Nerve growth factor-induced migration of endothelial cells

Lack of Direct Effects of Neurotrophic Factors in an In Vitro Model of Neuroinflammation

Neuroinflammation is associated with several neurological disorders including temporal lobe epilepsy. Seizures themselves can induce neuroinflammation. In an in vivo model of epilepsy, the supplementation of brain-derived neurotropic factor (BDNF) and fibroblast growth factor-2 (FGF-2) using a Herpes-based vector reduced epileptogenesis-associated neuroinflammation. The aim of this study was to test whether the attenuation of the neuroinflammation obtained in vivo with BDNF and FGF-2 was direct or secondary to other effects, for example, the reduction in the severity and frequency of spontaneous recurrent seizures. An in vitro model of neuroinflammation induced by lipopolysaccharide (LPS, 100 ng/mL) in a mouse primary mixed glial culture was used. The releases of cytokines and NO were analyzed via ELISA and Griess assay, respectively. The effects of LPS and neurotrophic factors on cell viability were determined by performing an MTT assay. BDNF and FGF-2 were tested alone and co-administered. LPS induced a significant increase in pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) and NO. BDNF, FGF-2, and their co-administration did not counteract these LPS effects. Our study suggests that the anti-inflammatory effect of BDNF and FGF-2 in vivo in the epilepsy model was indirect and likely due to a reduction in seizure frequency and severity.

Serum Cholesterol Concentration on Admission in 415 Dogs Envenomated by Daboia (Vipera) palaestinae as a Marker of Envenomation Severity and Outcome-A Retrospective Study

Daboia (Vipera) palaestinae (Dp), accounts for most envenomations in humans and dogs in Israel. In humans envenomed by Dp, serum cholesterol concentration (sChol) is inversely correlated with envenomation severity. This study examined the utility of sChol upon admission in dogs envenomed by Dp as an envenomation severity and outcome marker. Data upon admission, including sChol, were retrospectively collected from the medical records of dogs with proven Dp envenomation. The study included 415 dogs. The mortality rate was 11%. The heart rate upon admission was higher in non-survivors than in survivors. Signs of bleeding or hematoma and circulatory shock signs were more frequent among non-survivors compared to survivors. sChol, the platelet count, and serum albumin concentration (sAlb) were lower, while serum creatinine concentration was higher among non-survivors. sChol and sAlb were moderately, positively, and significantly correlated. sChol was significantly, negatively, albeit weakly, correlated with the length of hospitalization and the heart rate. sChol was lower in dogs admitted >12 h post-envenomation than in those admitted later. In dogs, sChol upon admission is a potential marker of severity and outcome of Dp envenomation. The platelet count, sAlb, and sCreat might also be potential markers.

Combined treatment of nerve growth factor and transcranical direct current stimulations to improve outcome in children with vegetative state after out-of-hospital cardiac arrest

BACKGROUND

Out-of-hospital cardiac arrest (OHCA) is one of the most dramatic events in pediatric age and, despite advanced neurointensive care, the survival rate remains low. Currently, no effective treatments can restore neuronal loss or produce significant improvement in these patients. Nerve Growth Factor (NGF) is a neurotrophin potentially able to counteract many of the deleterious effects triggered by OHCA. Transcranial Direct Current Stimulation (tDCS) has been reported to be neuroprotective in many neurological diseases, such as motor deficit and cognitive impairment. Children with the diagnosis of chronic vegetative state after OHCA were enrolled. These patients underwent a combined treatment of intranasal administration of human recombinant NGF (hr-NGF), at a total dose of 50 gamma/kg, and tDCS, in which current intensity was increased from zero to 2 mA from the first 5 s of stimulation and maintained constant for 20 min. The treatment schedule was performed twice, at one month distance each. Neuroradiogical evaluation with Positron Emission Tomography scan (PET), Single Photon Emission Computed Tomography (SPECT), Electroencephalography (EEG) and Power Spectral Density of the brain (PSD) was determined before the treatment and one month after the end. Neurological assessment was deepened by using modified Ashworth Scale, Gross Motor Function Measure, and Disability Rating Scale.

RESULTS

Three children with a chronic vegetative state secondary to OHCA were treated. The combined treatment with hr-NGF and tDCS improved functional (PET and SPECT) and electrophysiological (EEG and PSD) assessment. Also clinical conditions improved, mainly for the reduction of spasticity and with the acquisition of voluntary finger movements, improved facial mimicry and reaction to painful stimuli. No side effects were reported.

CONCLUSIONS

These promising preliminary results and the ease of administration of this treatment make it worthwhile to be investigated further, mainly in the early stages from OHCA and in patients with better baseline neurological conditions, in order to explore more thoroughly the benefits of this new approach on neuronal function recovery after OHCA.

Genomic Interplay between Neoneurogenesis and Neoangiogenesis in Carcinogenesis: Therapeutic Interventions

Angiogenesis, the generation of new blood vessels, is one of the hallmarks of cancer. The growing tumor requires nutrients and oxygen. Recent evidence has shown that tumors release signals to attract new nerve fibers and stimulate the growth of new nerve fibers. Neurogenesis, neural extension, and axonogenesis assist in the migration of cancer cells. Cancer cells can use both blood vessels and nerve fibers as routes for cells to move along. In this way, neurogenesis and angiogenesis both contribute to cancer metastasis. As a result, tumor-induced neurogenesis joins angiogenesis and immunosuppression as aberrant processes that are exacerbated within the tumor microenvironment. The relationship between these processes contributes to cancer development and progression. The interplay between these systems is brought about by cytokines, neurotransmitters, and neuromodulators, which activate signaling pathways that are common to angiogenesis and the nervous tissue. These include the AKT signaling pathways, the MAPK pathway, and the Ras signaling pathway. These processes also both require the remodeling of tissues. The interplay of these processes in cancer provides the opportunity to develop novel therapies that can be used to target these processes.

Acute intranasal treatment with nerve growth factor limits the onset of traumatic brain injury in young rats

BACKGROUND AND PURPOSE

Traumatic brain injury (TBI) comprises a primary injury directly induced by impact, which progresses into a secondary injury leading to neuroinflammation, reactive astrogliosis, and cognitive and motor damage. To date, treatment of TBI consists solely of palliative therapies that do not prevent and/or limit the outcomes of secondary damage and only stabilize the deficits. The neurotrophin, nerve growth factor (NGF), delivered to the brain parenchyma following intranasal application, could be a useful means of limiting or improving the outcomes of the secondary injury, as suggested by pre-clinical and clinical data.

EXPERIMENTAL APPROACH

We evaluated the effect of acute intranasal treatment of young (20-postnatal day) rats, with NGF in a TBI model (weight drop/close head), aggravated by hypoxic complications. Immediately after the trauma, rats were intranasally treated with human recombinant NGF (50 μg·kg^-1 ), and motor behavioural test, morphometric and biochemical assays were carried out 24 h later.

KEY RESULTS

Acute intranasal NGF prevented the onset of TBI-induced motor disabilities, and decreased reactive astrogliosis, microglial activation and IL-1β content, which after TBI develops to the same extent in the impact zone and the hypothalamus.

CONCLUSION AND IMPLICATIONS

Intranasal application of NGF was effective in decreasing the motor dysfunction and neuroinflammation in the brain of young rats in our model of TBI. This work forms an initial pre-clinical evaluation of the potential of early intranasal NGF treatment in preventing and limiting the disabling outcomes of TBI, a clinical condition that remains one of the unsolved problems of paediatric neurology.

Nervous System-Driven Osseointegration

Implants are essential therapeutic tools for treating bone fractures and joint replacements. Despite the in-depth study of osseointegration for more than fifty years, poor osseointegration caused by aseptic loosening remains one of the leading causes of late implant failures. Osseointegration is a highly sophisticated and spatiotemporal process in vivo involving the immune response, angiogenesis, and osteogenesis. It has been unraveled that the nervous system plays a pivotal role in skeletal health via manipulating neurotrophins, neuropeptides, and nerve cells. Herein, the research related to nervous system-driven osseointegration was systematically analyzed and reviewed, aiming to demonstrate the prominent role of neuromodulation in osseointegration. Additionally, it is indicated that the implant design considering the role of neuromodulation might be a promising way to prevent aseptic loosening.

Tumor Innervation: History, Methodologies, and Significance

The role of the nervous system in cancer development and progression has been under experimental and clinical investigation since nineteenth-century observations in solid tumor anatomy and histology. For the first half of the twentieth century, methodological limitations and opaque mechanistic concepts resulted in ambiguous evidence of tumor innervation. Differential spatial distribution of viable or disintegrated nerve tissue colocalized with neoplastic tissue led investigators to conclude that solid tumors either are or are not innervated. Subsequent work in electrophysiology, immunohistochemistry, pathway enrichment analysis, neuroimmunology, and neuroimmunooncology have bolstered the conclusion that solid tumors are innervated. Regulatory mechanisms for cancer-related neurogenesis, as well as specific operational definitions of perineural invasion and axonogenesis, have helped to explain the consensus observation of nerves at the periphery of the tumor signifying a functional role of nerves, neurons, neurites, and glia in tumor development.

Intranasal Delivery of Nerve Growth Factor in Neurodegenerative Diseases and Neurotrauma

Since the 1980s, the development of a pharmacology based on nerve growth factor (NGF) has been postulated for the therapy of Alzheimer’s disease (AD). This hypothesis was based on the rescuing effect of the neurotrophin on the cholinergic phenotype of the basal forebrain neurons, primarily compromised during the development of AD. Subsequently, the use of NGF was put forward to treat a broader spectrum of neurological conditions affecting the central nervous system, such as Parkinson’s disease, degenerative retinopathies, severe brain traumas and neurodevelopmental dysfunctions. While supported by solid rational assumptions, the progress of a pharmacology founded on these hypotheses has been hampered by the difficulty of conveying NGF towards the brain parenchyma without resorting to invasive and risky delivery methods. At the end of the last century, it was shown that NGF administered intranasally to the olfactory epithelium was able to spread into the brain parenchyma. Notably, after such delivery, pharmacologically relevant concentration of exogenous NGF was found in brain areas located at considerable distances from the injection site along the rostral-caudal axis. These observations paved the way for preclinical characterization and clinical trials on the efficacy of intranasal NGF for the treatment of neurodegenerative diseases and of the consequences of brain trauma. In this review, a summary of the preclinical and clinical studies published to date will be attempted, as well as a discussion about the mechanisms underlying the efficacy and the possible development of the pharmacology based on intranasal conveyance of NGF to the brain.

Do Neurotrophins Connect Neurological Disorders and Heart Diseases?

Neurotrophins (NTs) are one of the most characterized neurotrophic factor family members and consist of four members in mammals. Growing evidence suggests that there is a complex inter- and bi-directional relationship between central nervous system (CNS) disorders and cardiac dysfunction, so-called "brain-heart axis". Recent studies suggest that CNS disorders, including neurodegenerative diseases, stroke, and depression, affect cardiovascular function via various mechanisms, such as hypothalamic-pituitary-adrenal axis augmentation. Although this brain-heart axis has been well studied in humans and mice, the involvement of NT signaling in the axis has not been fully investigated. In the first half of this review, we emphasize the importance of NTs not only in the nervous system, but also in the cardiovascular system from the embryonic stage to the adult state. In the second half, we discuss the involvement of NTs in the pathogenesis of cardiovascular diseases, and then examine whether an alteration in NTs could serve as the mediator between neurological disorders and heart dysfunction. The further investigation we propose herein could contribute to finding direct evidence for the involvement of NTs in the axis and new treatment for cardiovascular diseases.

Many Voices in a Choir: Tumor-Induced Neurogenesis and Neuronal Driven Alternative Splicing Sound Like Suspects in Tumor Growth and Dissemination

Simple Summary

Significant progress has recently been made in understanding the role of the neuronal system in cancer biology, in many solid tumors such as prostate, breast, pancreatic, gastric and brain cancers. Solid tumors and the nervous system appear to influence each other’s development both directly and indirectly. A recurring element in such interactions is constituted by nerve-related substances such as neurotransmitters and neurotrophins, to which the first part of the current review is devoted. The second part of the review focuses on the potential role played by alternative splicing in cancer progression associated with neural signaling. Alternative splicing is the process where pre-mRNA is cut and re-ligated in different ways to give rise to multiple protein isoforms whose expression profile is often cancer specific. Alternative splicing is known to take place in the mRNA of genes that code for proteins involved in neuronal development and the creation of new nerve fibers. The change in alternative splicing patterns that occur as tumors develop and progress may make these splice variants potential targets for the development of drug treatments. They may also serve as diagnostic or prognostic biomarkers.

Abstract

During development, as tissues expand and grow, they require circulatory, lymphatic, and nervous system expansion for proper function and support. Similarly, as tumors arise and develop, they also require the expansion of these systems to support them. While the contribution of blood and lymphatic systems to the development and progression of cancer is well known and is targeted with anticancer drugs, the contribution of the nervous system is less well studied and understood. Recent studies have shown that the interaction between neurons and a tumor are bilateral and promote metastasis on one hand, and the formation of new nerve structures (neoneurogenesis) on the other. Substances such as neurotransmitters and neurotrophins being the main actors in such interplay, it seems reasonable to expect that alternative splicing and the different populations of protein isoforms can affect tumor-derived neurogenesis. Here, we report the different, documented ways in which neurons contribute to the development and progression of cancer and investigate what is currently known regarding cancer-neuronal interaction in several specific cancer types. Furthermore, we discuss the incidence of alternative splicing that have been identified as playing a role in tumor-induced neoneurogenesis, cancer development and progression. Several examples of changes in alternative splicing that give rise to different isoforms in nerve tissue that support cancer progression, growth and development have also been investigated. Finally, we discuss the potential of our knowledge in alternative splicing to improve tumor diagnosis and treatment.

Mechanisms driving the initiation and direction of endothelial sprouting in organotypic co-culture of aorta and spinal cord tissues

The resumption of blood supply in spinal cord (SC) after injury is a prerequisite of its recovery. To expose the mechanisms of damaged SC revascularization we have used an organotypic SC/aortic fragments (AF) co-culture where, as we showed previously, damaged SC tissue induces AF cell sprouting but repels them away. Supplementation of culture medium with exogenous VEGF-A₁₆₅ redirects the migrating aortic endothelial cells towards SC tissue. This effect and the pattern of sFlt1 expression (a soluble form of VEGFR1) suggest that the low level of SC-secreted VEGF and the presence of sFlt1 in SC slices together prevent the migration of aortic CD31⁺ cells to the SC in the absence of exogenous VEGF. VEGF-A₁₆₅ supplementation sequesters this inhibitory activity of sFlt1 by direct binding thus allowing CD31⁺ cell migration in to SC tissue. Proteome analysis has shown that migration/proliferation of CD31⁺ and αSMA⁺ aortic cells in neuronal culture medium used in our SC/AF model (which obstruct sprouting by itself) was resumed by combined action of several pro- (aFGF, bFGF, Osteopontin, TF, IGFBP2, SDF1) and anti-angiogenic (Endostatin/Collagen18) factors. The mutual influence of AF and SC tissues is a key factor balancing these factors and thus driving endothelial sprouting in SC injury zone.

Pleiotropic activity of nerve growth factor in regulating cardiac functions and counteracting pathogenesis

Cardiac innervation density generally reflects the levels of nerve growth factor (NGF) produced by the heart—changes in NGF expression within the heart and vasculature contribute to neuronal remodelling (e.g. sympathetic hyperinnervation or denervation). Its synthesis and release are altered under different pathological conditions. Although NGF is well known for its survival effects on neurons, it is clear that these effects are more wide ranging. Recent studies reported both in vitro and in vivo evidence for beneficial actions of NGF on cardiomyocytes in normal and pathological hearts, including prosurvival and antiapoptotic effects. NGF also plays an important role in the crosstalk between the nervous and cardiovascular systems. It was the first neurotrophin to be implicated in postnatal angiogenesis and vasculogenesis by autocrine and paracrine mechanisms. In connection with these unique cardiovascular properties of NGF, we have provided comprehensive insight into its function and potential effect of NGF underlying heart sustainable/failure conditions. This review aims to summarize the recent data on the effects of NGF on various cardiovascular neuronal and non‐neuronal functions. Understanding these mechanisms with respect to the diversity of NGF functions may be crucial for developing novel therapeutic strategies, including NGF action mechanism‐guided therapies.

Regulation of Eosinophil Recruitment and Allergic Airway Inflammation by Tropomyosin Receptor Kinase A

Eosinophilia is a hallmark of allergic airway inflammation (AAI). Identifying key molecules and specific signaling pathways that regulate eosinophilic inflammation is critical for development of novel therapeutics. Tropomycin receptor kinase A (TrkA) is the high-affinity receptor for nerve growth factor. AAI is associated with increased expression of TrkA by eosinophils; however, the functional role of TrkA in regulating eosinophil recruitment and contributing to AAI is poorly understood. This study identifies, to our knowledge, a novel mechanism of eotaxin-mediated activation of TrkA and its role in regulating eosinophil recruitment by using a chemical-genetic approach to specifically inhibit TrkA kinase activity with 1-NM-PP1 in TrkAF592A-knock-in (TrkA-KI) eosinophils. Blockade of TrkA by 1-NM-PP1 enhanced eosinophil spreading on VCAM-1 but inhibited eotaxin-1 (CCL11)-mediated eosinophil migration, calcium flux, cell polarization, and ERK1/2 activation, suggesting that TrkA is an important player in the signaling pathway activated by eotaxin-1 during eosinophil migration. Further, blockade of matrix metalloprotease with BB-94 inhibited eotaxin-1-induced TrkA activation and eosinophil migration, additively with 1-NM-PP1, indicating a role for matrix metalloproteases in TrkA activation. TrkA inhibition in Alternaria alternata-challenged TrkA-KI mice markedly inhibited eosinophilia and attenuated various features of AAI. These findings are indicative of a distinctive eotaxin-mediated TrkA-dependent signaling pathway, which, in addition to other TrkA-activating mediators, contributes to eosinophil recruitment during AAI and suggests that targeting the TrkA signaling pathway to inhibit eosinophil recruitment may serve as a therapeutic strategy for management of eosinophilic inflammation in allergic airway disease, including asthma.

Nerve Growth Factor-Induced Angiogenesis: 1. Endothelial Cell Tube Formation Assay

Nerve growth factor (NGF) is a neurotrophin promoting survival, proliferation, differentiation, and neuroprotection in the embryonal and adult nervous system. NGF also induces angiogenic effects in the cardiovascular system, which may be beneficial in engineering new blood vessels and for developing novel anti-angiogenesis therapies for cancer. Angiogenesis is a cellular process characterized by a number of events, including endothelial cell migration, invasion, and assembly into capillaries. In vitro endothelial tube formation assays are performed using primary human umbilical vein endothelial cells, human aortic endothelial cells, and other human or rodent primary endothelial cells isolated from the vasculature of both tumors and normal tissues. Immortalized endothelial cell lines are also used for these assays. When seeded onto Matrigel, these cells reorganize to create tubelike structure, which may be used as models for studying some aspects of in vitro angiogenesis. Image acquisition by light and fluorescence microscopy and/or quantification of fluorescently labeled cells can be carried out manually or digitally, using commercial software and automated image processing. Here we detail materials, procedure, assay conditions, and cell labeling for quantification of endothelial cell tube formation. This model can be applied to study cellular and molecular mechanisms by which NGF or other neurotrophins promote angiogenesis. This model may also be useful for the development of potential angiogenic and/or anti-angiogenic drugs targeting NGF receptors.

Quantification of Multicellular Organization, Junction Integrity, and Substrate Features in Collective Cell Migration

Quantitative analysis of multicellular organization, cell-cell junction integrity, and substrate properties is essential to understand the mechanisms underlying collective cell migration. However, spatially and temporally defining these properties is difficult within collectively migrating cell groups due to challenges in accurate cell segmentation within the monolayer. In this paper, we present Matlab®-based algorithms to spatially quantify multicellular organization (migration distance, interface roughness, and cell alignment, area, and morphology), cell-cell junction integrity, and substrate features in confocal microscopy images of two-dimensional collectively migrating endothelial monolayers. We used novel techniques, including measuring the migrating front roughness using a parametric curve formulation, automatically binning cells to obtain data as a function of distance from the migrating front, using iterative morphological closings to fully define cell boundaries, quantifying β-catenin localization as a measure of cell-cell junction integrity, and skeletonizing fibronectin to determine fiber length and orientation. These algorithms are widely accessible, as they use common fluorescent markers and Matlab® functions, and provide high-throughput critical feature quantification within collectively migrating cell groups. These image analysis algorithms can help standardize feature quantification among different experimental techniques, cell types, and research groups studying collective cell migration.

The role of stress and beta-adrenergic system in melanoma: current knowledge and possible therapeutic options

PURPOSE

The aim of the present review was to discuss recent findings on the role of beta-adrenergic system in melanoma, in order to provide information on the biological responses elicited by its activation and its potential application for melanoma treatment.

METHODS

A literature search was performed, and evidences regarding the involvement of stress and beta-adrenergic system in cancer and melanoma were found and discussed.

RESULTS

Our search pointed out that beta-adrenergic system is a key regulator of important biological processes involved in the onset and progression of some solid tumors. In the last decade, functional beta-adrenoceptors have been also identified on melanoma cells, as well as on their microenvironment cells. Similarly to other common cancers too, the activation of such adrenoceptors by catecholamines, usually released under stress conditions, has been found to trigger pro-tumorigenic pathways contributing to cell proliferation and motility, immune system regulation, apoptosis, epithelial-mesenchymal transition, invasion and neoangiogenesis.

CONCLUSIONS

The biological evidences we found clarify and sustain the clinical evidences reporting the involvement of chronic stress in melanoma onset and progression. In such scenario, it is conceivable that a therapeutic approach targeting beta-adrenergic system could constitute a novel and promising strategy for melanoma treatment.

An Oncogenic NTRK Fusion in a Patient with Soft-Tissue Sarcoma with Response to the Tropomyosin-Related Kinase Inhibitor LOXO-101

Oncogenic TRK fusions induce cancer cell proliferation and engage critical cancer-related downstream signaling pathways. These TRK fusions occur rarely, but in a diverse spectrum of tumor histologies. LOXO-101 is an orally administered inhibitor of the TRK kinase and is highly selective only for the TRK family of receptors. Preclinical models of LOXO-101 using TRK-fusion-bearing human-derived cancer cell lines demonstrate inhibition of the fusion oncoprotein and cellular proliferation in vitro, and tumor growth in vivo. The tumor of a 41-year-old woman with soft-tissue sarcoma metastatic to the lung was found to harbor an LMNA-NTRK1 gene fusion encoding a functional LMNA-TRKA fusion oncoprotein as determined by an in situ proximity ligation assay. In a phase I study of LOXO-101 (ClinicalTrials.gov no. NCT02122913), this patient's tumors underwent rapid and substantial tumor regression, with an accompanying improvement in pulmonary dyspnea, oxygen saturation, and plasma tumor markers.

SIGNIFICANCE

TRK fusions have been deemed putative oncogenic drivers, but their clinical significance remained unclear. A patient with a metastatic soft-tissue sarcoma with an LMNA-NTRK1 fusion had rapid and substantial tumor regression with a novel, highly selective TRK inhibitor, LOXO-101, providing the first clinical evidence of benefit from inhibiting TRK fusions.

The biology of neurotrophins: cardiovascular function

This chapter addresses the role of neurotrophins in the development of the heart, blood vessels, and neural circuits that control cardiovascular function, as well as the role of neurotrophins in the mature cardiovascular system. The cardiovascular system includes the heart and vasculature whose functions are tightly controlled by the nervous system. Neurons, cardiomyocytes, endothelial cells, vascular smooth muscle cells, and pericytes are all targets for neurotrophin action during development. Neurotrophin expression continues throughout life, and several common pathologies that impact cardiovascular function involve changes in the expression or activity of neurotrophins. These include atherosclerosis, hypertension, diabetes, acute myocardial infarction, and heart failure. In many of these conditions, altered expression of neurotrophins and/or neurotrophin receptors has direct effects on vascular endothelial and smooth muscle cells in addition to effects on nerves that modulate vascular resistance and cardiac function. This chapter summarizes the effects of neurotrophins in cardiovascular physiology and pathophysiology.

Vimocin and vidapin, cyclic KTS peptides, are dual antagonists of α1β1/α2β1 integrins with antiangiogenic activity

Obtustatin and viperistatin, members of the disintegrin protein family, served as lead compounds for the synthesis of linear and cyclic peptides containing the KTS binding motif. The most active linear peptide, a viperistatin analog, indicated the importance of Cys(19) and Cys(29), as well as the presence of Arg at position 24 for their biologic activity, and was used as the basic sequence for the synthesis of cyclic peptides. Vimocin (compound 6) and vidapin (compound 10) showed a high potency (IC50 = 0.17 nM) and intermediate efficacy (20 and 40%) in inhibition of adhesion of α1/α2 integrin overexpressor cells to respective collagens. Vimocin was more active in inhibition of the wound healing (53%) and corneal micropocket (17%) vascularization, whereas vidapin was more potent in inhibition of migration in the Matrigel tube formation assay (90%). Both compounds similarly inhibited proliferation (50-90%) of endothelial cells, and angiogenesis induced by vascular endothelial growth factor (80%) and glioma (55%) in the chorioallantoic membrane assay. These peptides were not toxic to endothelial cell cultures and caused no acute toxicity upon intravenous injection in mice, and were stable for 10-30 hours in human serum. The in vitro and in vivo potency of the peptides are consistent with conformational ensembles and "bioactive" space shared by obtustatin and viperistatin. These findings suggest that vimocin and vidapin can serve as dual α1β1/α2β1 integrin antagonists in antiangiogenesis and cancer therapy.

Coiled-coil-mediated grafting of bioactive vascular endothelial growth factor

Chimeric growth factors may represent a powerful alternative to their natural counterparts for the functionalization of tissue-engineered scaffolds and applications in regenerative medicine. Their rational design should provide a simple, readily scalable production strategy while improving retention at the site of action. In that endeavor, we here report the synthesis of a chimeric protein corresponding to human vascular endothelial growth factor 165 being N-terminally fused to an E5 peptide tag (E5-VEGF). E5-VEGF was successfully expressed as a homodimer in mammalian cells. Following affinity purification, in vitro surface plasmon resonance biosensing and cell survival assays confirmed diffusible E5-VEGF ability to bind to its receptor ectodomains, while observed morphological phenotypes confirmed its anti-apoptotic features. Additional surface plasmon resonance assays highlighted that E5-VEGF could be specifically captured with high stability when interacting with covalently immobilized K5 peptide (a synthetic peptide designed to bind to the E5 moiety of chimeric hVEGF). This immobilization strategy was applied to glass substrates and chimeric hVEGF was shown to be maintained in a functionally active state following capture. Altogether, our data demonstrated that stable hVEGF capture can be performed via coiled-coil interactions without impacting hVEGF bioactivity, thus opening up the way to future applications in the field of tissue engineering and regenerative medicine.

Pronerve growth factor induces angiogenesis via activation of TrkA: possible role in proliferative diabetic retinopathy

Proliferative diabetic retinopathy (PDR) is the leading cause of blindness in working age Americans. We demonstrated that diabetes disturbs the homeostasis of nerve growth factor (NGF) resulting in accumulation of its precursor proNGF. Increases in proNGF were positively correlated with progression of diabetic retinopathy, having the highest level in ocular fluids from PDR patients compared to nondiabetic patients. Here, we attempted to evaluate the contribution and the possible mechanism of proNGF to PDR. The angiogenic response of aqueous humor samples from PDR patients was examined in human retinal endothelial cells in the presence or absence of anti-proNGF antibody. Additional cultures were treated with mutant-proNGF in the presence of specific pharmacological inhibitors of TrkA and p75(NTR) receptors. PDR-aqueous humor samples exerted significant angiogenic response including cell proliferation, migration, and alignment into tube-like structures. These effects were significantly reduced by anti-proNGF antibody but not by IgG. Treatment of retinal endothelial cells with mutant-proNGF activated phosphorylation of TrkA and p38MAPK; however, it did not alter p75(NTR) expression. Inhibition of TrkA but not p75(NTR) significantly reduced mutant-proNGF-induced cell proliferation, cell migration, and tube formation. Taken together, these results provide evidence that proNGF can contribute to PDR at least in part via activation of TrkA.

Vixapatin (VP12), a c-type lectin-protein from Vipera xantina palestinae venom: characterization as a novel anti-angiogenic compound

A C-type lectin-like protein (CTL), originally identified as VP12 and lately named Vixapatin, was isolated and characterized from Israeli viper Vipera xantina palestinae snake venom. This CTL was characterized as a selective α2β1 integrin inhibitor with anti-melanoma metastatic activity. The major aim of the present study was to prove the possibility that this protein is also a potent novel anti-angiogenic compound. Using an adhesion assay, we demonstrated that Vixapatin selectively and potently inhibited the α2 mediated adhesion of K562 over-expressing cells, with IC(50) of 3 nM. 3 nM Vixapatin blocked proliferation of human dermal microvascular endothelial cells (HDMEC); 25 nM inhibited collagen I induced migration of human fibrosarcoma HT-1080 cells; and 50 nM rat C6 glioma and human breast carcinoma MDA-MB-231 cells. 1 µM Vixapatin reduced HDMEC tube formation by 75% in a Matrigel assay. Furthermore, 1 µM Vixapatin decreased by 70% bFGF-induced physiological angiogenesis, and by 94% C6 glioma-induced pathological angiogenesis, in shell-less embryonic quail chorioallantoic membrane assay. Vixapatin's ability to inhibit all steps of the angiogenesis process suggest that it is a novel pharmacological tool for studying α2β1 integrin mediated angiogenesis and a lead compound for the development of a novel anti-angiogenic/angiostatic/anti-cancer drug.

Importance of interaction between nerve growth factor and α9β1 integrin in glial tumor angiogenesis

NGF is a growth factor for which the role in the promotion of angiogenesis is still not completely understood. We found that NGF promotes the pathological neovascularization process in glioma through a direct interaction with α9β1 integrin, which is up-regulated on microvascular endothelial cells in cancer tissue. We propagated gHMVEC primary cells using a new method of immune-selection, and these cells demonstrated α9β1 integrin-dependent binding of NGF in a cell adhesion assay. Moreover, NGF induced gHMVEC proliferation and chemotaxis inhibited by specific blockers of α9β1 integrin, such as MLD-disintegrins and monoclonal antibody Y9A2. A Matrigel tube formation assay revealed that NGF significantly increased capillary-like growth from gHMVEC to a level comparable to treatment with VEGF. The snake venom disintegrin, VLO5, inhibited the agonistic effect of both growth factors, whereas the effect of Y9A2 was not statistically significant. Angiogenesis exogenously induced by NGF  was also α9β1-integrin dependent in an embryonic quail CAM system. However, angiogenesis pathologically induced by developing glioma in this system was only sensitive for inhibition with MLD-disintegrin, suggesting a more complex effect of cancer cells on the neovascularization process. The anti-angiogenic effect of MLD-disintegrins is probably related to their pro-apoptotic ability induced in activated tumoral endothelial cells. Therefore, the molecular basis of these disintegrins may be useful for developing new angiostatic pharmaceuticals for application in cancer therapy.

Pharmacological aspects of Vipera xantina palestinae venom

In Israel, Vipera xantina palestinae (V.x.p.) is the most common venomous snake, accounting for several hundred cases of envenomation in humans and domestic animals every year, with a mortality rate of 0.5 to 2%. In this review we will briefly address the research developments relevant to our present understanding of the structure and function of V.x.p. venom with emphasis on venom disintegrins. Venom proteomics indicated the presence of four families of pharmacologically active compounds: (i) neurotoxins; (ii) hemorrhagins; (iii) angioneurin growth factors; and (iv) different types of integrin inhibitors. Viperistatin, a α1β1selective KTS disintegrin and VP12, a α2β1 selective C-type lectin were discovered. These snake venom proteins represent promising tools for research and development of novel collagen receptor selective drugs. These discoveries are also relevant for future improvement of antivenom therapy towards V.x.p. envenomation.

Combined experimental and mathematical approach for development of microfabrication-based cancer migration assay

Migration of cancer cells is a key determinant of metastasis, which is correlated with poor prognosis in patients. Evidence shows that cancer cell motility is regulated by stromal cell interactions. To quantify the role of homotypic and heterotypic cell-cell interaction in migration, a two-dimensional migration assay has been developed by microfabrication techniques. Two breast cancer cell lines, MDA-MB-231 and MDA-MB-453, were used to develop micropatterns of cancer cells (cell islands) that revealed distinct migration profiles in this assay. Although the individual migration rates of these cells showed only a sevenfold difference, MDA-MB-453 islands migrated significantly lower than MDA-MB-231 islands, indicating differential regulation of migration in isolated cells vs. islands. Island size had the greatest impact on migration, primarily for MDA-MB-231 cells. Migration of MDA-MB-231 islands was decreased by interaction with homotypic cells, and significantly more by heterotypic non-cancer-associated fibroblasts. In addition, a mathematical model of island migration in multi-cellular population has been developed using Stefan-Maxwell's equation. The model showed qualitative agreement with experimental results and predicted a biphasic relation between cell densities and island sizes. The combined experimental and mathematical model can be used to quantitatively study the impact of cell-cell interactions on migration.

Non-thermal dielectric barrier discharge plasma induces angiogenesis through reactive oxygen species

Vascularization plays a key role in processes such as wound healing and tissue engineering. Non-thermal plasma, which primarily produces reactive oxygen species (ROS), has recently emerged as an efficient tool in medical applications including blood coagulation, sterilization and malignant cell apoptosis. Liquids and porcine aortic endothelial cells were treated with a non-thermal dielectric barrier discharge plasma in vitro. Plasma treatment of phosphate-buffered saline (PBS) and serum-free medium increased ROS concentration in a dose-dependent manner, with a higher concentration observed in serum-free medium compared with PBS. Species concentration inside cells peaked 1 h after treatment, followed by a decrease 3 h post treatment. Endothelial cells treated with a plasma dose of 4.2 J cm(-2) had 1.7 times more cells than untreated samples 5 days after plasma treatment. The 4.2 J cm(-2) plasma dose increased two-dimensional migration distance by 40 per cent compared with untreated control, while the number of cells that migrated through a three-dimensional collagen gel increased by 15 per cent. Tube formation was also enhanced by plasma treatment, with tube lengths in plasma-treated samples measuring 2.6 times longer than control samples. A fibroblast growth factor-2 (FGF-2) neutralizing antibody and ROS scavengers abrogated these angiogenic effects. These data indicate that plasma enhanced proliferation, migration and tube formation is due to FGF-2 release induced by plasma-produced ROS. Non-thermal plasma may be used as a potential tool for applying ROS in precise doses to enhance vascularization.

Peaceful use of disastrous neurotoxicants

The increasing exposure to environmental neurotoxicants in the last decades caused serious health problems in the world population. Some of the neurotoxic agents are being used in agriculture and household such as insecticides and rodenticides and others are of natural origin like snake and scorpion venoms. Additional group of harmful substances is the chemical warfare agents including nerve and blistering agents that are known for their disastrous effects on neuronal tissues. The present paper presents a combination of epidemiological/clinical and molecular approaches for investigating the effect of certain groups of neurotoxicants on a variety of pathologies. The work of Finkelstein and coworkers describes epidemiological and clinical studies on acute and chronic organophosphate (OP)-induced neurotoxicity in certain populations in Israel. They mainly investigated the neurotoxic effects of low-level long-term exposure to OP in agricultural areas but also dealt with acute exposures as well. A molecular approach to OP mechanism of neuronal injury was described by Milatovic and coworkers. They demonstrated OP-induced oxidative injury in pyramidal neurons in the CA1 hippocampal area and its suppression by antioxidants. Lecht and coworkers described the novel snake venom angioneurins as important mediators of the physiological cross-talk between the cardiovascular and nervous systems. They also showed that under certain conditions these angioneurins may induce pathologies such as tumor development or disruption of the vascular barrier function during envenomation. Additional mechanistic/therapeutic approach was presented by Brodsky, Rosengarten, Proscura, Shapira and Wormser. They developed a novel anti-inflammatory peptide that reduced skin irritation induced by heat and sulfur mustard (SM) stimuli. Since SM causes neuropsychiatric symptoms and alterations in neurological functions this peptide may serve as a potential treatment of neuronal injuries caused by environmental neurotoxicants. These reviews highlight different aspects of neurotoxicity, addressing epidemiology and mechanisms of toxicity; and identifying novel potential therapies.

Olfactory ensheathing cells: attractant of neural progenitor migration to olfactory bulb

Olfactory ensheathing cells (OECs) are the glial cells that derive from the olfactory placode, envelop olfactory axons in the course of migration from the olfactory epithelium to the olfactory bulb and reside primarily in the olfactory nerve layer. OECs transplantation as a promising experimental therapy for axonal injuries has been intensively studied; however, little is known about their roles in olfactory bulb development. In this study, we examined the effects of OECs on the migration of neural progenitors in rostral migratory stream (RMS). Initially, the neurosphere migration assay showed that OEC-conditioned medium promoted progenitors to migrate from RMS neurospheres in a concentration dependent manner. Moreover, co-culturing OECs nearby the RMS explants led to asymmetric migration of explants in different developing stages. However, OECs could influence the migration in a distance not further than 1.5 mm. Finally, slice assay that mimic the circumstance in vivo revealed that OECs had a chemoattractive activity on RMS neural progenitors. Together, these results demonstrate that OECs attract neural progenitors in RMS through the release of diffusible factors and it is likely that OECs mainly influence radial migration in the olfactory bulb but not tangential migration of the RMS invivo during development. This suggests a previously unknown function for OECs in olfactory development and a novel mechanism underlying the targeting of RMS cells.

Transient signaling of Erk1/2, Akt and PLCgamma induced by nerve growth factor in brain capillary endothelial cells

Cumulative evidences suggest that nerve growth factor (NGF) promotes angiogenic effects such as proliferation and migration of endothelial cells (ECs) from different vascular beds, induces capillary sprouting in chorioallantoic membrane and improves in vivo vascularization in a hind-limb ischemic model. In the present study, we sought to investigate the signaling properties of NGF in a microcapillary ECs model compared to those of a neuronal model. NGF-induced phosphorylation of signaling molecules Erk1/2, Akt and PLCgamma were measured using Western blotting and compared between mouse NGF (mNGF) and snake venom NGF analogues. NGFs-induced signaling was TrkA mediated as evident by inhibition with the TrkA antagonist K252a. NGF and its analogues-induced signaling in ECs were characterized by a transient effect in contrast to a prolonged stimulation in neuronal cells. The potency of mouse, cobra and viper NGFs to induce Erk1/2 phosphorylation in ECs was higher than in neurons. In ECs, mNGF exhibited the highest efficacy of stimulation of Erk1/2 phosphorylation, followed by viper and cobra NGFs. The efficacy of stimulation of Erk1/2 phosphorylation measured with neurons was opposite from that in ECs. NGF-induced temporal signaling differences between ECs and neurons may explain the dual vascular and neurotrophic effects of this growth factor.

Nerve growth factor promotes cardiac repair following myocardial infarction

RATIONALE

Nerve growth factor (NGF) promotes angiogenesis and cardiomyocyte survival, which are both desirable for postinfarction myocardial healing. Nonetheless, the NGF potential for cardiac repair has never been investigated.

OBJECTIVE

To define expression and localization of NGF and its high-affinity receptor TrkA (tropomyosin-related receptor A) in the human infarcted heart and to investigate the cardiac roles of both endogenous and engineered NGF using a mouse model of myocardial infarction (MI).

METHODS AND RESULTS

Immunostaining for NGF and TrkA was performed on heart samples from humans deceased of MI or unrelated pathologies. To study the post-MI functions of endogenous NGF, a NGF-neutralizing antibody (Ab-NGF) or nonimmune IgG (control) was given to MI mice. To investigate the NGF therapeutic potential, human NGF gene or control (empty vector) was delivered to the murine periinfarct myocardium. Results indicate that NGF is present in the infarcted human heart. Both cardiomyocytes and endothelial cells (ECs) possess TrkA, which suggests NGF cardiovascular actions in humans. In MI mice, Ab-NGF abrogated native reparative angiogenesis, increased EC and cardiomyocyte apoptosis and worsened cardiac function. Conversely, NGF gene transfer ameliorated EC and cardiomyocyte survival, promoted neovascularization and improved myocardial blood flow and cardiac function. The prosurvival/proangiogenic Akt/Foxo pathway mediated the therapeutic benefits of NGF transfer. Moreover, NGF overexpression increased stem cell factor (the c-kit receptor ligand) expression, which translated in higher myocardial abundance of c-kit(pos) progenitor cells in NGF-engineered hearts.

CONCLUSIONS

NGF elicits pleiotropic beneficial actions in the post-MI heart. NGF should be considered as a candidate for therapeutic cardiac regeneration.

Elevated glucose and fatty acid levels impair substance P-induced dermal microvascular endothelial cell migration and proliferation in an agarose gel model system

Substance P (SP), a sensory nerve derived neuropeptide, has been implicated in wound repair. Our hypothesis was that oxidative effects of elevated glucose and fatty acid levels as seen with diabetes mellitus inhibit SP-mediated endothelial cell directional migration and proliferation. Using a 2% agarose gel, immortalized human microvascular endothelial cells (HMEC-1) were plated into a 1.5-mm well, and agonist (SP; 10(-4) mol/L) was loaded into a 3-mm well; controls included NaCl, albumin (bovine serum albumin), and vascular endothelial cell growth factor. The SP receptor antagonist spantide 1 was used to confirm SP specificity. Elevated glucose (40 mmol/L) and fatty acids (40 micromol/L) were added to the medium with and without vitamin E and vitamin C treatment to determine whether endothelial cell responses to SP were altered by metabolic perturbations and whether they could be recovered with antioxidant treatment. Using computer-assisted image analysis, migration distance was measured. Cells were counted using a hemocytometer. Human microvascular endothelial cell 1 migration toward the SP exceeded NaCl or bovine serum albumin; vascular endothelial cell growth factor had similar effects. The SP receptor antagonist, spantide, inhibited SP-induced HMEC-1 migration. Substance P treatment was associated with increased cell number. Ki-67 staining was increased in SP-treated cells compared with controls. Elevated glucose and fatty acid levels diminished cell migration toward SP. The antioxidants vitamins C and E significantly improved proliferation but only marginally improved migration. Our data suggest that glucose and fatty acids perturb SP-induced HMEC-1 migration and proliferation in an agarose gel migration model.

Remodelling sympathetic innervation in rat pancreatic islets ontogeny

Background

Pancreatic islets are not fully developed at birth and it is not clear how they are vascularised and innervated. Nerve Growth Factor (NGF) is required to guide sympathetic neurons that innervate peripheral organs and also in cardiovascular system and ovary angiogenesis. Pancreatic beta cells of a transgenic mouse that over-expressed NGF in attracts sympathetic hyper-innervation towards them. Moreover, we have previously demonstrated that adult beta cells synthesize and secrete NGF; however, we do not know how is NGF secreted during development, nor if it might be trophic for sympathetic innervation and survival in the pancreas.

We analyzed sympathetic innervation and vasculature development in rat pancreatic islets at different developmental stages; foetal (F19), early postnatal (P1), weaning period (P20) and adults. We temporarily correlated these events to NGF secretion by islet cells.

Results

Sympathetic fibres reached pancreatic islets in the early postnatal period, apparently following blood vessels. The maximal number of sympathetic fibres (TH immunopositive) in the periphery of the islets was observed at P20, and then fibres entered the islets and reached the core where beta cells are mainly located. The number of fibres decreased from that stage to adulthood. At all stages studied, islet cells secreted NGF and also expressed the high affinity receptor TrkA. Foetal and neonatal isolated islet cells secreted more NGF than adults. TrkA receptors were expressed at all stages in pancreatic sympathetic fibres and blood vessels. These last structures were NGF–immunoreactive only at early stages (foetal and P0).

Conclusion

The results suggest that NGF signalling play an important role in the guidance of blood vessels and sympathetic fibres toward the islets during foetal and neonatal stages and could also preserve innervation at later stages of life.

Cardiovascular actions of neurotrophins

Neurotrophins were christened in consideration of their actions on the nervous system and, for a long time, they were the exclusive interest of neuroscientists. However, more recently, this family of proteins has been shown to possess essential cardiovascular functions. During cardiovascular development, neurotrophins and their receptors are essential factors in the formation of the heart and critical regulator of vascular development. Postnatally, neurotrophins control the survival of endothelial cells, vascular smooth muscle cells, and cardiomyocytes and regulate angiogenesis and vasculogenesis, by autocrine and paracrine mechanisms. Recent studies suggest the capacity of neurotrophins, via their tropomyosin-kinase receptors, to promote therapeutic neovascularization in animal models of hindlimb ischemia. Conversely, the neurotrophin low-affinity p75(NTR) receptor induces apoptosis of endothelial cells and vascular smooth muscle cells and impairs angiogenesis. Finally, nerve growth factor looks particularly promising in treating microvascular complications of diabetes or reducing cardiomyocyte apoptosis in the infarcted heart. These seminal discoveries have fuelled basic and translational research and thus opened a new field of investigation in cardiovascular medicine and therapeutics. Here, we review recent progress on the molecular signaling and roles played by neurotrophins in cardiovascular development, function, and pathology, and we discuss therapeutic potential of strategies based on neurotrophin manipulation.

Role of the CXCR4/CXCL12 signaling axis in breast cancer metastasis to the brain

Breast cancer is the most common malignancy and second leading cause of cancer death in women. Ninety percent of mortality in breast cancer is often associated with metastatic progression or relapse in patients. Critical stages in the development of aggressive breast cancer include the growth of primary tumors and their ability to spread to foreign organs and form metastases, as well as the establishment of an independent blood supply within the new tumors. Hence, it is imperative to characterize the key molecules that regulate the metastasis of human breast cancer cells. The expression of CXCR4/CXCL12 in breast tumors has been correlated with a poor prognosis, increased metastasis, resistance to conventional therapeutic agents and a poor outcome in the pathogenesis of breast cancer. However, effective anti-CXCR4 therapy remains a challenge. Here, we will review the putative involvement of the CXCR4/CXCL12 signaling axis in breast cancer metastasis to the brain. Characterization of signaling events important for breast cancer cell growth and their metastasis to the brain should provide insights into breast cancer therapies and improved, successful treatments for breast cancer.

Differential effects of cyclic and static stretch on coronary microvascular endothelial cell receptors and vasculogenic/angiogenic responses

Mechanical stretch, an important growth stimulus, results not only from pulsatile blood flow and diastolic stretch of the ventricles [cyclic stretch (CS)] but also from tissue expansion during growth [constant static stretch (SS)]. We compared growth factor receptor expression and vasculogenic/angiogenic responses of rat coronary microvascular endothelial cells (ECs) by exposing cells to CS (10% elongation at 30 cycles/min) and SS (constant 10% elongation). Both CS and SS increased VEGF receptor (VEGF-R)2 protein levels and the extent of tube formation and branching. Moreover, both CS and SS enhanced VEGF-induced cell proliferation and tube formation, indicating that both types of stretch increase the sensitivity of ECs to VEGF. Blockade of VEGF-R2 prevented the increases in EC proliferation and aggregate tube length. However, CS but not SS enhanced EC Tie-2 protein and migration. CS affected a greater increase in tube length and branch formation than did SS. A unique finding was that SS but not CS increased VEGFR-1 in ECs. Our study is the first to distinguish between the effects of CS and SS on growth factor receptor expression and rat coronary microvascular EC proliferation, migration, and tube formation. In conclusion, EC angiogenic responses to these two types of stretch display both differences and similarities, but both CS and SS are dependent on VEGF-R2 signaling for their vasculogenic/angiogenic effects.

Intraventricular nerve growth factor infusion improves cerebral blood flow and stimulates doublecortin expression in two infants with hypoxic-ischemic brain injury

OBJECTIVE AND IMPORTANCE

Hypoxic-ischemic brain injuries in childhood are associated with poor neurological outcome. Recently, experimental and clinical works show that nerve growth factor (NGF) reduces neurological deficits and promotes endothelial cells proliferation and angiogenesis following hypoxic-ischemic brain injuries. After brain stroke, new neurons express a protein, called doublecortin (DCX), which indicates a new marker for neurogenesis and migrating neuroblasts. This study investigates the effects of intraventricular NGF administration in two infants with severe hypoxic-ischemic brain damage and its role in both the cerebral perfusion and neurogenesis.

CLINICAL PRESENTATION

Two infants, aged 8 and 13 months, with hypoxic-ischemic brain damage, secondary to prolonged cardiorespiratory arrest, were treated with intraventricular NGF administration. Before the therapy, both infants were comatose, aphasic and showed flaccid tetraparesis. After 1 month NGF treatment, their neurological conditions improved, electro-encephalography (EEG) examinations showed increased alpha/theta ratio, and single photon emission computed tomography (SPECT) works demonstrated a better cerebral perfusion. The DCX expression in the cerebrospinal fluid (CSF) increased concomitantly with increasing levels of NGF.

INTERVENTION

The drug utilized was 2.5S NGF purified and lyophilized from male mouse submaxillary glands. The NGF administration was started 4 months after ischemic brain injury. NGF (0.1 mg) was administered via the external drainage catheter into the right cerebral ventricle once a day for 10 consecutive days.

CONCLUSION

Our study shows that the intraventricular NGF administration improves the cerebral perfusion and stimulates the pathway of neurogenesis differentiation with the activation of DCX biosynthesis.

Experimental characterization and computational modelling of two-dimensional cell spreading for skeletal regeneration

Limited cell ingrowth is a major problem for tissue engineering and the clinical application of porous biomaterials as bone substitutes. As a first step, migration and proliferation of an interacting cell population can be studied in two-dimensional culture. Mathematical modelling is essential to generalize the results of these experiments and to derive the intrinsic parameters that can be used for predictions. However, a more thorough evaluation of theoretical models is hampered by limited experimental observations. In this study, experiments and image analysis methods were developed to provide a detailed spatial and temporal picture of how cell distributions evolve. These methods were used to quantify the migration and proliferation of skeletal cell types including MG63 and human bone marrow stromal cells (HBMSCs). The high level of detail with which the cell distributions were mapped enabled a precise assessment of the correspondence between experimental results and theoretical model predictions. This analysis revealed that the standard Fisher equation is appropriate for describing the migration behaviour of the HBMSC population, while for the MG63 cells a sharp front model is more appropriate. In combination with experiments, this type of mathematical model will prove useful in predicting cell ingrowth and improving strategies and control of skeletal tissue regeneration.

Microtopography and flow modulate the direction of endothelial cell migration

The migration of vascular endothelial cells under flow can be modulated by the addition of chemical or mechanical stimuli. The aim of this study was to investigate how topographic cues derived from a substrate containing three-dimensional microtopography interact with fluid shear stress in directing endothelial cell migration. Subconfluent bovine aortic endothelial cells were seeded on fibronectin-coated poly(dimethylsiloxane) substrates patterned with a combinatorial array of parallel and orthogonal microgrooves ranging from 2 to 5 microm in width at a constant depth of 1 microm. During a 4-h time-lapse observation in the absence of flow, the majority of the prealigned cells migrated parallel to the grooves with the distribution of their focal adhesions (FAs) depending on the groove width. No change in this migratory pattern was observed after the cells were exposed to moderate shear stress (13.5 dyn/cm(2)), irrespective of groove direction with respect to flow. After 4-h exposure to high shear stress (58 dyn/cm(2)) parallel to the grooves, the cells continued to migrate in the direction of both grooves and flow. By contrast, when microgrooves were oriented perpendicular to flow, most cells migrated orthogonal to the grooves and downstream with flow. Despite the change in the migration direction of the cells under high shear stress, most FAs and actin microfilaments maintained their original alignment parallel to the grooves, suggesting that topographic cues were more effective than those derived from shear stress in guiding the orientation of cytoskeletal and adhesion proteins during the initial exposure to flow.

Brain-derived neurotrophic factor: a newly described mediator of angiogenesis

Recent studies indicate that, in addition to its neuropoietic actions, brain derived neurotrophic factor (BDNF) promotes endothelial cell survival and induces neoangiogenesis in ischemic tissues. Unlike many vascular growth factors that act on many vascular beds, BDNF activity is relatively restricted to central arteries, vessels of cardiac and skeletal muscle, and skin. Studies of newly described biologic mediators that act on large-vessel and microvascular beds in these organs will help us to better understand organ-specific vascular development, as well as to develop novel therapeutic strategies to improve the condition of patients with cardiac and peripheral vascular disease. In this review, we summarize dual proangiogenic actions of BDNF, which, through local activation of TrkB receptor, expressed on a subpopulation of endothelial cells and, in addition, by recruitment of bone marrow-derived cells, contribute to neoangiogenesis.

NGF promotes microglial migration through the activation of its high affinity receptor: modulation by TGF-beta

Activation and mobilization of microglia are early events in the majority of brain pathologies. Among the signalling molecules that can affect microglial behaviour, we investigated whether nerve growth factor (NGF) was able to influence microglial motility. We found that NGF induced chemotaxis of microglial cells through the activation of TrkA receptor. In addition, NGF chemotactic activity was increased in the presence of low concentrations (< or =0.2 ng/ml) of transforming growth factor-beta (TGF-beta), which at this concentration showed chemotactic activity per se. On the contrary, NGF-induced microglial migration was reduced in the presence of chemokinetic concentration of TGF-beta (> or =2 ng/ml). Finally, both basal and NGF-induced migratory activity of microglial cells was increased after a long-term exposure of primary mixed glial cultures to 2 ng/ml of TGF-beta. Our observations suggest that both NGF and TGF-beta contribute to microglial recruitment. The chemotactic activities of these two pleiotropic factors could be particularly relevant during chronic diseases in which recruited microglia remove apoptotic neurons in the absence of a typical inflammatory reaction.