Interaction of angiogenic basic fibroblast growth factor with endothelial cell heparan sulfate proteoglycans. Biological implications in neovascularization

Continuous negative-pressure wound therapy improves the survival rate of skin grafts and shortens the time required for skin graft survival

BACKGROUND

The effectiveness of negative-pressure wound therapy (NPWT) in skin graft fixation has been demonstrated in several clinical studies. However, in vitro and in vivo studies on skin graft fixation with NPWT have been scarce. In this in vivo study, we aimed to determine whether NPWT fixation enhances skin graft survival and how it contributes to improving skin graft survival biologically.

MATERIALS AND METHODS

We harvested skin from the bilateral abdominal wall of 88 mice after anesthetizing them. Full-thickness skin grafts (FTSGs) were performed on contralateral harvest sites, and grafts were fixed using NPWT (continuous and intermittent modes), conventional compression methods, and wrapping with polyurethane foam as a control group. On days 5 and 10 of grafting, the survival rates of the FTSGs were evaluated. Immunohistopathological analysis and measurement of the expression levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-2), and epidermal growth factor (EGF) were performed.

RESULTS

The survival rates of FTSG in the continuous NPWT group were significantly higher than those in the other groups. The number of capillaries in the dermis was significantly higher in the continuous NPWT group than in the other groups. In the wound bed, VEGF levels were significantly higher in both NPWT groups than in the other groups.

CONCLUSION

Continuous NPWT increases the survival rate of FTSGs and shortens the duration of skin graft survival.

Polysaccharides to combat viruses (Covid-19) and microbes: New updates

COVID-19, which is speedily distributed across the world and presents a significant challenge to public health, is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Following MERS coronavirus (MERS-CoV) and SARS, this is the third severe coronavirus outbreak in less than 20 years. To date, there are no exact agents and vaccines available for the treatment of COVID-19 that are clinically successful. Antimicrobial medications are effective in controlling infectious diseases. However, the extensive use of antibiotics makes microbes more resistant to drugs and demands novel bioactive agents' development. Polysaccharides are currently commonly used in the biomedical and pharmaceutical industries for their remarkable applications. Polysaccharides appear to have a wide range of anti-virus (anti-coronavirus) and antimicrobial applications. Polysaccharides are able to induce bacterial cell membrane disruption as they demonstrate potency in binding onto the surfaces of microbial cells. Here, the antiviral mechanisms of such polysaccharides and their success in the application of antiviral infections are reviewed. Additionally, this report provides a summary of current advancements of well-recognized polysaccharides as antimicrobial and anti-biofilm agents.

Prognostic and Therapeutic Role of Angiogenic Microenvironment in Thyroid Cancer

Simple Summary

Angiogenesis is an essential event for the progression of solid tumors and is promoted by angiogenic cytokines released in the tumor microenvironment by neoplastic and stromal cells. Over the last 20 years, the role of the microenvironment and the implication of several angiogenic factors in tumorigenesis of solid and hematological neoplasms have been widely studied. The tumor microenvironment has also been well-defined for thyroid cancer, clarifying the importance of angiogenesis in cancer progression, spread, and metastasis. Furthermore, recent studies have evaluated the association of circulating angiogenic factors with the clinical outcomes of differentiated thyroid cancer, potentially providing noninvasive, low-cost, and safe tests that can be used in screening, diagnosis, and follow-up. In this review, we highlight the mechanisms of action of these proangiogenic factors and their different molecular pathways, as well as their applications in the treatment and prognosis of thyroid cancer.

Abstract

Thyroid cancer is the most common endocrine malignancy, with a typically favorable prognosis following standard treatments, such as surgical resection and radioiodine therapy. A subset of thyroid cancers progress to refractory/metastatic disease. Understanding how the tumor microenvironment is transformed into an angiogenic microenvironment has a role of primary importance in the aggressive behavior of these neoplasms. During tumor growth and progression, angiogenesis represents a deregulated biological process, and the angiogenic switch, characterized by the formation of new vessels, induces tumor cell proliferation, local invasion, and hematogenous metastases. This evidence has propelled the scientific community’s effort to study a number of molecular pathways (proliferation, cell cycle control, and angiogenic processes), identifying mediators that may represent viable targets for new anticancer treatments. Herein, we sought to review angiogenesis in thyroid cancer and the potential role of proangiogenic cytokines for risk stratification of patients. We also present the current status of treatment of advanced differentiated, medullary, and poorly differentiated thyroid cancers with multiple tyrosine kinase inhibitors, based on the rationale of angiogenesis as a potential therapeutic target.

Syndecan-1 downregulates syndecan-4 expression by suppressing the ERK1/2 and p38 MAPK signaling pathways in cultured vascular endothelial cells

Syndecan-1 and syndecan-4 are members of the syndecan family of transmembrane heparan sulfate proteoglycans. Vascular endothelial cells synthesize both species of proteoglycans and use them to regulate the blood coagulation-fibrinolytic system and their proliferation via their heparin-like activity and FGF-2 binding activity, respectively. However, little is known about the crosstalk between the expressions of the proteoglycan species. Previously, we reported that biglycan, a small leucine-rich dermatan sulfate proteoglycan, intensifies ALK5-Smad2/3 signaling by TGF-β₁ and downregulates syndecan-4 expression in vascular endothelial cells. In the present study, we investigated the crosstalk between the expressions of syndecan-1 and other proteoglycan species (syndecan-4, perlecan, glypican-1, and biglycan) in bovine aortic endothelial cells in a culture system. These data suggested that syndecan-1 downregulated syndecan-4 expression by suppressing the endogenous FGF-2-dependent ERK1/2 pathway and FGF-2-independent p38 MAPK pathway in the cells. Moreover, this crosstalk was a one-way communication from syndecan-1 to syndecan-4, suggesting that syndecan-4 compensated for the reduced activity in the regulation of vascular endothelial cell functions caused by the decreased expression of syndecan-1 under certain conditions.

Heparan sulfate proteoglycan promotes fibroblast growth factor-2 function for ischemic heart repair

It is well known that the basic fibroblast growth factor (bFGF) promotes angiogenesis after myocardial infarction (MI), but its biological functions decrease in the event of diffusion, enzymolysis, and weak binding with co-receptors in vivo. Heparan sulfate proteoglycans (HSPG) are a major component of extracellular matrices and have been shown to regulate a wide range of cellular functions and bioprocesses by acting as a co-receptor for bFGF and affecting its bioactivities. However, the influence of HSPG on the function of bFGF after myocardial infarction is unknown. Here, exogenous HSPG along with bFGF was injected into the hearts of rats to deliver the angiogenic growth factor for ischemic heart repair following induced MI. The specific binding of HSPG with bFGF protein was demonstrated, which was about 6-fold stronger than the binding of bFGF with heparin. The biological mechanisms of HSPG binding with bFGF were further studied by cell adhesion assay, and assays of bFGF and matrix metalloproteinase 2 (MMP2) activities demonstrated that HSPG enhances cell adhesion, promotes the bioactivity of bFGF in angiogenesis, and protects bFGF from enzymolysis. Our results indicate that HSPG has potential clinical utility as a delivery agent for heparin-binding growth factors. Additionally, HSPG shows high binding affinities with different ECM proteins which also help to anchor bFGF to heart tissue. Therefore, extracellular proteins that mimic the bio-scaffold of the extracellular matrix could promote the activities of bFGF to facilitate ischemic heart repair.

Bioactive polysaccharides from natural resources including Chinese medicinal herbs on tissue repair

BACKGROUND

Functional polysaccharides can be derived from plants (including herbs), animals and microorganisms. They have been widely used in a broad of biomedical applications, such as immunoregulatory agents or drug delivery vehicles. In the past few years, increasing studies have started to develop natural polysaccharides-based biomaterials for various applications in tissue engineering and regenerative medicine.

MAIN BODY

We discuss in this article the emerging applications of natural polysaccharides-particularly those derived from Chinese medicine-for wound healing. First, we introduce natural polysaccharides of three natural sources and their biological activities. Then, we focus on certain natural polysaccharides with growth factor-binding affinities and their inspired polymeric tools, with an emphasis on how these polysaccharides could possibly benefit wound healing. Finally, we report the latest progress in the discovery of polysaccharides from Chinese medicinal herbs with identified activities favouring tissue repair.

CONCLUSION

Natural polysaccharides with clearly elucidated compositions/structures, identified cellular activities, as well as desirable physical properties have shown the potential to serve as therapeutic tools for tissue regeneration.

Attenuation of corneal neovascularization by topical low-molecular-weight heparin-taurocholate 7 without bleeding complication

AIM

To investigate the antiangiogenic effects and safety of topically administered low-molecular-weight heparin-taurocholate 7 (LHT7) on corneal neovascularization (CoNV).

METHODS

Twenty-four Sprague-Dawley rats were randomly distributed into four groups of six rats each. The central corneas were cauterized using a silver/potassium nitrate solution. From 2d after cauterization, 12.5 mg/mL (low LHT7 group) or 25 mg/mL (high LHT7 group) LHT7 was topically administered three times daily; 12.5 mg/mL bevacizumab was topically administered as positive control (bevacizumab) group, with normal saline (NS) administered as negative control (NS group). The corneas were digitally photographed to calculate the CoNV percentage from the neovascularized corneal area at 1 and 2wk.

RESULTS

The 4 study groups did not have different CoNV percentages at 1wk after injury (P>0.05). However, the low LHT, high LHT, and bevacizumab groups had significantly lower CoNV percentages than the NS group at 2wk (all P<0.05). No significant differences in CoNV percentage were found among the low LHT, high LHT, and bevacizumab groups (all P>0.05). All groups except the NS group had lower CoNV percentages at 2wk post-injury than the levels observed at 1wk (all P<0.05).

CONCLUSION

Topically-administered LHT7 inhibited CoNV without complication after chemical cauterization in the rat.

Molecular and clinical significance of fibroblast growth factor 2 (FGF2 /bFGF) in malignancies of solid and hematological cancers for personalized therapies

Fibroblast growth factor (FGF) signaling is essential for normal and cancer biology. Mammalian FGF family members participate in multiple signaling pathways by binding to heparan sulfate and FGF receptors (FGFR) with varying affinities. FGF2 is the prototype member of the FGF family and interacts with its receptor to mediate receptor dimerization, phosphorylation, and activation of signaling pathways, such as Ras-MAPK and PI3K pathways. Excessive mitogenic signaling through the FGF/FGFR axis may induce carcinogenic effects by promoting cancer progression and increasing the angiogenic potential, which can lead to metastatic tumor phenotypes. Dysregulated FGF/FGFR signaling is associated with aggressive cancer phenotypes, enhanced chemotherapy resistance and poor clinical outcomes. In vitro experimental settings have indicated that extracellular FGF2 affects proliferation, drug sensitivity, and apoptosis of cancer cells. Therapeutically targeting FGF2 and FGFR has been extensively assessed in multiple preclinical studies and numerous drugs and treatment options have been tested in clinical trials. Diagnostic assays are used to quantify FGF2, FGFRs, and downstream signaling molecules to better select a target patient population for higher efficacy of cancer therapies. This review focuses on the prognostic significance of FGF2 in cancer with emphasis on therapeutic intervention strategies for solid and hematological malignancies.

Designing Biopolymer Microthreads for Tissue Engineering and Regenerative Medicine

Native tissue structures possess elaborate extracellular matrix (ECM) architectures that inspire the design of fibrous structures in the field of regenerative medicine. We review the literature with respect to the successes and failures, as well as the future promise of biopolymer microthreads as scaffolds to promote endogenous and exogenous tissue regeneration. Biomimetic microthread tissue constructs have been proposed for the functional regeneration of tendon, ligament, skeletal muscle, and ventricular myocardial tissues. To date, biopolymer microthreads have demonstrated promising results as materials to recapitulate the hierarchical structure of simple and complex tissues and well as biochemical signaling cues to direct cell-mediated tissue regeneration. Biopolymer microthreads have also demonstrated exciting potential as a platform technology for the targeted delivery of stem cells and therapeutic molecules. Future studies will focus on the design of microthread-based tissue analogs that strategically integrate growth factors and progenitor cells to temporally direct cell-mediated processes that promote enhanced functional tissue regeneration.

Therapeutic Potential of Anti-Angiogenic Multitarget N,O-Sulfated E. Coli K5 Polysaccharide in Diabetic Retinopathy

Vascular endothelial growth factor (VEGF) blockers have been developed for the treatment of proliferative diabetic retinopathy (PDR), the leading cause of visual impairments in the working-age population in the Western world. However, limitations to anti-VEGF therapies may exist because of the local production of other proangiogenic factors that may cause resistance to anti-VEGF interventions. Thus, novel therapeutic approaches targeting additional pathways are required. Here, we identified a sulfated derivative of the Escherichia coli polysaccharide K5 [K5-N,OS(H)] as a multitarget molecule highly effective in inhibiting VEGF-driven angiogenic responses in different in vitro, ex vivo, and in vivo assays, including a murine model of oxygen-induced retinopathy. Furthermore, K5-N,OS(H) binds a variety of heparin-binding angiogenic factors upregulated in PDR vitreous humor besides VEGF, thus inhibiting their biological activity. Finally, K5-N,OS(H) hampers the angiogenic activity exerted in vitro and in vivo by human vitreous fluid samples collected from patients with PDR. Together, the data provide compelling experimental evidence that K5-N,OS(H) represents an antiangiogenic multitarget molecule with potential implications for the therapy of pathologic neovessel formation in the retina of patients with PDR.

Heparin/Heparan sulfate proteoglycans glycomic interactome in angiogenesis: biological implications and therapeutical use

Angiogenesis, the process of formation of new blood vessel from pre-existing ones, is involved in various intertwined pathological processes including virus infection, inflammation and oncogenesis, making it a promising target for the development of novel strategies for various interventions. To induce angiogenesis, angiogenic growth factors (AGFs) must interact with pro-angiogenic receptors to induce proliferation, protease production and migration of endothelial cells (ECs). The action of AGFs is counteracted by antiangiogenic modulators whose main mechanism of action is to bind (thus sequestering or masking) AGFs or their receptors. Many sugars, either free or associated to proteins, are involved in these interactions, thus exerting a tight regulation of the neovascularization process. Heparin and heparan sulfate proteoglycans undoubtedly play a pivotal role in this context since they bind to almost all the known AGFs, to several pro-angiogenic receptors and even to angiogenic inhibitors, originating an intricate network of interaction, the so called "angiogenesis glycomic interactome". The decoding of the angiogenesis glycomic interactome, achievable by a systematic study of the interactions occurring among angiogenic modulators and sugars, may help to design novel antiangiogenic therapies with implications in the cure of angiogenesis-dependent diseases.

Cross-talk between endothelial and tumor cells via basic fibroblast growth factor and vascular endothelial growth factor signaling promotes lung cancer growth and angiogenesis

The present study aimed to investigate the origin and potential mechanisms of angiogenesis in lung cancer cells. Normal endothelial cells (ECs) were isolated from human umbilical vein ECs (HUVECs) and cultured. The human lung cancer A549 cell line was also used. The cross-talk model between the HUVECs and the A549 cell line was constructed in vitro using a Millicell co-culture system. Cluster of differentiation (CD)31 and CD146 were selected as markers of the HUVECs. CD105 was used as a marker of activated blood vessel ECs in the tumor microenvironment and glucose-regulated protein-78 (GRP-78) was used as a biomarker of the A549 cells. The four markers were detected by immunofluorescence, and the mean optical density was calculated. The growth curves were constructed using the cell proliferation reagent, WST-1. The expression of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in the media was measured using an ELISA. The average proliferation rates of the co-cultured HUVECs and A549 cells were significantly higher than those observed in the control groups. The fluorescence intensity of CD105 expression in the co-cultured HUVECs was higher than that in the control group. The fluorescence intensity of GRP-78 in the co-cultured A549 cells was higher than that in the A549 cells cultured alone. The average expression levels of VEGF and bFGF in the co-cultured model were higher than in the control groups. Therefore, it was hypothesized that cancer cells may induce the differentiation of normal ECs into vascular ECs via the secretion of VEGF and bFGF. Furthermore, vascular ECs can affect the proliferation and differentiation of cancer cells.

Angiogenic growth factors interactome and drug discovery: The contribution of surface plasmon resonance

Angiogenesis is implicated in several pathological conditions, including cancer, and in regenerative processes, including the formation of collateral blood vessels after stroke. Physiological angiogenesis is the outcome of a fine balance between the action of angiogenic growth factors (AGFs) and anti-angiogenic molecules, while pathological angiogenesis occurs when this balance is pushed toward AGFs. AGFs interact with multiple endothelial cell (EC) surface receptors inducing cell proliferation, migration and proteases upregulation. On the contrary, free or extracellular matrix-associated molecules inhibit angiogenesis by sequestering AGFs (thus hampering EC stimulation) or by interacting with specific EC receptors inducing apoptosis or decreasing responsiveness to AGFs. Thus, angiogenesis results from an intricate network of interactions among pro- and anti-angiogenic molecules, EC receptors and various modulators. All these interactions represent targets for the development of pro- or anti-angiogenic therapies. These aims call for suitable technologies to study the countless interactions occurring during neovascularization. Surface plasmon resonance (SPR) is a label-free optical technique to study biomolecular interactions in real time. It has become the golden standard technology for interaction analysis in biomedical research, including angiogenesis. From a survey of the literature it emerges that SPR has already contributed substantially to the better understanding of the neovascularization process, laying the basis for the decoding of the angiogenesis "interactome" and the identification of "hub molecules" that may represent preferential targets for an efficacious modulation of angiogenesis. Here, the still unexploited full potential of SPR is enlightened, pointing to improvements in its use for a deeper understanding of the mechanisms of neovascularization and the identification of novel anti-angiogenic drugs.

Subconjunctival injection of low-molecular-weight heparin-taurocholate 7 inhibits corneal neovascularization

PURPOSE

To evaluate the effects of a subconjunctival injection of low-molecular-weight heparin-taurocholate 7 (LHT7) on corneal neovascularization (CoNV) in rats.

METHODS

Twenty-four Sprague-Dawley rats were divided into 4 groups of 6 animals each. Corneal centers were cauterized by the application of a silver/potassium nitrate solution for 8 seconds. Either 0.02 or 0.04 mL of 25 mg/mL of LHT7 (low- and high-LHT7 groups, respectively) was subconjunctivally injected on days 2 and 4 after the cauterization was done; 0.02 mL of 25 mg/mL of bevacizumab was injected into rats in the positive control group, with normal saline (NS) being administered to a negative control group. Digital photographs of the cornea were taken 1 and 2 weeks later to calculate the percentage of CoNV using the area of the neovascularized cornea. To compare the differences in CoNV between weeks 1 and 2, the change in CoNV was calculated by subtracting the percentage of CoNV at 1 week from that at 2 weeks.

RESULTS

The percentage of CoNV did not differ among the 4 groups either 1 or 2 weeks after the cauterization (P > 0.05). In all groups except the NS group, the percentage of CoNV significantly decreased at 2 weeks compared with that at 1 week (all P < 0.05). Moreover, the changes of CoNV in the high-LHT7 and bevacizumab groups significantly decreased compared with that in the NS group (all P < 0.05). Two corneal stromal hemorrhages occurred, 1 in each LHT7 group.

CONCLUSIONS

Despite complications, including corneal stromal hemorrhage, subconjunctival injection of LHT7 attenuated CoNV after chemical cauterization.

Fibroblast growth factor 2 involved in the pathogenesis of synovial chondromatosis of temporomandibular joint

BACKGROUND

Synovial chondromatosis (SC) of temporomandibular joint (TMJ) is a rare proliferative disorder characterized by the formation of cartilaginous or osteocartilaginous nodules in synovium and joint space. Fibroblast growth factor 2 (FGF-2) is frequently applied in chondrogenic differentiation assays. Therefore, we hypothesized that FGF-2 might involved in the pathogenesis of SC.

METHODS

SC synovium and loose bodies (LBs) specimens were observed by histological and immunohistochemical methods. Real-time PCR was conducted for comparing genes expressions in SC and normal synovium. SC synoviocytes were stimulated by FGF-2 in the presence or absence of its antagonist long pentraxin-3 (PTX3) for 6 days. Real-time PCR and alkaline phosphatase (ALP) activity were performed to examine the effects exerted by FGF-2 and PTX3.

RESULTS

SC synovium, no matter facing the articular cavity or covering LB, was characterized by increased quantity of synoviocytes and blood vessels. FGF-2 was expressed in chondrocytes and fibroblast-like cells of LBs, and the wall of blood vessels. Expressions of chondrogenic genes (Sox9 and Wnt-4), osteogenic genes (Foxc2), FGF-2, and VEGF-A mRNA were significantly higher in SC synovium than that of the control group. The stimulation of FGF-2 on SC synoviocytes increased ALP activity and expressions of chondrogenic genes (Sox9, Col2α1, and Aggrecan), osteogenic genes (Foxc2, osteocalcin, and Col1α1), and VEGF-A, but PTX3 inhibited these effects.

CONCLUSION

FGF-2 was responsible for the formation of cartilaginous loose bodies and involved in the pathogenesis of SC.

Molecular interaction studies of HIV-1 matrix protein p17 and heparin: identification of the heparin-binding motif of p17 as a target for the development of multitarget antagonists

Once released by HIV(+) cells, p17 binds heparan sulfate proteoglycans (HSPGs) and CXCR1 on leukocytes causing their dysfunction. By exploiting an approach integrating computational modeling, site-directed mutagenesis of p17, chemical desulfation of heparin, and surface plasmon resonance, we characterized the interaction of p17 with heparin, a HSPG structural analog, and CXCR1. p17 binds to heparin with an affinity (K(d) = 190 nm) that is similar to those of other heparin-binding viral proteins. Two stretches of basic amino acids (basic motifs) are present in p17 N and C termini. Neutralization (Arg→Ala substitution) of the N-terminal, but not of the C-terminal basic motif, causes the loss of p17 heparin-binding capacity. The N-terminal heparin-binding motif of p17 partially overlaps the CXCR1-binding domain. Accordingly, its neutralization prevents also p17 binding to the chemochine receptor. Competition experiments demonstrated that free heparin and heparan sulfate (HS), but not selectively 2-O-, 6-O-, and N-O desulfated heparins, prevent p17 binding to substrate-immobilized heparin, indicating that the sulfate groups of the glycosaminoglycan mediate p17 interaction. Evaluation of the p17 antagonist activity of a panel of biotechnological heparins derived by chemical sulfation of the Escherichia coli K5 polysaccharide revealed that the highly N,O-sulfated derivative prevents the binding of p17 to both heparin and CXCR1, thus inhibiting p17-driven chemotactic migration of human monocytes with an efficiency that is higher than those of heparin and HS. Here, we characterized at a molecular level the interaction of p17 with its cellular receptors, laying the basis for the development of heparin-mimicking p17 antagonists.

HIV-1 matrix protein p17 promotes angiogenesis via chemokine receptors CXCR1 and CXCR2

Vascular diseases supported by aberrant angiogenesis have increased incidence in HIV-1-infected patients. Several data suggest that endothelium dysfunction relies on action of HIV-1 proteins rather than on a direct effect of the virus itself. The HIV-1 matrix protein p17 is known to deregulate the biological activity of different immune cells. Recently, p17 was found to mimic IL-8 chemokine activity by binding to the IL-8 receptor CXCR1. Here we show that p17 binds with high affinity to CXCR2, a CXCR1-related receptor, and promotes the formation of capillary-like structures on human endothelial cells (ECs) by interacting with both CXCR1 and CXCR2 expressed on the EC surface. ERK signaling via Akt was defined as the pathway responsible for p17-induced tube formation. Ex vivo and in vivo experimental models confirmed the provasculogenic activity of p17, which was comparable to that induced by VEGF-A. The hypothesis of a major role for p17 in HIV-1-induced aberrant angiogenesis is enforced by the finding that p17 is detected, as a single protein, in blood vessels of HIV-1-patients and in particular in the nucleus of ECs. Localization of p17 in the nucleus of ECs was evidenced also in in vitro experiments, suggesting the internalization of exogenous p17 in ECs by mechanisms of receptor-mediated endocytosis. Recognizing p17 interaction with CXCR1 and CXCR2 as the key event in sustaining EC aberrant angiogenesis could help us to identify new treatment strategies in combating AIDS-related vascular diseases.

Inhibition of human respiratory syncytial virus infectivity by a dendrimeric heparan sulfate-binding peptide

Respiratory syncytial virus (RSV) interacts with cell surface heparan sulfate proteoglycans (HSPGs) to initiate infection. The interaction of RSV with HSPGs thus presents an attractive target for the development of novel inhibitors of RSV infection. In the present study, a minilibrary of linear, dimeric, and dendrimeric peptides containing clusters of basic amino acids was screened with the aim of identifying peptides able to bind HSPGs and thus block RSV attachment and infectivity. Of the compounds identified, the dendrimer SB105-A10 was the most potent inhibitor of RSV infectivity, with 50% inhibitory concentrations (IC(50)s) of 0.35 μM and 0.25 μM measured in Hep-2 and A549 cells, respectively. SB105-A10 was found to bind to both cell types via HSPGs, suggesting that its antiviral activity is indeed exerted by competing with RSV for binding to cell surface HSPGs. SB105-A10 prevented RSV infection when added before the viral inoculum, in line with its proposed HSPG-binding mechanism of action; moreover, antiviral activity was also exhibited when SB105-A10 was added postinfection, as it was able to reduce the cell-to-cell spread of the virus. The antiviral potential of SB105-A10 was further assessed using human-derived tracheal/bronchial epithelial cells cultured to form a pseudostratified, highly differentiated model of the epithelial tissue of the human respiratory tract. SB105-A10 strongly reduced RSV infectivity in this model and exhibited no signs of cytotoxicity or proinflammatory effects. Together, these features render SB105-A10 an attractive candidate for further development as a RSV inhibitor to be administered by aerosol delivery.

Long pentraxin 3/tumor necrosis factor-stimulated gene-6 interaction: a biological rheostat for fibroblast growth factor 2-mediated angiogenesis

OBJECTIVE

Angiogenesis is regulated by the balance between pro- and antiangiogenic factors and by extracellular matrix protein interactions. Fibroblast growth factor 2 (FGF2) is a major proangiogenic inducer inhibited by the interaction with the soluble pattern recognition receptor long pentraxin 3 (PTX3). PTX3 is locally coexpressed with its ligand tumor necrosis factor-stimulated gene-6 (TSG-6), a secreted glycoprotein that cooperates with PTX3 in extracellular matrix assembly. Here, we characterized the effect of TSG-6 on PTX3/FGF2 interaction and FGF2-mediated angiogenesis.

METHODS AND RESULTS

Solid phase binding and surface plasmon resonance assays show that TSG-6 and FGF2 bind the PTX3 N-terminal domain with similar affinity. Accordingly, TSG-6 prevents FGF2/PTX3 interaction and suppresses the inhibition exerted by PTX3 on heparan sulfate proteoglycan/FGF2/FGF receptor complex formation and on FGF2-dependent angiogenesis in vitro and in vivo. Also, endogenous PTX3 exerts an inhibitory effect on vascularization induced by FGF2 in a murine subcutaneous Matrigel plug assay, the inhibition being abolished in Ptx3-null mice or by TSG-6 treatment in wild-type animals.

CONCLUSION

TSG-6 reverts the inhibitory effects exerted by PTX3 on FGF2-mediated angiogenesis through competition of FGF2/PTX3 interaction. This may provide a novel mechanism to control angiogenesis in those pathological settings characterized by the coexpression of TSG-6 and PTX3, in which the relative levels of these proteins may fine-tune the angiogenic activity of FGF2.

Structural and functional modulation of early healing of full-thickness superficial digital flexor tendon rupture in rabbits by repeated subcutaneous administration of exogenous human recombinant basic fibroblast growth factor

The present study was designed to investigate the effects of basic fibroblast growth factor on the healing of the acute phase of complete superficial digital flexor tendon rupture in rabbits. A total of 40 skeletally mature female white New Zealand rabbits were randomly divided into 2 equal groups of injured treated and injured control. After tenotomy and surgical anastomosis, using a modified Kessler and running pattern, the injured legs were placed in casts for 14 days, and basic fibroblast growth factor was injected subcutaneously over the lesion on days 3, 7, and 10 after injury. The injured control rabbits received a normal saline injection in a similar protocol. The rabbits' weight, tendon diameter, clinical signs, radiographs, and ultrasound scans were evaluated weekly. The rabbits were killed 28 days after injury, and the tendons were evaluated at the macroscopic, histopathologic, and ultrastructural levels and for biomechanical and the percentage of dry weight analysis. Treatment significantly reduced the diameter and increased the echogenicity and dry weight content and enhanced the maturation rate of the tenoblasts, fibrillogenesis, collagen fibril diameter, fibrillar density, tensile strength, and stiffness and stress of the injured tendons. Treatment with basic fibroblast growth factor was effective in restoring the morphologic and biomechanical properties of the injured superficial digital flexor tendon and could be valuable in clinical trial studies.

Antiangiogenic potential of three triterpenic acids in human liver cancer cells

Three triterpenic acids, oleanolic acid, ursolic acid and maslinic acid, at 2 or 4 μmol/L were used to study their antiangiogenic potential in human liver cancer Hep3B, Huh7 and HA22T cell lines. The effects of these compounds upon the level and/or expression of hypoxia-inducible factor (HIF)-1α, basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), interleukin (IL)-8, urokinase plasminogen activator (uPA), reactive oxygen species (ROS), nitric oxide (NO) and cell invasion and migration were examined. Results showed that these triterpenic acids at 4 μmol/L significantly suppressed HIF-1α expression in three cell lines (P < 0.05); and these compounds at test doses failed to affect bFGF expression (P > 0.05). Three triterpenic acids dose-dependently decreased production and expression of VEGF and IL-8, retained glutathione level, lowered ROS and NO levels, and declined cell invasion and migration in test cell lines (P < 0.05). These compounds also dose-dependently reduced uPA production and expression in Hep3B and Huh7 cell lines (P < 0.05); but these agents only at 4 μmol/L significantly suppressed uPA production and expression in HA22T cells (P < 0.05). These findings suggest that these triterpenic acids are potent antiangiogenic agents to retard invasion and migration in liver cancer cells.

Heparin mimicking polymer promotes myogenic differentiation of muscle progenitor cells

Heparin and heparan sulfate mediated basic fibroblast growth factor (bFGF) signaling plays an important role in skeletal muscle homeostasis by maintaining a balance between proliferation and differentiation of muscle progenitor cells. In this study we investigate the role of a synthetic mimic of heparin, poly(sodium-4-styrenesulfonate) (PSS), on myogenic differentiation of C2C12 cells. Exogenous supplementation of PSS increased the differentiation of C2C12 cells in a dose-dependent manner, while the formation of multinucleated myotubes exhibited a nonmonotonic dependence with the concentration of PSS. Our results further suggest that one possible mechanism by which PSS promotes myogenic differentiation is by downregulating the mitogen activated extracellular regulated signaling kinase (MAPK/ERK) pathway. The binding ability of PSS to bFGF was found to be comparable to heparin through molecular docking calculations and by native PAGE. Such synthetic heparin mimics could offer a cost-effective alternative to heparin and also reduce the risk associated with batch-to-batch variation and contamination of heparin.

High antiangiogenic and low anticoagulant efficacy of orally active low molecular weight heparin derivatives

Heparin, an anticoagulant that is widely used clinically, is also known to bind to several kinds of proteins through electrostatic interactions because of its polyanionic character. These interactions are mediated by the physicochemical properties of heparin such as sequence composition, sulfation patterns, charge distribution, overall charge density, and molecular size. Although this electrostatic character mediates its binding to many proteins related with tumor progression, thereby providing its antiangiogenic property, the administration of heparin for treating cancer is limited in clinical applications due to several drawbacks, such as its low oral absorption, unsatisfactory therapeutic effects, and strong anticoagulant activity which induces hemorrhaging. Here, we evaluated novel, orally active, low molecular weight heparin (LMWH) derivatives (LHD) conjugated with deoxycholic acid (DOCA) that show reduced anticoagulant activity and enhanced antiangiogenic activity. The chemical conjugate of LMWH and DOCA was synthesized by conjugating the amine group of N-deoxycholylethylamine (EtDOCA) with the carboxylic groups of heparin at various DOCA conjugation ratios. The LMWH-DOCA conjugate series (LHD1, LHD1.5, LHD2, and LHD4) were further formulated with poloxamer 407 as a solubilizer for oral administration. An in vitro endothelial tubular formation and in vivo Matrigel plug assay were performed to verify the antiangiogenic potential of LHD. Finally, we evaluated tumor growth inhibition of oral LHD administration in a SCC7 model as well as in A549 human cancer cell lines in a mouse xenograft model. Increasing DOCA conjugation ratios showed decreased anticoagulant activity, eventually to zero. LHD could block angiogenesis in the tubular formation assay and the Matrigel plug assay. In particular, oral administration of LHD4, which has 4 molecules of DOCA per mole of LMWH, inhibited tumor growth in SCC7 mice model as well as A549 mice xenograft model. LHD4 was orally absorbable, showed minimal anticoagulant activity and inhibits tumor growth via antiangiogenesis. These findings demonstrate the therapeutic potential of LHD4 as a new oral anti-cancer drug.

Fibroblast growth factor 2-antagonist activity of a long-pentraxin 3-derived anti-angiogenic pentapeptide

Fibroblast growth factor-2 (FGF2) plays a major role in angiogenesis. The pattern recognition receptor long-pentraxin 3 (PTX3) inhibits the angiogenic activity of FGF2. To identify novel FGF2-antagonistic peptide(s), four acetylated (Ac) synthetic peptides overlapping the FGF2-binding region PTX3-(97-110) were assessed for their FGF2-binding capacity. Among them, the shortest pentapeptide Ac-ARPCA-NH(2) (PTX3-[100-104]) inhibits the interaction of FGF2 with PTX3 immobilized to a BIAcore sensorchip and suppresses FGF2-dependent proliferation in endothelial cells, without affecting the activity of unrelated mitogens. Also, Ac-ARPCA-NH(2) inhibits angiogenesis triggered by FGF2 or by tumorigenic FGF2-overexpressing murine endothelial cells in chick and zebrafish embryos, respectively. Accordingly, the peptide hampers the binding of FGF2 to Chinese Hamster ovary cells overexpressing the tyrosine-kinase FGF receptor-1 (FGFR1) and to recombinant FGFR1 immobilized to a BIAcore sensorchip without affecting heparin interaction. In all the assays the mutated Ac-ARPSA-NH(2) peptide was ineffective. In keeping with the observation that hydrophobic interactions dominate the interface between FGF2 and the FGF-binding domain of the Ig-like loop D2 of FGFR1, amino acid substitutions in Ac-ARPCA-NH(2) and saturation transfer difference-nuclear magnetic resonance analysis of its mode of interaction with FGF2 implicate the hydrophobic methyl groups of the pentapeptide in FGF2 binding. These results will provide the basis for the design of novel PTX3-derived anti-angiogenic FGF2 antagonists.

Thrombospondin-1 as a Paradigm for the Development of Antiangiogenic Agents Endowed with Multiple Mechanisms of Action

Uncontrolled neovascularization occurs in several angiogenesis-dependent diseases, including cancer. Neovascularization is tightly controlled by the balance between angiogenic growth factors and antiangiogenic agents. The various natural angiogenesis inhibitors identified so far affect neovascularization by different mechanisms of action. Thrombospondin-1 (TSP-1) is a matricellular modular glycoprotein that acts as a powerful endogenous inhibitor of angiogenesis. It acts both indirectly, by sequestering angiogenic growth factors and effectors in the extracellular environment, and directly, by inducing an antiangiogenic program in endothelial cells following engagement of specific receptors including CD36, CD47, integrins and proteoglycans (all involved in angiogenesis ). In view of its central, multifaceted role in angiogenesis, TSP-1 has served as a source of antiangiogenic tools, including TSP-1 fragments, synthetic peptides and peptidomimetics, gene therapy strategies, and agents that up-regulate TSP-1 expression. This review discusses TSP-1-based inhibitors of angiogenesis, their mechanisms of action and therapeutic potential, drawing our experience with angiogenic growth factor-interacting TSP-1 peptides, and the possibility of exploiting them to design novel antiangiogenic agents.

A review of the current research on the role of bFGF and VEGF in angiogenesis

Basic fibroblast growth factor and vascular endothelial growth factor are thought to play a synergistic role in angiogenesis. They are released into the wound bed during haemostasis and promote the formation of new blood vessels.

Quantitative analysis of heparanase gene expression in normal cervical, cervical intraepithelial neoplastic, and cervical carcinoma tissues

Heparanase is an endoglycosidase that specifically cleaves heparan sulfate side chains of heparan sulfate proteoglycans, the major proteoglycans in the extracellular matrix and cell surfaces. Traditionally, heparanase activity was implicated in cellular invasion associated with angiogenesis, inflammation, and cancer metastasis. More recently, heparanase up-regulation was documented in an increasing number of primary human tumors. Iotan this study, we sought to investigate the expression of heparanase messenger RNA (mRNA) in normal cervical tissue and intraepithelial cervical lesion and its clinicopathologic importance in invasive cervical cancer. Gene expression of heparanase was assessed by quantitative real-time reverse transcriptase polymerase chain reaction in 28 normal cervical, 26 intraepithelial neoplastic, and 48 cervical cancer tissue samples. Heparanase mRNA expression was different between the 3 groups and lower in normal cervical specimens in relationship with intraepithelial cervical lesions and invasive cervical cancer tissue samples (P = 0.048). Gradually increasing expression of heparanase was evident as the cells progressed from low-grade to high-grade squamous intraepithelial lesions (P = 0.002). In invasive cervical cancer cases, there was a direct correlation between heparanase expression and tumor size (P = 0.002). In cases treated with radical hysterectomy and pelvic lymphadenectomy, the heparanase mRNA expression was significantly higher in tumors exhibiting lymph vascular space invasion (P = 0.044) and in cases with big tumor size (P = 0.005). In our study, we did not find any significant correlation between disease-free and overall survival rates and expression of heparanase (P = 0.396 and P = 0.712, respectively). The results of this study suggest that the gene expression of heparanase in cervical cancer enhances growth, invasion, and angiogenesis of the tumor and may have therapeutic applications.

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.

Heterogeneity of Capillary Endothelial Cells for Basic Fibroblast Growth Factor-Induced Paracrine Signaling

In this study, the authors isolated morphologically different capillary endothelial cells, designated as BCE-1 and BCE-2 cells, from bovine adrenal cortex. By a series of experiments involving proliferation, migration, and tubular-like structure formation assays, the authors found that the two BCE clones showed a clearly different response to basic fibroblast growth factor (bFGF). Similar to these results, the ERK-1/2 in the BCE-1 cells was phosphorylated by bFGF or vascular endothelial growth factor (VEGF), whereas that of the BCE-2 cells was phosphorylated only by VEGF. However, when the BCE-2 cells were transfected with FGF receptor 1 cDNA, the ERK-1/2 of these cells was phosphorylated by exogenous bFGF. Receptor binding experiments revealed that BCE-2 cells expressed high-affinity tyrosine-kinase FGF receptors approximately twofold less than BCE-1 cells. Transfection and receptor binding studies suggest a possibility that the poor response of the BCE-2 cells to exogenous bFGF is derived from the limitation of functional availability of high affinity FGF receptors. On the other hand, when both BCE clones were treated with anti-bFGF antibodies, basal formation of tubular-like structure in both clones were strongly inhibited, indicating that endogenous bFGF plays a role in in vitro angiogenesis of both BCE clones. Taken together, these data show that the isolated capillary endothelial cells are heterogeneous for paracrine but not autocrine bFGF signaling, and suggest that the diversity of capillary endothelial cells can occur by angiogenic factors, such as bFGF.

Polyanionic drugs and viral oncogenesis: a novel approach to control infection, tumor-associated inflammation and angiogenesis

Polyanionic macromolecules are extremely abundant both in the extracellular environment and inside the cell, where they are readily accessible to many proteins for interactions that play a variety of biological roles. Among polyanions, heparin, heparan sulfate proteoglycans (HSPGs) and glycosphingolipids (GSLs) are widely distributed in biological fluids, at the cell membrane and inside the cell, where they are implicated in several physiological and/or pathological processes such as infectious diseases, angiogenesis and tumor growth. At a molecular level, these processes are mainly mediated by microbial proteins, cytokines and receptors that exert their functions by binding to HSPGs and/or GSLs, suggesting the possibility to use polyanionic antagonists as efficient drugs for the treatment of infectious diseases and cancer. Polysulfated (PS) or polysulfonated (PSN) compounds are a heterogeneous group of natural, semi-synthetic or synthetic molecules whose prototypes are heparin and suramin. Different structural features confer to PS/PSN compounds the capacity to bind and inhibit the biological activities of those same heparin-binding proteins implicated in infectious diseases and cancer. In this review we will discuss the state of the art and the possible future development of polyanionic drugs in the treatment of infectious diseases and cancer.

Fibroblast growth factor 2-induced angiogenesis in zebrafish: the zebrafish yolk membrane (ZFYM) angiogenesis assay

Angiogenesis plays a key role in tumour growth and metastasis. The teleost zebrafish (Danio rerio) represents a promising alternative model in cancer research. Here, we describe a zebrafish yolk membrane (ZFYM) angiogenesis assays based on the injection of 1-30 ng of human recombinant FGF2 (rFGF2) in the perivitelline space of zebrafish embryos in the proximity of developing subintestinal vein vessels (SIVs) at 48 hrs after fertilization. The rFGF2 induces a rapid and dose-dependent angiogenic response from the SIV basket, characterized by the ectopic growth of newly formed, alkaline phosphatase-positive blood vessels. These vessels are formed by proliferating cells that incorporate bromodeoxyuridine and express the endothelial cell markers vegfr2/kdr and fli1. Microangiography shows that rFGF2-induced vessels are patent and connected to the systemic circulation of the embryo. In keeping with these observations, fli1:EGFP(+) cells isolated from transgenic tg(fli1:EGFP)(y1) zebrafish embryos express the tyrosine kinase (TK) FGF receptor-1 (FGFR1) and activate extracellular signal-regulated kinase signalling when stimulated in vitro by rFGF2. The low molecular weight TK-FGFR1 inhibitor SU5402 and the high molecular weight FGF2 antagonist long-pentraxin 3 inhibit the angiogenic activity of rFGF2 when added to fish water or when co-injected with the growth factor, respectively. Moreover, similar to rFGF2, injection of the zebrafish form of vascular endothelial growth factor-A (VEGF-A) induces a significant angiogenic response in the ZFYM assay that is suppressed by the VEGF receptor-2/KDR TK inhibitor SU5416. The ZFYM assay represents a novel tool for testing the activity of low and high molecular weight inhibitors targeting a defined angiogenic growth factor in zebrafish. The assay may offer significant advantages when compared to other animal models.

Potent anti-angiogenic motifs within the Alzheimer beta-amyloid peptide

Abeta peptides are the major constituents of senile plaques and cerebrovascular deposits in the brains of patients with Alzheimer's disease. We have shown previously that Abeta1-40 and Abeta1-42 peptides are potently anti-angiogenic both in vitro and in vivo. The current study characterizes important sequences within the Abeta peptide that are required to exert its anti-angiogenic activity. We have used human umbilical vein endothelial cells to assess the anti-angiogenic activity of short fragments of Abetain vitro in a Matrigel network assay and in vivo in a rat corneal model of angiogenesis. The anti-angiogenic activity of these short peptide fragments is not related to effects on apoptosis or necrosis. Using normal and mutated peptide fragments, we show that the sequence VHHQKLVFF is sufficient to exhibit potent anti-angiogenic effects. This small peptide may therefore have clinical relevance as an anti-angiogenic agent.

Oligosaccharides as anti-angiogenic agents

BACKGROUND

Several studies of drugs that inhibit tumour angiogenesis have shown improvements in the survival of cancer patients, thus validating angiogenesis as a clinically relevant target. Both intracellular and extracellular approaches have shown promising results in clinical situations.

OBJECTIVES

To compare and contrast oligosaccharide therapies and other anti-angiogenic compounds for their benefits and toxicity.

METHODS

Analysis of the relevant literature including presentations at recent conferences.

RESULTS

Receptor tyrosine kinase inhibitors are orally available but have a broad spectrum of activity which is associated with toxicity. Antibodies are associated with different toxicities, however, they are administered parenterally. Oligosaccharides that act as competitive inhibitors of heparan sulfate (HS) are in the early and late phases of clinical development. The advantage of oligosaccharides should be that they can be designed to target several angiogenic molecules, that they are relatively safe and that they can be administered subcutaneously at home. The key questions concerning their development focus on whether compounds with sufficient affinity and relative specificity can be generated, whether they are active at doses that do not perturb the coagulation cascade to a clinically dangerous level, whether the synthetic routes are scalable and, whether the current Phase III trials will yield positive results.

CONCLUSIONS

Saccharides represent a novel and exciting therapeutic approach that targets a spectrum of angiogenic molecules that cannot be inhibited through established drug development programmes.

Skeletal muscle VEGF gradients in peripheral arterial disease: simulations of rest and exercise

VEGF is a key promoter of angiogenesis and a major target of proangiogenic therapy for peripheral arterial disease (PAD). Greater understanding of VEGF angiogenic signaling and guidance by gradients for new capillaries will aid in developing new proangiogenic therapies and improving existing treatments. However, in vivo measurements of VEGF concentration gradients at the cell scale are currently impossible. We have developed a computational model to quantify VEGF distribution in extensor digitorum longus skeletal muscle using measurements of VEGF, VEGF receptor (VEGFR), and neuropilin-1 (NRP1) expression in an experimental model of rat PAD. VEGF is secreted by myocytes, diffuses through and interacts with extracellular matrix and basement membranes, and binds VEGFRs and NRP1 on endothelial cell surfaces of blood vessels. We simulate the effects of increased NRP1 expression and of therapeutic exercise training on VEGF gradients, receptor signaling, and angiogenesis. Our study predicts that angiogenic therapy for PAD may be achieved not only through VEGF upregulation but also through modulation of VEGFRs and NRP1. We predict that expression of 10(4) NRP1/cell can increase VEGF binding to receptors by 1.7-fold (vs. no NRP1); in nonexercise-trained muscle with PAD, angiogenesis is hindered due to limited VEGF upregulation, signaling, and gradients; in exercise-trained muscle, VEGF signaling is enhanced by upregulation of VEGFRs and NRP1, and VEGF signaling is strongest within the first week of exercise therapy; and hypoxia-induced VEGF release is important to direct angiogenesis towards unperfused tissue.

Heparanase expression in circulating lymphocytes of breast cancer patients depends on the presence of the primary tumor and/or systemic metastasis

Heparanase is an endo-beta-glucuronidase that is capable of degrading heparan sulfate chains of proteoglycans, generating a variety of bioactive molecules such as growth factors and chemotactic and angiogenic agents. The expression of heparanase was investigated in the peripheral blood mononuclear cell fraction (PBMC) of 30 patients with breast cancer and 20 healthy control women by reverse transcription-polymerase chain reaction (RT-PCR) and immunocytochemistry. PBMC samples from all breast cancer patients at study entry showed the expression of heparanase, whereas no expression was observed for healthy women. Immunocytochemistry analysis demonstrated that heparanase was expressed in lymphocytes of breast cancer PBMC. Throughout follow-up, heparanase expression by RTPCR decreased significantly after surgery in patients treated with neoadjuvant chemotherapy (P = .002) and after tamoxifen treatment (P = .040), whereas it increased significantly with the advent of systemic metastasis (P = .027). In vitro, either serum from breast cancer patients or a medium originated from coculture experiments of MCF-7 cells and lymphocytes from healthy women stimulated heparanase expression in normal lymphocytes. The results suggest that there is a tumor-inducing effect on heparanase expression by lymphocytes present in the PBMCs of breast cancer patients, which depends, in turn, on the interaction between a tumor and normal lymphocytes.

Nonclassic Endogenous Novel Regulators of Angiogenesis

Angiogenesis, the process through which new blood vessels arise from preexisting ones, is regulated by several "classic" factors, among which the most studied are vascular endothelial growth factor (VEGF) and fibroblast growth factor-2 (FGF-2). In recent years, investigations showed that, in addition to the classic factors, numerous endogenous peptides play a relevant regulatory role in angiogenesis. Such regulatory peptides, each of which exerts well-known specific biological activities, are present, along with their receptors, in the blood vessels and may take part in the control of the "angiogenic switch." An in vivo and in vitro proangiogenic effect has been demonstrated for erythropoietin, angiotensin II (ANG-II), endothelins (ETs), adrenomedullin (AM), proadrenomedullin N-terminal 20 peptide (PAMP), urotensin-II, leptin, adiponectin, resistin, neuropeptide-Y, vasoactive intestinal peptide (VIP), pituitary adenylate cyclase-activating polypeptide (PACAP), and substance P. There is evidence that the angiogenic action of some of these peptides is at least partly mediated by their stimulating effect on VEGF (ANG-II, ETs, PAMP, resistin, VIP and PACAP) and/or FGF-2 systems (PAMP and leptin). AM raises the expression of VEGF in endothelial cells, but VEGF blockade does not affect the proangiogenic action of AM. Other endogenous peptides have been reported to exert an in vivo and in vitro antiangiogenic action. These include somatostatin and natriuretic peptides, which suppress the VEGF system, and ghrelin, that antagonizes FGF-2 effects. Investigations on "nonclassic" regulators of angiogenesis could open new perspectives in the therapy of diseases coupled to dysregulation of angiogenesis.

VEGF gradients, receptor activation, and sprout guidance in resting and exercising skeletal muscle

Extensive experimental studies have identified vascular endothelial growth factor (VEGF) concentrations and concentration gradients as major factors in angiogenesis; however, localized in vivo measurements of these parameters have not been possible. We developed a three-dimensional computational model of skeletal muscle fibers, blood vessels, and interstitial space. Here it is applied to rat extensor digitorum longus. VEGF isoforms are secreted by myocytes, diffuse through extracellular matrix and basement membranes, and bind endothelial cell surface receptors on blood vessels. In addition, one isoform, VEGF164, binds to proteoglycans in the interstitial space. VEGF secretion rate is determined from the predicted tissue oxygen level through its effect on the hypoxia inducible factor-1alpha transcription factor. We estimate VEGF secretion and its concentrations and gradients in resting muscle and for different levels of exercise. The effects of low levels of inspired oxygen are also studied. We predict that the high spatial heterogeneity of muscle fiber VEGF secretion in hypoxic tissue leads to significant gradients of VEGF concentration and VEGF receptor activation. VEGF concentration gradients are predicted to be significant in both resting and exercising muscle (4% and 6-8% change in VEGF over 10 microm, respectively), sufficient for chemotactic guidance of 50-microm-long sprout tip cells. VEGF gradients also result in heterogeneity in VEGF receptor activation--a possible explanation for the stochasticity of sprout location. In the absence of interstitial flow, gradients are 10-fold steeper in the transverse direction (i.e., perpendicular to the muscle fibers) than in the longitudinal direction. This may explain observed perpendicular anastomoses in skeletal muscle.

The vascular endothelial growth factor VEGF165 induces perlecan synthesis via VEGF receptor-2 in cultured human brain microvascular endothelial cells

A member of the vascular endothelial growth factor (VEGF) family, VEGF165, regulates vascular endothelial cell functions in autocrine and paracrine fashions in microvessels. Proteoglycans are highly glycosylated poly-anionic macromolecules that influence cellular behaviors such as proliferation and migration by interacting with cytokines/growth factors. In the present study, we investigated the regulation of proteoglycan synthesis by VEGF165 in cultured human brain microvascular endothelial cells. The cells were exposed to recombinant human VEGF165, and the proteoglycans were then characterized using biochemical techniques. VEGF165 treatment increased the accumulation of proteoglycans 1.4- and 1.6-fold in the cell layer and conditioned medium, respectively. This effect resulted from the activation of VEGFR-2, and was mimicked by vammin, a VEGFR-2 ligand from snake venom but not placenta growth factor, which binds specifically to VEGFR-1. VEGF165 stimulated the production and secretion of perlecan, substituted with shorter heparan sulfate side chains, but with unaltered sulfated disaccharide composition. The perlecan secreted by VEGF165-stimulated endothelial cells may be involved in the regulation of cellular behavior during angiogenesis, in diseases of the brain microvessels, and in the maintenance of the endothelial cell monolayer.

Extracellular angiogenic growth factor interactions: an angiogenesis interactome survey

Angiogenesis plays a key role in various physiological and pathological processes, including inflammation and tumor growth. Numerous angiogenic growth factors (AGFs) have been identified. Usually, the angiogenic process is assumed to represent the outcome of a straightforward interaction of AGFs with specific signalling receptors of the endothelial cell (EC) surface. Actually, the mechanisms by which AGFs induce neovascularization are much more complex. Indeed, angiogenesis is the result of the simultaneous actions of various AGFs and angiogenesis modulators; multiple EC surface receptors with different structure and biological properties are engaged by AGFs to exert a full angiogenic response; AGFs bind a variety of free and immobilized proteins, polysaccharides, and complex lipids of the extracellular milieu that affect AGF integrity, stability, and bioavailability; some of the AGF-binding molecules interact also with AGF receptors. In this review the authors summarize literature data and discuss the current knowledge about the extracellular molecules able to interact with AGFs, thus representing possible key regulators of the angiogenesis process and targets/templates for the development of novel antiangiogenic drugs. This work represents an attempt to highlight common theme in the AGF interactome that occurs at the extracellular level during neovascularization.

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.

In Vitro Angiogenic Effects of Pancreatic Bile Salt-Dependent Lipase

OBJECTIVE

Bile salt-dependent lipase (BSDL), a lipolytic enzyme secreted in the duodenum by pancreatic acinar cells, has been detected in the serum of all patients and in atheromatous plaque, suggesting its potential implication in vascular pathophysiology.

METHODS AND RESULTS

In vitro pancreatic BSDL evokes human umbilical vein endothelial cell (HUVEC) proliferation and chemotactic migration. BSDL at mitogen concentration is capable to heal wounded HUVEC monolayer and to promote capillary network formation. HUVEC proliferation depends on the displacement of basic fibroblast growth factor and vascular endothelial growth factor from the extracellular matrix and the activation of extracellular signal-regulated kinases (ERK1/2), p38 mitogen-activated protein kinase, and focal adhesion kinase signaling pathways.

CONCLUSIONS

For the first time to our knowledge, it is suggested that circulating BSDL could be involved in pathophysiological angiogenesis. We delineate the in vitro effects of pancreatic BSDL on endothelial cells, and we show that BSDL promotes proliferation, migration, capillary network formation, and wound-healing of HUVECs via the displacement of bFGF and VEGF from the ECM, suggesting that BSDL could be involved in angiogenesis.

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.

Intracoronary administration of FGF-2: a computational model of myocardial deposition and retention

This study uses a computational model to characterize the myocardial deposition and retention of basic fibroblast growth factor (FGF-2) at the cellular level after intracoronary (IC) administration of exogenous FGF-2. The model is applied to the in situ conditions present within the myocardium of a dog for which the plasma pharmacokinetics resulting from IC injection of FGF-2 were recorded. Our estimates show that the processes involved in FGF-2 signaling are not diffusion limited; rather, the response time is determined by the reaction time of FGF-2 binding to cell surface receptors. Additionally, the processes of receptor secretion and internalization are found to play crucial roles in the FGF-2 dynamics; future experiments are required to quantify these processes. The model predictions obtained in this study suggest that IC administration of FGF-2 via either a single bolus or repetitive injections causes a transient increase (time scale of hours) in myocardial FGF-2 concentration if the endogenous level of free interstitial FGF-2 is low enough to allow permeation of FGF-2 molecules from the microvascular to the interstitial spaces. The model shows that the majority (64%) of the extracellular FGF-2 ligands are located within the interstitium, and similar fractions are found in the basement membrane and extracellular matrix. Among the FGF-2 molecules found within the interstitium, 2% are free and 98% are bound to interstitial heparan sulfate proteoglycans. These results support the theory of extracellular control of the bioavailability of FGF-2 via dynamic storage of FGF-2 within the basement membrane and extracellular matrix.