Correlation of VEGF and angiopoietin expression with disruption of blood-brain barrier and angiogenesis after focal cerebral ischemia

Molecular physiology of preconditioning-induced brain tolerance to ischemia

Ischemic tolerance describes the adaptive biological response of cells and organs that is initiated by preconditioning (i.e., exposure to stressor of mild severity) and the associated period during which their resistance to ischemia is markedly increased. This topic is attracting much attention because preconditioning-induced ischemic tolerance is an effective experimental probe to understand how the brain protects itself. This review is focused on the molecular and related functional changes that are associated with, and may contribute to, brain ischemic tolerance. When the tolerant brain is subjected to ischemia, the resulting insult severity (i.e., residual blood flow, disruption of cellular transmembrane gradients) appears to be the same as in the naive brain, but the ensuing lesion is substantially reduced. This suggests that the adaptive changes in the tolerant brain may be primarily directed against postischemic and delayed processes that contribute to ischemic damage, but adaptive changes that are beneficial during the subsequent test insult cannot be ruled out. It has become clear that multiple effectors contribute to ischemic tolerance, including: 1) activation of fundamental cellular defense mechanisms such as antioxidant systems, heat shock proteins, and cell death/survival determinants; 2) responses at tissue level, especially reduced inflammatory responsiveness; and 3) a shift of the neuronal excitatory/inhibitory balance toward inhibition. Accordingly, an improved knowledge of preconditioning/ischemic tolerance should help us to identify neuroprotective strategies that are similar in nature to combination therapy, hence potentially capable of suppressing the multiple, parallel pathophysiological events that cause ischemic brain damage.

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.

Neuroplasticity and cellular therapy in cerebral infarction

Stroke is the second to third most common cause of death in adults, and more than a third of people who survive a stroke will have severe disability. Therapeutic options currently centre on fibrinolytic treatment, but its limitations restrict use to a small proportion of patients. Although a wide range of neuroprotective substances has been effective in experimental models, they have repeatedly failed in clinical trials because of toxicity or loss of effectiveness. Recent strategies based on neuroplasticity and cellular therapy have shown significant efficacy in improving functional recovery in experimental models, although further study is still necessary to clarify how the brain responds to ischaemic damage and is able to reorganize itself in the long term. Although steps must still be taken to ensure the safety and feasibility of treatments based on neuroplasticity and cellular therapy, neurorepair strategies provide promising future therapeutic options for stroke.

Neutrophil depletion decreases VEGF-induced focal angiogenesis in the mature mouse brain

To explore the role of neutrophil-derived matrix metalloproteinases (MMPs) during angiogenesis in the brain, we hypothesized that transient neutrophil depletion attenuates the angiogenic response to focal hyperstimulation with vascular endothelial growth factor (VEGF). Brain focal angiogenesis was achieved using an adeno-associated virus delivered VEGF (AAV-VEGF) gene transfer in the mature mouse. Four groups of mice underwent AAV vector injection in the brain parenchyma: (1) AAV-LacZ; (2) AAV-VEGF; (3) AAV-VEGF plus anti-polymorphonuclear (PMN) antibody; and (4) AAV-VEGF plus serum. Animals in groups 3 and 4 underwent 4 days of PMN antibody or serum treatment before transfection; treatment was sustained for an additional 14 days. Anti-PMN treatment decreased circulating neutrophils to 9% of baseline (P<0.001). Microvessels in the AAV-VEGF-group increased 25% compared with the AAV-lacZ-transduced group (256+/-15 versus 208+/-16; P<0.05). Anti-PMN treatment attenuated the increase to 10% compared with control serum treatment (234+/-16 versus 255+/-22; P<0.05). Similarly, compared with control serum treatment, anti-PMN treatment also reduced MMP-9 by 50% (2+/-0.9 versus 4+/-1.4; P<0.05) and MPO expression by 25% (2+/-0.8 versus 3+/-0.9; P<0.05); MMP-9 activity correlated with MPO expression (R(2)=0.8, P<0.05). Our study demonstrated that transient depletion of neutrophils suppressed VEGF-induced angiogenesis, indicating that circulating neutrophils contribute to VEGF-induced focal angiogenesis. In addition, brain MMP-9 activity was attenuated after neutrophil depletion, suggesting that neutrophil is an important source of MMP-9.

Effects of podocyte injury on glomerular development

To study the effects of podocyte injury on glomerular maturation and underlying mechanisms of such effects, puromycin aminonucleoside (PAN) was given to neonatal mice at 1 d post partum (1 dpp). Mice with PAN injection had smaller kidney weight (KW) and body weight (BW) at all times and smaller KW/BW at 4, 8, and 12 dpp versus normal saline (NS) controls. Electron microscopy (EM) revealed nearly complete podocyte foot process effacement and segmental microvillous transformation as early as 2 dpp, preceding proteinuria. PAN-injected kidneys showed significantly fewer glomerular capillary loops and decreased glomerular maturation index, as well as less CD31+ endothelium in cortical glomeruli at 12 dpp versus NS controls. Glomerular mesangial injury and glomerulosclerosis along with proteinuria were noted in PAN-injected kidneys starting from 30 dpp. Systolic blood pressure was increased significantly by 60 dpp in PAN mice. PAN mice also had significantly decreased Flk-1 and Tie2 mRNA expression and increased angiopoitein-1 (Ang-1) expression, without change in vascular endothelial growth factor (VEGF) at 2 dpp versus NS. Our study shows that podocyte injury in neonatal mice kidneys alters the expression of key capillary growth modulators in glomeruli, leading to abnormal development of glomerular capillaries, with subsequent development of proteinuria, hypertension, and glomerulosclerosis.

Neovascularization following traumatic brain injury: possible evidence for both angiogenesis and vasculogenesis

OBJECTIVE

Our goal was to characterize the angiogenic response following traumatic brain injury (TBI).

METHODS

Western analysis for vascular endothelial growth factor (VEGF) expression, double immunofluorescence labeling of endothelium and vascular endothelial growth factor receptor 2 (VEGFR2), bromodioxyuridine (BrdU) incorporation and measurement of capillary density, were all used to determine the temporal angiogenic response following TBI.

RESULTS

The angiogenic factors, VEGF and VEGFR2, increase following trauma. Capillary density increases and BrdU incorporation confirm the presence of newly formed vessels up to 48 hours post-injury.

DISCUSSION

Our results indicated that following TBI, there is a substantial increase in angiogenesis and based on morphologic characterization of BrdU-positive nuclei within the endothelium, we provide evidence for vasculogenesis following injury.

Buyang Huanwu Decoction can improve recovery of neurological function, reduce infarction volume, stimulate neural proliferation and modulate VEGF and Flk1 expressions in transient focal cerebral ischaemic rat brains

Buyang Huanwu Decoction is a classic formula for treating stroke-induced disability in traditional Chinese medicine (TCM). To explore its pharmacological basis, we investigated the effects of the whole formula and its herbal components on the neurological behavior performance and infarction volume in focal cerebral ischaemia rats. The neurological deficit scores and infarction volume were measured at days 3, 7 and 14 after 30 min of occlusion of middle cerebral artery. The results showed that Buyang Huanwu Decoction and its herbal components significantly improved the neurological behavior performances and reduced the infarction volume in the ischaemic brains. To elucidate the potential therapeutic mechanisms, we investigated the proliferation of progenitors by detecting the immunohistochemical staining of thymidine analog 5-bromo-2'-deoxyuridine (BrdU) and found that the formula stimulated the proliferation of the progenitors at hippocampus and subventricular zone (SVZ) in the ischaemic brains. As vascular endothelial growth factor (VEGF) and its receptor fetal liver kinase (Flk1) are important neurotrophic, neuroprotective and neuroproliferative factors, we studied the expressions of VEGF and Flk1 in the hippocampus, SVZ and cortex in the ischaemic brains and found that the formula led to increase the numbers of VEGF-positive and Flk1-positive cells in the SVZ and cortex in the ischaemic brains. The results indicate that the therapeutic effects of Buyang Huanwu Decoction for recovery of neurological deficits are associated with the stimulation of the proliferation of progenitors and the enhancement of the expressions of VEGF and Flk in ischaemic brains.

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.

Anaemia and the brain

PURPOSE OF REVIEW

This article reviews the physiological and pathophysiological effects of anaemia on the brain, focusing on the hypothesis that anaemia-induced cerebral hypoxia contributes to anaemic cerebral dysfunction and injury. It also reviews evidence that the regulated increase in cerebral blood flow observed during anaemia represents a compensatory neuroprotective mechanism invoked to optimize cerebral oxygen delivery, thereby protecting the brain from hypoxic injury.

RECENT FINDINGS

Severe anaemia, or low haematocrit, has been associated with cognitive dysfunction, impaired cerebral vascular regulation, neurological injury, and increased mortality, which suggests that the brain is vulnerable to anaemia-induced injury. Reduced cerebral tissue oxygen tension has been measured directly at haemoglobin concentrations near 35 g/l, suggesting that hypoxia may contribute to anaemic cerebral injury. A demonstration of increased hypoxic cerebral gene expression, including neuronal nitric oxide synthase, may provide a more sensitive means of determining the minimum haemoglobin concentration at which anaemia-induced cerebral hypoxia can be detected. The measurement of increased cerebral cortical neuronal nitric oxide synthase messenger RNA and protein levels in rats, at haemoglobin concentrations between 50 and 60 g/l, suggests that cerebral hypoxia occurred at these higher haemoglobin concentrations. Mechanisms regulating anaemic cerebral vasodilation and increased cerebral oxygen delivery, including nitric oxide, require further elucidation to establish their role in protecting the brain during anaemia.

SUMMARY

Characterization of mechanisms of anaemia-induced cerebral injury will contribute to the development of optimal therapeutic strategies for anaemic patients. Such strategies would include a clearer definition of transfusion triggers based on physiological endpoints. The overall goal of these efforts would be to minimize morbidity and mortality associated with anaemia.

A chronic grey matter penumbra, lateral microvascular intussusception and venous peduncular avulsion underlie diabetic vitreous haemorrhage

The landmark publications that gave such impetus to our understanding of proliferative diabetic retinopathy are reviewed in the light of more recent reports. Briefly, confluence of small areas of capillary closure in the midperipheral and peripheral retina results in arteriovenous shunting and abnormal oxygen partial pressure gradients. These gradients embrace a chronic ischaemic penumbra that stimulates neuroglial secretion of angiogenic growth factors and upregulation of their receptors in the retinal venous endothelium and adventitia. The blood shunting produces biomechanical stresses within the veins and induces microvascular intussusception near arteriovenous crossings, giving way to neovascular outgrowths and/or segmental venous lesions (such as omega loops and coils) that penetrate the inner limiting lamina. The lamellar collagenous matrix of the vitreous cortex is then exploited for integrin-dependent rete expansion along chemotactic gradients. During posterior vitreous detachment, haemorrhaging takes place from the arterialised veins as venous neovascular peduncles are avulsed.

Stroke-evoked angiogenesis results in a transient population of microvessels

The role of angiogenesis after stroke is unclear; if angiogenesis supports long-term recovery of blood flow, then microvessel hyperdensity consequent to angiogenesis should persist in infarcted cortex. Here, we assess the long-term stability of ischemia-induced microvessels after 2-h transient rat middle cerebral artery occlusion (tMCAo) followed by 30, 90, or 165 days of reperfusion. Stereological measures of microvessel density were taken adjacent to and within cortical cysts. Vascular permeability was documented by extravasation of immunoglobulin (IgG) and of fluorescein-dextran. After 30 days reperfusion, a significantly increased microvessel volume density (V(V)) was restricted to the inner margin of cystic infarcts as compared with the region external to the infarct or contralateral control cortex (F=42.675, P<0.001). The hyperdense ischemic vasculature was abnormally leaky to IgG and fluorescein-dextran. Between 30 and 90 days of reperfusion, this vessel hyperdensity regressed significantly and then regressed further but less drastically between 90 and 165 days. Phagocytic macrophages were restricted to the infarct and dynamic changes in their number correlated with microvessel regression. Additional ED-1 labeled inflammatory cells were widely distributed inside and external to the infarct, even after 165 days of reperfusion. These data show that ischemia evoked angiogenesis results, at least in part, in transient populations of leaky microvessels and phagocytic macrophages. This suggests that a major role of this angiogenesis is for the removal of necrotic brain tissue.

Brain protection using autologous bone marrow cell, metalloproteinase inhibitors, and metabolic treatment in cerebral ischemia

Despite advances in imaging, understanding the underlying pathways, and clinical translation of animal models of disease there remains an urgent need for therapies that reduce brain damage after stroke and promote functional recovery in patients. Blocking oxidant radicals, reducing matrix metalloproteinase-induced neuronal damage, and use of stem cell therapy have been proposed and tested individually in prior studies. Here we provide a comprehensive integrative management approach to reducing damage and promoting recovery by combining biological therapies targeting these areas. In a rat model of transient cerebral ischemia (middle cerebral artery occlusion) gene delivery vectors were used to overexpress tissue inhibitor of matrix metalloproteinase 1 and 2 (TIMP1 and TIMP2) 3 days before ischemia. After occlusion, autologous bone marrow cells alone or in combination with agents to improve NO bioavailability were administered intraarterially. When infarct size, BrdU incorporation, and motor function recovery were determined in the treatment groups the largest beneficial effect was seen in rats receiving the triple combined therapy, surpassing effects of single or double therapies. Our study highlights the utility of combined drug, gene, and cell therapy in the treatment of stroke.

Neurogenesis, Angiogenesis, and MRI Indices of Functional Recovery From Stroke

This article analyzes the mechanisms underlying the potentiation of functional recovery poststroke by cell-based and pharmacologic agents, which amplify endogenous neurogenesis in the subventricular zone and angiogenesis in the border of the ischemic lesion in the animal. Discussion of the interaction between angiogenesis and neurogenesis is provided and data are described demonstrating a role for matrix metalloproteinases expressed in periinfarct vasculature as chemotactic for neuroblasts migrating from the subventricular zone. Monitoring angiogenesis and structural changes in the ischemic brain associated with functional recovery by means of MRI is described. We demonstrate that injured brain can be stimulated to promote angiogenesis and neurogenesis, which are coupled restorative processes that contribute to functional recovery from stroke and that MRI indices of these neurorestorative events are highly correlative with neurologic function and may be used in real-time monitoring of recovery from stroke.

Whisker stimulation enhances angiogenesis in the barrel cortex following focal ischemia in mice

Post-ischemia angiogenesis and vascular plasticity help to restore blood flow to ischemic tissue and likely benefit long-term functional recovery. Physical activity has been shown to cause morphologic and functional effects, including promoting angiogenesis in normal or injured animals. A therapeutic effect of peripheral activity on central angiogenesis after cerebral ischemia, however, has not been studied. In the present study of whisker-barrel cortex ischemia in the mouse model, we tested the hypothesis that enhancing whisker activity and sensory input to the ischemic barrel cortex might promote post-ischemia cerebral angiogenesis. Three days after focal ischemia in adult mice, the whiskers corresponding to the ischemic barrel cortex were stimulated by two methods: (1) whiskers on the right side of the mouse face were trimmed away, so the left whiskers were overused by the animals, (2) left whiskers were manually stimulated to enhance input signals to the ischemic barrel cortex. Western blot analysis showed that whisker stimulation increased expression of the angiogenic factors vascular endothelial growth factor, basic fibroblast growth factor, Tie-1, angiopoietin-2 (Ang-2), and possibly Ang-1. Co-immunostaining with markers for proliferation (5-bromo-2'-deoxyuridine (BrdU)) and vascular endothelial cells (Glut-1/CD-31) identified vessel proliferation in the penumbra region. Whisker stimulation increased BrdU-positive endothelial cells and vessels in this region 7 and 14 days after ischemia. Whisker stimulation also attenuated endothelial cell death and increased local cerebral blood flow. Our data suggest that appropriately enhanced peripheral activity and afferent signals to the ischemic cortex can promote post-ischemic angiogenesis, which may imply beneficial effects of specific physical therapy on long-term recovery from ischemic stroke.

Endogenous neurogenesis in the human brain following cerebral infarction

Increased endogenous neurogenesis has a significant regenerative role in many experimental models of cerebrovascular diseases, but there have been very few studies in humans. We therefore examined whether there was evidence of altered endogenous neurogenesis in an 84-year-old patient who suffered a cerebrovascular accident 1 week prior to death. Using antibodies that specifically label neural stem/neural progenitor cells, we examined the presence of immunopositive cells around and distant from the infarcted area, and compared this with a control, age-matched individual. Interestingly, a large number of neural stem cells, vascular endothelial growth factor-immunopositive cells and new blood vessels were observed only around the region of infarction, and none in the corresponding brain areas of the healthy control. In addition, an increased number of neural stem cells was observed in the neurogenic region of the lateral ventricle wall. Our results suggest increased endogenous neurogenesis associated with neovascularization and migration of newly-formed cells towards a region of cerebrovascular damage in the adult human brain and highlight possible mechanisms underlying this process.

Blood–retinal barrier disruption and ultrastructural changes in the hypoxic retina in adult rats: the beneficial effect of melatonin administration

Reactive changes in astrocytes and Müller cells in the retina of adult rats subjected to hypoxia were investigated. Along with this, the integrity of the blood-retinal barrier (BRB) was assessed using fluorescent and electron-dense tracers. In hypoxic rats, mRNA and protein expression of glial fibrillary acidic protein (GFAP) and aquaporin-4 (AQ4) were significantly increased. AQ4 immunoreactive cells were identified as astrocytes and Müller cells by double immunofluorescence labelling. Another alteration in the hypoxic retina was marked reduction in melatonin content compared to controls. In this connection, administration of exogenous melatonin reduced the tissue concentration of vascular endothelial growth factor (VEGF) and nitric oxide (NO); both were elevated in hypoxic rats. A major structural change in the hypoxic retina was swelling of astrocyte and Müller cell processes but this was noticeably attenuated after melatonin administration. Following an intraperitoneal or intravenous injection of rhodamine isothiocyanate (RhIC) or horseradish peroxidase (HRP), leakage of both tracers was observed in the retina in hypoxic rats but not in the controls, indicating that the functional integrity of the BRB is compromised in hypoxia/reoxygenation. It is suggested that enhanced tissue concentration of VEGF and NO production in the hypoxic retina contribute to increased permeability of the retinal blood vessels. The concurrent up-regulation of AQ4, a water-transporting protein, in astrocytes and Müller cells in hypoxia suggests its involvement in oedema formation. Since melatonin effectively reduced the vascular permeability in the retina of hypoxic rats, as evidenced by reduced leakage of RhIC, we suggest that its administration may be of potential benefit in the management of retinal oedema associated with retinal hypoxia.

Effects of anti-VEGF antibody on blood-brain barrier disruption in focal cerebral ischemia

Since cerebral ischemia increases expression of vascular endothelial growth factor (VEGF) and exogenous VEGF can aggravate BBB disruption in cerebral ischemia, we hypothesized that inhibition of endogenous VEGF would attenuate BBB disruption. To test this hypothesis, rats were mechanically ventilated with isoflurane and a craniotomy (5 mm in diameter) was performed to expose the cerebral cortex. Anti-VEGF antibody was applied topically (75 mug) 1 h before middle cerebral artery (MCA) occlusion and additional anti-VEGF antibody was applied (25 mug) immediately after MCA occlusion (anti-VEGF group). For the control animals, normal saline was applied instead of anti-VEGF antibody on the surface of the cortex (control group). One hour after MCA occlusion, the transfer coefficient (K(i)) of (14)C-alpha-aminoisobutyric acid and volume of (3)H-dextran (70,000 Da) distribution were determined to measure the degree of BBB disruption. There was no significant difference in vital signs, blood gases, and pericranial temperature between the control and the anti-VEGF group. In both of the groups, the K(i) of the ischemic cortex (IC) was higher than that of the corresponding contralateral cortex (CC) (p<0.05). The K(i) of the IC of the anti-VEGF group was significantly lower than that of the IC of the control group (-34%, p<0.05). The K(i) of the CC and pons were similar between these two groups. The data of volume of dextran distribution followed the same pattern as that of K(i) but without a statistical significance. Our data demonstrated that inhibition of endogenous VEGF by topical application of anti-VEGF antibody in the ischemic cortex decreased the K(i) of (14)C-AIB and suggest that endogenous VEGF is in part responsible for the BBB disruption during the early stage of focal cerebral ischemia.

Decreased Expression of VEGF-A in Rat Experimental Autoimmune Encephalomyelitis and in Cerebrospinal Fluid Mononuclear Cells from Patients with Multiple Sclerosis

Vascular endothelial growth factor A (VEGF-A) stimulates angiogenesis, but is also pro-inflammatory and plays an important role in the development of neurological disease, where it can have both attenuating and exacerbating effects. VEGF-B, a related molecule, is highly expressed in the central nervous system and seems to be important in neurological injury. A few studies have indicated that VEGF-A may play a role in the pathogenesis of multiple sclerosis (MS), but the role of VEGF-B has not been studied. We have studied the expression of VEGF-A, -B and their receptors by mRNA in situ hybridization, immunohistochemistry and real-time PCR in spinal cord from LEW rats with experimental autoimmune encephalomyelitis (EAE) and in cerebrospinal fluid (CSF) and blood samples from MS patients. Whereas VEGF-A is downregulated in glia in EAE, the infiltrating inflammatory cells are positive for VEGF-A. Expression of VEGF-B and the VEGF receptors is unaltered. In addition, the levels of VEGF-A mRNA in mononuclear cells [corrected] in CSF are lower in MS patients compared with controls. These results demonstrate a complex regulation of VEGF-A during neuroinflammation and suggest that VEGF-B is not involved in the pathogenesis of MS.

Vascular fate of adipose tissue-derived adult stromal cells in the ischemic murine brain: A combined imaging-histological study

Increasing evidence indicates that fat tissue can provide a novel source of progenitor cells with therapeutic potential. Here, the fate of adipose tissue-derived stromal cells (ADSCs) transplanted into the mouse ischemic cortex was monitored in the long term using in vivo imaging, and subsequently characterized. The left middle cerebral artery (MCA) was occluded in C57BL/6J mice equipped with a closed cranial window chronically implanted over the left parietal cortex (n = 20). ADSCs expressing the green fluorescent protein (GFP) (approximately 18 x 10(3) cells in 0.5 microl) were transplanted into the ipsilateral cortex, 24 h after MCA occlusion. GFP+-ADSCs were monitored through the window using confocal fluorescence microscopy to assess their single fate in vivo. Co-localization of GFP with vascular, neuronal, glial or proliferation markers was investigated immunohistochemically. Repeated in vivo imaging revealed that GFP+-ADSCs migrated over 1 week toward the lesion, survived for at least 4 weeks, and exhibited a particular tropism for vessels. About 5% of the transplanted GFP+-ADSCs were scattered in the peri-ischemic area on histological sections. Immunohistochemistry evidenced that perivascular GFP+-ADSCs enfolded CD31-labeled endothelial cells, always outside their basal lamina, and occasionally expressed smooth muscle alpha-actin. Less than 1% GFP and BrdU co-labeling indicated a low proliferation rate of ADSCs. These results demonstrate that cerebral ischemia induces ADSCs survival, migration toward the lesion, especially toward microvessels, and occasional differentiation into smooth muscle cells.

Vascular endothelial growth factor improves recovery of sensorimotor and cognitive deficits after focal cerebral ischemia in the rat

Vascular endothelial growth factor (VEGF) is an angiogenesis factor with neurotrophic, neuroprotective and neuroproliferative effects. Depending on the dose, route and time of administration in relation to focal cerebral ischemia, VEGF can improve histological outcome and sensorimotor function in rodents. However, VEGF also increases vascular permeability, which can lead to brain edema and exacerbate ischemic brain injury. Thus, although VEGF is a candidate therapeutic for stroke and other ischemic disorders, its benefit relative to risk is uncertain. Considering that functional rather than histological measures of outcome are probably most relevant to therapeutic prospects for human stroke, we investigated the effects of VEGF after middle cerebral artery occlusion in rats using a series of behavioral tests. We report that VEGF improves functional outcome in ischemic rats, including both sensorimotor and cognitive deficiencies.

Effect of mesenchymal stem cell transplantation on cognitive functions in rats with ischemic stroke

The effect of intravenous transplantation of mesenchymal stem cells on the recovery of cognitive functions was studied in Wistar-Kyoto rats after brain stroke induced by occlusion of the middle cerebral artery in the left hemisphere. Analysis 2 and 5 weeks after stroke showed that transplantation of mesenchymal stem cells 3 days after middle cerebral artery occlusion reduced the area of cerebral injury, preserved cognitive functions, and decreased mortality in experimental animals.

Targeting vascular endothelial growth factor pathway offers new possibilities to counteract microvascular disturbances during ischemia/reperfusion of the pancreas

BACKGROUND

It is of crucial importance to explore new therapeutic strategies capable of combating or even preventing pancreatic graft failure after transplantation caused by ischemia reperfusion damage. So far, the role of the hypoxia induced mediator vascular endothelial growth factor (VEGF) upon pancreatic microcirculation has not been described. Therefore the aim of this study was to investigate its influence, using the novel tyrosinekinase inhibitor PTK787/ZK222584 (PTK/ZK), upon functional capillary density (FCD), leukocyte-endothelium interaction (LEI), and macromolecular permeability (P) of normal and postischemic pancreas tissue.

METHODS

Sprague-Dawley rats were anesthetized and randomly assigned to five groups (n=7/group): (a) sham, (b) ischemia/reperfusion (I/R) control, (c) I/R and PTK/ZK treatment, (d) VEGF-superfusion, (e) VEGF-superfusion and PTK/ZK-treatment. A recently established method of digital dynamic intravital epifluorescence microscopy was used for evaluating the effective microvascular permeability together with FCD and LEI.

RESULTS

Comparison between sham vs. I/R shows a significant upregulation of VEGF-expression followed by deterioration of microcirculation with decreased FCD, increased P and LEI. Treatment with PTK/ZK resulted in a significant decrease of P under conditions of superfusion with VEGF as well as I/R compared to corresponding groups without treatment.

CONCLUSION

VEGF plays a crucial causative role involving an increase in permeability in normal as well as in postischemic pancreatitis via tyrosinkinase receptors. VEGF seems to be partly accountable for a deterioration of FCD and an upregulation of LEI via VEGF-tyrosinekinase receptor independent mechanisms. VEGF might be a promising potential therapeutic target in order to minimize edema formation caused by I/R and pancreatitis in pancreas transplantation.

Increased expression of HIF-1alpha, nNOS, and VEGF in the cerebral cortex of anemic rats

This study tested the hypothesis that specific hypoxic molecules, including hypoxia-inducible factor-1alpha (HIF-1alpha), neuronal nitric oxide synthase (nNOS), and vascular endothelial growth factor (VEGF), are upregulated within the cerebral cortex of acutely anemic rats. Isoflurane-anesthetized rats underwent acute hemodilution by exchanging 50% of their blood volume with pentastarch. Following hemodilution, mean arterial pressure and arterial Pa(O(2)) values did not differ between control and anemic rats while the hemoglobin concentration decreased to 57 +/- 2 g/l. In anemic rats, cerebral cortical HIF-1alpha protein levels were increased, relative to controls (1.7 +/- 0.5-fold, P < 0.05). This increase was associated with an increase in mRNA levels for VEGF, erythropoietin, CXCR4, iNOS, and nNOS (P < 0.05 for all), but not endothelial NOS. Cerebral cortical nNOS and VEGF protein levels were increased in anemic rats, relative to controls (2.0 +/- 0.2- and 1.5 +/- 0.4-fold, respectively, P < 0.05 for both). Immunohistochemistry demonstrated increased HIF-1alpha and VEGF staining in perivascular regions of the anemic cerebral cortex and an increase in the number of nNOS-positive cerebral cortical cells (3.2 +/- 1.0-fold, P < 0.001). The nNOS-positive cells costained with the neuronal marker, Neu-N, but not with the astrocytic marker glial fibrillary acidic protein (GFAP). These nNOS-positive neurons frequently sent axonal projections toward cerebral blood vessels. Conversely, VEGF immunostaining colocalized with both neuronal (NeuN) and astrocytic markers (GFAP). In conclusion, acute normotensive, normoxemic hemodilution increased the levels of HIF-1alpha protein and mRNA for HIF-1-responsive molecules. nNOS and VEGF protein levels were also increased within the cerebral cortex of anemic rats at clinically relevant hemoglobin concentrations.

Surgically induced brain injury in rats: the effect of erythropoietin

Brain tissue at the edge of a surgical resection site is at risk for damage from direct trauma, retractor stretch, hemorrhage, edema, and electrocautery. In this study we used a new rodent model of surgically induced brain injury (SBI) to study this tissue at the edge of a resection site. The SBI model entails stereotaxic resection of part of the right frontal lobe. We tested pretreatment with erythropoietin, a known neuroprotectant, for protective effects in this model. Three groups of male Sprague-Dawley rats (280-330g) were used: SBI without treatment (n=63), SBI with EPO treatment (n=76), and Sham surgery (n=12). Rats were sacrificed 24h, 72h, and 7 days after SBI or Sham surgery. Postoperative assessment included mortality, histology, immunohistochemistry, Evans blue exudation, brain water content, and magnetic resonance imaging. No difference was found between untreated and EPO-treated groups in mortality, histology, TUNEL, magnetic resonance imaging, or blood-brain-barrier breakdown. The EPO-treated group had statistically more brain water content at 24h than the untreated group. Immunohistochemistry demonstrated a qualitative increase in VEGF in the EPO-treatment group. We conclude that EPO does not ameliorate damage in SBI, and may increase brain edema early after surgery.

Apoptosis: Future Targets for Neuroprotective Strategies

Focal permanent or transient cerebral artery occlusion produces massive cell death in the central core of the infarction, whereas in the peripheral zone (penumbra) nerve cells are subjected to various determining survival and death signals. Cell death in the core of the infarction and in the adult brain is usually considered a passive phenomenon, although events largely depend on the partial or complete disruption of crucial metabolic pathways. Cell death in the penumbra is currently considered an active process largely dependent on the activation of cell death programs leading to apoptosis. Yet cell death in the penumbra includes apoptosis, necrosis, intermediate and other forms of cell death. A rather simplistic view implies poor prospects regarding cell survival in the core of the infarction and therapeutic expectations in the control of cell death and cell survival in the penumbra. However, the capacity for neuroprotection depends on multiple factors, primarily the use of the appropriate agent, at the appropriate time and during the appropriate interval. Understanding the mechanisms commanding cell death and survival area is as important as delimiting the therapeutic time window and the facility of a drug to effectively impact on specific targets. Moreover, the detrimental effects of homeostasis and the activation of multiple pathways with opposing signals following ischemic stroke indicate that better outcome probably does not depend on a single compound but on several drugs acting in combination at the optimal time in a particular patient.

Neurorepair versus neuroprotection in stroke

Stroke is the second to third leading cause of death and the main cause of severe, long-term disability in adults. However, treatment is almost reduced to fibrinolysis, a therapy useful in a low percentage of patients. Given that the immediate treatment for stroke is often unfeasible in the clinical setting, the need for new therapy strategies is imperative. After stroke, the remaining impairment in functions essential for routine activities, such as movement programming and execution, sensorimotor integration, language and other cognitive functions have a deep and life-long impact on the quality of life. An interesting point is that a slow but consistent recovery can be observed in the clinical practice over a period of weeks and months. Whereas the recovery in the first few days likely results from edema resolution and/or from reperfusion of the ischemic penumbra, a large part of the recovery afterwards is due mainly to brain plasticity, by which some regions of the brain assume the functions previously performed by the damaged areas. Neurogenesis and angiogenesis are other possible mechanisms of recovery after stroke. An understanding of the mechanisms underlying functional recovery may shed light on strategies for neurorepair, an alternative with a wide therapeutic window when compared with neuroprotective strategies.

Contraindications of VEGF-based therapeutic angiogenesis: Effects on macrophage density and histology of normal and ischemic brains

Therapeutic angiogenesis by vascular endothelial growth factor (VEGF) is advocated as a promising treatment strategy for brain ischemic stroke. However, data in the literature demonstrating the benefit of therapeutic angiogenesis are contradictory. In this paper, we describe the effects of non-angiogenic and angiogenic doses of VEGF165 on macrophage density and histology of normal and ischemic brains of adult rats. VEGF165 was administered intra-arterially for 7 days following temporary occlusion of the middle cerebral artery. In contrast to ischemic brains treated with non-angiogenic doses of VEGF165 which showed preserved neuropil and reduced numbers of macrophages, ischemic brains treated by an angiogenic dose showed phagocytized neuropil and high macrophage density. Though neither non-angiogenic nor angiogenic doses caused macrophage infiltration in normal brains, damage of the brain matrix occurred with the angiogenic dose. These results suggest an angiogenic dose of VEGF165 injures the nervous tissue rather than promote recovery. Angiogenesis by VEGF monotherapy for ischemic stroke should be viewed with caution, or avoided. Since our data show intravascular administration of VEGF165 does not cause macrophage inflammation, in contrast to reports in the literature whereby VEGF165 was applied directly to the brain, our findings also indicate the relationships between VEGF, angiogenesis, and macrophage inflammation are governed by the route VEGF is administered to the brain.

Transplantation of vascular endothelial growth factor-transfected neural stem cells into the rat brain provides neuroprotection after transient focal cerebral ischemia

OBJECTIVE

Vascular endothelial growth factor (VEGF) stimulation and neural stem cell (NSC) transplantation have been implicated in the treatment of cerebral ischemia because of their crucial roles in neuroprotection, neurogenesis, and angiogenesis. However, effective delivery of VEGF or NSCs remains difficult. This study attempted to explore whether VEGF121 complementary deoxyribonucleic acid could be transferred into the NSCs and, furthermore, whether transplanting these VEGF121-transfected NSCs into the rat brain provides sufficient neuroprotection after transient focal cerebral ischemia.

METHODS

The VEGF121 gene was transfected to the NSCs isolated from E14 fetal rat hippocampus. In vitro studies revealed that VEGF messenger ribonucleic acid could be consistently expressed in NSCs from 1 day to up to 2 weeks.

RESULTS

After transplantation of VEGF121-transfected NSCs into the perifocal area of the ischemic rat brain, we found that these cells could survive and migrate in the ischemic region for 12 weeks. Furthermore, we observed a significant improvement of the Neurological Severity Scale score in the rats transplanted with VEGF121-transfected NSCs in comparison to the phosphate-buffered saline-injected or the sham-operated rats (P < 0.05). Transplantation of nontransfected NSCs into ischemic rat brain improved the Neurological Severity Scale score as well. Of note, the improvement in the Neurological Severity Scale score occurred earlier in the VEGF121-transfected NSC rats than in the nontransfected NSC rats (range, 2-12 wk versus 8-12 wk), suggesting a potent neuroprotection mediated by additional VEGF121 transfection.

CONCLUSION

We conclude that transplantation of VEGF121-transfected NSCs improved ischemic neurological deficiency. This finding provides a novel approach for the treatment of cerebral ischemia.

Reduced glioma infiltration in Src-deficient mice

Malignant brain tumors, such as glioblastoma, are characterized by extensive angiogenesis and permeability of the blood-brain barrier (BBB). The infiltration of glioma cells away from the primary tumor mass is a pathological characteristic of glial tumors. The infiltrating tumor cells represent a significant factor in tumor recurrence following surgical debulking, radiation, and chemotherapy treatments. Vascular endothelial growth factor (VEGF)-mediated vascular permeability (VP) has been associated with the progression of glioma tumor growth and infiltration into surrounding normal brain parenchyma. While VEGF induces a robust VP response in control mice (src+/+ or src+/-), the VP response is blocked in src-/- mice that demonstrate a 'leakage-resistant phenotype' in the brain. We used the Src-deficient mouse model to determine the role of Src in the maintenance of the BBB following orthotopic implantation and growth of glioma cells in the brain. Although solid tumor growth was the same in control and src-/- mice, the infiltrating component of glioma growth was reduced in src-/- mice. Characterization of the expression and localization of the extracellular matrix (ECM) protein fibrinogen was evaluated to determine the effect of a Src-mediated VP defect in the host compartment. These studies indicate that the reduced VP of host brain blood vessels of src-/- mice mediates a reduction in glioma cell invasion in a mouse brain tumor xenograft model.

Cerebral ischemia enhances tyrosine phosphorylation of occludin in brain capillaries

Cerebral ischemia induces disruption of the blood-brain barrier (BBB), and this disruption can initiate the development of brain injuries. Although the molecular structure of tight junctional complexes in the BBB has been identified, little is known about alterations of tight junctional proteins after cerebral ischemia. Therefore, we investigated alterations of tight junctional proteins, i.e., occludin and zonula occludens (ZO)-1, in isolated rat brain capillaries after microsphere-induced cerebral embolism. We demonstrated that the levels of occludin and ZO-1 had decreased after the embolism. The embolism also resulted in a marked increase in tyrosine phosphorylation of occludin, which was coincident with an increase in the activity of c-Src. These results suggest that a decrease in the levels of occludin and ZO-1, and an increase in tyrosine phosphorylation of occludin may play an important role in the disruption of tight junctions, which may lead to dysfunction of the BBB after cerebral ischemia.

Hypoxia-induced astrocytic reaction and increased vascular permeability in the rat cerebellum

Hypoxia is an important factor linked to induction of vascular leakage and formation of brain edema. In this connection, astrocytes associated closely with the blood vessels are deemed to be involved. This study investigated the response of astrocytes to hypoxia in the adult rat cerebellum, and along with this, the integrity of the blood-brain barrier (BBB) was assessed using fluorescent and electron dense tracers. In rats subjected to hypoxia, mRNA and protein expression of hypoxia inducible factor-1alpha (HIF-1alpha), vascular endothelial growth factor (VEGF), glial fibrillary acidic protein (GFAP), and aquaporin-4 (AQ4) was significantly increased. VEGF and AQ4 immunoreactive cells were identified as astrocytes by double immunofluorescence labeling. Increased VEGF tissue concentration and astrocytic swelling as observed in hypoxic rats were reduced after melatonin administration. Following intraperitoneal or intravenous injection of rhodamine isothiocyanate (RhIC) or horseradish peroxidase (HRP), leakage of both tracers was observed in hypoxic rats but not in the controls indicating that functional integrity of BBB is compromised in hypoxia/reoxygenation. Enhanced gene and protein expression of VEGF may contribute to increased permeability of blood vessels. AQ4, a water transporting protein, is upregulated in astrocytes in hypoxia suggesting the cells are involved in edema formation. To this end, melatonin may be beneficial in reducing edema as it reduced VEGF concentration and, hence, vascular permeability.

Neurogenesis in the adult ischemic brain: generation, migration, survival, and restorative therapy

This article reviews current data on the induction of neurogenesis after stroke in the adult brain. The discussion of neurogenesis is divided into production, migration, and survival of these newly formed cells. For production, the subpopulations and the types of cell division are presented. Discussion of cell migration entails presenting data on both the pathways as well as the molecular targeting of newly formed neural progenitor cells to sites of injury. The role of the vascular and the astrocytic microenvironment in promoting the survival and integration of progenitor cells is also presented. Cell-based and pharmacological therapies designed to restore neurological function that promote neurogenesis are described. These therapies also induce angiogenesis and astrocytic changes that brain tissue, which prime the ischemic brain to foster the survival of the newly formed progenitor cells. Signaling pathways that regulate neurogenesis and angiogenesis are also addressed. This review summarizes recent data on neurogenesis and provides insight into the potential for restorative treatments of stroke.

Neuroprotective effects of scutellarin on rat neuronal damage induced by cerebral ischemia/reperfusion

AIM

To investigate the neuroprotective effect and mechanisms of scutellarin, a flavonoid extracted from Erigeron breviscapus Hand Mazz, against neuronal damage following cerebral ischemia/reperfusion.

METHODS

Rats were pretreated ig with scutellarin for 7 d and then subjected to cerebral ischemia/reperfusion (I/R) injury induced by a middle cerebral artery occlusion (MCAO). The infarct volume and neurological deficit were determined by TTC staining and Longa's score. The permeability of the blood-brain barrier was evaluated by measurement of the Evans blue (EB) content in the brain with a spectrophotometer. The total NOx content was determined. Nitric oxide synthase (NOS) isoforms (iNOS, eNOS, nNOS) and the key angiogenic molecules, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), were detected by Western blotting.

RESULTS

Scutellarin significantly reduced infarct volume (P<0.05 or P<0.01), ameliorated the neurological deficit and reduced the permeability of the blood-brain barrier (BBB) (P<0.05). When rats were pretreated with scutellarin (50 or 75 mg/kg), upregulation of eNOS expression and downregulation of VEGF, bFGF, and iNOS expression was observed, whereas scutellarin had no effect on nNOS expression.

CONCLUSION

Scutellarin has protective effects for cerebral injury through regulating the expression of NOS isoforms and angiogenic molecules.

Intracarotid transplantation of bone marrow stromal cells increases axon-myelin remodeling after stroke

The present study investigates the induction of axon and myelin remodeling as a possible mechanism by which treatment of stroke with bone marrow stromal cells improves neurological functional recovery. Adult male Wistar rats were subjected to 2 h of middle cerebral artery occlusion, followed by an injection of 2 x 10(6) rat bone marrow stromal cells or phosphate-buffered saline into the internal carotid artery 24 h later. Animals were killed at 28 days after stroke. Functional tests, histo- and immunohistochemical staining were performed. Significant functional recovery was found after bone marrow stromal cell administration in all the three tests performed (modified neurological severity score, adhesive-removal and corner tests). Bone marrow stromal cell treatment markedly increased vessel sprouting, synaptophysin expression and NG2 positive cell numbers and density in the cortical peri-infarct area. In bone marrow stromal cell-treated rats, the number of Ki-67 positive proliferating cells and oligodendrocyte precursor cells in the corpus callosum increased significantly in concert with the enhancement of the areas of the corpus callosum in both hemispheres. These results suggest that bone marrow stromal cells facilitate axonal sprouting and remyelination in the cortical ischemic boundary zone and corpus callosum, which may underlie neurological functional improvement caused by bone marrow stromal cell treatment.

Characterization of vascular protein expression patterns in cerebral ischemia/reperfusion using laser capture microdissection and ICAT‐nanoLC‐MS/MS

Cerebral ischemia rapidly initiates structural and functional changes in brain vessels, including blood-brain barrier disruption, inflammation, and angiogenesis. Molecular events that accompany these changes were investigated in brain microvessels extracted using laser-capture microdissection (LCM) from Sprague-Dawley rats subjected to a 20 min transient global cerebral ischemia followed by 1, 6, or 24 h reperfusion. Proteins extracted from approximately 300 LCM captured microvessels (20-100 microm) were ICAT-labeled and analyzed by nanoLC-MS. In-house software was used to identify paired ICAT peaks, which were then sequenced by nanoLC-MS/MS. Pattern analyses using k-means clustering method classified 57 differentially expressed proteins in 7 distinct dynamic patterns. Protein function was assigned using Panther Classification system. Early reperfusion (1 h) was characterized by down-regulation of ion pumps, nutrient transporters, and cell structure/motility proteins, and up-regulation of transcription factors, signal transduction molecules and proteins involved in carbohydrate metabolism. The up-regulation of inflammatory cytokines and proteins involved in the extracellular matrix remodeling and anti-oxidative defense was observed in late reperfusion (6-24 h). The up-regulation of IL-1beta and TGF-1beta in ischemic brain vessels was confirmed by ELISA, quantitative PCR, and/or immunohistochemistry. A biphasic postischemic (1 and 24 h) BBB opening for (3)H-sucrose was evident in the same model. Differentially expressed proteins identified in brain vessels during reperfusion are likely involved in orchestrating functional vascular responses to ischemia, including the observed BBB disruption.

Combined treatment of vascular endothelial growth factor and human neural stem cells in experimental focal cerebral ischemia

Recent studies have indicated the beneficial effects of vascular endothelial growth factor (VEGF), and transplanted neural stem cells (NSCs) in cerebral ischemia. We investigated the effects of the combined administration of NSCs and VEGF on focal cerebral ischemia in adult rats. Four groups (n = 12, respectively)--group 1 (ischemia-only), group 2 (ischemia + VEGF), group 3 (ischemia + NSCs) and group 4 (ischemia + NSCs + VEGF)--were compared. Human NSCs (HB1.F3), labeled with Lac Z+ or PKH26, were given intravenously 24h after surgery (5 x 10(6) cells). At 48 h after surgery, recombinant human VEGF (50 microg/kg) was infused intravenously (1 microg/(kg min)). Behavioral tests using the modified limb placing and rotarod tests were performed every week following ischemia. Immunohistochemistry for endothelial barrier antigen (EBA), VEGF and Nissl staining were performed at day 35 after ischemia. Group 4 showed better behavioral recovery at 7, 14 and 28 days than group 3 (p = 0.020, 0.005 and 0.043, respectively). These functional recoveries were correlated with enhanced EBA immunoreactivities at day 35 after ischemia, especially in the ipsilesional striatum. Group 4 showed lesser degree of brain atrophy in cortex and striatum, when compared with other groups. The distribution of VEGF was not co-localized with NSCs. Our results suggest that VEGF may act synergistically on NSC-transplanted, ischemic brain via a pro-angiogenic effect.

Granulocyte colony-stimulating factor enhances angiogenesis after focal cerebral ischemia

Granulocyte colony-stimulating factor (G-CSF) is a neuroprotective agent and activates endothelial proliferation and bone marrow stem cell mobilization. We studied the effect of G-CSF on angiogenesis and neurological recovery after focal cerebral ischemia. After the induction of transient focal ischemia in rats, G-CSF (50 micro/day, i.p.) or PBS was administered for 3 days. We evaluated the functional recovery, infarct volume, inflammatory infiltration, blood-brain barrier (BBB) disruption, hemispheric atrophy, protein expressions of endothelial nitric oxide synthase (eNOS) and angiopoietins, and the therapeutic time window of G-CSF administration. We then analyzed endothelial cell proliferation, the vascular surface area, the number of branch points, and the vascular length. G-CSF treatment improved behavioral recovery and reduced the infarct volume, the inflammatory infiltration, the BBB disruption, and the hemispheric atrophy. G-CSF injection, starting at 2 h, 1 day, or 4 days after ischemia, resulted in a better functional recovery and a greater reduction in hemispheric atrophy than injection starting at day 7. The vascular surface area, the vascular branch points, the vascular length, the number of BrdU(+) endothelial cells, and eNOS/angiopoietin-2 expression were significantly increased in the G-CSF group compared with the ischemia-only group. G-CSF injection starting at 1 day induced larger endothelial proliferation compared with injection starting at 7 days. In this study, we provide evidences that G-CSF enhances the angiogenesis and reduces the ischemic damage, which promotes the long-term functional recovery.

VEGF protects brain against focal ischemia without increasing blood--brain permeability when administered intracerebroventricularly

Delayed administration of vascular endothelial growth factor (VEGF) promotes functional recovery after focal cerebral ischemia. However, early intravenous injection of VEGF increases blood-brain barrier (BBB) leakage, hemorrhagic transformation and infarct volume whereas its application to cortical surface is neuroprotective. We have investigated whether or not early intracerebroventricular administration of VEGF could replicate the neuroprotective effect observed with topical application and the mechanism of action of this protection. Mice were subjected to 90 mins middle cerebral artery (MCA) occlusion and 24 h of reperfusion. Vascular endothelial growth factor (8 ng, intracerebroventricular) was administered 1 or 3 h after reperfusion. Compared with the vehicle-treated (intracerebroventricular) group, VEGF decreased the infarct volume along with BBB leakage in both treatment groups. Neurologic disability scores improved in parallel to the changes in infarct volume. Independently of the decrease in infarct size, VEGF also reduced the number of TUNEL-positive apoptotic neurons. Phospo-Akt levels were significantly higher in ischemic hemispheres of the VEGF-treated mice. Contrary to intracerebroventricular route, intravenous administration of VEGF (15 microg/kg) enhanced the infarct volume as previously reported for the rat. In conclusion, single intracerebroventricular injection of VEGF protects brain against ischemia without adversely affecting BBB permeability, and has a relatively long therapeutic time window. This early neuroprotective action, observed well before recovery-promoting actions such as angiogenesis, possibly involves activation of the PI-3-Akt pathway.

Vascular changes in the subventricular zone after distal cortical lesions

One of the effects of cortical lesions is to produce cell proliferation in the subventricular zone (SVZ), a neurogenic zone of the adult brain distal from the lesion. The mechanisms of these effects are unknown. Recent evidence points to a relationship between the vasculature and neurogenesis both in vitro and in vivo. In the present study, we asked whether cortical lesions induced vascular modifications in the distal SVZ in vivo. Lesions of the frontoparietal cortex were produced by thermocoagulation of pial blood vessels, a method that leads to highly reproducible loss of all cortical layers, sparing the corpus callosum and underlying striatum. These lesions induced increased immunoreactivity for vascular endothelial growth factor (VEGF) around the walls of SVZ vessels, at a considerable distance from the lesion. Vascular permeability was markedly increased in both the SVZ and RMS by 3 days after the injury. A dramatic increase in endothelial proliferation was followed by expansion of the local SVZ vascular tree 7 days after the injury. This time course corresponded to the proliferative changes in the SVZ, and a tight correlation was observed between the number of blood vessels and the increase in SVZ cell number. The data demonstrate that thermocoagulatory cortical lesions induce distal vascular changes that could play a role in lesion-induced SVZ expansion.

VEGF and VEGF receptor expression after experimental brain contusion in rat

Angiogenesis following traumatic brain injury (TBI) may be of importance not only for post-traumatic reparative processes but also for the development of secondary injuries. Vascular endothelial growth factor (VEGF) is a major regulator of endothelial cell proliferation, angiogenesis, and vascular permeability, though its possible involvement in secondary injuries after TBI is largely unknown. This study was undertaken to analyze the expression of VEGF and the VEGF receptors in experimental brain contusion in rat. Twenty-three adult female Sprague-Dawley rats were subjected to a focal cerebral contusion injury by use of a weight-drop model. Four additional rats underwent craniotomy only. The animals were sacrificed 6 h, or 1, 2, 4, 6, 8, or 16 days post-injury. Expression of VEGF and the VEGF receptors VEGFR1 (Flt-1) and VEGFR2 (Flk-1) were studied by in situ hybridization and immunohistochemistry. VEGF messenger (m)RNA and protein expression were detected in astrocytes, neutrophils, and macrophages in or adjacent to the injury from 1 day after injury, with a peak expression after 4-6 days. Flt-1 and Flk-1 mRNA and protein were detected in vessels adjacent to the lesion from 1 day after injury throughout day 6 after injury. It was also noted that Flt-1/Flk-1 and VEGF-positive vessels often were negative for SMI-71, a marker for vessels in areas with blood-brain barrier (BBB). In conclusion, we have demonstrated that TBI leads to an upregulation of VEGF, Flt-1, and Flk-1 mRNA and protein in and around the lesion. The data provide a foundation for future pharmacological intervention studies focusing on posttraumatic angiogenesis and possible injury repair effects of the VEGF system in TBI.

Evaluation of cerebrospinal fluid uPA, PAI-1, and soluble uPAR levels in HIV-infected patients

To evaluate the potential role of the uPAR/uPA/PAI-1 system in HIV-induced blood-brain-barrier (BBB) disruption, CSF uPA-dependent plasminogen activation (PdPA) was analyzed by casein zymography, and CSF protein levels of all three molecules were measured by ELISA. CSF uPAR, but not uPA, PAI-1, or PdPA levels was significantly increased in neurologically compromised HIV+ patients. Only individual patients with severe AIDS dementia complex had increased levels of uPA (but not PAI-1) which fell upon initiation of antiretroviral therapy. The levels of all three molecules did not correlate with the CSF to serum albumin ratio suggesting not an important role in HIV-induced BBB disruption.

Intussusceptive angiogenesis: its emergence, its characteristics, and its significance

This review shall familiarize the reader with the various aspects of intussusceptive angiogenesis (IA). The basic event in IA is the formation of transvascular tissue pillars. Depending on location, timing, and frequency of pillar emergence, the IA process has different outcomes. In capillaries, a primary IA function is to expand the capillary bed in size and complexity (intussusceptive microvascular growth). It represents an alternative to capillary sprouting. Highly ordered pillar formation in a developing capillary network leads to the formation of vascular trees (intussusceptive arborization). In small arteries and veins, pillar formation at the vessels' branching angles leads either to remodeling of the branching geometry or even to vascular pruning (intussusceptive branching remodeling). It appears essential that future angiogenic research considers always both phenomena, sprouting and intussusception. Vascularization of tissues, organs, and tumors rely heavily on both mechanisms; neglecting one or the other would obscure our understanding of the angiogenesis process.

Hepatocyte growth factor improved learning and memory dysfunction of microsphere-embolized rats

Hepatocyte growth factor (HGF), an organotropic factor for regeneration and protection in various organs, has the ability to attenuate cerebral ischemia-induced cell death. The effect of HGF on learning and memory function after cerebral ischemia, however, remains unknown. We have demonstrated that administration of human recombinant HGF (hrHGF) into the ventricle reduced prolongation of the escape latency in acquisition and retention tests of the water maze task on Days 12-28 after microsphere embolism-induced cerebral ischemia. Treatment with hrHGF also attenuated the decrease in viable area and the density and number of perfused cerebral vessels, particularly those with a diameter smaller than 10 microm, of the ipsilateral hemisphere on Day 28 after the cerebral ischemia. We observed that treatment with hrHGF reduced the number of TUNEL-positive cerebral endothelial cells at the early stage after the ischemia. These results suggest that hrHGF prevents learning and memory dysfunction seen after sustained cerebral ischemia by protecting against injury to the endothelial cells. HGF treatment may be a potent therapeutic strategy for cerebrovascular diseases, including cerebral infarct and vascular dementia.