Nerve growth factor promotes differentiation and protects the oligodendrocyte precursor cells from in vitro hypoxia/ischemia.

Introduction: Nerve growth factor (NGF) is a pleiotropic molecule acting on different cell types in physiological and pathological conditions. However, the effect of NGF on the survival, differentiation and maturation of oligodendrocyte precursor cells (OPCs) and oligodendrocytes (OLs), the cells responsible for myelin formation, turnover, and repair in the central nervous system (CNS), is still poorly understood and heavily debated. Methods: Here we used mixed neural stem cell (NSC)-derived OPC/astrocyte cultures to clarify the role of NGF throughout the entire process of OL differentiation and investigate its putative role in OPC protection under pathological conditions. Results: We first showed that the gene expression of all the neurotrophin receptors (TrkA, TrkB, TrkC, and p75NTR ) dynamically changes during the differentiation. However, only TrkA and p75NTR expression depends on T3-differentiation induction, as Ngf gene expression induction and protein secretion in the culture medium. Moreover, in the mixed culture, astrocytes are the main producer of NGF protein, and OPCs express both TrkA and p75NTR . NGF treatment increases the percentage of mature OLs, while NGF blocking by neutralizing antibody and TRKA antagonist impairs OPC differentiation. Moreover, both NGF exposure and astrocyte-conditioned medium protect OPCs exposed to oxygenglucose deprivation (OGD) from cell death and NGF induces an increase of AKT/pAKT levels in OPCs nuclei by TRKA activation. Discussion: This study demonstrated that NGF is implicated in OPC differentiation, maturation, and protection in the presence of metabolic challenges, also suggesting implications for the treatment of demyelinating lesions and diseases.

Nerve Growth Factor (NGF) as Partaker in the Modulation of UV-Response in Cultured Human Conjunctival Fibroblasts.

Corroborating data sustain the pleiotropic effect of nerve growth factor (NGF) in the protection of the visual system from dangerous stimuli, including ultraviolet (UV). Since UV exposure might promote ocular surface changes (conjunctival inflammation and matrix rearrangement), as previously reported from in vivo studies sustaining some protective NGF effects, in vitro cultures of human conjunctival fibroblasts (FBs) were developed and exposed to a single UV exposure over 15 min (0.277 W/m2), either alone or supplemented with NGF (1-10-100 ng/mL). Conditioned media and cell monolayers were collected and analyzed for protein release (ELISA, ELLA microfluidic) and transcript expression (real-time PCR). A specific "inflammatory to remodeling" pattern (IL8, VEGF, IL33, OPN, and CYR61) as well as a few epigenetic transcripts (known as modulator of cell differentiation and matrix-remodeling (DNMT3a, HDAC1, NRF2 and KEAP1)) were investigated in parallel. UV-exposed FBs (i), showed no proliferation or significant cytoskeleton rearrangement; (ii), displayed a trkANGFR/p75NTR phenotype; and (iii), synthesized/released IL8, VEGF-A, IL33, OPN, and CYR61, as compared to unexposed ones. NGF addition counteracted IL8, IL33, OPN, and CYR61 protein release merely at lower NGF concentrations but not VEGF. NGF supplementation did not affect DNMT3a or HDAC1 transcripts, while it significantly upregulated NRF2 at lowest NGF doses and did not change KEAP1 expression. Taken together, a single UV exposure activated conjunctival FBs to release pro-inflammatory/fibrogenic factors in association with epigenetic changes. The effects were selectively counteracted by NGF supplementation in a dose-dependent fashion, most probably accountable to the trkANGFR/p75NTR phenotype. Further in vitro studies are underway to better understand this additional NGF pleiotropic effect. Since UV-shield impairments represent a worldwide alert and UV radiation can slowly affect ocular surface homeostasis (photo-ageing, cataract) or might exacerbate ocular diseases with a preexisting fibrosis (pterygium, VKC), these findings on NGF modulation of UV-exposed FBs might provide additional information for protecting the ocular surface (homeostasis) from low-grade long-lasting UV insults.

NGF and Retinitis Pigmentosa: Structural and Molecular Studies.

Nerve growth factor (NGF) is a neuroprotective molecule performing not only on central and peripheral neurons but also on cells of the visual system. Human retinitis pigmentosa (RP) is a major cause of blindness worldwide, and a resolute therapy is still lacking. Recent studies have shown that ocular NGF administration exerts a protective action on damaged retinal cells of mammalians, including human beings, although whether NGF also protects photoreceptors is not clear.We used the Royal College of Surgeons (RCS) strain in this study. The RCS is a rodent affected by inherited retinitis pigmentosa (RP) during postnatal life. For this study, we investigated whether ocular NGF treatment reduces/stops the progression of photoreceptor degeneration of rats with RP.This study was carried out in vitro on isolated photoreceptors to further investigate the action on these cells and whether the action is direct or mediated.The results indicate that ocular NGF administration can protect photoreceptors from degeneration into a model developing inherited RP and that the NGF action is direct. In this regard, we observed that binding of NGF to its receptor modulates expression of rhodopsin, a specific biological marker for photoreceptor survival and functionality.Part of the data reported in this chapter has been published in a previous study.

Retrobulbar administration of purified anti-nerve growth factor in developing rats induces structural and biochemical changes in the retina and cornea.

AIM: To develop an experimental model of endogenous nerve growth factor (NGF) deprivation by retrobulbar administration of purified neutralizing anti-NGF antibodies in young Sprague-Dawley rats and provide further information on NGF expression in the retina and cornea. METHODS: Sixty old pathogen-free Sprague Dawley rats (p14, post-natal days) were treated with repeated retrobulbar injections of neutralizing anti-NGF (2 µL, 100 µg/mL, every 3d). After 2wk (p28), retinal and corneal tissues were investigated for morphological, biochemical, and molecular expression of trkANGFR by using Western blotting or immunofluorescence. Rhodopsin as well as protein profile expression were also investigated. RESULTS: Chronic retrobulbar neutralizing anti-NGF antibodies changed the distribution of trkANGFR immunoreactivity at retinal level, while no changes were detected for global trkANGFR protein expression. By contrary, the treatment resulted in the increase of corneal trkANGFR expression. Retinal tissues showed a decreased rhodopsin expression as well as reduced number of both rhodopsin expressing and total retinal cells, as observed after single cell extraction. A decreased expression of ICAM-1, IL-17 and IL-13 as well as an increased expression of IL-21 typified retinal extracts. No significant changes were observed for corneal tissues. CONCLUSION: The reduced availability of endogenous NGF, as produced by chronic retrobulbar anti-NGF administration, produce a quick response from retinal tissues, with respect to corneal ones, suggesting the presence of early compensatory mechanisms to protect retinal networking.

Nerve Growth Factor: Early Studies and Recent Clinical Trials.

Since its discovery, nerve growth factor (NGF) has long occupied a critical role in developmental and adult neurobiology for its many important regulatory functions on the survival, growth and differentiation of nerve cells in the peripheral and central nervous system. NGF is the first discovered member of a family of neurotrophic factors, collectively indicated as neurotrophins, (which include brain-derived neurotrophic factor, neurotrophin-3 and neurotrophin 4/5). NGF was discovered for its action on the survival and differentiation of selected populations of peripheral neurons. Since then, an enormous number of basic and human studies were undertaken to explore the role of purified NGF to prevent the death of NGF-receptive cells. These studies revealed that NGF possesses important therapeutic properties, after topical administration, on human cutaneous pressure ulcer, corneal ulcers, glaucoma, retinal maculopathy, Retinitis Pigmentosa and in pediatric optic gliomas and brain traumas. The aim of this review is to present our previous, recent and ongoing clinical studies on the therapeutic properties of NGF.

NGF protects corneal, retinal, and cutaneous tissues/cells from phototoxic effect of UV exposure.

PURPOSE: Based on evidence that nerve growth factor (NGF) exerts healing action on damaged corneal, retinal, and cutaneous tissues, the present study sought to assess whether topical NGF application can prevent and/or protect epithelial cells from deleterious effects of ultraviolet (UV) radiation. METHODS: Eyes from 40 young-adult Sprague Dawley rats and cutaneous tissues from 36 adult nude mice were exposed to UVA/B lamp for 60 min, either alone or in the presence of murine NGF. Corneal, retinal, and cutaneous tissues were sampled/processed for morphological, immunohistochemical, and biomolecular analysis, and results were compared statistically. RESULTS: UV exposure affected both biochemical and molecular expression of NGF and trkANGFR in corneal, retinal, and cutaneous tissues while UV exposure coupled to NGF treatment enhanced NGF and trkANGFR expression as well as reduced cell death. CONCLUSIONS: Overall, the findings of this in vivo/ex vivo study show the NGF ability to reduce the potential UV damage. Although the mechanism underneath this effect needs further investigation, these observations prospect the development of a pharmacological NGF-based therapy devoted to maintain cell function when exposed to phototoxic UV radiation.

Recombinant Human Nerve Growth Factor Treatment Promotes Photoreceptor Survival in the Retinas of Rats with Retinitis Pigmentosa.

PURPOSE: Increasing evidence suggests that nerve growth factor (NGF) exerts protective effects against retinal degeneration in animal models of retinitis pigmentosa (RP). This study aims at investigating the effects of intravitreal injection of recombinant human NGF (rhNGF) on retinal photoreceptors apoptosis in an animal model of RP, the Royal College of Surgeons (RCS) rats. METHODS: Thirty-six RCS rats were treated with intravitreal injection of rhNGF or murine NGF (mNGF) or vehicle at 20 postnatal days (pd) and sacrificed at 40 pd. The eyes were enucleated and evaluated by histology, flow cytometric analysis for rhodopsin expression, Western blot for TrkA and activated (phosphorylated) TrkA (pTrkA) levels, and TUNEL assay for apoptosis' detection. RESULTS: RCS rats showed a significant retinal degeneration associated with cell apoptosis at 40 pd when compared to wild-type animals. Histology showed that rhNGF intravitreal treatment significantly increased retinal thickness when compared to untreated eyes. Photoreceptors' number evaluated by flow cytometry was significantly increased in both intravitreal rhNGF- and mNGF-treated groups when compared to untreated eyes. This protective effect was associated with an increase in TrkA and activated pTrkA levels and an inhibition of apoptosis. Intravitreal NGF injection was well tolerated and did not show clinical and histological signs of adverse effects. CONCLUSIONS: Intravitreal rhNGF injection proved safe and effective in favoring retinal cell survival in RCS rats. This is the first report showing that the novel rhNGF already proved safe in a phase I study exerts a biologic effect similar to the well-characterized mNGF-induced retinal protection. These results may trigger further studies to investigate rhNGF administration for the treatment of progressive degenerative retinal disorders such as retinitis pigmentosa.

NGF/anti-VEGF combined exposure protects RCS retinal cells and photoreceptors that underwent a local worsening of inflammation.

PURPOSE: Our previous study highlighted the potential nerve growth factor (NGF) effect on damaged photoreceptors from a rat model of spontaneous Retinitis Pigmentosa (RP). Herein, we tested the combined NGF/anti-vascular endothelial growth factor (αVEGF) effect on cultured retinal cells isolated from Royal College of Surgeons (RCS) rats receiving an intravitreal VEGF injection (iv-VEGF) to exacerbate retinal inflammation/neovascularization. METHODS: RCS (n = 75) rats were equally grouped as untreated (n = 25), iv-saline (single saline intravitreal injection; n = 25) and iv-VEGF (single VEGF intravitreal injection; n = 25). Morphological and biochemical analysis or in vitro stimulations with the biomolecular investigation were carried out on explanted retinas. Isolated retinal cells were treated with NGF and αVEGF, either alone or in combination, for 6 days and cells were harvested for morphological and biomolecular analyses. RESULTS: Infiltrating inflammatory cells were detected in iv-VEGF exposed RCS retinas, indicative of exacerbated inflammation and neovascularization. In cell cultures, NGF/αVEGF significantly increased retinal cell survival as well as rhodopsin expression and neurite outgrowth in photoreceptors. Particularly, NGF/αVEGF upregulated Bcl-2 mRNA, downregulated Bax mRNA, upregulated trkANGFR mRNA and finally upregulated both NGF mRNA and protein. CONCLUSIONS: These data confirm and extend our previous findings on NGF-photoreceptor crosstalk, highlighting that the NGF/αVEGF combination might be an interesting approach for improving neuroprotection of RCS retinal cells and likewise photoreceptors in the presence of neovascularization. Further studies are required to translate this in vitro approach into clinical practice.

Nerve growth factor: role in growth, differentiation and controlling cancer cell development.

Recent progress in the Nerve Growth Factor (NGF) research has shown that this factor acts not only outside its classical domain of the peripheral and central nervous system, but also on non-neuronal and cancer cells. This latter observation has led to divergent hypothesis about the role of NGF, its specific distribution pattern within the tissues and its implication in induction as well as progression of carcinogenesis. Moreover, other recent studies have shown that NGF has direct clinical relevance in certain human brain neuron degeneration and a number of human ocular disorders. These studies, by suggesting that NGF is involved in a plethora of physiological function in health and disease, warrant further investigation regarding the true role of NGF in carcinogenesis. Based on our long-lasting experience in the physiopathology of NGF, we aimed to review previous and recent in vivo and in vitro NGF studies on tumor cell induction, progression and arrest. Overall, these studies indicate that the only presence of NGF is unable to generate cell carcinogenesis, both in normal neuronal and non-neuronal cells/tissues. However, it cannot be excluded the possibility that the co-expression of NGF and pro-carcinogenic molecules might open to different consequence. Whether NGF plays a direct or an indirect role in cell proliferation during carcinogenesis remains to demonstrate.

Nerve Growth Factor: A Focus on Neuroscience and Therapy.

Nerve growth factor (NGF) is the firstly discovered and best characterized neurotrophic factor, known to play a critical protective role in the development and survival of sympathetic, sensory and forebrain cholinergic neurons. NGF promotes neuritis outgrowth both in vivo and in vitro and nerve cell recovery after ischemic, surgical or chemical injuries. Recently, the therapeutic property of NGF has been demonstrated on human cutaneous and corneal ulcers, pressure ulcer, glaucoma, maculopathy and retinitis pigmentosa. NGF eye drops administration is well tolerated, with no detectable clinical evidence of systemic or local adverse effects. The aim of this review is to summarize these biological properties and the potential clinical development of NGF.

Effect of purified murine NGF on isolated photoreceptors of a rodent developing retinitis pigmentosa.

A number of different studies have shown that neurotrophins, including nerve growth factor (NGF) support the survival of retinal ganglion neurons during a variety if insults. Recently, we have reported that that eye NGF administration can protect also photoreceptor degeneration in a mice and rat with inherited retinitis pigmentosa. However, the evidence that NGF acts directly on photoreceptors and that other retinal cells mediate the NGF effect could not be excluded. In the present study we have isolated retinal cells from rats with inherited retinitis pigmentosa (RP) during the post-natal stage of photoreceptor degenerative. In presence of NGF, these cells are characterized by enhanced expression of NGF-receptors and rhodopsin, the specific marker of photoreceptor and better cell survival, as well as neuritis outgrowth. Together these observations support the hypothesis that NGF that NGF acts directly on photoreceptors survival and prevents photoreceptor degeneration as previously suggested by in vivo studies.

NGF and therapeutic prospective: what have we learned from the NGF transgenic models?

It has been shown that topical nerve growth factor (NGF) administration induces healing action on human cutaneous, corneal and pressure ulcers, glaucoma, maculopathy and retinitis pigmentosa suggesting a therapeutic potential of NGF in human ophthalmology and cutaneous ulcers. A similar therapeutic suggestion has emerged for the NGF gene therapy of Alzheimer's disease and ischemic heart injury. Moreover, over the last few years, the role and biological properties of NGF have also been investigated with transgenic mice over-expressing and down-expressing NGF. However, the results obtained with these transgenic mice seem suitable to confirm and/or support the evidence obtained with exogenous administration of NGF regarding the suggested clinical potentiality of NGF. The aim of the present brief review is to report and comment on these two different findings of NGF's healing properties.

Nerve growth factor and autophagy: effect of nasal anti-NGF-antibodies administration on Ambra1 and Beclin-1 expression in rat brain.

Nerve growth factor (NGF) exerts protective actions in the healthy and diseased nervous system. Intranasal administration is a suitable and safe strategy to deliver NGF to CNS neurons. We investigated whether nasal anti-NGF-antibody (ANA) administration affects neuronal autophagy, in view of its putative regulatory role in this process. We focused on olfactory bulbs (OB), neocortex (Cx), hippocampus (HF) and septal complex (SC), known to be NGF-responsive and autophagically active. Our combined molecular/morphological results demonstrate that intranasally administered ANA reaches brain NGF-target neurons and lowers the levels of endogenous NGF and its receptors. Treatment also affects - in a brain region-dependent manner - the expression of the autophagic proteins Beclin-1 and Ambra1, as well as that of proteins belonging to the Bcl2 family, namely Bax and Bcl-2, reflecting apoptotic dysregulation. This study provides a nongenetically modified, NGF-defective animal model, representing a suitable tool to investigate novel properties of the neurotrophin, especially in relation to autophagy.

Intranasal nerve growth factor bypasses the blood-brain barrier and affects spinal cord neurons in spinal cord injury.

The purpose of this work was to investigate whether, by intranasal administration, the nerve growth factor bypasses the blood-brain barrier and turns over the spinal cord neurons and if such therapeutic approach could be of value in the treatment of spinal cord injury. Adult Sprague-Dawley rats with intact and injured spinal cord received daily intranasal nerve growth factor administration in both nostrils for 1 day or for 3 consecutive weeks. We found an increased content of nerve growth factor and enhanced expression of nerve growth factor receptor in the spinal cord 24 hours after a single intranasal administration of nerve growth factor in healthy rats, while daily treatment for 3 weeks in a model of spinal cord injury improved the deficits in locomotor behaviour and increased spinal content of both nerve growth factor and nerve growth factor receptors. These outcomes suggest that the intranasal nerve growth factor bypasses blood-brain barrier and affects spinal cord neurons in spinal cord injury. They also suggest exploiting the possible therapeutic role of intranasally delivered nerve growth factor for the neuroprotection of damaged spinal nerve cells.

NGF and VEGF effects on retinal ganglion cell fate: new evidence from an animal model of diabetes.

PURPOSE: To investigate if the survival effects of nerve growth factor (NGF) eyedrops on retinal ganglion cell (RGCs) are related to vascular endothelial growth factor (VEGF) in a rat model of diabetic retinopathy. METHODS: Diabetes was induced in adult rats by streptozotocin injection and changes in the NGF/TrkA and VEGF retina levels were related to the progression of RGC loss. Diabetic rats were subjected to administration of NGF eyedrops or intraocular injection of anti-NGF antibody. All morphologic, immunohistochemical, and biochemical analyses were performed on whole retinas dissected after 7 or 11 weeks after diabetes induction. RESULTS: Diabetes was successfully induced in rats as shown by glycemic levels >250 mg/dL. The NGF levels increased in diabetic retinas at 7 weeks and decreased at 11 weeks, while VEGF levels increased at all time points. The RGC loss in diabetic retinopathy worsened with anti-NGF administration, which did not alter retina VEGF levels significantly. Administration of NGF eyedrops restored TrkA levels in the retina, and protected RGCs from degeneration without influencing VEGF levels. CONCLUSIONS: The early increase of NGF in diabetic retina might be an endogenous response for protecting RGCs from degeneration. This protective mechanism is impaired at 11 weeks following diabetes induction, and results in a marked RGC degeneration that is improved by exogenous NGF administration and worsened by anti-NGF. The observed NGF-induced neuroprotection on damaged RGCs was not associated with changes in VEGF retina levels, which were constantly high in diabetic rats and were not altered by anti-NGF administration.

Nerve growth factor: basic studies and possible therapeutic applications.

The nerve growth factor (NGF) belongs to a family of neurotrophic factors called neurotrophins. It was discovered as a molecule that stimulates the survival and maturation of developing neurons in the peripheral nervous system and has later been shown to protect adult neurons in the degenerating mammalian brain. Basic and clinical studies have been undertaken to use NGF as a therapeutic agent aimed at restoring and maintaining neuronal function in the central nervous system and to determine the mechanisms to safely deliver the molecule into the brain. Recent studies have also recognized that the role of NGF extends far beyond the horizon of nerve cells and even beyond the peripheral and central nervous system. Studies published from our laboratory have shown that topical application of NGF possesses a protective action on human pressure ulcer, corneal ulcer and glaucoma. Here, we will review these studies, supporting the therapeutic potential of NGF.

Increased nerve growth factor signaling in sensory neurons of early diabetic rats is corrected by electroacupuncture.

Diabetic polyneuropathy (DPN), characterized by early hyperalgesia and increased nerve growth factor (NGF), evolves in late irreversible neuropathic symptoms with reduced NGF support to sensory neurons. Electroacupuncture (EA) modulates NGF in the peripheral nervous system, being effective for the treatment of DPN symptoms. We hypothesize that NGF plays an important pathogenic role in DPN development, while EA could be useful in the therapy of DPN by modulating NGF expression/activity. Diabetes was induced in rats by streptozotocin (STZ) injection. One week after STZ, EA was started and continued for three weeks. NGF system and hyperalgesia-related mediators were analyzed in the dorsal root ganglia (DRG) and in their spinal cord and skin innervation territories. Our results show that four weeks long diabetes increased NGF and NGF receptors and deregulated intracellular signaling mediators of DRG neurons hypersensitization; EA in diabetic rats decreased NGF and NGF receptors, normalized c-Jun N-terminal and p38 kinases activation, decreased transient receptor potential vanilloid-1 ion channel, and possibly activated the nuclear factor kappa-light-chain-enhancer of activated B cells (Nf- κ B). In conclusion, NGF signaling deregulation might play an important role in the development of DPN. EA represents a supportive tool to control DPN development by modulating NGF signaling in diabetes-targeted neurons.

Brain cholinergic markers and Tau phosphorylation are altered in experimental type 1 diabetes: normalization by electroacupuncture.

Diabetes often correlates with tau phosphorylation and the development of Alzheimer's disease. Both are associated with brain cholinergic dysfunction that could benefit from nerve growth factor (NGF)-based therapies. Electroacupuncture (EA) improves brain NGF availability and action. Here we assessed the variations of NGF and tau phosphorylation in the cortex and hippocampus, as well as the expression of choline acetyltransferase in the basal forebrain following diabetes induction and EA in adult rats. We found that EA counteracts diabetes-associated tau hyperphosphorylation and decreases in NGF and choline acetyltransferase, suggesting a possible beneficial effect of EA on brain cholinergic system in diabetes.

Capsaicin-induced corneal sensory denervation and healing impairment are reversed by NGF treatment.

PURPOSE: We aimed to evaluate the nerve growth factor (NGF) pathway and its influence on corneal healing mechanisms in normal conditions and in an animal model of corneal denervation induced by capsaicin. METHODS: Peripheral sensory damage was induced in rat pups by subcutaneous injection of capsaicin and the effects evaluated by hot-plate test, corneal nerve count, and tear secretion. Corneal damage was induced in capsaicin-treated and -untreated rats by epithelial scraping. Healing rate; NGF pathway (NGF, tyrosine kinase A [TrkA], p75); and the stem cell marker p63 were evaluated by RT-PCR, ELISA, Western blot, and immunohistochemistry. The effects of exogenous NGF administration as eye drop formulation were also tested. RESULTS: Capsaicin treatment induced a significant reduction of peripheral sensitivity, corneal innervation, tear secretion, and corneal healing rate. The ocular effects of capsaicin treatment were associated with an NGF pathway alteration. NGF eye drop treatment aided corneal healing mechanisms through a significant increase in the NGF receptors TrkA and p75, and in the stem cell marker p63. CONCLUSIONS: In this study, we show that an alteration in the NGF pathway is responsible for a delay in corneal healing in an animal model of sensory denervation. Moreover, we show that NGF eye drop administration modulates corneal innervation, epithelial cell healing, and corneal stem cells. These findings may trigger further research on the role of the NGF pathway in limbal stem cell deficiency.

Nerve growth factor: from the early discoveries to the potential clinical use.

The physiological role of the neurotrophin nerve growth factor (NGF) has been characterized, since its discovery in the 1950s, first in the sensory and autonomic nervous system, then in central nervous, endocrine and immune systems. NGF plays its trophic role both during development and in adulthood, ensuring the maintenance of phenotypic and functional characteristic of several populations of neurons as well as immune cells. From a translational standpoint, the action of NGF on cholinergic neurons of the basal forebrain and on sensory neurons in dorsal root ganglia first gained researcher's attention, in view of possible clinical use in Alzheimer's disease patients and in peripheral neuropathies respectively. The translational and clinical research on NGF have, since then, enlarged the spectrum of diseases that could benefit from NGF treatment, at the same time highlighting possible limitations in the use of the neurotrophin as a drug. In this review we give a comprehensive account for almost all of the clinical trials attempted until now by using NGF. A perspective on future development for translational research on NGF is also discussed, in view of recent proposals for innovative delivery strategies and/or for additional pathologies to be treated, such as ocular and skin diseases, gliomas, traumatic brain injuries, vascular and immune diseases.