Force From Filaments: The Role of the Cytoskeleton and Extracellular Matrix in the Gating of Mechanosensitive Channels

Genome-Wide Association Study of Age-Related Hearing Loss in CFW Mice Identifies Multiple Genes and Loci, Including Prkag2

PURPOSE

Age-related hearing loss (ARHL) is one of the most prevalent conditions affecting the elderly. ARHL is influenced by a combination of environmental and genetic factors; the identification of the genes that confer risk will aid in the prevention and treatment of ARHL. The mouse and human inner ears are functionally and genetically homologous. We used Carworth Farms White (CFW) mice to study the genetic basis of ARHL because they are genetically diverse and exhibit variability in the age of onset and severity of ARHL.

METHODS

Hearing at a range of frequencies was measured using auditory brainstem response (ABR) thresholds in 946 male and female CFW mice at the age of 1, 6, and 10 months. We genotyped the mice using low-coverage (mean coverage 0.27 ×) whole-genome sequencing (lcWGS) followed by imputation using STITCH. To determine the accuracy of the genotypes, we sequenced 8 samples at > 30 × coverage and used those data to estimate the accuracy of lcWGS genotyping, which was > 99.5%. We performed a genome-wide association study (GWAS) for the ABR thresholds for each frequency at each age, and we also performed a GWAS for age at deafness.

RESULTS

We obtained genotypes at 4.18 million single nucleotide polymorphisms (SNP). The SNP heritability for traits ranged from 0 to 42%. GWAS identified 10 significant associations with ARHL that contained potential candidate genes, including Dnah11, Rapgef5, Cpne4, Prkag2, and Nek11. Genetic ablation of Prkag2 caused ARHL at high frequencies, strongly suggesting that Prkag2 is the causal gene for one of the associations.

CONCLUSIONS

GWAS for ARHL in CFW outbred mice identified genetic risk factors for ARHL, including Prkag2. Our results will help to define novel therapeutic targets for the treatment and prevention of this common disorder.

Emerging roles of mechanically activated ion channels in autoimmune disease

Mechanically activated (MA) ion channels have rapidly gained prominence as vital conduits bridging aberrant mechanical cues in tissues with the dysregulated immune responses at the core of autoimmune diseases. Once regarded as peripheral players in inflammation, these channels, exemplified by PIEZO1, TRPV4, and specific K2P family members, now play a central role in modulating T-cell effector functions, B- cell activation and the activity of macrophages and dendritic cells. Their gating is intimately tied to physical distortions such as increased tissue stiffness, osmotic imbalances, or fluid shear, triggering a cascade of ionic fluxes that elevate proinflammatory signaling and drive tissue-destructive loops. Recognition of these channels as central mediators of mechanical stress-induced inflammation responses in autoimmune pathogenesis is rapidly expanding. In parallel, the emerging therapeutic strategies aim to restrain overactive mechanosensors or selectively harness them in affected tissues. Small molecules, peptide blockers, and gene-targeting approaches show preclinical promise, although off-target effects and the broader homeostatic roles of these channels warrant caution. This review explores how integrating mechanobiological concepts with established immunological paradigms enables a more detailed understanding of autoimmune pathogenesis. By elucidating how mechanical forces potentiate or dampen pathological immunity, we propose innovative strategies that exploit mechanosensitivity to recalibrate immune responses across a spectrum of autoimmune conditions.

Mechanotransduction in Development: A Focus on Angiogenesis

Cells respond to external mechanical cues and transduce these forces into biological signals. This process is known as mechanotransduction and requires a group of proteins called mechanosensors. This peculiar class of receptors include extracellular matrix proteins, plasma membrane proteins, the cytoskeleton and the nuclear envelope. These cell components are responsive to a wide spectrum of physical cues including stiffness, tensile force, hydrostatic pressure and shear stress. Among mechanotransducers, the Transient Receptor Potential (TRP) and the PIEZO family members are mechanosensitive ion channels, coupling force transduction with intracellular cation transport. Their activity contributes to embryo development, tissue remodeling and repair, and cell homeostasis. In particular, vessel development is driven by hemodynamic cues such as flow direction and shear stress. Perturbed mechanotransduction is involved in several pathological vascular phenotypes including hereditary hemorrhagic telangiectasia. This review is conceived to summarize the most recent findings of mechanotransduction in development. We first collected main features of mechanosensitive proteins. However, we focused on the role of mechanical cues during development. Mechanosensitive ion channels and their function in vascular development are also discussed, with a focus on brain vessel morphogenesis.

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.

Direct detection of deformation modes on varying length scales in active biopolymer networks

Correlated flows and forces that emerge from active matter orchestrate complex processes such as shape regulation and deformations in biological cells and tissues. The active materials central to cellular mechanics are cytoskeletal networks, where molecular motor activity drives deformations and remodeling. Here, we investigate deformation modes in contractile actin networks driven by the molecular motor myosin II through quantitative fluorescence microscopy. We examine the deformation anisotropy at different length scales in networks of sparsely cross-linked and bundled actin. In sparsely cross-linked networks, we find myosin-dependent biaxial buckling modes across length scales. Interestingly, both long and short-wavelength buckling may contribute to network contractility. In cross-linked bundled networks, uniaxial contraction predominates on long length scales, while the uniaxial or biaxial nature of the deformation depends on bundle microstructure at shorter length scales. The anisotropy of deformations may provide insight to the mechanical origins of contractility in actin networks and regulation of collective behavior in a variety of active materials.

Physical principles and mechanisms of cell migration

Cell migration is critical in processes such as developmental biology, wound healing, immune response, and cancer invasion/metastasis. Understanding its regulation is essential for developing targeted therapies in regenerative medicine, cancer treatment and immune modulation. This review examines cell migration mechanisms, highlighting fundamental physical principles, key molecular components, and cellular behaviors, identifying existing gaps in current knowledge, and suggesting potential directions for future research.

Advancing Neuroscience and Therapy: Insights into Genetic and Non-Genetic Neuromodulation Approaches

Neuromodulation stands as a cutting-edge approach in the fields of neuroscience and therapeutic intervention typically involving the regulation of neural activity through physical and chemical stimuli. The purpose of this review is to provide an overview and evaluation of different neuromodulation techniques, anticipating a clearer understanding of the future developmental trajectories and the challenges faced within the domain of neuromodulation that can be achieved. This review categorizes neuromodulation techniques into genetic neuromodulation methods (including optogenetics, chemogenetics, sonogenetics, and magnetogenetics) and non-genetic neuromodulation methods (including deep brain stimulation, transcranial magnetic stimulation, transcranial direct current stimulation, transcranial ultrasound stimulation, photobiomodulation therapy, infrared neuromodulation, electromagnetic stimulation, sensory stimulation therapy, and multi-physical-factor stimulation techniques). By systematically evaluating the principles, mechanisms, advantages, limitations, and efficacy in modulating neuronal activity and the potential applications in interventions of neurological disorders of these neuromodulation techniques, a comprehensive picture is gradually emerging regarding the advantages and challenges of neuromodulation techniques, their developmental trajectory, and their potential clinical applications. This review highlights significant advancements in applying these techniques to treat neurological and psychiatric disorders. Genetic methods, such as sonogenetics and magnetogenetics, have demonstrated high specificity and temporal precision in targeting neuronal populations, while non-genetic methods, such as transcranial magnetic stimulation and photobiomodulation therapy, offer noninvasive and versatile clinical intervention options. The transformative potential of these neuromodulation techniques in neuroscience research and clinical practice is underscored, emphasizing the need for integration and innovation in technologies, the optimization of delivery methods, the improvement of mediums, and the evaluation of toxicity to fully harness their therapeutic potential.

When sng meets acupuncture -- a paradigm-shift biomarker for translational research

The sensation of sng (pronounced/səŋ/, the Romanization form of or soreness in Taiwanese Southern Min) associated with de qi, a composite of unique sensations, is a novel phenotype for acupoint stimulation. It is perceived by test participants but also by experienced practitioners as a sensation of "taking the bait" (by fish when fishing), a characteristic heavy and tight sensation from the needle. Here, we propose that sng is a powerful biomarker for de qi associated with successful manual acupuncture. Sngception (sng-ception), a specific somatosensory function of acid-sensation or tether-mode mechano-sensation, may serve as the ideal molecular and physiological link between sng perception and needle manipulation (e.g., lifting, thrusting, and twisting). To explain how manual acupuncture can induce de qi, we constructed a hypothetical model of manual needling-driven sngception. In acupoints (e.g., ST36), an acupuncture needle can easily stick to extracellular matrix (ECM) proteins (e.g., fibronectin and laminin). While the acupuncture needle is manually twisted, it mingles with ECM and delivers a pulling force to ECM-tethered mechanically sensitive ion channels (e.g., acid-sensing ion channels) on somatosensory nerves to induce sngception. The concept of sng and sngception represents an emerging field for research into the peripheral mechanisms of acupuncture.

Anatomy and transcriptomics of the common jingle shell (Bivalvia, Anomiidae) support a sensory function for bivalve tentacles

Animals have evolved numerous mechanisms to perceive and interact with the environment that can be translated into different sensory modalities. However, the genomic and phenotypic features that support sensory functions remain enigmatic for many invertebrates, such as bivalves, an ecologically and economically important taxonomic group. No repertoire of sensory genes has been characterized in bivalves, representing a significant knowledge gap in molluscan sensory biology. Here, we gather multiple lines of evidence to explore the specialized sensory function of bivalve tentacles in the common jingle shell, Anomia simplex. In addition to applying microscopy techniques, we performed transcriptome sequencing of dissected tentacles using phylogenetically-informed annotation to identify candidate receptors. Our results demonstrate the expression of candidate GPCRs, including one opsin type, five small-molecule receptors, and 11 chemosensory-related receptors, supporting the involvement of sensory neurons in the organ, likely in association with the ciliated receptor cells observed along the tentacle surface. In addition, we identified seven ionotropic receptors as putative chemosensory receptors and one member of the Piezo mechanosensitive ion channel, which might be involved in touch sensation by ciliated sensory receptors. Our results provide the first evidence of putative sensory genes expressed in a bivalve sensory organ, representing an important starting point to investigate chemosensation in this class.

Increased keratinocyte activity and PIEZO1 signaling contribute to paclitaxel-induced mechanical hypersensitivity

Recent work demonstrates that epidermal keratinocytes are critical for normal touch sensation. However, it is unknown whether keratinocytes contribute to touch-evoked pain and hypersensitivity after tissue injury. Here, we used a mouse model of paclitaxel treatment to determine the extent to which keratinocyte activity contributes to the severe neuropathic pain that accompanies chemotherapy. We found that keratinocyte inhibition by either optogenetic or chemogenetic methods largely alleviated paclitaxel-induced mechanical hypersensitivity across acute and persistent time points from 2 days through 3 weeks. Furthermore, we found that paclitaxel exposure sensitized mouse and human keratinocytes to mechanical stimulation and enhanced currents of PIEZO1, a mechanosensitive channel highly expressed in keratinocytes. Deletion of PIEZO1 from keratinocytes alleviated paclitaxel-induced mechanical hypersensitivity in mice. These findings suggest that nonneuronal cutaneous cells contribute substantially to neuropathic pain and pave the way for the development of new pain relief strategies that target epidermal keratinocytes and PIEZO1.

Mechanosensory entities and functionality of endothelial cells

The endothelial cells of the blood circulation are exposed to hemodynamic forces, such as cyclic strain, hydrostatic forces, and shear stress caused by the blood fluid's frictional force. Endothelial cells perceive mechanical forces via mechanosensors and thus elicit physiological reactions such as alterations in vessel width. The mechanosensors considered comprise ion channels, structures linked to the plasma membrane, cytoskeletal spectrin scaffold, mechanoreceptors, and junctional proteins. This review focuses on endothelial mechanosensors and how they alter the vascular functions of endothelial cells. The current state of knowledge on the dysregulation of endothelial mechanosensitivity in disease is briefly presented. The interplay in mechanical perception between endothelial cells and vascular smooth muscle cells is briefly outlined. Finally, future research avenues are highlighted, which are necessary to overcome existing limitations.

The principles and promising future of sonogenetics for precision medicine

Sonogenetics is an emerging medical technology that uses acoustic waves to control cells through sonosensitive mediators (SSMs) that are genetically encoded, thus remotely and non-invasively modulating specific molecular events and/or biomolecular functions. Sonogenetics has opened new opportunities for targeted spatiotemporal manipulation in the field of gene and cell-based therapies due to its inherent advantages, such as its noninvasive nature, high level of safety, and deep tissue penetration. Sonogenetics holds impressive potential in a wide range of applications, from tumor immunotherapy and mitigation of Parkinsonian symptoms to the modulation of neural reward pathway, and restoration of vision. This review provides a detailed overview of the mechanisms and classifications of established sonogenetics systems and summarizes their applications in disease treatment and management. The review concludes by highlighting the challenges that hinder the further progress of sonogenetics, paving the way for future advances.

Piezo1 and its inhibitors: Overview and perspectives

The cation channel Piezo1, a crucial mechanotransducer found in various organs and tissues, has gained considerable attention as a therapeutic target in recent years. Following this trend, several Piezo1 inhibitors have been discovered and studied for potential pharmacological properties. This review provides an overview of the structural and functional importance of Piezo1, as well as discussing the biological activities of Piezo1 inhibitors based on their mechanism of action. The compounds addressed include the toxin GsMTx4, Aβ peptides, certain fatty acids, ruthenium red and gadolinium, Dooku1, as well as the natural products tubeimoside I, salvianolic acid B, jatrorrhzine, and escin. The findings revealed that misexpression of Piezo1 can be associated with a number of chronic diseases, including hypertension, cancer, and hemolytic anemia. Consequently, inhibiting Piezo1 and the subsequent calcium influx can have beneficial effects on various pathological processes, as shown by many in vitro and in vivo studies. However, the development of Piezo1 inhibitors is still in its beginnings, with many opportunities and challenges remaining to be explored.

Genome-wide association study for age-related hearing loss in CFW mice

Age-related hearing impairment is the most common cause of hearing loss and is one of the most prevalent conditions affecting the elderly globally. It is influenced by a combination of environmental and genetic factors. The mouse and human inner ears are functionally and genetically homologous. Investigating the genetic basis of age-related hearing loss (ARHL) in an outbred mouse model may lead to a better understanding of the molecular mechanisms of this condition. We used Carworth Farms White (CFW) outbred mice, because they are genetically diverse and exhibit variation in the onset and severity of ARHL. The goal of this study was to identify genetic loci involved in regulating ARHL. Hearing at a range of frequencies was measured using Auditory Brainstem Response (ABR) thresholds in 946 male and female CFW mice at the age of 1, 6, and 10 months. We obtained genotypes at 4.18 million single nucleotide polymorphisms (SNP) using low-coverage (mean coverage 0.27x) whole-genome sequencing followed by imputation using STITCH. To determine the accuracy of the genotypes we sequenced 8 samples at >30x coverage and used calls from those samples to estimate the discordance rate, which was 0.45%. We performed genetic analysis for the ABR thresholds for each frequency at each age, and for the time of onset of deafness for each frequency. The SNP heritability ranged from 0 to 42% for different traits. Genome-wide association analysis identified several regions associated with ARHL that contained potential candidate genes, including Dnah11, Rapgef5, Cpne4, Prkag2, and Nek11. We confirmed, using functional study, that Prkag2 deficiency causes age-related hearing loss at high frequency in mice; this makes Prkag2 a candidate gene for further studies. This work helps to identify genetic risk factors for ARHL and to define novel therapeutic targets for the treatment and prevention of ARHL.

Mechanobiological insight into brain diseases based on mechanosensitive channels: Common mechanisms and clinical potential

BACKGROUND

As physical signals, mechanical cues regulate the neural cells in the brain. The mechanosensitive channels (MSCs) perceive the mechanical cues and transduce them by permeating specific ions or molecules across the plasma membrane, and finally trigger a series of intracellular bioelectrical and biochemical signals. Emerging evidence supports that wide-distributed, high-expressed MSCs like Piezo1 play important roles in several neurophysiological processes and neurological disorders.

AIMS

To systematically conclude the functions of MSCs in the brain and provide a novel mechanobiological perspective for brain diseases.

METHOD

We summarized the mechanical cues and MSCs detected in the brain and the research progress on the functional roles of MSCs in physiological conditions. We then concluded the pathological activation and downstream pathways triggered by MSCs in two categories of brain diseases, neurodegenerative diseases and place-occupying damages. Finally, we outlined the methods for manipulating MSCs and discussed their medical potential with some crucial outstanding issues.

RESULTS

The MSCs present underlying common mechanisms in different brain diseases by acting as the "transportation hubs" to transduce the distinct signal patterns: the upstream mechanical cues and the downstream intracellular pathways. Manipulating the MSCs is feasible to alter the complicated downstream processes, providing them promising targets for clinical treatment.

CONCLUSIONS

Recent research on MSCs provides a novel insight into brain diseases. The common mechanisms mediated by MSCs inspire a wide range of therapeutic potentials targeted on MSCs in different brain diseases.

Effects of mechanical ventilation on the interstitial extracellular matrix in healthy lungs and lungs affected by acute respiratory distress syndrome: a narrative review

BACKGROUND

Mechanical ventilation, a lifesaving intervention in critical care, can lead to damage in the extracellular matrix (ECM), triggering inflammation and ventilator-induced lung injury (VILI), particularly in conditions such as acute respiratory distress syndrome (ARDS). This review discusses the detailed structure of the ECM in healthy and ARDS-affected lungs under mechanical ventilation, aiming to bridge the gap between experimental insights and clinical practice by offering a thorough understanding of lung ECM organization and the dynamics of its alteration during mechanical ventilation.

MAIN TEXT

Focusing on the clinical implications, we explore the potential of precise interventions targeting the ECM and cellular signaling pathways to mitigate lung damage, reduce inflammation, and ultimately improve outcomes for critically ill patients. By analyzing a range of experimental studies and clinical papers, particular attention is paid to the roles of matrix metalloproteinases (MMPs), integrins, and other molecules in ECM damage and VILI. This synthesis not only sheds light on the structural changes induced by mechanical stress but also underscores the importance of cellular responses such as inflammation, fibrosis, and excessive activation of MMPs.

CONCLUSIONS

This review emphasizes the significance of mechanical cues transduced by integrins and their impact on cellular behavior during ventilation, offering insights into the complex interactions between mechanical ventilation, ECM damage, and cellular signaling. By understanding these mechanisms, healthcare professionals in critical care can anticipate the consequences of mechanical ventilation and use targeted strategies to prevent or minimize ECM damage, ultimately leading to better patient management and outcomes in critical care settings.

Unraveling the Dual-Stretch-Mode Impact on Tension Gauge Tethers' Mechanical Stability

Tension gauge tethers (TGTs), short DNA segments serving as extracellular tension sensors, are instrumental in assessing the tension dynamics in mechanotransduction. These TGTs feature an initial shear-stretch region and an unzip-stretch region. Despite their utility, no theoretical model has been available to estimate their tension-dependent lifetimes [τ(f)], restricting insights from cellular mechanotransduction experiments. We have now formulated a concise expression for τ(f) of TGTs, accommodating contributions from both stretch regions. Our model uncovers a tension-dependent energy barrier shift occurring when tension surpasses a switching force of approximately 13 pN for the recently developed TGTs, greatly influencing τ(f) profiles. Experimental data from several TGTs validated our model. The calibrated expression can predict τ(f) of TGTs at 37 °C based on their sequences with minor fold changes, supporting future applications of TGTs.

A helping hand: roles for accessory cells in the sense of touch across species

During touch, mechanical forces are converted into electrochemical signals by tactile organs made of neurons, accessory cells, and their shared extracellular spaces. Accessory cells, including Merkel cells, keratinocytes, lamellar cells, and glia, play an important role in the sensation of touch. In some cases, these cells are intrinsically mechanosensitive; however, other roles include the release of chemical messengers, the chemical modification of spaces that are shared with neurons, and the tuning of neural sensitivity by direct physical contact. Despite great progress in the last decade, the precise roles of these cells in the sense of touch remains unclear. Here we review the known and hypothesized contributions of several accessory cells to touch by incorporating research from multiple organisms including C. elegans, D. melanogaster, mammals, avian models, and plants. Several broad parallels are identified including the regulation of extracellular ions and the release of neuromodulators by accessory cells, as well as the emerging potential physical contact between accessory cells and sensory neurons via tethers. Our broader perspective incorporates the importance of accessory cells to the understanding of human touch and pain, as well as to animal touch and its molecular underpinnings, which are underrepresented among the animal welfare literature. A greater understanding of touch, which must include a role for accessory cells, is also relevant to emergent technical applications including prosthetics, virtual reality, and robotics.

The Role of Mechanotransduction in Contact Inhibition of Locomotion and Proliferation

Contact inhibition (CI) represents a crucial tumor-suppressive mechanism responsible for controlling the unbridled growth of cells, thus preventing the formation of cancerous tissues. CI can be further categorized into two distinct yet interrelated components: CI of locomotion (CIL) and CI of proliferation (CIP). These two components of CI have historically been viewed as separate processes, but emerging research suggests that they may be regulated by both distinct and shared pathways. Specifically, recent studies have indicated that both CIP and CIL utilize mechanotransduction pathways, a process that involves cells sensing and responding to mechanical forces. This review article describes the role of mechanotransduction in CI, shedding light on how mechanical forces regulate CIL and CIP. Emphasis is placed on filamin A (FLNA)-mediated mechanotransduction, elucidating how FLNA senses mechanical forces and translates them into crucial biochemical signals that regulate cell locomotion and proliferation. In addition to FLNA, trans-acting factors (TAFs), which are proteins or regulatory RNAs capable of directly or indirectly binding to specific DNA sequences in distant genes to regulate gene expression, emerge as sensitive players in both the mechanotransduction and signaling pathways of CI. This article presents methods for identifying these TAF proteins and profiling the associated changes in chromatin structure, offering valuable insights into CI and other biological functions mediated by mechanotransduction. Finally, it addresses unanswered research questions in these fields and delineates their possible future directions.

The extracellular matrix as hallmark of cancer and metastasis: From biomechanics to therapeutic targets

The extracellular matrix (ECM) is essential for cell support during homeostasis and plays a critical role in cancer. Although research often concentrates on the tumor's cellular aspect, attention is growing for the importance of the cancer-associated ECM. Biochemical and physical ECM signals affect tumor formation, invasion, metastasis, and therapy resistance. Examining the tumor microenvironment uncovers intricate ECM dysregulation and interactions with cancer and stromal cells. Anticancer therapies targeting ECM sensors and remodelers, including integrins and matrix metalloproteinases, and ECM-remodeling cells, have seen limited success. This review explores the ECM's role in cancer and discusses potential therapeutic strategies for cell-ECM interactions.

Genetically encoded mediators for sonogenetics and their applications in neuromodulation

Sonogenetics is an emerging approach that harnesses ultrasound for the manipulation of genetically modified cells. The great penetrability of ultrasound waves enables the non-invasive application of external stimuli to deep tissues, particularly advantageous for brain stimulation. Genetically encoded ultrasound mediators, a set of proteins that respond to ultrasound-induced bio-effects, play a critical role in determining the effectiveness and applications of sonogenetics. In this context, we will provide an overview of these ultrasound-responsive mediators, delve into the molecular mechanisms governing their response to ultrasound stimulation, and summarize their applications in neuromodulation.

Keratinocyte Piezo1 drives paclitaxel-induced mechanical hypersensitivity

Recent work demonstrates that epidermal keratinocytes are critical for normal touch sensation. However, it is unknown if keratinocytes contribute to touch evoked pain and hypersensitivity following tissue injury. Here, we used inhibitory optogenetic and chemogenetic techniques to determine the extent to which keratinocyte activity contributes to the severe neuropathic pain that accompanies chemotherapeutic treatment. We found that keratinocyte inhibition largely alleviates paclitaxel-induced mechanical hypersensitivity. Furthermore, we found that paclitaxel exposure sensitizes mouse and human keratinocytes to mechanical stimulation through the keratinocyte mechanotransducer Piezo1. These findings demonstrate the contribution of non-neuronal cutaneous cells to neuropathic pain and pave the way for the development of new pain-relief strategies that target epidermal keratinocytes and Piezo1.

Modulation of Piezo1 influences human skin architecture and oxytocin expression

OBJECTIVE

Throughout our existence, the skin senses and analyses the mechanical forces imposed by the environment. In response to these environmental forces, skin can deform itself and achieve a biological response. The subsequent cutaneous plasticity emerges from mechanical properties arising from the collective action of the skin cells, particularly keratinocytes, that govern the tensile strength via cell-to-cell adhesions and via cell-matrix adhesion structures. In addition to serving as force-bearing entities, keratinocytes respond to forces by activating signalling pathways to control their own fate and function. To detect and adapt to mechanical signals, keratinocytes possess a panel of sensory receptors and junctional intercellular structures. Mechanically activated ion channel Piezo1 has been described as a force sensor and as being involved in pleasant touch perception. In this study, relationships between Piezo1 modulation and oxytocin synthesis were investigated.

METHODS

The expression of Piezo1 in the skin was studied and compared with the expression of TRPV1. Dooku1 antagonist and Jedi1 agonist were used to modulate Piezo1. The level of E-cadherin and oxytocin was monitored in ex vivo skin biopsies by immunodetection.

RESULTS

Taken together, our results illustrate the major role of mechanosensitive ion channel Piezo1 in skin barrier integrity, and in peripheral oxytocin synthesis in the skin.

CONCLUSION

In conclusion, this study highlights the relationships between pleasant touch, soft touch and local oxytocin synthesis.

Sonomechanobiology: Vibrational stimulation of cells and its therapeutic implications

All cells possess an innate ability to respond to a range of mechanical stimuli through their complex internal machinery. This comprises various mechanosensory elements that detect these mechanical cues and diverse cytoskeletal structures that transmit the force to different parts of the cell, where they are transcribed into complex transcriptomic and signaling events that determine their response and fate. In contrast to static (or steady) mechanostimuli primarily involving constant-force loading such as compression, tension, and shear (or forces applied at very low oscillatory frequencies (≤ 1 Hz) that essentially render their effects quasi-static), dynamic mechanostimuli comprising more complex vibrational forms (e.g., time-dependent, i.e., periodic, forcing) at higher frequencies are less well understood in comparison. We review the mechanotransductive processes associated with such acoustic forcing, typically at ultrasonic frequencies (> 20 kHz), and discuss the various applications that arise from the cellular responses that are generated, particularly for regenerative therapeutics, such as exosome biogenesis, stem cell differentiation, and endothelial barrier modulation. Finally, we offer perspectives on the possible existence of a universal mechanism that is common across all forms of acoustically driven mechanostimuli that underscores the central role of the cell membrane as the key effector, and calcium as the dominant second messenger, in the mechanotransduction process.

Vascular mechanotransduction

This review aims to survey the current state of mechanotransduction in vascular smooth muscle cells (VSMCs) and endothelial cells (ECs), including their sensing of mechanical stimuli and transduction of mechanical signals that result in the acute functional modulation and longer-term transcriptomic and epigenetic regulation of blood vessels. The mechanosensors discussed include ion channels, plasma membrane-associated structures and receptors, and junction proteins. The mechanosignaling pathways presented include the cytoskeleton, integrins, extracellular matrix, and intracellular signaling molecules. These are followed by discussions on mechanical regulation of transcriptome and epigenetics, relevance of mechanotransduction to health and disease, and interactions between VSMCs and ECs. Throughout this review, we offer suggestions for specific topics that require further understanding. In the closing section on conclusions and perspectives, we summarize what is known and point out the need to treat the vasculature as a system, including not only VSMCs and ECs but also the extracellular matrix and other types of cells such as resident macrophages and pericytes, so that we can fully understand the physiology and pathophysiology of the blood vessel as a whole, thus enhancing the comprehension, diagnosis, treatment, and prevention of vascular diseases.

Novel imaging methods and force probes for molecular mechanobiology of cytoskeleton and adhesion

Detection and conversion of mechanical forces into biochemical signals is known as mechanotransduction. From cells to tissues, mechanotransduction regulates migration, proliferation, and differentiation in processes such as immune responses, development, and cancer progression. Mechanosensitive structures such as integrin adhesions, the actin cortex, ion channels, caveolae, and the nucleus sense and transmit forces. In vitro approaches showed that mechanosensing is based on force-dependent protein deformations and reorganizations. However, the mechanisms in cells remained unclear since cell imaging techniques lacked molecular resolution. Thanks to recent developments in super-resolution microscopy (SRM) and molecular force sensors, it is possible to obtain molecular insight of mechanosensing in live cells. We discuss how understanding of molecular mechanotransduction was revolutionized by these innovative approaches, focusing on integrin adhesions, actin structures, and the plasma membrane.

Mechanosensitive Ion Channels and Their Role in Cancer Cells

Mechanical forces are an inherent element in the world around us. The effects of their action can be observed both on the macro and molecular levels. They can also play a prominent role in the tissues and cells of animals due to the presence of mechanosensitive ion channels (MIChs) such as the Piezo and TRP families. They are essential in many physiological processes in the human body. However, their role in pathology has also been observed. Recent discoveries have highlighted the relationship between these channels and the development of malignant tumors. Multiple studies have shown that MIChs mediate the proliferation, migration, and invasion of various cancer cells via various mechanisms. This could show MIChs as new potential biomarkers in cancer detection and prognosis and interesting therapeutic targets in modern oncology. Our paper is a review of the latest literature on the role of the Piezo1 and TRP families in the molecular mechanisms of carcinogenesis in different types of cancer.

Activation of Mechanosensitive Ion Channels by Ultrasound

Mechanosensitive channels (MSCs) play an important role in how cells transduce mechanical stimuli into electrical or chemical signals, which provides an interventional possibility through the manipulation of ion channel activation using different mechanical stimulation conditions. With good spatial resolution and depth of penetration, ultrasound is often proposed as the tool of choice for such therapeutic applications. Despite the identification of many ion channels as mechanosensitive in recent years, only a limited number of MSCs have been reported to be activated by ultrasound with substantial evidence. Furthermore, although many therapeutic implications using ultrasound have been explored, few offered insights into the molecular basis and the biological effects induced by ultrasound in relieving pain and accelerate tissue healing. In this review, we examined the literature, in particular studies that provided evidence of cellular responses to ultrasound, with and without the target ion channels. The ultrasound activation conditions were then summarized for these ion channels, and these conditions were related to their mode of activation based on the current biological concepts. The overall goal is to bridge the results relating to the activation of MSCs that is specific for ultrasound with the current knowledge in molecular structure and the available physiological evidence that may have facilitated such phenomena. We discussed how collating the information revealed by available scientific investigations helps in the design of a more effective stimulus device for the proposed translational purposes. Traditionally, studies on the effects of ultrasound have focused largely on its mechanical and physical interaction with the targeted tissue through thermal-based therapies as well as non-thermal mechanisms including ultrasonic cavitation; gas body activation; the direct action of the compressional, tensile and shear stresses; radiation force; and acoustic streaming. However, the current review explores and attempts to establish whether the application of low-intensity ultrasound may be associated with the activation of specific MSCs, which in turn triggers relevant cell signaling as its molecular mechanism in achieving the desired therapeutic effects. Non-invasive brain stimulation has recently become an area of intense research interest for rehabilitation, and the implication of low-intensity ultrasound is particularly critical given the need to minimize heat generation to preserve tissue integrity for such applications.

Biochemical Pathways of Cellular Mechanosensing/Mechanotransduction and Their Role in Neurodegenerative Diseases Pathogenesis

In this review, we shed light on recent advances regarding the characterization of biochemical pathways of cellular mechanosensing and mechanotransduction with particular attention to their role in neurodegenerative disease pathogenesis. While the mechanistic components of these pathways are mostly uncovered today, the crosstalk between mechanical forces and soluble intracellular signaling is still not fully elucidated. Here, we recapitulate the general concepts of mechanobiology and the mechanisms that govern the mechanosensing and mechanotransduction processes, and we examine the crosstalk between mechanical stimuli and intracellular biochemical response, highlighting their effect on cellular organelles' homeostasis and dysfunction. In particular, we discuss the current knowledge about the translation of mechanosignaling into biochemical signaling, focusing on those diseases that encompass metabolic accumulation of mutant proteins and have as primary characteristics the formation of pathological intracellular aggregates, such as Alzheimer's Disease, Huntington's Disease, Amyotrophic Lateral Sclerosis and Parkinson's Disease. Overall, recent findings elucidate how mechanosensing and mechanotransduction pathways may be crucial to understand the pathogenic mechanisms underlying neurodegenerative diseases and emphasize the importance of these pathways for identifying potential therapeutic targets.