Purification of the chick eye ciliary neuronotrophic factor

Beyond Trophic Factors: Exploiting the Intrinsic Regenerative Properties of Adult Neurons

Injuries and diseases of the peripheral nervous system (PNS) are common but frequently irreversible. It is often but mistakenly assumed that peripheral neuron regeneration is robust without a need to be improved or supported. However, axonal lesions, especially those involving proximal nerves rarely recover fully and injuries generally are complicated by slow and incomplete regeneration. Strategies to enhance the intrinsic growth properties of reluctant adult neurons offer an alternative approach to consider during regeneration. Since axons rarely regrow without an intimately partnered Schwann cell (SC), approaches to enhance SC plasticity carry along benefits to their axon partners. Direct targeting of molecules that inhibit growth cone plasticity can inform important regenerative strategies. A newer approach, a focus of our laboratory, exploits tumor suppressor molecules that normally dampen unconstrained growth. However several are also prominently expressed in stable adult neurons. During regeneration their ongoing expression “brakes” growth, whereas their inhibition and knockdown may enhance regrowth. Examples have included phosphatase and tensin homolog deleted on chromosome ten (PTEN), a tumor suppressor that inhibits PI3K/pAkt signaling, Rb1, the protein involved in retinoblastoma development, and adenomatous polyposis coli (APC), a tumor suppressor that inhibits β-Catenin transcriptional signaling and its translocation to the nucleus. The identification of several new targets to manipulate the plasticity of regenerating adult peripheral neurons is exciting. How they fit with canonical regeneration strategies and their feasibility require additional work. Newer forms of nonviral siRNA delivery may be approaches for molecular manipulation to improve regeneration.

Abdominal Aortic Transplantation of Bone Marrow Mesenchymal Stem Cells Regulates the Expression of Ciliary Neurotrophic Factor and Inflammatory Cytokines in a Rat Model of Spinal Cord Ischemia-Reperfusion Injury

Background

This study aimed to investigate the effects of abdominal aortic transplantation of bone marrow mesenchymal stem cells (BMMSCs) on the expression of inflammatory cytokines in a rat model of spinal cord ischemia-reperfusion injury.

Material/Methods

Adult female Sprague-Dawley rats (N=160) were divided into five groups: the sham operation group (N-32); the control group (N=32); the BMMSC transplanted group (N=32); the anti-ciliary neurotrophic factor (CNTF)-treated BMMSC transplanted group (N=32); and the CNTF small interfering RNA (siRNA)-treated BMMSC transplanted group (N=32). Motor behavior was assessed using the Basso, Beattie, and Bresnahan (BBB) locomotor scale. Motor evoked potentials (MEPs) and cortical somatosensory evoked potentials (CSEPs) were measured. Immunohistochemistry, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blot analysis evaluated the expression of spinal inflammatory cytokines.

Results

Following surgery, compared with the control group the findings in the BMMSC transplant groups included significantly increased BBB scores; the latency and the amplitude of MEP and CSEP were reduced and increased, respectively; spinal neuronal necrosis was reduced; the number of normal neurons increased; CNTF mRNA and protein expression levels increased; expression levels of interleukin-6 (IL-6) were reduced and IL-10 levels were significantly increased (P<0.05). The effects of abdominal aortic BMMSC transplantation were at least partially reversed by both anti-CNTF and CNTF siRNA treatment.

Conclusions

In a rat model of spinal cord ischemia-reperfusion injury, abdominal aortic transplantation of BMMSCs increased the expression of CNTF, which improved hindlimb locomotor recovery by regulating the expression of IL-6 and IL-10 to reduce inflammation of the spinal cord.

One-pot construction of a twice-condensed pDNA polyplex system for peripheral nerve crush injury therapy

Non-viral vector gene delivery is generally limited by its potential toxicity problems, poor transfection abilities, serum stability, or relatively complex construction processes of modified polyplexes. Thus, we develop an efficient and stable polyplex system through convenient construction methods. Here, polyethyleneimine (PEI) 1.8 kDa and glutaraldehyde (GA) are used to construct a novel twice-condensed pDNA polyplex system using a one-pot construction method, including pH-responsive C[double bond, length as m-dash]N linkages by which different PEI molecules on one single polyplex can link with each other. In this system, smaller particle sizes, higher zeta potentials and better serum stabilities are achieved without PEGylation or other chemical modifications using lyophobic segments, but via pH-responsive linkages that ensure the escape of nucleic acids. This polyplex system is used to deliver the pDNA of vascular endothelial growth factor (VEGF) whose half-life period in vivo is only around 30 minutes. Compared with polyplexes prepared using PEI 25 kDa, cells and rats treated with twice-condensed VEGF pDNA polyplexes express significantly more VEGF or myelin basic protein (MBP), and this new polyplex system showed fewer adverse effects in vitro and in vivo. In addition, revascularization and neurogenesis are also discovered in the rat sciatic nerve crush injury model.

Grafts of Fibroblasts Genetically Modified to Secrete Ngf, Bdnf, Nt-3, or Basic Fgf Elicit Differential Responses in the Adult Spinal Cord

Neuronal and axonal responses to neurotrophic factors in the developing spinal cord have been relatively well characterized, but little is known about adult spinal responses to neurotrophic factors. We genetically modified primary rat fibroblasts to produce either nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), or basic fibroblast growth factor (bFGF), then grafted these neurotrophic factor-secreting cells into the central gray matter of the spinal cord in adult rats. Spinal cord lesions were not made prior to grafting. From 2 wk to 6 mo later, sensory neurites of dorsal root origin extensively penetrated NGF-, NT-3-, and bFGF-producing grafts, whereas BDNF-secreting grafts elicited no growth responses. Putative noradrenergic neurites also penetrated NGF-secreting cell grafts. Local motor and corticospinal motor axons did not penetrate any of the neurotrophic factor-secreting grafts. These results indicate that unlesioned or minimally lesioned adult spinal cord sensory and putative noradrenergic populations retain significant neurotrophic factor responsiveness, whereas motor neurites are comparatively resistant even to those neurotrophic factors to which they exhibit survival dependence during development. Grafts of genetically modified cells can be a useful tool for characterizing neurotrophic factor responsiveness in the adult spinal cord and designing strategies to promote axonal regeneration after injury.

Rescue of Motoneurons from Axotomy-Induced Cell Death by Polymer Encapsulated Cells Genetically Engineered to Release CNTF

The neurodegenerative disease amyotrophic lateral sclerosis (ALS) results from the progressive loss of motoneurons, leading to death in a few years. Ciliary neurotrophic factor (CNTF), which decreases naturally occurring and axotomy-induced cell death, may result in slowing of motoneuron loss and has been evaluated as a treatment for ALS. Effective administration of this protein to motoneurons may be hampered by the exceedingly short half-life of CNTF, and the inability to deliver effective concentration into the central nervous system after systemic administration in vivo. The constitutive release of CNTF from genetically engineered cells may represent a solution to this delivery problem. In this work, baby hamster kidney (BHK) cells stably tranfected with a chimeric plasmid construct containing the gene for human or mouse CNTF were encapsulated in polymer fibers, which prevents immune rejection and allow long-term survival of the transplanted cells. In vitro bioassays show that the encapsulated transfected cells release bioactive CNTF. In vivo, systemic delivery of human and mouse CNTF from encapsulated cells was observed to rescue 26 and 27% more facial motoneurons, respectively, as compared to capsules containing parent BHK cells 1 wk postaxotomy in neonatal rats. With local application of CNTF on the nerve stump and by systemic delivery through repeated subcutaneous injections, 15 and 13% more rescue effects were observed. These data illustrate the potential of using encapsulated genetically engineered cells to continuously release CNTF to slow down motoneuron degeneration following axotomy and suggest that encapsulated cell delivery of neurotrophic factors may provide a general method for effective administration of therapeutic proteins for the treatment of neurodegenerative diseases.

RARβ regulates neuronal cell death and differentiation in the avian ciliary ganglion

Programmed cell death during chicken ciliary ganglion (CG) development is mostly discussed as an extrinsically regulated process, guided either by the establishment of a functional balance between preganglionic and postganglionic activity or the availability of target‐derived neurotrophic factors. We found that the expression of the gene coding for the nuclear retinoic acid receptor β (RARB) is transiently upregulated prior to and during the execution phase of cell death in the CG. Using retroviral vectors, the expression of RARB was knocked down during embryonic development in ovo. The knockdown led to a significant increase in CG neuron number after the cell death phase. BrdU injections and active caspase‐3 staining revealed that this increase in neuron number was due to an inhibition of apoptosis during the normal cell death phase. Furthermore, apoptotic neuron numbers were significantly increased at a stage when cell death is normally completed. While the cholinergic phenotype of the neurons remained unchanged after RARB knockdown, the expression of the proneural gene Cash1 was increased, but somatostatin‐like immunoreactivity, a hallmark of the mature choroid neuron population, was decreased. Taken together, these results point toward a delay in neuronal differentiation as well as cell death. The availability of nuclear retinoic acid receptor β (RARβ) and RARβ‐induced transcription of genes could therefore be a new intrinsic cue for the maturation of CG neurons and their predisposition to undergo cell death. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 75: 1204–1218, 2015

Codon optimization and factorial screening for enhanced soluble expression of human ciliary neurotrophic factor in Escherichia coli

BACKGROUND

Neurotrophic factors influence survival, differentiation, proliferation and death of neuronal cells within the central nervous system. Human ciliary neurotrophic factor (hCNTF) has neuroprotective properties and is also known to influence energy balance. Consequently, hCNTF has potential therapeutic applications in neurodegenerative, obesity and diabetes related disorders. Clinical and biological applications of hCNTF necessitate a recombinant expression system to produce large amounts of functional protein in soluble form. Earlier attempts to express hCNTF in Escherichia coli (E. coli) were limited by low amounts and the need to refold from inclusion bodies.

RESULTS

In this report, we describe a strategy to effectively identify constructs and conditions for soluble expression of hCNTF in E. coli. Small-scale expression screening with soluble fusion tags identified many conditions that yielded soluble expression. Codon optimized 6-His-hCNTF construct showed soluble expression in all the conditions tested. Large-scale culture of the 6-His-hCNTF construct yielded high (10 - 20 fold) soluble expression (8 - 9 fold) as compared to earlier published reports. Functional activity of recombinant 6-His-hCNTF produced was confirmed by its binding to hCNTF receptor (hCNTFRα) with an EC50 = 36 nM.

CONCLUSION

Our results highlight the combination of codon optimization and screening soluble fusion tags as a successful strategy for high yielding soluble expression of hCNTF in E. coli. Codon optimization of the hCNTF sequence seems to be sufficient for soluble expression of hCNTF. The combined approach of codon optimization and soluble fusion tag screen can be an effective strategy for soluble expression of pharmaceutical proteins in E. coli.

Effect of locally administered ciliary neurotrophic factor on the survival of transected and repaired adult sheep facial nerve

OBJECTIVE

to determine whether the administration of Ciliary Neurotrophic Factor (CNTF) at the site of repaired facial nerve enhances regeneration in the adult sheep model.

METHODS

Ten adult sheep were divided into 2 groups: control and study group (CNTF group). In the CNTF group, the buccal branch of the facial nerve was transected and then repaired by epineural sutures. CNTF was injected over the left depressor labii maxillaris muscle in the vicinity of the transected and repaired nerve for 28 days under local anesthesia. In the CNTF group, the sheep were again anesthetized after nine months and the site of facial nerve repair was exposed. Detailed electrophysiological, tension experiments and morphometric studies were carried out and then analyzed statistically.

RESULTS

The skin CV min, refractory period, Jitter and tension parameters were marginally raised in the CNTF group than the control but the difference was statistically insignificant between the two groups. Morphometric indices also did not show any significant changes in the CNTF group.

CONCLUSION

CNTF has no profound effect on neuronal regeneration of adult sheep animal model.

KEYWORDS

CNTF; Neurtrophic factors; Sheep; Facial nerve; Regeneration.

Stüve-Wiedemann syndrome: LIFR and associated cytokines in clinical course and etiology

Stüve-Wiedemann syndrome (STWS; OMIM #610559) is a rare bent-bone dysplasia that includes radiologic bone anomalies, respiratory distress, feeding difficulties, and hyperthermic episodes. STWS usually results in infant mortality, yet some STWS patients survive into and, in some cases, beyond adolescence. STWS is caused by a mutation in the leukemia inhibitory factor receptor (LIFR) gene, which is inherited in an autosomally recessive pattern. Most LIFR mutations resulting in STWS are null mutations which cause instability of the mRNA and prevent the formation of LIFR, impairing the signaling pathway. LIFR signaling usually follows the JAK/STAT3 pathway, and is initiated by several interleukin-6-type cytokines. STWS is managed on a symptomatic basis since there is no treatment currently available.

Randomized trial of ciliary neurotrophic factor delivered by encapsulated cell intraocular implants for retinitis pigmentosa

PURPOSE

To evaluate the safety and effect on visual function of ciliary neurotrophic factor delivered via an intraocular encapsulated cell implant for the treatment of retinitis pigmentosa (RP).

DESIGN

Ciliary neurotrophic factor for late-stage retinitis pigmentosa study 3 (CNTF3; n = 65) and ciliary neurotrophic factor for early-stage retinitis pigmentosa study 4 (CNTF4; n = 68) were multicenter, sham-controlled dose-ranging studies.

METHODS

Patients were randomly assigned to receive a high- or low-dose implant in 1 eye and sham surgery in the fellow eye. The primary endpoints were change in best-corrected visual acuity (BCVA) at 12 months for CNTF3 and change in visual field sensitivity at 12 months for CNTF4. Patients had the choice of retaining or removing the implant at 12 months for CNTF3 and 24 months for CNTF4.

RESULTS

There were no serious adverse events related to either the encapsulated cell implant or the surgical procedure. In CNTF3, there was no change in acuity in either ciliary neurotrophic factor- or sham-treated eyes at 1 year. In CNTF4, eyes treated with the high-dose implant showed a significant decrease in sensitivity while no change was seen in sham- and low dose-treated eyes at 12 months. The decrease in sensitivity was reversible upon implant removal. In both studies, ciliary neurotrophic factor treatment resulted in a dose-dependent increase in retinal thickness.

CONCLUSIONS

Long-term intraocular delivery of ciliary neurotrophic factor is achieved by the encapsulated cell implant. Neither study showed therapeutic benefit in the primary outcome variable.

Leukemia inhibitory factor protects axons in experimental autoimmune encephalomyelitis via an oligodendrocyte-independent mechanism

Leukemia inhibitory factor (LIF) and Ciliary Neurotrophic factor (CNTF) are members of the interleukin-6 family of cytokines, defined by use of the gp130 molecule as an obligate receptor. In the murine experimental autoimmune encephalomyelitis (EAE) model, antagonism of LIF and genetic deletion of CNTF worsen disease. The potential mechanism of action of these cytokines in EAE is complex, as gp130 is expressed by all neural cells, and could involve immuno-modulation, reduction of oligodendrocyte injury, neuronal protection, or a combination of these actions. In this study we aim to investigate whether the beneficial effects of CNTF/LIF signalling in EAE are associated with axonal protection; and whether this requires signalling through oligodendrocytes. We induced MOG_35–55 EAE in CNTF, LIF and double knockout mice. On a CNTF null background, LIF knockout was associated with increased EAE severity (EAE grade 2.1±0.14 vs 2.6±0.19; P<0.05). These mice also showed increased axonal damage relative to LIF heterozygous mice, as indicated by decreased optic nerve parallel diffusivity on MRI (1540±207 µm²−/s vs 1310±175 µm²−/s; P<0.05), and optic nerve (−12.5%) and spinal cord (−16%) axon densities; and increased serum neurofilament-H levels (2.5 fold increase). No differences in inflammatory cell numbers or peripheral auto-immune T-cell priming were evident. Oligodendrocyte-targeted gp130 knockout mice showed that disruption of CNTF/LIF signalling in these cells has no effect on acute EAE severity. These studies demonstrate that endogenous CNTF and LIF act centrally to protect axons from acute inflammatory destruction via an oligodendrocyte-independent mechanism.

Genome-wide analysis of pain-, nerve- and neurotrophin -related gene expression in the degenerating human annulus

Background

In spite of its high clinical relevance, the relationship between disc degeneration and low back pain is still not well understood. Recent studies have shown that genome-wide gene expression studies utilizing ontology searches provide an efficient and valuable methodology for identification of clinically relevant genes. Here we use this approach in analysis of pain-, nerve-, and neurotrophin-related gene expression patterns in specimens of human disc tissue. Control, non-herniated clinical, and herniated clinical specimens of human annulus tissue were studied following Institutional Review Board approval.

Results

Analyses were performed on more generated (Thompson grade IV and V) discs vs. less degenerated discs (grades I-III), on surgically operated discs vs. control discs, and on herniated vs. control discs. Analyses of more degenerated vs. less degenerated discs identified significant upregulation of well-recognized pain-related genes (bradykinin receptor B1, calcitonin gene-related peptide and catechol-0-methyltransferase). Nerve growth factor was significantly upregulated in surgical vs. control and in herniated vs. control discs. All three analyses also found significant changes in numerous proinflammatory cytokine- and chemokine-related genes. Nerve, neurotrophin and pain-ontology searches identified many matrix, signaling and functional genes which have known importance in the disc. Immunohistochemistry was utilized to confirm the presence of calcitonin gene-related peptide, catechol-0-methyltransferase and bradykinin receptor B1 at the protein level in the human annulus.

Conclusions

Findings point to the utility of microarray analyses in identification of pain-, neurotrophin and nerve-related genes in the disc, and point to the importance of future work exploring functional interactions between nerve and disc cells in vitro and in vivo. Nerve, pain and neurotrophin ontology searches identified numerous changes in proinflammatory cytokines and chemokines which also have significant relevance to disc biology. Since the degenerating human disc is primarily an avascular tissue site into which disc cells have contributed high levels of proinflammatory cytokines, these substances are not cleared from the tissue and remain there over time. We hypothesize that as nerves grow into the human annulus, they encounter a proinflammatory cytokine-rich milieu which may sensitize nociceptors and exacerbate pain production.

Constitutive expression of ciliary neurotrophic factor in mouse hypothalamus

Ciliary neurotrophic factor (CNTF) is a potent survival molecule for a large number of neuronal and glial cells in culture; its expression in glial cells is strongly upregulated after a variety of nerve tissue injuries. Exogenously administered CNTF produces an anorectic effect via activation of hypothalamic neurons and stimulates neurogenesis in mouse hypothalamus. To determine whether CNTF is produced endogenously in the hypothalamus, we sought cellular sources and examined their distribution in adult mouse hypothalamus by immunohistochemistry. CNTF immunoreactivity (IR) was predominantly detected in the ependymal layer throughout the rostrocaudal extension of the third ventricle, where numerous ependymocytes and tanycytes exhibited specific staining. Some astrocytes in the grey matter of the anterior hypothalamus and in the median eminence of the hypothalamic tuberal region were also positive. Stimulation of cells bearing CNTF receptor α (CNTFRα) induces specific activation of the signal transducer and activator of transcription 3 (STAT3) signalling system. Treatment with recombinant CNTF and detection of the nuclear expression of phospho-STAT3 (P-STAT3) showed that CNTF-producing ependymal cells and tanycytes were intermingled with, or very close to, P-STAT3-positive, CNTFRα-bearing cells. A fraction of CNTF-producing ependymal cells and tanycytes and some median eminence astrocytes also exhibited P-STAT3 IR. Thus, in normal adult mice the ependyma of the third ventricle is both a source of and a target for CNTF, which may play hitherto unknown roles in hypothalamic function in physiological conditions.

The anorexigenic cytokine ciliary neurotrophic factor stimulates POMC gene expression via receptors localized in the nucleus of arcuate neurons

Ciliary neurotrophic factor (CNTF) is a neural cytokine that reduces appetite and body weight when administrated to rodents or humans. We have demonstrated recently that the level of CNTF in the arcuate nucleus (ARC), a key hypothalamic region involved in food intake regulation, is positively correlated with protection against diet-induced obesity. However, the comprehension of the physiological significance of neural CNTF action was still incomplete because CNTF lacks a signal peptide and thus may not be secreted by the classical exocytosis pathways. Knowing that CNTF distribution shares similarities with that of its receptor subunits in the rat ARC, we hypothesized that CNTF could exert a direct intracrine effect in ARC cells. Here, we demonstrate that CNTF, together with its receptor subunits, translocates to the cell nucleus of anorexigenic POMC neurons in the rat ARC. Furthermore, the stimulation of hypothalamic nuclear fractions with CNTF induces the phosphorylation of several signaling proteins, including Akt, as well as the transcription of the POMC gene. These data strongly suggest that intracellular CNTF may directly modulate POMC gene expression via the activation of receptors localized in the cell nucleus, providing a novel plausible mechanism of CNTF action in regulating energy homeostasis.

Regulation of neurokine receptor signaling and trafficking

Leukemia inhibitory factor (LIF) and ciliary neurotrophic factor (CNTF) are neurally active cytokines, or neurokines. LIF signals through a receptor consisting of gp130 and the low affinity LIF receptor (LIFR), while the CNTF receptor consists of gp130, LIFR, and the low affinity CNTF receptor (CNTFR). Ser1044 of the LIFR is phosphorylated by Erk1/2 MAP kinase. Stimulation of neural cells with growth factors which strongly activate Erk1/2 decreases LIF-mediated signal transduction due to increased degradation of the LIFR as a consequence of Erk1/2-dependent phosphorylation of the receptor at Ser1044. The gp130 receptor subunit is phosphorylated, at least in part by calmodulin-dependent protein kinase II, at Ser782, which is adjacent to a dileucine internalization motif. Ser782 appears to negatively regulate cytokine receptor expression, as mutagenesis of Ser782 results in increased gp130 expression and cytokine-induced neuropeptide gene transcription. The LIFR and gp130 are transmembrane proteins, while CNTFR is a peripheral membrane protein attached to the cell surface via a glycosylphosphatidylinositol tail. In unstimulated cells, CNTFR but not LIFR and gp130 is localized to detergent-resistant lipid rafts. Stimulation of cells with CNTFR causes translocation of LIFR and gp130 into the lipid rafts, while stimulation with LIF does not induce receptor translocation, raising the possibility that CNTF could induce different patterns of signaling and/or receptor trafficking than caused by LIF. We used a compartmentalized culture system to examine the mechanisms for retrograde signaling by LIF and CNTF from distal neurites to the cell bodies of mouse sympathetic neurons. Stimulation with neurokines of the distal neurites of sympathetic neurons grown in a compartmentalized culture system resulted in the activation and nuclear translocation of the transcription factor Stat3. Retrograde signaling required Jak kinase activity in the cell body but not the distal neurites, and could be blocked by inhibitors of microtubule but not microfilament function. The results are consistent with a signaling endosomes model in which the ctyokine/receptor complex is transported back to the cell body where Stat3 is activated. While both LIF and CNTF mediate retrograde activation of Stat3, the kinetics for retrograde signaling differ for the two neurokines.

CNTF and retina

Ciliary neurotrophic factor (CNTF) is one of the most studied neurotrophic factors for neuroprotection of the retina. A large body of evidence demonstrates that CNTF promotes rod photoreceptor survival in almost all animal models. Recent studies indicate that CNTF also promotes cone photoreceptor survival and cone outer segment regeneration in the degenerating retina and improves cone function in dogs with congenital achromotopsia. In addition, CNTF is a neuroprotective factor and an axogenesis factor for retinal ganglion cells (RGCs). This review focuses on the effects of exogenous CNTF on photoreceptors and RGCs in the mammalian retina and the potential clinical application of CNTF for retinal degenerative diseases.

Motor neuron trophic factors: therapeutic use in ALS?

The modest effects of neurotrophic factor (NTF) treatment on lifespan in both animal models and clinical studies of Amyotropic Lateral Sclerosis (ALS) may result from any one or combination of the four following explanations: 1.) NTFs block cell death in some physiological contexts but not in ALS; 2.) NTFs do not rescue motoneurons (MNs) from death in any physiological context; 3.) NTFs block cell death in ALS but to no avail; and 4.) NTFs are physiologically effective but limited by pharmacokinetic constraints. The object of this review is to critically evaluate the role of both NTFs and the intracellular cell death pathway itself in regulating the survival of spinal and cranial (lower) MNs during development, after injury and in response to disease. Because the role of molecules mediating MN survival has been most clearly resolved by the in vivo analysis of genetically engineered mice, this review will focus on studies of such mice expressing reporter, null or other mutant alleles of NTFs, NTF receptors, cell death or ALS-associated genes.

Leukemia inhibitory factor regulates trafficking of T-type Ca2+ channels

Neuropoietic cytokines such as ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF) stimulate the functional expression of T-type Ca(2+) channels in developing sensory neurons. However, the molecular and cellular mechanisms involved in the cytokine-evoked membrane expression of T-type Ca(2+) channels are not fully understood. In this study we investigated the role of LIF in promoting the trafficking of T-type Ca(2+) channels in a heterologous expression system. Our results demonstrate that transfection of HEK-293 cells with the rat green fluorescent protein (GFP)-tagged T-type Ca(2+) channel α(1H)-subunit resulted in the generation of transient Ca(2+) currents. Overnight treatment of α(1H)-GFP-transfected cells with LIF caused a significant increase in the functional expression of T-type Ca(2+) channels as indicated by changes in current density. LIF also evoked a significant increase in membrane fluorescence compared with untreated cells. Disruption of the Golgi apparatus with brefeldin A inhibited the stimulatory effect of LIF, indicating that protein trafficking regulates the functional expression of T-type Ca(2+) channels. Trafficking of α(1H)-GFP was also disrupted by cotransfection of HEK-293 cells with the dominant-negative form of ADP-ribosylation factor (ARF)1 but not ARF6, suggesting that ARF1 regulates the LIF-evoked membrane trafficking of α(1H)-GFP subunits. Trafficking of T-type Ca(2+) channels required transient activation of the JAK and ERK signaling pathways since stimulation of HEK-293 cells with LIF evoked a considerable increase in the phosphorylation of the downstream JAK targets STAT3 and ERK. Pretreatment of HEK-293 cells with the JAK inhibitor P6 or the ERK inhibitor U0126 blocked ERK phosphorylation. Both P6 and U0126 also inhibited the stimulatory effect of LIF on T-type Ca(2+) channel expression. These findings demonstrate that cytokines like LIF promote the trafficking of T-type Ca(2+) channels.

F-spondin regulates neuronal survival through activation of disabled-1 in the chicken ciliary ganglion

The extracellular membrane-associated protein F-spondin has been implicated in cell-matrix and cell-cell adhesion and plays an important role in axonal pathfinding. We report here that F-spondin is expressed in non-neuronal cells in the embryonic chicken ciliary ganglion (CG) and robustly promotes survival of cultured CG neurons. Using deletion constructs of F-spondin we found that the amino-terminal Reelin/Spondin domain cooperates with thrombospondin type 1 repeat (TSR) 6, a functional TGFβ-activation domain. In ovo treatment with blocking antibodies raised against the Reelin/Spondin domain or the TSR-domains caused increased apoptosis of CG neurons during the phase of programmed cell death and loss of about 30% of the neurons compared to controls. The Reelin/Spondin domain receptor - APP and its downstream signalling molecule disabled-1 are expressed in CG neurons. F-spondin induced rapid phosphorylation of disabled-1. Moreover, both blocking the central APP domain and interference with disabled-1 signalling disrupted the survival promoting effect of F-spondin. Taken together, our data suggest that F-spondin can promote neuron survival by a mechanism involving the Reelin/Spondin and the TSR domains.

Spatio-temporal expression of a novel neuron-derived neurotrophic factor (NDNF) in mouse brains during development

Background

Neuron-derived neurotrophic factor (NDNF) is evolutionarily well conserved, being present in invertebrate animals such as the nematode, Caenorhabditis elegans, as well as in the fruit fly, Drosophila melanogaster. Multiple cysteines are conserved between species and secondary structure prediction shows that NDNF is mainly composed of beta-strands. In this study, we aimed to investigate the function of NDNF.

Results

NDNF is a glycosylated, disulfide-bonded secretory protein that contains a fibronectin type III domain. NDNF promoted migration and growth and elicited neurite outgrowth of mouse hippocampal neurons in culture. NDNF also protected cultured hippocamal neurons against excitotoxicity and amyloid beta-peptide toxicity. Western blotting showed that NDNF was exclusively expressed in the brain and spinal cord. Immunostaining indicated that NDNF was expressed by neurons and not by astrocytes. Cajal-Retzius cells, cortex neurons, hippocampus neurons, olfactory mitral cells, cerebellar purkinje cells, cerebellar granular cells and spinal neurons were found to be NDNF-positive. NDNF expression was observed in the neurons during development.

Conclusions

The results of this study indicated that NDNF is a novel neurotrophic factor derived from neurons that may be useful in the treatment of neuronal degeneration diseases and nerve injuries.

Transplantation of ciliary neurotrophic factor-expressing adult oligodendrocyte precursor cells promotes remyelination and functional recovery after spinal cord injury

Demyelination contributes to the dysfunction after traumatic spinal cord injury (SCI). We explored whether the combination of neurotrophic factors and transplantation of adult rat spinal cord oligodendrocyte precursor cells (OPCs) could enhance remyelination and functional recovery after SCI. Ciliary neurotrophic factor (CNTF) was the most effective neurotrophic factor to promote oligodendrocyte (OL) differentiation and survival of OPCs in vitro. OPCs were infected with retroviruses expressing enhanced green fluorescent protein (EGFP) or CNTF and transplanted into the contused adult thoracic spinal cord 9 d after injury. Seven weeks after transplantation, the grafted OPCs survived and integrated into the injured spinal cord. The survival of grafted CNTF-OPCs increased fourfold compared with EGFP-OPCs. The grafted OPCs differentiated into adenomatus polyposis coli (APC(+)) OLs, and CNTF significantly increased the percentage of APC(+) OLs from grafted OPCs. Immunofluorescent and immunoelectron microscopic analyses showed that the grafted OPCs formed central myelin sheaths around the axons in the injured spinal cord. The number of OL-remyelinated axons in ventrolateral funiculus (VLF) or lateral funiculus (LF) at the injured epicenter was significantly increased in animals that received CNTF-OPC grafts compared with all other groups. Importantly, 75% of rats receiving CNTF-OPC grafts recovered transcranial magnetic motor-evoked potential and magnetic interenlargement reflex responses, indicating that conduction through the demyelinated axons in VLF or LF, respectively, was partially restored. More importantly, recovery of hindlimb locomotor function was significantly enhanced in animals receiving grafts of CNTF-OPCs. Thus, combined treatment with OPC grafts expressing CNTF can enhance remyelination and facilitate functional recovery after traumatic SCI.

Neuroprotective properties of ciliary neurotrophic factor for cultured adult rat dorsal root ganglion neurons

We observed that recombinant ciliary neurotrophic factor (CNTF) enhanced survival and neurite outgrowth of cultured adult rat dorsal root ganglion (DRG) neurons. Among other neurotrophic factors (NGF and GDNF) and interleukin (IL)-6 cytokine members [IL-6, LIF, cardiotrophin-1, and oncostatin M (OSM)] at the same concentration (50 ng/ml), CNTF, as well as LIF and OSM, displayed high efficacy for the promotion of the number of viable neurons and neurite-bearing cells. CNTF enhanced the number of neurite-bearing cells in both small neurons (soma diameter <30 microm) and large neurons (soma diameter > or =30 microm), whereas NGF and GDNF promoted that in only small neurons. Western blot analysis revealed that CNTF induced phosphorylation of STAT3, Akt, and ERK1/2 in the neurons. Furthermore, the neurite outgrowth-promoting activity of CNTF was diminished by co-treatment with Janus kinase (JAK) 2 inhibitor, AG490; STAT3 inhibitor, STA-21; phosphatidyl inositol-3'-phosphate-kinase (PI3K) inhibitor, LY294002; and mitogen-activated protein kinase kinase (MEK) inhibitor, PD98059, in a concentration-dependent manner. Its survival-promoting activity was also affected by AG490, STA-21, and LY294002 at higher concentrations, but not by PD98059. These findings suggest the involvement of JAK2/STAT3, PI3K/Akt, and MEK/ERK signaling pathways in CNTF-induced neurite outgrowth, where the former two pathways are thought to play major roles in mediating the survival response of neurons to CNTF.

Effects of electro-acupuncture on CNTF expression in spared dorsal root ganglion and the associated spinal lamina II and nucleus dorsalis following adjacent dorsal root ganglionectomies in cats

It is well known that plasticity occurs in deafferented spinal cord, and that electro-acupuncture (EA) could promote functional restoration. The underlying mechanism is, however, unknown. Ciliary neurotrophic factor (CNTF) plays a crucial role in neurite outgrowth and neuronal survival both in vivo and in vitro, and its expression might explain some of the mechanism. In this study, we investigated the effects of EA on CNTF expression in the spared L(6) dorsal root ganglion (DRG), and spinal lamina II at spinal segments L(3) and L(6) as well as nucleus dorsalis (ND) of L(3) spinal segment following removal of L(1)-L(5) and L(7)-S(2) (DRG) in the cat. After ganglionectomies, the total and small-to-medium-sized numbers of immunoreactive neurons decreased at 3 dpo, and returned to the sham-operated level as early as 7 dpo. After EA, immunoreactive neurons in L(6) DRG noticeably increased at 7 dpo, compared with the non-acupunctured group. Notable increase in the large neurons was seen at 14 dpo, while their numbers in L(3) and L(6) spinal cord segments significantly declined at 3 dpo. Those in L(3) segment did not reach the sham-operated level until 14 dpo, but their numbers in L(6) segment returned to the sham-operated level as early as 7 dpo. CNTF immunopositive neurons in the ND of L(3) segment returned to the sham-operated level at 14 dpo. After EA, their number significantly increased as early as 7 dpo in lamina II of L(6) segment, and as late as 14 dpo in ND of L(3) segment. Western blot analysis showed CNTF changes corresponding to those shown in immunohistochemical staining. It is concluded that CNTF expression was involved in the EA promoted plastic changes in L(6) DRG and the associated deafferented spinal lamina and ND.

Neurotrophic interactions in the development of spinal cord motoneurons

The final number of spinal cord motoneurons is attained by a two-step process involving the proliferation of precursor cells and the loss by cell death of a proportion (approximately 50%) of the post-mitotic neurons. Although the mechanisms responsible for the proliferation of stereotyped numbers of motoneurons are not understood, considerable evidence from in vitro as well as in vivo studies indicates that the second step in attaining population size (cell death) is controlled by the interaction of motoneurons with both their efferent targets and their afferent inputs. Target influences on motoneuron survival are thought to be regulated by muscular activity and by competition for limited amounts of neurotrophic factors derived from striated skeletal muscles. However, evidence that such putative neurotrophic factors actually modulate motoneuron survival in vivo has been lacking. Using crude and partially purified extracts from embryonic hindlimbs (Days 8-9) we have found that the treatment of chick embryos in ovo with these agents during the normal cell death period (Days 5-10) rescues a significant number of motoneurons from degeneration. Kidney or lung extracts and heat-inactivated hindlimb extracts were ineffective. The survival-inducing activity of partially purified extract was dose dependent and developmentally regulated. The survival of sensory, sympathetic and a population of cholinergic sympathetic preganglionic neurons was unaffected by treatment with hindlimb extract. The massive motoneuron death that occurs after early target (hindlimb) removal was partially ameliorated by daily treatment with the hindlimb extract. Survival-inducing activity of the extract is lost after trypsin treatment. Taken collectively these results indicate that a target-derived protein or polypeptide neurotrophic factor is involved in the regulation of motoneuron survival in vivo.

Neurotrophic factors and neuronal death

The well-documented physiological role of nerve growth factor (NGF) in peripheral sympathetic and neural-crest-derived sensory neurons in vivo has its exact counterpart in vitro. This provided the conceptual basis for developing in vitro analytical procedures for the purification of new neurotrophic molecules. The experimental approaches used are discussed in the context of the purification of new neurotrophic factors, brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF). The importance of the modulatory role played by extracellular matrix molecules, in particular laminin, on both NGF-mediated and BDNF-mediated survival effects is also delineated. BDNF is a very basic (pI approximately 10) molecule of about 12 kDa, having physico-chemical characteristics close to those of the monomer of NGF. However, the spectrum of its biological actions is distinctly different from that of NGF. In particular, BDNF supports the survival of retinal ganglion cells and placode-derived peripheral sensory neurons which are not supported by NGF. The trophic supply of primary sensory neurons projecting to both the central nervous system and the periphery is discussed. It is hypothesized that sensory neurons receive limited quantities of neurotrophic molecules from both peripheral and central axons, a mechanism ensuring the survival of neurons adequately connected with both peripheral and central targets.

Expression and histochemical localization of ciliary neurotrophic factor in cultured adult rat dorsal root ganglion neurons

Ciliary neurotrophic factor (CNTF) is abundantly expressed in Schwann cells in adult mammalian peripheral nerves, but not in neurons. After peripheral nerve injury, CNTF released from disrupted Schwann cells is likely to promote neuronal survival and axonal regeneration. In the present study, we examined the expression and histochemical localization of CNTF in adult rat DRG in vivo and in vitro. In contrast to the restricted expression in Schwann cells in vivo, we observed abundant CNTF mRNA and protein expression in DRG neurons after 3 h, 2, 7, and 15 days in dissociated cell culture. At later stages (7 and 15 days) of culture, CNTF immunoreactivity was detected in both neuronal cell bodies and regenerating neurites. These results suggest that CNTF is synthesized and transported to neurites in cultured DRG neurons. Since we failed to observe CNTF immunoreactivity in DRG neurons in explant culture, disruption of cell-cell interactions, rather than the culture itself, may be an inducible factor for localization of CNTF in the neurons.

Neutralization of ciliary neurotrophic factor reduces astrocyte production from transplanted neural stem cells and promotes regeneration of corticospinal tract fibers in spinal cord injury

Transplantation of neural stem cells (NSC) into lesioned spinal cord offers the potential to increase regeneration by replacing lost neurons or oligodendrocytes. The majority of transplanted NSC, however, typically differentiate into astrocytes that may exacerbate glial scar formation. Here we show that blocking of ciliary neurotrophic factor (CNTF) with anti-CNTF antibodies after NSC transplant into spinal cord injury (SCI) resulted in a reduction of glial scar formation by 8 weeks. Treated animals had a wider distribution of transplanted NSC compared with the control animals. The NSC around the lesion coexpressed either nestin or markers for neurons, oligodendrocytes, or astrocytes. Approximately 20% fewer glial fibrillary acidic protein-positive/bromodeoxyuridine (BrdU)-positive cells were seen at 2, 4, and 8 weeks postgrafting, compared with the control animals. Furthermore, more CNPase(+)/BrdU(+) cells were detected in the treated group at 4 and 8 weeks. These CNPase(+) or Rip(+) mature oligodendrocytes were seen in close proximity to host corticospinal tract (CST) and 5HT(+) serotonergic axon. We also demonstrate that the number of regenerated CST fibers both at the lesion and at caudal sites in treated animals was significantly greater than that in the control animals at 8 weeks. We suggest that the blocking of CNTF at the beginning of SCI provides a more favorable environment for the differentiation of transplanted NSC and the regeneration of host axons.

CNTF promotes the survival and differentiation of adult spinal cord-derived oligodendrocyte precursor cells in vitro but fails to promote remyelination in vivo

Delivery of factors capable of promoting oligodendrocyte precursor cell (OPC) survival and differentiation in vivo is an important therapeutic strategy for a variety of pathologies in which demyelination is a component, including multiple sclerosis and spinal cord injury. Ciliary neurotrophic factor (CNTF) is a neuropoietic cytokine that promotes both survival and maturation of a variety of neuronal and glial cell populations, including oligodendrocytes. Present results suggest that, although CNTF has a potent survival and differentiation promoting effect in vitro on OPCs isolated from the adult spinal cord, CNTF administration in vivo is not sufficient to promote oligodendrocyte remyelination in the glial-depleted environment of unilateral ethidium bromide (EB) lesions.

NT-3 and CNTF exert dose-dependent, pleiotropic effects on cells in the immature dorsal root ganglion: Neuregulin-mediated proliferation of progenitor cells and neuronal differentiation

Neurons in the nascent dorsal root ganglia are born and differentiate in a complex cellular milieu composed of postmitotic neurons, and mitotically active glial and neural progenitor cells. Neurotrophic factors such as NT-3 are critically important for promoting the survival of postmitotic neurons in the DRG. However, the factors that regulate earlier events in the development of the DRG such as the mitogenesis of DRG progenitor cells and the differentiation of neurons are less defined. Here we demonstrate that both NT-3 and CNTF induce distinct dose-dependent responses on cells in the immature DRG: at low concentrations, they induce the proliferation of progenitor cells while at higher concentrations they promote neuronal differentiation. Furthermore, the mitogenic response is indirect; that is, NT-3 and CNTF first bind to nascent neurons in the DRG--which then stimulates those neurons to release mitogenic factors including neuregulin. Blockade of this endogenous neuregulin activity completely blocks the CNTF-induced proliferation and reduces about half of the NT-3-mediated proliferation. Thus, the genesis and differentiation of neurons and glia in the DRG are dependent upon reciprocal interactions among nascent neurons, glia, and mitotically active progenitor cells.

Neurotrophic factors in peripheral neuropathies: therapeutic implications

Neurotrophic factors are proteins which promote the survival of specific neuronal populations. Many have other physiological effects on neurons such as inducing morphological differentiation, enhancing nerve regeneration, stimulating neurotransmitter expression, and otherwise altering the physiological characteristics of neurons. These properties suggest that neurotrophic factors are highly promising as potential therapeutic agents for neurological disease. Neurotrophic factors will most likely be applied to the peripheral nervous system initially, since there are fewer problems for large proteins to gain access to peripheral neurons. Many of the most intensively studied factors are active in the peripheral nervous system. These include the neurotrophins (nerve growth factor, brain derived neurotrophic factor, neurotrophin-3, neurotrophin-4/5), the insulin like growth factors, ciliary neurotrophic factor, and glial cell derived neurotrophic factor and its related proteins. The biology of these factors and their receptors in the peripheral nervous system is reviewed here. We also review data suggesting that abnormal availability of some factors may contribute towards the pathogenesis of certain types of peripheral neuropathy. Finally, the pre-clinical data suggesting that individual factors might be effective in treating neuropathy is reviewed, along with data relating to possible side effects of neurotrophic factor therapy. Several factors have already entered clinical trials with variable success. The data from these trials is reviewed as well.

Depolarization promotes survival of ciliary ganglion neurons by BDNF-dependent and -independent mechanisms

Membrane activity upregulates brain derived neurotrophic factor (BDNF) expression to coordinately support neuronal survival in many systems. In parasympathetic ciliary ganglion (CG) neurons, activity mimicked by KCl depolarization provides nearly full trophic support. While BDNF has been considered unable to influence CG neuronal survival, we now document its expression during CG development and show that low concentrations do support survival via high-affinity TrkB receptors. Furthermore, a contribution of BDNF to activity-induced trophic support was demonstrated by showing that KCl depolarization increased BDNF mRNA and protein in, and release of BDNF from, CG neuron cultures. Application of anti-BDNF blocking antibody or mitogen activated protein kinase (MAPK) kinase inhibitor, attenuated depolarization-supported survival, implicating canonical BDNF/TrkB signaling. Ca2+-Calmodulin kinase II (CaMKII) was also required since its inhibition combined with anti-BDNF or MAPK kinase inhibitor abolished or greatly reduced the trophic effects of depolarization. Membrane activity may thus support CG neuronal survival both by stimulating release of BDNF that binds high-affinity TrkB receptors to activate MAPK and by recruiting CaMKII. This mechanism could have relevance late in development in vivo as ganglionic transmission and the effectiveness of BDNF over other growth factors both increase.

Therapeutic potential of neurotrophic factors in neurodegenerative diseases

There is a vast amount of evidence indicating that neurotrophic factors play a major role in the development, maintenance, and survival of neurons and neuron-supporting cells such as glia and oligodendrocytes. In addition, it is well known that alterations in levels of neurotrophic factors or their receptors can lead to neuronal death and contribute to the pathogenesis of neurodegenerative diseases such as Parkinson disease, Alzheimer disease, Huntington disease, amyotrophic lateral sclerosis, and also aging. Although various treatments alleviate the symptoms of neurodegenerative diseases, none of them prevent or halt the neurodegenerative process. The high potency of neurotrophic factors, as shown by many experimental studies, makes them a rational candidate co-therapeutic agent in neurodegenerative disease. However, in practice, their clinical use is limited because of difficulties in protein delivery and pharmacokinetics in the central nervous system. To overcome these disadvantages and to facilitate the development of drugs with improved pharmacotherapeutic profiles, research is underway on neurotrophic factors and their receptors, and the molecular mechanisms by which they work, together with the development of new technologies for their delivery into the brain.

Differential proteomic analysis of proteins induced by glucocorticoids in cultured murine podocytes

BACKGROUND

The glomerular podocyte is the kidney cell most affected during the development of nephrotic syndrome, and mutations in podocyte proteins are responsible for a variety of inherited forms of nephrotic syndrome. Although glucocorticoids are a primary treatment for nephrotic syndrome, neither their target cell nor mechanism of action are known. In order to describe the proteome of the podocyte, and to identify podocyte proteins whose expression is altered by glucocorticoids, we performed a differential proteomic analysis of control and dexamethasone-treated cultured murine podocytes.

METHODS

Podocyte proteins were separated by two-dimensional-polyacrylamide gel electrophoresis (PAGE) and identified by matrix-assisted laser desorption time-of-flight (MALDI-TOF) mass spectrometry and peptide fingerprinting. Comparisons of stained two-dimensional-PAGE separations were used to identify proteins whose expression was altered by treatment with the glucocorticoid dexamethasone, and these results were confirmed by quantitative Western blotting.

RESULTS

A total of 106 protein spots yielded MALDI-TOF results, and 92 were identified by protein fingerprinting. Of the 88 unique proteins and four protein isoforms identified, six proteins were found whose expression was altered by dexamethasone. The proteome of cultured murine podocytes is particularly rich in actin cytoskeletal proteins and proteins involved in responses to cellular stress. The change in expression of three proteins [ciliary neurotrophic factor (CNTF), alphaB-crystallin, and heat shock protein 27 (hsp27)] was confirmed by quantitative Western blotting.

CONCLUSION

Three proteins with known roles in protecting cells from injury were up-regulated by dexamethasone, demonstrating that glucocorticoids exert a direct effect on cultured podocytes resulting in changes in the expression of proteins with potential relevance to the therapeutic action of glucocorticoids in diseases such as nephrotic syndrome.

Effects of glial transplantation on functional recovery following acute spinal cord injury

Numerous efforts have been made to maximize the efficacy of treatment for spinal cord injury (SCI). Recently, oligodendrocyte-type 2 astrocyte (O-2A) progenitor cells have been reported to remyelinate focal areas of demyelinated spinal cord in adult rats. We conducted a study to investigate the therapeutic potential of transplantation of O-2A cells in a rat model of acute SCI. SCI was induced with an NYU Impactor at T9 of rats. O-2A cells labeled with bromodeoxyuridine (BrdU) were transplanted into sites of SCI at 1 week after the induction of SCI. At 6 weeks after cell transplantation, a behavioral test showed significant functional improvement in animals that had received O-2A-cell transplants as compared to animals given cell-culture medium alone. An electrophysiological study revealed that the transplants did not improve the amplitude or latency of somatosensory evoked potentials, but a recording of motor evoked potentials showed that the latency of these potentials in the O-2A-cell-transplant group was significantly shorter than that in the group treated with cell-culture medium. Following transplantation of BrdU-labeled O-2A cells, cells positive for BrdU were detected at and near sites of SCI. Cells labeled for both BrdU and 2',3' -cyclic nucleotide-3-phosphodiesterase were also detected, showing that the transplanted O-2A cells differentiated into oligodendrocytes. By contrast, cells labeled for BrdU and glial fibrillary acidic protein, or for neuronal nuclei antigen, were not detected. Furthermore, a tract-tracing study showed that numbers of retrogradely labeled neurons increased in areas of the brain stem after O-2A-cell transplantation. The study data showed that after being transplanted into an animal with SCI, O-2A cells migrated to the area adjacent to the site of injury and differentiated into oligodendrocytes. The behavioral test and the electrophysiological and morphological studies showed that transplantation of O-2A cells may play an important role in functional recovery and the regeneration of axons after SCI.

Mesenchymal stem cells that produce neurotrophic factors reduce ischemic damage in the rat middle cerebral artery occlusion model

Mesenchymal stem cells (MSC) were reported to ameliorate functional deficits after stroke in rats, with some of this improvement possibly resulting from the action of cytokines secreted by these cells. To enhance such cytokine effects, we previously transfected the telomerized human MSC with the BDNF gene using a fiber-mutant adenovirus vector and reported that such treatment contributed to improved ischemic recovery in a rat transient middle cerebral artery occlusion (MCAO) model. In the present study, we investigated whether other cytokines in addition to BDNF, i.e., GDNF, CNTF, or NT3, might have a similar or greater effect in this model. Rats that received MSC-BDNF (P < 0.05) or MSC-GDNF (P < 0.05) showed significantly more functional recovery as demonstrated by improved behavioral test results and reduced ischemic damage on MRI than did control rats 7 and 14 days following MCAO. On the other hand, rats that received MSC-CNTF or MSC-NT3 showed neither functional recovery nor ischemic damage reduction compared to control rats. Thus, MSC transfected with the BDNF or GDNF gene resulted in improved function and reduced ischemic damage in a rat model of MCAO. These data suggest that gene-modified cell therapy may be a useful approach for the treatment of stroke.

Pathophysiology of peripheral nerve injury: a brief review

Clinicians caring for patients with brachial plexus and other nerve injuries must possess a clear understanding of the peripheral nervous system's response to trauma. In this article, the authors briefly review peripheral nerve injury (PNI) types, discuss the common injury classification schemes, and describe the dynamic processes of degeneration and reinnervation that characterize the PNI response.

Neurotrophic factors in Huntington's disease

Huntington's disease is a neurodegenerative disorder characterized by the selective loss of striatal neurons and, to a lesser extent, cortical neurons. The neurodegenerative process is caused by the mutation of huntingtin gene. Recent studies have established a link between mutant huntingtin, excitotoxicity and neurotrophic factors. Neurotrophic factors prevent cell death in degenerative processes but they can also enhance growth and function of neurons that are affected in Huntington's disease. The endogenous regulation of the expression of neurotrophic factors and their receptors in the striatum and its connections can be important to protect striatal cells and maintains basal ganglia connectivity. The administration of exogenous neurotrophic factors, in animal models of Huntington's disease, has been used to characterize the trophic requirements of striatal and cortical neurons. Neurotrophins, glial cell line-derived neurotrophic factor family members and ciliary neurotrophic factor have shown a potent neuroprotective effects on different neuronal populations of the striatum. Furthermore, they are also useful to maintain the integrity of the corticostriatal pathway. Thus, these neurotrophic factors may be suitable for the development of a neuroprotective therapy for neurodegenerative disorders of the basal ganglia.

Ciliary neurotrophic factor inhibits differentiation of photoreceptor-like cells in rat pineal glands in vitro

Ciliary neurotrophic factor (CNTF) is a unique member of the interleukin-6 (IL-6) family, whose receptor subunit for ligand binding is exclusively expressed in the nervous system and muscle. The role of CNTF in mammalian development remains unknown. We recently reported the specific expression of CNTF in the pineal gland and eyes. To further examine the expression pattern and role of CNTF in development, we prepared a polyclonal antibody against rat CNTF, performed western blotting with this antibody, and confirmed a strong and specific expression of the CNTF protein in pineal glands and a moderate expression in the eyes among the various tissues examined in newborn rats. In pineal organ cultures of newborn rats, exogenously added recombinant rat CNTF potently inhibited the differentiation of photoreceptor-like cells in a dose-dependent manner, while CNTF did not influence the survival of pineal cells. Among several cell growth factors known to have a similar effect in retinal cultures examined, strong inhibitory effects were seen only with CNTF and the leukemia inhibitory factor (LIF), both of which belong to the IL-6 cytokine family. This inhibitory effect was the strongest during three to 6 days of culture when CNTF was added to these cultures. These results suggest that CNTF plays an inhibitory role in the development of photoreceptor-like cells in early postnatal rat pineal glands.

Distribution of CNTF receptor alpha protein in the central nervous system of the chick embryo

Ciliary neurotrophic factor (CNTF) promotes the survival and differentiation of various neuronal and glial cell populations in the nervous system of vertebrates. In mammals, the ligand-binding alpha-subunit of the CNTF receptor (CNTFRalpha) is expressed in a variety of neuronal populations, including all CNTF-responsive cells. Previous studies suggested that functional differences in the CNTF/CNTF receptor system between chicks and mammals exist. The purpose of the present study was to examine the temporal and spatial expression pattern of the chick CNTFRalpha protein during CNS development. Receptor expression was detectable by immunoblotting in all CNS areas tested but showed area-specific developmental regulation. Interestingly, two variants of CNTFRalpha, 69 and 65 kD, were identified by immunoblotting with a shift from the higher to the lower molecular mass species occurring during development. Immunoreactivity for CNTFRalpha protein was preferentially observed in neuropil and white matter structures of the developing CNS while neuronal somata generally appeared unlabeled. For example, expression was observed in the olfactory system, in the telencephalon, in parts of the somatosensory system, in components of the tectofugal pathway, in the cerebellum, and in auditory brainstem nuclei. Fiber tracts that exhibit CNTFRalpha immunoreactivity were the lateral forebrain bundle, occipitomesencephalic tract, quintofrontal tract, and vestibular nerve. Our study identifies potential new targets of a chick CNTF-related molecule and reveals significant regional differences of CNTFRalpha protein expression between chick and mammals. These results suggest that the CNTF receptor performs distinct developmental functions in different animals.

Corneal nerves: structure, contents and function

This review provides a comprehensive analysis of the structure, neurochemical content, and functions of corneal nerves, with special emphasis on human corneal nerves. A revised interpretation of human corneal nerve architecture is presented based on recent observations obtained by in vivo confocal microscopy (IVCM), immunohistochemistry, and ultrastructural analyses of serial-sectioned human corneas. Current data on the neurotransmitter and neuropeptide contents of corneal nerves are discussed, as are the mechanisms by which corneal neurochemicals and associated neurotrophins modulate corneal physiology, homeostasis and wound healing. The results of recent clinical studies of topically applied neuropeptides and neurotrophins to treat neurotrophic keratitis are reviewed. Recommendations for using IVCM to evaluate corneal nerves in health and disease are presented.