Unraveling the mechanobiology of immune cells

Phosphatidylserine-functional polydimethylsiloxane substrates regulate macrophage M2 polarization via modulus-dependent NF-κB/PPARγ pathway

Macrophages, highly plastic innate immune cells, critically influence the success of implantable devices by responding to biochemical and physical cues. However, the mechanisms underlying their synergistic regulation of macrophage polarization on implant surfaces remain poorly understood. Therefore, we constructed anti-inflammatory phosphatidylserine (PS) modified polydimethylsiloxane (PDMS) substrates with low, medium, and high modulus (1-100 kPa) to investigate the combined effects and underlying mechanisms of substrate modulus and biochemical signal on macrophage polarization. The introduction of PS on the PDMS surface not only significantly enhanced the polarization of M0 to M2 but also potently suppressed lipopolysaccharide (LPS)-induced M1 activation, with this effect further potentiated by a reduction in substrate modulus. In vivo subcutaneous implantation experiments also corroborated the synergistic effect of PS functionalization and low modulus PDMS in inhibiting M1 activation and promoting M2 polarization. Notably, reduced modulus led to decreased integrin αV/β3 clustering and cytoskeletal protein aggregation, ultimately diminishing YAP activation and nuclear translocation. Concomitantly, this disruption of the Piezo1-cytoskeletal protein positive feedback loop resulted in reduced p65/IκB phosphorylation and inflammation, while concurrently promoting PPARγ expression. Overall, our findings underscore the pivotal role of substrate modulus in modulating PS-mediated biomaterial-cell interactions, synergistically potentiating PS-induced M2 macrophage polarization, thus paving the way for the design of advanced immunomodulatory biomaterials.

Formation and biological activities of foreign body giant cells in response to biomaterials

The integration of biomaterials in medical applications triggers the foreign body response (FBR), a multi-stage immune reaction characterized by the formation of foreign body giant cells (FBGCs). Originating from the fusion of monocyte/macrophage lineage cells, FBGCs are pivotal participants during tissue-material interactions. This review provides an in-depth examination of the molecular processes during FBGC formation, highlighting signaling pathways and fusion mediators in response to both exogenous and endogenous stimuli. Moreover, a wide range of material-specific characteristics, such as surface chemical and physical properties, has been proven to influence the fusion of macrophages into FBGCs. Multifaceted biological activities of FBGCs are also explored, with emphasis on their phagocytic capabilities and extracellular secretory functions, which profoundly affect the vascularization, degradation, and encapsulation of the biomaterials. This review further elucidates the heterogeneity of FBGCs and their diverse roles during FBR, as demonstrated by their distinct behaviors in response to different materials. By presenting a comprehensive understanding of FBGCs, this review intends to provide strategies and insights into optimizing biocompatibility and the therapeutic potential of biomaterials for enhanced stability and efficacy in clinical applications. STATEMENT OF SIGNIFICANCE: As a hallmark of the foreign body response (FBR), foreign body giant cells (FBGCs) significantly impact the success of implantable biomaterials, potentially leading to complications such as chronic inflammation, fibrosis, and device failure. Understanding the role of FBGCs and modulating their responses are vital for successful material applications. This review provides a comprehensive overview of the molecules and signaling pathways guiding macrophage fusion into FBGCs. By elucidating the physical and chemical properties of materials inducing distinct levels of FBGCs, potential strategies of materials in modulating FBGC formation are investigated. Additionally, the biological activities of FBGCs and their heterogeneity in responses to different material categories in vivo are highlighted in this review, offering crucial insights for improving the biocompatibility and efficacy of biomaterials.

Gut mechanoimmunology: Shaping immune response through physical cues

The gut immune system embodies a complex interplay between the gut mucosal barrier, the host's immune cells, and gut microbiota. These components exist within a dynamic environment characterized by a variety of physical cues, e.g., compression, tension, shear stress, stiffness, and viscoelasticity. The physical cues can be modified under specific pathological conditions. Given their dynamic nature, comprehending the specific effects of these physical cues on the gut immune system is critical for pathological and therapeutic studies of intestinal immune-related diseases. This review aims to discuss how physical cues influence gut immunology by affecting the gut mucosal barrier, host immune cells, and gut microbiota, defining this concept as gut mechanoimmunology. This review seeks to highlight that an enhanced understanding of gut mechanoimmunology carries therapeutic implications, not only for intestinal diseases but also for extraintestinal diseases.

Mechanical control of antigen detection and discrimination by T and B cell receptors

The adaptive immune response is orchestrated by just two cell types, T cells and B cells. Both cells possess the remarkable ability to recognize virtually any antigen through their respective antigen receptors-the T cell receptor (TCR) and B cell receptor (BCR). Despite extensive investigations into the biochemical signaling events triggered by antigen recognition in these cells, our ability to predict or control the outcome of T and B cell activation remains elusive. This challenge is compounded by the sensitivity of T and B cells to the biophysical properties of antigens and the cells presenting them-a phenomenon we are just beginning to understand. Recent insights underscore the central role of mechanical forces in this process, governing the conformation, signaling activity, and spatial organization of TCRs and BCRs within the cell membrane, ultimately eliciting distinct cellular responses. Traditionally, T cells and B cells have been studied independently, with researchers working in parallel to decipher the mechanisms of activation. While these investigations have unveiled many overlaps in how these cell types sense and respond to antigens, notable differences exist. To fully grasp their biology and harness it for therapeutic purposes, these distinctions must be considered. This review compares and contrasts the TCR and BCR, placing emphasis on the role of mechanical force in regulating the activity of both receptors to shape cellular and humoral adaptive immune responses.

In vitro encapsulation and expansion of T and CAR-T cells using 3D synthetic thermo-responsive matrices

Suspension cell culture and rigid commercial substrates are the most common methods to clinically manufacture therapeutic CAR-T cells ex vivo. However, suspension culture and nano/micro-scale commercial substrates poorly mimic the microenvironment where T cells naturally develop, leading to profound impacts on cell proliferation and phenotype. To overcome this major challenge, macro-scale substrates can be used to emulate that environment with higher precision. This work employed a biocompatible thermo-responsive material with tailored mechanical properties as a potential synthetic macro-scale scaffold to support T cell encapsulation and culture. Cell viability, expansion, and phenotype changes were assessed to study the effect of two thermo-responsive hydrogel materials with stiffnesses of 0.5 and 17 kPa. Encapsulated Pan-T and CAR-T cells were able to grow and physically behave similar to the suspension control. Furthermore, matrix stiffness influenced T cell behavior. In the softer polymer, T cells had higher activation, differentiation, and maturation after encapsulation obtaining significant cell numbers. Even when terpolymer encapsulation affected the CAR-T cell viability and expansion, CAR T cells expressed favorable phenotypical profiles, which was supported with cytokines and lactate production. These results confirmed the biocompatibility of the thermo-responsive hydrogels and their feasibility as a promising 3D macro-scale scaffold for in vitro T cell expansion that could potentially be used for cell manufacturing process.

Harnessing Biomaterials to Amplify Immunity in Aged Mice through T Memory Stem Cells

The durability of a protective immune response generated by a vaccine depends on its ability to induce long-term T cell immunity, which tends to decline in aging populations. The longest protection appears to arise from T memory stem cells (TMSCs) that confer high expandability and effector functions when challenged. Here we engineered artificial antigen presenting cells (aAPC) with optimized size, stiffness and activation signals to induce human and mouse CD8+ TMSCs in vitro. This platform was optimized as a vaccine booster of TMSCs (Vax-T) with prolonged release of small-molecule blockade of the glycogen synthase kinase-3β together with target antigens. By using SARS-CoV-2 antigen as a model, we show that a single injection of Vax-T induces durable antigen-specific CD8+ TMSCs in young and aged mice, and generates humoral responses at a level stronger than or similar to soluble vaccines. This Vax-T approach can boost long-term immunity to fight infectious diseases, cancer, and other diseases.

Toward innovative approaches for exploring the mechanically regulated tumor-immune microenvironment

Within the complex tumor microenvironment, cells experience mechanical cues-such as extracellular matrix stiffening and elevation of solid stress, interstitial fluid pressure, and fluid shear stress-that significantly impact cancer cell behavior and immune responses. Recognizing the significance of these mechanical cues not only sheds light on cancer progression but also holds promise for identifying potential biomarkers that would predict therapeutic outcomes. However, standardizing methods for studying how mechanical cues affect tumor progression is challenging. This challenge stems from the limitations of traditional in vitro cell culture systems, which fail to encompass the critical contextual cues present in vivo. To address this, 3D tumor spheroids have been established as a preferred model, more closely mimicking cancer progression, but they usually lack reproduction of the mechanical microenvironment encountered in actual solid tumors. Here, we review the role of mechanical forces in modulating tumor- and immune-cell responses and discuss how grasping the importance of these mechanical cues could revolutionize in vitro tumor tissue engineering. The creation of more physiologically relevant environments that better replicate in vivo conditions will eventually increase the efficacy of currently available treatments, including immunotherapies.

Mechanical forces amplify TCR mechanotransduction in T cell activation and function

Adoptive T cell immunotherapies, including engineered T cell receptor (eTCR) and chimeric antigen receptor (CAR) T cell immunotherapies, have shown efficacy in treating a subset of hematologic malignancies, exhibit promise in solid tumors, and have many other potential applications, such as in fibrosis, autoimmunity, and regenerative medicine. While immunoengineering has focused on designing biomaterials to present biochemical cues to manipulate T cells ex vivo and in vivo, mechanical cues that regulate their biology have been largely underappreciated. This review highlights the contributions of mechanical force to several receptor-ligand interactions critical to T cell function, with central focus on the TCR-peptide-loaded major histocompatibility complex (pMHC). We then emphasize the role of mechanical forces in (i) allosteric strengthening of the TCR-pMHC interaction in amplifying ligand discrimination during T cell antigen recognition prior to activation and (ii) T cell interactions with the extracellular matrix. We then describe approaches to design eTCRs, CARs, and biomaterials to exploit TCR mechanosensitivity in order to potentiate T cell manufacturing and function in adoptive T cell immunotherapy.

CD97 inhibits osteoclast differentiation via Rap1a/ERK pathway under compression

Acceleration of tooth movement during orthodontic treatment is challenging, with osteoclast-mediated bone resorption on the compressive side being the rate-limiting step. Recent studies have demonstrated that mechanoreceptors on the surface of monocytes/macrophages, especially adhesion G protein-coupled receptors (aGPCRs), play important roles in force sensing. However, its role in the regulation of osteoclast differentiation remains unclear. Herein, through single-cell analysis, we revealed that CD97, a novel mechanosensitive aGPCR, was expressed in macrophages. Compression upregulated CD97 expression and inhibited osteoclast differentiation; while knockdown of CD97 partially rescued osteoclast differentiation. It suggests that CD97 may be an important mechanosensitive receptor during osteoclast differentiation. RNA sequencing analysis showed that the Rap1a/ERK signalling pathway mediates the effects of CD97 on osteoclast differentiation under compression. Consistently, we clarified that administration of the Rap1a inhibitor GGTI298 increased osteoclast activity, thereby accelerating tooth movement. In conclusion, our results indicate that CD97 suppresses osteoclast differentiation through the Rap1a/ERK signalling pathway under orthodontic compressive force.

[The Three-dimensional Environment of Type Ⅰ Collagen Gels With Varying Stiffness Modulates the Immunological Functions of NK Cells]

Objective

To construct type Ⅰ collagen gels with different stiffness and to investigate the effects of three-dimensional (3D) culture environments of the gels on the morphology, free migration ability, and cell killing function of natural killer (NK) cells.

Methods

Type Ⅰ collagen was isolated from the tails of Sprague Dawley (SD) rats and collagen gels with different levels of stiffnesses were prepared accordingly. The microstructure of the collagen gels was observed by laser confocal microscopy. The stiffness of the collagen gels was assessed by measuring the plateau modulus with a rheometer. NK-92MI cells were cultured in collagen gels with different levels of stiffness. The morphology of NK-92MI cells was observed by inverted microscope. High content imaging system was used to record the free migration process of NK-92MI cells and analyze the migration speed and distance. NK-92MI cells were cultured with type Ⅰ collagen gels with different levels of stiffness for 24 h and 48 h and, then, co-cultured with human colorectal DLD-1, a human adenocarcinoma epithelial cell line. CCK8 assay was performed to determine the proliferation rate of DLD-1 cells and analyze the cell killing ability of NK-92MI cells.

Results

Low-stiffness type Ⅰ collagen gel and high-stiffness type Ⅰ collagen gel with the respective stiffness of (10.970±2.10) Pa and (114.50±3.40) Pa were successfully prepared. Compared with those cultured with the low-stiffness type Ⅰ collagen gel, the NK-92MI cells in the high-stiffness type Ⅰ collagen gel showed a more elongated shape (P<0.05), the mean area of the cells was reduced ([69.88±26.97] μm2 vs. [46.59±21.62] μm2, P<0.05), the roundness of the cells decreased (0.82±0.12 vs. 0.78±0.18, P<0.05), cell migration speed decreased ([2.50±0.91] μm/min vs. [1.70±0.72] μm/min, P<0.001) and the migration distance was shortened ([147.10±53.74] μm vs. [98.03± 40.95] μm, P<0.0001), with all the differences being statistically significant. Compared with those cultured with the low-stiffness type Ⅰ collagen gel, NK-92MI cells cultured with high-stiffness type Ⅰ collagen gel for 24 h could promote DLD-1 cell proliferation, with the proliferation rate being (46.39±12.79)% vs. (65.87±4.45)% (P<0.05) and reduce the cell killing ability. Comparison of the cells cultured for 48 h led to similar results, with the proliferation rates being (31.36±2.88)% vs. (74.57±2.16)% (P<0.05), and the differences were all statistically significant.

Conclusion

The 3D culture environment of type Ⅰ collagen gels with different levels of stiffness alters the morphology, migration ability, and killing function of NK-92MI cells. This study provides the research basis for exploring and understanding the mechanisms by which the biomechanical microenvironment affects the immune response of NK cells, as well as laying the theoretical foundation for optimizing immunotherapy protocols.

T helper cell subsets: diversification of the field

Polarized T helper cell (Th cell) responses are important determinants of host protection. Th cell subsets tailor their functional repertoire of cytokines to their cognate antigens to efficiently contribute to their clearance. In contrast, in settings of immune abrogation, these polarized cytokine patterns of Th cells can mediate tissue damage and pathology resulting in allergy or autoimmunity. Recent technological developments in single-cell genomics and proteomics as well as advances in the high-dimensional bioinformatic analysis of complex datasets have challenged the prevailing Th cell subset classification into Th1, Th2, Th17, and other subsets. Additionally, systems immunology approaches have revealed that instructive input from the peripheral tissue microenvironment can have differential effects on the overall phenotype and molecular wiring of Th cells depending on their spatial distribution. Th cells from the blood or secondary lymphoid organs are therefore expected to follow distinct rules of regulation. In this review, the functional heterogeneity of Th cell subsets will be reviewed in the context of new technological developments and T-cell compartmentalization in tissue niches. This work will especially focus on challenges to the traditional boundaries of Th cell subsets and will discuss the underlying regulatory checkpoints, which could reveal new therapeutic strategies for various immune-mediated diseases.

Piezo1 facilitates optimal T cell activation during tumor challenge

Functional effector T cells in the tumor microenvironment (TME) are critical for successful anti-tumor responses. T cell anti-tumor function is dependent on their ability to differentiate from a naïve state, infiltrate into the tumor site, and exert cytotoxic functions. The factors dictating whether a particular T cell can successfully undergo these processes during tumor challenge are not yet completely understood. Piezo1 is a mechanosensitive cation channel with high expression on both CD4+ and CD8+ T cells. Previous studies have demonstrated that Piezo1 optimizes T cell activation and restrains the CD4+ regulatory T cell (Treg) pool in vitro and under inflammatory conditions in vivo. However, little is known about the role Piezo1 plays on CD4+ and CD8+ T cells in cancer. We hypothesized that disruption of Piezo1 on T cells impairs anti-tumor immunity in vivo by hindering inflammatory T cell responses. We challenged mice with T cell Piezo1 deletion (P1KO) with tumor models dependent on T cells for immune rejection. P1KO mice had the more aggressive tumors, higher tumor growth rates and were unresponsive to immune-mediated therapeutic interventions. We observed a decreased CD4:CD8 ratio in both the secondary lymphoid organs and TME of P1KO mice that correlated inversely with tumor size. Poor CD4+ helper T cell responses underpinned the immunodeficient phenotype of P1KO mice. Wild type CD8+ T cells are sub-optimally activated in vivo with P1KO CD4+ T cells, taking on a CD25loPD-1hi phenotype. Together, our results suggest that Piezo1 optimizes T cell activation in the context of a tumor response.

YAP localization mediates mechanical adaptation of human cancer cells during extravasation in vivo

Biophysical profiling of primary tumors has revealed that individual tumor cells fall along a highly heterogeneous continuum of mechanical phenotypes. One idea is that a subset of tumor cells is "softer" to facilitate detachment and escape from the primary site, a step required to initiate metastasis. However, it has also been postulated that cells must be able to deform and generate sufficient force to exit into distant sites. Here, we aimed to dissect the mechanical changes that occur during extravasation and organ colonization. Using multiplexed methods of intravital microscopy and optical tweezer based active microrheology, we obtained longitudinal images and mechanical profiles of cells during organ colonization in vivo. We determined that cells were softer, more liquid like upon exit of the vasculature but stiffened and became more solid like once in the new organ microenvironment. We also determined that a YAP mediated mechanogenotype influenced the global dissemination in our in vivo and in vitro models and that reducing mechanical heterogeneity could reduce extravasation. Moreover, our high throughput analysis of mechanical phenotypes of patient samples revealed that this mechanics was in part regulated by the external hydrodynamic forces that the cancer cells experienced within capillary mimetics. Our findings indicate that disseminated cancer cells can keep mutating with a continuum landscape of mechano-phenotypes, governed by the YAP-mediated mechanosensing of hydrodynamic flow.

Extreme environments and human health: From the immune microenvironments to immune cells

Exposure to extreme environments causes specific acute and chronic physiological responses in humans. The adaptation and the physiological processes under extreme environments predominantly affect multiple functional systems of the organism, in particular, the immune system. Dysfunction of the immune system affected by several extreme environments (including hyperbaric environment, hypoxia, blast shock, microgravity, hypergravity, radiation exposure, and magnetic environment) has been observed from clinical macroscopic symptoms to intracorporal immune microenvironments. Therefore, simulated extreme conditions are engineered for verifying the main influenced characteristics and factors in the immune microenvironments. This review summarizes the responses of immune microenvironments to these extreme environments during in vivo or in vitro exposure, and the approaches of engineering simulated extreme environments in recent decades. The related microenvironment engineering, signaling pathways, molecular mechanisms, clinical therapy, and prevention strategies are also discussed.

Mechanobiology of Ferroptotic Cancer Cells as a Novel "Eat-Me" Signal: Regulating Efferocytosis through Layer-by-Layer Coating

The importance of the clearance of dead cells is shown to have a regulatory role for normal tissue homeostasis and for the modulation of immune responses. However, how mechanobiological properties of dead cells affect efferocytosis remains largely unknown. Here, it is reported that the Young's modulus of cancer cells undergoing ferroptosis is reduced. To modulate their Young's modulus a layer-by-layer (LbL) nanocoating is developed. Scanning electron and fluorescence microscopy confirm coating efficiency of ferroptotic cells while atomic force microscopy reveals encapsulation of the dead cells increases their Young's modulus dependent on the number of applied LbL layers which increases their efferocytosis by primary macrophages. This work demonstrates the crucial role of mechanobiology of dead cells in regulating their efferocytosis by macrophages which can be exploited for the development of novel therapeutic strategies for diseases where modulation of efferocytosis can be potentially beneficial and for the design of drug delivery systems for cancer therapy.

Beyond matrix stiffness: targeting force-induced cancer drug resistance

During tumor progression, mechanical abnormalities in the tumor microenvironment (TME) trigger signaling pathways in cells that activate cellular programs, resulting in tumor growth and drug resistance. In this review, we describe mechanisms of action for anti-cancer therapies and mechanotransduction programs that regulate cellular processes, including cell proliferation, apoptosis, survival and phenotype switching. We discuss how the therapeutic response is impacted by the three main mechanical TME abnormalities: high extracellular matrix (ECM) composition and stiffness; interstitial fluid pressure (IFP); and elevated mechanical forces. We also review drugs that normalize these abnormalities or block mechanosensors and mechanotransduction pathways. Finally, we discuss current challenges and perspectives for the development of new strategies targeting mechanically induced drug resistance in the clinic.

Tailored biomedical materials for wound healing

Wound healing is a long-term, multi-stage biological process that mainly includes haemostatic, inflammatory, proliferative and tissue remodelling phases. Controlling infection and inflammation and promoting tissue regeneration can contribute well to wound healing. Smart biomaterials offer significant advantages in wound healing because of their ability to control wound healing in time and space. Understanding how biomaterials are designed for different stages of wound healing will facilitate future personalized material tailoring for different wounds, making them beneficial for wound therapy. This review summarizes the design approaches of biomaterials in the field of anti-inflammatory, antimicrobial and tissue regeneration, highlights the advanced precise control achieved by biomaterials in different stages of wound healing and outlines the clinical and practical applications of biomaterials in wound healing.

Mechanosensitive traction force generation is regulated by the neutrophil activation state

The generation of traction forces by neutrophils regulates many crucial effector functions responsible for host defense, such as attachment, spreading, migration, phagocytosis, and NETosis. The activation state of the cell is a strong determinant of the functional efficacy of the neutrophil; however, the effect of activation on traction force production has not yet been determined experimentally. Previously, the mapping of cellular-generated forces produced by human neutrophils via a Traction Force Microscopy (TFM) method has required a three-dimensional imaging modality to capture out-of-plane forces, such as confocal or multiphoton techniques. A method newly developed in our laboratories can capture out-of-plane forces using only a two-dimensional imaging modality. This novel technique-combined with a topology-based single particle tracking algorithm and finite element method calculations-can construct high spatial frequency three-dimensional traction fields, allowing for traction forces in-plane and out-of-plane to the substrate to now be differentially visualized and quantified with a standard epifluorescence microscope. Here we apply this technology to determine the effect of neutrophil activation on force generation. Sepsis is a systemic inflammatory response that causes dysregulated neutrophil activation in vivo. We found that neutrophils from septic patients produced greater total forces than neutrophils from healthy donors and that the majority of this dysregulation occurred in-plane to the substrate. Ex vivo activation of neutrophils from healthy donors showed differential consequences depending on activation stimuli with mechanosensitive force decreases observed in some cases. These findings demonstrate the feasibility of epifluorescence-based microscopy in mapping traction forces to ask biologically significant questions regarding neutrophil function.

Mechanosensitive Piezo1 protein as a novel regulator in macrophages and macrophage-mediated inflammatory diseases

Macrophages are the most important innate immune cells in humans. They are almost ubiquitous in peripheral tissues with a large variety of different mechanical milieus. Therefore, it is not inconceivable that mechanical stimuli have effects on macrophages. Emerging as key molecular detectors of mechanical stress, the function of Piezo channels in macrophages is becoming attractive. In this review, we addressed the architecture, activation mechanisms, biological functions, and pharmacological regulation of the Piezo1 channel and review the research advancements in functions of Piezo1 channels in macrophages and macrophage-mediated inflammatory diseases as well as the potential mechanisms involved.

Mechanobiology in Cells and Tissues

This Editorial is a comment on the success of the Special Issue "Mechanobiology in Cells and Tissues" published in the International Journal of Molecular Sciences [...].

Mechanotherapy in oncology: Targeting nuclear mechanics and mechanotransduction

Mechanotherapy is proposed as a new option for cancer treatment. Increasing evidence suggests that characteristic differences are present in the nuclear mechanics and mechanotransduction of cancer cells compared with those of normal cells. Recent advances in understanding nuclear mechanics and mechanotransduction provide not only further insights into the process of malignant transformation but also useful references for developing new therapeutic approaches. Herein, we present an overview of the alterations of nuclear mechanics and mechanotransduction in cancer cells and highlight their implications in cancer mechanotherapy.

Biophysical determinants of cancer organotropism

Metastasis remains the leading cause of cancer lethality. The 'seed/soil' hypothesis provides the framework to explain this cancer phenomenon where the concept of organotropism has been in part mechanistically explained by the properties of the tumor cells and their compatibility with the stromal environment of the distal site. The 'mechanical' hypothesis counters that non-random seeding is driven solely by the circulation patterns and vascular networks of organ systems. We incorporate concepts of mechanobiology and revisit the two hypotheses to provide additional insights into the mechanisms that regulate organ selection during metastatic outgrowth. We focus on the latter stages of the metastatic cascade and examine the role of the endothelium in regulating organ selectivity.

Cells function as a ternary logic gate to decide migration direction under integrated chemical and fluidic cues

Cells sense various environmental cues and subsequently process intracellular signals to decide their migration direction in many physiological and pathological processes. Although several signaling molecules and networks have been identified in these directed migrations, it still remains ambiguous to predict the migration direction under multiple and integrated cues, specifically chemical and fluidic cues. Here, we investigated the cellular signal processing machinery by reverse-engineering directed cell migration under integrated chemical and fluidic cues. We imposed controlled chemical and fluidic cues to cells using a microfluidic platform and analyzed the extracellular coupling of the cues with respect to the cellular detection limit. Then, the cell's migratory behavior was reverse-engineered to build a cellular signal processing system as a logic gate, which is based on a "selection" gate. This framework is further discussed with a minimal intracellular signaling network of a shared pathway model. The proposed framework of the ternary logic gate suggests a systematic view to understand how cells decode multiple cues and make decisions about the migration direction.

The T Cell Journey: A Tour de Force

T cells act as the puppeteers in the adaptive immune response, and their dysfunction leads to the initiation and progression of pathological conditions. During their lifetime, T cells experience myriad forces that modulate their effector functions. These forces are imposed by interacting cells, surrounding tissues, and shear forces from fluid movement. In this review, a journey with T cells is made, from their development to their unique characteristics, including the early studies that uncovered their mechanosensitivity. Then the studies pertaining to the responses of T cell activation to changes in antigen-presenting cells' physical properties, to their immediate surrounding extracellular matrix microenvironment, and flow conditions are highlighted. In addition, it is explored how pathological conditions like the tumor microenvironment can hinder T cells and allow cancer cells to escape elimination.

Engineered hydrogels for mechanobiology

Cells' local mechanical environment can be as important in guiding cellular responses as many well-characterized biochemical cues. Hydrogels that mimic the native extracellular matrix can provide these mechanical cues to encapsulated cells, allowing for the study of their impact on cellular behaviours. Moreover, by harnessing cellular responses to mechanical cues, hydrogels can be used to create tissues in vitro for regenerative medicine applications and for disease modelling. This Primer outlines the importance and challenges of creating hydrogels that mimic the mechanical and biological properties of the native extracellular matrix. The design of hydrogels for mechanobiology studies is discussed, including appropriate choice of cross-linking chemistry and strategies to tailor hydrogel mechanical cues. Techniques for characterizing hydrogels are explained, highlighting methods used to analyze cell behaviour. Example applications for studying fundamental mechanobiological processes and regenerative therapies are provided, along with a discussion of the limitations of hydrogels as mimetics of the native extracellular matrix. The article ends with an outlook for the field, focusing on emerging technologies that will enable new insights into mechanobiology and its role in tissue homeostasis and disease.

Topography-mediated immunomodulation in osseointegration; Ally or Enemy

Osteoimmunology is at full display during endosseous implant osseointegration. Bone formation, maintenance and resorption at the implant surface is a result of bidirectional and dynamic reciprocal communication between the bone and immune cells that extends beyond the well-defined osteoblast-osteoclast signaling. Implant surface topography informs adherent progenitor and immune cell function and their cross-talk to modulate the process of bone accrual. Integrating titanium surface engineering with the principles of immunology is utilized to harness the power of immune system to improve osseointegration in healthy and diseased microenvironments. This review summarizes current information regarding immune cell-titanium implant surface interactions and places these events in the context of surface-mediated immunomodulation and bone regeneration. A mechanistic approach is directed in demonstrating the central role of osteoimmunology in the process of osseointegration and exploring how regulation of immune cell function at the implant-bone interface may be used in future control of clinical therapies. The process of peri-implant bone loss is also informed by immunomodulation at the implant surface. How surface topography is exploited to prevent osteoclastogenesis is considered herein with respect to peri-implant inflammation, osteoclastic precursor-surface interactions, and the upstream/downstream effects of surface topography on immune and progenitor cell function.

Three-dimensional (3D) scaffolds as powerful weapons for tumor immunotherapy

Though increasing understanding and remarkable clinical successes have been made, enormous challenges remain to be solved in the field of cancer immunotherapy. In this context, biomaterial-based immunomodulatory strategies are being developed to boost antitumor immunity. For the local immunotherapy, macroscale biomaterial scaffolds with 3D network structures show great superiority in the following aspects: facilitating the encapsulation, localized delivery, and controlled release of immunotherapeutic agents and even immunocytes for more efficient immunomodulation. The concentrating immunomodulation in situ could minimize systemic toxicities, but still exert abscopal effects to harness the power of overall anticancer immune response for eradicating malignancy. To promote such promising immunotherapies, the design requirements of macroscale 3D scaffolds should comprehensively consider their physicochemical and biological properties, such as porosity, stiffness, surface modification, cargo release kinetics, biocompatibility, biodegradability, and delivery modes. To date, increasing studies have focused on the relationships between these parameters and the biosystems which will guide/assist the 3D biomaterial scaffolds to achieve the desired immunotherapeutic outcomes. In this review, by highlighting some recent achievements, we summarized the latest advances in the development of various 3D scaffolds as niches for cancer immunotherapy. We also discussed opportunities, challenges, current trends, and future perspectives in 3D macroscale biomaterial scaffold-assisted local treatment strategies. More importantly, this review put more efforts to illustrate how the 3D biomaterial systems affect to modulate antitumor immune activities, where we discussed how significant the roles and behaviours of 3D macroscale scaffolds towards in situ cancer immunotherapy in order to direct the design of 3D immunotherapeutic.

Can't handle the stress? Mechanobiology and disease

Mechanobiology is a rapidly growing research area focused on how mechanical forces and properties influence biological systems at the cell, molecular, and tissue level, and how those biological systems, in turn, control mechanical parameters. Recently, it has become apparent that disrupted mechanobiology has a significant role in many diseases, from cardiovascular disease to muscular dystrophy and cancer. An improved understanding of this intricate process could be harnessed toward developing alternative and more targeted treatment strategies, and to advance the fields of regenerative and personalized medicine. Modulating the mechanical properties of the cellular microenvironment has already been used successfully to boost antitumor immune responses and to induce cardiac and spinal regeneration, providing inspiration for further research in this area.

Mechanical force modulates macrophage proliferation via Piezo1-AKT-Cyclin D1 axis

Orthodontic tooth movement (OTM) is induced by biomechanical stimuli and facilitated by periodontal tissue remodeling, where multiple immune cells participate in this progression. It has been demonstrated that macrophage is essential for mechanical force-induced tissue remodeling. In this study, we first found that mechanical force significantly induced macrophage proliferation in human periodontal samples and murine OTM models. Yet, how macrophages perceive mechanical stimuli and thereby modulate their biological behaviors remain elusive. To illustrate the mechanisms of mechanical force-induced macrophage proliferation, we subsequently identified Piezo1, a novel mechanosensory ion channel, to modulate macrophage response subjected to mechanical stimuli. Mechanical force upregulates Piezo1 expression in periodontal tissues and cultured bone-marrow-derived macrophages (BMDMs). Remarkably, suppressing Piezo1 with GsMTx4 retarded OTM through reduced macrophage proliferation. Moreover, knockdown of Piezo1 effectively inhibited mechanical force-induced BMDMs proliferation. RNA sequencing was further performed to dissect the underlying mechanisms of Piezo1-mediated mechanotransduction utilizing mechanical stretch system. We revealed that Piezo1-activated AKT/GSK3β signaling was closely associated with macrophage proliferation upon mechanical stimuli. Importantly, Cyclin D1 (Ccnd1) was authenticated as a critical downstream factor of Piezo1 that facilitated proliferation by enhancing Rb phosphorylation. We generated genetically modified mice in which Ccnd1 could be deleted in macrophages in an inducible manner. Conditional ablation of Ccnd1 inhibited periodontal macrophage proliferation and therefore delayed OTM. Overall, our findings highlight that proliferation driven by mechanical force is a key process by which macrophages infiltrate in periodontal tissue during OTM, where Piezo1-AKT-Ccnd1 axis plays a pivotal role.

Extracellular Matrix Stiffness in Lung Health and Disease

The extracellular matrix (ECM) provides structural support and imparts a wide variety of environmental cues to cells. In the past decade, a growing body of work revealed that the mechanical properties of the ECM, commonly known as matrix stiffness, regulate the fundamental cellular processes of the lung. There is growing appreciation that mechanical interplays between cells and associated ECM are essential to maintain lung homeostasis. Dysregulation of ECM-derived mechanical signaling via altered mechanosensing and mechanotransduction pathways is associated with many common lung diseases. Matrix stiffening is a hallmark of lung fibrosis. The stiffened ECM is not merely a sequelae of lung fibrosis but can actively drive the progression of fibrotic lung disease. In this article, we provide a comprehensive view on the role of matrix stiffness in lung health and disease. We begin by summarizing the effects of matrix stiffness on the function and behavior of various lung cell types and on regulation of biomolecule activity and key physiological processes, including host immune response and cellular metabolism. We discuss the potential mechanisms by which cells probe matrix stiffness and convert mechanical signals to regulate gene expression. We highlight the factors that govern matrix stiffness and outline the role of matrix stiffness in lung development and the pathogenesis of pulmonary fibrosis, pulmonary hypertension, asthma, chronic obstructive pulmonary disease (COPD), and lung cancer. We envision targeting of deleterious matrix mechanical cues for treatment of fibrotic lung disease. Advances in technologies for matrix stiffness measurements and design of stiffness-tunable matrix substrates are also explored. © 2022 American Physiological Society. Compr Physiol 12:3523-3558, 2022.

The Nuclear Envelope as a Regulator of Immune Cell Function

The traditional view of the nuclear envelope (NE) was that it represented a relatively inert physical barrier within the cell, whose main purpose was to separate the nucleoplasm from the cytoplasm. However, recent research suggests that this is far from the case, with new and important cellular functions being attributed to this organelle. In this review we describe research suggesting an important contribution of the NE and its constituents in regulating the functions of cells of the innate and adaptive immune system. One of the standout properties of immune cells is their ability to migrate around the body, allowing them to carry out their physiological/pathophysiology cellular role at the appropriate location. This together with the physiological role of the tissue, changes in tissue matrix composition due to disease and aging, and the activation status of the immune cell, all result in immune cells being subjected to different mechanical forces. We report research which suggests that the NE may be an important sensor/transducer of these mechanical signals and propose that the NE is an integrator of both mechanical and chemical signals, allowing the cells of the innate immune system to precisely regulate gene transcription and functionality. By presenting this overview we hope to stimulate the interests of researchers into this often-overlooked organelle and propose it should join the ranks of mitochondria and phagosome, which are important organelles contributing to immune cell function.

Electrospun fiber-based strategies for controlling early innate immune cell responses: Towards immunomodulatory mesh designs that facilitate robust tissue repair

Electrospun fibrous meshes are widely used for tissue repair due to their ability to guide a host of cell responses including phenotypic differentiation and tissue maturation. A critical factor determining the eventual biological outcomes of mesh-based regeneration strategies is the early innate immune response following implantation. The natural healing process involves a sequence of tightly regulated, temporally varying and delicately balanced pro-/anti-inflammatory events which together promote mesh integration with host tissue. Matrix designs that do not account for the immune milieu can result in dysregulation, chronic inflammation and fibrous capsule formation, thus obliterating potential therapeutic outcomes. In this review, we provide systematic insights into the effects of specific fiber/mesh properties and mechanical stimulation on the responses of early innate immune modulators viz., neutrophils, monocytes and macrophages. We identify matrix characteristics that promote anti-inflammatory immune phenotypes, and we correlate such responses with pro-regenerative in vivo outcomes. We also discuss recent advances in 3D fabrication technologies, bioactive functionalization approaches and biomimetic/bioinspired immunomodulatory mesh design strategies for tissue repair and wound healing. The mechanobiological insights and immunoregulatory strategies discussed herein can help improve the translational outcomes of fiber-based regeneration and may also be leveraged for intervention in degenerative diseases associated with dysfunctional immune responses. STATEMENT OF SIGNIFICANCE: The crucial role played by immune cells in promoting biomaterial-based tissue regeneration is being increasingly recognized. In this review focusing on the interactions of innate immune cells (primarily neutrophils, monocytes and macrophages) with electrospun fibrous meshes, we systematically elucidate the effects of the fiber microenvironment and mechanical stimulation on biological responses, and build upon these insights to inform the rational design of immunomodulatory meshes for effective tissue repair. We discuss state-of-the-art fabrication methods and mechanobiological advances that permit the orchestration of temporally controlled phenotypic switches in immune cells during different phases of healing. The design strategies discussed herein can also be leveraged to target several complex autoimmune and inflammatory diseases.

Lung Cancer Induces NK Cell Contractility and Cytotoxicity Through Transcription Factor Nuclear Localization

Actomyosin-mediated cellular contractility is highly conserved for mechanotransduction and signalling. While this phenomenon has been observed in adherent cell models, whether/how contractile forces regulate the function of suspension cells like natural killer (NK) cells during cancer surveillance, is unknown. Here, we demonstrated in coculture settings that the evolutionarily conserved NK cell transcription factor, Eomes, undergoes nuclear shuttling during lung cancer cell surveillance. Biophysical and biochemical analyses revealed mechanistic enhancement of NK cell actomyosin-mediated contractility, which is associated with nuclear flattening, thus enabling nuclear entry of Eomes associated with enhanced NK cytotoxicity. We found that NK cells responded to the presumed immunosuppressive TGFβ in the NK-lung cancer coculture medium to sustain its intracellular contractility through myosin light chain phosphorylation, thereby promoting Eomes nuclear localization. Therefore, our results demonstrate that lung cancer cells provoke NK cell contractility as an early phase activation mechanism and that Eomes is a plausible mechano-responsive protein for increased NK cytotoxicity. There is scope for strategic application of actomyosin-mediated contractility modulating drugs ex vivo, to reinvigorate NK cells prior to adoptive cancer immunotherapy in vivo (177 words).

Immunoengineering strategies to enhance vascularization and tissue regeneration

Immune cells have emerged as powerful regulators of regenerative as well as pathological processes. The vast majority of regenerative immunoengineering efforts have focused on macrophages; however, growing evidence suggests that other cells of both the innate and adaptive immune system are as important for successful revascularization and tissue repair. Moreover, spatiotemporal regulation of immune cells and their signaling have a significant impact on the regeneration speed and the extent of functional recovery. In this review, we summarize the contribution of different types of immune cells to the healing process and discuss ways to manipulate and control immune cells in favor of vascularization and tissue regeneration. In addition to cell delivery and cell-free therapies using extracellular vesicles, we discuss in situ strategies and engineering approaches to attract specific types of immune cells and modulate their phenotypes. This field is making advances to uncover the extraordinary potential of immune cells and their secretome in the regulation of vascularization and tissue remodeling. Understanding the principles of immunoregulation will help us design advanced immunoengineering platforms to harness their power for tissue regeneration.

Gut feelings: mechanosensing in the gastrointestinal tract

The primary function of the gut is to procure nutrients. Synchronized mechanical activities underlie nearly all its endeavours. Coordination of mechanical activities depends on sensing of the mechanical forces, in a process called mechanosensation. The gut has a range of mechanosensory cells. They function either as specialized mechanoreceptors, which convert mechanical stimuli into coordinated physiological responses at the organ level, or as non-specialized mechanosensory cells that adjust their function based on the mechanical state of their environment. All major cell types in the gastrointestinal tract contain subpopulations that act as specialized mechanoreceptors: epithelia, smooth muscle, neurons, immune cells, and others. These cells are tuned to the physical properties of the surrounding tissue, so they can discriminate mechanical stimuli from the baseline mechanical state. The importance of gastrointestinal mechanosensation has long been recognized, but the latest discoveries of molecular identities of mechanosensors and technical advances that resolve the relevant circuitry have poised the field to make important intellectual leaps. This Review describes the mechanical factors relevant for normal function, as well as the molecules, cells and circuits involved in gastrointestinal mechanosensing. It concludes by outlining important unanswered questions in gastrointestinal mechanosensing.

Changes in Blood Cell Deformability in Chorea-Acanthocytosis and Effects of Treatment With Dasatinib or Lithium

Misshaped red blood cells (RBCs), characterized by thorn-like protrusions known as acanthocytes, are a key diagnostic feature in Chorea-Acanthocytosis (ChAc), a rare neurodegenerative disorder. The altered RBC morphology likely influences their biomechanical properties which are crucial for the cells to pass the microvasculature. Here, we investigated blood cell deformability of five ChAc patients compared to healthy controls during up to 1-year individual off-label treatment with the tyrosine kinase inhibitor dasatinib or several weeks with lithium. Measurements with two microfluidic techniques allowed us to assess RBC deformability under different shear stresses. Furthermore, we characterized leukocyte stiffness at high shear stresses. The results showed that blood cell deformability–including both RBCs and leukocytes - in general was altered in ChAc patients compared to healthy donors. Therefore, this study shows for the first time an impairment of leukocyte properties in ChAc. During treatment with dasatinib or lithium, we observed alterations in RBC deformability and a stiffness increase for leukocytes. The hematological phenotype of ChAc patients hinted at a reorganization of the cytoskeleton in blood cells which partly explains the altered mechanical properties observed here. These findings highlight the need for a systematic assessment of the contribution of impaired blood cell mechanics to the clinical manifestation of ChAc.

Peptides Regulating Proliferative Activity and Inflammatory Pathways in the Monocyte/Macrophage THP-1 Cell Line

This study evaluates the effects of five different peptides, the Epitalon^® tetrapeptide, the Vilon^® dipeptide, the Thymogen^® dipeptide, the Thymalin^® peptide complex, and the Chonluten^® tripeptide, as regulators of inflammatory and proliferative processes in the human monocytic THP-1, which is a human leukemia monocytic cell line capable of differentiating into macrophages by PMA in vitro. These peptides (Khavinson Peptides^®), characterized by Prof. Khavinson from 1973 onwards, were initially isolated from animal tissues and found to be organ specific. We tested the capacity of the five peptides to influence cell cultures in vitro by incubating THP-1 cells with peptides at certain concentrations known for being effective on recipient cells in culture. We found that all five peptides can modulate key proliferative patterns, increasing tyrosine phosphorylation of mitogen-activated cytoplasmic kinases. In addition, the Chonluten tripeptide, derived from bronchial epithelial cells, inhibited in vitro tumor necrosis factor (TNF) production of monocytes exposed to pro-inflammatory bacterial lipopolysaccharide (LPS). The low TNF release by monocytes is linked to a documented mechanism of TNF tolerance, promoting attenuation of inflammatory action. Therefore, all peptides inhibited the expression of TNF and pro-inflammatory IL-6 cytokine stimulated by LPS on terminally differentiated THP-1 cells. Lastly, by incubating the THP1 cells, treated with the peptides, on a layer of activated endothelial cells (HUVECs activated by LPS), we observed a reduction in cell adhesion, a typical pro-inflammatory mechanism. Overall, the results suggest that the Khavinson Peptides^® cooperate as natural inducers of TNF tolerance in monocyte, and act on macrophages as anti-inflammatory molecules during inflammatory and microbial-mediated activity.

Integrin Regulated Autoimmune Disorders: Understanding the Role of Mechanical Force in Autoimmunity

The pathophysiology of autoimmune disorders is multifactorial, where immune cell migration, adhesion, and lymphocyte activation play crucial roles in its progression. These immune processes are majorly regulated by adhesion molecules at cell–extracellular matrix (ECM) and cell–cell junctions. Integrin, a transmembrane focal adhesion protein, plays an indispensable role in these immune cell mechanisms. Notably, integrin is regulated by mechanical force and exhibit bidirectional force transmission from both the ECM and cytosol, regulating the immune processes. Recently, integrin mechanosensitivity has been reported in different immune cell processes; however, the underlying mechanics of these integrin-mediated mechanical processes in autoimmunity still remains elusive. In this review, we have discussed how integrin-mediated mechanotransduction could be a linchpin factor in the causation and progression of autoimmune disorders. We have provided an insight into how tissue stiffness exhibits a positive correlation with the autoimmune diseases’ prevalence. This provides a plausible connection between mechanical load and autoimmunity. Overall, gaining insight into the role of mechanical force in diverse immune cell processes and their dysregulation during autoimmune disorders will open a new horizon to understand this physiological anomaly.

Emerging Piezo1 signaling in inflammation and atherosclerosis; a potential therapeutic target

Purpose of Review: Atherosclerosis is the principal cause of cardiovascular diseases (CVDs) which are the major cause of death worldwide. Mechanical force plays an essential role in cardiovascular health and disease. To bring the awareness of mechanosensitive Piezo1 role in atherosclerosis and its therapeutic potentials we review recent literature to highlight its involvement in various mechanisms of the disease. Recent Findings: Recent studies reported Piezo1 channel as a sensor, and transducer of various mechanical forces into biochemical signals, which affect various cellular activities such as proliferation, migration, apoptosis and vascular remodeling including immune/inflammatory mechanisms fundamental phenomenon in atherogenesis. Summary: Numerous evidences suggest Piezo1 as a player in different mechanisms of cell biology, including immune/inflammatory and other cellular mechanisms correlated with atherosclerosis. This review discusses mechanistic insight about this matter and highlights the drugability and therapeutic potentials consistent with emerging functions Piezo1 in various mechanisms of atherosclerosis. Based on the recent works, we suggest Piezo1 as potential therapeutic target and a valid candidate for future research. Therefore, a deeper exploration of Piezo1 biology and translation towards the clinic will be a novel strategy for treating atherosclerosis and other CVDs.

Mechanobiology of immune cells: Messengers, receivers and followers in leishmaniasis aiding synthetic devices

Cytokines are influential molecules which can direct cells behavior. In this review, cytokines are referred as messengers, immune cells which respond to cytokine stimulus are referred as receivers and the immune cells which gets modulated due to their plasticity induced by infectious pathogen leishmania, are referred as followers. The advantage of plasticity of cells is taken by the parasite to switch them from parasite eliminating form to parasite survival favoring form through a process called as reciprocity which is undergone by cytokines, wherein pro-inflammatory to anti-inflammatory switch occur rendering immune cell population to switch their phenotype. Detailed study of this switch can help in identification of important targets which can help in restoring the phenotype to parasite eliminating form and this can be done through synthetic circuit, finding its wider applicability in therapeutics.

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Cytokines as messengers for governing reciprocity in infection.

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Leishmania induces reciprocity modulating the immune cells plasticity.

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Reciprocity of cytokines identifies important target for therapeutics.

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Therapeutic targets aiding the design of synthetic devices to combat infection.

Tailoring the physicochemical properties of nanomaterials for immunomodulation

Immunomodulation is poised to revolutionize the treatment of cancer, autoimmune diseases, and many other inflammation-related disorders. The immune system in these conditions can be either activated or suppressed by nanocarriers loaded with bioactive molecules. Although immunomodulation via these therapeutics has long been recognized, and a broad range of nanocarriers have been designed to accommodate varied usages, less studies have focused on the effects of nanomaterial physicochemical properties on immune responses, especially the immunity altered by nanocarrier materials alone. Conclusions are sometimes seemly inconsistent due to the complexities of nanomaterials and the immune system. An in-depth understanding of the nanocarrier-induced immune responses is essential for clinical applications. In this review, we summarize recent studies of the immune responses influenced by nanomaterial physicochemical properties with an emphasis on the intrinsic features of nanomaterials that modulate the innate and adaptive immunities. We then provide our perspectives on the design of nanomaterials for immunomodulation.

Generation of programmable dynamic flow patterns in microfluidics using audio signals

Customised audio signals, such as musical notes, can be readily generated by audio software on smartphones and played over audio speakers. Audio speakers translate electrical signals into the mechanical motion of the speaker cone. Coupling the inlet tube to the speaker cone causes the harmonic oscillation of the tube, which in turn changes the velocity profile and flow rate. We employ this strategy for generating programmable dynamic flow patterns in microfluidics. We show the generation of customised rib and vortex patterns through the application of multi-tone audio signals in water-based and whole blood samples. We demonstrate the precise capability to control the number and extent of the ribs and vortices by simply setting the frequency ratio of two- and three-tone audio signals. We exemplify potential applications of tube oscillation for studying the functional responses of circulating immune cells under pathophysiological shear rates. The system is programmable, compact, low-cost, biocompatible, and durable. These features make it suitable for a variety of applications across chemistry, biology, and physics.

Stretching the Function of Innate Immune Cells

The importance of innate immune cells to sense and respond to their physical environment is becoming increasingly recognized. Innate immune cells (e.g. macrophages and neutrophils) are able to receive mechanical signals through several mechanisms. In this review, we discuss the role of mechanosensitive ion channels, such as Piezo1 and transient receptor potential vanilloid 4 (TRPV4), and cell adhesion molecules, such as integrins, selectins, and cadherins in biology and human disease. Furthermore, we explain that these mechanical stimuli activate intracellular signaling pathways, such as MAPK (p38, JNK), YAP/TAZ, EDN1, NF-kB, and HIF-1α, to induce protein conformation changes and modulate gene expression to drive cellular function. Understanding the mechanisms by which immune cells interpret mechanosensitive information presents potential targets to treat human disease. Important areas of future study in this area include autoimmune, allergic, infectious, and malignant conditions.

Mechanosensing by Piezo1 and its implications for physiology and various pathologies

Piezo1 is a mechanosensitive ion channel with essential roles in cardiovascular, lung, urinary, and immune functions. Piezo1 is widely distributed in different tissues in the human body and its specific roles have been identified following a decade of research; however, not all are well understood. Many structural and functional characteristics of Piezo1 have been discovered and are known to differ greatly from the characteristics of other mechanosensitive ion channels. Understanding the mechanisms by which this ion channel functions may be useful in determining its physiological roles in various organ systems. This review provides insight into the signalling pathways activated by mechanical stimulation of Piezo1 in various organ systems and cell types. We discuss downstream targets of Piezo1 and the overall effects resulting from Piezo1 activation, which may provide insights into potential treatment targets for diseases involving this ion channel.

Rational Design of Immunomodulatory Hydrogels for Chronic Wound Healing

With all the advances in tissue engineering for construction of fully functional skin tissue, complete regeneration of chronic wounds is still challenging. Since immune reaction to the tissue damage is critical in regulating both the quality and duration of chronic wound healing cascade, strategies to modulate the immune system are of importance. Generally, in response to an injury, macrophages switch from pro-inflammatory to an anti-inflammatory phenotype. Therefore, controlling macrophages' polarization has become an appealing approach in regenerative medicine. Recently, hydrogels-based constructs, incorporated with various cellular and molecular signals, have been developed and utilized to adjust immune cell functions in various stages of wound healing. Here, the current state of knowledge on immune cell functions during skin tissue regeneration is first discussed. Recent advanced technologies used to design immunomodulatory hydrogels for controlling macrophages' polarization are then summarized. Rational design of hydrogels for providing controlled immune stimulation via hydrogel chemistry and surface modification, as well as incorporation of cell and molecules, are also dicussed. In addition, the effects of hydrogels' properties on immunogenic features and the wound healing process are summarized. Finally, future directions and upcoming research strategies to control immune responses during chronic wound healing are highlighted.

Matrix biophysical cues direct mesenchymal stromal cell functions in immunity

Hydrogels have been used to design synthetic matrices that capture salient features of matrix microenvironments to study and control cellular functions. Recent advances in understanding of both extracellular matrix biology and biomaterial design have shown that biophysical cues are powerful mediators of cell biology, especially that of mesenchymal stromal cells (MSCs). MSCs have been tested in many clinical trials because of their ability to modulate immune cells in different pathological conditions. While roles of biophysical cues in MSC biology have been studied in the context of multilineage differentiation, their significance in regulating immunomodulatory functions of MSCs is just beginning to be elucidated. This review first describes design principles behind how biophysical cues in native microenvironments influence the ability of MSCs to regulate immune cell production and functions. We will then discuss how biophysical cues can be leveraged to optimize cell isolation, priming, and delivery, which can help improve the success of MSC therapy for immunomodulation. Finally, a perspective is presented on how implementing biophysical cues in MSC potency assay can be important in predicting clinical outcomes. STATEMENT OF SIGNIFICANCE: Stromal cells of mesenchymal origin are known to direct immune cell functions in vivo by secreting paracrine mediators. This property has been leveraged in developing mesenchymal stromal cell (MSC)-based therapeutics by adoptive transfer to treat immunological rejection and tissue injuries, which have been tested in over one thousand clinical trials to date, but with mixed success. Advances in biomaterial design have enabled precise control of biophysical cues based on how stromal cells interact with the extracellular matrix in microenvironments in situ. Investigators have begun to use this approach to understand how different matrix biophysical parameters, such as fiber orientation, porosity, dimensionality, and viscoelasticity impact stromal cell-mediated immunomodulation. The insights gained from this effort can potentially be used to precisely define the microenvironmental cues for isolation, priming, and delivery of MSCs, which can be tailored based on different disease indications for optimal therapeutic outcomes.

Maintaining proteostasis under mechanical stress

Cell survival, tissue integrity and organismal health depend on the ability to maintain functional protein networks even under conditions that threaten protein integrity. Protection against such stress conditions involves the adaptation of folding and degradation machineries, which help to preserve the protein network by facilitating the refolding or disposal of damaged proteins. In multicellular organisms, cells are permanently exposed to stress resulting from mechanical forces. Yet, for long time mechanical stress was not recognized as a primary stressor that perturbs protein structure and threatens proteome integrity. The identification and characterization of protein folding and degradation systems, which handle force-unfolded proteins, marks a turning point in this regard. It has become apparent that mechanical stress protection operates during cell differentiation, adhesion and migration and is essential for maintaining tissues such as skeletal muscle, heart and kidney as well as the immune system. Here, we provide an overview of recent advances in our understanding of mechanical stress protection.