Electrical Stimulation Directs Migration, Enhances and Orients Cell Division and Upregulates the Chemokine Receptors CXCR4 and CXCR2 in Endothelial Cells

Bioelectret Materials and Their Bioelectric Effects for Tissue Repair: A Review

Biophysical and clinical medical studies have confirmed that biological tissue lesions and trauma are related to the damage of an intrinsic electret (i.e., endogenous electric field), such as wound healing, embryonic development, the occurrence of various diseases, immune regulation, tissue regeneration, and cancer metastasis. As exogenous electrical signals, such as conductivity, piezoelectricity, ferroelectricity, and pyroelectricity, bioelectroactives can regulate the endogenous electric field, thus controlling the function of cells and promoting the repair and regeneration of tissues. Materials, once polarized, can harness their inherent polarized static electric fields to generate an electric field through direct stimulation or indirect interactions facilitated by physical signals, such as friction, ultrasound, or mechanical stimulation. The interaction with the biological microenvironment allows for the regulation and compensation of polarized electric signals in damaged tissue microenvironments, leading to tissue regeneration and repair. The technique shows great promise for applications in the field of tissue regeneration. In this paper, the generation and change of the endogenous electric field and the regulation of exogenous electroactive substances are expounded, and the latest research progress of the electret and its biological effects in the field of tissue repair include bone repair, nerve repair, drug penetration promotion, wound healing, etc. Finally, the opportunities and challenges of electret materials in tissue repair were summarized. Exploring the research and development of new polarized materials and the mechanism of regulating endogenous electric field changes may provide new insights and innovative methods for tissue repair and disease treatment in biological applications.

Advances in electroactive biomaterials: Through the lens of electrical stimulation promoting bone regeneration strategy

The regenerative capacity of bone is indispensable for growth, given that accidental injury is almost inevitable. Bone regenerative capacity is relevant for the aging population globally and for the repair of large bone defects after osteotomy (e.g., following removal of malignant bone tumours). Among the many therapeutic modalities proposed to bone regeneration, electrical stimulation has attracted significant attention owing to its economic convenience and exceptional curative effects, and various electroactive biomaterials have emerged. This review summarizes the current knowledge and progress regarding electrical stimulation strategies for improving bone repair. Such strategies range from traditional methods of delivering electrical stimulation via electroconductive materials using external power sources to self-powered biomaterials, such as piezoelectric materials and nanogenerators. Electrical stimulation and osteogenesis are related via bone piezoelectricity. This review examines cell behaviour and the potential mechanisms of electrostimulation via electroactive biomaterials in bone healing, aiming to provide new insights regarding the mechanisms of bone regeneration using electroactive biomaterials.

The translational potential of this article

This review examines the roles of electroactive biomaterials in rehabilitating the electrical microenvironment to facilitate bone regeneration, addressing current progress in electrical biomaterials and the mechanisms whereby electrical cues mediate bone regeneration. Interactions between osteogenesis-related cells and electroactive biomaterials are summarized, leading to proposals regarding the use of electrical stimulation-based therapies to accelerate bone healing.

Electrical stimulation induced pre-vascularization of engineered dental pulp tissue

Vascularization is a key step to achieve pulp tissue regeneration and in vitro pre-vascularized dental pulp tissue could be applied as a graft substitute for dental pulp tissue repair. In this study, human dental pulp stem cells (DPSCs) and human umbilical vein endothelial cells (hUVECs) were co-cultured in 3D Matrigel and 150 mV/mm electric fields (EFs) were used to promote the construction of pre-vascularized dental pulp tissue. After optimizing co-cultured ratio of two cell types, immunofluorescence staining, and live/dead detection were used to investigate the effect of EFs on cell survival, differentiation and vessel formation in 3D engineered dental pulp tissue. RNA sequencing was used to investigate the potential molecular mechanisms by which EF regulates vessel formation in 3D engineered dental pulp tissue. Here we identified that EF-induced pre-vascularized engineered dental pulp tissue not only had odontoblasts, but also had a rich vascular network, and smooth muscle-like cells appeared around the blood vessels. The GO enrichment analysis showed that these genes were significantly enriched in regulation of angiogenesis, cell migration and motility. The most significant term of the KEGG pathway analysis were NOTCH signaling pathway and Calcium signaling pathway etc. The PPI network revealed that NOTCH1 and IL-6 were central hub genes. Our study indicated that EFs significantly promoted the maturation and stable of blood vessel in 3D engineered pulp tissue and provided an experimental basis for the application of EF in dental pulp angiogenesis and regeneration.

A novel conductive microtubule hydrogel for electrical stimulation of chronic wounds based on biological electrical wires

Electrical stimulation (ES) is considered a promising therapy for chronic wounds via conductive dressing. However, the lack of a clinically suitable conductive dressing is a serious challenge. In this study, a suitable conductive biomaterial with favorable biocompatibility and conductivity was screened by means of an inherent structure derived from the body based on electrical conduction in vivo. Ions condensed around the surface of the microtubules (MTs) derived from the cell's cytoskeleton are allowed to flow in the presence of potential differences, effectively forming a network of biological electrical wires, which is essential to the bioelectrical communication of cells. We hypothesized that MT dressing could improve chronic wound healing via the conductivity of MTs applied by ES. We first developed an MT-MAA hydrogel by a double cross-linking method using UV and calcium chloride to improve chronic wound healing by ES. In vitro studies showed good conductivity, mechanical properties, biocompatibility, and biodegradability of the MT-MAA hydrogel, as well as an elevated secretion of growth factors with enhanced cell proliferation and migration ability in response to ES. The in vivo experimental results from a full-thickness diabetic wound model revealed rapid wound closure within 7d in C57BL/6J mice, and the wound bed dressed by the MT-MAA hydrogel was shown to have promoted re-epithelization, enhanced angiogenesis, accelerated nerve growth, limited inflammation phases, and improved antibacterial effect under the ES treatment. These preclinical findings suggest that the MT-MAA hydrogel may be an ideal conductive dressing for chronic wound healing. Furthermore, biomaterials based on MTs may be also promising for treating other diseases.

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 promoting the angiogenesis in diabetic rat perforator flap through attenuating oxidative stress-mediated inflammation and apoptosis

Background

Skin flap transplantation is one of the effective methods to treat the diabetes-related foot ulceration, but the intrinsic damage to vessels in diabetes mellitus (DM) leads to the necrosis of skin flaps. Therefore, the discovery of a non-invasive and effective approach for promoting the survival of flaps is of the utmost importance. Electrical stimulation (ES) promotes angiogenesis and increases the proliferation, migration, and elongation of endothelial cells, thus being a potential effective method to improve flap survival.

Objective

The purpose of this study was to elucidate the mechanism used by ES to effectively restore the impaired function of endothelial cells caused by diabetes.

Methods

A total of 79 adult male Sprague-Dawley rats were used in this study. Gene and protein expression was assessed by PCR and western blotting, respectively. Immunohistochemistry and hematoxylin-eosin staining were performed to evaluate the morphology and density of the microvessels in the flap.

Results

The optimal duration for preconditioning the flap with ES was 7 days. The flap survival area percentage and microvessels density in the DMES group were markedly increased compared to the DM group. VEGF, MMP2, and MMP9 protein expression was significantly upregulated. ROS intensity was significantly decreased and GSH concentration was increased. The expression of IL-1β, MCP‑1, cleaved caspase-3, and Bax were downregulated in the DMES group, while TGF-β expression was upregulated.

Conclusions

ES improves the angiogenesis in diabetic ischemic skin flaps by attenuating oxidative stress-mediated inflammation and apoptosis, eventually increasing their viability.

Bioelectricity in dental medicine: a narrative review

BACKGROUND

Bioelectric signals, whether exogenous or endogenous, play crucial roles in the life processes of organisms. Recently, the significance of bioelectricity in the field of dentistry is steadily gaining greater attention.

OBJECTIVE

This narrative review aims to comprehensively outline the theory, physiological effects, and practical applications of bioelectricity in dental medicine and to offer insights into its potential future direction. It attempts to provide dental clinicians and researchers with an electrophysiological perspective to enhance their clinical practice or fundamental research endeavors.

METHODS

An online computer search for relevant literature was performed in PubMed, Web of Science and Cochrane Library, with the keywords "bioelectricity, endogenous electric signal, electric stimulation, dental medicine."

RESULTS

Eventually, 288 documents were included for review. The variance in ion concentration between the interior and exterior of the cell membrane, referred to as transmembrane potential, forms the fundamental basis of bioelectricity. Transmembrane potential has been established as an essential regulator of intercellular communication, mechanotransduction, migration, proliferation, and immune responses. Thus, exogenous electric stimulation can significantly alter cellular action by affecting transmembrane potential. In the field of dental medicine, electric stimulation has proven useful for assessing pulp condition, locating root apices, improving the properties of dental biomaterials, expediting orthodontic tooth movement, facilitating implant osteointegration, addressing maxillofacial malignancies, and managing neuromuscular dysfunction. Furthermore, the reprogramming of bioelectric signals holds promise as a means to guide organism development and intervene in disease processes. Besides, the development of high-throughput electrophysiological tools will be imperative for identifying ion channel targets and precisely modulating bioelectricity in the future.

CONCLUSIONS

Bioelectricity has found application in various concepts of dental medicine but large-scale, standardized, randomized controlled clinical trials are still necessary in the future. In addition, the precise, repeatable and predictable measurement and modulation methods of bioelectric signal patterns are essential research direction.

Lymphangiogenic responses of lymphatic endothelial cells to steady direct-current electric fields

Lymphangiogenesis plays pivotal roles in diverse physiological and pathological conditions. Steady direct-current electric fields (DC EFs) induce vascular endothelial behaviors related to angiogenesis have been observed. This study investigated the effects of DC EFs on the lymphangiogenic response of lymphatic endothelial cells (LECs). We demonstrated that EFs stimulation induced directional migration, reorientation, and elongation of human LECs in culture. These lymphangiogenic responses required VEGF receptor 3 (VEGFR-3) activation and were mediated through the PI3K-Akt, Erk1/2, and p38 MAPK signaling pathways in relation to the reorganization of the actin cytoskeleton. Our results indicate that endogenous EFs may play a role in lymphangiogenesis in vivo, and VEGFR-3 signaling activation may be involved in the cellular function of LECs driven by EFs.

A review of the evidence to support electrical stimulation-induced vascularization in engineered tissue

Tissue engineering presents a promising solution for regenerative medicine and the success depends on the supply of oxygen/nutrients to the cells by rapid vascularization. More and more technologies are being developed to facilitate vascularization of engineered tissues. In this review, we indicated that a regulatory system which influences all angiogenesis associated cells to achieve their desired functional state is ideal for the construction of vascularized engineered tissues in vitro. We presented the evidence that electrical stimulation (ES) enhances the synergistic promotion of co-cultured angiogenesis associated cells and its potential regulatory mechanisms, highlighted the potential advantages of a combination of mesenchymal stem cells (MSCs), endothelial cells (ECs) and ES to achieve tissue vascularization, with particular emphasis on the different biological pathways of ES-regulated ECs. Finally, we proposed the future direction of using ES to reconstruct engineered tissue blood vessels, pointed out the potential advantages and disadvantages of ES application on tissue vascularization.

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

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

Autophagy promotes directed migration of HUVEC in response to electric fields through the ROS/SIRT1/FOXO1 pathway

Endogenous electric fields (EFs) have been confirmed to facilitate angiogenesis through guiding directional migration of endothelial cells (ECs), but the underlying mechanisms remain obscure. Recent studies suggest that the directed migration of ECs in angiogenesis is correlated with autophagy, and the latter of which could be augmented by EFs. We hypothesize that autophagy may participate in the EFs-guided migration of ECs during angiogenesis. Herein, we showed that EFs induced human umbilical vein endothelial cells (HUVEC) migration toward the cathode with enhanced autophagy. Genetic ablation of autophagy by silencing the autophagy-related gene (Atg) 5 abolished the EFs-directed migration of HUVEC, indicating that autophagy is definitely required for EFs-guided migration of cells. Mechanistically, we identified the intracellular reactive oxygen species (ROS) as a crucial mediator in EFs-triggered autophagy through augmenting the silencing information regulator 2 related enzyme1 (SIRT1)/forkhead box protein O1 (FOXO1) signaling. Either ROS scavenging or SIRT1 knockdown eliminated the EFs-triggered autophagy in HUVEC. Further study showed that SIRT1 promoted FOXO1 deacetylation, facilitating its nuclear accumulation and transcriptional activity, and thereby activating autophagy in EFs-treated HUVECs. In conclusion, our study demonstrated a pivotal role for autophagy in EFs-induced directed migration of HUVECs through the ROS/SIRT1/FOXO1 pathway, and provided a novel theoretical foundation for angiogenesis.

A Shock to the (Nervous) System: Bioelectricity Within Peripheral Nerve Tissue Engineering

The peripheral nervous system has the remarkable ability to regenerate in response to injury. However, this is only successful over shorter nerve gaps and often provides poor outcomes for patients. Currently, the gold standard of treatment is the surgical intervention of an autograft, whereby patient tissue is harvested and transplanted to bridge the nerve gap. Despite being the gold standard, more than half of patients have dissatisfactory functional recovery after an autograft. Peripheral nerve tissue engineering aims to create biomaterials that can therapeutically surpass the autograft. Current tissue-engineered constructs are designed to deliver a combination of therapeutic benefits to the regenerating nerve, such as supportive cells, alignment, extracellular matrix, soluble factors, immunosuppressants, and other therapies. An emerging therapeutic opportunity in nerve tissue engineering is the use of electrical stimulation (ES) to modify and enhance cell function. ES has been shown to positively affect four key cell types, such as neurons, endothelial cells, macrophages, and Schwann cells, involved in peripheral nerve repair. Changes elicited include faster neurite extension, cellular alignment, and changes in cell phenotype associated with improved regeneration and functional recovery. This review considers the relevant modes of administration and cellular responses that could underpin incorporation of ES into nerve tissue engineering strategies. Impact Statement Tissue engineering is becoming increasingly complex, with multiple therapeutic modalities often included within the final tissue-engineered construct. Electrical stimulation (ES) is emerging as a viable therapeutic intervention to be included within peripheral nerve tissue engineering strategies; however, to date, there have been no review articles that collate the information regarding the effects of ES on key cell within peripheral nerve injury. This review article aims to inform the field on the different therapeutic effects that may be achieved by using ES and how they may become incorporated into existing strategies.

Biofeedback electrostimulation for bionic and long-lasting neural modulation

Invasive electrical stimulation (iES) is prone to cause neural stimulus-inertia owing to its excessive accumulation of exogenous charges, thereby resulting in many side effects and even failure of nerve regeneration and functional recovery. Here, a wearable neural iES system is well designed and built for bionic and long-lasting neural modulation. It can automatically yield biomimetic pulsed electrical signals under the driven of respiratory motion. These electrical signals are full of unique physiological synchronization can give biofeedback to respiratory behaviors, self-adjusting with different physiological states of the living body, and thus realizing a dynamic and biological self-matched modulation of voltage-gated calcium channels on the cell membrane. Abundant cellular and animal experimental evidence confirm an effective elimination of neural stimulus-inertia by these bioelectrical signals. An unprecedented nerve regeneration and motor functional reconstruction are achieved in long-segmental peripheral nerve defects, which is equal to the gold standard of nerve repair -- autograft. The wearable neural iES system provides an advanced platform to overcome the common neural stimulus-inertia and gives a broad avenue for personalized iES therapy of nerve injury and neurodegenerative diseases.

Designing wereable neural invasive electrical stimulation system remains a challenge. Here, researchers provide an effective technology platform for the elimination of tricky neural stimulus-inertia using bionic electronic modulation, which is a significant step forward for long-lasting treatment of nervous system diseases.

Electrical stimulation promotes the wound-healing properties of diabetic human skin fibroblasts

This study evaluated the effect of low (20 and 40 mV/mm) intensities of electrical stimulation on the proliferation and migration of skin fibroblasts from diabetic donors. We also examined the effect of electrical stimulation on modulating the capacity of fibroblasts to contract collagen gel, express alpha-smooth muscle actin, and secrete proteolytic enzymes involved in regulating extracellular matrix synthesis and degradation. Our study shows that 20 and 40 mV/mm of stimulation increased the growth of fibroblasts extracted from diabetic patients but not from non-diabetic donors. Electrical stimulation increased the migration of diabetic fibroblasts, their capacity to contract collagen gel, and the expression of alpha-smooth muscle actin and promoted different proteolytic enzymes involved in accelerating wound healing. Overall results confirm the effectiveness of electrical stimulation in modulating the wound healing activities of fibroblasts extracted from diabetic skin donors. This study, therefore, suggests the possible use of electrical stimulation to promote diabetic foot ulcer healing by stimulating the wound healing properties of skin fibroblasts.

The effects of electrical stimulation on diabetic ulcers of foot and lower limb: A systematic review

Diabetic foot ulcer (DFU) is a life-threatening condition affecting a third of diabetic patients. Many adjuvant therapies aimed at improving the healing rate (HR) and accelerating healing time are currently under investigation. Electrical stimulation (ES) is a physical-based therapy able to increase cells activity and migration into wound bed as well as inhibiting bacterial activity. The aim of this paper was to collect and analyse findings on the effects of ES used in combination with standard wound care (SWC) in the treatment of diabetic foot ulceration compared with SWC alone. A systematic review was performed to synthesise data from quantitative studies from eight databases. Article quality was assessed using the Crowe critical appraisal tool. Seven articles out of 560 publications met the inclusion criteria. A meta-analysis was not performed due to the heterogeneity of the studies and the results were narratively synthetised. Findings showed that HR appears to be higher among diabetic ulcers treated with ES; however, the reliability of these findings is affected by the small sample sizes of the studies. Furthermore, four studies are considered as moderate or high risk of bias. The evidence to suggest the systematic usage of ES in the treatment of DFUs is still insufficient.

Physiologically Self-Regulated, Fully Implantable, Battery-Free System for Peripheral Nerve Restoration

The long-segment peripheral nerve injury (PNI) represents a global medical challenge, leading to incomplete nerve tissue recovery and unsatisfactory functional reconstruction. However, the current electrical stimulation (ES) apparatuses fail perfect nerve repair due to their inability of the variable synchronous self-regulated function with physiological states. It is urgent to develop an implantable ES platform with physiologically adaptive function to provide instantaneous and nerve-preferred ES. Here, a physiologically self-regulated electrical signal is generated by integrating a novel tribo/piezoelectric hybrid nanogenerator with a nanoporous nerve guide conduit to construct a fully implantable neural electrical stimulation (FI-NES) system. The optimal neural ES parameters completely originate from the body itself and are highly self-responsive to different physiological states. The morphological evaluation, representative protein expression level, and functional reconstruction of the regenerated nerves are conducted to assess the PNI recovery process. Evidence shows that the recovery effect of 15 mm length nerve defects under the guidance of the FI-NES system is significantly close to the autograft. The designed FI-NES system provides an effective method for long-term accelerating the recovery of PNI in vivo and is also appropriate for other tissue injury or neurodegenerative diseases.

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.

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.

Electric field stimulation for tissue engineering applications

Electric fields are involved in numerous physiological processes, including directional embryonic development and wound healing following injury. To study these processes in vitro and/or to harness electric field stimulation as a biophysical environmental cue for organised tissue engineering strategies various electric field stimulation systems have been developed. These systems are overall similar in design and have been shown to influence morphology, orientation, migration and phenotype of several different cell types. This review discusses different electric field stimulation setups and their effect on cell response.

Orientation of the Mitotic Spindle in Blood Vessel Development

Angiogenesis requires coordinated endothelial cell specification, proliferation, and collective migration. The orientation of endothelial cell division is tightly regulated during the earliest stages of blood vessel formation in response to morphogenetic cues and the controlled orientation of the mitotic spindle. Consequently, oriented cell division is a vital mechanism in vessel morphogenesis, and defective spindle orientation can perturb the spatial arrangement of daughter cells and consequently contribute to several diseases related to vascular development. Many factors affect endothelial cell proliferation and orientation and therefore blood vessel formation, with the relationship between improper spindle orientation in endothelial cells and various diseases extensively studied. Here we review the molecular mechanisms driving the orientation of endothelial cell division, particularly with respect to the mitotic spindle, and how these processes affect vascular development, disease pathogenesis, and their potential as novel targets.

Percutaneous Bioelectric Current Stimulation for Chronic Cluster Headache - A Possible Transformative Approach to Cluster Headache

Background

Cluster headache (CH) is considered to be a catastrophic disease presenting the most severe human pain condition. Available pharmacological treatments are hampered by unwanted side effects, and there is an urgent need for non-pharmacological treatment alternatives. We present a novel therapeutic approach for chronic CH, having evolved from an episodic CH, using a non-invasive percutaneous bioelectric current stimulation (PBCS), which generates static electric fields in the range of the naturally occurring electric potentials.

Patients and Methods

This study employed a retrospective data analysis of 20 cases of chronic cluster headache (CCH) patients, four of those having had cluster-related surgery (SPG, ONS). All patients were treated with PBCS between 2014 and 2018. Data of these patients were analyzed with respect to frequency of CH attacks and triptan application and followed up for one (20 cases) or two (12 cases) years.

Results

Four weeks after the first PBCS treatment, cluster headache attacks were reduced from 2.8 to 1.7 per day and triptan application decreased from 2.5 to 1.5 times/day. Six non-responders, 4 of which had pre-CH surgery, did not show any reaction to PBCS, while 14 responders improved within 4 weeks from 2.2 to 0.7 attacks/day and 2.0 to 0.4 triptan applications/day. A 50% or greater reduction of attack frequency was observed in 10 patients after 4 weeks and in 11 patients after 12 weeks. One year after the first treatment, 13/20 patients experienced a reduction of attack frequency of 50% or more, while remarkably 10 patients were completely free of attack. After 2 years, 8 of 12 patients experienced a reduction of attack frequency of 50% or more and 7 of those were completely symptom-free. No serious adverse effects were observed.

Conclusion

PBCS is a promising transformative treatment approach for CCH patients. Drug consumption was reduced significantly, and the CCH may revert back to an episodic cluster headache with increasingly long times of remission. Responders can be clearly differentiated from non-responders. The data support the need for randomized controlled trials.

Direct Current Electric Field Stimulates Nitric Oxide Production and Promotes NO-Dependent Angiogenesis: Involvement of the PI3K/Akt Signaling Pathway

Electric fields (EFs) promote angiogenesis in vitro and in vivo. These results indicate the feasibility of the application of EFs to modulate angiogenesis. Nitric oxide (NO) derived from endothelial nitric oxide synthase (eNOS) is an important regulator of angiogenesis. However, the role of direct current EFs in eNOS activity and expression in association with angiogenesis of endothelial cells has not been investigated. In the present study, we stimulated human umbilical vein endothelial cells (HUVECs) with EFs and evaluated the activity and expression of eNOS. EFs induced significant phosphorylation of eNOS, upregulation of the expression of eNOS protein, and an increase in NO production from HUVECs. L-NAME, a specific inhibitor of eNOS, abolished EF-induced HUVEC angiogenesis. EFs stimulated Akt activation. Inhibition of PI3K activity inhibited EF-mediated Akt and eNOS activation and inhibited NO production in the endothelial cells. Moreover, EFs stimulated HUVEC proliferation and enhanced the S phase cell population of the cell cycle. We conclude that EFs stimulate eNOS activation and NO production via a PI3K/Akt-dependent pathway. Thus, activation of eNOS appears to be one of the key signaling pathways necessary for EF-mediated angiogenesis. These novel findings suggest that NO signaling may have an important role in EF-mediated endothelial cell function.

Electrical stimulation in bone tissue engineering treatments

Electrical stimulation (EStim) has been shown to promote bone healing and regeneration both in animal experiments and clinical treatments. Therefore, incorporating EStim into promising new bone tissue engineering (BTE) therapies is a logical next step. The goal of current BTE research is to develop combinations of cells, scaffolds, and chemical and physical stimuli that optimize treatment outcomes. Recent studies demonstrating EStim's positive osteogenic effects at the cellular and molecular level provide intriguing clues to the underlying mechanisms by which it promotes bone healing. In this review, we discuss results of recent in vitro and in vivo research focused on using EStim to promote bone healing and regeneration and consider possible strategies for its application to improve outcomes in BTE treatments. Technical aspects of exposing cells and tissues to EStim in in vitro and in vivo model systems are also discussed.

Three dimensional printed degradable and conductive polymer scaffolds promote chondrogenic differentiation of chondroprogenitor cells

We report a conductive and biodegradable 3D printed polymer scaffold that promotes chondrogenic differentiation of chondroprogenitor cells. The conductive material consists of tetraniline-b-polycaprolactone-b-tetraaniline and polycaprolactone.

Concentrically Integrative Bioassembly of a Three-Dimensional Black Phosphorus Nanoscaffold for Restoring Neurogenesis, Angiogenesis, and Immune Homeostasis

Black phosphorus is well known for its excellent electromechanical properties. Although it has previously been used for therapeutic drug delivery in cancer, it has never been applied as an electroactive polymer for post-trauma tissue regeneration (e.g., in cardiac muscles and neurons). The major concern currently preventing such applications is its controversial biosafety profile in vivo. Here, we demonstrate the production of a concentrically integrative layer-by-layer bioassembled black phosphorus nanoscaffold. This scaffold has remarkable electrical conductivity, permitting smooth release into the surrounding microenvironment. We confirmed that, under mild oxidative stress, our black phosphorus nanoscaffold induced angiogenesis and neurogenesis and stimulated calcium-dependent axon regrowth and remyelination. Long-term in vivo implantation of this nanoscaffold during severe neurological defect regeneration induced negligible toxicity levels. These results provide new insight into the regenerative capability of manufactured 3D scaffolds using neuroengineered 2D black phosphorus nanomaterials.