Rodent Models Of Amyotrophic Lateral Sclerosis Research Articles

Behavioral Paradigms in Rodent Models of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) remains an untreatable neurodegenerative disease without a cure or effective treatment, mainly due to elusive underlying mechanisms. ALS is primarily characterized by motor neuron dysfunction in the brain and spinal cord. However, it also exhibits non-motor symptoms such as executive, behavioral, and language dysfunction, making it challenging to establish informative disease models for relevant preclinic and clinical research. The discovery of ALS- causing genes, such as C9orf72 and SOD1, has paved the way for developing various animal models. Among these models, rodents have emerged as particularly valuable, demonstrating unique ALS-related behavioral defects in multiple behavioral tests. These models enable further understanding of disease mechanisms and provide sensitive and precise functional assessments of ALS-related defects for drug development. This report endeavors to present a chronological overview of various behavioral assessments, encompassing motion ability tests, cognitive evaluations, sensory analyses, and other paradigms described in rodent models of ALS. Our goal is to summarize and compare the behavioral alterations observed in diverse rodent models of ALS with distinct gene mutations, thus providing comprehensive references and guidance for advancing pathogenic and therapeutic research in ALS.

Human iPSC-derived neural progenitor cells secreting GDNF provide protection in rodent models of ALS and retinal degeneration.

Human induced pluripotent stem cells (iPSCs) are a renewable cell source that can be differentiated into neural progenitor cells (iNPCs) and transduced with glial cell line-derived neurotrophic factor (iNPC-GDNFs). The goal of the current study is to characterize iNPC-GDNFs and test their therapeutic potential and safety. Single-nuclei RNA-seq show iNPC-GDNFs express NPC markers. iNPC-GDNFs delivered into the subretinal space of the Royal College of Surgeons rodent model of retinal degeneration preserve photoreceptors and visual function. Additionally, iNPC-GDNF transplants in the spinal cord of SOD1G93A amyotrophic lateral sclerosis (ALS) rats preserve motor neurons. Finally, iNPC-GDNF transplants in the spinal cord of athymic nude rats survive and produce GDNF for 9months, with no signs of tumor formation or continual cell proliferation. iNPC-GDNFs survive long-term, are safe, and provide neuroprotection in models of both retinal degeneration and ALS, indicating their potential as a combined cell and gene therapy for various neurodegenerative diseases.

Assessing the therapeutic impact of resveratrol in ALS SOD1-G93A mice with electrical impedance myography.

To aid in the identification of new treatments for amyotrophic lateral sclerosis (ALS), convenient biomarkers are needed to effectively and uniformly measure drug efficacy. To this end, we assessed the effects of the nutraceutical resveratrol (RSV) on disease onset and overall survival in SOD1-G93A (ALS) mice and compared several standard biomarkers including body mass, motor score (MS), paw grip endurance (PGE), and compound motor action potential (CMAP) amplitude, with the technique of electrical impedance myography (EIM) to follow disease progression. Eighteen ALS mice (nine females, nine males) received RSV in the chow (dose: 120 mg/kg/day) starting at 8 weeks of age; 19 ALS mice (nine females, 10 males) received normal chow; 10 wild type (WT) littermates (five females, five males) fed standard chow served as controls. Biomarker assessments were performed weekly beginning at 8 weeks. No differences in either disease onset or overall survival were found between RSV-treated and untreated ALS mice of either sex; moreover, all biomarkers failed to identify any beneficial effect of RSV when administered at this dose. Therefore, for the comparative evaluation of the ability of the various biomarkers to detect the earliest symptoms of disease, data from all animals (i.e., RSV-treated and untreated ALS mice of both sexes) were combined. Of the biomarkers tested, EIM impedance values, i.e., surface EIM longitudinal phase at 50 kHz (LP 50 kHz), and CMAP amplitude showed the earliest significant changes from baseline. LP 50 kHz values showed a rate of decline equivalent to that of CMAP amplitude and correlated with both PGE and CMAP amplitude [Spearman rho = 0.806 (p = 0.004) and 0.627 (p = 0.044), respectively]. Consistent with previous work, these findings indicate that surface EIM can serve as an effective non-invasive biomarker for preclinical drug testing in rodent models of ALS.

A novel assessment of fine-motor function reveals early hindlimb and detectable forelimb deficits in an experimental model of ALS

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder associated with the loss of cortical and spinal motor neurons (MNs) and muscle degeneration (Kiernan et al. in Lancet 377:942–955, 2011). In the preclinical setting, functional tests that can detect early changes in motor function in rodent models of ALS are critical to understanding the etiology of the disease and treatment development. Here, we established a string-pulling paradigm that can detect forelimb and hindlimb motor deficits in the SOD1 mouse model of ALS earlier than traditional motor performance tasks. Additionally, our findings indicate that early loss of forelimb and hindlimb function is correlated with cortical and spinal MN loss, respectively. This task is not only ecological, low-cost, efficient, and non-onerous, it also requires little animal handling and reduces the stress placed on the animal. It has long been a concern in the field that the SOD1 mouse does not display forelimb motor deficits and does not give researchers a complete picture of the disease. Here, we provide evidence that the SOD1 model does in fact develop early forelimb motor deficits due to the task’s ability to assess fine-motor function, reconciling this model with the various clinical presentation of ALS. Taken together, the string-pulling paradigm may provide novel insights into the pathogenesis of ALS, offer nuanced evaluation of prospective treatments, and has high translational potential to the clinic.

Modelling amyotrophic lateral sclerosis in rodents.

The efficient study of human disease requires the proper tools, one of the most crucial of which is an accurate animal model that faithfully recapitulates the human condition. The study of amyotrophic lateral sclerosis (ALS) is no exception. Although the majority of ALS cases are considered sporadic, most animal models of this disease rely on genetic mutations identified in familial cases. Over the past decade, the number of genes associated with ALS has risen dramatically and, with each new genetic variant, there is a drive to develop associated animal models. Rodent models are of particular importance as they allow for the study of ALS in the context of a living mammal with a comparable CNS. Such models not only help to verify the pathogenicity of novel mutations but also provide critical insight into disease mechanisms and are crucial for the testing of new therapeutics. In this Review, we aim to summarize the full spectrum of ALS rodent models developed to date.

Imaging immunological processes from blood to brain in amyotrophic lateral sclerosis

Neuropathology studies of amyotrophic lateral sclerosis (ALS) and animal models of ALS reveal a strong association between aberrant protein accumulation and motor neurone damage, as well as activated microglia and astrocytes. While the role of neuroinflammation in the pathology of ALS is unclear, imaging studies of the central nervous system (CNS) support the idea that innate immune activation occurs early in disease in both humans and rodent models of ALS. In addition, emerging studies also reveal changes in monocytes, macrophages and lymphocytes in peripheral blood as well as at the neuromuscular junction. To more clearly understand the association of neuroinflammation (innate and adaptive) with disease progression, the use of biomarkers and imaging modalities allow monitoring of immune parameters in the disease process. Such approaches are important for patient stratification, selection and inclusion in clinical trials, as well as to provide readouts of response to therapy. Here, we discuss the different imaging modalities, e.g. magnetic resonance imaging, magnetic resonance spectroscopy and positron emission tomography as well as other approaches, including biomarkers of inflammation in ALS, that aid the understanding of the underlying immune mechanisms associated with motor neurone degeneration in ALS.

Muscle fiber-type specific terminal Schwann cell pathology leads to sprouting deficits following partial denervation in SOD1G93A mice

Amyotrophic lateral sclerosis (ALS) is an adult-onset disease characterized by the progressive death of motoneurons and denervation of muscle fibers. To restore motor function, surviving motoneurons in partially denervated muscles typically sprout axons to reinnervate denervated endplates. However, studies on the SOD1G93A rodent models of ALS indicate that sprouting is significantly limited in fast, but not slow, twitch muscles after disease onset. This limitation hastens the rate of muscle weakness and loss of motor function. The causes of this limitation are currently unknown. Sprouting could be limited because the SOD1G93A mutation weakens motoneurons making them incapable of expanding their field of innervation. Alternatively, motoneurons may be capable of sprouting, but unable to do so due to the loss of a permissive sprouting environment. To distinguish between the two possibilities, we compared the sprouting capacity of motoneuron subtypes by partially denervating the fast twitch plantaris (composed of type IIa/IIb muscle fibers) and slow twitch soleus muscles (type I/IIa fibers) prior to disease onset and weakening in SOD1G93A and WT mice. We found that only motoneurons innervating the SOD1G93A plantaris had a limited sprouting capacity. This was correlated with the selective loss of terminal Schwann cells (TSCs) at IIb fibers and an increase in macrophage infiltration. Treating SOD1G93A mice with the tyrosine kinase inhibitor, masitinib, significantly reduced infiltration, prevented TSC loss, and increased the sprouting capacity to near normal. These results suggest that TSCs at denervated type IIb muscle fibers are aberrantly targeted by infiltrating macrophages in SOD1G93A mice, and their loss accounts, at least in part, for the compromised sprouting capacity of the largest motoneurons during early stages of ALS.

Respiratory Muscle Activity during Maximal Efforts in ALS Patients and Healthy Controls

Amyotrophic lateral sclerosis (ALS) is a type of neurodegenerative disease involving upper and lower motor neuron loss. ALS patients usually die of respiratory failure due to breathing muscle weakness from motor neuron death. It is important to better understand how breathing changes in ALS to design effective treatments to target breathing insufficiency. Breathing capacity is preserved until late stages of disease in the SOD1G93A rodent model of ALS. Possible mechanisms preserving breathing in ALS rats include: 1) spinal synaptic plasticity; 2) neuromuscular junction plasticity; and 3) transition in balance from more affected muscles (eg. diaphragm) to less affected accessory respiratory muscles. If these mechanisms also exist in humans with ALS, we predict that characteristic patterns of altered respiratory muscle activity would precede ventilatory failure, assessed via traditional pulmonary function tests. Thus, using surface EMGs (sEMG) in ALS patients, we tested the hypothesis that ALS patients exhibit differential recruitment patterns of inspiratory muscle activity during a maximal inspiratory pressure (MIP) test versus healthy age‐ and sex‐ matched controls. EMG electrodes (Bagnoli surface electrode, Delsys, Massachusetts, USA) were bilaterally placed on the diaphragm, 2nd parasternal, scalene and sternocleidomastoid muscles. Subjects (8 patients and 8 controls) were instructed to perform the MIP test. The test was repeated until 3 measurements were obtained within 10% variability. RMS EMG amplitude of MIP testing was calculated using a 100ms sliding window with MATLAB v.9.2., and relationships between MIP and EMG activity were evaluated using a linear regression. A moderate relationship (r=0.65) was seen between parasternal muscle activity and MIP in ALS patients, while the controls showed moderate correlations between neck muscle activity (sternocleidomastoid and scalene) and MIP (rSCM= 0.56 and rscalene=0.69). Moreover, MIP‐generated parasternal (r=0.76) and diaphragm (r=0.7) activity corresponded strongly with disease severity of patients, as measured by the ALS‐FRS scale. Interestingly, we did not see a clear relationship between diaphragm surface EMG activity and MIP in either patients or controls. Several factors could account for this, including the use of surface electrodes and the mass‐effort nature of the MIP test. Further analyses are underway to assess respiratory muscle activity during other inspiratory challenges and compare the amount of sEMG output distribution between controls and ALS patients. These preliminary results support the idea that ALS patients use a different pattern of muscle activity during maximal breathing effort from controls.Support or Funding InformationSupported by: UF Clinical and Translational Science Institute (supported byNIH UL1TR001427), UF “Moonshot” grant initiative, and UF McKnight Brain Institute

Reduction of ephrin-A5 aggravates disease progression in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that affects motor neurons in the brainstem, spinal cord and motor cortex. ALS is characterized by genetic and clinical heterogeneity, suggesting the existence of genetic factors that modify the phenotypic expression of the disease. We previously identified the axonal guidance EphA4 receptor, member of the Eph-ephrin system, as an ALS disease-modifying factor. EphA4 genetic inhibition rescued the motor neuron phenotype in zebrafish and a rodent model of ALS. Preventing ligands from binding to the EphA4 receptor also successfully improved disease, suggesting a role for EphA4 ligands in ALS. One particular ligand, ephrin-A5, is upregulated in reactive astrocytes after acute neuronal injury and inhibits axonal regeneration. Moreover, it plays a role during development in the correct pathfinding of motor axons towards their target limb muscles. We hypothesized that a constitutive reduction of ephrin-A5 signalling would benefit disease progression in a rodent model for ALS. We discovered that in the spinal cord of control and symptomatic ALS mice ephrin-A5 was predominantly expressed in neurons. Surprisingly, reduction of ephrin-A5 levels in SOD1G93A mice accelerated disease progression and reduced survival without affecting disease onset, motor neuron numbers or innervated neuromuscular junctions in symptomatic mice. These findings suggest ephrin-A5 as a modifier of disease progression that might play a role in the later stages of the disease. Similarly, we identified a more aggressive disease progression in patients with lower ephrin-A5 protein levels in the cerebrospinal fluid without modifying disease onset. In summary, we identified reduced expression of ephrin-A5 to accelerate disease progression in a mouse model of ALS as well as in humans. Combined with our previous findings on the role of EphA4 in ALS our current data suggests different contribution for various members of the Eph-ephrin system in the pathophysiology of a motor neuron disease.

Mesenchymal Stem Cells: A Potential Therapeutic Approach for Amyotrophic Lateral Sclerosis?

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the degeneration of both upper and lower motor neurons. Patients show both motor and extra-motor symptoms. A cure is not available at this time, and the disease leads to death within 3–5 years, mainly due to respiratory failure. Stem cell therapy is arising as a new promising approach for the treatment of neurodegenerative disorders. In particular, mesenchymal stem cells (MSCs) seem the most suitable type of stem cells, thanks to their demonstrated beneficial effects in different experimental models, to the easy availability, and to the lack of ethical problems. In this review, we focused on the studies involving ALS rodent models and clinical trials in order to understand the potential beneficial effects of MSC transplantation. In different ALS rodent models, the administration of MSCs induced a delay in disease progression and at least a partial recovery of the motor function. In addition, clinical trials evidenced the feasibility and safety of MSC transplantation in ALS patients, given that no major adverse events were recorded. However, only partial improvements were shown. For this reason, more studies and trials are needed to clarify the real effectiveness of MSC-based therapy in ALS.

Hypoglossal Motor Neuron Death Via Intralingual CTB–saporin (CTB–SAP) Injections Mimic Aspects of Amyotrophic Lateral Sclerosis (ALS) Related to Dysphagia

Amyotrophic lateral sclerosis (ALS) is a devastating disease leading to degeneration of motor neurons and skeletal muscles, including those required for swallowing. Tongue weakness is one of the earliest signs of bulbar dysfunction in ALS, which is attributed to degeneration of motor neurons in the hypoglossal nucleus in the brainstem, the axons of which directly innervate the tongue. Despite its fundamental importance, dysphagia (difficulty swallowing) and strategies to preserve swallowing function have seldom been studied in ALS models. It is difficult to study dysphagia in ALS models since the amount and rate at which hypoglossal motor neuron death occurs cannot be controlled, and degeneration is not limited to the hypoglossal nucleus. Here, we report a novel experimental model using intralingual injections of cholera toxin B conjugated to saporin (CTB–SAP) to study the impact of only hypoglossal motor neuron death without the many complications that are present in ALS models. Hypoglossal motor neuron survival, swallowing function, and hypoglossal motor output were assessed in Sprague–Dawley rats after intralingual injection of either CTB–SAP (25 g) or unconjugated CTB and SAP (controls) into the genioglossus muscle. CTB–SAP treated rats exhibited significant (p ≤ 0.05) deficits vs. controls in: (1) lick rate (6.0 ± 0.1 vs. 6.6 ± 0.1 Hz; (2) hypoglossal motor output (0.3 ± 0.05 vs. 0.6 ± 0.10 mV); and (3) hypoglossal motor neuron survival (398 ± 34 vs. 1018 ± 41 neurons). Thus, this novel, inducible model of hypoglossal motor neuron death mimics the dysphagia phenotype that is observed in ALS rodent models, and will allow us to study strategies to preserve swallowing function.

Antisense-mediated reduction of EphA4 in the adult CNS does not improve the function of mice with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal adult onset motor neuron disease characterized by progressive denervation and subsequent motor impairment. EphA4, a negative regulator of axonal growth, was recently identified as a genetic modifier in fish and rodent models of ALS. To evaluate the therapeutic potential of EphA4 for ALS, we examined the effect of CNS-directed EphA4 reduction in preclinical mouse models of ALS, and assessed if the levels of EPHA4 mRNA in blood correlate with disease onset and progression in human ALS patients. We developed antisense oligonucleotides (ASOs) to specifically reduce the expression of EphA4 in the central nervous system (CNS) of adult mice. Intracerebroventricular administration of an Epha4-ASO in wild-type mice inhibited Epha4 mRNA and protein in the brain and spinal cord, and promoted re-innervation and functional recovery after sciatic nerve crush. In contrast, lowering of EphA4 in the CNS of two mouse models of ALS (SOD1G93A and PFN1G118V) did not improve their motor function or survival. Furthermore, the level of EPHA4 mRNA in human blood correlated weakly with age of disease onset, and it was not a significant predictor of disease progression as measured by ALS Functional Rating Scores (ALSFRS). Our data demonstrates that lowering EphA4 in the adult CNS may not be a stand-alone viable strategy for treating ALS.

Complement C5a-C5aR1 signalling drives skeletal muscle macrophage recruitment in the hSOD1G93A mouse model of amyotrophic lateral sclerosis

BackgroundThe terminal pathway of the innate immune complement system is implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). Terminal complement activation leads to generation of C5a, which through its receptor, C5aR1, drives immune cell recruitment and activation. Importantly, genetic or pharmacological blockage of C5aR1 improves motor performance and reduces disease pathology in hSOD1G93A rodent models of ALS. In this study, we aimed to explore the potential mechanisms of C5aR1-mediated pathology in hSOD1G93A mice by examining their skeletal muscles.ResultsWe found elevated levels of C1qB, C4, fB, C3, C5a, and C5aR1 in tibialis anterior muscles of hSOD1G93A mice, which increased with disease progression. Macrophage cell numbers also progressively increased in hSOD1G93A muscles in line with disease progression. Immuno-localisation demonstrated that C5aR1 was expressed predominantly on macrophages within hSOD1G93A skeletal muscles. Notably, hSOD1G93A × C5aR1-/- mice showed markedly decreased numbers of infiltrating macrophages, along with reduced neuromuscular denervation and improved grip strength in hind limb skeletal muscles, when compared to hSOD1G93A mice.ConclusionThese results indicate that terminal complement activation and C5a production occur in skeletal muscle tissue of hSOD1G93A mice, and that C5a-C5aR1 signalling contributes to the recruitment of macrophages that may accelerate muscle denervation in these ALS mice.

Rodent Models of Amyotrophic Lateral Sclerosis.

Amyotrophic Lateral Sclerosis (ALS) is a motor neuron disease affecting upper and lower motor neurons in the central nervous system. Patients with ALS develop extensive muscle wasting and atrophy leading to paralysis and death 3 to 5 years after disease onset. The condition may be familial (fALS 10%) or sporadic ALS (sALS, 90%). The large majority of fALS cases are due to genetic mutations in the Superoxide dismutase 1 gene (SOD1, 15% of fALS) and repeat nucleotide expansions in the gene encoding C9ORF72 (∼ 40% to 50% of fALS and ∼ 10% of sALS). Studies suggest that ALS is mediated through aberrant protein homeostasis (i.e., ER stress and autophagy) and/or changes in RNA processing (as in all non-SOD1-mediated ALS). In all of these cases, animal models suggest that the disorder is mediated non-cell autonomously, i.e., not only motor neurons are involved, but glial cells including microglia, astrocytes, and oligodendrocytes, and other neuronal subpopulations are also implicated in the pathogenesis. Provided in this unit is a review of ALS rodent models, including discussion of their relative advantages and disadvantages. Emphasis is placed on correlating the model phenotype with the human condition and the utility of the model for defining the disease process. Information is also presented on RNA processing studies in ALS research, with particular emphasis on the newest ALS rodent models.

Dysfunction of endocytic kinase AAK1 in ALS.

Mechanisms of human mutant superoxide dismutase 1 (SOD1)-induced toxicity in causing the familial form of amyotrophic lateral sclerosis (ALS) remain elusive. Identification of new proteins that can selectively interact with mutant SOD1s and investigation of their potential roles in ALS are important to discover new pathways that are involved in disease pathology. Using the yeast two-hybrid system, we identified the adaptor-associated kinase 1 (AAK1), a regulatory protein in clathrin-coated vesicle endocytic pathway that selectively interacted with the mutant but not the wild-type SOD1. Using both transgenic mouse and rat SOD1-linked familial ALS (FALS) models, we found that AAK1 was partially colocalized with the endosomal and presynaptic protein markers under the normal physiological condition, but was mislocated into aggregates that contained mutant SOD1s and the neurofilament proteins in rodent models of ALS in disease. AAK1 protein levels were also decreased in ALS patients. These results suggest that dysfunction of a component in the endosomal and synaptic vesicle recycling pathway is involved in ALS pathology.

Astrocytes show reduced support of motor neurons with aging that is accelerated in a rodent model of ALS

Astrocytes play a crucial role in supporting motor neurons in health and disease. However, there have been few attempts to understand how aging may influence this effect. Here, we report that rat astrocytes show an age-dependent senescence phenotype and a significant reduction in their ability to support motor neurons. In a rodent model of familial amyotrophic lateral sclerosis (ALS) overexpressing mutant superoxide dismutase 1 (SOD1), the rate of astrocytes acquiring a senescent phenotype is accelerated and they subsequently provide less support to motor neurons. This can be partially reversed by glial cell line–derived neurotrophic factor (GDNF). Replacing aging astrocytes with young ones producing GDNF may therefore have a significant survival promoting affect on aging motor neurons and those lost through diseases such as ALS.

In vivo detection of free radicals using molecular MRI and immuno-spin trapping in a mouse model for amyotrophic lateral sclerosis

Free radicals associated with oxidative stress play a major role in amyotrophic lateral sclerosis (ALS). By combining immuno-spin trapping and molecular magnetic resonance imaging, in vivo trapped radical adducts were detected in the spinal cords of SOD1G93A-transgenic (Tg) mice, a model for ALS. For this study, the nitrone spin trap DMPO (5,5-dimethyl-1-pyrroline N-oxide) was administered (ip) over 5 days before administration (iv) of an anti-DMPO probe (anti-DMPO antibody covalently bound to an albumin–gadolinium–diethylenetriamine pentaacetic acid–biotin MRI contrast agent) to trap free radicals. MRI was used to detect the presence of the anti-DMPO radical adducts by a significant sustained increase in MR signal intensities (p < 0.05) or anti-DMPO probe concentrations measured from T1 relaxations (p < 0.01). The biotin moiety of the anti-DMPO probe was targeted with fluorescence-labeled streptavidin to locate the probe in excised tissues. Negative controls included either Tg ALS mice initially administered saline rather than DMPO followed by the anti-DMPO probe or non-Tg mice initially administered DMPO and then the anti-DMPO probe. The anti-DMPO probe was found to bind to neurons via colocalization fluorescence microscopy. DMPO adducts were also confirmed in diseased/nondiseased tissues from animals administered DMPO. Apparent diffusion coefficients from diffusion-weighted images of spinal cords from Tg mice were significantly elevated (p < 0.001) compared to wild-type controls. This is the first report regarding the detection of in vivo trapped radical adducts in an ALS model. This novel, noninvasive, in vivo diagnostic method can be applied to investigate the involvement of free radical mechanisms in ALS rodent models.

Intrapleural CTB‐saporin selectively kills phrenic motor neurons: a motor neuron disease model

Amyotrophic lateral sclerosis (ALS) is a devastating disease leading to progressive motor neuron degeneration and ultimately, ventilatory failure. In a rodent model of ALS (SOD1G93Arats), ventilatory capacity is preserved despite &gt;;50% loss of phrenic and intercostal motor neurons (i.e. compensatory respiratory plasticity preserves breathing capacity). Here, our intent was to develop an experimental model to study compensatory plasticity without many of the complications attendant to ALS. Thus, we tested the hypothesis that intrapleural injections of cholera toxin B fragment conjugated to saporin (CTB‐SAP) selectively kill respiratory motor neurons to mimic motor neuron death in ALS. Phrenic motor output was assessed in anesthetized, paralyzed and ventilated Sprague Dawley rats 3–28 days following bilateral intrapleural injections of: 1) CTB‐SAP (25–50μg), or 2) un‐conjugated CTB and SAP (control). CTB‐SAP elicited dose‐dependent phrenic motor neuron death; 25μg CTB‐SAP (7 days) most closely resembled cell death in end‐stage (ES) ALS rats (36±7% survival; n=9; p&lt;0.05 vs. controls); CTB‐SAP diminished phrenic motor output (CTB‐SAP: 0.3±0.07 volts vs. Control: 1.5±0.3; n=9; p&lt;0.05) to a level resembling ES ALSrats (0.4 volts). Intrapleural CTB‐SAP injections represent a novel inducible and repeatable model to study the impact of respiratory motor neuron death on breathing.[Supported by NIH NS057778 and HL080209 and the Francis Families Foundation]

Neural Stem Cells as a Therapeutic Approach for Amyotrophic Lateral Sclerosis

Proliferating neural stem cells (NSCs) were first identified in the late 1960s in the adult rat brain1 as multipotent self-renewing stem cells, able to differentiate into neurons, astrocytes, and oligodendrocytes. NSC transplantation is being evaluated to treat traumatic brain or spinal cord injury and neurodegenerative diseases. Amyotrophic lateral sclerosis (ALS) is a fatal neuro­degenerative disorder characterized by progressive loss of upper and lower motor neurons and chronic inflammation leading to paralysis and death due to respiratory failure. In the December issue of Science Translational Medicine, Teng et al.2 reported successful use of transplanted, undifferen­tiated multipotent NSCs to prolong survival in a mouse model of ALS. They found that the experimental treatment is both safe and potentially beneficial to preserve neurons that have been spared by the disease at the time of treatment. The results further indicate the benefits of early intervention and suggest that targeting the spinal cord at different sites will protect both motor and respiratory function. The authors conclude that a combination of therapeutic approaches, from gene therapy to cell transplantation, targeting different pathogenic mechanisms of the disorder, is likely to lead to successful therapy.

Genetic strategies to study TDP-43 in rodents and to develop preclinical therapeutics for amyotrophic lateral sclerosis.

The neuropathological hallmark of the majority of amyotrophic lateral sclerosis (ALS) and a class of frontotemporal lobar degeneration is ubiquitinated cytoplasmic aggregates composed of transactive response DNA binding protein 43 kDa (TDP-43). Genetic manipulation of TDP-43 in animal models has been used to study the protein's role in pathogenesis. Transgenic rodents for TDP-43 have recapitulated key aspects of ALS such as paralysis, loss of spinal motor neurons and muscle atrophy. Viral vectors are an alternate approach to express pathological proteins in animals. Use of the recombinant adeno-associated virus vector serotype 9 has permitted widespread transgene expression throughout the central nervous system after intravenous administration. Expressing TDP-43 in rats with this method produced a phenotype that was consistent with and similar to TDP-43 transgenic lines. Increased levels of TDP-43 in the nucleus are toxic to neurons and sufficient to produce ALS-like symptoms. Animal models based on TDP-43 will address the relationships between TDP-43 expression levels, pathology, neuronal loss, muscle atrophy, motor function and causative mechanisms of disease. New targets that modify TDP-43 function, or targets from previous ALS models and other models of spinal cord diseases, could be tested for efficacy in the recent rodent models of ALS based on TDP-43. The vector approach could be an important therapeutic channel because the entire spinal cord can be affected from a one-time peripheral administration.