Objective
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease in which glia are central mediators of motor neuron (MN) death. Since multiple cell types are involved in disease ...pathogenesis, the objective of this study was to determine the benefit of co‐targeting independent pathogenic mechanisms in a familial ALS mouse model.
Methods
Recently, our laboratory identified that ALS microglia induce MN death in an NF‐κB‐dependent mechanism. We also demonstrated that a single, post‐natal, intravenous injection of adeno‐associated viral vector serotype 9 encoding a shRNA against mutant SOD1 is able to traverse the blood–brain barrier of ALS mice and reduce SOD1‐expression in astrocytes and MNs. Reducing mutant SOD1 in MNs and astrocytes led to a robust increase in survival. To evaluate the benefit of co‐targeting multiple cell types in ALS, we combined microglial NF‐κB suppression with SOD1 reduction in astrocytes and MNs.
Results
Targeting both astrocytes and microglia resulted in an additive increase in survival and motor function by delaying both onset and progression. Strikingly, targeting all three cell types (astrocytes, motor neurons MNs, and microglia) resulted in an additive increase in lifespan and motor function, with maximum survival reaching 204 days, 67 days longer than the mean survival of untreated control animals.
Interpretation
Our data suggest that a combinatorial approach co‐targeting different pathogenic mechanisms in independent cell types is a beneficial therapeutic strategy for ALS.
Fifteen children with spinal muscular atrophy type 1 received gene-replacement therapy with a single dose of adeno-associated virus containing SMN. In marked contrast to well-characterized historical ...cohorts, all the patients survived at least 20 months and most reached motor milestones.
Neuroinflammation is one of the most striking hallmarks of amyotrophic lateral sclerosis (ALS). Nuclear factor-kappa B (NF-κB), a master regulator of inflammation, is upregulated in spinal cords of ...ALS patients and SOD1-G93A mice. In this study, we show that selective NF-κB inhibition in ALS astrocytes is not sufficient to rescue motor neuron (MN) death. However, the localization of NF-κB activity and subsequent deletion of NF-κB signaling in microglia rescued MNs from microglial-mediated death in vitro and extended survival in ALS mice by impairing proinflammatory microglial activation. Conversely, constitutive activation of NF-κB selectively in wild-type microglia induced gliosis and MN death in vitro and in vivo. Taken together, these data provide a mechanism by which microglia induce MN death in ALS and suggest a novel therapeutic target that can be modulated to slow the progression of ALS and possibly other neurodegenerative diseases by which microglial activation plays a role.
•NF-κB is activated in ALS, predominantly in microglia•Inhibition of microglial NF-κB delays disease progression by 47% in SOD1-G93A mice•Inhibition of NF-κB dampens proinflammatory microglial activation•Constitutive activation of microglial NF-κB induces pathological hallmarks of ALS
Frakes et al. demonstrate NF-κB is activated in microglia to kill motor neurons in ALS. These findings identify a novel therapeutic target to slow the progression of ALS and possibly other neurodegenerative disease in which microglial activation plays a role.
Spinal muscular atrophy is an autosomal recessive disease of motor neurons caused by lack of the SMN gene. Foust et al. achieve long-term correction of the disease phenotype in a mouse model by ...intravenous delivery of SMN using the viral vector scAAV9.Spinal muscular atrophy (SMA), the most common autosomal recessive neurodegenerative disease affecting children, results in impaired motor neuron function1. Despite knowledge of the pathogenic role of decreased survival motor neuron (SMN) protein levels, efforts to increase SMN have not resulted in a treatment for patients. We recently demonstrated that self-complementary adeno-associated virus 9 (scAAV9) can infect ∼60% of motor neurons when injected intravenously into neonatal mice2,3,4. Here we use scAAV9-mediated postnatal day 1 vascular gene delivery to replace SMN in SMA pups and rescue motor function, neuromuscular physiology and life span. Treatment on postnatal day 5 results in partial correction, whereas postnatal day 10 treatment has little effect, suggesting a developmental period in which scAAV9 therapy has maximal benefit. Notably, we also show extensive scAAV9-mediated motor neuron transduction after injection into a newborn cynomolgus macaque. This demonstration that scAAV9 traverses the blood-brain barrier in a nonhuman primate emphasizes the clinical potential of scAAV9 gene therapy for SMA.
Spinal muscular atrophy (SMA), the most common autosomal recessive neurodegenerative disease affecting children, results in impaired motor neuron function. Despite knowledge of the pathogenic role of ...decreased survival motor neuron (SMN) protein levels, efforts to increase SMN have not resulted in a treatment for patients. We recently demonstrated that self-complementary adeno-associated virus 9 (scAAV9) can infect ∼60% of motor neurons when injected intravenously into neonatal mice. Here we use scAAV9-mediated postnatal day 1 vascular gene delivery to replace SMN in SMA pups and rescue motor function, neuromuscular physiology and life span. Treatment on postnatal day 5 results in partial correction, whereas postnatal day 10 treatment has little effect, suggesting a developmental period in which scAAV9 therapy has maximal benefit. Notably, we also show extensive scAAV9-mediated motor neuron transduction after injection into a newborn cynomolgus macaque. This demonstration that scAAV9 traverses the blood-brain barrier in a nonhuman primate emphasizes the clinical potential of scAAV9 gene therapy for SMA.
Adeno-associated virus type 9 (AAV9) is a powerful tool for delivering genes throughout the central nervous system (CNS) following intravenous injection. Preclinical results in pediatric models of ...spinal muscular atrophy (SMA) and lysosomal storage disorders provide a compelling case for advancing AAV9 to the clinic. An important translational step is to demonstrate efficient CNS targeting in large animals at various ages. In the present study, we tested systemically injected AAV9 in cynomolgus macaques, administered at birth through 3 years of age for targeting CNS and peripheral tissues. We show that AAV9 was efficient at crossing the blood–brain barrier (BBB) at all time points investigated. Transgene expression was detected primarily in glial cells throughout the brain, dorsal root ganglia neurons and motor neurons within the spinal cord, providing confidence for translation to SMA patients. Systemic injection also efficiently targeted skeletal muscle and peripheral organs. To specifically target the CNS, we explored AAV9 delivery to cerebrospinal fluid (CSF). CSF injection efficiently targeted motor neurons, and restricted gene expression to the CNS, providing an alternate delivery route and potentially lower manufacturing requirements for older, larger patients. Our findings support the use of AAV9 for gene transfer to the CNS for disorders in pediatric populations.
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