Basic fibroblast growth factor modulates integrin expression in microvascular endothelial cells

Sustained growth factor delivery from bioactive PNIPAM-grafted-chitosan/heparin multilayers as a tool to promote growth and migration of cells

Delivery of growth factors (GFs) is challenging for regulation of cell proliferation and differentiation due to their rapid inactivation under physiological conditions. Here, a bioactive polyelectrolyte multilayer (PEM) is engineered by the combination of thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and glycosaminoglycans to be used as reservoir for GF storage. PNIPAM-grafted-chitosan (PChi) with two degrees of substitution (DS) are synthesized, namely LMW* (DS 0.14) and HMW (DS 0.03), by grafting low (2 kDa) and high (10 kDa) molecular weight of PNIPAM on the backbone of chitosan (Chi) to be employed as polycations to form PEM with the polyanion heparin (Hep) at pH 4. Subsequently, PEMs are chemically crosslinked to improve their stability at physiological pH 7.4. Resulting surface and mechanical properties indicate that PEM containing HMW is responsive to temperature at 20 °C and 37 °C, while LMW is not. More importantly, Hep as terminal layer combined with HMW allows not only a better retention of the adhesive protein vitronectin but also a sustained release of FGF-2 at 37 °C. With the synergistic effect of vitronectin and matrix-bound FGF-2, significant promotion on adhesion, proliferation, and migration of 3T3 mouse embryonic fibroblasts is achieved on HMW-containing PEM compared to Chi-containing PEM and exogenously added FGF-2. Thus, PEM containing PNIPAM in combination with bioactive glycosaminoglycans like Hep represents a versatile approach to fabricate a GF delivery system for efficient cell culture, which can be potentially served as cell culture substrate for production of (stem) cells and bioactive wound dressing for tissue regeneration.

Role of Herbal Extracts of Catechu from Uncaria gambir in the Treatment of Chronic Diabetic Wounds

Catechu is a dried decoction from twigs with the leaves of Uncaria gambir. Its antioxidant, anti-inflammatory, and antimicrobial activities have been previously reported because of its high catechin and epicatechin content (>21%). It is also one of the components used in traditional Chinese herbal medicine, “Jinchuang Ointment,” which has excellent efficacy in treating chronic diabetic wounds. An in vivo zebrafish embryo platform and an in vitro cell-based tube formation assay were used to measure the angiogenic activity of catechu extracts. Interestingly, for the first time, catechu extracts stimulated angiogenic activity on both platforms. The expression of the IL-8 gene was induced in HMEC1 cells after treatment with catechu extracts for 1 h only. In contrast, the upregulation of FGFR2, FGFR3, NF-κB, STAT3, and vimentin persisted for 24 h. A summary of the possible mechanisms underlying the angiogenic activity of catechu extracts in HMEC1 cells is shown. Unexpectedly, catechu extracts inhibited the migration of HaCaT cells. These results can account for the intense blood flow flux in porcine excisional wound sites in our previous studies, which provides insights into the therapeutic activity of catechu extract in chronic diabetic wounds.

Dichotomous role of integrin-β5 in lung endothelial cells

Pulmonary arterial hypertension (PAH) is a progressive, devastating disease, and its main histological manifestation is an occlusive pulmonary arteriopathy. One important functional component of PAH is aberrant endothelial cell (EC) function including apoptosis-resistance, unchecked proliferation, and impaired migration. The mechanisms leading to and maintaining physiologic and aberrant EC function are not fully understood. Here, we tested the hypothesis that in PAH, ECs have increased expression of the transmembrane protein integrin-β5, which contributes to migration and survival under physiologic and pathological conditions, but also to endothelial-to-mesenchymal transition (EnMT). We found that elevated integrin-β5 expression in pulmonary artery lesions and lung tissue from PAH patients and rats with PH induced by chronic hypoxia and injection of CD117+ rat lung EC clones. These EC clones exhibited elevated expression of integrin-β5 and its heterodimerization partner integrin-αν and showed accelerated barrier formation. Inhibition of integrin-ανβ5 in vitro partially blocked transforming growth factor (TGF)-β1-induced EnMT gene expression in rat lung control ECs and less in rat lung EC clones and human lung microvascular ECs. Inhibition of integrin-ανβ5 promoted endothelial dysfunction as shown by reduced migration in a scratch assay and increased apoptosis in synergism with TGF-β1. In vivo, blocking of integrin-ανβ5 exaggerated PH induced by chronic hypoxia and CD117+ EC clones in rats. In summary, we found a role for integrin-ανβ5 in lung endothelial survival and migration, but also a partial contribution to TGF-β1-induced EnMT gene expression. Our results suggest that integrin-ανβ5 is required for physiologic function of ECs and lung vascular homeostasis.

Toxoplasma effector-induced ICAM-1 expression by infected dendritic cells potentiates transmigration across polarised endothelium

The obligate intracellular parasite Toxoplasma gondii makes use of infected leukocytes for systemic dissemination. Yet, how infection impacts the processes of leukocyte diapedesis has remained unresolved. Here, we addressed the effects of T. gondii infection on the trans-endothelial migration (TEM) of dendritic cells (DCs) across polarised brain endothelial monolayers. We report that upregulated expression of leukocyte ICAM-1 is a feature of the enhanced TEM of parasitised DCs. The secreted parasite effector GRA15 induced an elevated expression of ICAM-1 in infected DCs that was associated with enhanced cell adhesion and TEM. Consequently, gene silencing of Icam-1 in primary DCs or deletion of parasite GRA15 reduced TEM. Further, the parasite effector TgWIP, which impacts the regulation of host actin dynamics, facilitated TEM across polarised endothelium. The data highlight that the concerted action of the secreted effectors GRA15 and TgWIP modulate the leukocyte-endothelial interactions of TEM in a parasite genotype-related fashion to promote dissemination. In addition to the canonical roles of endothelial ICAM-1, this study identifies a previously unappreciated role for leukocyte ICAM-1 in infection-related TEM.

FGF-2 promotes angiogenesis through a SRSF1/SRSF3/SRPK1-dependent axis that controls VEGFR1 splicing in endothelial cells

Background

Angiogenesis is the process by which new blood vessels arise from pre-existing ones. Fibroblast growth factor-2 (FGF-2), a leading member of the FGF family of heparin-binding growth factors, contributes to normal as well as pathological angiogenesis. Pre-mRNA alternative splicing plays a key role in the regulation of cellular and tissular homeostasis and is highly controlled by splicing factors, including SRSFs. SRSFs belong to the SR protein family and are regulated by serine/threonine kinases such as SRPK1. Up to now, the role of SR proteins and their regulators in the biology of endothelial cells remains elusive, in particular upstream signals that control their expression.

Results

By combining 2D endothelial cells cultures, 3D collagen sprouting assay, a model of angiogenesis in cellulose sponges in mice and a model of angiogenesis in zebrafish, we collectively show that FGF-2 promotes proliferation, survival, and sprouting of endothelial cells by activating a SRSF1/SRSF3/SRPK1-dependent axis. In vitro, we further demonstrate that this FGF-2-dependent signaling pathway controls VEGFR1 pre-mRNA splicing and leads to the generation of soluble VEGFR1 splice variants, in particular a sVEGFR1-ex12 which retains an alternative last exon, that contribute to FGF-2-mediated angiogenic functions. Finally, we show that sVEGFR1-ex12 mRNA level correlates with that of FGF-2/FGFR1 in squamous lung carcinoma patients and that sVEGFR1-ex12 is a poor prognosis marker in these patients.

Conclusions

We demonstrate that FGF-2 promotes angiogenesis by activating a SRSF1/SRSF3/SRPK1 network that regulates VEGFR1 alternative splicing in endothelial cells, a process that could also contribute to lung tumor progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01103-3.

Cardiac and lung endothelial cells in response to fluid shear stress on physiological matrix stiffness and composition

OBJECTIVE

Preconditioning of endothelial cells from different vascular beds has potential value for re-endothelialization and implantation of engineered tissues. Understanding how substrate stiffness and composition affects tissue-specific cell response to shear stress will aid in successful endothelialization of engineered tissues. We developed a platform to test biomechanical and biochemical stimuli.

METHODS

A novel polydimethylsiloxane-based parallel plate flow chamber enabled application of laminar fluid shear stress of 2 dynes/cm² for 12 hours to microvascular cardiac and lung endothelial cells cultured on cardiac and lung-derived extracellular matrix. Optical imaging of cells was used to quantify cell changes in cell alignment. Analysis of integrin expression was performed using flow cytometry.

RESULTS

Application of fluid shear stress caused the greatest cell alignment in cardiac endothelial cells seeded on polystyrene and lung endothelial cells on polydimethylsiloxane. This resulted in elongation of the lung endothelial cells. α_v and β₃ integrin expression decreased after application of shear stress in both cell types.

CONCLUSION

Substrate stiffness plays an important role in regulating tissue-specific endothelial response to shear stress, which may be due to differences in their native microenvironments. Furthermore, cardiac and lung endothelial cell response to shear stress was significantly regulated by the type of coating used.

TMT-based quantitative proteomics revealed follicle-stimulating hormone (FSH)-related molecular characterizations for potentially prognostic assessment and personalized treatment of FSH-positive non-functional pituitary adenomas

BACKGROUND

Non-functional pituitary adenoma (NFPA) is highly heterogeneous with different hormone expression subtypes. Of them, follicle-stimulating hormone (FSH)-positive expression is an important subtype of NFPAs. It is well-known that FSH exerted its functions through binding its receptor. However, the expression rate of FSH receptor was significantly higher in aggressive pituitary adenomas. This study aimed to investigate the molecular characteristics of FSH-positive NFPAs for effective stratification of patient, target treatment, prognostic assessment, and personalized treatment of FSH-positive NFPAs.

METHODS

Tandem mass tag (TMT)-based quantitative proteomics was used to investigate differentially expressed proteins (DEPs) between FSH-positive and negative NFPAs. Gene ontology and KEGG pathway enrichment analyses were used to analyze the DEPs. Differentially expressed genes (DEGs) between invasive and non-invasive NFPAs from GEO database were analyzed with pathway enrichment analysis. Protein-protein interaction (PPI) networks were constructed based on DEPs in excetral cellular matrix (ECM)-receptor interaction, focal adhesion, and PI3K-Akt pathways. Cytoscape was used to obtain most significant modules. Western blot was used to validate the expressions of upregulated proteins (ITGA1, ITGA6, and ITGB4), the expression and phosphorylated status of Akt in PI3K-Akt pathway, and the expression of FSH receptors in FSH-positive relative to negative NFPAs.

RESULTS

A total of 594 DEPs (374 upregulated and 220 downregulated) were identified between FSH-positive and negative NFPAs. Nineteen KEGG pathway networks were identified to involve DEPs, and reveal molecular differences between FSH-positive and negative NFPAs, including three important pathways that were significantly associated with tumor invasiveness and aggressiveness: ECM-receptor interaction, focal adhesion, and PI3K-Akt signaling pathways. Further, focal adhesion pathway was also confirmed with invasiveness-related NFPA DEG data that were derived from GEO database. Moreover, the significantly upregulated DEPs (ITGA1, ITGA6, and ITGB4) that were associated with tumor invasiveness and aggressiveness were confirmed by immunoaffinity analysis in FSH-positive vs. negative NFPAs. Also, the phosphorylation level but not its expression level of AKT in PI3K-AKT signaling was significantly increased, and the expression level of FSH receptor was significantly increased in FSH-positive relative to negative NFPAs. Also, overlapping analysis of 594 DEPs and 898 DEGs revealed 45 invasiveness-related DEPs, including 11 upregulated DEPs (ITGA6, FARP1, PALLD, PPBP, LIMA1, SCD, UACA, BAG3, CLU, PLEC, and GATM) that were also upregulated genes in invasive NFPAs, and 8 downregulated DEPs (ALCAM, HP, FSTL4, IL13RA2, NPTX2, DPP6, CRABP2, and SLC27A2) that were also downregulated genes in invasive NFPAs.

CONCLUSIONS

FSH-positive expression was an important NFPA subtype. It was the first time for this study to reveal FSH-related proteomic variations and the corresponding molecular network alterations in FSH-positive relative to negative NFPAs. Also, three signaling pathways (ECM-receptor interaction, focal adhesion, and PI3K-Akt signaling pathways) and involved upregulated proteins (ITGA1, ITGA6, ITGB4, pAKT, and FSHR) were significantly associated with tumor invasiveness and aggressiveness, and a set of invasiveness-related DEPs were identified with overlapping analysis of 594 DEPs in FSH-positive vs. negative NFPAs and 898 DEGs in invasive vs. non-invasive NFPAs. These findings offered the scientific evidence to in-depth understand molecular characteristics of FSH-positive NFPAs, and effectively stratify the post-surgery patients for personalized prognostic assessment and targeted treatment of FSH-positive NFPAs.

Synergistic effect of co-immobilized FGF-2 and vitronectin-derived peptide on feeder-free expansion of induced pluripotent stem cells

Expansion of human induced pluripotent stem cells (h-iPSCs) on mouse derived feeder layers or murine cells secretions such as Matrigel hamper their clinical applications. Alternative methods have introduced novel substrates as stem cell niches or/and optimized combinations of humanized soluble factors as fully defined mediums. Accordingly vitronectin as a main part of ECM have been commercialized significantly as a stem cell niche-forming substrate. In this work, we used a functional peptide derived from vitronectin (VTN) and co-immobilized it with FGF-2 (as an indisputable ingredient of defined culture mediums) on chitosan film surface. After chemical and physical characterization of the pristine chitosan surface as well as ones modified by VTN or/and FGF-2, h-iPS cells were cultured on them at the xeno/feeder-free conditions. Our results demonstrated that co-immobilization of these two biomolecules has a synergistic effect on adhesion and clonal growth of h-iPS cells with maintained expression of pluripotency markers in a FGF-2 density-dependent manner. This is the first report of co-immobilization of an ECM derived molecule and a growth factor for stem cell culture.

Sex Steroids, Adult Neurogenesis, and Inflammation in CNS Homeostasis, Degeneration, and Repair

Sex steroidal hormones coordinate the development and maintenance of tissue architecture in many organs, including the central nervous systems (CNS). Within the CNS, sex steroids regulate the morphology, physiology, and behavior of a wide variety of neural cells including, but not limited to, neurons, glia, endothelial cells, and immune cells. Sex steroids spatially and temporally control distinct molecular networks, that, in turn modulate neural activity, synaptic plasticity, growth factor expression and function, nutrient exchange, cellular proliferation, and apoptosis. Over the last several decades, it has become increasingly evident that sex steroids, often in conjunction with neuroinflammation, have profound impact on the occurrence and severity of neuropsychiatric and neurodegenerative disorders. Here, I review the foundational discoveries that established the regulatory role of sex steroids in the CNS and highlight recent advances toward elucidating the complex interaction between sex steroids, neuroinflammation, and CNS regeneration through adult neurogenesis. The majority of recent work has focused on neuroinflammatory responses following acute physical damage, chronic degeneration, or pharmacological insult. Few studies directly assess the role of immune cells in regulating adult neurogenesis under healthy, homeostatic conditions. As such, I also introduce tractable, non-traditional models for examining the role of neuroimmune cells in natural neuronal turnover, seasonal plasticity of neural circuits, and extreme CNS regeneration.

Transforming growth factor-β in stem cells and tissue homeostasis

TGF-β 1-3 are unique multi-functional growth factors that are only expressed in mammals, and mainly secreted and stored as a latent complex in the extracellular matrix (ECM). The biological functions of TGF-β in adults can only be delivered after ligand activation, mostly in response to environmental perturbations. Although involved in multiple biological and pathological processes of the human body, the exact roles of TGF-β in maintaining stem cells and tissue homeostasis have not been well-documented until recent advances, which delineate their functions in a given context. Our recent findings, along with data reported by others, have clearly shown that temporal and spatial activation of TGF-β is involved in the recruitment of stem/progenitor cell participation in tissue regeneration/remodeling process, whereas sustained abnormalities in TGF-β ligand activation, regardless of genetic or environmental origin, will inevitably disrupt the normal physiology and lead to pathobiology of major diseases. Modulation of TGF-β signaling with different approaches has proven effective pre-clinically in the treatment of multiple pathologies such as sclerosis/fibrosis, tumor metastasis, osteoarthritis, and immune disorders. Thus, further elucidation of the mechanisms by which TGF-β is activated in different tissues/organs and how targeted cells respond in a context-dependent way can likely be translated with clinical benefits in the management of a broad range of diseases with the involvement of TGF-β.

Basic Fibroblast Growth Factor Affects the Expression of Angiogenin and Cell Proliferation in A375 Human Melanoma Cells

Aims and background

Human malignant melanoma is a very aggressive and highly angiogenesis-dependent tumor. Basic fibroblast growth factor and angiogenin are the potentially important angiogenic factors for melanoma progression and metastasis. Many studies have mainly focused on how they induce angiogenesis. In the present study, we investigated the effects of basic fibroblast growth factor on the expression of angiogenin and melanoma cell growth.

Methods and study design

Angiogenin mRNA and protein expression were investigated by means of semi-quantitative reverse transcriptase polymerase chain reaction assay and western blotting. We analyzed cell proliferation using MTT, flow cytometry and soft agar assay. Immunofluorescence staining was applied to investigate co-localization and nuclear translocation.

Results

We found that basic fibroblast growth factor negatively affected the expression of angiogenin in A375 cells. The result showed that down-regulation of basic fibroblast growth factor induced decreased cell proliferation of A375 cells, and in basic fibroblast growth factor up-regulated cells, cell proliferation was increased. We demonstrated that basic fibroblast growth factor protein was co-localized with angiogenin and that it underwent nuclear translocation in A375 cells.

Conclusion

These findings suggest that there is a cooperation mechanism between basic fibroblast growth factor and angiogenin in A375 cells, and the cooperation mechanism affects the progress of tumor cell proliferation and angiogenesis. Free full text available at www.tumorionline.it

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.

What Kind of Signaling Maintains Pluripotency and Viability in Human-Induced Pluripotent Stem Cells Cultured on Laminin-511 with Serum-Free Medium?

Xeno-free medium contains no animal-derived components, but is composed of minimal growth factors and is serum free; the medium may be supplemented with insulin, transferrin, and selenium (ITS medium). Serum-free and xeno-free culture of human-induced pluripotent stem cells (hiPSCs) uses a variety of components based on ITS medium and Dulbecco's modified Eagle's medium/Ham's nutrient mixture F12 (DMEM/F12) that contain high levels of iron salt and glucose. Culture of hiPSCs also requires scaffolding materials, such as extracellular matrix, collagen, fibronectin, laminin, proteoglycan, and vitronectin. The scaffolding component laminin-511, which is composed of α5, β1, and γ1 chains, binds to α3β1, α6β1, and α6β4 integrins on the cell membrane to induce activation of the PI3K/AKT- and Ras/MAPK-dependent signaling pathways. In hiPSCs, the interaction of laminin-511/α6β1 integrin with the cell–cell adhesion molecule E-cadherin confers protection against apoptosis through the Ras homolog gene family member A (RhoA)/Rho kinase (ROCK) signaling pathway (the major pathways for cell death) and the proto-oncogene tyrosine-protein kinase Fyn (Fyn)-RhoA-ROCK signaling pathway. The expression levels of α6β1 integrin and E-cadherin on cell membranes are controlled through the activation of insulin receptor/insulin, FGF receptor/FGF2, or activin-like kinase 5 (ALK5)-dependent TGF-β signaling. A combination of growth factors, medium constituents, cell membrane-located E-cadherin, and α6β1 integrin-induced signaling is required for pluripotent cell proliferation and for optimal cell survival on a laminin-511 scaffold. In this review, we discuss and explore the influence of growth factors on the cadherin and integrin signaling pathways in serum-free and xeno-free cultures of hiPSCs during the preparation of products for regenerative medicinal therapies. In addition, we suggest the optimum serum-free medium components for use with laminin-511, a new scaffold for hiPSC culture.

Anti-glycation and anti-angiogenic activities of 5'-methoxybiphenyl-3,4,3'-triol, a novel phytochemical component of Osteomeles schwerinae

Advanced glycation end products (AGEs) are involved in the development of diabetic complications such as diabetic retinopathy. 5'-methoxybiphenyl-3,4,3'-triol (referred to as K24) was isolated using bioactivity-guided fractionation of Osteomeles schwerinae C. K. Schneid. and identified as a potent AGE inhibitor. To identify the protective effect of K24 on disruption of the blood-retinal barrier, AGE-RSA was intravitreally injected into rat eyes. K24 had an inhibitory effect on AGE-RSA-induced retinal vascular leakage by suppressing the expression of vascular endothelial growth factor (VEGF) and decreasing the loss of occludin. In addition, we examined whether K24 has a preventive effect against retinal pathogenic angiogenesis in an oxygen-induced retinopathy (OIR) mouse model. K24 significantly reduced the retinal non-perfused area and neovascular tufts in the OIR mice. These data indicate that K24 could serve as an innovative pharmaceutical agent to prevent blood-retinal barrier breakage and retinal pathogenic angiogenesis through an anti-VEGF mechanism.

Role of angiogenesis in bone repair

Bone vasculature plays a vital role in bone development, remodeling and homeostasis. New blood vessel formation is crucial during both primary bone development as well as fracture repair in adults. Both bone repair and bone remodeling involve the activation and complex interaction between angiogenic and osteogenic pathways. Interestingly studies have demonstrated that angiogenesis precedes the onset of osteogenesis. Indeed reduced or inadequate blood flow has been linked to impaired fracture healing and old age related low bone mass disorders such as osteoporosis. Similarly the slow penetration of host blood vessels in large engineered bone tissue grafts has been cited as one of the major hurdle still impeding current bone construction engineering strategies. This article reviews the current knowledge elaborating the importance of vascularization during bone healing and remodeling, and the current therapeutic strategies being adapted to promote and improve angiogenesis.

Bone marrow mesenchymal stem cells and TGF-β signaling in bone remodeling

During bone resorption, abundant factors previously buried in the bone matrix are released into the bone marrow microenvironment, which results in recruitment and differentiation of bone marrow mesenchymal stem cells (MSCs) for subsequent bone formation, temporally and spatially coupling bone remodeling. Parathyroid hormone (PTH) orchestrates the signaling of many pathways that direct MSC fate. The spatiotemporal release and activation of matrix TGF-β during osteoclast bone resorption recruits MSCs to bone-resorptive sites. Dysregulation of TGF-β alters MSC fate, uncoupling bone remodeling and causing skeletal disorders. Modulation of TGF-β or PTH signaling may reestablish coupled bone remodeling and be a potential therapy.

Genomics and proteomics approaches in understanding tumor angiogenesis

Functional genomic and proteomic approaches have begun to revolutionize cancer research. The advent of powerful technologies, such as DNA microarrays, serial analysis of gene expression, RNA interference and proteomics, has accelerated investigations of gene identification and function at a scale never before accomplished. Approaches integrating these technologies with high-throughput forward and reverse genetic screens, are already providing insights into the mechanistic understanding of angiogenesis, leading to the identification of proteins that can be used for selective targeting of tumor vessels.

Activation of the ERK1/2 signaling pathway during the osteogenic differentiation of mesenchymal stem cells cultured on substrates modified with various chemical groups

The current study examined the influence of culture substrates modified with the functional groups –OH, –COOH, –NH₂, and –CH₃ using SAMs technology, in conjunction with TAAB control, on the osteogenic differentiation of rabbit BMSCs. The CCK-8 assay revealed that BMSCs exhibited substrate-dependent cell viability. The cells plated on –NH₂- and –OH-modified substrates were well spread and homogeneous, but those on the –COOH- and –CH₃-modified substrates showed more rounded phenotype. The mRNA expression of BMSCs revealed that –NH₂-modified substrate promoted the mRNA expression and osteogenic differentiation of the BMSCs. The contribution of ERK1/2 signaling pathway to the osteogenic differentiation of BMSCs cultured on the –NH₂-modified substrate was investigated in vitro. The –NH₂-modified substrate promoted the expression of integrins; the activation of FAK and ERK1/2. Inhibition of ERK1/2 activation by PD98059, a specific inhibitor of the ERK signaling pathway, blocked ERK1/2 activation in a dose-dependent manner, as revealed for expression of Cbfα-1 and ALP. Blockade of ERK1/2 phosphorylation in BMSCs by PD98059 suppressed osteogenic differentiation on chemical surfaces. These findings indicate a potential role for ERK in the osteogenic differentiation of BMSCs on surfaces modified by specific chemical functional groups, indicating that the microenvironment affects the differentiation of BMSCs. This observation has important implications for bone tissue engineering.

Emerging antiangiogenic therapies for non-small-cell lung cancer

Lung cancer remains the leading cause of cancer-related deaths. Antiangiogenic therapy has increasingly been studied for advanced non-small-cell lung cancer (NSCLC). Bevacizumab is the only approved antiangiogenic agent for NSCLC and has shown progression-free survival benefits in large Phase III studies and an overall survival benefit in the Phase III E4599 trial in advanced nonsquamous NSCLC. New antiangiogenic treatment strategies are being evaluated that target multiple receptors within a family (VEGF receptor [VEGFR]-1, VEGFR-2) or multiple angiogenic pathways (targets VEGFR and PDGF receptor pathways), and agents that inhibit alternative mediators of angiogenesis (integrins and established vasculature). As data become available from ongoing studies, it will be important to determine how these new antiangiogenic agents will best fit into the current NSCLC treatment paradigm.

Importance of fibroblast growth factor receptor in neovascularization and tumor escape from antiangiogenic therapy

Therapeutic inhibition of pathways involved in angiogenesis has become the standard of care in renal cell carcinoma (RCC). Most currently available antiangiogenic agents inhibit the vascular endothelial growth factor (VEGF) pathway. Although these drugs have produced exciting benefits, some tumors do not respond to these agents. In addition most if not all tumors that initially respond will eventually develop resistance. Tumor escape from antiangiogenic therapy may include various signaling pathways that are involved in angiogenesis, including the fibroblast growth factor (FGF) signaling pathway. Emerging preclinical data suggest that FGF and VEGF act distinctly and synergistically to promote tumor vascularization. The current review discusses the role of FGF signaling in resistance to anti-VEGF therapies and outlines potential therapeutic implications.

Fibroblast growth factor signaling in non-small-cell lung cancer

Despite recent progress in the treatment on non-small cell lung cancer (NSCLC), outcomes remain suboptimal. Treatment advances that target the epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) signaling pathways highlight the need to understand the multiple convergent growth factor signaling pathways involved in the pathogenesis of NSCLC. Signaling through fibroblast growth factors (FGF), long recognized for its pro-angiogenic activity, has recently emerged as a contributing factor in the pathogenesis and progression of NSCLC through an autocrine signaling loop. In addition, this pathway may function as a mechanism of resistance to anti-EGFR and anti-VEGF treatment. Clinical experience with FGF receptor (FGFR) inhibitors is mounting, and more specific inhibitors of this signaling pathway are in development. This review describes the structure of the FGF signaling pathway, delineates its dual roles in angiogenesis and proliferation in NSCLC, evaluates FGF ligand and receptor expression as prognostic biomarkers in NSCLC, and discusses the development of FGF pathway inhibitors for the treatment of lung malignancies.

Seeding of endothelial cells on the luminal surface of a sheet model of cold-stored (at 4°C) sheep carotid arteries

Cold-stored arteries are biomaterials that potentially represent an abundant "off-the-shelf" source of vascular grafts for use in vascular surgery. One of the keys to reestablishing the antithrombogenic endothelial cell (EC) lining of cold-stored arterial grafts is to maximize the number of ECs that attach following seeding. In this study, the cold-stored sheep carotid artery is used as a substrate to determine the conditions that maximize EC adherence following seeding. The effect of serum concentration, duration of seeding incubation, seeding density, and period of cold storage on attachment of ECs following seeding of 4-week cold-stored sheep carotid arteries (n = 5 arteries), 8-week cold-stored sheep carotid arteries (n = 5 arteries), and 12-week cold-stored sheep carotid arteries (n = 5 arteries) was examined. Three experiments (serum concentration, time of incubation, and seeding density) were conducted to determine the conditions that maximized the number of cultured sheep carotid artery ECs that attached to cold-stored sheep carotid artery following seeding. A flat sheet model was used. Serum concentration (0%, 10%, 20%, and 30%) in the seeding suspension did not have a significant effect on overall EC adherence on 4-, 8-, and 12-week cold-stored arteries. Time of seeding incubation (30, 60, and 90 min) did not have a significant effect on overall EC adherence on 4-, 8-, and 12-week cold-stored arteries. Seeding density (500,000 cells/ml, 1,000,000 cells/ml, and 2,000,000 cells/ml) had a significant effect (p = 0.036) on overall EC adherence on 4-, 8-, and 12-week cold-stored arteries. The period of cold storage (4, 8, and 12 weeks) of the artery had a significant effect (p = 0.002, p < 0.0001, p < 0.0001 in serum, time, and seeding density experiments, respectively) on overall EC adherence following seeding. Pairwise comparisons of EC adherence revealed the following. In the serum experiment, EC adherence on 4-week cold-stored arteries was significantly greater than on 8-week cold-stored arteries (p = 0.003) and 12-week cold-stored arteries (p = 0.002). This effect was due largely to the significant difference between EC adherence on 4-week and 8-week cold-stored arteries (p = 0.0002) and between EC adherence on 4-week and 12-week cold-stored arteries (p = 0.0091) at 20% serum. In the time experiment, EC adherence on 4-week cold-stored arteries was significantly greater than on 12-week cold-stored arteries (p < 0.0001). In the seeding density experiment, EC adherence on 4-week cold-stored arteries was significantly greater than on 8-week cold-stored arteries (p < 0.0001) and 12-week cold-stored arteries (p < 0.0001). In the same experiment, EC adherence following seeding at a density of 1,000,000 cells/ml and 2,000,000 cells/ml was significantly greater (p = 0.03 and p = 0.02, respectively) than EC adherence following seeding at a density of 500,000 cells/ml. Thus, it was determined that 4-week cold-stored arteries were superior to 8- and 12-week cold-stored arteries in terms of the number of ECs that adhered. It was also determined that a seeding density of 1,000,000 or 2,000,000 cells/ml was superior to a seeding density of 500,000 cells/ml in terms of producing maximal EC attachment. The ideal conditions, from those examined, for maximizing EC attachment to cold-stored arteries were 4 weeks of cold storage, a serum concentration of 20%, a seeding density of 2,000,000 cells/ml, and a duration of incubation of 30-90 min.

Rationale for targeting VEGF, FGF, and PDGF for the treatment of NSCLC

Lung cancer remains a leading cause of death globally, with the most frequent type, nonsmall cell lung cancer (NSCLC), having a 5-year survival rate of less than 20%. While platinum-based doublet chemotherapy is currently first-line therapy for advanced disease, it is associated with only modest clinical benefits at the cost of significant toxicities. In an effort to overcome these limitations, recent research has focused on targeted therapies, with recently approved agents targeting the epidermal growth factor receptor and vascular endothelial growth factor (VEGF) signaling pathways. However, these agents (gefitinib, erlotinib, and bevacizumab) provide antitumor activity for only a small proportion of patients, and patients whose tumors respond inevitably develop resistance to treatment. As angiogenesis is a crucial step in tumor growth and metastasis, antiangiogenic treatments might be expected to have antitumor activity. Important targets for the development of novel antiangiogenic therapies include VEGF, fibroblast growth factor, platelet-derived growth factor, and their receptors. It is hypothesized that targeting multiple angiogenic pathways may not only improve antitumor activity but also reduce the risk of resistance. Several novel agents, such as BIBF 1120, sorafenib, sunitinib, and cediranib have shown promising preliminary activity and tolerability in Phase II studies, and results of ongoing Phase III randomized studies will be necessary to establish the potential place of these new therapies in the management of individual patients with NSCLC.

Mediators of ocular angiogenesis

Angiogenesis is the formation of new blood vessels from pre-existing vasculature. Pathologic angiogenesis in the eye can lead to severe visual impairment. In our review, we discuss the roles of both pro-angiogenic and anti-angiogenic molecular players in corneal angiogenesis, proliferative diabetic retinopathy, exudative macular degeneration and retinopathy of prematurity, highlighting novel targets that have emerged over the past decade.

Angiogenesis as a strategic target for prostate cancer therapy

It is becoming increasingly clear that angiogenesis plays a crucial role in prostate cancer (CaP) survival, progression, and metastasis. Tumor angiogenesis is a hallmark of advanced cancers and an attractive treatment target in multiple solid tumors. By understanding the molecular basis of resistance to androgen withdrawal and chemotherapy in CaP, the rational design of targeted therapeutics is possible. This review summarizes the recent advancements that have improved our understanding of the role of angiogenesis in CaP metastasis and the potential therapeutic efficacy of inhibiting angiogenesis in this disease. Current therapeutic options for patients with metastatic hormone-refractory CaP are very limited. Targeting vasculature is a developing area, which shows promise for the control of late stage and recurrent CaP disease and for overcoming drug resistance. We discuss angiogenesis and its postulated mechanisms and focus on the regulation of angiogenesis in CaP progression and the therapeutic beneficial effects associated with targeting of the CaP vasculature to overcome the resistance to current treatments and CaP recurrence.

Exploiting Surface Plasmon Resonance (SPR) Technology for the Identification of Fibroblast Growth Factor-2 (FGF2) Antagonists Endowed with Antiangiogenic Activity

Angiogenesis, the process of new blood vessel formation, is implicated in various physiological/pathological conditions, including embryonic development, inflammation and tumor growth. Fibroblast growth factor-2 (FGF2) is a heparin-binding angiogenic growth factor involved in various physiopathological processes, including tumor neovascularization. Accordingly, FGF2 is considered a target for antiangiogenic therapies. Thus, numerous natural/synthetic compounds have been tested for their capacity to bind and sequester FGF2 in the extracellular environment preventing its interaction with cellular receptors. We have exploited surface plasmon resonance (SPR) technique in search for antiangiogenic FGF2 binders/antagonists. In this review we will summarize our experience in SPR-based angiogenesis research, with the aim to validate SPR as a first line screening for the identification of antiangiogenic compounds.

Translating biomaterial properties to intracellular signaling

Bioactive materials present important micro-environmental cues that induce specific intracellular signaling responses which ultimately determine cell behavior. For example, vascular endothelial cells on a normal vessel wall resist inflammation and thrombosis, but the same cells seeded on an artificial vascular graft or stent do not. What makes these cells behave so differently when they are adhered to different materials? Intracellular signaling from integrins and other cell-surface receptors is an important part of the answer, but these signaling responses constitute a highly-branched, interconnected network of molecules. In order to perform rational design of biomaterials, one must understand how altering the properties of the material (micro-environment) causes changes in cell behavior, and this in turn requires understanding the complex signaling response. Systems biology and mathematical modeling aid analysis of the connectivity of this network. This review summarizes applicable systems biology and mathematical modeling techniques including ordinary differential equations-based models, principal component analysis, and Bayesian networks. Next covered is biomaterials research which studies the intracellular signaling responses generated by variation of biomaterial properties. Finally, the review details ways in which modeling has been or could be applied to better understand the link between biomaterial properties and intracellular signaling.

Integrins in the endometrium

The endometrium expresses many of the same integrins displayed by other tissues. Endometrial epithelial cells maintain the ‘classic’ epithelial integrins, including α2, α3, α6, and β4, while the stroma expresses the fibronectin receptor, α5β1. During the menstrual cycle, the endometrium undergoes dynamic changes in morphology in preparation for implantation. With these histological changes are concomitant alterations in integrin expression that appear to ‘frame’ the window of implantation, by the co-expression of glandular αvβ3 and α4β1 during days 20 to 24 of the menstrual cycle. The changes in integrin expression shift from epithelial to stroma predominance late in the menstrual cycle, extending into early pregnancy. Decidual integrins that appear upregulated in pregnancy include α1β1, α3β1, α6β1 and αvβ3. Markers of uterine receptivity hold promise for a better understanding of the implantation process and may help to explain many different types of infertility. These markers will be essential for monitoring and improving infertility therapies. The importance of integrins in the human endometrium now seems well established and promises to be an area of great clinical and basic science activity in the future.

Single and combined effects of alphavbeta3- and alpha5beta1-integrins on capillary tube formation in a human fibrinous matrix

The fibrinous exudate of a wound or tumor stroma facilitates angiogenesis. We studied the involvement of RGD-binding integrins during tube formation in human plasma-derived fibrin clots and human purified fibrin matrices. Capillary-like tube formation by human microvascular endothelial cells in a 3D plasma-derived fibrinous matrix was induced by FGF-2 and TNF-α and depended largely on cell-bound u-PA and plasmin activities. While tube formation was minimally affected by the addition of either the αvβ3-integrin inhibiting mAb LM609 or the α5-integrin inhibiting mAb IIA1, the general RGD-antagonist echistatin completely inhibited this process. Remarkably, when αvβ3- and α5β1-integrins were inhibited simultaneously, tube formation was reduced by 78%. It was accompanied by a 44% reduction of u-PA antigen accumulation and 41% less production of fibrin degradation products. αvβ5-integrin-blocking antibodies further enhanced the inhibition by mAb LM609 and mAb IIA1 to 94%, but had no effect by themselves. αv-specific cRGD only inhibited angiogenesis when α5β1-integrin was simultaneously blocked. Endostatin mimicked the effect of α5β1-integrin and inhibited tube formation only in the presence of LM609 or cRGD (73 and 80%, respectively). Comparable results were obtained when purified fibrin matrices were used instead of the plasma-derived fibrinous matrices. These data show that blocking of tube formation in a fibrinous exudate requires the simultaneous inhibition of αvβ3- and α5β1-integrins. This may bear impact on attempts to influence angiogenesis in a fibrinous environment.

Modulation of expression of LDH isoenzymes in endothelial cells by laminin: implications for angiogenesis

Endothelial cell (EC) matrix interaction is critical in angiogenesis. Although matrix components can regulate the process of angiogenesis by acting as a reservoir of various cytokines, it is not clear if extracellular matrix (ECM) can modulate the production and activity of angiogenic cytokines. Investigations were therefore carried out to study the influence of the basement membrane (BM) protein, laminin (Ln) on the activity of vascular endothelial growth factor (VEGF), the major angiogenic cytokine, using isolated human umbilical vein ECs (HUVECs) in culture. Analysis of the biochemical markers of angiogenesis confirmed proangiogenic effect of Ln. The levels of VEGF protein and mRNA were not different in cells maintained on Ln, collagen I or polylysine substrata. Chorioallantoic membrane assay using VEGF isolated from cell extracts however revealed that Ln increased its angiogenic potency. Immunoblotting and HPLC analysis showed considerable reduction in poly adenosyl ribosylation of VEGF associated with a significant decrease in the levels of NAD+, in cells maintained on Ln substrata. Further, a shift in the isoenzymic pattern of LDH towards the B rich forms and an upregulation of LDH B gene were observed in cells maintained on Ln. Ln modulates expression of LDH gene through alpha(6)beta(4) integrin mediated downstream signaling involving p38 mitogen activated protein kinases (MAPK) pathway. It thus appears that Ln can affect aerobic metabolism of ECs by modulating the expression of LDH isoenzymes resulting in a decrease in the level of NAD+ that can cause a reduction in the poly adenosyl ribosylation of VEGF altering its angiogenic potency.

Pathobiology of pulmonary hypertension

A variety of conditions can lead to the development of pulmonary arterial hypertension (PAH). Current treatments can improve symptoms and reduce the severity of the hemodynamic abnormality, but most patients remain quite limited, and deterioration in their condition necessitates a lung transplant. This review discusses current experimental and clinical studies that investigate the pathobiology of PAH. An emerging theme is the consideration of ways in which one might reverse the advanced occlusive structural changes in the pulmonary circulation causing PAH. The current debate concerning the role of regeneration through stem cells is presented. This review also highlights investigations in a number of laboratories relating the pathobiology of PAH to mutations causing loss of function of bone morphogenetic protein receptor II in patients with familial PAH, as well as sporadic cases.

Alpha6beta4 integrin and dystroglycan cooperate to stabilize the myelin sheath

Schwann cells integrate signals deriving from the axon and the basal lamina to myelinate peripheral nerves. Integrin alpha6beta4 is a laminin receptor synthesized by Schwann cells and displayed apposed to the basal lamina. alpha6beta4 integrin expression in Schwann cells is induced by axons at the onset of myelination, and rises in adulthood. The beta4 chain has a uniquely long cytoplasmic domain that interacts with intermediate filaments such as dystonin, important in peripheral myelination. Furthermore, alpha6beta4 integrin binds peripheral myelin protein 22, whose alteration causes the most common demyelinating hereditary neuropathy. All these data suggest a role for alpha6beta4 integrin in peripheral nerve myelination. Here we show that ablating alpha6beta4 integrin specifically in Schwann cells of transgenic mice does not affect peripheral nerve development, myelin formation, maturation, or regeneration. However, consistent with maximal expression in adult nerves, alpha6beta4 integrin-null myelin is more prone to abnormal folding with aging. When the laminin receptor dystroglycan is also ablated, major folding abnormalities occur, associated with acute demyelination in some peripheral nervous system districts. These data indicate that, similar to its role in skin, alpha6beta4 integrin confers stability to myelin in peripheral nerves.

Targeting vasculature in urologic tumors: mechanistic and therapeutic significance

Recent advances toward understanding the molecular mechanisms regulating cancer initiation and progression provide new insights into the therapeutic value of targeting tumor vascularity by interfering with angiogenic signaling pathways. The functional contribution of key angiogenic factors toward increased vascularity characterizing metastatic tumors and their therapeutic exploitation is considered in three major urologic malignancies, renal, bladder, and prostate cancer. With the realization that the success of the therapeutic efficacy of the various anti-angiogenic approaches for the treatment of urologic tumors has yet to be proven clinically, the challenge remains to select critical angiogenesis pathways that can be targeted for an individual tumor. Here we discuss the major mechanisms that support formation of vasculature in renal, bladder, and prostate tumors and the current results of targeting of specific molecules/regulators for therapeutic intervention against metastastic disease.

JNK signaling pathway is required for bFGF-mediated surface cadherin downregulation on HUVEC

Angiogenesis, the process of new blood vessel formation, is important in wound healing, inflammation, tumorigenesis and metastases. During this process, it is a critical step of the loosening of cellular interactions between endothelial cells, which are dependent on the architecture of adherens junction constructed by homophilic interactions of cell surface cadherins. Several studies suggested that the dynamic changes of cadherins are necessary during angiogenesis. However, the mechanism of cadherins regulation on endothelial cells requires further delineation. Here, we showed that basic fibroblast growth factor (bFGF), a pivotal pro-angiogenic factor, can downregulate typical cadherins (E-, N-, P- and VE-cadherin) expression on the surface of human umbilical vein endothelial cells (HUVECs) via FGF receptor 1 (FGFR1) signaling. The bFGF-mediated surface cadherin downregulation was significantly reversed only when the HUVECs were treated with JNK inhibitor (SP600125), but not ERK (PD98059) or p38 inhibitor (SB203580). Infecting HUVECs with a dominant negative H-Ras mutant (Ras(S17N)) interferes bFGF-mediated cadherin downregulation, and the result suggests that bFGF attenuates surface cadherin expression on HUVECs via FGFR1 and intracellular Ras-JNK signaling. However, after growth factors withdrawal, FGFR1 blockade or JNK inhibition for 16 h, cadherins were re-expressed on cell surface of HUVECs. But the mRNA or total protein of cadherins had no significant change, suggesting that the effect of bFGF on cadherin expression may work through a post-translational control. Our data first suggest that JNK participates in bFGF-mediated surface cadherin downregulation. Loss of surface cadherins may affect the cell-cell interaction between endothelial cells and facilitate angiogenesis.

bFGF influences human articular chondrocyte differentiation

BACKGROUND

The possible functional role of basic fibroblast growth factor (bFGF) in regulating the mitotic and metabolic activity of primary human articular chondrocytes was investigated.

METHODS

[EF1]Chondrocytes were enzymatically isolated from femoral head cartilage, and were cultured in vitro in monolayer. bFGF-dependent cell proliferation, production of collagen type II and aggrecan were monitored 10 days after isolation. Furthermore, effect of bFGF on cell cycle, cell morphology, and mRNA expression of integrins and chondrogenic markers determined by real time PCR were analyzed.

RESULTS

bFGF concentrations in supernatants of primary human articular chondrocytes peaked immediately after isolation and then declined. In a dose-dependent manner, bFGF enhanced cell amplification and viability. BFGF induced a decrease in the apoptotic cell population, while the number of proliferating cells remained unchanged. Supplementation of cell culture with bFGF reduced collagen type II mRNA by 49%, but increased expression of the integrin alpha(2) by 70%. bFGF did not significantly regulate the integrins alpha(1), alpha(5), alpha(10), alpha(v) and type I collagen. bFGF reduced the amount of collagen type II by 53%, which was correlated with diminished mRNA production. Monolayer cultured chondrocytes secreted significant amounts of aggrecan that decreased over time. Secretion of this cartilage-specific marker was further reduced by the addition of bFGF.

DISCUSSION

These findings highlight the potential role of bFGF as an endogenous chondrocyte mediator that can enhance cell amplification and regulate cell differentiation.

Transduction of beta3 integrin subunit cDNA confers on human keratinocytes the ability to adhere to gelatin

alphavbeta3 is a multiligand integrin receptor that interacts with fibrinogen (FG), fibrin (FB), fibronectin (FN), vitronectin (VN), and denatured collagen. We previously reported that cultured normal human keratinocytes, like in vivo keratinocytes, do not express alphavbeta3 on the cell surface, and do not adhere to and migrate on FG and FB. Furthermore, we reported that human keratinocytes transduced with beta3 integrin subunit cDNA by a retrovirus-mediated transduction method express alphavbeta3 on the cell surface and adhere to FG, FB, FN, and VN significantly compared with beta-galactosidase (beta-gal) cDNA-transduced keratinocytes (control). In this study, we determined whether these beta3 integrin subunit cDNA-transduced keratinocytes or normal human keratinocytes adhere to denatured collagen (gelatin) using a 1 h cell adhesion assay. beta3 cDNA-transduced keratinocytes adhered to gelatin, whereas no significant adhesion was observed with the control cells (beta-gal cDNA-transduced keratinocytes and normal human keratinocytes). The adhesion to gelatin was inhibited by LM609, a monoclonal antibody to alphavbeta3, and RGD peptides but not by normal mouse IgG1 nor RGE peptides. Thus, transduction of beta3 integrin subunit cDNA confers on human keratinocytes the ability to adhere to denatured collagen (gelatin) as well as to FG, FB, VN, and FN. Otherwise, normal human keratinocytes do not adhere to gelatin. These data support the idea that beta3 cDNA-transduced human keratinocytes can be a good material for cultured epithelium to achieve better take rate with acute or chronic wounds, in which FG, FB, and denatured collagen are abundantly present.

Integrin regulation by vascular endothelial growth factor in human brain microvascular endothelial cells: role of alpha6beta1 integrin in angiogenesis

The precise role of vascular endothelial growth factor (VEGF) in regulating integrins in brain microvascular endothelial cells is unknown. Here, we analyzed VEGF effects on integrin expression and activation in human brain microvascular endothelial cells (HBMECs). Using human cDNA arrays and ribonuclease (RNase) protection assays, we observed that VEGF up-regulated the mRNA expression of alpha(6) integrin in HBMECs. VEGF significantly increased alpha(6)beta(1) integrin expression, but not alpha(6)beta(4) integrin expression in these cells. Specific down-regulation of alpha(6) integrin expression by small interfering RNA (siRNA) oligonucleotides inhibited both the capillary morphogenesis of HBMECs and their adhesion and migration. Additionally, VEGF treatment resulted in activation of alpha(6)beta(1) integrins in HBMECs. Functional blocking of alpha(6) integrin with its specific antibody inhibited the VEGF-induced adhesion and migration as well as in vivo angiogenesis, and markedly suppressed tumor angiogenesis and breast carcinoma growth in vivo. Thus, VEGF can modulate angiogenesis via increased expression and activation of alpha(6)beta(1) integrins, which may promote VEGF-driven tumor angiogenesis in vivo.

Induction of complete regressions of oncogene-induced breast tumors in mice

Over the past decade, mouse models of cancer have come to resemble human disease much more closely than simple subcutaneous or orthotopic systems. Intervention strategies that work on these new model systems are more likely to have an impact clinically. We have shown recently that antiangiogenic stress imposed by loss of Id protein in endothelial progenitor cells results in dramatic central necrosis in breast tumors initiated in mice by overexpression of the her2/neu oncogene. Tumor cells remain viable at the periphery, perhaps via the hypoxic response pathway which allows the lesions to expand. Inhibition of this pathway by the inactivation of the Hif-1alpha chaperone Hsp90 in combination with antiangiogenic stress leads to the first reported complete regression of these aggressive breast tumors.

Multiple myeloma in a murine syngeneic model:modulation of growth and angiogenesis by a monoclonal antibody to kininogen

Multiple myeloma (MM), a B-cell malignancy characterized by proliferation of monoclonal plasma cells remains incurable. Murine plasma cell tumors share common features with human MM. We used two cell lines (B38 and C11C1) derived from P3X63Ag8 myeloma cells. The new cell lines were implanted subcutaneously in the strain of origin (Balb/c mice) and used as a model to monitor the effects of C11C1 monoclonal antibody (mAb) to kininogen (HK). We assessed their behavior by intraperitoneal and subcutaneous implantation, by implanting them together and by treating B38-MM with purified mAb C11C1. We evaluated growth, microvascular density (MVD), and cellular expression of urokinase-type plasminogen activator-receptor (uPAR), fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor (VEGF), bradykinin-1 receptor (B1R), bradykinin-2 receptor (B2R) and HK. We found that both MM-cell-lines are uPAR positive, that mAb C11C1 inhibits its own tumor growth in vivo, slows down B38-MM growth rate when both MM are implanted together and when mAb C11C1 is injected intraperitoneally. MAb C11C1-treated-MM showed decreased MVD and HK binding in vivo without FGF-2, B1R or B2R expression changes. We propose that the B38-extramedullary-myeloma-model is a useful tool to study the interactions of this hematopoietic tumor and its environment and that mAb C11C1 may improve the efficacy of conventional MM treatment with minimal side effects.

Growth factor- and heparin-dependent regulation of constitutive and agonist-mediated human endothelial barrier function

We report functional differences in constitutive and agonist-mediated endothelial barrier function between cultured primary and Clonetics human umbilical vein endothelial cells (pHUVEC and cHUVEC) grown in soluble growth factors and heparin. Basal transendothelial resistance (TER) was much lower in pHUVEC than in cHUVEC grown in medium supplemented with growth factors, such as basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and human epithelial growth factor (EGF), and heparin. On the basis of a numerical model of TER, the increased basal TER in cHUVEC was due to effects on cell-matrix adhesion and membrane capacitance. Heparin and bFGF increased constitutive TER in cultured pHUVEC, and heparin mediated additional increases in constitutive TER in pHUVEC supplemented with bFGF. EGF attenuated bFGF-mediated increases in TER. On the basis of the numerical model, in contrast to cHUVEC, heparin and bFGF augmented TER through effects on cell-cell adhesion and membrane capacitance in pHUVEC. Thrombin mediated quantitatively greater amplitude and a more sustained decline in TER in cultured cHUVEC than pHUVEC. Thrombin-mediated barrier dysfunction was attenuated in pHUVEC conditioned in EGF in the presence or absence of heparin. Thrombin-mediated barrier dysfunction was also attenuated when monolayers were exposed to low concentrations of heparin and further attenuated in the presence of bFGF. cAMP stimulation mediated differential attenuation of thrombin-mediated barrier dysfunction between pHUVEC and cHUVEC. VEGF displayed differential effects in TER in serum-free medium. Taken together, these data demonstrate marked differential regulation of constitutive and agonist-mediated endothelial barrier function in response to mitogens and heparin stimulation.

Regulative Mechanisms of Chondrocyte Adhesion

Interaction between chondrocytes and extracellular matrix is considered a key factor in the generation of grafts for matrix-associated chondrocyte transplantation. Therefore, our objective was to study the influence of differentiation status on cellular attachment. Adhesion of chondrocytes to collagen type II increased after removal from native cartilage up to the third day in monolayer in a dose-dependent manner. Following dedifferentiation after the second passage, adhesion to collagen types I (-84%) and II (-46%) decreased, whereas adhesion to fibrinogen (+59%) and fibronectin (+43%) increased. A cartilage construct was developed based on a clinically established collagen type I scaffold. In this matrix, more than 80% of the cells could be immobilized by mechanisms of adhesion, filtration, and cell entrapment. Confocal laser microscopy revealed focal adhesion sites as points of cell-matrix interaction, as well as collagen type II expression in the cartilage graft after two weeks of in vitro cultivation. Basic fibroblast growth factor (bFGF) treated chondrocytes showed increased adhesion to collagen types I and II, fibronectin, and fibrinogen. Attachment to these investigated proteins significantly enhanced cell proliferation. Matrix design in cartilage engineering must meet the biological demands of amplified cells, because adhesion of chondrocytes depends on their differentiation status and is regulated by bFGF.

FGF-2 binding to fibrin(ogen) is required for augmented angiogenesis

We have shown previously that fibrin(ogen) binds fibroblast growth factor 2 (FGF-2) and potentiates stimulation of endothelial-cell (EC) proliferation. We have now used 2 FGF-2 mutants differing only in the 5 residues constituting the binding site to characterize the importance of this interaction in angiogenesis. The nonbinding (2212) and binding (221*2) mutants stimulated EC proliferation by 2.2 +/- 0.4-fold and 2.9 +/- 0.3-fold over control, respectively, and both were similar to wild-type (wt) FGF-2 (2.5 +/- 0.3-fold). Proliferation was augmented by fibrinogen to 5.3 +/- 1.2-fold and 4.8 +/- 0.8-fold with wtFGF-2 and 221*2, whereas no augmentation occurred with 2212 and fibrinogen. Using a placental explant model in a fibrin matrix, wtFGF-2 resulted in 2.6 +/- 0.9-fold more growth over control, and 221*2 increased growth 3.3 plus or minus 0.9-fold. Vessel outgrowth with 2212 was minimal and comparable to control. Similarly, fibrinogen potentiated wtFGF-2 or 221*2-mediated angiogenesis in the chicken chorioallantoic membrane model. In a mouse Matrigel implant model, fibrinogen significantly increased angiogenesis with either wtFGF-2 or 221*2, whereas there was no augmentation with 2212. These results demonstrate that binding of FGF-2 to fibrin(ogen) mediated by the 5-residue FGF-2-fibrin(ogen) interactive site is required for augmented angiogenesis.

Immunopathogenesis of conjunctival remodelling in vernal keratoconjunctivitis

PURPOSE

To study the processes involved in mediating conjunctival remodelling in vernal keratoconjunctivitis (VKC) by investigating the expression of integrin receptors, epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), transforming growth factor-beta(TGF-beta), basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), and Ki67 antigen, which is a marker for cell proliferation.

METHODS

Conjunctival biopsy specimens from 16 patients with active VKC and nine control subjects were studied by immunohistochemical techniques using monoclonal and polyclonal antibodies directed against the integrin alpha3 and alpha6 subunits, EGFR, VEGF, TGF-beta, bFGF, PDGF, and Ki67 antigen. The phenotype of inflammatory cells expressing growth factors was examined by double immunohistochemistry.

RESULTS

In the normal conjunctiva, very weak immunoreactivity was observed for EGFR and VEGF in epithelial cells, and for alpha3 and alpha6 integrin subunits on basal epithelial cells, and on vascular endothelial cells in the upper substantia propria. There was no immunoreactivity for the other antibodies. In VKC specimens, strong staining for alpha3 and alpha6 integrin subunits was observed on the membranes of basal and suprabasal epithelial cells, and all vascular endothelial cells. Immunoreactivity for Ki67 antigen was observed in the nuclei of the basal and suprabasal epithelial cells. Strong immunoreactivity was observed for EGFR in the deeper layers of the epithelium, and for VEGF in all epithelial cells. Inflammatory cells expressing EGFR, VEGF, TGF-beta, bFGF, and PDGF were noted in 8, 9, 11, 10, and 10 specimens, respectively. The majority of inflammatory cells expressing growth factors were eosinophils (45+/-4%) and monocytes/macrophages (35+/-4%).

CONCLUSIONS

Chronic conjunctival inflammation in VKC is associated with increased staining of alpha3, and alpha6 integrin subunits, EGFR, VEGF, TGF-beta, bFGF, and PDGF that might mediate conjunctival remodelling.

Deletion of Mouse Embryo Fibroblast N-Acetylglucosaminyltransferase V Stimulates α5β1 Integrin Expression Mediated by the Protein Kinase C Signaling Pathway

An N-linked glycan often increased during oncogenic transformation contains beta(1,6)-linked GlcNAc, synthesized by the N-acetylglucosaminyltransferase V (GnT-V). The progression of polyoma middle T-antigen oncoprotein-induced mammary carcinomas in GnT-V null mice was significantly retarded compared with that observed in wild-type mice. The matrix adhesion of mouse embryonic fibroblasts (MEF) from GnT-V null and wild-type mice was investigated to understand the mechanism by which deletion of GnT-V could retard tumor progression. GnT-V null MEF displayed enhanced adhesion to and spreading on fibronectin-coated plates with concomitant inhibition of cell migration. GnT-V null MEF also showed increased focal adhesion kinase tyrosine phosphorylation, consistent with decreased cell motility on fibronectin-coated plates. Expression of GnT-V cDNA in the null MEF reversed these abnormal characteristics, indicating the direct involvement of N-glycosylation events in these phenotypic changes. The alpha5beta1 fibronectin receptors exhibited increased clustering on the null MEF cell surfaces, consistent with previous studies that observed less integrin clustering in cells overexpressing GnT-V. Most surprisingly, GnT-V null MEF displayed increased expression levels of both alpha5 and beta1 subunits in lysates and on the cell surface. Increased alpha5beta1 expression in the null MEF was because of increased alpha5beta1 transcript levels that declined after re-expression of GnT-V cDNA, confirming that increased alpha5beta1 expression in null MEF was because of changes in GnT-V expression. The increased null MEF transcripts were shown to be caused at least in part by increased integrin promoter activity. Moreover, increased alpha5beta1 integrin transcripts in GnT-V null MEF were not due to a differential response to fibronectin; rather, they appeared to be mediated by activation of a protein kinase C signaling pathway. These results demonstrate that deletion of MEF GnT-V resulted in enhanced integrin clustering and activation of alpha5beta1 transcription by protein kinase C signaling, which in turn up-regulated levels of cell surface alpha5beta1 fibronectin receptors that resulted in increased matrix adhesion and inhibition of migration.

Fibroblast growth factor/fibroblast growth factor receptor system in angiogenesis

Fibroblast growth factors (FGFs) are a family of heparin-binding growth factors. FGFs exert their pro-angiogenic activity by interacting with various endothelial cell surface receptors, including tyrosine kinase receptors, heparan-sulfate proteoglycans, and integrins. Their activity is modulated by a variety of free and extracellular matrix-associated molecules. Also, the cross-talk among FGFs, vascular endothelial growth factors (VEGFs), and inflammatory cytokines/chemokines may play a role in the modulation of blood vessel growth in different pathological conditions, including cancer. Indeed, several experimental evidences point to a role for FGFs in tumor growth and angiogenesis. This review will focus on the relevance of the FGF/FGF receptor system in adult angiogenesis and its contribution to tumor vascularization.

Effect of an oversulfated exopolysaccharide on angiogenesis induced by fibroblast growth factor-2 or vascular endothelial growth factor in vitro

The aim of this study was to determine the angiogenic properties of an oversulfated exopolysaccharide (OS-EPS) derived from a polysaccharide secreted by the mesophilic bacterium Alteromonas infernus. We compared the effect of this OS-EPS with that of a non-oversulfated exopolysaccharide (EPS) on human umbilical vein endothelial cell (HUVEC) proliferation, migration and differentiation induced by basic fibroblast growth factor (FGF-2) or vascular endothelial growth factor (VEGF). OS-EPS enhanced HUVEC proliferation by 58% when used alone, and by respectively 30% and 70% in the presence of FGF-2 and VEGF. OS-EPS also increased the density of tubular structures on Matrigel in the presence of FGF-2 or VEGF. Vascular tube formation was related to alpha(6) integrin subunit expression, which was enhanced by 50% in the presence of the growth factors. Indeed, a monoclonal anti-alpha(6) blocking antibody abolished this vascular tube formation. EPS had no effect in any of the experimental conditions, underlying the importance of sulfation in the angiogenic effects of exopolysaccharide. By potentiating the angiogenic activity of FGF-2 and/or VEGF, OS-EPS, which possesses low anticoagulant activity and thus a low hemorrhagic risk, could potentially be used to accelerate vascular wound healing or to promote the growth of collateral blood vessels in ischemic tissues.