ECM remodeling regulates angiogenesis: endothelial integrins look for new ligands

Acetyl-NPKY of integrin-β1 binds KINDLIN2 to control endothelial cell proliferation and junctional integrity

Integrin-dependent crosstalk between cell-matrix adhesions and cell-cell junctions is critical for controlling endothelial permeability and proliferation in cancer and inflammatory diseases but remains poorly understood. Here, we investigated how acetylation of the distal NPKY-motif of Integrin-β1 influences endothelial cell physiology and barrier function. Expression of an acetylation-mimetic β1-K794Q-GFP mutant led to the accumulation of immature cell-matrix adhesions accompanied by a transcriptomic reprograming of endothelial cells, involving genes associated with cell adhesion, proliferation, polarity, and barrier function. β1-K794Q-GFP induced constitutive MAPK signaling, junctional impairment, proliferation, and reduced contact inhibition at confluence. Structural analysis of Integrin-β1 interaction with KINDLIN2, biochemical pulldown assay, and binding energy determination by using molecular dynamics simulation showed that acetylation of K794 and the K794Q-mutant increased KINDLIN2 binding affinity to the Integrin-β1. Thus, enhanced recruitment of KINDLIN2 to Lysine-acetylated Integrin-β1 and resulting modulation of barrier function, offers new therapeutic possibilities for controlling vascular permeability and disease conditions.

Flow-induced reprogramming of endothelial cells in atherosclerosis

Atherosclerotic diseases such as myocardial infarction, ischaemic stroke and peripheral artery disease continue to be leading causes of death worldwide despite the success of treatments with cholesterol-lowering drugs and drug-eluting stents, raising the need to identify additional therapeutic targets. Interestingly, atherosclerosis preferentially develops in curved and branching arterial regions, where endothelial cells are exposed to disturbed blood flow with characteristic low-magnitude oscillatory shear stress. By contrast, straight arterial regions exposed to stable flow, which is associated with high-magnitude, unidirectional shear stress, are relatively well protected from the disease through shear-dependent, atheroprotective endothelial cell responses. Flow potently regulates structural, functional, transcriptomic, epigenomic and metabolic changes in endothelial cells through mechanosensors and mechanosignal transduction pathways. A study using single-cell RNA sequencing and chromatin accessibility analysis in a mouse model of flow-induced atherosclerosis demonstrated that disturbed flow reprogrammes arterial endothelial cells in situ from healthy phenotypes to diseased ones characterized by endothelial inflammation, endothelial-to-mesenchymal transition, endothelial-to-immune cell-like transition and metabolic changes. In this Review, we discuss this emerging concept of disturbed-flow-induced reprogramming of endothelial cells (FIRE) as a potential pro-atherogenic mechanism. Defining the flow-induced mechanisms through which endothelial cells are reprogrammed to promote atherosclerosis is a crucial area of research that could lead to the identification of novel therapeutic targets to combat the high prevalence of atherosclerotic disease.

The regulation and functions of the matricellular CCN proteins induced by shear stress

Shear stress is a frictional drag generated by the flow of fluid, such as blood or interstitial fluid, and plays a critical role in regulating cellular gene expression and functional phenotype. The matricellular CCN family proteins are dynamically regulated by shear stress of different flow patterns, and their expression significantly alters the microenvironment of cells. Secreted CCN proteins mainly bind to several cell surface integrin receptors to mediate their diverse functions in regulating cell survival, function, and behavior. Gene-knockout studies indicate major functions of CCN proteins in the cardiovascular and skeletal systems, the two primary systems in which CCN expressions are regulated by shear stress. In the cardiovascular system, the endothelium is directly exposed to vascular shear stress. Unidirectional laminar blood flow generates laminar shear stress, which promotes a mature endothelial phenotype and upregulates anti-inflammatory CCN3 expression. In contrast, disturbed flow generates oscillatory shear stress, which induces endothelial dysfunction through the induction of CCN1 and CCN2. Shear-induced CCN1 binds to integrin α6β1 and promotes superoxide production, NF-κB activation, and inflammatory gene expression in endothelial cells. Although the interaction between shear stress and CCN4-6 is not clear, CCN 4 exhibits a proinflammatory property and CCN5 inhibits vascular cell growth and migration. The crucial roles of CCN proteins in cardiovascular development, homeostasis, and disease are evident but not fully understood. In the skeletal system, mechanical loading on bone generates shear stress from interstitial fluid in the lacuna-canalicular system and promotes osteoblast differentiation and bone formation. CCN1 and CCN2 are induced and potentially mediate fluid shear stress mechanosensing in osteocytes. However, the exact roles of interstitial shear stress-induced CCN1 and CCN2 in bone are still not clear. In contrast to other CCN family proteins, CCN3 inhibits osteoblast differentiation, although its regulation by interstitial shear stress in osteocytes has not been reported. The induction of CCN proteins by shear stress in bone and their functions remain largely unknown and merit further investigation. This review discusses the expression and functions of CCN proteins regulated by shear stress in physiological conditions, diseases, and cell culture models. The roles between CCN family proteins can be compensatory or counteractive in tissue remodeling and homeostasis.

CD73-Positive Cell Spheroid Transplantation Attenuates Colonic Atrophy

The incidence of inflammatory bowel diseases (IBD) is increasing worldwide. Mesenchymal stem/stromal cells (MSCs) have immunomodulatory functions and are a promising source for cell transplantation therapy for IBD. However, owing to their heterogeneous nature, their therapeutic efficacy in colitis is controversial and depends on the delivery route and form of transplanted cells. Cluster of differentiation (CD) 73 is widely expressed in MSCs and used to obtain a homogeneous MSC population. Herein, we determined the optimal method for MSC transplantation using CD73+ cells in a colitis model. mRNA sequencing analysis showed that CD73+ cells exhibited a downregulation of inflammatory gene expression and an upregulation of extracellular matrix-related gene expression. Furthermore, three-dimensional CD73+ cell spheroids showed enhanced engraftment at the injured site through the enteral route, facilitated extracellular matrix remodeling, and downregulated inflammatory gene expression in fibroblasts, leading to the attenuation of colonic atrophy. Therefore, the interaction between intestinal fibroblasts and exogenous MSCs via tissue remodeling is one mechanism that can be exploited for colitis prevention. Our results highlight that the transplantation of homogeneous cell populations with well-characterized properties is beneficial for IBD treatment.

The Tumor Microenvironment in Tumorigenesis and Therapy Resistance Revisited

Tumorigenesis is a complex and dynamic process involving cell-cell and cell-extracellular matrix (ECM) interactions that allow tumor cell growth, drug resistance and metastasis. This review provides an updated summary of the role played by the tumor microenvironment (TME) components and hypoxia in tumorigenesis, and highlight various ways through which tumor cells reprogram normal cells into phenotypes that are pro-tumorigenic, including cancer associated- fibroblasts, -macrophages and -endothelial cells. Tumor cells secrete numerous factors leading to the transformation of a previously anti-tumorigenic environment into a pro-tumorigenic environment. Once formed, solid tumors continue to interact with various stromal cells, including local and infiltrating fibroblasts, macrophages, mesenchymal stem cells, endothelial cells, pericytes, and secreted factors and the ECM within the tumor microenvironment (TME). The TME is key to tumorigenesis, drug response and treatment outcome. Importantly, stromal cells and secreted factors can initially be anti-tumorigenic, but over time promote tumorigenesis and induce therapy resistance. To counter hypoxia, increased angiogenesis leads to the formation of new vascular networks in order to actively promote and sustain tumor growth via the supply of oxygen and nutrients, whilst removing metabolic waste. Angiogenic vascular network formation aid in tumor cell metastatic dissemination. Successful tumor treatment and novel drug development require the identification and therapeutic targeting of pro-tumorigenic components of the TME including cancer-associated- fibroblasts (CAFs) and -macrophages (CAMs), hypoxia, blocking ECM-receptor interactions, in addition to the targeting of tumor cells. The reprogramming of stromal cells and the immune response to be anti-tumorigenic is key to therapeutic success. Lastly, this review highlights potential TME- and hypoxia-centered therapies under investigation.

Regenerative Potential of A Bovine ECM-Derived Hydrogel for Biomedical Applications

Recent advancements in regenerative medicine have enhanced the development of biomaterials as multi-functional dressings, capable of accelerating wound healing and addressing the challenge of chronic wounds. Hydrogels obtained from decellularized tissues have a complex composition, comparable to the native extracellular environment, showing highly interesting characteristics for wound healing applications. In this study, a bovine pericardium decellularized extracellular matrix (dECM) hydrogel was characterized in terms of macromolecules content, and its immunomodulatory, angiogenic and wound healing potential has been evaluated. The polarization profile of human monocytes-derived macrophages seeded on dECM hydrogel was assessed by RT-qPCR. Angiogenic markers expression has been evaluated by Western blot and antibody array on cell lysates derived from endothelial cells cultured on dECM hydrogel, and a murine in vivo model of hindlimb ischemia was used to evaluate the angiogenic potential. Fibroblast migration was assessed by a transwell migration assay, and an in vivo murine wound healing model treated with dECM hydrogels was also used. The results showed a complex composition, of which the major component is collagen type I. The dECM hydrogel is biocompatible, able to drive M2 phenotype polarization, stimulate the expression of angiogenic markers in vitro, and prevent loss of functionality in hindlimb ischemia model. Furthermore, it drives fibroblast migration and shows ability to facilitate wound closure in vivo, demonstrating its great potential for regenerative applications.

Mechanistic characterization of endothelial sprouting mediated by pro-angiogenic signaling

Objective

We aim to quantitatively characterize the crosstalk between VEGF‐ and FGF‐mediated angiogenic signaling and endothelial sprouting, to gain mechanistic insights and identify novel therapeutic strategies.

Methods

We constructed an experimentally validated hybrid agent‐based mathematical model that characterizes endothelial sprouting driven by FGF‐ and VEGF‐mediated signaling. We predicted the total sprout length, number of sprouts, and average length by the mono‐ and co‐stimulation of FGF and VEGF.

Results

The experimentally fitted and validated model predicts that FGF induces stronger angiogenic responses in the long‐term compared with VEGF stimulation. Also, FGF plays a dominant role in the combination effects in endothelial sprouting. Moreover, the model suggests that ERK and Akt pathways and cellular responses contribute differently to the sprouting process. Last, the model predicts that the strategies to modulate endothelial sprouting are context‐dependent, and our model can identify potential effective pro‐ and anti‐angiogenic targets under different conditions and study their efficacy.

Conclusions

The model provides detailed mechanistic insight into VEGF and FGF interactions in sprouting angiogenesis. More broadly, this model can be utilized to identify targets that influence angiogenic signaling leading to endothelial sprouting and to study the effects of pro‐ and anti‐angiogenic therapies.

The Mesangial cell - the glomerular stromal cell

Mesangial cells are stromal cells that are important for kidney glomerular homeostasis and the glomerular response to injury. A growing body of evidence demonstrates that mesenchymal stromal cells, such as stromal fibroblasts, pericytes and vascular smooth muscle cells, not only specify the architecture of tissues but also regulate developmental processes, vascularization and cell fate specification. In addition, through crosstalk with neighbouring cells and indirectly through the remodelling of the matrix, stromal cells can regulate a variety of processes such as immunity, inflammation, regeneration and in the context of maladaptive responses - fibrosis. Insights into the molecular phenotype of kidney mesangial cells suggest that they are a specialized stromal cell of the glomerulus. Here, we review our current understanding of mesenchymal stromal cells and discuss how it informs the function of mesangial cells and their role in disease. These new insights could lead to a better understanding of kidney disease pathogenesis and the development of new therapies for chronic kidney disease.

Cooperation of cell adhesion and autophagy in the brain: Functional roles in development and neurodegenerative disease

Cellular adhesive connections directed by the extracellular matrix (ECM) and maintenance of cellular homeostasis by autophagy are seemingly disparate functions that are molecularly intertwined, each regulating the other. This is an emerging field in the brain where the interplay between adhesion and autophagy functions at the intersection of neuroprotection and neurodegeneration. The ECM and adhesion proteins regulate autophagic responses to direct protein clearance and guide regenerative programs that go awry in brain disorders. Concomitantly, autophagic flux acts to regulate adhesion dynamics to mediate neurite outgrowth and synaptic plasticity with functional disruption contributed by neurodegenerative disease. This review highlights the cooperative exchange between cellular adhesion and autophagy in the brain during health and disease. As the mechanistic alliance between adhesion and autophagy has been leveraged therapeutically for metastatic disease, understanding overlapping molecular functions that direct the interplay between adhesion and autophagy might uncover therapeutic strategies to correct or compensate for neurodegeneration.

Transcriptome profiling of human pluripotent stem cell-derived cerebellar organoids reveals faster commitment under dynamic conditions

Human-induced pluripotent stem cells (iPSCs) have great potential for disease modeling. However, generating iPSC-derived models to study brain diseases remains a challenge. In particular, the ability to recapitulate cerebellar development in vitro is still limited. We presented a reproducible and scalable production of cerebellar organoids by using the novel single-use Vertical-Wheel bioreactors, in which functional cerebellar neurons were obtained. Here, we evaluate the global gene expression profiles by RNA sequencing (RNA-seq) across cerebellar differentiation, demonstrating a faster cerebellar commitment in this novel dynamic differentiation protocol. Furthermore, transcriptomic profiles suggest a significant enrichment of extracellular matrix (ECM) in dynamic-derived cerebellar organoids, which can better mimic the neural microenvironment and support a consistent neuronal network. Thus, an efficient generation of organoids with cerebellar identity was achieved for the first time in a continuous process using a dynamic system without the need of organoids encapsulation in ECM-based hydrogels, allowing the possibility of large-scale production and application in high-throughput processes. The presence of factors that favors angiogenesis onset was also detected in dynamic conditions, which can enhance functional maturation of cerebellar organoids. We anticipate that large-scale production of cerebellar organoids may help developing models for drug screening, toxicological tests, and studying pathological pathways involved in cerebellar degeneration.

Shear-Regulated Extracellular Microenvironments and Endothelial Cell Surface Integrin Receptors Intertwine in Atherosclerosis

Mechanical forces imposed by blood flow shear stress directly modulate endothelial gene expression and functional phenotype. The production of extracellular matrix proteins and corresponding cell-surface integrin receptors in arterial endothelial cells is intricately regulated by blood flow patterns. Laminar blood flow promotes mature and atheroresistant endothelial phenotype, while disturbed flow induces dysfunctional and atheroprone endothelial responses. Here, we discuss how hemodynamic changes orchestrate the remodeling of extracellular microenvironments and the expression profile of the integrin receptors in endothelial cells leading to oxidative stress and inflammation. Targeting the interaction between matrix proteins and their corresponding integrins is a potential therapeutic approach for atherosclerosis.

Talin-dependent integrin activation is required for endothelial proliferation and postnatal angiogenesis

Integrin activation contributes to key blood cell functions including adhesion, proliferation and migration. An essential step in the cell signaling pathway that activates integrin requires the binding of talin to the β-integrin cytoplasmic tail. Whereas this pathway is understood in platelets in detail, considerably less is known regarding how integrin-mediated adhesion in endothelium contributes to postnatal angiogenesis. We utilized an inducible EC-specific talin1 knock-out mouse (Tln1 EC-KO) and talin1 L325R knock-in mutant (Tln1 L325R) mouse, in which talin selectively lacks the capacity to activate integrins, to assess the role of integrin activation during angiogenesis. Deletion of talin1 during postnatal days 1-3 (P1-P3) caused lethality by P8 with extensive defects in retinal angiogenesis and widespread hemorrhaging. Tln1 EC-KO mice displayed reduced retinal vascular area, impaired EC sprouting and proliferation relative to Tln1 CTRLs. In contrast, induction of talin1 L325R in neonatal mice resulted in modest defects in retinal angiogenesis and mice survived to adulthood. Interestingly, deletion of talin1 or expression of talin1 L325R in ECs increased MAPK/ERK signaling. Strikingly, B16-F0 tumors grown in Tln1 L325R adult mice were 55% smaller and significantly less vascularized than tumors grown in littermate controls. EC talin1 is indispensable for postnatal development angiogenesis. The role of EC integrin activation appears context-dependent as its inhibition is compatible with postnatal development with mild defects in retinal angiogenesis but results in marked defects in tumor growth and angiogenesis. Inhibiting EC pan-integrin activation may be an effective approach to selectively target tumor blood vessel growth.

Angiogenic Potential in Biological Hydrogels

Hydrogels are three-dimensional (3D) materials able to absorb and retain water in large amounts while maintaining their structural stability. Due to their considerable biocompatibility and similarity with the body’s tissues, hydrogels are one of the most promising groups of biomaterials. The main application of these hydrogels is in regenerative medicine, in which they allow the formation of an environment suitable for cell differentiation and growth. Deriving from these hydrogels, it is, therefore, possible to obtain bioactive materials that can regenerate tissues. Because vessels guarantee the right amount of oxygen and nutrients but also assure the elimination of waste products, angiogenesis is one of the processes at the base of the regeneration of a tissue. On the other hand, it is a very complex mechanism and the parameters to consider are several. Indeed, the factors and the cells involved in this process are numerous and, for this reason, it has been a challenge to recreate a biomaterial able to adequately sustain the angiogenic process. However, in this review the focal point is the application of natural hydrogels in angiogenesis enhancing and their potential to guide this process.

A Role of Agrin in Maintaining the Stability of Vascular Endothelial Growth Factor Receptor-2 during Tumor Angiogenesis

Endothelial cell (EC) recruitment is central to the vascularization of tumors. Although several proteoglycans have been implicated in cancer and angiogenesis, their roles in EC recruitment and vascularization during tumorigenesis remain poorly understood. Here, we reveal that Agrin, which is secreted in liver cancer, promotes angiogenesis by recruiting ECs within tumors and metastatic lesions and facilitates adhesion of cancer cells to ECs. In ECs, Agrin-induced angiogenesis and adherence to cancer cells are mediated by Integrin-β1, Lrp4-MuSK pathways involving focal adhesion kinase. Mechanistically, we uncover that Agrin regulates VEGFR2 levels that sustain the angiogenic property of ECs and adherence to cancer cells. Agrin attributes an ECM stiffness-based stabilization of VEGFR2 by enhancing interactions with Integrin-β1-Lrp4 and additionally stimulates endothelial nitric-oxide synthase (e-NOS) signaling. Therefore, we propose that cross-talk between Agrin-expressing cancer and ECs favor angiogenesis by sustaining the VEGFR2 pathway.

Monitoring matrix remodeling in the cellular microenvironment using microrheology for complex cellular systems

Multiple particle tracking (MPT) microrheology was employed for monitoring the development of extracellular matrix (ECM) mechanical properties in the direct microenvironment of living cells. A customized setup enabled us to overcome current limitations: (i) Continuous measurements were enabled using a cell culture chamber, with this, matrix remodeling by fibroblasts in the heterogeneous environment of macroporous scaffolds was monitored continuously. (ii) Employing tracer laden porous scaffolds for seeding human mesenchymal stem cells (hMSCs), we followed conventional differentiation protocols. Thus, we were, for the first time able to study the massive alterations in ECM elasticity during hMSC differentiation. (iii) MPT measurements in 2D cell cultures were enabled using a long distance objective. Exemplarily, local mechanical properties of the ECM in human umbilical vein endothelial cell (HUVEC) cultures, that naturally form 2D layers, were investigated scaffold-free. Using our advanced setup, we measured local, apparent elastic moduli G_0,app in a range between 0.08 and 60 Pa. For fibroblasts grown in collagen-based scaffolds, a continuous decrease of local matrix elasticity resulted during the first 10 hours after seeding. The osteogenic differentiation of hMSC cells cultivated in similar scaffolds, led to an increase of G_0,app by 100 %, whereas after adipogenic differentiation it was reduced by 80 %. The local elasticity of ECM that was newly secreted by HUVECs increased significantly upon addition of protease inhibitor and in high glucose conditions even a twofold increase in G_0,app was observed. The combination of these advanced methods opens up new avenues for a broad range of investigations regarding cell-matrix interactions and the propagation of ECM mechanical properties in complex biological systems. STATEMENT OF SIGNIFICANCE: Cells sense the elasticity of their environment on a micrometer length scale. For studying the local elasticity of extracellular matrix (ECM) in the direct environment of living cells, we employed an advanced multipleparticle tracking microrheology setup. MPT is based on monitoring the Brownian motion oftracer particles, which is restricted by the surrounding network. Network elasticity can thusbe quantified. Overcoming current limitations, we realized continuous investigations of ECM elasticityduring fibroblast growth. Furthermore, MPT measurements of stem cell ECM showed ECMstiffening during osteogenic differentiation and softening during adipogenic differentiation.Finally, we characterized small amounts of delicate ECM newly secreted in scaffold-freecultures of endothelial cells, that naturally form 2D layers.

Flow-induced Reorganization of Laminin-integrin Networks Within the Endothelial Basement Membrane Uncovered by Proteomics

The vessel wall is continuously exposed to hemodynamic forces generated by blood flow. Endothelial mechanosensors perceive and translate mechanical signals via cellular signaling pathways into biological processes that control endothelial development, phenotype and function. To assess the hemodynamic effects on the endothelium on a system-wide level, we applied a quantitative mass spectrometry approach combined with cell surface chemical footprinting. SILAC-labeled endothelial cells were subjected to flow-induced shear stress for 0, 24 or 48 h, followed by chemical labeling of surface proteins using a non-membrane permeable biotin label, and analysis of the whole proteome and the cell surface proteome by LC-MS/MS analysis. These studies revealed that of the >5000 quantified proteins 104 were altered, which were highly enriched for extracellular matrix proteins and proteins involved in cell-matrix adhesion. Cell surface proteomics indicated that LAMA4 was proteolytically processed upon flow-exposure, which corresponded to the decreased LAMA4 mass observed on immunoblot. Immunofluorescence microscopy studies highlighted that the endothelial basement membrane was drastically remodeled upon flow exposure. We observed a network-like pattern of LAMA4 and LAMA5, which corresponded to the localization of laminin-adhesion molecules ITGA6 and ITGB4. Furthermore, the adaptation to flow-exposure did not affect the inflammatory response to tumor necrosis factor α, indicating that inflammation and flow trigger fundamentally distinct endothelial signaling pathways with limited reciprocity and synergy. Taken together, this study uncovers the blood flow-induced remodeling of the basement membrane and stresses the importance of the subendothelial basement membrane in vascular homeostasis.

Integrin-dependent regulation of the endothelial barrier

The endothelium physically separates blood from surrounding tissue and yet allows for the regulated passage of nutrients, waste, and leukocytes into and out of the circulation. Trans-endothelium flux occurs across endothelial cells (transcellular) and between endothelial cells (paracellular). Paracellular endothelial barrier function depends on the regulation of cell-cell junctions. Interestingly, a functional relationship between cell-cell junctions and cell-matrix adhesions has long been appreciated but the molecular mechanisms underpinning this relationship are not fully understood. Here we review the evidence that supports the notion that cell-matrix interactions contribute to the regulation of cell-cell junctions, focusing primarily on the important adherens junction protein VE-cadherin. In particular, we will discuss recent insights gained into how integrin signaling impacts VE-cadherin stability in adherens junctions and endothelial barrier function.

Substrate stiffness directs diverging vascular fates

Embryonic stem cells (ESC) are excellent cell culture systems for elucidating developmental signals that may be part of the stem cell niche. Although stem cells are traditionally induced using predominately soluble signals, the mechanical environment of the niche can also play a role in directing cells towards differential cell lineages. Interested in diverging vascular fates, we set out to examine to what extent mechanical signaling played a role in endothelial cell and/or smooth muscle fate. Using chemically-defined staged vascular differentiation methods, vascular progenitor cells (VPC) fate was examined on single stiffness polyacrylamide hydrogels of 10 kPa, 40 kPa and >0.1 GPa. Emergence of vascular cell populations aligned with corresponding hydrogel stiffness: EC-lineages favoring the softer material and SMC lineages favoring the stiffest material. Statistical significance was observed on both cell lines on almost all days. Transcriptome analysis indicated that the populations on the varying stiffness emerge in distinct categories. Lastly, blocking studies show that αvβ1, and not αvβ6, activation mediates stiffness-directed vascular differentiation. Overall, these studies indicate that softer materials direct VPCs into a more EC-like fate compared to stiffer materials. STATEMENT OF SIGNIFICANCE: Although stem cells are traditionally induced using predominately soluble signals, the mechanical environment of the niche also plays a role in directing cell fate. Several studies have examined the stiffness-induced cell fate from mesenchymal stem cells (MSCs) and undifferentiated embryonic stem cells (ESCs). This is the first study that rigorously examines the role of matrix stiffness in diverging vascular fates from a purified population of vascular progenitor cells (VPCs). We show that the emergence of endothelial cell (EC) versus smooth muscle cell (SMC) populations corresponds with hydrogel stiffness: EC-lineages favoring the softness material and SMC lineages favoring the stiffest material, and that αvβ1 activation mediates this stiffness-directed vascular differentiation.

Emerging roles of ECM remodeling processes in cancer

Extracellular matrix (ECM) plays a central and dynamic role in the creation of tumor microenvironment. Herein we discuss the emerging biophysical and biochemical aspects of ECM buildup and proteolysis in cancer niche formation. Dysregulated ECM remodeling by cancer cells facilitate irreversible proteolysis and crosslinking, which in turn influence cell signaling, micro environmental cues, angiogenesis and tissue biomechanics. Further, we introduce the emerging roles of cancer microbiome in aberrant tumor ECM remodeling and membrane bound nano-sized vesicles called exosomes in creation of distant pre-metastatic niches. A detailed molecular and biophysical understanding of the ECM morphologies and its components such as key enzymes, structural and signaling molecules are critical in identifying the next generation of therapeutic and diagnostic targets in cancer.

CCN1 interlinks integrin and hippo pathway to autoregulate tip cell activity

CCN1 (CYR61) stimulates active angiogenesis in various tumours, although the mechanism is largely unknown. Here, we report that CCN1 is a key regulator of endothelial tip cell activity in angiogenesis. Microvessel networks and directional vascular cell migration patterns were deformed in ccn1-knockdown zebrafish embryos. CCN1 activated VEGFR2 and downstream MAPK/PI3K signalling pathways, YAP/TAZ, as well as Rho effector mDia1 to enhance tip cell activity and CCN1 itself. VEGFR2 interacted with integrin αvβ3 through CCN1. Integrin αvβ3 inhibitor repressed tip cell number and sprouting in postnatal retinas from endothelial cell-specific Ccn1 transgenic mice, and allograft tumours in Ccn1 transgenic mice showed hyperactive vascular sprouting. Cancer patients with high CCN1 expression have poor survival outcomes and positive correlation with ITGAV and ITGB3 and high YAP/WWTR1. Thus, our data underscore the positive feedback regulation of tip cells by CCN1 through integrin αvβ3/VEGFR2 and increased YAP/TAZ activity, suggesting a promising therapeutic intervention for pathological angiogenesis.

Talin-Dependent Integrin Activation Regulates VE-Cadherin Localization and Endothelial Cell Barrier Function

RATIONALE

Endothelial barrier function depends on the proper localization and function of the adherens junction protein VE (vascular endothelial)-cadherin. Previous studies have suggested a functional relationship between integrin-mediated adhesion complexes and VE-cadherin yet the underlying molecular links are unclear. Binding of the cytoskeletal adaptor protein talin to the β-integrin cytoplasmic domain is a key final step in regulating the affinity of integrins for extracellular ligands (activation) but the role of integrin activation in VE-cadherin mediated endothelial barrier function is unknown.

OBJECTIVE

To test the requirement of talin-dependent activation of β1 integrin in VE-cadherin organization and endothelial cell (EC) barrier function.

METHODS AND RESULTS

EC-specific deletion of talin in adult mice resulted in impaired stability of intestinal microvascular blood vessels, hemorrhage, and death. Talin-deficient endothelium showed altered VE-cadherin organization at EC junctions in vivo. shRNA (short hairpin RNA)-mediated knockdown of talin1 expression in cultured ECs led to increased radial actin stress fibers, increased adherens junction width and increased endothelial monolayer permeability measured by electrical cell-substrate impedance sensing. Restoring β1-integrin activation in talin-deficient cells with a β1-integrin activating antibody normalized both VE-cadherin organization and EC barrier function. In addition, VE-cadherin organization was normalized by reexpression of talin or integrin activating talin head domain but not a talin head domain mutant that is selectively deficient in activating integrins.

CONCLUSIONS

Talin-dependent activation of EC β1-integrin stabilizes VE-cadherin at endothelial junctions and promotes endothelial barrier function.

c-Abl regulates YAPY357 phosphorylation to activate endothelial atherogenic responses to disturbed flow

Local flow patterns determine the uneven distribution of atherosclerotic lesions. This research aims to elucidate the mechanism of regulation of nuclear translocation of Yes-associated protein (YAP) under oscillatory shear stress (OSS) in the atheroprone phenotype of endothelial cells (ECs). We report here that OSS led to tyrosine phosphorylation and strong, continuous nuclear translocation of YAP in ECs that is dependent on integrin α5β1 activation. YAP overexpression in ECs blunted the anti-atheroprone effect of an integrin α5β1-blocking peptide (ATN161) in Apoe-/- mice. Activation of integrin α5β1 induced tyrosine, but not serine, phosphorylation of YAP in ECs. Blockage of integrin α5β1 with ATN161 abolished the phosphorylation of YAP at Y357 induced by OSS. Mechanistic studies showed that c-Abl inhibitor attenuated the integrin α5β1-induced YAP tyrosine phosphorylation. Furthermore, the phosphorylation of c-Abl and YAPY357 was significantly increased in ECs in atherosclerotic vessels of mice and in human plaques versus normal vessels. Finally, bosutinib, a tyrosine kinase inhibitor, markedly reduced the level of YAPY357 and the development of atherosclerosis in Apoe-/- mice. The c-Abl/YAPY357 pathway serves as a mechanism for the activation of integrin α5β1 and the atherogenic phenotype of ECs in response to OSS, and provides a potential therapeutic strategy for atherogenesis.

Identification and characterization of agnuside, a natural proangiogenic small molecule

Due to its important role in regulating angiogenesis, vascular homeostasis and remodeling, and arteriogenesis in blood vascular and lymphatic endothelial cells, VEGFR2 stimulation has demonstrated promise in preclinical studies as an endovascular treatment for ischemic myocardial and peripheral disease. However, the short half-life of protein- and cytokine-based strategies and transduction inefficiency of vector-based modalities have hindered its clinical therapeutic applications. In the present study, we used a streamlined bioinformatics strategy combining ligand-based pharmacophore development and validation, virtual screening, and molecular docking to identify agnuside, a non-toxic, natural small molecule extract of Vitex agnus-castus possessing strong binding affinity, druggable physiochemical properties, and conformationally stable hydrogen bond and hydrophobic interactions with catalytically important residues within VEGFR2's active and allosteric sites. In-vitro proliferation, tube formation, and scratch wound migration assays provide evidence that agnuside promotes endothelial cell angiogenesis. Agnuside increases HUVEC proliferation with an EC50 of 1.376 μg/mL, stimulates tubulogenesis dose-dependently, and increases scratch wound migration rate. An additional angiogenesis assay suggests that agnuside may actively compete with a VEGFR2 inhibitor for VEGFR2 binding site occupancy to increase total length and branching length of HUVEC tubular networks. Chemometric analysis of molecular interaction fields (MIFs) by partial least squares (PLS)-derived quantitative structure activity relationship (QSAR) analysis and MIF contours provides the framework for the formulation of agnuside analogues possessing greater potency. Our research supports that agnuside may be a lead molecule for therapeutic angiogenesis.

Beyond the Matrix: The Many Non-ECM Ligands for Integrins

The traditional view of integrins portrays these highly conserved cell surface receptors as mediators of cellular attachment to the extracellular matrix (ECM), and to a lesser degree, as coordinators of leukocyte adhesion to the endothelium. These canonical activities are indispensable; however, there is also a wide variety of integrin functions mediated by non-ECM ligands that transcend the traditional roles of integrins. Some of these unorthodox roles involve cell-cell interactions and are engaged to support immune functions such as leukocyte transmigration, recognition of opsonization factors, and stimulation of neutrophil extracellular traps. Other cell-cell interactions mediated by integrins include hematopoietic stem cell and tumor cell homing to target tissues. Integrins also serve as cell-surface receptors for various growth factors, hormones, and small molecules. Interestingly, integrins have also been exploited by a wide variety of organisms including viruses and bacteria to support infectious activities such as cellular adhesion and/or cellular internalization. Additionally, the disruption of integrin function through the use of soluble integrin ligands is a common strategy adopted by several parasites in order to inhibit blood clotting during hematophagy, or by venomous snakes to kill prey. In this review, we strive to go beyond the matrix and summarize non-ECM ligands that interact with integrins in order to highlight these non-traditional functions of integrins.

Biologic Scaffolds

Biologic scaffold materials composed of allogeneic or xenogeneic extracellular matrix are commonly used for the repair and functional reconstruction of injured and missing tissues. These naturally occurring bioscaffolds are manufactured by the removal of the cellular content from source tissues while preserving the structural and functional molecular units of the remaining extracellular matrix (ECM). The mechanisms by which these bioscaffolds facilitate constructive remodeling and favorable clinical outcomes include release or creation of effector molecules that recruit endogenous stem/progenitor cells to the site of scaffold placement and modulation of the innate immune response, specifically the activation of an anti-inflammatory macrophage phenotype. The methods by which ECM biologic scaffolds are prepared, the current understanding of in vivo scaffold remodeling, and the associated clinical outcomes are discussed in this article.

Comparative surface energetic study of Matrigel® and collagen I interactions with endothelial cells

Understanding of the surface energetic aspects of the spontaneously deposited proteins on biomaterial surfaces and how this influences cell adhesion and differentiation is an area of regenerative medicine that has not received adequate attention. Current controversies surround the role of the biomaterial substratum surface chemistry, the range of influence of said substratum, and the effects of different surface energy components of the protein interface. Endothelial cells (ECs) are a highly important cell type for regenerative medicine applications, such as tissue engineering, and In-vivo they interact with collagen I based stromal tissue and basement membranes producing different behavioral outcomes. The surface energetic properties of these tissue types and how they control EC behavior is not well known. In this work we studied the surface energetic properties of collagen I and Matrigel^® on various previously characterized substratum polyurethanes (PU) via contact angle analysis and examined the subsequent EC network forming characteristics. A combinatorial surface energy approach was utilized that compared Zisman's critical surface tension, Kaelble's numerical method, and van Oss-Good-Chaudhury theory (vOGCT). We found that the unique, rapid network forming characteristics of ECs on Matrigel^® could be attributed to the apolar or monopolar basic interfacial characteristics according to Zisman/Kaelble or vOGCT, respectively. We also found a lack of significant substratum influence on EC network forming characteristics for Matrigel^® but collagen I showed a distinct influence where more apolar PU substrata tended to produce higher Lewis acid character collagen I interfaces which led to a greater interaction with ECs. Collagen I interfaces on more polar PU substrata lacked Lewis acid character and led to similar EC network characteristics as Matrigel^®. We hypothesized that bipolar character of the protein film favored cell-substratum over cell-cell adhesive interactions which resulted in less rapidly forming but more stable networks.

Engineering a Cell Home for Stem Cell Homing and Accommodation

Distilling complexity to advance regenerative medicine from laboratory animals to humans, in situ regeneration will continue to evolve using biomaterial strategies to drive endogenous cells within the human body for therapeutic purposes; this approach avoids the need for delivering ex vivo-expanded cellular materials. Ensuring the recruitment of a significant number of reparative cells from an endogenous source to the site of interest is the first step toward achieving success. Subsequently, making the "cell home" cell-friendly by recapitulating the natural extracellular matrix (ECM) in terms of its chemistry, structure, dynamics, and function, and targeting specific aspects of the native stem cell niche (e.g., cell-ECM and cell-cell interactions) to program and steer the fates of those recruited stem cells play equally crucial roles in yielding a therapeutically regenerative solution. This review addresses the key aspects of material-guided cell homing and the engineering of novel biomaterials with desirable ECM composition, surface topography, biochemistry, and mechanical properties that can present both biochemical and physical cues required for in situ tissue regeneration. This growing body of knowledge will likely become a design basis for the development of regenerative biomaterials for, but not limited to, future in situ tissue engineering and regeneration.

Degradation of endothelial network in disordered tumor-containing cell sheet

Tumor angiogenesis is an important event in tumor malignancy; and the vasculature formed in tumor region is typically dysfunctional. Multiple factors are associated with tumor vessel abnormalities, but the precise mechanism has not been fully understood. In the present study, a tumor-containing cell sheet was prepared by mixing a small population of human embryonal rhabdomyosarcoma (RMS) cells (RDs) with human skeletal muscle myoblasts (HSMMs) to mimic muscle tissue invaded by RMS cells. Sheet fluidity and the extracellular matrix (ECM) meshwork of the tumor-containing cell sheet were found to be elevated and disordered, demonstrating the disruptive effect of tumor cells on sheet structure. When green fluorescent protein expressing human umbilical vein endothelial cells (GFP-HUVECs) were co-cultured with the tumor-containing cell sheet, an endothelial network was formed, but degraded faster as a result of activated migration of endothelial cells in the tumor-containing cell sheet. This study suggested that disorganized tissue structure facilitate tumor angiogenesis by activation of endothelial cell migration.

Integrin signaling in atherosclerosis

Atherosclerosis, a chronic lipid-driven inflammatory disease affecting large arteries, represents the primary cause of cardiovascular disease in the world. The local remodeling of the vessel intima during atherosclerosis involves the modulation of vascular cell phenotype, alteration of cell migration and proliferation, and propagation of local extracellular matrix remodeling. All of these responses represent targets of the integrin family of cell adhesion receptors. As such, alterations in integrin signaling affect multiple aspects of atherosclerosis, from the earliest induction of inflammation to the development of advanced fibrotic plaques. Integrin signaling has been shown to regulate endothelial phenotype, facilitate leukocyte homing, affect leukocyte function, and drive smooth muscle fibroproliferative remodeling. In addition, integrin signaling in platelets contributes to the thrombotic complications that typically drive the clinical manifestation of cardiovascular disease. In this review, we examine the current literature on integrin regulation of atherosclerotic plaque development and the suitability of integrins as potential therapeutic targets to limit cardiovascular disease and its complications.

Inhibition of major integrin αV β3 reduces Staphylococcus aureus attachment to sheared human endothelial cells

Essentials Staphylococcus aureus (S. aureus) binds and impairs function of vascular endothelial cells (EC). We investigated the molecular signals triggered by S. aureus adhesion to EC. Inhibition of the EC integrin αVβ3 reduces S. aureus binding and rescues EC function. αVβ3 blockade represents an attractive target to treat S. aureus bloodborne infections.

SUMMARY

Background Vascular endothelial dysfunction with associated edema and organ failure is one of the hallmarks of sepsis. Although a large number of microorganisms can cause sepsis, Staphylococcus aureus (S. aureus) is one of the primary etiologic agents. Currently, there are no approved specific treatments for sepsis, and the initial management bundle is therefore focused on cardiorespiratory resuscitation and mitigation of the immediate threat of uncontrolled infection. The continuous emergence of antibiotic-resistant strains of bacteria necessitates the development of new therapeutic approaches for this disease. Objective To identify the molecular mechanisms leading to endothelial dysfunction as a result of S. aureus binding.

METHODS

Binding of wild type and Clumping factor A (ClfA) deficient S. aureus Newman to the endothelium was measured in vitro and in the mesenteric circulation of C57Bl/6 mice. The effects of the αV β3 blocker-cilengitide-on bacterial binding, endothelial VE-cadherin expression, apoptosis, proliferation and permeability were assessed. Results The major S. aureus cell wall protein ClfA bound to endothelial cell αV β3 in the presence of fibrinogen. This interaction resulted in disturbances in barrier function mediated by VE-cadherin in endothelial cell monolayers, and ultimately cell death by apoptosis. With a low concentration of cilengitide, ClfA binding to αV β3 was significantly inhibited both in vitro and in vivo. Moreover, preventing S. aureus from attaching to αV β3 resulted in a significant reduction in endothelial dysfunction following infection. Conclusion Inhibition of S. aureus ClfA binding to endothelial cell αV β3 by cilengitide prevents endothelial dysfunction.

Peptides for bone tissue engineering

Molecular signals in the form of growth factors are the main modulators of cell behavior. However, the use of growth factors in tissue engineering has several drawbacks, including their costs, difficult production, immunogenicity and short half-life. Furthermore, many of them are pleiotropic and, since a single growth factor can have different active domains, their effect is not always fully controllable. A very interesting alternative that has recently emerged is the use of biomimetic peptides. Sequences derived from the active domains of soluble or extracellular matrix proteins can be used to functionalize the biomaterials used as scaffolds for new tissue growth to either direct the attachment of cells or to be released as soluble ligands. Since these short peptides can be easily designed and cost-effectively synthesized in vitro, their use has opened up a world of new opportunities to obtain cheaper and more effective implants for regenerative medicine strategies. In this extensive review we will go through many of the most important peptides with potential interest for bone tissue engineering, not limiting to those that only mediate cell adhesion or induce the osteogenic differentiation of progenitor cells, but also focusing on those that direct angiogenesis because of its close relation with bone formation.

Blood Brothers: Hemodynamics and Cell-Matrix Interactions in Endothelial Function

SIGNIFICANCE

Alterations in endothelial function contribute to a variety of vascular diseases. In pathological conditions, the endothelium shows a reduced ability to regulate vasodilation (endothelial dysfunction) and a conversion toward a proinflammatory and leaky phenotype (endothelial activation). At the interface between the vessel wall and blood, the endothelium exists in a complex microenvironment and must translate changes in these environmental signals to alterations in vessel function. Mechanical stimulation and endothelial cell interactions with the vascular matrix, as well as a host of soluble factors, coordinately contribute to this dynamic regulation.

RECENT ADVANCES

Blood hemodynamics play an established role in the regulation of endothelial function. However, a growing body of work suggests that subendothelial matrix composition similarly and coordinately regulates endothelial cell phenotype such that blood flow affects matrix remodeling, which affects the endothelial response to flow.

CRITICAL ISSUES

Hemodynamics and soluble factors likely affect endothelial matrix remodeling through multiple mechanisms, including transforming growth factor β signaling and alterations in cell-matrix receptors, such as the integrins. Likewise, differential integrin signaling following matrix remodeling appears to regulate several key flow-induced responses, including nitric oxide production, regulation of oxidant stress, and activation of proinflammatory signaling and gene expression. Microvascular remodeling responses, such as angiogenesis and arteriogenesis, may also show coordinated regulation by flow and matrix.

FUTURE DIRECTIONS

Identifying the mechanisms regulating the dynamic interplay between hemodynamics and matrix remodeling and their contribution to the pathogenesis of cardiovascular disease remains an important research area with therapeutic implications across a variety of conditions. Antioxid. Redox Signal. 25, 415-434.

Integrin α6β1 Expressed in ESCs Instructs the Differentiation to Endothelial Cells

Adhesion of embryonic stem cells (ESCs) to the extracellular matrix may influence differentiation potential and cell fate decisions. Here, we investigated the inductive role of binding of integrin α6β1 expressed in mouse (m)ESCs to laminin-1 (LN1) in mediating the differentiation of ESCs to endothelial cells (ECs). We observed that α6β1 binding to LN1 was required for differentiation to ECs. α6β1 functioned by recruiting the adaptor tetraspanin protein CD151, which activated FAK and Akt signaling and mediated the EC lineage-specifying transcription factor Er71. In contrast, association of the ESC-expressed α3β1, another highly expressed LN1 binding integrin, with CD151, prevented α6β1-mediated differentiation. CD151 thus functioned as a bifurcation router to direct ESCs toward ECs when α6β1 associated with CD151, or prevented transition to ECs when α3β1 associated with CD151. These observations were recapitulated in mice in which α6 integrin or CD151 knockdown reduced the expression of Er71-regulated angiogenesis genes and development of blood vessels. Thus, interaction of α6β1 in ESCs with LN1 activates α6β1/CD151 signaling which programs ESCs toward the EC lineage fate.

APTES-modified nanosilica--but neither APTES nor nanosilica--inhibits endothelial cell growth via arrest of cell cycle at G1 phase

The adverse effects of nanomaterials on the living system have attracted considerable attention in the past few years. Such effects may come from either the core nanomaterials or the chemical agents used to modify the nanomaterials - the latter being largely overlooked. In a free form, these modifying agents might have little impact on living cells; however, they may exhibit distinct biological effects when they assemble into a larger dimension. Here, we report that (3-aminopropyl)triethoxysilane - a small molecule compound ubiquitously employed to functionalise nanosilica surface - could decrease the viability of human umbilical vein endothelial cells when it was grafted onto the nanosilica surface. However, intriguingly, such effect was not found in 3-aminopropyl)triethoxysilane itself, the unmodified silica nanoparticles or the 3-aminopropyl)triethoxysilane-modified microparticles. Change of surface charge was excluded as a cause and apoptosis was not observed. Nevertheless, the 3-aminopropyl)triethoxysilane-modified nanoparticles could exclusively arrest cell cycle at G1 phase. Our findings suggest that substances could gain 'new' functions at the nanoscale, which may not be found in their larger or smaller counterparts. Understanding of such effects will provide critical insights for better evaluation and thus safer use of nanomaterials, in particular those having been pre-modified with other agents.

Physical supports from liver cancer cells are essential for differentiation and remodeling of endothelial cells in a HepG2-HUVEC co-culture model

Blood vessel remodeling is crucial in tumor growth. Growth factors released by tumor cells and endothelium-extracellular matrix interactions are highlighted in tumor angiogenesis, however the physical tumor-endothelium interactions are highly neglected. Here, we report that the physical supports from hepatocellular carcinoma, HepG2 cells, are essential for the differentiation and remodeling of endothelial cells. In a HepG2-HUVEC co-culture model, endothelial cells in direct contact with HepG2 cells could differentiate and form tubular structures similar to those plated on matrigel. By employing HepG2 cell sheet as a supportive layer, endothelial cells formed protrusions and sprouts above it. In separate experiments, fixed HepG2 cells could stimulate endothelial cells differentiation while the conditioned media could not, indicating that physical interactions between tumor and endothelial cells were indispensable. To further investigate the endothelium-remodeling mechanisms, the co-culture model was treated with inhibitors targeting different angiogenic signaling pathways. Inhibitors targeting focal adhesions effectively inhibited the differentiation of endothelial cells, while the growth factor receptor inhibitor displayed little effect. In conclusion, the co-culture model has provided evidences of the essential role of cancer cells in the differentiation and remodeling of endothelial cells, and is a potential platform for the discovery of new anti-angiogenic agents for liver cancer therapy.

Control of vascular permeability by adhesion molecules

Vascular permeability is a vital function of the circulatory system that is regulated in large part by the limited flux of solutes, water, and cells through the endothelial cell layer. One major pathway through this barrier is via the inter-endothelial junction, which is driven by the regulation of cadherin-based adhesions. The endothelium also forms attachments with surrounding proteins and cells via 2 classes of adhesion molecules, the integrins and IgCAMs. Integrins and IgCAMs propagate activation of multiple downstream signals that potentially impact cadherin adhesion. Here we discuss the known contributions of integrin and IgCAM signaling to the regulation of cadherin adhesion stability, endothelial barrier function, and vascular permeability. Emphasis is placed on known and prospective crosstalk signaling mechanisms between integrins, the IgCAMs- ICAM-1 and PECAM-1, and inter-endothelial cadherin adhesions, as potential strategic signaling nodes for multipartite regulation of cadherin adhesion.

Establishment and evaluation of a murine ανβ3-integrin-expressing cell line with increased susceptibility to Foot-and-mouth disease virus

Integrin ανβ3 plays a major role in various signaling pathways, cell apoptosis, and tumor angiogenesis. To examine the functions and roles of ανβ3 integrin, a stable CHO-677 cell line expressing the murine ανβ3 heterodimer (designated as "CHO-677-mανβ3" cells) was established using a highly efficient lentiviral-mediated gene transfer technique. Integrin subunits αν and β3 were detected at the gene and protein levels by polymerase chain reaction (PCR) and indirect immunofluorescent assay (IFA), respectively, in the CHO-677-mανβ3 cell line at the 20th passage, implying that these genes were successfully introduced into the CHO-677 cells and expressed stably. A plaque-forming assay, 50% tissue culture infective dose (TCID50), real-time quantitative reverse transcription-PCR, and IFA were used to detect the replication levels of Foot-and-mouth disease virus (FMDV) in the CHO-677-mανβ3 cell line. After infection with FMDV/O/ZK/93, the cell line showed a significant increase in viral RNA and protein compared with CHO-677 cells. These findings suggest that we successfully established a stable ανβ3-receptor-expressing cell line with increased susceptibility to FMDV. This cell line will be very useful for further investigation of ανβ3 integrin, and as a cell model for FMDV research.

Acquisition of anoikis resistance up-regulates syndecan-4 expression in endothelial cells

Anoikis is a programmed cell death induced upon cell detachment from extracellular matrix, behaving as a critical mechanism in preventing adherent-independent cell growth and attachment to an inappropriate matrix, thus avoiding colonization of distant organs. Cell adhesion plays an important role in neoplastic transformation. Tumors produce several molecules that facilitate their proliferation, invasion and maintenance, especially proteoglycans. The syndecan-4, a heparan sulfate proteoglycan, can act as a co-receptor of growth factors and proteins of the extracellular matrix by increasing the affinity of adhesion molecules to their specific receptors. It participates together with integrins in cell adhesion at focal contacts connecting the extracellular matrix to the cytoskeleton. Changes in the expression of syndecan-4 have been observed in tumor cells, indicating its involvement in cancer. This study investigates the role of syndecan-4 in the process of anoikis and cell transformation. Endothelial cells were submitted to sequential cycles of forced anchorage impediment and distinct lineages were obtained. Anoikis-resistant endothelial cells display morphological alterations, high rate of proliferation, poor adhesion to fibronectin, laminin and collagen IV and deregulation of the cell cycle, becoming less serum-dependent. Furthermore, anoikis-resistant cell lines display a high invasive potential and a low rate of apoptosis. This is accompanied by an increase in the levels of heparan sulfate and chondroitin sulfate as well as by changes in the expression of syndecan-4 and heparanase. These results indicate that syndecan-4 plays a important role in acquisition of anoikis resistance and that the conferral of anoikis resistance may suffice to transform endothelial cells.

MicroRNA-206 functions as a pleiotropic modulator of cell proliferation, invasion and lymphangiogenesis in pancreatic adenocarcinoma by targeting ANXA2 and KRAS genes

Recent advances in cancer biology have emerged important roles for microRNAs (miRNAs) in regulating tumor responses. However, their function in mediating intercellular communication within the tumor microenvironment is thus far poorly explored. Here, we found miR-206 to be abrogated in human pancreatic ductal adenocarcinoma (PDAC) specimens and cell lines. We show that miR-206 directly targets the oncogenes KRAS and annexin a2 (ANXA2), thereby acting as tumor suppressor in PDAC cells by blocking cell cycle progression, cell proliferation, migration and invasion. Importantly, we identified miR-206 as a negative regulator of oncogenic KRAS-induced nuclear factor-κB transcriptional activity, resulting in a concomitant reduction of the expression and secretion of pro-angiogenic and pro-inflammatory factors including the cytokine interleukin-8, the chemokines (C-X-C motif) ligand 1 and (C–C motif) ligand 2, and the granulocyte macrophage colony-stimulating factor. We further show that miR-206 abrogates the expression and secretion of the potent pro-lymphangiogenic factor vascular endothelial growth factor C in pancreatic cancer cells through an NF-κB-independent mechanism. By using in vitro and in vivo approaches, we reveal that re-expression of miR-206 in PDAC cells is sufficient to inhibit tumor blood and lymphatic vessel formation, thus leading to a significant delay of tumor growth and progression. Taken together, our study sheds light onto the role of miR-206 as a pleiotropic modulator of different hallmarks of cancer, and as such raising the intriguing possibility that miR-206 may be an attractive candidate for miRNA-based anticancer therapies.

Huachansu injection inhibits metastasis of pancreatic cancer in mice model of human tumor xenograft

Background

Huachansu injection (HCS) is a water-soluble preparation made from Bufo gargarizans’s skin, which has been widely used in clinics for tumor therapy in China. Though the anti-cancer activity of HCS has been verified through studies in vitro and in vivo, there is little research about its potential anti-metastasis effect. The primary objective of this study was to assess the effects of HCS on both the invasion of pancreatic cancer cells in vitro and on the progression of liver metastasis in vivo in this study.

Methods

HCS anti-metastasis potential was accessed using both assay of Cell viability and invasion in vitro, and then further Establishing xenograft model in nude mice. In the cell-based assay, mRNA and protein expression of MMP-2, MMP-9 and VEGF was detected by semi-quantitative RT-PCR and western blotting. In animal experiment, liver metastasis nodules and change of liver-body ratio was observed. Meanwhile, correlation of the CA19-9 and CEA content in serum with the progression of liver metastasis was analyzed.

Result

We observed that HCS prevented the invasion of cancer cells, with inhibiting the expressions of MMP-2 and MMP-9, and reduced not only the number of metastasis nodules but the ratio of liver-body weight as well. Furthermore, HCS decreased the expression of MMP-2, MMP-9 and VEGF in liver metastasis, while also reducing CA19-9 contents in serum. In addition, correlation analysis indicated that the level of CA19-9 in serum was closely related to the number of liver metastasis nodules.

Conclusion

Our experimental results suggest that HCS has some anti-metastasis potential to suppress the growth of liver metastasis by decreasing the expression of MMP-2 and MMP-9 as well as VEGF.

Electronic supplementary material

The online version of this article (doi:10.1186/1472-6882-14-483) contains supplementary material, which is available to authorized users.

Mechanical interaction of angiogenic microvessels with the extracellular matrix

Angiogenesis is the process by which new blood vessels sprout from existing blood vessels, enabling new vascular elements to be added to an existing vasculature. This review discusses our investigations into the role of cell-matrix mechanics in the mechanical regulation of angiogenesis. The experimental aspects of the research are based on in vitro experiments using an organ culture model of sprouting angiogenesis with the goal of developing new treatments and techniques to either promote or inhibit angiogenic outgrowth, depending on the application. Computational simulations were performed to simulate angiogenic growth coupled to matrix deformation, and live two-photon microscopy was used to obtain insight into the dynamic mechanical interaction between angiogenic neovessels and the extracellular matrix. In these studies, we characterized how angiogenic neovessels remodel the extracellular matrix (ECM) and how properties of the matrix such as density and boundary conditions influence vascular growth and alignment. Angiogenic neovessels extensively deform and remodel the matrix through a combination of applied traction, proteolytic activity, and generation of new cell-matrix adhesions. The angiogenic phenotype within endothelial cells is promoted by ECM deformation and remodeling. Sensitivity analysis using our finite element model of angiogenesis suggests that cell-generated traction during growth is the most important parameter controlling the deformation of the matrix and, therefore, angiogenic growth and remodeling. Live two-photon imaging has also revealed numerous neovessel behaviors during angiogenesis that are poorly understood such as episodic growth/regression, neovessel colocation, and anastomosis. Our research demonstrates that the topology of a resulting vascular network can be manipulated directly by modifying the mechanical interaction between angiogenic neovessels and the matrix.

Akt1 activity regulates vessel maturation in a tissue engineering model of angiogenesis

Akt kinase is a central signal transduction node that integrates extracellular cues that regulate cell migratory, proliferative, and morphological functions during angiogenesis. However, how Akt activity is modulated and contributes to subsequent vessel maturation is unclear. In this study we investigated the role of Akt1 in vessel maturation using human dermal microvascular endothelial cells (HDMVECs) expressing constitutively active and hemiphosphorylated Akt1 epi-alleles with graded kinase activity. HDMVECs expressing Akt1 epi-alleles were analyzed in vivo in a tissue engineering setting using a model of angiogenesis comprising cell-seeded poly-L-lactic acid scaffolds implanted subcutaneously into NOD/SCID murine hosts. The resultant intraimplant microvasculature was quantified for vascular parameters, including vessel diameter, perfusion, vascular density, and pericyte coverage. We found that constitutive Akt1 kinase activity in implanted HDMVECs correlated with loss of neovasculature function. Further, we found that the presence of coimplanted vascular smooth muscle cells (vSMCs) in the implants failed to promote blood vessel growth and maturation in a graded, Akt1 kinase activity-dependent manner. These results indicate that constitutive Akt1 activity disrupts the normal blood vessel growth and maturation. Therefore, we suggest that a downregulation of Akt1 activity is necessary for vSMC-induced maturation of newly formed blood vessels to occur.