title: Effect of thymic stimulation of CD4+ T cell expansion on disease onset and progression in mutant SOD1 mice.
abstract: BACKGROUND
  The peripheral immune system is implicated in modulating microglial activation, neurodegeneration and disease progression in amyotrophic lateral sclerosis (ALS). Specifically, there is reduced thymic function and regulatory T cell (Treg) number in ALS patients and mutant superoxide dismutase 1 (SOD1) mice, while passive transfer of Tregs ameliorates disease in mutant SOD1 mice. Here, we assessed the effects of augmenting endogenous CD4+ T cell number by stimulating the thymus using surgical castration on the phenotype of transgenic SOD1(G93A) mice.
  
  
  METHODS
  Male SOD1(G93A) mice were castrated or sham operated, and weight loss, disease onset and progression were examined. Thymus atrophy and blood CD4+, CD8+ and CD4+ FoxP3+ T cell numbers were determined by fluorescence activated cell sorting (FACS). Motor neuron counts, glial cell activation and androgen receptor (AR) expression in the spinal cord were investigated using immunohistochemistry and Western blotting. Differences between castrated and sham mice were analysed using an unpaired t test or one-way ANOVA.
  
  
  RESULTS
  Castration significantly increased thymus weight and total CD4+ T cell numbers in SOD1(G93A) mice, although Tregs levels were not affected. Despite this, disease onset and progression were similar in castrated and sham SOD1(G93A) mice. Castration did not affect motor neuron loss or astrocytic activation in spinal cords of SOD1(G93A) mice; however, microglial activation was reduced, specifically M1 microglia. We also show that AR is principally expressed in spinal motor neurons and progressively downregulated in spinal cords of SOD1(G93A) mice from disease onset which is further enhanced by castration.
  
  
  CONCLUSIONS
  These results demonstrate that increasing thymic function and CD4+ T cell number by castration confers no clinical benefit in mutant SOD1 mice, which may reflect an inability to stimulate neuroprotective Tregs. Nonetheless, castration decreases M1 microglial activation in the spinal cord without any clinical improvement and motor neuron rescue, in contrast to other approaches to suppress microglia in mutant SOD1 mice. Lastly, diminished AR expression in spinal motor neurons, which links to another motor neuron disorder, spinal bulbar muscular atrophy (SBMA), may contribute to ALS pathogenesis and suggests a common disease pathway in ALS and SBMA mediated by disruption of AR signalling in motor neurons.
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, Victoria, 3052, Australia. rebecca.sheean@florey.edu.au.
authors.forename: Rebecca K
authors.initials: RK
authors.lastname: Sheean
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, Victoria, 3052, Australia. christineaweston@bigpond.com.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Weston
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, Victoria, 3052, Australia. nirma.perera@florey.edu.au.|Centre for Neuroscience, University of Melbourne, 30 Royal Parade, Parkville, Victoria, 3052, Australia. nirma.perera@florey.edu.au.
authors.forename: Nirma D
authors.initials: ND
authors.lastname: Perera
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, University of Melbourne, 1G Royal Parade, Parkville, Victoria, 3052, Australia. damico@wehi.edu.au.
authors.forename: Angela
authors.initials: A
authors.lastname: D'Amico
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, University of Melbourne, 1G Royal Parade, Parkville, Victoria, 3052, Australia. nutt@wehi.edu.au.
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Nutt
authors.affiliation: The Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, Victoria, 3052, Australia. bradley.turner@florey.edu.au.|Centre for Neuroscience, University of Melbourne, 30 Royal Parade, Parkville, Victoria, 3052, Australia. bradley.turner@florey.edu.au.
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Turner
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics* / Q000473:pathology* / Q000601:surgery; D000818:Animals; D015703:Antigens, CD / Q000097:blood; D015496:CD4-Positive T-Lymphocytes / Q000473:pathology*; D002369:Castration; D004195:Disease Models, Animal; D018450:Disease Progression; D005434:Flow Cytometry; D051858:Forkhead Transcription Factors / Q000378:metabolism; D006801:Humans; D008297:Male; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000473:pathology; D013116:Spinal Cord / Q000473:pathology; D013482:Superoxide Dismutase / Q000235:genetics*; D013950:Thymus Gland / Q000473:pathology* / Q000601:surgery
chemical_list: D015703:Antigens, CD; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; C109415:SOD1 G93A protein; D013482:Superoxide Dismutase