Molecular bioelectricity: how endogenous voltage potentials control cell behavior and instruct pattern regulation in vivo

Promotion of quiescence and maintenance of function of mesenchymal stem cells on substrates with surface potential

The widespread use of human mesenchymal stem cells(hMSCs) is impeded by functional loss during prolonged expansion. Although multiple approaches have been attempted to preserve hMSCs stemness, a suitable culture system remains to be modified. The interaction between electrical signals and stem cells is expected to better maintain the function of stem cells. However, it remains unclear whether the surface potential of substrates has the potential to preserve stem cell function during in vitro expansion. In our study, hMSCs cultured on materials with different surface potentials could be induced into a reversible quiescent state, and we demonstrated that quiescent hMSCs could be reactivated and transitioned back into the proliferation cell cycle. hMSCs cultured under appropriate potential displayed superior differentiation and proliferation abilities within the same generation compared to conventional conditions. These findings underscore the importance of surface potential as a critical physical factor regulating hMSCs stemness. Manipulating the surface potential of hMSCs culture substrates holds promise for optimising preservation and culture conditions, thereby enhancing their application in tissue repair and regeneration engineering.

Transcriptomic analysis of digitoxin: Synergy with doxorubicin in HER2-overexpressing MDA-MB-453 breast cancer cells

The aim of this research is to further elucidate the mechanism of action of digitoxin and explore its potential synergistic effects with doxorubicin. MDA-MB-453 breast cancer cells, characterized by HER2 overexpression and low ER levels, were exposed to digitoxin at three doses (0.1 (0.13 μM), 0.2, and 1.0 μg/ml). RNA was extracted over 6 and 24-h periods to subject to transcriptomic analysis, using IPA software. To validate the findings, cell growth inhibitory, Western blot, and enzymatic assays were performed. In addition, molecular docking was carried out to assess the interaction of digitoxin and doxorubicin with the Na+/K+-ATPase. IPA analysis indicates that the effects of digitoxin are dose and time-dependent; at the highest dose, digitoxin activates the transcription of cholesterol biosynthetic genes at early times, and the stress response gene ATF3 at later times. Key genes at the central point of the pathways altered by digitoxin include: (activated) TP53, CREB1, and TGFB1 at the highest dose at 6 and 24 h and (repressed) MYCN at the middle dose at 24 h. ATF3 also plays a role in the action of doxorubicin, and digitoxin exhibits synergy with doxorubicin in MDA-MB-453 cells. Molecular docking studies demonstrated binding potential of both digitoxin and doxorubicin to Na+/K+-ATPase, with doxorubicin showing a stronger binding affinity. Our results highlight the role of bioelectric signaling through ion channel proteins, like Na+/K+-ATPase, in cancer development. Our findings suggest it is worthwhile to study the use of digitoxin, alone or combined with doxorubicin, for treating estrogen receptor-negative breast cancer, but caution of possible risks to patients who take both drugs in combination.

Electrical Stimulation of Oral Tissue-Derived Stem Cells: Unlocking New Potential for Dental and Periodontal Regeneration

The tooth and its supporting periodontium are essential structures of the oral cavity, frequently compromised by conditions such as dental defects, aries, and periodontal diseases, which, if poorly treated, often lead to tooth loss. These conditions, affecting billions of people worldwide, remain significant healthcare and socio-economic challenges. Regenerative dentistry has emerged as a possible therapeutic option, leveraging advances in tissue engineering (TE), stem cell biology, and biophysical stimulation. Oral tissue-derived mesenchymal stem/stromal cells (OMSCs) hold great potential for dental and periodontal regeneration. Electrical stimulation (ES), a biophysical cue known to regulate key cellular behaviors such as migration, proliferation, and differentiation, has gained increasing attention for enhancing the therapeutic capacities of OMSCs. This review explores the biological properties of OMSCs under ES, its role in regenerative dentistry, and recent breakthroughs in ES-based dental and periodontal TE strategies. Furthermore, the current challenges and future directions for translating these innovative approaches into clinical practice are discussed.

The Science of Tai Chi and Qigong as Whole Person Health-Part I: Rationale and State of the Science

Background: The emerging paradigm of whole person health shares many core principles with traditional complementary and integrative health frameworks, including Tai Chi and Qigong (TCQ). Methods: In the Fall of 2023, the Harvard Medical School Osher Center for Integrative Health hosted the inaugural international conference on The Science of Tai Chi & Qigong as Whole Person Health: Advancing the Integration of Mind-Body Practices into Contemporary Healthcare held at Harvard Medical School. A two-part white paper was written to summarize key conference topics, findings, and issues. Results and Discussion: Part I presented here summarizes the rationale for the conference and synthesizes the state of evidence for TCQ as rehabilitative and preventive tools for a range of clinical conditions, including falls and balance, cognition, mental health, sleep, cardiorespiratory health, musculoskeletal health, cancer, as well as translational evidence related to the neurophysiology, brain and immune function, and biomarkers of inflammation. The state of science of TCQ, viewed through the lens of traditional East Asian health constructs, is also discussed. Part II of this white paper outlines evidence gaps and opportunities and discusses strategies to address challenges in TCQ research, dissemination, and implementation.

Is there a relationship between embryonic bioelectric currents and differentiation waves?

Differentiation waves usually spread in embryonic epithelia until they reach boundaries whose stopping power has been unexplained. Bioelectricity in embryos has two ranges: cell-to-cell and long-range. It is postulated here that the long-range component somehow alters gap junctions and/or intermediate filaments, creating the boundaries for the trajectories of differentiation waves. A combined EIT (Electric Impedance Tomography)/visual microscope is proposed to investigate this proposed correlation.

Precise Electromagnetic Modulation of the Cell Cycle and Its Applications in Cancer Therapy

Precise modulation of the cell cycle via electromagnetic (EM) control presents a groundbreaking approach for cancer therapy, especially in the development of personalized treatment strategies. EM fields can precisely regulate key cellular homeostatic mechanisms such as proliferation, apoptosis, and repair by finely tuning parameters like frequency, intensity, and duration. This review summarizes the mechanisms through which EM fields influence cancer cell dynamics, highlighting recent developments in high-throughput electromagnetic modulation platforms that facilitate precise cell cycle regulation. Additionally, the integration of electromagnetic modulation with emerging technologies such as artificial intelligence, immunotherapy, and nanotechnology is explored, collectively enhancing targeting precision, immune activation, and therapeutic efficacy. A systematic analysis of existing clinical studies indicates that EM modulation technology significantly overcomes key challenges such as tumor heterogeneity, microenvironment complexity, and treatment-related adverse effects. This review summarizes the prospects of electromagnetic modulation in clinical translation and future research directions, emphasizing its critical potential as a core element in individualized and multimodal cancer treatment strategies.

Processes and measurements: a framework for understanding neural oscillations in field potentials

Various neuroscientific theories maintain that brain oscillations are important for neuronal computation, but opposing views claim that these macroscale dynamics are 'exhaust fumes' of more relevant processes. Here, we approach the question of whether oscillations are functional or epiphenomenal by distinguishing between measurements and processes, and by reviewing whether causal or inferentially useful links exist between field potentials, electric fields, and neurobiological events. We introduce a vocabulary for the role of brain signals and their underlying processes, demarcating oscillations as a distinct entity where both processes and measurements can exhibit periodicity. Leveraging this distinction, we suggest that electric fields, oscillating or not, are causally and computationally relevant, and that field potential signals can carry information even without causality.

Electroactive Electrospun Nanofibrous Scaffolds: Innovative Approaches for Improved Skin Wound Healing

The incidence and burden of skin wounds, especially chronic and complex wounds, have a profound impact on healthcare. Effective wound healing strategies require a multidisciplinary approach, and advances in materials science and bioengineering have paved the way for the development of novel wound healing dressing. In this context, electrospun nanofibers can mimic the architecture of the natural extracellular matrix and provide new opportunities for wound healing. Inspired by the bioelectric phenomena in the human body, electrospun nanofibrous scaffolds with electroactive characteristics are gaining widespread attention and gradually emerging. To this end, this review first summarizes the basic process of wound healing, the causes of chronic wounds, and the current status of clinical treatment, highlighting the urgency and importance of wound dressings. Then, the biological effects of electric fields, the preparation materials, and manufacturing techniques of electroactive electrospun nanofibrous (EEN) scaffolds are discussed. The latest progress of EEN scaffolds in enhancing skin wound healing is systematically reviewed, mainly including treatment and monitoring. Finally, the importance of EEN scaffold strategies to enhance wound healing is emphasized, and the challenges and prospects of EEN scaffolds are summarized.

Electric Field-Induced Effects in Eukaryotic Cells: Current Progress and Limitations

Electric fields (EFs) offer a powerful tool for manipulating cells and modulating their behavior, holding significant promise for regenerative medicine and cell biology. We provide a comprehensive overview of the effects of different types of EF on eukaryotic cells with the special focus on physical mechanisms and signaling pathways involved. Direct current EF induces electrophoresis and electroosmosis, influencing cell migration, proliferation, and differentiation. Alternating current EF, through dielectric polarization and dielectrophoresis, enables cell manipulation, trapping, and sorting. Pulsed EF, particularly high-intensity, short-duration pulses, induces reversible and irreversible electroporation, facilitating drug and gene delivery. The review covers some technological aspects of EF generation, emphasizing the importance of experimental setups, and integration with microfluidic platforms for high-throughput analysis and precise manipulations. Furthermore, the synergistic potential of combining EFs with optical tweezers is highlighted, enabling fine-tuned control of cell positioning, intercellular interactions, and measurement of biophysical properties. Finally, the review addresses limitations of EF application, such as field heterogeneity and potential side effects, and outlines the directions for future studies, including developing the minimally invasive delivery methods.

Transient Receptor Potential Channels in Prostate Cancer: Associations with ERG Fusions and Survival

Calcium movement and concentration in the cell plays significant roles in normal physiology and in diseases such as cancer. The significance of this ion in oncogenesis suggests that membrane-relevant proteins are involved in its regulation and are deregulated in various cancers. These channels and transporters could be targets for therapeutic interventions. An evaluation of the expression of transient receptor potential (TRP) channels in prostate cancer was performed using publicly available genomic and proteome data. Two TRP family members with high expression in prostate cancers, TRPML2 and TRPM4, were chosen for further analysis the uncover the associations of their level of expression with clinical and pathologic prostate cancer characteristics. Several TRP channels were expressed in prostate cancers at the protein level including TRPM4, TRPML1, TRPML2, TRPC1 and TRPP3. At the mRNA level, MCOLN2 and TRPM4 were strongly expressed in a sub-set of prostate cancers. Cases with high MCOLN2 mRNA expression were associated with frequent ERG fusions and a trend for better survival outcomes. In contrast, prostate cancer cases with high TRPM4 mRNA expression were associated with lower ERG fusion frequency than cases with low TRPM4 mRNA expression. The prognosis of prostate cancers with high TRPM4 expression was not different from the prognosis with counterparts having low TRPM4 mRNA expression. TRP channels were expressed in sub-sets of prostate cancers. The two well-expressed channels of the super family, TRPML2 and TRPM4, have divergent associations with the most prevalent prostate cancer molecular aberrations, ERG fusions. These results imply diverse regulations of the TRP channels that would have to be taken into consideration when devising therapeutic interventions targeting individual channels.

Statistical mechanics of cell aggregates: explaining the phase transition and paradoxical piezoelectric behavior of soft biological tissues

Piezoelectricity in biological soft tissues is a controversial issue with differing opinions. While there is compelling experimental evidence to suggest a piezoelectric-like response in tissues such as the aortic wall (among others), there are equally compelling experiments that argue against this notion. In addition, the lack of a polar structure in the underlying components of most soft biological tissues supports the latter. In this paper, we address the collective behavior of cells within a two-dimensional cell aggregate from the viewpoint of statistical mechanics. Our starting point is the simplest form of energy for cell behavior that only includes known observable facts e.g., the electrical Maxwell stress or electrostriction, resting potential across cell membranes, elasticity, and we explicitly exclude any possibility of electromechanical coupling reminiscent of piezoelectricity at the cellular level. We coarse-grain our cellular aggregate to obtain its emergent mechanical, physical, and electromechanical properties. Our findings indicate that the fluctuation of cellular strain (E) plays a similar role as the absolute temperature in a conventional atomistic-level statistical model. The coarse-grained effective free energy reveals several intriguing features of the collective behavior of cell aggregates, such as solid-fluid phase transitions and a distinct piezoelectric-like coupling, even though it is completely absent at the microscale. Closed-form formulas are obtained for key electromechanical properties, including stiffness, effective resting potential, critical E2-temperature (or fluctuation) for solid-fluid phase transitions, and apparent piezoelectric coupling in terms of fluctuation and electric potential regulated by active cellular processes.

Regulation of Yeast Cytokinesis by Calcium

The role of calcium, an essential secondary messenger, in cell division remains an outstanding question in cell biology despite several significant findings over the past few decades. Among them is the landmark discovery of intracellular calcium waves during cytokinesis, the last stage of cell division, in fish cells. Nevertheless, subsequent studies have been largely unable to determine the underlying molecular mechanism of these cytokinetic transients. At the center of this stalemate stands two challenging questions, how these calcium transients rise and what they do during cytokinesis. Yeast, despite its proven prowess as a model organism to study cell cycle, has not drawn much interest in addressing these questions. However, the recent discovery of cytokinetic calcium spikes in the fission yeast Schizosaccharomyces pombe has provided novel insights into how calcium regulates cytokinesis. In this review, I will primarily focus on our current understanding of the molecular mechanism of cytokinetic calcium transients in yeast cells. First, I will briefly recount the discovery of cytokinetic calcium transients in animal cells. This will be followed by an introduction to the intracellular calcium homeostasis. Next, I will discuss yeast cytokinetic calcium spikes, the ion channel Pkd2 that promotes these spikes, and the potential molecular targets of these spikes. I will also compare the calcium regulation of cytokinesis between yeast and animal cells. I will conclude by presenting a few critical questions in our continued quest to understand how calcium regulates cytokinesis.

How Physical Information Underlies Causation and the Emergence of Systems at all Biological Levels

To bring clarity, the term 'information' is resolved into three distinct meanings: physical pattern, statistical relations and knowledge about things. In parallel, three kinds of 'causation' are resolved: the action of physical force constrained by physical pattern (efficient cause), cybernetic (formal cause) and statistical inference. Cybernetic causation is an expression of fundamental (necessary) logical relations, statistical inference is phenomenological, but physical information and causation are proposed as what actually happens in the physical world. Examples of the latter are given to illustrate the underlying material dynamics in a range of biological systems from the appearance of 'synergistic information' among multiple variables (mainly in neuroscience); positional information in multicellular development; and the organisational structure of ecological communities, especially incorporating niche construction theory. A rigorous treatment of multi-level causation is provided as well as an explanation of the causal power of non-physical information structure, especially of interaction networks. The focus on physical information as particular pattern, echoing the insights of Howard Pattee, provides a more physically grounded view of emergence, downward causation and the concept of 'closure to efficient causation', all now prevalent in the organisational approach to biology.

Toward measurements of absolute membrane potential in Bacillus subtilis using fluorescence lifetime

Membrane potential (MP) changes can provide a simple readout of bacterial functional and metabolic state or stress levels. While several optical methods exist for measuring fast changes in MP in excitable cells, there is a dearth of such methods for absolute and precise measurements of steady-state MPs in bacterial cells. Conventional electrode-based methods for the measurement of MP are not suitable for calibrating optical methods in small bacterial cells. While optical measurement based on Nernstian indicators have been successfully used, they do not provide absolute or precise quantification of MP or its changes. We present a novel, calibrated MP recording approach to address this gap. In this study, we used a fluorescence lifetime-based approach to obtain a single-cell-resolved distribution of the membrane potential and its changes upon extracellular chemical perturbation in a population of bacterial cells for the first time. Our method is based on 1) a unique VoltageFluor (VF) optical transducer, whose fluorescence lifetime varies as a function of MP via photoinduced electron transfer and 2) a quantitative phasor-FLIM analysis for high-throughput readout. This method allows MP changes to be easily visualized, recorded and quantified. By artificially modulating potassium concentration gradients across the membrane using an ionophore, we have obtained a Bacillus subtilis-specific MP versus VF lifetime calibration and estimated the MP for unperturbed B. subtilis cells to be -65 mV (in minimal salts glycerol glutamate [MSgg]), -127 mV (in M9), and that for chemically depolarized cells as -14 mV (in MSgg). We observed a population-level MP heterogeneity of ∼6-10 mV indicating a considerable degree of diversity of physiological and metabolic states among individual cells. Our work paves the way for deeper insights into bacterial electrophysiology and bioelectricity research.

Self-powered biomedical devices: biology, materials, and their interfaces

Integrating biomedical electronic devices holds profound promise for advancements in healthcare and enhancing individuals' quality of life. However, the persistent challenges associated with the traditional batteries' limited lifespan and bulkiness hinder these devices' long-term functionality and consistent power supply. Here, we delve into the biology and material interfaces in self-powered medical devices by summarizing the intrinsic electric demands in humans, analyzing material and biological mechanisms for electricity generation and storage, and discussing the pathways toward self-chargeable powering. As a result, the current challenges in material designs and biological integrations emerged to shape the future directions in advancing self-powered medical devices. This paper calls on the community to integrate biology and material science to develop self-powering medical devices and improve their clinical prospects.

Influence of Super-Low-Intensity Microwave Radiation on Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) have emerged as a promising tool for regenerative medicine due to their multipotency and immunomodulatory properties. According to recent research, exposing MSCs to super-low-intensity microwave radiation can have a significant impact on how they behave and operate. This review provides an overview of the most recent studies on the effects of microwave radiation on MSCs with power densities that are much below thermal values. Studies repeatedly show that non-thermal mechanisms affecting calcium signaling, membrane transport, mitochondrial activity, along ion channel activation may increase MSC proliferation, differentiation along mesodermal lineages, paracrine factor secretion, and immunomodulatory capabilities during brief, regulated microwave exposures. These bioeffects greatly enhance MSC regeneration capability in preclinical models of myocardial infarction, osteoarthritis, brain damage, and other diseases. Additional study to understand microwave treatment settings, biological processes, and safety assessments will aid in the translation of this unique, non-invasive strategy of activating MSCs with microwave radiation to improve cell engraftment, survival, and tissue healing results. Microwave-enhanced MSC treatment, if shown safe and successful, might have broad relevance as a novel cell-based approach for a variety of regenerative medicine applications.

Probing the orientation and membrane permeation of rhodamine voltage reporters through molecular simulations and free energy calculations

The transmembrane potential of plasma membranes and membrane-bound organelles plays a fundamental role in cellular functions such as signal transduction, ATP synthesis, and homeostasis. Rhodamine voltage reporters (RhoVRs), which operate based on the photoinduced electron transfer (PeT) mechanism, are non-invasive, small-molecule voltage sensors that can detect rapid voltage changes, with some of them specifically targeting the inner mitochondrial membrane. In this work, we conducted extensive molecular dynamics simulations and free-energy calculations to investigate the physicochemical properties governing the orientation as well as membrane permeation barriers of three RhoVRs. Our results indicate that the positioning of the most polarized functional group relative to the hydrophobic molecular wire dictates the alignment of RhoVRs with the membrane normal, thereby, significantly affecting their voltage sensitivity. Free-energy calculations in different membrane systems identify significantly higher barriers against the permeation of RhoVR 1 compared to SPIRIT RhoVR 1, explaining their distinct subcellular localization profiles. Subsequent free-energy calculations of the distinguishing components from the two different RhoVRs provide additional insight into the physicochemical properties governing their membrane permeation. The connection between chemical composition and membrane orientation, as well as permeation behaviors of RhoVRs revealed by our calculations provides general guiding principles for the rational design of PeT-based fluorescent dyes with enhanced voltage sensitivity and desired subcellular distribution.

Bioelectricity is a universal multifaced signaling cue in living organisms

The cellular electrical signals of living organisms were discovered more than a century ago and have been extensively investigated in the neuromuscular system. Neuronal depolarization and hyperpolarization are essential for our neuromuscular physiological and pathological functions. Bioelectricity is being recognized as an ancient, intrinsic, fundamental property of all living cells, and it is not limited to the neuromuscular system. Instead, emerging evidence supports a view of bioelectricity as an instructional signaling cue for fundamental cellular physiology, embryonic development, regeneration, and human diseases, including cancers. Here, we highlight the current understanding of bioelectricity and share our views on the challenges and perspectives.

Piezoelectric hydrogels for accelerating healing of diverse wound types

The skin, as the body's largest organ, plays a crucial role in protecting against mechanical forces and infections, maintaining fluid balance, and regulating body temperature. Therefore, skin wounds can significantly threaten human health and cause a heavy economic burden on society. Recently, bioelectric fields and electrical stimulation (ES) have been recognized as a promising pathway for modulating tissue engineering and regeneration of wounded skin. However, conventional hydrogel dressing lacks electrical generation capabilities and usually requires external stimuli to initiate the cell regeneration process, and the role of ES in different stages of healing is not fully understood. Therefore, to endow hydrogel-based wound dressings with piezoelectric properties, which can accelerate wound healing and potentially suppress infection via introducing ES, piezoelectric hydrogels (PHs) have emerged recently, combining the advantages of both piezoelectric nanomaterials and hydrogels beneficial for wound healing. Given the scarcity of systematic literature on the application of PHs in wound healing, this paper systematically discusses the principles of the piezoelectric effects, the design and fabrication of PHs, their piezoelectric properties, the way PHs trigger ES and the mechanisms by which they promote wound healing. Additionally, it summarizes the recent applications of PHs in various types of wounds, including traumatic wounds, pressure injuries, diabetic wounds, and infected wounds. Finally, the paper proposes future directions and challenges for the development of PH wound dressings for wound healing.

Skin disease-associated GJB4 variants differentially influence connexin stability, cell viability and channel function

Here we characterize seven Cx30.3 gene variants (R22H, S26Y, P61R, C86S, E99K, T130M and M190L) clinically associated with the rare skin disorder erythrokeratodermia variabilis et progressiva (EKVP) in tissue-relevant and differentiation-competent rat epidermal keratinocytes (REKs). We found that all variants, when expressed alone or together with wildtype (WT) Cx30.3, had the capacity to traffic and form gap junctions with an efficiency like WT Cx30.3. Cx30.3 was found to have a slower relative turnover than Cx43. However, turnover was more rapid for the R22H and P61R variants relative to Cx30.3. Furthermore, REKs that expressed the P61R variant exhibited reduced viability and were more permeable to fluorescent dyes, indicative of leaky hemichannels and/or the loss of membrane integrity associated with cell death. In connexin-null AD-293 cells, dual patch clamp studies revealed that the variants had either reduced (C86S) or no (S26Y and T130M) gap junction channel function. The remaining variants formed functional gap junction channels with enhanced transjunctional voltage (Vj)-dependent gating. Moreover, WT Cx30.3 and functional variant gap junction channels had similar unitary conductance of ∼34-42 pS, though variant channels appeared to have lower open probability than WT Cx30.3 channels at high Vjs. In conclusion, EKVP-associated Cx30.3 variants each alter one or more Cx30.3 characteristics although the molecular changes identified for E99K were limited to enhanced Vj gating. The breadth of molecular changes identified may all be sufficient to cause EKVP, but this remains to be firmly established as more familial patients are genotyped for these variants. KEY POINTS: Here we characterize seven Cx30.3 variants (R22H, S26Y, P61R, C86S, E99K, T130M and M190L) that have been clinically associated with the rare skin disorder erythrokeratodermia variabilis et progressiva (EKVP). We discovered human Cx30.3 undergoes relatively slow turnover compared with Cx43 and exhibits kinetically slow and limited voltage gating. Wildtype Cx30.3 and all variants localized to intracellular compartments and gap junctions in rat epidermal keratinocytes. Each EKVP-associated Cx30.3 variant altered one or more Cx30.3 characteristics related to protein stability, cell viability and/or channel function. The breadth of molecular changes identified for each Cx30.3 variant may independently be sufficient to cause EKVP, but this remains to be firmly established through additional genetic and molecular analysis.

The role of ribosomal protein networks in ribosome dynamics

Accurate protein synthesis requires ribosomes to integrate signals from distant functional sites and execute complex dynamics. Despite advances in understanding ribosome structure and function, two key questions remain: how information is transmitted between these distant sites, and how ribosomal movements are synchronized? We recently highlighted the existence of ribosomal protein networks, likely evolved to participate in ribosome signaling. Here, we investigate the relationship between ribosomal protein networks and ribosome dynamics. Our findings show that major motion centers in the bacterial ribosome interact specifically with r-proteins, and that ribosomal RNA exhibits high mobility around each r-protein. This suggests that periodic electrostatic changes in the context of negatively charged residues (Glu and Asp) induce RNA-protein 'distance-approach' cycles, controlling key ribosomal movements during translocation. These charged residues play a critical role in modulating electrostatic repulsion between RNA and proteins, thus coordinating ribosomal dynamics. We propose that r-protein networks synchronize ribosomal dynamics through an 'electrostatic domino' effect, extending the concept of allostery to the regulation of movements within supramolecular assemblies.

Plant Compounds Inhibit the Growth of W12 Cervical Precancer Cells Containing Episomal or Integrant HPV DNA; Tanshinone IIA Synergizes with Curcumin in Cervical Cancer Cells

This study explores the effects of plant compounds on human papillomavirus (HPV)-induced W12 cervical precancer cells and bioelectric signaling. The aim is to identify effective phytochemicals, both individually and in combination, that can prevent and treat HPV infection and HPV associated cervical cancer. Phytochemicals were tested using growth inhibition, combination, gene expression, RT PCR, and molecular docking assays. W12 cells, derived from a cervical precancerous lesion, contain either episomal or integrated HPV16 DNA. Several compounds, including digoxin, tanshinone IIA, dihydromethysticin and carrageenan, as well as fractions of turmeric, ginger and pomegranate inhibited the growth of W12 precancer and cervical cancer cells. Curcumin and tanshinone IIA were the most active and relatively nontoxic compounds. RT-PCR analysis showed that tanshinone IIA activated the expression of p53, while repressing the expression of HPV16 E1, E2, E4, E6, and E7 viral transcripts in W12 (type 1 and 2) integrant cells. In addition, curcumin synergized with tanshinone IIA in HeLa cells. Molecular docking studies suggested tanshinone IIA and curcumin bind to the Na+/K+-ATPase ion channel, with curcumin binding with higher affinity. Our findings highlight the potential of these multifaceted phytochemicals to prevent and treat HPV-induced cervical cancer, offering a promising approach for combinatorial therapeutic intervention.

Towards measurements of absolute membrane potential in Bacillus subtilis using fluorescence lifetime

Membrane potential (MP) changes can provide a simple readout of bacterial functional and metabolic state or stress levels. While several optical methods exist for measuring fast changes in MP in excitable cells, there is a dearth of such methods for absolute and precise measurements of steady-state membrane potentials (MPs) in bacterial cells. Conventional electrode-based methods for the measurement of MP are not suitable for calibrating optical methods in small bacterial cells. While optical measurement based on Nernstian indicators have been successfully used, they do not provide absolute or precise quantification of MP or its changes. We present a novel, calibrated MP recording approach to address this gap. In this study, we used a fluorescence lifetime-based approach to obtain a single-cell resolved distribution of the membrane potential and its changes upon extracellular chemical perturbation in a population of bacterial cells for the first time. Our method is based on (i) a unique VoltageFluor (VF) optical transducer, whose fluorescence lifetime varies as a function of MP via photoinduced electron transfer (PeT) and (ii) a quantitative phasor-FLIM analysis for high-throughput readout. This method allows MP changes to be easily visualized, recorded and quantified. By artificially modulating potassium concentration gradients across the membrane using an ionophore, we have obtained a Bacillus subtilis-specific MP versus VF lifetime calibration and estimated the MP for unperturbed B. subtilis cells to be -65 mV (in MSgg), 127 mV (in M9) and that for chemically depolarized cells as -14 mV (in MSgg). We observed a population level MP heterogeneity of ~6-10 mV indicating a considerable degree of diversity of physiological and metabolic states among individual cells. Our work paves the way for deeper insights into bacterial electrophysiology and bioelectricity research.

Impact of dcEF on microRNA profiles in glioblastoma and exosomes using a novel microfluidic bioreactor

Glioblastoma multiforme, the most common type of highly aggressive primary brain tumor, is influenced by complex molecular signaling pathways, where microRNAs (miRNAs) play a critical regulatory role. Originating from glial cells, glioblastoma cells are affected by the physiological direct current electric field (dcEF) in the central nervous system. While dcEF has been shown to affect glioblastoma migration (electrotaxis), the specific impact on glioblastoma intercellular communication and miRNA expression in glioblastoma cells and their exosomes remains unclear. This study aims to fill this gap by investigating the differential expression of microRNAs in glioblastoma cells and exosomes under dcEF stimulation. We have developed a novel, reversibly sealed dcEF stimulation bioreactor that ensures uniform dcEF stimulation across a large cell culture area, specifically targeting glioblastoma cells and primary human astrocytes. Using microarray analysis, we examined differential miRNA profiles in both cellular and exosomal RNAs. Our study identified shared molecular targets and pathways affected by dcEF stimulation. Our findings reveal significant changes in miRNA expression due to dcEF stimulation, with specific miRNAs, such as hsa-miR-4440 being up-regulated and hsa-miR-3201 and hsa-mir-548g being down-regulated. Future research will focus on elucidating the molecular mechanisms of these miRNAs and their potential as diagnostic biomarkers. The developed platform offers high-quality dcEF stimulation and rapid sample recovery, with potential applications in tissue engineering and multi-omics molecular analysis.

Multifunctional scaffolds for bone repair following age-related biological decline: Promising prospects for smart biomaterial-driven technologies

The repair of large bone defects due to trauma, disease, and infection can be exceptionally challenging in the elderly. Despite best clinical practice, bone regeneration within contemporary, surgically implanted synthetic scaffolds is often problematic, inconsistent, and insufficient where additional osteobiological support is required to restore bone. Emergent smart multifunctional biomaterials may drive important and dynamic cellular crosstalk that directly targets, signals, stimulates, and promotes an innate bone repair response following age-related biological decline and when in the presence of disease or infection. However, their role remains largely undetermined. By highlighting their mechanism/s and mode/s of action, this review spotlights smart technologies that favorably align in their conceivable ability to directly target and enhance bone repair and thus are highly promising for future discovery for use in the elderly. The four degrees of interactive scaffold smartness are presented, with a focus on bioactive, bioresponsive, and the yet-to-be-developed autonomous scaffold activity. Further, cell- and biomolecular-assisted approaches were excluded, allowing for contemporary examination of the capabilities, demands, vision, and future requisites of next-generation biomaterial-induced technologies only. Data strongly supports that smart scaffolds hold significant promise in the promotion of bone repair in patients with a reduced osteobiological response. Importantly, many techniques have yet to be tested in preclinical models of aging. Thus, greater clarity on their proficiency to counteract the many unresolved challenges within the scope of aging bone is highly warranted and is arguably the next frontier in the field. This review demonstrates that the use of multifunctional smart synthetic scaffolds with an engineered strategy to circumvent the biological insufficiencies associated with aging bone is a viable route for achieving next-generation therapeutic success in the elderly population.

Measurement methods, influencing factors and applications of intercellular receptor-ligand binding kinetics in diseases

Receptor-ligand binding on contacting cells dictates the extent of transmembrane signaling through membrane receptors during cell communication, influencing both the physiological and pathological activities of cells. This process is integral to fundamental biological mechanisms including signal transduction, cancer metastasis, immune responses, and inflammatory cascades, all of which are profoundly influenced by the cell microenvironment. This article provides an overview of the kinetic theory of receptor-ligand binding and examines methods for measuring this interaction, along with their respective advantages and disadvantages. Furthermore, it comprehensively explores the factors that impact receptor-ligand binding, encompassing protein-membrane interactions, the bioelectric microenvironment, auxiliary factors, hydrogen bond strength, pH levels, cis and trans interactions between ligands and receptors. The application of receptor-ligand binding kinetics in various diseases such as immunity, cancer, and inflammation are also discussed. Additionally, the investigation into how functional substances alter receptor-ligand binding dynamics within specific cellular microenvironments presents a promising new approach to treating related diseases.

Molecular Spies in Action: Genetically Encoded Fluorescent Biosensors Light up Cellular Signals

Cellular function is controlled through intricate networks of signals, which lead to the myriad pathways governing cell fate. Fluorescent biosensors have enabled the study of these signaling pathways in living systems across temporal and spatial scales. Over the years there has been an explosion in the number of fluorescent biosensors, as they have become available for numerous targets, utilized across spectral space, and suited for various imaging techniques. To guide users through this extensive biosensor landscape, we discuss critical aspects of fluorescent proteins for consideration in biosensor development, smart tagging strategies, and the historical and recent biosensors of various types, grouped by target, and with a focus on the design and recent applications of these sensors in living systems.

Recent Development of Chemigenetic Hybrid Voltage Indicators Enabled by Bioconjugation Chemistry

Fluorescent voltage indicators enable the optical recording of electrophysiology across large cell populations with subcellular resolution; however, their application is often constrained by a limited photon budget. To address this limitation, advanced bioconjugation methods have been employed to site-specifically attach bright and photostable organic dyes to cell-specific protein scaffolds in live cells. The resulting chemigenetic hybrid voltage indicators enable sustained monitoring of voltage fluctuations with an exceptional signal-to-noise ratio, both in vitro and in vivo. This Viewpoint discusses recent advancements in the development of these indicators through bioconjugation chemistry.

Antisenescence Expansion of Mesenchymal Stem Cells Using Piezoelectric β-Poly(vinylidene fluoride) Film-Based Culture

Regenerative therapies based on mesenchymal stem cells (MSCs) show promise in treating a wide range of disorders. However, the replicative senescence of MSCs during in vitro expansion poses a challenge to obtaining a substantial quantity of high-quality MSCs. In this investigation, a piezoelectric β-poly(vinylidene fluoride) film-based culture plate (β-CP) was developed with an antisenescence effect on cultured human umbilical cord-derived MSCs. Compared to traditional tissue culture plates (TCPs) and α-poly(vinylidene fluoride) film-based culture plates, the senescence markers of p21, p53, interleukin-6 and insulin-like growth factor-binding protein-7, stemness markers of OCT4 and NANOG, and telomere length of MSCs cultured on β-CPs were significantly improved. Additionally, MSCs at passage 18 cultured on β-CPs showed significantly better multipotency and pro-angiogenic capacities in vitro, and higher wound healing abilities in a mouse model. Mechanistically, β-CPs rejuvenated senescent MSCs by improving mitochondrial functions and mitigating oxidative and glycoxidative stresses. Overall, this study presents β-CPs as a promising approach for efficient and straightforward antisenescence expansion of MSCs while preserving their stemness, thereby holding great potential for large-scale production of MSCs for clinical application in cell therapies.

Functional Recovery in a Child With Adrenoleukodystrophy Following Neuroregenerative Effects of Radio Electric Asymmetric Conveyer (REAC) Neuro-Regenerative (RGN-N) Treatment: A Detailed Case Report

This case report describes the treatment of a 9-year-old boy with advanced adrenoleukodystrophy (ALD) who received radioelectric asymmetric conveyer (REAC) neuro-regenerative (RGN-N) therapy after hematopoietic stem cell transplantation (HSCT) failed to produce therapeutic benefits. ALD is a devastating neurodegenerative disorder for which limited treatment options exist, and interventions are often ineffective in advanced cases. Post-transplant, the patient's symptoms worsened until REAC RGN-N therapy was introduced. After treatment, notable improvements were observed in motor function, swallowing, spasticity, and overall quality of life. These results suggest that REAC RGN-N treatment may be an effective intervention to slow neurodegenerative progression and support recovery in ALD cases unresponsive to HSCT.

Efficacy of REAC Neurobiological Optimization Treatments in Post-Polio Syndrome: A Manual Muscle Testing Evaluation

Background: This study evaluated the effectiveness of radio electric asymmetric conveyer (REAC) neurobiological optimization treatments on muscle strength (MS) in individuals with post-polio syndrome (PPS), a condition causing new muscle weakness in polio survivors. Traditional treatments focus on symptom management, whereas REAC technology uses radio electric symmetric conveyed fields to modulate neurotransmission and cellular function. Methods: This open-label study involved 17 PPS patients who maintained their existing medications. The participants underwent four REAC treatment protocols: neuro-postural optimization (NPO), neuro-psycho-physical optimization (NPPO), neuro-psycho-physical optimization-cervical brachial (NPPO-CB), and neuromuscular optimization (NMO). MS was assessed using manual muscular tests (MMT) before and after each protocol. Results: A statistical analysis via repeated measures ANOVA showed significant MS improvements, particularly in the proximal muscles of the left lower limb (LLL), distal muscles of both lower limbs (LLs), and distal muscles of the left upper limb. The LLL, the most severely affected limb at this study's start, exhibited the greatest improvement. Conclusions: These results suggest REAC treatments could enhance MS in PPS patients, potentially reorganizing motor patterns and reducing functional overload on less affected limbs.

Mutant analysis of Kcng4b reveals how the different functional states of the voltage-gated potassium channel regulate ear development

The voltage gated (Kv) slow-inactivating delayed rectifier channel regulates the development of hollow organs of the zebrafish. The functional channel consists of the tetramer of electrically active Kcnb1 (Kv2.1) subunits and Kcng4b (Kv6.4) modulatory or electrically silent subunits. The two mutations in zebrafish kcng4b gene - kcng4b-C1 and kcng4b-C2 (Gasanov et al., 2021) - have been studied during ear development using electrophysiology, developmental biology and in silico structural modelling. kcng4b-C1 mutation causes a C-terminal truncation characterized by mild Kcng4b loss-of-function (LOF) manifested by failure of kinocilia to extend and formation of ectopic otoliths. In contrast, the kcng4b-C2-/- mutation causes the C-terminal domain to elongate and the ectopic seventh transmembrane (TM) domain to form, converting the intracellular C-terminus to an extracellular one. Kcng4b-C2 acts as a Kcng4b gain-of-function (GOF) allele. Otoliths fail to develop and kinocilia are reduced in kcng4b-C2-/-. These results show that different mutations of the silent subunit Kcng4 can affect the activity of the Kv channel and cause a wide range of developmental defects.

Advancements in stimulation therapies for peripheral nerve regeneration

Soft-tissue injuries affecting muscles, nerves, vasculature, tendons, and ligaments often diminish the quality of life due to pain, loss of function, and financial burdens. Both natural healing and surgical interventions can result in scarring, which potentially may impede functional recovery and lead to persistent pain. Scar tissue, characterized by a highly disorganized fibrotic extracellular matrix, may serve as a physical barrier to regeneration and drug delivery. While approaches such as drugs, biomaterials, cells, external stimulation, and other physical forces show promise in mitigating scarring and promoting regenerative healing, their implementation remains limited and challenging. Ultrasound, laser, electrical, and magnetic forms of external stimulation have been utilized to promote soft tissue as well as neural tissue regeneration. After stimulation, neural tissues experience increased proliferation of Schwann cells, secretion of neurotropic factors, production of myelin, and growth of vasculature, all aimed at supporting axon regeneration and innervation. Yet, the outcomes of healing vary depending on the pathophysiology of the damaged nerve, the timing of stimulation following injury, and the specific parameters of stimulation employed. Increased treatment intensity and duration have been noted to hinder the healing process by inducing tissue damage. These stimulation modalities, either alone or in combination with nerve guidance conduits and scaffolds, have been demonstrated to promote healing. However, the literature currently lacks a detailed understanding of the stimulation parameters used for nerve healing applications. In this article, we aim to address this gap by summarizing existing reports and providing an overview of stimulation parameters alongside their associated healing outcomes.

Gap-junction-mediated bioelectric signaling required for slow muscle development and function in zebrafish

Bioelectric signaling, intercellular communication facilitated by membrane potential and electrochemical coupling, is emerging as a key regulator of animal development. Gap junction (GJ) channels can mediate bioelectric signaling by creating a fast, direct pathway between cells for the movement of ions and other small molecules. In vertebrates, GJ channels are formed by a highly conserved transmembrane protein family called the connexins. The connexin gene family is large and complex, creating challenges in identifying specific connexins that create channels within developing and mature tissues. Using the embryonic zebrafish neuromuscular system as a model, we identify a connexin conserved across vertebrate lineages, gjd4, which encodes the Cx46.8 protein, that mediates bioelectric signaling required for slow muscle development and function. Through mutant analysis and in vivo imaging, we show that gjd4/Cx46.8 creates GJ channels specifically in developing slow muscle cells. Using genetics, pharmacology, and calcium imaging, we find that spinal-cord-generated neural activity is transmitted to developing slow muscle cells, and synchronized activity spreads via gjd4/Cx46.8 GJ channels. Finally, we show that bioelectrical signal propagation within the developing neuromuscular system is required for appropriate myofiber organization and that disruption leads to defects in behavior. Our work reveals a molecular basis for GJ communication among developing muscle cells and reveals how perturbations to bioelectric signaling in the neuromuscular system may contribute to developmental myopathies. Moreover, this work underscores a critical motif of signal propagation between organ systems and highlights the pivotal role of GJ communication in coordinating bioelectric signaling during development.

Piezoelectric Hydrogels: Hybrid Material Design, Properties, and Biomedical Applications

Hydrogels show great potential in biomedical applications due to their inherent biocompatibility, high water content, and resemblance to the extracellular matrix. However, they lack self-powering capabilities and often necessitate external stimulation to initiate cell regenerative processes. In contrast, piezoelectric materials offer self-powering potential but tend to compromise flexibility. To address this, creating a novel hybrid biomaterial of piezoelectric hydrogels (PHs), which combines the advantageous properties of both materials, offers a systematic solution to the challenges faced by these materials when employed separately. Such innovative material system is expected to broaden the horizons of biomedical applications, such as piezocatalytic medicinal and health monitoring applications, showcasing its adaptability by endowing hydrogels with piezoelectric properties. Unique functionalities, like enabling self-powered capabilities and inducing electrical stimulation that mimics endogenous bioelectricity, can be achieved while retaining hydrogel matrix advantages. Given the limited reported literature on PHs, here recent strategies concerning material design and fabrication, essential properties, and distinctive applications are systematically discussed. The review is concluded by providing perspectives on the remaining challenges and the future outlook for PHs in the biomedical field. As PHs emerge as a rising star, a comprehensive exploration of their potential offers insights into the new hybrid biomaterials.

Promoting Human Intestinal Organoid Formation and Stimulation Using Piezoelectric Nanofiber Matrices

Human organoid model systems have changed the landscape of developmental biology and basic science. They serve as a great tool for human specific interrogation. In order to advance our organoid technology, we aimed to test the compatibility of a piezoelectric material with organoid generation, because it will create a new platform with the potential for sensing and actuating organoids in physiologically relevant ways. We differentiated human pluripotent stem cells into spheroids following the traditional human intestinal organoid (HIO) protocol atop a piezoelectric nanofiber scaffold. We observed that exposure to the biocompatible piezoelectric nanofibers promoted spheroid morphology three days sooner than with the conventional methodology. At day 28 of culture, HIOs grown on the scaffold appeared similar. Both groups were readily transplantable and developed well-organized laminated structures. Graft sizes between groups were similar. Upon characterizing the tissue further, we found no detrimental effects of the piezoelectric nanofibers on intestinal patterning or maturation. Furthermore, to test the practical feasibility of the material, HIOs were also matured on the nanofiber scaffolds and treated with ultrasound, which lead to increased cellular proliferation which is critical for organoid development and tissue maintenance. This study establishes a proof of concept for integrating piezoelectric materials as a customizable platform for on-demand electrical stimulation of cells using remote ultrasonic waveforms in regenerative medicine.

Physical cues of scaffolds promote peripheral nerve regeneration

The effective treatment of long-gap peripheral nerve injury (PNI) remains a challenge in clinical settings. The autograft, the gold standard for the long-gap PNI therapy, has several limitations, including a limited supply of donor nerve, size mismatch between the donor and recipient sites, functional loss at the donor site, neuroma formation, and the requirement for two operations. With the increasing abundance of biocompatible materials with adjustable structures and properties, tissue engineering provides a promising avenue for bridging peripheral nerve gaps and addressing the above issues of autograft. The physical cues provided by tissue engineering scaffolds, essential for regulating the neural cell fate and microenvironments, have received considerable research attention. This review elaborates on three major physical cues of tissue engineering scaffolds for peripheral nerve regeneration: topological structure, mechanical support, and electrical stimulation. These three aspects are analogs to Lego bricks, wherein different combinations result in diverse functions. Innovative and more effective bricks, along with multi-level and all-around integration, are expected to provide new advances in tissue engineering for peripheral nerve generation.

Aging as a loss of morphostatic information: A developmental bioelectricity perspective

Maintaining order at the tissue level is crucial throughout the lifespan, as failure can lead to cancer and an accumulation of molecular and cellular disorders. Perhaps, the most consistent and pervasive result of these failures is aging, which is characterized by the progressive loss of function and decline in the ability to maintain anatomical homeostasis and reproduce. This leads to organ malfunction, diseases, and ultimately death. The traditional understanding of aging is that it is caused by the accumulation of molecular and cellular damage. In this article, we propose a complementary view of aging from the perspective of endogenous bioelectricity which has not yet been integrated into aging research. We propose a view of aging as a morphostasis defect, a loss of biophysical prepattern information, encoding anatomical setpoints used for dynamic tissue and organ homeostasis. We hypothesize that this is specifically driven by abrogation of the endogenous bioelectric signaling that normally harnesses individual cell behaviors toward the creation and upkeep of complex multicellular structures in vivo. Herein, we first describe bioelectricity as the physiological software of life, and then identify and discuss the links between bioelectricity and life extension strategies and age-related diseases. We develop a bridge between aging and regeneration via bioelectric signaling that suggests a research program for healthful longevity via morphoceuticals. Finally, we discuss the broader implications of the homologies between development, aging, cancer and regeneration and how morphoceuticals can be developed for aging.

From Short Circuit to Completed Circuit: Conductive Hydrogel Facilitating Oral Wound Healing

The primary challenges posed by oral mucosal diseases are their high incidence and the difficulty in managing symptoms. Inspired by the ability of bioelectricity to activate cells, accelerate metabolism, and enhance immunity, a conductive polyacrylamide/sodium alginate crosslinked hydrogel composite containing reduced graphene oxide (PAA-SA@rGO) is developed. This composite possesses antibacterial, anti-inflammatory, and antioxidant properties, serving as a bridge to turn the "short circuit" of the injured site into a "completed circuit," thereby prompting fibroblasts in proximity to the wound site to secrete growth factors and expedite tissue regeneration. Simultaneously, the PAA-SA@rGO hydrogel effectively seals wounds to form a barrier, exhibits antibacterial and anti-inflammatory properties, and prevents foreign bacterial invasion. As the electric field of the wound is rebuilt and repaired by the PAA-SA@rGO hydrogel, a 5 × 5 mm2 wound in the full-thickness buccal mucosa of rats can be expeditiously mended within mere 7 days. The theoretical calculations indicate that the PAA-SA@rGO hydrogel can aggregate and express SOX2, PITX1, and PITX2 at the wound site, which has a promoting effect on rapid wound healing. Importantly, this PAA-SA@rGO hydrogel has a fast curative effect and only needs to be applied for the first three days, which significantly improves patient satisfaction during treatment.

Sex-specific expression of distinct serotonin receptors mediates stress vulnerability of adult hippocampal neural stem cells in mice

Women are more vulnerable to stress and have a higher likelihood of developing mood disorders. The serotonin (5HT) system has been highly implicated in stress response and mood regulation. However, sex-dependent mechanisms underlying serotonergic regulation of stress vulnerability remain poorly understood. Here, we report that adult hippocampal neural stem cells (NSCs) of the Ascl1 lineage (Ascl1-NSCs) in female mice express functional 5HT1A receptors (5HT1ARs), and selective deletion of 5HT1ARs in Ascl1-NSCs decreases the Ascl1-NSC pool only in females. Mechanistically, 5HT1AR deletion in Ascl1-NSCs of females leads to 5HT-induced depolarization mediated by upregulation of 5HT7Rs. Furthermore, repeated restraint stress (RRS) impairs Ascl1-NSC maintenance through a 5HT1AR-mediated mechanism. By contrast, Ascl1-NSCs in males express 5HT7R receptors (5HT7Rs) that are downregulated by RRS, thus maintaining the Ascl1-NSC pool. These findings suggest that sex-specific expression of distinct 5HTRs and their differential interactions with stress may underlie sex differences in stress vulnerability.

Optical Estimation of Membrane Potential Values Using Fluorescence Lifetime Imaging Microscopy and Hybrid Chemical-Genetic Voltage Indicators

Introduction

Membrane potential (Vm), the voltage across a cell membrane, is an important biophysical phenomenon, central to the physiology of cells, tissues, and organisms. Voltage-sensitive fluorescent indicators are a powerful method for interrogating membrane potential in living systems, but most indicators are best suited for detecting changes in membrane potential rather than measuring values of the membrane potential. One promising approach is to use fluorescence lifetime imaging microscopy (FLIM) in combination of chemically synthesized dyes to estimate a value of membrane potential. However, a drawback is that chemically synthesized dyes show poor specificity of staining.

Objectives

To address this problem, we applied a chemical-genetic voltage imaging approach to FLIM to enable optical estimation of membrane potential values from genetically defined cells.

Results

In this report, we detail the characterization and evaluation of two of these systems in mammalian cells. We further validate the use of a FLIM-based chemical genetic voltage indicator in mammalian neurons.

Conclusions

Finally, we discuss opportunities for future improvements to chemical-genetic FLIM-based voltage indicators.

Modified Carbon Nanotubes Favor Fibroblast Growth by Tuning the Cell Membrane Potential

As is known, carbon nanotubes favor cell growth in vitro, although the underlying mechanisms are not yet fully elucidated. In this study, we explore the hypothesis that electrostatic fields generated at the interface between nonexcitable cells and appropriate scaffold might favor cell growth by tuning their membrane potential. We focused on primary human fibroblasts grown on electrospun polymer fibers (poly(lactic acid)─PLA) with embedded multiwall carbon nanotubes (MWCNTs). The MWCNTs were functionalized with either the p-methoxyphenyl (PhOME) or the p-acetylphenyl (PhCOMe) moiety, both of which allowed uniform dispersion in a solvent, good mixing with PLA and the consequent smooth and homogeneous electrospinning process. The inclusion of the electrically conductive MWCNTs in the insulating PLA matrix resulted in differences in the surface potential of the fibers. Both PLA and PLA/MWCNT fiber samples were found to be biocompatible. The main features of fibroblasts cultured on different substrates were characterized by scanning electron microscopy, immunocytochemistry, Rt-qPCR, and electrophysiology revealing that fibroblasts grown on PLA/MWCNT reached a healthier state as compared to pure PLA. In particular, we observed physiological spreading, attachment, and Vmem of fibroblasts on PLA/MWCNT. Interestingly, the electrical functionalization of the scaffold resulted in a more suitable extracellular environment for the correct biofunctionality of these nonexcitable cells. Finally, numerical simulations were also performed in order to understand the mechanism behind the different cell behavior when grown either on PLA or PLA/MWCNT samples. The results show a clear effect on the cell membrane potential, depending on the underlying substrate.

Gap junction mediated bioelectric coordination is required for slow muscle development, organization, and function

Bioelectrical signaling, intercellular communication facilitated by membrane potential and electrochemical coupling, is emerging as a key regulator of animal development. Gap junction (GJ) channels can mediate bioelectric signaling by creating a fast, direct pathway between cells for the movement of ions and other small molecules. In vertebrates, GJ channels are formed by a highly conserved transmembrane protein family called the Connexins. The connexin gene family is large and complex, presenting a challenge in identifying the specific Connexins that create channels within developing and mature tissues. Using the embryonic zebrafish neuromuscular system as a model, we identify a connexin conserved across vertebrate lineages, gjd4, which encodes the Cx46.8 protein, that mediates bioelectric signaling required for appropriate slow muscle development and function. Through a combination of mutant analysis and in vivo imaging we show that gjd4/Cx46.8 creates GJ channels specifically in developing slow muscle cells. Using genetics, pharmacology, and calcium imaging we find that spinal cord generated neural activity is transmitted to developing slow muscle cells and synchronized activity spreads via gjd4/Cx46.8 GJ channels. Finally, we show that bioelectrical signal propagation within the developing neuromuscular system is required for appropriate myofiber organization, and that disruption leads to defects in behavior. Our work reveals the molecular basis for GJ communication among developing muscle cells and reveals how perturbations to bioelectric signaling in the neuromuscular system_may contribute to developmental myopathies. Moreover, this work underscores a critical motif of signal propagation between organ systems and highlights the pivotal role played by GJ communication in coordinating bioelectric signaling during development.

Information integration during bioelectric regulation of morphogenesis of the embryonic frog brain

Spatiotemporal patterns of cellular resting potential regulate several aspects of development. One key aspect of the bioelectric code is that transcriptional and morphogenetic states are determined not by local, single-cell, voltage levels but by specific distributions of voltage across cell sheets. We constructed and analyzed a minimal dynamical model of collective gene expression in cells based on inputs of multicellular voltage patterns. Causal integration analysis revealed a higher-order mechanism by which information about the voltage pattern was spatiotemporally integrated into gene activity, as well as a division of labor among and between the bioelectric and genetic components. We tested and confirmed predictions of this model in a system in which bioelectric control of morphogenesis regulates gene expression and organogenesis: the embryonic brain of the frog Xenopus laevis. This study demonstrates that machine learning and computational integration approaches can advance our understanding of the information-processing underlying morphogenetic decision-making, with a potential for other applications in developmental biology and regenerative medicine.

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.

Trifunctional Saxitoxin Conjugates for Covalent Labeling of Voltage-Gated Sodium Channels

Voltage-gated sodium ion channels (NaV s) are integral membrane protein complexes responsible for electrical signal conduction in excitable cells. Methods that enable selective labeling of NaV s hold potential value for understanding how channel regulation and post-translational modification are influenced during development and in response to diseases and disorders of the nervous system. We have developed chemical reagents patterned after (+)-saxitoxin (STX) - a potent and reversible inhibitor of multiple NaV isoforms - and affixed with a reactive electrophile and either a biotin cofactor, fluorophore, or 'click' functional group for labeling wild-type channels. Our studies reveal enigmatic structural effects of the probes on the potency and efficiency of covalent protein modification. Among the compounds analyzed, a STX-maleimide-coumarin derivative is most effective at irreversibly blocking Na+ conductance when applied to recombinant NaV s and endogenous channels expressed in hippocampal neurons. Mechanistic analysis supports the conclusion that high-affinity toxin binding is a prerequisite for covalent protein modification. Results from these studies are guiding the development of next-generation tool compounds for selective modification of NaV s expressed in the plasma membranes of cells.

Regenerative bioelectronics: A strategic roadmap for precision medicine

In the past few decades, stem cell-based regenerative engineering has demonstrated its significant potential to repair damaged tissues and to restore their functionalities. Despite such advancement in regenerative engineering, the clinical translation remains a major challenge. In the stance of personalized treatment, the recent progress in bioelectronic medicine likewise evolved as another important research domain of larger significance for human healthcare. Over the last several years, our research group has adopted biomaterials-based regenerative engineering strategies using innovative bioelectronic stimulation protocols based on either electric or magnetic stimuli to direct cellular differentiation on engineered biomaterials with a range of elastic stiffness or functional properties (electroactivity/magnetoactivity). In this article, the role of bioelectronics in stem cell-based regenerative engineering has been critically analyzed to stimulate futuristic research in the treatment of degenerative diseases as well as to address some fundamental questions in stem cell biology. Built on the concepts from two independent biomedical research domains (regenerative engineering and bioelectronic medicine), we propose a converging research theme, 'Regenerative Bioelectronics'. Further, a series of recommendations have been put forward to address the current challenges in bridging the gap in stem cell therapy and bioelectronic medicine. Enacting the strategic blueprint of bioelectronic-based regenerative engineering can potentially deliver the unmet clinical needs for treating incurable degenerative diseases.

A Novel Injectable Piezoelectric Hydrogel for Periodontal Disease Treatment

Periodontal disease is a multifactorial, bacterially induced inflammatory condition characterized by the progressive destruction of periodontal tissues. The successful nonsurgical treatment of periodontitis requires multifunctional technologies offering antibacterial therapies and promotion of bone regeneration simultaneously. For the first time, in this study, an injectable piezoelectric hydrogel (PiezoGEL) was developed after combining gelatin methacryloyl (GelMA) with biocompatible piezoelectric fillers of barium titanate (BTO) that produce electrical charges when stimulated by biomechanical vibrations (e.g., mastication, movements). We harnessed the benefits of hydrogels (injectable, light curable, conforms to pocket spaces, biocompatible) with the bioactive effects of piezoelectric charges. A thorough biomaterial characterization confirmed piezoelectric fillers' successful integration with the hydrogel, photopolymerizability, injectability for clinical use, and electrical charge generation to enable bioactive effects (antibacterial and bone tissue regeneration). PiezoGEL showed significant reductions in pathogenic biofilm biomass (∼41%), metabolic activity (∼75%), and the number of viable cells (∼2-3 log) compared to hydrogels without BTO fillers in vitro. Molecular analysis related the antibacterial effects to be associated with reduced cell adhesion (downregulation of porP and fimA) and increased oxidative stress (upregulation of oxyR) genes. Moreover, PiezoGEL significantly enhanced bone marrow stem cell (BMSC) viability and osteogenic differentiation by upregulating RUNX2, COL1A1, and ALP. In vivo, PiezoGEL effectively reduced periodontal inflammation and increased bone tissue regeneration compared to control groups in a mice model. Findings from this study suggest PiezoGEL to be a promising and novel therapeutic candidate for the treatment of periodontal disease nonsurgically.

Bioelectrical State of Bacteria Is Linked to Growth Dynamics and Response to Neurotransmitters: Perspectives for the Investigation of the Microbiota-Brain Axis

Inter-cellular communication is mediated by a sum of biochemical, biophysical, and bioelectrical signals. This might occur not only between cells belonging to the same tissue and/or animal species but also between cells that are, from an evolutionary point of view, far away. The possibility that bioelectrical communication takes place between bacteria and nerve cells has opened exciting perspectives in the study of the gut microbiota-brain axis. The aim of this paper is (i) to establish a reliable method for the assessment of the bioelectrical state of two bacterial strains: Bacillus subtilis (B. subtilis) and Limosilactobacillus reuteri (L. reuteri); (ii) to monitor the bacterial bioelectrical profile throughout its growth dynamics; and (iii) to evaluate the effects of two neurotransmitters (glutamate and γ-aminobutyric acid-GABA) on the bioelectrical signature of bacteria. Our results show that membrane potential (Vmem) and the proliferative capacity of the population are functionally linked in B. subtilis in each phase of the cell cycle. Remarkably, we demonstrate that bacteria respond to neural signals by changing Vmem properties. Finally, we show that Vmem changes in response to neural stimuli are present also in a microbiota-related strain L. reuteri. Our proof-of-principle data reveal a new methodological approach for the better understanding of the relation between bacteria and the brain, with a special focus on gut microbiota. Likewise, this approach will open exciting perspectives in the study of the inter-cellular mechanisms which regulate the bi-directional communication between bacteria and neurons and, ultimately, for designing gut microbiota-brain axis-targeted treatments for neuropsychiatric diseases.

Impact of REAC Regenerative Endogenous Bioelectrical Cell Reprogramming on MCF7 Breast Cancer Cells

Human breast adenocarcinoma is a form of cancer which has the tendency to metastasize to other tissues, including bones, lungs, brain, and liver. Several chemotherapeutic drugs are used to treat breast tumors. Their combination is used to simultaneously target different mechanisms involved in cell replication. Radio electric asymmetric conveyer (REAC) technology is an innovative technology, used both in vitro and in vivo, to induce cell reprogramming and counteract senescence processes. Within this context, we treated MCF-7 cells with a regenerative (RGN) REAC treatment for a period ranging between 3 and 7 days. We then analyzed cell viability by trypan blue assays and gene and protein expression by real time-qPCR and confocal microscope, respectively. We also detected the levels of the main proteins involved in tumor progression, DKK1 and SFRP1, by ELISA and cell senescence by β-galactosidase tests. Our results showed the ability of REAC RGN to counteract MCF-7 proliferation, probably inducing autophagy via the upregulation of Beclin-1 and LC3-I, and the modulation of specific tumorigenic biomarkers, such as DKK1 and SPFR1. Our results could suggest the application of the REAC RGN in future in vivo experiments, as an aid for the therapeutic strategies usually applied for breast cancer treatment.