VEGF and ALS

The Ambiguous Role of Growth Factors in Autism: What Do We Really Know?

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition with multifactorial origins, including the potential involvement of neurotrophins and growth factors. These molecules, which are crucial for neuronal survival, synaptic plasticity, and brain development, have been implicated in ASD pathophysiology. Altered levels of neurotrophins such as NGF, BDNF, NT3, and NT4, as well as growth factors like IGF1, VEGF, and FGF, have been associated with cognitive deficits, sensory processing abnormalities, and behavioral issues in ASD patients. However, the literature presents conflicting results, often due to differences in research methodologies, sample sizes, patient populations, and diagnostic criteria. Despite these inconsistencies, the potential of neurotrophins and growth factors as biomarkers and therapeutic targets for ASD remains promising. Future research with standardized methodologies, larger cohorts, and a clearer understanding of genetic influences is needed to further elucidate their roles in ASD diagnosis and treatment.

VEGF expression disparities in brainstem motor neurons of the SOD1G93A ALS model: Correlations with neuronal vulnerability

Amyotrophic lateral sclerosis (ALS) is a rare neuromuscular disease characterized by severe muscle weakness mainly due to degeneration and death of motor neurons. A peculiarity of the neurodegenerative processes is the variable susceptibility among distinct neuronal populations, exemplified by the contrasting resilience of motor neurons innervating the ocular motor system and the more vulnerable facial and hypoglossal motor neurons. The crucial role of vascular endothelial growth factor (VEGF) as a neuroprotective factor in the nervous system is well-established since a deficit of VEGF has been related to motoneuronal degeneration. In this study, we investigated the survival of ocular, facial, and hypoglossal motor neurons utilizing the murine SOD1G93A ALS model at various stages of the disease. Our primary objective was to determine whether the survival of the different brainstem motor neurons was linked to disparate VEGF expression levels in resilient and susceptible motor neurons throughout neurodegeneration. Our findings revealed a selective loss of motor neurons exclusively within the vulnerable nuclei. Furthermore, a significantly higher level of VEGF was detected in the more resistant motor neurons, the extraocular ones. We also examined whether TDP-43 dynamics in the brainstem motor neuron of SOD mice was altered. Our data suggests that the increased VEGF levels observed in extraocular motor neurons may potentially underlie their resistance during the neurodegenerative processes in ALS in a TDP-43-independent manner. Our work might help to better understand the underlying mechanisms of selective vulnerability of motor neurons in ALS.

A Biosafety Study of Human Umbilical Cord Blood Mononuclear Cells Transduced with Adenoviral Vector Carrying Human Vascular Endothelial Growth Factor cDNA In Vitro

The biosafety of gene therapy remains a crucial issue for both the direct and cell-mediated delivery of recombinant cDNA encoding biologically active molecules for the pathogenetic correction of congenital or acquired disorders. The diversity of vector systems and cell carriers for the delivery of therapeutic genes revealed the difficulty of developing and implementing a safe and effective drug containing artificial genetic material for the treatment of human diseases in practical medicine. Therefore, in this study we assessed changes in the transcriptome and secretome of umbilical cord blood mononuclear cells (UCB-MCs) genetically modified using adenoviral vector (Ad5) carrying cDNA encoding human vascular endothelial growth factor (VEGF165) or reporter green fluorescent protein (GFP). A preliminary analysis of UCB-MCs transduced with Ad5-VEGF165 and Ad5-GFP with MOI of 10 showed efficient transgene expression in gene-modified UCB-MCs at mRNA and protein levels. The whole transcriptome sequencing of native UCB-MCs, UCB-MC+Ad5-VEGF165, and UCB-MC+Ad5-GFP demonstrated individual sample variability rather than the effect of Ad5 or the expression of recombinant vegf165 on UCB-MC transcriptomes. A multiplex secretome analysis indicated that neither the transduction of UCB-MCs with Ad5-GFP nor with Ad5-VEGF165 affects the secretion of the studied cytokines, chemokines, and growth factors by gene-modified cells. Here, we show that UCB-MCs transduced with Ad5 carrying cDNA encoding human VEGF165 efficiently express transgenes and preserve transcriptome and secretome patterns. This data demonstrates the biosafety of using UCB-MCs as cell carriers of therapeutic genes.

Neuroprotective Effect of Vascular Endothelial Growth Factor on Motoneurons of the Oculomotor System

Vascular endothelial growth factor (VEGF) was initially characterized as a potent angiogenic factor based on its activity on the vascular system. However, it is now well established that VEGF also plays a crucial role as a neuroprotective factor in the nervous system. A deficit of VEGF has been related to motoneuronal degeneration, such as that occurring in amyotrophic lateral sclerosis (ALS). Strikingly, motoneurons of the oculomotor system show lesser vulnerability to neurodegeneration in ALS compared to other motoneurons. These motoneurons presented higher amounts of VEGF and its receptor Flk-1 than other brainstem pools. That higher VEGF level could be due to an enhanced retrograde input from their target muscles, but it can also be produced by the motoneurons themselves and act in an autocrine way. By contrast, VEGF’s paracrine supply from the vicinity cells, such as glial cells, seems to represent a minor source of VEGF for brainstem motoneurons. In addition, ocular motoneurons experiment an increase in VEGF and Flk-1 level in response to axotomy, not observed in facial or hypoglossal motoneurons. Therefore, in this review, we summarize the differences in VEGF availability that could contribute to the higher resistance of extraocular motoneurons to injury and neurodegenerative diseases.

Epidural Stimulation Combined with Triple Gene Therapy for Spinal Cord Injury Treatment

The translation of new therapies for spinal cord injury to clinical trials can be facilitated with large animal models close in morpho-physiological scale to humans. Here, we report functional restoration and morphological reorganization after spinal contusion in pigs, following a combined treatment of locomotor training facilitated with epidural electrical stimulation (EES) and cell-mediated triple gene therapy with umbilical cord blood mononuclear cells overexpressing recombinant vascular endothelial growth factor, glial-derived neurotrophic factor, and neural cell adhesion molecule. Preliminary results obtained on a small sample of pigs 2 months after spinal contusion revealed the difference in post-traumatic spinal cord outcomes in control and treated animals. In treated pigs, motor performance was enabled by EES and the corresponding morpho-functional changes in hind limb skeletal muscles were accompanied by the reorganization of the glial cell, the reaction of stress cell, and synaptic proteins. Our data demonstrate effects of combined EES-facilitated motor training and cell-mediated triple gene therapy after spinal contusion in large animals, informing a background for further animal studies and clinical translation.

Sources and lesion-induced changes of VEGF expression in brainstem motoneurons

Motoneurons of the oculomotor system show lesser vulnerability to neurodegeneration compared to other cranial motoneurons, as seen in amyotrophic lateral sclerosis (ALS). The overexpression of vascular endothelial growth factor (VEGF) is involved in motoneuronal protection. As previously shown, motoneurons innervating extraocular muscles present a higher amount of VEGF and its receptor Flk-1 compared to facial or hypoglossal motoneurons. Therefore, we aimed to study the possible sources of VEGF to brainstem motoneurons, such as glial cells and target muscles. We also studied the regulation of VEGF in response to axotomy in ocular, facial, and hypoglossal motor nuclei. Basal VEGF expression in astrocytes and microglial cells of the cranial motor nuclei was low. Although the presence of VEGF in the different target muscles for brainstem motoneurons was similar, the presynaptic element of the ocular neuromuscular junction showed higher amounts of Flk-1, which could result in greater efficiency in the capture of the factor by oculomotor neurons. Seven days after axotomy, a clear glial reaction was observed in all the brainstem nuclei, but the levels of the neurotrophic factor remained low in glial cells. Only the injured motoneurons of the oculomotor system showed an increase in VEGF and Flk-1, but such an increase was not detected in axotomized facial or hypoglossal motoneurons. Taken together, our findings suggest that the ocular motoneurons themselves upregulate VEGF expression in response to lesion. In conclusion, the low VEGF expression observed in glial cells suggests that these cells are not the main source of VEGF for brainstem motoneurons. Therefore, the higher VEGF expression observed in motoneurons innervating extraocular muscles is likely due either to the fact that this factor is more avidly taken up from the target muscles, in basal conditions, or is produced by these motoneurons themselves, and acts in an autocrine manner after axotomy.

Vascular Endothelial Growth Factor (VEGF) Prevents the Downregulation of the Cholinergic Phenotype in Axotomized Motoneurons of the Adult Rat

Vascular endothelial growth factor (VEGF) was initially characterized by its activity on the vascular system. However, there is growing evidence indicating that VEGF also acts as a neuroprotective factor, and that its administration to neurons suffering from trauma or disease is able to rescue them from cell death. We questioned whether VEGF could also maintain damaged neurons in a neurotransmissive mode by evaluating the synthesis of their neurotransmitter, and whether its action would be direct or through its well-known angiogenic activity. Adult rat extraocular motoneurons were chosen as the experimental model. Lesion was performed by monocular enucleation and immediately a gelatine sponge soaked in VEGF was implanted intraorbitally. After 7 days, abducens, trochlear, and oculomotor nuclei were examined by immunohistochemistry against choline acetyltransferase (ChAT), the biosynthetic enzyme of the motoneuronal neurotransmitter acetylcholine. Lesioned motoneurons exhibited a noticeable ChAT downregulation which was prevented by VEGF administration. To explore whether this action was mediated via an increase in blood vessels or in their permeability, we performed immunohistochemistry against laminin, glucose transporter-1 and the plasmatic protein albumin. The quantification of the immunolabeling intensity against these three proteins showed no significant differences between VEGF-treated, axotomized and control animals. Therefore, the present data indicate that VEGF is able to sustain the cholinergic phenotype in damaged motoneurons, which is a first step for adequate neuromuscular neurotransmission, and that this action seems to be mediated directly on neurons since no sign of angiogenic activity was evident. These data reinforces the therapeutical potential of VEGF in motoneuronal diseases.

Synaptic loss and firing alterations in Axotomized Motoneurons are restored by vascular endothelial growth factor (VEGF) and VEGF-B

Vascular endothelial growth factor (VEGF), also known as VEGF-A, was discovered due to its vasculogenic and angiogenic activity, but a neuroprotective role for VEGF was later proven for lesions and disorders. In different models of motoneuronal degeneration, VEGF administration leads to a significant reduction of motoneuronal death. However, there is no information about the physiological state of spared motoneurons. We examined the trophic role of VEGF on axotomized motoneurons with recordings in alert animals using the oculomotor system as the experimental model, complemented with a synaptic study at the confocal microscopy level. Axotomy leads to drastic alterations in the discharge characteristics of abducens motoneurons, as well as to a substantial loss of their synaptic inputs. Retrograde delivery of VEGF completely restored the discharge activity and synaptically-driven signals in injured motoneurons, as demonstrated by correlating motoneuronal firing rate with motor performance. Moreover, VEGF-treated motoneurons recovered a normal density of synaptic boutons around motoneuronal somata and in the neuropil, in contrast to the low levels of synaptic terminals found after axotomy. VEGF also reduced the astrogliosis induced by axotomy in the abducens nucleus to control values. The administration of VEGF-B produced results similar to those of VEGF. This is the first work demonstrating that VEGF and VEGF-B restore the normal operating mode and synaptic inputs on injured motoneurons. Altogether these data indicate that these molecules are relevant synaptotrophic factors for motoneurons and support their clinical potential for the treatment of motoneuronal disorders.

Extraocular motoneurons of the adult rat show higher levels of vascular endothelial growth factor and its receptor Flk-1 than other cranial motoneurons

Recent studies show a relationship between the deficit of vascular endothelial growth factor (VEGF) and motoneuronal degeneration, such as that occurring in amyotrophic lateral sclerosis (ALS). VEGF delivery protects motoneurons from cell death and delayed neurodegeneration in animal models of ALS. Strikingly, extraocular motoneurons show lesser vulnerability to neurodegeneration in ALS compared to other cranial or spinal motoneurons. Therefore, the present study investigates possible differences in VEGF and its main receptor VEGFR-2 or Flk-1 between extraocular and non-extraocular brainstem motoneurons. We performed immunohistochemistry and Western blot to determine the presence of VEGF and Flk-1 in rat motoneurons located in the three extraocular motor nuclei (abducens, trochlear and oculomotor) and to compare it to that observed in two other brainstem nuclei (hypoglossal and facial) that are vulnerable to degeneration. Extraocular motoneurons presented higher amounts of VEGF and its receptor Flk-1 than other brainstem motoneurons, and thus these molecules could be participating in their higher resistance to neurodegeneration. In conclusion, we hypothesize that differences in VEGF availability and signaling could be a contributing factor to the different susceptibility of extraocular motoneurons, when compared with other motoneurons, in neurodegenerative diseases.

State of the field: An informatics-based systematic review of the SOD1-G93A amyotrophic lateral sclerosis transgenic mouse model

Numerous sub-cellular through system-level disturbances have been identified in over 1300 articles examining the superoxide dismutase-1 guanine 93 to alanine (SOD1-G93A) transgenic mouse amyotrophic lateral sclerosis (ALS) pathophysiology. Manual assessment of such a broad literature base is daunting. We performed a comprehensive informatics-based systematic review or 'field analysis' to agnostically compute and map the current state of the field. Text mining of recaptured articles was used to quantify published data topic breadth and frequency. We constructed a nine-category pathophysiological function-based ontology to systematically organize and quantify the field's primary data. Results demonstrated that the distribution of primary research belonging to each category is: systemic measures an motor function, 59%; inflammation, 46%; cellular energetics, 37%; proteomics, 31%; neural excitability, 22%; apoptosis, 20%; oxidative stress, 18%; aberrant cellular chemistry, 14%; axonal transport, 10%. We constructed a SOD1-G93A field map that visually illustrates and categorizes the 85% most frequently assessed sub-topics. Finally, we present the literature-cited significance of frequently published terms and uncover thinly investigated areas. In conclusion, most articles individually examine at least two categories, which is indicative of the numerous underlying pathophysiological interrelationships. An essential future path is examination of cross-category pathophysiological interrelationships and their co-correspondence to homeostatic regulation and disease progression.

Neural progenitor cell implants in the lesioned medial longitudinal fascicle of adult cats regulate synaptic composition and firing properties of abducens internuclear neurons

Transplants of neural progenitor cells (NPCs) into the injured CNS have been proposed as a powerful tool for brain repair, but, to date, few studies on the physiological response of host neurons have been reported. Therefore, we explored the effects of NPC implants on the discharge characteristics and synaptology of axotomized abducens internuclear neurons, which mediate gaze conjugacy for horizontal eye movements. NPCs were isolated from the subventricular zone of neonatal cats and implanted at the site of transection in the medial longitudinal fascicle of adult cats. Abducens internuclear neurons of host animals showed a complete restoration of axotomy-induced alterations in eye position sensitivity, but eye velocity sensitivity was only partially regained. Analysis of the inhibitory and excitatory components of the discharge revealed a normal re-establishment of inhibitory inputs, but only partial re-establishment of excitatory inputs. Moreover, their inhibitory terminal coverage was similar to that in controls, indicating that there was ultimately no loss of inhibitory synaptic inputs. Somatic coverage by synaptophysin-positive contacts, however, showed intermediate values between control animals and animals that had undergone axotomy, likely due to partial loss of excitatory inputs. We also demonstrated that severed axons synaptically contacted NPCs, most of which were VEGF immunopositive, and that abducens internuclear neurons expressed the VEGF receptor Flk1. Together, our results suggest that VEGF neurotrophic support might underlie the increased inhibitory-to-excitatory balance observed in the postimplant cells. The noteworthy improvement of firing properties of injured neurons following NPC implants indicates that these cells might provide a promising therapeutic strategy after neuronal lesions.

Roles of vascular endothelial growth factor in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal devastating neurodegenerative disorder, involving progressive degeneration of motor neurons in spinal cord, brainstem, and motor cortex. Riluzole is the only drug approved in ALS but it only confers a modest improvement in survival. In spite of a high number of clinical trials no other drug has proved effectiveness. Recent studies support that vascular endothelial growth factor (VEGF), originally described as a key angiogenic factor, also plays a key role in the nervous system, including neurogenesis, neuronal survival, neuronal migration, and axon guidance. VEGF has been used in exploratory clinical studies with promising results in ALS and other neurological disorders. Although VEGF is a very promising compound, translating the basic science breakthroughs into clinical practice is the major challenge ahead. VEGF-B, presenting a single safety profile, protects motor neurons from degeneration in ALS animal models and, therefore, it will be particularly interesting to test its effects in ALS patients. In the present paper the authors make a brief description of the molecular properties of VEGF and its receptors and review its different features and therapeutic potential in the nervous system/neurodegenerative disease, particularly in ALS.

scAAV9 intracisternal delivery results in efficient gene transfer to the central nervous system of a feline model of motor neuron disease

On the basis of previous studies suggesting that vascular endothelial growth factor (VEGF) could protect motor neurons from degeneration, adeno-associated virus vectors (serotypes 1 and 9) encoding VEGF (AAV.vegf) were administered in a limb-expression 1 (LIX1)-deficient cat-a large animal model of lower motor neuron disease-using three different delivery routes to the central nervous system. AAV.vegf vectors were injected into the motor cortex via intracerebral administration, into the cisterna magna, or intravenously in young adult cats. Intracerebral injections resulted in detectable transgene DNA and transcripts throughout the spinal cord, confirming anterograde transport of AAV via the corticospinal pathway. However, such strategy led to low levels of VEGF expression in the spinal cord. Similar AAV doses injected intravenously resulted also in poor spinal cord transduction. In contrast, intracisternal delivery of AAV exhibited long-term transduction and high levels of VEGF expression in the entire spinal cord, yet with no detectable therapeutic clinical benefit in LIX1-deficient animals. Altogether, we demonstrate (i) that intracisternal delivery is an effective AAV delivery route resulting in high transduction of the entire spinal cord, associated with little to no off-target gene expression, and (ii) that in a LIX1-deficient cat model, however, VEGF expressed at high levels in the spinal cord has no beneficial impact on the disease course.

Clinical perspective on oxidative stress in sporadic amyotrophic lateral sclerosis

Sporadic amyotrophic lateral sclerosis (ALS) is one of the most devastating neurological diseases; most patients die within 3 to 4 years after symptom onset. Oxidative stress is a disturbance in the pro-oxidative/antioxidative balance favoring the pro-oxidative state. Autopsy and laboratory studies in ALS indicate that oxidative stress plays a major role in motor neuron degeneration and astrocyte dysfunction. Oxidative stress biomarkers in cerebrospinal fluid, plasma, and urine are elevated, suggesting that abnormal oxidative stress is generated outside of the central nervous system. Our review indicates that agricultural chemicals, heavy metals, military service, professional sports, excessive physical exertion, chronic head trauma, and certain foods might be modestly associated with ALS risk, with a stronger association between risk and smoking. At the cellular level, these factors are all involved in generating oxidative stress. Experimental studies indicate that a combination of insults that induce modest oxidative stress can exert additive deleterious effects on motor neurons, suggesting that multiple exposures in real-world environments are important. As the disease progresses, nutritional deficiency, cachexia, psychological stress, and impending respiratory failure may further increase oxidative stress. Moreover, accumulating evidence suggests that ALS is possibly a systemic disease. Laboratory, pathologic, and epidemiologic evidence clearly supports the hypothesis that oxidative stress is central in the pathogenic process, particularly in genetically susceptive individuals. If we are to improve ALS treatment, well-designed biochemical and genetic epidemiological studies, combined with a multidisciplinary research approach, are needed and will provide knowledge crucial to our understanding of ALS etiology, pathophysiology, and prognosis.

Cellular and molecular mechanisms involved in the neuroprotective effects of VEGF on motoneurons

Vascular endothelial growth factor (VEGF), originally described as a factor with a regulatory role in vascular growth and development, it is also known for its direct effects on neuronal cells. The discovery in the past decade that transgenic mice expressing reduced levels of VEGF developed late-onset motoneuron pathology, reminiscent of amyotrophic lateral sclerosis (ALS), opened a new field of research on this disease. VEGF has been shown to protect motoneurons from excitotoxic death, which is a relevant mechanism involved in motoneuron degeneration in ALS. Thus, VEGF delays motoneuron degeneration and increases survival in animal models of ALS. VEGF exerts its anti-excitotoxic effects on motoneurons through molecular mechanisms involving the VEGF receptor-2 resulting in the activation of the PI3-K/Akt signaling pathway, upregulation of GluR2 subunit of AMPA receptors, inhibition of p38MAPK, and induction of the anti-apoptotic molecule Bcl-2. In addition, VEGF acts on astrocytes to reduce astroglial activation and to induce the release of growth factors. The potential use of VEGF as a therapeutic tool in ALS is counteracted by its vascular effects and by its short effective time frame. More studies are needed to assess the optimal isoform, route of administration, and time frame for using VEGF in the treatment of ALS.

Vascular endothelial growth factor promotes anatomical and functional recovery of injured peripheral nerves in the avascular cornea

Peripheral nerve injury is a major neurological disorder that can cause severe motor and sensory dysfunction. Neurogenic effects of vascular endothelial growth factor (VEGF) have been found in the central nervous system, and we examined whether VEGF could promote anatomical and functional recovery of peripheral nerves after injury using an avascular corneal nerve injury model. We found that VEGF enhanced neurite elongation in isolated trigeminal ganglion neurons in a dose-dependent manner. This effect was suppressed by neutralizing antibodies for VEGF receptor (VEGFR) 1 and 2 or neuropilin receptor 1 or by VEGFR2 inhibitors (SU 1498 and Ki 8751). In vivo, mice receiving sustained VEGF via implanted pellets showed increased corneal nerve regeneration after superficial injury compared with those receiving vehicle. VEGF injected subconjunctivally at the time of injury accelerated reinnervation, the recovery of mechanosensation, and epithelial wound healing. Endogenous VEGF expression was up-regulated in the corneal epithelium and stroma after wounding. Thus, VEGF can mediate peripheral neuron growth but requires the activation of multiple VEGF receptor types. In addition, VEGF can accelerate the return of sensory and trophic functions of damaged peripheral nerves. Wounding induces the expression of VEFG, which may modulate physiological nerve repair.

TDP-43 and FUS RNA-binding proteins bind distinct sets of cytoplasmic messenger RNAs and differently regulate their post-transcriptional fate in motoneuron-like cells

The RNA-binding proteins TDP-43 and FUS form abnormal cytoplasmic aggregates in affected tissues of patients with amyotrophic lateral sclerosis and frontotemporal lobar dementia. TDP-43 and FUS localize mainly in the nucleus where they regulate pre-mRNA splicing, but they are also involved in mRNA transport, stability, and translation. To better investigate their cytoplasmic activities, we applied an RNA immunoprecipitation and chip analysis to define the mRNAs associated to TDP-43 and FUS in the cytoplasmic ribonucleoprotein complexes from motoneuronal NSC-34 cells. We found that they bind different sets of mRNAs although converging on common cellular pathways. Bioinformatics analyses identified the (UG)(n) consensus motif in 80% of 3'-UTR sequences of TDP-43 targets, whereas for FUS the binding motif was less evident. By in vitro assays we validated binding to selected target 3'-UTRs, including Vegfa and Grn for TDP-43, and Vps54, Nvl, and Taf15 for FUS. We showed that TDP-43 has a destabilizing activity on Vegfa and Grn mRNAs and may ultimately affect progranulin protein content, whereas FUS does not affect mRNA stability/translation of its targets. We also demonstrated that three different point mutations in TDP-43 did not change the binding affinity for Vegfa and Grn mRNAs or their protein level. Our data indicate that TDP-43 and FUS recognize distinct sets of mRNAs and differently regulate their fate in the cytoplasm of motoneuron-like cells, therefore suggesting complementary roles in neuronal RNA metabolism and neurodegeneration.

Identifying potential risk factors for developing amyotrophic lateral sclerosis

SUMMARY Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of adult life, characterized by the progressive loss of upper motor neurons in the primary motor cortex and of the spinal and bulbar lower motor neurons. The cause of sporadic cases and of the majority of hereditary cases remains elusive. So far a total of 17 genes or genetic loci of familial ALS have been identified, related to DNA/RNA processing, protein aggregation, membrane trafficking and axonal transport and mitochondrial dysfunction. A large range of environmental factors have also been studied, with inconclusive results, with the possible exception of cigarette smoking. ALS is now considered a complex multifactorial neurodegenerative disorder, but studies analyzing genetic and environmental factors together are still underway.

Intramuscular administration of a VEGF zinc finger transcription factor activator (VEGF-ZFP-TF) improves functional outcomes in SOD1 rats

Amyotrophic lateral sclerosis (ALS) is characterized by motor neuron loss leading to paralysis and death. Vascular endothelial growth factor (VEGF) has angiogenic, neurotrophic, and neuroprotective properties, and has preserved neuromuscular function and protected motor neurons in rats engineered to overexpress the human gene coding the mutated G93A form of the superoxide dismutase-1 (SOD1). We assessed the effects of intramuscular administration of a plasmid that encodes a zinc finger protein transcription factor (ZFP-TF) engineered to induce VEGF expression in the SOD1 rat model of ALS. Weekly injections of the plasmid preserved ipsilateral hindlimb grip strength and markedly improved rotarod performance in SOD1 rats compared to the vehicle-treated group. The number of motor neurons and the proportion of innervated neuromuscular junctions were similar in both groups. In conclusion, our data suggest that administration of the VEGF-ZFP-TF may be neuroprotective and has potential as a safe and practical approach for the management of motor disability in ALS.

Emerging drugs for amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegenerative disease that results in increasing disability and that is uniformly fatal. Since its approval in the 1990s, riluzole remains the sole treatment for ALS offering modest survival benefit. While significant advances have been made in the symptomatic management of the disease, more effective drug therapy targeting disease progression is sorely needed.

AREAS COVERED

Advances in the understanding of pathogenic mechanisms involved in disease development and progression have provided multiple avenues for developing effective treatment strategies. This review highlights recent discoveries relating to these diverse mechanisms and their implications for the development of drug therapy. Previous human clinical trials that have targeted these pathways are mentioned and ongoing drug trials are discussed.

EXPERT OPINION

The search for effective drug therapy faces important challenges in the areas of basic science and animal research, translation of these results into human clinical trials, inherent bias in human studies and issues related to delays in clinical diagnosis. How these issues may be addressed and why ALS research constitutes fertile grounds for drug development not only for this devastating disease, but also for other more prevalent neurodegenerative diseases, is discussed in this review.

SOD1 and TDP-43 animal models of amyotrophic lateral sclerosis: recent advances in understanding disease toward the development of clinical treatments

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease with no cure. Breakthroughs in understanding ALS pathogenesis came with the discovery of dominant mutations in the superoxide dismutase 1 gene (SOD1) and other genes, including the gene encoding transactivating response element DNA binding protein-43 (TDP-43). This has led to the creation of animal models to further our understanding of the disease and identify a number of ALS-causing mechanisms, including mitochondrial dysfunction, protein misfolding and aggregation, oxidative damage, neuronal excitotoxicity, non-cell autonomous effects and neuroinflammation, axonal transport defects, neurotrophin depletion, effects from extracellular mutant SOD1, and aberrant RNA processing. Here we summarise the SOD1 and TDP-43 animal models created to date, report on recent findings supporting the potential mechanisms of ALS pathogenesis, and correlate this understanding with current developments in the clinic.

Evolution of the VEGF-regulated vascular network from a neural guidance system

The vascular network is closely linked to the neural system, and an interdependence is displayed in healthy and in pathophysiological responses. How has close apposition of two such functionally different systems occurred? Here, we present a hypothesis for the evolution of the vascular network from an ancestral neural guidance system. Biological cornerstones of this hypothesis are the vascular endothelial growth factor (VEGF) protein family and cognate receptors. The primary sequences of such proteins are conserved from invertebrates, such as worms and flies that lack discernible vascular systems compared to mammals, but all these systems have sophisticated neuronal wiring involving such molecules. Ancestral VEGFs and receptors (VEGFRs) could have been used to develop and maintain the nervous system in primitive eukaryotes. During evolution, the demands of increased morphological complexity required systems for transporting molecules and cells, i.e., biological conductive tubes. We propose that the VEGF-VEGFR axis was subverted by evolution to mediate the formation of biological tubes necessary for transport of fluids, e.g., blood. Increasingly, there is evidence that aberrant VEGF-mediated responses are also linked to neuronal dysfunctions ranging from motor neuron disease, stroke, Parkinson's disease, Alzheimer's disease, ischemic brain disease, epilepsy, multiple sclerosis, and neuronal repair after injury, as well as common vascular diseases (e.g., retinal disease). Manipulation and correction of the VEGF response in different neural tissues could be an effective strategy to treat different neurological diseases.

Injectable VEGF hydrogels produce near complete neurological and anatomical protection following cerebral ischemia in rats

Vascular endothelial growth factor (VEGF) is a potent proangiogenic peptide and its administration has been considered as a potential neuroprotective strategy following cerebral stroke. Because VEGF has a short half-life and limited access to the brain parenchyma following systemic administration, approaches are being developed to deliver it directly to the site of infarction. In the present study, VEGF was incorporated into a sustained release hydrogel delivery system to examine its potential benefits in a rat model of cerebral ischemia. The hydrogel loaded with VEGF (1 μg) was stereotaxically injected into the striatum of adult rats 15 min prior to a 1-h occlusion of the middle cerebral artery. Two days after surgery, animals were tested for motor function using the elevated bias swing test (EBST) and Bederson neurological battery. Control animals received either stroke alone, stroke plus injections of a blank gel, or a single bolus injection of VEGF (1 μg). Behavioral testing confirmed that the MCA occlusion resulted in significant deficits in the the EBST and Bederson tests. In contrast, the performance of animals receiving VEGF gels was significantly improved relative to controls, with only modest impairments observed. Cerebral infarction analyzed using 2,3,5-triphenyl-tetrazolium chloride staining confirmed that the VEGF gels significantly and potently reduced the lesion volume. No neurological or histological benefits were conferred by either blank gel or bolus VEGF injections. These data demonstrate that VEGF, delivered from a hydrogel directly to the brain, can induce significant functional and structural protection from ischemic damage in a rat model of stroke.

[Mechanisms of deregulated response to hypoxia in sporadic amyotrophic lateral sclerosis: a clinical study]

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of upper and lower motorneurons, leading to death in 3 to 5 years. Respiratory insufficiency and hypoxemia are closely linked during the clinical course of ALS. Chronic respiratory insufficiency and hypoxemia generally occur late in the disease course but rapid episodes of intermittent hypoxemia followed by reoxygenation can occur early and insidiously. Two pathways are involved in the response to hypoxemia: (i) hypoxia inducible factor-1 (HIF-1) and VEGF/HIF-2 and an erythropoietin (EPO) mediated pathway, in response to prolonged hypoxemia; and (ii) nuclear factor kappa-B (NFkappa-B) during acute hypoxemia followed by reoxygenation episodes, inducing inflammatory mediators: interleukin-6 (IL-6), TNF-alpha, cyclo oxygenase-2 (COX-2) and prostaglandin E-2 (PGE-2). Our aim was to specify the role of the different functional pathways of response to hypoxemia in sporadic ALS patients, compared with neurological controls and according to the level of hypoxemia. We report the results of several studies of hypoxemic and/or inflammatory mediators in the cerebrospinal fluid (CSF) from ALS patients, according to their respiratory status, showing a selective defect of HIF-1 mediated angiogenic factors (VEGF and angiogenin [ANG]) during chronic hypoxia in sporadic ALS patients, compared to hypoxemic neurological controls; contrasting with an early activation of the NFkappa-B pathway since the isolated desaturation stage (IL-6, TNF-alpha, PGE-2, angiopoietin-2) in the same cohort of sporadic ALS patients. All these results are consistent with a selective impairment of the HIF-1 pathway during chronic hypoxemia in ALS patients. Inflammatory mediators were strongly elevated, since the early stage of the disease until chronic hypoxemia, suggesting a compensatory mechanism.

Injectable hydrogels providing sustained delivery of vascular endothelial growth factor are neuroprotective in a rat model of Huntington's disease

Vascular endothelial growth factor (VEGF) is a potent peptide with well-documented pro-angiogenic effects. Recently, it has also become clear that exogenous administration of VEGF is neuroprotective in animal models of central nervous system diseases. In the present study, VEGF was incorporated into a sustained release hydrogel delivery system to examine its potential benefits in a rat model of Huntington's disease (HD). The VEGF-containing hydrogel was stereotaxically injected into the striatum of adult rats. Three days later, quinolinic acid (QA; 225 nmol) was injected into the ipsilateral striatum to produce neuronal loss and behavioral deficits that mimic those observed in HD. Two weeks after surgery, animals were tested for motor function using the placement and cylinder tests. Control animals received either QA alone or QA plus empty hydrogel implants. Behavioral testing confirmed that the QA lesion resulted in significant deficits in the ability of the control animals to use their contralateral forelimb. In contrast, the performance of those animals receiving VEGF was significantly improved relative to controls with only modest motor impairments observed. Stereological counts of NeuN-positive neurons throughout the striatum demonstrated that VEGF implants significantly protected against the loss of striatal neurons induced by QA. These data are the first to demonstrate that VEGF can be used to protect striatal neurons from excitotoxic damage in a rat model of HD.

Selective regulation of growth factor expression in cultured cortical astrocytes by neuro-pathological toxins

Astrocytes are integrated in the complex regulation of neurodegeneration and neuronal damage in the CNS. It is well-known that astroglia produces a plethora of growth factors which might be protective for neurons. Growth factors prevent neurons from cell death and promote proliferation and differentiation of precursor cells. Previous data suggest that astrocytes may respond to toxic stimuli by a selective mobilization of guarding molecules. In the present study, we have investigated the potency of different pathological stimuli such as lipopolysaccharides, tumor necrosis factor alpha, glutamate, and hydrogen peroxide to activate cultured cortical astroglia and stimulate growth factor expression. Astroglial cultures were exposed to the above factors for 24h at non-toxic concentrations for astrocytes. Growth factor expression was analyzed by real-time PCR, oligo-microarray technique, and ELISA. Insulin-like growth factor-1 was selectively down-regulated by lipopolysaccharides and tumor necrosis factor alpha, bone morphogenetic protein 6 by all stimuli. In contrast, lipopolysaccharides, tumor necrosis factor alpha, and glutamate increased leukemia inhibitory factor. Fibroblast growth factor 2 was up-regulated by lipopolysaccharides and tumor necrosis factor alpha and down-regulated by hydrogen peroxide. Besides hydrogen peroxide, all other stimuli promoted vascular epithelial growth factor A mRNA and protein expression. It appears that lipopolysaccharides but not tumor necrosis factor alpha effects on vascular epithelial growth factor A depend on the classic NFkappaB pathway. Our data clearly demonstrate that astroglia actively responses to diverse pathological compounds by a selective expression pattern of growth factors. These findings make astrocytes likely candidates to participate in disease-specific characteristics of neuronal support or damage.