Neural driven angiogenesis by overexpression of nerve growth factor

TrkA+ Neurons Induce Pathologic Regeneration After Soft Tissue Trauma

Heterotopic ossification (HO) is a dynamic, complex pathologic process that often occurs after severe polytrauma trauma, resulting in an abnormal mesenchymal stem cell differentiation leading to ectopic bone growth in soft-tissues including tendons, ligaments, and muscles. The abnormal bone structure and location induce pain and loss of mobility. Recently, we observed that NGF (Nerve growth factor)-responsive TrkA (Tropomyosin receptor kinase A)-expressing nerves invade sites of soft-tissue trauma, and this is a necessary feature for heterotopic bone formation at sites of injury. Here, we assayed the effects of the partial TrkA agonist Gambogic amide (GA) in peritendinous heterotopic bone after extremity trauma. Mice underwent HO induction using the burn/tenotomy model with or without systemic treatment with GA, followed by an examination of the injury site via radiographic imaging, histology, and immunohistochemistry. Single-cell RNA Sequencing confirmed an increase in neurotrophin signaling activity after HO-inducing extremity trauma. Next, TrkA agonism led to injury site hyper-innervation, more brisk expression of cartilage antigens within the injured tendon, and a shift from FGF to TGFβ signaling activity among injury site cells. Nine weeks after injury, this culminated in higher overall levels of heterotopic bone among GA-treated animals. In summary, these studies further link injury site hyper-innervation with increased vascular ingrowth and ultimately heterotopic bone after trauma. In the future, modulation of TrkA signaling may represent a potent means to prevent the trauma-induced heterotopic bone formation and improve tissue regeneration.

H2O2-responsive VEGF/NGF gene co-delivery nano-system achieves stable vascularization in ischemic hindlimbs

Peripheral vascular disease (PVD) is a common clinical manifestation of atherosclerosis. Vascular endothelial growth factor (VEGF) gene therapy is a promising approach for PVD treatment. However, due to single-gene therapy limitations and high H₂O₂ pathological microenvironment, VEGF gene therapy are not as expectations and its clinical application are limited. Synergistic effects of Nerve factors and vascular factors in angiogenesis have attracted attention in recent years. In this study, VEGF and nerve growth factor (NGF) genes co-delivery nanoparticles (VEGF/NGF-NPs) were prepared by using H₂O₂ responsive 6s-PLGA-Po-PEG as a carrier. 6s-PLGA-Po-PEG could react with H₂O₂ specifically due to the internal peroxalate bond. Angiogenic effects of VEGF/NGF-NPs has been evaluated in cells and hindlimb ischemia mice model. Results showed that VEGF/NGF-NPs promoted VEGF and NGF co-expression simultaneously, eliminated excessive H₂O₂, strengthened reactions between SH-SY5Ys and HUVECs, and finally enhanced migration, tube formation, proliferation and H₂O₂ damage resistance of HUVECs. VEGF/NGF-NPs also recovered blood perfusion, promoted the expression of VEGF, NGF, eNOS and NO, and enhanced vascular coverage of pericytes. Treatment effects of VEGF/NGF-NPs may related to VEGF/eNOS/NO pathway. Altogether, VEGF/NGF-NPs eliminated excessive H₂O₂ while achieving gene co-delivery, and promoted stable angiogenesis. It’s a promising way for PVD treatment by using VEGF/NGF-NPs.

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.

Parasympathetic, but not sympathetic denervation, suppressed colorectal cancer progression

Disruption in the nerve-tumor interaction is now considered as a possible anticancer strategy for treating various cancer types, particularly colorectal cancer. However, the underlying mechanisms are not still fully understood. Therefore, the present study aimed to evaluate the effects of sympathetic and parasympathetic denervation on the inhibition of colorectal cancer progression in early and late phases and assess the involvement of nerve growth factor in denervation mediated anticancer effects. One-hundred and fifty male Wistar rats were assigned into 15 groups. Seven groups comprising the control group, 1,2-dimethylhydrazine (DMH) group, sympathetic denervation group (celiac-mesenteric ganglionectomy and guanethidine sulphate administration), parasympathetic denervation group (vagotomy and atropine administration), and combination group were used in the early-stage protocol. For the late-stage protocol, eight groups comprising the control, DMH, surgical and pharmacological sympathetic and parasympathetic denervation groups, combination group, and 5-flourouracil group were considered. After 8 weeks, sympathetic and parasympathetic denervation significantly reduced ACF numbers in rats receiving DMH. On the other hand, in the late stages, parasympathetic but not sympathetic denervation resulted in significant reductions in tumor incidence, tumor volume and weight, cell proliferation (indicated by reduced immunostaining of PCNA and ki-67), and angiogenesis (indicated by reduced immunostaining of CD31 and VEGF expression levels), and downregulated NGF, β2 adrenergic, and M3 receptors. It can be concluded that parasympathetic denervation may be of high importance in colon carcinogenesis and suggested as a possible therapeutic modality in late stages of colorectal cancer.

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.

Simultaneous fluorescence imaging of distinct nerve and blood vessel patterns in dual Thy1-YFP and Flt1-DsRed transgenic mice

Blood vessels and nerve tissues are critical to the development and functionality of many vital organs. However, little is currently known about their interdependency during development and after injury. In this study, dual fluorescence transgenic reporter mice were utilized to observe blood vessels and nervous tissues in organs postnatally. Thy1-YFP and Flt1-DsRed (TYFD) mice were interbred to achieve dual fluorescence in the offspring, with Thy1-YFP yellow fluorescence expressed primarily in nerves, and Flt1-DsRed fluorescence expressed selectively in blood vessels. Using this dual fluorescent mouse strain, we were able to visualize the networks of nervous and vascular tissue simultaneously in various organ systems both in the physiological state and after injury. Using ex vivo high-resolution imaging in this dual fluorescent strain, we characterized the organizational patterns of both nervous and vascular systems in a diverse set of organs and tissues. In the cornea, we also observed the dynamic patterns of nerve and blood vessel networks following epithelial debridement injury. These findings highlight the versatility of this dual fluorescent strain for characterizing the relationship between nerve and blood vessel growth and organization.

Cross talk of vascular endothelial growth factor and neurotrophins in mammary gland development

During the period of lactation, there is extensive growth and development of the mammary gland in order to fulfil the increased demands of milk for the growing infant. Angiogenesis plays a key role in alveolar development and facilitates optimal milk production. Vascular endothelial growth factor (VEGF) is one of the key growth factors regulating angiogenesis in mammary gland. Apart from VEGF, neurotrophins are also known to regulate angiogenesis through direct or indirect mechanisms. Few studies have demonstrated mRNA levels of neurotrophins and their receptors in mammary gland both in humans and rodents. A cross talk between VEGF and neurotrophins has been described in placental development. The enteric and central nervous system are not fully developed at birth, making it imperative to have appropriate levels of angiogenic factors and neurotrophins during postnatal period. The current review summarises studies which describe the role of neurotrophins and angiogenic factors in the mammary gland development.

cAMP-inducible coactivator CRTC3 attenuates brown adipose tissue thermogenesis

In response to cold exposure, placental mammals maintain body temperature by increasing sympathetic nerve activity in brown adipose tissue (BAT). Triggering of β-adrenergic receptors on brown adipocytes stimulates thermogenesis via induction of the cAMP/PKA pathway. Although cAMP response element-binding protein (CREB) and its coactivators-the cAMP-regulated transcriptional coactivators (CRTCs)-mediate transcriptional effects of cAMP in most tissues, other transcription factors such as ATF2 appear critical for induction of thermogenic genes by cAMP in BAT. Brown adipocytes arise from Myf5-positive mesenchymal cells under the control of PRDM16, a coactivator that concurrently represses differentiation along the skeletal muscle lineage. Here, we show that the CREB coactivator CRTC3 is part of an inhibitory feedback pathway that antagonizes PRDM16-dependent differentiation. Mice with a knockout of CRTC3 in BAT (BKO) have increased cold tolerance and reduced adiposity, whereas mice overexpressing constitutively active CRTC3 in adipose tissue are more cold sensitive and have greater fat mass. CRTC3 reduced sympathetic nerve activity in BAT by up-regulating the expression of miR-206, a microRNA that promotes differentiation along the myogenic lineage and that we show here decreases the expression of VEGFA and neurotrophins critical for BAT innervation and vascularization. Sympathetic nerve activity to BAT was enhanced in BKO mice, leading to increases in catecholamine signaling that stimulated energy expenditure. As reexpression of miR-206 in BAT from BKO mice reversed the salutary effects of CRTC3 depletion on cold tolerance, our studies suggest that small-molecule inhibitors against this coactivator may provide therapeutic benefit to overweight individuals.

Proangiogenic features in chronic pelvic pain caused by adenomyosis

AIM

The study of peculiarities of expression of vascular endothelial growth factor (VEGF) in the tissues of the endometrium and myometrium in patients with adenomyosis, associated with chronic pelvic pain syndrome.

MATERIALS AND METHODS

Uterus macro-preparations obtained after hysterectomy in 60 patients with pelvic pain on a background of diffuse adenomyosis II-III degree were used for morphological examination, and macro-preparations received from 30 women with adenomyosis without pain syndrome. The diagnosis of adenomyosis was confirmed by sonography and magnetic resonance imaging. The expression of VEGF in tissues of the endometrium and myometrium was determined using the immune-histochemical method. The significance of differences of the compared parameters was determined using the criterion of Wilcoxon and Mann-Whitney. The differences were considered statistically significant when p < 0.05.

RESULTS

It was found that a higher expression of VEGF is characteristic for patients with pelvic pain associated with adenomyosis, compared to women with adenomyosis and abnormal uterine bleeding, both in epithelial cells of ectopic endometrium (14.7 ± 1.6% against 10.7 ± 1.6%, p < 0.01), and in smooth myocytes of the myometrium (12.6 ± 1.4% against 9.6 ± 1.2%, p < 0.01) and in the stromal cells of the myometrium (10.1 ± 1.9% versus 7.4 ± 1.8%, p < 0.01).

CONCLUSIONS

An increased expression of VEGF in the tissues of the uterus is one of the most important pathogenetic mechanisms of algogenesis with adenomyosis, associated syndrome of chronic pelvic pain, compared to the silent form of the disease.

A New Role for Browning as a Redox and Stress Adaptive Mechanism?

The worldwide epidemic of obesity and metabolic disorders is focusing the attention of the scientific community on white adipose tissue (WAT) and its biology. This tissue is characterized not only by its capability to change in size and shape but also by its heterogeneity and versatility. WAT can be converted into brown fat-like tissue according to different physiological and pathophysiological situations. The expression of uncoupling protein-1 in brown-like adipocytes changes their function from energy storage to energy dissipation. This plasticity, named browning, was recently rediscovered and convergent recent accounts, including in humans, have revived the idea of using these oxidative cells to fight against metabolic diseases. Furthermore, recent reports suggest that, beside the increased energy dissipation and thermogenesis that may have adverse effects in situations such as cancer-associated cachexia and massive burns, browning could be also considered as an adaptive stress response to high redox pressure and to major stress that could help to maintain tissue homeostasis and integrity. The aim of this review is to summarize the current knowledge concerning brown adipocytes and the browning process and also to explore unexpected putative role(s) for these cells. While it is important to find new browning inducers to limit energy stores and metabolic diseases, it also appears crucial to develop new browning inhibitors to limit adverse energy dissipation in wasting-associated syndromes.

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.

Peripheral changes in endometriosis-associated pain

BACKGROUND

Pain remains the cardinal symptom of endometriosis. However, to date, the underlying mechanisms are still only poorly understood. Increasing evidence points towards a close interaction between peripheral nerves, the peritoneal environment and the central nervous system in pain generation and processing. Recently, studies demonstrating nerve fibres and neurotrophic and angiogenic factors in endometriotic lesions and their vicinity have led to increased interest in peripheral changes in endometriosis-associated pain. This review focuses on the origin and function of these nerves and factors as well as possible peripheral mechanisms that may contribute to the generation and modulation of pain in women with endometriosis.

METHODS

We conducted a systematic search using several databases (PubMed, MEDLINE, EMBASE and CINAHL) of publications from January 1977 to October 2013 to evaluate the possible roles of the peripheral nervous system in endometriosis pathophysiology and how it can contribute to endometriosis-associated pain.

RESULTS

Endometriotic lesions and peritoneal fluid from women with endometriosis had pronounced neuroangiogenic properties with increased expression of new nerve fibres, a shift in the distribution of sensory and autonomic fibres in some locations, and up-regulation of several neurotrophins. In women suffering from deep infiltrating endometriosis and bowel endometriosis, in which the anatomical distribution of lesions is generally more closely related to pelvic pain symptoms, endometriotic lesions and surrounding tissues present higher nerve fibre densities compared with peritoneal lesions and endometriomas. More data are needed to fully confirm a direct correlation between fibre density in these locations and the amount of perceived pain. A better correlation between the presence of nerve fibres and pain symptoms seems to exist for eutopic endometrium. However, this appears not to be exclusive to endometriosis. No correlation between elevated neurotrophin levels and pain severity appears to exist, suggesting the involvement of other mediators in the modulation of pain.

CONCLUSIONS

The increased expression of neurotrophic factors and nerve fibres in endometriotic lesions, eutopic endometrium and the peritoneum imply a role of such peripheral changes in the pathogenesis of endometriosis-associated pain. However, a clear link between these findings and pain in patients with endometriosis has so far not been demonstrated.

Balanced levels of nerve growth factor are required for normal pregnancy progression

Nerve growth factor (NGF), the first identified member of the family of neurotrophins, is thought to play a critical role in the initiation of the decidual response in stress-challenged pregnant mice. However, the contribution of this pathway to physiological events during the establishment and maintenance of pregnancy remains largely elusive. Using NGF depletion and supplementation strategies alternatively, in this study, we demonstrated that a successful pregnancy is sensitive to disturbances in NGF levels in mice. Treatment with NGF further boosted fetal loss rates in the high-abortion rate CBA/J x DBA/2J mouse model by amplifying a local inflammatory response through recruitment of NGF-expressing immune cells, increased decidual innervation with substance P(+) nerve fibres and a Th1 cytokine shift. Similarly, treatment with a NGF-neutralising antibody in BALB/c-mated CBA/J mice, a normal-pregnancy model, also induced abortions associated with increased infiltration of tropomyosin kinase receptor A-expressing NK cells to the decidua. Importantly, in neither of the models, pregnancy loss was associated with defective ovarian function, angiogenesis or placental development. We further demonstrated that spontaneous abortion in humans is associated with up-regulated synthesis and an aberrant distribution of NGF in placental tissue. Thus, a local threshold of NGF expression seems to be necessary to ensure maternal tolerance in healthy pregnancies, but when surpassed may result in fetal rejection due to exacerbated inflammation.

Nerve growth factor in diabetic retinopathy: beyond neurons

Diabetic retinopathy (DR), a major ocular complication of diabetes, is a leading cause of blindness in US working age adults with limited treatments. Neurotrophins (NTs), a family of proteins essential for growth, differentiation and survival of retinal neurons, have emerged as potential players in the pathogenesis of DR. NTs can signal through their corresponding tropomyosin kinase related receptor to mediate cell survival or through the p75 neurotrophin receptor with the co-receptor, sortilin, to mediate cell death. This review focuses on the role of NGF, the first discovered NT, in the development of DR. Impaired processing of proNGF has been found in ocular fluids from diabetic patients as well as experimental models. Evidence from literature and our studies support the notion that NTs appear to play multiple potential roles in DR, hence, understanding their contribution to DR may lead to promising therapeutic approaches for this devastating disease.

Neurotrophic and metabotrophic potential of nerve growth factor and brain-derived neurotrophic factor: Linking cardiometabolic and neuropsychiatric diseases

One of biggest recent achievements of neurobiology is the study on neurotrophic factors. The neurotrophins are exciting examples of these factors. They belong to a family of proteins consisting of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), NT-4/5, NT-6, and NT-7. Today, NGF and BDNF are well recognized to mediate a dizzying number of trophobiological effects, ranging from neurotrophic through immunotrophic and epitheliotrophic to metabotrophic effects. These are implicated in the pathogenesis of various diseases. In the same vein, recent studies in adipobiology reveal that this tissue is the body’s largest endocrine and paracrine organ producing multiple signaling proteins collectively termed adipokines, with NGF and BDNF being also produced from adipose tissue. Altogether, neurobiology and adipobiology contribute to the improvement of our knowledge on diseases beyond obesity such as cardiometabolic (atherosclerosis, type 2 diabetes, and metabolic syndrome) and neuropsychiatric (e.g., Alzheimer’s disease and depression) diseases. The present review updates evidence for (1) neurotrophic and metabotrophic potentials of NGF and BDNF linking the pathogenesis of these diseases, and (2) NGF- and BDNF-mediated effects in ampakines, NMDA receptor antagonists, antidepressants, selective deacetylase inhibitors, statins, peroxisome proliferator-activated receptor gamma agonists, and purinergic P2X₃ receptor up-regulation. This may help to construct a novel paradigm in the field of translational pharmacology of neuro-metabotrophins, particularly NGF and BDNF.

Metabolic syndrome--from the neurotrophic hypothesis to a theory

Metabolic syndrome (MetS) is a complex and heterogeneous disease characterized by central obesity, impaired glucose metabolism, dyslipidemia, arterial hypertension, insulin resistance and high-sensitivity C-reactive protein. In 2006, a neurotrophic hypothesis of the etiopathogenesis of MetS was launched. This hypothesis considered the neurotrophins a key factor in MetS development. Chronic inflammatory and/or psychoemotional distress provoke a series of neuroimmunoendocrine interactions such as increased tissue and plasma levels of proinflammatory cytokines and neurotrophins, vegetodystonia, disbalance of neurotransmitters, hormones and immunity markers, activation of the hypothalamo-pituitary-adrenal axis, insulin resistance, and atherosclerosis. An early and a late clinical stage in the course of MetS are defined. Meanwhile, evidence of supporting results from the world literature accumulates. This enables the transformation of the definition of the neurotrophic hypothesis into a neurotrophic theory of MetS. The important role of two neurotrophic factors, i.e. the nerve growth factor and brain-derived neurotrophic factor as well as of the proinflammatory cytokines, neurotransmitters, adipokines and, especially, of leptin for the development of MetS, obesity and type 2 diabetes mellitus is illustrated. There are reliable scientific arguments that the metabotrophic deficit due to reduced neurotrophins could be implicated in the pathogenesis of MetS, type 2 diabetes mellitus, and atherosclerosis as well. A special attention is paid to the activity of the hypothalamo-pituitary-adrenal axis after stress. The application of the neurotrophic theory of MetS could contribute to the etiological diagnosis and individualized management of MetS by eliminating the chronic distress, hyponeurotrophinemia and consequent pathology. It helps estimating the risk, defining the prognosis and implementing the effective prevention of this socially significant disease as evidenced by the dramatic recent growth of the world publication output on this interdisciplinary topic.

Effect of antiangiogenic treatment on peritoneal endometriosis-associated nerve fibers

OBJECTIVE

To investigate the effect of antiangiogenic treatment on experimental endometriotic lesion nerve fibers.

DESIGN

Heterologous mouse model of endometriosis.

SETTING

University Institute IVI, University Hospital La Fe.

ANIMAL(S)

Ovariectomized nude mice (n = 16) receiving human endometrial fragments from oocyte donors (n = 4).

INTERVENTION(S)

Endometrium fragments stuck in the peritoneum of 5-week-old female nude mice treated with vehicle (n = 8) and antiangiogenic agent cabergoline (n = 8; Cb(2,) 0.05 mg/kg/day) for 14 days.

MAIN OUTCOME MEASURE(S)

Immunofluorescence analysis of von-Willebrand factor (vWF) and vascular smooth muscle cells (αSMA) for evaluating the number of immature blood vessels (IBV) and microvascular density (MVD); immunochemical analysis of protein-gene product 9.5 (PGP 9.5) to assess nerve fibers density (NFD), and blue toluidine staining to confirm presence of mast cells and macrophages in endometriotic lesions.

RESULT(S)

All the results were quantified by morphometric techniques. The IBV, NFD, and number of macrophages and mast cells were statistically significantly decreased in the Cb2-treated group when compared with controls.

CONCLUSION(S)

Antiangiogenic treatment statistically significantly diminishes new blood vessel formation after macrophage, mast cell, and nerve fiber reduction, providing a rationale to test antiangiogenic agents as a novel therapeutic approach to severe pelvic pain associated with human peritoneal endometriosis.

Regenerative therapies for diabetic microangiopathy

Hyperglycaemia occurring in diabetes is responsible for accelerated arterial remodeling and atherosclerosis, affecting the macro- and the microcirculatory system. Vessel injury is mainly related to deregulation of glucose homeostasis and insulin/insulin-precursors production, generation of advanced glycation end-products, reduction in nitric oxide synthesis, and oxidative and reductive stress. It occurs both at extracellular level with increased calcium and matrix proteins deposition and at intracellular level, with abnormalities of intracellular pathways and increased cell death. Peripheral arterial disease, coronary heart disease, and ischemic stroke are the main causes of morbidity/mortality in diabetic patients representing a major clinical and economic issue. Pharmacological therapies, administration of growth factors, and stem cellular strategies are the most effective approaches and will be discussed in depth in this comprehensive review covering the regenerative therapies of diabetic microangiopathy.

Paracrine control of vascular innervation in health and disease

Proper vascular regulation is of paramount importance for the control of blood flow to tissues. In particular, the regulation of peripheral resistance arteries is essential for several physiological processes, including control of blood pressure, thermoregulation and increase of blood flow to central nervous system and heart under stress conditions such as hypoxia. Arterial tone is regulated by the periarterial autonomic nervous plexus, as well as by endothelium-dependent, myogenic and humoral mechanisms. Underscoring the importance of proper vascular regulation, defects in these processes can lead to diseases such as hypertension, orthostatic hypotension, Raynaud's phenomenon, defective thermoregulation, hand-foot syndrome, migraine and congestive heart failure. Here, we review the molecular mechanisms controlling the development of the periarterial nerve plexus, retrograde and localized signalling at neuro-effector junctions, the molecular and cellular mechanisms of vascular regulation and adult plasticity and maintenance of periarterial innervation. We particularly highlight a newly discovered role for vascular endothelial growth factor in the structural and functional maintenance of arterial neuro-effector junctions. Finally, we discuss how defects in neuronal vascular regulation can lead to disease.

Nerve growth factor promotes breast cancer angiogenesis by activating multiple pathways

Background

Although several anti-angiogenic therapies have been approved in the treatment of cancer, the survival benefits of such therapies are relatively modest. Discovering new molecules and/or better understating signaling pathways of angiogenesis is therefore essential for therapeutic improvements. The objective of the present study was to determine the involvement of nerve growth factor (NGF) in breast cancer angiogenesis and the underlying molecular mechanisms.

Results

We showed that both recombinant NGF and NGF produced by breast cancer cells stimulated angiogenesis in Matrigel plugs in immunodeficient mice. NGF strongly increased invasion, cord formation and the monolayer permeability of endothelial cells. Moreover, NGF-stimulated invasion was under the control of its tyrosine kinase receptor (TrkA) and downstream signaling pathways such as PI3K and ERK, leading to the activation of matrix metalloprotease 2 and nitric oxide synthase. Interestingly, NGF increased the secretion of VEGF in both endothelial and breast cancer cells. Inhibition of VEGF, with a neutralizing antibody, reduced about half of NGF-induced endothelial cell invasion and angiogenesis in vivo.

Conclusions

Our findings provided direct evidence that NGF could be an important stimulator for breast cancer angiogenesis. Thus, NGF, as well as the activated signaling pathways, should be regarded as potential new targets for anti-angiogenic therapy against breast cancer.

Endothelial progenitor cells (EPCs) mobilized and activated by neurotrophic factors may contribute to pathologic neovascularization in diabetic retinopathy

Diabetic retinopathy is characterized by pathological retinal neovascularization. Accumulating evidence has indicated that high levels of circulating endothelial progenitor cells (EPCs) are an important risk factor for neovascularization. Paradoxically, the reduction and dysfunction of circulating EPCs has been extensively reported in diabetic patients. We hypothesized that EPCs are differentially altered in the various vasculopathic complications of diabetes mellitus, exhibiting distinct behaviors in terms of angiogenic response to ischemia and growth factors and potentially playing a potent role in motivating vascular precursors to induce pathological neovascularization. Circulating levels of EPCs from diabetic retinopathy patients were analyzed by flow cytometry and by counting EPC colony-forming units, and serum levels of neurotrophic factors were measured by enzyme-linked immunosorbent assay. We found increased levels of nerve growth factor and brain-derived neurotrophic factor in the blood of diabetic retinopathy patients; this increase was correlated with the levels of circulating EPCs. In addition, we demonstrated that retinal cells released neurotrophic factors under hypoxic conditions to enhance EPC activity in vitro and to increase angiogenesis in a mouse ischemic hindlimb model. These results suggest that neurotrophic factors may induce neoangiogenesis through EPC activation, leading to the pathological retinal neovascularization. Thus, we propose that neovascularization in the ischemic retina might be regulated by overexpression of neurotrophic factors.

Brain angiogenesis in developmental and pathological processes: regulation, molecular and cellular communication at the neurovascular interface

The vascular network of the brain is formed by the invasion of vascular sprouts from the pia mater toward the ventricles. Following angiogenesis of the primary vascular network, brain vessels experience a maturation process known as barriergenesis, in which the blood-brain barrier is formed. In this minireview, we discuss the processes of brain angiogenesis and barriergenesis, as well as the molecular and cellular mechanisms underlying brain vessel formation. At the molecular level, angiogenesis and barriergenesis occur via the coordinated action of oxygen-responsive molecules (e.g. hypoxia-inducible factor and Src-suppressed C kinase substrate/AKAP12) and soluble factors (e.g. vascular endothelial growth factor and angiopoietin-1), as well as axon guidance molecules and neurotrophic factors. At the cellular level, we focus on neurovascular cells, such as pericytes, astrocytes, vascular smooth muscle cells, neurons and brain macrophages. Each cell type plays a unique role, and works with other types to maintain environmental homeostasis and to respond to certain stimuli. Taken together, this minireview emphasizes the importance of the coordinated action of molecules and cells at the neurovascular interface, with regards to the regulation of angiogenesis and barriergenesis.

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.

Injury-induced changes in mRNA levels differ widely between anterior cruciate ligament and medial collateral ligament

BACKGROUND

The drastic difference in healing capacity between the anterior cruciate ligament and the medial collateral ligament is still largely unexplained. Few studies have compared the profiles of messenger ribonucleic acid expression for healing-associated molecules in ligaments during the course of healing.

HYPOTHESIS

Injury responses of the injured anterior cruciate ligament and medial collateral ligament are characterized by very different profiles of angiogenesis-promoting and repair-associated gene expression during the healing process.

STUDY DESIGN

Controlled laboratory study.

METHODS

Reverse-transcriptase polymerase chain reaction was used to assay expression of messenger ribonucleic acid for 11 healing- and angiogenesis-associated molecules at 3 days and 2, 6, and 16 weeks after anterior cruciate ligament or medial collateral ligament injury in adult female New Zealand White rabbits.

RESULTS

Marked differences were found in the postinjury changes in messenger ribonucleic acid levels in the anterior cruciate ligament compared to the medial collateral ligament. Notably, messenger ribonucleic acid levels for the important repair-associated growth factor transforming growth factor-beta1 did not increase in injured anterior cruciate ligament at any time point. Similarly, unlike the injured medial collateral ligament, no statistically significant increases in messenger ribonucleic acid levels for the important scar matrix protein collagen III were detected in injured anterior cruciate ligament. In contrast, matrix metalloproteinase messenger ribonucleic acid levels were markedly elevated in injured anterior cruciate ligament but only modestly increased in medial collateral ligament.

CONCLUSION

The results suggest that injury leads to an antifibrotic, catabolic response in the rabbit anterior cruciate ligament, possibly to prevent fibrosis and diminish the risk for loss of joint motion.

CLINICAL RELEVANCE

The development of effective biologically based treatments for anterior cruciate ligament injuries will need to incorporate strategies to deal with the significant differences in the molecular responses to injury of these tissues.

Recent progress in histochemistry

The progress in discerning the structure and function of cells and tissues in health and disease has been achieved to a large extent by the continued development of new reagents for histochemistry, the improvement of existing techniques and new imaging techniques. This review will highlight some advancements made in these fields.

Nerve growth factor as an angiogenic factor

Nerve growth factor (NGF), a neurotrophin that plays a crucial role in promoting neurotrophic and neurotropic effects in sympathetic neurons, has recently been identified as a novel angiogenic molecule, which exerts a variety of effects in the cardiovascular system and on endothelial cells. In fact, NGF may contribute to maintenance, survival, and function of endothelial cells by autocrine and/or paracrine mechanisms. This review summarizes the involvement of NGF in the regulation of angiogenesis in both normal and pathological conditions.

Up-regulation of VEGF expression by NGF that enhances reparative angiogenesis during thymic regeneration in adult rat

Angiogenesis is important for adult tissue regeneration as well as normal development. Vascular endothelial growth factor (VEGF) is a unique potent angiogenic factor, and plays an essential role in regulating angiogenesis during embryonic development, normal tissue growth, and tissue regeneration. Recent evidence shows that nerve growth factor (NGF) also plays a role as an angiogenic regulator as well as a well-known neurotrophic factor. The aim of this study was to investigate whether thymus regeneration accompanies reparative angiogenesis and also to evaluate whether the thymic expression of VEGF is regulated by NGF in vivo and in vitro. Here, we show that high VEGF mRNA and protein levels are concomitant with reparative angiogenesis that occurs dramatically during regeneration following acute involution induced by cyclophosphamide (CY) in the rat thymus. Fluorescent thymus angiography using FITC-dextran showed that thymic regeneration is associated with a much denser capillary network compared with normal control thymus. Furthermore, the expressions of NGF and TrkA were highly increased during thymic regeneration. We also show that NGF mediates thymic epithelial induction of VEGF expression in vitro and in vivo. Taken together, our results suggest that NGF-mediated VEGF up-regulation in thymic epithelial cells may contribute to reparative angiogenesis during thymic regeneration in adult.

The histochemistry and cell biology vade mecum: a review of 2005–2006

The procurement of new knowledge and understanding in the ever expanding discipline of cell biology continues to advance at a breakneck pace. The progress in discerning the physiology of cells and tissues in health and disease has been driven to a large extent by the continued development of new probes and imaging techniques. The recent introduction of semi-conductor quantum dots as stable, specific markers for both fluorescence light microscopy and electron microscopy, as well as a virtual treasure-trove of new fluorescent proteins, has in conjunction with newly introduced spectral imaging systems, opened vistas into the seemingly unlimited possibilities for experimental design. Although it oftentimes proves difficult to predict what the future will hold with respect to advances in disciplines such as cell biology and histochemistry, it is facile to look back on what has already occurred. In this spirit, this review will highlight some advancements made in these areas in the past 2 years.