were divided into 10 groups. The animals were submitted to cutaneous lesion of the open wound type (1.5 × 1.5 cm). Photobiomodulation at a wavelength of 660 and 830 nm and total energy of 3.6 J were used, applied at 1, 4, 5, and 9 points, for 14 days. The animals were subjected to analysis of the lesion area, skin temperature, and histological analysis. Macroscopic analysis results showed a difference (p < 0.05) between the irradiated groups and the sham group at 14 days PO. There was no statistical difference in skin temperature. Histological analysis findings showed better results for the epidermis thickness. Regarding the number of blood vessels, a difference was found between the 1- and 5-point 830-nm photobiomodulation groups and between the 4-point 660-nm group and the naive group. A significant difference in the number of fibroblasts was observed between the 830- and 660-nm photobiomodulation groups and the naive and sham groups. When comparing photobiomodulation wavelength, the 830-nm groups were more effective, and we emphasize the groups irradiated at 5 points, which showed an improvement in macroscopic analysis and epidermis thickness, an increase in the number of vessels, and a lower number of fibroblasts on the 14th day after skin injury.

Flexible electrical stimulation device with Chitosan-Vaseline® dressing accelerates wound healing in diabetes

The healing process of diabetic wounds is typically disordered and prolonged and requires both angiogenesis and epithelialization. Disruptions of the endogenous electric fields (EFs) may lead to disordered cell migration. Electrical stimulation (ES) that mimics endogenous EFs is a promising method in treating diabetic wounds; however, a microenvironment that facilitates cell migration and a convenient means that can be used to apply ES are also required. Chitosan-Vaseline® gauze (CVG) has been identified to facilitate wound healing; it also promotes moisture retention and immune regulation and has antibacterial activity. For this study, we created a wound dressing using CVG together with a flexible ES device and further evaluated its potential as a treatment for diabetic wounds. We found that high voltage monophasic pulsed current (HVMPC) promoted healing of diabetic wounds in vivo. In studies carried out in vitro, we found that HVMPC promoted the proliferation and migration of human umbilical vein endothelial cells (HUVECs) by activating PI3K/Akt and ERK1/2 signaling. Overall, we determined that the flexible ES-chitosan dressing may promoted healing of diabetic wounds by accelerating angiogenesis, enhancing epithelialization, and inhibiting scar formation. These findings provide support for the ongoing development of this multidisciplinary product for the care and treatment of diabetic wounds.

A Narrative Review of the Use of Neuromuscular Electrical Stimulation in Individuals With Diabetic Foot Ulceration

This review aims to summarize the evidence reported on the use of neuromuscular electrical stimulation (NMES) in individuals with diabetic foot ulceration (DFU). A systematic search of EMBASE and MEDLINE databases was performed in February 2019, using search terms relating to the domains DFU and NMES. All primary evidence assessing outcomes of NMES in DFU were included. Of 344 references obtained from database searching, 7 met the inclusion criteria and included a total of 140 participants, 77 of whom had DFU. All included studies used prospective designs. Two studies demonstrated improvements in chronic ulcer healing with NMES use; however, in each study, only 3 of the included participants had DFU and subgroup analyses based on ulcer etiology was omitted. The remaining 5 studies were produced by the same research group and positive effects of NMES (in combination with heat therapy) on DFU healing were consistently demonstrated. They reported significantly better healing rates with NMES in DFU than in nondiabetic wounds of a similar grade (healing rate: 70.0 ± 32.3% in DFU vs 38.4 ± 22.3% in nondiabetic ulcers [ P < .01]). These studies did not provide data assessing the isolated effects of NMES without concomitant heat exposure. Data on device tolerability and compliance were lacking. The existing data support a potential role for NMES in individuals with DFU; however, the identified studies inadequately controlled for confounding and were underpowered. Given the significant morbidity and mortality associated with DFU, higher quality evidence is needed to assess the adjunctive role for NMES in this group.

Wireless Direct Microampere Current in Wound Healing: Clinical and Immunohistological Data from Two Single Case Reports

Chronic pressure ulcers are hard-to-heal wounds that decrease the patient’s quality of life. Wireless Micro Current Stimulation (WMCS) is an innovative, non-invasive, similar to electrode-based electrostimulation (ES) technology, that generates and transfers ions that are negatively-charged to the injured tissue, using accessible air gases as a transfer medium. WMCS is capable of generating similar tissue potentials, as electrode-based ES, for injured tissue. Here, through immunohistochemistry, we intended to characterize the induced tissue healing biological mechanisms that occur during WMCS therapy. Two single cases of bedridden due to serious stroke white men with chronic non-healing pressure ulcers have been treated with WMCS technology. WMCS suppresses inflammatory responses by decreasing the aggregation of granulocytes, followed by stimulating myofibroblastic activity and a new formation of collagen fibers, as depicted by immunohistochemistry. As a result, WMCS provides a special adjunct or stand-alone therapy choice for chronic and non-healing injuries, similar to electrode-based ES, but with added (i.e., contactless) benefits towards its establishment as a routine clinical wound healing regime.

In-situ doping of a conductive hydrogel with low protein absorption and bacterial adhesion for electrical stimulation of chronic wounds

Electrical stimulation (ES) via electrodes is promising for treating chronic wounds, but this electrode-based strategy is unable to stimulate the whole wound area and the therapeutic outcome may be compromised. In this study, a conductive poly(2-hydroxyethyl methacrylate) (polyHEMA)/polypyrrole (PPY) hydrogel was developed, and 3-sulfopropyl methacrylate was covalently incorporated in the hydrogel's network to in-situ dope the PPY and maintain the hydrogel's conductivity in the weak alkaline physiological environment. The obtained hydrogel was superior to the commercial Hydrosorb® dressing for preventing bacterial adhesion and protein absorption, and this is helpful to reduce the possibilities of infection and secondary damage during dressing replacement. The in vitro scratch assay demonstrates that ES through the hydrogel enhanced fibroblast migration, and this enhancement effect remained even after the ES was ended. The in vivo assay using diabetic rats shows that when ES was conducted with this polyHEMA/PPY hydrogel, the healing rate was faster than that achieved by the electrode-based ES strategy. Therefore, this polyHEMA/PPY hydrogel shows a great potential for developing the next generation of ES treatment for chronic wounds. STATEMENT OF SIGNIFICANCE: Electrical stimulation (ES) via separated electrodes is promising for treating chronic wounds, but this electrode-based strategy is unable to stimulate the whole wound area, compromising the therapeutic outcome. Herein, a hydrogel was developed with stable electrical conductivity in the physiological environment and strong resistance to protein absorption and bacterial adhesion. The in vitro and in vivo tests proved that ES applied through the flexible and conductive hydrogel that covered the wound was superior to ES through electrodes for promoting the healing of the chronic wound. This hydrogel-based ES strategy combines the advantages of ES and hydrogel dressing and will pave the way for the next generation of ES treatment for chronic wounds.

Low-intensity current (LIC) stimulation of subcutaneous adipose derived stem cells (ADSCs) - A missing link in the course of LIC based wound healing

Millions of people die as a result of fatal injuries accounting for 9% of the total global annual deaths. Non fatal injuries generally result in variety of wounds. The normal wound healing process is slow and takes weeks to months, depending on the type of wound. In last two decades, electrotherapy called low-intensity currents (LIC) for the treatment became popular for faster wound healing, as well as in management of nonresponding and ulcerative wounds. It was reported that LIC mimics 'the current of injury' which is generated by body on wounding and helps in faster wound healing. Researchers have also studied the migration of localized cell and other bio-molecules under the influence of LIC helping the wound to heal faster. Literature review has also suggested that, electrical stimulation of isolated adipose tissue derived stem cells (ADSCs) releases growth factors and differentiates in to specialized cells like fibroblasts and keratinocytes in laboratory conditions. These research areas are well explored and emerged as independent state-of-the-arts therapies and technologies. Considering the fact, that adipose tissue (along with ADSCs) is present subcutaneously, a new hypothesis is proposed which states that 'low intensity current (LIC) stimulation of wound stimulates subcutaneous adipose tissue containing ADSCs which releases different growth factors and also differentiates into certain cells like fibroblasts, neurons and keratinocytes. These cells easily migrate to wound site due to lipolysis and loosening of fat tissue, resulting in faster wound healing'. Thus this hypothesis provides a missing link between two state of the art technologies; first one is 'LIC based electrotherapy' and second one is 'in-vitro LIC stimulation of ADCSs' where role and significance of in-situ ADCSs were never studied.

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.

Electrically stimulated cell migration and its contribution to wound healing

Naturally occurring electric fields are known to be morphogenetic cues and associated with growth and healing throughout mammalian and amphibian animals and the plant kingdom. Electricity in animals was discovered in the eighteenth century. Electric fields activate multiple cellular signaling pathways such as PI3K/PTEN, the membrane channel of KCNJ15/Kir4.2 and intracellular polyamines. These pathways are involved in the sensing of physiological electric fields, directional cell migration (galvanotaxis, also known as electrotaxis), and possibly other cellular responses. Importantly, electric fields provide a dominant and over-riding signal that directs cell migration. Electrical stimulation could be a promising therapeutic method in promoting wound healing and activating regeneration of chronic and non-healing wounds. This review provides an update of the physiological role of electric fields, its cellular and molecular mechanisms, its potential therapeutic value, and questions that still await answers.