Piezo type mechanosensitive ion channel component 1 functions as a regulator of the cell fate determination of mesenchymal stem cells

Targeting micromotion for mimicking natural bone healing by using NIPAM/Nb2C hydrogel

Natural fracture healing is most efficient when the fine-tuned mechanical force and proper micromotion are applied. To mimick this micromotion at the fracture gap, a near-infrared-II (NIR-II)-activated hydrogel was fabricated by integrating two-dimensional (2D) monolayer Nb2C nanosheets into a thermally responsive poly(N-isopropylacrylamide) (NIPAM) hydrogel system. NIR-II-triggered deformation of the NIPAM/Nb2C hydrogel was designed to generate precise micromotion for co-culturing cells. It was validated that micromotion at 1/300 Hz, triggering a 2.37-fold change in the cell length/diameter ratio, is the most favorable condition for the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Moreover, mRNA sequencing and verification revealed that micromotion-induced augmentation was mediated by Piezo1 activation. Suppression of Piezo1 interrupts the mechano-sensitivity and abrogates osteogenic differentiation. Calvarial and femoral shaft defect models were established to explore the biocompatibility and osteoinductivity of the Micromotion Biomaterial. A series of research methods, including radiography, micro-CT scanning, and immunohistochemical staining have been performed to evaluate biosafety and osteogenic efficacy. The in vivo results revealed that tunable micromotion strengthens the natural fracture healing process through the sequential activation of endochondral ossification, promotion of neovascularization, initiation of mineral deposition, and combinatory acceleration of full-thickness osseous regeneration. This study demonstrated that Micromotion Biomaterials with controllable mechanophysical characteristics could promote the osteogenic differentiation of BMSCs and facilitate full osseous regeneration. The design of NIPAM/Nb2C hydrogel with highly efficient photothermal conversion, specific features of precisely controlled micromotion, and bionic-mimicking bone-repair capabilities could spark a new era in the field of regenerative medicine.

Osteogenic differentiation of bone mesenchymal stem cells on linearly aligned triangular micropatterns

Mesenchymal stem cells (MSCs) hold promise for regenerative medicine, particularly for bone tissue engineering. However, directing MSC differentiation towards specific lineages, such as osteogenic, while minimizing undesired phenotypes remains a challenge. Here, we investigate the influence of micropatterns on the behavior and lineage commitment of rat bone marrow-derived MSCs (rBMSCs), focusing on osteogenic differentiation. Linearly aligned triangular micropatterns (TPs) and circular micropatterns (CPs) coated with fibronectin were fabricated to study their effects on rBMSC morphology and differentiation and the underlying mechanobiological mechanisms. TPs, especially TP15 (15 μm), induced the cell elongation and thinning, while CPs also promoted the cell stretching, as evidenced by the decreased circularity and increased aspect ratio. TP15 significantly promoted osteogenic differentiation, with increased expression of osteogenic genes (Runx2, Spp1, Alpl, Bglap, Col1a1) and decreased expression of adipogenic genes (Pparg, Cebpa, Fabp4). Conversely, CPs inhibited both osteogenic and adipogenic differentiation. Mechanistically, TP15 increased Piezo1 activity, cytoskeletal remodeling including the aggregates of F-actin and myosin filaments at the cell periphery, YAP1 nuclear translocation, and integrin upregulation. Piezo1 inhibition suppressed the osteogenic genes expression, myosin remodeling, and YAP1 nuclear translocation, indicating Piezo1-mediated the mechanotransduction in rBMSCs on TPs. TP15 also induced osteogenic differentiation of BMSCs from aging rats, with upregulated Piezo1 and nuclear translocation of YAP1. Therefore, triangular micropatterns, particularly TP15, promote osteogenesis and inhibit adipogenesis of rBMSCs through Piezo1-mediated myosin and YAP1 pathways. Our study provides novel insights into the mechanobiological mechanisms governing MSC behaviors on micropatterns, offering new strategies for tissue engineering and regenerative medicine.

Piezo regulates epithelial topology and promotes precision in organ size control

Mechanosensitive Piezo channels regulate cell division, cell extrusion, and cell death. However, systems-level functions of Piezo in regulating organogenesis remain poorly understood. Here, we demonstrate that Piezo controls epithelial cell topology to ensure precise organ growth by integrating live-imaging experiments with pharmacological and genetic perturbations and computational modeling. Notably, the knockout or knockdown of Piezo increases bilateral asymmetry in wing size. Piezo's multifaceted functions can be deconstructed as either autonomous or non-autonomous based on a comparison between tissue-compartment-level perturbations or between genetic perturbation populations at the whole-tissue level. A computational model that posits cell proliferation and apoptosis regulation through modulation of the cutoff tension required for Piezo channel activation explains key cell and tissue phenotypes arising from perturbations of Piezo expression levels. Our findings demonstrate that Piezo promotes robustness in regulating epithelial topology and is necessary for precise organ size control.

Mechanoactivation of Single Stem Cells in Microgels Using a 3D-Printed Stimulation Device

In this study, the novel 3D-printed pressure chamber for encapsulated single-cell stimulation (3D-PRESS) platform is introduced for the mechanical stimulation of single stem cells in 3D microgels. The custom-designed 3D-PRESS, allows precise pressure application up to 400 kPa at the single-cell level. Microfluidics is employed to encapsulate single mesenchymal stem cells within ionically cross-linked alginate microgels with cell adhesion RGD peptides. Rigorous testing affirms the leak-proof performance of the 3D-PRESS device up to 400 kPa, which is fully biocompatible. 3D-PRESS is implemented on mesenchymal stem cells for mechanotransduction studies, by specifically targeting intracellular calcium signaling and the nuclear translocation of a mechanically sensitive transcription factor. Applying 200 kPa pressure on individually encapsulated stem cells reveals heightened calcium signaling in 3D microgels compared to conventional 2D culture. Similarly, Yes-associated protein (YAP) translocation into the nucleus occurs at 200 kPa in 3D microgels with cell-binding RGD peptides unveiling the involvement of integrin-mediated mechanotransduction in singly encapsulated stem cells in 3D microgels. Combining live-cell imaging with precise mechanical control, the 3D-PRESS platform emerges as a versatile tool for exploring cellular responses to pressure stimuli, applicable to various cell types, providing novel insights into single-cell mechanobiology.

Radial extracorporeal shockwave promotes osteogenesis-angiogenesis coupling of bone marrow stromal cells from senile osteoporosis via activating the Piezo1/CaMKII/CREB axis

Radial extracorporeal shockwave (r-ESW) and bone marrow stromal cells (BMSCs) have been reported to alleviate senile osteoporosis (SOP), but its regulatory mechanism remains unclear. In this study, we firstly isolated human BMSCs from bone marrow samples and treated with varying r-ESW doses. And we found that r-ESW could enhance the proliferation of SOP-BMSCs in a dose-dependent manner by EdU assay. Subsequently, the impact of r-ESW on the proliferation, apoptosis and multipotency of BMSCs was assessed. And the outcomes of flow cytometry, Alizarin red S (ARS), and tube formation test demonstrated that the optimal shockwave obviously boosted SOP-BMSCs osteogenesis and angiogenesis but exhibited no significant impact on cell apoptosis. Additionally, the signaling of Piezo1 and CaMKII/CREB was examined by Western blotting, qPCR and immunofluorescence. And the results showed that r-ESW promoted the expression of Piezo1, increased intracellular Ca2+ and activated the CaMKII/CREB signaling pathway. Then, the application of Piezo1 siRNA hindered the r-ESW-induced enhancement ability of osteogenesis coupling with angiogenesis of SOP-BMSCs. The use of the CaMKII/CREB signaling pathway inhibitor KN93 suppressed the Piezo1-induced increase in osteogenesis and angiogenesis in SOP-BMSCs. Finally, we also found that r-ESW might alleviate SOP in the senescence-accelerated mouse prone 6 (SAMP6) model by activating Piezo1. In conclusion, our research offers experimental evidence and an elucidated underlying molecular mechanism to support the use of r-ESW as a credible rehabilitative treatment for senile osteoporosis.

Yoda1 pretreated BMSC derived exosomes accelerate osteogenesis by activating phospho-ErK signaling via Yoda1-mediated signal transmission

Segmental bone defects, arising from factors such as trauma, tumor resection, and congenital malformations, present significant clinical challenges that often necessitate complex reconstruction strategies. Hydrogels loaded with multiple osteogenesis-promoting components have emerged as promising tools for bone defect repair. While the osteogenic potential of the Piezo1 agonist Yoda1 has been demonstrated previously, its hydrophobic nature poses challenges for effective loading onto hydrogel matrices.In this study, we address this challenge by employing Yoda1-pretreated bone marrow-derived mesenchymal stem cell (BMSCs) exosomes (Exo-Yoda1) alongside exosomes derived from BMSCs (Exo-MSC). Comparatively, Exo-Yoda1-treated BMSCs exhibited enhanced osteogenic capabilities compared to both control groups and Exo-MSC-treated counterparts. Notably, Exo-Yoda1-treated cells demonstrated similar functionality to Yoda1 itself. Transcriptome analysis revealed activation of osteogenesis-associated signaling pathways, indicating the potential transduction of Yoda1-mediated signals such as ErK, a finding validated in this study. Furthermore, we successfully integrated Exo-Yoda1 into gelatin methacryloyl (GelMA)/methacrylated sodium alginate (SAMA)/β-tricalcium phosphate (β-TCP) hydrogels. These Exo-Yoda1-loaded hydrogels demonstrated augmented osteogenesis in subcutaneous ectopic osteogenesis nude mice models and in rat skull bone defect model. In conclusion, our study introduces Exo-Yoda1-loaded GELMA/SAMA/β-TCP hydrogels as a promising approach to promoting osteogenesis. This innovative strategy holds significant promise for future widespread clinical applications in the realm of bone defect reconstruction.

Nanoporous Titanium Implant Surface Accelerates Osteogenesis via the Piezo1/Acetyl-CoA/β-Catenin Pathway

Osseointegration is the most important factor determining implant success. The surface modification of TiO2 nanotubes prepared by anodic oxidation has remarkable advantages in promoting bone formation. However, the mechanism behind this phenomenon is still unintelligible. Here we show that the nanomorphology exhibited open and clean nanotube structure and strong hydrophilicity, and the nanomorphology significantly facilitated the adhesion, proliferation, and osteogenesis differentiation of stem cells. Exploring the mechanism, we found that the nanomorphology can enhance mitochondrial oxidative phosphorylation (OxPhos) by activating Piezo1 and increasing intracellular Ca2+. The increase in OxPhos can significantly uplift the level of acetyl-CoA in the cytoplasm but not significantly raise the level of acetyl-CoA in the nucleus, which was beneficial for the acetylation and stability of β-catenin and ultimately promoted osteogenesis. This study provides a new interpretation for the regulatory mechanism of stem cell osteogenesis by nanomorphology.

Regulation and mechanistic insights into tensile strain in mesenchymal stem cell osteogenic differentiation

Bone marrow mesenchymal stem cells (BMSCs) are integral to bone remodeling and homeostasis, as they are capable of differentiating into osteogenic and adipogenic lineages. This differentiation is substantially influenced by mechanosensitivity, particularly to tensile strain, which is a prevalent mechanical stimulus known to enhance osteogenic differentiation. This review specifically examines the effects of various cyclic tensile stress (CTS) conditions on BMSC osteogenesis. It delves into the effects of different loading devices, magnitudes, frequencies, elongation levels, dimensionalities, and coculture conditions, providing a comparative analysis that aids identification of the most conducive parameters for the osteogenic differentiation of BMSCs. Subsequently, this review delineates the signaling pathways activated by CTS, such as Wnt/β-catenin, BMP, Notch, MAPK, PI3K/Akt, and Hedgehog, which are instrumental in mediating the osteogenic differentiation of BMSCs. Through a detailed examination of these pathways, this study elucidates the intricate mechanisms whereby tensile strain promotes osteogenic differentiation, offering valuable guidance for optimizing therapeutic strategies aimed at enhancing bone regeneration.

The role of the Piezo1 channel in osteoblasts under cyclic stretching: A study on osteogenic and osteoclast factors

OBJECTIVES

Orthodontic tooth movement is a mechanobiological reaction induced by appropriate forces, including bone remodeling. The mechanosensitive Piezo channels have been shown to contribute to bone remodeling. However, information about the pathways through which Piezo channels affects osteoblasts remains limited. Thus, we aimed to investigate the influence of Piezo1 on the osteogenic and osteoclast factors in osteoblasts under mechanical load.

MATERIALS AND METHODS

Cyclic stretch (CS) experiments on MC3T3-E1 were conducted using a BioDynamic mechanical stretching device. The Piezo1 channel blocker GsMTx4 and the Piezo1 channel agonist Yoda1 were used 12 h before the application of CS. MC3T3-E1 cells were then subjected to 15% CS, and the expression of Piezo1, Piezo2, BMP-2, OCN, Runx2, RANKL, p-p65/p65, and ALP was measured using quantitative real-time polymerase chain reaction, western blot, alkaline phosphatase staining, and immunofluorescence staining.

RESULTS

CS of 15% induced the highest expression of Piezo channel and osteoblast factors. Yoda1 significantly increased the CS-upregulated expression of Piezo1 and ALP activity but not Piezo2 and RANKL. GsMTx4 downregulated the CS-upregulated expression of Piezo1, Piezo2, Runx2, OCN, p-65/65, and ALP activity but could not completely reduce CS-upregulated BMP-2.

CONCLUSIONS

The appropriate force is more suitable for promoting osteogenic differentiation in MC3T3-E1. The Piezo1 channel participates in osteogenic differentiation of osteoblasts through its influence on the expression of osteogenic factors like BMP-2, Runx2, and OCN and is involved in regulating osteoclasts by influencing phosphorylated p65. These results provide a foundation for further exploration of osteoblast function in orthodontic tooth movement.

The emerging role of Piezo1 in the musculoskeletal system and disease

Piezo1, a mechanosensitive ion channel, has emerged as a key player in translating mechanical stimuli into biological signaling. Its involvement extends beyond physiological and pathological processes such as lymphatic vessel development, axon growth, vascular development, immunoregulation, and blood pressure regulation. The musculoskeletal system, responsible for structural support, movement, and homeostasis, has recently attracted attention regarding the significance of Piezo1. This review aims to provide a comprehensive summary of the current research on Piezo1 in the musculoskeletal system, highlighting its impact on bone formation, myogenesis, chondrogenesis, intervertebral disc homeostasis, tendon matrix cross-linking, and physical activity. Additionally, we explore the potential of targeting Piezo1 as a therapeutic approach for musculoskeletal disorders, including osteoporosis, muscle atrophy, intervertebral disc degeneration, and osteoarthritis.

Impact of mechanical cues on key cell functions and cell-nanoparticle interactions

In recent years, it has been recognized that mechanical forces play an important regulative role in living organisms and possess a direct impact on crucial cell functions, ranging from cell growth to maintenance of tissue homeostasis. Advancements in mechanobiology have revealed the profound impact of mechanical signals on diverse cellular responses that are cell type specific. Notably, numerous studies have elucidated the pivotal role of different mechanical cues as regulatory factors influencing various cellular processes, including cell spreading, locomotion, differentiation, and proliferation. Given these insights, it is unsurprising that the responses of cells regulated by physical forces are intricately linked to the modulation of nanoparticle uptake kinetics and processing. This complex interplay underscores the significance of understanding the mechanical microenvironment in shaping cellular behaviors and, consequently, influencing how cells interact with and process nanoparticles. Nevertheless, our knowledge on how localized physical forces affect the internalization and processing of nanoparticles by cells remains rather limited. A significant gap exists in the literature concerning a systematic analysis of how mechanical cues might bias the interactions between nanoparticles and cells. Hence, our aim in this review is to provide a comprehensive and critical analysis of the existing knowledge regarding the influence of mechanical cues on the complicated dynamics of cell-nanoparticle interactions. By addressing this gap, we would like to contribute to a detailed understanding of the role that mechanical forces play in shaping the complex interplay between cells and nanoparticles.

Dentin Mechanobiology: Bridging the Gap between Architecture and Function

It is remarkable how teeth maintain their healthy condition under exceptionally high levels of mechanical loading. This suggests the presence of inherent mechanical adaptation mechanisms within their structure to counter constant stress. Dentin, situated between enamel and pulp, plays a crucial role in mechanically supporting tooth function. Its intermediate stiffness and viscoelastic properties, attributed to its mineralized, nanofibrous extracellular matrix, provide flexibility, strength, and rigidity, enabling it to withstand mechanical loading without fracturing. Moreover, dentin's unique architectural features, such as odontoblast processes within dentinal tubules and spatial compartmentalization between odontoblasts in dentin and sensory neurons in pulp, contribute to a distinctive sensory perception of external stimuli while acting as a defensive barrier for the dentin-pulp complex. Since dentin's architecture governs its functions in nociception and repair in response to mechanical stimuli, understanding dentin mechanobiology is crucial for developing treatments for pain management in dentin-associated diseases and dentin-pulp regeneration. This review discusses how dentin's physical features regulate mechano-sensing, focusing on mechano-sensitive ion channels. Additionally, we explore advanced in vitro platforms that mimic dentin's physical features, providing deeper insights into fundamental mechanobiological phenomena and laying the groundwork for effective mechano-therapeutic strategies for dentinal diseases.

Mechanical strain regulates osteogenesis via Antxr1/LncRNA H19/Wnt/β-catenin axis

Alleviating bone loss is an essential way to prevent osteoporotic fractures. Proper exercise improves bone density without the side effects of long-term medications, but the mechanism is unclear. Our study explored the role of Antxr1/LncRNA H19/Wnt/β-catenin axis in the process of exercise-mediated alleviation of bone loss. Here we discovered that moderate-intensity treadmill exercise alleviates bone loss caused by ovariectomy and ameliorates bone strength accompanied by an increased lncRNA H19 expression. Concomitantly, Antxr1, a mechanosensitive protein was found downregulated by exercise but upregulated by ovariectomy. Interestingly, knockdown expression of Antxr1 increased lncRNA H19 expression and Wnt/β-catenin signaling pathway in bone marrow mesenchymal stem cells, whereas overexpression of Antxr1 decreased lncRNA H19 expression and Wnt/β-catenin signaling pathway. Hence, our study demonstrates the regulation of Antxr1/LncRNA H19/Wnt/β-catenin axis in the process of mechanical strain-induced osteogenic differentiation, which provides further mechanistic insight into the role of mechanical regulation in bone metabolism.

Low-intensity pulsed ultrasound promotes the osteogenesis of mechanical force-treated periodontal ligament cells via Piezo1

Background

Low-intensity pulsed ultrasound (LIPUS) can accelerate tooth movement and preserve tooth and bone integrity during orthodontic treatment. However, the mechanisms by which LIPUS affects tissue remodeling during orthodontic tooth movement (OTM) remain unclear. Periodontal ligament cells (PDLCs) are pivotal in maintaining periodontal tissue equilibrium when subjected to mechanical stimuli. One notable mechano-sensitive ion channel, Piezo1, can modulate cellular function in response to mechanical cues. This study aimed to elucidate the involvement of Piezo1 in the osteogenic response of force-treated PDLCs when stimulated by LIPUS.

Method

After establishing rat OTM models, LIPUS was used to stimulate rats locally. OTM distance and alveolar bone density were assessed using micro-computed tomography, and histological analyses included hematoxylin and eosin staining, tartrate-resistant acid phosphatase staining and immunohistochemical staining. GsMTx4 and Yoda1 were respectively utilized for Piezo1 functional inhibition and activation experiments in rats. We isolated human PDLCs (hPDLCs) in vitro and evaluated the effects of LIPUS on the osteogenic differentiation of force-treated hPDLCs using real-time quantitative PCR, Western blot, alkaline phosphatase and alizarin red staining. Small interfering RNA and Yoda1 were employed to validate the role of Piezo1 in this process.

Results

LIPUS promoted osteoclast differentiation and accelerated OTM in rats. Furthermore, LIPUS alleviated alveolar bone resorption under pressure and enhanced osteogenesis of force-treated PDLCs both in vivo and in vitro by downregulating Piezo1 expression. Subsequent administration of GsMTx4 in rats and siPIEZO1 transfection in hPDLCs attenuated the inhibitory effect on osteogenic differentiation under pressure, whereas LIPUS efficacy was partially mitigated. Yoda1 treatment inhibited osteogenic differentiation of hPDLCs, resulting in reduced expression of Collagen Ⅰα1 and osteocalcin in the periodontal ligament. However, LIPUS administration was able to counteract these effects.

Conclusion

This research unveils that LIPUS promotes the osteogenesis of force-treated PDLCs via downregulating Piezo1.

Research progress on the regulatory mechanism of integrin-mediated mechanical stress in cells involved in bone metabolism

Mechanical stress is an internal force between various parts of an object that resists external factors and effects that cause an object to deform, and mechanical stress is essential for various tissues that are constantly subjected to mechanical loads to function normally. Integrins are a class of transmembrane heterodimeric glycoprotein receptors that are important target proteins for the action of mechanical stress stimuli on cells and can convert extracellular physical and mechanical signals into intracellular bioelectrical signals, thereby regulating osteogenesis and osteolysis. Integrins play a bidirectional regulatory role in bone metabolism. In this paper, relevant literature published in recent years is reviewed and summarized. The characteristics of integrins and mechanical stress are introduced, as well as the mechanisms underlying responses of integrin to mechanical stress stimulation. The paper focuses on integrin-mediated mechanical stress in different cells involved in bone metabolism and its associated signalling mechanisms. The purpose of this review is to provide a theoretical basis for the application of integrin-mediated mechanical stress to the field of bone tissue repair and regeneration.

Analysis of pressure-activated Piezo1 open and subconductance states at a single channel level

Mechanically activated Piezo1 channels undergo transitions from closed to open-state in response to pressure and other mechanical stimuli. However, the molecular details of these mechanosensitive gating transitions are unknown. Here, we used cell-attached pressure-clamp recordings to acquire single channel data at steady-state conditions (where inactivation has settled down), at various pressures and voltages. Importantly, we identify and analyze subconductance states of the channel which were not reported before. Pressure-dependent activation of Piezo1 increases the occupancy of open and subconductance state at the expense of decreased occupancy of shut-states. No significant change in the mean open time of subconductance states was observed with increasing negative pipette pressure or with varying voltages (ranging from -40 to -100 mV). Using Markov-chain modeling, we identified a minimal four-states kinetic scheme, which recapitulates essential characteristics of the single channel data, including that of the subconductance level. This study advances our understanding of Piezo1-gating mechanism in response to discrete stimuli (such as pressure and voltage) and paves the path to develop cellular and tissue level models to predict Piezo1 function in various cell types.

Piezo1 contributes to alveolar bone remodeling by activating β-catenin under compressive stress

INTRODUCTION

The mechanosensitive ion channel, Piezo1, is responsible for transducing mechanical stimuli into intracellular biochemical signals and has been identified within periodontal ligament cells (PDLCs). Nonetheless, the precise biologic function of Piezo1 in the regulation of alveolar bone remodeling by PDLCs during compressive forces remains unclear. Therefore, this study focused on elucidating the role of the Piezo1 channel in alveolar bone remodeling and uncovering its underlying mechanisms.

METHODS

PDLCs were subjected to compressive force and Piezo1 inhibitors. Piezo1 and β-catenin expressions were quantified by quantitative reverse transcription polymerase chain reaction and Western blot. The intracellular calcium concentration was measured using Fluo-8 AM staining. The osteogenic and osteoclastic activities were assessed using alkaline phosphatase staining, enzyme-linked immunosorbent assay, quantitative reverse transcription polymerase chain reaction, and Western blot. In vivo, orthodontic tooth movement was used to determine the effects of Piezo1 on alveolar bone remodeling.

RESULTS

Piezo1 and activated β-catenin expressions were upregulated under compressive force. Piezo1 inhibition reduced β-catenin activation, osteogenic differentiation, and osteoclastic activities. β-catenin knockdown reversed the increased osteogenic differentiation but had little impact on osteoclastic activities. In vivo, Piezo1 inhibition led to decreased tooth movement distance, accompanied by reduced β-catenin activation and expression of osteogenic and osteoclastic markers on the compression side.

CONCLUSIONS

The Piezo1 channel is a key mechanotransduction component of PDLCs that senses compressive force and activates β-catenin to regulate alveolar bone remodeling.

Fibrosis-on-Chip: A Guide to Recapitulate the Essential Features of Fibrotic Disease

Fibrosis, which is primarily marked by excessive extracellular matrix (ECM) deposition, is a pathophysiological process associated with many disorders, which ultimately leads to organ dysfunction and poor patient outcomes. Despite the high prevalence of fibrosis, currently there exist few therapeutic options, and importantly, there is a paucity of in vitro models to accurately study fibrosis. This review discusses the multifaceted nature of fibrosis from the viewpoint of developing organ-on-chip (OoC) disease models, focusing on five key features: the ECM component, inflammation, mechanical cues, hypoxia, and vascularization. The potential of OoC technology is explored for better modeling these features in the context of studying fibrotic diseases and the interplay between various key features is emphasized. This paper reviews how organ-specific fibrotic diseases are modeled in OoC platforms, which elements are included in these existing models, and the avenues for novel research directions are highlighted. Finally, this review concludes with a perspective on how to address the current gap with respect to the inclusion of multiple features to yield more sophisticated and relevant models of fibrotic diseases in an OoC format.

Interaction between immuno-stem dual lineages in jaw bone formation and injury repair

The jawbone, a unique structure in the human body, undergoes faster remodeling than other bones due to the presence of stem cells and its distinct immune microenvironment. Long-term exposure of jawbones to an oral environment rich in microbes results in a complex immune balance, as shown by the higher proportion of activated macrophage in the jaw. Stem cells derived from the jawbone have a higher propensity to differentiate into osteoblasts than those derived from other bones. The unique immune microenvironment of the jaw also promotes osteogenic differentiation of jaw stem cells. Here, we summarize the various types of stem cells and immune cells involved in jawbone reconstruction. We describe the mechanism relationship between immune cells and stem cells, including through the production of inflammatory bodies, secretion of cytokines, activation of signaling pathways, etc. In addition, we also comb out cellular interaction of immune cells and stem cells within the jaw under jaw development, homeostasis maintenance and pathological conditions. This review aims to eclucidate the uniqueness of jawbone in the context of stem cell within immune microenvironment, hopefully advancing clinical regeneration of the jawbone.

Newly identified roles for PIEZO1 mechanosensor in controlling normal megakaryocyte development and in primary myelofibrosis

Mechanisms through which mature megakaryocytes (Mks) and their progenitors sense the bone marrow extracellular matrix to promote lineage differentiation in health and disease are still partially understood. We found PIEZO1, a mechanosensitive cation channel, to be expressed in mouse and human Mks. Human mutations in PIEZO1 have been described to be associated with blood cell disorders. Yet, a role for PIEZO1 in megakaryopoiesis and proplatelet formation has never been investigated. Here, we show that activation of PIEZO1 increases the number of immature Mks in mice, while the number of mature Mks and Mk ploidy level are reduced. Piezo1/2 knockout mice show an increase in Mk size and platelet count, both at basal state and upon marrow regeneration. Similarly, in human samples, PIEZO1 is expressed during megakaryopoiesis. Its activation reduces Mk size, ploidy, maturation, and proplatelet extension. Resulting effects of PIEZO1 activation on Mks resemble the profile in Primary Myelofibrosis (PMF). Intriguingly, Mks derived from Jak2V617F PMF mice show significantly elevated PIEZO1 expression, compared to wild-type controls. Accordingly, Mks isolated from bone marrow aspirates of JAK2V617F PMF patients show increased PIEZO1 expression compared to Essential Thrombocythemia. Most importantly, PIEZO1 expression in bone marrow Mks is inversely correlated with patient platelet count. The ploidy, maturation, and proplatelet formation of Mks from JAK2V617F PMF patients are rescued upon PIEZO1 inhibition. Together, our data suggest that PIEZO1 places a brake on Mk maturation and platelet formation in physiology, and its upregulation in PMF Mks might contribute to aggravating some hallmarks of the disease.

Nociceptor mechanisms underlying pain and bone remodeling via orthodontic forces: toward no pain, big gain

Orthodontic forces are strongly associated with pain, the primary complaint among patients wearing orthodontic braces. Compared to other side effects of orthodontic treatment, orthodontic pain is often overlooked, with limited clinical management. Orthodontic forces lead to inflammatory responses in the periodontium, which triggers bone remodeling and eventually induces tooth movement. Mechanical forces and subsequent inflammation in the periodontium activate and sensitize periodontal nociceptors and produce orthodontic pain. Nociceptive afferents expressing transient receptor potential vanilloid subtype 1 (TRPV1) play central roles in transducing nociceptive signals, leading to transcriptional changes in the trigeminal ganglia. Nociceptive molecules, such as TRPV1, transient receptor potential ankyrin subtype 1, acid-sensing ion channel 3, and the P2X3 receptor, are believed to mediate orthodontic pain. Neuropeptides such as calcitonin gene-related peptides and substance P can also regulate orthodontic pain. While periodontal nociceptors transmit nociceptive signals to the brain, they are also known to modulate alveolar bone remodeling in periodontitis. Therefore, periodontal nociceptors and nociceptive molecules may contribute to the modulation of orthodontic tooth movement, which currently remains undetermined. Future studies are needed to better understand the fundamental mechanisms underlying neuroskeletal interactions in orthodontics to improve orthodontic treatment by developing novel methods to reduce pain and accelerate orthodontic tooth movement-thereby achieving "big gains with no pain" in clinical orthodontics.

Mechanobiology of Dental Pulp Cells

The dental pulp is the inner part of the tooth responsible for properly functioning during its lifespan. Apart from the very big biological heterogeneity of dental cells, tooth microenvironments differ a lot in the context of mechanical properties-ranging from 5.5 kPa for dental pulp to around 100 GPa for dentin and enamel. This physical heterogeneity and complexity plays a key role in tooth physiology and in turn, is a great target for a variety of therapeutic approaches. First of all, physical mechanisms are crucial for the pain propagation process from the tooth surface to the nerves inside the dental pulp. On the other hand, the modulation of the physical environment affects the functioning of dental pulp cells and thus is important for regenerative medicine. In the present review, we describe the physiological significance of biomechanical processes in the physiology and pathology of dental pulp. Moreover, we couple those phenomena with recent advances in the fields of bioengineering and pharmacology aiming to control the functioning of dental pulp cells, reduce pain, and enhance the differentiation of dental cells into desired lineages. The reviewed literature shows great progress in the topic of bioengineering of dental pulp-although mainly in vitro. Apart from a few positions, it leaves a gap for necessary filling with studies providing the mechanisms of the mechanical control of dental pulp functioning in vivo.

[Role of Piezo mechanosensitive ion channels in the osteoarticular system]

Objective

To summarize the role of Piezo mechanosensitive ion channels in the osteoarticular system, in order to provide reference for subsequent research.

Methods

Extensive literature review was conducted to summarize the structural characteristics, gating mechanisms, activators and blockers of Piezo ion channels, as well as their roles in the osteoarticular systems.

Results

The osteoarticular system is the main load-bearing and motor tissue of the body, and its ability to perceive and respond to mechanical stimuli is one of the guarantees for maintaining normal physiological functions of bones and joints. The occurrence and development of many osteoarticular diseases are closely related to abnormal mechanical loads. At present, research shows that Piezo mechanosensitive ion channels differentiate towards osteogenesis by responding to stretching stimuli and regulating cellular Ca 2+ influx signals; and it affects the proliferation and migration of osteoblasts, maintaining bone homeostasis through cellular communication between osteoblasts-osteoclasts. Meanwhile, Piezo1 protein can indirectly participate in regulating the formation and activity of osteoclasts through its host cells, thereby regulating the process of bone remodeling. During mechanical stimulation, the Piezo1 ion channel maintains bone homeostasis by regulating the expressions of Akt and Wnt1 signaling pathways. The sensitivity of Piezo1/2 ion channels to high strain mechanical signals, as well as the increased sensitivity of Piezo1 ion channels to mechanical transduction mediated by Ca 2+ influx and inflammatory signals in chondrocytes, is expected to become a new entry point for targeted prevention and treatment of osteoarthritis. But the specific way mechanical stimuli regulate the physiological/pathological processes of bones and joints still needs to be clarified.

Conclusion

Piezo mechanosensitive ion channels give the osteoarticular system with important abilities to perceive and respond to mechanical stress, playing a crucial mechanical sensing role in its cellular fate, bone development, and maintenance of bone and cartilage homeostasis.

The role of mechanically sensitive ion channel Piezo1 in bone remodeling

Piezo1 (2010) was identified as a mechanically activated cation channel capable of sensing various physical forces, such as tension, osmotic pressure, and shear force. Piezo1 mediates mechanosensory transduction in different organs and tissues, including its role in maintaining bone homeostasis. This review aimed to summarize the function and possible mechanism of Piezo1 in the mechanical receptor cells in bone tissue. We found that it is a potential therapeutic target for the treatment of bone diseases.

Piezo channels in the intestinal tract

The intestine is the largest mechanosensitive organ in the human body whose epithelial cells, smooth muscle cells, neurons and enteroendocrine cells must sense and respond to various mechanical stimuli such as motility, distension, stretch and shear to regulate physiological processes including digestion, absorption, secretion, motility and immunity. Piezo channels are a newly discovered class of mechanosensitive ion channels consisting of two subtypes, Piezo1 and Piezo2. Piezo channels are widely expressed in the intestine and are involved in physiological and pathological processes. The present review summarizes the current research progress on the expression, function and regulation of Piezo channels in the intestine, with the aim of providing a reference for the future development of therapeutic strategies targeting Piezo channels.

Piezo Mediates the Mechanosensation and Injury-Repair of Pulpo-Dentinal Complex

OBJECTIVES

The aim of this research was to investigate the functions of Piezo channels in dentin defect, including mechanical signalling and odontoblast responses.

METHODS

Rat dentin-defect models were constructed, and spatiotemporal expression of Piezo proteins was detected in the pulpo-dentinal complex. Real-time polymerase chain reaction (rtPCR) was used to investigate the functional expression pattern of Piezo channels in odontoblasts. Moreover, RNA interference technology was employed to uncover the underlying mechanisms of the Piezo-driven inflammatory response and repair under fluid shear stress (FSS) conditions in vitro.

RESULTS

Piezo1 and Piezo2 were found to be widely expressed in the odontoblast layer and dental pulp in the rat dentin-defect model during the end stage of reparative dentin formation. The expression levels of the Piezo1 and Piezo2 genes in MDPC-23 cells were high in the initial stage under FSS loading and then decreased over time. Moreover, the expression trends of inflammatory, odontogenic, and mineralisation genes were generally contrary to those of Piezo1 and Piezo2 over time. After silencing of Piezo1/Piezo2, FSS stimulation resulted in significantly higher expression of inflammatory, odontogenesis, and mineralisation genes in MDPC-23 cells. Finally, the expression of genes involved in the integrin β1/ERK1 and Wnt5b/β-catenin signalling pathways was changed in response to RNA silencing of Piezo1 and Piezo2.

CONCLUSIONS

Piezo1 and Piezo2 may be involved in regulating the expression of inflammatory and odontogenic genes in odontoblasts stimulated by FSS.

Biomaterials regulates BMSCs differentiation via mechanical microenvironment

Bone mesenchymal stem cells (BMSCs) are crucial for bone tissue regeneration, the mechanical microenvironment of hard tissues, including bone and teeth, significantly affects the osteogenic differentiation of BMSCs. Biomaterials may mimic the microenvironment of the extracellular matrix and provide mechanical signals to regulate BMSCs differentiation via inducing the secretion of various intracellular factors. Biomaterials direct the differentiation of BMSCs via mechanical signals, including tension, compression, shear, hydrostatic pressure, stiffness, elasticity, and viscoelasticity, which can be transmitted to cells through mechanical signalling pathways. Besides, biomaterials with piezoelectric effects regulate BMSCs differentiation via indirect mechanical signals, such as, electronic signals, which are transformed from mechanical stimuli by piezoelectric biomaterials. Mechanical stimulation facilitates achieving vectored stem cell fate regulation, while understanding the underlying mechanisms remains challenging. Herein, this review summarizes the intracellular factors, including translation factors, epigenetic modifications, and miRNA level, as well as the extracellular factor, including direct and indirect mechanical signals, which regulate the osteogenic differentiation of BMSCs. Besides, this review will also give a comprehensive summary about how mechanical stimuli regulate cellular behaviours, as well as how biomaterials promote the osteogenic differentiation of BMSCs via mechanical microenvironments. The cellular behaviours and activated signal pathways will give more implications for the design of biomaterials with superior properties for bone tissue engineering. Moreover, it will also provide inspiration for the construction of bone organoids which is a useful tool for mimicking in vivo bone tissue microenvironments.

Mechanical Unloading Promotes Osteoclastic Differentiation and Bone Resorption by Modulating the MSC Secretome to Favor Inflammation

Aging, space flight, and prolonged bed rest have all been linked to bone loss, and no effective treatments are clinically available at present. Here, with the rodent hindlimb unloading (HU) model, we report that the bone marrow (BM) microenvironment was significantly altered, with an increased number of myeloid cells and elevated inflammatory cytokines. In such inflammatory BM, the osteoclast-mediated bone resorption was greatly enhanced, leading to a shifted bone remodeling balance that ultimately ends up with disuse-induced osteoporosis. Using Piezo1 conditional knockout (KO) mice (Piezo1fl/fl;LepRCre), we proved that lack of mechanical stimuli on LepR+ mesenchymal stem cells (MSCs) is the main reason for the pathological BM inflammation. Mechanically, the secretome of MSCs was regulated by mechanical stimuli. Inadequate mechanical load leads to increased production of inflammatory cytokines, such as interleukin (IL)-1α, IL-6, macrophage colony-stimulating factor 1 (M-CSF-1), and so on, which promotes monocyte proliferation and osteoclastic differentiation. Interestingly, transplantation of 10% cyclic mechanical stretch (CMS)-treated MSCs into HU animals significantly alleviated the BM microenvironment and rebalanced bone remodeling. In summary, our research revealed a new mechanism underlying mechanical unloading-induced bone loss and suggested a novel stem cell-based therapy to potentially prevent disuse-induced osteoporosis.

Remote Activation of Mechanotransduction via Integrin Alpha-5 via Aptamer-Conjugated Magnetic Nanoparticles Promotes Osteogenesis

Bone regeneration and repair are complex processes in the adult skeleton, and current research has focused on understanding and controlling these processes. Magnetic nanoparticle (MNP)-based platforms have shown potential in tissue engineering and regenerative medicine through the use of magnetic nanomaterials combined with remotely applied dynamic fields. Previous studies have demonstrated the ability of MNP-induced mechanoactivation to trigger downstream signaling and promote new bone formation. In this study, we aimed to compare the osteogenic induction achieved using the mechanoreceptor targets, Piezo1, Fzd1, Fzd2, and integrin alpha-5. We compared the binding efficacy of different types of agonists (antibodies vs. aptamers) to these receptors. Moreover, we optimized the aptamer concentration (2.5, 5, and 10 μg/mg) for the selected receptor to determine the optimum concentration for promoting bone formation. Our data demonstrated that the mechanoactivation of integrins (CD49e) significantly upregulated the RUNX2 and LEF1 genes compared to other selected receptors. Furthermore, comparing the mechanoactivation of cells using MNPs conjugated with CD49e antibodies and aptamers revealed that MNP-aptamers significantly enhanced the upregulation of LEF1 genes. This suggests that aptamer-mediated mechanoactivation is a promising alternative to antibody-mediated activation. Finally, our results showed that the concentration of the aptamer loaded onto the MNPs strongly influenced the mechanoactivation of the cells. These findings provide valuable insights into the use of MNP platforms for bone regeneration and highlight the potential of aptamers in promoting signaling pathways related to bone formation. The novelty of our study lies in elucidating the unique advantages of aptamers in mediating mechanoactivation, presenting a promising avenue for advancing bone regenerative strategies.

Magnetic Aggregation-Induced Bone-Targeting Nanocarrier with Effects of Piezo1 Activation and Osteogenic-Angiogenic Coupling for Osteoporotic Bone Repair

Osteoporosis, characterized by an imbalance in bone homeostasis, is a global health concern. Bone defects are difficult to heal in patients with osteoporosis. Classical drug treatments for osteoporotic bone defects have unsatisfactory efficacy owing to side effects and imprecise delivery problems. In this study, a magnetic aggregation-induced bone-targeting poly(lactic-co-glycolic acid, PLGA)-based nanocarrier (ZOL-PLGA@Yoda1/SPIO) is synthesized to realize dual-targeted delivery and precise Piezo1-activated therapy for osteoporotic bone defects. Piezo1 is an important mechanotransducer that plays a key role in regulating bone homeostasis. To achieve dual-targeting properties, ZOL-PLGA@Yoda1/SPIO is fabricated using zoledronate (ZOL)-decorated PLGA, superparamagnetic iron oxide (SPIO), and Piezo1-activated molecule Yoda1 via the emulsion solvent diffusion method. Bone-targeting molecular mediation and magnetic aggregation-induced properties can jointly and effectively achieve precise delivery to localized bone defects. Moreover, Yoda1 loading enables targeted and efficient mimicking of mechanical signals and activation of Piezo1. Experiments in vivo and in vitro demonstrate that ZOL-PLGA@Yoda1/SPIO can activate Piezo1 in bone defect areas of osteoporotic mice, improve osteogenesis through YAP/β-catenin signaling axis, promote a well-coordinated osteogenesis-angiogenesis coupling, and significantly accelerate bone reconstruction within the defects without noticeable side effects. Overall, this novel dual-targeting nanocarrier provides a potentially effective strategy for the clinical treatment of osteoporotic bone defects.

Piezo1 channel causes lens sclerosis via transglutaminase 2 activation

Presbyopia is caused by age-related lenticular hardening, resulting in near vision loss, and it occurs in almost every individual aged ≥50 years. The lens experiences mechanical pressure during for focal adjustment to change its thickness. As lenticular stiffening results in incomplete thickness changes, near vision is reduced, which is known as presbyopia. Piezo1 is a mechanosensitive channel that constantly senses pressure changes during the regulation of visual acuity, and changes in Piezo1 channel activity may contribute to presbyopia. However, no studies have reported on Piezo1 activation or the onset of presbyopia. To elucidate the relevance of Piezo1 activation and cross-linking in the development of presbyopia, we analysed the function of Piezo1 in the lens. The addition of Yoda1, a Piezo1 activator, induced an increase in transglutaminase 2 (TGM2) mRNA expression and activity through the extra-cellular signal-regulated kinase (ERK) 1/2 and c-Jun-NH2-terminal kinase1/2 pathways. In ex vivo lenses, Yoda1 treatment induced γ-crystallin cross-linking via TMG2 activation. Furthermore, Yoda1 eye-drops in mice led to lenticular hardening via TGM2 induction and activation in vivo, suggesting that Yoda1-treated animals could serve as a model for presbyopia. Our findings indicate that this presbyopia-animal model could be useful for screening drugs for lens-stiffening inhibition.

Acoustofluidic Interfaces for the Mechanobiological Secretome of MSCs

While mesenchymal stem cells (MSCs) have gained enormous attention due to their unique properties of self-renewal, colony formation, and differentiation potential, the MSC secretome has become attractive due to its roles in immunomodulation, anti-inflammatory activity, angiogenesis, and anti-apoptosis. However, the precise stimulation and efficient production of the MSC secretome for therapeutic applications are challenging problems to solve. Here, we report on Acoustofluidic Interfaces for the Mechanobiological Secretome of MSCs: AIMS. We create an acoustofluidic mechanobiological environment to form reproducible three-dimensional MSC aggregates, which produce the MSC secretome with high efficiency. We confirm the increased MSC secretome is due to improved cell-cell interactions using AIMS: the key mediator N-cadherin was up-regulated while functional blocking of N-cadherin resulted in no enhancement of the secretome. After being primed by IFN-γ, the secretome profile of the MSC aggregates contains more anti-inflammatory cytokines and can be used to inhibit the pro-inflammatory response of M1 phenotype macrophages, suppress T cell activation, and support B cell functions. As such, the MSC secretome can be modified for personalized secretome-based therapies. AIMS acts as a powerful tool for improving the MSC secretome and precisely tuning the secretory profile to develop new treatments in translational medicine.

C-terminus of PIEZO1 governs Ca2+ influx and intracellular ERK1/2 signaling pathway in mechanotransduction

Cells sense and respond to extracellular mechanical stress through mechanotransduction receptors and ion channels, which regulate cellular behaviors such as cell proliferation and differentiation. Among them, PIEZO1, piezo-type mechanosensitive ion channel component 1, has recently been highlighted as a mechanosensitive ion channel in various cell types including mesenchymal stem cells. We previously reported that PIEZO1 is essential for ERK1/2 phosphorylation and osteoblast differentiation in bone marrow-derived mesenchymal stem cells (BMSCs), induced by hydrostatic pressure loading and treatment with the PIEZO1-specific activator Yoda1. However, the molecular mechanism underlying how PIEZO1 induces mechanotransduction remains unclear. In this study, we investigated that the role of the C-terminus in regulating extracellular Ca2+ influx and activating the ERK1/2 signaling pathway. We observed the activation of Fluo-4 AM in the Yoda1-stimulated human BMSC line UE7T-13, but not in a calcium-depleted cell culture medium. Similarly, Western blotting analysis revealed that Yoda1 treatment induced ERK1/2 phosphorylation, but this induction was not observed in calcium-depleted cell culture medium. To investigate the functional role of the C-terminus of PIEZO1, we generated HEK293 cells stably expressing the full-length mouse PIEZO1 (PIEZO1-FL) and a deletion-type PIEZO1 lacking the C-terminal intracellular region containing the R-Ras-binding domain (PIEZO1-ΔR-Ras). We found that Yoda1 treatment predominantly activated Flou-4 AM and ERK1/2 in PIEZO1-FL-trasfected cells but neither in PIEZO1-ΔR-Ras-transfected cells nor control cells. Our results indicate that the C-terminus of PIEZO1, which contains the R-Ras binding domain, plays an essential role in Ca2+ influx and activation of the ERK1/2 signaling pathway, suggesting that this domain is crucial for the mechanotransduction of osteoblastic differentiation in BMSCs.

The Critical Role of The Piezo1/β-catenin/ATF4 Axis on The Stemness of Gli1+ BMSCs During Simulated Microgravity-Induced Bone Loss

Disuse osteoporosis is characterized by decreased bone mass caused by abnormal mechanical stimulation of bone. Piezo1 is a major mechanosensitive ion channel in bone homeostasis. However, whether intervening in the action of Piezo1 can rescue disuse osteoporosis remains unresolved. In this study, a commonly-used hindlimb-unloading model is employed to simulate microgravity. By single-cell RNA sequencing, bone marrow-derived mesenchymal stem cells (BMSCs) are the most downregulated cell cluster, and coincidentally, Piezo1 expression is mostly enriched in those cells, and is substantially downregulated by unloading. Importantly, activation of Piezo1 by systemically-introducing yoda1 mimics the effects of mechanical stimulation and thus ameliorates bone loss under simulated microgravity. Mechanistically, Piezo1 activation promotes the proliferation and osteogenic differentiation of Gli1+ BMSCs by activating the β-catenin and its target gene activating transcription factor 4 (ATF4). Inhibiting β-catenin expression substantially attenuates the effect of yoda1 on bone loss, possibly due to inhibited proliferation and osteogenic differentiation capability of Gli1+ BMSCs mediated by ATF4. Lastly, Piezo1 activation also slightly alleviates the osteoporosis of OVX and aged mice. In conclusion, impaired function of Piezo1 in BMSCs leads to insufficient bone formation especially caused by abnormal mechanical stimuli, and is thus a potential therapeutic target for osteoporosis.

Joining forces: crosstalk between mechanosensitive PIEZO1 ion channels and integrin-mediated focal adhesions

Both integrin-mediated focal adhesions (FAs) and mechanosensitive ion channels such as PIEZO1 are critical in mechanotransduction processes that influence cell differentiation, development, and cancer. Ample evidence now exists for regulatory crosstalk between FAs and PIEZO1 channels with the molecular mechanisms underlying this process remaining unclear. However, an emerging picture is developing based on spatial crosstalk between FAs and PIEZO1 revealing a synergistic model involving the cytoskeleton, extracellular matrix (ECM) and calcium-dependent signaling. Already cell type, cell contractility, integrin subtypes and ECM composition have been shown to regulate this crosstalk, implying a highly fine-tuned relationship between these two major mechanosensing systems. In this review, we summarize the latest advances in this area, highlight the physiological implications of this crosstalk and identify gaps in our knowledge that will improve our understanding of cellular mechanosensing.

Disrupted Neural Regeneration in Dry Eye Secondary to Ankylosing Spondylitis-With a Theoretical Link between Piezo2 Channelopathy and Gateway Reflex, WDR Neurons, and Flare-Ups

This study aimed at analyzing the corneal neural regeneration in ankylosing spondylitis patients using in vivo corneal confocal microscopy in correlation with Langerhans cell density, morphology, and dry eye parameters. Approximately 24 ankylosing spondylitis subjects and 35 age- and gender-matched control subjects were enrolled. Data analysis showed that all corneal nerve-fiber descriptives were lower in the ankylosing spondylitis group, implicating disrupted neural regeneration. Peripheral Langerhans cell density showed a negative correlation with nerve fiber descriptions. A negative correlation between tear film break-up time and corneal nerve fiber total branch density was detected. The potential role of somatosensory terminal Piezo2 channelopathy in the pathogenesis of dry eye disease and ankylosing spondylitis is highlighted in our study, exposing the neuroimmunological link between these diseases. We hypothesized earlier that spinal neuroimmune-induced sensitization due to this somatosensory terminal primary damage could lead to Langerhans cell activation in the cornea, in association with downregulated Piezo1 channels on these cells. This activation could lead to a Th17/Treg imbalance in dry eye secondary to ankylosing spondylitis. Hence, the corneal Piezo2 channelopathy-induced impaired Piezo2-Piezo1 crosstalk could explain the disrupted neural regeneration. Moreover, the translation of our findings highlights the link between Piezo2 channelopathy-induced gateway to pathophysiology and the gateway reflex, not to mention the potential role of spinal wide dynamic range neurons in the evolution of neuropathic pain and the flare-ups in ankylosing spondylitis and dry eye disease.

Mechanotransductive receptor Piezo1 as a promising target in the treatment of fibrosis diseases

Fibrosis could happen in every organ, leading to organic malfunction and even organ failure, which poses a serious threat to global health. Early treatment of fibrosis has been reported to be the turning point, therefore, exploring potential correlates in the pathogenesis of fibrosis and how to reverse fibrosis has become a pressing issue. As a mechanism-sensitive cationic calcium channel, Piezo1 turns on in response to changes in the lipid bilayer of the plasma membrane. Piezo1 exerts multiple biological roles, including inhibition of inflammation, cytoskeletal stabilization, epithelial-mesenchymal transition, stromal stiffness, and immune cell mechanotransduction, interestingly enough. These processes are closely associated with the development of fibrotic diseases. Recent studies have shown that deletion or knockdown of Piezo1 attenuates the onset of fibrosis. Therefore, in this paper we comprehensively describe the biology of this gene, focusing on its potential relevance in pulmonary fibrosis, renal fibrosis, pancreatic fibrosis, and cardiac fibrosis diseases, except for the role of drugs (agonists), increased intracellular calcium and mechanical stress using this gene in alleviating fibrosis.

Effect of whole body vibration therapy in the rat model of steroid-induced osteonecrosis of the femoral head

Background: Steroid-induced Osteonecrosis of the Femoral Head (SIONFH) is a skeletal disease with a high incidence and a poor prognosis. Whole body vibration therapy (WBVT), a new type of physical training, is known to promote bone formation. However, it remains unclear whether WBVT has a therapeutic effect on SIONFH. Materials and methods: Thirty adult male and female Sprague-Dawley (SD) rats were selected and randomly assigned to three experimental groups: the control group, the model group, and the mechanical vibration group, respectively. SIONFH induction was achieved through the combined administration of lipopolysaccharides (LPS) and methylprednisolone sodium succinate for injection (MPS). The femoral head samples underwent hematoxylin and eosin (H&E) staining to visualize tissue structures. Structural parameters of the region of interest (ROI) were compared using Micro-CT analysis. Immunohistochemistry was employed to assess the expression levels of Piezo1, BMP2, RUNX2, HIF-1, VEGF, CD31, while immunofluorescence was used to examine CD31 and Emcn expression levels. Results: The H&E staining results revealed a notable improvement in the ratio of empty lacuna in various groups following WBVT intervention. Immunohistochemical analysis showed that the expression levels of Piezo1, BMP2, RUNX2, HIF-1, VEGF, and CD31 in the WBVT group exhibited significant differences when compared to the Model group (p < 0.05). Additionally, immunofluorescence analysis demonstrated statistically significant differences in CD31 and Emcn expression levels between the WBVT group and the Model group (p < 0.05). Conclusion: WBVT upregulates Piezo1 to promote osteogenic differentiation, potentially by enhancing the HIF-1α/VEGF axis and regulating H-vessel angiogenesis through the activation of the Piezo1 ion channel. This mechanism may lead to improved blood flow supply and enhanced osteogenic differentiation within the femoral head.

The Mechanotransduction Signaling Pathways in the Regulation of Osteogenesis

Bones are constantly exposed to mechanical forces from both muscles and Earth's gravity to maintain bone homeostasis by stimulating bone formation. Mechanotransduction transforms external mechanical signals such as force, fluid flow shear, and gravity into intracellular responses to achieve force adaptation. However, the underlying molecular mechanisms on the conversion from mechanical signals into bone formation has not been completely defined yet. In the present review, we provide a comprehensive and systematic description of the mechanotransduction signaling pathways induced by mechanical stimuli during osteogenesis and address the different layers of interconnections between different signaling pathways. Further exploration of mechanotransduction would benefit patients with osteoporosis, including the aging population and postmenopausal women.

Applications of Bioinspired Platforms for Enhancing Immunomodulatory Function of Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSCs) have attracted scientific and medical interest due to their self-renewing properties, pluripotency, and paracrine function. However, one of the main limitations to the clinical application of MSCs is their loss of efficacy after transplantation in vivo. Various bioengineering technologies to provide stem cell niche-like conditions have the potential to overcome this limitation. Here, focusing on the stem cell niche microenvironment, studies to maximize the immunomodulatory potential of MSCs by controlling biomechanical stimuli, including shear stress, hydrostatic pressure, stretch, and biophysical cues, such as extracellular matrix mimetic substrates, are discussed. The application of biomechanical forces or biophysical cues to the stem cell microenvironment will be beneficial for enhancing the immunomodulatory function of MSCs during cultivation and overcoming the current limitations of MSC therapy.

The functional effects of Piezo channels in mesenchymal stem cells

Mesenchymal stem cells (MSCs) are widely used in cell therapy, tissue engineering, and regenerative medicine because of their self-renewal, pluripotency, and immunomodulatory properties. The microenvironment in which MSCs are located significantly affects their physiological functions. The microenvironment directly or indirectly affects cell behavior through biophysical, biochemical, or other means. Among them, the mechanical signals provided to MSCs by the microenvironment have a particularly pronounced effect on their physiological functions and can affect osteogenic differentiation, chondrogenic differentiation, and senescence in MSCs. Mechanosensitive ion channels such as Piezo1 and Piezo2 are important in transducing mechanical signals, and these channels are widely distributed in sites such as skin, bladder, kidney, lung, sensory neurons, and dorsal root ganglia. Although there have been numerous studies on Piezo channels in MSCs in recent years, the function of Piezo channels in MSCs is still not well understood, and there has been no summary of their relationship to illustrate which physiological functions of MSCs are affected by Piezo channels and the possible underlying mechanisms. Therefore, based on the members, structures, and functions of Piezo ion channels and the fundamental information of MSCs, this paper focused on summarizing the advances in Piezo channels in MSCs from various tissue sources to provide new ideas for future research and practical applications of Piezo channels and MSCs.

A potential therapeutic drug for osteoporosis: prospect for osteogenic LncRNAs

Long non-coding RNAs (LncRNAs) play essential roles in multiple physiological processes including bone formation. Investigators have revealed that LncRNAs regulated bone formation through various signaling pathways and micro RNAs (miRNAs). However, several problems exist in current research studies on osteogenic LncRNAs, including sophisticated techniques, high cost for in vivo experiment, as well as low homology of LncRNAs between animal model and human, which hindered translational medicine research. Moreover, compared with gene editing, LncRNAs would only lead to inhibition of target genes rather than completely knocking them out. As the studies on osteogenic LncRNA gradually proceed, some of these problems have turned osteogenic LncRNA research studies into slump. This review described some new techniques and innovative ideas to address these problems. Although investigations on osteogenic LncRNAs still have obtacles to overcome, LncRNA will work as a promising therapeutic drug for osteoporosis in the near future.

Compressive stress induces spinal vertebral growth plate chondrocytes apoptosis via Piezo1

Many clinical studies have indicated an association between biomechanical factors and the incidence and pathological progression of adolescent idiopathic scoliosis (AIS). However, at present, the research on AIS is mainly focused on the etiology, and there are few studies reporting the causes of progressive aggravation of AIS. In the present study, we aim to investigate the role of Piezo1 in compressive stress-induced mouse spinal vertebral growth plate chondrocytes apoptosis. First, a scoliosis mouse model was established, and the expression of Piezo1 as well as the degree of apoptosis were investigated. We found that the expression of Piezo1 and the degree of apoptosis were significantly higher on the concave sides than that on the convex sides of the vertebral growth plate in mice with scoliosis. Spinal vertebral growth plate chondrocytes were further isolated and treated with Yoda1 to mimic Piezo1 overload. Excess Piezo1 significantly promoted apoptosis of spinal vertebral growth plate chondrocytes. Moreover, static gas compressive stress was used to simulate the increased concave compressive stress in the process of scoliosis with or without GsMTx4, a Piezo inhibitor. It was observed that with the increase of static compressive stress, the expression of Piezo1 increased, and the chondrocytes of vertebral growth plate treated with Piezo1 inhibitor GsMTx4 weakened the above phenomena. In conclusion, our results indicated that compressive stress is strongly associated with the different degrees of apoptosis on both sides on the convex and concave sides of the vertebral growth plate in scoliosis via inducing different expressions of Piezo1. Reducing the expression of Piezo1 in the concave side of the vertebral growth plate and inhibiting the apoptosis of chondrocytes in the bilateral vertebral growth plate caused by asymmetric stress on both sides of the concave vertebral body may be a promising treatment strategy for AIS.

Cellular mechanotransduction in health and diseases: from molecular mechanism to therapeutic targets

Cellular mechanotransduction, a critical regulator of numerous biological processes, is the conversion from mechanical signals to biochemical signals regarding cell activities and metabolism. Typical mechanical cues in organisms include hydrostatic pressure, fluid shear stress, tensile force, extracellular matrix stiffness or tissue elasticity, and extracellular fluid viscosity. Mechanotransduction has been expected to trigger multiple biological processes, such as embryonic development, tissue repair and regeneration. However, prolonged excessive mechanical stimulation can result in pathological processes, such as multi-organ fibrosis, tumorigenesis, and cancer immunotherapy resistance. Although the associations between mechanical cues and normal tissue homeostasis or diseases have been identified, the regulatory mechanisms among different mechanical cues are not yet comprehensively illustrated, and no effective therapies are currently available targeting mechanical cue-related signaling. This review systematically summarizes the characteristics and regulatory mechanisms of typical mechanical cues in normal conditions and diseases with the updated evidence. The key effectors responding to mechanical stimulations are listed, such as Piezo channels, integrins, Yes-associated protein (YAP) /transcriptional coactivator with PDZ-binding motif (TAZ), and transient receptor potential vanilloid 4 (TRPV4). We also reviewed the key signaling pathways, therapeutic targets and cutting-edge clinical applications of diseases related to mechanical cues.

A multi-well bioreactor for cartilage tissue engineering experiments

Cartilage tissue engineering necessitates the right mechanical cues to regenerate impaired tissue. For this reason, bioreactors can be employed to induce joint-relevant mechanical loading, such as compression and shear. However, current articulating joint bioreactor designs are lacking in terms of sample size and usability. In this paper, we describe a new, simple-to-build and operate, multi-well kinematic load bioreactor and investigate its effect on the chondrogenic differentiation of human bone marrow-derived stem cells (MSCs). We seeded MSCs into a fibrin-polyurethane scaffold and subsequently exposed the samples to a combination of compression and shear for 25 days. The mechanical loading activates transforming growth factor beta 1, upregulates chondrogenic genes, and increases sulfated glycosaminoglycan retention within the scaffolds. Such a higher-throughput bioreactor could be operated in most cell culture laboratories, dramatically accelerating and improving the testing of cells, new biomaterials, and tissue-engineered constructs.

Neural Regeneration in Dry Eye Secondary to Systemic Lupus Erythematosus Is Also Disrupted like in Rheumatoid Arthritis, but in a Progressive Fashion

Our objective in this study was to analyze the aberrant neural regeneration activity in the cornea by means of in vivo confocal microscopy in systemic lupus erythematosus patients with concurrent dry eye disease. We examined 29 systemic lupus erythematosus patients and 29 age-matched healthy control subjects. Corneal nerve fiber density (CNFD, the number of fibers/mm²) and peripheral Langerhans cell morphology were lower (p < 0.05) in systemic lupus erythematosus patients compared to the control group. Interestingly, corneal nerve branch density, corneal nerve fiber length, corneal nerve fiber total branch density, and corneal nerve fiber area showed a negative correlation with disease duration. A negative correlation was also demonstrated between average corneal nerve fiber density and central Langerhans cell density. This is in line with our hypothesis that corneal somatosensory terminal Piezo2 channelopathy-induced impaired Piezo2-Piezo1 crosstalk not only disrupts regeneration and keeps transcription activated, but could lead to Piezo1 downregulation and cell activation on Langerhans cells when we consider a chronic path. Hence, Piezo2 containing mechanosensory corneal nerves and dendritic Langerhans cells could also be regarded as central players in shaping the ocular surface neuroimmune homeostasis through the Piezo system. Moreover, lost autoimmune neuroinflammation compensation, lost phagocytic self-eating capacity, and lost transcription regulation, not to mention autoantibodies against vascular heparin sulfate proteoglycans and phospholipids, could all contribute to the progressive fashion of dry eye disease in systemic lupus erythematosus.

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.

Integrating physicomechanical and biological strategies for BTE: biomaterials-induced osteogenic differentiation of MSCs

Large bone defects are a major global health concern. Bone tissue engineering (BTE) is the most promising alternative to avoid the drawbacks of autograft and allograft bone. Nevertheless, how to precisely control stem cell osteogenic differentiation has been a long-standing puzzle. Compared with biochemical cues, physicomechanical stimuli have been widely studied for their biosafety and stability. The mechanical properties of various biomaterials (polymers, bioceramics, metal and alloys) become the main source of physicomechanical stimuli. By altering the stiffness, viscoelasticity, and topography of materials, mechanical stimuli with different strengths transmit into precise signals that mediate osteogenic differentiation. In addition, externally mechanical forces also play a critical role in promoting osteogenesis, such as compression stress, tensile stress, fluid shear stress and vibration, etc. When exposed to mechanical forces, mesenchymal stem cells (MSCs) differentiate into osteogenic lineages by sensing mechanical stimuli through mechanical sensors, including integrin and focal adhesions (FAs), cytoskeleton, primary cilium, ions channels, gap junction, and activating osteogenic-related mechanotransduction pathways, such as yes associated proteins (YAP)/TAZ, MAPK, Rho-GTPases, Wnt/β-catenin, TGFβ superfamily, Notch signaling. This review summarizes various biomaterials that transmit mechanical signals, physicomechanical stimuli that directly regulate MSCs differentiation, and the mechanical transduction mechanisms of MSCs. This review provides a deep and broad understanding of mechanical transduction mechanisms and discusses the challenges that remained in clinical translocation as well as the outlook for the future improvements.

The Migration and the Fate of Dental Pulp Stem Cells

Human dental pulp stem cells (hDPSCs) are adult mesenchymal stem cells (MSCs) obtained from dental pulp and derived from the neural crest. They can differentiate into odontoblasts, osteoblasts, chondrocytes, adipocytes and nerve cells, and they play a role in tissue repair and regeneration. In fact, DPSCs, depending on the microenvironmental signals, can differentiate into odontoblasts and regenerate dentin or, when transplanted, replace/repair damaged neurons. Cell homing depends on recruitment and migration, and it is more effective and safer than cell transplantation. However, the main limitations of cell homing are the poor cell migration of MSCs and the limited information we have on the regulatory mechanism of the direct differentiation of MSCs. Different isolation methods used to recover DPSCs can yield different cell types. To date, most studies on DPSCs use the enzymatic isolation method, which prevents direct observation of cell migration. Instead, the explant method allows for the observation of single cells that can migrate at two different times and, therefore, could have different fates, for example, differentiation and self-renewal. DPSCs use mesenchymal and amoeboid migration modes with the formation of lamellipodia, filopodia and blebs, depending on the biochemical and biophysical signals of the microenvironment. Here, we present current knowledge on the possible intriguing role of cell migration, with particular attention to microenvironmental cues and mechanosensing properties, in the fate of DPSCs.

Evidence of Disruption in Neural Regeneration in Dry Eye Secondary to Rheumatoid Arthritis

The purpose of our study was to analyze abnormal neural regeneration activity in the cornea through means of confocal microscopy in rheumatoid arthritis patients with concomitant dry eye disease. We examined 40 rheumatoid arthritis patients with variable severity and 44 volunteer age- and gender-matched healthy control subjects. We found that all examined parameters were significantly lower (p < 0.05) in rheumatoid arthritis patients as opposed to the control samples: namely, the number of fibers, the total length of the nerves, the number of branch points on the main fibers and the total nerve-fiber area. We examined further variables, such as age, sex and the duration of rheumatoid arthritis. Interestingly, we could not find a correlation between the above variables and abnormal neural structural changes in the cornea. We interpreted these findings via implementing our hypotheses. Correspondingly, one neuroimmunological link between dry eye and rheumatoid arthritis could be through the chronic Piezo2 channelopathy-induced K_2P-TASK1 signaling axis. This could accelerate neuroimmune-induced sensitization on the spinal level in this autoimmune disease, with Langerhans-cell activation in the cornea and theorized downregulated Piezo1 channels in these cells. Even more importantly, suggested principal primary-damage-associated corneal keratocyte activation could be accompanied by upregulation of Piezo1. Both activation processes on the periphery would skew the plasticity of the Th17/Treg ratio, resulting in Th17/Treg imbalance in dry eye, secondary to rheumatoid arthritis. Hence, chronic somatosensory-terminal Piezo2 channelopathy-induced impaired Piezo2-Piezo1 crosstalk could result in a mixed picture of disrupted functional regeneration but upregulated morphological regeneration activity of these somatosensory axons in the cornea, providing the demonstrated abnormal neural corneal morphology.