Focal adhesion kinase modulates cell adhesion strengthening via integrin activation

Inhibiting fibronectin assembly in the breast tumor microenvironment increases cell death and improves response to doxorubicin

Purpose

Effective therapies for solid tumors, including breast cancers, are hindered by several roadblocks that can be largely attributed to the fibrotic extracellular matrix (ECM). Fibronectin (FN) is a highly upregulated ECM component in the fibrotic tumor stroma and is associated with poor patient prognosis. This study aimed to investigate the therapeutic potential of an anti-fibrotic peptide that specifically targets FN and blocks the fibrillar assembly of FN.

Methods

To target FN, we used PEGylated Functional Upstream Domain (PEG-FUD), which binds to the 70 kDa N-terminal region of FN with high affinity, localizes to mammary tumors, and potently inhibits FN assembly in vitro and in vivo. Here, we used the 4T1 tumor model to investigate the efficacy and mechanisms of PEG-FUD to inhibit tumor growth.

Results

Our data demonstrates that PEG-FUD monotherapy reduces tumor growth without systemic toxicity. Analysis of the tumor microenvironment revealed that PEG-FUD effectively inhibited FN matrix assembly within tumors and reduced adhesion-mediated signaling through α5 integrin and FAK leading to enhanced tumor cell death. Notably, signaling through FAK has been associated with resistance mechanisms to doxorubicin (DOX). Therefore, we tested the combination of PEG-FUD and Dox, which significantly reduced tumor growth by 60% compared to vehicle control and 30% compared to Dox monotherapy.

Conclusions

Our findings demonstrate that PEG-FUD significantly modifies the peritumoral ECM of breast cancer, leading to increased tumor cell death, and potentiates the efficacy of conventional breast cancer therapy.

White spot syndrome virus IE1 protein blocks the integrin-FAK signaling to enhance viral infection in shrimp

DNA viruses commonly utilize immediate-early proteins to manipulate cellular signaling pathways in order to facilitate their infection. Our previous research has suggested that IE1, an immediate-early protein encoded by the white spot syndrome virus (WSSV), may modulate the shrimp integrin-FAK signaling pathway. However, the specific molecular mechanism and role of IE1 in regulating this signaling pathway remain unclear. In this study, we demonstrated that IE1 competes for binding to the cytoplasmic tail of Penaeus vannamei integrin-α5, resulting in the inhibition of the integrin-α5-FAK interaction, thereby suppressing FAK activation and cell adhesion. Furthermore, we observed a significant increase in the expression of P. vannamei integrin-α5 and FAK following WSSV infection. Additionally, knockdown of integrin-α5 or FAK through RNA interference has been shown to reduce cell adhesion and enhance WSSV infection. In conclusion, our findings reveal that IE1 disrupts integrin-FAK signaling to inhibit cell adhesion, ultimately promoting WSSV infection in shrimp.

Optimizing gelation time for cell shape control through active learning

Hydrogels are popular platforms for cell encapsulation in biomedicine and tissue engineering due to their soft, porous structures, high water content, and excellent tunability. Recent studies highlight that the timing of network formation can be just as important as mechanical properties in influencing cell morphologies. Conventionally, time-dependent properties can be achieved through multi-step processes. In contrast, one-pot synthesis can improve both the efficiency and uniformity of cell encapsulation. Reaction kinetics are sensitive to temperatures and pH conditions, thus, monitoring gelation time across different conditions is essential for formulation. In this work, we choose tetra-poly(ethylene glycol) (TPEG) macromers as a model system to examine the relationship between the rate of polymer network formation and cell morphology. Previous studies of this system focused on reactions at neutral pH and room temperature, leaving much of the formulation space underexplored. We use Gaussian process regression (GPR) to minimize response surface errors by strategically selecting additional investigation points based on prior knowledge. Then we extend the knowledge from pre-trained data at neutral pH to a new surface at physiological pH. We find that the gelation time surface can effectively predict the aspect ratio of the encapsulated cells. Additionally, through focal adhesion kinase inhibition, we show that cell shape is influenced by the properties of the forming network in the initial hours as cells develop connections with the matrix. We demonstrate the utility of a high-throughput microrheology approach in enhancing fabrications of synthetic extracellular matrix and cell assemblies.

Coordination of Focal Adhesion Nanoarchitecture and Dynamics in Mechanosensing for Cardiomyoblast Differentiation

Focal adhesions (FAs) are force-bearing multiprotein complexes, whose nanoscale organization and signaling are essential for cell growth and differentiation. However, the specific organization of FA components to exert spatiotemporal activation of FA proteins for force sensing and transduction remains unclear. In this study, we unveil the intricacies of FA protein nanoarchitecture and that its dynamics are coordinated by a molecular scaffold protein, BNIP-2, to initiate downstream signal transduction for cardiomyoblast differentiation. Within the FAs, BNIP-2 regulates the nano-organization of focal adhesion kinase (FAK), and the dynamics of FAK, paxillin, and vinculin. Depletion of BNIP-2 resulted in altered focal adhesion numbers and sizes per cell, reduced traction force, and decreased FA sensitivity for mechanosensing. At the molecular level, the loss of BNIP-2 disrupted the FAK-paxillin signaling axis, where FAK inhibition reproduces the effects of BNIP-2 loss by impairing the phosphorylation of both FAK and paxillin. Mechanistically, BNIP-2 preferentially binds to constitutively active FAK and acts as a molecular scaffold to mediate interactions between FAK and paxillin and between paxillin and vinculin. We have validated BNIP-2's role in the FAK-paxillin signaling axis in human embryonic stem cells (hESC). Furthermore, we showed that depletion of BNIP-2 resulted in changes in signature gene targets at the cardiac progenitor stage of differentiation. In summary, we showed that the intricate interplay of FA nanoarchitecture and dynamics, governed by BNIP-2, is crucial for force transduction and biochemical signaling in driving cardiomyoblast differentiation.

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.

Phytoconstituent-derived zingerone nanoparticles disrupt the cell adhesion mechanism and suppress cell motility in melanoma B16F10 cells

Combining phytochemicals and nanotechnology to improve the unfavorable innate properties of phytochemicals and develop them into potent nanomedicines to enhance antitumor efficacy has become a novel strategy for cancer chemoprevention. Melanoma is the most aggressive, metastatic, and deadly disease of the primary cutaneous neoplasms. In this study, we fabricated phytoconstituent-derived zingerone nanoparticles (NPs) and validated their effects on cell adhesion and motility in melanoma B16F10 cells. Our data indicated that zingerone NPs significantly induced cytotoxicity and anti-colony formation and inhibited cell migration and invasion. Moreover, zingerone NPs dramatically interfered with the cytoskeletal reorganization and markedly delayed the period of cell adhesion. Our results also revealed that zingerone NPs-mediated downregulation of MMPs (matrix metalloproteinases) activity is associated with inhibiting cell adhesion and motility. We further evaluated the effects of zingerone NPs on Src/FAK /Paxillin signaling, our data showed that zingerone NPs significantly inhibited the protein activities of Src, FAK, and Paxillin, indicating that they play important roles in zingerone NP-mediated anti-motility and anti-invasion in melanoma cells. Accordingly, the phytoconstituent-zingerone NPs can strengthen the inhibition of tumor growth, invasion, and metastasis in malignant melanoma. Altogether, these multi-pharmacological benefits of zingerone NPs will effectively achieve the purpose of melanoma prevention and invasion inhibition.

Microfluidic Wound-Healing Assay for Comparative Study on Fluid Dynamic, Chemical and Mechanical Wounding on Microglia BV2 Migration

Microglial cells, or brain immune cells, are highly dynamic and continuously migrate in pathophysiological conditions. Their adhesion, as a physical characteristic, plays a key role in migration. In this study, we presented a microfluidic chip combination of two assays: a microglial BV2 adhesion assay and a wound-healing migration assay. The chip could create the cell-free area (wound) under chemical stimuli with trypsin (chemical assay) and also mechanical stimuli with the PBS flow (mechanical assay). The microfluidic chip functioned as the cell adhesion assay during wounding, when the cell adhesion of microglia BV2 cells was characterized by the cell removal time under various shear stress ranges. The cell detachment pattern on the glass substrate was found under physiological conditions. After wounding, the chip operated as a migration assay; it was shown that cell migration in the cell-free area generated chemically with trypsin was highly improved compared to mechanical cell-free area creations with PBS flow and the scratch assay. Our findings indicated that the increase in inlet flow rate in the mechanical assay led to a reduced experiment time and mechanical force on the cells, which could improve cell migration. Furthermore, the study on the effect of the device geometry showed that the increased channel width had an inhibitory effect on cell migration. The bi-functional chip offers an opportunity for the development of new models for a better understanding of cellular adhesion and migration in in vitro microenvironments.

Interface-Mediated Neurogenic Signaling: The Impact of Surface Geometry and Chemistry on Neural Cell Behavior for Regenerative and Brain-Machine Interfacing Applications

Nanomaterial advancements have driven progress in central and peripheral nervous system applications such as tissue regeneration and brain-machine interfacing. Ideally, neural interfaces with native tissue shall seamlessly integrate, a process that is often mediated by the interfacial material properties. Surface topography and material chemistry are significant extracellular stimuli that can influence neural cell behavior to facilitate tissue integration and augment therapeutic outcomes. This review characterizes topographical modifications, including micropillars, microchannels, surface roughness, and porosity, implemented on regenerative scaffolding and brain-machine interfaces. Their impact on neural cell response is summarized through neurogenic outcome and mechanistic analysis. The effects of surface chemistry on neural cell signaling with common interfacing compounds like carbon-based nanomaterials, conductive polymers, and biologically inspired matrices are also reviewed. Finally, the impact of these extracellular mediated neural cues on intracellular signaling cascades is discussed to provide perspective on the manipulation of neuron and neuroglia cell microenvironments to drive therapeutic outcomes.

Calpain Small Subunit Mediated Secretion of Galectin-3 Regulates Traction Stress

The complex regulation of traction forces (TF) produced during cellular migration remains poorly understood. We have previously found that calpain 4 (Capn4), the small non-catalytic subunit of the calpain 1 and 2 proteases, regulates the production of TF independent of the proteolytic activity of the larger subunits. Capn4 was later found to facilitate tyrosine phosphorylation and secretion of the lectin-binding protein galectin-3 (Gal3). In this study, recombinant Gal3 (rGal3) was added to the media-enhanced TF generated by capn4-/- mouse embryonic fibroblasts (MEFs). Extracellular Gal3 also rescued defects in the distribution, morphology, and adhesive strength of focal adhesions present in capn4-/- MEF cells. Surprisingly, extracellular Gal3 does not influence mechanosensing. c-Abl kinase was found to affect Gal3 secretion and the production of TF through phosphorylation of Y107 on Gal3. Our study also suggests that Gal3-mediated regulation of TF occurs through signaling pathways triggered by β1 integrin but not by focal adhesion kinase (FAK) Y397 autophosphorylation. Our findings provide insights into the signaling mechanism by which Capn4 and secreted Gal3 regulate cell migration through the modulation of TF distinctly independent from a mechanosensing mechanism.

Sarcoma Cells Secrete Hypoxia-Modified Collagen VI to Weaken the Lung Endothelial Barrier and Promote Metastasis

Intratumoral hypoxia correlates with metastasis and poor survival in patients with sarcoma. Using an impedance sensing assay and a zebrafish intravital microinjection model, we demonstrated here that the hypoxia-inducible collagen-modifying enzyme lysyl hydroxylase PLOD2 and its substrate collagen type VI (COLVI) weaken the lung endothelial barrier and promote transendothelial migration. Mechanistically, hypoxia-induced PLOD2 in sarcoma cells modified COLVI, which was then secreted into the vasculature. Upon reaching the apical surface of lung endothelial cells, modified COLVI from tumor cells activated integrin β1 (ITGβ1). Furthermore, activated ITGβ1 colocalized with Kindlin2, initiating their interaction with F-actin and prompting its polymerization. Polymerized F-actin disrupted endothelial adherens junctions and induced barrier dysfunction. Consistently, modified and secreted COLVI was required for the late stages of lung metastasis in vivo. Analysis of patient gene expression and survival data from The Cancer Genome Atlas (TCGA) revealed an association between the expression of both PLOD2 and COLVI and patient survival. Furthermore, high levels of COLVI were detected in surgically resected sarcoma metastases from patient lungs and in the blood of tumor-bearing mice. Together, these data identify a mechanism of sarcoma lung metastasis, revealing opportunities for therapeutic intervention.

SIGNIFICANCE

Collagen type VI modified by hypoxia-induced PLOD2 is secreted by sarcoma cells and binds to integrin β1 on endothelial cells to induce barrier dysfunction, which promotes sarcoma vascular dissemination and metastasis.

Biomechanical Effects of Mechanical Stress on Cells Involved in Fracture Healing

Fracture healing is a complex staged repair process in which the mechanical environment plays a key role. Bone tissue is very sensitive to mechanical stress stimuli, and the literature suggests that appropriate stress can promote fracture healing by altering cellular function. However, fracture healing is a coupled process involving multiple cell types that balance and limit each other to ensure proper fracture healing. The main cells that function during different stages of fracture healing are different, and the types and molecular mechanisms of stress required are also different. Most previous studies have used a single mechanical stimulus on individual mechanosensitive cells, and there is no relatively uniform standard for the size and frequency of the mechanical stress. Analyzing the mechanisms underlying the effects of mechanical stimulation on the metabolic regulation of signaling pathways in cells such as in bone marrow mesenchymal stem cells (BMSCs), osteoblasts, chondrocytes, and osteoclasts is currently a challenging research hotspot. Grasping how stress affects the function of different cells at the molecular biology level can contribute to the refined management of fracture healing. Therefore, in this review, we summarize the relevant literature and describe the effects of mechanical stress on cells associated with fracture healing, and their possible signaling pathways, for the treatment of fractures and the further development of regenerative medicine.

Gefitinib induces anoikis in cervical cancer cells

Gefitinib exerts anticancer effects on various types of cancer, such as lung, ovarian, breast, and colon cancers. However, the therapeutic effects of gefitinib on cervical cancer and the underlying mechanisms remain unclear. Thus, this study aimed to explore whether gefitinib can be used to treat cervical cancer and elucidate the underlying mechanisms. Results showed that gefitinib induced a caspase-dependent apoptosis of HeLa cells, which consequently became round and detached from the surface of the culture plate. Gefitinib induced the reorganization of actin cytoskeleton and downregulated the expression of p-FAK, integrin β1 and E-cadherin, which are important in cell-extracellular matrix adhesion and cell-cell interaction, respectively. Moreover, gefitinib hindered cell reattachment and spreading and suppressed interactions between detached cells in suspension, leading to poly (ADP-ribose) polymerase cleavage, a hallmark of apoptosis. It also induced detachment-induced apoptosis (anoikis) in C33A cells, another cervical cancer cell line. Taken together, these results suggest that gefitinib triggers anoikis in cervical cancer cells. Our findings may serve as a basis for broadening the range of anticancer drugs used to treat cervical cancer. [BMB Reports 2024; 57(2): 104-109].

HPIP and RUFY3 are noncanonical guanine nucleotide exchange factors of Rab5 to regulate endocytosis-coupled focal adhesion turnover

While the role of endocytosis in focal adhesion turnover-coupled cell migration has been established in addition to its conventional role in cellular functions, the molecular regulators and precise molecular mechanisms that underlie this process remain largely unknown. In this study, we report that proto-oncoprotein hematopoietic PBX-interacting protein (HPIP) localizes to focal adhesions as well as endosomal compartments along with RUN FYVE domain-containing protein 3 (RUFY3) and Rab5, an early endosomal protein. HPIP contains two coiled-coil domains (CC1 and CC2) that are necessary for its association with Rab5 and RUFY3 as CC domain double mutant, that is, mtHPIPΔCC1-2 failed to support it. Furthermore, we show that HPIP and RUFY3 activate Rab5 by serving as noncanonical guanine nucleotide exchange factors of Rab5. In support of this, either deletion of coiled-coil domains or silencing of HPIP or RUFY3 impairs Rab5 activation and Rab5-dependent cell migration. Mechanistic studies further revealed that loss of HPIP or RUFY3 expression severely impairs Rab5-mediated focal adhesion disassembly, FAK activation, fibronectin-associated-β1 integrin trafficking, and thus cell migration. Together, this study underscores the importance of HPIP and RUFY3 as noncanonical guanine nucleotide exchange factors of Rab5 and in integrin trafficking and focal adhesion turnover, which implicates in cell migration.

Engineered Biomimetic Fibrillar Fibronectin Matrices Regulate Cell Adhesion Initiation, Migration, and Proliferation via α5β1 Integrin and Syndecan-4 Crosstalk

Cells regulate adhesion to the fibrillar extracellular matrix (ECM) of which fibronectin is an essential component. However, most studies characterize cell adhesion to globular fibronectin substrates at time scales long after cells polarize and migrate. To overcome this limitation, a simple and scalable method to engineer biomimetic 3D fibrillar fibronectin matrices is introduced and how they are sensed by fibroblasts from the onset of attachment is characterized. Compared to globular fibronectin substrates, fibroblasts accelerate adhesion initiation and strengthening within seconds to fibrillar fibronectin matrices via α5β1 integrin and syndecan-4. This regulation, which additionally accelerates on stiffened fibrillar matrices, involves actin polymerization, actomyosin contraction, and the cytoplasmic proteins paxillin, focal adhesion kinase, and phosphoinositide 3-kinase. Furthermore, this immediate sensing and adhesion of fibroblast to fibrillar fibronectin guides migration speed, persistency, and proliferation range from hours to weeks. The findings highlight that fibrillar fibronectin matrices, compared to widely-used globular fibronectin, trigger short- and long-term cell decisions very differently and urge the use of such matrices to better understand in vivo interactions of cells and ECMs. The engineered fibronectin matrices, which can be printed onto non-biological surfaces without loss of function, open avenues for various cell biological, tissue engineering and medical applications.

CAP1 (cyclase-associated protein 1) mediates the cyclic AMP signals that activate Rap1 in stimulating matrix adhesion of colon cancer cells

We previously reported that CAP1 (Cyclase-Associated Protein 1) regulates matrix adhesion in mammalian cells through FAK (Focal Adhesion Kinase). More recently, we discovered a phosphor-regulation mechanism for CAP1 through the Ser307/Ser309 tandem site that is of critical importance for all CAP1 functions. However, molecular mechanisms underlying the CAP1 function in adhesion and its regulation remain largely unknown. Here we report that Rap1 also facilitates the CAP1 function in adhesion, and more importantly, we identify a novel signaling pathway where CAP1 mediates the cAMP signals, through the cAMP effectors Epac (Exchange proteins directly activated by cAMP) and PKA (Protein Kinase A), to activate Rap1 in stimulating matrix adhesion in colon cancer cells. Knockdown of CAP1 led to opposite adhesion phenotypes in SW480 and HCT116 colon cancer cells, with reduced matrix adhesion and reduced FAK and Rap1 activities in SW480 cells while it stimulated matrix adhesion as well as FAK and Rap1 activities in HCT116 cells. Importantly, depletion of CAP1 abolished the stimulatory effects of the cAMP activators forskolin and isoproterenol, as well as that of Epac and PKA, on matrix adhesion in both cell types. Our results consistently support a required role for CAP1 in the cAMP activation of Rap1. Identification of the key role for CAP1 in linking the major second messenger cAMP to activation of Rap1 in stimulating adhesion, which may potentially also regulate proliferation in other cell types, not only vertically extends our knowledge on CAP biology, but also carries important translational potential for targeting CAP1 in cancer therapeutics.

Study on the influence of scaffold morphology and structure on osteogenic performance

The number of patients with bone defects caused by various bone diseases is increasing yearly in the aging population, and people are paying increasing attention to bone tissue engineering research. Currently, the application of bone tissue engineering mainly focuses on promoting fracture healing by carrying cytokines. However, cytokines implanted into the body easily cause an immune response, and the cost is high; therefore, the clinical treatment effect is not outstanding. In recent years, some scholars have proposed the concept of tissue-induced biomaterials that can induce bone regeneration through a scaffold structure without adding cytokines. By optimizing the scaffold structure, the performance of tissue-engineered bone scaffolds is improved and the osteogenesis effect is promoted, which provides ideas for the design and improvement of tissue-engineered bones in the future. In this study, the current understanding of the bone tissue structure is summarized through the discussion of current bone tissue engineering, and the current research on micro-nano bionic structure scaffolds and their osteogenesis mechanism is analyzed and discussed.

GSNOR deficiency promotes tumor growth via FAK1 S-nitrosylation

Nitric oxide (NO) production in the tumor microenvironment is a common element in cancer. S-nitrosylation, the post-translational modification of cysteines by NO, is emerging as a key transduction mechanism sustaining tumorigenesis. However, most oncoproteins that are regulated by S-nitrosylation are still unknown. Here we show that S-nitrosoglutathione reductase (GSNOR), the enzyme that deactivates S-nitrosylation, is hypo-expressed in several human malignancies. Using multiple tumor models, we demonstrate that GSNOR deficiency induces S-nitrosylation of focal adhesion kinase 1 (FAK1) at C658. This event enhances FAK1 autophosphorylation and sustains tumorigenicity by providing cancer cells with the ability to survive in suspension (evade anoikis). In line with these results, GSNOR-deficient tumor models are highly susceptible to treatment with FAK1 inhibitors. Altogether, our findings advance our understanding of the oncogenic role of S-nitrosylation, define GSNOR as a tumor suppressor, and point to GSNOR hypo-expression as a therapeutically exploitable vulnerability in cancer.

Nestin Modulates Airway Smooth Muscle Cell Migration by Affecting Spatial Rearrangement of Vimentin Network and Focal Adhesion Assembly

Airway smooth muscle cell migration plays a role in the progression of airway remodeling, a hallmark of allergic asthma. However, the mechanisms that regulate cell migration are not yet entirely understood. Nestin is a class VI intermediate filament protein that is involved in the proliferation/regeneration of neurons, cancer cells, and skeletal muscle. Its role in cell migration is not fully understood. Here, nestin knockdown (KD) inhibited the migration of human airway smooth muscle cells. Using confocal microscopy and the Imaris software, we found that nestin KD attenuated focal adhesion sizes during cell spreading. Moreover, polo-like kinase 1 (Plk1) and vimentin phosphorylation at Ser-56 have been previously shown to affect focal adhesion assembly. Here, nestin KD reduced Plk1 phosphorylation at Thr-210 (an indication of Plk1 activation), vimentin phosphorylation at Ser-56, the contacts of vimentin filaments to paxillin, and the morphology of focal adhesions. Moreover, the expression of vimentin phosphorylation-mimic mutant S56D (aspartic acid substitution at Ser-56) rescued the migration, vimentin reorganization, and focal adhesion size of nestin KD cells. Together, our results suggest that nestin promotes smooth muscle cell migration. Mechanistically, nestin regulates Plk1 phosphorylation, which mediates vimenitn phosphorylation, the connection of vimentin filaments with paxillin, and focal adhesion assembly.

SMAD 3, Integrin and VEGF Expression in a Periodontal Ligament During Orthodontic Tooth Movement Induced by Hyperbaric Oxygen Therapy and Stichopus hermanii

Purpose

The aim of this study is to analyze SMAD 3, integrin and VEGF expressions in the periodontal ligament during orthodontic tooth movement induced by hyperbaric oxygen therapy and Stichopus hermanii.

Materials and Methods

Thirty Cavia cobaya were divided into 5 groups, namely, a normal control group (KN) without installation of helical springs or administration of HBOT and Stichopus hermanii gel. The negative control K(-) had helical spring without administration of HBOT and Stichopus hermanii gel for 14 days, while P1 had helical spring for 14 days then on day 3–14, Stichopus hermanii gel was added. Also, the helical spring was installed in P2 for 14 days then on day 8–14, HBOT 2.4 ATA was added 3 × 30 minutes a day, while P3 had helical spring for 14 days then on day 3–14, the gel was applied, and on day 8–14, HBOT 2.4 ATA was administered 3 × 30 minutes a day. Furthermore, SMAD3, integrin, and VEGF expressions were examined using immunohistochemical staining.

Results

SMAD3, integrins, and VEGF expressions showed significant differences within the groups. The combination of HBOT and Stichopus hermanii increased the expression of SMAD3 and VEGF compared to the single administration of Stichopus hermanii. The combination treatment also decreased integrin expression compared to a single HBOT administration.

Conclusion

The combination of HBOT and Stichopus hermanii increases the expression of SMAD3, integrins, and VEGF compared to control but did not show significant differences compared to single HBOT treatment.

FRET Visualization of Cyclic Stretch-Activated ERK via Calcium Channels Mechanosensation While Not Integrin β1 in Airway Smooth Muscle Cells

Mechanical stretch is one type of common physiological activities such as during heart beating, lung breathing, blood flow through the vessels, and physical exercise. The mechanical stimulations regulate cellular functions and maintain body homeostasis. It still remains to further characterize the mechanical-biomechanical coupling mechanism. Here we applied fluorescence resonance energy transfer (FRET) technology to visualize ERK activity in airway smooth muscle (ASM) cells under cyclic stretch stimulation in airway smooth muscle (ASM) cells, and studied the mechanosensing pathway. FRET measurements showed apparent ERK activation by mechanical stretch, which was abolished by ERK inhibitor PD98059 pretreatment. Inhibition of extracellular Ca²⁺ influx reduced ERK activation, and selective inhibition of inositol 1,4,5-trisphosphate receptor (IP₃R) Ca²⁺ channel or SERCA Ca²⁺ pump on endoplasmic reticulum (ER) blocked the activation. Chemical inhibition of the L-type or store-operated Ca²⁺ channels on plasma membrane, or inhibition of integrin β1 with siRNA had little effect on ERK activation. Disruption of actin cytoskeleton but not microtubule one inhibited the stretch-induced ERK activation. Furthermore, the ER IP₃R-dependent ERK activation was not dependent on phospholipase C-IP₃ signal, indicating possibly more mechanical mechanism for IP₃R activation. It is concluded from our study that the mechanical stretch activated intracellular ERK signal in ASM cells through membrane Ca²⁺ channels mechanosensation but not integrin β1, which was mediated by actin cytoskeleton.

Mechanotransduction in Mesenchymal Stem Cells (MSCs) Differentiation: A Review

Mechanotransduction is the process by which physical force is converted into a biochemical signal that is used in development and physiology; meanwhile, it is intended for the ability of cells to sense and respond to mechanical forces by activating intracellular signals transduction pathways and the relative phenotypic adaptation. It encompasses the role of mechanical stimuli for developmental, morphological characteristics, and biological processes in different organs; the response of cells to mechanically induced force is now also emerging as a major determinant of disease. Due to fluid shear stress caused by blood flowing tangentially across the lumen surface, cells of the cardiovascular system are typically exposed to a variety of mechanotransduction. In the body, tissues are continuously exposed to physical forces ranging from compression to strain, which is caused by fluid pressure and compressive forces. Only lately, though, has the importance of how forces shape stem cell differentiation into lineage-committed cells and how mechanical forces can cause or exacerbate disease besides organizing cells into tissues been acknowledged. Mesenchymal stem cells (MSCs) are potent mediators of cardiac repair which can secret a large array of soluble factors that have been shown to play a huge role in tissue repair. Differentiation of MSCs is required to regulate mechanical factors such as fluid shear stress, mechanical strain, and the rigidity of the extracellular matrix through various signaling pathways for their use in regenerative medicine. In the present review, we highlighted mechanical influences on the differentiation of MSCs and the general factors involved in MSCs differentiation. The purpose of this study is to demonstrate the progress that has been achieved in understanding how MSCs perceive and react to their mechanical environment, as well as to highlight areas where more research has been performed in previous studies to fill in the gaps.

Cell adhesion tunes inflammatory TPL2 kinase signal transduction

Signaling through adhesion-related molecules is important for cancer growth and metastasis and cancer cells are resistant to anoikis, a form of cell death ensued by cell detachment from the extracellular matrix. Herein, we report that detached carcinoma cells and immortalized fibroblasts display defects in TNF and CD40 ligand (CD40L)-induced MEK-ERK signaling. Cell detachment results in reduced basal levels of the MEK kinase TPL2, compromises TPL2 activation and sensitizes carcinoma cells to death-inducing receptor ligands, mimicking the synthetic lethal interactions between TPL2 inactivation and TNF or CD40L stimulation. Focal Adhesion Kinase (FAK), which is activated in focal adhesions and mediates anchorage-dependent survival signaling, was found to sustain steady state TPL2 protein levels and to be required for TNF-induced TPL2 signal transduction. We show that when FAK levels are reduced, as seen in certain types of malignancy or malignant cell populations, the formation of cIAP2:RIPK1 complexes increases, leading to reduced TPL2 expression levels by a dual mechanism: first, by the reduction in the levels of NF-κΒ1 which is required for TPL2 stability; second, by the engagement of an RelA NF-κΒ pathway that elevates interleukin-6 production, leading to activation of STAT3 and its transcriptional target SKP2 which functions as a TPL2 E3 ubiquitin ligase. These data underscore a new mode of regulation of TNF family signal transduction on the TPL2-MEK-ERK branch by adhesion-related molecules that may have important ramifications for cancer therapy.

The Netrin-1-Neogenin-1 signaling axis controls neuroblastoma cell migration via integrin-β1 and focal adhesion kinase activation

Neuroblastoma is a highly metastatic tumor that emerges from neural crest cell progenitors. Focal Adhesion Kinase (FAK) is a regulator of cell migration that binds to the receptor Neogenin-1 and is upregulated in neuroblastoma. Here, we show that Netrin-1 ligand binding to Neogenin-1 leads to FAK autophosphorylation and integrin β1 activation in a FAK dependent manner, thus promoting neuroblastoma cell migration. Moreover, Neogenin-1, which was detected in all tumor stages and was required for neuroblastoma cell migration, was found in a complex with integrin β1, FAK, and Netrin-1. Importantly, Neogenin-1 promoted neuroblastoma metastases in an immunodeficient mouse model. Taken together, these data show that Neogenin-1 is a metastasis-promoting protein that associates with FAK, activates integrin β1 and promotes neuroblastoma cell migration.

Strain induced mechanoresponse depends on cell contractility and BAG3-mediated autophagy

Basically all mammalian tissues are constantly exposed to a variety of environmental mechanical signals. Depending on the signal strength, mechanics intervenes in a multitude of cellular processes and is thus capable to induce simple cellular adaptations but also complex differentiation processes and even apoptosis. The underlying recognition typically depends on mechanosensitive proteins, which most often sense the mechanical signal for the induction of a cellular signaling cascade by changing their protein conformation. However, the fate of mechanosensors after mechanical stress application is still poorly understood and it remains unclear whether protein degradation pathways affect the mechanosensitivity of cells. Here, we show that cyclic stretch induces autophagosome formation in a time-dependent manner. Formation depends on the cochaperone BAG3 and thus likely involves BAG3-mediated chaperone-assisted selective autophagy. Furthermore, we demonstrate that strain-induced cell reorientation is clearly delayed upon inhibition of autophagy, suggesting a bidirectional crosstalk between mechanotransduction and autophagic degradation. The strength of the observed delay depends on stable adhesion structures and stress fiber formation in a RhoA-dependent manner.

Endothelial neuropilin-2 influences angiogenesis by regulating actin pattern development and α5-integrin-p-FAK complex recruitment to assembling adhesion sites

The ability to form a variety of cell-matrix connections is crucial for angiogenesis to take place. Without stable anchorage to the extracellular matrix (ECM), endothelial cells (ECs) are unable to sense, integrate and disseminate growth factor stimulated responses that drive growth of a vascular bed. Neuropilin-2 (NRP2) is a widely expressed membrane-bound multifunctional non-tyrosine kinase receptor, which has previously been implicated in influencing cell adhesion and migration by interacting with α5-integrin and regulating adhesion turnover. α5-integrin, and its ECM ligand fibronectin (FN) are both known to be upregulated during the formation of neo-vasculature. Despite being descriptively annotated as a candidate biomarker for aggressive cancer phenotypes, the EC-specific roles for NRP2 during developmental and pathological angiogenesis remain unexplored. The data reported here support a model whereby NRP2 actively promotes EC adhesion and migration by regulating dynamic cytoskeletal remodeling and by stimulating Rab11-dependent recycling of α5-integrin-p-FAK complexes to newly assembling adhesion sites. Furthermore, temporal depletion of EC-NRP2 in vivo impairs primary tumor growth by disrupting vessel formation. We also demonstrate that EC-NRP2 is required for normal postnatal retinal vascular development, specifically by regulating cell-matrix adhesion. Upon loss of endothelial NRP2, vascular outgrowth from the optic nerve during superficial plexus formation is disrupted, likely due to reduced FAK phosphorylation within sprouting tip cells.

An optogenetic model reveals cell shape regulation through FAK and fascin

Cell shape regulation is important, but the mechanisms that govern shape are not fully understood, in part due to limited experimental models in which cell shape changes and underlying molecular processes can be rapidly and non-invasively monitored in real time. Here, we used an optogenetic tool to activate RhoA in the middle of mononucleated macrophages to induce contraction, resulting in a side with the nucleus that retained its shape and a non-nucleated side that was unable to maintain its shape and collapsed. In cells overexpressing focal adhesion kinase (FAK; also known as PTK2), the non-nucleated side exhibited a wide flat morphology and was similar in adhesion area to the nucleated side. In cells overexpressing fascin, an actin-bundling protein, the non-nucleated side assumed a spherical shape and was similar in height to the nucleated side. This effect of fascin was also observed in fibroblasts even without inducing furrow formation. Based on these results, we conclude that FAK and fascin work together to maintain cell shape by regulating adhesion area and height, respectively, in different cell types. This article has an associated First Person interview with the first author of the paper.

Synthesis and evaluation of FAK inhibitors with a 5-fluoro-7H-pyrrolo[2,3-d]pyrimidine scaffold as anti-hepatocellular carcinoma agents

Focal adhesion kinase (FAK) is a ubiquitous intracellular non-receptor tyrosine kinase, which is involved in multiple cellular functions, including cell adhesion, migration, invasion, survival, and angiogenesis. In this study, a series of 7H-pyrrolo[2,3-d]pyrimidines were designed and synthesized according to the E-pharmacophores generated by docking a library of 667 fragments into the ATP pocket of the co-crystal complex of FAK and PF-562271 (PDB ID: 3BZ3). The 5-fluoro-7H-pyrrolo[2,3-d]pyrimidine derivatives demonstrated excellent activity against FAK and the cell lines SMMC7721 and YY8103. 2-((2-((3-(Acetamidomethyl)phenyl)amino)-5-fluoro-7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino)-N-methylbenzamide (16c) was selected for further bioactivity evaluations in vivo, including preliminary pharmacokinetic profiling in rats and toxicity assays in mice, and tumor growth inhibition studies in a xenograft tumor model. The results showed that 16c did not affect the body weight gain of the animals up to a dose of 200 mg/kg, and significantly inhibited tumor growth with a tumor growth inhibition rate of 78.6% compared with the negative control group. Furthermore, phosphoantibody array analyses of a sample of the tumor suggested that 16c inhibited the malignant proliferation of hepatocellular carcinoma (HCC) cells through decreasing the phosphorylation in the FAK cascade.

Investigation of the Structural Mechanism and Film Growth on Cytoprotective Type I Collagen-Based Nanocoating of Individual Cellular Surfaces

Cell surface coating using the layer-by-layer assembly (LbL) method has many advantages for biomedical applications. Because the cell surface is a dynamic and highly complex structure, it is hypothesized that LbL multilayer films on cells have characteristics different from those observed in traditional film characterization results. Here, to demonstrate the mechanism of LbL-film formation on cells, LbL films are prepared on HeLa cells using collagen (Col) and hyaluronic acid (HA). The growth behavior of the film and the main driving forces inducing the formation of an LbL film on the cells are investigated. Col self-assembles via electrostatic and hydrophobic interactions; therefore, the Col-based film on the cells grows laterally rather than volumetrically. For the film construction conditions, the ionic density and chain conformation of the polymers change, resulting in mainly hydrophobic interactions. Additional interactions, such as hydrophobic interactions and biological recognition between the substrate and building blocks, also exist and tightly stabilize the films on the cells. The Col/HA film shows an even distribution on the cell surface as the extracellular matrix, and it activates proliferation and the cytoprotective signaling pathway under harsh conditions, resulting in the focal adhesion kinase signaling pathway and low lactate dehydrogenase release. Therefore, information for film construction on cells is beneficial to understand the effectiveness of an LbL film for cells.

Maintenance of HDACs and H3K9me3 Prevents Arterial Flow-Induced Venous Endothelial Damage

The transition of flow microenvironments from veins to arteries in vein graft surgery induces “peel-off” of venous endothelial cells (vECs) and results in restenosis. Recently, arterial laminar shear stress (ALS) and oscillatory shear stress (OS) have been shown to affect the cell cycle and inflammation through epigenetic controls such as histone deacetylation by histone deacetylases (HDACs) and trimethylation on lysine 9 of histone 3 (H3K9me3) in arterial ECs. However, the roles of H3K9me3 and HDAC in vEC damage under ALS are not known. We hypothesized that the different responses of HDACs and H3K9me3 might cause vEC damage under the transition of venous flow to arterial flow. We found that arterial ECs showed high expression of H3K9me3 protein and were retained in the G0 phase of the cell cycle after being subjected to ALS. vECs became round under ALS with a decrease in the expression of H3K9me3, HDAC3, and HDAC5, and an increase in the expression of vascular cell adhesion molecule 1 (VCAM-1). Inhibition of HDACs activity by a specific inhibitor, phenylbutyrate, in arterial ECs caused similar ALS-induced inflammation and cell loss as observed in vECs. Activation of HDACs and H3K9me3 by ITSA-1, an HDAC activator, could prevent ALS-induced peel-off and reduced VCAM-1 expression in vECs. Moreover, shear stress modulates EC morphology by the regulation of focal adhesion kinase (FAK) expression. ITSA-1 or EGF could increase phosphorylated (p)-FAK expression in vECs under ALS. We found that perturbation of the activity of p-FAK and increase in p-FAK expression restored ALS-induced H3K9me3 expression in vECs. Hence, the abnormal mechanoresponses of H3K9me3 and HDAC in vECs after being subjected to ALS could be reversed by ITSA-1 or EGF treatment: this offers a strategy to prevent vein graft failure.

Distinct roles for the RNA-binding protein Staufen1 in prostate cancer

BACKGROUND

Prostate cancer is one of the most common malignant cancers with the second highest global rate of mortality in men. During the early stages of disease progression, tumour growth is local and androgen-dependent. Despite treatment, a large percentage of patients develop androgen-independent prostate cancer, which often results in metastases, a leading cause of mortality in these patients. Our previous work on the RNA-binding protein Staufen1 demonstrated its novel role in cancer biology, and in particular rhabdomyosarcoma tumorigenesis. To build upon this work, we have focused on the role of Staufen1 in other forms of cancer and describe here the novel and differential roles of Staufen1 in prostate cancer.

METHODS

Using a cell-based approach, three independent prostate cancer cell lines with different characteristics were used to evaluate the expression of Staufen1 in human prostate cancer relative to control prostate cells. The functional impact of Staufen1 on several key oncogenic features of prostate cancer cells including proliferation, apoptosis, migration and invasion were systematically investigated.

RESULTS

We show that Staufen1 levels are increased in all human prostate cancer cells examined in comparison to normal prostate epithelial cells. Furthermore, Staufen1 differentially regulates growth, migration, and invasion in the various prostate cancer cells assessed. In LNCaP prostate cancer cells, Staufen1 regulates cell proliferation through mTOR activation. Conversely, Staufen1 regulates migration and invasion of the highly invasive, bone metastatic-derived, PC3 prostate cells via the activation of focal adhesion kinase.

CONCLUSIONS

Collectively, these results show that Staufen1 has a direct impact in prostate cancer development and further demonstrate that its functions vary amongst the prostate cancer cell types. Accordingly, Staufen1 represents a novel target for the development of much-needed therapeutic strategies for prostate cancer.

Manipulation of Focal Adhesion Signaling by Pathogenic Microbes

Focal adhesions (FAs) serve as dynamic signaling hubs within the cell. They connect intracellular actin to the extracellular matrix (ECM) and respond to environmental cues. In doing so, these structures facilitate important processes such as cell-ECM adhesion and migration. Pathogenic microbes often modify the host cell actin cytoskeleton in their pursuit of an ideal replicative niche or during invasion to facilitate uptake. As actin-interfacing structures, FA dynamics are also intimately tied to actin cytoskeletal organization. Indeed, exploitation of FAs is another avenue by which pathogenic microbes ensure their uptake, survival and dissemination. This is often achieved through the secretion of effector proteins which target specific protein components within the FA. Molecular mimicry of the leucine-aspartic acid (LD) motif or vinculin-binding domains (VBDs) commonly found within FA proteins is a common microbial strategy. Other effectors may induce post-translational modifications to FA proteins through the regulation of phosphorylation sites or proteolytic cleavage. In this review, we present an overview of the regulatory mechanisms governing host cell FAs, and provide examples of how pathogenic microbes have evolved to co-opt them to their own advantage. Recent technological advances pose exciting opportunities for delving deeper into the mechanistic details by which pathogenic microbes modify FAs.

Expression regulation of cold-inducible protein RBM3 by FAK/Src signaling for neuroprotection against rotenone under mild hypothermia

Mild hypothermia is a well-established technique for alleviating neurological injuries in clinical surgery. RNA-binding protein motif 3 (RBM3) has been identified as a crucial factor in mediating hypothermic neuroprotection, providing its induction as a promising strategy for mimicking therapeutic hypothermia. However, little is known about molecular control of RBM3 and signaling pathways affected by hypothermia. In the present study, human SH-SY5Y neuroblastoma cells were used as a neural cell model. Screening of signaling pathways showed that cold exposure led to inactivation of ERK and AMPK pathways, and activation of FAK and PLCγ pathways, with activities of p38, JNK and AKT pathways moderately changed. Next, various small molecule inhibitors specific to these signaling pathways were applied. Interestingly, only FAK-specific inhibitor exhibited a significant inhibitory effect on hypothermia-induced RBM3 gene transcription and protein expression. Likewise, FAK silencing using siRNA technique significantly abrogated the induction of RBM3 by hypothermia. Moreover, FAK inhibition accounted for an inactivation of Src, a known kinase downstream of FAK. Next, either the silencing of Src by siRNA or its inactivation by a chemical inhibitor, strongly blocked the induction of RBM3 by cooling. Notably, in HEK293 and PC12 cells, FAK/Src activation was also shown to be indispensable for hypothermia-stimulated RBM3 expression. Lastly, the CCK8 and Western blot assays showed that both FAK/Src inacitivation and their knockdown substantially abrogate the neuroprotective effects of mild hypothermia against rotenone in SH-SY5Y cells. These data suggest that FAK/Src signaling axis regulates the transcription of Rbm3 gene and mediates neuroprotective effects of mild hypothermia.

Progress in the Development of Small Molecular Inhibitors of Focal Adhesion Kinase (FAK)

Focal adhesion kinase (FAK) is a nonreceptor intracellular tyrosine kinase that plays an essential role in cancer cell adhesion, survival, proliferation, and migration through both its enzymatic activities and scaffolding functions. Overexpression of FAK has been found in many human cancer cells from different origins, which promotes tumor progression and influences clinical outcomes in different classes of human tumors. Therefore, FAK has been considered as a promising target for small molecule anticancer drug development. Many FAK inhibitors targeting different domains of FAK with various mechanisms of functions have been reported, including kinase domain inhibitors, FERM domain inhibitors, and FAT domain inhibitors. In addition, FAK-targeting PROTACs, which can induce the degradation of FAK, have also been developed. In this Perspective, we summarized the progress in the development of small molecular FAK inhibitors and proposed the perspectives for the future development of agents targeting FAK.

The Intersection of Mechanotransduction and Regenerative Osteogenic Materials

Mechanical signals play a central role in cell fate determination and differentiation in both physiologic and pathologic circumstances. Such signals may be delivered using materials to generate discrete microenvironments for the purposes of tissue regeneration and have garnered increasing attention in recent years. Unlike the addition of progenitor cells or growth factors, delivery of a microenvironment is particularly attractive in that it may reduce the known untoward consequences of the former two strategies, such as excessive proliferation and potential malignant transformation. Additionally, the ability to spatially modulate the fabrication of materials allows for the creation of multiple microenvironments, particularly attractive for regenerating complex tissues. While many regenerative materials have been developed and tested for augmentation of specific cellular responses, the intersection between cell biology and material interactions have been difficult to dissect due to the complexity of both physical and chemical interactions. Specifically, modulating materials to target individual signaling pathways is an avenue of interdisciplinary research that may lead to a more effective method of optimizing regenerative materials. In this work, the aim is to summarize the major mechanotransduction pathways for osteogenic differentiation and to consolidate the known materials and material properties that activate such pathways.

In vitro biocompatibility of biohybrid polymers membrane evaluated in human gingival fibroblasts

The biohybrid polymer membrane (BHM) is a new biomaterial designed for the treatment of soft periodontal tissue defects. We aimed to evaluate the in vitro biocompatibility of the membrane in human gingival fibroblasts and the capability to induce cell adhesion, migration, differentiation and improving the production of the extracellular matrix. BHM and Mucograft® collagen matrix (MCM) membranes were punched into 6 mm diameter round discs and placed in 96-well plates. Human primary gingival fibroblasts were seeded on the membranes or tissue culture plastic (TCP) serving as the control. Cell proliferation/viability and morphology were evaluated after 3, 7, and 14 days of culture by cell counting kit (CCK)-8 assay and scanning electron microscopy, respectively. Additionally, the gene expression of transforming growth factor (TGF)-β1, focal adhesion kinase (FAK), collagen type 1 (Col1), alpha-smooth muscle actin (α-SMA), and fibroblasts growth factor (FGF)-2 was analyzed at 3, 7, and 14 days of culture by qPCR. Cell proliferation on BHM was significantly higher than on MCM and similar to TCP. Gene expression of TGF-β1, FAK, Col1, and α-SMA were significantly increased on BHM compared to TCP at most investigated time points. However, the gene expression of FGF-2 was significantly decreased on BHM at Day 7 and recovered at Day 14 to the levels similar to TCP. The finding of this study showed that BHM is superior for gingival fibroblasts in terms of adhesion, proliferation, and gene expression, suggesting that this membrane may promote the healing of soft periodontal tissue.

Substrate stiffness effects on SH-SY5Y: The dichotomy of morphology and neuronal behavior

Like many other cell types, neuroblastoma cells are also known to respond to mechanical cues in their microenvironment in vitro. They were shown to have mechanotransduction pathways, which result in enhanced neuronal morphology on stiff substrates. However, in previous studies, the differentiation process was monitored only by morphological parameters. Motivated by the lack of comprehensive studies that investigate the effects of mechanical cues on neuroblastoma differentiation, we used SH-SY5Y cells differentiated on polyacrylamide (PA) gels as a model. Cells differentiated on the surface of PA hydrogels with three different elastic moduli (0.1, 1, and 50 kPa) were morphologically evaluated and their electrophysiological responsiveness was probed using calcium imaging. Immunodetection of neural marker TUJ1 and p-FAK was used for biochemical characterization. Groups with defined stiffness that are matching and nonmatching to neural tissue extracellular matrix were used to distinguish biomimetic results from other effects. Results show that while cells display morphologies that do not resemble neurons on soft substrates, they are in fact electrophysiologically more responsive and abundant in neuronal marker TUJ1. Our findings suggest that while neuronal differentiation occurs more efficiently in microenvironments mechanically mimicking neural tissue, the SH-SY5Y model demonstrates morphologies that conflict with neuronal behavior under these conditions. These results are expected to contribute considerable input to researchers that use SH-SY5Y as a neuron model.

The Importance of Mechanical Forces for in vitro Endothelial Cell Biology

Blood and lymphatic vessels are lined by endothelial cells which constantly interact with their luminal and abluminal extracellular environments. These interactions confer physical forces on the endothelium, such as shear stress, stretch and stiffness, to mediate biological responses. These physical forces are often altered during disease, driving abnormal endothelial cell behavior and pathology. Therefore, it is critical that we understand the mechanisms by which endothelial cells respond to physical forces. Traditionally, endothelial cells in culture are grown in the absence of flow on stiff substrates such as plastic or glass. These cells are not subjected to the physical forces that endothelial cells endure in vivo, thus the results of these experiments often do not mimic those observed in the body. The field of vascular biology now realize that an intricate analysis of endothelial signaling mechanisms requires complex in vitro systems to mimic in vivo conditions. Here, we will review what is known about the mechanical forces that guide endothelial cell behavior and then discuss the advancements in endothelial cell culture models designed to better mimic the in vivo vascular microenvironment. A wider application of these technologies will provide more biologically relevant information from cultured cells which will be reproducible to conditions found in the body.

Activation of cell migration via morphological changes in focal adhesions depends on shear stress in MYCN-amplified neuroblastoma cells

Neuroblastoma is the most common solid tumour of childhood, and it metastasizes to distant organs. However, the mechanism of metastasis, which generally depends on the cell motility of the neuroblastoma, remains unclear. In many solid tumours, it has been reported that shear stress promotes metastasis. Here, we investigated the relationship between shear stress and cell motility in the MYCN-amplified human neuroblastoma cell line IMR32, using a microfluidic device. We confirmed that most of the cells migrated downstream, and cell motility increased dramatically when the cells were exposed to a shear stress of 0.4 Pa, equivalent to that expected in vivo. We observed that the morphological features of focal adhesion were changed under a shear stress of 0.4 Pa. We also investigated the relationship between malignancy and the motility of IMR32 cells under shear stress. Decreasing the expression of MYCN in IMR32 cells via siRNA transfection inhibited cell motility by a shear stress of 0.4 Pa. These results suggest that MYCN-amplified neuroblastoma cells under high shear stress migrate to distant organs due to high cell motility, allowing cell migration to lymphatic vessels and venules.

Self-Assembly of Integrin Ligands on the Apical Membrane Inhibits the Migration of Glioma Cells

Malignant brain cancer remains challenging in treatment due to the highly invasive quality of gliomas. Inspired by the upregulated expression of integrin β1 subunits in tumors, we designed and synthesized an integrin-targeting self-assembling ligand based on a laminin-derived peptide that selectively forms nanofibrous microdomains on the apical membrane of glioma cells, inhibiting their migration and invasion.

A Surface-Tailoring Method for Rapid Non-Thermosensitive Cell-Sheet Engineering via Functional Polymer Coatings

Cell sheet engineering, a technique utilizing a monolayer cell sheet, has recently emerged as a promising technology for scaffold-free tissue engineering. In contrast to conventional tissue-engineering approaches, the cell sheet technology allows cell harvest as a continuous cell sheet with intact extracellular matrix proteins and cell-cell junction, which facilitates cell transplantation without any other artificial biomaterials. A facile, non-thermoresponsive method is demonstrated for a rapid but highly reliable platform for cell-sheet engineering. The developed method exploits the precise modulation of cell-substrate interactions by controlling the surface energy of the substrate via a series of functional polymer coatings to enable prompt cell sheet harvesting within 100 s. The engineered surface can trigger an intrinsic cellular response upon the depletion of divalent cations, leading to spontaneous cell sheet detachment under physiological conditions (pH 7.4 and 37 °C) in a non-thermoresponsive manner. Additionally, the therapeutic potential of the cell sheet is successfully demonstrated by the transplantation of multilayered cell sheets into mouse models of diabetic wounds and ischemia. These findings highlight the ability of the developed surface for non-thermoresponsive cell sheet engineering to serve as a robust platform for regenerative medicine and provide significant breakthroughs in cell sheet technology.

Putative Receptors for Gravity Sensing in Mammalian Cells: The Effects of Microgravity

Gravity is a constitutive force that influences life on Earth. It is sensed and translated into biochemical stimuli through the so called “mechanosensors”, proteins able to change their molecular conformation in order to amplify external cues causing several intracellular responses. Mechanosensors are widely represented in the human body with important structures such as otholiths in hair cells of vestibular system and statoliths in plants. Moreover, they are also present in the bone, where mechanical cues can cause bone resorption or formation and in muscle in which mechanical stimuli can increase the sensibility for mechanical stretch. In this review, we discuss the role of mechanosensors in two different conditions: normogravity and microgravity, emphasizing their emerging role in microgravity. Microgravity is a singular condition in which many molecular changes occur, strictly connected with the modified gravity force and free fall of bodies. Here, we first summarize the most important mechanosensors involved in normogravity and microgravity. Subsequently, we propose muscle LIM protein (MLP) and sirtuins as new actors in mechanosensing and signaling transduction under microgravity.

Biophysics of Cell-Substrate Interactions Under Shear

Cells adhere to substrates through mechanosensitive focal adhesion complexes. Measurements that probe how cells detach from substrates when they experience an applied force connect molecular-scale aspects of cell adhesion with the biophysical properties of adherent cells. Such forces can be applied through shear devices that flow fluid in a controlled manner across cells. The signaling pathways associated with focal adhesions, in particular those that involve integrins and receptor tyrosine kinases, are complex, receiving mechano-chemical feedback from the sensing of substrate stiffness as well as of external forces. This article reviews the signaling processes involved in mechanosensing and mechanotransduction during cell-substrate interactions, describing the role such signaling plays in cancer metastasis. We examine some recent progress in quantifying the strength of these interactions, describing a novel fluid shear device that allows for the visualization of the cell and its sub-cellular structures under a shear flow. We also summarize related results from a biophysical model for cellular de-adhesion induced by applied forces. Quantifying cell-substrate adhesions under shear should aid in the development of mechano-diagnostic techniques for diseases in which cell-adhesion is mis-regulated, such as cancers.

Augmenting cancer cell proteomics with cellular images - A semantic approach to understand focal adhesion

If monolayers of cancer cells are exposed to microgravity, some of the cells cease adhering to the bottom of a culture flask and join three-dimensional aggregates floating in the culture medium. Searching reasons for this change in phenotype, we performed proteome analyses and learnt that accumulation and posttranslational modification of proteins involved in cell-matrix and cell-cell adhesion are affected. To further investigate these proteins, we developed a methodology to find histological images about focal adhesion complex (FA) proteins. Selecting proteins expressed by human FTC-133 and MCF-7 cancer cells and known to be incorporated in FA, we transformed the experimental data to RDF to establish a core semantic knowledgebase. Applying iterative SPARQL queries to Linked Open Databases, we augmented these data with additional functional, transformation- and aggregation-related relationships. Using reasoning, we retrieved publications with images about the spatial arrangement of proteins incorporated in FA. Contextualizing those images enabled us to gain insights about FA of cells changing their site of growth, and to independently validate our experimental results. This new way to link experimental proteome data to biomedical knowledge from various sources via searching images may generally be applied in science when images are a tool of knowledge dissemination.

Chondroitin sulfate-D promotes neurite outgrowth by acting as an extracellular ligand for neuronal integrin αVβ3

BACKGROUND

Chondroitin sulfate (CS) chains are prominent extra/pericellular matrix components in the central nervous system (CNS) and can exert positive or negative regulatory effects on neurite outgrowth, depending on the CS structure and the amount. Despite the remarkable abilities of highly sulfated forms of CS chains to enhance neurite outgrowth, the neuronal recognition systems for such promotional CS chains, including CS-D polysaccharide, remain to be fully elucidated.

METHODS

We explored the molecular basis of the CS-D-mediated neurite extension using primary hippocampal neurons cultured on substrate precoated with CS-D polysaccharides, and evaluated functional involvement of a distinct integrin heterodimer as a novel neuronal CS receptor for CS-D.

RESULTS

We identified an extracellular matrix receptor, integrin αVβ3, as a functional receptor for CS-D. CS-D, but not CS-C (a precursor form of CS-D) showed significant binding affinity toward recombinant integrin αVβ3 heterodimer and activated intracellular signaling(s) involving focal adhesion kinase (FAK) and Src/Fyn kinase. Functional blockade of the respective players for integrin signaling abrogated the promotional effects of CS-D. We also found the existence of CS-D-induced integrin activation system in neuronal stem/progenitor cell population.

CONCLUSIONS

The neuronal cell surface integrin αVβ3 can function as a CS receptor for a highly sulfated CS subtype, CS-D.

GENERAL SIGNIFICANCE

Our findings are the first to demonstrate that CS-dependent neurite outgrowth promotion is exerted via direct activation of specific integrin heterodimers on neuronal cell surfaces, providing new insights into understanding the CS-sensing machineries that regulate CNS development and regeneration.

Evaluation of human mesenchymal stem cell senescence, differentiation and secretion behavior cultured on polycarbonate cell culture inserts

Polycarbonate (PC) substrate is well suited for culturing human mesenchymal stem cells (MSCs) with high proliferation rate, low cell apoptosis rate and negligible cytotoxic effects. However, little is known about the influence of PC on MSC activity including senescence, differentiation and secretion. In this study, the PC cell culture insert was applied for human MSC culture and was compared with polystyrene (PS) and standard tissue culture plate (TCP). The results showed that MSCs were able to adhere on PC surface, exhibiting a spindle-shaped morphology. The size and distribution of focal adhesions of MSCs were similar on PC and TCP. The senescence level of MSCs on PC was comparable to that on TCP, but was significantly lower than that on PS. MSCs on PC were capable of self-renewal and differentiation into multiple cell lineages, including osteogenic and adipogenic lineages. MSCs cultured on PC secreted a higher level inflammatory cytokines and pro-angiogenic factors including FGF2 and VEGF. Conclusively, PC represents a promising cell culture material for human MSCs.

CRISPR/Cas9 engineering of ERK5 identifies its FAK/PYK2 dependent role in adhesion-mediated cell survival

Extracellular signal-regulated kinase 5 (ERK5) is now considered a key regulator of breast cancer cell proliferation, migration and invasion. It is also implicated in growth factor induced anti-apoptotic signaling. But its contribution to adhesion-induced survival signaling is not clear. In the present study, using CRISPR/Cas9 editing, we knocked-out ERK5 expression in several cancer cell lines. Then MDA-MB 231 breast cancer cells lacking ERK5 were used to understand its role in adhesion-mediated cell viability. We demonstrated that ERK5 deficient cells exhibited reduced cell attachment to matrix proteins fibronectin and vitronectin. The adhesion ability of these cells was further reduced upon chemical inhibition of focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (PYK2) by PF 431396. FAK/PYK2 inhibited ERK5 knock-out cells also showed markedly reduced cell-viability and increased apoptotic signaling. This was evident from the detection of cleaved PARP and caspase 9 in these cells. Thus, our data suggests a FAK/PYK2 regulated pro-survival role of ERK5 in response to cell adhesion.

Molecular basis for autoinhibition of RIAM regulated by FAK in integrin activation

RAP1-interacting adapter molecule (RIAM) mediates RAP1-induced integrin activation. The RAS-association (RA) segment of the RA-PH module of RIAM interacts with GTP-bound RAP1 and phosphoinositol 4,5 bisphosphate but this interaction is inhibited by the N-terminal segment of RIAM. Here we report the structural basis for the autoinhibition of RIAM by an intramolecular interaction between the IN region (aa 27-93) and the RA-PH module. We solved the crystal structure of IN-RA-PH to a resolution of 2.4-Å. The structure reveals that the IN segment associates with the RA segment and thereby suppresses RIAM:RAP1 association. This autoinhibitory configuration of RIAM can be released by phosphorylation at Tyr45 in the IN segment. Specific inhibitors of focal adhesion kinase (FAK) blocked phosphorylation of Tyr45, inhibited stimulated translocation of RIAM to the plasma membrane, and inhibited integrin-mediated cell adhesion in a Tyr45-dependent fashion. Our results reveal an unusual regulatory mechanism in small GTPase signaling by which the effector molecule is autoinhibited for GTPase interaction, and a modality of integrin activation at the level of RIAM through a FAK-mediated feedforward mechanism that involves reversal of autoinhibition by a tyrosine kinase associated with integrin signaling.

Biomaterial substrate modifications that influence cell-material interactions to prime cellular responses to nonviral gene delivery

IMPACT STATEMENT

This review summarizes how biomaterial substrate modifications (e.g. chemical modifications like natural coatings, ligands, or functional side groups, and/or physical modifications such as topography or stiffness) can prime the cellular response to nonviral gene delivery (e.g. affecting integrin binding and focal adhesion formation, cytoskeletal remodeling, endocytic mechanisms, and intracellular trafficking), to aid in improving gene delivery for applications where a cell-material interface might exist (e.g. tissue engineering scaffolds, medical implants and devices, sensors and diagnostics, wound dressings).