Touch, Tension, and Transduction - The Function and Regulation of Piezo Ion Channels

Piezo1 in microglial cells: Implications for neuroinflammation and tumorigenesis

Microglia, the central nervous system (CNS) resident immune cells, are pivotal in regulating neurodevelopment, maintaining neural homeostasis, and mediating neuroinflammatory responses. Recent research has highlighted the importance of mechanotransduction, the process by which cells convert mechanical stimuli into biochemical signals, in regulating microglial activity. Among the various mechanosensitive channels, Piezo1 has emerged as a key player in microglia, influencing their behavior under both physiological and pathological conditions. This review focuses on the expression and role of Piezo1 in microglial cells, particularly in the context of neuroinflammation and tumorigenesis. We explore how Piezo1 mediates microglial responses to mechanical changes within the CNS, such as alterations in tissue stiffness and fluid shear stress, which are common in conditions like multiple sclerosis, Alzheimer's disease, cerebral ischemia, and gliomas. The review also discusses the potential of targeting Piezo1 for therapeutic intervention, given its involvement in the modulation of microglial activity and its impact on disease progression. This review integrates findings from recent studies to provide a comprehensive overview of Piezo1's mechanistic pathways in microglial function. These insights illuminate new possibilities for developing targeted therapies addressing CNS disorders with neuroinflammation and pathological tissue mechanics.

Gas Bubbles from Biodegradable Magnesium Implants Convey Mechanical Cues and Promote Immune Cell Stimulation

In ever-increasing numbers, patients are treated with biodegradable magnesium implants. While gas bubbles frequently arise in soft tissue overlying magnesium implants, their biological implications remain uncertain. This study investigates how bubble accumulation and evolution across various biological lengths and time scales influence adjacent tissue and cell behavior in rats. Bubbles accumulate in tissues around magnesium during initial postimplantation days, then fully resorb. Alterations in tissue and cell geometry around bubbles coincide with accumulation of cells, many with macrophage phenotypes, and increased expression of the mechanosensitive ion-channel Piezo1. Using spatially resolved transcriptomics, strong proinflammatory pathway activation is revealed near bubbles with marked expression of the proliferative macrophage marker secreted phosphoprotein 1 (Spp1). Spatial transcriptomics also reveals strong enrichment of cytoskeletal rearrangement genes, demonstrating that cells respond to mechanical cues from bubbles. Notably, both time and bubble-implant distance strongly influence the cellular response. Over time, as bubbles are located farther from the implant, regenerative processes decline, and inflammation predominates. These findings suggest that bubbles from magnesium implant degradation create an intricate local response influencing tissue healing through inflammatory and mechanical pathways. This study underscores the need for magnesium implants with controlled gas release and meticulous monitoring of bubble evolution in patients.

Piezo1 regulates fibrocartilage stem cell in cartilage growth and osteoarthritis

OBJECTIVE

The temporomandibular joint (TMJ) is essential for maxillofacial mechanics, with the condyle serving as the primary site for mandibular growth and development. Mechanical forces regulate condylar development and homeostasis, while aberrant loading contributes to temporomandibular joint osteoarthritis (TMJOA). Although mechanical stimuli are known to influence TMJ function, the role of mechanosensitive ion channels, particularly Piezo1, remains underexplored.

METHODS

To investigate the role of Piezo1, we performed single-cell ribonucleic acid sequencing (scRNA-seq) on human TMJ samples to assess mechanosensitive ion channel expression. Conditional knockout (CKO) mice were generated using Gli1-CreERT2; Piezo1fl/fl mice to delete Piezo1 in Gli1+ cells. Unilateral partial discectomy was performed to model TMJOA, followed by histological and immunohistochemical analyses to evaluate the effects of Piezo1 deletion on condylar development and homeostasis.

RESULTS

scRNA-seq revealed high expression of PIEZO1 in both cartilage and bone of the human condyle. Piezo1-tdTomato reporter mice confirmed its consistent expression across different ages. CKO of Piezo1 in Gli1+ cells impaired condylar development and homeostasis by disrupting fibrocartilage stem cell (FCSC) differentiation. In the TMJOA model, Piezo1 deletion mitigated arthritic symptoms, preserved condylar morphology, and reduced cartilage damage.

CONCLUSION

Piezo1 is a key mechanosensitive ion channel in the cartilage, regulating condylar development and homeostasis. Its deletion in Gli1+ cells disrupts FCSC differentiation and endochondral ossification, leading to developmental deficiencies. However, in pathological conditions, Piezo1 deletion protects against TMJOA, highlighting its potential as a therapeutic target for osteoarthritis prevention and treatment.

Ion-Channel Proteins in the Prepubertal Bitch Reproductive System: The Immunolocalization of ASIC2, ASIC4, and PIEZO2

Ion channels play a crucial role in various physiological processes, yet their functions in the reproductive system remain underexplored. This study investigates the expression and the localization of ASIC2, ASIC4, and PIEZO2 ion channels in the reproductive tracts of prepubertal bitches. Western blotting on samples from eight prepubertal bitches confirmed the presence of these ion channels in ovarian, uterine, and uterine tubes tissues, and validated antibody specificity. Immunohistochemistry revealed that all primordial follicles expressed these ion channels, while only some developing follicles showed immunolabeling. These findings suggest ion channels' potential involvement in oocyte differentiation and maturation. The localization of these channels in uterine tubes, uterine lining, and glandular epithelium suggests a role in tissue maintenance, oocyte transport, and embryo implantation. Additionally, their expression in the tunica media of reproductive vasculature points to a potential role in vascular regulation. Future studies are needed to elucidate the specific mechanisms underlying the role of these channels in reproductive physiology.

Implications of mechanosensitive ion channels in the pathogenesis of osteoarthritis: a comprehensive review

Osteoarthritis (OA) is the predominant cause of joint pain and limited mobility in older people, and its prevalence is increasing as the population ages. Given the lack of effective therapeutic interventions, the disability rate associated with OA is a staggering 53%, which significantly affects the wellbeing of those affected and represents a significant social and family financial burden. Consequently, OA has emerged as a pressing social and public health concern globally. Various forms of mechanical strain, such as dynamic compression, fluid shear, tissue shear, and hydrostatic pressure, serve as crucial physical stimuli perceived by chondrocytes. Recent studies indicate that aberrant mechanical loading represents a fundamental risk factor for OA. Upon exposure to mechanical loading, chondrocytes translate mechanical cues into chemical signals primarily via mechanosensitive ion channels, resulting in alterations in cartilage metabolism. Numerous studies have demonstrated the significance of mechanosensitive ion channels in the pathogenesis of OA, suggesting that therapeutic interventions targeting these channels on chondrocytes may offer potential benefits.

Optical Tweezer-Driven Mechanotransduction: Probing pN-Scale Forces and Calcium-Mediated Redox Signaling in Single Endothelial Cells

Endothelial cells (ECs) regulate vascular function by converting mechanical forces into biochemical signals; however, the molecular mechanisms of pN-scale mechanotransduction remain elusive. Here, we develop an optical tweezer-integrated confocal microscopy system that allows precise, noninvasive manipulation of the cell membrane localization with mechanical stimuli within the 0-100 pN range while monitoring Ca2+-mediated NO/ROS redox signaling in situ in single ECs under varying force parameters. We show that pN-scale mechanical stimulation regulates extracellular Ca2+ influx, triggering downstream production of NO and ROS, which subsequently affects intracellular redox homeostasis. Key mechanosensitive ion channels (e.g., Piezo1 and TRPV4) and cytoskeletal components (e.g., F-actin) facilitate force-induced redox signaling. We further delineate the roles of membrane tension-dominant versus hybrid tension-tether models in mechanotransduction, revealing their differential engagement in force transmission pathways. This mechanistic framework establishes direct connections between pN-scale mechanical input characteristics and redox-regulated vascular homeostasis.

Bio-inspired artificial mechanoreceptors with built-in synaptic functions for intelligent tactile skin

Tactile perception involves the preprocessing of signals from slowly adapting and fast-adapting afferent neurons, which exhibit synapse-like interactions between mechanoreceptors and their dendrites or terminals, transmitting signals to the brain. Emulating these adaptation and sensory memory functions is crucial for artificial tactile sensing systems. Here, inspired by human tactile afferent systems, we present an array of artificial synaptic mechanoreceptors with built-in synaptic functions by vertically integrating synaptic transistors with a reduced graphene oxide channel, an ionogel gate dielectric and an elastomeric fingerprint-like receptive layer in an all-in-one platform. Triboelectric-capacitive gating between the receptive layer and gate dielectric in response to tactile stimulation governs excitatory post-synaptic current patterns, enabling slowly adapting and fast-adapting characteristics for signal preprocessing. The artificial synaptic mechanoreceptor array demonstrated handwriting style, surface pattern and texture discrimination via machine learning using fused slowly adapting and fast-adapting post-synaptic values, offering high data efficiency and potential for intelligent skin.

Piezo1 is a pathogenic gene and therapeutic target for neurological diseases

Piezo1 is a ubiquitously expressed non-selective cation channel protein found across various species. It possesses the ability to detect and respond to external mechanical forces, converting mechanical cues into intracellular bioelectrical events, thereby facilitating the propagation of electrochemical signals. Within the nervous system, Piezo1 is integral to synaptogenesis and myelination, modulation of pro-inflammatory mediators, neuropathic pain, cognitive processes, angiogenesis, and the regulation of cerebral hemodynamics, consequently impacting the pathogenesis and progression of neurological disorders. This review meticulously summarizes and synthesizes existing literature to provide an exhaustive overview of Piezo1's roles and mechanisms in a spectrum of neurological diseases, including neurodegenerative disorders, cerebrovascular accidents, traumatic brain injuries, gliomas, multiple sclerosis, and epilepsy. Additionally, it explores the potential therapeutic applications of targeting Piezo1. The discussion also encompasses the current research limitations, the imperative need for future investigations, and prospective strategies. Our analysis indicates that Piezo1 is a susceptibility gene for neurological conditions, and its expression inhibition may confer therapeutic benefits. In summary, this comprehensive review offers novel insights into the involvement of Piezo1 in neurological diseases and establishes a theoretical groundwork for the future development of Piezo1-targeted therapeutic interventions.

Potentiation of macrophage Piezo1 by atherogenic 7-ketocholesterol

The mechanosensitive ion channel Piezo1 present in endothelial and smooth muscle cells, as well as in macrophages, is emerging as a novel, important player in the etiology of atherosclerosis. Here, we show that myeloid-specific deficiency of Piezo1 in atherogenic Ldlr-/- mice reduces plaque formation. Moreover, chronic oxLDL, as well as its main oxysterol 7-ketocholesterol (7-KC), promotes Piezo1 opening by pressure stimulation in both mouse macrophages and transfected HEK cells. 7-KC dramatically enhances Piezo1 current amplitude and slows down inactivation and deactivation. This up-modulation involves an increase in Piezo1 expression, as well as a potentiation of mechanical gating that depends on membrane cholesterol depletion and decreased order. By contrast, Piezo1 is inhibited by the athero-protective free docosahexaenoic acid, either without or with 7-KC. Altogether, these findings indicate that macrophage Piezo1 is differentially modulated by pro- and anti-atherogenic lipids, pointing to the role of Piezo1 and its potentiation by oxysterols in atherosclerosis.

A new mechanism of diabetic kidney disease progression by Piezo proteins: mediators between mechanical stimuli and fibrosis

Glomerular hypertrophy promotes fibrosis by activating Piezo proteins.

Cellular Signaling at the Nano-Bio Interface: Spotlighting Membrane Curvature

No longer viewed as a passive consequence of cellular activities, membrane curvature-the physical shape of the cell membrane-is now recognized as an active constituent of biological processes. Nanoscale topographies on extracellular matrices or substrate surfaces impart well-defined membrane curvatures on the plasma membrane. This review examines biological events occurring at the nano-bio interface, the physical interface between the cell membrane and surface nanotopography, which activates intracellular signaling by recruiting curvature-sensing proteins. We encompass a wide range of biological processes at the nano-bio interface, including cell adhesion, endocytosis, glycocalyx redistribution, regulation of mechanosensitive ion channels, cell migration, and differentiation. Despite the diversity of processes, we call attention to the critical role of membrane curvature in each process. We particularly highlight studies that elucidate molecular mechanisms involving curvature-sensing proteins with the hope of providing comprehensive insights into this rapidly advancing area of research.

Chromosome-Level Genome Assembly of the Loach Goby Rhyacichthys aspro Offers Insights Into Gobioidei Evolution

The percomorph fish clade Gobioidei is a suborder that comprises over 2200 species distributed in nearly all aquatic habitats. To understand the genetics underlying their species diversification, we sequenced and annotated the genome of the loach goby, Rhyacichthys aspro, an early-diverging group, and compared it with nine additional Gobioidei species. Within Gobioidei, the loach goby possesses the smallest genome at 594 Mb, and a rise in species diversity from early-diverging to more recently diverged lineages is mirrored by enlarged genomes and a higher presence of transposable elements (TEs), particularly DNA transposons. These DNA transposons are enriched in genic and regulatory regions and their copy number increase is strongly correlated with substitution rate, suggesting that DNA repair after transposon excision/insertion leads to nearby mutations. Consequently, the proliferation of DNA transposons might be the crucial driver of Gobioidei diversification and adaptability. The loach goby genome also points to mechanisms of ecological adaptation. It contains relatively few genes for lateral line development but an overrepresentation of synaptic function genes, with genes putatively under selection linked to synapse organisation and calcium signalling, implicating a sensory system distinct from other Gobioidei species. We also see an overabundance of genes involved in neurocranium development and renal function, adaptations likely connected to its flat morphology suited for strong currents and an amphidromous life cycle. Comparative analyses with hill-stream loaches and the European eel reveal convergent adaptations in body shape and saltwater balance. These findings shed new light on the loach goby's survival mechanisms and the broader evolutionary trends within Gobioidei.

Interfacing with the Brain: How Nanotechnology Can Contribute

Interfacing artificial devices with the human brain is the central goal of neurotechnology. Yet, our imaginations are often limited by currently available paradigms and technologies. Suggestions for brain-machine interfaces have changed over time, along with the available technology. Mechanical levers and cable winches were used to move parts of the brain during the mechanical age. Sophisticated electronic wiring and remote control have arisen during the electronic age, ultimately leading to plug-and-play computer interfaces. Nonetheless, our brains are so complex that these visions, until recently, largely remained unreachable dreams. The general problem, thus far, is that most of our technology is mechanically and/or electrically engineered, whereas the brain is a living, dynamic entity. As a result, these worlds are difficult to interface with one another. Nanotechnology, which encompasses engineered solid-state objects and integrated circuits, excels at small length scales of single to a few hundred nanometers and, thus, matches the sizes of biomolecules, biomolecular assemblies, and parts of cells. Consequently, we envision nanomaterials and nanotools as opportunities to interface with the brain in alternative ways. Here, we review the existing literature on the use of nanotechnology in brain-machine interfaces and look forward in discussing perspectives and limitations based on the authors' expertise across a range of complementary disciplines─from neuroscience, engineering, physics, and chemistry to biology and medicine, computer science and mathematics, and social science and jurisprudence. We focus on nanotechnology but also include information from related fields when useful and complementary.

Exploring the differential localization of protein kinase A isoforms in Candida albicans

The cAMP-dependent protein kinase A (PKA) plays important roles in a wide range of biological processes in eukaryotic organisms. In the fungal pathogen Candida albicans, PKA is a critical regulator of morphological transitions, which are a key virulence trait. PKA is composed of two catalytic isoforms, Tpk1 and Tpk2, which are often thought to act together in a complex with the regulatory subunit Bcy1. Although Tpk1 and Tpk2 have some redundant functions, they also have distinct cellular functions for which the mechanistic underpinnings remain largely elusive. Here, we constructed functional GFP-tagged fusion proteins for Tpk1, Tpk2, and Bcy1 to explore the localization of PKA isoforms. We observed that the PKA holoenzyme is mainly found in the cytoplasm, as Bcy1 is always excluded from the nucleus. Under glucose-replete conditions, both Tpk1 and Tpk2 translocate into the nucleus from the cytosol. In the presence of glycerol, Tpk1 resides in the cytosol, whereas Tpk2 and Bcy1 become enriched on the vacuolar membrane. As the C-terminal domains of Tpk are highly homologous, we investigated the localization and function of hybrid Tpk proteins with exchanged N-terminal domains. We found the catalytic C-terminus of Tpk1 is required for morphogenesis in solid medium, whereas the C-terminus of Tpk2 is critical for filamentation in liquid. Interestingly, the N-terminus of Tpk2 drives its localization to the vacuolar membrane. Our work highlights environmentally contingent localization patterns for the PKA subunits and suggests that the nuclear localization of Tpk is not sufficient to induce the filamentation program in a leading fungal pathogen of humans.IMPORTANCEFungal pathogens have a devastating impact on human health worldwide. They infect billions of people and kill more than 2.5 million per year. Candida albicans is a leading human fungal pathogen responsible for causing life-threatening systemic disease in immunocompromised individuals. A key virulence trait in C. albicans is the ability to switch between yeast and filamentous forms. The conserved protein kinase A (PKA) regulates diverse functions in the cell, including growth and filamentation. Although PKA has been studied in C. albicans for decades, the subcellular localization of PKA has not been thoroughly investigated. Here, we constructed functional GFP-tagged PKA subunits to explore their localization. We identified differential localization patterns for the PKA subunits that are carbon-source dependent and report that these proteins localize into foci in response to diverse environmental stresses. These findings further our understanding of a critical regulator of growth and virulence in C. albicans.

The mechanopathology of the tumor microenvironment: detection techniques, molecular mechanisms and therapeutic opportunities

The mechanical properties of the tumor microenvironment (TME) undergo significant changes during tumor growth, primarily driven by alterations in extracellular (ECM) stiffness and tumor viscoelasticity. These mechanical changes not only promote tumor progression but also hinder therapeutic efficacy by impairing drug delivery and activating mechanotransduction pathways that regulate crucial cellular processes such as migration, proliferation, and resistance to therapy. In this review, we examine the mechanisms through which tumor cells sense and transmit mechanical signals to maintain homeostasis in the biomechanically altered TME. We explore current computational modelling strategies for mechanotransduction pathways, highlighting the need for developing models that incorporate additional components of the mechanosignaling machinery. Furthermore, we review available methods for measuring the mechanical properties of tumors in clinical settings and strategies aiming at restoring the TME and blocking deregulated mechanotransduction pathways. Finally, we propose that proper characterization and a deeper understanding of the mechanical landscape of the TME, both at the tissue and cellular levels, are essential for developing therapeutic strategies that account for the influence of mechanical forces on treatment efficacy.

TRPV4 activation in Schwann cells mediates mechanically induced pain of oral cancer

Introduction

Patients with oral cancer often experience intense functional pain due to mechanical stimulation at the cancer site. The role of mechanosensitive ion channels in oral cancer pain, such as TRPV4, is not fully understood.

Objectives

Our objective was to investigate the role of Schwann cell TRPV4 in oral cancer pain.

Methods

We examined the impact of TRPV4 inhibition on oral cancer pain in NU/J and C57BL/6J mice injected with human tongue cancer cell line (HSC-3) and mouse oral cancer cell line (MOC2) in the hind paw or tongue. Mechanical and heat sensitivity were assessed using the von Frey and Hargreaves tests, respectively. TRPV4 expression and functional activity in Schwann cells were analyzed using immunohistochemistry, qRT-PCR, Ca2+ imaging, and patch-clamp electrophysiology. The effect of TRPV4 activation on Schwann cell responses to mechanical stimulation was evaluated using a piezo stimulator. Conditioned media (CM) from TRPV4-activated Schwann cells were injected into the mouse paw to evaluate the contribution of TRPV4 in Schwann cells to mechanical hypersensitivity.

Results

TRPV4 inhibition reduced paw cancer mechanical nociception in mice dose-dependently without affecting heat sensitivity. TRPV4 inhibition also decreased facial nociception in tongue cancer mice. TRPV4 was expressed mainly on the plasma membrane of mouse Schwann cells and activation of TRPV4 induced Ca2+ responses and whole-cell membrane currents in human Schwann cells. Mechanoactivated currents in human Schwann cells were inhibited by the TRPV4 antagonist HC-067047. Schwann cell CM induced mechanical hypersensitivity in mice, which was blocked by pre-treatment with HC-067047.

Conclusion

TRPV4 activation plays a role in mediating mechanically induced pain of oral cancer.

Mechanosensitive Ion Channels: The Unending Riddle of Mechanotransduction

Sensation begins at the periphery, where distinct transducer proteins, activated by specific physical stimuli, initiate biological events to convert the stimulus into electrical activity. These evoked pulse trains encode various properties of the stimulus and travel to higher centers, enabling perception of the physical environment. Transduction is an essential process in all of the five senses described by Aristotle. A substantial amount of information is already available on how G-protein coupled receptor proteins transduce exposure to light, odors, and tastants. Functional studies have revealed the presence of mechanosensitive (MS) ion channels, which act as force transducers, in a wide range of organisms from archaea to mammals. However, the molecular basis of mechanosensitivity is incompletely understood. Recently, the structure of a few MS channels and the molecular mechanisms linking mechanical force to channel gating have been partially revealed. This article reviews recent developments focusing on the molecular basis of mechanosensitivity and emerging methods to investigate MS channels.

Piezo1 Regulates Odontogenesis via a FAM83G-Mediated Mechanism in Dental Papilla Cells In Vitro and In Vivo

This study explored the role of Piezo1 in the odontogenic differentiation of dental papilla cells (DPCs) and tissue, focusing on a mechanism involving family with sequence similarity 83, member G (FAM83G). Here, we found Piezo1, a mechanosensitive cation channel, was upregulated during odontogenesis in DPCs and dental papilla tissues. Knockdown of Piezo1 impaired odontogenic differentiation, while its activation by Yoda1 enhanced the process. Using a 3D culture model and an ectopic transplantation model, we confirmed Piezo1's role in vivo. RNA sequencing (RNA-seq) analysis revealed that FAM83G was upregulated in Piezo1-knockdown cells, and FAM83G silencing enhanced odontogenesis in DPCs. These findings indicate that Piezo1 positively regulates odontogenesis by inhibiting FAM83G in DPCs both in vitro and in vivo, with Piezo1 representing a potential target for dental tissue regeneration.

High-frequency MHz-order vibration enables cell membrane remodeling and lipid microdomain manipulation

We elucidate the mechanism underpinning a recently discovered phenomenon in which cells respond to MHz-order mechanostimuli. Deformations induced along the plasma membrane under these external mechanical cues are observed to decrease the membrane tension, which, in turn, drives transient and reversible remodeling of its lipid structure. In particular, the increase and consequent coalescence of ordered lipid microdomains leads to closer proximity to mechanosensitive ion channels-Piezo1, in particular-that, due to crowding, results in their activation to mobilize influx of calcium (Ca2+) ions into the cell. It is the modulation of this second messenger that is responsible for the downstream signaling and cell fates that ensue. In addition, we show that such spatiotemporal control over the membrane microdomains in cells-without necessitating biochemical factors-facilitates aggregation and association of intrinsically disordered tau proteins in neuroblastoma cells, and their transformation to pathological conditions implicated in neurodegenerative diseases, thereby paving the way for the development of therapeutic intervention strategies.

Infrared nanosensors of piconewton to micronewton forces

Mechanical force is an essential feature for many physical and biological processes1-7, and remote measurement of mechanical signals with high sensitivity and spatial resolution is needed for diverse applications, including robotics8, biophysics9,10, energy storage11 and medicine12,13. Nanoscale luminescent force sensors excel at measuring piconewton forces, whereas larger sensors have proven powerful in probing micronewton forces14-16. However, large gaps remain in the force magnitudes that can be probed remotely from subsurface or interfacial sites, and no individual, non-invasive sensor is capable of measuring over the large dynamic range needed to understand many systems14,17. Here we demonstrate Tm3+-doped avalanching-nanoparticle18 force sensors that can be addressed remotely by deeply penetrating near-infrared light and can detect piconewton to micronewton forces with a dynamic range spanning more than four orders of magnitude. Using atomic force microscopy coupled with single-nanoparticle optical spectroscopy, we characterize the mechanical sensitivity of the photon-avalanching process and reveal its exceptional force responsiveness. By manipulating the Tm3+ concentrations and energy transfer within the nanosensors, we demonstrate different optical force-sensing modalities, including mechanobrightening and mechanochromism. The adaptability of these nanoscale optical force sensors, along with their multiscale-sensing capability, enable operation in the dynamic and versatile environments present in real-world, complex structures spanning biological organisms to nanoelectromechanical systems.

Sonogenetics is a novel antiarrhythmic mechanism

Arrhythmia of the heart is a dangerous and potentially fatal condition. The current widely used treatment is the implantable cardioverter defibrillator (ICD), but it is invasive and affects the patient's quality of life. The sonogenetic mechanism proposed here focuses ultrasound on a cardiac tissue, controls endogenous stretch-activated Piezo1 ion channels on the focal region's cardiomyocyte sarcolemma, and restores normal heart rhythm. In contrast to anchoring the implanted ICD lead at a fixed position in the myocardium, the size and position of the ultrasound focal region can be selected dynamically by adjusting the signals of every piezoelectric chip on the ultrasonic phased array, and it allows novel and efficient defibrillations. Based on the developed interdisciplinary electro-mechanical model of sonogenetic treatment, our analysis shows that the proposed ultrasound intensity and frequency will be safe and painless for humans and well below the limits established by the U.S. Food and Drug Administration.

Vibrotactile stimulation at 40 Hz inhibits Aβ-induced changes in SH-SY5Y, BV2 cells, and pericytes

Alzheimer's disease (AD) poses a major societal challenge, yet no definitive cure exists. Noninvasive brain stimulation methods, such as transcranial magnetic stimulation and transcranial direct current stimulation, have shown promise in alleviating cognitive symptoms associated with neurodegenerative disorders. This study investigated the effects of 40 Hz vibrotactile stimulation on AD-related cellular responses using SH-SY5Y neuroblastoma cells, primary human brain pericytes, and BV2 microglia. SH-SY5Y cells and brain pericytes treated with oligomeric beta-amyloid (Aβ) underwent 40 Hz vibrational stimulation for varying durations. Cell viability was determined via the CCK-8 assay, while intracellular calcium levels in pericytes were assessed. Protein expression was measured using western blotting, and gene expression was quantified via a real-time quantitative polymerase chain reaction. Detailed vibrational parameters were employed to ensure precise stimulation. Notably, 40 Hz vibrotactile stimulation improved cell viability in Aβ-exposed SH-SY5Y cells, reduced intracellular calcium ion (Ca2+) levels in Aβ-treated pericytes, activated autophagy, and mitigated tau hyperphosphorylation in SH-SY5Y cells. Additionally, it exhibited anti-neuroinflammatory properties in BV2 microglia. These findings highlight the potential of 40 Hz vibrotactile stimulation as a therapeutic strategy for AD.

Mechanoelectrical Transduction through Anion Recognition with Naphthalenediimide Monolayers at the Air-Water Interface

In biological systems, various stimuli and energies are transduced into membrane potentials via ion transport or binding. The application of this concept to artificial devices may result in biomimetic signal transmitters and energy harvesters. In this study, we investigated the mechanical control of fluoride anion recognition with naphthalenediimide (NDI) monolayers at the air-water interface. Similar to the mechanosensitive ion channels in biological membranes, mechanical stimuli modulated the packing manner of the NDI monolayers, which reproducibly triggered anion binding and concomitant shifts in the membrane potential. Furthermore, mechanical stimuli resulted in anion binding or release, depending on the structure of the alkyl side chains attached to the NDI core, which was explained by the difference in the packing manner of the NDI monolayers. These findings provide insights into the development of novel mechanoelectrical transduction systems that mimic biological processes.

Piezo1 Mediates Glycolysis-Boosted Pancreatic Ductal Adenocarcinoma Chemoresistance within a Biomimetic Three-Dimensional Matrix Stiffness

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with a very low 5-year survival rate, which is partially attributed to chemoresistance. Although the regulation of chemoresistance through biochemical signaling is well-documented, the influence of three-dimensional (3D) matrix stiffness is poorly understood. In this study, gelatin methacrylate (GelMA) hydrogels were reconstructed with stiffnesses spanning the range from normal to cancerous PDAC tissues, which are termed as the soft group and stiff group. The PDAC cell lines (Mia-PaCa2 and CFPAC-1) encapsulated in the stiff group displayed a chemoresistance phenotype and were prominent against gemcitabine. RNA-sequencing and bioinformatics analysis indicated that glycolysis was apparently enriched in the stiff group versus the soft group, which was also validated through assays of glucose uptake, lactate production, and the expression of GLUT2, HK2, and LDHA. A rescue assay with 2-deoxy-d-glucose and N-acetylcysteine demonstrated that glycolysis is involved in chemoresistance. Furthermore, the expression of Piezo1 and the content of Ca2+ were elevated in the stiff group. The addition of Yoda1 (Piezo1 agonist) in the soft group promoted glycolysis, whereas in the stiff group, treatment with GsMTx4 (Piezo1 inhibitor) inhibited glycolysis, which showcased that Piezo1 participated in 3D matrix stiffness-induced glycolysis. Taken together, Piezo1-mediated glycolysis was involved in PDAC chemoresistance triggered by the 3D matrix stiffness. Our study sheds light on the mechanism underlying chemoresistance in PDAC from the perspective of 3D mechanical cues.

Elevated Shear Stress Modulates Heterogenous Cellular Subpopulations to Induce Vascular Remodeling

Rationale: Elevated shear stress (ESS) induces vascular remodeling in veins exposed to arterial blood flow, which can lead to arteriovenous (AV) fistula failure. The molecular mechanisms driving remodeling have not been comprehensively examined with a single-cell resolution before. Objective: Using an in vivo animal mode, single-cell RNA sequencing, and histopathology, we precisely manipulate blood flow to comprehensively characterize all cell subpopulations important during vascular remodeling. Methods: AV loops were created in saphenous vessels of rats using a contralateral saphenous vein interposition graft to promote ESS. Saphenous veins with no elevated shear stress (NSS) were anastomosed as controls. Findings: ESS promoted transcriptional homogeneity, and NSS promoted considerable heterogeneity. Specifically, ESS endothelial cells (ECs) showed a more homogeneous transcriptional response promoting angiogenesis and upregulating endothelial-to-mesenchymal transition inhibiting genes (Klf2). NSS ECs upregulated antiproliferation genes such as Cav1, Cst3, and Btg1. In macrophages, ESS promoted a large homogeneous subpopulation, creating a mechanically activated, proinflammatory and thus proangiogenic myeloid phenotype, whereas NSS myeloid cells expressed the anti-inflammatory and antiangiogenetic marker Mrc1. Conclusion: ESS activates unified gene expression profiles to induce adaption of the vessel wall to hemodynamic alterations. Targeted depletion of the identified cellular subpopulations may lead to novel therapies to prevent excessive venous remodeling, intimal hyperplasia, and AV fistula failure.

The activation thresholds and inactivation kinetics of poking-evoked PIEZO1 and PIEZO2 currents are sensitive to subtle variations in mechanical stimulation parameters

PIEZO1 and PIEZO2 are mechanically activated ion channels that confer mechanosensitivity to various cell types. PIEZO channels are commonly examined using the so-called poking technique, where currents are recorded in the whole-cell configuration of the patch-clamp technique, while the cell surface is mechanically stimulated with a small fire-polished patch pipette. Currently, there is no gold standard for mechanical stimulation, and therefore, stimulation protocols differ significantly between laboratories with regard to stimulation velocity, angle, and size of the stimulation probe. Here, we systematically examined the impact of variations in these three stimulation parameters on the outcomes of patch-clamp recordings of PIEZO1 and PIEZO2. We show that the inactivation kinetics of PIEZO1 and, to a lesser extent, of PIEZO2 change with the angle at which the probe that is used for mechanical stimulation is positioned and, even more prominently, with the size of its tip. Moreover, we found that the mechanical activation threshold of PIEZO2, but not PIEZO1, decreased with increasing stimulation speeds. Thus, our data show that two key outcome parameters of PIEZO-related patch-clamp studies are significantly affected by common variations in the mechanical stimulation protocols, which calls for caution when comparing data from different laboratories and highlights the need to establish a gold standard for mechanical stimulation to improve comparability and reproducibility of data obtained with the poking technique.

Pharmacology of PIEZO1 channels

PIEZO1 is a eukaryotic membrane protein that assembles as trimers to form calcium-permeable, non-selective cation channels with exquisite capabilities for mechanical force sensing and transduction of force into effect in diverse cell types that include blood cells, endothelial cells, epithelial cells, fibroblasts and stem cells and diverse systems that include bone, lymphatics and muscle. The channel has wide-ranging roles and is considered as a target for novel therapeutics in ailments spanning cancers and cardiovascular, dental, gastrointestinal, hepatobiliary, infectious, musculoskeletal, nervous system, ocular, pregnancy, renal, respiratory and urological disorders. The identification of PIEZO1 modulators is in its infancy but useful experimental tools emerged for activating, and to a lesser extent inhibiting, the channels. Elementary structure-activity relationships are known for the Yoda series of small molecule agonists, which show the potential for diverse physicochemical and pharmacological properties. Intriguing effects of Yoda1 include the stimulated removal of excess cerebrospinal fluid. Despite PIEZO1's broad expression, opportunities are suggested for selective positive or negative modulation without intolerable adverse effects. Here we provide a focused, non-systematic, narrative review of progress with this pharmacology and discuss potential future directions for research in the area.

Biological sensing of fluid flow-lessons from PIEZO1

The flow sensing endothelial cell lining of blood and lymphatic vessels is essential in vertebrates. While the mechanisms are still mysterious in many regards, several critical components became apparent through molecular biology studies. In this article, we focus on PIEZO1, which forms unusual force-sensing ion channels capable of rapid transduction of force into biological effect. We describe current knowledge and emerging challenges. We suggest the idea of using computation to construct the flow sensing mechanism of endothelium to advance understanding, develop testable hypotheses and potentially design novel therapeutic strategies and synthetic flow sensing devices.

Force-sensing protein expression in response to cardiovascular mechanotransduction

Force-sensing biophysical cues in microenvironment, including extracellular matrix performances, stretch-mediated mechanics, shear stress and flow-induced hemodynamics, have a significant influence in regulating vascular morphogenesis and cardiac remodeling by mechanotransduction. Once cells perceive these extracellular mechanical stimuli, Piezo activation promotes calcium influx by forming integrin-adhesion-coupling receptors. This induces robust contractility of cytoskeleton structures to further transmit biomechanical alternations into nuclei by regulating Hippo-Yes associated protein (YAP) signaling pathway between cytoplasmic and nuclear translocation. Although biomechanical stimuli are widely studied in cardiovascular diseases, the expression of force-sensing proteins in response to cardiovascular mechanotransduction has not been systematically concluded. Therefore, this review will summarize the force-sensing Piezo, cytoskeleton and YAP proteins to mediate extracellular mechanics, and also give the prominent emphasis on intrinsic connection of these mechanical proteins and cardiovascular mechanotransduction. Extensive insights into cardiovascular mechanics may provide some new strategies for cardiovascular clinical therapy.

PIEZO-dependent mechanosensing is essential for intestinal stem cell fate decision and maintenance

Stem cells perceive and respond to biochemical and physical signals to maintain homeostasis. Yet, it remains unclear how stem cells sense mechanical signals from their niche in vivo. In this work, we investigated the roles of PIEZO mechanosensitive channels in the intestinal stem cell (ISC) niche. We used mouse genetics and single-cell RNA sequencing analysis to assess the requirement for PIEZO channels in ISC maintenance. In vivo measurement of basement membrane stiffness showed that ISCs reside in a more rigid microenvironment at the bottom of the crypt. Three-dimensional and two-dimensional organoid systems combined with bioengineered substrates and a stretching device revealed that PIEZO channels sense extracellular mechanical stimuli to modulate ISC function. This study delineates the mechanistic cascade of PIEZO activation that coordinates ISC fate decision and maintenance.

Recent Advances in Artificial Sensory Neurons: Biological Fundamentals, Devices, Applications, and Challenges

Spike-based neural networks, which use spikes or action potentials to represent information, have gained a lot of attention because of their high energy efficiency and low power consumption. To fully leverage its advantages, converting the external analog signals to spikes is an essential prerequisite. Conventional approaches including analog-to-digital converters or ring oscillators, and sensors suffer from high power and area costs. Recent efforts are devoted to constructing artificial sensory neurons based on emerging devices inspired by the biological sensory system. They can simultaneously perform sensing and spike conversion, overcoming the deficiencies of traditional sensory systems. This review summarizes and benchmarks the recent progress of artificial sensory neurons. It starts with the presentation of various mechanisms of biological signal transduction, followed by the systematic introduction of the emerging devices employed for artificial sensory neurons. Furthermore, the implementations with different perceptual capabilities are briefly outlined and the key metrics and potential applications are also provided. Finally, we highlight the challenges and perspectives for the future development of artificial sensory neurons.

EPHB4-RASA1 Inhibition of PIEZO1 Ras Activation Drives Lymphatic Valvulogenesis

BACKGROUND

EPHB4 (ephrin receptor B4) and the RASA1 (p120 Ras GTPase-activating protein) are necessary for the development of lymphatic vessel (LV) valves. However, precisely how EPHB4 and RASA1 regulate LV valve development is unknown. In this study, we examine the mechanisms by which EPHB4 and RASA1 regulate the development of LV valves.

METHODS

We used LV-specific inducible EPHB4-deficient mice and EPHB4 knockin mice that express a form of EPHB4 that is unable to bind RASA1 yet retains protein tyrosine kinase activity (EPHB4 2YP) to study the role of EPHB4 and RASA1 in LV valve development in the embryo and LV valve maintenance in adults. We also used human dermal lymphatic endothelial cells in vitro to study the role of EPHB4 and RASA1 as regulators of LV valve specification induced by oscillatory shear stress, considered the trigger for LV valve specification in vivo.

RESULTS

LV valve specification, continued valve development postspecification, and LV valve maintenance were blocked upon induced loss of EPHB4 in LV. LV valve specification and maintenance were also impaired in EPHB4 2YP mice. Defects in LV valve development were reversed by inhibition of the Ras-MAPK (mitogen-activated protein kinase) signaling pathway. In human dermal lymphatic endothelial cells, loss of expression of EPHB4 or its ephrin b2 ligand, loss of expression of RASA1, and inhibition of physical interaction between EPHB4 and RASA1 resulted in dysregulated oscillatory shear stress-induced Ras-MAPK activation and impaired expression of LV specification markers that could be rescued by Ras-MAPK pathway inhibition. The same results were observed when human dermal lymphatic endothelial cells were stimulated with the Yoda1 agonist of the PIEZO1 oscillatory shear stress sensor. Although Yoda1 increased the number of LV valves when administered to wild-type embryos, it did not increase LV valve number when administered to EPHB4 2YP embryos.

CONCLUSIONS

EPHB4 is necessary for LV valve specification, continued valve development postspecification, and valve maintenance. LV valve specification requires physical interaction between EPHB4 and RASA1 to limit activation of the Ras-MAPK pathway in lymphatic endothelial cells. Specifically, EPHB4-RASA1 physical interaction is necessary to dampen Ras-MAPK activation induced through the PIEZO1 oscillatory shear stress sensor. These findings reveal the mechanism by which EPHB4 and RASA1 regulate the development of LV valves.

Stimulative piezoelectric nanofibrous scaffolds for enhanced small extracellular vesicle production in 3D cultures

Small extracellular vesicles (sEVs) have great promise as effective carriers for drug delivery. However, the challenges associated with the efficient production of sEVs hinder their clinical applications. Herein, we report a stimulative 3D culture platform for enhanced sEV production. The proposed platform consists of a piezoelectric nanofibrous scaffold (PES) coupled with acoustic stimulation to enhance sEV production of cells in a 3D biomimetic microenvironment. Combining cell stimulation with a 3D culture platform in this stimulative PES enables a 15.7-fold increase in the production rate per cell with minimal deviations in particle size and protein composition compared with standard 2D cultures. We find that the enhanced sEV production is attributable to the activation and upregulation of crucial sEV production steps through the synergistic effect of stimulation and the 3D microenvironment. Moreover, changes in cell morphology lead to cytoskeleton redistribution through cell-matrix interactions in the 3D cultures. This in turn facilitates intracellular EV trafficking, which impacts the production rate. Overall, our work provides a promising 3D cell culture platform based on piezoelectric biomaterials for enhanced sEV production. This platform is expected to accelerate the potential use of sEVs for drug delivery and broad biomedical applications.

Activation of PIEZO1 Attenuates Kidney Cystogenesis In Vitro and Ex Vivo

Key Points

Background

The disruption of calcium signaling associated with polycystin deficiency is a key factor in abnormal epithelial growth in autosomal dominant polycystic kidney disease. Calcium homeostasis can be influenced by mechanotransduction. The mechanosensitive cation channel PIEZO1 has been implicated in sensing intrarenal pressure and regulating urinary osmoregulation, but its role in kidney cystogenesis is unclear.

Methods

We hypothesized that altered mechanotransduction contributes to cystogenesis in autosomal dominant polycystic kidney disease and that activation of mechanosensitive cation channels could be a therapeutic strategy.

Results

We demonstrate that Yoda1, a PIEZO1 activator, increases intracellular calcium and reduces forskolin-induced cAMP levels in mouse inner medullary collecting duct (mIMCD3) cells. Notably, knockout of polycystin-2 attenuated the efficacy of Yoda1 in reducing cAMP levels in mIMCD3 cells. Yoda1 also reduced forskolin-induced mIMCD3 cyst surface area in vitro and cystic index in mouse metanephros ex vivo in a dose-dependent manner. However, collecting duct–specific PIEZO1 knockout neither induced cystogenesis in wild-type mice nor altered cystogenesis in the Pkd1RC/RC mouse model.

Conclusions

These findings support the potential role of PIEZO1 agonists in mitigating cystogenesis by increasing intracellular calcium and reducing cAMP levels, but the unaltered in vivo cystic phenotype after PIEZO1 knockout in the collecting duct suggests possible redundancy in mechanotransductive pathways.

Functional characterization of native Piezo1 as calcium and magnesium influx pathway in human myeloid leukemia cells

Piezo1 is a Ca2+-permeable mechanically activated ion channel that is involved in various physiological processes and cellular responses to mechanical stimuli. The study of biophysical characteristics of Piezo1 is important for understanding the mechanisms of its function and regulation. Stretch activation, a routine approach that is applied to stimulate Piezo1 activity in the plasma membrane, has a number of significant limitations that complicate precise single-channel analysis. Here, we aimed to determine pore properties of native Piezo1, specifically to examine permeation for physiologically relevant signaling divalent ions (calcium and magnesium) in human myeloid leukemia K562 cells using Piezo1-specific chemical agonist, Yoda1. Using a combination of low-noise single-current patch-clamp recordings of Piezo1 activity in response to Yoda1, we have determined single-channel characteristics of native Piezo1 under various ionic conditions. Whole-cell assay allowed us to directly measure Piezo1 single currents carried by Ca2+ or Mg2+ ions in the absence of other permeable cations in the extracellular solutions; unitary conductance values estimated at various concentrations of Mg2+ revealed strong saturation effect. Patch clamp data complemented with fluorescent imaging clearly evidenced Ca2+ and Mg2+ entry via native Piezo1 channel in human leukemia K562 cells. Mg2+ influx via Piezo1 was detected under quasi-physiological conditions, thus showing that Piezo1 channels could potentially provide the physiological relevant pathway for Mg2+ ion transport and contribute to the regulation of Mg2+-dependent intracellular signaling.

Role of mechanosensitive channel Piezo1 protein in intestinal inflammation regulation: A potential target

The intestine is a hollow tract that primarily transports and digests food. It often encounters mechanical forces and exotic threats, resulting in increased intestinal inflammation attributed to the consistent threat of foreign pathogens. Piezo1, a mechanosensitive ion channel, is distributed broadly and abundantly in the intestinal tissue. It transduces mechanical signals into electrochemical signals and participates in many critical life activities, such as proliferation, differentiation, cell apoptosis, immune cell activation, and migration. Its effect on inflammation has been discussed in detail in systems, such as musculoskeletal (osteoarthritis) and cardiac (myocarditis), but the effects on intestinal inflammation remain unelucidated. Piezo1 regulates mucosal layer and epithelial barrier homeostasis during the complex intestinal handling of foreign antigens and tissue trauma. It initiates and spreads immune responses and causes distant effects of inflammation in the vascular and lymphatic systems, but reports of the effects of Piezo1 in intestinal inflammation are scarce. Therefore, this study aimed to discuss the role of Piezo1 in intestinal inflammation and explore novel therapeutic targets.

Piezo1: the key regulators in central nervous system diseases

The occurrence and development of central nervous system (CNS) diseases is a multi-factor and multi-gene pathological process, and their diagnosis and treatment have always posed a serious challenge in the medical field. Therefore, exploring the relevant factors in the pathogenesis of CNS and improving the diagnosis and treatment rates has become an urgent problem. Piezo1 is a recently discovered mechanosensitive ion channel that opens in response to mechanical stimuli. A number of previous studies have shown that the Piezo channel family plays a crucial role in CNS physiology and pathology, especially in diseases related to CNS development and mechanical stimulation. This article comprehensively describes the biological properties of Piezo1, focuses on the potential association between Piezo1 and CNS disorders, and explores the pharmacological roles of Piezo1 agonists and inhibitors in treating CNS disorders.

Genetic Code Expansion for Mechanistic Studies in Ion Channels: An (Un)natural Union of Chemistry and Biology

Ion channels play central roles in biology and human health by catalyzing the transmembrane flow of electrical charge. These proteins are ideal targets for genetic code expansion (GCE) methods because it is feasible to measure ion channel activity from miniscule amounts of protein and to analyze the resulting data via rigorous, established biophysical methods. In an ideal scenario, the encoding of synthetic, noncanonical amino acids via GCE allows the experimenter to ask questions inaccessible to traditional methods. For this reason, GCE has been successfully applied to a variety of ligand- and voltage-gated channels wherein extensive structural, functional, and pharmacological data exist. Here, we provide a comprehensive summary of GCE as applied to ion channels. We begin with an overview of the methods used to encode noncanonical amino acids in channels and then describe mechanistic studies wherein GCE was used for photochemistry (cross-linking; caged amino acids) and atomic mutagenesis (isosteric manipulation of charge and aromaticity; backbone mutation). Lastly, we cover recent advances in the encoding of fluorescent amino acids for the real-time study of protein conformational dynamics.

Low hepatic artery blood flow mediates NET extravasation through the regulation of PIEZO1/SRC signaling to induce biliary complications after liver transplantation

Rationale: Biliary complications after liver transplantation persistently affect patient prognosis and graft survival. Neutrophil-mediated immune injury is an important factor leading to biliary injury. However, the mechanism by which neutrophils reach the periphery of the bile duct and further mediate bile duct injury is not fully understood. Methods: First, we obtained hepatic tissue samples from grafted rats subjected to warm and nonwarm ischemic injury. We constructed a protein map via proteomics and analyzed the correlations between neutrophil extracellular traps (NETs) and biliary injury. HuCCT1 cells were cocultured with NETs isolated from the peripheral blood of grafted rats in vitro to evaluate the role of NETs in bile duct injury. Next, we assessed NET extravasation through the PIEZO1/SRC pathway in liver samples from rats with liver grafts via proteomic analysis, immunohistochemical staining and immunofluorescence. Finally, we evaluated the correlations between hepatic arterial blood flow and the PIEZO1/SRC pathway in a liver graft model. Results: The results revealed a close correlation between NET formation by activated neutrophils and bile duct injury. Low hepatic arterial blood flow leads to NET extravasation through the activation of the mechanosensitive ion channel PIEZO1 and its downstream signaling events, including phosphorylation of tyrosine kinases sarcoma (SRC) protein. The extravasated NETs accumulate around the bile ducts and subsequently mediate biliary cell apoptosis. Verapamil was further used to increase hepatic artery blood flow to inhibit the PIEZO1/SRC axis, which reduced bile duct injury caused by extravasated NETs. Conclusions: Suppressing NET extravasation by increasing hepatic arterial blood flow is a potential strategy for the treatment of biliary complications after liver transplantation.

Chemical mapping of the surface interactome of PIEZO1 identifies CADM1 as a modulator of channel inactivation

The propeller-shaped blades of the PIEZO1 and PIEZO2 ion channels partition into the plasma membrane and respond to indentation or stretching of the lipid bilayer, thus converting mechanical forces into signals that can be interpreted by cells, in the form of calcium flux and changes in membrane potential. While PIEZO channels participate in diverse physiological processes, from sensing the shear stress of blood flow in the vasculature to detecting touch through mechanoreceptors in the skin, the molecular details that enable these mechanosensors to tune their responses over a vast dynamic range of forces remain largely uncharacterized. To survey the molecular landscape surrounding PIEZO channels at the cell surface, we employed a mass spectrometry-based proteomic approach to capture and identify extracellularly exposed proteins in the vicinity of PIEZO1. This PIEZO1-proximal interactome was enriched in surface proteins localized to cell junctions and signaling hubs within the plasma membrane. Functional screening of these interaction candidates by calcium imaging and electrophysiology in an overexpression system identified the adhesion molecule CADM1/SynCAM that slows the inactivation kinetics of PIEZO1 with little effect on PIEZO2. Conversely, we found that CADM1 knockdown accelerates inactivation of endogenous PIEZO1 in Neuro-2a cells. Systematic deletion of CADM1 domains indicates that the transmembrane region is critical for the observed effects on PIEZO1, suggesting that modulation of inactivation is mediated by interactions in or near the lipid bilayer.

Biomechanism of abnormal stress on promoting osteoarthritis of temporomandibular joint through Piezo1 ion channel

OBJECTIVE

This study aimed to investigate whether flow fluid shear stress (FFSS)-mediated signal transduction affects the function of Piezo1 ion channel in chondrocyte and to further explore the role of mechanical overloading in development of temporomandibular joint osteoarthritis (TMJ OA).

METHODS

Immunohistochemical staining was used to determine the expression of Piezo1 in TMJ OA tissue collected from rat unilateral anterior crossbite (UAC) models. Chondrocytes harvested from normal adult SD rats were treated with FFSS (0, 4, 8, 12 dyn/cm2) in vitro. Immunofluorescent staining, real-time polymerase chain reaction, western blotting, flow cytometry and phalloidin assay were performed to detect the changes of cellular morphology as well as the expression of Piezo1 and certain pro-inflammatory and degradative factors in chondrocyte.

RESULTS

Immunohistochemical analysis revealed that significantly increased Piezo1 expression was associated with UAC stimulation (p < .05). As applied FFSS escalated (4, 8 and 12 dyn/cm2), the expression levels of Piezo1, ADAMTS-5, MMP-13 and Col-X gradually increased, compared with the non-FFSS group (p < .05). Administering Piezo1 ion channel inhibitor to chondrocytes beforehand, it was observed that expression of ADAMTS-5, MMP-13 and Col-X was substantially decreased following FFSS treatment (p < .05) and the effect of cytoskeletal thinning was counteracted. The activated Piezo1 ion channel enhanced intracellular Ca2+ excess in chondrocytes during abnormal mechanical stimulation and the increased intracellular Ca2+ thinned the cytoskeleton of F-actin.

CONCLUSIONS

Mechanical overloading activates Piezo1 ion channel to promote pro-inflammation and degradation and to increase Ca2+ concentration in chondrocyte, which may eventually result in TMJ OA.

Alteration of Piezo1 signaling in type 2 diabetic mice: focus on endothelium and BKCa channel

Piezo1 mechanosensitive ion channel plays a important role in vascular physiology and disease. This study aimed to elucidate the altered signaling elicited by Piezo1 activation in the arteries of type 2 diabetes. Ten- to 12-week-old male C57BL/6 (control) and type 2 diabetic mice (db-/db-) were used. The second-order mesenteric arteries (~ 150 μm) were used for isometric tension experiments. Western blot analysis and immunofluorescence staining were performed to observe protein expression. Piezo1 was significantly decreased in mesenteric arteries of type 2 diabetic mice compared to control mice, as analyzed by western blot and immunofluorescence staining. Piezo1 agonist, Yoda1, concentration-dependently induced relaxation of mesenteric arteries in both groups. Interestingly, the relaxation response was significantly greater in control mice than in db-/db- mice. The removal of endothelium reduced relaxation responses induced by Yoda1, which was greater in control mice than db-/db- mice. Furthermore, the relaxation response was reduced by pre-treatment with various types of K+ channel blockers in endothelium-intact arteries in control mice. In endothelium-denuded arteries, pre-incubation with charybdotoxin, an Ca2+-activated K+ channel (BKCa channel) blocker, significantly attenuated Yoda1-induced relaxation in db-/db- mice, while there was no effect in control mice. Co-immunofluorescence staining showed co-localization of Piezo1 and BKCa channel was more pronounced in db-/db- mice than in control mice. These results indicate that the vascular responses induced by Piezo1 activation are different in the mesenteric resistance arteries in type 2 diabetic mice.

Preeclampsia and transport of ions and small molecules: A literature review

Preeclampsia (PE) is a prevalent obstetric complication affecting approximately 3-5% of pregnancies worldwide and is a major cause of maternal and perinatal morbidity and mortality. Preeclampsia is considered a disease of the endothelial system that can progress to eclampsia, characterized by seizures. Early diagnosis and appropriate management are crucial to improving maternal and fetal outcomes, as preeclampsia can lead to severe complications such as placental abruption, fetal growth restriction, and stroke. The pathophysiology of PE is complex, involving a combination of genetic, acquired, and immunological factors. A central feature of the condition is inadequate placentation and impaired uteroplacental perfusion, leading to local hypoxia, endothelial dysfunction, vasoconstriction, and immunological dysregulation. Recent evidence suggests that dysregulation of ion transporters may play a significant role in the adaptation of uterine circulation during placentation. These transporters are essential for maintaining maternal-fetal homeostasis, influencing processes such as nutrient exchange, hormone synthesis, trophoblast cell migration, and the function of smooth muscle cells in blood vessels. In preeclampsia, adverse conditions like hypoxia and oxidative stress result in the downregulation of ion, solute, and water transporters, impairing their function. This review focuses on membrane transporters involved in PE, discussing functional alterations and their physiological implications. The goal of this investigation is to enhance understanding of how dysregulation of ion and small molecule transporters contributes to the development and progression of preeclampsia, underscoring the importance of exploring these signaling pathways for potential therapeutic interventions.

Mechanosensitive ion channels in glaucoma pathophysiology

Force sensing is a fundamental ability that allows cells and organisms to interact with their physical environment. The eye is constantly subjected to mechanical forces such as blinking and eye movements. Furthermore, elevated intraocular pressure (IOP) can cause mechanical strain at the optic nerve head, resulting in retinal ganglion cell death (RGC) in glaucoma. How mechanical stimuli are sensed and affect cellular physiology in the eye is unclear. Recent studies have shown that mechanosensitive ion channels are expressed in many ocular tissues relevant to glaucoma and may influence IOP regulation and RGC survival. Furthermore, variants in mechanosensitive ion channel genes may be associated with risk for primary open angle glaucoma. These findings suggest that mechanosensitive channels may be important mechanosensors mediating cellular responses to pressure signals in the eye. In this review, we focus on mechanosensitive ion channels from three major channel families-PIEZO, two-pore potassium and transient receptor potential channels. We review the key properties of these channels, their effects on cell function and physiology, and discuss their possible roles in glaucoma pathophysiology.

The mechanism and potential therapeutic target of piezo channels in pain

Pain is a common symptom of many clinical diseases; it adversely affects patients' physical and mental health, reduces their quality of life, and heavily burdens patients and society. Pain treatment is one of the most difficult problems today. There is an urgent need to explore the potential factors involved in the pathogenesis of pain to improve its diagnosis and treatment rate. Piezo1/2, a newly identified mechanosensitive ion channel opens in response to mechanical stimuli and plays a critical role in regulating pain-related diseases. Inhibition or downregulation of Piezo1/2 alleviates disease-induced pain. Therefore, in this study, we comprehensively discussed the biology of this gene, focusing on its potential relevance in pain-related diseases, and explored the pharmacological effects of drugs using this gene for the treatment of pain.

Functional Role of Piezo1 in the Human Eosinophil Cell Line AML14.3D10: Implications for the Immune and Sensory Nervous Systems

Mechanosensitive ion channels, particularly Piezo channels, are widely expressed in various tissues. However, their role in immune cells remains underexplored. Therefore, this study aimed to investigate the functional role of Piezo1 in the human eosinophil cell line AML14.3D10. We detected Piezo1 mRNA expression, but not Piezo2 expression, in these cells, confirming the presence of the Piezo1 protein. Activation of Piezo1 with Yoda1, its specific agonist, resulted in a significant calcium influx, which was inhibited by the Piezo1-specific inhibitor Dooku1, as well as other nonspecific inhibitors (Ruthenium Red, Gd3+, and GsMTx-4). Further analysis revealed that Piezo1 activation modulated the expression and secretion of both pro-inflammatory and anti-inflammatory cytokines in AML14.3D10 cells. Notably, supernatants from Piezo1-activated AML14.3D10 cells enhanced capsaicin and ATP-induced calcium responses in the dorsal root ganglion neurons of mice. These findings elucidate the physiological role of Piezo1 in AML14.3D10 cells and suggest that factors secreted by these cells can modulate the activity of transient receptor potential 1 (TRPV1) and purinergic receptors, which are associated with pain and itch signaling. The results of this study significantly advance our understanding of the function of Piezo1 channels in the immune and sensory nervous systems.

A bioinspired tactile scanner for computer haptics

Computer haptics (CH) is about integration of tactile sensation and rendering in Metaverse. However, unlike computer vision (CV) where both hardware infrastructure and software programs are well developed, a generic tactile data capturing device that serves the same role as what a camera does for CV, is missing. Bioinspired by electrophysiological processes in human tactile somatosensory nervous system, here we propose a tactile scanner along with a neuromorphically-engineered system, in which a closed-loop tactile acquisition and rendering (re-creation) are preliminarily achieved. Based on the architecture of afferent nerves and intelligent functions of mechano-gating and leaky integrate-and-fire models, such a tactile scanner is designed and developed by using piezoelectric transducers as axon neurons and thin film transistor (TFT)-based neuromorphic circuits to mimic synaptic behaviours and neural functions. As an example, the neuron-like tactile information of surface textures is captured and further used to render the texture friction of a virtual surface for "recreating" a "true" feeling of touch.

David Julius and Ardem Patapoutian: Pioneers in Sensory Biology and Neuroscience

Sensory biology is a critical area within neuroscience, exploring how organisms respond to environmental stimuli such as temperature, pain, and mechanical forces. David Julius and Ardem Patapoutian have made landmark contributions to this field by identifying crucial receptors. Julius's discovery of transient receptor potential (TRP) channels, including transient receptor potential cation channel subfamily V member 1 (TRPV1), which detects heat and pain, revolutionized sensory biology and opened new paths for pain management. Similarly, Patapoutian's identification of Piezo channels, which respond to mechanical stimuli like touch and pressure, has deepened our understanding of sensory perception. Their combined work has not only advanced scientific knowledge but also introduced potential treatments for chronic pain and sensory disorders. This paper reviews their contributions and the broader implications for sensory biology and therapeutic developments.

Three-dimensional matrix stiffness modulates mechanosensitive and phenotypic alterations in oral squamous cell carcinoma spheroids

Extracellular biophysical cues such as matrix stiffness are key stimuli tuning cell fate and affecting tumor progression in vivo. However, it remains unclear how cancer spheroids in a 3D microenvironment perceive matrix mechanical stiffness stimuli and translate them into intracellular signals driving progression. Mechanosensitive Piezo1 and TRPV4 ion channels, upregulated in many malignancies, are major transducers of such physical stimuli into biochemical responses. Most mechanotransduction studies probing the reception of changing stiffness cues by cells are, however, still limited to 2D culture systems or cell-extracellular matrix models, which lack the major cell-cell interactions prevalent in 3D cancer tumors. Here, we engineered a 3D spheroid culture environment with varying mechanobiological properties to study the effect of static matrix stiffness stimuli on mechanosensitive and malignant phenotypes in oral squamous cell carcinoma spheroids. We find that spheroid growth is enhanced when cultured in stiff extracellular matrix. We show that the protein expression of mechanoreceptor Piezo1 and stemness marker CD44 is upregulated in stiff matrix. We also report the upregulation of a selection of genes with associations to mechanoreception, ion channel transport, extracellular matrix organization, and tumorigenic phenotypes in stiff matrix spheroids. Together, our results indicate that cancer cells in 3D spheroids utilize mechanosensitive ion channels Piezo1 and TRPV4 as means to sense changes in static extracellular matrix stiffness, and that stiffness drives pro-tumorigenic phenotypes in oral squamous cell carcinoma.

Stimulative piezoelectric nanofibrous scaffolds for enhanced small extracellular vesicle production in 3D cultures

Small extracellular vesicles (sEVs) have great promise as effective carriers for drug delivery. However, the challenges associated with the efficient production of sEVs hinder their clinical applications. Herein, we report a stimulative 3D culture platform for enhanced sEV production. The proposed platform consists of a piezoelectric nanofibrous scaffold (PES) coupled with acoustic stimulation to enhance sEV production of cells in a 3D biomimetic microenvironment. Combining cell stimulation with a 3D culture platform in this stimulative PES enables a 15.7-fold increase in the production rate per cell with minimal deviations in particle size and protein composition compared with standard 2D cultures. We find that the enhanced sEV production is attributable to the activation and upregulation of crucial sEV production steps through the synergistic effect of stimulation and the 3D microenvironment. Moreover, changes in cell morphology lead to cytoskeleton redistribution through cell-matrix interactions in the 3D cultures. This in turn facilitates intracellular EV trafficking, which impacts the production rate. Overall, our work provides a promising 3D cell culture platform based on piezoelectric biomaterials for enhanced sEV production. This platform is expected to accelerate the potential use of sEVs for drug delivery and broad biomedical applications.