Ciliary neurotrophic factor prevents retrograde neuronal death in the adult central nervous system

The Neuroprotective Effects of Exosomes Derived from TSG101-Overexpressing Human Neural Stem Cells in a Stroke Model

Although tissue-type plasminogen activator was approved by the FDA for early reperfusion of occluded vessels, there is a need for an effective neuroprotective drug for stroke patients. In this study, we established tumor susceptibility gene (TSG)101-overexpressing human neural stem cells (F3.TSG) and investigated whether they showed enhanced secretion of exosomes and whether treatment with exosomes during reperfusion alleviated ischemia-reperfusion-mediated brain damage. F3.TSG cells secreted higher amounts of exosomes than the parental F3 cells. In N2A cells subjected to oxygen–glucose deprivation (OGD), treatment with exosomes or coculture with F3.TSG cells significantly attenuated lactate dehydrogenase release, the mRNA expression of proinflammatory factors, and the protein expression of DNA-damage-related proteins. In a middle cerebral artery occlusion (MCAO) rat model, treatment with exosomes, F3 cells, or F3.TSG cells after 2 h of occlusion followed by reperfusion reduced the infarction volume and suppressed inflammatory cytokines, DNA-damage-related proteins, and glial fibrillary acidic protein, and upregulated several neurotrophic factors. Thus, TSG101-overexpressing neural stem cells showed enhanced exosome secretion; exosome treatment protected against MCAO-induced brain damage via anti-inflammatory activities, DNA damage pathway inhibition, and growth/trophic factor induction. Therefore, exosomes and F3.TSG cells can affect neuroprotection and functional recovery in acute stroke patients.

Dendrimer as a momentous tool in tissue engineering and regenerative medicine

Dendrimers have been comprehensively used for cargo delivery, nucleic acid delivery (genes, miRNA/siRNAs), delivery of macromolecules, and other various biomedical applications. Dendrimers are highly versatile in function and can be engineered as multifunctional biomacromolecules by modifying the surface for fulfilling different applications. Dendrimers are being used for crosslinking of existing synthetic and natural polymeric scaffolds to regulate their binding efficiency, stiffness, biocompatibility, transfection, and many other properties to mimic the in vivo extracellular matrix in tissue engineering and regenerative medicine (TERM). Dendritic inter-cellular linkers can enhance the linkages between cells and result in scaffold-independent tissue constructs. Effectively engineered dendrimers are the ideal molecules for delivering bioactive molecules such as cytokines, chemokines, growth factors, etc., and other metabolites for efficaciously regulating cell behavior. Dendrimeric nanostructures have shown tremendous results in various TERM fields like stem cells survival, osteogenesis, increased crosslinking for eye and corneal repair, and proliferation in cartilage. This review highlights the role and various aspects of dendritic polymers for TERM in general and with respect to specific tissues. This review also covers novel explorations and insights into the use of dendrimers in TERM, focusing on the developments in the past decade and perspective of the future.

Nanotechnology for Medical and Surgical Glaucoma Therapy-A Review

Glaucoma is the second leading cause of blindness worldwide. Even though significant advances have been made in its management, currently available antiglaucoma therapies suffer from considerable drawbacks. Typically, the success and efficacy of glaucoma medications are undermined by their limited bioavailability to target tissues and the inadequate adherence demonstrated by patients with glaucoma. The latter is due to a gradual decrease in tolerability of lifelong topical therapies and the significant burden to patients of prescribed stepwise antiglaucoma regimens with frequent dosing which impact quality of life. On the other hand, glaucoma surgery is restricted by the inability of antifibrotic agents to efficiently control the wound healing process without causing severe collateral damage and long-term complications. Evolution of the treatment paradigm for patients with glaucoma will ideally include prevention of retinal ganglion cell degeneration by the successful delivery of neurotrophic factors, anti-inflammatory drugs, and gene therapies. Nanotechnology-based treatments may surpass the limitations of currently available glaucoma therapies through optimized targeted drug delivery, increased bioavailability, and controlled release. This review addresses the recent advances in glaucoma treatment strategies employing nanotechnology, including medical and surgical management, neuroregeneration, and neuroprotection.

Neuroprotective effects of human neural stem cells over-expressing choline acetyltransferase in a middle cerebral artery occlusion model

Stroke is one of the most-devastating brain diseases causing acute death or permanent disability. Although tissue-type plasminogen activator was approved by Food and Drug Administration for early reperfusion of the occluded vessels, oxidative injury may cause extensive brain infarction. Accordingly, there is a need for effective neuroprotection during reperfusion, and stem cell-based therapeutic approaches should fulfill this requirement. We established human neural stem cells (NSCs) encoding gene of choline acetyltransferase (F3.ChAT), an acetylcholine-synthesizing enzyme, and investigated whether infusion of the F3.ChAT cells attenuate the ischemia-reperfusion brain damage in a rat model of middle cerebral artery occlusion (MCAO). F3.ChAT cells were found to produce much higher amounts of ChAT as well as neuroprotective and anti-inflammatory neurotrophins than their parental F3 NSCs. After 2-h occlusion, the artery was reperfused, along with intravenous infusion of the stem cells (1 × 10⁶ cells/rat). Administration of the F3.ChAT cells markedly reduced the infarction volume and improved both the cognitive dysfunction and behavioural deficits of MCAO animals, in which F3.ChAT cells were superior to F3 cells. F3.ChAT cells not only restored microtubule-associated protein-2, a neuronal cytoskeletal protein, and preserved microvessels, but also suppressed lipid peroxidation, pro-inflammatory cytokines, glial fibrillary acidic protein, and intercellular adhesion molecule-1 in the brain tissues. The results demonstrate that early intravenous infusion of NSCs expressing ChAT and neurotrophins attenuate brain and capillary injuries and restore neurobehavioural functions via neuroprotective and anti-inflammatory activities, and that F3.ChAT cells could be a candidate for the neuroprotection and functional recovery of acute stroke patients.

Cortical AAV-CNTF Gene Therapy Combined with Intraspinal Mesenchymal Precursor Cell Transplantation Promotes Functional and Morphological Outcomes after Spinal Cord Injury in Adult Rats

Ciliary neurotrophic factor (CNTF) promotes survival and enhances long-distance regeneration of injured axons in parts of the adult CNS. Here we tested whether CNTF gene therapy targeting corticospinal neurons (CSN) in motor-related regions of the cerebral cortex promotes plasticity and regrowth of axons projecting into the female adult F344 rat spinal cord after moderate thoracic (T10) contusion injury (SCI). Cortical neurons were transduced with a bicistronic adeno-associated viral vector (AAV1) expressing a secretory form of CNTF coupled to mCHERRY (AAV-CNTF^mCherry) or with control AAV only (AAV-GFP) two weeks prior to SCI. In some animals, viable or nonviable F344 rat mesenchymal precursor cells (rMPCs) were injected into the lesion site two weeks after SCI to modulate the inhibitory environment. Treatment with AAV-CNTF^mCherry, as well as with AAV-CNTF^mCherry combined with rMPCs, yielded functional improvements over AAV-GFP alone, as assessed by open-field and Ladderwalk analyses. Cyst size was significantly reduced in the AAV-CNTF^mCherry plus viable rMPC treatment group. Cortical injections of biotinylated dextran amine (BDA) revealed more BDA-stained axons rostral and alongside cysts in the AAV-CNTF^mCherry versus AAV-GFP groups. After AAV-CNTF^mCherry treatments, many sprouting mCherry-immunopositive axons were seen rostral to the SCI, and axons were also occasionally found caudal to the injury site. These data suggest that CNTF has the potential to enhance corticospinal repair by transducing parent CNS populations.

Cellular Delivery of Cntf but not Nt-4/5 Prevents Degeneration of Striatal Neurons in a Rodent Model of Huntington's Disease

The delivery of neurotrophic factors to the central nervous system (CNS) has gained considerable attention as a potential treatment strategy for neurodegenerative disorders such as Huntington's disease (HD). In the present study, we directly compared the ability of two neurotrophic factors, ciliary neurotrophic factor (CNTF), and neurotrophin-4/5 (NT-4/5), to prevent the degeneration of striatal neurons following intrastriatal injections of quinolinic acid (QA). Expression vectors containing either the human CNTF or NT-4/5 gene were transfected into a baby hamster kidney fibroblast cell line (BHK). Using a polymeric device, encapsulated BHK-control cells and those secreting either CNTF (BHK-CNTF) or NT-4/5 (BHK-NT-4/5) were transplanted unilaterally into the rat lateral ventricle. Seven days later, the same animals received unilateral injections of QA (225 nmol) into the ipsilateral striatum. Nissl-stained sections demonstrated that the BHK-CNTF cells significantly reduced the volume of striatal damage produced by QA. Quantitative analysis of striatal neurons further demonstrated that both choline acetyltransferase (ChAT)- and glutamic acid decarboxylase (GAD)-immunoreactive neurons were protected by CNTF implants. In contrast, the volume of striatal damage and loss of striatal ChAT and GAD-positive neurons in animals receiving BHK-NT-4/5 implants did not differ from control-implanted animals. These results help better define the scope of neuronal protection that can be afforded following cellular delivery of various neurotrophic factors. Moreover, these data further support the concept that implants of polymer-encapsulated CNTF-releasing cells can be used to protect striatal neurons from excitotoxic damage, and that this strategy may ultimately prove relevant for the treatment of HD.

Cellular Delivery of Human Cntf Prevents Motor and Cognitive Dysfunction in a Rodent Model of Huntington's Disease

The delivery of ciliary neurotrophic factor (CNTF) to the central nervous system has recently been proposed as a potential means of halting or slowing the neural degeneration associated with Huntington's disease (HD). The following set of experiments examined, in detail, the ability of human CNTF (hCNTF) to prevent the onset of behavioral dysfunction in a rodent model of HD. A DHFR-based expression vector containing the hCNTF gene was transfected into a baby hamster kidney fibroblast cell line (BHK). Using a polymeric device, encapsulated BHK-control cells and those secreting hCNTF were transplanted bilaterally into rat lateral ventricles. Eight days later, the same animals received bilateral injections of quinolinic acid (QA, 225 nmol) into the previously implanted striata. A third group received sham surgery (incision only) and served as a normal control group. Bilateral infusions of QA produced a significant loss of body weight and mortality that was prevented by prior implantation with hCNTF-secreting cells. Moreover, QA produced a marked hyperactivity, an inability to use the forelimbs to retrieve food pellets in a staircase test, increased the latency of the rats to remove adhesive stimuli from their paws, and decreased the number of steps taken in a bracing test that assessed motor rigidity. Finally, the QA-infused animals were impaired in tests of cognitive function — the Morris water maze spatial learning task, and the delayed nonmatching-to-position operant test of working memory. Prior implantation with hCNTF-secreting cells prevented the onset of all the above deficits such that implanted animals were nondistinguishable from sham-lesioned controls. At the conclusion of behavioral testing, 19 days following QA, the animals were sacrificed for neurochemical determination of striatal choline acetyltransferase (ChAT) and glutamic acid decarboxylase (GAD) levels. This analysis revealed that QA decreased striatal ChAT levels by 35% and striatal GAD levels by 45%. In contrast, hCNTF-treated animals did not exhibit any decrease in ChAT levels and only a 10% decrease in GAD levels. These results support the concepts that implants of polymer-encapsulated hCNTF-releasing cells can be used to protect striatal neurons from excitotoxic damage, produce extensive behavioral protection as a result of that neuronal sparing, and that this strategy may ultimately prove relevant for the treatment of HD.

Implantation of autologous peripheral nerve grafts into the substantia nigra of subjects with idiopathic Parkinson's disease treated with bilateral STN DBS: a report of safety and feasibility

OBJECTIVE One avenue of intense efforts to treat Parkinson's disease (PD) involves the delivery of neurotrophic factors to restore dopaminergic cell function. A source of neurotrophic factors that could be used is the Schwann cell from the peripheral nervous system. The authors have begun an open-label safety study to examine the safety and feasibility of implanting an autologous peripheral nerve graft into the substantia nigra of PD patients undergoing deep brain stimulation (DBS) surgery. METHODS Multistage DBS surgery targeting the subthalamic nucleus was performed using standard procedures in 8 study participants. After the DBS leads were implanted, a section of sural nerve containing Schwann cells was excised and unilaterally delivered into the area of the substantia nigra. Adverse events were continuously monitored. RESULTS Eight of 8 participants were implanted with DBS systems and grafts. Adverse event profiles were comparable to those of standard DBS surgery. Postoperative MR images did not reveal edema, hemorrhage, or significant signal changes in the graft target region. Three participants reported a patch of numbness on the outside of the foot below the sural nerve harvest site. CONCLUSIONS Based on the safety outcome of the procedure, targeted peripheral nerve graft delivery to the substantia nigra at the time of DBS surgery is feasible and may provide a means to deliver neurorestorative therapy. Clinical trial registration no.: NCT01833364 ( clinicaltrials.gov ).

Ciliary neurotrophic factor (CNTF): New facets of an old molecule for treating neurodegenerative and metabolic syndrome pathologies

Ciliary neurotrophic factor (CNTF) is the most extensively studied member of the cytokine family that signal through intracellular chains of the gp130/LIFRβ receptor. The severe phenotype in patients suffering from mutations inactivating LIFRβ indicates that members of this cytokine family play key, non-redundant roles during development. Accordingly, three decades of research has revealed potent and promising trophic and regulatory activities of CNTF in neurons, oligodendrocytes, muscle cells, bone cells, adipocytes and retinal cells. These findings led to clinical trials to test the therapeutic potential of CNTF and CNTF derivatives for treating neurodegenerative and metabolic diseases. Promising results have encouraged continuation of studies for treating retinal degenerative diseases. Results of some clinical trials showed that side-effects may limit the systemically administrated doses of CNTF. Therefore, therapies being currently tested rely on local delivery of CNTF using encapsulated cytokine-secreting implants. Since the side effects of CNTF might be linked to its ability to activate the alternative IL6Rα-LIFRβ-gp130 receptor, CNTFR-specific mutants of CNTF have been developed that bind to the CNTFRα-LIFRβ-gp130 receptor. These developments may prove to be a breakthrough for therapeutic applications of systemically administered CNTF in pathologies such as multiple sclerosis or Alzheimer's disease. The "designer cytokine approach" offers future opportunities to further enhance specificity by conjugating mutant CNTF with modified soluble CNTFRα to target therapeutically relevant cells that express gp130-LIFRβ and a specific cell surface marker.

The amino acid exchange R28E in ciliary neurotrophic factor (CNTF) abrogates interleukin-6 receptor-dependent but retains CNTF receptor-dependent signaling via glycoprotein 130 (gp130)/leukemia inhibitory factor receptor (LIFR)

Ciliary neurotrophic factor (CNTF) is a neurotrophic factor with therapeutic potential for neurodegenerative diseases. Moreover, therapeutic application of CNTF reduced body weight in mice and humans. CNTF binds to high or low affinity receptor complexes consisting of CNTFR·gp130·LIFR or IL-6R·gp130·LIFR, respectively. Clinical studies of the CNTF derivative Axokine revealed intolerance at higher concentrations, which may rely on the low-affinity binding of CNTF to the IL-6R. Here, we aimed to generate a CNTFR-selective CNTF variant (CV). CV-1 contained the single amino acid exchange R28E. Arg(28) is in close proximity to the CNTFR binding site. Using molecular modeling, we hypothesized that Arg(28) might contribute to IL-6R/CNTFR plasticity of CNTF. CV-2 to CV-5 were generated by transferring parts of the CNTFR-binding site from cardiotrophin-like cytokine to CNTF. Cardiotrophin-like cytokine selectively signals via the CNTFR·gp130·LIFR complex, albeit with a much lower affinity compared with CNTF. As shown by immunoprecipitation, all CNTF variants retained the ability to bind to CNTFR. CV-1, CV-2, and CV-5, however, lost the ability to bind to IL-6R. Although all variants induced cytokine-dependent cellular proliferation and STAT3 phosphorylation via CNTFR·gp130·LIFR, only CV-3 induced STAT3 phosphorylation via IL-6R·gp130·LIFR. Quantification of CNTF-dependent proliferation of CNTFR·gp130·LIFR expressing cells indicated that only CV-1 was as biologically active as CNTF. Thus, the CNTFR-selective CV-1 will allow discriminating between CNTFR- and IL-6R-mediated effects in vivo.

Neurogenic differentiation capacity of subacromial bursal tissue-derived stem cells

In this study, analysis and comprehensive comparison of neurogenic differentiation capacity of human bursal tissue-derived-stem cells (hBT-SCs) was aimed with human bone marrow derived mesenchymal stem cells (hBM-MSCs). hBT-SCs was isolated from subacromial bursa tissue (n = 3) by collagen type-II digestion. The expression of stem cell markers, differentiation capacity and telomerase activity were determined for both cell lines. The expression levels of neurogenic cell markers were compared consecutively. With respect to the surface marker profile, both cells display similar pluripotency phenotypes. Both cells successfully differentiated into osteo- and adipogenic cell lines. The immune staining of mesenchymal, stem cell and neurogenic markers gave positive reaction. The gene expression level for Tubb3, Nestin, Gfap, Map2, Nf-h, and Nf-l was higher in hBT-SCs than hBM-MSCs. The high level of neurotrophic factors, like Tenascin C, NGF, BDNF, VEGF, and CNTF might indicate their regeneration and maintenance capacity in damaged neural tissue. Besides they are alternative source for human mesenchymal stem cells, hBT-SCs assess the possibility to use in clinical studies.

Antineuroinflammatory and neurotrophic effects of CNTF and C16 peptide in an acute experimental autoimmune encephalomyelitis rat model

Experimentalallergic encephalomyelitis (EAE) is an animal model for inflammatory demyelinating autoimmune disease, i.e., multiple sclerosis (MS). In the present study, we investigated the antineuroinflammatory/neuroprotective effects of C16, an ανβ3 integrin-binding peptide, and recombinant rat ciliary neurotrophic factor (CNTF), a cytokine that was originally identified as a survival factor for neurons, in an acute rodent EAE model. In this model, C16 peptide was injected intravenously every day for 2 weeks, and CNTF was delivered into the cerebral ventricles with Alzet miniosmotic pumps. Disease severity was assessed weekly using a scale ranging from 0 to 5. Multiple histological and molecular biological assays were employed to assess inflammation, axonal loss, neuronal apoptosis, white matter demyelination, and gliosis in the brain and spinal cord of different groups. Our results showed that the EAE induced rats revealed a significant increase in inflammatory cells infiltration, while C16 treatment could inhibit the infiltration of leukocytes and macrophages down to 2/3–1/3 of vehicle treated EAE control (P < 0.05). The delayed onset of disease, reduced clinical score (P < 0.01) in peak stage and more rapid recovery also were achieved in C16 treated group. Besides impairing inflammation, CNTF treatment also exerted direct neuroprotective effects, decreasing demyelination and axon loss score (P < 0.05 versus vehicle treated EAE control), and reducing the neuronal death from 40 to 50% to 10 to 20% (P < 0.05). Both treatments suppressed the expression of cytokine tumor necrosis factor-α and interferon-γ when compared with the vehicle control (P < 0.05). Combined treatment with C16 and CNTF produced more obvious functional recovery and neuroprotective effects than individually treatment (P < 0.05). These results suggested that combination treatment with C16 and CNTF, which target different neuroprotection pathways, may be an effective therapeutic alternative to traditional therapy.

Ciliary neurotrophic factor receptor regulation of adult forebrain neurogenesis

Appropriately targeted manipulation of endogenous neural stem progenitor (NSP) cells may contribute to therapies for trauma, stroke, and neurodegenerative disease. A prerequisite to such therapies is a better understanding of the mechanisms regulating adult NSP cells in vivo. Indirect data suggest that endogenous ciliary neurotrophic factor (CNTF) receptor signaling may inhibit neuronal differentiation of NSP cells. We challenged subventricular zone (SVZ) cells in vivo with low concentrations of CNTF to anatomically characterize cells containing functional CNTF receptors. We found that type B "stem" cells are highly responsive, whereas type C "transit-amplifying" cells and type A neuroblasts are remarkably unresponsive, as are GFAP(+) astrocytes found outside the SVZ. CNTF was identified in a subset of type B cells that label with acute BrdU administration. Disruption of in vivo CNTF receptor signaling in SVZ NSP cells, with a "floxed" CNTF receptor α (CNTFRα) mouse line and a gene construct driving Cre recombinase (Cre) expression in NSP cells, led to increases in SVZ-associated neuroblasts and new olfactory bulb neurons, as well as a neuron subtype-specific, adult-onset increase in olfactory bulb neuron populations. Adult-onset receptor disruption in SVZ NSP cells with a recombinant adeno-associated virus (AAV-Cre) also led to increased neurogenesis. However, the maintenance of type B cell populations was apparently unaffected by the receptor disruption. Together, the data suggest that endogenous CNTF receptor signaling in type B stem cells inhibits adult neurogenesis, and further suggest that the regulation may occur in a neuron subtype-specific manner.

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.

Intranasal delivery of neurotrophic factors BDNF, CNTF, EPO, and NT-4 to the CNS

Injury to the central nervous system (CNS) generally results in significant neuronal death and functional loss. In vitro experiments have demonstrated that neurotrophic factors such as brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), and neurotrophin-4/5 (NT-4/5) can promote neuronal survival. However, delivery to the injured CNS is difficult as these large protein molecules do not efficiently cross the blood-brain barrier. Intranasal delivery of 70 microg [(125)I]-radiolabeled BDNF, CNTF, NT-4, or erythropoietin (EPO) resulted in 0.1-1.0 nM neurotrophin concentrations within 25 min in brain parenchyma. In addition, not only did these neurotrophic factors reach the CNS, they were present in sufficient concentrations to activate the prosurvival PI3Kinase/Akt pathway, even where lower levels of neurotrophic factors were measured. Currently traumatic, ischemic and compressive injuries to the CNS have no effective treatment. There is potential clinical relevancy of this method for rescuing injured CNS tissues in order to maintain CNS function in affected patients. The intranasal delivery method has great clinical potential due to (1) simplicity of administration, (2) noninvasive drug administration, (3) relatively rapid CNS delivery, (4) ability to repeat dosing easily, (5) no requirement for drug modification, and (6) minimal systemic exposure.

Functionalized poly(lactic-co-glycolic acid) enhances drug delivery and provides chemical moieties for surface engineering while preserving biocompatibility

Poly(lactic-co-glycolic acid) (PLGA) is one of the more widely used polymers for biomedical applications. Nonetheless, PLGA lacks chemical moieties that facilitate cellular interactions and surface chemistries. Furthermore, incorporation of hydrophilic molecules is often problematic. The integration of polymer functionalities would afford the opportunity to alter device characteristics, thereby enabling control over drug interactions, conjugations and cellular phenomena. In an effort to introduce amine functionalities and improve polymer versatility, we synthesized two block copolymers (PLGA-PLL 502H and PLGA-PLL 503H) composed of PLGA and poly(epsilon-carbobenzoxy-l-lysine) utilizing dicyclohexyl carbodiimide coupling. PLGA-PLL microspheres encapsulated approximately sixfold (502H) and threefold (503H) more vascular endothelial growth factor, and 41% (503H) more ciliary neurotrophic factor than their PLGA counterparts. While the amine functionalities were amenable to the delivery of large molecules and surface conjugations, they did not compromise polymer biocompatibility. With the versatile combination of properties, biocompatibility and ease of synthesis, these block copolymers have the potential for diverse utility in the fields of drug delivery and tissue engineering.

Overexpression of CNTF in Mesenchymal Stem Cells reduces demyelination and induces clinical recovery in experimental autoimmune encephalomyelitis mice

Human Mesenchymal Stem Cells (MSCs) were previously reported to ameliorate neuronal functional deficits in the MOG35-55-induced experimental autoimmune encephalomyelitis (EAE) mice by inducing T cell anergy. Human Ciliary neurotrophic factor (CNTF) recently was found to promote myelogenesis and reduce inflammation in CNTF-deficient EAE mice. We ectopically overexpressed CNTF in human MSCs to investigate its potential role in promoting remyelination and improving functional recovery in EAE mice. MSCs transfected by Ad-CNTF-IRES-EGFP (MSC-CNTF) were injected intravenously into EAE mice 10 days after the immunization. Neurological functional tests were scored daily by grading clinical signs (score 0-6). Immunofluorescence microscopy was used to detect MSC-CNTF in spinal cord. Expression of NG2, CNTF, and cleaved caspase-3 was measured by immunohistochemistry. CNTF expression was also analyzed by Western blot. Myelin was detected by Solochrome Cyanin staining. Our results found that CNTF concentration in MSC-CNTF cells was 20-fold higher than that in either MSC or Ad-EGFP-transfected MSCs (MSC-EGFP) in vitro. Mice receiving MSC-CNTF cells showed remarkable neuronal functional recovery: the cumulative clinical scores were significantly decreased, and the disease onset was statistically delayed. Mice receiving MSC-CNTF cells showed reduced TNF-alpha, IFN-gamma and increased the level of cytokine IL-10 in peripheral blood and a large number of MSC-CNTF cells were detected in the spleen, but were not detected in other organs such as lung, liver and kidney. In the lesions of these mice, 1) the number of cleaved caspase3-positive cells was significantly reduced; 2) MSC-CNTF- and NG2-positive cells were significantly increased; and 3) the expression of CNTF was dramatically increased. In addition, demyelination was significantly reduced in MSC-CNTF mice. These data indicated that MSC-CNTF may improve functional recovery in EAE mice, possibly by exerting their immunoregulatory activity, inhibiting inflammation, homing MSC-CNTF cells to the lesions, elevating CNTF expression, reducing demyelination, and stimulating oligodendrogenesis.

CNTF receptor alpha is expressed by magnocellular neurons and expression is upregulated in the rat supraoptic nucleus during axonal sprouting

Ciliary neurotrophic factor (CNTF) is expressed by glial cells at multiple levels of the magnocellular neurosecretory system (MNS). CNTF is present in astrocytes in the hypothalamic supraoptic nucleus (SON) as well as in perivascular cells in the neurohypophysis, and a several fold increase in CNTF immunoreactivity occurs in the SON following either axotomy of magnocellular neurons or during axonal sprouting by intact magnocellular neurons. CNTF also promotes survival and stimulates process outgrowth from magnocellular neurons in vitro. While these findings suggest that CNTF may act as a growth factor in support of neuronal plasticity in the MNS, little is known regarding possible expression of receptors for CNTF in the MNS. We have therefore used immunocytochemistry and in situ hybridization to examine the expression of CNTF receptor alpha (CNTFRalpha) in the rat MNS. Robust immunoreactivity for CNTFRalpha was observed associated with oxytocinergic and vasopressinergic neurons distributed throughout the SON. Astrocytes located within the ventral glial lamina (VGL) of the SON were also immunoreactive for CNTFRalpha. Robust hybridization of an anti-sense [(35)S]-cRNA probe to CNTFRalpha mRNA was observed throughout the SON, while binding of a control sense probe was much lower. Grains were found clustered predominantly over neuronal somata, indicative of expression by magnocellular neurons within the SON. We next examined changes in expression of CNTFRalpha mRNA by magnocellular neurons 7 days following unilateral transection of the hypothalamo-neurohypophysial tract. The level of CNTFRalpha mRNA was increased 32% (compared to age-matched intact controls; p<0.05) in magnocellular neurons in the SON contralateral to the lesion, which are undergoing extensive collateral axonal sprouting, but was unchanged in axotomized magnocellular neurons in the SON ipsilateral to the lesion. These findings suggest that CNTF produced by MNS glia and acting via CNTFRalpha may exert neurotrophic effects on magnocellular neurons.

Poly(lactic-co-glycolic acid) nanospheres and microspheres for short- and long-term delivery of bioactive ciliary neurotrophic factor

Ciliary neurotrophic factor (CNTF) has been shown to be neuroprotective in the central nervous system (CNS). However, systemic administration and bolus injections have shown significant side effects and limited efficacy. Sustained, local delivery may lead to effective neuroprotection and avoid or limit adverse side effects, but sustained CNTF delivery has proven difficult to achieve and control. For controlled, sustained delivery, we investigated several processing variables in making poly(DL-lactic-co-glycolic acid) (PLGA) nano- and microspheres to optimize CNTF encapsulation and release. Nano- and microspheres were 314.9 +/- 24.9 nm and 11.69 +/- 8.16 microm in diameter, respectively. CNTF delivery from nanospheres was sustained over 14 days, and delivery from microspheres continued over more than 70 days. To assess protein bioactivity after encapsulation, neural stem cells (NSCs) were treated with CNTF released from nanospheres and compared to those treated with unencapsulated CNTF as a control. NSCs treated with CNTF expressed markers specific to mature cells, notably astrocytes; some increase in oligodendrocytic and neuronal marker expression was also observed. Significantly, cells treated with CNTF released by nanospheres exhibited a similar degree of differentiation when compared to those treated with control CNTF of equivalent concentration, showing that the process of protein encapsulation did not reduce its potency.

A new and simple transection knife for study of neurodegeneration and neuroregeneration in animal model

BACKGROUND

The purpose of this study was to design and make a simple, inexpensive brain knife that could produce consistent results following transection in animal model.

MATERIALS AND METHODS

After testing various materials including commercially available products, microelectrode recording needles as used in deep brain stimulation (DBS) surgery were selected as ideal candidates. They were modified to serve as type of wire-knife for the purposes of study. For this study, the major pathway for dopaminergic neuron from substantia nigra to striatum was selected for transection. A total of 40 Sprague-Dawley rats were assigned to 8 groups; normal, 1-4, 6, 8, and 10 weeks post-transection. Degree of cell death was determined and surviving neurons were counted by means of fluorescent microscopic examination, immunohistochemistry involving tyrosine hydroxylase (TH)-immunoreactive staining, and mapping to verify complete transection.

RESULTS

Compared to control, percentage of remaining neurons in each group was 61.3, 36.8, 29.9, 5.1, 5.9, 7.0%, respectively. Completeness of lesion was correlated with the absence of TH-immunoreactivity in the striatum.

CONCLUSION

Our model seems to provide complete cell death in early period after transection with consistent results. Thus, this type of brain knife can be very handy, without any extra cost, in any research model involving transection of fiber bundle for studies on neurodegeneration and neuroregeneration.

Continued administration of ciliary neurotrophic factor protects mice from inflammatory pathology in experimental autoimmune encephalomyelitis

Multiple sclerosis is an inflammatory disease of the central nervous system that leads to loss of myelin and oligodendrocytes and damage to axons. We show that daily administration (days 8 to 24) of murine ciliary neurotrophic factor (CNTF), a neurotrophic factor that has been described as a survival and differentiation factor for neurons and oligodendrocytes, significantly ameliorates the clinical course of a mouse model of multiple sclerosis. In the acute phase of experimental autoimmune encephalomyelitis induced by myelin oligodendrocyte glycoprotein peptide 35-55, treatment with CNTF did not change the peripheral immune response but did reduce the number of perivascular infiltrates and T cells and the level of diffuse microglial activation in spinal cord. Blood brain barrier permeability was significantly reduced in CNTF-treated animals. Beneficial effects of CNTF did not persist after it was withdrawn. After cessation of CNTF treatment, inflammation and symptoms returned to control levels. However, slight but significantly higher numbers of oligodendrocytes, NG2-positive cells, axons, and neurons were observed in mice that had been treated with high concentrations of CNTF. Our results show that CNTF inhibits inflammation in the spinal cord, resulting in amelioration of the clinical course of experimental autoimmune encephalomyelitis during time of treatment.

Delivery of neurotrophic factors and therapeutic proteins for retinal diseases

Neurotrophic factors have the ability to protect and initiate growth of neurons. In the central nervous system, neurotrophic factors are neuroprotective in a wide range of disease states. Similarly, disease pathologies of the neurosensory retina respond favourably in animal models of retinitis pigmentosa, macular degeneration, glaucoma and others. With advances in drug delivery and cell therapy, an almost universal increase in efficacy is being realised. Now, repeated injections of neurotrophic factors are being replaced by controlled delivery of cell-mediated factor secretion, reducing the number of potential acute side effects. Tissue engineering strategies in conjunction with gene-modulated protein therapy or gene transfer are creating a unique treatment niche and are quickly gaining acclaim in the clinic. This review surveys the founding and current work on neurotrophic factors such as CNTF, BDNF, GDNF, LEDGF, PEDF and others. Ongoing clinical trials and successful preclinical studies are summarised as well.

Penetrating brain injury leads to activation of ciliary neurotrophic factor receptors

Endogenous injury response mechanisms likely reduce secondary neuronal loss following CNS trauma by activating growth factor receptors. Therefore, it is important to determine which growth factor receptors are activated in vivo by CNS trauma and which signal transduction pathways are affected in which cell types. We present a model of penetrating brain injury utilizing stereotaxic insertion of a fine needle. This procedure can be used to anatomically characterize injury response mechanisms through immediate, local application of pharmacological agents. We find, through immunohistochemistry, that injury of the rat facial motor nucleus leads to activation of STAT3, a neuronal survival factor, in the dendrites, nuclei and cytoplasm of the motor neurons. A similar response was observed with the trigeminal motor nucleus. Use of the ciliary neurotrophic factor (CNTF) receptor antagonist, AADH-CNTF, indicated that the STAT3 activation resulted largely, and perhaps entirely, from injury-induced activation of CNTF receptors.

Expression of ciliary neurotrophic factor (CNTF), CNTF receptor alpha (CNTFR-alpha) following experimental intracerebral hemorrhage in rats

Ciliary neurotrophic factor (CNTF) is known as a neuro-survival factor in the developing and developed CNS, as well as in the CNS following injury. However, little is known about the expression of CNTF or that of its receptor (CNTFR-alpha) in cases of intracerebral hemorrhage (ICH). We investigated the temporal and spatial profiles of CNTF and CNTFR-alpha expression using a collagenase-induced ICH rat model. CNTF expression was up-regulated from the day following ICH induction and reached a peak level at 5 to 14 days, with increased expression observed in brain tissue surrounding the hematoma lesion and white matter structures in association with astroglial proliferation. Further, CNTFR-alpha was transiently expressed in the cerebral cortex surrounding the hematoma, with a peak at 5 days. Administration of exogenous CNTF into the lesion following initiation of ICH resulted in a prolonged expression of CNTFR-alpha on cortical neurons neighboring the hematoma. Our findings suggest differential regulation of CNTF and CNTFR-alpha, and the possibility of a therapeutic strategy using CNTF administration for ICH.

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.

Ciliary neurotrophic factor protects retinal ganglion cells from axotomy-induced apoptosis via modulation of retinal gliain vivo

Adenoviral-mediated transfer of ciliary neurotrophic factor (CNTF) to the retina rescued retinal ganglion cells (RGCs) from axotomy-induced apoptosis, presumably via activation of the high affinity CNTF receptor alpha (CNTFRalpha) expressed on RGCs. CNTF can also activate astrocytes, via its low affinity leukemia inhibitory receptor beta expressed on mature astrocytes, suggesting that CNTF may also protect injured neurons indirectly by modulating glia. Adenoviral-mediated overexpression of CNTF in normal and axotomized rat retinas was examined to determine if it could increase the expression of several glial markers previously demonstrated to have a neuroprotective function in the injured brain and retina. Using Western blotting, the expression of glial fibrillary acid protein (GFAP), glutamate/aspartate transporter-1 (GLAST-1), glutamine synthetase (GS), and connexin 43 (Cx43) was examined 7 days after intravitreal injections of Ad.CNTF or control Ad.LacZ. Compared to controls, intravitreal injection of Ad.CNTF led to significant changes in the expression of CNTFRalpha, pSTAT(3), GFAP, GLAST, GS, and Cx43 in normal and axotomized retinas. Taken together, these results suggest that the neuroprotective effects of CNTF may result from a shift of retinal glia cells to a more neuroprotective phenotype. Moreover, the modulation of astrocytes may buffer high concentrations of glutamate that have been shown to contribute to the death of RGCs after optic nerve transection.

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.

Long-term effects of ciliary neurotrophic factor on the survival of vasopressin magnocellular neurones in the rat supraoptic nucleus in vitro

The use of hypothalamic organotypic cultures for the long-term study of mechanisms in magnocellular neurones (MCNs) of the hypothalamic-neurohypophysial system has been limited by the relatively poor maintenance of the vasopressin MCNs in vitro. Recent studies have shown that addition of ciliary neurotrophic factor (CNTF) to the media significantly reduced the apoptosis of both oxytocin and vasopressin MCNs. Here, we studied various temporal factors in the CNTF treatment that can influence the efficacy of MCN survival. Immunohistochemistry was used to identify and count surviving vasopressin and oxytocin MCNs in the supraoptic nucleus (SON) in hypothalamic slices cultured in the presence of CNTF (10 ng/ml media) for various time intervals, and in situ hybridization for vasopressin mRNA was used to evaluate the vasopressin mRNA gene expression in the SON under the same conditions. The presence of CNTF in the medium for 10 days produced a maximal increase in the survival of vasopressin MCNs (by 11-fold) and in the survival of oxytocin-MCNs (by approximately four-fold) over controls. These effects persisted for an additional 7-10 days even in the absence of CNTF. The ability of CNTF to increase survival of the MCNs or increase vasopressin mRNA levels in the SON required that the CNTF be present during the initial 7-10 days of culture. CNTF failed to rescue vasopressin or oxytocin MCNs when added to the media only for the last 7 days of a total of 14 days in vitro. Similar results were observed when SON vasopressin mRNA levels were measured. These results indicate that the presence of CNTF is required at the outset to rescue the vasopressin and oxytocin MCN from axotomy induced apoptosis, and that, after 10 days in CNTF, the MCNs no longer require the CNTF for survival.

Gene expression profiling of ciliary neurotrophic factor-overexpressing rat striatal progenitor cells (ST14A) indicates improved stress response during the early stage of differentiation

Neuronal progenitor cells delivering neurotrophic factors are a promising therapeutic tool for treatment of neurodegenerative diseases. Although several promising results have come from studies in different animal models, detailed knowledge of the action of neurotrophic factors in the CNS is still lacking. A clonally derived, immortalized rat striatal cell line (ST14A) expressing ciliary neurotrophic factor (CNTF) offers a stable and controlled background with which to analyze CNTF actions on the transcriptional level in CNS progenitor cells. To identify early transcriptional changes induced by CNTF expression, we transfected the CNTF gene into ST14A cells, which differentiate at the nonpermissive temperature of 39 degrees C via suppression of the immortalizing SV40 large T antigen. This shows a CNTF-dependent hypoxic/ischemic stress response during the earliest stage of differentiation, with expression of specific transcripts and evidence of translational repression leading to decreased protein synthesis in the transfected cells. This process is mediated by the Ras/MAP kinase pathway and is accompanied by impaired proliferation and metabolism as well as signs of neuronal differentiation. The stress-like response in the early stage of differentiation improves the ability of the transfected cells to respond to and cope with a stressful environment in vivo. The present data indicate higher viability, longer life, and greater differentiation capacity of CNTF-ST14A cells if they are used for transplantation. We conclude that the stress-like response during the early stage of differentiation improves the ability of the CNTF-ST14A cells to respond and adapt to a stressful environment, which renders them useful candidate cells for in vivo trials of treatment for neurodegenerative diseases in animal models, e.g., of Huntington's disease.

Neurotrophic factors and their receptors in axonal regeneration and functional recovery after peripheral nerve injury

Over a half a century of research has confirmed that neurotrophic factors promote the survival and process outgrowth of isolated neurons in vitro. The mechanisms by which neurotrophic factors mediate these survival-promoting effects have also been well characterized. In vivo, peripheral neurons are critically dependent on limited amounts of neurotrophic factors during development. After peripheral nerve injury, the adult mammalian peripheral nervous system responds by making neurotrophic factors once again available, either by autocrine or paracrine sources. Three families of neurotrophic factors were compared, the neurotrophins, the GDNF family of neurotrophic factors, and the neuropoetic cytokines. Following a general overview of the mechanisms by which these neurotrophic factors mediate their effects, we reviewed the temporal pattern of expression of the neurotrophic factors and their receptors by axotomized motoneurons as well as in the distal nerve stump after peripheral nerve injury. We discussed recent experiments from our lab and others which have examined the role of neurotrophic factors in peripheral nerve injury. Although our understanding of the mechanisms by which neurotrophic factors mediate their effects in vivo are poorly understood, evidence is beginning to emerge that similar phenomena observed in vitro also apply to nerve regeneration in vivo.

Signaling of human ciliary neurotrophic factor (CNTF) revisited. The interleukin-6 receptor can serve as an alpha-receptor for CTNF

Human ciliary neurotrophic factor (CNTF) is a neurotrophic cytokine that exerts a neuroprotective effect in multiple sclerosis and amyotrophic lateral sclerosis. Clinical application of human CNTF, however, was prevented by high toxicity at higher dosages. Human CNTF elicits cellular responses by induction of a receptor complex consisting of the CNTF alpha-receptor (CNTFR), which is not involved in signal transduction, and the beta-receptors gp130 and leukemia inhibitory factor receptor (LIFR). Previous studies with rat CNTF demonstrated that rat CNTF is unable to interact with the human interleukin-6 alpha-receptor, whereas at high concentrations, it can directly induce a signaling heterodimer of human gp130 and human LIFR in the absence of the CNTF receptor. Here, we demonstrate that human CNTF cannot directly induce a heterodimer of human gp130 and LIFR. However, human CNTF can use both the membrane-bound and the soluble human IL-6R as a substitute for its cognate alpha-receptor and thus widen the target spectrum of human CNTF. Engineering a CNTFR-specific human CNTF variant may therefore be a prerequisite to improving the safety profile of CNTF.

Ciliary neurotrophic factor increases the survival of magnocellular vasopressin and oxytocin neurons in rat supraoptic nucleus in organotypic cultures

Organotypic cultures of the rat hypothalamus are very useful models for the long-term study of parvocellular vasopressin (VP) neurons in the paraventricular (PVN) and suprachiasmatic (SCN) nuclei. However, they do not preserve significant numbers of VP magnocellular neurons (VP-MCNs) in either the PVN or the supraoptic nucleus (SON). Vutskits et al. [(1998) Neuroscience 87:571-582] reported that ciliary neurotrophic factor (CNTF) was a selective survival factor for rat VP-MCNs in organotypic cultures of the rat hypothalamic paraventricular nucleus (PVN). We examined the effects of CNTF on the survival of these neurons in rat and mouse SONs. CNTF (10 ng/ml) in the culture media increased the survival of VP-MCNs by 6-fold and OT-MCNs by 3-fold. In the mouse, both OT- and VP-MCNs survive very well in organotypic cultures under standard culture conditions and the addition of CNTF had no further effect. Consistent with these results, in situ hybridization showed substantially higher levels of VP- and OT-mRNA in rat PVNs and SONs in the presence of CNTF, but produced no changes in these nuclei in the mouse. The optimum period for the survival effect of CNTF on MCNs in the rat hypothalamic cultures was in the first 7-10 days of culture and this effect is maintained for at least 5 additional days if CNTF is then removed from the medium. Therefore, using CNTF in the culture media can provide an opportunity for long-term studies of rat VP- and OT-MCNs in SONs in organotypic cultures.

Ciliary neurotrophic factor activates spinal cord astrocytes, stimulating their production and release of fibroblast growth factor-2, to increase motor neuron survival

At focal CNS injury sites, several cytokines accumulate, including ciliary neurotrophic factor (CNTF) and interleukin-1beta (IL-1beta). Additionally, the CNTF alpha receptor is induced on astrocytes, establishing an autocrine/paracrine loop. How astrocyte function is altered as a result of CNTF stimulation remains incompletely characterized. Here, we demonstrate that direct injection of CNTF into the spinal cord increases GFAP expression and astroglial size and that primary cultures of spinal cord astrocytes treated with CNTF, IL-1beta, or leukemia inhibitory factor exhibit nuclear hypertrophy comparable to that observed in vivo. Using a coculture bioassay, we further demonstrate that CNTF treatment of astrocytes increases their ability to support ChAT(+) ventral spinal cord neurons (presumably motor neurons) more than twofold compared with untreated astrocytes. Also, the complexity of neurites was significantly increased in neurons cultured with CNTF-treated astrocytes compared with untreated astrocytes. RT-PCR analysis demonstrated that CNTF increased levels of FGF-2 and nerve growth factor (NGF) mRNA and that IL-1beta increased NGF and hepatocyte growth factor mRNA levels. Furthermore, both CNTF and IL-1beta stimulated the release of FGF-2 from cultured spinal cord astrocytes. These findings demonstrate that cytokine-activated astrocytes better support CNS neuron survival via the production of neurotrophic molecules. We also show that CNTF synergizes with FGF-2, but not epidermal growth factor, to promote DNA synthesis in spinal cord astrocyte cultures. The significance of these findings is discussed by presenting a new model depicting the sequential activation of astrocytes by cytokines and growth factors in the context of CNS injury and repair.

In vivo localization and characterization of functional ciliary neurotrophic factor receptors which utilize JAK-STAT signaling

The ciliary neurotrophic factor receptor is critically involved in embryonic motor neuron development. Postnatally, it may contribute to neuronal maintenance and regeneration. In addition, pharmacological stimulation of the receptor may slow the progression of several neurodegenerative disorders. The widespread nervous system expression of ciliary neurotrophic factor receptor components and the effects of low ciliary neurotrophic factor concentrations on a wide variety of cells in culture combine to suggest that functional ciliary neurotrophic factor receptors are expressed by many classes of neurons in vivo. However, the in vivo signaling properties and distribution of functional ciliary neurotrophic factor receptors have not been directly determined. We developed a novel in vivo assay of functional ciliary neurotrophic factor receptors which revealed that, in the adult nervous system, cranial and spinal motor neurons are very sensitive to ciliary neurotrophic factor and display a rapid, robust increase in phospho-STAT3 in their dendrites, cell bodies and nuclei, which is specifically blocked by the ciliary neurotrophic factor receptor antagonist, AADH-CNTF. In distinct contrast, several other classes of ciliary neurotrophic factor receptor expressing neurons fail to increase phospho-STAT3 levels following ciliary neurotrophic factor treatment, even when ciliary neurotrophic factor is applied at high concentrations. Leukemia inhibitory factor and epidermal growth factor elicit the same cell-type-dependent pattern of phospho-STAT3 increases. Responsive and non-responsive neurons express comparable levels of STAT3.Therefore, in vivo ciliary neurotrophic factor receptor-initiated STAT3 signal transduction is regulated in a very cell-type-dependent manner. The present data suggest that at least some of this regulation occurs at the STAT3 tyrosine phosphorylation step. These unexpected results also suggest that other forms of receptor-initiated STAT3 signal transduction may be similarly regulated.

Neuroprotective gene therapy for Huntington's disease using a polymer encapsulated BHK cell line engineered to secrete human CNTF

Huntington's disease (HD) is an autosomal dominant genetic disease with devastating clinical effects on cognitive, psychological, and motor functions. These clinical symptoms primarily relate to the progressive loss of medium-spiny GABA-ergic neurons of the striatum. There is no known treatment to date. Several neurotrophic factors have, however, demonstrated the capacity to protect striatal neurons in various experimental models of HD. This includes the ciliary neurotrophic factor (CNTF), the substance examined in this protocol. An ex vivo gene therapy approach based on encapsulated genetically modified BHK cells will be used for the continuous and long-term intracerebral delivery of CNTF. A device, containing up to 106 human CNTF-producing BHK cells surrounded by a semipermeable membrane, will be implanted into the right lateral ventricle of 6 patients. Capsules releasing 0.15-0.5 microg CNTF/day will be used. In this phase I study, the principal goal will be the evaluation of the safety and tolerability of the procedure. As a secondary goal, HD symptoms will be analyzed using a large battery of neuropsychological, motor, neurological, and neurophysiological tests and the striatal pathology monitored using MRI and PET-scan imaging. It is expected that the gene therapy approach described in this protocol will mitigate the side effects associated with the peripheral administration of recombinant hCNTF and allow a well-tolerated, continuous intracerebroventricular delivery of the neuroprotective factor.

Functional recovery of transected nerves treated with systemic BDNF and CNTF

The purpose of this study was to investigate the effect of systemic co-injections of ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF) on the functional recovery of transected sciatic nerves repaired by epineurial coaptation (EC) or collagen tubulization (CT). Forty Sprague-Dawley rats underwent transection of their sciatic nerves and repair by either EC or CT. With each repair technique, systemic injections of neurotrophic factors or control injections of lactated Ringer's solution were given. This resulted in four treatment groups: EC, EC + BDNF/CNTF, CT, and CT + BDNF/CNTF. Nerve function was assessed using sciatic functional indices (SFI). Animals whose nerves were repaired by CT (P = 0.01), CT + BDNF/CNTF (P = 0.04), and EC + BDNF/CNTF (P = 0.04) all had better functional recovery than those whose nerves were repaired by EC. There were no significant differences among these three groups, however. Animals in the CT group manifested the most rapid rate of recovery (P = 0.02 compared with EC). Collagen tubulization and systemic co-injections of BDNF/CNTF improve the rate and extent of sciatic functional recovery after nerve repair. The improvement in recovery conferred is not additive.

Schwann cells, neurotrophic factors, and peripheral nerve regeneration

The peripheral nervous system retains a considerable capacity for regeneration. However, functional recovery rarely returns to the preinjury level no matter how accurate the nerve repair is, and the more proximal the injury the worse the recovery. Among a variety of approaches being used to enhance peripheral nerve regeneration are the manipulation of Schwann cells and the use of neurotrophic factors. Such factors include, first, nerve growth factor (NGF) and the other recently identified members of the neurotrophin family, namely, brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), neurotrophin-4/5 (NT-4/5); second, the neurokines ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF); and third, the transforming growth factors (TGFs)-beta and their distant relative, glial cell line-derived neurotrophic factor (GDNF). In this review article we focus on the roles in peripheral nerve regeneration of Schwann cells and of the neurotrophin family, CNTF and GDNF, and the relationship between these. Finally, we discuss what remains to be understood about the possible clinical use of neurotrophic factors.

Adenovirus-mediated expression of ciliary neurotrophic factor (CNTF) rescues axotomized rat retinal ganglion cells but does not support axonal regeneration in vivo

Rat optic nerve (ON) transection leads to mainly apoptotic cell death of about 85% of the retinal ganglion cell (RGC) population within 14 days after lesion. In the present study, we tested the effect of adenovirally delivered CNTF (Ad-CNTF) on survival and regeneration of axotomized adult RGCs in vivo. Single intravitreal Ad-CNTF injection led to stable CNTF mRNA and protein expression for at least 18 days and significantly enhanced RGC survival by 155% when compared to control animals 14 days after ON transection. ON stump application of Ad-CNTF also resulted in an increased number of surviving RGCs. Ad-CNTF injection led to better preservation of intraretinal RGC axons but did not support regeneration of axotomized RGCs into a peripheral nerve graft. Thus, adenovirus-mediated neurotrophic factor supply is a suitable approach for reducing axotomy-induced RGC death in vivo and may constitute a relevant strategy for clinical treatment of traumatic brain injury.

Cellular delivery of trophic factors for the treatment of Huntington's disease: is neuroprotection possible?

The elucidation of the genetic defect in patients with Huntington's disease (HD) has allowed for the detection of individuals at risk for HD prior to the onset of symptoms. Thus "neuroprotection strategies" aimed at preventing the neuropathological and behavioral sequelae of this disease might be powerful therapeutically since they could be introduced to healthy patients before the initiation of a massive degenerative cascade principally localized to the striatum. A variety of trophic factors potently protect vulnerable striatal neurons in animal models of HD. A number of experimental variables are critical in determining the success of trophic factors in animal models. In this regard, the method of trophic factor delivery may be crucial, as delivery via genetically modified cells often produces greater and more widespread effects on striatal neurons than infusions of that same factor. The mechanisms by which cellularly delivered trophic factors forestall degeneration and prevent behavioral deficits are complex and often appear to be unrelated to the trophic factor binding to its cognate receptor. In this regard, cells genetically modified to secrete nerve growth factor (NGF) or ciliary neurotrophic factor (CNTF) protect degenerating striatal neurons which do not express either NGF or CNTF receptors. This review will discuss some of the non-receptor-based events that might underlie these effects and present the hypothesis that cellular delivery of certain trophic factors using genetically modified cells may be ready for clinical testing in HD patients.

Synergistic effects of brain-derived neurotrophic factor and ciliary neurotrophic factor on cultured basal forebrain cholinergic neurons from postnatal 2-week-old rats

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, and ciliary neurotrophic factor (CNTF), a member of the neurocytokine family, are known to have synergistic effects on motoneurons, but such synergistic effect has not been studied in detail especially in the brain. In the present study, we examined the synergistic effects of BDNF and CNTF on the survival of basal forebrain cholinergic neurons cultured from postnatal 2-week-old (P2w) rats. Although BDNF is well-known to promote the survival of basal forebrain cholinergic neurons in P2w culture, CNTF had little effect on the survival of choline acetyltransferase (ChAT)-positive neurons and did not increase ChAT activity in the culture. However, CNTF enhanced BDNF-mediated promotion of cell survival of cholinergic neurons when added concomitantly. BDNF alone induced only a three-fold increase in ChAT activity in control cultures, but the concomitant addition of CNTF resulted in an eight-fold increase. CNTF did not enhance BDNF-mediated cell survival of total neurons from the basal forebrain, hippocampus or cerebellum, suggesting that the synergistic effects of CNTF on the BDNF-mediated increase of viability might be strong in basal forebrain cholinergic neurons. CNTF also enhanced the neurotrophin-4/5-mediated increase of ChAT activity, but not the nerve growth factor (NGF)-mediated one. Furthermore, the BDNF-mediated increase was also enhanced by leukemia inhibitory factor but not by interleukin-6. Similar synergistic pattern between neurotrophins and cytokines were also observed in the induction of ChAT activity in embryonic basal forebrain culture. These results suggest that TrkB, a functional high-affinity receptor of BDNF and NT-4/5, and LIFR beta, a receptor component contained in CNTF and LIF receptor complex, might be involved in the observed synergistic effects.

Receptor recognition sites of cytokines are organized as exchangeable modules. Transfer of the leukemia inhibitory factor receptor-binding site from ciliary neurotrophic factor to interleukin-6

Interleukin-6 (IL-6) and ciliary neurotrophic factor (CNTF) are "4-helical bundle" cytokines of the IL-6 type family of neuropoietic and hematopoietic cytokines. IL-6 signals by induction of a gp130 homodimer (e.g. IL-6), whereas CNTF and leukemia inhibitory factor (LIF) signal via a heterodimer of gp130 and LIF receptor (LIFR). Despite binding to the same receptor component (gp130) and a similar protein structure, IL-6 and CNTF share only 6% sequence identity. Using molecular modeling we defined a putative LIFR binding epitope on CNTF that consists of three distinct regions (C-terminal A-helix/N-terminal AB loop, BC loop, C-terminal CD-loop/N-terminal D-helix). A corresponding gp130-binding site on IL-6 was exchanged with this epitope. The resulting IL-6/CNTF chimera lost the capacity to signal via gp130 on cells without LIFR, but acquired the ability to signal via the gp130/LIFR heterodimer and STAT3 on responsive cells. Besides identifying a specific LIFR binding epitope on CNTF, our results suggest that receptor recognition sites of cytokines are organized as modules that are exchangeable even between cytokines with limited sequence homology.

Magnocellular vasopressinergic neurons in explant cultures are rescued from cell death by ciliary neurotrophic factor and leukemia inhibiting factor

Selective death of magnocellular vasopressinergic neurons in the hypothalamus has been reported in cases of hereditary and idiopathic diabetes insipidus and after experimental lesions of the hypothalamo-neurohypophyseal pathway. To identify trophic factors that promote survival of these neurons, an in vitro model system was established in which organotypic cultures of the rat hypothalamic paraventricular nucleus were maintained in chemically-defined medium. We observe that the majority of magnocellular vasopressinergic neurons die in these cultures, while other cell populations such as corticotrophin-releasing factor producing parvicellular and oxytocin producing magnocellular cells retain a well preserved cytoarchitectonic organization. Degenerating vasopressinergic cells exhibit morphological signs of apoptosis and stained positively when analysed by the terminal deoxynucleotidyl transferase biotinylated dUTP nick end-labelling assay. Partial survival of vasopressinergic neurons occurred after co-culturing the paraventricular nucleus with neurohypophyseal explants, indicating that target-derived factors may be required for the survival of these neurons. Cell survival is dramatically increased by the administration of ciliary neurotrophic factor and leukemia inhibiting factor, but not by interleukin 6 or the members of the neurotrophin family. Reverse transcription-polymerase chain reaction followed by Southern analysis shows the presence of ciliary neurotrophic factor messenger RNA in the neurohypophysis. Thus, endogenous ciliary neurotrophic factor and leukemia inhibiting factor, produced by neurohypophyseal cells may function as a physiological survival factor for neurosecretory vasopressinergic neurons.

Increased ciliary neurotrophic factor expression in reactive astrocytes following spinal cord injury in the rat

Expression of ciliary neurotrophic factor (CNTF) was observed in reactive astrocytes in injured spinal cord of the adult rat. After unilateral incision of the dorsal funiculus at a midthoracic level, the rats were sacrificed on the day of postoperation (DPO) 3, 7, 14 or 28. Western blot analysis of spinal cord extracts showed that the intensity of the CNTF-immunoreactive band of 24 kDa was increased on DPO 3 and 7 and decreased on DPO 14. CNTF- or glial fibrillary acidic protein (GFAP)-like immunoreactivity was also increased progressively in the injured dorsal funiculus and adjacent gray matter. Double immunofluorescence histochemistry revealed that all CNTF-like immunoreactive cells showed GFAP-like immunoreactivity. The CNTF upregulation in the reactive astrocytes may play important roles in repair process after spinal cord injury.

Peripheral nerve grafts exert trophic and tropic effects on anterior thalamic neurons

Peripheral nerve grafting into the central nervous system (CNS) has been used to study the regenerative capabilities of central neurons given access to a peripheral nervous system (PNS) environment. It is well documented that many CNS neurons regenerate axons along peripheral nerve grafts placed in close proximity to their cell bodies and that these grafts can ameliorate axotomy-induced retrograde degeneration. In the present study, we placed peripheral nerve grafts in proximity to axotomized neurons of the anterior thalamus. Standard histological and retrograde tracing techniques were used to examine these preparations 2 months after grafting. Three effects of these grafts were observed: amelioration of retrograde degeneration of axotomized anterior thalamic neurons, hypertrophy of many thalamic neurons in the local environment of the graft, and ingrowth of axons of axotomized anterior thalamic neurons as well as nonaxotomized neurons from surrounding nuclei. We conclude from these studies that peripheral nerve grafts not only provide a matrix for axonal outgrowth but also exert marked trophic and tropic effects on axotomized anterior thalamic neurons.

Ciliary neurotrophic factor stimulates astroglial hypertrophy in vivo and in vitro

After insult or trauma, astrocytes become activated and endeavor to restore the brain's delicately balanced microenvironment. An index of their activated state is that they become enlarged or hypertrophic. Ciliary neurotrophic factor (CNTF), a member of the alpha helical family of cytokines, is synthesized by astrocytes and is generally regarded to be an autocrine and paracrine injury signal. To determine whether CNTF might be an endogenous signal that stimulates astrocyte hypertrophy in vivo, we intracerebrally injected 200 ng of recombinant human CNTF into the adult rat neocortex. To study the astrocytes their cytosol was stained with antibodies against S100beta and their nuclei were stained with propidium iodide (PI). Fluorescent images of astrocytic nuclei and somas were acquired using a confocal laser-scanning microscope and their areas were measured using the NIH image software. Within 24 h of treatment, CNTF induced a volume increase of the somas and nuclei of protoplasmic and fibrous astrocytes in vivo, and this effect persisted for at least 48 h. To determine whether CNTF activates astrocytes directly, glial cultures were treated with CNTF (10 ng/ml) and were evaluated by measuring the area of PI stained nuclei. CNTF stimulation increased the size of both polygonal and process-bearing astroglia. Since our studies in vivo have shown that CNTF induces other key aspects of gliosis (S. W. Levison et al., 1996; Exp. Neurol. 141, 256), we conclude that CNTF is a powerful activator of astrocytes and that it is likely responsible for the persistent glial hypertrophy observed following injuries and diseases of the CNS.