VEGF-A angiogenesis induces a stable neovasculature in adult murine brain

Temporal Pattern of micro-CT Angiography Vascular Parameters and VEGF mRNA Expression in Fracture Healing: a Radiograph and Molecular Comparison

Angiogenesis plays an important role in fracture healing with vascular endothelial growth factor (VEGF) as the main protein involved. Micro-computed tomography (CT) angiography may be used to analyze this revascularization with several parameters such as number of branches, total volume, and diameter. This systematic review is aimed to assess available studies on the temporal pattern of vascular imaging on micro-CT angiographs, especially in terms of the number of branches, total volume, and diameter as well as the temporal pattern of VEGF mRNA expression as the molecular comparison during bone fracture healing. This review was conducted according to the PRISMA guidelines. Electronic database searches were performed using PubMed, ProQuest, ScienceDirect, EBSCOhost, Taylor & Francis Online, and hand searching. The search strategy and keywords were adjusted to each database using the Boolean operators and other available limit functions to identify most relevant articles based on our inclusion and exclusion criteria. Screening and filtration were done in several stages by removing the duplicates and analyzing each title, abstract, and full-text in all included entries. Data extraction was done for syntheses to summarize the temporal pattern of each parameter. A total of 28 articles were eligible and met all criteria, 11 articles were synthesized in its angiograph's analysis, 16 articles were synthesized in its VEGF mRNA expression analysis, and 1 article had both parameters analyzed. The overall temporal pattern of both three micro-CT angiographic parameters and VEGF mRNA expression was in line qualitatively. The number of branches, total volume, and diameter of the blood vessels in micro-CT angiography showed an exponential rise at week 2 and decline at week 3 of fracture healing, with the VEGF mRNA expression concurrently showing a consistent pattern in the phase.

Ciliogenesis mechanisms mediated by PAK2-ARL13B signaling in brain endothelial cells is responsible for vascular stability

In the developing vasculature, cilia, microtubule-based organelles that project from the apical surface of endothelial cells (ECs), have been identified to function cell autonomously to promote vascular integrity and prevent hemorrhage. To date, the underlying mechanisms of endothelial cilia formation (ciliogenesis) are not fully understood. Understanding these mechanisms is likely to open new avenues for targeting EC-cilia to promote vascular stability. Here, we hypothesized that brain ECs ciliogenesis and the underlying mechanisms that control this process are critical for brain vascular stability. To investigate this hypothesis, we utilized multiple approaches including developmental zebrafish model system and primary cell culture systems. In the p21 activated kinase 2 (pak2a) zebrafish vascular stability mutant [redhead (rhd)] that shows cerebral hemorrhage, we observed significant decrease in cilia-inducing protein ADP Ribosylation Factor Like GTPase 13B (Arl13b), and a 4-fold decrease in cilia numbers. Overexpressing ARL13B-GFP fusion mRNA rescues the cilia numbers (1-2-fold) in brain vessels, and the cerebral hemorrhage phenotype. Further, this phenotypic rescue occurs at a critical time in development (24 h post fertilization), prior to initiation of blood flow to the brain vessels. Extensive biochemical mechanistic studies in primary human brain microvascular ECs implicate ligands platelet-derived growth factor-BB (PDGF-BB), and vascular endothelial growth factor-A (VEGF-A) trigger PAK2-ARL13B ciliogenesis and signal through cell surface VEGFR-2 receptor. Thus, collectively, we have implicated a critical brain ECs ciliogenesis signal that converges on PAK2-ARL13B proteins to promote vascular stability.

Transcranial Direct Current Stimulation Enhances Neuroplasticity and Accelerates Motor Recovery in a Stroke Mouse Model

BACKGROUND

More effective strategies are needed to promote poststroke functional recovery. Here, we evaluated the impact of bihemispheric transcranial direct current stimulation (tDCS) on forelimb motor function recovery and the underlying mechanisms in mice subjected to focal ischemia of the motor cortex.

METHODS

Photothrombotic stroke was induced in the forelimb brain motor area, and tDCS was applied once per day for 3 consecutive days, starting 72 hours after stroke. Grid-walking, single pellet reaching, and grip strength tests were conducted to assess motor function. Local field potentials were recorded to evaluate brain connectivity. Western immunoblotting, ELISA, quantitative real-time polymerase chain reaction, and Golgi-Cox staining were used to uncover tDCS-mediated stroke recovery mechanisms.

RESULTS

Among our results, tDCS increased the rate of motor recovery, anticipating it at the early subacute stage. In this window, tDCS enhanced BDNF (brain-derived neurotrophic factor) expression and dendritic spine density in the peri-infarct motor cortex, along with increasing functional connectivity between motor and somatosensory cortices. Treatment with the BDNF TrkB (tropomyosin-related tyrosine kinase B) receptor inhibitor, ANA-12, prevented tDCS effects on motor recovery and connectivity as well as the increase of spine density, pERK (phosphorylated extracellular signal-regulated kinase), pCaMKII (phosphorylated calcium/calmodulin-dependent protein kinase II), pMEF (phosphorylated myocyte-enhancer factor), and PSD (postsynaptic density)-95. The tDCS-promoted rescue was paralleled by enhanced plasma BDNF level, suggesting its potential role as circulating prognostic biomarker.

CONCLUSIONS

The rate of motor recovery is accelerated by tDCS applied in the subacute phase of stroke. Anticipation of motor recovery via vicariate pathways or neural reserve recruitment would potentially enhance the efficacy of standard treatments, such as physical therapy, which is often delayed to a later stage when plastic responses are progressively lower.

Reconciling VEGF With VPF: The Importance of Increased Vascular Permeability for Stroma Formation in Tumors, Healing Wounds, and Chronic Inflammation

It is widely believed that vascular endothelial growth factor (VEGF) induces angiogenesis by its direct mitogenic and motogenic actions on vascular endothelial cells. However, these activities are only detected when endothelial cells are cultured at very low (0.1%) serum concentrations and would not be expected to take place at the much higher serum levels found in angiogenic sites in vivo. This conundrum can be resolved by recalling VEGF’s original function, that of an extremely potent vascular permeability factor (VPF). In vivo VPF/VEGF increases microvascular permeability such that whole plasma leaks into the tissues where it undergoes clotting by tissue factor that is expressed on tumor and host connective tissue cells to deposit fibrin and generate serum. By providing tissue support and by reprogramming the gene expression patterns of cells locally, fibrin and serum can together account for the formation of vascular connective tissue stroma. In sum, by increasing vascular permeability, VPF/VEGF triggers the “wound healing response,” setting in motion a fundamental pathophysiological process that induces the mature stroma that is found not only in healing wounds but also in solid tumors and chronic inflammatory diseases. Once initiated by increased vascular permeability, this response may be difficult to impede, perhaps contributing to the limited success of anti-VEGF therapies in treating cancer.

The Role of Vasculature Engineering in Dental Pulp Regeneration

Creating an optimal microenvironment that supports angiogenesis, cell-cell cross talk, cell migration, and differentiation is crucial for pulp/dentin regeneration. It was shown that dental stem cells being seeded onto a scaffold and transplanted in vivo could give rise to a new tissue similar to that of the native pulp. However, the unique structure of the tooth with a pulp space encased within hard dentin allows only a single blood supply from a small apical opening located at the apex of the root canals. Therefore, a further strategy that can address this limitation such as the incorporation of endothelial/endothelial progenitor cells or cells with high angiogenic potential into the transplant is required so that the added cells can contribute to the vascularization within the implant. However, the placement of 2 or more different cell types inside 3-dimensional porous scaffolds is technologically challenging. In contrast to the conventional scaffolding approach, self-assembly of monodispersed cells into 3-dimensional tissue mimics permits true physiological interactions between and among different types of cells without any influence from a secondary material. In this review, we discuss potential strategies that can be used in vasculature engineering in dental pulp regeneration with a specific emphasis on combining prevascularization and scaffold-based or scaffold-free approaches.

REST upregulates gremlin to modulate diffuse intrinsic pontine glioma vasculature

Diffuse intrinsic pontine glioma (DIPG) is a highly aggressive glial tumor that occurs in children. The extremely poor median and 5-year survival in children afflicted with DIPG highlights the need for novel biology-driven therapeutics. Here, we have implicated the chromatin remodeler and regulator of brain development called RE1 Silencing Transcription Factor (REST), in DIPG pathology. We show that REST protein is aberrantly elevated in at least 21% of DIPG tumors compared to normal controls. Its knockdown in DIPG cell lines diminished cell growth and decreased their tumorigenicity in mouse intracranial models. DIPGs are vascularized tumors and interestingly, REST loss in DIPG cells also caused a substantial decline in tumor vasculature as measured by a decrease in CD31 and VEGFR2 staining. These observations were validated in vitro, where a significant decline in tube formation by human umbilical vein endothelial cells (HUVEC) was seen following REST-loss in DIPG cells. Mechanistically, REST controlled the secretion of a pro-angiogenic molecule and ligand for VEGFR2 called Gremlin-1 (GREM-1), and was associated with enhanced AKT activation. Importantly, the decline in tube formation caused by REST loss could be rescued by addition of recombinant GREM-1, which also caused AKT activation in HUVECs and human brain microvascular endothelial cells (HBMECs). In summary, our study is the first to demonstrate autocrine and paracrine functions for REST in DIPG development. It also provides the foundation for future investigations on anti-angiogenic therapies targeting GREM-1 in combination with drugs that target REST-associated chromatin remodeling activities.

Mechanisms of vascularization in murine models of primary and metastatic tumor growth

Directed capillary ingrowth has long been considered synonymous with tumor vascularization. However, the vasculature of primary tumors and metastases is not necessarily formed by endothelial cell sprouting; instead, malignant tumors can acquire blood vessels via alternative vascularization mechanisms, such as intussusceptive microvascular growth, vessel co-option, and glomeruloid angiogenesis. Importantly, in response to anti-angiogenic therapies, malignant tumors can switch from one vascularization mechanism to another. In this article, we briefly review the biological features of these mechanisms and discuss on their significance in medical oncology.

Dynamic effects of point source electroporation on the rat brain tissue

In spite of aggressive therapy, existing treatments offer poor prognosis for glioblastoma multiforme due to tumor infiltration into the surrounding brain as well as poor blood-brain barrier penetration of most therapeutic agents. In this paper we present a novel approach for a minimally invasive treatment and a non-invasive response assessment methodology consisting of applying intracranial point-source electroporation and assessing treatment effect volumes using magnetic resonance imaging. Using a unique setup of a single intracranial electrode and an external surface electrode we treated rats' brains with various electroporation protocols and applied magnetic resonance imaging to study the dependence of the physiological effects on electroporation treatment parameters. The extent of blood-brain barrier disruption and later volumes of permanent brain tissue damage were found to correlate significantly with the treatment voltages (r(2)=0.99, p<0.001) and the number of treatment pulses (r(2)=0.94, p<0.002). Blood-brain barrier disruption depicted 3.2±0.3 times larger volumes than the final permanent damage volumes (p<0.0001). These results indicate that it may be beneficial to use more than one modality of electroporation when planning a treatment for brain tumors.

Neurovascular abnormalities in brain disorders: highlights with angiogenesis and magnetic resonance imaging studies

The coupling between neuronal activity and vascular responses is controlled by the neurovascular unit (NVU), which comprises multiple cell types. Many different types of dysfunction in these cells may impair the proper control of vascular responses by the NVU. Magnetic resonance imaging, which is the most powerful tool available to investigate neurovascular structures or functions, will be discussed in the present article in relation to its applications and discoveries. Because aberrant angiogenesis and vascular remodeling have been increasingly reported as being implicated in brain pathogenesis, this review article will refer to this hallmark event when suitable.

Inhibitors of Glioma Growth that Reveal the Tumour to the Immune System

Treated glioblastoma patients survive from 6 to 14 months. In the first part of this review, we describe glioma origins, cancer stem cells and the genomic alterations that generate dysregulated cell division, with enhanced proliferation and diverse response to radiation and chemotherapy. We review the pathways that mediate tumour cell proliferation, neo-angiogenesis, tumor cell invasion, as well as necrotic and apoptotic cell death. Then, we examine the ability of gliomas to evade and suppress the host immune system, exhibited at the levels of antigen recognition and immune activation, limiting the effective signaling between glioma and host immune cells.The second part of the review presents current therapies and their drawbacks. This is followed by a summary of the work of our laboratory during the past 20 years, on oligosaccharide and glycosphingolipid inhibitors of astroblast and astrocytoma division. Neurostatins, the O-acetylated forms of gangliosides GD1b and GT1b naturally present in mammalian brain, are cytostatic for normal astroblasts, but cytotoxic for rat C6 glioma cells and human astrocytoma grades III and IV, with ID50 values ranging from 200 to 450 nM. The inhibitors do not affect neurons or fibroblasts up to concentrations of 4 μM or higher.At least four different neurostatin-activated, cell-mediated antitumoral processes, lead to tumor destruction: (i) inhibition of tumor neovascularization; (ii) activation of microglia; (iii) activation of natural killer (NK) cells; (iv) activation of cytotoxic lymphocytes (CTL). The enhanced antigenicity of neurostatin-treated glioma cells, could be related to their increased expression of connexin 43. Because neurostatins and their analogues show specific activity and no toxicity for normal cells, a clinical trial would be the logical next step.

Expression of matrix metalloproteinase-9, type IV collagen and vascular endothelial growth factor in adamantinous craniopharyngioma

To explore the expression of matrix metalloproteinase 9 (MMP-9), type IV collagen (Col IV) and vascular endothelial growth factor (VEGF) in adamantinomatous craniopharyngioma (ACP) and analyze the correlation between the level of these markers and adamantimous craniopharyngiomas recurrence. Expressions of MMP-9, Col IV and VEGF were tested by immunohistochemistry (IHC) in 40 cases of ACP, including 24 cases of primary group and 16 cases of recurred group. The expression level of MMP-9 and VEGF in recurred group were significantly higher than primary group (93.7% vs. 41.7%, P < 0.05, 87.5% vs. 45.8%, P < 0.05, respectively). The expression of Col IV in the recurred group was significant different from the primary group (Z = -2.619, P < 0.05). MMP-9, Col IV and VEGF may be the potential specific bio-marker related to the recurrence of ACP.

Stem cell therapy - Hype or hope? A review

While the regeneration of a lost tissue is known to mankind for several years, it is only in the recent past that research on regenerative medicine/dentistry has gained momentum and eluded the dramatic yet scientific advancements in the field of molecular biology. The growing understanding of biological concepts in the regeneration of oral/dental tissues coupled with experiments on stem cells is likely to result in a paradigm shift in the therapeutic armamentarium of dental and oral diseases culminating in an intense search for “biological solutions to biological problems.” Stem cells have been successfully isolated from variety of human tissues including orofacial tissues. Initial evidence from pioneering studies has documented the likely breakthrough that stem cells offer for various life-threatening diseases that have so far defeated modern medical care. The evidence gathered so far has propelled many elegant studies exploring the role of stem cells and their manifold dental applications. This review takes you on a sojourn of the origin of stem cells, their properties, characteristics, current research, and their potential applications. It also focuses on the various challenges and barriers that we have to surmount before translating laboratory results to successful clinical applications heralding the dawn of regenerative dentistry.

Croix B. GPR124, an orphan G protein-coupled receptor, is required for CNS-specific vascularization and establishment of the blood-brain barrier

Every organ in the body requires blood vessels for efficient delivery of oxygen and nutrients, but independent vascular beds are highly specialized to meet the individual needs of specific organs. The vasculature of the brain is tightly sealed, with blood-brain barrier (BBB) properties developing coincident with neural vascularization. G protein-coupled receptor 124 (GPR124) (tumor endothelial marker 5, TEM5), an orphan member of the adhesion family of G protein-coupled receptors, was previously identified on the basis of its overexpression in tumor vasculature. Here, we show that global deletion or endothelial-specific deletion of GPR124 in mice results in embryonic lethality associated with abnormal angiogenesis of the forebrain and spinal cord. Expression of GPR124 was found to be required for invasion and migration of blood vessels into neuroepithelium, establishment of BBB properties, and expansion of the cerebral cortex. Thus, GPR124 is an important regulator of neurovasculature development and a potential drug target for cerebrovascular diseases.

Dental pulp and dentin tissue engineering and regeneration: advancement and challenge

Hard tissue is difficult to repair especially dental structures. Tooth enamel is incapable of self-repairing whereas dentin and cementum can regenerate with limited capacity. Enamel and dentin are commonly under the attack by caries. Extensive forms of caries destroy enamel and dentin and can lead to dental pulp infection. Entire pulp amputation followed by the pulp space disinfection and filling with an artificial rubber-like material is employed to treat the infection -- commonly known as root canal or endodontic therapy. Regeneration of dentin relies on having vital pulps; however, regeneration of pulp tissue has been difficult as the tissue is encased in dentin without collateral blood supply except from the root apical end. With the advent of modern tissue engineering concept and the discovery of dental stem cells, regeneration of pulp and dentin has been tested. This article will review the recent endeavor on pulp and dentin tissue engineering and regeneration. The prospective outcomes of current advancements and challenges in this line of research are discussed.

Pulp and dentin tissue engineering and regeneration: current progress

Dental pulp tissue is vulnerable to infection. Entire pulp amputation followed by pulp-space disinfection and filling with an artificial rubber-like material is employed to treat the infection - commonly known as root-canal therapy. Regeneration of pulp tissue has been difficult as the tissue is encased in dentin without collateral blood supply except from the root apical end. However, with the advent of the concept of modern tissue engineering and the discovery of dental stem cells, regeneration of pulp and dentin has been tested. This article will review the early attempts to regenerate pulp tissue and the current endeavor of pulp and dentin tissue engineering, and regeneration. The prospective outcome of the current advancement in this line of research will be discussed.

Apexification: the beginning of its end

Apexification is a procedure for treating and preserving immature permanent teeth that have lost pulp vitality. It contrasts apexogenesis in terms of its outcome in that apical maturation and normal root thickness cannot be obtained. Apexification has been a routine practice for such teeth for many decades, and despite a literature replete with discussion, including recent artificial barrier methods with mineral trioxide aggregate, ultimately there has been no major breakthrough to improve this treatment. Recently, two new clinical concepts have emerged. One involves a revitalization approach to achieve tissue generation and regeneration. In this method, new living tissue is expected to form in the cleaned canal space, allowing continued root development in terms of both length and thickness. The other is the active pursuit of pulp/dentine regeneration via tissue engineering technology to implant or re-grow pulps. Although the technology is still at its infancy, it has the potential to benefit immature pulpless teeth by allowing continued growth and maturation. With this understanding, it may be predicted that apexification will become less needed in years to come. This study will overview the recent concept of pulp revitalization in the treatment of immature teeth with nonvital pulps and the emerging research on pulp tissue engineering and regeneration.

Development of a cerebral microvascular dysplasia model in rodents

Normal vasculature development of the central nervous system is extremely important because patients with vascular malformations are at life-threatening risk for intracranial hemorrhage or cerebral ischemia. The etiology and pathogenesis of abnormal vasculature development in the central nervous system are unknown, and progress is hampered by the lack of animal models for human cerebrovascular diseases. Here, we report our current study on cerebral microvascular dysplasia (CMVD) development. Using vascular endothelial growth factor hyper-stimulation, we demonstrated that aberrant microvessels could be developed in the rodent brain under certain conditions (such as genetic deficient background, local cytokine and chemokine release, or exogenous vessel dilating stimulation) that may speed up focal angiogenesis and lead to cerebral vascular dysplasia.

Why are tumour blood vessels abnormal and why is it important to know?

Tumour blood vessels differ from their normal counterparts for reasons that have received little attention. We report here that they are of at least six distinct types, we describe how each forms, and, looking forward, encourage the targeting of tumour vessel subsets that have lost their vascular endothelial growth factor-A (VEGF-A) dependency and so are likely unresponsive to anti-VEGF-A therapies.

The hidden treasure in apical papilla: the potential role in pulp/dentin regeneration and bioroot engineering

Some clinical case reports have shown that immature permanent teeth with periradicular periodontitis or abscess can undergo apexogenesis after conservative endodontic treatment. A call for a paradigm shift and new protocol for the clinical management of these cases has been brought to attention. Concomitantly, a new population of mesenchymal stem cells residing in the apical papilla of permanent immature teeth recently has been discovered and was termed stem cells from the apical papilla (SCAP). These stem cells appear to be the source of odontoblasts that are responsible for the formation of root dentin. Conservation of these stem cells when treating immature teeth may allow continuous formation of the root to completion. This article reviews current findings on the isolation and characterization of these stem cells. The potential role of these stem cells in the following respects will be discussed: (1) their contribution in continued root maturation in endodontically treated immature teeth with periradicular periodontitis or abscess and (2) their potential utilization for pulp/dentin regeneration and bioroot engineering.

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.

Malignant astrocytic glioma: genetics, biology, and paths to treatment

Malignant astrocytic gliomas such as glioblastoma are the most common and lethal intracranial tumors. These cancers exhibit a relentless malignant progression characterized by widespread invasion throughout the brain, resistance to traditional and newer targeted therapeutic approaches, destruction of normal brain tissue, and certain death. The recent confluence of advances in stem cell biology, cell signaling, genome and computational science and genetic model systems have revolutionized our understanding of the mechanisms underlying the genetics, biology and clinical behavior of glioblastoma. This progress is fueling new opportunities for understanding the fundamental basis for development of this devastating disease and also novel therapies that, for the first time, portend meaningful clinical responses.

Advances in ischemic stroke treatment: neuroprotective and combination therapies

Thrombolysis with intravenous alteplase (recombinant tissue-type plasminogen activator) continues to be the sole recourse for acute ischemic stroke therapy, provided that patients seek treatment preferably within 3 h of stroke onset. The narrow window of efficacy, coupled with the significant risk of hemorrhage and the high mortality rate, preclude the use of alteplase beyond this time frame. Moreover, in part because of safety concerns, only a small percentage (6-15%) of eligible patients is treated with alteplase. Clearly, safer and more effective treatments that focus on improving the shortcomings of the present thrombolysis for stroke need to be identified. Therefore, newer thrombolytics are being developed with the goal of minimizing side effects, while also shortening the time of cerebral reperfusion and extending the therapeutic window of efficacy. Besides thrombolytics, new and potentially useful drugs and devices are also being studied either as monotherapeutic agents or for use in conjunction with alteplase. In animal models of stroke, neuroprotective agents that affect various components of the ischemic injury cascade that results in neurodegeneration have shown promise for the latter. Examples of such agents include spin traps that block oxidative stress, metalloprotease inhibitors that prevent vascular damage, anti-inflammatory drugs that suppress inflammation and transcranial infrared laser irradiation, which promotes recovery of function. Ideally, a successful combination of neuroprotectant (drug or device) and thrombolytic therapy for stroke would minimize the side effects of thrombolysis followed by supplementary neuroprotection thereafter.

Can angiogenesis be exploited to improve stroke outcome? Mechanisms and therapeutic potential

Recent developments in our understanding of the pathophysiological events that follow acute ischaemic stroke suggest an important role for angiogenesis which, through new blood vessel formation, results in improved collateral circulation and may impact on the medium-to-long term recovery of patients. Future treatment regimens may focus on optimization of this process in the ischaemic boundary zones or 'penumbra' region adjacent to the infarct, where partially affected neurons exposed to intermediate perfusion levels have the capability of survival if perfusion is maintained or normalized. In this review, we present evidence that angiogenesis is a key feature of ischaemic stroke recovery and neuronal post-stroke re-organization, examine the signalling mechanisms through which it occurs, and describe the therapeutic potential of treatments aimed at stimulating revascularization and neuroprotection after stroke.

Upregulation of Hypoxia-Inducible Factor (HIF)-1α and HIF-2α in Leptomeningeal Vascular Malformations of Sturge-Weber Syndrome

Cutaneous and leptomeningeal vascular malformations are hallmarks of the Sturge-Weber Syndrome (SWS), resulting in chronic ischemic tissue damage. The mechanisms underlying the pathobiology of these progressive lesions are unknown. Aberrant expression of angiogenic factors has been implicated in the genesis and maintenance of vascular malformations. To assess the role of angiogenesis in SWS vascular lesions we determined the expression of key angiogenic factors by immunohistochemistry and in situ hybridization in 8 SWS patients (age: 8 months to 18 years). We observed increased expression of vascular endothelial growth factor (VEGF), its cognate receptors VEGFR-1, VEGFR-2, and neuropilin (NP)-1 as well as Tie2 in leptomeningeal SWS blood vessels. Intriguingly, these factors are known to be transcriptionally induced by hypoxia-inducible factor (HIF). The HIF system has emerged as the key regulatory system of responses to hypoxia. Immunohistochemical analysis demonstrated markedly elevated nuclear HIF-1alpha and HIF-2alpha protein levels in SWS vessels. Concomitantly, SWS vessels revealed signs of enhanced endothelial cell (EC) turnover as evidenced by increased EC proliferation and apoptosis. Thus, in terms of angiogenesis, vascular malformations in SWS are not static lesions but constitute dynamic structures. Our observation of a dysregulated HIF-alpha expression in SWS vessels are in agreement with recent findings that EC-specific HIF activation provides a setting which supports and sustains angiogenesis and could be of potential use for developing therapeutic strategies to treat these currently incurable lesions.

Microvascular density and vascular endothelial growth factor have little correlation with prognosis of craniopharyngioma

BACKGROUND

Craniopharyngioma is histologically a benign epithelial tumor located in the supersellar cistern that often presents aggressive growth and repeated recurrence. The authors hypothesized that craniopharyngioma recurrence and invasive growth are angiogenesis dependent and evaluated the significance of vascularization in the prognosis of craniopharyngioma by a prospective cohort study.

METHODS

The cohorts consisted of 32 patients with AE and 31 patients with SP tumor. The primary and recurrence removal specimens of the cohort patients were gathered. Microvascular density and VEGF protein in the recurrence group and recurrence-free group were detected by the immunohistochemistry avidin-biotin-peroxidase method and analyzed quantitatively through computer-assisted microscopy to evaluate the correlation of MVD and VEGF with prognosis of craniopharyngiomas.

RESULTS

The average follow-up phase was 63.34 months; 14 of 32 patients with AE and 6 of 31 patients with SP had recurrence and underwent operation again. Although MVD and VEGF have significant difference between AE and SP (P=.000, P=.018, respectively), MVD and VEGF have no statistical difference between the recurrence group and recurrence-free group (P>.05).

CONCLUSIONS

Microvascular density and VEGF in craniopharyngioma tissue have no correlation with prognosis of the tumor, which may be explained by the minimal blood circulation in the craniopharyngioma. Adamantine epithelioma showed more tendency to recur than SP.

A reassessment of vascular endothelial growth factor in central nervous system pathology

✓ Overexpression of vascular endothelial growth factor (VEGF) is associated with several central nervous system (CNS) diseases and abnormalities, and is often postulated as a causative factor and promising therapeutic target in these settings. The authors' goal was to reassess the contribution of VEGF to the biology and pathology of the CNS.

The authors review the literature relating to the following aspects of VEGF: 1) the biology of VEGF in normal brain; 2) the involvement of VEGF in CNS disorders other than tumors (traumatic and ischemic injuries, arteriovenous malformations, inflammation); and 3) the role of VEGF in brain tumor biology (gliomas and the associated vasogenic edema, and hemangioblastomas).

The authors conclude the following: first, that VEGF overexpression contributes to the phenotype associated with many CNS disorders, but VEGF is a reactive rather than a causative factor in many cases; and second, that use of VEGF as a therapeutic agent or target is complicated by the effects of VEGF not only on the cerebral vasculature, but also on astrocytes, neurons, and inflammatory cells. In many cases, therapeutic interventions targeting the VEGF/VEGF receptor axis are likely to be ineffective or even detrimental. Clinical manipulation of VEGF levels in the CNS must be approached with caution.

Sustained vascular endothelial growth factor delivery enhances angiogenesis and perfusion in ischemic hind limb

PURPOSE

We hypothesized that sustained delivery of vascular endothelial growth factor (VEGF) using a polymer [85:15 poly(lactide-co-glycolide) (PLG)] would enhance angiogenesis and improve perfusion of ischemic tissue.

METHODS

C57BL/6J mice (n = 20/group) underwent unilateral hind limb ischemia surgery and were randomized to groups of no scaffold implantation (0-Implant), unloaded scaffold implantation (Empty-PLG), or implantation of scaffolds incorporating 3 microg of VEGF165 (PLG-VEGF). Endpoints included laser Doppler perfusion imaging (LDPI, ischemic/nonischemic limb, %), local vessel counts, immunohistochemistry for CD31, and alpha-smooth muscle actin. In vitro release kinetics of VEGF from PLG was also measured.

RESULTS

PLG-VEGF resulted in improved lower extremity perfusion vs. controls as measured by LDPI% at 7, 14, 21, and 28 days (p < 0.05). PLG-VEGF was associated with significantly greater percentage of vessels staining for CD31 and alpha-smooth muscle actin compared to the Empty-PLG or 0-Implant (p < 0.05 for both).

CONCLUSIONS

The PLG-VEGF scaffolds resulted in sustained VEGF delivery, improved tissue perfusion, greater capillary density, and more mature vasculature compared to the controls. The sustained-release PLG polymer vehicle is a promising delivery system for therapeutic neovascularization applications.