title: Hind limb muscle atrophy precedes cerebral neuronal degeneration in G93A-SOD1 mouse model of amyotrophic lateral sclerosis: a longitudinal MRI study.
abstract: Amyotrophic lateral sclerosis (ALS) is a progressive, fatal, neurodegenerative disorder caused by the degeneration of motor neurons in the CNS, which results in complete paralysis of skeletal muscles. Recent experimental studies have suggested that the disease could initiate in skeletal muscle, rather than in the motor neurons. To establish the timeframe of motor neuron degeneration in relation to muscle atrophy in motor neuron disease, we have used MRI to monitor changes throughout disease in brain and skeletal muscle of G93A-SOD1 mice, a purported model of ALS. Longitudinal MRI examination of the same animals indicated that muscle volume in the G93A-SOD1 mice was significantly reduced from as early as week 8 of life, 4 weeks prior to clinical onset. Progressive muscle atrophy from week 8 onwards was confirmed by histological analysis. In contrast, brain MRI indicated that neurodegeneration occurs later in G93A-SOD1 mice, with hyperintensity MRI signals detected only at weeks 10-18. Neurodegenerative changes were observed only in the motor nuclei areas of the brainstem; MRI changes indicative of neurodegeneration were not detected in the motor cortex where first motor neurons originate, even at the late disease stage. This longitudinal MRI study establishes unequivocally that, in the experimental murine model of ALS, muscle degeneration occurs before any evidence of neurodegeneration and clinical signs, supporting the postulate that motor neuron disease can initiate from muscle damage and result from retrograde dying-back of the motor neurons.
authors.affiliation: Department of Neurology IV, Neuromuscular Diseases and Neuroimmunology, Fondazione Istituto Neurologico Carlo Besta, Milan, 20133, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Marcuzzo
authors.forename: Ileana
authors.initials: I
authors.lastname: Zucca
authors.forename: Alfonso
authors.initials: A
authors.lastname: Mastropietro
authors.forename: Nicole Kerlero
authors.initials: NK
authors.lastname: de Rosbo
authors.forename: Paola
authors.initials: P
authors.lastname: Cavalcante
authors.forename: Silvia
authors.initials: S
authors.lastname: Tartari
authors.forename: Silvia
authors.initials: S
authors.lastname: Bonanno
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Preite
authors.forename: Renato
authors.initials: R
authors.lastname: Mantegazza
authors.forename: Pia
authors.initials: P
authors.lastname: Bernasconi
mesh_terms: D000409:Alanine / Q000235:genetics; D000690:Amyotrophic Lateral Sclerosis / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D000818:Animals; D001921:Brain / Q000201:enzymology / Q000473:pathology*; D004195:Disease Models, Animal; D005998:Glycine / Q000235:genetics; D006614:Hindlimb / Q000473:pathology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000201:enzymology / Q000473:pathology*; D018482:Muscle, Skeletal / Q000201:enzymology / Q000473:pathology*; D009134:Muscular Atrophy, Spinal / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D012183:Retrograde Degeneration / Q000201:enzymology / Q000235:genetics / Q000473:pathology*
chemical_list: D000409:Alanine; D005998:Glycine