CNS-targeted gene therapy improves survival and motor function in a mouse model of spinal muscular atrophy
Marco A. Passini, … , Lamya S. Shihabuddin, Seng H. Cheng
Marco A. Passini, … , Lamya S. Shihabuddin, Seng H. Cheng
Published March 15, 2010
Citation Information: J Clin Invest. 2010;120(4):1253-1264. https://doi.org/10.1172/JCI41615.
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Research Article Neuroscience

CNS-targeted gene therapy improves survival and motor function in a mouse model of spinal muscular atrophy

Abstract

Spinal muscular atrophy (SMA) is a neuromuscular disease caused by a deficiency of survival motor neuron (SMN) due to mutations in the SMN1 gene. In this study, an adeno-associated virus (AAV) vector expressing human SMN (AAV8-hSMN) was injected at birth into the CNS of mice modeling SMA. Western blot analysis showed that these injections resulted in widespread expression of SMN throughout the spinal cord, and this translated into robust improvement in skeletal muscle physiology, including increased myofiber size and improved neuromuscular junction architecture. Treated mice also displayed substantial improvements on behavioral tests of muscle strength, coordination, and locomotion, indicating that the neuromuscular junction was functional. Treatment with AAV8-hSMN increased the median life span of mice with SMA-like disease to 50 days compared with 15 days for untreated controls. Moreover, injecting mice with SMA-like disease with a human SMN–expressing self-complementary AAV vector — a vector that leads to earlier onset of gene expression compared with standard AAV vectors — led to improved efficacy of gene therapy, including a substantial extension in median survival to 157 days. These data indicate that CNS-directed, AAV-mediated SMN augmentation is highly efficacious in addressing both neuronal and muscular pathologies in a severe mouse model of SMA.

Authors

Marco A. Passini, Jie Bu, Eric M. Roskelley, Amy M. Richards, S. Pablo Sardi, Catherine R. O’Riordan, Katherine W. Klinger, Lamya S. Shihabuddin, Seng H. Cheng

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Figure 2

Human SMN is expressed in the proper intracellular compartments and in motor neurons with AAV8-hSMN treatment.

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Human SMN is expressed in the proper intracellular compartments and in m...
In situ hybridization (A and B) and immunohistochemistry (C–K) of the lumbar segment in AAV8-hSMN–treated (A, C, E–K) and untreated (B and D) SMA mice at 16 days (A–D) and 58–66 days (E–K) after injection. The low level of endogenous hSMN in untreated SMA mice was below the threshold of detection using these assays (B and D). Vector-derived hSMN was abundantly detected in the cytoplasm and in the nucleus of transduced cells, as illustrated by the pair of gem-like structures in the nucleus (E, the arrowhead points to the hSMN immunosignal magnified in the inset). hSMN was also detected in the dendrites (F and G) and in the axons (H) of neurons. The colocalization of hSMN (I) with mChAT (J) showed that a subset of transduced cells consisted of motor neurons (K). Shown are the average numbers of ChAT immunopositive cell counts from the lumbar, thoracic, and cervical segments at both time points (L). SMA (n = 8 at 16 days); AAV (n = 8 at 16 days, n = 5 at 58–66 days); WT, untreated WT (n = 8 at 16 days, n = 5 at 58–66 days). Values represent the mean ± SEM. Scale bars: 500 microns (A–D); 10 microns (E and H); 50 microns (F); 12 microns (G), 100 microns (I–K). Statistical comparisons were performed with 1-way ANOVA and Bonferroni’s multiple post hoc tests at 16 days and with unpaired 2-tailed Student’s t tests at 58–66 days (L). *P < 0.05; **P < 0.01.