Angiogenic activity of syndecan-binding laminin peptide AG73 (RKRLQVQLSIRT)

The AG73 peptide (RKRLQVQLSIRT, mouse laminin alpha 1 chain 2719-2730) promotes cell adhesion and tumor metastasis, and interacts with transmembrane syndecan proteoglycans. Here, we demonstrate AG73 peptide angiogenic activity using in vitro, ex vivo, and in vivo models. AG73 induced murine endothelial cell (SVEC4-10) tube formation on Cultrex Basement Membrane Extract (Cultrex BME) and stimulated sprouting of aortic rings. None of the homologous sequences from the laminin alpha2, alpha3, alpha4, or alpha5 chains was as active as AG73 in promoting sprouting formation. AG73 also mediated angiogenesis in the chick chorioallantonic membrane (CAM) assay. Using subcutaneously injected Cultrex BME supplemented with AG73, we observed a large angiogenic response. Furthermore, AG73-conjugated to a chitosan membrane promoted a strong angiogenic response in the CAM assay. These results indicate that the AG73 peptide is a potent syndecan-binding angiogenesis stimulator and may be useful for therapeutic application to treat ischemic injuries.     

Collagenolysis-dependent angiogenesis mediated by matrix metalloproteinase-13 (collagenase-3)

We have demonstrated previously that new blood vessel formation induced by angiogenic growth factors in onplants placed on the chorioallantoic membrane (CAM) of the chick embryos is critically dependent on the cleavage of fibrillar collagen by a previously unidentified interstitial collagenase. In the present study we have used a quantitative CAM angiogenesis system to search for and functionally characterize host avian collagenases responsible for the collagen remodeling associated with angiogenesis. Among the matrix metalloproteinases (MMPs) identified in the CAM onplant tissue, the chicken MMP-13 (chMMP-13) was the only enzyme whose induction and expression coincided with the onset of angiogenesis and blood vessel formation. The chMMP-13 cDNA has been cloned and recombinantly expressed. The chMMP-13 protein has been purified, characterized in vitro, and examined in situ in the CAM. MMP-13-positive cells appear in the CAM shortly after angiogenic stimulation and then accumulate in the collagen onplant tissue. Morphologically, the chMMP-13-containing cells appear as hematopoietic cells of monocyte/macrophage lineage. In vitro, the chMMP-13 proenzyme is rapidly and efficiently activated through the urokinase plasminogen activator/plasminogen/plasmin cascade into a collagenase capable of cleaving native but not the (r/r) mutant collagenase-resistant collagen. Surprisingly, nanogram levels of purified chMMP-13 elicit an angiogenic response in the CAM onplants comparable with that induced by the angiogenic growth factors. The chMMP-13-mediated response was efficiently blocked by select protease inhibitors indicating that plasmin-activated chMMP-13 can function as an angiogenic factor in vivo. Altogether, the results of this study extend the physiological role of MMP-13, previously associated with cartilage/bone resorption, to the collagen remodeling involved in the angiogenic cascade.     

An assay for cancer stem cell-induced angiogenesis on chick chorioallantoic membrane

Angiogenesis is generally involved in tumor growth and metastasis. Cancer stem cells (CSCs) are considered to facilitate the angiogenesis. Therefore, CSCs could be the effective targets to stop angiogenesis. Recently, our group successfully generated CSC models from induced pluripotent stem cells (iPSCs) in the presence of conditioned medium derived from cancer derived cells. These novel model CSCs has been characterized by highly tumorigenic, angiogenic and metastatic potentials in vivo. The angiogenic potential of CSCs has been explained by the expression of both angiogenic factors and their receptors implying the angiogenesis in autocrine manner. In this protocol we optimized the method to evaluate tumor angiogenesis with the CSC model, which was described effective to assess sorafenib as an antiangiogenic drug, on chick chorioallantoic membrane (CAM) assay. Our results demonstrate that CSCs developed from iPSCs and CAM assay are a robust and cost-effective tool to evaluate tumor angiogenesis with CSCs. Collectively, CSCs in CAM assay could serve as a very useful model for the screening of potential therapeutic agents targeting tumor angiogenesis.     

Control of Angiogenesis by Galectins Involves the Release of Platelet-Derived Proangiogenic Factors

Platelets contribute to vessel formation through the release of angiogenesis-modulating factors stored in their α-granules. Galectins, a family of lectins that bind β-galactoside residues, are up-regulated in inflammatory and cancerous tissues, trigger platelet activation and mediate vascularization processes. Here we aimed to elucidate whether the release of platelet-derived proangiogenic molecules could represent an alternative mechanism through which galectins promote neovascularization. We show that different members of the galectin family can selectively regulate the release of angiogenic molecules by human platelets. Whereas Galectin (Gal)-1, -3, and -8 triggered vascular endothelial growth factor (VEGF) release, only Gal-8 induced endostatin secretion. Release of VEGF induced by Gal-8 was partially prevented by COX-1, PKC, p38 and Src kinases inhibitors, whereas Gal-1-induced VEGF secretion was inhibited by PKC and ERK blockade, and Gal-3 triggered VEGF release selectively through a PKC-dependent pathway. Regarding endostatin, Gal-8 failed to stimulate its release in the presence of PKC, Src and ERK inhibitors, whereas aspirin or p38 inhibitor had no effect on endostatin release. Despite VEGF or endostatin secretion, platelet releasates generated by stimulation with each galectin stimulated angiogenic responses in vitro including endothelial cell proliferation and tubulogenesis. The platelet angiogenic activity was independent of VEGF and was attributed to the concerted action of other proangiogenic molecules distinctly released by each galectin. Thus, secretion of platelet-derived angiogenic molecules may represent an alternative mechanism by which galectins promote angiogenic responses and its selective blockade may lead to the development of therapeutic strategies for angiogenesis-related diseases.     

Soluble multimer of recombinant endostatin expressed in E. coli has anti-angiogenesis activity

The bioactivity, refolding, and multimer formation of endostatin, particularly of recombinant endostatin produced from bacteria, are proved challenging for clinical application. In order to determine the biological activity of recombinant endostatin multimer, first, we expressed endostatin in Escherichia coli and purified it with ion-exchange chromatography. The purified active protein could elicit multimer formation spontaneously, but still has comparable activity. Aim to determine the anti-angiogenic activity of multimer endostatin, by use of RP-HPLC, we then successfully separated endostatin monomer and multimer for subjecting to anti-angiogenesis assay. The results from CAM (chorioallantoic membrane) inhibition assay showed that both monomer and multimer suppressed CAM vascularization significantly. At the dosage of 0.8 microg, inhibition rates of multimeric and monomeric proteins were about 58% and 38%, respectively. Multimeric endostatin exerted a higher activity than monomeric endostatin (p < 0.05). However, when the protein dosage is less than 0.4 microg/ml, there is no significance between their inhibition rates (p > 0.05), although both of them show a high inhibition effect in contrast to control. The results from HUVEC proliferation assay also showed similar effects at dosages of 0.6 and 1.6 microg/ml, multimer exerted a higher activity on inhibition of HUVEC proliferation comparing with monomer (p < 0.05). In conclusion, our results suggest that endostatin multimer has a comparable or higher bioactivity and multimerization will not affect its bioactivity, implying that endostatin activity is insensitive to structure conformation contributed by disulfide bonds.     

Use of adenovirus vectors for functional gene analysis in the chicken chorioallantoic membrane

The chicken chorioallantoic membrane (CAM) assay represents one of the most widely used in vivo screening assay for genes with angiogenic (blood vessel-inducing) or angiostatic (inhibition of vessel formation or their destruction) activities. Here we show that adenovirus gene transfer vectors infect cells in the CAM and lead to expression of the viral transgene. Furthermore, infection with an adenovirus vector containing the human vascular endothelial growth factor gene induced the formation of new blood vessels. This improved method saves a considerable amount of time in the identification of genes that can influence blood vessel formation because the expensive and time-consuming production and purification of recombinant protein can be omitted.     

Serum levels of angiogenic and anti-angiogenic factors: their prognostic relevance in locally advanced hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a prototype tumor wherein angiogenesis plays a vital role in its progression. The role of VEGF, a major angiogenic factor in HCC is known; however, the role of anti-angiogenic factors simultaneously with the angiogenic factors has not been studied before. Hence, in this study, the serum levels of major angiogenic [Vascular Endothelial Growth Factor (VEGF), angiopoietin-2 (Ang-2)] and anti-angiogenic (endostatin, angiostatin) factors were analyzed and correlated with clinico-radiological features and with outcome. A total of 150 patients (50 HCC, 50 cirrhosis and 50 chronic hepatitis) and 50 healthy controls were enrolled in this study. Serum levels of VEGF, Ang-2, endostatin, and angiostatin were estimated by enzyme-linked immunosorbent assay. HCC shows significantly elevated serum levels of angiogenic factors VEGF and Ang-2 and of anti-angiogenic factors endostatin and angiostatin. ROC curve analysis for serum VEGF yielded an optimal cut-off value of 225.14 pg/ml, with a sensitivity of 78 % and specificity of 84.7 % for a diagnosis of HCC and its distinction from other group. Using this value, the univariate and multivariate analysis revealed significantly poor outcome in patients with higher levels of serum VEGF (p = 0.009). Combinatorial analysis revealed that patients with higher levels of both angiogenic and anti-angiogenic factors showed poor outcome. Serum VEGF correlates with poor survival of HCC patients and, therefore, serves as a non-invasive biomarker of poor prognosis. Moreover, elevated levels of anti-angiogenic factors occur endogenously in HCC patients.     

Behavior of endothelial cells on Matrigel and development of a method for a rapid and reproducible in vitro angiogenesis assay

During the process of angiogenesis, the normally quiescent endothelial cells that line the vasculature are induced to proliferate, migrate and align to form new blood vessels by angiogenic stimuli. Assays for angiogenic factors mostly involve in vivo approaches. The two most commonly used in vivo assays—the chick chorioallantoic membrane (CAM) assay and the rabbit corneal assay are tedious to perform and are technically demanding. Several in vitro assays have also been developed, based on the ability of endothelial cells to form tubes in 3-D matrices. Here, we describe the modification of a microcarrier bead-based assay. This assay combines cells grown on Cytodex-3 microcarrier beads with Matrigel to provide an easy, rapid, and reliable method for evaluating and measuring angiogenic activity. We also describe the differential behavior of normal and transformed endothelial cells cultured in Matrigel.     

The role of fibroblast growth factor-2 in the vascularization of the chick embryo chorioallantoic membrane

The CAM is an extraembryonic membrane which serves as a gas exchange surface and its respiratory function is provided by an extensive capillary network. The development of the vascular system of the CAM is a complex, highly regulated process that depends on genetic and epigenetic factors expressed by endothelial and non-endothelial cells. In spite of the evidence that several growth factors are angiogenic in the CAM assay, poorly investigated is their role in the development of the CAM's vascular system. This article reviews our studies concerning the role of exogenous and endogenous fibroblast growth factor-2 (FGF-2) in the CAM vascularization. The findings in all these studies support the importance of FGF-2 as an autocrine paracrine stimulator of angiogenesis and its key role in the development of the vascular system in the avian embryo.     

Design and synthesis of antiangiogenic/heparin-binding arginine dendrimer mimicking the surface of endostatin

We designed and synthesized the antiangiogenic arginine-rich dendrimers, TX-1943 and TX-1944, which mimic the surface structure of endostatin. TX-1944 containing 16 arginine residues is more similar in surface structure to endostatin than TX-1943 with eight arginine residues, and has stronger in vivo antiangiogenic activity at 10 microg/CAM in the chicken embryo chorioallantoic membrane (CAM) assay. TX-1944 also has stronger activity to bind heparin and to inhibit the growth of rat lung endothelial (RLE) cells than TX-1943.     

Mitogenic activity of chicken chorioallantoic fluid is temporally correlated to vascular growth in the chorioallantoic membrane and related to fibroblast growth factors

The chorioallantoic membrane (CAM) is one of the most vascularized tissues in the chicken embryo. Capillary growth proceeds until day 10 of development and thereafter abruptly regresses. As it is generally accepted that the formation of new blood vessel is regulated by growth factors, we have investigated the presence of angiogenic and mitogenic factors in the chicken chorioallantois. In the present study, we show that chorioallantoic fluid (CAF) contains angiogenic substances that are probably synthesized in the CAM or the embryonic kidney. When applied in the chorioallantoic membrane assay, CAF from 9 day chicken embryos elicits a strong angiogenic response. This angiogenic activity of CAF is associated with pronounced mitogenic effects in vitro. Comparison of different embryonic fluids reveals that mitogenic activity is particularly evident in the CAF but not detectable in embryonic serum and amnion fluid. Expression of mitogenic activity is found to be temporally correlated with vascular growth in the CAM. High activity is detected in CAF prior to day 10 and then sharply decreases, thus preceding termination of capillary growth by one day. Heparin-sepharose affinity chromatography suggests that the biological activities of CAF probably correspond to the presence of acidic and basic fibroblast growth factor (aFGF and bFGF). In Western blot analyses of CAF, an immunoreactive bFGF-like protein of about 17 x 10(3) Mr is recognized by a monospecific anti-bFGF antiserum. This protein elutes at 2.4 M NaCl from the heparin-sepharose. The mitogenic activity of the CAF can be specifically blocked by the anti-bFGF antibody indicating bFGF to be the active mitogenic principle of the CAF. These results strongly suggest that basic and probably acidic FGF play an important role in the regulation of chorioallantoic vascular growth.     

Tryptase and chymase are angiogenic in vivo in the chorioallantoic membrane assay

Human mast cells (MCs) are divided in two types depending on the expression of tryptase and chymase in their granules. Literature data indicate that both tryptase and chymase are angiogenic, but there is currently no evidence of their direct angiogenic activity in vivo. In this study, we have investigated the capacity of tryptase and chymase to promote vasoproliferation in chick embryo chorioallantoic membrane (CAM), a well established in vivo assay to study angiogenesis and anti-angiogenesis. The results showed that both tryptase and chymase stimulate angiogenesis and that the response is similar to that obtained with vascular endothelial growth factor (VEGF), a well-known angiogenic cytokine, and confirm the angiogenic activity of these two proteases stored in MC granules.     

High serum level of endostatin in multiple myeloma at diagnosis but not in the plateau phase after treatment

We investigated the serum concentration of endostatin in 84 patients with multiple myeloma (MM) and in 13 healthy controls. The level of measured anti-angiogenic agent was correlated with the phase and stage of the disease, and most importantly with clinical and laboratory parameters depicting the disease activity (haemoglobin, creatinine, albumins, calcium, M-component, C-reactive protein, beta2-microglobulin, lactate dehydrogenase, stage of bone disease) as well as serum levels of pro-angiogenic cytokines such as vascular endothelial growth factor, hepatocyte growth factor, fibroblast growth factor and transforming growth factor-beta. The median serum level of endostatin in MM patients was 58 ng/ml and was statistically significantly higher than in the control group (median, 40 ng/ml; p=0.015). MM patients in phase I (at diagnosis) had higher levels of endostatin (median, 69 ng/ml) than those in phase II (plateau phase after treatment) (median, 49 pg/ml; p=0.044). We did not find any statistical correlation between the level of endostatin and stage of MM according to the Durie and Salmon system. The serum concentration of endostatin in MM patients with a normal level of albumins was significantly higher than in others with hypoalbuminaemia (median, 62 ng/ml versus 39 ng/ml; p=0.033). Also, patients with a normal value of lactate dehydrogenase had a higher concentration of endostatin than those with values >425 U/l (median, 70 ng/ml versus 39 ng/ml; p=0.019). We did not show any statistical correlation between the concentration of endostatin and level of haemoglobin, creatinine, calcium, C-reactive protein, beta2-microglobulin and stage of bone disease. We failed to find positive or negative correlations between the level of endostatin and vascular endothelial growth factor, hepatocyte growth factor, fibroblast growth factor and transforming growth factor-beta. The concentration of endostatin did not influence the probability of survival in MM patients in our study. In conclusion, our data indicate that endostatin has a higher level in MM patients than in healthy controls. Highest values were stated in active phases of the disease (at presentation and in progression). Different clinical and laboratory parameters generally do not influence the concentration of endostatin (except albumins and lactate dehydrogenase).     

Osteocalcin is angiogenic in vivo

The exact function of osteocalcin (OC), a protein synthesized by osteoblasts during the matrix mineralization phase, is still unknown. In this study we investigated the capacity of OC to promote vasoproliferation in chick embryo chorioallantoic membrane (CAM), a well established in vivo assay for angiogenesis and anti-angiogenesis. The results showed that OC stimulates angiogenesis and that the response is similar to that obtained with FGF-2, a well-known angiogenic cytokine. It has previously been demonstrated that OC is involved in bone repair, so the angiogenic activity reported here might also play a crucial role in bone formation.     

Endostatin's antiangiogenic signaling network

It is here demonstrated that the set of gene expressions underlying the angiogenic balance in tissues can be molecularly reset en masse by a single protein. Using genome-wide expression profiling, coupled with RT-PCR and phosphorylation analysis, we show that the endogenous angiogenesis inhibitor endostatin downregulates many signaling pathways in human microvascular endothelium associated with proangiogenic activity. Simultaneously, endostatin is found to upregulate many antiangiogenic genes. The result is a unique alignment between the direction of gene regulation and angiogenic status. Profiling further reveals the regulation of genes not heretofore associated with angiogenesis. Our analysis of coregulated genes shows complex interpathway communications in an intricate signaling network that both recapitulates and extends on current understanding of the angiogenic process. More generally, insights into the nature of genetic networking from the cell biologic and therapeutic perspectives are revealed.     

Accelerated wound healing of oral soft tissues and angiogenic effect induced by a pool of aminoacids combined to sodium hyaluronate (AMINOGAM)

In this study we investigated the property of a new medical substance, in the form of a gel compound containing four aminoacids (glycine, leucine, proline, lysine) and sodium hyaluronate (AMINOGAM), to accelerate the wound healing process of the soft oral tissues and to promote angiogenesis in vivo in the vascular proliferation in chick embryo chorioallantoic membrane (CAM) assay. Furthermore, we investigated the capacity of AMINOGAM to induce the expression of an angiogenic cytokine, namely vascular endothelial growth factor (VEGF) in human fibroblasts in vitro. Results showed that AMINOGAM promoted wound healing in post-surgical wounds (after teeth extraction, oral laser surgery with secondary healing without direct suture of the surgical wound, and after dental implant insertion). Stimulated angiogenesis in vivo in the CAM assay and the response was similar to that obtained with vascular endothelial growth factor, a well-known angiogenic cytokine, tested in the same assay, and confirmed by clinical outcomes, which showed reduction of the healing time of oral soft tissues after three different kinds of surgery and also the absence of post-operative infections.     

Whole-Body Vibrations Do Not Elevate the Angiogenic Stimulus when Applied during Resistance Exercise

Knowledge about biological factors involved in exercise-induced angiogenesis is to date still scanty. The present study aimed to investigate the angiogenic stimulus of resistance exercise with and without superimposed whole-body vibrations. Responses to the exercise regimen before and after a 6-week training intervention were investigated in twenty-six healthy male subjects. Serum was collected at the initial and final exercise sessions and circulating levels of matrix metalloproteinases (MMP) -2 and -9, Vascular Endothelial Growth Factor (VEGF) and endostatin were determined via ELISA. Furthermore, we studied the proliferative effect of serum-treated human umbilical vein endothelial cells in vitro via BrdU-incorporation assay. It was found that circulating MMP-2, MMP-9, VEGF and endostatin levels were significantly elevated (P<0.001) from resting levels after both exercise interventions, with higher post-exercise VEGF concentrations in the resistance exercise (RE) group compared to the resistive vibration exercise (RVE) group. Moreover, RE provoked increased endothelial cell proliferation in vitro and higher post-exercise circulating endostatin concentrations after 6 weeks of training. These effects were elusive in the RVE group. The present findings suggest that resistance exercise leads to a transient rise in circulating angiogenic factors and superimposing vibrations to this exercise type might not further trigger a potential signaling of angiogenic stimulation in skeletal muscle.     

In situ hybridization and immunogold localization of vascular endothelial growth factor receptor-2 on the pericytes of the chick chorioallantoic membrane

This paper describes the expression of VEGF and of VEGFR-2 in the vasculature of the chorioallantoic membrane (CAM) as revealed by in situ hybridization and immunoelectron microscopy. Results showed that VEGFR-2 is expressed in both the endothelial cells and the pericytes, while VEGF in the chorionic epithelial cells. VEGF may therefore be released to promote both angiogenesis, by initiating an angiogenic response by endothelial cells expressing VEGFR-2, and the recruitment of pericytes along the capillary wall, playing also a crucial role in maturation and stabilization of the CAM blood vessels.