Integrins can collaborate with growth factors for phosphorylation of receptor tyrosine kinases and MAP kinase activation: roles of integrin aggregation and occupancy of receptors

Matrix Stiffness and Biochemistry Govern Colorectal Cancer Cell Growth and Signaling in User-Programmable Synthetic Hydrogels

Colorectal cancer (CRC) studies in vitro have been conducted almost exclusively on 2D cell monolayers or suspension spheroid cultures. Though these platforms have shed light on many important aspects of CRC biology, they fail to recapitulate essential cell-matrix interactions that often define in vivo function. Toward filling this knowledge gap, synthetic hydrogel biomaterials with user-programmable matrix mechanics and biochemistry have gained popularity for culturing cells in a more physiologically relevant 3D context. Here, using a poly(ethylene glycol)-based hydrogel model, we systematically assess the role of matrix stiffness and fibronectin-derived RGDS adhesive peptide presentation on CRC colony morphology and proliferation. Highlighting platform generalizability, we demonstrate that these hydrogels can support the viability and promote spontaneous spheroid or multicellular aggregate formation of six CRC cell lines that are commonly utilized in biomedical research. These gels are engineered to be fully degradable via a "biologically invisible" sortase-mediated reaction, enabling the triggered recovery of single cells and spheroids for downstream analysis. Using these platforms, we establish that substrate mechanics play a significant role in colony growth: soft conditions (∼300 Pa) encourage robust colony formation, whereas stiffer (∼2 kPa) gels severely restrict growth. Tuning the RGDS concentration did not affect the colony morphology. Additionally, we observe that epidermal growth factor receptor (EGFR) signaling in Caco-2 cells is influenced by adhesion ligand identity─whether the adhesion peptide was derived from collagen type I (DGEA) or fibronectin (RGDS)─with DGEA yielding a marked decrease in the level of downstream protein kinase phosphorylation. Taken together, this study introduces a versatile method to culture and probe CRC cell-matrix interactions within engineered 3D biomaterials.

Interaction of Serratia proteamaculans with Integrins Activates Invasion-Promoting Signaling Pathways

The opportunistic bacteria Serratia proteamaculans are able to penetrate human cells. It was previously shown that the bacterial surface protein OmpX promotes bacterial adhesion. In addition, infection with bacteria that synthesize the OmpX protein enhances the expression of EGFR and β1 integrin involved in the invasion of S. proteamaculans. Therefore, this work was aimed at determining the mechanism of interaction of S. proteamaculans with receptors of eukaryotic cells. Both integrin-linked kinase (ILK) and EGFR tyrosine kinase have been shown to be involved in the invasion of these bacteria. During infection, EGFR is first phosphorylated at Tyr845, which is carried out by c-Src kinase transmitting a signal from nearby receptors. The S. proteamaculans invasion depends on c-Src and focal adhesion kinase (FAK), which can both transmit a signal between β1 integrin and EGFR and participate in cytoskeletal rearrangements. These bacteria have been shown to interact with integrin not through the RGD binding site, and integrin binding to the RGD peptide enhances adhesion, invasion, and expression of α5 and β1 integrin subunits in response to infection. On the other hand, bacterial adhesion and increased expression of integrins during infection are caused by OmpX. Thus, OmpX interacts with integrins, and the participation of the α5 and β1 integrin subunits in the S. proteamaculans invasion allows us to assume that the receptor of OmpX is α5β1 integrin.

Mesodermal fibronectin controls cell shape, polarity, and mechanotransduction in the second heart field during cardiac outflow tract development

Failure in the elongation of the cardiac outflow tract (OFT) results in congenital heart disease due to the misalignment of the great arteries with the left and right ventricles. The OFT lengthens via the accretion of progenitors from the second heart field (SHF). SHF cells are exquisitely regionalized and organized into an epithelial-like layer, forming the dorsal pericardial wall (DPW). Tissue tension, cell polarity, and proliferation within the DPW are important for the addition of SHF-derived cells to the heart and OFT elongation. However, the genes controlling these processes are not completely characterized. Using conditional mutagenesis in the mouse, we show that fibronectin (FN1) synthesized by the mesoderm coordinates multiple cellular behaviors in the anterior DPW. FN1 is enriched in the anterior DPW and plays a role in OFT elongation by maintaining a balance between pro- and anti-adhesive cell-extracellular matrix (ECM) interactions and controlling DPW cell shape, polarity, cohesion, proliferation, and mechanotransduction.

Cell Adhesion Molecules as Modulators of the Epidermal Growth Factor Receptor

Cell adhesion molecules (CAMs) are cell surface glycoproteins mediating interactions of cells with other cells and the extracellular matrix. By mediating the adhesion and modulating activity of other plasma membrane proteins, CAMs are involved in regulating a multitude of cellular processes, including growth, proliferation, migration, and survival of cells. In this review, we present evidence showing that various CAMs interact with the epidermal growth factor receptor (EGFR), a receptor tyrosine kinase inducing pro-proliferative and anti-apoptotic intracellular signaling in response to binding to several soluble ligands, including the epidermal growth factor. We discuss that CAMs are involved in regulating EGFR signaling by either potentiating or inhibiting the soluble ligand-dependent activation of EGFR. In addition, CAMs induce soluble ligand-independent forms of EGFR activity and regulate the levels of EGFR and its ligand-induced degradation. The CAM-dependent modulation of EGFR activity plays a key role in regulating the growth, proliferation, and survival of cells. Future research is needed to determine whether these processes can be targeted in both normal and cancerous cells by regulating interactions of EGFR with various CAMs.

Unveiling the intracellular dynamics of α4β2 nAChR-mediated ERK activation through the interplay of arrestin, Gβγ, and PKCβII

AIMS

In contrast to G protein-coupled receptors or receptor tyrosine kinases, the mechanism underlying ERK activation through nicotine acetylcholine receptors (nAChRs), members of the ligand-gated ion channel family, remains poorly elucidated. This study aimed to delineate the signaling pathway responsible for ERK activation by the α4β2 nAChR subtype, which is implicated in nicotine addiction and various mental disorders.

MATERIALS AND METHODS

Loss-of-function strategies and mutants of arrestin2/PKCβII with distinct functional characteristics were employed to identify the cellular components and processes involved in ERK activation.

KEY FINDINGS

ERK activation via α4β2 nAChR was observed within the nucleus and necessitated the nuclear translocation of arrestin2 and PKCβII, which exhibited mutual augmentation. Activation of PKCβII by α4β2 nAChR stimulation facilitated the nuclear translocation of arrestin2 by enhancing its interaction with importin β1. Apart from scaffolding ERK activation in the nucleus, arrestin2, in cooperation with GRK2, facilitated the activation of the Src/Syk/PKCβII signaling cascade, leading to the nuclear entry of PKCβII in a Gβγ-dependent manner. Upon nuclear localization, PKCβII underwent ubiquitination by Mdm2 and interacted with MEK1, resulting in ERK activation. In summary, α4β2 nAChR-mediated ERK activation in the nucleus involves the nuclear translocation of arrestin2 and PKCβII, which is reciprocally facilitated via positive feedback augmentation.

SIGNIFICANCE

As α4β2 nAChRs play a pivotal role in various cellular processes including drug addiction and mental disorders, our findings will offer insights into understanding the pathogenesis of α4β2 nAChR-related disorders and may facilitate the development of targeted therapeutic interventions.

Talin1 promotes HCC progression by regulating NRG1/PI3K/AKT pathway

OBJECTIVE OF THE STUDY

Hepatocellular carcinoma (HCC) stands as the third leading cause of cancer-related mortality globally. Metastasis, responsible for treatment failures, underscores the urgency to comprehend molecular drivers of invasion and migration. Central to the invasive and migratory processes underlying metastasis is the protein Talin1. However, the role and underlying mechanisms governing Talin1's involvement in HCC have remained elusive.

METHODS

A total of 100 HCC specimens were collected from patients who underwent hepatectomy in our center. The expression level of talin1 was measured to evaluate the correlationship of talin1 and the development of HCC. In vitro and in vivo experiments were conducted to verify the characteristic of talin1 in HCC. RNA-seq and bioinformatics analysis were performed to identify the downstream signal pathway of talin1 and their impact on HCC development.

RESULTS

Here, we reported elevated levels of Talin1 mRNA and protein in HCC tissues. Meanwhile, downregulation of Talin1 significantly reduced the HCC cell proliferation and metastasis in vitro and in vivo. Furthermore, elevating NRG-1, a downstream target of Talin1, enhanced metastasis of HCC cells. More importantly, attenuation of Talin1 inhibited HCC progression through decreasing the stabilization of NRG1 mRNA, consequently regulating the expression of NRG1 and its involvement in mediating the PI3K/AKT pathway.

CONCLUSION

Taken together, Talin1 regulates cellular proliferation, metastasis, and invasiveness by modulating NRG1/PI3K/AKT axis, suggesting that Talin1 emerges as a promising candidate for treating HCC.

Integrin signalling in joint development, homeostasis and osteoarthritis

Integrins are key regulators of cell-matrix interactions during joint development and joint tissue homeostasis, as well as in the development of osteoarthritis (OA). The signalling cascades initiated by the interactions of integrins with a complex network of extracellular matrix (ECM) components and intracellular adaptor proteins orchestrate cellular responses necessary for maintaining joint tissue integrity. Dysregulated integrin signalling, triggered by matrix degradation products such as matrikines, disrupts this delicate balance, tipping the scales towards an environment conducive to OA pathogenesis. The interplay between integrin signalling and growth factor pathways further underscores the multifaceted nature of OA. Moreover, emerging insights into the role of endocytic trafficking in regulating integrin signalling add a new layer of complexity to the understanding of OA development. To harness the therapeutic potential of targeting integrins for mitigation of OA, comprehensive understanding of their molecular mechanisms across joint tissues is imperative. Ultimately, deciphering the complexities of integrin signalling will advance the ability to treat OA and alleviate its global burden.

Biological importance of human amniotic membrane in tissue engineering and regenerative medicine

The human amniotic membrane (hAM) is the innermost layer of the placenta. Its distinctive structure and the biological and physical characteristics make it a highly biocompatible material in a variety of regenerative medicine applications. It also acts as a supply of bioactive factors and cells, which indicate the advantages over other tissues. In this review, we firstly discussed the biological properties of hAM-derived cells in vivo or in vitro, along with their stemness of markers, pointing out a promising source of stem cells for regenerative medicine. Then, we systematically summarized current knowledge on the collection, preparation, preservation, and decellularization of hAM, as well as their characteristics helping to improve the understanding of applications in tissue engineering. Finally, we highlighted the recent advances in which hAM has undergone additional modifications to achieve an adequate perspective of regenerative medicine applications. More investigations are required in utilizing appropriate modifications to enhance the therapeutic effectiveness of hAM in the future.

Understanding and targeting anoikis in metastasis for cancer therapies

The development of effective treatments for cancers requires investigations for a more detailed and comprehensive understanding of the basic cellular mechanisms involved in carcinogenesis, cancer progression, and metastasis. One of those driving mechanisms is anoikis, a special type of apoptosis, which is induced by losing anchorage from the extracellular matrix (ECM). In other words, resisting death in detached cells (cells without ECM) forms an anoikis-resistant phenotype. Since the anoikis-resistance state compensates for the initial steps of cancer metastasis, this review aimed to discuss mechanisms of gaining anoikis/anoikis resistance phenotype in tumor cells. Finally, we highlighted the significance of anoikis in malignancies so as to provide clear insight into cancer diagnosis and therapy development.

How cells sense and integrate information from different sources

Cell signaling is a fundamental cellular process that enables cells to sense and respond to information in their surroundings. At the molecular level, signaling is primarily carried out by transmembrane protein receptors that can initiate complex downstream signal transduction cascades to alter cellular behavior. In the human body, different cells can be exposed to a wide variety of environmental conditions, and cells express diverse classes of receptors capable of sensing and integrating different signals. Furthermore, different receptors and signaling pathways can crosstalk with each other to calibrate the cellular response. Crosstalk occurs through multiple mechanisms at different levels of signaling pathways. In this review, we discuss how cells sense and integrate different chemical, mechanical, and spatial signals as well as the mechanisms of crosstalk between pathways. To illustrate these concepts, we use a few well-studied signaling pathways, including receptor tyrosine kinases and integrin receptors. Finally, we discuss the implications of dysregulated cellular sensing on driving diseases such as cancer. This article is categorized under: Cancer > Molecular and Cellular Physiology Metabolic Diseases > Molecular and Cellular Physiology.

Advances in non-invasive biosensing measures to monitor wound healing progression

Impaired wound healing is a significant financial and medical burden. The synthesis and deposition of extracellular matrix (ECM) in a new wound is a dynamic process that is constantly changing and adapting to the biochemical and biomechanical signaling from the extracellular microenvironments of the wound. This drives either a regenerative or fibrotic and scar-forming healing outcome. Disruptions in ECM deposition, structure, and composition lead to impaired healing in diseased states, such as in diabetes. Valid measures of the principal determinants of successful ECM deposition and wound healing include lack of bacterial contamination, good tissue perfusion, and reduced mechanical injury and strain. These measures are used by wound-care providers to intervene upon the healing wound to steer healing toward a more functional phenotype with improved structural integrity and healing outcomes and to prevent adverse wound developments. In this review, we discuss bioengineering advances in 1) non-invasive detection of biologic and physiologic factors of the healing wound, 2) visualizing and modeling the ECM, and 3) computational tools that efficiently evaluate the complex data acquired from the wounds based on basic science, preclinical, translational and clinical studies, that would allow us to prognosticate healing outcomes and intervene effectively. We focus on bioelectronics and biologic interfaces of the sensors and actuators for real time biosensing and actuation of the tissues. We also discuss high-resolution, advanced imaging techniques, which go beyond traditional confocal and fluorescence microscopy to visualize microscopic details of the composition of the wound matrix, linearity of collagen, and live tracking of components within the wound microenvironment. Computational modeling of the wound matrix, including partial differential equation datasets as well as machine learning models that can serve as powerful tools for physicians to guide their decision-making process are discussed.

Cardiac differentiation of human pluripotent stem cells using defined extracellular matrix proteins reveals essential role of fibronectin

Research and therapeutic applications using human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) require robust differentiation strategies. Efforts to improve hPSC-CM differentiation have largely overlooked the role of extracellular matrix (ECM). The present study investigates the ability of defined ECM proteins to promote hPSC cardiac differentiation. Fibronectin (FN), laminin-111, and laminin-521 enabled hPSCs to attach and expand. However, only addition of FN promoted cardiac differentiation in response to growth factors Activin A, BMP4, and bFGF in contrast to the inhibition produced by laminin-111 or laminin-521. hPSCs in culture produced endogenous FN which accumulated in the ECM to a critical level necessary for effective cardiac differentiation. Inducible shRNA knockdown of FN prevented Brachyury+ mesoderm formation and subsequent hPSC-CM generation. Antibodies blocking FN binding integrins α4β1 or αVβ1, but not α5β1, inhibited cardiac differentiation. Furthermore, inhibition of integrin-linked kinase led to a decrease in phosphorylated AKT, which was associated with increased apoptosis and inhibition of cardiac differentiation. These results provide new insights into defined matrices for culture of hPSCs that enable production of FN-enriched ECM which is essential for mesoderm formation and efficient cardiac differentiation.

Blood Flow Restriction Training for the Intervention of Sarcopenia: Current Stage and Future Perspective

Sarcopenia is a geriatric syndrome that is characterized by a progressive and generalized skeletal muscle disorder and can be associated with many comorbidities, including obesity, diabetes, and fracture. Its definitions, given by the AWGS and EWGSOP, are widely used. Sarcopenia is measured by muscle strength, muscle quantity or mass and physical performance. Currently, the importance and urgency of sarcopenia have grown. The application of blood flow restriction (BFR) training has received increased attention in managing sarcopenia. BFR is accomplished using a pneumatic cuff on the proximal aspect of the exercising limb. Two main methods of exercise, aerobic exercise and resistance exercise, have been applied with BFR in treating sarcopenia. Both methods can increase muscle mass and muscle strength to a certain extent. Intricate mechanisms are involved during BFRT. Currently, the presented mechanisms mainly include responses in the blood vessels and related hormones, such as growth factors, tissue hypoxia-related factors and recruitment of muscle fiber as well as muscle satellite cells. These mechanisms contribute to the positive balance of skeletal muscle synthesis, which in turn mitigates sarcopenia. As a more suited and more effective way of treating sarcopenia and its comorbidities, BFRT can serve as an alternative to traditional exercise for people who have marked physical limitations or even show superior outcomes under low loads. However, the possibility of causing stress or muscle damage must be considered. Cuff size, pressure, training load and other variables can affect the outcome of sarcopenia, which must also be considered. Thoroughly studying these factors can help to better determine an ideal BFRT scheme and better manage sarcopenia and its associated comorbidities. As a well-tolerated and novel form of exercise, BFRT offers more potential in treating sarcopenia and involves deeper insights into the function and regulation of skeletal muscle.

PEAK1 Y635 phosphorylation regulates cell migration through association with Tensin3 and integrins

Integrins mediate cell adhesion by connecting the extracellular matrix to the intracellular cytoskeleton and orchestrate signal transduction in response to chemical and mechanical stimuli by interacting with many cytoplasmic proteins. We used BioID to interrogate the interactomes of β1 and β3 integrins in epithelial cells and identified PEAK1 as an interactor of the RGD-binding integrins α5β1, αVβ3, and αVβ5 in focal adhesions. We demonstrate that the interaction between integrins and PEAK1 occurs indirectly through Tensin3, requiring both the membrane-proximal NPxY motif on the integrin β tail and binding of the SH2 domain of Tensin3 to phosphorylated Tyr-635 on PEAK1. Phosphorylation of Tyr-635 is mediated by Src and regulates cell migration. Additionally, we found that Shc1 localizes in focal adhesions in a PEAK1 phosphorylated Tyr-1188-dependent fashion. Besides binding Shc1, PEAK1 also associates with a protein cluster that mediates late EGFR/Shc1 signaling. We propose a model in which PEAK1 binds Tensin3 and Shc1 to converge integrin and growth factor receptor signal transduction.

Plasma membrane proteoglycans syndecan-2 and syndecan-4 engage with EGFR and RON kinase to sustain carcinoma cell cycle progression

Epidermal growth factor receptor (EGFR) is a causal factor in carcinoma, yet many carcinoma patients are resistant to EGFR inhibitors. Potential insight into this resistance stems from prior work that showed EGFR in normal epithelial cells docks to the extracellular domain of the plasma membrane proteoglycan syndecan-4 (Sdc4) engaged with α3β1 and α6β4 integrins. We now report that this receptor complex is modified by the recruitment of syndecan-2 (Sdc2), the Recepteur d'Origine Nantais (RON) tyrosine kinase, and the cellular signaling mediator Abelson murine leukemia viral oncogene homolog 1 (ABL1) in triple-negative breast carcinoma and head and neck squamous cell carcinoma, where it contributes to EGFR kinase-independent proliferation. Treatment with a peptide mimetic of the EGFR docking site in the extracellular domain of Sdc4 (called SSTNEGFR) disrupts the entire complex and causes a rapid, global arrest of the cell cycle. Normal epithelial cells do not recruit these additional receptors to the adhesion mechanism and are not arrested by SSTNEGFR. Although EGFR docking with Sdc4 in the tumor cells is required, cell cycle progression does not depend on EGFR kinase. Instead, progression depends on RON kinase, activated by its incorporation into the complex. RON activates ABL1, which suppresses p38 mitogen-activated protein kinase and prevents a p38-mediated signal that would otherwise arrest the cell cycle. These findings add to the growing list of receptor tyrosine kinases that support tumorigenesis when activated by their association with syndecans at sites of matrix adhesion and identify new potential targets for cancer therapy.

Review of Label-Free Monitoring of Bacteria: From Challenging Practical Applications to Basic Research Perspectives

Novel biosensors already provide a fast way to detect the adhesion of whole bacteria (or parts of them), biofilm formation, and the effect of antibiotics. Moreover, the detection sensitivities of recent sensor technologies are large enough to investigate molecular-scale biological processes. Usually, these measurements can be performed in real time without using labeling. Despite these excellent capabilities summarized in the present work, the application of novel, label-free sensor technologies in basic biological research is still rare; the literature is dominated by heuristic work, mostly monitoring the presence and amount of a given analyte. The aims of this review are (i) to give an overview of the present status of label-free biosensors in bacteria monitoring, and (ii) to summarize potential novel directions with biological relevancies to initiate future development. Optical, mechanical, and electrical sensing technologies are all discussed with their detailed capabilities in bacteria monitoring. In order to review potential future applications of the outlined techniques in bacteria research, we summarize the most important kinetic processes relevant to the adhesion and survival of bacterial cells. These processes are potential targets of kinetic investigations employing modern label-free technologies in order to reveal new fundamental aspects. Resistance to antibacterials and to other antimicrobial agents, the most important biological mechanisms in bacterial adhesion and strategies to control adhesion, as well as bacteria-mammalian host cell interactions are all discussed with key relevancies to the future development and applications of biosensors.

Applications of the amniotic membrane in tissue engineering and regeneration: the hundred-year challenge

The amniotic membrane (Amnio-M) has various applications in regenerative medicine. It acts as a highly biocompatible natural scaffold and as a source of several types of stem cells and potent growth factors. It also serves as an effective nano-reservoir for drug delivery, thanks to its high entrapment properties. Over the past century, the use of the Amnio-M in the clinic has evolved from a simple sheet for topical applications for skin and corneal repair into more advanced forms, such as micronized dehydrated membrane, amniotic cytokine extract, and solubilized powder injections to regenerate muscles, cartilage, and tendons. This review highlights the development of the Amnio-M over the years and the implication of new and emerging nanotechnology to support expanding its use for tissue engineering and clinical applications.

EGFR-Dependent Extracellular Matrix Protein Interactions Might Light a Candle in Cell Behavior of Non-Small Cell Lung Cancer

Lung cancer remains the leading cause of cancer-related death and is associated with a poor prognosis. Lung cancer is divided into 2 main types: the major in incidence is non-small cell lung cancer (NSCLC) and the minor is small cell lung cancer (SCLC). Although NSCLC progression depends on driver mutations, it is also affected by the extracellular matrix (ECM) interactions that activate their corresponding signaling molecules in concert with integrins and matrix metalloproteinases (MMPs). These signaling molecules include cytoplasmic kinases, small GTPases, adapter proteins, and receptor tyrosine kinases (RTKs), particularly the epidermal growth factor receptor (EGFR). In NSCLC, the interplay between ECM and EGFR regulates ECM stiffness, angiogenesis, survival, adhesion, migration, and metastasis. Furthermore, some tumor-promoting ECM components (e.g., glycoproteins and proteoglycans) enhance activation of EGFR and loss of PTEN. On the other hand, other tumor-suppressing glycoproteins and -proteoglycans can inhibit EGFR activation, suppressing cell invasion and migration. Therefore, deciphering the molecular mechanisms underlying EGFR and ECM interactions might provide a better understanding of disease pathobiology and aid in developing therapeutic strategies. This review critically discusses the crosstalk between EGFR and ECM affecting cell behavior of NSCLC, as well as the involvement of ECM components in developing resistance to EGFR inhibition.

The ECM: To Scaffold, or Not to Scaffold, That Is the Question

The extracellular matrix (ECM) has pleiotropic effects, ranging from cell adhesion to cell survival. In tissue engineering, the use of ECM and ECM-like scaffolds has separated the field into two distinct areas-scaffold-based and scaffold-free. Scaffold-free techniques are used in creating reproducible cell aggregates which have massive potential for high-throughput, reproducible drug screening and disease modeling. Though, the lack of ECM prevents certain cells from surviving and proliferating. Thus, tissue engineers use scaffolds to mimic the native ECM and produce organotypic models which show more reliability in disease modeling. However, scaffold-based techniques come at a trade-off of reproducibility and throughput. To bridge the tissue engineering dichotomy, we posit that finding novel ways to incorporate the ECM in scaffold-free cultures can synergize these two disparate techniques.

Syndecans and Their Synstatins: Targeting an Organizer of Receptor Tyrosine Kinase Signaling at the Cell-Matrix Interface

Receptor tyrosine kinases (RTKs) and integrin matrix receptors have well-established roles in tumor cell proliferation, invasion and survival, often functioning in a coordinated fashion at sites of cell-matrix adhesion. Central to this coordination are syndecans, another class of matrix receptor, that organize RTKs and integrins into functional units, relying on docking motifs in the syndecan extracellular domains to capture and localize RTKs (e.g., EGFR, IGF-1R, VEGFR2, HER2) and integrins (e.g., αvβ3, αvβ5, α4β1, α3β1, α6β4) to sites of adhesion. Peptide mimetics of the docking motifs in the syndecans, called “synstatins”, prevent assembly of these receptor complexes, block their signaling activities and are highly effective against tumor cell invasion and survival and angiogenesis. This review describes our current understanding of these four syndecan-coupled mechanisms and their inhibitory synstatins (SSTN_IGF1R, SSTN_VEGFR2, SSTN_VLA-4, SSTN_EGFR and SSTN_HER2).

Mechanisms underlying unidirectional laminar shear stress-mediated Nrf2 activation in endothelial cells: Amplification of low shear stress signaling by primary cilia

Endothelial cells are sensitive to mechanical stress and respond differently to oscillatory flow versus unidirectional flow. This review highlights the mechanisms by which a wide range of unidirectional laminar shear stress induces activation of the redox sensitive antioxidant transcription factor nuclear factor-E2-related factor 2 (Nrf2) in cultured endothelial cells. We propose that fibroblast growth factor-2 (FGF-2), brain-derived neurotrophic factor (BDNF) and 15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) are potential Nrf2 activators induced by laminar shear stress. Shear stress-dependent secretion of FGF-2 and its receptor-mediated signaling is tightly controlled, requiring neutrophil elastase released by shear stress, αvβ3 integrin and the cell surface glycocalyx. We speculate that primary cilia respond to low laminar shear stress (<10 dyn/cm2), resulting in secretion of insulin-like growth factor 1 (IGF-1), which facilitates αvβ3 integrin-dependent FGF-2 secretion. Shear stress induces generation of heparan-binding epidermal growth factor-like growth factor (HB-EGF), which contributes to FGF-2 secretion and gene expression. Furthermore, HB-EGF signaling modulates FGF-2-mediated NADPH oxidase 1 activation that favors casein kinase 2 (CK2)-mediated phosphorylation/activation of Nrf2 associated with caveolin 1 in caveolae. Higher shear stress (>15 dyn/cm2) induces vesicular exocytosis of BDNF from endothelial cells, and we propose that BDNF via the p75NTR receptor could induce CK2-mediated Nrf2 activation. Unidirectional laminar shear stress upregulates gene expression of FGF-2 and BDNF and generation of 15d-PGJ2, which cooperate in sustaining Nrf2 activation to protect endothelial cells against oxidative damage.

Chronic Wound Healing by Amniotic Membrane: TGF-β and EGF Signaling Modulation in Re-epithelialization

The application of amniotic membrane (AM) on chronic wounds has proven very effective at resetting wound healing, particularly in re-epithelialization. Historically, several aspects of AM effect on wound healing have been evaluated using cell models. In keratinocytes, the presence of AM induces the activation of mitogen-activated protein (MAP) kinase and c-Jun N-terminal kinase (JNK) pathways, together with the high expression of c-Jun, an important transcription factor for the progression of the re-epithelialization tongue. In general, the levels of transforming growth factor (TGF)-β present in a wound are critical for the process of wound healing; they are elevated during the inflammation phase and remain high in some chronic wounds. Interestingly, the presence of AM, through epidermal growth factor (EGF) signaling, produces a fine-tuning of the TGF-β signaling pathway that re-conducts the stalled process of wound healing. However, the complete suppression of TGF-β signaling has proven negative for the AM stimulation of migration, suggesting that a minimal amount of TGF-β signaling is required for proper wound healing. Regarding migration machinery, AM contributes to the dynamics of focal adhesions, producing a high turnover and thus speeding up remodeling. This is clear because proteins, such as Paxillin, are activated upon treatment with AM. On top of this, AM also produces changes in the expression of Paxillin. Although we have made great progress in understanding the effects of AM on chronic wound healing, a long way is still ahead of us to fully comprehend its effects.

Integrins Within the Tumor Microenvironment: Biological Functions, Importance for Molecular Targeting, and Cancer Therapeutics Innovation

Many cellular functions important for solid tumor initiation and progression are mediated by members of the integrin family, a diverse family of cell attachment receptors. With recent studies emphasizing the role of the tumor microenvironment (TME) in tumor initiation and progression, it is not surprising that considerable attention is being paid to integrins. Several integrin antagonists are under clinical trials, with many demonstrating promising activity in patients with different cancers. A deeper knowledge of the functions of integrins within the TME is still required and might lead to better inhibitors being discovered. Integrin expression is commonly dysregulated in many tumors with integrins playing key roles in signaling as well as promotion of tumor cell invasion and migration. Integrins also play a major role in adhesion of circulating tumor cells to new sites and the resulting formation of secondary tumors. Furthermore, integrins have demonstrated the ability to promoting stem cell-like properties in tumor cells as well as drug resistance. Anti-integrin therapies rely heavily on the doses or concentrations used as these determine whether the drugs act as antagonists or as integrin agonists. This expert review offers the latest synthesis in terms of the current knowledge of integrins functions within the TME and as potential molecular targets for cancer therapeutics innovation.

Biomechanical and biological responses of periodontium in orthodontic tooth movement: up-date in a new decade

Nowadays, orthodontic treatment has become increasingly popular. However, the biological mechanisms of orthodontic tooth movement (OTM) have not been fully elucidated. We were aiming to summarize the evidences regarding the mechanisms of OTM. Firstly, we introduced the research models as a basis for further discussion of mechanisms. Secondly, we proposed a new hypothesis regarding the primary roles of periodontal ligament cells (PDLCs) and osteocytes involved in OTM mechanisms and summarized the biomechanical and biological responses of the periodontium in OTM through four steps, basically in OTM temporal sequences, as follows: (1) Extracellular mechanobiology of periodontium: biological, mechanical, and material changes of acellular components in periodontium under orthodontic forces were introduced. (2) Cell strain: the sensing, transduction, and regulation of mechanical stimuli in PDLCs and osteocytes. (3) Cell activation and differentiation: the activation and differentiation mechanisms of osteoblast and osteoclast, the force-induced sterile inflammation, and the communication networks consisting of sensors and effectors. (4) Tissue remodeling: the remodeling of bone and periodontal ligament (PDL) in the compression side and tension side responding to mechanical stimuli and root resorption. Lastly, we talked about the clinical implications of the updated OTM mechanisms, regarding optimal orthodontic force (OOF), acceleration of OTM, and prevention of root resorption.

Transient Receptor Potential C 1/4/5 Is a Determinant of MTI-101 Induced Calcium Influx and Cell Death in Multiple Myeloma

Multiple myeloma (MM) is a currently incurable hematologic cancer. Patients that initially respond to therapeutic intervention eventually relapse with drug resistant disease. Thus, novel treatment strategies are critically needed to improve patient outcomes. Our group has developed a novel cyclic peptide referred to as MTI-101 for the treatment of MM. We previously reported that acquired resistance to HYD-1, the linear form of MTI-101, correlated with the repression of genes involved in store operated Ca²⁺ entry (SOCE): PLCβ, SERCA, ITPR3, and TRPC1 expression. In this study, we sought to determine the role of TRPC1 heteromers in mediating MTI-101 induced cationic flux. Our data indicate that, consistent with the activation of TRPC heteromers, MTI-101 treatment induced Ca²⁺ and Na⁺ influx. However, replacing extracellular Na⁺ with NMDG did not reduce MTI-101-induced cell death. In contrast, decreasing extracellular Ca²⁺ reduced both MTI-101-induced Ca²⁺ influx as well as cell death. The causative role of TRPC heteromers was established by suppressing STIM1, TRPC1, TRPC4, or TRPC5 function both pharmacologically and by siRNA, resulting in a reduction in MTI-101-induced Ca²⁺ influx. Mechanistically, MTI-101 treatment induces trafficking of TRPC1 to the membrane and co-immunoprecipitation studies indicate that MTI-101 treatment induces a TRPC1-STIM1 complex. Moreover, treatment with calpeptin inhibited MTI-101-induced Ca²⁺ influx and cell death, indicating a role of calpain in the mechanism of MTI-101-induced cytotoxicity. Finally, components of the SOCE pathway were found to be poor prognostic indicators among MM patients, suggesting that this pathway is attractive for the treatment of MM.

Fibrinogen in equine pregnancy as a mediator of cell adhesion, an epigenetic and functional investigation

Preimplantation equine embryos synthesize and secrete fibrinogen, which is a peculiar finding as fibrinogen synthesis almost exclusively occurs in the liver. This study investigated the hypothesis that conceptus-derived fibrinogen mediates cell adhesion during fixation. On day 21 of pregnancy, five integrin subunits, including ITGA5, ITGB1, ITGAV, and ITGB1, displayed significantly higher transcript abundance than on day 16 of pregnancy. Endometrial epithelial cells adhered to fibrinogen in an integrin-dependent manner in an in vitro cell adhesion assay. Bilaminar trophoblast and allantochorion expressed fibrinogen transcript, indicating that fibrinogen expression persists past fixation. Preimplantation-phase endometrium, conceptuses, and microcotyledonary tissue expressed components of the clotting cascade regulating fibrin homeostasis, leaving open the possibility that fibrinogen is converted to fibrin. Fibrinogen is likely to have functions beyond mediating cell adhesion, such trapping growth factors and triggering signaling cascades, and has remarkable parallels to the expression of fibrinogen by some tumors. The deposition of fibrinogen within tumor stroma is characteristic of breast carcinoma, and tumor-derived fibrinogen has been implicated in the metastatic potential of circulating tumor cells. DNA methylation of the fibrinogen locus in equine conceptuses was examined in comparison to liver and endometrium, and across the full gene cluster, was significantly higher for endometrium than liver and conceptus. DNA methylation of regulatory regions did not differ between liver and conceptus, and was significantly lower than in endometrium. These results, therefore, support the hypothesis of DNA methylation being a regulator of fibrinogen expression in the conceptus.

Forcing a growth factor response - tissue-stiffness modulation of integrin signaling and crosstalk with growth factor receptors

Research throughout the 90s established that integrin crosstalk with growth factor receptors stimulates robust growth factor signaling. These insights were derived chiefly from comparing adherent versus suspension cell cultures. Considering the new understanding that mechanosensory inputs tune adhesion signaling, it is now timely to revisit this crosstalk in different mechanical environments. Here, we present a brief historical perspective on integrin signaling against the backdrop of the mechanically diverse extracellular microenvironment, then review the evidence supporting the mechanical regulation of integrin crosstalk with growth factor signaling. We discuss early studies revealing distinct signaling consequences for integrin occupancy (binding to matrix) and aggregation (binding to immobile ligand). We consider how the mechanical environments encountered in vivo intersect with this diverse signaling, focusing on receptor endocytosis. We discuss the implications of mechanically tuned integrin signaling for growth factor signaling, using the epidermal growth factor receptor (EGFR) as an illustrative example. We discuss how the use of rigid tissue culture plastic for cancer drug screening may select agents that lack efficacy in the soft in vivo tissue environment. Tuning of integrin signaling via external mechanical forces in vivo and subsequent effects on growth factor signaling thus has implications for normal cellular physiology and anti-cancer therapies.

Thermosensitive "Smart" Surfaces for Biorecognition Based Cell Adhesion and Controlled Detachment

The biorecognition-based control of attachment/detachment of MCF-7 cancer cells from polymer-coated surfaces is demonstrated. A glass surface is coated with a thermoresponsive statistical copolymer of poly(N-isopropylacrylamide-co-acrylamide) [p(NIPAm-co-Am)], which is end-capped with the Gly-Arg-Gly-Asp-Ser (GRGDS) peptide, and the hydrophilic polymer poly(ethylene glycol) (PEG). Below the lower critical solution temperature (LCST) of p(NIPAm-co-Am) (38 °C), the copolymers are in the extended conformation, allowing for accessibility of the GRGDS peptides to membrane-associated integrins thus enabling cell attachment. Above the LCST, the p(NIPAm-co-Am) polymers collapse into globular conformations, resulting in the shielding of the GRGDS peptides into the PEG brush with consequent inaccessibility to cell-surface integrins, causing cell detachment. The surface coating is carried out by a multi-step procedure that included: glass surface amination with 3-aminopropyltriethoxysilane; reaction of mPEG_5kDa -N-hydroxysuccinimide (NHS) and p(NIPam-co-Am)_15.1kDa -bis-NHS with the surface aminopropyl groups and conjugation of GRGDS to the carboxylic acid termini of p(NIPam-co-Am)_15.1kDa -COOH. A range of spectrophotometric, surface, and microscopy assays confirmed the identity of the polymer-coated substrates. Competition studies prove that MCF-7 cancer cells are attached via peptide recognition at the coated surfaces according to the mPEG_5kDa /p(NIPam-co-Am)_15.1kDa -GRGDS molar ratio. These data suggest the system can be exploited to modulate cell integrin/GRGDS binding for controlled cell capture and release.

Building an Artificial Cardiac Microenvironment: A Focus on the Extracellular Matrix

The increased knowledge in cell signals and stem cell differentiation, together with the development of new technologies, such as 3D bioprinting, has made the generation of artificial tissues more feasible for in vitro studies and in vivo applications. In the human body, cell fate, function, and survival are determined by the microenvironment, a rich and complex network composed of extracellular matrix (ECM), different cell types, and soluble factors. They all interconnect and communicate, receiving and sending signals, modulating and responding to cues. In the cardiovascular field, the culture of stem cells in vitro and their differentiation into cardiac phenotypes is well established, although differentiated cardiomyocytes often lack the functional maturation and structural organization typical of the adult myocardium. The recreation of an artificial microenvironment as similar as possible to the native tissue, though, has been shown to partly overcome these limitations, and can be obtained through the proper combination of ECM molecules, different cell types, bioavailability of growth factors (GFs), as well as appropriate mechanical and geometrical stimuli. This review will focus on the role of the ECM in the regulation of cardiac differentiation, will provide new insights on the role of supporting cells in the generation of 3D artificial tissues, and will also present a selection of the latest approaches to recreate a cardiac microenvironment in vitro through 3D bioprinting approaches.

Mechanisms in blood-brain barrier opening and metabolism-challenged cerebrovascular ischemia with emphasis on ischemic stroke

Stroke is the leading cause of disability among adults as well as the 2nd leading cause of death globally. Ischemic stroke accounts for about 85% of strokes, and currently, tissue plasminogen activator (tPA), whose therapeutic window is limited to up to 4.5 h for the appropriate population, is the only FDA approved drug in practice and medicine. After a stroke, a cascade of pathophysiological events results in the opening of the blood-brain barrier (BBB) through which further complications, disabilities, and mortality are likely to threaten the patient's health. Strikingly, tPA administration in eligible patients might cause hemorrhagic transformation and sustained damage to BBB integrity. One must, therefore, delineate upon stroke onset which cellular and molecular factors mediate BBB permeability as well as what key roles BBB rupture plays in the pathophysiology of stroke. In this review article, given our past findings of mechanisms underlying BBB opening in stroke animal models, we elucidate cellular, subcellular, and molecular factors involved in BBB permeability after ischemic stroke. The contribution of each factor to stroke severity and outcome is further discussed. Determinant factors in BBB permeability and stroke include mitochondria, miRNAs, matrix metalloproteinases (MMPs), immune cells, cytokines, chemokines, and adhesion proteins. Once these factors are interrogated and their roles in the pathophysiology of stroke are determined, novel targets for drug discovery and development can be uncovered in addition to novel therapeutic avenues for human stroke management.

Role of αVβ3 in Prostate Cancer: Metastasis Initiator and Important Therapeutic Target

In prostate cancer, distant organ metastasis is the leading cause of patient death. Although the mechanism of malignant tumor metastasis is unclear, studies have confirmed that integrin αVβ3 plays an important role in this process. In prostate cancer, αVβ3 mediates adhesion, invasion, immune escape and neovascularization through interactions with different ligands. Among these ligands and in addition to proteins that are directly related to tumor invasion, other proteins that contain the RGD structure could also bind to αVβ3 and cause a number of biological effects. In this article, we summarized the ligand and downstream proteins related to αVβ3-mediated prostate cancer metastasis as well as some diagnostic and therapeutic measures targeting αVβ3.

Strategic Trastuzumab Mediated Crosslinking Driving Concomitant HER2 and HER3 Endocytosis and Degradation in Breast Cancer

Efficacious anticancer therapies for targeting plasma membrane receptors with antibody based therapeutics are often contingent on sufficient endocytic delivery of receptor and conjugate to lysosomes. This results in downregulation of receptor activity and, in the case of antibody-drug conjugates (ADCs), intracellular release of a drug payload. The oncogenic receptor HER2 is a priority therapeutic target in breast cancer. Known as an "endocytosis resistant" receptor, HER2 thwarts the receptor downregulating efficiency of the frontline treatment trastuzumab and reduces the potential of trastuzumab-based therapies such as trastuzumab-emtansine. We previously demonstrated that strategically inducing trastuzumab and HER2 crosslinking in breast cancer cells promoted endocytosis and lysosomal delivery of the HER2-trastuzumab complex, stimulating downregulation of the receptor. Here we reveal that HER3, but not EGFR, is also concomitantly downregulated with HER2 after crosslinking. This is accompanied by strong activation of MEK/ERK pathway that we show does not directly contribute to HER2/trastuzumab endocytosis. We show that crosslinking induced trastuzumab endocytosis occurs via clathrin-dependent and independent pathways and is an actin-dependent process. Detailed ultrastructural studies of the plasma membrane highlight crosslinking-specific remodelling of microvilli and induction of extensive ruffling. Investigations in a cell model of acquired trastuzumab resistance demonstrate, for the first time, that they are refractory to crosslinking induced HER2 endocytosis and downregulation. This implicates further arrest of HER2 internalisation in developing trastuzumab resistance. Overall our findings highlight the potential of receptor crosslinking as a therapeutic strategy for cancer while exposing the ability of cancer cells to develop resistance via endocytic mechanisms.

Design Considerations for Hydrogel Wound Dressings: Strategic and Molecular Advances

Wound dressings are traditionally used to protect a wound and to facilitate healing. Currently, their function is expanding. There is an urgent need for new smart products that not only act as a protective barrier but also actively support the wound healing process. Hydrogel dressings are an example of such innovative products and typically facilitate wound healing by providing a hospitable and moist environment in which cells can thrive, while the wound can still breathe and exudate can be drained. These dressings also tend to be less painful or have a soothing effect and allow for additional drug delivery. In this review, various strategic and molecular design considerations are discussed that are relevant for developing a hydrogel into a wound dressing product. These considerations vary from material choice to ease of use and determine the dressing's final properties, application potential, and benefits for the patient. The focus of this review lies on identifying and explaining key aspects of hydrogel wound dressings and their relevance in the different phases of wound repair. Molecular targets of wound healing are discussed that are relevant when tailoring hydrogels toward specific wound healing scenarios. In addition, the potential of hydrogels is reviewed as medicine advances from a repair-based wound healing approach toward a regenerative-based one. Hydrogels can play a key role in the transition toward personal wound care and facilitating regenerative medicine strategies by acting as a scaffold for (stem) cells and carrier/source of bioactive molecules and/or drugs. Impact statement Improved wound healing will lead to a better quality of life around the globe. It can be expected that this coincides with a reduction in health care spending, as the duration of treatment decreases. To achieve this, new and modern wound care products are desired that both facilitate healing and improve comfort and outcome for the patient. It is proposed that hydrogel wound dressings can play a pivotal role in improving wound care, and to that end, this review aims to summarize the various design considerations that can be made to optimize hydrogels for the purpose of a wound dressing.

Modulation of bone turnover aberration: A target for management of primary osteoporosis in experimental rat model

Osteoporosis is a skeletal degenerative disease characterised by abnormal bone turnover with scant bone formation and overabundant bone resorption. The present approach was intended to address the potency of nanohydroxyapatite (nHA), chitosan/hydroxyapatite nanocomposites (nCh/HA) and silver/hydroxyapatite nanoparticles (nAg/HA) to modulate bone turnover deviation in primary osteoporosis induced in the experimental model. Characterisation techniques such as TEM, zeta-potential, FT-IR and XRD were used to assess the morphology, the physical as well as the chemical features of the prepared nanostructures. The in vivo experiment was conducted on forty-eight adult female rats, randomised into 6 groups (8 rats/group), (1) gonad-intact, (2) osteoporotic group, (3) osteoporotic + nHA, (4) osteoporotic + nCh/HA, (5) osteoporotic + nAg/HA and (6) osteoporotic + alendronate (ALN). After three months of treatment, serum sclerostin (SOST), bone alkaline phosphatase (BALP) and bone sialoprotein (BSP) levels were quantified using ELISA. Femur bone receptor activator of nuclear factor-kappa B (NF-κB) ligand (RANKL) and cathepsin K (CtsK) mRNA levels were evaluated by quantitative RT-PCR. Moreover, alizarin red S staining was applied to determine the mineralisation intensity of femur bone. Findings in the present study indicated that treatment with nHA, nCh/HA or nAg/HA leads to significant repression of serum SOST, BALP and BSP levels parallel to a significant down-regulation of RANKL and CtsK gene expression levels. On the other side, significant enhancement in the calcification intensity of femur bone has been noticed. The outcomes of this experimental setting ascertained the potentiality of nHA, nCh/HA and nAg/HA as promising nanomaterials in attenuating the excessive bone turnover in the primary osteoporotic rat model. The mechanisms behind the efficacy of the investigated nanostructures involved the obstacle of serum and tissue indices of bone resorption besides the strengthening of bone mineralisation.

Extracellular matrix-cell interactions: Focus on therapeutic applications

Extracellular matrix (ECM) macromolecules together with a multitude of different molecules residing in the extracellular space play a vital role in the regulation of cellular phenotype and behavior. This is achieved via constant reciprocal interactions between the molecules of the ECM and the cells. The ECM-cell interactions are mediated via cell surface receptors either directly or indirectly with co-operative molecules. The ECM is also under perpetual remodeling process influencing cell-signaling pathways on its part. The fragmentation of ECM macromolecules provides even further complexity for the intricate environment of the cells. However, as long as the interactions between the ECM and the cells are in balance, the health of the body is retained. Alternatively, any dysregulation in these interactions can lead to pathological processes and finally to various diseases. Thus, therapeutic applications that are based on retaining normal ECM-cell interactions are highly rationale. Moreover, in the light of the current knowledge, also concurrent multi-targeting of the complex ECM-cell interactions is required for potent pharmacotherapies to be developed in the future.

The postmitotic midbody: Regulating polarity, stemness, and proliferation

Peterman and Prekeris review abscission and discuss the diverse roles for the postmitotic midbody in regulating polarity, tumorigenesis, and stemness.

Abscission, the final stage of cell division, requires well-orchestrated changes in endocytic trafficking, microtubule severing, actin clearance, and the physical sealing of the daughter cell membranes. These processes are highly regulated, and any missteps in localized membrane and cytoskeleton dynamics often lead to a delay or a failure in cell division. The midbody, a microtubule-rich structure that forms during cytokinesis, is a key regulator of abscission and appears to function as a signaling platform coordinating cytoskeleton and endosomal dynamics during the terminal stages of cell division. It was long thought that immediately following abscission and the conclusion of cell division, the midbody is either released or rapidly degraded by one of the daughter cells. Recently, the midbody has gained prominence for exerting postmitotic functions. In this review, we detail the role of the midbody in orchestrating abscission, as well as discuss the relatively new field of postabscission midbody biology, particularly focusing on how it may act to regulate cell polarity and its potential to regulate cell tumorigenicity or stemness.

Dynamic Assembly of Human Salivary Stem/Progenitor Microstructures Requires Coordinated α1β1 Integrin-Mediated Motility

A tissue engineering approach can provide replacement salivary gland structures to patients with hyposalivation disorders and xerostomia. Salivary human stem/progenitor cells (hS/PCs) were isolated from healthy regions of parotid glands of head and neck surgery patients, expanded, then encapsulated in biocompatible hyaluronate (HA)-based hydrogels. These bioactive hydrogels provide a surrogate territorial matrix suitable for the dynamic assembly, growth and reorganization of salivary gland components. This study examined the dynamics of salivary microstructure formation, growth, and reorganization using time-lapse imaging over 15 h. Immunofluorescence detection monitored production of individual basement membrane components forming around developing microstructures, and Ki67 assessed proliferation. Dynamic movements in hydrogels were quantified by measuring angular velocity (ω) of rotating salivary microstructures and changes in basement membrane architecture during microstructure growth. Integrin involvement in the dynamic reassembly was assessed using knockdown and inhibitor approaches. Single hS/PCs expanded over 5 days into spherical microstructures typically containing 3–10 cells. In larger macrostructures, proliferation occurred near the peripheral basement membrane that underwent growth-associated cycles of thinning and collapse. De novo secretion of laminin/collagen IV from reorganizing hS/PCs preceded that of perlecan/HSPG2. Microstructures routinely expressed β₁ integrin-containing complexes at basement membrane-associated regions and exhibited spontaneous and coordinated rotation during basement membrane maturation. β₁ integrin siRNA knockdown at the single-cell state prevented hS/PC microstructure growth. After microstructure formation, β₁ integrin knockdown reduced rotation and mean ω by 84%. Blockade of the α₁ integrin subunit (CD49a) that associates with β₁ reduced mean ω by 66%. Studies presented here show that initial hS/PC structure growth and basement membrane maturation depends on α₁β₁-integrin mediated signaling. Coordinated cellular motility during neotissue reorganization reminiscent of salivary gland acini was critically dependent both on hS/PC-secretion of laminin,collagen type-IV, and perlecan/HSPG2 and the force-driven interactions of α₁β₁-integrin activation. We conclude that α₁β₁-integrin plays a critical role in establishing human salivary gland coordinated structure and function, and that its activation in tissue engineered systems is essential to tissue assembly.

The Role of Extracellular Matrix Expression, ERK1/2 Signaling and Cell Cohesiveness for Cartilage Yield from iPSCs

Current therapies involving chondrocytes or mesenchymal stromal cells (MSCs) remain inefficient in restoring cartilage properties upon injury. The induced pluripotent stem-cell (iPSC)-derived mesenchymal progenitor cells (iMPCs) have been put forward as a promising alternative cell source due to their high proliferation and differentiation potential. However, the observed cell loss during in vitro chondrogenesis is currently a bottleneck in establishing articular chondrocyte generation from iPSCs. In a search for candidate mechanisms underlying the low iPSC-derived cartilage tissue yield, global transcriptomes were compared between iMPCs and MSCs and the cell properties were analyzed via a condensation assay. The iMPCs had a more juvenile mesenchymal gene signature than MSCs with less myofibroblast-like characteristics, including significantly lower ECM- and integrin-ligand-related as well as lower α-smooth-muscle-actin expression. This correlated with less substrate and more cell-cell adhesion, impaired aggregate formation and consequently inferior cohesive tissue properties of the iMPC-pellets. Along lower expression of pro-survival ECM molecules, like decorin, collagen VI, lumican and laminin, the iMPC populations had significantly less active ERK1/2 compared to MSCs. Overall, this study proposes that this ECM and integrin-ligand shortage, together with insufficient pro-survival ERK1/2-activity, explains the loss of a non-aggregating iMPC sub-fraction during pellet formation and reduced survival of cells in early pellets. Enhancing ECM production and related signaling in iMPCs may be a promising new means to enrich the instructive microenvironment with pro-survival cues allowing to improve the final cartilage tissue yield from iPSCs.

The post-abscission midbody is an intracellular signaling organelle that regulates cell proliferation

Once thought to be a remnant of cell division, the midbody (MB) has recently been shown to have roles beyond its primary function of orchestrating abscission. Despite the emerging roles of post-abscission MBs, how MBs accumulate in the cytoplasm and signal to regulate cellular functions remains unknown. Here, we show that extracellular post-abscission MBs can be internalized by interphase cells, where they reside in the cytoplasm as a membrane-bound signaling structure that we have named the MBsome. We demonstrate that MBsomes stimulate cell proliferation and that MBsome formation is a phagocytosis-like process that depends on a phosphatidylserine/integrin complex, driven by actin-rich membrane protrusions. Finally, we show that MBsomes rely on dynamic actin coats to slow lysosomal degradation and propagate their signaling function. In summary, MBsomes may sometimes serve as intracellular organelles that signal via integrin and EGFR-dependent pathways to promote cell proliferation and anchorage-independent growth and survival.

Role of Integrins in Resistance to Therapies Targeting Growth Factor Receptors in Cancer

Integrins contribute to cancer progression and aggressiveness by activating intracellular signal transduction pathways and transducing mechanical tension forces. Remarkably, these adhesion receptors share common signaling networks with receptor tyrosine kinases (RTKs) and support their oncogenic activity, thereby promoting cancer cell proliferation, survival and invasion. During the last decade, preclinical studies have revealed that integrins play an important role in resistance to therapies targeting RTKs and their downstream pathways. A remarkable feature of integrins is their wide-ranging interconnection with RTKs, which helps cancer cells to adapt and better survive therapeutic treatments. In this context, we should consider not only the integrins expressed in cancer cells but also those expressed in stromal cells, since these can mechanically increase the rigidity of the tumor microenvironment and confer resistance to treatment. This review presents some of these mechanisms and outlines new treatment options for improving the efficacy of therapies targeting RTK signaling.

D2A sequence of the urokinase receptor induces cell growth through αvβ3 integrin and EGFR

The urokinase receptor (uPAR) stimulates cell proliferation by forming a macromolecular complex with αvβ3 integrin and the epidermal growth factor receptor (EGFR, ErbB1 or HER1) that we name the uPAR proliferasome. uPAR transactivates EGFR, which in turn mediates uPAR-initiated mitogenic signal to the cell. EGFR activation and EGFR-dependent cell growth are blocked in the absence of uPAR expression or when uPAR activity is inhibited by antibodies against either uPAR or EGFR. The mitogenic sequence of uPAR corresponds to the D2A motif present in domain 2. NMR analysis revealed that D2A synthetic peptide has a particular three-dimensional structure, which is atypical for short peptides. D2A peptide is as effective as EGF in promoting EGFR phosphorylation and cell proliferation that were inhibited by AG1478, a specific inhibitor of the tyrosine kinase activity of EGFR. Both D2A and EGF failed to induce proliferation of NR6-EGFR-K721A cells expressing a kinase-defective mutant of EGFR. Moreover, D2A peptide and EGF phosphorylate ERK demonstrating the involvement of the MAP kinase signalling pathway. Altogether, this study reveals the importance of sequence D2A of uPAR, and the interdependence of uPAR and EGFR.

Co-Transplantation of Adipose Tissue-Derived Stromal Cells and Olfactory Ensheathing Cells for Spinal Cord Injury Repair

Patients suffering from spinal cord injury (SCI) still have a dismal prognosis. Despite all the efforts developed in this area, currently there are no effective treatments. Therefore, cell therapies have been proposed as a viable alternative to the current treatments used. Adipose tissue-derived stromal cells (ASCs) and olfactory ensheathing cells (OECs) have been used with promising results in different models of SCI, namely due to the regenerative properties of the secretome of the first, and the guidance capability of the second. Using an in vitro model of axonal growth, the dorsal root ganglia explants, we demonstrated that OECs induce neurite outgrowth mainly through cell-cell interactions, while ASCs' effects are strongly mediated by the release of paracrine factors. A proteomic analysis of ASCs' secretome revealed the presence of proteins involved in VEGF, PI3K, and Cadherin signaling pathways, which may be responsible for the effects observed. Then, the cotransplantation of ASCs and OECs showed to improve motor deficits of SCI-rats. Particular parameters of movement such as stepping, coordination, and toe clearance were improved in rats that received the transplant of cells, in comparison to nontreated rats. A histological analysis of the spinal cord tissues revealed that transplantation of ASCs and OECs had a major effect on the reduction of inflammatory cells close the lesion site. A slight reduction of astrogliosis was also evident. Overall, the results obtained with the present work indicate that the cotransplantation of ASCs and OECs brings important functional benefits to the injured spinal cord. Stem Cells 2018;36:696-708.

Galectin-8 induces partial epithelial-mesenchymal transition with invasive tumorigenic capabilities involving a FAK/EGFR/proteasome pathway in Madin-Darby canine kidney cells

Epithelial cells can acquire invasive and tumorigenic capabilities through epithelial–mesenchymal-transition (EMT). The glycan-binding protein galectin-8 (Gal-8) activates selective β1-integrins involved in EMT and is overexpressed by certain carcinomas. Here we show that Gal-8 overexpression or exogenous addition promotes proliferation, migration, and invasion in nontumoral Madin–Darby canine kidney (MDCK) cells, involving focal-adhesion kinase (FAK)-mediated transactivation of the epidermal growth factor receptor (EGFR), likely triggered by α5β1integrin binding. Under subconfluent conditions, Gal-8–overexpressing MDCK cells (MDCK-Gal-8^H) display hallmarks of EMT, including decreased E-cadherin and up-regulated expression of vimentin, fibronectin, and Snail, as well as increased β-catenin activity. Changes related to migration/invasion included higher expression of α5β1 integrin, extracellular matrix-degrading MMP13 and urokinase plasminogen activator/urokinase plasminogen activator receptor (uPA/uPAR) protease systems. Gal-8–stimulated FAK/EGFR pathway leads to proteasome overactivity characteristic of cancer cells. Yet MDCK-Gal-8^H cells still develop apical/basolateral polarity reverting EMT markers and proteasome activity under confluence. This is due to the opposite segregation of Gal-8 secretion (apical) and β1-integrins distribution (basolateral). Strikingly, MDCK-Gal-8^H cells acquired tumorigenic potential, as reflected in anchorage-independent growth in soft agar and tumor generation in immunodeficient NSG mice. Therefore, Gal-8 can promote oncogenic-like transformation of epithelial cells through partial and reversible EMT, accompanied by higher proliferation, migration/invasion, and tumorigenic properties.

The fibrotic tumor stroma

Intratumoral fibrosis results from the deposition of a cross-linked collagen matrix by cancer-associated fibroblasts (CAFs). This type of fibrosis has been shown to exert mechanical forces and create a biochemical milieu that, together, shape intratumoral immunity and influence tumor cell metastatic behavior. In this Review, we present recent evidence that CAFs and tumor cells are regulated by provisional matrix molecules, that metastasis results from a change in the type of stromal collagen cross-link, and that fibrosis and inflammation perpetuate each other through proteolytic and chemotactic mediators released into the tumor stroma. We also discuss aspects of the emerging biology that have potential therapeutic value.

Molecular Regulation of Sprouting Angiogenesis

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

Endothelium-derived fibronectin regulates neonatal vascular morphogenesis in an autocrine fashion

Fibronectin containing alternatively spliced EIIIA and EIIIB domains is largely absent from mature quiescent vessels in adults, but is highly expressed around blood vessels during developmental and pathological angiogenesis. The precise functions of fibronectin and its splice variants during developmental angiogenesis however remain unclear due to the presence of cardiac, somitic, mesodermal and neural defects in existing global fibronectin KO mouse models. Using a rare family of surviving EIIIA EIIIB double KO mice, as well as inducible endothelial-specific fibronectin-deficient mutant mice, we show that vascular development in the neonatal retina is regulated in an autocrine manner by endothelium-derived fibronectin, and requires both EIIIA and EIIIB domains and the RGD-binding α5 and αv integrins for its function. Exogenous sources of fibronectin do not fully substitute for the autocrine function of endothelial fibronectin, demonstrating that fibronectins from different sources contribute differentially to specific aspects of angiogenesis.

Laminin-Coated Poly(Methyl Methacrylate) (PMMA) Nanofiber Scaffold Facilitates the Enrichment of Skeletal Muscle Myoblast Population

Myoblasts, the contractile cells of skeletal muscle, have been invaluable for fundamental studies of muscle development and clinical applications for muscle loss. A major limitation to the myoblast-based therapeutic approach is contamination with non-contractile fibroblasts, which overgrow during cell expansion. To overcome these limitations, this study was carried out to establish a 3D culture environment using nanofiber scaffolds to enrich the myoblast population during construct formation. Poly(methyl methacrylate) (PMMA) nanofiber (PM) scaffolds were fabricated using electrospinning techniques and coated with extracellular matrix (ECM) proteins, such as collagen or laminin, in the presence or absence of genipin. A mixed population of myoblasts and fibroblasts was isolated from human skeletal muscle tissues and cultured on plain surfaces, as well as coated and non-coated PM scaffolds. PMMA can produce smooth fibers with an average diameter of 360 ± 50 nm. Adsorption of collagen and laminin on PM scaffolds is significantly enhanced in the presence of genipin, which introduces roughness to the nanofiber surface without affecting fiber diameter and mechanical properties. It was also demonstrated that laminin-coated PM scaffolds significantly enhance myoblast proliferation (0.0081 ± 0.0007 h-1) and migration (0.26 ± 0.04 μm/min), while collagen-coated PM scaffolds favors fibroblasts proliferation (0.0097 ± 0.0009 h-1) and migration (0.23 ± 0.03 μm/min). Consequently, the myoblast population was enriched on laminin-coated PM scaffolds throughout the culture process. Therefore, laminin coating of nanofiber scaffolds could be a potential scaffold for the development of a tissue-engineered muscle substitute.