Marais, T. | bioRxiv Science

bioRxiv2026

GDF5 as a Multimodal Protector of the Motor Unit in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis is characterized by the progressive dismantling of the motor unit. While "dying back" hypothesis suggests that peripheral neuromuscular dysfunction precedes motor neuron loss, the molecular mechanisms limiting endogenous compensatory responses remain poorly understood. We longitudinally examined neuromuscular decline and GDF5-SMAD1/5/8 signaling in SOD1G93A mice. Our findings revealed a translational checkpoint linked to the lncRNA Myoparr that suppresses GDF5 production at symptom onset. To overcome this deficit, we delivered AAV9-GDF5 at the symptomatic stage. GDF5 supplementation restored SMAD signaling balance, shifting the motor unit from a pro-atrophic TGF-{beta}-SMAD2/3 toward a pro-myogenic SMAD1/5 profile. Treatment preserved muscle mass, reduced mitochondrial reactive oxygen species, and maintained neuromuscular junction integrity, including peri-synaptic glial support. GDF5 also promoted molecular recovery of spinal MNs by enhancing homeostatic marker expression. Together, these findings identify GDF5 as a multimodal stabilizer of the motor unit and highlight its potential as therapeutic target in combinatorial strategies aimed at coupling motor unit stabilization with central neuroprotective interventions.

physiology↗

bioRxiv2025

Pre-clinical evaluation of a gene therapy candidate for SOD1-ALS shows improved survival and signs of inflammation in the CNS of treated mice.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by motor neurons loss (MN). In 15-20% of familial ALS cases, mutations in the superoxide dismutase 1 (SOD1) gene are the underlying cause. Targeting human SOD1 (hSOD1) toxicity has emerged as a promising approach to treat SOD1-ALS. We previously demonstrated the efficacy of an exon-skipping strategy using a self-complementary AAVrh10-U7-hSOD1 vector in SOD1G93A mice achieving significant hSOD1 silencing. In this study, we optimized the therapeutic protocol by conducting a dose-finding and biodistribution study of scAAVrh10-U7-hSOD1 following a single intracerebroventricular injection in adult SOD1G93A mice. Our findings demonstrate a dose-dependent reduction in mutant hSOD1 levels in the cortex, spinal cord, and peripheral tissues, sustained for up to 60 days post-injection. In vivo, some adverse effects were noted mostly at the highest dose, with inflammation early post-injection and persistent microglial activation in the brain observed around the injection site. Importantly, the medium-dose treatment extended mean survival by up to 27% with a much milder early toxicity, which will provide a great possibility for future applications. Additionally, no major off-target effects were observed in human cell models, highlighting the targeting specificity of this approach and the potential safety for translation. These findings confirm and extend the therapeutic potential of scAAVrh10-U7-hSOD1 gene therapy while emphasizing the need for further technological development to minimize adverse effects and maximize potential clinical benefit.

pharmacology and toxicology↗