Platelet Vascular Endothelial Growth Factor Research Articles

Optimization of Platelet-Rich Plasma Preparation for Regenerative Medicine: Comparison of Different Anticoagulants and Resuspension Media.

Platelet-rich plasma (PRP) has emerged as a promising therapy in regenerative medicine. However, the lack of standardization in PRP preparation protocols presents a challenge in achieving reproducible and accurate results. This study aimed to optimize the PRP preparation protocol by investigating the impact of two different anticoagulants, sodium citrate (SC) and ethylenediaminetetraacetic acid (EDTA), and resuspension media, plasma versus sodium chloride (NaCl). Platelet recovery rates were calculated and compared between groups, in addition to platelet activity and vascular endothelial growth factor (VEGF) released into plasma after PRP activation. The platelet recovery rate was higher with EDTA in comparison to SC (51.04% vs. 29.85%, p = 0.005). Platelet activity was also higher, with a higher expression of two platelet antibodies, platelet surface P-Selectin (CD62p) and PAC-1, in the EDTA group. The concentration of VEGF was higher with SC in comparison to EDTA (628.73 vs. 265.44 pg/mL, p = 0.013). Platelet recovery rates and VEGF levels were higher in PRP resuspended in plasma when compared to NaCl (61.60% vs. 48.61%, p = 0.011 and 363.32 vs. 159.83 pg/mL, p = 0.005, respectively). Our study reinforces the superiority of EDTA (as anticoagulant) and plasma (for resuspension) in obtaining a higher platelet recovery and preserving platelet functionality during PRP preparation.

Mutual regulation between phosphofructokinase 1 platelet isoform and VEGF promotes glioblastoma tumor growth

Glioblastoma (GBM) is a highly vascular malignant brain tumor that overexpresses vascular endothelial growth factor (VEGF) and phosphofructokinase 1 platelet isoform (PFKP), which catalyzes a rate-limiting reaction in glycolysis. However, whether PFKP and VEGF are reciprocally regulated during GBM tumor growth remains unknown. Here, we show that PFKP can promote EGFR activation-induced VEGF expression in HIF-1α-dependent and -independent manners in GBM cells. Importantly, we demonstrate that EGFR-phosphorylated PFKP Y64 has critical roles in both AKT/SP1-mediated transcriptional expression of HIF-1α and in the AKT-mediated β-catenin S552 phosphorylation, to fully enhance VEGF transcription, subsequently promoting blood vessel formation and brain tumor growth. Levels of PFKP Y64 phosphorylation in human GBM specimens are positively correlated with HIF-1α expression, β-catenin S552 phosphorylation, and VEGF expression. Conversely, VEGF upregulates PFKP expression in a PFKP S386 phosphorylation-dependent manner, leading to increased PFK enzyme activity, aerobic glycolysis, and proliferation in GBM cells. These findings highlight a novel mechanism underlying the mutual regulation that occurs between PFKP and VEGF for promoting GBM tumor growth and also suggest that targeting the PFKP/VEGF regulatory loop might show therapeutic potential for treating GBM patients.

Potential mechanisms involved on how systemic IgG antibodies specific to vascular endothelial growth factor (VEGF) and induced by active immunotherapy decrease platelet derived free-VEGF

CIGB-247 is a vascular endothelial growth factor (VEGF)-based active immunotherapy and it is currently under investigation for cancer treatment. This specific active immunotherapy encompasses two vaccine candidates that use a human VEGF variant molecule as antigen, in combination with two clinically tested adjuvants: VSSP or aluminum phosphate. CIGB-247 has been evaluated in patients with advanced solid tumors, recruited in two phase I clinical trials, and it has been shown to be safe and immunogenic by activating both cellular and humoral immune responses against human VEGF. The immunization induces specific IgG antibodies, and also shows as effect, the reduction of free-VEGF levels within platelets (platelet-derived free VEGF). The production of systemic IgG antibodies and the presence of VEGF in another compartment, almost exclusively within platelets, have arisen some questions about this effect detected in the vaccinated-cancer patients. Based on some relevant published works about platelet endocytosis and VEGF pharmacodynamics during bevacizumab treatment as well as the phase I clinical data of CIGB-247, this investigation aims to hypothesize and analyze the potential mechanisms involved in the reduction of platelet-derived free VEGF as a result of vaccination with CIGB-247. Abbreviations: FcγR: Fc gamma receptors; IC: immune complexes; VEGF: vascular endothelial growth factor; VEGFR1: vascular endothelial growth factor receptor 1; VEGFR2: vascular endothelial growth factor receptor 2.

Effects of plasma lipopolysaccharide changes on platelet release of vascular endothelial growth factor and thromobospondin-1 in patients with cirrhotic portal hypertension after TIPS procedure

Objective: To investigate the effects of plasma lipopolysaccharide (LPS) concentration changes on platelet release of vascular endothelial growth factor (VEGF) and thrombospondin (TSP)-1 in patients with decompensated cirrhotic portal hypertension after transjugular intrahepatic portosystemic shunt (TIPS) procedure. Methods: 169 cases with cirrhotic portal hypertension were enrolled, of which 81 cases received TIPS treatment. LPS, VEGF, and TSP-1 concentrations with different Child-Pugh class in peripheral blood plasma of patients were measured. After pre-incubation of normal human platelets with different concentrations of LPS and stimulated by collagen in vitro, platelet PAC-1 expression rate, VEGF, and TSP-1 concentrations were detected. PAC-1 expression rate and the concentrations of LPS, VEGF and TSP-1 in peripheral blood plasma of patients before and after TIPS procedure were detected. The relationship between plasma LPS, VEGF and TSP-1 concentrations and Child-Pugh score changes in patients after TIPS procedure was analyzed. Statistical analysis was performed by t-test, one-way ANOVA or Pearson's rho according to different data. Results: Plasma LPS and TSP-1 concentrations were significantly higher in Child-Pugh class C patients than class A and B, but the concentration of plasma VEGF was significantly lower than class A and B (P < 0.01). In vitro experiments showed that concentration of LPS, TSP-1, and platelet PAC-1 expression rate was higher in the supernatant, but the difference in the concentration of VEGF in the supernatant was not statistically significant. Portal vein pressure and platelet activation were significantly decreased (P < 0.01) in patients after TIPS procedure. Portal venous pressure, platelet activation, plasma LPS, and TSP-1 levels were significantly decreased continuously, while VEGF levels were significantly increased continuously after TIPS procedure. Plasma LPS concentration was positively correlated with TSP-1 concentration (r = 0.506, P < 0.001), and negatively correlated with VEGF concentration (r = -0.167, P = 0.010). Child-Pugh score change range was negatively correlated with change range of plasma VEGF concentration (r = -0.297, P = 0.016), and positively correlated with change range of plasma TSP-1 concentration (r = 0.145, P = 0.031) after TIPS. Conclusion: Portal venous pressure gradient, plasma LPS concentration and corresponding platelet activation was decreased in cirrhotic portal hypertension after TIPS procedure, and with TSP-1 reduction and VEGF elevation it is possible to reduce the liver function injury caused by portal venous shunt.

The Impact of Lower Limb Immobilization and Rehabilitation on Angiogenic Proteins and Capillarization in Skeletal Muscle.

Skeletal muscle vascularization is important for tissue regeneration after injury and immobilization. We examined whether complete immobilization influences capillarization and oxygen delivery to the muscle and assessed the efficacy of rehabilitation by aerobic exercise training. Young healthy males had one leg immobilized for 14 d and subsequently completed 4 wk of intense aerobic exercise training. Biopsies were obtained from musculus vastus lateralis, and arteriovenous blood sampling for assessment of oxygen extraction and leg blood flow during exercise was done before and after immobilization and training. Muscle capillarization, muscle and platelet content of vascular endothelial growth factor (VEGF), and muscle thrombospondin-1 were determined. Immobilization did not have a significant impact on capillary per fiber ratio or capillary density. The content of VEGF protein in muscle samples was reduced by 36% (P = 0.024), and VEGF to thrombospondin-1 ratio was 94% lower (P = 0.046). The subsequent 4-wk training period increased the muscle VEGF content and normalized the muscle VEGF to thrombospondin-1 ratio but did not influence capillarization. Platelet VEGF content followed the trend of muscle VEGF. At the functional level, oxygen extraction, blood flow, and oxygen delivery at rest and during submaximal exercise were not affected by immobilization or training. The results demonstrate that just 2 wk of leg immobilization leads to a strongly reduced angiogenic potential as evidenced by reduced muscle and platelet VEGF content and a reduced muscle VEGF to thrombospondin-1 ratio. Moreover, a subsequent period of intensive aerobic exercise training fails to increase capillarization in the previously immobilized leg, possibly because of the angiostatic condition caused by immobilization.

Platelet Rich Fibrin (PRF) and Its Related Products: Biomolecular Characterization of the Liquid Fibrinogen.

Liquid fibrinogen is an injectable platelet concentrate rich in platelets, leukocytes, and fibrinogen obtained by blood centrifugation. The aim of this study was to analyze the release of different growth factors in the liquid fibrinogen at different times and to assess possible correlations between growth factors and cell counts. The concentration of transforming growth factor beta 1 (TGF-β1), platelet-derived growth factor-AB (PDGF-AB), platelet-derived growth factor-BB (PDGF-BB), bone morphogenetic protein 2 (BMP-2), fibroblast growth factor 2 (FGF-2) and vascular endothelial growth factor (VEGF) released by liquid fibrinogen were examined with ELISA at three time points (T0, time of collection; T7, 7 days; T14, 14 days). The cellular content of the liquid fibrinogen and whole blood was also calculated for each volunteer. A mean accumulation of platelets of almost 1.5-fold in liquid fibrinogen compared to whole blood samples was found. An increase of TGF-β1, PDGF-AB, FGF-2, and VEGF levels was detected at T7. At T14, the level of TGF-β1 returned to T0 level; PDGF-AB amount remained high; the levels of FGF-2 and VEGF decreased with respect to T7, but remained higher than the T0 levels; PDGF-BB was high at all time points; BMP-2 level was low and remained constant at all time points. TGF-β1, PDGF-AB, and PDGF-BB showed a correlation with platelet amount, whereas BMP-2, FGF-2, and VEGF showed a mild correlation with platelet amount. Due to the high concentration of platelets, liquid fibrinogen does contain important growth factors for the regeneration of both soft and hard tissue. The centrifugation protocol tested in this study provides a valid solution to stimulate wound healing in oral and periodontal surgery.

Evaluation of platelet-rich plasma from diabetic donors shows increased platelet vascular endothelial growth factor release.

Platelet-rich plasma (PRP) contains pro-angiogenic growth factors including vascular endothelial growth factor (VEGF). Angiogenesis is a necessary component of wound healing in instances of diabetic foot ulcers (DFU). PRP composition varies depending on methods and donor health status. Our group has developed an improved PRP protocol for diabetes treatment. The aims of this study were to examine the levels of the pro-angiogenic factor VEGF in these patient populations with and without diabetes. PRP was prepared using 24 mL of whole blood from 13 diabetic and 10 non-diabetic patients registered at Klinik Hayandra. Whole blood in sodium citrate tubes were centrifuged at 1,000 rpm for 5 minutes followed by plasma separation. Plasma samples were centrifuged at 3,000 rpm for 5 minutes. Upper platelet-poor plasma layers were discarded, leaving 5 mL of concentrated platelet containing plasma (PRP). Concentrated plasma samples were mixed, aliquoted, stored at -86 °C, and pooled for platelet count, VEGF, and total protein analyses. Platelet counting was also performed using fresh whole blood and PRP to measure changes following PRP preparation. Diabetic donors had higher whole blood platelet counts than non-diabetic donors, but this difference was not statistically significant. An average increase of more than 250% in platelet number after PRP preparation using our method was noted in both groups. Freezing-thawing samples at -86 °C lysed more than 90% of PRP platelets regardless of diabetes status. Diabetic PRP had lower mean total protein and higher VEGF concentrations. Lysed platelets from diabetic donors released more VEGF than those from non-diabetic donors. PRP from diabetic donors had higher VEGF content making autologous PRP application a promising treatment for DFU. However, this should be investigated another appropriate clinical trial.

Evaluation of methodologies to determine the effect of specific active immunotherapy on VEGF levels in phase I clinical trial patients with advanced solid tumors

Two phase I clinical trials were conducted to evaluate, among other parameters, the humoral response elicited by a vascular endothelial growth factor (VEGF)-based therapeutic vaccine in cancer patients with advanced solid tumors. VEGF reduction was studied using an indirect methodology named as “Platelet VEGF”. This methodology is based on the estimation of VEGF within platelets by subtracting the plasma VEGF level from the serum level and dividing this by the platelet count, and then this latter expression is additionally corrected by the hematocrit. However, there is broad debate, whether serum or plasma VEGF or platelet-derived VEGF measurements is the most appropriate strategy to study the changes that occur on ligand bioavailability when patients are submitted to a VEGF-based immunotherapy.The current research is a retrospective study evaluating the changes on VEGF levels in serum and plasma as well as platelet-derived measurements. Changes in VEGF levels were related with the humoral response seen in cancer patients after an active immunotherapy with a VEGF-based vaccine. The present study indicates that “Platelet VEGF” is the most reliable methodology to investigate the effect of VEGF-based immunotherapies on ligand bioavailability. “Platelet VEGF” was associated with those groups of individuals that exhibited the best specific humoral response and the variation of “Platelet VEGF” showed the strongest negative correlation with VEGF-specific IgG antibody levels. This methodology will be very useful for the investigation of this VEGF-based vaccine in phase II clinical trials and could be applied to immunotherapies directed to other growth factors that are actively sequestered by platelets.

Platelets from glioblastoma patients promote angiogenesis of tumor endothelial cells and exhibit increased VEGF content and release

Glioblastoma multiforme (GBM) is the most common and fatal intracranial cancer in humans and exhibits intense and aberrant angiogenesis that sustains its malignancy and involves several angiogenic signals. Among them, vascular endothelial growth factor (VEGF) plays a key role and is overexpressed in GBM. Different cells appear to act as triggers of the aberrant angiogenesis, and, among them, platelets act as key participants. In order to provide further insights into the platelet features and angiogenic role in GBM, this study investigated the effects of platelet releasate on GBM-derived endothelial cells (GECs) and the levels of VEGF and endostatin, as pro- and anti-angiogenic components of platelet releasate from GBM patients. We demonstrate for the first time that: 1) platelet releasate exerts powerful pro-angiogenic effect on GECs, suggesting it might exert a role in the aberrant angiogenesis of GBM; 2) ADP and thrombin stimulation leads to significantly higher level of VEGF, but not of endostatin, in the releasate of platelets from GBM patients than those from healthy subjects; and 3) the intraplatelet concentrations of VEGF were significantly elevated in GBM patients as compared to controls. Moreover, we found a direct correlation between platelet-released VEGF and overall survival in our patient cohort. Although preliminary, these findings prompt further investigations to clarify the biologic relevance of platelet VEGF in GBM and prospective studies for screening GBM patients for anti-VEGF therapy and/or to optimize this treatment.

Protective effects of BMSCs in combination with erythropoietin in bronchopulmonary dysplasia-induced lung injury.

Bronchopulmonary dysplasia (BPD) is the most common type of chronic lung disease in infancy, for which no effective therapy is currently available. The aim of the present study was to investigate the effect of treatment with bone marrow mesenchymal stem cells (BMSCs) in combination with recombinant human erythropoietin (rHuEPO) on BPD‑induced mouse lung injury, and discuss the underlying mechanism. The BPD model was established by the exposure of neonatal mice to continuous high oxygen exposure for 14days, following which 1x106 BMSCs and 5,000U/kgrHuEPO were injected into the mice 1h prior to and 7days following exposure to hyperoxia. The animals received four treatments in total (n=10 in each group). After 14days, the body weights, airway structure, and levels of matrix metalloproteinase‑9 (MMP‑9) and vascular endothelial growth factor (VEGF) were detected using histological and immunohistochemical analyses. The effect on cell differentiation was observed by examining the presence of platelet endothelial cell adhesion molecule (PECAM) and VEGF using immunofluorescence. Compared with the administration of BMSCs alone, the body weight, airway structure, and the levels of MMP‑9 and VEGF were significantly improved in the BMSCs/rHuEPO group. The results of the present study demonstrated that the intravenous injection of BMSCs significantly improved lung damage in the hyperoxia‑exposed neonatal mouse model. Furthermore, the injection of BMSCs in combination with intraperitoneal injection of rHuEPO had a more marked effect, compared with BMSCs alone, and the mechanism may be mediated by the promoting effects of BMSCs and EPO. The results of the present study provided information, which may assist in future clinical trials.

Circulating TGF-β1 and VEGF and risk of cancer among liver transplant recipients.

Transplant recipients have elevated cancer risk, perhaps partly due to direct carcinogenic effects of immunosuppressive medications. Experimental evidence indicates that calcineurin inhibitors given to transplant recipients increase cellular expression of transforming growth factor β1 (TGF-β1) and vascular endothelial growth factor (VEGF), which could promote cancer. To assess the potential role of these pathways in the transplantation setting, we conducted a case–control study nested in a cohort of liver recipients. Cases had nonmelanoma skin cancer (N = 84), cancer of the lung (N = 29), kidney (N = 20), or colorectum (N = 17), or melanoma (N = 3). We selected N = 463 recipients without cancer as controls. TGF-β1 and VEGF levels were measured in sera obtained, on average, approximately 3 years before case diagnosis/control selection. We also measured platelet factor 4 (PF4), a marker of ex vivo platelet degranulation, because TGF-β1 and VEGF can be released from platelets, and we developed a statistical model to isolate the platelet-derived fraction from the remaining circulating component. Compared with controls, lung cancer cases had higher levels of TGF-β1 (median 22.8 vs. 19.4 ng/mL, P = 0.02) and VEGF (277 vs. 186 pg/mL, P = 0.02). However, lung cancer cases also had higher platelet counts (P = 0.08) and PF4 levels (P = 0.02), while residual serum levels of TGF-β1 and VEGF, after accounting for PF4, were unassociated with lung cancer (P = 0.40 and P = 0.15, respectively). Associations were not seen for other cancers. In conclusion, TGF-β1 and VEGF levels were increased in association with lung cancer among transplant recipients, which may be explained by increased platelet counts and platelet degranulation in lung cancer cases.

Platelet VEGF and serum TGF-β1 levels predict chemotherapy response in non-small cell lung cancer patients.

We examined the levels of platelet vascular endothelial growth factor (VEGF(PLT)) and serum level of transforming growth factor beta 1 (TGF-β1) in non-small cell lung cancer (NSCLC) patients before and after chemotherapy to assess their clinical value as biomarkers. A total of 115 subjects were recruited at the First Hospital of Qinhuangdao between July 2012 and October 2013, including 65 NSCLC patients receiving chemotherapy (NSCLC group) and 50 healthy controls (control group). All NSCLC patients received gemcitabine plus cisplatin (GP regimen) for a total of two courses. VEGF(PLT) and serum TGF-β1 levels were measured before and after chemotherapy using enzyme-linked immunosorbent assay (ELISA). Platelet count was obtained using the Abbott CD-1600 auto blood analyzer. NSCLC group was categorized into complete response (CR) plus partial response (PR) group and stable disease (SD) plus progressive disease (PD) group based on the results of CT scans obtained 1 week after chemotherapy. Our results revealed that VEGF(PLT) and serum TGF-β1 levels were significantly higher in NSCLC group before chemotherapy, compared to the control group (VEGF(PLT), 0.813 ± 0.072 vs. 0.547 ± 0.024; t = 26.48; P < 0.001 and TGF-β1, 46.00 ± 4.47 vs. 16.43 ± 2.12; t = 44.87; P < 0.001). Importantly, VEGF(PLT) and serum TGF-β1 levels decreased significantly after chemotherapy in CR + PR group in comparison with before chemotherapy (VEGF(PLT), 0.453 ± 0.078 vs. 0.814 ± 0.127; t = 15.51; P < 0.001 and TGF-β1, 20.17 ± 2.43 vs. 42.13 ± 4.54; t = 27.31; P < 0.001). By contrast, VEGF(PLT) and serum TGF-β1 levels were markedly higher after chemotherapy in the SD + PD group in comparison with before chemotherapy (VEGF(PLT), 0.816 ± 0.043 vs. 1.065 ± 0.016; t = 22.38; P < 0.001 and TGF-β1, 41.80 ± 5.46 vs. 45.83 ± 4.62; t = 2.32; P = 0. 03). Our results show that NSCLC patients exhibit high VEGF(PLT) and serum TGF-β1 levels, and VEGF(PLT) and TGF-β1 levels correlate with chemotherapy response to GP regimen. Therefore, VEGF(PLT) and serum TGF-β1 levels are valuable biomarkers in clinical monitoring of NSCLC patients.

Platelet Vascular Endothelial Growth Factor is a Potential Mediator of Transfusion-Related Acute Lung Injury.

ObjectiveThe occurrence of non-hemolytic transfusion reactions is highest with platelet and plasma administration. Some of these reactions are characterized by endothelial leak, especially transfusion related acute lung injury (TRALI). Elevated concentrations of inflammatory mediators secreted by contaminating leukocytes during blood product storage may contribute to such reactions, but platelet-secreted mediators may also contribute. We hypothesized that platelet storage leads to accumulation of the endothelial permeability mediator vascular endothelial growth factor (VEGF), and that intravascular administration of exogenous VEGF leads to extensive binding to its lung receptors.MethodsSingle donor, leukocyte-reduced apheresis platelet units were sampled over 5 days of storage. VEGF protein content of the centrifuged supernatant was determined by ELISA, and the potential contribution of VEGF from contaminating leukocytes was quantified. Isolated-perfused rat lungs were used to study the uptake of radiolabeled VEGF administered intravascularly, and the effect of unlabeled VEGF on lung leak.ResultsThere was a time-dependent release of VEGF into the plasma fraction of the platelet concentrates (62 ± 9 pg/ml on day one, 149 ± 23 pg/ml on day 5; mean ± SEM, p<0.01, n=8) and a contribution by contaminating leukocytes was excluded. Exogenous 125I-VEGF bound avidly and specifically to the lung vasculature, and unlabeled VEGF in the lung perfusate caused vascular leak.ConclusionRising concentrations of VEGF occur during storage of single donor platelet concentrates due to platelet secretion or disintegration, but not due to leukocyte contamination. Exogenous VEGF at these concentrations rapidly binds to its receptors in the lung vessels. At higher VEGF concentrations, VEGF causes vascular leak in uninjured lungs. These data provide further evidence that VEGF may contribute to the increased lung permeability seen in TRALI associated with platelet products.

Expression of angiogenesis regulatory proteins and epithelial-mesenchymal transition factors in platelets of the breast cancer patients.

Platelets play a role in tumor angiogenesis and growth and are the main transporters of several angiogenesis regulators. Here, we aimed to determine the levels of angiogenesis regulators and epithelial-mesenchymal transition factors sequestered by circulating platelets in breast cancer patients and age-matched healthy controls. Platelet pellets (PP) and platelet-poor plasma (PPP) were collected by routine protocols. Vascular endothelial growth factor (VEGF), platelet-derived growth factor BB (PDGF-BB), thrombospondin-1 (TSP-1), platelet factor 4 (PF4), and transforming growth factor-β1 (TGF-β1) were measured by enzyme-linked immunosorbent assay. Angiogenesis-associated expression of VEGF (2.1 pg/106 platelets versus 0.9 pg/106 platelets, P < 0.001), PF4 (21.2 ng/106 platelets versus 10.2 ng/106 platelets, P < 0.001), PDGF-BB (42.9 pg/106 platelets versus 19.1 pg/106 platelets, P < 0.001), and TGF-β1 (15.3 ng/106 platelets versus 4.3 ng/106 platelets, P < 0.001) differed in the PP samples of cancer and control subjects. In addition, protein concentrations were associated with clinical characteristics (P < 0.05). Circulating platelets in breast cancer sequester higher levels of PF4, VEGF, PDGF-BB, and TGF-β1, suggesting a possible target for early diagnosis. VEGF, PDGF, and TGF-β1 concentrations in platelets may be associated with prognosis.

VEGF, PF4 and PDGF are elevated in platelets of colorectal cancer patients

Platelets sequester angiogenesis regulatory proteins which suggests an avenue for developing biomarkers to monitor disease. We describe a comparison of angiogenesis regulatory proteins found in platelets of colorectal cancer patients and normal controls. Platelet and plasma content of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet derived growth factor (PDGF), platelet factor 4 (PF4), thrombospondin-1 (TSP-1) and endostatin in 35 patients with colon cancer were compared with 84 age-matched healthy controls using ELISAs. We standardized the platelet preparation procedure, introduced process controls and normalized the respective protein levels to platelet numbers using an actin ELISA. Statistically significant differences were found in the median levels of VEGF, PF4 and PDGF in platelets of patients with cancer compared to healthy individuals. Platelet concentrations in cancer patients versus controls were: VEGF 1.3 versus 0.6pg/10(6), PF4 18.5 versus 9.4ng/10(6), and PDGF 34.1 versus 21.0pg/10(6). Multivariable logistic regression analysis indicated that PDGF, PF4 and VEGF were independent predictors of colorectal carcinoma and as a set provided statistically significant discrimination (area under the curve=0.893, P<.0001). No significant differences were detected for bFGF, endostatin, or TSP-1. Reference Change Value analysis determined that the differences seen were not clinically significant. Plasma levels yielded no correlations.

Enhanced angiogenesis by multiple release of platelet-rich plasma contents and basic fibroblast growth factor from gelatin hydrogels

The objective of this study is to evaluate the angiogenic effects induced by biodegradable gelatin hydrogel granules incorporating mixed platelet-rich plasma (PRP) growth factor mixture (PGFM) and bioactive basic fibroblast growth factor (bFGF). The PRP was prepared by a double-spinning technique for isolating animal bloods, followed by treatment with different concentrations of calcium chloride (CaCl2) solution. The CaCl2 solution treatment activated the platelets of PRP, allowing the release of various growth factors, such as platelet-derived growth factor (PDGF)-BB, vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β1, and epithelial growth factor (EGF). In the PRP treated with different CaCl2 solutions, high amounts of representative platelet growth factor, PDGF-BB, VEGF, EGF, and TGF-β1 were detected in the CaCl2 concentrations of 1, 2, and 4wt.% compared with higher or lower ones. The PRP treated was impregnated into gelatin hydrogel granules freeze-dried at 37°C for 1h, and then the percentage of PGFM desorbed from the gelatin hydrogel granules was evaluated. The percentages of PDGF-BB, VEGF, EGF, and TGF-β1 desorbed tended to decrease with decreasing CaCl2 concentration. Taken together, the CaCl2 concentration to activate PRP for PGFM release was fixed at 2wt.%. In vitro release tests demonstrated that the PGFM was released from the gelatin hydrogel granules with time. For the gelatin hydrogels incorporating PGFM and bFGF, the time profile of PDGF-BB or bFGF release was in good correspondence with that of gelatin hydrogel degradation. The gelatin hydrogel granules incorporating mixed PGFM and bFGF were prepared and intramuscularly injected to a mouse leg ischemia model to evaluate the angiogenic effects in terms of histological and laser Doppler perfusion imaging examinations. As controls, hydrogel granules incorporating bFGF, PGFM, and platelet-poor plasma were used for the angiogenic evaluation. The number of blood vessels newly formed and the percentage of anti-α-smooth muscle actin antibody-positive cells increased around ischemic sites injected with the gelatin hydrogel granules incorporating mixed PGFM and bFGF, in marked contrast to other control groups. The blood reperfusion level of ischemic tissues was enhanced by the hydrogel granules incorporating mixed PGFM and bFGF, whereas no enhancement was observed for other groups. It is concluded that the dual-release system of PGFM and bFGF from gelatin hydrogel granules shows promise as a method to enhance angiogenic effects.

Vascular Endothelial Growth Factor in the Circulation in Cancer Patients May Not Be a Relevant Biomarker

BackgroundLevels of circulating vascular endothelial growth factor (VEGF) have widely been used as biomarker for angiogenic activity in cancer. For this purpose, non-standardized measurements in plasma and serum were used, without correction for artificial VEGF release by platelets activated ex vivo. We hypothesize that “true” circulating (c)VEGF levels in most cancer patients are low and unrelated to cancer load or tumour angiogenesis.MethodologyWe determined VEGF levels in PECT, a medium that contains platelet activation inhibitors, in citrate plasma, and in isolated platelets in 16 healthy subjects, 18 patients with metastatic non-renal cancer (non-RCC) and 12 patients with renal cell carcinoma (RCC). In non-RCC patients, circulating plasma VEGF levels were low and similar to VEGF levels in controls if platelet activation was minimized during the harvest procedure by PECT medium. In citrate plasma, VEGF levels were elevated in non-RCC patients, but this could be explained by a combination of increased platelet activation during blood harvesting, and by a two-fold increase in VEGF content of individual platelets (controls: 3.4 IU/106, non-RCC: 6.2 IU/106 platelets, p = 0.001). In contrast, cVEGF levels in RCC patients were elevated (PECT plasma: 64 pg/ml vs. 21 pg/ml, RCC vs. non-RCC, p<0.0001), and not related to platelet VEGF concentration.ConclusionsOur findings suggest that “true” freely cVEGF levels are not elevated in the majority of cancer patients. Previously reported elevated plasma VEGF levels in cancer appear to be due to artificial release from activated platelets, which in cancer have an increased VEGF content, during the blood harvest procedure. Only in patients with RCC, which is characterized by excessive VEGF production due to a specific genetic defect, were cVEGF levels elevated. This observation may be related to limited and selective success of anti-VEGF agents, such as bevacizumab and sorafenib, as monotherapy in RCC compared to other forms of cancer.

Serum levels of platelet‐derived growth factor‐BB and vascular endothelial growth factor as prognostic factors for patients with fulminant hepatic failure

In animal models for acute liver injury, the administration of some angiogenic factors such as vascular endothelial growth factor (VEGF) and granulocyte-colony stimulating factor (G-CSF) are shown to reduce liver injury and improve liver proliferative capacity. The aim of the present study was to assess the role of angiogenic factors in fulminant hepatic failure (FHF). Serum levels of nine angiogenic factors (angiopoietin-2, follistatin, G-CSF, hepatocyte growth factor [HGF], interleukin-8, leptin, platelet-derived growth factor [PDGF]-BB, platelet endothelial cell adhesion molecule-1 and VEGF) were measured using the Bio-Plex Protein Array System in 30 patients, 17 of whom were diagnosed with FHF, 13 with acute hepatitis (AH), and 20 controls. Serum levels of PDGF-BB and VEGF were lower in FHF patients than AH patients and controls (PDGF-BB; 2050±1572 pg/mL vs 4521±2419 pg/mL vs 8506±5500 pg/mL, VEGF; 39±38 pg/mL vs 144±122 pg/mL vs 205±121 pg/mL). By using univariate logistic regression models, serum levels of PDGF-BB and VEGF were associated with poor outcomes. Serum PDGF-BB levels were strongly correlated with serum VEGF levels (r=0.70). Furthermore, serum PDGF-BB levels were significantly correlated with platelet counts (r=0.79), PT activity (r=0.37) and D.Bil/T.Bil ratio (r=0.50), while serum VEGF levels were significantly correlated with platelet counts (r=0.68) and PT activity (r=0.38). We consider that serum levels of PDGF-BB and VEGF are worth investigating as biomarkers for predicting outcomes of FHF patients.

VEGF-A gene promoter polymorphisms and microvascular complications in patients with essential hypertension

Objectives We investigated the possible involvement of vascular endothelial growth factor ( VEGF-A) gene promoter polymorphisms in essential hypertension (EH). Design and methods 1225 bp of the VEGF-A gene promoter were screened for polymorphisms using PCR amplification and direct DNA sequence analysis in 62 EH and 62 normotensive (HS) individuals. Circulating VEGF-A levels were determined by immunoassay. Results − 152G/A ( p = 0.009) and − 116G/A ( p = 0.016) polymorphisms were correlated to hypertension ( p < 0.05). Median platelet VEGF-A load in EH was 2.10 fg/plt. Patients with microvascular complications (MC) had higher platelet VEGF-A load than those without ( p = 0.005). Multivariate analyses showed that − 116 A allele was an independent predictor of microalbuminuria ( p = 0.014) and increased platelet VEGF-A load ( p = 0.009) in EH. Platelet VEGF-A load independently predicted MC ( p = 0.049) in addition to − 116G/A polymorphism ( p = 0.035). Conclusions Abnormal regulation of VEGF-A due to polymorphism at position − 116 might represent a genetic factor for increased VEGF-A production and MC in EH.

Normal ranges of angiogenesis regulatory proteins in human platelets

Platelets sequester angiogenesis regulatory proteins early in tumor growth, which suggests a new avenue for monitoring disease. To date, there are no clinically relevant reference ranges for markers of early angiogenesis. We introduce a new ELISA-based method for accurate and reproducible measurement of vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), platelet factor 4 (PF4), thrombospondin-1 (TSP-1), fibroblast growth factor, basic (bFGF), and endostatin in platelets. To facilitate clinical applicability, the platelet levels in isolated samples were determined utilizing a new actin ELISA method. Platelets from healthy donors at single and repetitive time points were used for the assessment of normal ranges of these proteins. The physiological levels in platelets were: VEGF (0.74 +/- 0.37 pg/10(6) platelets); PDGF (23 +/- 6 pg/10(6)); PF4 (12 +/- 5 ng/10(6)); TSP-1 (31 +/- 12 ng/10(6)); bFGF (0.44 +/- 0.15 pg/10(6)); and endostatin (5.6 +/- 3.0 pg/10(6)). There was an excellent correlation (R(2) = 0.7) between the platelet levels calculated with the actin ELISA and complete blood count. The levels of the platelets were higher than those in platelet-poor plasma by factors of: VEGF (215-fold); PDGF (914-fold); PF-4 (516-fold); TSP-1 (813-fold); and bFGF (17-fold). The endostatin levels were nearly equivalent. The biovariability of the platelet proteins in eight healthy subjects over a 5-week period was found to be minimal. We describe accurate and direct measurements of the concentrations of VEGF, bFGF, PDGF, TSP-1, endostatin, and PF4 in platelets of healthy human subjects. In contrast to the highly variable levels in plasma and serum, the platelet-derived measurements were accurate and reproducible with minimal biovariability.