Beneficial effects of insulin-like growth factor-I on wobbler mouse motoneuron disease

Research progress on astrocyte-derived extracellular vesicles in the pathogenesis and treatment of neurodegenerative diseases

Neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD), pose significant global health risks and represent a substantial public health concern in the contemporary era. A primary factor in the pathophysiology of these disorders is aberrant accumulation and aggregation of pathogenic proteins within the brain and spinal cord. Recent investigations have identified extracellular vesicles (EVs) in the central nervous system (CNS) as potential carriers for intercellular transport of misfolded proteins associated with neurodegenerative diseases. EVs are involved in pathological processes that contribute to various brain disorders including neurodegenerative disorders. Proteins linked to neurodegenerative disorders are secreted and distributed from cell to cell via EVs, serving as a mechanism for direct intercellular communication through the transfer of biomolecules. Astrocytes, as active participants in CNS intercellular communication, release astrocyte-derived extracellular vesicles (ADEVs) that are capable of interacting with diverse target cells. This review primarily focuses on the involvement of ADEVs in the development of neurological disorders and explores their potential dual roles - both advantageous and disadvantageous in the context of neurological disorders. Furthermore, this review examines the current studies investigating ADEVs as potential biomarkers for the diagnosis and treatment of neurodegenerative diseases. The prospects and challenges associated with the application of ADEVs in clinical settings were also comprehensively reviewed.

Neuroprotective effects of exercise on the aging human neuromuscular system

Human biological aging from maturity to senescence is associated with a gradual loss of muscle mass and neuromuscular function. It is not until very old age (>80 years) however, that these changes often manifest into functional impairments. A driving factor underlying the age-related loss of muscle mass and function is the reduction in the number and quality of motor units (MUs). A MU consists of a single motoneuron, located either in the spinal cord or the brain stem, and all of the muscle fibres it innervates via its peripheral axon. Throughout the adult lifespan, MUs are slowly, but progressively lost. The compensatory process of collateral reinnervation attempts to recapture orphaned muscle fibres following the death of a motoneuron. Whereas this process helps mitigate loss of muscle mass during the latter decades of adult aging, the neuromuscular system has fewer and larger MUs, which have lower quality connections between the axon terminal and innervated muscle fibres. Whether this process of MU death and degradation can be attenuated with habitual physical activity has been a challenging question of great interest. This review focuses on age-related alterations of the human neuromuscular system, with an emphasis on the MU, and presents findings on the potential protective effects of lifelong physical activity. Although there is some discrepancy across studies of masters athletes, if one considers all experimental limitations as well as the available literature in animals, there is compelling evidence of a protective effect of chronic physical training on human MUs. Our tenet is that high-levels of physical activity can mitigate the natural trajectory of loss of quantity and quality of MUs in old age.

Dysregulation of IGF-1/GLP-1 signaling in the progression of ALS: potential target activators and influences on neurological dysfunctions

The prominent causes for motor neuron diseases like ALS are demyelination, immune dysregulation, and neuroinflammation. Numerous research studies indicate that the downregulation of IGF-1 and GLP-1 signaling pathways plays a significant role in the progression of ALS pathogenesis and other neurological disorders. In the current review, we discussed the dysregulation of IGF-1/GLP-1 signaling in neurodegenerative manifestations of ALS like a genetic anomaly, oligodendrocyte degradation, demyelination, glial overactivation, immune deregulation, and neuroexcitation. In addition, the current review reveals the IGF-1 and GLP-1 activators based on the premise that the restoration of abnormal IGF-1/GLP-1 signaling could result in neuroprotection and neurotrophic effects for the clinical-pathological presentation of ALS and other brain diseases. Thus, the potential benefits of IGF-1/GLP-1 signal upregulation in the development of disease-modifying therapeutic strategies may prevent ALS and associated neurocomplications.

Central and Peripheral Neuromuscular Adaptations to Ageing

Ageing is accompanied by a severe muscle function decline presumably caused by structural and functional adaptations at the central and peripheral level. Although researchers have reported an extensive analysis of the alterations involving muscle intrinsic properties, only a limited number of studies have recognised the importance of the central nervous system, and its reorganisation, on neuromuscular decline. Neural changes, such as degeneration of the human cortex and function of spinal circuitry, as well as the remodelling of the neuromuscular junction and motor units, appear to play a fundamental role in muscle quality decay and culminate with considerable impairments in voluntary activation and motor performance. Modern diagnostic techniques have provided indisputable evidence of a structural and morphological rearrangement of the central nervous system during ageing. Nevertheless, there is no clear insight on how such structural reorganisation contributes to the age-related functional decline and whether it is a result of a neural malfunction or serves as a compensatory mechanism to preserve motor control and performance in the elderly population. Combining leading-edge techniques such as high-density surface electromyography (EMG) and improved diagnostic procedures such as functional magnetic resonance imaging (fMRI) or high-resolution electroencephalography (EEG) could be essential to address the unresolved controversies and achieve an extensive understanding of the relationship between neural adaptations and muscle decline.

The Role of Insulin-Like Growth Factors and Insulin-Like Growth Factor-Binding Proteins in the Nervous System

The insulin-like growth factors (IGF-I and IGF-II) and their receptors are widely expressed in nervous tissue from early embryonic life. They also cross the blood brain barriers by active transport, and their regulation as endocrine factors therefore differs from other tissues. In brain, IGFs have paracrine and autocrine actions that are modulated by IGF-binding proteins and interact with other growth factor signalling pathways. The IGF system has roles in nervous system development and maintenance. There is substantial evidence for a specific role for this system in some neurodegenerative diseases, and neuroprotective actions make this system an attractive target for new therapeutic approaches. In developing new therapies, interaction with IGF-binding proteins and other growth factor signalling pathways should be considered. This evidence is reviewed, gaps in knowledge are highlighted, and recommendations are made for future research.

Neuromuscular Junction Morphology and Gene Dysregulation in the Wobbler Model of Spinal Neurodegeneration

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset neuromuscular disease for which there is currently no effective treatment. The progression of ALS includes loss of motor neurons controlling the voluntary muscles, with much of this loss occurring at the neuromuscular junction. In an effort to better understand changes at the neuromuscular junction, we utilized the wobbler mouse model of motor neuron loss. We examined biceps and end plate morphologies and monitored selected factors involved in end plate function. Structural volumes were determined from 3D reconstructions that were generated for the end plates. Wobbler mice exhibited size reductions of both the muscle fibers and the end plates within the biceps, and we found that the end plate volumes were the most sensitive indicator of the degeneration. Concurrently, we found increases in calcitonin gene-related peptide (CGRP) and its receptor in wobbler biceps and spinal cord. We also found increases in gene expression of two acetylcholine receptors within the wobbler biceps, which may be a result of altered CGRP/CALCRL (calcitonin receptor-like receptor) expression.

Sarcopenia: Neurological Point of View

Sarcopenia is an age-related geriatric syndrome which is characterized by the gradual loss of muscle mass, muscle strength, and muscle quality. There are a lot of neurologic insults on sarcopenia at various levels from the brain to the neuromuscular junctions (NMJs) to generate a volitional task. Dopaminergic downregulation, inadequate motor programming and motor coordination impairment lead to decline of supraspinal drive. Motor unit reorganization and inflammatory changes in motor neuron decrease conduction velocity and amplitude of compound muscle action potential. Furthermore, NMJ remodeling and age related neurophysiological alterations may contribute to neuromuscular impairment. Sarcopenia is an age-associated, lifelong process which links to multiple etiological factors. Although not all the causes are completely understood, we suggest that compromised nervous system function may be one of the important contributors to the sarcopenia.

The therapeutic potential of insulin-like growth factor-1 in central nervous system disorders

Central nervous system (CNS) development is a finely tuned process that relies on multiple factors and intricate pathways to ensure proper neuronal differentiation, maturation, and connectivity. Disruption of this process can cause significant impairments in CNS functioning and lead to debilitating disorders that impact motor and language skills, behavior, and cognitive functioning. Recent studies focused on understanding the underlying cellular mechanisms of neurodevelopmental disorders have identified a crucial role for insulin-like growth factor-1 (IGF-1) in normal CNS development. Work in model systems has demonstrated rescue of pathophysiological and behavioral abnormalities when IGF-1 is administered, and several clinical studies have shown promise of efficacy in disorders of the CNS, including autism spectrum disorder (ASD). In this review, we explore the molecular pathways and downstream effects of IGF-1 and summarize the results of completed and ongoing pre-clinical and clinical trials using IGF-1 as a pharmacologic intervention in various CNS disorders. This aim of this review is to provide evidence for the potential of IGF-1 as a treatment for neurodevelopmental disorders and ASD.

Recombinant human insulin-like growth factor I (rhIGF-I) for the treatment of amyotrophic lateral sclerosis/motor neuron disease

BACKGROUND

Recombinant human insulin-like growth factor I (rhIGF-I) is a possible disease modifying therapy for amyotrophic lateral sclerosis (ALS, which is also known as motor neuron disease (MND)).

OBJECTIVES

To examine the efficacy of rhIGF-I in affecting disease progression, impact on measures of functional health status, prolonging survival and delaying the use of surrogates (tracheostomy and mechanical ventilation) to sustain survival in ALS. Occurrence of adverse events was also reviewed.

SEARCH METHODS

We searched the Cochrane Neuromuscular Disease Group Specialized Register (21 November 2011), CENTRAL (2011, Issue 4), MEDLINE (January 1966 to November 2011) and EMBASE (January 1980 to November 2011) and sought information from the authors of randomised clinical trials and manufacturers of rhIGF-I.

SELECTION CRITERIA

We considered all randomised controlled clinical trials involving rhIGF-I treatment of adults with definite or probable ALS according to the El Escorial Criteria. The primary outcome measure was change in Appel Amyotrophic Lateral Sclerosis Rating Scale (AALSRS) total score after nine months of treatment and secondary outcome measures were change in AALSRS at 1, 2, 3, 4, 5, 6, 7, 8, 9 months, change in quality of life (Sickness Impact Profile scale), survival and adverse events.

DATA COLLECTION AND ANALYSIS

Each author independently graded the risk of bias in the included studies. The lead author extracted data and the other authors checked them. We generated some missing data by making ruler measurements of data in published graphs. We collected data about adverse events from the included trials.

MAIN RESULTS

We identified three randomised controlled trials (RCTs) of rhIGF-I, involving 779 participants, for inclusion in the analysis. In a European trial (183 participants) the mean difference (MD) in change in AALSRS total score after nine months was -3.30 (95% confidence interval (CI) -8.68 to 2.08). In a North American trial (266 participants), the MD after nine months was -6.00 (95% CI -10.99 to -1.01). The combined analysis from both RCTs showed a MD after nine months of -4.75 (95% CI -8.41 to -1.09), a significant difference in favour of the treated group. The secondary outcome measures showed non-significant trends favouring rhIGF-I. There was an increased risk of injection site reactions with rhIGF-I (risk ratio 1.26, 95% CI 1.04 to 1.54). . A second North American trial (330 participants) used a novel primary end point involving manual muscle strength testing. No differences were demonstrated between the treated and placebo groups in this study. All three trials were at high risk of bias.

AUTHORS' CONCLUSIONS

Meta-analysis revealed a significant difference in favour of rhIGF-I treatment; however, the quality of the evidence from the two included trials was low. A third study showed no difference between treatment and placebo. There is no evidence for increase in survival with IGF1. All three included trials were at high risk of bias.

Impairments to the GH-IGF-I axis in hSOD1G93A mice give insight into possible mechanisms of GH dysregulation in patients with amyotrophic lateral sclerosis

GH deficiency has been found in subjects with amyotrophic lateral sclerosis (ALS). Disrupted endocrine function could contribute to the progressive muscle loss and hypermetabolism seen in ALS. It is not possible to study all the elements of the GH-IGF-I axis in ALS patients. Consequently, it remains unclear whether dysfunctional GH secretion contributes to disease pathogenesis and why GH and IGF-I directed treatment strategies are ineffective in human ALS. The hSOD1(G93A) transgenic mouse model is useful for the detailed investigation of the pathogenesis of ALS. We report that symptomatic male hSOD1(G93A) transgenic mice exhibit a deficiency in GH secretion similar to that seen in human ALS. Further characterization of the GH-IGF-I axis in hSOD1(G93A) mice reveals central and peripheral abnormalities that are not found in wild-type age-matched controls. Specifically, we observe aberrant endogenous pulsatile GH secretion, reduced pituitary GH content, and decreased circulating levels of IGF-I, indicating global GH deficiency in hSOD1(G93A) mice. Furthermore, a reduction in the expression of the IGF-I receptor α-subunit in skeletal muscle and lumbar spinal cords of hSOD1(G93A) mice suggests impaired IGF-I signaling within these tissues. This is the first account of disrupted GH secretion in a transgenic mouse model of ALS. These observations are essential for the development of effective GH and IGF-I targeted therapies in ALS.

Insulin-like growth factors in the peripheral nervous system

Insulin-like growth factors (IGFs) play an integral role in development, growth, and survival. This article details the current understanding of the effects of IGFs in the peripheral nervous system (PNS) during health and disease, and introduces how the IGF system regulates PNS development and impacts growth and survival of PNS cells. Also discussed are implications of IGF signaling in neurodegeneration and the status and prospects of IGF therapies for PNS conditions. There is substantial support for the application of IGF therapies in the treatment of PNS injury and disease.

Motor neuron trophic factors: therapeutic use in ALS?

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

Role of the nervous system in sarcopenia and muscle atrophy with aging: strength training as a countermeasure

Aging is characterized by loss of spinal motor neurons (MNs) due to apoptosis, reduced insulin-like growth factor I signaling, elevated amounts of circulating cytokines, and increased cell oxidative stress. The age-related loss of spinal MNs is paralleled by a reduction in muscle fiber number and size (sarcopenia), resulting in impaired mechanical muscle performance that in turn leads to a reduced functional capacity during everyday tasks. Concurrently, maximum muscle strength, power, and rate of force development are decreased with aging, even in highly trained master athletes. The impairment in muscle mechanical function is accompanied and partly caused by an age-related loss in neuromuscular function that comprise changes in maximal MN firing frequency, agonist muscle activation, antagonist muscle coactivation, force steadiness, and spinal inhibitory circuitry. Strength training appears to elicit effective countermeasures in elderly individuals even at a very old age (>80 years) by evoking muscle hypertrophy along with substantial changes in neuromuscular function, respectively. Notably, the training-induced changes in muscle mass and nervous system function leads to an improved functional capacity during activities of daily living.

IGF-1:tetanus toxin fragment C fusion protein improves delivery of IGF-1 to spinal cord but fails to prolong survival of ALS mice

To improve delivery of human insulin-like growth factor-1 (hIGF-1) to brain and spinal cord, we generated a soluble IGF-1:tetanus toxin fragment C fusion protein (IGF-1:TTC) as a secreted product from insect cells. IGF-1:TTC exhibited IGF-1 and TTC activity in vitro; it increased levels of immunoreactive phosphoAkt in treated MCF-7 cells and bound to immobilized ganglioside GT1b. In mice, the fusion protein underwent retrograde transport by spinal cord motor neurons following intramuscular injection, and exhibited both TTC- and IGF-1 activity in the CNS following intrathecal infusion. Analogous to the case with TTC, intrathecal infusion of the fusion protein resulted in substantial levels of IGF-1:TTC in spinal cord tissue extracts. Tissue concentrations of hIGF-1 in lumbar spinal cords of mice infused with IGF-1:TTC were estimated to be approximately 500-fold higher than those in mice treated with unmodified recombinant hIGF-1 (rhIGF-1). Like rhIGF-1, infusion of IGF-1:TTC reduced levels of IGF-1 receptor immunoreactivity in the same extracts. Despite raising levels of exogenous hIGF-1 in spinal cord, intramuscular- or intrathecal administration of IGF-1:TTC had no significant effect on disease progression or survival of high-expressing SOD1(G93A) transgenic mice. IGF-1:TTC may prove to be neuroprotective in other animal models of CNS disease or injury known to be responsive to unmodified IGF-1.

Insulin-like growth factor-I for the treatment of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that affects both upper and lower motorneurons (MN) resulting in weakness, paralysis and subsequent death. Insulin-like growth factor-I (IGF-I) is a potent neurotrophic factor that has neuroprotective properties in the central and peripheral nervous systems. Due to the efficacy of IGF-I in the treatment of other diseases and its ability to promote neuronal survival, IGF-I is being extensively studied in ALS therapeutic trials. This review covers in vitro and in vivo studies examining the efficacy of IGF-I in ALS model systems and also addresses the mechanisms by which IGF-I asserts its effects in these models, the status of the IGF-I system in ALS patients, results of clinical trials, and the need for the development of better delivery mechanisms to maximize IGF-I efficacy. The knowledge obtained from these studies suggests that IGF-I has the potential to be a safe and efficacious therapy for ALS.

Intraspinal cord delivery of IGF-I mediated by adeno-associated virus 2 is neuroprotective in a rat model of familial ALS

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a devastating disease that is characterized by the progressive loss of motor neurons. Patients with ALS usually die from respiratory failure due to respiratory muscle paralysis. Consequently, therapies aimed at preserving segmental function of the respiratory motor neurons could extend life for these patients. Insulin-like growth factor-I (IGF-I) is known to be a potent survival factor for motor neurons. In this study we induced high levels of IGF-I expression in the cervical spinal cord of hSOD1(G93A) rats with intraspinal cord (ISC) injections of an adeno-associated virus serotype 2 vector (CERE-130). This approach reduced the extent of motor neuron loss in the treated segments of the spinal cord. However, a corresponding preservation of motor function was observed in male, but not female, hSOD1(G93A) rats. We conclude that ISC injection of CERE-130 has the potential to protect motor neurons and preserve neuromuscular function in ALS.

Recombinant human insulin-like growth factor I (rhIGF-I) for amyotrophic lateral sclerosis/motor neuron disease

BACKGROUND

Trophic factors, including recombinant human insulin-like growth factor I (rhIGF-I) are possible disease modifying therapies for amyotrophic lateral sclerosis.

OBJECTIVES

To examine the efficacy of recombinant human insulin-like growth factor I in amyotrophic lateral sclerosis.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group Trials Register (March 2006), MEDLINE (January 1966 to March 2006) and EMBASE (January 1980 to March 2006) and asked the authors of randomised clinical trials and manufacturers of recombinant human insulin-like growth factor I.

SELECTION CRITERIA

We considered all randomised controlled clinical trials involving rhIGF-I treatment of amyotrophic lateral sclerosis in adults with a clinical diagnosis of definite or probable amyotrophic lateral sclerosis according to the El Escorial Criteria. The primary outcome measure was change in Appel Amyotrophic Lateral Sclerosis Rating Scale (AALSRS) total score after nine months treatment and secondary outcome measures were change in AALSRS at 1, 2, 3, 4, 5, 6, 7, 8, 9 months, change in quality of life (Sickness Impact Profile scale), survival and adverse events.

DATA COLLECTION AND ANALYSIS

We identified three randomised clinical trials. Only two were included in the analysis. Each author graded the studies for methodological quality. Data were extracted and entered by the lead author and checked by the other two. Some missing data had to be regenerated by calculations based on ruler measurements of data presented in published graphs.

MAIN RESULTS

In a European trial with 59 participants on placebo and 124 on rhIGF-I, 0.1 mg/kg/day the mean difference (MD) in change in AALSRS total score after nine months was -3.30 (95% confidence interval (CI) -8.68 to 2.08), non-significantly less in the treated than the placebo group. In a North American trial, in which 90 participants on placebo were compared with 89 on recombinant human insulin-like growth factor I 0.05 mg/kg/day, and 87 participants on 0.1 mg/kg/day, the MD after nine months was -6.00 (95%CI -10.99 to -1.01), significantly less on treatment. The combined analysis from both randomised clinical trials showed a weighted mean difference after nine months of -4.75 (95% CI -8.41 to -1.09), a significant difference in favour of the treated group. The secondary outcome measures showed non-significant trends favouring rhIGF-I. Similarly the data with the 0.05 mg/kg/day dose showed trends favouring rhIGF-I at all time points but did not reach significance at the five per cent level at any point. There was an increased risk of injection site reactions with rhIGF-I (relative risk 2.53, 95% CI 1.40 to 4.59).

AUTHORS' CONCLUSIONS

The available randomised placebo controlled trials do not permit a definitive assessment of the clinical efficacy of rhIGF-I on ALS. More research is needed and one trial is in progress. Future trials should include survival as an outcome measure.

Potential utility of rhIGF-1 in neuromuscular and/or degenerative disease

Neuromuscular/neurodegenerative disorders, such as the death of spinal cord motor neurons in amyotrophic lateral sclerosis (ALS) or the degeneration of spinal cord motor neuron axons in certain peripheral neuropathies, present a unique opportunity for therapeutic intervention with neurotrophic proteins. We have found that in mixed rat embryonic spinal cord cultures or in purified motor neuron preparations, recombinant human insulin-like growth factor 1 (rhIGF-1) enhances the survival of motor neurons at EC50 concentrations of 2 nM, consistent with an interaction at the tyrosine kinase-coupled rhIGF-1 receptor. In a model of programmed cell death in ovo, administration of rhIGF-1 produces a marked survival of motor neurons. In a variety of models of predominantly motor neuron or nerve injury in rodents, administration of rhIGF-1 prevents the death of motor neurons in neonatal facial nerve lesions, attenuates the loss of cholinergic phenotype in adult hypoglossal nerve axotomy and hastens recovery from sciatic nerve crush in mice. In a genetic model of motor neuron compromise, the wobbler mouse, rhIGF-1 (1 mg/kg s.c. daily) delayed the deterioration of grip strength and provided for a more normal distribution of fibre types. In addition, rhIGF-1 (0.3-1.0 mg/kg s.c. daily) prevents the motor and/or sensory neuropathy in rodents caused by vincristine, cisplatinum or Taxol. These combined data indicate that rhIGF-1 has marked effects on the survival of compromised motor neurons and the maintenance of their axons and functional connections. They also suggest the potential utility of rhIGF-1 for the treatment of diseases such as ALS and certain neuropathies.

Intraparenchymal spinal cord delivery of adeno-associated virus IGF-1 is protective in the SOD1G93A model of ALS

The potent neuroprotective activities of neurotrophic factors, including insulin-like growth factor 1 (IGF-1), make them promising candidates for treatment of amyotrophic lateral sclerosis (ALS). In an effort to maximize rate of motor neuron transduction, achieve high levels of spinal IGF-1 and thus enhance therapeutic benefit, we injected an adeno-associated virus 2 (AAV2)-based vector encoding human IGF-1 (CERE-130) into lumbar spinal cord parenchyma of SOD1(G93A) mice. We observed robust and long-term intraspinal IGF-1 expression and partial rescue of lumbar spinal cord motor neurons, as well as sex-specific delayed disease onset, weight loss, decline in hindlimb grip strength and increased animal survival.

Laryngeal muscle surface receptors identified using random phage library

OBJECTIVES

The ultimate goal of this study is to improve the efficiency of gene transfer in mammalian muscle by developing targeted adenoviral vectors. Altering the tropism of viral vectors to recognize tissue specific antigens is one method to achieve this goal. This approach requires identification of cell-surface receptors and the insertion of target peptide sequences into the adenoviral fiber protein. In this study, phage biopanning was performed on cultured rat skeletal and laryngeal muscle to identify cell-surface receptors.

STUDY DESIGN

In vitro cell culture and in vivo animal model.

METHODS

M-13 Phage biopanning was used for muscle cell-surface receptor analysis on cultured rat skeletal and laryngeal muscle. Nonbinding and binding phage to cultured skeletal and laryngeal muscle were screened for muscle specific surface peptides. In vivo studies were then performed using muscle specific phage.

RESULTS

Skeletal muscle specific binding by the YASTNPM phage was observed by in vivo immunostaining. Phage titering demonstrated a 10(9)-fold increase in skeletal muscle binding compared with nontarget tissue. A peptide sequence (NPSQVKH) specific for laryngeal muscle yielded a 10(7)-fold increase in laryngeal muscle phage titer compared with nontarget tissue.

CONCLUSIONS

These results identify muscle cell-surface receptors that may be used as potential targets for genetic modification of adenovirus tropism. Moreover, phage specificity for skeletal and laryngeal muscle indicates specific muscle groups may be targeted.

Therapeutic benefit of intrathecal injection of insulin-like growth factor-1 in a mouse model of Amyotrophic Lateral Sclerosis

Insulin-like growth factor (IGF)-1 has been shown to have a protective effect on motor neurons both in vitro and in vivo, but has limited efficacy in patients with amyotrophic lateral sclerosis (ALS) when given subcutaneously. To examine the possible effectiveness of IGF-1 in a mouse model of familial ALS, transgenic mice expressing human Cu/Zn superoxide dismutase (SOD1) with a G93A mutation were treated by continuous IGF-1 delivery into the intrathecal space of the lumbar spinal cord. We found that the intrathecal administration of IGF-1 improved motor performance, delayed the onset of clinical disease, and extended survival in the G93A transgenic mice. Furthermore, it increased the expression of phosphorylated Akt and ERK in spinal motor neurons, and partially prevented motor neuron loss in these mice. Taken together, the results suggest that direct administration of IGF-1 into the intrathecal space may have a therapeutic benefit for ALS.

IGF-I prevents glutamate-induced motor neuron programmed cell death

Insulin-like growth factor I (IGF-I) is currently in clinical trials for treatment of amyotrophic lateral sclerosis (ALS), but little is known about how it promotes the survival of motor neurons. In the current study, we examined IGF-I-mediated neuroprotection in an in vitro model of ALS utilizing enriched cultures of embryonic rat spinal cord motor neurons. IGF-I binds to the IGF-I receptor (IGF-IR) in motor neurons and activates MAPK and the downstream effector of phosphatidylinositol 3-kinase (PI-3K) signaling, Akt. IGF-I:IGF-IR signaling involves phosphorylation of IRS-1 and Shc, but not IRS-2. Glutamate, which is elevated in the cerebrospinal fluid of ALS patients, induced DNA fragmentation and caspase-3 cleavage in the spinal cord motor neurons. These effects of glutamate were blocked by co-treatment with IGF-I. However, a delay of IGF-I treatment for as little as 30 min eliminated its neuroprotective effect. Finally, alone, neither the MAPK pathway inhibitor PD98059 nor the PI-3K inhibitor LY294002 blocked the neuroprotective effect of IGF-I, but both inhibitors together were effective in this regard. These results suggest that the dose and timing of IGF-I administration are critical for producing a neuroprotective effect, and also suggest that both the MAPK and PI-3K/Akt pathways can promote the survival of motor neurons. We discuss our results in terms of novel strategies for ALS therapy.

Cerebrospinal fluid insulin-like growth factor-1, insulin growth factor binding protein-2 or nitric oxide are not increased in MS or ALS

OBJECTIVES

Many studies have shown that nitric oxide (NO) and growth factors including insulin growth factors (IGFs) may be involved in the pathogenesis of multiple sclerosis (MS) and neurodegenerative diseases. Our previous studies suggested a relationship between cerebrospinal fluid (CSF) NO metabolites (nitrates and nitrites, NN(x)) and IGF-1 in patients with progressive encephalopathy, hypsarrhythmia and optic atrophy syndrome.

MATERIAL AND METHODS

We examined CSF concentrations of NN(x), IGF-1 and IGF binding protein-2 (IGFBP-2) in 25 controls, 14 patients with MS and 14 patients with amyotrophic lateralis sclerosis (ALS).

RESULTS

There were no significant differences in CSF levels of NN(x), IGF-1 or IGFBP-2 between the groups. CSF IGFBP-2 concentrations correlated significantly with age in controls, which may reflect age-related changes in the blood-brain barrier function.

CONCLUSION

Upregulation of the production of NO and IGF-1 in the brain or spinal cord does not influence CSF levels of these molecules in MS or ALS.

Timing of Human Insulin-Like Growth Factor-1 Gene Transfer in Reinnervating Laryngeal Muscle

OBJECTIVES/HYPOTHESIS

The authors have designed a rat laryngeal paralysis model to study gene transfer strategies using a muscle-specific expression system to enhance local delivery of human insulin-like growth factor-1 (hIGF-1). In preliminary studies, a nonviral vector containing the alpha-actin promoter and human hIGF-1 sequence produced both neurotrophic and myotrophic effects 1 month after single injection of plasmid formulation into paralyzed rat thyroarytenoid muscle in vivo. Based on these findings, it is hypothesized that the effects of hIGF-1 will enhance the results of laryngeal muscle innervation procedures. The timing of gene delivery relative to nerve repair is likely to be important, to optimize the results.

STUDY DESIGN

Prospective analysis.

METHODS

The effects of nonviral gene transfer for the delivery of hIGF-1 were evaluated in rats treated immediately following recurrent laryngeal nerve transection and repair and in rats receiving a delayed treatment schedule, 30 days after nerve transection and repair. Gene transfer efficiency was determined using polymerase chain reaction and reverse transcriptase-polymerase chain reaction techniques. Muscle fiber diameter, motor endplate length, and percentage of motor endplates with nerve contact were examined to assess hIGF-1 trophic effects.

RESULTS

Compared with reinnervated untreated control samples, both early and delayed hIGF-1 transfer resulted in significant increase in muscle fiber diameter. Motor endplate length was significantly decreased and nerve/motor endplate contact was significantly increased following delayed gene transfer, but not after early treatment.

CONCLUSION

We infer from results of the study that delayed hIGF-1 gene transfer delivered by a single intramuscular injection will enhance the process of muscle reinnervation. The clinical relevance of these findings supports the future application of gene therapy using nonviral vectors for management of laryngeal paralysis and other peripheral nerve injuries.

Effects of insulin-like growth factor-1 gene transfer on myosin heavy chains in denervated rat laryngeal muscle

OBJECTIVES/HYPOTHESIS

To determine whether the myotrophic activity of human insulin-like growth factor (hIGF)-1 promotes restoration of normal myosin heavy chain (MHC) composition after nerve injury, MHC composition was analyzed after hIGF-1 gene transfer in denervated rat laryngeal muscle.

STUDY DESIGN

Animal model to study effects of gene transfer on laryngeal paralysis.

METHODS

In anesthetized rats, the left recurrent and superior laryngeal nerves are cut and suture ligated. A midline thyrotomy is performed, and the thyroarytenoid muscle is injected with a polyvinyl-based formulation containing a muscle specific expression system and hIGF-1 DNA (treatment group) or saline (control group). After 30 days, animals were killed, and the thyroarytenoid muscle was removed and processed for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Densitometric measurements were obtained to determine composition of MHCs.

RESULTS

As previously described, MHC composition in denervated laryngeal muscle was characterized by a decrease in type IIB and IIL and up-regulation of IIA/IIX. Compared with controls, hIGF-1 treated animals demonstrated a significant increase in expression of type IIB and IIL and a significant decrease in expression of type IIA/X.

CONCLUSIONS

These findings suggest that the myotrophic effect of hIGF-1 gene transfer results in normalization of MHC composition in denervated muscle, with suppression of type IIA/X MHC and promotion of type IIL expression.

Insulin-like growth factor-I improves cerebellar dysfunction but does not prevent cerebellar neurodegeneration in the calcium channel mutant mouse, leaner

The effects of insulin-like growth factor-I (IGF-I) on cerebellar dysfunction and neurodegeneration were investigated in leaner mice, which exhibit cerebellar ataxia and neurodegeneration related to P/Q-type calcium channel mutations. Leaner mice showed significantly reduced serum and cerebellar IGF-I concentrations compared to wild-type mice at postnatal day 30. Behavioral assessment of leaner mice injected with IGF-I subcutaneously for 4 weeks showed partially improved cerebellar function. Histological analysis of IGF-I treated leaner cerebella showed no difference in the number of dying Purkinje cells compared to control leaner cerebella. These results further support potential use of IGF-I as a therapeutic aid for cerebellar ataxia related to calcium channel mutations. Nonetheless, IGF-I administration does not rescue dying cerebellar neurons, which suggests that the beneficial effects of IGF-I may have been achieved through surviving cerebellar neurons.

Ciliary neurotrophic factor (CNTF) for amyotrophic lateral sclerosis/motor neuron disease

BACKGROUND

Amyotrophic lateral sclerosis, also known as motor neuron disease, is a fatal neuromuscular disease characterized by progressive muscle weakness resulting in paralysis, which might be treated with ciliary neurotrophic factor.

OBJECTIVES

The objective of this review was to examine the efficacy of ciliary neutrophic factor in amyotrophic lateral sclerosis.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group trials register (searched June 2003) for randomized trials, MEDLINE (from January 1966 to October 2003) and EMBASE (from January 1980 to October 2003), checked the reference lists of papers identified and contacted the authors of studies identified to get additional unpublished results.

SELECTION CRITERIA

We considered the following selection criteria: Types of studies: randomized controlled clinical trials;

TYPES OF PARTICIPANTS

adults with a diagnosis of either probable or definite amyotrophic lateral sclerosis according to the El Escorial criteria; Types of interventions: treatment with ciliary neurotrophic factor for at least six months, in a placebo-controlled randomized format; Types of outcome measures Primary: survival; Secondary: muscle strength, respiratory function, changes in bulbar functions, changes in quality of life, proportion of patients with adverse side effects (such as cough, asthenia, nausea, anorexia, weight loss and increased salivation).

DATA COLLECTION AND ANALYSIS

We identified two randomized trials. The data were extracted and examined independently by the reviewers. Some missing data were obtained from investigators.

MAIN RESULTS

Two trials, with a total population of 1,300 amyotrophic lateral sclerosis patients treated with subcutaneous injections of recombinant human ciliary neurotrophic factor, were examined in this review. The methodological quality of these trials was considered adequate. No significant difference was observed between ciliary neurotrophic factor and placebo groups for survival, the primary outcome measure. The relative risk was 1.07 (95% CI 0.81 to 1.41). No significant differences between the groups were observed for most of the secondary outcomes. However, a significant increase of the incidence of several adverse events was noted in groups treated with higher doses of CNTF.

REVIEWERS' CONCLUSIONS

Ciliary neurotrophic factor treatment has no effect on amyotrophic lateral sclerosis progression. At high concentration, several side effects were observed. A combination of ciliary neurotrophic factor with other neurotrophic factors (as suggested by results on animal models), and more efficient delivery methods should be tested.

Brainstem motor nuclei respond differentially to degenerative disease in the mutant mouse wobbler

Degenerative motoneurone diseases, whether in humans, animals, or transgenic mouse models, do not affect all types of motoneurone to the same degree. Understanding the relative differences in vulnerability of certain motor pools may be the key to developing therapies. Expression of calbindin (CB) and parvalbumin (PV) immunoreactivity, which are potentially neuroprotective calcium-binding proteins, and NADPH-diaphorase (NADPH-d) histochemical reactivity, a marker for neurodegeneration, was studied in brainstem sections from mutant wobbler mice and their normal littermates during the motoneurone degeneration phase (3-8 weeks of age). The motor trigeminal and facial nuclei reacted in a manner previously observed in spinal somatic motoneurones in the wobbler. Many motoneurones expressed moderate NADPH-d reactivity, correlated with the appearance of vacuolated motoneurones in Nissl-stained sections. This was not observed in littermate controls. Motoneurone counts from Nissl-stained sections from 14-month-old wobblers and littermates revealed significantly fewer (approximately 27%) motoneurones in the trigeminal nucleus of wobblers. In contrast, the wobbler hypoglossal nucleus contained neither vacuolated nor NADPH-d reactive motoneurones. However, expression of CB immunoreactivity by the majority of wobbler hypoglossal motoneurones was observed but not in littermate controls or in any other motor nucleus. Counts in older animals showed a smaller but still significant difference in motoneurone number between wobblers and controls (approximately 9% reduction). Finally, the wobbler abducens nucleus displayed neither vacuolated neurones, nor NADPH-d reactivity nor CB immunoreactivity. Motor nuclei innervating extraocular muscles appear to be protected in many forms of motoneurone disease in man and other species. However, there were still markedly fewer abducens motoneurones in the old wobblers compared to controls (approximately 29% reduction). Sparing of oculomotor neurones in other diseases has been attributed to their relatively high PV expression, which we also observed in the abducens nucleus of both wobblers and littermates, and to a lesser extent in the other motor nuclei too. In conclusion, our results suggest that, in the wobbler mouse, motoneurone degeneration may occur without overt signs such as cell body vacuolation and NADPH-d expression. Induced CB expression may be neuroprotective but that constitutive expression of PV may not.

Co-administration of IGF-I and glycosaminoglycans greatly delays motor neurone disease and affects IGF-I expression in the wobbler mouse: a long-term study

The study on wobbler mouse has shown that the combined treatment with low doses of glycosaminoglycans (GAGs) and insulin-like growth factor-I (IGF-I) fully prevented motor neurone death and forelimb impairment up to 9-12 weeks of a mouse's life. The effect was accompanied by the prevention of the early hypertrophy of wobbler neurones, an effect likely due to the promotion of neuronal survival. At the 18th week, wobbler mice treated with IGF-I + GAGs still showed significantly improved forelimb function, reduced muscle atrophy and a higher number of cervical motor neurones. IGF-I alone and GAGs alone were active up to the 3rd week of treatment; thereafter the beneficial effects of single treatments decreased drastically. GAGs and IGF-I treatments also affected IGF-I plasma and muscle levels. In wobbler mice there was a progressive reduction in IGF-I plasma levels that was prevented by IGF-I or GAGs alone and greatly increased, even above heterozygote levels, by the combination treatment. Such a powerful increase was correlated by a small enhancement in insulin-like growth factor binding protein-3 (IGFBP-3) plasma levels, while treatment with IGF-I alone affected very significantly both IGFBP-1 and IGFBP-3. Co-treatment also prevented the decrease in IGF-I content observed in vehicle-treated wobbler mice forelimb muscles.

Motoneuron morphological alterations before and after the onset of the disease in the wobbler mouse

The wobbler mutant mouse displays a recessively inherited neurological disease with degeneration of motoneurons and is considered to be an animal model for human motoneuron diseases. Mutant mice can be clinically recognised at about 3-4 weeks of age but a polymorphic marker close to the wobbler gene offers the opportunity of a preclinical diagnosis. Using this polymorphic marker we performed morphometric (cell size) analysis of spinal cord motoneurons from 10 to 40 days post natal (PN). We observed at day 16 PN a transient appearance of swollen motoneurons, probably those that present vacuolar degeneration a little later and possibly die. One week later, from 21 days onwards, we found that the subpopulation of large motoneurons was depleted in the mutant mice. The absence of large motoneurons may have important physiological consequences and the loss or absence of differentiation of this particular subpopulation of motoneurons may be a key event in the course of the disease.

Three mouse models of muscular dystrophy: the natural history of strength and fatigue in dystrophin-, dystrophin/utrophin-, and laminin alpha2-deficient mice

To optimize and evaluate treatments for muscular dystrophy, it is important to know the natural history of the disease in the absence of therapeutic intervention. Here we characterized disease progression of three mutant mouse strains of muscular dystrophy: mdx mice, which lack dystrophin; mdx:utrn-/- mice, which also lack utrophin; and dy/dy mice, which are deficient in laminin alpha2. Normal mice show a marked increase in forelimb strength over the first 10 weeks of life and little fatigue (<5%) over five consecutive strength trials. Mdx and mdx:utrn-/- mice demonstrate less strength then normal mice and approximately 40% fatigue at each age. Mdx mice become obese but mdx:utrn-/- mice do not. Dy/dy mice remain small and are much weaker than mdx and mdx:utrn-/- mice at all ages even when normalized to weight; however, they show only minimal fatigue (10%). This work demonstrates a distinct pattern of disease progression in each model and provides a foundation for assessing strategies for improving strength in each model.

Delayed application of IGF-I and GDNF can rescue already injured postnatal motor neurons

IGF-I, GDNF, and other neurotrophic factors, when applied at the time of injury, can protect postnatal motor neurons from slow glutamate injury in organotypic spinal cord. However, in human spinal cord diseases, motor neuron injury is already established when treatment could begin. We tested whether neurotrophic factors can protect already-injured motor neurons, and whether combinations of factors can further lengthen the therapeutic time window. Our data show that during a 7--8 week process of slow neurodegeneration either IGF-I or GDNF treatment, though delayed up to 4 weeks, still allowed substantial rescue of already injured motor neurons. However, the combination of both factors additively provided better neuroprotection than either factor alone, even after a 4-week delay. This proof of principle is relevant to the potential of IGF-I and GDNF as therapy for acquired disorders affecting motor neurons.

Cellular basis of steroid neuroprotection in the wobbler mouse, a genetic model of motoneuron disease

1. The Wobbler mouse suffers an autosomal recessive mutation producing severe motoneuron degeneration and astrogliosis in the spinal cord. It has been considered a suitable model of human motoneuron disease, including the sporadic form of amyotrophic lateral sclerosis (ALS). 2. Evidences exist demonstrating increased oxidative stress in the spinal cord of Wobbler mice, whereas antioxidant therapy delayed neurodegeneration and improved muscle trophism. 21-Aminosteroids are glucocorticoid-derived hydrophobic compounds with antioxidant potency 3 times higher than vitamin E and 100 times higher than methylprednisolone. They do not bind to intracellular receptors, and prevent lipid peroxidation by insertion into membrane lipid bilayers. 3. In common with the spinal cord of ALS patients, Wobbler mice present astrocytosis with hyperexpression of glial fibrillary acidic protein (GFAP), and increased expression of nitric oxide synthase (NOS) and growth-associated protein (GAP-43) in motoneurons. Here, we review our studies on the effects of a 21-aminosteroid on GFAP, NOS, and GAP-43. 4. First, we showed that 21-aminosteroid treatment further increased GFAP-expressing astrocytes in gray matter of the Wobbler spinal cord. This effect may provide neuroprotection if one considers a trophic and beneficial function of astrocytes during the course of degeneration. Other neuroprotectans used in Wobbler mice (T-588) also increased pre-existing astrocytosis. 5. Second, histochemical determination of NADPH-diaphorase, a parameter indicative of neuronal NOS activity, showed that the 21-aminosteroid down-regulated the high activity of this enzyme in ventral horn motoneurons. Therefore, suppression of nitric oxide by decreasing NADPH-diaphorase (NOS) activity may provide neuroprotection considering that excess NO is highly toxic to motoneurons. 6. Finally, 21-aminosteroid treatment significantly attenuated the aberrant expression of both GAP-43 protein and mRNA in Wobbler motoneurons. Hyperexpression of GAP-43 possibly indicated abnormal synaptogenesis, denervation, and muscle atrophy, parameters which may return to normal following antioxidant steroid treatment. 7. Besides 21-aminosteroids, other steroids also behave as neuroprotectans. In this regard, degenerative diseases may constitute potential targets of these hormones, based on the fact that the spinal cord expresses in a regional and cell-specific fashion, receptors for androgens. progesterone, adrenal steroids, and estrogens.

IGF-I treatment improves the functional properties of fast- and slow-twitch skeletal muscles from dystrophic mice

Although insulin-like growth factor-I (IGF-I) has been proposed for use by patients suffering from muscle wasting conditions, few studies have investigated the functional properties of dystrophic skeletal muscle following IGF-I treatment. 129P1 ReJ-Lama2(dy) (129 ReJ dy/dy) dystrophic mice suffer from a deficiency in the structural protein, laminin, and exhibit severe muscle wasting and weakness. We tested the hypothesis that 4 weeks of IGF-I treatment ( approximately 2 mg/kg body mass, 50 g/h via mini-osmotic pump, subcutaneously) would increase the mass and force producing capacity of skeletal muscles from dystrophic mice. IGF-I treatment increased the mass of the extensor digitorum longus (EDL) and soleus muscles of dystrophic mice by 20 and 29%, respectively, compared with untreated dystrophic mice (administered saline-vehicle only). Absolute maximum force (P(o)) of the EDL and soleus muscle was increased by 40 and 32%, respectively, following IGF-I treatment. Specific P(o) (sP(o)) was increased by 23% in the EDL muscles of treated compared with untreated mice, but in the soleus muscle sP(o) was unchanged. IGF-I treatment increased the proportion of type IIB and type IIA fibres and decreased the proportion of type I fibres in the EDL muscles of dystrophic mice. In the soleus muscles of dystrophic mice, IGF-I treatment increased the proportion of type IIA fibres and decreased the proportion of type I fibres. Average fibre cross-sectional area was increased in the EDL and soleus muscles of treated compared with untreated mice. We conclude that IGF-I treatment ameliorates muscle wasting and improves the functional properties of skeletal muscles of dystrophic mice. The findings have important implications for the role of IGF-I in ameliorating muscle wasting associated with the muscular dystrophies.

Systemic administration of antisense p75(NTR) oligodeoxynucleotides rescues axotomised spinal motor neurons

The 75 kD low-affinity neurotrophin receptor (p75(NTR)) is expressed in developing and axotomised spinal motor neurons. There is now convincing evidence that p75(NTR) can, under some circumstances, become cytotoxic and promote neuronal cell death. We report here that a single application of antisense p75(NTR) oligodeoxynucleotides to the proximal nerve stumps of neonatal rats significantly reduces the loss of axotomised motor neurons compared to controls treated with nonsense oligodeoxynucleotides or phosphate-buffered saline. Our investigations also show that daily systemic intraperitoneal injections of antisense p75(NTR) oligodeoxynucleotides for 14 days significantly reduce the loss of axotomised motor neurons compared to controls. Furthermore, we found that systemic delivery over a similar period continues to be effective following axotomy when intraperitoneal injections were 1) administered after a delay of 24 hr, 2) limited to the first 7 days, or 3) administered every third day. In addition, p75(NTR) protein levels were reduced in spinal motor neurons following treatment with antisense p75(NTR) oligodeoxynucleotides. There were also no obvious side effects associated with antisense p75(NTR) oligodeoxynucleotide treatments as determined by behavioural observations and postnatal weight gain. Our findings indicate that antisense-based strategies could be a novel approach for the prevention of motor neuron degeneration associated with injuries or disease.

Increased expression of insulin-like growth factor I in skin in amyotrophic lateral sclerosis

OBJECTIVES

Insulin-like growth factor I (IGF-I) has potent effects on motor neuron survival and is being studied as a possible therapeutic agent for ALS. However, little is known concerning IGF-I in the skin of patients with amyotrophic lateral sclerosis (ALS). The aim was to evaluate IGF-I immunoreactivity of skin in patients with ALS.

METHODS

IGF-I immunoreactivity of skin from 18 patients with ALS and 16 controls was examined.

RESULTS

IGF-I immunoreactivity was markedly positive in the epidermis and dermal blood vessels and glands and was moderately positive in the reticular dermis in all patients with ALS. On the other hand, the epidermis and dermal blood vessels and glands and the reticular dermis showed a weak IGF-I immunoreactivity in controls. The optical density for IGF-I immunoreactivity of the epidermis and dermal blood vessels and glands, and the reticular dermis in patients with ALS was significantly higher than in diseased controls, and was significantly increased with duration of illness.

CONCLUSIONS

These data suggest that a metabolic alteration of IGF-I may take place in the skin of patients with ALS.

Glycosaminoglycans co-administration enhance insulin-like growth factor-I neuroprotective and neuroregenerative activity in traumatic and genetic models of motor neuron disease: a review

In this report it is shown how glycosaminoglycans and insulin-like growth factor-I (IGF-I) promote muscle reinnervation and prevent motor neuron death in experimental models of motor neuron disease. Such effect appears to be mediated by insulin-like growth factor-1. The glycosaminoglycan moiety of proteoglycans is a constituent of the basal lamina active on nerve regeneration by means of the interaction with laminin and with several growth factors. We have previously shown that supplementation by means of subcutaneous injections of glycosaminoglycans affects neuronal degeneration and regeneration. In this study we report that following neonatal lesion of the rat sciatic nerve, glycosaminoglycan treatment promoted extensor digitorum longus muscle reinnervation with consequent improvement of muscle morphology. In saline-treated rats, reinnervation was only partial and there was a marked muscle fibre atrophy, whereas, glycosaminoglycan treatment of lesioned rats increased IGF-I mRNA and protein in the reinnervated muscle, and IGF-I and insulin-like growth factor binding protein-3 plasma levels. Similarly, treatment of lesioned rats with IGF-I promoted muscle reinnervation, and prevented muscle fibre atrophy, higher levels of IGF-I in the reinnervated muscle, of IGF-I, and insulin-like growth factor binding proteins in plasma. In the wobbler mouse IGF-I and glycosaminoglycans alone promote only a partial motor neuron survival and the preservation of forelimb function decays after 3 weeks of treatment. However when glycosaminoglycans and insulin-like growth factor are administered together the motor neuron disease in the wobbler mouse is halted and there is no more loss of motor neurons.

Prevention by insulin-like growth factor-I and riluzole in motor neuron death after neonatal axotomy

Transection of the sciatic nerve in neonatal rats results discernable loss of motor neurons in the spinal cord. This neuronal death could be due to lack of retrogradely transported target derived neurotrophic factors, since some of these factors have been shown to be effective in injury induced motor neuron death. Another hypothesis suggests that glutamate and its receptors has been implicated as possible mechanism for motor neuron death, because inhibitor of glutamate release and antagonists of glutamate receptors are effective in preventing axotomized motor neuron death. To investigate the effect of insulin-like growth factor-I (IGF-I) and riluzole, a drug that inhibits glutamate release, on axotomy induced motor neuron death. Newborn rats were anesthetized with hypothermia. Sciatic nerve was cut near the obturator tendon in the left thigh. Animals were then treated daily with different doses of IGF-I and riluzole for 14 days with intraperitoneal injections. Control rats received PBS in the same fashion. After the treatment, the number of surviving motor neurons and the motor neuron diameter in the L(4) was assessed. Both IGF-I (1.0 mg/kg) and riluzole (5.0 mg/kg) rescued motor neuron death in a similar way. Co-administration of IGF-I (1.0 mg/kg) and riluzole (5.0 mg/kg) was more effective than either agent alone and there was a statistically significant difference between co-administration and IGF-I alone. However there was no significant difference between simultaneous treatment and riluzole alone. As for diameter of motor neurons, riluzole (5.0 mg/kg) preserved the motor neuron diameter in the lesion side. Nonetheless, no further increase in motor neuron diameter was seen when riluzole (5 mg/kg) and IGF-I (1.0 mg/kg) were applied in combination. Both agents did not affect diameter of motor neurons in the non-axotomy side. Riluzole is available in amyotrophic lateral sclerosis (ALS) and the positive results of clinical trials with IGF-I suggests that combination treatment of IGF-I and riluzole in ALS remains to be determined.

Long-term neuroprotective effects of glycosaminoglycans-IGF-I cotreatment in the motor neuron degeneration (mnd) mutant mouse

This study shows that cotreatment with insulin-like growth factor-I (IGF-I) and glycosaminoglycans (GAGs) prevents the onset of neuromuscular deficit in the m/m mutant mouse. These mice show a mid-to-late-life onset of progressive paralysis of the hind limb, that is correlated with altered innervation and reduced nerve-evoked isometric twitch tension in the extensor digitorum longus (EDL) muscle. Almost 50% of EDL nerve endings are negative for antisynaptophysin staining, while retrograde labelling with beta-cholera-toxin coupled to type IV horseradish and quantitative histological analysis show a small loss of EDL and lumbar cord motor neurons. At 10 months of age also forelimb function evaluated as grip strength is significantly reduced. Animals treated either with glycosaminoglycans alone or with IGF-I alone at low and high doses showed only a partial improvement of their condition. However, cotreatment of m/m mice with IGF-I and GAGs fully prevented the neuromuscular abnormalities, the twitch tension loss, the motor neuron decrease and the reduction of forelimb grip strength.

Glycosaminoglycans boost insulin-like growth factor-I-promoted neuroprotection: blockade of motor neuron death in the wobbler mouse

Wobbler mice display forelimb weakness, altered paw positioning, reduced running speed, muscle atrophy and motor neuron loss; co-treatment with glycosaminoglycans and insulin-like growth factor-I counteracts the progression of the disease. Reportedly, treatment with glycosaminoglycans or insulin-like growth factor-I slows the early stages of progressive forelimb dysfunction in wobbler mice. Our aim was to study whether the combination of these two drugs would result in greater neuroprotective effects. In a group of wobbler mice, combined treatment with daily s.c. administration of 20 microg/kg insulin-like growth factor-I and 1 mg/kg glycosaminoglycans was begun upon diagnosis at three weeks of age and continued for the next six weeks. This treatment halted motor neuron loss and markedly reduced the decay of forelimb muscle morphometry and function. Moreover, the mouse phenotype itself was strikingly improved. The effect of the combination treatment was significantly higher than that of the single drugs, even at a dosage as high as 1 mg/kg insulin-like growth factor-I. The ability of the insulin-like growth factor-I/glycosaminoglycans pharmacological cocktail to arrest the progression of motor neuron disease in wobbler mice and the safety of the low dose of insulin-like growth factor-I used hold promise that this combination might represent a novel approach for the treatment of motor neuron disease and peripheral neuropathies.

Neurotrophic factors and neuro-muscular disease: II. GDNF, other neurotrophic factors, and future directions

This is the second of two reviews in which we discuss the essential aspects of neurotrophic factor neurobiology, the characteristics of each neurotrophic factor, and their clinical relevance to neuromuscular diseases. The previous paper reviewed the neurotrophin family and neuropoietic cytokines. In the present article, we focus on the GDNF family and other neurotrophic factors and then consider future approaches that may be utilized in neurotrophic factor treatment.

Insulin-like growth factor-1 (IGF-1) and growth hormone (GH) in immunity and inflammation

In recent years many efforts have been undertaken to elucidate the complex interactions between mediators of the endocrine system and the immune system. The main effector of growth hormone (GH) is insulin-like growth factor-1 (IGF-1), an endocrine mediator of growth and development under physiological conditions. Besides this important function, IGF-1 also plays a prominent role in the regulation of immunity and inflammation. This article will address the involvement of IGF-1 in innate as well as acquired immunity and host-defense. We also discuss the role of IGF-1 in the course of inflammatory disorders, including sepsis and sepsis-induced catabolism as well as degenerative arthritis. Based on recent insights, we finally examine the pathophysiological background, potential pitfalls and perspectives of IGF-1 suppletion therapy in these conditions.

Preventive effects of insulinlike growth factor-I on steroid-induced muscle atrophy

We examined the effects of simultaneous administration of recombinant insulinlike growth factor-I (IGF-I) and glucocorticoid on the diameter of muscle fibers in rats. The steroid group received subcutaneous injection of triamcinolone, the IGF-treated group received IGF-I alone, and the steroid plus IGF group received both triamcinolone and IGF-I. After 14 days, each rat was subjected to muscle biopsy of the extensor digitorum longus and soleus. Glucocorticoid treatment caused significant reduction in diameter of muscle fibers, compared to controls. Simultaneous administration of IGF-I significantly attenuated glucocorticoid-induced muscle atrophy. Glucocorticoid increased both urinary concentration of 3-methylhistidine and urinary creatine/creatinine ratio. IGF-I reduced those changes in the urine. We conclude that IGF-I administration prevents, at least partially, the development of steroid myopathy.

Onset and progression of motor deficits in motor neuron degeneration (mnd) mice are unaltered by the glycine/NMDA receptor antagonist L-701,324 or the MAO-B inhibitor R(-)-deprenyl

NMDA-mediated neurotoxicity and oxidative stress have been implicated in the etiology of a number of degenerative diseases including motor neuron disease. The present study examined the effect of chronic administration of the glycine/NMDA receptor antagonist L-701,324 and the monoamine oxidase B inhibitor (r)-deprenyl on the onset and rate of progression of neurological impairment in the motor neuron degeneration (mnd) mouse, a murine model of neurodegeneration. Neurological assessment of mnd mice revealed an onset of motor deficits at 6 months of age as observed by the loss of hindlimb reflex extension. By 7 months, balance was also markedly impaired as measured by deficits in rotarod performance and ability to remain on balancing beams. At 8 months of age mnd mice exhibited gross abnormalities in walking pattern; animals were unable to flex their hindlimbs and tended to walk in small labored movements. Daily administration of L-701,324 (10 mg/kg p.o.) or r(-)-deprenyl (1 mg/kg p.o.) to mnd mice from 4 to 8 months of age failed to delay the onset of symptoms or slow the rate of deterioration of motor performance. These findings suggest that excessive activation of NMDA receptors may not be involved in the pathological process leading to motor neuron dysfunction in mnd mice and do not suggest a protective effect of deprenyl on motor neurons in these mice.

p70 S6 kinase activation is not required for insulin-like growth factor-induced differentiation of rat, mouse, or human skeletal muscle cells

Insulin-like growth factors (IGFs) are potent stimulators of muscle differentiation, and phosphatidylinositol 3-kinase (PI 3-kinase) is an essential second messenger in this process. Little is known about the downstream effectors of the IGF/PI 3-kinase myogenic cascade, and contradictory observations have been reported concerning the involvement of p70 S6 kinase. In an attempt to clarify the role of p70 S6 kinase in myogenesis, here we have studied the effect of rapamycin on rat, mouse, and human skeletal muscle cell differentiation. Both insulin and IGF-II activated p70 S6 kinase in rat L6E9 and mouse Sol8 myoblasts, which was markedly inhibited at 1 ng/ml rapamycin concentrations. Consistent with previous observations in a variety of cell lines, rapamycin exerted a potent inhibitory effect on L6E9 and Sol8 serum-induced myoblast proliferation. In contrast, even at high concentrations (20 ng/ml), rapamycin had no effect on IGF-II-induced proliferation or differentiation. Indeed, neither the morphological differentiation, as assessed by myotube formation, nor the expression of muscle-specific markers such as myogenin, myosin heavy chain, or GLUT4 (glucose transporter-4) glucose carriers was altered by rapamycin. Moreover, here we extended our studies on IGF-II-induced myogenesis to human myoblasts derived from skeletal muscle biopsies. We show that, as observed for rat and mouse muscle cells, human myoblasts can be induced to form multinucleated myotubes in the presence of exogenous IGF-II. Moreover, IGF-II-induced human myotube formation was totally blocked by LY294002, a specific PI 3-kinase inhibitor, but remained unaffected in the presence of rapamycin.

Reinnervation of motor endplates and increased muscle fiber size after human insulin-like growth factor I gene transfer into the paralyzed larynx

Current surgical strategies for the treatment of laryngeal paralysis are limited by the muscle atrophy associated with denervation. Moreover, attempts at reinnervation have not effected significant change in surgical outcome. To address this clinical problem, we have developed a rat laryngeal paralysis model to study novel gene transfer strategies. Using this model, the human insulin-like growth factor I (hIGF-I) gene was introduced into paralyzed rat laryngeal muscle to assess the benefit of sustained local hIGF-I production. A muscle-specific nonviral vector containing the alpha-actin promoter and hIGF-I gene was used in formulation with a polyvinyl-based delivery system and injected into paralyzed adult rat laryngeal muscle. Twenty-eight days after a single injection, gene transfer efficiency, muscle fiber size, motor endplate length, and nerve-to-motor endplate contact were evaluated. Gene transfer was detected in 100% of injected animals by PCR. Gene transfer with expression, as measured by RT-PCR for hIGF-I mRNA, occurred in 81.3 % of injected animals. When compared with controls, hIGF-I-transfected animals presented a significant increase in muscle fiber diameter [17.56 (+/-0.97 SD) microm versus 14.70 (+/-1.43 SD) microm; p = 0.0002], a significant decrease in motor endplate length [20.88 (+/-1.42 SD) microm versus 25.41 (+/-3.19 SD) microm; p = 0.0025], and a significant increase in percentage of endplates with nerve contact (20.3% (+/-13.9 SD) versus 4.4% (+/-4.2 SD); p = 0.0079). In the context of laryngeal paralysis, gene therapy represents a tremendous opportunity to augment current surgical treatment modalities by preventing or reversing muscle atrophy, and by enhancing nerve sprouting and reinnervation.