CNS-targeted Viral Delivery of G-CSF in an Animal Model for ALS: Improved Efficacy and Preservation of the Neuromuscular Unit

Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of motoneurons. We have recently uncovered a new neurotrophic growth factor, granulocyte-colony stimulating factor (G-CSF), which protects α-motoneurons, improves functional outcome, and increases life expectancy of SOD-1 (G93A) mice when delivered subcutaneously. However, chronic systemic delivery of G-CSF is complicated by elevation of neutrophilic granulocytes. Here, we used adeno-associated virus (AAV) to directly target and confine G-CSF expression to the spinal cord. Whereas intramuscular injection of AAV failed to transduce motoneurons retrogradely, and caused a high systemic load of G-CSF, intraspinal delivery led to a highly specific enrichment of G-CSF in the spinal cord with moderate peripheral effects. Intraspinal delivery improved motor functions, delayed disease progression, and increased survival by 10%, longer than after systemic delivery. Mechanistically, we could show that G-CSF in addition to rescuing motoneurons improved neuromuscular junction (NMJ) integrity and enhanced motor axon regeneration after nerve crush injury. Collectively, our results show that intraspinal delivery improves efficacy of G-CSF treatment in an ALS mouse model while minimizing the systemic load of G-CSF, suggesting a new therapeutic option for ALS treatment.

Structural Insight into the Unique Properties of Adeno-Associated Virus Serotype 9

“…Recently, a single intravenous injection of AAV9 vectors expressing ␣-N-acetylglucosaminidase (NAGLU) in mice with mucopolysaccharidosis IIIB (MPS IIIB; lysosomal storage disease) led to correction of their lysosomal storage pathology in the central and peripheral nervous systems and correction of astrocytosis and neurodegeneration (25). Given these properties, AAV9 is currently under development for treatment of neurodegenerative diseases, such as spinal muscle atrophy, amyotrophic lateral sclerosis, Parkinson's disease, and MPS IIIB (7,25,29,30,45,80) (Table 1). Furthermore, while preexisting antibodies to AAVs have been shown to be detrimental to AAV gene delivery, the prevalence of antibodies to AAV9 is lower in humans than those of other serotypes, for example, AAV1 and AAV2 (8), making this serotype an even more attractive candidate for development as a gene delivery vector.…”

Brain delivery of AAV9 expressing an anti-PrP monovalent antibody delays prion disease in mice

“…27 Moreover, studies of AAV9 vectors may be also useful for the therapeutic approach to other neurodegenerative disorders. Currently, experimental AAV2-based therapies for AD, 28 amyotrophic lateral sclerosis, 29 Huntington's disease 30 and Parkinson disease have been proposed, peaking a phase I clinical trial for Parkinson disease. 31,32 However, the diffusion and transduction efficiency of the AAV2 vectors is limited and could be improved by using the AAV9 serotype as delivery system.…”

Research advances in gene therapy approaches for the treatment of amyotrophic lateral sclerosis

“…Furthermore, G-CSF protects motor neurons, ameliorates functional outcomes, and improves lifespan of SOD-1(G93A) mice when administered subcutaneously [85]. In 2010, Henriques et al [86] used AAV to directly target G-CSF expression to the spinal cord, showing that intraspinal delivery improved motor function, delayed disease progression, and increased survival by 10%.…”