Environmental sensing through focal adhesions

Engineering multifunctional surface topography to regulate multiple biological responses

Surface topography or curvature plays a crucial role in regulating cell behavior, influencing processes such as adhesion, proliferation, and gene expression. Recent advancements in nano- and micro-fabrication techniques have enabled the development of biomimetic systems that mimic native extracellular matrix (ECM) structures, providing new insights into cell-adhesion mechanisms, mechanotransduction, and cell-environment interactions. This review examines the diverse applications of engineered topographies across multiple domains, including antibacterial surfaces, immunomodulatory devices, tissue engineering scaffolds, and cancer therapies. It highlights how nanoscale features like nanopillars and nanospikes exhibit bactericidal properties, while many microscale patterns can direct stem cell differentiation and modulate immune cell responses. Furthermore, we discuss the interdisciplinary use of topography for combined applications, such as the simultaneous regulation of immune and tissue cells in 2D and 3D environments. Despite significant advances, key knowledge gaps remain, particularly regarding the effects of topographical cues on multicellular interactions and dynamic 3D contexts. This review summarizes current fabrication methods, explores specific and interdisciplinary applications, and proposes future research directions to enhance the design and utility of topographically patterned biomaterials in clinical and experimental settings.

Inhibition of Talin2 dedifferentiates myofibroblasts and reverses lung and kidney fibrosis

Fibrosis is involved in 45% of deaths in the United States, and no treatment exists to reverse progression of the disease. To find novel targets for fibrosis therapeutics, we developed a model for the differentiation of monocytes to myofibroblasts that allowed us to screen for proteins involved in myofibroblast differentiation. Inhibition of a novel protein target generated by our model, talin2, reduces myofibroblast-specific morphology, α-smooth muscle actin content, and collagen I content and lowers the pro-fibrotic secretome of myofibroblasts. We find that knockdown of talin2 de-differentiates myofibroblasts and reverses bleomycin-induced lung fibrosis in mice, and further that Tln2-/- mice are resistant to bleomycin-induced lung fibrosis and resistant to unilateral ureteral obstruction-induced kidney fibrosis. Talin2 inhibition is thus a potential treatment for reversing lung and kidney fibroses.

Androgen receptor plays critical role in regulating cervical cancer cell migration

Cervical cancer (CC) is the second most common cancer among women in India and the fourth worldwide. While major genes and pathways have been studied, further research is needed to identify newer candidates for targeted therapy in metastatic disease. This study used a graph-theory-based network analysis to identify important interacting proteins (IIPs) with maximum connectivity, high centrality scores, and significant global and local network perturbation scores. Among the identified IIPs, the Androgen receptor (AR) emerged as one of the crucial yet understudied regulator in cervical cancer. Patient samples, ex vivo, and in vitro experiments showed significant downregulation of AR in cervical cancer. Ligand-dependent overexpression of AR reduced cancer cell migration while failed to induce apoptosis in CC cell lines. Downregulation of mesenchymal markers and restoration of epithelial markers upon exogenous expression of AR suggested its potential in reversing invasive properties of cervical cancer cells. AR overexpression followed by activation upregulated its downstream target PTEN and downregulated pPI3K levels, which in turn restored GSK3β activity by interfering with AKT phosphorylation, probably leading to degradation of mesenchymal markers in cervical cancer cells. Further studies showed that AR reduced cell motility by hindering focal adhesion formation and Actin filament assembly. An increased G-Actin ratio suggested AR disrupted cytoskeletal dynamics through altering the RhoA/ROCK1/LIMK1/CFL1 pathway eventually impeding cervical cancer cell spread.

Synphilin-1 regulates mechanotransduction in rigidity sensing through interaction with zyxin

BACKGROUND

Synphilin-1 has been studied extensively in the context of Parkinson's disease pathology. However, the biophysical functions of synphilin-1 remain unexplored. To investigate its novel functionalities herein, cellular traction force and rigidity sensing ability are analyzed based on synphilin-1 overexpression using elastomeric pillar arrays and substrates of varying stiffness. Molecular changes are analyzed using RNA sequencing-based transcriptomic and liquid chromatography-tandem mass spectrometry-based proteomic analyses.

RESULTS

Synphilin-1 overexpression reduces cell area, with a decline of local contraction on elastomeric pillar arrays. Cells overexpressing synphilin-1 exhibit an impaired ability to respond to substrate rigidity; however, synphilin-1 knockdown restores rigidity sensing abilities. Integrated omics analysis and in silico prediction corroborate the phenotypic alterations induced by synphilin-1 overexpression at a biophysical level. Zyxin emerges as a novel synphilin-1 binding protein, and synphilin-1 overexpression reduces the nuclear translocation of yes-associated protein.

CONCLUSION

These findings provide novel insights into the biophysical functions of synphilin-1, suggesting a potential protective role to the altered extracellular matrix, which may be relevant to neurodegenerative conditions such as Parkinson's disease.

The Importance of Coating Surface and Composition for Attachment and Survival of Neuronal Cells Under Mechanical Stimulation

Cell culture of neuronal cells places high demands on the surface for these cells to adhere to and grow on. Native extracellular matrix (ECM) proteins are often applied to the cell culture surface. The substrate is even more important when mechanical strain is applied to the cells in culture. These cells will easily detach and die, precluding the study of how mechanical factors affect these cells. Mechanical factors are, for example, important in the eye disorder glaucoma, which is characterized by the loss of the retinal ganglion cells (RGCs), the retinal neurons that transfer the visual information from the retina via the optic nerve to the brain. High intraocular pressure is the main risk factor of glaucoma. Here, we aimed to find an optimal coating formulation for mechanical testing of the two cell types that are often used for in vitro studies on glaucoma: primary rat retinal ganglion cells (RGCs) and the neuronal PC-12 cell line. Glass and polymer coverslips as well as well plate wells were coated with various substrates: fibronectin, collagen 1, RGD peptide, polyethyleneimine (PEI), poly-D-lysine (PDL), and laminin. We used a thermomixer for 1 min at 500RPM and 37°C to apply mechanical strain and test cell attachment in medium throughput during mechanical stimulation. Cell density, morphology, and cell death were measured to evaluate the coatings. First, a screen of various surfaces and coatings was performed using PC-12 cells, after which a selection of coating strategies was tested with RGCs. For PC-12 cells, the best results were obtained using a coating with a mixture of 10 μg/mL PDL with 2 or 50 μg/mL laminin in PBS (M2). This resulted in the highest cell density, with and without mechanical stimulation. Many other coating strategies failed to provide an effective substrate for adherence and growth of PC-12 cells. Coating composition as well as coating strategy influenced cell attachment and survival. Contrary to PC-12 cells, RGCs performed better in a sequential coating of first 10 μg/mL PDL and then 2 μg/mL laminin (S2). With this protocol, RGCs showed best neurite growth and highest cell density. Based on this difference between PC-12 cells and RGCs, we conclude that the optimal coating depends on the cell type. When reporting cell culture studies, it is important to fully specify culture surface, surface treatment, and coating protocol since all these factors influence cell attachment, growth, and survival.

Guided neural stem cell differentiation by dynamic loading of 3D printed elastomeric scaffolds

The limited regenerative ability of "permanent" cells is a major barrier to treating conditions like spinal cord injury (SCI) and myocardial infarction (MI). The delivery of stem cells, which can generate various cell types, offer potential for personalized therapy with reduced immunoreaction and recovery time. However, restoring function to these tissues also requires new or replacement cells to align properly. Neurons, for example, must organize and extend parallel axons, mimicking their natural structure for directional signal propagation. Current stem cell differentiation methods lack guidance, resulting in randomly distributed axons and limited repair effectiveness. Advancing methods and materials to guide stem cell differentiation into functional, aligned nerve bundles is crucial for improving SCI treatment outcomes. This study aimed to develop an in vitro system to promote aligned neural differentiation by applying cyclic uniaxial tension to PC-12 stem cells adhered to 3D-printed elastic scaffolds. We created a simple loading device which can apply cyclic and controllable stretching force to a scaffold, which in turn transmits uniaxial tension to cells adhered to the scaffold during their differentiation. An elastomer ink for 3D printing scaffolds was formulated and surface treatment processes were investigated to enhance the cell-scaffold adhesion to support the dynamic loading. It was revealed that a corona discharge treatment while the scaffold is soaked with type I collagen can significantly enhance cell adhesion. A range of strain magnitudes and frequencies were revealed to enhance the differentiation of neural tissue derived PC-12 cells to neuron cells and increase the length of their neurites up to 76%. The combination of 3% maximum strain and 1 Hz loading frequency maximized differentiation and neurite extension. These findings demonstrate that dynamic mechanical stimulation enhances neural differentiation and organization, offering an alternative approach for regenerative therapies targeting SCI and similar conditions.

Nano-Topography Enhanced Topological-Cell-Analysis in Radiation-Therapy

Radiotherapy (RT) is a cancer treatment technique that involves exposing cells to ionizing radiation, including X-rays, electrons, or protons. RT offers promise to treat cancer, however, some inherent limitations can hamper its performance. Radio-resistance, whether innate or acquired, refers to the ability of tumor cells to withstand treatment, making it a key factor in RT failure. This perspective hypothesizes that nanoscale surface topography can impact on the topology of cancer cells network under radiation, and that this understanding can possibly advance the assessment of cell radio-resistance in RT applications. An experimental plan is proposed to test this hypothesis, using cancer cells exposed to various RT forms. By examining the influence of 2D surface and 3D scaffold nanoscale architecture on cancer cells, this approach diverges from traditional methodologies, such as clonogenic assays, offering a novel viewpoint that integrates fields such as tissue engineering, artificial intelligence, and nanotechnology. The hypotheses at the base of this perspective not only may advance cancer treatment but also offers insights into the broader field of structural biology. Nanotechnology and label-free Raman phenotyping of biological samples are lenses through which scientists can possibly better elucidate the structure-function relationship in biological systems.

Spatial regulation of mitochondrial membrane potential by α5β1 integrin engagement in collective cell migration

The mechanistic links between mechanical forces and bioenergetics remain elusive. We report an increase in mitochondrial membrane potential (MMP) along the leading row of collectively migrating Xenopus laevis mesendoderm cells at sites where fibronectin-α5β1 integrin substrate traction stresses are greatest. Real-time metabolic analyses reveal α5β1 integrin-dependent increases in respiration efficiency in cells on fibronectin substrates. Elevation of metabolic activity is reduced following pharmacologic inhibition of focal adhesion kinase (FAK; also known as PTK2) signaling. Attachment of mesendoderm cells to fibronectin fragments that support differing α5β1 integrin conformational and ligand-binding affinity states, increases MMP when both the Arg-Gly-Asp (RGD) and Pro-Pro-Ser-Arg-Asn (PPSRN) synergy sites of fibronectin are engaged by the receptor. Cell stretch on deformable fibronectin substrates also results in a FAK-dependent increase in MMP. Inhibition of MMP or ATP-synthase activity slows collective cell migration velocity in vivo, further suggesting that integrin-dependent adhesion and signaling contribute to metabolic changes. These data highlight an underexplored link between extracellular matrix (ECM)-integrin adhesion and metabolic activity in embryonic cell migration. We propose that fibronectin-integrin adhesion and signaling help shape the metabolic landscape of collectively migrating cells.

Specific Cell Adhesion at Nano-Biointerfaces: Synergistic Effect of Topographical Matching and Molecular Recognition

Specific cell adhesion is essential for functional biointerfaces, especially in cancer diagnosis. However, the role of surface nanotopography in this process remains unclear. Herein, we reveal the critical role of surface nanotopography by measuring adhesion forces utilizing fluidic force microscopy (FluidFM). The antibody-coated nanospiky surface exhibits cell adhesion force 1 to 2 orders of magnitude higher than those of the flat, nanospiky, and antibody-coated flat surfaces. This amplified effect is related to a time-dependent reversal, with adhesion force on nanospiky surfaces initially weaker than that on flat surfaces but eventually surpassing it. Mathematical simulations further demonstrate that micro-nanostructured surfaces maximize contact points, enabling multiscale, multipoint cell-substrate interactions, consistent with experimental results. From thermodynamic and kinetic perspectives, we propose a multiscale, multipoint recognition model based on the synergistic effect of topographical matching and molecular recognition. Our findings provide valuable clues for biointerface design in cancer diagnosis, drug screening, and tissue engineering.

The formin FMNL2 plays a role in the response of melanoma cells to substrate stiffness

BACKGROUND

Cells constantly sense and respond to changes in their local environment to adapt their behaviour and morphology. These external stimuli include chemical and mechanical signals, and much recent work has revealed the complexity of the cellular response to changes in substrate stiffness. We investigated the effects of substrate stiffness on the morphology and motility of A2058 human melanoma cells. FMNL2, a formin protein associated with actin cytoskeleton dynamics, regulates melanoma cell morphology and motility, but its role in stiffness sensing remains unclear. This study examines how A2058 cells respond to substrates of varying stiffness and evaluates the impact of FMNL2 depletion on these responses.

RESULTS

We found that with increasing substrate stiffness the cells transitioned from a rounded cell morphology to progressively more elongated morphologies with a concomitant increase in actin stress fiber alignment. Depletion of FMNL2 expression amplified these morphological changes, with knockdown cells showing consistently greater elongation and more pronounced stress fiber alignment compared to controls. Notably, the orientational order parameter (S) revealed higher alignment of actin filaments along the cell's long axis in knockdown cells. Substrate stiffness also affected cell motility, indicated by an apparent optimal stiffness that maximized motility followed by a notable decrease in distance travelled during migration on progressively stiffer substrates. This decrease was largely attributable to a decrease in the time the cells spent in motion as the substrate stiffness increased. FMNL2 depletion significantly exacerbated this effect, with knockdown cells traveling shorter net distances and spending less time moving across all substrates.

CONCLUSIONS

This study demonstrates that substrate stiffness profoundly influences A2058 melanoma cell morphology and motility, with FMNL2 playing a pivotal regulatory role. Our observations suggest that FMNL2 is critical for maintaining motility and morphological adaptability under increased stiffness. Loss of FMNL2 enhanced stress fiber alignment and cell elongation while impairing motility, particularly on stiff substrates, revealing FMNL2 as a mechanosensitive effector. This work highlights the need to study metastatic cell behaviour on substrates with biologically relevant properties and provides the foundation for future effort to determine the mechanism by which FMNL2 participates in the melanoma cell response to substrate stiffness.

Effect of elastic modulus of tumour and non-tumour cells on vibration-induced behaviours

The mechanical behaviour of tumour and non-tumour cells under vibration remains insufficiently explored, particularly the role of elastic modulus in dynamic responses. This study investigates the vibration-induced mechanical behaviour in cellular structures with varying elastic moduli (E = 0.1 , 1 , and 10 kPa) and aspect ratios ([Formula: see text] and 4), focusing on vertical and horizontal forced vibrations. Finite element analysis was conducted to evaluate the natural frequencies, mode shapes, membrane accelerations, and stress responses. The intermediate aspect-ratio structures ([Formula: see text]) exhibited higher natural frequencies but a 64.2% increase in stress concentration, making them more susceptible to localised deformation under resonance. Conversely, higher aspect-ratio structures ([Formula: see text]) demonstrated improved vibrational stability with reduced resonance peaks and 64.6% lower localised stress. This study further confirmed that vertical vibrations generate higher stress and acceleration than horizontal vibrations owing to gravitational effects. Stress contour analysis indicated that under low-intensity vibrations, intermediate aspect-ratio structures may exceed their yield stress thresholds, leading to potential membrane rupture. These findings suggest that vibration-induced mechanical stimulation can be sensed differently depending on the elastic moduli and aspect ratios of tumour and non-tumour cells.

Actin Binding to the BAR Domain and Arf GAP Activity of ASAP1 Coordinately Control Actin Stress Fibers and Focal Adhesions

BACKGROUND

Actin stress fibers (SFs) and focal adhesions (FAs) are dynamic structures crucial to a range of cell behaviors including cell morphology, cell migration, proliferation, survival, and differentiation. The Arf GAP ASAP1 affects both SFs and FAs. Here, we test the hypothesis that two domains with distinct biochemical activities in ASAP1, the BAR domain that binds actin and nonmuscle myosin 2 (NM2) and the Arf GAP domain, which is necessary for inducing hydrolysis of GTP bound to Arf, coordinately regulate the structures.

RESULTS

We found that ASAP1 associated with bundled actin, including SFs, colocalizing with α-actinin and nonmuscle myosin 2A (NM2A), and with paxillin in FAs. Reducing ASAP1 expression altered both SFs and FAs in four cell lines that we examined. The effects of reducing ASAP1 expression could be reversed by ectopic expression of ASAP1. Reduced expression of Arf5, a substrate for ASAP1, or expression of either dominant negative or GTPase deficient mutants of Arf5, affected SFs and FAs similarly to ASAP1 knockdown. Both an active GAP domain and a BAR domain contained in the same ASAP1 polypeptide were necessary to maintain FAs and SFs.

CONCLUSIONS AND SIGNIFICANCE

Taken together, the results support the idea that ASAP1 coordinates the maintenance of FAs and SFs through integrated function of the BAR and GAP domains. We speculate that ASAP1 regulates SFs and their interaction with FAs through direct binding to components of the actin cytoskeleton. We discuss hypotheses related to this Arf-dependent activity of ASAP1 and propose the function of ASAP1 is not control of Arf•GTP levels.

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

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

Focal adhesion in the tumour metastasis: from molecular mechanisms to therapeutic targets

The tumour microenvironment is the "hotbed" of tumour cells, providing abundant extracellular support for growth and metastasis. However, the tumour microenvironment is not static and is constantly remodelled by a variety of cellular components, including tumour cells, through mechanical, biological and chemical means to promote metastasis. Focal adhesion plays an important role in cell-extracellular matrix adhesion. An in-depth exploration of the role of focal adhesion in tumour metastasis, especially their contribution at the biomechanical level, is an important direction of current research. In this review, we first summarize the assembly of focal adhesions and explore their kinetics in tumour cells. Then, we describe in detail the role of focal adhesion in various stages of tumour metastasis, especially its key functions in cell migration, invasion, and matrix remodelling. Finally, we describe the anti-tumour strategies targeting focal adhesion and the current progress in the development of some inhibitors against focal adhesion proteins. In this paper, we summarize for the first time that focal adhesion play a positive feedback role in pro-tumour metastatic matrix remodelling by summarizing the five processes of focal adhesion assembly in a multidimensional way. It is beneficial for researchers to have a deeper understanding of the role of focal adhesion in the biological behaviour of tumour metastasis and the potential of focal adhesion as a therapeutic target, providing new ideas for the prevention and treatment of metastases.

Effects of hydrogel stiffness and viscoelasticity on organoid culture: a comprehensive review

As an emerging technology, organoids are promising new tools for basic and translational research in disease. Currently, the culture of organoids relies mainly on a type of unknown composition scaffold, namely Matrigel, which may pose problems in studying the effect of mechanical properties on organoids. Hydrogels, a new material with adjustable mechanical properties, can adapt to current studies. In this review, we summarized the synthesis of recent advance in developing definite hydrogel scaffolds for organoid culture and identified the critical parameters for regulating mechanical properties. In addition, classified by different mechanical properties like stiffness and viscoelasticity, we concluded the effect of mechanical properties on the development of organoids and tumor organoids. We hope this review enhances the understanding of the development of organoids by hydrogels and provides more practical approaches to investigating them.

AP2A1 modulates cell states between senescence and rejuvenation

Aging proceeds with the accumulation of senescent cells in multiple organs. These cells exhibit increased size compared to young cells, which promotes further senescence and age-related diseases. Currently, the molecular mechanism behind the maintenance of such huge cell architecture undergoing senescence remains poorly understood. Here we focus on the reorganization of actin stress fibers induced upon replicative senescence in human fibroblasts, widely used as a senescent cell model. We identified, together with our previous proteomic study, that AP2A1 (alpha 1 adaptin subunit of the adaptor protein 2) is upregulated in senescent cells along the length of enlarged stress fibers. Knockdown of AP2A1 reversed senescence-associated phenotypes, exhibiting features of cellular rejuvenation, while its overexpression in young cells advanced senescence phenotypes. Similar functions of AP2A1 were identified in UV- or drug-induced senescence and were observed in epithelial cells as well. Furthermore, we found that AP2A1 is colocalized with integrin β1, and both proteins move linearly along stress fibers. With the observations that focal adhesions are enlarged in senescent cells and that this coincides with strengthened cell adhesion to the substrate, these results suggest that senescent cells maintain their large size by reinforcing their effective anchorage through integrin β1 translocation along stress fibers. This mechanism may work efficiently in senescent cells, compared with a case relying on random diffusion of integrin β1, given the enlarged cell size and resulting increase in travel time and distance for endocytosed vesicle transportation.

The influence of the cytoskeleton on the development and behavior of viral factories in mammalian orthoreovirus

Cytosolic viral factories (VFs) of mammalian orthoreovirus (MRV) are sites for viral genome replication and assembly of virus progeny. Despite advancements in reverse genetics, the formation and dynamics of VFs still need to be clarified. MRV exploits host cytoskeletal components like microtubules (MTs) throughout its life cycle, including cell entry, replication, and release. MRV VFs, membrane-less cytosolic inclusions, rely on the viral proteins μ2 and μNS for formation. Protein μ2 interacts and stabilizes MTs through acetylation, supporting VF formation and viral replication, while scaffold protein μNS influences cellular components to aid VF maturation. The disruption of the MT network reduces viral replication, underscoring its importance. Additionally, μ2 associates with MT-organizing centers, modulating the MT dynamics to favor viral replication. In summary, MRV subverts the cytoskeleton to facilitate VF dynamics and promote viral replication and assembly to promote VF dynamics, replication, and assembly, highlighting the critical role of the cytoskeleton in viral replication.

Exploring Morphological and Molecular Properties of Different Adipose Cell Models: Monolayer, Spheroids, Gellan Gum-Based Hydrogels, and Explants

White adipose tissue (WAT) plays a crucial role in energy homeostasis and secretes numerous adipokines with far-reaching effects. WAT is linked to diseases such as diabetes, cardiovascular disease, and cancer. There is a high demand for suitable in vitro models to study diseases and tissue metabolism. Most of these models are covered by 2D-monolayer cultures. This study aims to evaluate the performance of different WAT models to better derive potential applications. The stability of adipocyte characteristics in spheroids and two 3D gellan gum hydrogels with ex situ lobules and 2D-monolayer culture is analyzed. First, the differentiation to achieve adipocyte-like characteristics is determined. Second, to evaluate the maintenance of differentiated ASC-based models, an adipocyte-based model, and explants over 3 weeks, viability, intracellular lipid content, perilipin A expression, adipokine, and gene expression are analyzed. Several advantages are supported using each of the models. Including, but not limited to, the strong differentiation in 2D-monolayers, the self-assembling within spheroids, the long-term stability of the stem cell-containing hydrogels, and the mature phenotype within adipocyte-containing hydrogels and the lobules. This study highlights the advantages of 3D models due to their more in vivo-like behavior and provides an overview of the different adipose cell models.

Deep plasma and tissue proteome profiling of knockout mice reveals pathways associated with Svep1 deficiency

Despite strong causal associations with cardiovascular and metabolic disorders including coronary artery disease, hypertension, and type 2 diabetes, as well as a range of other diseases, the exact function of the protein SVEP1 remains largely unknown. Animal models have been employed to investigate how SVEP1 contributes to disease, with a focus on murine models exploring its role in development, cardiometabolic disease and platelet biology. In this study, we aimed to comprehensively phenotype the proteome of Svep1 +/- mice compared to wild-type (WT) littermates using liquid chromatography-tandem mass spectrometry (LC-MS/MS) bottom-up proteomics in plasma, heart, aorta, lung, and kidney to identify dysregulated pathways and biological functions associated with Svep1 deficiency. Our findings reveal that Svep1 deficiency leads to significant proteomic alterations across the mouse, with the highest number of dysregulated proteins observed in plasma and kidney. Key dysregulated proteins in plasma include upregulation of ADGRV1, CDH1, and MYH6, and downregulation of MTIF2 and AKAP13 which, alongside other proteins dysregulated across tissues, indicate disruption in cell adhesion, extracellular matrix organisation, platelet degranulation, and Rho GTPase pathways. Novel findings include significant enrichment of complement cascades in plasma, suggesting dysregulation of innate immune responses and hemostasis due to Svep1 deficiency. Pathways related to chylomicron assembly and lipid metabolism were also enriched. Additionally, we developed a high-throughput quantitative targeted LC-MS/MS assay to measure endogenous levels of murine SVEP1. SVEP1 was detectable in lung homogenate and showed a significant reduction in SVEP1 levels in Svep1 +/- vs. WT, but was not identified in plasma, heart, aorta, or kidney, likely due to expression levels below the assay's detection limit. Overall, this deep phenotyping study provides insight into the systemic impact of Svep1 deficiency.

G3BP1 ribonucleoprotein complexes regulate focal adhesion protein mobility and cell migration

The subcellular localization of mRNAs plays a pivotal role in biological processes, including cell migration. For instance, β-actin mRNA and its associated RNA-binding protein (RBP), ZBP1/IGF2BP1, are recruited to focal adhesions (FAs) to support localized β-actin synthesis, crucial for cell migration. However, whether other mRNAs and RBPs also localize at FAs remains unclear. Here, we identify hundreds of mRNAs that are enriched at FAs (FA-mRNAs). FA-mRNAs share characteristics with stress granule (SG) mRNAs and are found in ribonucleoprotein (RNP) complexes with the SG RBP. Mechanistically, G3BP1 binds to FA proteins in an RNA-dependent manner, and its RNA-binding and dimerization domains, essential for G3BP1 to form RNPs in SG, are required for FA localization and cell migration. We find that G3BP1 RNPs promote cell speed by enhancing FA protein mobility and FA size. These findings suggest a previously unappreciated role for G3BP1 RNPs in regulating FA function under non-stress conditions.

Focal Adhesion Kinase Alleviates Simulated Microgravity-Induced Inhibition of Osteoblast Differentiation by Activating Transcriptional Wnt/β-Catenin-BMP2-COL1 and Metabolic SIRT1-PGC-1α-CPT1A Pathways

The metabolic poise, or balance, between glycolysis and fatty acid oxidation (FAO) has recently been found to play a critical role in osteogenic differentiation and homeostasis. While simulated microgravity (SMG) is known to impede osteoblast differentiation (OBD) by inhibiting the Wnt/β-catenin pathway, how it affects osteoblast metabolism in this context remains unclear. We previously analyzed the effect of SMG on the differentiation of pre-osteoblast MC3T3-E1 cells and found that it reduced focal adhesion kinase (FAK) activity. This, in turn, downregulated Wnt/β-catenin and two of its downstream targets critical for OBD bone morphogenic protein-2 (BMP2) and type-1 collagen (COL1) formation, leading to a reduction in alkaline phosphatase (ALP) activity and cell matrix mineralization. In this study, we further analyzed how SMG-induced alterations in energy metabolism contribute to the inhibition of OBD in MC3T3-E1 cells. Consistent with our earlier findings, we demonstrated that SMG inhibits OBD by downregulating the collective activity of FAK and the Wnt/β-catenin-BMP2-COL1 transcriptional pathway. Interestingly, we observed that SMG also reduces the abundance of sirtuin-1 (SIRT1), peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) and carnitine palmitoyl transferase-1α (CPT1A), which are all key metabolic factors regulating mitochondrial number and FAO capacity. Accordingly, we found that the mitochondrial content and FAO potential of MC3T3-E1 cells were lower upon exposure to SMG but were both rescued upon administration of the FAK activator cytotoxic necrotizing factor-1 (CNF1), thereby allowing cells to overcome SMG-induced inhibition of OBD. Taken together, our study indicates that the metabolic regulator SIRT1 may be a new target for reversing SMG-induced bone loss.

Transcriptomic Analysis Divulges Differential Expressions of Microglial Genes After Microglial Repopulation in Mice

Microglia are key immune cells in the central nervous system (CNS) and maintain hemostasis in physiological conditions. Microglial depletion leads to rapid repopulation, but the gene expression and signaling pathways related to repopulation remain unclear. Here, we used RNA sequencing (RNA-Seq) analysis to profile the transcriptome of microglia-depleted tissue by taking advantage of a conditional genetic microglial depletion model (CX3CR1CreER/+ system). Differential gene expression (DGE) sequencing analysis showed that 1226 genes were differentially up- and downregulated in both groups compared to control. Our data demonstrated that many microglial genes were highly regulated on day 3 after depletion but the numbers of differentially expressed genes were reduced by day 7. Gene ontology (GO) analysis categorized these differentially expressed genes on day 3 and day 7 to the specific biological processes, such as cell proliferation, cell activation, and cytokine and chemokine production. DGE analysis indicated that specific genes related to proliferation were regulated after depletion. Consistent with the changes in transcriptome, the histological analysis of transgenic mice revealed that the microglia after depletion undergo proliferation and activation from day 3 to day 7. Collectively, these results suggest that transcriptomic changes in microglial genes during depletion have a profound implication for the renewal and activation of microglia and may help to understand the regulatory mechanism of microglial activation in disease conditions.

Hierarchical TiO2 nanotube arrays enhance mesenchymal stem cell adhesion and regenerative potential through surface nanotopography

The concept of preconditioning mesenchymal stem cells (MSCs) under different stress conditions or with bioactive molecules is introduced to optimize their therapeutic potential. This study investigates the physicochemical effect of hierarchical TiO2 nanotube arrays, a versatile and easy-to-prepare nanosurface, on MSC behaviour. By precisely controlling the nanotopography through anodization, we demonstrate the significant influence of surface properties on MSC adhesion, proliferation and differentiation. Electrostatic interactions between surface charge and proteins play a crucial role in these cellular responses. In addition, preconditioning MSCs under specific conditions enhances their therapeutic potential by optimizing paracrine signalling and homing properties. Higher surface charges and increasing spiky character of surface roughness of titania samples after anodization at 60 V significantly upregulated chemokine receptor type 4 (CXCR4) and vascular endothelial growth factor A (VEGFA), indicating the enhanced migratory and angiogenic potential of MSCs. The study reveals the mechanotransductive effects of nanotopography on MSC differentiation, suggesting that tailored surface features can direct cellular fate. These findings highlight the potential of hierarchical TiO2 nanotube arrays as a promising platform for regenerative medicine, offering a novel approach to improve tissue engineering and therapeutic outcomes.

Competing elastic and viscous gradients determine directional cell migration

Cell migration regulates central life processes including embryonic development, tissue regeneration, and tumor invasion. To establish the direction of migration, cells follow exogenous cues. Durotaxis, the directed cell migration towards elastic stiffness gradients, is the classical example of mechanical taxis. However, whether gradients of the relaxation properties in the extracellular matrix may also induce tactic responses (viscotaxis) is not well understood. Moreover, whether and how durotaxis and viscotaxis interact with each other has never been investigated. Here, we integrate clutch models for cell adhesions with an active gel theory of cell migration to reveal the mechanisms that govern viscotaxis. We show that viscotaxis is enabled by an asymmetric expression of cell adhesions that further polarize the intracellular motility forces to establish the cell front, similar to durotaxis. More importantly, when both relaxation and elastic gradients coexist, durotaxis appears more efficient in controlling directed cell migration, which we confirm with experimental results. However, the presence of opposing relaxation gradients to an elastic one can arrest or shift the migration direction. Our model rationalizes for the first time the mechanisms that govern viscotaxis and its competition with durotaxis through a mathematical model.

Connecting single-molecule and superresolution microscopies to cell biology through theoretical modeling

Recent developments of single-molecule and superresolution microscopies reveal novel spatial-temporal features of various cellular processes with unprecedented details, and greatly facilitate the development of theoretical models. In this review, we synthesize our view of how to meaningfully integrate these experimental approaches with theoretical modeling to obtain deeper understanding of the physical mechanisms of cell biology.

Angiomotin cleavage promotes leader formation and collective cell migration

Collective cell migration (CCM) is involved in multiple biological processes, including embryonic morphogenesis, angiogenesis, and cancer invasion. However, the molecular mechanisms underlying CCM, especially leader cell formation, are poorly understood. Here, we show that a signaling pathway regulating angiomotin (AMOT) cleavage plays a role in CCM, using mammalian epithelial cells and mouse models. In a confluent epithelial monolayer, full-length AMOT localizes at cell-cell junctions and limits cell motility. After cleavage, the C-terminal fragment of AMOT (AMOT-CT) translocates to the cell-matrix interface to promote the maturation of focal adhesions (FAs), generate traction force, and induce leader cell formation. Meanwhile, decreased full-length AMOT at cell-cell junctions leads to tissue fluidization and coherent migration of cell collectives. Hence, the cleavage of AMOT serves as a molecular switch to generate polarized contraction, promoting leader cell formation and CCM.

Phagocytosis by the retinal pigment epithelium: New insights into polarized cell mechanics

The retinal pigment epithelium (RPE) is a specialized epithelium at the back of the eye that carries out a variety of functions essential for visual health. Recent studies have advanced our molecular understanding of one of the major functions of the RPE; phagocytosis of spent photoreceptor outer segments (POS). Notably, a mechanical link, formed between apical integrins bound to extracellular POS and the intracellular actomyosin cytoskeleton, is proposed to drive the internalization of POS. The process may involve a "nibbling" action, as an initial step, to sever outer segment tips. These insights have led us to hypothesize an "integrin adhesome-like" network, atypically assembled at apical membrane RPE-POS contacts. I propose that this hypothetical network orchestrates the complex membrane remodeling events required for particle internalization. Therefore, its analysis and characterization will likely lead to a more comprehensive understanding of the molecular mechanisms that control POS phagocytosis.

GFRα1 Promotes Axon Regeneration after Peripheral Nerve Injury by Functioning as a Ligand

The neurotrophic factor, Glial cell line derived neurotrophi factor (GDNF), exerts a variety of biological effects through binding to its receptors, GDNF family receptor alpha-1 (GFRα1), and RET. However, the existence of cells expressing GFRα1 but not RET raises the possibility that GFRα1 can function independently from RET. Here, it is shown that GFRα1 released from repair Schwann cells (RSCs) functions as a ligand in a GDNF-RET-independent manner to promote axon regeneration after peripheral nerve injury (PNI). Local administration of GFRα1 into injured nerve promoted axon regeneration, even more when combined with GDNF blockade. GFRα1 bound to a receptor complex consisting of NCAM and integrin α7β1 of dorsal root ganglion neurons in a GDNF-RET independent manner. This is further confirmed by the Ret Y1062F knock-in mice, which cannot transmit most of GDNF-RET signaling. Finally, local administration of GFRα1 into injured sciatic nerve promoted functional recovery. These findings reveal a novel role of GFRα1 as a ligand, the molecular mechanism supporting axon regeneration by RSCs, and a novel therapy for peripheral nerve repair.

Collagen signaling and matrix stiffness regulate multipotency in glandular epithelial stem cells in mice

Glandular epithelia, including mammary gland (MG) and prostate, are composed of luminal and basal cells. During embryonic development, glandular epithelia arise from multipotent stem cells (SCs) that are replaced after birth by unipotent basal and unipotent luminal SCs. Different conditions, such as basal cell transplantation, luminal cell ablation, and oncogene expression can reinduce adult basal SC (BaSCs) multipotency in different glandular epithelia. The mechanisms regulating the reactivation of multipotency are incompletely understood. Here, we have found that Collagen I expression is commonly upregulated in BaSCs across the different multipotent conditions. Increasing collagen concentration or stiffness of the extracellular matrix (ECM) promotes BaSC multipotency in MG and prostate organoids. Single cell RNA-seq of MG organoids in stiff conditions have uncovered the importance of β1 integrin/FAK/AP-1 axis in the regulation of BaSC multipotency. Altogether our study uncovers the key role of Collagen signaling and ECM stiffness in the regulation of multipotency in glandular epithelia.

Unravelling molecular mechanobiology using DNA-based fluorogenic tension sensors

Investigations of the biological system have revealed many principles that govern regular life processes. Recently, the analysis of tiny mechanical forces associated with many biological processes revealed their significance in understanding biological functions. Consequently, this piqued the interest of researchers, and a series of technologies have been developed to understand biomechanical cues at the molecular level. Notable techniques include single-molecule force spectroscopy, traction force microscopy, and molecular tension sensors. Well-defined double-stranded DNA structures could possess programmable mechanical characteristics, and hence, they have become one of the central molecules in molecular tension sensor technology. With the advancement of DNA technology, DNA or nucleic acid-based robust tension sensors offer the possibility of understanding mechanobiology in the bulk to single-molecule level range with desired spatiotemporal resolution. This review presents a comprehensive account of molecular tension sensors with a special emphasis on DNA-based fluorogenic tension sensors. Along with a detailed discussion on irreversible and reversible DNA-based tension sensors and their application in super-resolution microscopy, a discussion on biomolecules associated with cellular mechanotransduction and key findings in the field are included. This review ends with an elaborate discussion on the current challenges and future prospects of molecular tension sensors.

Exercise, exerkines and exercise mimetic drugs: Molecular mechanisms and therapeutics

Chronic diseases linked with sedentary lifestyles and poor dietary habits are increasingly common in modern society. Exercise is widely acknowledged to have a plethora of health benefits, including its role in primary prevention of various chronic conditions like type 2 diabetes mellitus, obesity, cardiovascular disease, and several musculoskeletal as well as degenerative disorders. Regular physical activity induces numerous physiological adaptations that contribute to these positive effects, primarily observed in skeletal muscle but also impacting other tissues. There is a growing interest among researchers in developing pharmaceutical interventions that mimic the beneficial effects of exercise for therapeutic applications. Exercise mimetic medications have the potential to be helpful aids in enhancing functional outcomes for patients with metabolic dysfunction, neuromuscular and musculoskeletal disorders. Some of the potential targets for exercise mimetics include pathways involved in metabolism, mitochondrial function, inflammation, and tissue regeneration. The present review aims to provide an exhaustive overview of the current understanding of exercise physiology, the role of exerkines and biomolecular pathways, and the potential applications of exercise mimetic drugs for the treatment of several diseases.

Biophysics of ACL Injuries

Anterior Cruciate Ligament (ACL) injuries rank among the most prevalent and severe types of injuries, significantly impacting both athletes and non-athletes alike. These injuries not only result in immediate physical impairment, such as intense pain, substantial swelling, and a marked loss of mobility, but also carry long-term health consequences that can alter a person's quality of life. Chronic pain, persistent instability, and an increased risk of developing osteoarthritis are among the lasting effects that can follow an ACL injury. An in-depth understanding of the biophysics behind ACL injuries is paramount for devising effective prevention and treatment protocols. Biophysics, which combines principles from physics with biological systems, provides crucial insights into the mechanical and structural integrity of the ACL and its susceptibility to injury under various conditions. This systematic review aims to collate and synthesize the current knowledge surrounding the biophysical mechanisms that underlie ACL injuries.

Dynamic duo: Cell-extracellular matrix interactions in hair follicle development and regeneration

Ectodermal organs, such as hair follicles, originate from simple epithelial and mesenchymal sheets through a complex developmental process driven by interactions between these cell types. This process involves dermal condensation, placode formation, bud morphogenesis, and organogenesis, and all of these processes require intricate interactions among various tissues. Recent research has emphasized the crucial role of reciprocal and dynamic interactions between cells and the extracellular matrix (ECM), referred to as the "dynamic duo", in the development of ectodermal organs. These interactions provide spatially and temporally changing biophysical and biochemical cues within tissues. Using the hair follicle as an example, this review highlights two types of cell-ECM adhesion units-focal adhesion-type and hemidesmosome-type adhesion units-that facilitate communication between epithelial and mesenchymal cells. This review further explores how these adhesion units, along with other cell-ECM interactions, evolve during hair follicle development and regeneration, underscoring their importance in guiding both developmental and regenerative processes.

Advances in mechanotransduction and sonobiology: effects of audible acoustic waves and low-vibration stimulations on mammalian cells

In recent decades, research on mechanotransduction has advanced considerably, focusing on the effects of audible acoustic waves (AAWs) and low-vibration stimulation (LVS), which has propelled the field of sonobiology forward. Taken together, the current evidence demonstrates the influence of these biosignals on key cellular processes, such as growth, differentiation and migration in mammalian cells, emphasizing the determining role of specific physical parameters during stimulation, such as frequency, sound pressure level/amplitude and exposure time. These mechanical waves interact with various cellular elements, including ion channels, primary cilia, cell-cell adhesion receptors, cell-matrix and extracellular matrix proteins, and focal adhesion complexes. These components connect with the cytoskeletal fibre network, enabling the transmission of mechanical stimuli towards the nucleus. The nucleus, in turn, linked to the cytoskeleton via the linkers of the nucleoskeleton and cytoskeleton complex, acts as a mechanosensitive centre, not only responding to changes in cytoskeletal stiffness and nuclear tension but also regulating gene expression through the transcriptional co-activator YAP/TAZ and interactions between chromatin and the nuclear envelope. This intricate chain of mechanisms highlights the potential of sonobiology in various fields, including dentistry, regenerative medicine, tissue engineering and cancer research. However, progress in these fields requires the establishment of standardized measurement methodologies and biocompatible experimental setups to ensure the reproducibility of results.

Surface modification strategies to reinforce the soft tissue seal at transmucosal region of dental implants

Soft tissue seal around the transmucosal region of dental implants is crucial for shielding oral bacterial invasion and guaranteeing the long-term functioning of implants. Compared with the robust periodontal tissue barrier around a natural tooth, the peri-implant mucosa presents a lower bonding efficiency to the transmucosal region of dental implants, due to physiological structural differences. As such, the weaker soft tissue seal around the transmucosal region can be easily broken by oral pathogens, which may stimulate serious inflammatory responses and lead to the development of peri-implant mucositis. Without timely treatment, the curable peri-implant mucositis would evolve into irreversible peri-implantitis, finally causing the failure of implantation. Herein, this review has summarized current surface modification strategies for the transmucosal region of dental implants with improved soft tissue bonding capacities (e.g., improving surface wettability, fabricating micro/nano topographies, altering the surface chemical composition and constructing bioactive coatings). Furthermore, the surfaces with advanced soft tissue bonding abilities can be incorporated with antibacterial properties to prevent infections, and/or with immunomodulatory designs to facilitate the establishment of soft tissue seal. Finally, we proposed future research orientations for developing multifunctional surfaces, thus establishing a firm soft tissue seal at the transmucosal region and achieving the long-term predictability of dental implants.

Leucine-rich repeat proteins of Leptospira interrogans that interact to host glycosaminoglycans and integrins

Pathogenic spirochaetes of the genus Leptospira are the etiological agents of leptospirosis, a zoonotic infection worldwide. The disease is considered an emerging and re-emerging threat due to global warming, followed by heavy rainfall and flooding when outbreaks of leptospirosis occur. Adhesion to host tissues is mediated by surface/extracellular proteins expressed by pathogens during infection. Leucine-rich repeat (LRR) domain-containing proteins seem to be important for the virulence of pathogenic Leptospira and their role has been recently examined. Here, we report the characterization of two LRR-proteins encoded by LIC11051 and LIC11505. They present 7 and 17 LRR motifs, respectively. LIC11051 was found mainly in the P1 subclade, whereas LIC11505 was identified with higher identity in subclade P1, but was also found in subclades P2, S1, and S2. The recombinant proteins were recognized by antibodies in leptospirosis serum samples, suggesting their expression during infection. rLIC11505 contains a broad spectrum of ligands, including GAG and integrin receptors, whereas rLIC11051 showed limited binding activity. The attachment of proteins to ligands was specific, dose-dependent, and saturable. Compared to their role in adhesion, both proteins were shown to be secreted, with the ability to reassociate with the bacteria. Taken together, our data suggested that LIC11051 and LIC11505 participate in leptospiral pathogenesis. To the best of our knowledge, this is the first report showing leptospiral LRR-proteins exhibiting GAG and integrin receptor-binding properties.

Spatial organization of PI3K-PI(3,4,5)P3-AKT signaling by focal adhesions

The class I phosphatidylinositol 3-kinase (PI3K)-AKT signaling pathway is a key regulator of cell survival, growth, and proliferation and is among the most frequently mutated pathways in cancer. However, where and how PI3K-AKT signaling is spatially activated and organized in mammalian cells remains poorly understood. Here, we identify focal adhesions (FAs) as subcellular signaling hubs organizing the activation of PI3K-PI(3,4,5)P3-AKT signaling in human cancer cells containing p110α mutations under basal conditions. We find that class IA PI3Ks are preferentially recruited to FAs for activation, resulting in localized production of PI(3,4,5)P3 around FAs. As the effector protein of PI(3,4,5)P3, AKT1 molecules are dynamically recruited around FAs for activation. The spatial recruitment/activation of the PI3K-PI(3,4,5)P3-AKT cascade is regulated by activated FA kinase (FAK). Furthermore, combined inhibition of p110α and FAK results in a more potent inhibitory effect on cancer cells. Thus, our results unveil a growth-factor independent, compartmentalized organization mechanism for PI3K-PI(3,4,5)P3-AKT signaling.

Rotating culture regulates the formation of HepaRG-derived liver organoids via YAP translocation

BACKGROUND

Liver organoid serves as an alternative model for liver pathophysiology in carbohydrate or lipid metabolism and xenobiotic metabolism transformation. Biomechanical cues including spaceflight mission can affect liver organoid construction and their related functions, but their underlying mechanisms are not fully understood yet. Here, a rotating cell culture device, namely Rotating Flat Chamber (RFC), was specifically designed for adhering cells or cell aggregated to elucidate the effects of altered gravity vector on HepaRG-derived liver organoids construction.

RESULTS

The organoids so formed under RFC presented the fast growth rate and large projection area. Meanwhile, the expressions of two pluripotency markers of SOX9 and CD44 were enhanced. This finding was positively correlated with the increased YAP expression and nuclear translocation as well as the elevated α4β6-integrin expression. Inhibition of YAP expression and nuclear translocation decreased the expression of SOX9 and CD44 under RFC, thereby attenuating the pluripotency of HepaRG-derived liver organoids.

CONCLUSIONS

In conclusion, we proposed a novel liver organoid construction method using rotating culture, by which the pluripotency of liver organoids so constructed is mediated by α4β6-integrin and YAP translocation. This work furthered the understanding in how the gravity vector orientation affects the construction of liver organoids and the related mechanotransductive pathways.

Enhancing Tumor Targeted Therapy: The Role of iRGD Peptide in Advanced Drug Delivery Systems

Chemotherapy remains the primary therapeutic approach in treating cancer. The tumor microenvironment (TME) is the complex network surrounding tumor cells, comprising various cell types, such as immune cells, fibroblasts, and endothelial cells, as well as ECM components, blood vessels, and signaling molecules. The often stiff and dense network of the TME interacts dynamically with tumor cells, influencing cancer growth, immune response, metastasis, and resistance to therapy. The effectiveness of the treatment of solid tumors is frequently reduced due to the poor penetration of the drug, which leads to attaining concentrations below the therapeutic levels at the site. Cell-penetrating peptides (CPPs) present a promising approach that improves the internalization of therapeutic agents. CPPs, which are short amino acid sequences, exhibit a high ability to pass cell membranes, enabling them to deliver drugs efficiently with minimal toxicity. Specifically, the iRGD peptide, a member of CPPs, is notable for its capacity to deeply penetrate tumor tissues by binding simultaneously integrins ανβ3/ανβ5 and neuropilin receptors. Indeed, ανβ3/ανβ5 integrins are characteristically expressed by tumor cells, which allows the iRGD peptide to home onto tumor cells. Notably, the respective dual-receptor targeting mechanism considerably increases the permeability of blood vessels in tumors, enabling an efficient delivery of co-administered drugs or nanoparticles into the tumor mass. Therefore, the iRGD peptide facilitates deeper drug penetration and improves the efficacy of co-administered therapies. Distinctively, we will focus on the iRGD mechanism of action, drug delivery systems and their application, and deliberate future perspectives in developing iRGD-conjugated therapeutics. In summary, this review discusses the potential of iRGD in overcoming barriers to drug delivery in cancer to maximize treatment efficiency while minimizing side effects.

Talin and vinculin combine their activities to trigger actin assembly

Focal adhesions (FAs) strengthen their link with the actin cytoskeleton to resist force. Talin-vinculin association could reinforce actin anchoring to FAs by controlling actin polymerization. However, the actin polymerization activity of the talin-vinculin complex is not known because it requires the reconstitution of the mechanical and biochemical activation steps that control the association of talin and vinculin. By combining kinetic and binding assays with single actin filament observations in TIRF microscopy, we show that the association of talin and vinculin mutants, mimicking mechanically stretched talin and activated vinculin, triggers a sequential mechanism in which filaments are nucleated, capped and released to elongate. In agreement with these observations, FRAP experiments in cells co-expressing the same constitutive mutants of talin and vinculin revealed accelerated growth of stress fibers. Our findings suggest a versatile mechanism for the regulation of actin assembly in FAs subjected to various combinations of biochemical and mechanical cues.

Macrophage proteomic analysis of covalent immobilization of hyaluronic acid and graphene oxide on CoCr alloy in a tribocorrosive environment

In this work, a sequential covalent immobilization of graphene oxide (GO) and hyaluronic acid (HA) is performed to obtain a biocompatible wear-resistant nanocoating on the surface of the biomedical grade cobalt-chrome (CoCr) alloy. Nanocoated CoCr surfaces were characterized by Raman spectroscopy and electrochemical impedance spectroscopy (EIS) in 3 g/L HA electrolyte. Tribocorrosion tests of the nanocoated CoCr surfaces were carried out in a pin on flat tribometer. The biological response of covalently HA/GO biofunctionalized CoCr surfaces with and without wear-corrosion processes was studied through the analysis of the proteome of macrophages. Raman spectra revealed characteristic bands of GO and HA on the functionalized CoCr surfaces. The electrochemical response by EIS showed a stable and protective behavior over 23 days in the simulated biological environment. HA/GO covalently immobilized on CoCr alloy is able to protect the surface and reduce the wear volume released under tribocorrosion tests. Unsupervised classification analysis of the macrophage proteome via hierarchical clustering and principal component analysis (PCA) revealed that the covalent functionalization on CoCr enhances the macrophage biocompatibility in vitro. On the other hand, disruption of the HA/GO nanocoating by tribocorrosion processes induced a macrophage proteome which was differently clustered and was distantly located in the PCA space. In addition, tribocorrosion induced an increase in the percentage of upregulated and downregulated proteins in the macrophage proteome, revealing that disruption of the covalent nanocoating impacts the macrophage proteome. Although macrophage inflammation induced by tribocorrosion of HA/GO/CoCr surfaces is observed, it is ameliorated by the covalently grafting of HA, which provides immunomodulation by eliciting downregulations in characteristic pro-inflammatory signaling involved in inflammation and aseptic loosening of CoCr joint arthroplasties. Covalent HA/GO nanocoating on CoCr provides potential applications for in vivo joint prostheses led a reduced metal-induced inflammation and degradation by wear-corrosion.

Advancing Scaffold-Assisted Modality for In Situ Osteochondral Regeneration: A Shift From Biodegradable to Bioadaptable

Over the decades, the management of osteochondral lesions remains a significant yet unmet medical challenge without curative solutions to date. Owing to the complex nature of osteochondral units with multi-tissues and multicellularity, and inherently divergent cellular turnover capacities, current clinical practices often fall short of robust and satisfactory repair efficacy. Alternative strategies, particularly tissue engineering assisted with biomaterial scaffolds, achieve considerable advances, with the emerging pursuit of a more cost-effective approach of in situ osteochondral regeneration, as evolving toward cell-free modalities. By leveraging endogenous cell sources and innate regenerative potential facilitated with instructive scaffolds, promising results are anticipated and being evidenced. Accordingly, a paradigm shift is occurring in scaffold development, from biodegradable and biocompatible to bioadaptable in spatiotemporal control. Hence, this review summarizes the ongoing progress in deploying bioadaptable criteria for scaffold-based engineering in endogenous osteochondral repair, with emphases on precise control over the scaffolding material, degradation, structure and biomechanics, and surface and biointerfacial characteristics, alongside their distinguished impact on the outcomes. Future outlooks of a highlight on advanced, frontier materials, technologies, and tools tailoring precision medicine and smart healthcare are provided, which potentially paves the path toward the ultimate goal of complete osteochondral regeneration with function restoration.

Carbon quantum dots in breast cancer modulate cellular migration via cytoskeletal and nuclear structure

Carbon nanomaterials have been widely applied for cutting edge therapeutic applications as they offer tunable physio-chemical properties with economic scale-up options. Nuclear delivery of cancer drugs has been of prime focus since it controls important cellular signaling functions leading to greater anti-cancer drug efficacies. Better cellular drug uptake per unit drug injection drastically reduces severe side-effects of cancer therapies. Similarly, carbon dots (CDs) uptaken by the nucleus can also be used to set-up cutting edge nano delivery systems. In an earlier paper, we showed the cellular uptake and plasma membrane impact of combustion generated yellow luminescing CDs produced by our group from fuel rich combustion reactors in a one-step tunable production. In this paper, we aim to specifically study the nucleus by establishing the uptake kinetics of these combustion-generated yellow luminescing CDs. At sub-lethal doses, after crossing the plasma membrane, they impact the actin and microtubule mesh, affecting cell adhesion and migration; enter nucleus by diffusion processes; modify the overall appearance of the nucleus in terms of morphology; and alter chromatin condensation. We thus establish how this one-step produced, cost and bulk production friendly carbon dots from fuel rich combustion flames can be innovatively repurposed as potential nano delivery agents in cancer cells.

Mechanosensory entities and functionality of endothelial cells

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

Integrin β5, a noninvasive diagnostic biomarker, is associated with unfavorable prognosis and immunotherapy efficacy in gastric cancer

BACKGROUND

Integrin β5 (ITGB5) is a pivotal player in the pathogenesis of gastric cancer (GC). We aimed to explore the potential value of ITGB5 as a predictor of diagnosis and immunotherapy in gastric cancer.

METHODS

The expression of ITGB5 in GC was assessed using The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, and verified through quantitative polymerase chain reaction (qPCR) and immunohistochemistry. Kaplan-Meier curves were conducted to evaluate the prognostic significance. The immune cells infiltration, tumor mutational burden (TMB), and immunophenoscore (IPS) were examined using CIBERSORT, TIMER, and TISIDB. In addition, colony formation, scratch assays, and transwell assays were employed to determine the impact on tumor progression and metastasis. CD276 expression was detected by western blotting following the knockdown of ITGB5. ELISA was utilized to measure serum ITGB5 levels.

RESULTS

The expression of ITGB5 in GC tissue surpassed that in normal tissue, it might contribute to GC pathogenesis through pathways including PI3K-AKT, ECM-receptor interaction, and TGF-beta. The elevated ITGB5 expression is associated with poor prognosis in GC patients. In addition, a strong positive association between ITGB5 overexpression and the infiltration levels of macrophages and monocytes, and it significantly influenced immune response. Moreover, lower expression of ITGB5 was associated with better immunotherapy efficacy. Subsequent investigation demonstrated that silencing of ITGB5 suppressed the proliferation and migration of GC cell lines in vitro. ITGB5 expression was positively correlated with CD276 expression and the knockdown of ITGB5 resulted a notable decrease CD276 expression. Futhermore, a significantly high level of serum ITGB5 was observed in GC patients. The combined assessment of ITGB5, CEA, and CA19-9 improved the diagnostic accuracy.

CONCLUSIONS

ITGB5 potentially serve as both a diagnostic biomarker and therapeutic target in managing GC.

Time and space modulation of substrate curvature to regulate cell mechanical identity

Recently, a variety of microenvironmental biophysical stimuli have been proved to play a crucial role in regulating cell functions. Among them, morpho-physical cues, like curvature, are emerging as key regulators of cellular behavior. Changes in substrate curvature have been shown to impact the arrangement of Focal Adhesions (FAs), influencing the direction and intensity of cytoskeleton generated forces and resulting in an overall alteration of cell mechanical identity. In their native environment, cells encounter varying degrees of substrate curvature, and in specific organs, they are exposed to dynamic changes of curvature due to periodic tissue deformation. However, the mechanism by which cells perceive substrate curvature remains poorly understood. To this aim, a micro-pneumatic device was designed and implemented. This device enables the controlled application of substrate curvature, both statically and dynamically. Employing a combined experimental and simulative approach, human adipose-derived stem cells were exposed to controlled curvature intensity and frequency. During this exposure, measurements were taken on FAs extension and orientation, cytoskeleton organization and cellular/nuclear alignment. The data clearly indicated a significant influence of the substrate curvature on cell adhesion processes. These findings contribute to a better understanding of the mechanisms through which cells perceive and respond to substrate curvature signals. STATEMENT OF SIGNIFICANCE: This work is our contribution to the comprehension of substrate curvature's function as a crucial regulator of cell adhesion at the scale of focal adhesions and cell mechanical identity. In recent years, a large body of knowledge is continuously growing providing comprehension of the role of various microenvironmental biophysical stimuli in regulating cell functions. Nevertheless, little is known about the role of substrate curvature, in particular, when cells are exposed to this stimulus in a dynamic manner. To address the role of substrate curvature on cellular behavior, a micro-pneumatic device was designed and implemented. This device enables the controlled application of substrate curvature, both statically and dynamically. The experiment data made it abundantly evident that the substrate curvature had a major impact on the mechanisms involved in cell adhesion.

Dasatinib induces endothelial dysfunction leading to impaired recovery from ischaemia

Chronic myeloid leukaemia (CML) management is complicated by treatment-emergent vascular adverse events seen with tyrosine kinase inhibitors (TKIs) such as nilotinib, dasatinib and ponatinib. Pleural effusion and pulmonary arterial hypertension (PAH) have been associated with dasatinib treatment. Endothelial dysfunction and impaired angiogenesis are hallmarks of PAH. In this study, we explored, at cellular and whole animal levels, the connection between dasatinib exposure and disruption of endothelial barrier integrity and function, leading to impaired angiogenesis. Understanding the mechanisms whereby dasatinib initiates PAH will provide opportunities for intervention and prevention of such adverse effects, and for future development of safer TKIs, thereby improving CML management.

Aggravated Ulcerative Colitis via circNlgn-Mediated Suppression of Nuclear Actin Polymerization

Colitis is a chronic bowel disease characterized by damage to the lining of the large intestine, with its precise underlying causes remaining incompletely understood. In this study, we provide evidence that circular RNA circNlgn plays a pivotal role in promoting the development of colitis. Colitis patients produce significant higher levels of circNlgn. Transgenic mice expressing circNlgn exhibit heightened susceptibility to colitis development and progression, primarily attributed to the presence of the protein isoform Nlgn173 encoded by circNlgn. Nlgn173 undergoes translocation into cell nuclei, where it interacts with actin, impeding the binding of actin-related protein 2 and 3 (Arp2/3) complex to actin molecules. Consequently, this leads to a reduction in actin polymerization. Mechanistically, Nlgn173 enhances tyrosine-53 phosphorylation of nuclear actin, diminishing its capacity to interact with the Arp2/3 complex and causing a decrease in filamentous actin levels. These alterations in actin dynamics result in inhibited cell cycle progression, increased apoptosis, and decreased proliferation of colonic epithelial cells, thereby exacerbating colitis development and progression. In contrast, the silencing of circNlgn or the targeted inhibition of Nlgn173 translation and nuclear translocation leads to the promotion of nuclear actin polymerization, enhanced cell survival, and reduced apoptosis and ultimately improves the outcome of colitis in vivo. Interestingly, nuclear actin polymerization is highly related with expression of PIAS3, which modulates signal transducer and activator of transcription 3 and NF-κB activity in colitis. Strategies such as circNlgn knockdown and targeting nuclear actin polymerization of the colonic epithelium may explore a novel avenue for acute ulcerative colitis clinical intervention.

Shp2 contributes to the regulation of nuclear shape and cellular viscoelasticity in response to substrate spatial cues

Cell polarization can be guided by substrate topology through space constraints and adhesion induction, which are part of cellular mechanosensing pathways. Here, we demonstrated that protein tyrosine phosphatase Shp2 plays a crucial role in mediating the response of cells to substrate spatial cues. When compared to cells spreading on surfaces coated uniformly with fibronectin (FN), cells attached to 10 μm-width FN-strip micropattern (MP), which provides spatial cues for uniaxial spreading, exhibited elongated focal adhesions (FAs) and aligned stress fibers in the direction of the MP. As a result of uniaxial cell spreading, nuclei became elongated, dependent on ROCK-mediated actomyosin contractility. Additionally, intracellular viscoelasticity also increased. Shp2-deficient cells did not display elongated FAs mediated by MP, well-aligned stress fibers, or changes in nuclear shape and intracellular viscoelasticity. Overall, our data suggest that Shp2 is involved in regulating FAs and the actin cytoskeleton to modulate nuclear shape and intracellular physical properties in response to substrate spatial cues.

Biological behavior of mesenchymal stem cells on two types of commercial dermal scaffolds: An in vitro study

Background

Acellular dermal matrix (ADM) has been introduced as an alternative to autogenous grafts. This study assessed the biological behavior of mesenchymal stem cells (MSCs) on two types of commercial ADM scaffolds.

Methods

The present in vitro study investigated the behavior of MSCs cultured on scaffold type I CenoDerm® (Tissue Regeneration Corporation) and type II Acellular Dermis (Iranian Tissue Product Co.) as the test groups and an empty well plate as the control group (n=78). Cell attachment was assessed after 12 hours of incubation using 6,4-diamidino-2-phenylindole (DAPI) staining and methyl thiazole tetrazolium (MTT) assay. Cell proliferation was assessed using the MTT assay at 24- and 84-hour and 7-day intervals. Cell morphology was also assessed under a scanning electron microscope (SEM) at 24 hours. MTT assay and DAPI staining were repeated for five samples in all the three groups. Mann-Whitney, ANOVA, and post hoc Tukey tests were used for statistical analysis.

Results

The DAPI staining and MTT assay showed similar results concerning cell attachment between all the groups at 12 hours (P=0.4). At 24 hours, cell proliferation was significantly higher in scaffold groups (P<0.001). At seven days, the lowest cell proliferation was noted in the scaffold II group, with a significant difference between the groups (P=0.01). At 24 hours, cell expansion was greater in the control group, followed by the scaffold I group.

Conclusion

Both scaffolds were similar in MSC attachment, but scaffold I appeared superior to scaffold II in terms of MSC proliferation and morphology in vitro.