Administration Of Vascular Endothelial Growth Factor Research Articles

Glomerular Disturbances in Preeclampsia: Disruption Between Glomerular Endothelium and Podocyte Symbiosis

Background. Preeclampsia (PE) is the commonest cause of glomerular disease worldwide. Glomerular endotheliosis has been considered as the hallmark of PE, but this lesion is also found in non-proteinuric hypertensive pregnant women. Lately, podocyte alterations have been related to PE. Proposal. Although it has been demonstrated that glomerular endothelium and podocyte alterations are related to PE, we could locate no formal academic discussion that integrates these two phenomena. The demonstration that alterations of the expression of vascular endothelial growth factor (VEGF) by podocytes result in a dramatic endothelial phenotype and that induced production of endothelin-1 by glomerular endothelium provokes podocyte damage could indicate that glomerular lesions in PE result from disruption of the symbiosis between these cells rather than from events occurring independently. We shall try to describe a holistic way of viewing renal disease in PE women, in which the hypertensive emergency is produced by the effects of antiangiogenic proteins on the vascular endothelium, while renal lesion and proteinuria result from the effects of these proteins on both the glomerular endothelium and the podocyte. Conclusions. VEGF deficiency within the glomerulus in women with PE leads to the disruption of podocyte and glomerular endothelium symbiosis. The evidence demonstrating that exogenous VEGF administration in a rat model of PE could alleviate hypertension and proteinuria in these animals are encouraging in view of looking for therapeutic approaches in this direction, nonetheless further evidence should be provided in humans to directly demonstrate that VEGF supplementation could mitigate the symptoms of PE.

Optimal Dose of Plasmid Vascular Endothelial Growth Factor for Enhancement of Angiogenesis in the Rat Brain Ischemia Model

Vascular endothelial growth factor (VEGF) administration has recently been assessed as a therapeutic strategy for ischemic diseases including brain ischemia because of its angiogenic effect. However, VEGF also causes detrimental adverse effects by increasing vascular permeability. This study examined whether plasmid human VEGF (phVEGF) administration induced angiogenic effects in the rat brain ischemia model caused by permanent ligation of both common carotid arteries, and investigated the occurrence of adverse effects. Administration of various doses (0-200 microg) of phVEGF in the temporal muscle was followed by encephalo-myo-synangiosis. Thirty days after treatment, the numbers and areas of capillaries per field in the extracted brains were analyzed with the National Institutes of Health Image software program. The maximal angiogenic effect occurred with a 100 microg dose of phVEGF in the numbers and areas of capillaries in the VEGF-treated brains. Histological examination showed no apparent adverse effects in the brain parenchyma even at the highest administration dose (200 microg) of phVEGF. The maximal angiogenic effect at the optimal dose of phVEGF can be considered under the threshold to cause serious adverse effects in the rat brain.

Role of Vascular Endothelial Growth Factor in Kidney Disease

Vascular endothelial growth factor (VEGF) is a main regulator of blood vessel growth and plays an important role in promoting endothelial survival and maintaining the microvasculature. The kidney is a highly vascularized organ and has two important microvasculatures; glomerular and peritubular capillaries. Loss of these capillaries is strongly associated with the progression of chronic kidney disease (CKD) to end-stage renal disease. In several kidney disease animal models, VEGF expression in the kidney is decreased and administration of VEGF is protective. Recent clinical observations revealed that blocking VEGF by endogenous inhibitor (soluble Flt-1) in preeclampsia and monoclonal antibody against VEGF in cancer patients cause proteinuria and renal dysfunction. However, plasma VEGF levels in diabetic nephropathy patients are increased and blocking VEGF improved diabetic nephropathy in animal models. Increased plasma VEGF levels have been reported in CKD patients. Deleterious effects of VEGF have been demonstrated in atherosclerosis and sepsis, which are frequent complications in CKD patients. Although administrating VEGF or novel drugs that activate VEGF pathway may improve the progression of CKD, careful monitoring will be required when CKD patients have complications of diabetes, atherosclerosis or sepsis.

VEGF elicits epithelial-mesenchymal transition (EMT) in prostate intraepithelial neoplasia (PIN)-like cells via an autocrine loop

Vascular endothelial growth factor (VEGF) is overexpressed during the transition from prostate intraepithelial neoplasia (PIN) to invasive carcinoma. We have mimicked such a process in vitro using the PIN-like C3(1)/Tag-derived Pr-111 cell line, which expresses low levels of VEGF and exhibits very low tumorigenicity in vivo. Elevated expression of VEGF164 in Pr-111 cells led to a significant increase in tumorigenicity, invasiveness, proliferation rates and angiogenesis. Moreover, VEGF164 induced strong changes in cell morphology and cell transcriptome through an autocrine mechanism, with changes in TGF-beta1- and cytoskeleton-related pathways, among others. Further analysis of VEGF-overexpressing Pr-111 cells or following exogenous addition of recombinant VEGF shows acquisition of epithelial-mesenchymal transition (EMT) features, with an increased expression of mesenchymal markers, such as N-cadherin, Snail1, Snail2 (Slug) and vimentin, and a decrease in E-cadherin. Administration of VEGF led to changes in TGF-beta1 signaling, including reduction of Smad7 (TGF-beta inhibitory Smad), increase in TGF-betaR-II, and translocation of phospho-Smad3 to the nucleus. Our results suggest that increased expression of VEGF in malignant cells during the transition from PIN to invasive carcinoma leads to EMT through an autocrine loop, which would promote tumor cell invasion and motility. Therapeutic blockade of VEGF/TGF-beta1 in PIN lesions might impair not only tumor angiogenesis, but also the early dissemination of malignant cells outside the epithelial layer.

Atrial Natriuretic Peptide Reduces Vascular Leakage and Choroidal Neovascularization

Atrial natriuretic peptide (ANP) is a hormone with diuretic, natriuretic, and vasodilatory properties. ANP blocks vascular endothelial growth factor (VEGF) production and signaling in vitro; however, its role in vascular leakage and angiogenesis is unknown. In vitro, retinal barrier permeability (transepithelial electrical resistance (TEER)) was measured in cultured retinal endothelial (HuREC) and retinal epithelial (ARPE-19) cells with VEGF (10 ng/ml), ANP (1 pM to 1 micromol/L), and/or isatin, an ANP receptor antagonist. In vivo, blood-retinal barrier (BRB) leakage was studied using the Evans Blue dye technique in rats treated with intravitreal injections of ANP, VEGF, or vehicle. Choroidal neovascularization was generated by laser injury, and 7 days later, lesion size and leakage was quantitated. ANP significantly reversed VEGF-induced BRB TEER reduction in both HuREC and ARPE-19 cells, modeling the inner and the outer BRB, respectively. Isatin, a specific ANP receptor antagonist, reversed ANP's effect. ANP reduced the response of ARPE-19 cells to VEGF apically but not basolaterally, suggesting polarized expression of the ANP receptors in these cells. ANP's TEER response was concentration but not time dependent. In vivo, ANP significantly reduced VEGF-induced BRB leakage and the size of laser-induced choroidal neovascularization lesions. In sum, ANP is an effective inhibitor of VEGF-induced vascular leakage and angiogenesis in vivo. These results may lead to new treatments for ocular diseases where VEGF plays a central role, such as age-related macular degeneration or diabetic retinopathy.

Role of renal microcirculation in experimental renovascular disease

Renal artery stenosis (RAS) causes renal injury partly via microvascular (MV) endothelial dysfunction and damage. Vascular endothelial growth factor (VEGF) is crucial for preservation of microvasculature and promotes vascular proliferation and endothelial repair. We have previously shown that MV rarefaction is associated with decreased VEGF in the kidney exposed to chronic RAS, accompanied by deteriorated renal function and fibrosis. We hypothesized that preserving the renal microcirculation in the stenotic kidney will halt the progression of renal damage. Unilateral RAS was induced in 16 pigs. In eight, VEGF (0.05 micrograms/kg) was infused intra-renally at the onset of RAS. After 6 weeks, single-kidney haemodynamics and function were assessed using in vivo multi-detector computed tomography (CT). Renal microvessels, angiogenic pathways and morphology were investigated ex vivo using micro-CT, real-time PCR and histology. Blood pressure and degree of RAS was similar in RAS and RAS + VEGF pigs. Single-kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were reduced in RAS compared to Normal (221.1 +/- 46.5 and 29.9 +/- 3.8 vs. 522.5 +/- 60.9 and 49.3 +/- 3.4 mL/min, respectively, P < 0.05), accompanied by decreased cortical MV density and increased renal fibrosis. Pre-emptive administration of VEGF preserved MV architecture, attenuated fibrosis and normalized RBF and GFR (510.8 +/- 50.9 and 39.9.1 +/- 4.1 mL/min, P = not significant vs. Normal). This study underscores the importance of the renal microcirculation in renovascular disease. Intra-renal administration of VEGF preserved renal MV architecture and function of the stenotic kidney, which in turn preserved renal haemodynamics and function and decreased renal fibrosis. These observations suggest that preventing renal MV loss may be a potential target for therapeutic approaches for patients with chronic renovascular disease.

Can the biology of VEGF and haem oxygenases help solve pre-eclampsia?

Pre-eclampsia, a pregnancy-specific multi-organ syndrome characterized by widespread endothelial damage, is a new risk factor for cardiovascular disease. No therapies exist to prevent or treat this condition, even to achieve a modest improvement in pregnancy length or birth weight. Co-administration of soluble VEGFR-1 [VEGF (vascular endothelial growth factor) receptor-1; more commonly known as sFlt-1 (soluble Fms-like tyrosine kinase-1)] and sEng (soluble endoglin) to pregnant rats elicits severe pre-eclampsia-like symptoms. These two anti-angiogenic factors are increased dramatically prior to the clinical onset of pre-eclampsia and are quite possibly the 'final common pathway' responsible for the accompanying signs of hypertension and proteinuria as they can be reversed by VEGF administration in animal models. HO-1 (haem oxygenase-1), an anti-inflammatory enzyme, and its metabolite, CO (carbon monoxide), exert protective effects in several organs against oxidative stimuli. In a landmark publication, we showed that the HO-1 pathway inhibits sFlt-1 and sEng in cultured cells and human placental tissue explants. Both CO and NO (nitric oxide) promote vascular homoeostasis and vasodilatation, and activation of VEGFR-1 or VEGFR-2 induced eNOS (endothelial nitric oxide synthase) phosphorylation, NO release and HO-1 expression. Our studies established the HO-1/CO pathway as a negative regulator of cytokine-induced sFlt-1 and sEng release and eNOS as a positive regulator of VEGF-mediated vascular morphogenesis. These findings provide compelling evidence for a protective role of HO-1 in pregnancy and identify it as a target for the treatment of pre-eclampsia. Any agent that is known to up-regulate HO-1, such as statins, may have potential as a therapy. Any intervention achieving even a modest prolongation of pregnancy or amelioration of the condition could have a significant beneficial health impact worldwide.

VEGF autoregulates its proliferative and migratory ERK1/2 and p38 cascades by enhancing the expression of DUSP1 and DUSP5 phosphatases in endothelial cells

Vascular endothelial growth factor (VEGF) is a key angiogenic factor that regulates proliferation and migration of endothelial cells via phosphorylation of extracellular signal-regulated kinase-1/2 (ERK1/2) and p38, respectively. Here, we demonstrate that VEGF strongly induces the transcription of two dual-specificity phosphatase (DUSP) genes DUSP1 and DUSP5 in endothelial cells. Using fluorescence microscopy, fluorescence lifetime imaging (FLIM), and fluorescence cross-correlation spectroscopy (FCCS), we found that DUSP1/mitogen-activated protein kinases phosphatase-1 (MKP-1) was localized in both the nucleus and cytoplasm of endothelial cells, where it existed in complex with p38 (effective dissociation constant, K(D)(eff), values of 294 and 197 nM, respectively), whereas DUSP5 was localized in the nucleus of endothelial cells in complex with ERK1/2 (K(D)(eff) 345 nM). VEGF administration affected differentially the K(D)(eff) values of the DUSP1/p38 and DUSP5/ERK1/2 complexes. Gain-of-function and lack-of-function approaches revealed that DUSP1/MKP-1 dephosphorylates primarily VEGF-phosphorylated p38, thereby inhibiting endothelial cell migration, whereas DUSP5 dephosphorylates VEGF-phosphorylated ERK1/2 inhibiting proliferation of endothelial cells. Moreover, DUSP5 exhibited considerable nuclear anchoring activity on ERK1/2 in the nucleus, thereby diminishing ERK1/2 export to the cytoplasm decreasing its further availability for activation.

Vascular endothelial growth factor enhances migration of astroglial cells in subventricular zone neurosphere cultures

Vascular endothelial growth factor (VEGF) is an endothelial and neuronal survival factor and a mitogen for endothelial cells and astrocytes in both explant and in vivo injury models. In the CNS, interplay between the vasculature and neural stem progenitor (NSP) cells is required for the maintenance of angiogenic/neurogenic coordination in the germinal niche in the subventricular zone (SVZ) of the lateral ventricle. Using an in vitro SVZ neurosphere (NS) model, this study aimed to understand the direct effects of VEGF and its receptor signaling on neonatal NSP cell growth and migration. Our data indicate that VEGF administration, compared with untreated or brain-derived neurotrophic factor-treated NS, significantly increased growth and migratory capacity of glial fibrillary acidic protein (GFAP)(+) and nestin(+) NSP cells and in secondary cultures induced a stellate astrocyte morphology. Blockade of both VEGF, which is normally expressed in some NS cells, and its flt-1 receptor signaling by neutralizing antibodies caused morphological changes specifically in GFAP(+) cells and disrupted sphere formation and outward migration. These cells did not appear as conventional polygonal astrocytes; their process growth was severely restricted, and overall migration was reduced by up to 76% of control cultures. Blockade of VEGF's flk-1 receptor reduced VEGF expression and caused a lesser, though significant, decrease (29%) in NSP (GFAP(+)) cell migration. The results show that both VEGF and, in particular, flt-1 receptor signaling are critical to the proper configuration of the NS and its subsequent development. VEGF is also an important growth and migratory factor particularly for GFAP(+) cells developing in SVZ-derived NS in culture.

Implications of Vascular Endothelial Growth Factor for Postischemic Neurovascular Remodeling

Neurovascular remodeling has been recently recognized as a promising target for neurologic therapies. Hopes have emerged that, by stimulating vessel growth, it may be possible to stabilize brain perfusion, and at the same time promote neuronal survival, brain plasticity, and neurologic recovery. In this review, we outline the role of vascular endothelial growth factor (VEGF) in the ischemic brain, analyzing how this growth factor contributes to brain remodeling. Studies with therapeutic VEGF administration resulted in quite variable results depending on the route and time point of delivery. Local VEGF administration consistently enhanced neurologic recovery, whereas acute intravenous delivery exacerbated brain infarcts due to enhanced brain edema. Future studies should answer the following questions: (1) whether increased vessel density translates into improvements in blood flow in the hemodynamically compromised brain; (2) how VEGF influences brain plasticity and contributes to motor and nonmotor recovery; (3) what are the actions of VEGF not only in young animals with preserved vasculature, on which previous studies have been conducted, but also in aged animals and in animals with preexisting atherosclerosis; and (4) whether the effects of VEGF can be mimicked by pharmacological compounds or by cell-based therapies. Only on the basis of such information can more definite conclusions be made with regard to whether the translation of therapeutic angiogenesis into clinics is promising.

Injectable Hydrogels Providing Sustained Delivery of Vascular Endothelial Growth Factor are Neuroprotective in a Rat Model of Huntington’s Disease

Vascular endothelial growth factor (VEGF) is a potent peptide with well-documented pro-angiogenic effects. Recently, it has also become clear that exogenous administration of VEGF is neuroprotective in animal models of central nervous system diseases. In the present study, VEGF was incorporated into a sustained release hydrogel delivery system to examine its potential benefits in a rat model of Huntington's disease (HD). The VEGF-containing hydrogel was stereotaxically injected into the striatum of adult rats. Three days later, quinolinic acid (QA; 225 nmol) was injected into the ipsilateral striatum to produce neuronal loss and behavioral deficits that mimic those observed in HD. Two weeks after surgery, animals were tested for motor function using the placement and cylinder tests. Control animals received either QA alone or QA plus empty hydrogel implants. Behavioral testing confirmed that the QA lesion resulted in significant deficits in the ability of the control animals to use their contralateral forelimb. In contrast, the performance of those animals receiving VEGF was significantly improved relative to controls with only modest motor impairments observed. Stereological counts of NeuN-positive neurons throughout the striatum demonstrated that VEGF implants significantly protected against the loss of striatal neurons induced by QA. These data are the first to demonstrate that VEGF can be used to protect striatal neurons from excitotoxic damage in a rat model of HD.

Local VEGF Administration Enhances Healing of Colonic Anastomoses in a Rabbit Model

Background/Aims: Many studies report the role of vascular endothelial growth factor (VEGF) in wound healing, but few describe local VEGF administration to the digestive tract. Leakage from colonic anastomoses, including those due to ischemia, represents a major complication causing increased mortality and morbidity. Angiogenesis is crucial to anastomotic healing and restoration of blood supply, and VEGF is a potent angiogenic factor showing improved healing in various models of reconstruction and anastomosis. Here, we examine the effects of local VEGF-A₁₆₅ administration on postoperative rabbit colon anastomosis. Methods: Two colotomies per animal were made in the sinistral colon on opposite sides of the mesentery. Randomly assigned VEGF (10 μg/0.1 ml) or saline (0.1 ml) was injected into the muscularis propria on both sides of each colonic anastomosis before closing the access laparotomy using single-layer sutures. On postoperative days 3, 4 and 7, the bursting pressure of partially healed anastomoses was measured. On postoperative day 4, anastomotic tissues were examined for the following: hydroxyproline; histopathologically for inflammatory infiltrate and tissue organization and immunohistochemically for capillary proliferation and density; vessel density of midzone collaterals around anastomoses by microangiography. Results: Compared to saline, VEGF administration significantly improved bursting pressure (p = 0.014, paired t test) and increased hydroxyproline (p = 0.027, paired t test) on postoperative day 4. Inflammatory cell infiltration and fibroblast proliferation were prominent, and submucosal capillary vascular counts were significantly higher for VEGF. Conclusions: Administration of VEGF to colonic anastomosis accelerates wound healing and strengthens the anastomosis by increased angiogenesis.

Effect of VEGF Treatment on the Blood-Spinal Cord Barrier Permeability in Experimental Spinal Cord Injury: Dynamic Contrast-Enhanced Magnetic Resonance Imaging

Compromised blood-spinal cord barrier (BSCB) is a factor in the outcome following traumatic spinal cord injury (SCI). Vascular endothelial growth factor (VEGF) is a potent stimulator of angiogenesis and vascular permeability. The role of VEGF in SCI is controversial. Relatively little is known about the spatial and temporal changes in the BSCB permeability following administration of VEGF in experimental SCI. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) studies were performed to noninvasively follow spatial and temporal changes in the BSCB permeability following acute administration of VEGF in experimental SCI over a post-injury period of 56 days. The DCE-MRI data was analyzed using a two-compartment pharmacokinetic model. Animals were assessed for open field locomotion using the Basso-Beattie-Bresnahan score. These studies demonstrate that the BSCB permeability was greater at all time points in the VEGF-treated animals compared to saline controls, most significantly in the epicenter region of injury. Although a significant temporal reduction in the BSCB permeability was observed in the VEGF-treated animals, BSCB permeability remained elevated even during the chronic phase. VEGF treatment resulted in earlier improvement in locomotor ability during the chronic phase of SCI. This study suggests a beneficial role of acutely administered VEGF in hastening neurobehavioral recovery after SCI.

Gene profiling studies in the neonatal ovine lung show enhancing effects of VEGF on the immune response

Preterm and young neonates have an increased predisposition to respiratory distress syndrome (RDS) associated with an immature development of lung surfactant. Glucocorticoids (GCs) are the major immunomodulatory agents used to increase lung development and reduce the mortality and morbidity of preterm infants with RDS. However, their safety remains uncertain, and the precise mechanisms by which they improve lung function are unclear. In previous studies, we found that vascular endothelial growth factor (VEGF) enhances the innate immune response by respiratory epithelial cells, causes a monocytic infiltration into the lung, and reduces the severity of infection by respiratory syncytial virus (RSV), a respiratory pathogen known to affect preterm infants at a high prevalence. The purpose of this study is to measure the effects of VEGF administration on local immune responses in neonatal lambs, as the ovine lung is well suited for comparison to the human lung, due to similarities in alveolar development, immune responses, and RSV susceptibility. We hypothesized that VEGF induces the expression of genes necessary for host immune responses. We analyzed global gene expression profiles in the lungs of neonate lambs treated with VEGF by real-time qPCR. We report that VEGF induced the expression of chemokines (IL-8, RANTES, MCP-1), cytokines (IFN-γ, IL-6, TNF-α, GMCSF), Toll-like receptor (TLR)-4, complement family members (C3, CFB, CFH) and collectins (SP-A, SP-D). These results suggest that VEGF can regulate local immune gene expression in vivo and should be further explored as a potential exogenous therapy for various lung diseases.

Improvement of Full-Thickness Skin Graft Survival by Application of Vascular Endothelial Growth Factor in Rats

The effect of vascular endothelial growth factor (VEGF) on skin graft survival was studied in rats. Models of skin grafting on muscle and periosteum were designed. For the study of skin grafting on muscle model, 32 rats were divided into 4 groups. VEGF was administrated systemically after skin graft placement intrafascially injected into the recipient bed at the time of graft placement and topically applied to the recipient bed at the time of graft placement. Control groups consisted of grafts placed on sites without systemic or local VEGF treatment. With the study of skin grafting on periosteum, 40 rats were divided into 4 groups. VEGF was systemically, intraperiosteally, and topically applied to the recipient bed. The control animals received no treatment. On the fifth postoperative day, the survival area of each skin graft was measured and the graft was harvested for histology with CD31 immunohistochemical staining. The results showed that in skin grafting on muscle model, the mean viable percentage of the skin graft was 66.1% +/- 10.2% in the group receiving systemic application of VEGF and 56.1% +/- 9.8% in the group receiving VEGF intrafascia injection. The survival percentages were significantly higher than those found in the control group (22.5% +/- 7.7%) and the group with VEGF topical application (30.8% +/- 4.1%). In skin grafting on periosteum, the group receiving VEGF intraperiosteum injection reached a survival percentage of 50.5% +/- 4.3%, significantly higher than the groups with VEGF systemic application (28.7 +/- 5.5%), VEGF topical application (32.5% +/- 4.8%), and the control (25.8% +/- 6.0%). Histology showed that sections taken from grafts with VEGF intrafascia and intraperiosteum treatment revealed angiogenesis. The data demonstrated that administration of VEGF into the either muscular or periosteal recipient beds for skin grafting can improve the skin graft survival.

Vascular endothelial growth factor decreases blood pressure in hypertensive pregnant rats

We have recently shown that placental ischemia in the pregnant rat results in hypertension and elevated concentrations of circulating soluble fms‐like tyrosine kinase‐1 (sFlt‐1), a naturally occurring vascular endothelial growth factor (VEGF) antagonist that is over‐expressed in preeclampsia. We hypothesized that chronic VEGF administration during the last trimester of pregnancy would attenuate the hypertension associated with placental ischemia in our well characterized model of reduced uterine perfusion pressure (RUPP). VEGF (80 ug/kg/day) was administered for five days via osmotic mini‐pump placed intraperitoneal. Arterial pressure (AP) and tissues were obtained on gestation day 19 from RUPP+VEGF, RUPP and normal pregnant (NP) dams. VEGF administration attenuated the hypertension produced by RUPP (115 ± 1 vs. 135 ± 3 vs. 104 ± 1 mmHg; P &lt; 0.001) but did not normalize AP to NP levels (mmHg; P &lt; 0.01). VEGF ameliorated the fetal (1.9 ± 0.2 vs. 1.8 ± 0.1 vs.2.2 ± 0.1; P &lt; 0.05) and placental (0.46 ± 0.12 vs. 0.36 ± 0.07 vs.0.57 ± 0.03; P &lt; 0.05) growth restriction observed in RUPP compared to NP dams. These data demonstrate that VEGF may be an effective treatment for reducing high blood pressure associated with placental ischemia. Further, these results indicate that VEGF supplementation may also promote fetal and placental growth despite reductions in uterine perfusion pressure.

Dendritic Epidermal T Cells Promote Wound Healing by Production of Vascular Endothelial Growth Factor Mediated by HIF‐1α Signaling

Local hypoxia is general consequence of an acute skin wound due to vascular disruption and high oxygen consumption by cells at the edge of the wound. The resident γδ T cells in the skin, Dendritic Epidermal T Cells (DETC), are known to support local tissue homeostasis and wound repair by local production of growth factors, such as keratinocyte growth factors (KGFs) and insulin‐like growth factor (IGF)‐1. We have analyzed the functional role of DETC in response to local tissue hypoxia generated by an acute skin wound. The hypoxic status of the skin wound induced HIF‐1α expression in DETC. HIF‐1α signalling during hypoxia induced expression of vascular endothelial growth factor (VEGF) by DETC. Wound healing was impaired after HIF‐1α gene‐silencing in DETC and this impairment was rescued by VEGF administration. Together this data demonstrates that acute skin wound induces HIF‐1α signaling in DETC, which promote VEGF production with the result of enhancing skin wound healing.Grant: NIH‐AI‐36964

Vascular endothelial growth factor (VEGF) receptors expresion and VEGF–mediated permeability of human amnion to calcium in chorioamnionitis (ChA)

VEGF is a mediator of inflammation and an angiogenic factor. VEGF receptor type 1 (VEGFR1) regulates vascular permeability, while VEGFR2 is necessary for proliferation during the process of angiogenesis. ChA may change neovasculatization and permeability of placental membranes. We examined expression of VEGFR1 and VEGFR2 within amniotic epithelial cells and VEGF–mediated permeability of human amnion to calcium ions in ChA. 16 pieces of isolated extraplacental amnion obtained after near to term pregnancies complicated by ChA were compared with 16 gestationally matched amnion samples from normal pregnancies (Group I and II, respectively). Expression of VEGFR1 and VEGFR2 within amniotic epithelium was examined in calibrated areas of immunostained paraffin sections using morphometry for quantitative analysis. Diffusion of Ca++ was measured using a system of plastic container divided into two chambers by the mounted amnion. The effect of VEGF administration (doses range: 100–500 pg/ml) on the transport coefficient for Ca++ was examined in both groups. Expression of VEGFR1 was significantly increased in Group I and was positively correlated with increased VEGF‐mediated amnion permeability for Ca++ (p &lt; 0.05). Our results indicate important influence of proinflammatory cytokine VEGF on calcium‐dependent biological phenomena, including preterm myometrial contractionsSupported by AM grant: 2M2‐W2‐07.

Effects of Vascular Endothelial Growth Factor on Ischemic Spinal Cord Injury Caused by Aortic Cross-Clamping in Rabbits

Spinal cord injury remains a devastating complication of thoracic and thoracoabdominal aortic operations. We aim to investigate neuro-protective role of vascular endothelial growth factor (VEGF) administered to rabbits after occlusion against ischemia-reperfusion (I/R) injury. Occlusion of the abdominal aorta was applied to adult rabbits, followed by removal of aortic clamp and reperfusion. The abdominal aortas of New Zealand White albino rabbits were occluded for 30 min. Experimental groups were as follows: control group (sham operation group, n = 7), I/R group (n = 9) undergoing occlusion but receiving no pharmacologic intervention, and VEGF-treated group (n = 7) receiving 0.8 microg/kg VEGF intravenously after occlusion. Neurological status was assessed at 6, 24, and 48 h after the operation. All animals were killed at 48 h after the operation. Spinal cords were harvested for histopathologic and biochemical analyses. According to Tarlov's scale, neurological status of the rabbits at postoperative h 48 was better in the VEGF-treated group compared to the I/R group (P < 0.05). Decreased tissue and serum malondialdehyde levels and increased tissue and serum glutathione levels were observed in VEGF-treated group (P < 0.05). In the same group tissue and serum nitrate levels were decreased (P < 0.05). Histopathologic analyses demonstrated typical morphological changes characteristic of necrosis in the I/R group. VEGF attenuated ischemia-induced necrosis. This is the first study that shows the effects of VEGF administered after occlusion on induced oxidative damage to injured spinal cords. VEGF administration may significantly reduce the incidence of spinal cord injury following temporary aortic occlusion.

Vascular Endothelial Growth Factor Improves Myocardial Functional Recovery Following Ischemia/Reperfusion Injury

Vascular endothelial growth factor (VEGF) is a central growth and survival factor for both the endothelium and the myocardium. Recent evidence also suggests that VEGF may play a critical role in stem-cell-mediated paracrine cardioprotection. However, the acute effect of exogenous VEGF on myocardium after ischemia, indeed whether isolated VEGF alone may be a clinically useful therapeutic modality, remains unknown. We hypothesize that infusion of exogenous VEGF immediately prior to ischemia will improve myocardial functional recovery. Adult male Sprague Dawley rat hearts were isolated and perfused via Langendorff model. All hearts were subject to 15-min equilibration, 25-min warm global ischemia, and 40-min reperfusion. Experimental hearts received a VEGF infusion of 3 x physiological (13 nM, n = 4), 5x physiological (20 nM, n = 4), or 10x physiological (40 nM, n = 5) immediately prior to ischemia. Controls (n = 5) were infused with perfusate vehicle. Functional indices (left ventricular developed pressure), end diastolic pressure, +/-dP/dt were continuously recorded. End diastolic pressure (mmHg) was elevated in response to ischemia/reperfusion. However, hearts infused with 10x VEGF demonstrated significantly (P < 0.05, analysis of variance and Bonferroni's) decreased end diastolic pressure throughout reperfusion compared to control (49.82 +/- 10.35 mmHg versus 80.73 +/- 6.08 mmHg at end reperfusion). 10x VEGF-treated hearts also exhibited significantly (P < 0.05, analysis of variance and Bonferroni's) greater recovery of left ventricular developed pressure (69.97 +/- 9.69% versus 39.74 +/- 7.01% of equilibration), +dP/dt, and -dP/dt at end reperfusion. However, neither 3 x nor 5x VEGF improved recovery after ischemia. VEGF also did not influence coronary flow after ischemia. This is the first demonstration that exogenous VEGF administration acutely improves myocardial functional recovery after ischemia. These findings may help elucidate the role of VEGF in acute stem-cell-mediated paracrine effects and suggests that isolated VEGF may be of therapeutic value.