Serum levels of VEGF and basic FGF in the subacute phase of myocardial infarction

Angiopoietins, vascular endothelial growth factors and secretory phospholipase A2 in heart failure patients with preserved ejection fraction

BACKGROUND

Heart failure (HF) is a growing public health burden, with high prevalence and mortality rates. A proportion of patients with HF have a normal ventricular ejection fraction (EF), referred to as HF with preserved EF (HFpEF), as opposed to patients with HF with reduced ejection fraction (HFrEF). HFpEF currently accounts for about 50% of all HF patients, and its prevalence is rising. Angiopoietins (ANGPTs), vascular endothelial growth factors (VEGFs) and secretory phospholipases A₂ (sPLA₂s) are proinflammatory mediators and key regulators of endothelial cells.

METHODS

The aim of this study was to analyze the plasma concentrations of angiogenic (ANGPT1, ANGPT2, VEGF-A) and lymphangiogenic (VEGF-C, VEGF-D) factors and the plasma activity of sPLA₂ in patients with HFpEF and HFrEF compared to healthy controls.

RESULTS

The concentration of ANGPT1 was reduced in HFrEF compared to HFpEF patients and healthy controls. ANGPT2 levels were increased in both HFrEF and HFpEF subjects compared to controls. The ANGPT2/ANGPT1 ratio was increased in HFrEF patients compared to controls. The concentrations of both VEGF-A and VEGF-C did not differ among the three groups examined. VEGF-D was increased in both HFrEF and HFpEF patients compared to controls. Plasma activity of sPLA₂ was increased in HFrEF but not in HFpEF patients compared to controls.

CONCLUSIONS

Our results indicate that three different classes of proinflammatory regulators of vascular permeability and smoldering inflammation are selectively altered in HFrEF or HFpEF patients. Studies involving larger cohorts of these patients will be necessary to demonstrate the clinical implications of our findings.

Angiopoietins, Vascular Endothelial Growth Factors and Secretory Phospholipase A2 in Ischemic and Non-Ischemic Heart Failure

Heart failure (HF) is a growing public health burden, with high prevalence and mortality rates. In contrast to ischemic heart failure (IHF), the diagnosis of non-ischemic heart failure (NIHF) is established in the absence of coronary artery disease. Angiopoietins (ANGPTs), vascular endothelial growth factors (VEGFs) and secretory phospholipases A₂ (sPLA₂s) are proinflammatory mediators and key regulators of endothelial cells. In the present manuscript, we analyze the plasma concentrations of angiogenic (ANGPT1, ANGPT2, VEGF-A) and lymphangiogenic (VEGF-C, VEGF-D) factors and the plasma activity of sPLA₂ in patients with IHF and NIHF compared to healthy controls. The concentrations of ANGPT1, ANGPT2 and their ratio significantly differed between HF patients and healthy controls. Similarly, plasma levels of VEGF-D and sPLA₂ activity were higher in HF as compared to controls. Concentrations of ANGPT2 and the ANGPT2/ANGPT1 ratio (an index of vascular permeability) were increased in NIHF patients. VEGF-A and VEGF-C concentrations did not differ among the three examined groups. Interestingly, VEGF-D was selectively increased in IFH patients compared to controls. Plasma activity of sPLA₂ was increased in IHF and NIHF patients compared to controls. Our results indicate that several regulators of vascular permeability and smoldering inflammation are specifically altered in IHF and NIHF patients. Studies involving larger cohorts of these patients will be necessary to demonstrate the clinical implications of our findings.

Serum vascular endothelial growth factor level is elevated in patients with impaired glucose tolerance and type 2 diabetes mellitus

Objective

This study was performed to investigate the serum vascular endothelial growth factor (VEGF) levels in Chinese patients with impaired glucose tolerance (IGT) and newly diagnosed type 2 diabetes mellitus (T2DM).

Methods

A total of 189 subjects (41 controls, 40 patients with IGT, and 108 patients with newly diagnosed T2DM) were recruited. Serum VEGF levels were determined by ELISA; other metabolic parameters were assessed by standard laboratory methods.

Results

There were significant differences in serum VEGF levels among the T2DM, IGT, and control groups (T2DM vs. controls: 72.00 [45.40, 98.35] pg/mL vs. 53.10 [36.30, 116.25] pg/mL; IGT vs. controls: 78.17 [55.52, 137.25] pg/mL vs. 53.10 [36.30, 116.25] pg/mL). Moreover, serum VEGF levels were positively associated with the homeostasis model assessment for insulin resistance (HOMA-IR) value. Multiple linear regression analysis indicated that the HOMA-IR value was an independent risk factor for elevated serum VEGF level.

Conclusions

Both IGT and T2DM patients exhibited increased serum VEGF levels, compared with controls; increased serum VEGF level was positively associated with the HOMA-IR value. Therefore, the increased serum VEGF level might partially result from increased insulin resistance in these patients.

MicroRNA-135a-3p regulates angiogenesis and tissue repair by targeting p38 signaling in endothelial cells

Angiogenesis is a critical process in repair of tissue injury that is regulated by a delicate balance between pro- and antiangiogenic factors. In disease states associated with impaired angiogenesis, we identified that miR-135a-3p is rapidly induced and serves as an antiangiogenic microRNA (miRNA) by targeting endothelial cell (EC) p38 signaling in vitro and in vivo. MiR-135a-3p overexpression significantly inhibited EC proliferation, migration, and network tube formation in matrigel, whereas miR-135-3p neutralization had the opposite effects. Mechanistic studies using transcriptomic profiling, bioinformatics, 3'-UTR reporter and miRNA ribonucleoprotein complex -immunoprecipitation assays, and small interfering RNA dependency studies revealed that miR-135a-3p inhibits the p38 signaling pathway in ECs by targeting huntingtin-interacting protein 1 (HIP1). Local delivery of miR-135a-3p inhibitors to wounds of diabetic db/db mice markedly increased angiogenesis, granulation tissue thickness, and wound closure rates, whereas local delivery of miR-135a-3p mimics impaired these effects. Finally, through gain- and loss-of-function studies in human skin organoids as a model of tissue injury, we demonstrated that miR-135a-3p potently modulated p38 signaling and angiogenesis in response to VEGF stimulation by targeting HIP1. These findings establish miR-135a-3p as a pivotal regulator of pathophysiological angiogenesis and tissue repair by targeting a VEGF-HIP1-p38K signaling axis, providing new targets for angiogenic therapy to promote tissue repair.-Icli, B., Wu, W., Ozdemir, D., Li, H., Haemmig, S., Liu, X., Giatsidis, G., Cheng, H. S., Avci, S. N., Kurt, M., Lee, N., Guimaraes, R. B., Manica, A., Marchini, J. F., Rynning, S. E., Risnes, I., Hollan, I., Croce, K., Orgill, D. P., Feinberg, M. W. MicroRNA-135a-3p regulates angiogenesis and tissue repair by targeting p38 signaling in endothelial cells.

VEGF-A plasma levels are associated with microvascular obstruction in patients with ST-segment elevation myocardial infarction

BACKGROUND

Microvascular obstruction (MVO) is associated with poor outcome after ST-segment elevation myocardial infarction (STEMI). Vascular endothelial growth factor-A (VEGF-A) is a vascular permeability inducer playing a key role in MVO pathogenesis. We aimed to assess whether VEGF-A levels are associated with MVO, when evaluated by magnetic resonance imaging (MRI) in STEMI patients.

METHODS

The multicenter prospective PREGICA study included a CMR substudy with all consecutive patients with a first STEMI who had undergone cardiac MRI at baseline and at 6-month follow-up. Patients with initial TIMI flow >1 were excluded. VEGF-A levels were measured in blood samples drawn at inclusion.

RESULTS

Between 2010 and 2017, 147 patients (mean age 57 ± 10 years; 84% males) were included. MVO was present in 65 (44%) patients. After multivariate analysis, higher troponin peak (OR 1.005; 95% CI 1.001-1.008; p = 0.007) and VEGF-A levels (OR 1.003; 95% CI 1.001-1.005; p = 0.015) were independently associated with MVO. When considering only patients with successful percutaneous coronary intervention (final TIMI flow 3, n = 130), higher troponin peak (p = 0.004) and VEGF-A levels (p = 0.03) remained independently predictive of MVO. Moreover, MVO was associated with adverse left ventricular (LV) remodeling and VEGF-A levels were significantly and inversely correlated with LV ejection fraction (EF) at 6-month follow-up.

CONCLUSION

Our results show that VEGF-A levels were independently associated with MVO during STEMI and correlated with mid-term LVEF alteration. VEGF-A could therefore be considered as a biomarker of MVO in STEMI patients and be used to stratify patient prognosis.

Circulating Hepatocyte Growth Factor Level but Not Basic Fibroblast Growth Factor Level Is Elevated in Angiography-Proven Symptomatic Peripheral Artery Disease

Circulating vasogenic factors may be up-regulated in response to ischemia to promote angiogenesis in patients with peripheral artery disease (PAD). Studies on this are limited in number and size, and results are inconsistent, especially regarding basic fibroblast growth factor (bFGF) level. From March 1999 to April 2004, all consecutive patients with lower limb PAD having serum samples at the time of intervention were recruited. The diameter of the primary PAD lesion had to be at least 70% stenotic at the lower limb artery. Control subjects, who underwent angiography, were free of PAD, coronary disease, and other major medical diseases. Serum samples were analyzed for circulating hepatocyte growth factor (HGF) and bFGF levels. Patients with PAD (n = 60) had higher circulating HGF levels (mean ± SEM, 1544 ± 238 vs 970 ± 129 pg/mL; P = .04) but similar bFGF distribution tertiles (P = .55) compared with control subjects (n = 30). Thirty-six patients with summed PAD lesion lengths exceeding 5 cm demonstrated a significantly higher circulating HGF level compared with control subjects (mean ± SEM, 1701 ± 335 vs 970 ± 129 pg/mL; P = .048). Patients with concurrent coronary artery disease tend to have a higher circulating HGF level (mean ± SEM, 1606 ± 365 vs 970 ± 129 pg/mL; P = .06) but not a higher bFGF level compared with control subjects. Circulating HGF level, but not bFGF level, is significantly elevated in patients with symptomatic angiographically documented PAD, especially in those with more extensive involvement.

The no-reflow phenomenon: State of the art

Primary percutaneous coronary intervention (PCI) is the best available reperfusion strategy for acute ST-segment elevation myocardial infarction (STEMI), with nearly 95% of occluded coronary vessels being reopened in this setting. Despite re-establishing epicardial coronary vessel patency, primary PCI may fail to restore optimal myocardial reperfusion within the myocardial tissue, a failure at the microvascular level known as no-reflow (NR). NR has been reported to occur in up to 60% of STEMI patients with optimal coronary vessel reperfusion. When it does occur, it significantly attenuates the beneficial effect of reperfusion therapy, leading to poor outcomes. The pathophysiology of NR is complex and incompletely understood. Many phenomena are known to contribute to NR, including leukocyte infiltration, vasoconstriction, activation of inflammatory pathways and cellular oedema. Vascular damage and haemorrhage may also play important roles in the establishment of NR. In this review, we describe the pathophysiological mechanisms of NR and the tools available for diagnosing it. We also describe the microvasculature and the endothelial mechanisms involved in NR, which may provide relevant therapeutic targets for reducing NR and improving the prognosis for patients.

Improved Insulin Secretion by Autologous Islet Transplantation, Compared to Oral Antidiabetic Agents, after Distal Pancreatectomy

In this study, the effects of autologous islet transplantation (ITx) were compared to those of oral antidiabetic drugs (OAD) after distal pancreatectomy (NCT01922492). We enrolled nondiabetic patients who underwent distal pancreatectomy for benign tumors. In the ITx group, islets were isolated from the normal part of the resected pancreas and implanted via the portal vein. Patients who did not receive ITx were regularly monitored and were enrolled in the OAD group if diabetes mellitus developed. The OAD group was treated with metformin with or without vildagliptin. Metabolic parameters were monitored for 12 months postoperatively. Nine patients in the ITx group and 10 in the OAD group were included in the analysis. After 12 months, hemoglobin A1c significantly increased by 5% of the baseline in each group. Area under the curve for blood glucose (AUCglucose) of the 75-g oral glucose tolerance test increased similarly in the immediate postoperative period in both groups but significantly reduced only in the ITx group thereafter. Insulinogenic index (INSindex) significantly decreased from 25.6 ± 18.9 to 4.7 ± 3.7 in the OAD group, while no significant change was observed in the ITx group (from 15.0 ± 4.5 to 11.0 ± 8.2). In the multiple regression analysis, ITx was an independent factor for changes in AUCglucose and INSindex. In addition, changes in INSindex in the ITx group after postoperative 6 months were associated with the efficacy of islet isolation, amount of grafts, and peak serum HMGB1 and VEGF levels after ITx. ITx was superior to OAD in maintaining insulin secretory capacity and glucose tolerance after distal pancreatectomy.

Stable phase post-MI patients have elevated VEGF levels correlated with inflammation markers, but not with atherosclerotic burden

BACKGROUND

The role of vascular endothelial growth factor (VEGF) in patients in the stable phase after myocardial infarction (MI) has not yet been explored. Therefore, we compared the values of VEGF in post-MI patients with those obtained in healthy controls. Furthermore, we investigated whether the values of VEGF correlate to either inflammation markers or the atherosclerotic burden.

METHODS

41 male patients (on average 44 years old) in the stable phase after MI (on average 20.5 months after MI) were recruited, while 25 healthy age-matched males served as controls. Plasma levels of VEGF and several markers of inflammation were measured by standard procedures. The atherosclerotic burden was determined by the angiographic severity of coronary atherosclerosis, endothelial dysfunction (measured by ultrasound measurement of the flow mediated dilation of the brachial artery), the intima-media thickness of the common carotid artery and the ankle-brachial pressure index.

RESULTS

VEGF values were significantly elevated in post-MI patients compared to the controls (53.8 ± 42.7 pg/ml vs. 36.3 ± 8.9 pg/ml, p = 0.014). The elevated VEGF values significantly correlated to the (increased) values of the inflammatory molecules interleukin 6 and 8 (r = 0.37, p = 0.017; and r = 0.45, p = 0.003; respectively). In contrast, no correlation was found between VEGF and the parameters of the atherosclerotic burden, although FMD and IMT were significantly impaired in patients.

CONCLUSIONS

We found that plasma levels of VEGF are increased in the stable phase after MI and correlate with inflammation cytokines, but not with the atherosclerotic burden. Thus, this suggests that increased levels of VEGF are a part of ongoing inflammatory activity. Since VEGF in these patients stimulates neovascularization of inflamed plaques and induces their destabilization, the VEGF level can have an important negative prognostic value. Clearly, further studies are needed to clarify the role of VEGF as a prognostic marker.

Relationship between vascular endothelial growth factor and left ventricular dimension in patients with acute myocardial infarction

BACKGROUND

Although vascular endothelial growth factor (VEGF) is elevated in patients with acute myocardial infarction (AMI), the clinical significance of its elevation remains unclear. The present study was designed to determine the relationship between VEGF and left ventricular dimension in patients with AMI.

METHODS AND RESULTS

Plasma VEGF levels were examined by enzyme-linked immunosorbent assay daily for one week and then weekly for four weeks in 38 patients with AMI (65.4 ± 1.7 years). Left ventriculography was performed at 14 days, 6 months, and 2 years after the onset of AMI. Plasma VEGF levels were significantly elevated and reached a peak on day 6. Peak plasma VEGF levels positively correlated with both end-diastolic and end-systolic volume indices at 14 days after the onset of AMI. When patients with AMI were divided into two groups according to plasma VEGF levels on admission, left ventricular volume indices were higher in the high VEGF group than in the low VEGF group at the subacute phase of AMI (14 days). These differences were no longer present in the chronic phase of AMI.

CONCLUSION

Plasma VEGF levels were increased in patients with AMI, and peak levels were associated with left ventricular volume indices in the subacute phase, suggesting an important role of endogenous VEGF in the left ventricular dimension in patients with AMI.

Comparison of Various Niches for Endothelial Progenitor Cell Therapy on Ischemic Myocardial Repair

Objective—

Comparative studies are lacking that show the effects of different microenvironments on the activity of engrafted stem cells after myocardial infarction (MI). Here, we analyzed the temporal and spatial variations of angiogenesis, collateralization, and the expression of Akt-related signals after MI to test whether the effects of endothelial progenitor cells (EPCs) were different.

Methods and Results—

After the induction of MI, pigs were selected that did not develop a collateral coronary circulation (R0) or developed a significant collateral coronary circulation (R2). Both sets were allocated randomly to 4 groups: phosphate-buffered saline (intramyocardial injection of phosphate-buffered saline), EPC transplantation, LY294002 (intramyocardial injection of an Akt inhibitor), and EPCs plus LY294002. Infarcted porcine hearts at different time points and under different collateralized conditions exhibited a variety of vascular microenvironments. At 14 days post-MI, angiogenesis and the expression of Akt-mediated angiogenic cytokines predominated in R2 porcine hearts. When grafted into this microenvironment, EPCs induced the greatest effects in impeding the development of heart failure, preserving left ventricular function and dimensions, and inhibiting infarct expansion. LY294002 significantly reduced these effects.

Conclusion—

These findings suggest that the microenvironment that coexists with collateralization and Akt-mediated angiogenesis appears to be more beneficial to cardiac repair induced by EPC therapy than other niches after MI.

Vascular endothelial growth factor in coronary sinus: Evidence for its association with coronary collaterals

OBJECTIVES

To explore whether local growth factors concentration, including vascular endothelial growth factor (VEGF) and transforming growth factor beta one (TGF-beta(1)), influence the formation of coronary collaterals.

DESIGN

Thirty-six patients scheduled for coronary angiography received a 6F Goodale-Lubin catheterization to collect blood from the coronary sinus (CS) and right atrium (RA).

RESULTS

Patients with coronary collaterals had a higher number of diseased vessels (2.6+/-0.2 vs. 1.4+/-0.3, p = 0.005), higher percentage of severity of stenosis (93+/-2 vs. 48+/-8, P < 0.001) and higher VEGF concentrations in CS (38.9+/-3.9 pg/ml vs. 20.8+/-1.4 pg/ml, P < 0.001) and in RA (31.7+/-3.1 pg/ml vs. 22.0+/-2.3 pg/ml, p = 0.004). There was no significant relationship between coronary collateral formation and TGF-beta(1) concentration. By binary logistic regression analysis, VEGF concentrations in CS (p = 0.030) and stenosis severity (p = 0.042) are correlated positively with collateral formation.

CONCLUSIONS

The association between local, endogenous secretion of VEGF and coronary collateral formation is compatible with a paracrine role for this growth factor in pathophysiologic collateral formation.

Vascular endothelial growth factors in cardiovascular medicine

The discovery of vascular endothelial growth factors (VEGFs) and their receptors has considerably improved the understanding of the development and function of endothelial cells. Each member of the VEGF family appears to have a specific function: VEGF-A induces angiogenesis (i.e. growth of new blood vessels from preexisting ones), placental growth factor mediates both angiogenesis and arteriogenesis (i.e. the formation of collateral arteries from preexisting arterioles), VEGF-C and VEGF-D act mainly as lymphangiogenic factors. The study of the biology of these endothelial growth factors has allowed a major progress in the comprehension of the genesis of the vascular system and its abnormalities observed in various pathologic conditions (atherosclerosis and coronary artery disease). The role of VEGF in the atherogenic process is still unclear, but actual evidence suggests both detrimental (development of a neoangiogenetic process within the atherosclerotic plaque) and beneficial (promotion of collateral vessel formation) effects. VEGF and other angiogenic growth factors (fibroblast growth factor), although initially promising in experimental studies and in initial phase I/II clinical trials in patients with ischemic heart disease or peripheral arterial occlusive disease, have subsequently failed to show significant therapeutic improvements in controlled clinical studies. Challenges still remain about the type or the combination of angiogenic factors to be administered, the form (protein vs. gene), the route, and the duration of administration.

Chemotaxis analysis of circulating monocytes in patients with a recent acute coronary syndrome

BACKGROUND

Monocytes/macrophages are crucially involved in the process of atherogenesis. Presence of an acute coronary syndrome (ACS) is associated with macrophage activation. We investigated whether ligand-induced monocyte chemotaxis can serve as biomarker in recent ACS and discriminate ACS from stable coronary artery disease (CAD).

METHODS

In a prospective study, the migratory response of monocytes towards the chemotactic ligands vascular endothelial growth factor-A (VEGF-A) and monocyte chemoattractant protein-1 (MCP-1) in patients with recent ACS (n=29) (median time period since cardiovascular event, 11 days) and stable CAD patients (n=41) was analysed. Furthermore, blood levels of C-reactive protein (CRP), VEGF-A and soluble vascular endothelial growth factor receptor-1 (sVEGRF-1) were determined.

RESULTS

Unexpectedly, VEGF-A-induced monocyte chemotaxis did not differ between ACS and CAD. The same was true for the chemotactic response of monocytes towards MCP-1. In addition, we could not find any difference in VEGF-A and sVEGFR-1 levels between recent ACS and stable CAD. CRP was significantly enhanced in the ACS group, but did not correlate with the VEGF-A- and MCP-1-induced chemotaxis.

CONCLUSIONS

Recent ACS is not associated with enhanced monocyte chemotaxis towards VEGF-A and MCP-1. Therefore, VEGF-A- and MCP-1-induced monocyte chemotaxis as a potential novel biomarker remains unaffected by recent ACS.

Identification of serum endoglin as a novel prognostic marker after acute myocardial infarction

Endoglin is a proliferation-associated and hypoxia-inducible protein expressed in endothelial cells. The levels of soluble circulating endoglin and their prognostic significance in patients with acute myocardial infarction (AMI) are not known. In this observational prospective study serum endoglin levels were measured by ELISA in 183 AMI patients upon admission to hospital and 48 hrs later and in 72 healthy controls. Endoglin levels in AMI patients on admission were significantly lower than in healthy controls (4.25 ± 0.99 ng/ml versus 4.59 ± 0.87 ng/ml; P= 0.013), and decreased further in the first 48 hours (3.65 ± 0.76 ng/ml, P < 0.001). Upon follow-up (median 319 days), patients who died had a significantly greater decrease in serum endoglin level over the first 48 hrs than those who survived (1.03 ± 0.91 versus 0.54 ± 0.55 ng/ml; P= 0.025). Endoglin decrease was an independent predictor of short-term (30 days) (hazard ratio 2.33;95% CI = 1.27–4.23; P= 0.006) cardiovascular mortality, and also predicts overall cardiovascular mortality during the follow-up (median 319 days) in AMI patients (hazard ratio 2.13;95% CI = 1.20–3.78; P= 0.01). In conclusion, early changes in serum endoglin may predict mortality after AMI.

Fibroblast growth factor-2 and cardioprotection

Boosting myocardial resistance to acute as well as chronic ischemic damage would ameliorate the detrimental effects of numerous cardiac pathologies and reduce the probability of transition to heart failure. Experimental cardiology has pointed to ischemic and pharmacological pre- as well as post-conditioning as potent acute cardioprotective manipulations. Additional exciting experimental strategies include the induction of true regenerative and/or angiogenic responses to the damaged heart, resulting in sustained structural and functional beneficial effects. Fibroblast growth factor-2 (FGF-2), an endogenous multifunctional protein with strong affinity for the extracellular matrix and basal lamina and well-documented paracrine, autocrine and intracellular modes of action, has been shown over the years to exert acute and direct pro-survival effects, irrespectively of whether it is administered before, during or after an ischemic insult to the heart. FGF-2 is also a potent angiogenic protein and a crucial agent for the proliferation, expansion, and survival of several cell types including those with stem cell properties. Human clinical trials have pointed to a good safety record for this protein. In this review, we will present a case for the low molecular weight isoform of fibroblast growth factor-2 (lo-FGF-2) as a very promising therapeutic agent to achieve powerful acute as well as sustained benefits for the heart, due to its cytoprotective and regenerative properties.

Coordinate release of angiogenic growth factors after acute myocardial infarction: evidence of a two-wave production

BACKGROUND

Previous studies have shown that angiopoietic growth factors, including vascular endothelial growth factor (VEGF), angiopoietin-2 (Ang-2), hepatocyte growth factor (HGF) and transforming growth factor (TGF)-beta1 are released after acute myocardial infarction (AMI). It was suggested that the release of these factors, triggered by ischemia, may be related to a reparative neoangiogenetic process.

METHODS

Plasma VEGF, Ang-2, HGF and TGF-beta levels were measured on admission (baseline) and at various times during the acute (0-48 h) and the subacute (48-240 h) phase in 44 patients with AMI.

RESULTS

In the present study, we have explored in detail the kinetics of release of these growth factors after AMI with the precise aim of evaluating the existence of a double wave of release of these factors: (i) a first wave in the acute and (ii) a second one in the subacute period. The results of these analyses provided evidence for an early (peak at 24-28 h) and late (peak at approximately 170 h) increase of VEGF, Ang-2 and TGF-beta.

CONCLUSIONS

According to these data, we suggest that two waves of release of angiogenic factors occur after AMI. The early release makes part of an acute phase response, whereas the late release may underlie the induction of angiogenetic mechanisms involved in tissue reparation.

Effect of heparin on blood vascular endothelial growth factor levels in patients with ST-elevation acute myocardial infarction undergoing primary percutaneous coronary intervention

It has been demonstrated that high blood vascular endothelial growth factor (VEGF) levels in patients with myocardial infarction decrease rapidly after reperfusion, possibly in response to heparin administration. We measured serum VEGF concentration before and after heparin infusion in 105 patients with ST-elevation acute myocardial infarction (STEMI) who underwent primary percutaneous coronary intervention (PCI). Serum VEGF concentration in patients with STEMI was significantly higher than in healthy controls. After PCI, the concentration of VEGF decreased by approximately 70%, with the greatest decrease seen in patients with the highest initial VEGF levels. To determine whether heparin could decrease VEGF concentration by sequestering VEGF in the endothelium, a fixed dose of recombinant VEGF was incubated for 40 minutes with EA.hy926 endothelial cells in vitro. Recovery of VEGF from medium after culture was decreased by up to 15% with increasing doses of heparin. Concentration of VEGF did not change in the absence of heparin and/or endothelial cells. In conclusion, these results suggest that a rapid decrease in blood VEGF after PCI may be related to the administration of heparin, which binds simultaneously to VEGF and endothelial cells.

Tissue plasminogen activator in chronic subdural hematomas as a predictor of recurrence

Object

Chronic subdural hematomas (CSDHs) recur in 7 to 18% of cases. The present study was conducted to determine whether serum or lesion concentrations of coagulofibrinolytic and angiogenic factors, which have been reported to be potential markers of CSDH development, might predict such recurrences.

Methods

Sixty consecutive patients (mean age 71.5 years) with CSDHs (74 affected sides) were studied. Samples of serum in preoperative peripheral venous blood and of hematomas (obtained during surgery) were collected and analyzed. The CSDH recurred in six (8.1%) of the 74 affected sides in six patients. None of the values of the coagulative factors or tests in serum showed significant variation between cases with and those without recurrence. Among coagulofibrinolytic factors, tissue plasminogen activator (TPA) in hematomas demonstrated significantly greater levels in recurrent than in nonrecurrent cases; a similar tendency was noted for α2-plasmin inhibitor–plasmin complex in hematomas. Both factors were greater in the lesions than in the serum. Among the angiogenic factors, levels of hepatic growth factor (HGF) and vascular endothelial growth factor (VEGF) in hematomas were significantly greater than in serum, whereas those of basic fibroblast growth factor were rather lower. Note that comparisons between recurrent and nonrecurrent cases revealed no significant difference.

Conclusions

Patients harboring CSDHs with high TPA concentrations on sampling at the initial surgery have a relatively high probability of recurrence and require follow up with computerized tomography scanning. Angiogenic factors, such as HGF and VEGF, might be candidate markers of CSDH enlargement but are not useful as predictors of recurrence.

Changes in circulating mesenchymal stem cells, stem cell homing factor, and vascular growth factors in patients with acute ST elevation myocardial infarction treated with primary percutaneous coronary intervention

OBJECTIVE

To investigate the spontaneous occurrence of circulating mesenchymal stem cells (MSC) and angiogenic factors in patients with ST elevation acute myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI).

DESIGN

In 20 patients with STEMI, blood samples were obtained on days 1, 3, 7, 14, 21, and 28 after the acute PCI. Fifteen patients with a normal coronary angiography formed a control group. MSC (CD45-/CD34-), plasma stromal derived factor 1 (SDF-1), vascular endothelial growth factor A (VEGF-A), and fibroblast growth factor 2 (FGF-2) were measured by multiparametric flow cytometry and enzyme linked immunosorbent assay (ELISA).

RESULTS

Circulating CD45-/CD34- cells were significantly decreased on day 7 compared with day 3. Cell counts normalised one month after the acute onset of STEMI. The changes were mainly seen in patients with a large infarction. Plasma SDF-1 increased significantly from day 3 to day 28, and VEGF-A and FGF-2 increased significantly from day 7 to day 28.

CONCLUSIONS

Spontaneous sequential fluctuations in MSC and the increase in vascular growth factor concentrations after STEMI suggest that the optimal time for additional stem cell therapy is three weeks after a myocardial infarction to obtain the maximum effects by stimulating endogenous growth factors on the delivered stem cells.

Effects of Total Coronary Artery Occlusion on Vascular Endothelial Growth Factor and Transforming Growth Factor β

Vascular endothelial growth factor (VEGF) and transforming growth factor beta (TGF-beta1) play an important role in angiogenesis. We wanted to determine if concentrations of growth factors in the coronary sinus (CS) and right atrium (RA) are higher in coronary artery disease patients with total occlusions than in those with partial occlusions. Fifty-one patients scheduled for coronary artery angiography were evaluated for possible recruitment. A 6F Goodale-Lubin catheter was used to collect blood from the CS and RA. Data for all but four patients were gathered successfully, leaving 47 study patients. The reviewer was blinded to growth factor data when interpreting coronary angiographic findings. Of the 47 enrolled patients, 32 had at least one diseased vessel, seven of whom had at least one major total epicardial coronary occlusion. In all 32 patients, the concentrations of VEGF in the CS were higher than those in the RA (31.5 +/- 2.7 vs 27.1 +/- 1.8 pg/mL; p = 0.005). Patients with total occlusions had higher VEGF concentrations in the CS than those with non-total occlusions (38.9 +/- 8.0 vs 29.5 +/- 2.6 pg/mL; p = 0.037). The differences in TGF-beta1 in the two groups were not statistically significant. The higher CS VEGF concentrations in patients with total occlusion indicate that VEGF may play a part in the development of angiogenesis.

Effects of calcium and thrombin on growth factor release from platelet concentrates: kinetics and regulation of endothelial cell proliferation

Platelet concentrates (PCs) constitute new biological mediators used in osseous reconstructive surgery. In this study, we assessed (i) the effects of various concentrations of calcium and thrombin on the kinetics of platelet-derived growth factor (PDGF-BB), transforming growth factor-beta1(TGF-beta 1), basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) release by PCs and (ii) the contribution of PC supernatants to endothelial cell proliferation. Our results indicate that high concentrations of calcium (Ca) and thrombin (Thr) trigger an immediate and significant increase in bFGF, TGF-beta 1 and PDGF-BB concentrations. Thereafter, PDGF-BB, VEGF and TGF-beta 1 levels remained generally constant over a 6-day period while a decrease in bFGF concentrations was noted after 24h. Lower Ca and Thr concentrations tended to reduce and delay growth factors release from PCs. Endothelial cell proliferation was greatly enhanced with PC supernatants (mean: 20-fold increase). This was especially evident when endothelial cells were treated with supernatants harvested early after PC treatment with high concentrations of Ca and Thr or later after PC treatment with low Ca and Thr concentrations. Additional research aiming to measure the effects of Ca and Thr on bone formation in vivo is needed.

Increased circulating hematopoietic and endothelial progenitor cells in the early phase of acute myocardial infarction

Endothelial progenitor cell (EPC) mobilization has been reported following tissue damage, whereas no data are available regarding the mobilization of hematopoietic progenitor cells (HPCs). We performed the phenotypic and functional analysis of circulating CD34+ progenitor cells in patients with acute myocardial infarction (AMI), assessed from admission up to 60 days, in patients with stable angina pectoris (SA), and in healthy controls (CTRLs). In patients with AMI at admission (T0), the number of circulating CD34+ cells was higher (P < .001) than in CTRLs and became comparable with CTRLs within 60 days. Both the number of CD34+ cells coexpressing CD33, CD38, or CD117 and the number of HPCs was higher (P < .02 for all) in patients with AMI at T0 than in CTRLs, as was the number of hematopoietic colonies (P < .03). Patients with AMI (T0) had a significantly increased number of CD34+ vascular endothelial growth factor receptor 2-positive (VEGFR-2+) cells (P < .002) with respect to CTRLs, including CD34(+) CD133(+)VEGFR-2+ and CD34+ CD117(+)VEGFR-2+ EPCs. The number of endothelial colonies was higher in patients with AMI (T0) than in CTRLs (P < .05). No significant difference was documented between patients with SA and CTRLs. Spontaneous mobilization of both HPCs and EPCs occurs within a few hours from the onset of AMI and is detectable until 2 months.

Plasma angiopoietin-1, angiopoietin-2, angiopoietin receptor tie-2, and vascular endothelial growth factor levels in acute coronary syndromes

BACKGROUND

Angiopoietin (Ang) -1 and -2, their receptor Tie-2, and vascular endothelial growth factor (VEGF) regulate angiogenesis and may be important in myocardial collateral development. Elevated levels of growth factors and their receptors are reported in myocardial infarction (MI), but changes after an acute coronary event are unknown.

METHODS AND RESULTS

Plasma Ang-1, Ang-2, Tie-2, and VEGF levels were measured on admission (baseline) and at 48 hours (acute stage) in 126 patients with acute coronary syndrome (82 MI, 44 unstable angina pectoris). Baseline levels were compared with those of 40 patients with stable angina and 40 healthy controls. Measurements were repeated in 38 MI patients at 6 and 18 weeks (chronic stage). Baseline Ang-2 and Tie-2 levels were highest in MI patients (P<0.001). Patients with MI and unstable angina pectoris had higher VEGF levels compared with stable angina patients and healthy control subjects (P<0.001). In patients with acute MI, serial changes in all indexes from baseline to 18 weeks were observed (all P<0.001). Ang-1 levels were unchanged from baseline to 6 weeks but were elevated at 18 weeks. Ang-2 changes followed a biphasic pattern, being higher at baseline and 6 weeks but lower at 48 hours and 18 weeks. Tie-2 levels increased from baseline and remained elevated in the chronic phase. VEGF peaked at 6 weeks and then decreased toward baseline at 18 weeks.

CONCLUSIONS

Plasma Ang-2, Tie-2, and VEGF levels but not Ang-1 levels were increased in patients with acute coronary syndrome. Serial changes in the plasma levels and interrelationships among Ang-1, Ang-2, Tie-2, and VEGF levels from the acute to the chronic stages in MI may reflect the progressive stages of angiogenesis activity in the ischemic-necrotic myocardium in vivo.

Hepatocyte growth factor and vascular endothelial growth factor in ischaemic heart disease

BACKGROUND

Hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) are endothelial cell-specific growth factors, but the production of these growth factors in cardiomyocytes has also been demonstrated. However, there have been no reports focusing their attention on the changes in these growth factors after coronary intervention. We investigated the time-course changes of the serum VEGF and HGF levels in angina pectoris (AP) and acute myocardial infarction (AMI).

METHODS

The serum HGF and VEGF levels were measured in 60 patients with AP, in 62 patients with AMI (AP, before heparin administration, and at 24 and 48 hours, and one week after intervention; AMI, before heparin, and at 48 and 72 hours, and one, two, three and four weeks) and in 56 patients with neurocirculatory asthenia as controls. We defined the patients with remodelling who showed an increase in left ventricular end-diastolic volume index (LVEDVI) in the sub-acute phase of AMI.

RESULTS

Hepatocyte growth factor levels in the AP and AMI were significantly higher than that in the control (p<0.0001). The AMI level was also significantly higher than AP (p<0.001). In the AMI and AP, HGF peaked at 48 hours. Vascular endothelial growth factor level in the AMI was significantly higher than that in the control and AP (p<0.0001). In the AMI, VEGF peaked at two weeks. There was a significant positive correlation between the peak VEGF and LVEDVI in the sub-acute phase of AMI (p=0.0089, r=0.436). Peak VEGF in the remodelling (+) group was significantly higher than that in the remodelling (-) group (p<0.001). In the AP, VEGF was unchanged.

CONCLUSION

While both myocardial and vascular damage contribute to an increase in HGF level, vascular damage is not associated with the increase in VEGF. Vascular endothelial growth factor might be related to left ventricular remodelling in the sub-acute phase of myocardial infarction.

Pulmonary expression of vascular endothelial growth factor in sepsis

CONTEXT

Vascular endothelial growth factor (VEGF), an angiogenic and chemotactic peptide, is abundantly expressed in normal lung tissue, especially in alveolar and bronchial epithelium, glandular cells of the bronchi, and activated alveolar macrophages.

OBJECTIVE

To investigate the role of VEGF in progressively impaired lung function as the major complication and cause of death in septic patients.

MATERIALS AND METHODS

We evaluated pulmonary VEGF expression in lung autopsy material from septic patients who had been cared for by intensive care medicine using enzyme-linked immunosorbent assay (ELISA), reverse transcriptase-polymerase chain reaction (RT-PCR), and immunohistochemical methods.

RESULTS

Compared with expression in nonseptic control individuals (n = 10), pulmonary VEGF expression as determined by ELISA was significantly (P <.001) decreased in septic patients (n = 8). As monitored by RT-PCR, mRNA for the 2 splice variants, VEGF(121) and VEGF(165), and for VEGFR-2/KDR were expressed in both groups, the yields being lower in the sepsis group. Samples from septic patients lacked or showed only sparse immunoreaction on bronchial and alveolar epithelium, whereas this reaction was strong in all control samples. However, alveolar macrophages were similarly immunopositive in both groups.

CONCLUSIONS

The precise underlying mechanisms for the distinctly different expression of pulmonary VEGF in septic patients and nonseptic control individuals are not clear at present. Particularly the role of VEGF in the development of sepsis-induced lung injury and acute respiratory distress syndrome in mechanically ventilated patients suffering from severe sepsis remains to be clarified.

Vascular endothelial growth factor mRNA synthesis by peripheral blood mononuclear cells in patients with acute myocardial infarction

We studied vascular endothelial growth factor (VEGF) mRNA synthesis by peripheral blood mononuclear cells (PBMCs) in 30 patients with acute myocardial infarction (AMI) and 20 healthy individuals. PBMCs were isolated from all patients on days 3 and 14 after the onset of aMI, and from all of control individuals. To prepare samples containing identical amounts of GAPDH cDNA, competitive PCR was performed by co-amplifying serial dilutions of GAPDH mutant templates. Next, to measure VEGF cDNA quantitatively in the samples containing identical amounts of GAPDH, we also used competitive PCR by co-amplifying mutant templates of VEGF. The serum VEGF concentrations on day 14 in patients with aMI were measured by an ELISA method. Higher levels of VEGF mRNA in PBMCs were present on day 14 than either on day 3 or in the control group. Serum VEGF concentrations correlated with the VEGF mRNA levels of PBMCs on day 14. Peak serum CK levels correlated well with VEGF mRNA levels of PBMCs on day 14. The present findings suggest that PBMCs may be one of the candidates responsible for elevated circulatory VEGF protein following aMI. In addition, VEGF mRNA may be overexpressed in PBMCs in response to cardiac muscle damage.

Ischemic preconditioning upregulates vascular endothelial growth factor mRNA expression and neovascularization via nuclear translocation of protein kinase C epsilon in the rat ischemic myocardium

Ischemic preconditioning (IP) exerts cardioprotection through protein kinase C (PKC) activation, whereas myocardial ischemia enhances vascular endothelial growth factor (VEGF) mRNA expression. However, the IP effect or the involvement of PKC on the VEGF expression is unknown in myocardial infarction. We investigated whether IP enhances VEGF gene expression and angiogenesis through PKC activation in the in vivo myocardial infarction model. Sprague-Dawley rats were assigned into the following 3 groups: the sham group; the IP group, which underwent 3 cycles of 3 minutes of ischemia and 5 minutes of reperfusion (IP procedure); and the non-IP group. The latter 2 groups were subsequently subjected to left anterior descending coronary artery occlusion. To examine the involvement of PKC, the PKC inhibitor chelerythrine (5 mg/kg) or bisindolylmaleimide (1 mg/kg) was injected intravenously before the IP procedures. PKCepsilon was translocated to the nucleus after 10 minutes of ischemia after the IP procedure but was not translocated in the non-IP and the sham groups. VEGF mRNA expression 3 hours after infarction was significantly higher in the IP group than in the non-IP and the sham groups. Capillary density in the infarction was significantly higher, whereas the infarct size was smaller in the IP group than in the non-IP group at 3 days of infarction. Chelerythrine but not bisindolylmaleimide blocked all of the IP effects on the nuclear translocation of PKCepsilon, enhancement of VEGF mRNA expression and angiogenesis, and infarct size limitation. These results show that IP may enhance VEGF gene expression and angiogenesis through nuclear translocation of PKCepsilon in the infarcted myocardium.

Pitfalls in the Measurement of Circulating Vascular Endothelial Growth Factor

Background: Vascular endothelial growth factor (VEGF) is a protein with antiapoptotic, mitogenic, and permeability-increasing activities specific for vascular endothelium. VEGF mRNA, which has five isoforms, is produced by nonmalignant cells in response to hypoxia and inflammation and by tumor cells in constitutively high concentrations. Because VEGF plays a crucial role in physiological and pathophysiological angiogenesis, measurements of circulating VEGF are of diagnostic and prognostic value, e.g., in cardiovascular failures, inflammatory diseases, and malignancies. However, there are major quantitative differences in the published results. This review attempts to identify reasons for these disparities.

Approach: The literature was reviewed through a Medline search covering 1995 to 2000. A selection of exemplary references had to be made for this perspective overview.

Content: Data are included from studies on healthy humans, gynecological patients, and persons suffering from inflammatory or malignant diseases. The results indicate that competitive immunoassays detect the total amount of circulating VEGF, which enables observations regarding the increase in VEGF in pregnancy and preeclampsia to be made. In these cases, capture immunoassays utilizing neutralizing antibodies are insufficient because of an accompanying increase in VEGF-binding soluble receptors (sFlt-1). Measurements of circulating free VEGF are useful for study of malignant diseases, which are associated with both genetically and hypoxia-induced overproduction of VEGF. The VEGF isoform specificity of the antibodies is also critical because both VEGF121 and VEGF165 are secreted. It is important to consider that platelets and leukocytes release VEGF during blood clotting.

Conclusions: Future efforts should concentrate on the balance between free VEGF, total VEGF, and sFlt-1. Plasma, rather than serum, should be used for analysis.

Increased serum levels of basic fibroblast growth factor in lung cancer patients: relevance to response of therapy and prognosis

Angiogenesis is controlled by inhibitors and angiogenic factors. Among these, basic fibroblast growth factor (bFGF) is closely involved in cancer proliferation and has been related to progression and prognosis of various cancers, including lung cancer. To evaluate the role of bFGF, we measured serum levels of bFGF from healthy controls (Ctrl) and 106 patients with lung cancer, including 31 adenocarcinomas (AD), 29 squamous cell carcinomas (SQ), and 46 small cell carcinomas (SCLC), by enzyme-linked immunosorbent assays. Moreover, we evaluated the relationship between serum levels of bFGF and clinical outcome. Serum levels of bFGF in AD, SQ, SCLC, and Ctrl were 7.6 (0.5-32.5) (median (range)), 7.4 (0.5-36.7), 7.1 (0.5-34.8) and 3.0 (1.5-6.0) pg/ml, respectively (P<0.05). Serum bFGF levels did not differ between clinical stages in non-small cell lung cancer (NSCLC; AD+SQ). In SCLC, we found a significant difference in serum levels of bFGF between chemotherapy (and/or radiotherapy) responders (complete response+partial response) and non-responders (no change+progressive disease) (9.2 (0.6-34.8), 4.4 (0.5-17.4) pg/ml, respectively (P=0.018)), whereas there was no difference in NSCLC. Moreover, serum bFGF levels in SCLC patients had significant impact in prognosis by uni and multivariate analysis (P=0.014, 0.018, respectively). We concluded that bFGF has an important role in the prognosis of patients with SCLC.

Role of vascular endothelial growth factor in diabetic vascular complications

BACKGROUND

Much of the morbidity and mortality associated with diabetes mellitus predominantly reflects its deleterious effects on microcirculation and macrocirculation. During the past few years, rapid advancement has been made in our understanding of the mechanisms and molecules involved in the pathogenesis of diabetic microvasculopathy. This is particularly true with regard to retinal vascular disease and the role of the angiogenesis- and vasopermeability-inducing molecule, vascular endothelial growth factor (VEGF).

METHODS

Biochemical studies in many relevant cell types have been performed. Effects of VEGF action and inhibition have been evaluated in animals. Interventions that block the biochemical pathways initiated by VEGF have been tested both in culture and in animals. Human clinical trials have begun.

RESULTS

VEGF induces vascular endothelial cell proliferation, migration and vasopermeability in many cells and tissues. In vivo, VEGF has been identified as a primary initiator of proliferative diabetic retinopathy, and as a potential mediator of nonproliferative retinopathy. In addition, VEGF has been implicated in the development of neuropathy and nephropathy in the patient with diabetes. In patients with diabetes and coronary artery or peripheral vascular disease, VEGF may induce development of cardiac and limb vascular collateralization, respectively. Many biochemical processes mediating these actions have now been elucidated.

CONCLUSIONS

VEGF appears to play a central role in mediating diabetic vasculopathy in many organs. Improved understanding of the molecular mechanisms underlying these processes has permitted development of novel therapeutic interventions, several of which are now in human clinical trials. These scientific advances and various implications for the future care of vasculopathy associated with diabetes will be discussed.

Expression of vascular endothelial growth factor in patients with acute myocardial infarction

OBJECTIVE

The purpose of this study was to investigate the clinical significance of vascular endothelial growth factor (VEGF) in acute myocardial infarction (AMI). We also examined the involvement of peripheral blood mononuclear cells (PBMCs), which are a possible source of VEGF in AMI.

BACKGROUND

VEGF is a potent endothelial cell-specific mitogen and could affect the outcome of AMI.

METHODS

Thirty patients with AMI were used for this study. Serum and PBMCs were isolated from peripheral blood on days 1, 7, 14 and 21 after the onset of AMI. PBMCs were cultured at a density of 5 x 10(6) cells/ml for 24 h. VEGF levels in serum and the culture media were measured by enzyme-linked immunosorbent assay using a specific anti-human VEGF antibody.

RESULTS

Serum VEGF levels elevated gradually after the onset of AMI and reached a peak on day 14. VEGF levels in the culture medium of PBMCs after incubation for 24 h (PBMC-VEGF) were maximally elevated 7 days after the onset. Maximum serum VEGF levels showed significant positive correlations with maximum creatine phosphokinase (CPK) levels (r = +0.70, p < 0.001), but maximum PBMC-VEGF levels did not correlate with maximum CPK levels. Patients showing improvement in left ventricular systolic function during the course of AMI showed significantly higher PBMC-VEGF levels than patients without improvement.

CONCLUSIONS

The extent of myocardial damage contributes to the elevation of serum VEGF levels in AMI. VEGF produced by PBMCs may play an important role in the improvement of left ventricular function by promoting angiogenesis and reendothelialization after AMI.

Elevation of vascular endothelial growth factor-A serum levels following acute myocardial infarction. Evidence for its origin and functional significance

Following the onset of acute myocardial infarction (AMI), a number of serum parameters show well-defined changes reflecting myocardial injury. During the consecutive repair phase, compensatory processes are initiated including the formation of a collateral circulation on the basis of angiogenesis and arteriogenesis. An important angiogenic factor is vascular endothelial growth factor-A (VEGF-A), shown to be upregulated in the ischemic myocardium. It is unclear, however, whether acute myocardial ischemia leads to a detectable elevation of VEGF-A serum concentrations. With the use of an immunoradiometric assay, we measured the levels of VEGF-A in the serum of patients after AMI at defined time intervals, of patients with unstable angina pectoris (UAP) and of healthy individuals. In addition, in a small group of patients with subacute myocardial infarction VEGF-A concentrations were measured in coronary sinus blood. The data are given as median followed by the 25th and 75th percentiles. In the group with AMI serum VEGF-A measured 105 [78; 176] pg/ml on day 1 and 114 pg/ml [72; 163] pg/ml on day 3 after onset of AMI. Serum levels of VEGF-A significantly increased on day 7 after AMI to 189 [119; 373] pg/ml (P=0.0103) and on day 10 to 255 [162; 371] pg/ml (P=0.0007). The VEGF-A serum level in healthy controls and in patients with UAP measured 98 [75; 137] pg/ml and 116 [57; 140] pg/ml, respectively. Serum at day 10 after AMI contained VEGF-A at a biologically relevant concentration capable of stimulating proliferation of endothelial cells. Surprisingly, VEGF-A serum levels were similar in samples taken from the coronary sinus with 61 [43; 83] pg/ml. Therefore the main source for VEGF-A in the blood stream is not the infarcted myocardium. However, the number of platelets, a rich source of VEGF-A, is significantly increased after myocardial infarction, i.e. 284 [252; 363] x 10(9)/litre v 220 [177; 250] x 10(9)/litre. In conclusion, the time course of VEGF-A elevation following AMI strongly suggests that VEGF-A plays a role as an endogenous activator of coronary collateral formation in the human heart. The most likely source of the elevated VEGF-A are platelets, rather than the infarcted myocardium.