Hepatocyte growth factor is a major mediator in heparin-induced angiogenesis

Heparin has a potent angiogenic effect in experimental animals and patients with ischemic diseases; however, the precise mechanism behind this angiogenesis remains to be clarified. The aim of this study was to determine whether the administration of heparin affects the levels of heparin-binding angiogenic factors in human plasma, and to identify the molecule responsible for heparin-induced angiogenesis. Plasma levels of hepatocyte growth factor (HGF), basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) were measured before and after administration of 100 U, 3,000 U or 10,000 U of heparin in patients with coronary artery disease. Administration of 3,000 U or 10,000 U of heparin caused significant increases in plasma HGF (40- and 54-fold, respectively), in absence of obvious increases in bFGF and VEGF levels. Furthermore, compared with the serum collected before heparin administration, the serum collected after heparin administration had more prominent growth-promoting and vascular tube-inducing properties on endothelial cells, and these increased activities were completely inhibited by neutralization of HGF, whereas neutralization of bFGF and VEGF had no effect. These findings suggest that HGF plays a significant role in heparin-induced angiogenesis.     

Differential effects of cyclic and static stretch on coronary microvascular endothelial cell receptors and vasculogenic/angiogenic responses

Mechanical stretch, an important growth stimulus, results not only from pulsatile blood flow and diastolic stretch of the ventricles [cyclic stretch (CS)] but also from tissue expansion during growth [constant static stretch (SS)]. We compared growth factor receptor expression and vasculogenic/angiogenic responses of rat coronary microvascular endothelial cells (ECs) by exposing cells to CS (10% elongation at 30 cycles/min) and SS (constant 10% elongation). Both CS and SS increased VEGF receptor (VEGF-R)2 protein levels and the extent of tube formation and branching. Moreover, both CS and SS enhanced VEGF-induced cell proliferation and tube formation, indicating that both types of stretch increase the sensitivity of ECs to VEGF. Blockade of VEGF-R2 prevented the increases in EC proliferation and aggregate tube length. However, CS but not SS enhanced EC Tie-2 protein and migration. CS affected a greater increase in tube length and branch formation than did SS. A unique finding was that SS but not CS increased VEGFR-1 in ECs. Our study is the first to distinguish between the effects of CS and SS on growth factor receptor expression and rat coronary microvascular EC proliferation, migration, and tube formation. In conclusion, EC angiogenic responses to these two types of stretch display both differences and similarities, but both CS and SS are dependent on VEGF-R2 signaling for their vasculogenic/angiogenic effects.     

Angiostatin is negatively associated with coronary collateral growth in patients with coronary artery disease

Angiostatin, an inhibitor of tumor angiogenesis, is produced by the actions of matrix metalloproteinases (MMP) on plasminogen. Recently, we reported that angiostatin levels are increased in a model of inadequate coronary collateral growth and angiogenesis in response to ischemia, despite high levels of vascular endothelial growth factor (VEGF). We hypothesized that angiostatin levels are negatively associated with collateral formation in patients. Coronary angiograms from 37 patients undergoing coronary bypass surgery were evaluated for the absence of angiographically visible collaterals (Rentrop scores of 0) or the presence of Rentrop classification grade 3 (well developed) collaterals. Pericardial fluid was obtained from each patient during the bypass procedure, and the sample was analyzed for angiostatin, plasminogen, and VEGF (Western analysis) and for combined activities of MMP-2 and MMP-9 (zymographic analysis). In patients with no collaterals, angiostatin level was greater compared with that in patients with well-developed collaterals (3.1 +/- 0.2 vs. 2.3 +/- 0.1 optical density units, P < 0.05). Neither MMP activities nor VEGF levels were different between the two groups of patients. The higher levels of angiostatin in patients with no visible collaterals were reflective of a higher concentration of plasmin/plasminogen (6.2 +/- 0.7 vs. 4.2 +/- 0.5 optical density units, P < 0.05) compared with those in patients with well-developed collateral vessels. Our results support the concept that the growth inhibitor angiostatin may have a negative impact on coronary collateral growth in patients. Perhaps therapies attempting to provoke coronary collateral growth should incorporate approaches to limit or neutralize the effects of growth inhibitors.     

Alterations in plasma angiogenic growth factor concentrations after coronary artery bypass graft surgery: relationships with post-operative complications

To determine whether angiogenic growth factor levels are altered during and after cardiac surgery, plasma concentrations of basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF) and transforming growth factor beta1 (TGFbeta1) were measured in 32 patients undergoing coronary artery bypass graft (CABG) surgery with extracorporeal circulation (ECC). EGF levels significantly decreased during ECC and remained low until the 24th post-operative hour with no difference between complicated and uncomplicated patients. TGFbeta1 and bFGF concentrations significantly increased at the end of ECC and after cross-clamp release, and returned to pre-operative values at the 6th post-operative hour suggesting that the source of these elevations are the lungs and heart. After cross-clamp release bFGF levels but not TGFbeta1 ones were higher in patients with respiratory impairments. VEGF values increased significantly at the 6th and 24th post-operative hours. At the 24th post-operative hour plasma VEGF levels were higher in patients with cardiovascular and hematological impairments. In conclusion, these results highlight that the angiogenic network is profoundly altered in patients undergoing cardiopulmonary bypass as previously demonstrated for lipidic, cytokine and haematopoietic growth factor ones and identify an association between specific post-CABG complications and systemic release of bFGF and VEGF.     

Magnitude-dependent effects of cyclic stretch on HGF- and VEGF-induced pulmonary endothelial remodeling and barrier regulation

Mechanical ventilation at high tidal volumes compromises the blood-gas barrier and increases lung vascular permeability, which may lead to ventilator-induced lung injury and pulmonary edema. Using pulmonary endothelial cell (ECs) exposed to physiologically [5% cyclic stretch (CS)] and pathologically (18% CS) relevant magnitudes of CS, we evaluated the potential protective effects of hepatocyte growth factor (HGF) on EC barrier dysfunction induced by CS and vascular endothelial growth factor (VEGF). In static culture, HGF enhanced EC barrier function in a Rac-dependent manner and attenuated VEGF-induced EC permeability and paracellular gap formation. The protective effects of HGF were associated with the suppression of Rho-dependent signaling triggered by VEGF. Five percent CS promoted HGF-induced enhancement of the cortical F-actin rim and activation of Rac-dependent signaling, suggesting synergistic barrier-protective effects of physiological CS and HGF. In contrast, 18% CS further enhanced VEGF-induced EC permeability, activation of Rho signaling, and formation of actin stress fibers and paracellular gaps. These effects were attenuated by HGF pretreatment. EC preconditioning at 5% CS before HGF and VEGF further promoted EC barrier maintenance. Our data suggest synergistic effects of HGF and physiological CS in the Rac-mediated mechanisms of EC barrier protection. In turn, HGF reduced the barrier-disruptive effects of VEGF and pathological CS via downregulation of the Rho pathway. These results support the importance of HGF-VEGF balance in control of acute lung injury/acute respiratory distress syndrome severity via small GTPase-dependent regulation of lung endothelial permeability.     

VEGF gene mRNA expression in patients with coronary artery disease

To assess the expression of vascular endothelium growth factor (VEGF) mRNA in unstimulated peripheral blood mononuclear cells of patients with and without coronary artery disease (CAD). We also studied whether the functional VEGF -2,578C/A polymorphism may influence the level of VEGF mRNA expression in individuals undergoing coronary angiography because chest pain. We assessed 50 consecutive patients with angiographically confirmed CAD (CAD+). Also, 50 consecutive individuals with normal coronary studies were included in the study for comparison. VEGF mRNA expression was examined using quantitative real-time PCR and genotyping for VEGF -2,578C/A was performed using ARMS-PCR technique. VEGF mRNA expression was significantly decreased in CAD+ patients when compared to CAD- individuals (p = 0.01). The frequency of VEGF -2578 allele C and genotype CC was increased in CAD+ patients. In this regard, homozygosity for the CC genotype was more commonly observed in CAD+ (30 %) than in those without CAD disease (18 %). However, the difference was slightly out of the range of significance (p = 0.1). In addition, a trend for reduction in the expression of VEGF mRNA was observed when patients carrying the VEGF -2,578AA genotype were compared with those VEGF -2,578AC heterozygous or those homozygous for the VEGF -2,578CC genotype. VEGF gene expression is decreased in individuals with CAD+ disease. The VEGF -2,578C/A polymorphism may influences the expression of VEGF.     

VEGF gene therapy for coronary artery disease and peripheral vascular disease

Coronary artery disease (CAD) and peripheral arterial disease (PAD) are significant medical problems worldwide. Although substantial progress has been made in prevention as well as in the treatment, particularly of CAD, there are a large number of patients, who despite maximal medical treatment have substantial symptomatology and who are not candidates for mechanical revascularization. Therapeutic angiogenesis represents a novel, conceptually appealing treatment option. Ad(GV)VEGF121.10 (BIOBYPASS) is an adenovector, carrying the transgene encoding for human vascular endothelial growth factor 121 (VEGF(121)). A number of preclinical studies have demonstrated angiogenic activity of BIOBYPASS, not only anatomically but also functionally. Phase I clinical studies have demonstrated that intramyocardial infection of BIOBYPASS in patients with severe CAD as well as intramuscular injections of BIOBYPASS in patients with severe peripheral vascular disease (PVD) was well tolerated; furthermore, these studies provided some intriguing indications of activity, which led to initiation of major randomized Phase II "proof-of-concept" studies. This paper provides a review of the rationale behind BIOBYPASS as well as a summary of pertinent preclinical and early clinical data.     

Dysregulated miR-361-5p/VEGF Axis in the Plasma and Endothelial Progenitor Cells of Patients with Coronary Artery Disease

Dysfunction and reduction of circulating endothelial progenitor cell (EPC) is correlated with the onset of cardiovascular disorders including coronary artery disease (CAD). VEGF is a known mitogen for EPC to migrate out of bone marrow to possess angiogenic activities, and the plasma levels of VEGF are inversely correlated to the progression of CAD. Circulating microRNAs (miRNAs) in patient body fluids have recently been considered to hold the potential of being novel disease biomarkers and drug targets. However, how miRNAs and VEGF cooperate to regulate CAD progression is still unclear. Through the small RNA sequencing (smRNA-seq), we deciphered the miRNome patterns of EPCs with different angiogenic activities, hypothesizing that miRNAs targeting VEGF must be more abundant in EPCs with lower angiogenic activities. Candidates of anti-VEGF miRNAs, including miR-361-5p and miR-484, were enriched in not only diseased EPCs but also the plasma of CAD patients. However, we found out only miR-361-5p, but not miR-484, was able to suppress VEGF expression and EPC activities. Reporter assays confirmed the direct binding and repression of miR-361-5p to the 3′-UTR of VEGF mRNA. Knock down of miR-361-5p not only restored VEGF levels and angiogenic activities of diseased EPCs in vitro, but further promoted blood flow recovery in ischemic limbs of mice. Collectively, we discovered a miR-361-5p/VEGF-dependent regulation that could help to develop new therapeutic modalities not only for ischemia-related diseases but also for tumor angiogenesis.     

Serum levels of angiogenic cytokines in systemic lupus erythematosus and their correlation with disease activity

We investigated the serum concentration of hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and transforming growth factor beta1 (TGF-beta1) using an enzyme-linked immunosorbent assay (ELISA) in a group of 60 patients with systemic lupus erythematosus (SLE), and 20 healthy controls. We also examined the possible association between the serum concentrations of these factors and certain clinical, laboratory parameters and SLE activity. HGF, VEGF and TGF-beta1 were detectable in all patients with SLE, and in all normal individuals. bFGF was measurable in 70% of the patients with SLE and in 65% of the healthy controls. The HGF level was higher in active SLE (median 1,019.5pg/ml) than in inactive SLE (median 787.8 pg/ml) (p < 0.005) or in the control group (median 847.0 pg/ml) (p < 0.009). The level of VEGF in active SLE was also higher (203.5 pg/ml) than in inactive disease (116.1 pg/ml) (p < 0.05) or in healthy persons (133.5 pg/ml) (p < 0.04). The levels of bFGF and TGF-beta1 were similar for both the active and inactive SLE, and the control group (p > 0.05). We found a significant, positive correlation between the levels of HGF and bFGF (r = 0.268, p < 0.04), HGF and TGF-beta1 (r = 0.365, p < 0.005) and HGF and VEGF (r = 0.327, p < 0.02) as well as VEGF and TGF-beta1 (r = 0.543, p < 0.001). We found a positive correlation between VEGF serum levels and platelet counts (r = 0.272, p < 0.04), and the TGF-beta1 concentration and platelet count (r = 0.313; p < 0.02). There was also a positive correlation between HGF serum concentration and the SLE activity score (r = 0.435, p < 0.001), as well as between the level of VEGF and SLE activity (r = 0.252, p = 0.05). In conclusion, serum levels of the angiogenic factors HGF and VEGF may be relevant in SLE pathogenesis. Their concentrations seem to be markers of SLE activity.     

No influence of tumor growth by intramuscular injection of hepatocyte growth factor plasmid DNA: safety evaluation of therapeutic angiogenesis gene therapy in mice

Recently, a novel therapeutic treatment for ischemic diseases using angiogenic growth factors to augment collateral artery development has been proposed. As intramuscular injection of naked human hepatocyte growth factor (HGF) plasmid DNA induced therapeutic angiogenesis in several animal test subjects, we have started a clinical trial to treat peripheral arterial disease. However, one might assume that over-expression of angiogenic growth factors could enhance tumor growth. To resolve this issue, we examined the over-expression of HGF in tumor bearing mice. Tumors on their backs were prepared with an intradermal inoculation of A431, human epidermoid cancer cells expressing c-Met. These mice were intramuscularly injected with human HGF plasmid or control plasmid into the femoral muscle. Human HGF concentration was increased only in the femoral muscle, but not in blood. Although recombinant HGF stimulated the growth of A431 cells in vitro, temporally and locally HGF elevation in hindlimb had no effect on tumor growth in mice.     

Thymosin beta10 inhibits cell migration and capillary-like tube formation of human coronary artery endothelial cells

Thymosin beta10 is a cytoplasm G-actin sequestering protein whose functions are largely unknown. To determine the direct effects of exogenous thymosin beta10 on angiogenic potentials as endothelial cell migration and capillary-like tube formation, human coronary artery endothelial cells (HCAECs) were incubated with increasing doses of thymosin beta10 (25-100 ng/ml). By using a modified Boyden chamber assay, thymosin beta10 inhibited cell migration in a dose- and time-dependent manner with the maximal effect being a 36% reduction at 100 ng/ml as compared to controls (P < 0.01). In addition, thymosin beta10 (100 ng/ml) significantly inhibited the capillary-like tube-formation of HCAECs on Matrigel, showing a 21% reduction of the total tube length as compared to negative controls (P < 0.01). Furthermore, by using real time PCR analysis, thymosin beta10 significantly decreased mRNA levels of vascular endothelial growth factor (VEGF), VEGF receptor-1 (VEGFR-1) and integrin alphaV after 24 h treatment in HCAECs. By contrast, thymosin beta4 significantly increased HCAEC migration. These results indicate that thymosin beta10, but not thymosin beta4, have direct inhibitive effects on endothelial migration and tube formation that might be mediated via downregulation of VEGF, VEGFR-1 and integrin alphaV in HCAECs. This study suggests a potential therapeutic application of thymosin beta10 to the diseases with excessive angiogenesis such as cancer.     

Mechanisms of coronary angiogenesis in response to stretch: role of VEGF and TGF-beta

To test the hypotheses that cyclic stretch of 1) cardiac myocytes produces factors that trigger angiogenic events in coronary microvascular endothelial cells (CMEC) and 2) CMEC enhances the expression of growth factors, cardiac myocytes and CMEC were subjected to cyclic stretch in a Flexercell Strain Unit. Vascular endothelial growth factor (VEGF) but not basic fibroblast growth factor mRNA and protein levels increased approximately twofold in myocytes after 1 h of stretch. CMEC DNA synthesis increased approximately twofold when conditioned medium from stretched myocytes or VEGF protein was added, and addition of VEGF neutralizing antibody blocked the increase. CMEC migration and tube formation increased with the addition of conditioned media but were markedly attenuated by VEGF neutralizing antibody. Myocyte transforming growth factor-beta [corrected] (TGF-beta) increased 2.5-fold after 1 h of stretch, and the addition of TGF-beta neutralizing antibodies inhibited the stretch-induced upregulation of VEGF. Stretch of CMEC increased VEGF mRNA in these cells (determined by Northern blot and RT-PCR) and increased the levels of VEGF protein (determined by ELISA analysis) in the conditioned media. Therefore, cyclic stretch of cardiac myocytes and CMEC appears to be an important primary stimulus for coronary angiogenesis through both paracrine and autocrine VEGF pathways. These data indicate that 1) CMEC DNA synthesis, migration, and tube formation are increased in response to VEGF secreted from stretched cardiac myocytes; 2) VEGF in CMEC subjected to stretch is upregulated and secreted; and 3) TGF-beta signaling may regulate VEGF expression in cardiac myocytes.     

Circulating angiogenesis regulators in cancer patients

BACKGROUND/AIMS: To date, numerous studies have demonstrated that several angiogenesis regulators circulate in the blood and may function as endocrine factors in cancer patients. This review aims to give a comprehensive insight into the possible clinical value of circulating angiogenesis regulators, mainly basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and hepatocyte growth factor (HGF), angiogenin, pleiotrophin, thrombospondin (TSP) and endostatin (ES) in cancer patients. METHODS: A computerized (MEDLINE) and a manual search based on the reference lists of the publications were performed to identify articles published on this topic. RESULTS: In a detailed literature search, approximately 100 publications were found up to the end of 1999. Circulating angiogenic factors such as bFGF, VEGF, HGF and angiogenin have been evaluated not only as diagnostic and/or prognostic factors but also as predictive factors in cancer patients. On the other hand, little is known about the clinical significance of negative regulators. Neither the source nor the mechanism of protein externalization has been clarified in detail. CONCLUSIONS: Although there are no known factors with established clinical utility, circulating angiogenesis regulators may be useful in several situations. They could be used to determine the risk of developing cancer, to screen for early detection, to distinguish benign from malignant disease, and to distinguish between different types of malignancies. In patients with established malignancies such factors might be used to determine prognosis, to predict the response to therapy, and to monitor the clinical course. Further investigations are warranted to assess the specific utility of each factor.     

Helicobacter pylori infection and coronary artery disease

The aim of this investigation was to determine the seroprevalence of H. pylori in patients with coronary artery disease (CAD). Patients with coronary artery disease (n = 90) and control group (n = 90) were enrolled into this randomized, multi-centre study. CAD risk factors analyzed included age, male gender, diabetes mellitus, systemic hypertension, cigarette smoking, hypercholesterolemia and socioeconomic status. The results of this study showed a higher seroprevalence of Helicobacter pylori infection in patients with CAD compared to controls (78.8% versus 58.3%, p < 0.05). However, Helicobacter pylori seropositivity was not associated with coronary artery risk factors (smoking, body mass index, diabetes mellitus, hypertension, total cholesterol and socioeconomic status) either in the whole study population or in the patients and control subjects analyzed separately (P > 0.05). Further study are needed to clarify the precise role of Helicobacter pylori infection on the development of coronary artery disease.     

Down-regulation of vascular endothelial growth factor and up-regulation of pigment epithelium-derived factor: a possible mechanism for the anti-angiogenic activity of plasminogen kringle 5.

We have previously shown that intravitreal injection of plasminogen kringle 5 (K5), a potent angiogenic inhibitor, inhibits ischemia-induced retinal neovascularization in a rat model. Here we report that K5 down-regulates an endogenous angiogenic stimulator, vascular endothelial growth factor (VEGF) and up-regulates an angiogenic inhibitor, pigment epithelium-derived factor (PEDF) in a dose-dependent manner in vascular cells and in the retina. The regulation of VEGF and PEDF by K5 in the retina correlates with its anti-angiogenic effect in a rat model of ischemia-induced retinopathy. Retinal RNA levels of VEGF and PEDF are also changed by K5. K5 inhibits the p42/p44 MAP kinase activation and nuclear translocation of hypoxia-inducible factor-1alpha, which may be responsible for the down-regulation of VEGF. Down-regulation of endogenous angiogenic stimulators and up-regulation of endogenous angiogenic inhibitors, thus leading toward restoration of the balance in angiogenic control, may represent a mechanism for the anti-angiogenic activity of K5.     

Erythropoietin stimulates the coronary collateral development in patients with coronary chronic total occlusion

Objective

Erythropoietin (EPO) improves cardiac function and induces neovascularisation in post-myocardial infarction heart failure. The aim of this study was to analyse the association between the serum erythropoietin level and coronary collateral development in patients with coronary artery disease and chronic total occlusion.

Methods

A total of 168 patients consisting of 117 with coronary artery disease (CAD, (62 with chronic total occlusion (CTO), 55 without CTO)) and 51 with healthy coronary arteries were included in the study. The patients were assigned as coronary artery disease without CTO (group 0), CAD with CTO (group 1: poor collateral development, group 2: good collateral development) and normal coronary arteries (group 3).

Results

There was a significant positive correlation between serum EPO levels and the Rentrop scores in angiography (r = 0.243, p = 0.001). Similarly, a positive correlation was found between serum EPO levels and the Syntax scores (r = 0.253, p = 0.001). Echocardiography revealed a negative correlation between serum EPO levels and the cardiac ejection fraction (r = ?0.210, p = 0.006).

Conclusions

Serum EPO is a useful biomarker for coronary collateral development in patients with CTO.

     

Combined transfer of human VEGF165 and HGF genes renders potent angiogenic effect in ischemic skeletal muscle

Increased interest in development of combined gene therapy emerges from results of recent clinical trials that indicate good safety yet unexpected low efficacy of "single-gene" administration. Multiple studies showed that vascular endothelial growth factor 165 aminoacid form (VEGF165) and hepatocyte growth factor (HGF) can be used for induction of angiogenesis in ischemic myocardium and skeletal muscle. Gene transfer system composed of a novel cytomegalovirus-based (CMV) plasmid vector and codon-optimized human VEGF165 and HGF genes combined with intramuscular low-voltage electroporation was developed and tested in vitro and in vivo. Studies in HEK293T cell culture, murine skeletal muscle explants and ELISA of tissue homogenates showed efficacy of constructed plasmids. Functional activity of angiogenic proteins secreted by HEK293T after transfection by induction of tube formation in human umbilical vein endothelial cell (HUVEC) culture. HUVEC cells were used for in vitro experiments to assay the putative signaling pathways to be responsible for combined administration effect one of which could be the ERK1/2 pathway. In vivo tests of VEGF165 and HGF genes co-transfer were conceived in mouse model of hind limb ischemia. Intramuscular administration of plasmid encoding either VEGF165 or HGF gene resulted in increased perfusion compared to empty vector administration. Mice injected with a mixture of two plasmids (VEGF165+HGF) showed significant increase in perfusion compared to single plasmid injection. These findings were supported by increased CD31+ capillary and SMA+ vessel density in animals that received combined VEGF165 and HGF gene therapy compared to single gene therapy. Results of the study suggest that co-transfer of VEGF and HGF genes renders a robust angiogenic effect in ischemic skeletal muscle and may present interest as a potential therapeutic combination for treatment of ischemic disorders.     

Epithelial Ovarian Cancer-Induced Angiogenic Phenotype of Human Omental Microvascular Endothelial Cells May Occur Independently of VEGF Signaling

Epithelial ovarian cancer (EOC) metastasizes transcoelomically to the peritoneum and omentum, and despite surgery and chemotherapy, recurrent disease is likely. Metastasis requires the induction of proangiogenic changes in the omental microenvironment and EOC-induced omental angiogenesis is currently a key therapeutic target. In particular, antiangiogenic therapies targeting the vascular endothelial growth factor A (VEGFA) pathway are commonly used, although, with limited effects. Here, using human omental microvascular endothelial cells (HOMECs) and ovarian cancer cell lines as an in vitro model, we show that factors secreted from EOC cells increased proliferation, migration, and tube-like structure formation in HOMECs. However, EOC-induced angiogenic tube-like formation and migration were unaffected by inhibition of tyrosine kinase activity of VEGF receptors 1 and 2 (Semaxanib; SU5416) or neutralization of VEGFA (neutralizing anti-VEGFA antibody), although VEGFA₁₆₅-induced HOMEC migration and tube-like structure formation were abolished. Proteomic investigation of the EOC secretome identified several alternative angiogenesis-related proteins. We screened these for their ability to induce an angiogenic phenotype in HOMECs, i.e., proliferation, migration, and tube-like structure formation. Hepatocyte growth factor (HGF) and insulin-like growth factor binding protein 7 (IGFBP-7) increased all three parameters, and cathepsin L (CL) increased migration and tubule formation. Further investigation confirmed expression of the HGF receptor c-Met in HOMECs. HGF- and EOC-induced proliferation and angiogenic tube structure formation were blocked by the c-Met inhibitor PF04217903. Our results highlight key alternative angiogenic mediators for metastatic EOC, namely, HGF, CL, and IGFBP-7, suggesting that effective antiangiogenic therapeutic strategies for this disease require inhibition of multiple angiogenic pathways.     

The coronary circulation in exercise training

Exercise training (EX) induces increases in coronary transport capacity through adaptations in the coronary microcirculation including increased arteriolar diameters and/or densities and changes in the vasomotor reactivity of coronary resistance arteries. In large animals, EX increases capillary exchange capacity through angiogenesis of new capillaries at a rate matched to EX-induced cardiac hypertrophy so that capillary density remains normal. However, after EX coronary capillary exchange area is greater (i.e., capillary permeability surface area product is greater) at any given blood flow because of altered coronary vascular resistance and matching of exchange surface area and blood flow distribution. The improved coronary capillary blood flow distribution appears to be the result of structural changes in the coronary tree and alterations in vasoreactivity of coronary resistance arteries. EX also alters vasomotor reactivity of conduit coronary arteries in that after EX, α-adrenergic receptor responsiveness is blunted. Of interest, α- and β-adrenergic tone appears to be maintained in the coronary microcirculation in the presence of lower circulating catecholamine levels because of increased receptor responsiveness to adrenergic stimulation. EX also alters other vasomotor control processes of coronary resistance vessels. For example, coronary arterioles exhibit increased myogenic tone after EX, likely because of a calcium-dependent PKC signaling-mediated alteration in voltage-gated calcium channel activity in response to stretch. Conversely, EX augments endothelium-dependent vasodilation throughout the coronary arteriolar network and in the conduit arteries in coronary artery disease (CAD). The enhanced endothelium-dependent dilation appears to result from increased nitric oxide bioavailability because of changes in nitric oxide synthase expression/activity and decreased oxidant stress. EX also decreases extravascular compressive forces in the myocardium at rest and at comparable levels of exercise, mainly because of decreases in heart rate and duration of systole. EX does not stimulate growth of coronary collateral vessels in the normal heart. However, if exercise produces ischemia, which would be absent or minimal under resting conditions, there is evidence that collateral growth can be enhanced. While there is evidence that EX can decrease the progression of atherosclerotic lesions or even induce the regression of atherosclerotic lesions in humans, the evidence of this is not strong due to the fact that most prospective trials conducted to date have included other lifestyle changes and treatment strategies by necessity. The literature from large animal models of CAD also presents a cloudy picture concerning whether EX can induce the regression of or slow the progression of atherosclerotic lesions. Thus, while evidence from research using humans with CAD and animal models of CAD indicates that EX increases endothelium-dependent dilation throughout the coronary vascular tree, evidence that EX reverses or slows the progression of lesion development in CAD is not conclusive at this time. This suggests that the beneficial effects of EX in CAD may not be the result of direct effects on the coronary artery wall. If this suggestion is true, it is important to determine the mechanisms involved in these beneficial effects.