Gene therapy for motor neuron disease.
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Adenoviridae↗
Biomedical subjects
M Sendtner
Publications and source records attributed to M Sendtner.
Adenoviral gene transfer of ciliary neurotrophic factor and brain-derived neurotrophic factor leads to long-term survival of axotomized motor neurons.
The neurotrophic factors ciliary neurotrophic factor and brain-derived neurotrophic factor can prevent motor neuron cell death during development and after nerve lesion in neonatal rodents. However, local and systemic application of these factors to newborn rats with damaged motor nerves rescues motor neurons only transiently during the first two weeks after axotomy. In order to test the effect of continuous delivery of these factors, the effect of localized injection of CNTF- or BDNF-transducing recombinant adenoviruses into the lesioned nerves was investigated. Under such conditions, survival of axotomized motor neurons is maintained for at least 5 weeks. This way of delivery corresponds to the physiological situation in adult rodents, under which endogenous CNTF is present in the cytosol of Schwann cells and BDNF expression is upregulated after nerve lesion, making these factors available to the damaged motor neurons. Recent results show that overexpression of muscle-derived neurotrophin-3 prevents degeneration of axons and motor endplates, but has only little effect on the number of motor neuron cell bodies in a murine animal model of motor neuron disease. Therefore, techniques suitable for tonic exposure to both nerve- and muscle-derived neurotrophic factors may have implications for the design of future therapeutic strategies against human motor neuron disease.
Adenoviridae↗
Cryptic physiological trophic support of motoneurons by LIF revealed by double gene targeting of CNTF and LIF.
BACKGROUND: The survival and differentiation of motoneurons during embryonic development, and the maintenance of their function in the postnatal phase, are regulated by a great variety of neurotrophic molecules which mediate their effects through different receptor systems. The multifactorial support of motoneurons represents a system of high security, because the inactivation of individual ligands has either no detectable, or relatively small, atrophic or degenerative effect on motoneurons. RESULTS: Leukaemia inhibitory factor (LIF) has been demonstrated to support motoneuron survival in vitro and in vivo under different experimental conditions. However, when LIF was inactivated by gene targeting, there were no apparent changes in the number and structure of motoneurons and no impairment of their function. The slowly appearing, relatively mild degenerating effects in motoneurons that resulted from ciliary neurotrophic factor (CNTF) gene targeting were substantially potentiated by simultaneous inactivation of the LIF gene, however. Thus, in mice deficient in LIF and CNTF, the degenerative changes in motoneurons were more extensive and appeared earlier. These changes were also functionally reflected by a marked reduction in grip strength. CONCLUSIONS: Degenerative disorders of the nervous system, in particular those of motoneurons, may be based on multifactorial inherited and/or acquired defects which individually do not result in degenerative disorders, but which become apparent when additional (cryptic) inherited disturbances or sub-threshold concentrations of noxious factors come into play. Accordingly, the inherited inactivation of the CNTF gene in a high proportion of the Japanese population may represent a predisposing factor for degenerative disorders of motoneurons.
Animals↗
Treatment with ciliary neurotrophic factor does not improve regeneration in experimental autoimmune neuritis of the Lewis rat.
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Animals↗
Microencapsulated ciliary neurotrophic factor: physical properties and biological activities.
Controlled drug release in the CNS and PNS is still an obstacle to the treatment of neurodegenerative disorders. We have prepared a variety of microspheres containing either ciliary neurotrophic factor (CNTF) or genetically engineered cells able to synthesize and release this cytokine. CNTF is a multifunctional cytokine that can regulate the survival and differentiation of many types of developing and adult neurons. However, when given in therapeutically effective doses by systemic injections, it produces numerous adverse side effects. In order to minimize these effects we have microencapsulated it in biopolymers (chitosans, alginates, and copolymers in various proportions to achieve different kinetic properties). Size distribution profiles were determined by an image analysis system and surface characteristics were assessed by electron microscopy. The total content of CNTF as well as the amounts released per day were determined by ELISA and in vitro bioassays. The results from the release kinetics demonstrate that long-term secretion (up to 24 days) of CNTF is achieved by combining chitosan with copolymerized lactic and glycolic acid, whereas microspheres made of alginate provided only relatively short-term release (2-12 days). Neuron survival and neurite outgrowth in cultures of ciliary ganglia were supported by microencapsulated CNTF, indicating biological stability of CNTF. Genetically engineered human kidney cells 293 continued synthesizing CNTF within spheres and the released amounts of CNTF in the culture medium were comparable to the amounts secreted from monolayers (1 ng/ml of supernatant from confluent cultures) or even higher. These studies provide a basis for future testing of CNTF in encapsulated preparations using animal models of neurodegenerative disorders.
Alginates↗
Pharmacokinetics of intrathecally applied BDNF and effects on spinal motoneurons.
Brain-derived neurotrophic factor (BDNF) is a potential drug for treatment of amyotrophic lateral sclerosis. Previous studies have demonstrated little or no penetration of the blood-brain barrier by BDNF, hence systemic application does not result in significant penetration into the spinal cord to produce direct action on motoneurons. Intrathecal (i.th) application of BDNF to sheep was investigated as a mean of topical administration. After continuous infusion a caudalcranial gradient of BDNF concentration in cerebrospinal fluid (CSF) and at the meninges was observed. BDNF did not penetrate spinal parenchyma but accumulated in spinal motoneurons probably due to axonal uptake in ventral roots and subsequent retrograde transport. Spinal motoneurons showed reduced levels of tropomyosin receptor kinase (trk) B and increased levels of c-fos at high BDNF doses in comparison to treatment with saline, even after treatment periods of several months. After bolus injection and cessation of continuous delivery multiphasic reduction of the BDNF concentration in CSF was detected. Our study demonstrates that i.th. application of BDNF is feasible, setting the stage for future clinical trials.
Animals↗
Ciliary neurotrophic factor enhances the rate of oligodendrocyte generation.
Although ciliary neurotrophic factor (CNTF) is a potent survival factor for many types of neurons and glial cells in vitro, there is currently no evidence that it participates in normal development. Here we show that CNTF greatly enhances the rate of oligodendrocyte generation. Proliferation of oligodendrocyte precursor cells purified from rodent optic nerves and cultured in platelet-derived growth factor-containing medium is significantly increased by CNTF. Similarly, the number of proliferating oligodendrocyte precursor cells in developing optic nerves of transgenic mice lacking CNTF is decreased by up to threefold and the number of oligodendrocytes is transiently decreased; proliferation is restored to normal by the delivery of exogenous CNTF into the developing optic nerve. Both oligodendrocyte number and myelination ultimately attain wild-type values in CNTF-deficient adult mice, indicating that CNTF is not necessary for either oligodendrocyte differentiation or myelination, although it normally accelerates oligodendrocyte development by enhancing the proliferation of oligodendrocyte precursor cells.
Animals↗
The response of motoneurons to neurotrophins.
The ongoing search for neurotrophic factors for motoneurons has led to the identification of a number of molecules which regulate motoneuron survival and function. Among these factors, the neurotrophins brain derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and NT-4/5 but not nerve growth factor (NGF), can prevent embryonic and postnatal motoneuron cell death in a variety of experimental paradigms. Analysis of expression of p75, trkB and trkC-components of the neurotrophin receptors-supports a potential physiological role for these factors as muscle- and glial-derived trophic factors for motoneurons. However, the survival of motoneurons during embryonic development is not reduced in the absence of BDNF, NT-3 or NT-4, as revealed by gene knockout experiments. This points to the involvement of additional trophic factors in the regulation of embryonic and postnatal motoneuron survival. The purpose of this review is to bring together the often prophetic observations from earlier studies-prior to the identification and characterization of these neurotrophins-with more recent results.
Animals↗
Neurotrophic factors for experimental treatment of motoneuron disease.
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Animals↗
Inactivation of bcl-2 results in progressive degeneration of motoneurons, sympathetic and sensory neurons during early postnatal development.
Bcl-2 is a major regulator of programmed cell death, a critical process in shaping the developing nervous system. To assess whether Bcl-2 is involved in regulating neuronal survival and in mediating the neuroprotective action of neurotrophic factors, we generated Bcl-2-deficient mice. At birth, the number of facial motoneurons, sensory, and sympathetic neurons was not significantly changed, and axotomy-induced degeneration of facial motoneurons could still be prevented by brain-derived neurotrophic factor (BDNF) or ciliary neurotrophic factor (CNTF). Interestingly, substantial degeneration of motoneurons, sensory, and sympathetic neurons occurred after the physiological cell death period. Accordingly, Bcl-2 is not a permissive factor for the action of neurotrophic factors, and although it does not influence prenatal neuronal survival, it is crucial for the maintenance of specific populations of neurons during the early postnatal period.
Animals↗
Essential function of LIF receptor in motor neurons.
Development and maintenance of the mammalian nervous system is dependent upon neurotrophic cytokines. One class of neurotrophic factor acts through receptor complexes involving the low-affinity leukaemia inhibitory factor receptor subunit (LIF-R). Members of this family of cytokines, such as ciliary neurotrophic factor (CNTF) and leukaemia inhibitory factor (LIF), have profound effects on the survival and maintenance of motor neurons. Recently it was reported that mice lacking LIF-R die shortly after birth unlike mice lacking CNTF or LIF which are viable. Here we describe histopathological analyses of lifr mutants that reveal a loss > 35% of facial motor neurons, 40% of spinal motor neurons and 50% of neurons in the nucleus ambiguus. These findings point to the existence of a ligand for LIF-R that is required for the normal development of motor neurons in both brainstem nuclei and spinal cord.
Animals↗
Expression of neurotrophins in skeletal muscle: quantitative comparison and significance for motoneuron survival and maintenance of function.
Neurotrophins play a crucial role in the regulation of survival and maintenance of specific functions of various populations of neurons. Brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and neurotrophin 4/5 (NT-4) have been shown to support motoneuron survival during embryonic development and, after birth, to protect motoneurons from degeneration after nerve lesion. We have compared the levels of these neurotrophins in skeletal muscle by quantitative Northern blot analysis, both during embryonic development and postnatally. We localized the sites of expression of these neurotrophins by in situ hybridisation and analysed the expression of trkB in the spinal cord by in situ hybridisation and immunohistochemistry. NT-3 is most abundantly expressed both during embryonic development and in the postnatal phase, followed by NT-4. The levels of BDNF are very low, in particular after birth. After nerve lesion, NT-3 mRNA essentially remained unchanged, whereas NT-4 mRNA rapidly decreased. The slow increase in BDNF expression seems to be essentially due to the expression in Schwann cells rather than skeletal muscle, demonstrated by in situ hybridisation. Our data indicate that motoneurons can receive trophic support from several members of the neurotrophin gene family during the period of naturally occurring cell death. Postnatally, the predominant ligand acting via trkB on motoneurons is NT-4, whereas BDNF expression seems to play a role mainly after nerve lesion.
Animals↗
Molecular biology of neurotrophic factors.
The survival and functional maintenance of spinal motoneurones and of peripheral neurones, such as sensory, sympathetic and parasympathetic neurones, has been shown to depend on neurotrophic factors, both during the period of developmental cell death and in adulthood. A variety of such factors has been identified over recent years, among them factors of the NGF gene family, for example BDNF, NT-3, NT-4/5 and NT-6, and factors such as CNTF and LIF acting on neuronal target cells via receptor components shared with cytokines such as IL-6. In addition, pluripotent mitogens, such as IGF-I and IGF-II can support the survival of a variety of neuronal cell types, including spinal motoneurones both in cell culture and in vivo. The establishment of mice in which the genes for these factors and their receptors have been inactivated by homologous recombination has been a major step in the understanding of their physiological function. It is not clear so far whether or not similar gene defects in human are associated with any neurological disease. However, some of these factors have been demonstrated to be effective in animal models of neuropathy and motoneurone disorders, so that first clinical trials using these factors for symptomatic treatment of amyotrophic lateral sclerosis (ALS) and peripheral neuropathies have already been initiated.
Animals↗
Neurodegenerative disease. Oxidative stress and motorneuron disease.
Transgenic mice carrying mutated Cu/Zn superoxide dismutase genes provide insights into the pathogenesis of human motorneuron diseases and may be useful as models in the development and testing of therapies.
Amyotrophic Lateral Sclerosis↗
Ciliary neurotrophic factor: pharmacokinetics and acute-phase response in rat.
Ciliary neurotrophic factor (CNTF) supports the survival of motoneurons in vitro and in vivo. Recombinant CNTF is an investigational drug for the treatment of amyotrophic lateral sclerosis. We determined the pharmacokinetics of radioiodinated CNTF after intravenous injection into rats. CNTF shows a biphasic clearance with an initial plasma half-life of 2.9 minutes and is removed from the circulation by the liver. No accumulation of radioactivity was detectable in nerve tissue or skeletal muscle after intravenous injection of 0.1 microgram and 0.5 microgram of CNTF. Radioactive degradation products accumulate in the skin. Liver cells express specific binding proteins for CNTF, and the incorporation and degradation of intravenously injected CNTF by the liver may occur after association of CNTF with the soluble CNTF receptor alpha in the circulation. Probably as a consequence of its binding to hepatocytes, CNTF induces acute-phase responses in liver. The short half-life and the inflammatory side effect may limit the clinical usefulness of systematically administered CNTF in the treatment of human motoneuron disorders.
Acute-Phase Reaction↗
Ciliary neurotrophic factor.
Ciliary neurotrophic factor (CNTF) was first identified and partially purified from embryonic chick eye tissues. Subsequently, it was shown that CNTF is also present in large amounts in sciatic nerves of adult rats and rabbits, which led to its final purification and cloning. CNTF is not secreted by the classical secretory pathway involving the endoplasmatic reticulum and Golgi complex, but can be detected in high quantities within the cytoplasm of myelinating Schwann cells and astrocytes using immunohistochemistry. CNTF supports survival and/or differentiation of a variety of neuronal cell types including sensory, sympathetic, and motoneurons. Also, nonneuronal cells, such as oligodendrocytes, microglial cells, liver cells, and skeletal muscle cells, respond to exogenously administered CNTF, both in vitro and in vivo. During development, expression of CNTF is very low, if indeed it is expressed at all, and the phenotype of mice lacking endogenous CNTF after inactivation of the CNTF gene by homologous recombination suggests that CNTF does not play a crucial role for responsive cells during embryonic development. However, motoneurons are lost postnatally in mice lacking endogenous CNTF, suggesting that CNTF acts physiologically on the maintenance of these cells. The ability of exogenous CNTF to protect against motoneuron loss following lesion or in other animal models indicates that CNTF might be useful in the treatment of human motoneuron disorders, provided appropriate means of administration can be found.
Amino Acid Sequence↗
Actions of CNTF and neurotrophins on degenerating motoneurons: preclinical studies and clinical implications.
Spinal motoneurons innervating skeletal muscle were amongst the first neurons shown to require the presence of their target cells to develop appropriately. Isolated embryonic chick and rat motoneurons have been used to identify neurotrophic factors and cytokines capable of supporting the survival of developing motoneurons. Such factors include ciliary neurotrophic factor (CNTF), which is present physiologically in high amounts in myelinating Schwann cells of peripheral nerves, and brain-derived neurotrophic factor (BDNF) which is synthesized in skeletal muscle and, after peripheral nerve lesion, in Schwann cells. These factors have been further analyzed for their physiological significance in maintaining motoneuron function in vivo, and for their potential therapeutic usefulness in degenerative motoneuron disease. Both CNTF and BDNF are capable of rescuing injured facial motoneurons in newborn rats. Furthermore, CNTF prolongs survival and improves motor function of pmn mice, an animal model for degenerative motoneuron disease, by preventing degeneration of motoneuron axons and somata. Thus treatment of human motoneuron disease with neurotrophic factors should be possible, provided that rational means for application of these factors can be established considering also the appearance of potential side effects.
Animals↗
Members of several gene families influence survival of rat motoneurons in vitro and in vivo.
The survival and functional maintenance of spinal motoneurons, both during the period of developmental cell death and in adulthood, have been shown to be dependent on trophic factors. In vitro experiments have previously been used to identify several survival factors for motoneurons, including CNTF, LIF, and members of the neurotrophin, FGF, and IGF gene families. Some of these factors have also been shown to be active in vivo, either on chick motoneurons during embryonic development or on lesioned facial and spinal motoneurons of the newborn rat. Here we demonstrate that lesioned newborn rat facial motoneurons can be rescued by NT-4/5, IGF-I, and LIF. Furthermore, in contrast to chick motoneurons, the survival of isolated embryonic rat motoneurons can be maintained by the neurotrophins BDNF, NT-3, and NT-4/5. IGF-I and FGF-5 were also active in this system, each supporting more than 50% of the originally plated neurons. The responsiveness of motoneurons to multiple factors in vitro and in vivo suggests that motoneuron survival and function are regulated by the coordinated actions of members of different gene families.
Animals↗