Major Vascular Endothelial Growth Factor Isoforms Research Articles

Angiogenic gene therapy for refractory angina: results of the epicardial delivery of XC001 gene therapy for refractory angina coronary treatment (EXACT) phase 2 trial

Abstract Background Refractory or "no option" angina (RA) is a debilitating condition with increasing global prevalence. Exogenous transduction of vascular endothelial growth factor (VEGF) induces angiogenesis and improves perfusion of ischemic myocardium in preclinical studies. XC001 (AdVEGFXC1) is a novel adenoviral-5 vector expressing the three major isoforms of VEGF (-121, -165, -189) in ratios shown to enhance potency and improve safety. Purpose EXACT is a single-arm, multicenter, open-label, phase 2 trial to explore the safety, tolerability, and preliminary efficacy of trans-epicardial delivery of XC001 to improve exercise capacity and ischemic burden in RA patients. Methods Patients were required to have stable Canadian Cardiovascular Society (CCS) class II-IV angina on maximally tolerated medical therapy with exercise limited by angina after 90 but before 540 seconds on a modified Bruce protocol, demonstrable ischemia on stress positron emission tomography (PET) and lack revascularization options. XC001 (1x1011 viral particles) was injected directly into ischemic myocardium via surgical transthoracic epicardial access. The primary outcome was safety by adverse event monitoring. Efficacy assessments included difference from baseline to six months in total exercise time (TET), myocardial ischemia by PET, angina class, angina frequency, and quality of life. Results Thirty-two patients (mean/median ages of 64/64, 34% female) were enrolled at 13 sites between March 2021 and July 2022. Median anti-anginal use was 3, 75% had prior revascularization with CABG and 88% with PCI. Fifty-five serious adverse events (SAEs) were observed in 21 patients (66%). None were attributed to study drug. Twenty-one SAEs in 14 patients were related to the surgical procedure, all of which were expected. One non-CV death occurred in month 3 following respiratory infection (Covid) deemed unrelated to surgery or study drug. Compared to baseline, total exercise time at 6-months increased by 85.5 seconds (95% CI 31.3-139.7) [Figure 1A] while total myocardial ischemic deficit in the treated region on PET decreased by 14.4% (95% CI, 3.01–25.73) [Figure 1B]. Angina frequency and nitroglycerin use measured during a two-week diary decreased by 6.6 episodes (95% CI, 3.5–9.7) and 4.1 doses (95% CI, 1.3–6.9), respectively. Canadian Cardiovascular Society angina grade decreased from 3.1 to 1.8, mean difference 1.3 classes (95% CI, 1.0–1.6) [Figure 2] while Seattle Angina Questionnaire Frequency score improved from 41.3 to 67.4, mean difference of 26.1 (95% CI, 16.3–35.9). Conclusions VEGF gene therapy with XC001 administered via minimally invasive epicardial delivery appears safe and well tolerated. Improvements in objective and subjective measures including total exercise time, myocardial perfusion, angina frequency and quality of life support a clinically meaningful biologic effect. This therapy warrants study in larger randomized studies.

EXACT Trial: Results of the Phase 1 Dose-Escalation Study.

New therapies are needed for patients with refractory angina. Encoberminogene rezmadenovec (XC001), a novel adenoviral-5 vector coding for all 3 major isoforms of VEGF (vascular endothelial growth factor), demonstrated enhanced local angiogenesis in preclinical models; however, the maximal tolerated dose and safety of direct epicardial administration remain unknown. In the phase 1 portion of this multicenter, open-label, single-arm, dose-escalation study, patients with refractory angina received increasing doses of encoberminogene rezmadenovec (1×109, 1×1010, 4×1010, and 1×1011 viral particles) to evaluate its safety, tolerability, and preliminary efficacy. Patients had class II to IV angina on maximally tolerated medical therapy, demonstrable ischemia on stress testing, and were angina-limited on exercise treadmill testing. Patients underwent minithoracotomy with epicardial delivery of 15 0.1-mL injections of encoberminogene rezmadenovec. The primary outcome was safety via adverse event monitoring over 6 months. Efficacy assessments included difference from baseline to months 3, 6 (primary), and 12 in total exercise duration, myocardial perfusion deficit using positron emission tomography, angina class, angina frequency, and quality of life. From June 2, 2020 to June 25, 2021, 12 patients were enrolled into 4 dosing cohorts with 1×1011 viral particle as the highest planned dose. Seventeen serious adverse events were reported in 7 patients; none were related to study drug. Six serious adverse events in 4 patients were related to the thoracotomy, 3 non-serious adverse events were possibly related to study drug. The 2 lowest doses did not demonstrate improvements in total exercise duration, myocardial perfusion deficit, or angina frequency; however, there appeared to be improvements in all parameters with the 2 higher doses. Epicardial delivery of encoberminogene rezmadenovec via minithoracotomy is feasible, and up to 1×1011 viral particle appears well tolerated. A dose response was observed across 4 dosing cohorts in total exercise duration, myocardial perfusion deficit, and angina class. The highest dose (1×1011 viral particle) was carried forward into phase 2. URL: https://www. gov; Unique identifier: NCT04125732.

Can We Identify Predictive Biomarkers for Antiangiogenic Therapy of Cancer Using Mathematical Modeling?

Can We Identify Predictive Biomarkers for Antiangiogenic Therapy of Cancer Using Mathematical Modeling?

Effect of tumor microenvironment on tumor VEGF during anti-VEGF treatment: systems biology predictions.

Vascular endothelial growth factor (VEGF) is known to be a potent promoter of angiogenesis under both physiological and pathological conditions. Given its role in regulating tumor vascularization, VEGF has been targeted in various cancer treatments, and anti-VEGF therapy has been used clinically for treatment of several types of cancer. Systems biology approaches, particularly computational models, provide insight into the complexity of tumor angiogenesis. These models complement experimental studies and aid in the development of effective therapies targeting angiogenesis. We developed an experiment-based, molecular-detailed compartment model of VEGF kinetics and transport to investigate the distribution of two major VEGF isoforms (VEGF121 and VEGF165) in the body. The model is applied to predict the dynamics of tumor VEGF and, importantly, to gain insight into how tumor VEGF responds to an intravenous injection of an anti-VEGF agent. The model predicts that free VEGF in the tumor interstitium is seven to 13 times higher than plasma VEGF and is predominantly in the form of VEGF121 (>70%), predictions that are validated by experimental data. The model also predicts that tumor VEGF can increase or decrease with anti-VEGF treatment depending on tumor microenvironment, pointing to the importance of personalized medicine. This computational study suggests that the rate of VEGF secretion by tumor cells may serve as a biomarker to predict the patient population that is likely to respond to anti-VEGF treatment. Thus, the model predictions have important clinical relevance and may aid clinicians and clinical researchers seeking interpretation of pharmacokinetic and pharmacodynamic observations and optimization of anti-VEGF therapies.

Predicting the Effects of Anti-angiogenic Agents Targeting Specific VEGF Isoforms

Vascular endothelial growth factor (VEGF) is a key mediator of angiogenesis, whose effect on cancer growth and development is well characterized. Alternative splicing of VEGF leads to several different isoforms, which are differentially expressed in various tumor types and have distinct functions in tumor blood vessel formation. Many cancer therapies aim to inhibit angiogenesis by targeting VEGF and preventing intracellular signaling leading to tumor vascularization; however, the effects of targeting specific VEGF isoforms have received little attention in the clinical setting. In this work, we investigate the effects of selectively targeting a single VEGF isoform, as compared with inhibiting all isoforms. We utilize a molecular-detailed whole-body compartment model of VEGF transport and kinetics in the presence of breast tumor. The model includes two major VEGF isoforms, VEGF(121) and VEGF(165), receptors VEGFR1 and VEGFR2, and co-receptors Neuropilin-1 and Neuropilin-2. We utilize the model to predict the concentrations of free VEGF, the number of VEGF/VEGFR2 complexes (considered to be pro-angiogenic), and the receptor occupancy profiles following inhibition of VEGF using isoform-specific anti-VEGF agents. We predict that targeting VEGF(121) leads to a 54% and 84% reduction in free VEGF in tumors that secrete both VEGF isoforms or tumors that overexpress VEGF(121), respectively. Additionally, 21% of the VEGFR2 molecules in the blood are ligated following inhibition of VEGF(121), compared with 88% when both isoforms are targeted. Targeting VEGF(121) reduces tumor free VEGF and is an effective treatment strategy. Our results provide a basis for clinical investigation of isoform-specific anti-VEGF agents.

Allergic Rhinitis and Vascular Endothelial Growth Factor

Vascular endothelial growth factor (VEGF) was identified in 1980s as a protein that increases vascular permeability and induces endothelial cell-specific mitosis. VEGF plays an important role in angiogenesis during the embryonic stage and in angiogenesis and in increasing vascular permeability during postnatal life, both physiologically and pathologically. Great progress has been made in studies of VEGF, mainly in the field of oncology, and VEGF-targeted therapy has been successfully used to treat patients with cancer. In research related to chronic inflammation, several reports concerning rheumatoid arthritis or retinopathy and VEGF have been published. In the lower respiratory tract, increased levels of VEGF have been detected in biological samples from patients with asthma. However, VEGF has not been studied in detail in upper-airway diseases, such as rhinosinusitis. This review article focuses on VEGF and allergic rhinitis to advance studies of VEGF in chronic inflammation of the upper respiratory tract. VEGF levels in nasal secretions and nasal lavage fluid were higher in perennial allergic rhinitis than in nonallergic rhinosinusitis, after, rather than before, the antigen provocation test. The major VEGF isoforms were confirmed to be VEGF₁₂₁ and VEGF₁₆₅ in allergic rhinitis. Expression of VEGF mRNA was higher in serous versus mucous acini. In allergic rhinitis, serous acini produced significant quantities of VEGF, which was hypersecreted after antigen provocation. VEGF seems to play an important role in the pathophysiology of allergic rhinitis. Modulation of VEGF function seems to contribute to the successful treatment of conditions with airway inflammation such as allergic rhinitis.

A two-compartment model of VEGF distribution in the mouse.

Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis – the growth of new microvessels from existing microvasculature. Angiogenesis is a complex process involving numerous molecular species, and to better understand it, a systems biology approach is necessary. In vivo preclinical experiments in the area of angiogenesis are typically performed in mouse models; this includes drug development targeting VEGF. Thus, to quantitatively interpret such experimental results, a computational model of VEGF distribution in the mouse can be beneficial. In this paper, we present an in silico model of VEGF distribution in mice, determine model parameters from existing experimental data, conduct sensitivity analysis, and test the validity of the model.The multiscale model is comprised of two compartments: blood and tissue. The model accounts for interactions between two major VEGF isoforms (VEGF120 and VEGF164) and their endothelial cell receptors VEGFR-1, VEGFR-2, and co-receptor neuropilin-1. Neuropilin-1 is also expressed on the surface of parenchymal cells. The model includes transcapillary macromolecular permeability, lymphatic transport, and macromolecular plasma clearance. Simulations predict that the concentration of unbound VEGF in the tissue is approximately 50-fold greater than in the blood. These concentrations are highly dependent on the VEGF secretion rate. Parameter estimation was performed to fit the simulation results to available experimental data, and permitted the estimation of VEGF secretion rate in healthy tissue, which is difficult to measure experimentally. The model can provide quantitative interpretation of preclinical animal data and may be used in conjunction with experimental studies in the development of pro- and anti-angiogenic agents. The model approximates the normal tissue as skeletal muscle and includes endothelial cells to represent the vasculature. As the VEGF system becomes better characterized in other tissues and cell types, the model can be expanded to include additional compartments and vascular elements.

The Presence of VEGF Receptors on the Luminal Surface of Endothelial Cells Affects VEGF Distribution and VEGF Signaling

Vascular endothelial growth factor (VEGF) is a potent cytokine that binds to specific receptors on the endothelial cells lining blood vessels. The signaling cascade triggered eventually leads to the formation of new capillaries, a process called angiogenesis. Distributions of VEGF receptors and VEGF ligands are therefore crucial determinants of angiogenic events and, to our knowledge, no quantification of abluminal vs. luminal receptors has been performed. We formulate a molecular-based compartment model to investigate the VEGF distribution in blood and tissue in humans and show that such quantification would lead to new insights on angiogenesis and VEGF-dependent diseases. Our multiscale model includes two major isoforms of VEGF (VEGF121 and VEGF165), as well as their receptors (VEGFR1 and VEGFR2) and the non-signaling co-receptor neuropilin-1 (NRP1). VEGF can be transported between tissue and blood via transendothelial permeability and the lymphatics. VEGF receptors are located on both the luminal and abluminal sides of the endothelial cells. In this study, we analyze the effects of the VEGF receptor localization on the endothelial cells as well as of the lymphatic transport. We show that the VEGF distribution is affected by the luminal receptor density. We predict that the receptor signaling occurs mostly on the abluminal endothelial surface, assuming that VEGF is secreted by parenchymal cells. However, for a low abluminal but high luminal receptor density, VEGF binds predominantly to VEGFR1 on the abluminal surface and VEGFR2 on the luminal surface. Such findings would be pertinent to pathological conditions and therapies related to VEGF receptor imbalance and overexpression on the endothelial cells and will hopefully encourage experimental receptor quantification for both luminal and abluminal surfaces on endothelial cells.

Generation of a Mouse Monoclonal Antibody Recognizing Both the Native and Denatured Forms of Human VEGF

Vascular endothelial growth factor (VEGF) and its related member, placental growth factor (PlGF), play important roles in stimulating vascular growth (angiogenesis) in both physiological conditions such as embryonic development and pathological conditions such as inflammation and tumor growth. Development of monoclonal antibodies (MAbs) capable of blocking the interaction of VEGF and its receptors, which in turn block VEGF-mediated angiogenesis, has become a novel and very powerful approach for cancer management. Here we report the generation of a mouse monoclonal antibody M23, which binds to both the natural and denatured forms of human VEGF165, as well as to two other major VEGF isoforms (VEGF121 and VEGF189) being tested. MAb M23 does not bind to other VEGF-related proteins such as PlGF. This MAb will have great future potential in VEGF-related research, diagnosis, and treatment.

Vascular Endothelial Growth Factor mRNA Expression and Peritumoral Edema in Canine Primary Central Nervous System Tumors

Vascular endothelial growth factor (VEGF) is an important regulator of tumor angiogenesis and vascular permeability, and has been implicated both in progression of central nervous system (CNS) tumors and development of vasogenic peritumoral edema. A retrospective study was done to characterize the levels of expression of the 3 major canine VEGF isoforms (VEGF(120), VEGF(164), VEGF(188)) in a variety of spontaneous canine CNS tumors using quantitative TaqMan reverse transcription real-time polymerase chain reaction. Presence and degree of peritumoral edema also were determined in sampled tumors using magnetic resonance imaging (MRI). Increased expression of VEGF relative to normal cerebral cortex tissue was seen predominantly in high grade astrocytic (grade IV) and oligodendroglial (grade III) tumors, with lower expression in low grade astrocytomas (grade II) and meningiomas (grade I). All 3 major VEGF isoforms were present; VEGF(164) was the predominant isoform, particularly in the tumors with the highest VEGF expression. Peritumoral edema was present in all tumor types; however, a significant association between the extent of peritumoral edema and the level of VEGF expression was not apparent.

VEGF Expression and Receptor Activation in the Choroid during Development and in the Adult

Previous studies have demonstrated a role for the retinal pigment epithelium (RPE) in the development and maintenance of the choroidal vasculature, suggesting that RPE serves a trophic role for the choroidal vessels. The goal of this study was to determine the expression pattern of vascular endothelial growth factor (VEGF) and its receptors and their activation status in embryonic and adult choroid, with the purpose of providing cues regarding the role of VEGF in development and stabilization of the choroidal vasculature. Transgenic VEGF-LacZ mice were used to examine VEGF expression in embryonic and adult eyes. Expression of VEGF isoforms and receptors in the RPE-choroid complex was assessed by RT-PCR and real-time PCR. VEGF receptor 2 expression was assessed by immunohistochemistry and its activation state was examined by immunoprecipitation followed by phosphotyrosine blot. VEGF is expressed by RPE throughout the choroidal vascular development and in the adult. The major VEGF isoforms detected in adult RPE were VEGF120 and VEGF164, with almost no detectable VEGF188. RT-PCR analysis showed expression of VEGF receptors and coreceptors in the RPE-choroid complex. VEGFR2 was detected in the choriocapillaris underlying the RPE. Immunoprecipitation and phosphotyrosine blot of this receptor revealed that VEGFR2 is activated in adult mouse and bovine choroids. The observations suggest that VEGF signaling is involved, not only in choroidal vessel formation, but perhaps also in the maintenance of the choriocapillaris.

An engineered vascular endothelial growth factor-activating transcription factor induces therapeutic angiogenesis in ApoE knockout mice with hindlimb ischemia

Angiogenesis is the growth and proliferation of blood vessels from existing vascular structures, and therapeutic angiogenesis seeks to promote blood vessel growth to improve tissue perfusion. Vascular endothelial growth factor (VEGF) is a prototypic angiogenic agent that exists in vivo in multiple isoforms, and studies with VEGF to date had used single isoform therapy with disappointing results. We tested plasmid and adenoviral vectors encoding a zinc-finger DNA-binding transcription factor (ZFP-32E) that was designed to increase the expression of all major VEGF isoforms in a preclinical model of peripheral arterial obstructive disease (PAOD) in hypercholesterolemic (ApoE knock-out) mice. Unilateral femoral artery ligation/excision was performed in 117 mice. At 7 days postoperatively, the ischemic tibialis anterior (TA) and gastrocnemius (GAS) muscles received either ZFP-32E treatment (125 microg of plasmid, 2.5 x 10(11) viral particle units [vpu] of adenovirus; some mice received a second plasmid injection 3 days later) or no-ZFP treatment (125 microg of beta-galactosidase [beta-gal], a plasmid-lacking insert, or an equal dose of adenoviral encoding beta-gal; some mice received a second plasmid injection 3 days later). Group 1 mice (n = 31) were euthanized 3 days later, and VEGF messenger RNA (mRNA) and protein levels were measured. Group 2 mice (n = 38) were euthanized 7 days later, and measures of capillary density, cell proliferation, and apoptosis were quantified. Group 3 mice (n = 48) were euthanized 28 days later, and changes in lower limb blood flow perfusion were measured. In group 1, VEGF mRNA and protein levels were significantly higher in those with ZFP-32E treatment vs beta-gal. In group 2, capillary density and proliferating cells were significantly greater and apoptosis was significantly lower in those with ZFP-32E treatment vs beta-gal. Finally, in group 3, changes in the perfusion ratio (ischemic/nonischemic limb) at 21 days after injection were significantly greater in those with ZFP-32E treatment vs no-ZFP treatment. The ability of this engineered zinc-finger VEGF-activating transcription factor to induce therapeutic angiogenesis in hypercholesterolemic mice suggests this approach warrants investigation as a novel approach to treat PAOD.

Alteration of splicing signals in a genomic/cDNA hybrid VEGF gene to modify the ratio of expressed VEGF isoforms enhances safety of angiogenic gene therapy

Vascular endothelial growth factor (VEGF)-mediated physiological angiogenesis results from the concerted action of three major VEGF isoforms (VEGF121, 165, 189), which arise from alternate splicing. We have previously shown that expression of a mixture of VEGF isoforms via gene transfer is considerably more potent than expression of a single VEGF isoform. To test the hypothesis that different mixtures of VEGF isoforms may offer the same therapeutic benefit with a better safety profile, we compared the efficacy and safety of an adenovirus gene transfer vector expressing the three major VEGF isoforms (AdVEGF-All) in the normal ratio to those of AdVEGF-All6A+, in which the splicing sequences for exon 6A were altered to promote expression of VEGF189 at the expense of VEGF121. Both vectors were equally potent in mediating recovery of hind-limb blood flow following experimental ischemia. By contrast, intravenous administration of AdVEGF-All6A+ yielded enhanced survival and a lower capacity to support tumor growth compared to AdVEGF-All, and intratracheal administration of AdVEGF-All6A+ resulted in less pulmonary edema than that of AdVEGF-All. We conclude that AdVEGF-All and AdVEGF-All6A+ are similar in potency but that AdVEGF-All6A+ is safer. This suggests that AdVEGF-All6A+ may be the preferred candidate for clinical development.

Overexpression of VEGF121, but not VEGF165 or FGF-1, improves oxygenation in MCF-7 breast tumours.

Vascular endothelial growth factor (VEGF) is an intensively studied molecule that has significant potential, both in stimulating angiogenesis and as a target for antiangiogenic approaches. We utilised MCF-7 breast cancer cells transfected with either of two of the major VEGF isoforms, VEGF121 or VEGF165, or fibroblast growth factor-1 (FGF-1) to distinguish the effects of these factors on tumour growth, vascular function, and oxygen delivery. While each transfectant demonstrated substantially increased tumorigenicity and growth rate compared to vector controls, only VEGF121 produced a combination of significantly reduced total and perfused vessel spacing, as well as a corresponding reduction in overall tumour hypoxia. Such pathophysiological effects are of potential importance, since antiangiogenic agents designed to block VEGF isoforms could in turn result in the development of therapeutically unfavourable environments. If antiangiogenic agents are also combined with conventional therapies such as irradiation or chemotherapy, microregional deficiencies in oxygenation could play a key role in ultimate therapeutic success.

Reduced vascular endothelial growth factor correlates with alveolar epithelial damage after experimental ischemia and reperfusion

Background: After clinical lung transplantation, the amount of vascular endothelial growth factor (VEGF) was found to be decreased in the bronchoalveolar lavage from lungs with acute lung injury. Since Type II pneumocytes are a major site of VEGF synthesis, VEGF depression may be an indicator of pulmonary epithelial damage after ischemia and reperfusion. Methods: Using an established rat lung model, we investigated the relationship between VEGF protein expression, oxygenation capacity and structural integrity after extracorporeal ischemia and reperfusion (ischemia 6 hours at 10°C, reperfusion 50 minutes) and preservation with either low-potassium dextran solution (Perfadex 40 kD, n = 8) or Celsior ( n = 6). Untreated, non-ischemic lungs served as controls ( n = 5 per group). Perfusate oxygenation was recorded during reperfusion. An enzyme-linked immunoassay (ELISA) for VEGF protein and reverse transcription–polymerase chain reaction (RT-PCR) for mRNA splice variants were determined on tissue collected from the left lungs, whereas the right lungs were fixed by vascular perfusion for VEGF immunohistochemistry as well as structural analysis by light and electron microscopy. Tissue collection by systematic uniform random sampling was representative for the whole organ and allowed for quantification of structures by stereological means. Results: After ischemia and reperfusion, the 3 major VEGF isoforms, VEGF 120, VEGF 164 and VEGF 188, were present. VEGF protein expression was reduced, which correlated significantly with perfusate oxygenation ( r = 0.736; p = 0.002) at the end of reperfusion. It was inversely related to Type II cell volume ( r = 0.600; p = 0.047). VEGF protein was localized by immunohistochemistry in Type II pneumocytes, alveolar macrophages as well as bronchial epithelium, and staining intensity of Type II cells was reduced after ischemia and reperfusion. Alveolar edema did not occur but significant interstitial edema accumulated around vessels and in the blood-gas barrier, which showed a higher degree of epithelial damage after preservation with Celsior compared with the other groups. Conclusions: Depression in VEGF protein expression can be considered an indicator for increased alveolar epithelial damage. Preservation with low-potassium dextran solution resulted in improved oxygenation and tissue integrity compared with Celsior.

Expression of VEGF and MMP-9 in giant cell tumor of bone and other osteolytic lesions

This study aims to investigate the expression of vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) in giant cell tumor of bone (GCT) and other osteolytic lesions in bone. By using semi-quantitative RT-PCR, we showed that three major isoforms of VEGF (121, 165 and 189) were expressed in GCTs, with isoform 121 being the most abundant. The expression levels of VEGF and MMP-9 mRNA were significantly higher in advanced GCTs (stage II/III) than in stage I GCTs. We further elucidated the cellular localization of VEGF and MMP-9 gene transcripts in GCT and other osteolytic lesions using an in situ hybridization assay. The results showed that stromal tumor cells and osteoclast-like giant cells of GCT, fibrous stromal cells in anuerysmal bone cysts and fibrous dysplasia, and Langerhans-type giant cells as well as histocytes in eosinophillic granuloma, were all strongly positive for VEGF and MMP-9 mRNA expression. In a prospective study, we performed VEGF and MMP-9 immuno-staining on paraffin sections of pathological tissues harvested from 48 patients (14 GCT, 10 anuerysmal bone cysts, 10 eosinophillic granuloma, 4 fibrous dysplasia, 2 simple bone cyst, 2 osteomyelitis and 6 patients with fractured femoral head as control). The results showed that the differences in VEGF and MMP-9 expression between Stage I and other advanced Stages (II, III and recurrent) were highly significant (p < 0.001), with advanced stages showing a higher mean expression. The difference between recurrent and Stage II and III lesions, was also statistically significant (p = 0.03 for VEGF, and p = 0.01 for MMP-9 expression), with recurrent lesions showing a higher mean expression of both VEGF and MMP-9. In conclusion, VEGF and MMP-9 expression in osteolytic lesions of bone co-relates well with the extent of bone destruction and local recurrence. Their expression may therefore provide some prognostic indication of the possible aggressive behavior of the underlying pathology.

Expression of Vascular Endothelial Growth Factor in the Dental Follicle

Tooth eruption requires the presence of the dental follicle to recruit mononuclear cells, which fuse to form osteoclasts that resorb the alveolar bone such that the tooth can erupt. In the rat first mandibular molar, there is a major burst of osteoclastogenesis at day 3 postnatally and a lesser burst at day 10. Eruption molecules, such as CSF-1, are maximally expressed at day 3 in the dental follicle to promote this maximal osteoclast formation, but by the time of the secondary burst of osteoclastogenesis their expression is dramatically reduced. Because vascular endothelial growth factor (VEGF) can substitute for CSF-1 to promote osteoclastogenesis, we examined its gene expression in vivo in the dental follicle and found that it and its two major isoforms (VEGF 120 and 164) were all maximally expressed at days 9-11, the time of the secondary burst. Treatment of the cells with phorbolmyristate acetate (PMA), a protein kinase C (PKC) activator, enhanced expression of the 2 major VEGF isoforms in the cultured dental follicle cells, whereas adding a specific PKC inhibitor prevented this. Treatment with PMA also increased the protein level of VEGF. Thus, VEGF may be involved in promoting the secondary burst of osteoclastogenesis, and activation of PKC may upregulate its expression.

Effects of high glucose and TGF-β1 on the expression of collagen IV and vascular endothelial growth factor in mouse podocytes

Effects of high glucose and TGF-beta1 on the expression of collagen IV and vascular endothelial growth factor in mouse podocytes. The podocyte takes center stage in the pathogenesis of glomerular basement membrane (GBM) thickening and proteinuria in diabetic glomerulopathy. In part, GBM thickening may occur when the podocyte synthesizes increased amounts of collagen IV. Proteinuria may develop if the podocyte secretes excessive amounts of vascular endothelial growth factor (VEGF), which may increase the glomerular permeability to macromolecules. The augmented production of collagen IV and VEGF may be caused by metabolic mediators of diabetes such as hyperglycemia and transforming growth factor-beta (TGF-beta). The effects of high glucose and exogenous TGF-beta1 were examined on a mouse podocyte cell line that retains its differentiated phenotype. The gene expression and protein production of certain alpha chains of collagen IV, the major isoforms of VEGF, and components of the TGF-beta system were assayed. An inhibitor of TGF-beta signaling was used to determine whether some of the high glucose effects might be mediated by the TGF-beta system. Compared with normal glucose (5.5 mmol/L), high glucose (HG, 25 mmol/L) for 14 days stimulated [3H]-proline incorporation, a measure of collagen production, by 1.8-fold, and exogenous TGF-beta1 (2 ng/mL) for 24 hours stimulated proline incorporation by 2.4-fold. Northern analysis showed that exposure to HG for 14 days increased the mRNA level of alpha1(IV) collagen by 51% and alpha5(IV) by 90%, whereas treatment with TGF-beta1 (2 ng/mL) for 24 hours decreased the mRNA level of alpha1(IV) by 36% and alpha5(IV) by 40%. Consistent with these effects on mRNA expression, Western blotting showed that HG increased alpha1(IV) protein by 44% and alpha5(IV) by 28%, while TGF-beta1 decreased alpha1(IV) protein by 29% and alpha5(IV) by 7%. In contrast to their opposing actions on alpha1 and alpha5(IV), both HG and exogenous TGF-beta1 increased alpha3(IV) collagen and VEGF, with TGF-beta1 having the greater effect. An inhibitor of the TGF-beta type I receptor (ALK5) was able to prevent the stimulation of alpha3(IV) and VEGF proteins by HG. Unlike in other renal cell types, HG did not increase TGF-beta1 mRNA or protein in the podocyte, but HG did induce the expression of the ligand-binding TGF-beta type II receptor (TbetaRII). Because HG had up-regulated TbetaRII after two weeks, the addition of physiological-dose TGF-beta1 (0.010 ng/mL) for 24 hours stimulated the production of alpha3(IV) and VEGF proteins to a greater extent in high than in normal glucose. Up-regulation of TbetaRII in the podocyte was corroborated by immunohistochemistry of the kidney cortex in the db/db mouse, a model of type 2 diabetes. High glucose and exogenous TGF-beta1 exert disparate effects on the expression of alpha1 and alpha5(IV) collagen. However, high glucose and TGF-beta1 coordinately induce the production of alpha3(IV) collagen and VEGF in the podocyte. The HG-induced increases in alpha3(IV) collagen and VEGF proteins are mediated by the TGF-beta system. By increasing the expression of TbetaRII, high glucose may augment the response of the podocyte to ambient levels of TGF-beta1.

Vascular endothelial growth factor is increased following coronary artery occlusion in the dog heart.

Vascular endothelial growth factor (VEGF) is a hypoxia-inducible factor expressed into several molecular forms in mammalian tissues of which VEGF 120, VEGF 164, and VEGF 188 are the major isoforms. While VEGF 164 is the predominant isoform in most tissues, VEGF 188 has been reported to be dominant in cardiac tissues such as that in guinea pig, rat, and mouse. In the dog heart, an important model for studies of myocardial ischemia and angiogenesis, the expression of VEGF remains to be established. We investigated the expression of the various isoforms of VEGF in normal and ischemic dog heart tissues using Reverse transcription-Polymerase chain reaction, Ribonuclease Protection Assay and Western blotting. The nucleotide sequences of the major isoforms of VEGF were also determined using homology cloning techniques. Our study showed that the nucleotide sequences of dog VEGF were highly homologous to human VEGF especially in the c-terminal region spanning exons 58. A single amino acid-deletion (Glu5 in human VEGF), similar to that reported in other animal species, was observed in the major isoforms resulting in monomers of 120, 164, and 188 amino acids. A novel splice site similar to that in human VEGF183 was also identified in the dog heart, resulting in the 182 amino acid-containing isoform (VEGF 182). Moreover, VEGF 164 was expressed at a higher level as compared with VEGF 182 or VEGF 188 in both normal and ischemic tissues. The identification of the nucleotide sequences of VEGF isoforms in the dog heart should prove useful in investigating the molecular expression of VEGF in canine tissues.

Vascular endothelial growth factor (VEGF) and its receptors in tumor-bearing dogs.

The molecular biology of the angiogenic growth factor, vascular endothelial growth factor (VEGF), has been studied in the dog. All major isoforms of VEGF are present in the dog. The amino acid sequences are identical between human and dog in the loop regions that are responsible for receptor binding. Accordingly, the VEGF receptors of dogs and humans are very similar and permit functional exchange of the growth factor. Here we show that canine VEGF activates human endothelial cells to the same extent as human VEGF. Similarly, the two proteins display identical cell binding properties. The VEGF receptor 1 (Flt-1) shows the same alternative splicing in humans and dogs and is overexpressed in the majority of tumors in both species. VEGF occurs also in canine tumors in similar relative quantities as in human malignancies. Based on the literature and our study we suggest that the molecular biology and the function of the VEGF signaling system are virtually identical in humans and canines and in healthy as well as in disease conditions.