VEGF enhances angiogenesis and promotes blood-brain barrier leakage in the ischemic brain

Intraventricular pre-treatment with rAAV-VEGF induces intracranial hypertension and aggravates ischemic injury at the early stage of transient focal cerebral ischemia in rats

OBJECTIVE

To examine the effects of intraventricular pre-treatment with recombinant adeno-associated virus vectors encoding VEGF (rAAV-VEGF) on early stroke in a rat model of transient middle cerebral artery occlusion (tMCAO).

METHODS

rAAV-VEGF, rAAV-null or physiologic saline was delivered into the lateral ventricle of 93 Wistar rats, respectively. Eight weeks later, the rats were subjected to tMCAO for 2 hours. During the early stage following ischemic reperfusion, intracranial pressure (ICP) and brain water content were measured to make a correlation analysis, T2-weighted MRI was performed to observe cerebral edema volume, and TTC-derived cerebral infarct volume and modified neurological severity scores (NSS) were determined to evaluate the therapeutic efficacy of rAAV-VEGF in tMCAO.

RESULTS

Twenty-four hours following tMCAO, the rAAV-VEGF group, with VEGF overexpression in the rats brain, showed a significantly increase in ICP, brain water content and cerebral edema volume compared with two control groups (p<0.05). The ICP significantly correlated with the brain water content in the infarct hemisphere in all three groups during 24 hours following tMCAO (r=0.93, p<0.05). Forty-eight hours following tMCAO, a 1.3-fold larger infarct volume and 1.3-fold higher NSS were observed in the rAAV-VEGF group than both control groups (p<0.05).

CONCLUSION

Our results indicate that intraventricular rAAV-VEGF pre-treatment can result in deleterious intracranial hypertension and augment secondary ischemic insults at the early stage of tMCAO, and pre-ischemic VEGF gene transfer via intraventricular approach may not be a favorable therapeutic strategy for tMCAO which should be adopted with caution or avoided in experimental stroke.

Attenuation of edema and infarct volume following focal cerebral ischemia by early but not delayed administration of a novel small molecule KDR kinase inhibitor

Vascular endothelial growth factor (VEGF) may mediate increases in vascular permeability and hence plasma extravasation and edema following cerebral ischemia. To better define the role of VEGF in edema, we examined the effectiveness of a novel small molecule KDR kinase inhibitor Compound-1 in reducing edema and infarct volume following focal cerebral ischemia in studies utilizing treatment regimens initiated both pre- and post-ischemia, and with study durations of 24-72 h. Rats were subjected to 90 min of middle cerebral artery occlusion (MCAO) followed by reperfusion. Pretreatment with Compound-1 (40 mg/kg p.o.) starting 0.5h before occlusion significantly reduced infarct volume at 72 h post-MCAO (vehicle, 194.1+/-22.9 mm(3) vs. Compound-1, 127.6+/-22.8mm(3) and positive control MK-801, 104.4+/-22.6mm(3), both p<0.05 compared to vehicle control), whereas Compound-1 treatment initiated at 2h after occlusion did not affect infarct volume. Compound-1 pretreatment also significantly reduced brain water content at 24h (vehicle, 80.3+/-0.2% vs. Compound-1, 79.7+/-0.2%, p<0.05) but not at 72 h after MCAO. These results demonstrate that early pretreatment administration of a KDR kinase inhibitor elicited an early, transient decrease in edema and subsequent reduction in infarct volume, implicating VEGF as a mediator of stroke-related vascular permeability and ischemic injury.

Increased tissue perfusion promotes capillary dysplasia in the ALK1-deficient mouse brain following VEGF stimulation

Loss-of-function activin receptor-like kinase 1 gene mutation (ALK1+/-) is associated with brain arteriovenous malformations (AVM) in hereditary hemorrhagic telangiectasia type 2. Other determinants of the lesional phenotype are unknown. In the present study, we investigated the influence of high vascular flow rates on ALK1+/- mice by manipulating cerebral blood flow (CBF) using vasodilators. Adult male ALK1+/- mice underwent adeno-associated viral-mediated vascular endothelial growth factor (AAVVEGF) or lacZ (AAVlacZ as a control) gene transfer into the brain. Two weeks after vector injection, hydralazine or nicardipine was infused intraventricularly for another 14 days. CBF was measured to evaluate relative tissue perfusion. We analyzed the number and morphology of capillaries. Results demonstrated that hydralazine or nicardipine infusion increased focal brain perfusion in all mice. It was noted that focal CBF increased most in AAVVEGF-injected ALK1+/- mice following hydralazine or nicardipine infusion (145+/-23% or 150+/-11%; P<0.05). There were more detectable dilated and dysplastic capillaries (2.4+/-0.3 or 2.0+/-0.4 dysplasia index; P<0.01) in the brains of ALK1+/- mice treated with AAVVEGF and hydralazine or nicardipine compared with the mice treated with them individually. We concluded that increased focal tissue perfusion and angiogenic factor VEGF stimulation could have a synergistic effect to promote capillary dysplasia in a genetic deficit animal model, which may have relevance to further studies of AVMs.

Neuroprotective effects of vascular endothelial growth factor following hypoxic ischemic brain injury in neonatal rats

Vascular Endothelial Growth Factor (VEGF) protects the brain against ischemic injury in adult animals. We evaluated whether VEGF has neuroprotective effects against hypoxic-ischemic (HI) brain injury in newborn rats. Seven-day-old rat pups had the right carotid artery permanently ligated followed by 140 min of hypoxia (8% oxygen). VEGF (5, 10, 20, or 40 ng) or vehicle was administered intracerebroventricularly 5 min after reoxygenation following HI. Brain damage was evaluated by weight loss of the right hemisphere at 22 d after HI and by gross and microscopic morphology. Body weight, rectal temperature, and mortality were not significantly different in the VEGF and vehicle treated groups. VEGF treatment increased brain VEGF levels at 15 min after injection. VEGF (10 and 20 ng) significantly reduced brain weight loss (p < 0.05) and gross brain injury (p < 0.05); however, treatment with 5 or 40 ng did not. VEGF (10 ng) also decreased brain damage assessed by histologic scoring. VEGF increased phosphorylation of protein kinase B (Akt) and extracellular-signal regulated kinase 1/2 (ERK1/2) in the cortex (p < 0.05). These results suggest that VEGF has neuroprotective effects in the neonatal rat HI model that may be related to activation of the Akt/ERK signaling pathway.

Transplantation of vascular cells derived from human embryonic stem cells contributes to vascular regeneration after stroke in mice

Background

We previously demonstrated that vascular endothelial growth factor receptor type 2 (VEGF-R2)-positive cells induced from mouse embryonic stem (ES) cells can differentiate into both endothelial cells (ECs) and mural cells (MCs) and these vascular cells construct blood vessel structures in vitro. Recently, we have also established a method for the large-scale expansion of ECs and MCs derived from human ES cells. We examined the potential of vascular cells derived from human ES cells to contribute to vascular regeneration and to provide therapeutic benefit for the ischemic brain.

Methods

Phosphate buffered saline, human peripheral blood mononuclear cells (hMNCs), ECs-, MCs-, or the mixture of ECs and MCs derived from human ES cells were intra-arterially transplanted into mice after transient middle cerebral artery occlusion (MCAo).

Results

Transplanted ECs were successfully incorporated into host capillaries and MCs were distributed in the areas surrounding endothelial tubes. The cerebral blood flow and the vascular density in the ischemic striatum on day 28 after MCAo had significantly improved in ECs-, MCs- and ECs+MCs-transplanted mice compared to that of mice injected with saline or transplanted with hMNCs. Moreover, compared to saline-injected or hMNC-transplanted mice, significant reduction of the infarct volume and of apoptosis as well as acceleration of neurological recovery were observed on day 28 after MCAo in the cell mixture-transplanted mice.

Conclusion

Transplantation of ECs and MCs derived from undifferentiated human ES cells have a potential to contribute to therapeutic vascular regeneration and consequently reduction of infarct area after stroke.

Contribution of bone marrow-derived cells associated with brain angiogenesis is primarily through leukocytes and macrophages

OBJECTIVE

We investigated the role of bone marrow-derived cells (BMDCs) in an angiogenic focus, induced by VEGF stimulation.

METHODS AND RESULTS

BM from GFP donor mice was isolated and transplanted into lethally irradiated recipients. Four weeks after transplantation, groups of mice received adeno-associated viral vector (AAV)-VEGF or AAV-lacZ gene (control) injection and were euthanized at 1 to 24 weeks. BMDCs were characterized by double-labeled immunostaining. The function of BMDCs was further examined through matrix metalloproteinase (MMP)-2 and -9 activity. We found that capillary density increased after 2 weeks, peaked at 4 weeks (P<0.01), and sustained up to 24 weeks after gene transfer. GFP-positive BMDCs infiltration in the angiogenic focus began at 1 week, peaked at 2 weeks, and decreased thereafter. The GFP-positive BMDCs were colocalized with CD45 (94%), CD68 (71%), 5% Vimentin (5%), CD31/von Willebrand factor (vWF) (1%), and alpha-smooth muscle actin (alpha -SMA, 0.5%). Infiltrated BMDCs expressed MMP-9. MMP-9 KO mice confirmed the dependence of the angiogenic response on MMP-9 availability.

CONCLUSIONS

Nearly all BMDCs in the angiogenic focus showed expression for leukocytes/macrophages, indicating that BMDCs minimally incorporated into the neovasculature. Colocalization of MMPs with GFP suggests that BMDCs play a critical role in VEGF-induced angiogenic response through up-regulation of MMPs.

VEGF overexpression improves mice cognitive abilities after unilateral common carotid artery occlusion

Angiogenesis and neurogenesis are adaptive responses protecting cerebral tissue from hypoxic-ischemic injury. Both processes seem to be governed by hypoxia-induced growth factors, of which vascular endothelial growth factor (VEGF) is a prominent example. The aim of this study was to investigate the influence of VEGF overexpression (V1 mice) on mice cognitive function and cerebral structure under moderate cerebral oligemia. In 33 V1 and wild-type (wt) mice, the left common carotid artery was permanently occluded (CCAO) under acute (48 h) and subchronic (12 days) conditions. Sham operation was performed in 35 mice (controls). Psychometric testing was done using holeboard test and Morris Water Maze system, immunohistochemistry was performed for detection of cerebral apoptosis, nestin and CD31 expression. The results show that under control conditions V1 mice showed better spatial cognitive abilities as compared to their wt littermates. During CCAO, time and distance to reach a hidden platform in Water Maze were shorter in V1 mice as compared to wt animals, indicative of faster learning and better spatial memory processes. While no signs of necrosis or apoptosis were detected, immunohistochemistry showed that VEGF transgenity was related to higher number of nestin-positive precursor cells. Finally, acute CCAO was paralleled by a reduction of CD31 staining in wt but not V1 mice. We conclude that VEGF overexpression led to a protective effect on cognitive function, because V1 mice showed evidence for faster spatial learning and better memory, as well as an increased number of neuronal precursor cells and a prevention of endothelial cell loss after CCAO.

eNOS and stroke: prevention, treatment and recovery

It is common knowledge that ischemic stroke has major social and economic consequences. However, until now, translation of experimental studies into clinical reality has been sorely lacking. So far, most studies have focused on acute stroke outcome and early treatment paradigms affording neuroprotection. It is increasingly recognized that it will be necessary to harness the capacity of the brain for neuroregeneration to improve longer-term outcome. Endothelial nitric oxide synthase (eNOS) is emerging as a key target in molecular stroke research. eNOS ameliorates acute ischemic injury and promotes recovery following cerebral ischemia. This review summarizes the effects of eNOS on the regulation of cerebral blood flow, hemostasis, inflammation, angiogenesis as well as neurogenesis. The possible impact on stroke prevention as well as on strategies aimed at improving long-term stroke outcome are discussed.

Blood-brain barrier tight junction permeability and ischemic stroke

The blood-brain barrier (BBB) is formed by the endothelial cells of cerebral microvessels, providing a dynamic interface between the peripheral circulation and the central nervous system. The tight junctions (TJs) between the endothelial cells serve to restrict blood-borne substances from entering the brain. Under ischemic stroke conditions decreased BBB TJ integrity results in increased paracellular permeability, directly contributing to cerebral vasogenic edema, hemorrhagic transformation, and increased mortality. This loss of TJ integrity occurs in a phasic manner, which is contingent on several interdependent mechanisms (ionic dysregulation, inflammation, oxidative and nitrosative stress, enzymatic activity, and angiogenesis). Understanding the inter-relation of these mechanisms is critical for the development of new therapies. This review focuses on those aspects of ischemic stroke impacting BBB TJ integrity and the principle regulatory pathways, respective to the phases of paracellular permeability.

VEGF increases blood-brain barrier permeability to Evans blue dye and tetanus toxin fragment C but not adeno-associated virus in ALS mice

Entry of most compounds into the CNS is impeded by the blood-brain barrier (BBB). Because vascular endothelial growth factor (VEGF) is important in the formation and maintenance of the BBB and is known to modulate BBB permeability in newborn rodents, we tested the hypothesis that VEGF may enhance BBB permeability in adult mice. We examined the effect of VEGF on the CNS distribution of three different agents: a small molecule (Evans blue dye) that is known to bind plasma proteins, an exogenous protein (tetanus toxin fragment C; TTC), and a viral vector (recombinant adeno-associated virus serotype 2/5 marked with lacZ; rAAV2/5-lacZ). Pretreatment with VEGF (20 mug; i.v.) increased permeability of the BBB to Evans blue dye and TTC as detected by augmented concentrations of these substances in the cerebrum, brainstem, and spinal cord. By contrast, VEGF did not alter BBB permeability to AAV2/5-lacZ, as defined by beta-galactosidase activity assay. These data demonstrate the potential utility of VEGF for pharmacological modulation of the BBB, and indicate that the increase in BBB permeability mediated by VEGF is limited by the size of the delivered substance.

Therapeutics for neonatal brain injury

Neonatal brain injury is an important cause of death and neurodevelopmental delay. Multiple pathways of oxidant stress, inflammation, and excitotoxicity lead to both early and late phases of cell damage and death. Therapies targeting these different pathways have shown potential in protecting the brain from ongoing injury. More recent therapies, such as growth factors, have demonstrated an ability to increase cell proliferation and repair over longer periods of time. Even though hypothermia, which decreases cerebral metabolism and possibly affects other mechanisms, may show some benefit in particular cases, no widely effective therapeutic interventions for human neonates exist. In this review, we summarize recent findings in neuroprotection and neurogenesis for the immature brain, including combination therapy to optimize repair.

Effects of visual experience on vascular endothelial growth factor expression during the postnatal development of the rat visual cortex

The development of the cortical vascular network depends on functional maturation. External inputs are an essential requirement in the modeling of the visual cortex, mainly during the critical period, when the functional and structural properties of visual cortical neurons are particularly susceptible to alterations. Vascular endothelial growth factor (VEGF) is the major angiogenic factor, a key signal in the induction of vessel growth. Our study focused on the role of visual stimuli on the development of the vascular pattern correlated with VEGF levels. Vascular density and the expression of VEGF were examined in the primary visual cortex of rats reared under different visual environments (dark rearing, dark-rearing in conditions of enriched environment, enriched environment, and laboratory standard conditions) during postnatal development (before, during, and after the critical period). Our results show a restricted VEGF cellular expression to astroglial cells. Quantitative differences appeared during the critical period: higher vascular density and VEGF protein levels were found in the enriched environment group; both dark-reared groups showed lower vascular density and VEGF levels, which means that enriched environment without the physical exercise component does not exert effects in dark-reared rats.

HIF-1alpha inhibition ameliorates neonatal brain injury in a rat pup hypoxic-ischemic model

Hypoxia-inducible factor-1alpha (HIF-1alpha) has been considered as a regulator of both prosurvival and prodeath pathways in the nervous system. The present study was designed to elucidate the role of HIF-1alpha in neonatal hypoxic-ischemic (HI) brain injury. Rice-Vannucci model of neonatal hypoxic-ischemic brain injury was used in seven-day-old rats, by subjecting unilateral carotid artery ligation followed by 2 h of hypoxia (8% O2 at 37 degrees C). HIF-1alpha activity was inhibited by 2-methoxyestradiol (2ME2) and enhanced by dimethyloxalylglycine (DMOG). Results showed that 2ME2 exhibited dose-dependent neuroprotection by decreasing infarct volume and reducing brain edema at 48 h post HI. The neuroprotection was lost when 2ME2 was administered 3 h post HI. HIF-1alpha upregulation by DMOG increased the permeability of the BBB and brain edema compared with HI group. 2ME2 attenuated the increase in HIF-1alpha and VEGF 24 h after HI. 2ME2 also had a long-term effect of protecting against the loss of brain tissue. The study showed that the early inhibition of HIF-1alpha acutely after injury provided neuroprotection after neonatal hypoxia-ischemia which was associated with preservation of BBB integrity, attenuation of brain edema, and neuronal death.

Ischemic stroke and neurogenesis in the subventricular zone

The subventricular zone (SVZ) of the lateral ventricle contains neural stem and progenitor cells that generate neuroblasts, which migrate to the olfactory bulb where they differentiate into interneurons. Ischemic stroke induces neurogenesis in the SVZ and these cells migrate to the boundary of the ischemic lesion. This article reviews current data on cytokinetics, signaling pathways and vascular niche that are involved in processes of proliferation, differentiation, and migration of neural progenitor cells after stroke.

Del-1 gene transfer induces cerebral angiogenesis in mice

Developmental endothelial locus-1 (Del-1) is a novel angiomatrix protein that has been shown to stimulate a potent angiogenic response and promote functional recovery in hind-limb and cardiac ischemia in animal models; however, its impact on cerebral angiogenesis is unknown. In this study, we investigated whether Del-1 overexpression via gene transfer induces cerebral angiogenesis in a murine model, and examined Del-1 expression after ischemic stroke. Cerebral Del-1 overexpression was achieved with AAV (adeno-associated virus) transduction system via stereotactic injection. Control mice were injected with AAV-lacZ. Del-1 gene transduction led to a significant induction of cerebral angiogenesis compared to AAV-lacZ treatment at 4 weeks after gene transfer (Del-1: 97+/-7 vs lacZ: 64+/-28, vessels/field, p<0.05). Mice transduced with AAV-Del-1 showed significantly elevated vascular densities for up to 6 weeks after gene delivery. In addition, double immunofluorescent staining showed co-localization of endothelial cell marker CD31 with BrdU (specific marker for proliferating cells), indicating that Del-1 promoted endogenous endothelial cell proliferation and angiogenesis. Our immunohistochemical staining also showed that Del-1 expression was markedly up-regulated in the peri-infarct area at 3 days after permanent focal cerebral ischemia compared to the sham-operated non-ischemic control. Our data suggest that Del-1 may participate in modulating cerebral angiogenesis, and that gene transfer of Del-1 may provide a novel and potent means for stimulating cerebral angiogenesis.

Neuronal HIF-1 alpha protein and VEGFR-2 immunoreactivity in functionally related motor areas following a focal M1 infarct

Clinical and experimental data support a role for the intact cortex in recovery of function after stroke, particularly ipsilesional areas interconnected to the infarct. There is, however, little understanding of molecular events in the intact cortex, as most studies focus on the infarct and peri-infarct regions. This study investigated neuronal immunoreactivity for hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) receptor-2 (VEGFR-2) in remote cortical areas 3 days after a focal ischemic infarct, as both HIF-1alpha and VEGFR-2 have been implicated in peri-infarct neuroprotection. For this study, intracortical microstimulation techniques defined primary motor (M1) and premotor areas in squirrel monkeys (genus Saimiri). An infarct was induced in the M1 hand representation, and immunohistochemical techniques identified neurons, HIF-1alpha and VEGFR-2. Stereologic techniques quantified the total neuronal populations and the neurons immunoreactive for HIF-1alpha or VEGFR-2. The results indicate that HIF-1alpha upregulation is confined to the infarct and peri-infarct regions. Increases in VEGFR-2 immunoreactivity occurred; however, in two remote regions: the ventral premotor hand representation and the M1 hindlimb representation. Neurons in these representations were previously shown to undergo significant increases in VEGF protein immunoreactivity, and comparison of the two data sets showed a significant correlation between levels of VEGF and VEGFR-2 immunoreactivity. Thus, while remote areas undergo a molecular response to the infarct, we hypothesize that there is a delay in the initiation of the response, which ultimately may increase the 'window of opportunity' for neuroprotective interventions in the intact cortex.

High levels of erythropoietin are associated with protection against neurological sequelae in African children with cerebral malaria

Cerebral malaria (CM) in children is associated with a high mortality and long-term neurocognitive sequelae. Both erythropoietin (Epo) and vascular endothelial growth factor (VEGF) have been shown to be neuroprotective. We hypothesized that high plasma and cerebrospinal fluid (CSF) levels of these cytokines would prevent neurological sequelae in children with CM. We measured Epo, VEGF, and tumor necrosis factor in paired samples of plasma and CSF of Kenyan children admitted with CM. Logistic regression models were used to identify risk and protective factors associated with the development of neurological sequelae. Children with CM (n = 124) were categorized into three groups: 76 without sequelae, 32 with sequelae, and 16 who died. Conditional logistic regression analysis matching the 32 patients with CM and neurological sequelae to 64 patients with CM without sequelae stratified for hemoglobin level estimated that plasma Epo (>200 units/liter) was associated with >80% reduction in the risk of developing neurological sequelae [adjusted odds ratio (OR) 0.18; 95% C.I. 0.05-0.93; P = 0.041]. Admission with profound coma (adjusted OR 5.47; 95% C.I. 1.45-20.67; P = 0.012) and convulsions after admission (adjusted OR 16.35; 95% C.I. 2.94-90.79; P = 0.001) were also independently associated with neurological sequelae. High levels of Epo were associated with reduced risk of neurological sequelae in children with CM. The age-dependent Epo response to anemia and the age-dependent protective effect may influence the clinical epidemiology of CM. These data support further study of Epo as an adjuvant therapy in CM.

Therapeutic benefits by human mesenchymal stem cells (hMSCs) and Ang-1 gene-modified hMSCs after cerebral ischemia

Transplantation of human mesenchymal stem cells (hMSCs) prepared from adult bone marrow has been reported to ameliorate functional deficits after cerebral artery occlusion in rats. Although several hypotheses to account for these therapeutic effects have been suggested, current thinking is that both neuroprotection and angiogenesis are primarily responsible. In this study, we compared the effects of hMSCs and angiopoietin-1 gene-modified hMSCs (Ang-hMSCs) intravenously infused into rats 6 h after permanent middle cerebral artery occlusion. Magnetic resonance imaging and histologic analyses revealed that rats receiving hMSCs or Ang-hMSCs exhibited comparable reduction in gross lesion volume as compared with the control group. Although both cell types indeed improved angiogenesis near the border of the ischemic lesions, neovascularization and regional cerebral blood flow were greater in some border areas in Ang-hMSC group. Both hMSC- and Ang-hMSC-treated rats showed greater improved functional recovery in the treadmill stress test than did control rats, but the Ang-hMSC group was greater. These results indicate the intravenous administration of genetically modified hMSCs to express angiopoietin has a similar effect on reducing lesion volume as hMSCs, but the Ang-hMSC group showed enhanced regions of increased angiogenesis at the lesion border, and modest additional improvement in functional outcome.

Mechanisms of ischemic brain damage

In the United States stroke is the third leading cause of death and the leading cause of disability. Brain injury following stroke results from the complex interplay of multiple pathways including excitotoxicity, acidotoxicity, ionic imbalance, peri-infarct depolarization, oxidative and nitrative stress, inflammation and apoptosis. There are very few treatments for stroke and the development of new treatments requires a comprehensive understanding of the diverse mechanisms of ischemic brain damage that are responsible for neuronal death. Here, we discuss the underlying pathophysiology of this devastating disease and reveal the intertwined pathways that are the target of therapeutic intervention.

Augmented healing process in female mice with acute myocardial infarction

BACKGROUND

It is well established that premenopausal women are protected from cardiovascular disease. This gender difference in favor of females is also demonstrated in animal studies. Our research group previously found that female mice had much lower incidence of cardiac rupture and mortality than did males during the acute phase of myocardial infarction (MI); however, the mechanisms responsible for such protection are not fully understood.

OBJECTIVE

The aim of this study was to determine whether the favorable cardiac effect observed in female mice with MI is due to an augmented healing process that includes less inflammation, reduced matrix degradation, and enhanced neovascularization.

METHODS

Twelve-week-old male and female C57BL/6J mice were subjected to MI by ligating the left anterior descending coronary artery and then euthanized at 1, 4, 7, or 14 days post-MI. Inflammatory cell infiltration and myofibroblast transformation, matrix metalloproteinase (MMP)-2 and MMP-9 activity, tissue inhibitor of metalloproteinase (TIMP)-I expression, and neovascularization were examined by immunohistochemistry, zymography, Western blot, and laser scanning confocal microscopy, respectively. Cardiac function was evaluated by echocardiography on day 14.

RESULTS

We found that: (1) neutrophil infiltration during the early phase of MI (1-4 days) was much lower in females than in males and was associated with lower MMP-9 activity and higher TIMP-1 protein expression, indicating less-exaggerated inflammation and extracellular matrix degradation in females; (2) myofibroblast transformation, as indicated by expression of alpha-smooth muscle actin, was significantly greater in females than in males at day 7 of MI (P<0.05), indicating facilitated collagen deposition and scar formation; and (3) neovascularization (vascular area in the infarct border) was markedly increased in females, and was associated with better preserved cardiac function and less left ventricular dilatation.

CONCLUSION

Our data suggest that less-exaggerated early inflammation and augmented reparative fibrotic response, indicated by enhanced myofibroblast transformation, may contribute greatly to low rupture rates in females during the acute and subacute phases of MI, whereas enhanced neovascularization may lead to better preserved cardiac function post-MI.

The clinical significance of acute brain injury in subarachnoid hemorrhage and opportunity for intervention

Aneurysmal subarachnoid hemorrhage (SAH) is a devastating neurological event that accounts for 3-7% of all strokes and carries a mortality rate as high as 40%. Delayed cerebral vasospasm has traditionally been recognized as the most treatable cause of morbidity and mortality from SAH. However, evidence is mounting that the physiological and cellular events of acute brain injury, which occur during the 24-72 h following aneurysm rupture, make significant contributions to patient outcomes, and may even be a more significant factor than delayed cerebral vasospasm. Acute brain injury in aneurysmal SAH is the result of physiological derangements such as increased intracranial pressure and decreased cerebral blood flow that result in global cerebral ischemia, and lead to the acute development of edema, oxidative stress, inflammation, apoptosis, and infarction. The consequence of these events is often death or significant neurological disability. In this study of acute brain injury, we elucidate some of the complex molecular signaling pathways responsible for these poor outcomes. Continued research in this area and the development of therapies to interrupt these cascades should be a major focus in the future as we continue to seek effective therapies for aneurysmal SAH.

HIF-1 alpha inhibition ameliorates neonatal brain damage after hypoxic-ischemic injury

BACKGROUND

Hypoxia-inducible-factor-1alpha (HIF-1alpha) has been considered as a regulator of both prosurvival and prodeath pathways in the nervous system. This study was designed to elucidate the role of HIF-1alpha in neonatal hypoxia-ischemia (HI) brain injury.

METHODS

2-methoxyestradiol (2ME2), a HIF-1alpha inhibitor, was tested at different dosages (1.5, 15 and 150 mg/kg) and a therapeutic window was tested by administrating 2-methoxyestradiol (15 mg/kg) immediately or 3 hours after the induction of a hypoxic ischemic injury. Infarct size using TTC staining and brain edema were measured at 48 hours post hypoxia-ischemia. Blood-brain barrier (BBB) permeability was examined by IgG staining. Vascular endothelial growth factor (VEGF) and HIF-1alpha expression and distribution were studied by immunohistochemistry and western blotting analysis.

FINDINGS

2ME2 exhibited dose-dependent neuroprotection by decreasing infarct volume and attenuating brain edema. 2ME2 also attenuated BBB disruption, and decreased HIF-1alpha and vascular endothelial growth factor (VEGF) expression. The neuroprotection, however, was lost when 2ME2 was administered 3 hours after neonatal HI.

CONCLUSION

The study shows that the acute inhibition of HIF-1alpha is neuroprotective in neonatal hypoxic-ischemic injury by preserving BBB integrity and reducing brain edema.

Chronic hydrocephalus-induced hypoxia: increased expression of VEGFR-2+ and blood vessel density in hippocampus

Chronic hydrocephalus (CH) is a neurological disease characterized by increased cerebrospinal fluid volume and pressure that is often associated with impaired cognitive function. By and large, CH is a complex and heterogeneous cerebrospinal fluid (CSF) disorder where the exact site of brain insult is uncertain. Several mechanisms including neural compression, fiber stretch, and local or global hypoxia have been implicated in the underlying pathophysiology of CH. Specifically, the hippocampus, which plays a significant role in memory processing and is in direct contact with expanding CSF ventricles, may be involved. Using our model of chronic hydrocephalus, we quantified the density of vascular endothelial growth factor receptor 2 (VEGFR-2(+)) neurons, glial, endothelial cells, and blood vessels in hippocampal regions CA1, CA2-3, dentate gyrus and hilus using immunohistochemical and stereological methods. Density and %VEGFR-2(+) cell populations were estimated for CH animals (2-3 weeks vs. 12-16 weeks) and surgical controls (SC). Overall, we found approximately six- to eightfold increase in the cellular density of VEGFR-2(+) and more than double blood vessel density (BVd) in the hippocampus of CH compared with SC. There were no significant regional differences in VEGFR-2(+) cellular and BVd expression in the CH group. VEGFR-2(+) and BVds were significantly related to changes in CSF volume (P<or=0.05), and not intracranial pressure (ICP). The %VEGFR-2(+) was significantly greater in CH than SC (P<or=0.05), and was significantly correlated with BVd (P<or=0.05). These results showed that CH elicited a profound increase in VEGFR-2(+) in hippocampus that corresponded to increased BVd. It was unclear whether increased VEGFR-2(+) and blood vessel expression was related to focal compression alone or in combination with global ischemia/hypoxia conditions as previously described. These findings suggest that VEGFR-2 may play an adaptive role in angiogenesis after CH-induced hypoxia. Modulation of vascular endothelial growth factor/VEGFR-2(+) may be important in developing treatments for hypoxic conditions including hydrocephalus and other forms of cerebral ischemia.

Induction of platelet derived-endothelial cell growth factor in the brain after ischemia

OBJECTIVES

Platelet derived-endothelial cell growth factor (PD-ECGF) is a highly potent angiogenic factor. Although angiogenesis plays an active role in pathophysiology of stroke, the expression pattern of this molecule in ischemic brain has not been investigated. In the present study, therefore, we investigated the change of PD-ECGF expression in the brain after ischemia.

METHODS

Using male Wistar rats, the right middle cerebral artery was occluded by a nylon thread for 90 minutes. The animals were decapitated 3 hours, 1, 4 and 10 days after the reperfusion, and frozen sections were prepared. We then performed immunohistochemistry for PD-ECGF and identified the cell phenotype which strongly expressed it by fluorescent double staining.

RESULTS

In the sham-operated brain, only small numbers of cells slightly expressed PD-ECGF. The number of positively stained cells increased at the peri-ischemic area from hour 3 of reperfusion. Not only small-sized cells but also large-sized cells became stained. The number of stained cells further increased, and peaked at day 4 for large-sized cells and at day 10 as to small-sized cells. Fluorescent double staining revealed that both large-sized and small-sized cells were neurons, indicating that neurons are the main source of PD-ECGF production in the ischemic brain.

DISCUSSION

PD-ECGF has a strong angiogenic property without vascular permeability increasing effect. This molecule may have a therapeutic potential for ischemic stroke treatment.

Ectopic decorin expression up-regulates VEGF expression in mouse cerebral endothelial cells via activation of the transcription factors Sp1, HIF1alpha, and Stat3

We demonstrate that a proteoglycan decorin (DCN) up-regulates the vascular endothelial growth factor (VEGF) expression with activation of VEGF regulating transcription factors Sp1, hypoxia-inducible factor 1alpha (HIF1alpha), and signal transducer and activator of transcription 3 (Stat3) via epidermal growth factor receptor (EGFR), mitogen-activated protein kinase extracellular signal-regulated kinase 1/2 (ERK1/2), and protein kinase B (AKT) pathways in DCN transfected mouse cerebral endothelial (MCE) cells. Treatment with pharmacological inhibitors and small interfering RNAs reveal that induction and activation of Sp1, HIF1alpha, and Stat3 facilitate their nuclear localization and binding to their specific motifs of the VEGF promoter and induce VEGF expression via two independent pathways, DCN/EGFR/phosphoinositide-3 kinase/AKT and DCN/EGFR/ERK1/2, respectively, in DCN synthesizing MCE cells. The cell type specific glycosylation protects Sp1 and HIF1alpha from proteosome degradation and plays an important and novel role in the regulation of VEGF in DCN transfected MCE cells. Induction of gelatinases (matrix metalloproteinase 2 and 9), the serine protease tissue plasminogen activator and plasmin by DCN transfection in MCE cells leads to extracellular proteolysis and to release of matrix-bound VEGF and activation of angiogenesis. In this study, we demonstrate that two independent downstream signal pathways, DCN/EGFR/ERK1/2 and DCN/EGFR/phosphoinositide-3 kinase/AKT, mediate up-regulation and activation of transcription factors of VEGF such as HIF1alpha, Stat3, and Sp1 and increase VEGF transcription and angiogenesis in MCE cells.

Vascular endothelial growth factor gene-transferred bone marrow stromal cells engineered with a herpes simplex virus type 1 vector can improve neurological deficits and reduce infarction volume in rat brain ischemia

OBJECTIVE

Several reports recently suggested that vascular endothelial growth factor (VEGF) may have a therapeutic benefit against experimental cerebral infarction animal models. In addition, bone marrow stromal cells (BMSCs) are known to have therapeutic potency in improving neurological deficits after occlusive cerebrovascular diseases. In the present study, we evaluated the hypothesis that intracerebral transplantation of VEGF gene-transferred BMSCs could provide a greater therapeutic effect than intracerebral transplantation of native (non-gene-transformed) BMSCs by using a transient middle cerebral artery occlusion (MCAO) rat model.

METHODS

Adult Wistar rats (Japan SLC, Inc., Hamamatsu, Japan) were anesthetized. VEGF gene-transferred BMSCs engineered with a replication-deficient herpes simplex virus type 1 1764/4-/pR19-hVEGF165 vector, native BMSCs, or phosphate-buffered saline were administered intracerebrally 24 hours after transient MCAO. All animals underwent behavioral testing for 28 days, and the infarction volume was determined 14 days after MCAO. The brain water contents in the ipsilateral and contralateral hemispheres of the MCAO were measured 2 and 7 days after the MCAO. Fourteen days after MCAO, immunohistochemical staining for VEGF was performed.

RESULTS

The group receiving VEGF-modified BMSCs demonstrated significant functional recovery compared with those receiving native BMSCs. Fourteen days after the MCAO, there was a significantly lower infarct volume without aggravating cerebral edema in the group treated with VEGF gene-modified BMSCs compared with the control groups. The transplanted VEGF gene-modified BMSCs strongly expressed VEGF protein for at least 14 days.

CONCLUSION

Our data suggest that the intracerebral transplantation of VEGF gene-transferred BMSCs may provide a more potent autologous cell transplantation therapy for stroke than the transplantation of native BMSCs alone.

Antagonism of endothelin action normalizes altered levels of VEGF and its signaling in the brain of stroke-prone spontaneously hypertensive rat

Stroke-prone spontaneously hypertensive rats (SHRSP) often suffer from spontaneous stroke, in part, due to abnormalities in the cerebrovasculature. Here, we investigate the profile of key angiogenic factors and their basic signaling molecules in the brain of SHRSP during the age-dependent stages of hypertension. The profile of VEGF and its receptor, Flk-1, was dependent on age and stage of hypertension (i.e., down regulated at pre-hypertensive and malignant hypertensive stages, but up regulated at typical hypertensive stage), while that of its downstream components, pAkt and eNOS, were down regulated in a time-dependent manner in the frontal cortex of SHRSP compared to age-matched genetic control, normotensive WKY rats. On the other hand, the expression of endothelin-1 and its type A receptor (endothelin ETA receptor) were up regulated, depending on age and stage of hypertension. In contrast, levels of endothelin type B receptor were down regulated. The regional cerebral blood flow decreased during the development of malignant hypertension. Thus, subsequent experiments were designed to investigate whether endothelin-1 receptor antagonism, using endothelin-A/-B dual receptor antagonist SB209670, could normalize the molecular profile of these factors in SHRSP brain. Interestingly, blockage of endothelin-1 receptor restored to normal, levels of cerebral endothelin-1, endothelin ETA receptor and endothelin ETB receptor; VEGF and Flk-1; endothelial nitric oxide synthase (eNOS) and pAkt, in SHRSP, compared to age-matched WKY. Endothelin receptor blocker might be important to prevent the progression in the defect in VEGF and its angiogenic signaling cascade in the pathogenesis of hypertension-induced vascular remodeling in frontal cortex of SHRSP rats.

The PI3K/Akt Pathway Mediates the Neuroprotective Effect of Atorvastatin in Extending Thrombolytic Therapy After Embolic Stroke in the Rat

Objective— We tested the hypothesis that the phosphatidylinositol-3 kinase (PI3K)/Akt pathway mediates the neuroprotective effect of combination therapy of atorvastatin and tissue-type plasminogen activator (tPA) in rats after stroke.

Methods and Results— Combination of atorvastatin (20 mg/kg) and tPA (10 mg/kg) significantly reduced ischemic lesion volume, whereas monotherapy with atorvastatin and tPA did not reduce the lesion volume, when the treatments were initiated 4 hours after embolic middle cerebral artery occlusion (MCAo). Western blot analysis revealed that treatment with atorvastatin alone and in combination treatment with tPA significantly increased Akt phosphorylation compared with treatment with saline and tPA alone. Inhibition of the PI3K/Akt pathway with wortmannin completely abolished the reduction of lesion volume afforded by combination of atorvastatin and tPA. Real-time RT-PCR analysis of cerebral endothelial cells isolated by laser-capture microdissection from the ischemic boundary region showed that MCAo upregulated early growth response 1 (Egr-1) and vascular endothelial growth factor (VEGF) mRNA levels and tPA monotherapy further increased Egr-1 and VEGF mRNA levels. However, combination of atorvastatin and tPA significantly suppressed Egr-1 and VEGF mRNA levels in cerebral endothelial cells.

Conclusions— Activation of Akt and downregulation of cerebral endothelial Egr-1 and VEGF gene expression by atorvastatin contribute to the neuroprotective effect of combination treatment with atorvastatin and tPA.

Adeno-associated viral vector-mediated hypoxia-regulated VEGF gene transfer promotes angiogenesis following focal cerebral ischemia in mice

Uncontrolled expression of vascular endothelial growth factor (VEGF) in vivo may cause unexpected side effects, such as brain hemangioma or tumor growth. Because hypoxia-inducible factor-1 (HIF-1) is upregulated during cerebral ischemia and regulates gene expression by binding to a cis-acting hypoxia-responsive element (HRE), we therefore used a novel HRE, originating in the 3'-end of the erythropoietin (Epo) gene, to control gene expression in the ischemic brain. A concatemer of nine copies (H9) of the consensus sequence of HRE was used to mediate hypoxia induction. Three groups of adult CD-1 mice received AAVH9-VEGF, AAVH9-lacZ or saline injection, and then underwent 45 min of transient middle cerebral artery occlusion (tMCAO). Results show that HIF-1 was persistently expressed in the ischemic brain. VEGF was overexpressed in the ischemic perifocal region in AAVH9-VEGF-transduced mice. Double-labeled immunostaining showed that VEGF expressed in neurons and astrocytes but not endothelial cells, suggesting that adeno-associated virus (AAV) vectors transduced neurons and astrocytes predominantly. The total number of microvessels/enlarged microvessels was greatly increased in the AAVH9-VEGF-transduced mice (180+/-29/27+/-4) compared to the AAVH9-lacZ (118+/-19/14+/-3) or saline-treated (119+/-20/14+/-2) mice after tMCAO (P<0.05). Cell proliferation examination demonstrated that these microvessels were newly formed. Regional cerebral blood flow recovery in the AAVH9-VEGF-transduced mice was also better than in AAVH9-lacZ or saline-treated mice (P<0.05). Our data indicated that HRE is a novel trigger for the control of VEGF expression in the ischemic brain. VEGF overexpression through AAVH9-VEGF gene transfer showed stable focal angiogenic effects in post-ischemic repair process, providing an opportunity to rebuild injured brain tissue.

Novel pyrazolo[1,5-a]pyrimidines as c-Src kinase inhibitors that reduce IKr channel blockade

To improve the in vitro potency of the c-Src inhibitor 1a and to address its hERG liability, a structure-activity study was carried out, focusing on two regions of the lead compound. The blockade of the delayed cardiac current rectifier K(+) (I(Kr)) channel was overcome by replacing the ethylenediamino group with an amino alcohol group at the 7-position. In addition, modifying the substituents at the 5-position and the side chain groups on the amino alcohols at the 7-position enhanced the intracellular c-Src inhibitory activity and increased central nervous system (CNS) penetration. In the present study, 6l exhibited significant in vivo efficacy in a middle cerebral artery (MCA) occlusion model in rats.

The kinetic change of the serum angiogenin level in patients with acute cerebral infarction

Serum angiogenin (ANG) levels were measured with ELISA in 30 cerebral infarction patients at different time points (within 48 h and on days 3, 7 and 14 after onset of cerebral infarction) and in 20 control subjects. Serum ANG levels in patients were 415.1 +/- 76.8, 410.6 +/- 82.1, 443.6 +/- 91.1 and 395.3 +/- 83.9 ng/ml within 48 h and on days 3, 7 and 14 after cerebral infarction, respectively. Serum ANG level in control group was 334.9 +/- 93.9 ng/ml. Serum ANG levels were significantly higher in patients with cerebral infarction within 48 h and on days 3 and 7 than in the control group (p < 0.05). Serum ANG level decreased on day 14. Serum ANG levels were significantly higher in patients with large infarction than in those with moderate and small infarction at each time point (p < 0.05). Our observations that serum ANG levels increase significantly in patients with cerebral infarction and the increase in ANG levels correlates with the infarct size suggest that ANG might be involved in the pathophysiologic process of ischemic brain damage.

The increase of circulating endothelial progenitor cells after acute ischemic stroke is associated with good outcome

BACKGROUND AND PURPOSE

Increased circulating endothelial progenitor cells (EPC) have been associated with a low cardiovascular risk and may be involved in endothelial cell regeneration. The present study was designed to evaluate the prognostic value of EPC in acute ischemic stroke.

METHODS

Forty-eight patients with a first-ever nonlacunar ischemic stroke were prospectively included in the study within 12 hours of symptoms onset. Stroke severity was evaluated by the National Institutes of Health Stroke Scale, and functional outcome was assessed at 3 months by the modified Rankin Scale (mRS). Infarct volume growth between admission and days 4 to 7 was measured on multiparametric MRI. EPC colonies were defined as early outgrowth colony-forming unit-endothelial cell (CFU-EC). The increment of CFU-EC was quantified during the first week and defined as the absolute difference between the number of CFU-EC at day 7 and admission. The influence of CFU-EC increase on good functional outcome (mRS <or=2) and infarct growth was analyzed by logistic regression and linear models.

RESULTS

Patients with good outcome (n=25) showed a higher CFU-EC increment during the first week (median [quartiles], 23 [11, 36] versus -3 [-7, 1], P<0.0001) compared with patients with poor outcome. CFU-EC increment >or=4 during the first week was associated with good functional outcome at 3 months (odds ratio, 30.7; 95% CI, 2.4 to 375.7; P=0.004) after adjustment for baseline stroke severity, ischemic volume and thrombolytic treatment. For each unit increase in the CFU-EC the mean reduction in the growth of infarct volume was 0.39 (0.03 to 0.76) mL (P=0.033).

CONCLUSIONS

The increase of circulating EPC after acute ischemic stroke is associated with good functional outcome and reduced infarct growth. These findings suggest that EPC might participate in neurorepair after ischemic stroke.

Intravenous infusion of dihydroginsenoside Rb1 prevents compressive spinal cord injury and ischemic brain damage through upregulation of VEGF and Bcl-XL

Red ginseng root (Panax Ginseng CA Meyer) has been used clinically by many Asian people for thousands of years without any detrimental effects. One of the major components of Red ginseng root is ginsenoside Rb(1) (gRb1). Previously, we showed that intravenous infusion of gRb1 ameliorated ischemic brain damage through upregulation of an anti-apoptotic factor, Bcl-x(L) and that topical application of gRb1 to burn wound lesion facilitated wound healing through upregulation of vascular endothelial growth factor (VEGF). In the present study, we produced dihydroginsenoside Rb1 (dgRb1), a stable chemical derivative of gRb1, and showed that intravenous infusion of dgRb1 improved spinal cord injury (SCI) as well as ischemic brain damage. As we expected, the effective dose of dgRb1 was ten times lower than that of gRb1. Intravenous infusion of dgRb1 at this effective dose did not affect brain temperature, blood pressure or cerebral blood flow, suggesting that dgRb1 rescued damaged neurons without affecting systemic parameters. In subsequent in vitro studies that focused on dgRb1-induced expression of gene products responsible for neuronal death or survival, we showed that dgRb1 could upregulate the expression of not only Bcl-x(L), but also a potent angiogenic and neurotrophic factor, VEGF. We also showed that dgRb1-induced expression of bcl-x(L) and VEGF mRNA was HRE (hypoxia response element) and STRE (signal transducers and activators of transcription 5 (Stat5) response element) dependent, respectively.

Endothelial progenitor cells and cerebrovascular diseases

Identifying factors that may increase the risk of stroke and assessing if treatment of such conditions may lower that risk are important in the management of cerebrovascular disease. Tobacco smoking, poor diet, hypertension and hyperlipidemia remain the major risk factors, and treatment of these conditions has been shown to significantly reduce stroke. In recent years, research has shown that stem cells from a variety of sources can be used as a tool to study and prevent the events that lead to stroke. In this regard, a population of adult stem cells, called endothelial progenitor cells (EPCs), have been identified in peripheral blood and may play an important role in tissue vascularization and endothelium homeostasis in the adult. Most of the studies on EPCs have been carried out on patients with cardiovascular diseases; however, there is emerging evidence which suggests that the introduction or mobilization of EPCs can restore tissue vascularization even after cerebrovascular diseases (CVD), such as ischemic stroke or intracerebral haemorrhage. In this review, we discuss the present level of knowledge about the characteristics of EPCs, their possible therapeutic role in CVD and how they could alter clinical practice in the future.

Matrix metalloproteinase-9 inhibition attenuates vascular endothelial growth factor-induced intracerebral hemorrhage

BACKGROUND AND PURPOSE

Human brain arteriovenous malformation tissue displays increased levels of vascular endothelial growth factor (VEGF) as well as matrix metalloproteinase (MMP)-9, a tissue protease associated with various intracerebral hemorrhage (ICH). We hypothesized that increased MMP-9 was associated with ICH induced by vascular endothelial growth factor hyperstimulation and that this effect could be attenuated by nonspecific MMP inhibition.

METHODS

We used a mouse model with adenoviral vector-mediated vascular endothelial growth factor transduction in the brain. The association of MMP-9 expression and the brain tissue hemoglobin levels, an index of ICH, after stereotactic injection of adenoviral vector-mediated vascular endothelial growth factor into caudate putamen was assessed. A dose-response study with adenoviral vector-mediated vascular endothelial growth factor and a time course study at both 24 and 48 hours postinjection were performed. Effects of minocycline, a nonspecific MMP inhibitor, and pyrrolidine dithiocarbamate, an upstream regulator of MMPs, on MMP-9 activity and thereby the degree of ICH were also tested.

RESULTS

Adenoviral vector-mediated vascular endothelial growth factor at the higher dose and at 48 hours induced MMP-9 levels 6-fold (n=6, P=0.02) and increased brain tissue hemoglobin (43.4+/-11.5 versus 30.3+/-4.1 mug/mg, n=6, P=0.003) compared with the adenoviral vector control. Immnunostaining was positive for MMP-9 around the cerebral vessels and the hemorrhagic areas. Minocycline and pyrrolidine dithiocarbamate administration suppressed vascular endothelial growth factor-induced MMP-9 activity (n=6, P=0.003 and P=0.01, respectively) and the associated increases in hemoglobin levels (n=5-6, P=0.001 and P=0.02, respectively).

CONCLUSIONS

Vascular endothelial growth factor-induced ICH is associated with increased MMP-9 expression. Suppression of MMP-9 by minocycline or pyrrolidine dithiocarbamate attenuated ICH, suggesting the therapeutic potential of MMP inhibitors in cerebral vascular rupture.

Neurotrophic and growth factor gene expression profiling of mouse bone marrow stromal cells induced by ischemic brain extracts

Treatment of rodents after stroke with bone marrow stromal cells (BMSCs) improves functional outcome. However, the mechanisms underlying this benefit have not been ascertained. This study focused on the contribution of neurotrophic and growth factors produced by BMSCs to therapeutic benefit. Rats were subjected to middle cerebral artery occlusion and the ischemic brain extract supernatant was collected to prepare the conditioned medium. The counterpart normal brain extract from non-ischemic rats was employed as the experimental control. Using microarray assay, we measured the changes of the neurotrophin associated gene expression profile in BMSCs cultured in different media. Furthermore, real-time RT-PCR and fluorescent immunocytochemistry were utilized to validate the gene changes. The morphology of BMSCs, cultured in the ischemic brain-conditioned medium for 12 h, was dramatically altered from a polygonal and flat appearance to a fibroblast-like long and thin cell appearance, compared to those in the normal brain-conditioned medium and the serum replacement medium. Forty-four neurotrophin-associated genes in BMSCs were identified by microarray assay under all three culture media. Twelve out of the 44 genes (7 neurotrophic and growth factor genes, 5 receptor genes) increased in BMSCs cultured in the ischemic brain-conditioned medium compared to the normal brain-conditioned medium. Real time RT-PCR and immunocytochemistry validated that the ischemic brain-conditioned medium significantly increased 6/7 neurotrophic and growth factor genes, compared with the normal brain-conditioned medium. These six genes consisted of fibroblast growth factor 2, insulin-like growth factor 1, vascular endothelial growth factor A, nerve growth factor beta, brain-derived neurotrophic factor and epidermal growth factor. Our results indicate that transplanted BMSCs may work as 'small molecular factories' by secreting neurotrophins, growth factors and other supportive substances after stroke, which may produce therapeutic benefits in the ischemic brain.

Flt-1, but not Flk-1 mediates hyperpermeability through activation of the PI3-K/Akt pathway

Vascular endothelial growth factor (VEGF), a potent mediator of endothelial proliferation and migration, has an important role also in brain edema formation during hypoxia and ischemia. VEGF binds to the tyrosine kinase receptors Flt-1 and Flk-1. Yet, their relative importance for hypoxia-induced hyperpermeability is not well understood. We used an in vitro blood-brain barrier (BBB) model consisting of porcine brain microvascular endothelial cells (BMEC) to determine the role of Flt-1 in VEGF-induced endothelial cell (EC) barrier dysfunction. Soluble Flt-1 abolished hypoxia/VEGF-induced hyperpermeability. Furthermore, selective antisense oligonucleotides to Flt-1, but not to Flk-1, inhibited hypoxia-induced permeability changes. Consistent with these data, addition of the receptor-specific homolog placenta-derived growth factor, which binds Flt-1 but not Flk-1, increased endothelial permeability to the same extent as VEGF, whereas adding VEGF-E, a viral VEGF molecule from the orf virus family activating Flk-1 and neuropilin-1, but not Flt-1, did not show any effect. Using the carcinoma submandibular gland cell line (CSG), only expressing Flt-1, it was demonstrated that activation of Flt-1 is sufficient to induce hyperpermeability by hypoxia and VEGF. Hyperpermeability, induced by hypoxia/VEGF, depends on activation of phosphatidylinositol 3-kinase/Akt (PI3-K/Akt), nitric oxide synthase (NOS) and protein kinase G (PKG). The activation of the PI3-K/Akt pathway by hypoxia was confirmed using an in vivo mice hypoxia model. These results demonstrate that hypoxia/VEGF-induced hyperpermeability can be mediated by activation of Flt-1 independently on the presence of Flk-1 and indicate a central role for activation of the PI3-K/Akt pathway, followed by induction of NOS and PKG activity.

Nitric oxide donor upregulation of stromal cell-derived factor-1/chemokine (CXC motif) receptor 4 enhances bone marrow stromal cell migration into ischemic brain after stroke

Stromal cell-derived factor-1 (SDF1) and its chemokine (CXC motif) receptor 4 (CXCR4), along with matrix metalloproteinases (MMPs), regulate bone marrow stromal cell (BMSC) migration. We tested the hypothesis that a nitric oxide donor, DETA-NONOate, increases endogenous ischemic brain SDF1 and BMSC CXCR4 and MMP9 expression, which promotes BMSC migration into ischemic brain and thereby enhances functional outcome after stroke. C57BL/6J mice were subjected to middle cerebral artery occlusion (MCAo), and 24 hours later, the following were intravenously administered (n = 9 mice per group): (a) phosphate-buffered saline; (b) BMSCs (5 x 10(5)); (c) 0.4 mg/kg DETA-NONOate; (d) combination of CXCR4-inhibition BMSCs with DETA-NONOate; and (e) combination of BMSCs with DETA-NONOate. To elucidate the mechanisms underlying combination-enhanced BMSC migration, transwell cocultures of BMSC with mouse brain endothelial cells (MBECs) or astrocytes were performed. Combination treatment significantly improved functional outcome after stroke compared with BMSC monotherapy and MCAo control, and it increased SDF1 expression in the ischemic brain compared with DETA-NONOate monotherapy and MCAo control. The number of BMSCs in the ischemic brain was significantly increased after combination BMSC with DETA-NONOate treatment compared with monotherapy with BMSCs. The number of engrafted BMSCs was significantly correlated with functional outcome after stroke. DETA-NONOate significantly increased BMSC CXCR4 and MMP9 expression and promoted BMSC adhesion and migration to MBECs and astrocytes compared with nontreatment BMSCs. Inhibition of CXCR4 or MMPs in BMSCs significantly decreased DETA-NONOate-induced BMSC adhesion and migration. Our data demonstrate that DETA-NONOate enhanced the therapeutic potency of BMSCs, possibly via upregulation of SDF1/CXCR4 and MMP pathways, and increased BMSC engraftment into the ischemic brain.