title: The optic nerve head is the site of axonal transport disruption, axonal cytoskeleton damage and putative axonal regeneration failure in a rat model of glaucoma.
abstract: The neurodegenerative disease glaucoma is characterised by the progressive death of retinal ganglion cells (RGCs) and structural damage to the optic nerve (ON). New insights have been gained into the pathogenesis of glaucoma through the use of rodent models; however, a coherent picture of the early pathology remains elusive. Here, we use a validated, experimentally induced rat glaucoma model to address fundamental issues relating to the spatio-temporal pattern of RGC injury. The earliest indication of RGC damage was accumulation of proteins, transported by orthograde fast axonal transport within axons in the optic nerve head (ONH), which occurred as soon as 8 h after induction of glaucoma and was maximal by 24 h. Axonal cytoskeletal abnormalities were first observed in the ONH at 24 h. In contrast to the ONH, no axonal cytoskeletal damage was detected in the entire myelinated ON and tract until 3 days, with progressively greater damage at later time points. Likewise, down-regulation of RGC-specific mRNAs, which are sensitive indicators of RGC viability, occurred subsequent to axonal changes at the ONH and later than in retinas subjected to NMDA-induced somatic excitotoxicity. After 1 week, surviving, but injured, RGCs had initiated a regenerative-like response, as delineated by Gap43 immunolabelling, in a response similar to that seen after ON crush. The data presented here provide robust support for the hypothesis that the ONH is the pivotal site of RGC injury following moderate elevation of IOP, with the resulting anterograde degeneration of axons and retrograde injury and death of somas.
authors.affiliation: Ophthalmic Research Laboratories, South Australian Institute of Ophthalmology, Hanson Institute Centre for Neurological Diseases, Adelaide, SA, Australia. glyn.chidlow@health.sa.gov.au
authors.forename: Glyn
authors.initials: G
authors.lastname: Chidlow
authors.forename: Andreas
authors.initials: A
authors.lastname: Ebneter
authors.forename: John P M
authors.initials: JP
authors.lastname: Wood
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Casson
mesh_terms: D016564:Amyloid beta-Protein Precursor / Q000378:metabolism; D000818:Animals; D001370:Axonal Transport / Q000502:physiology*; D002772:Cholera Toxin / Q000378:metabolism; D003599:Cytoskeleton / Q000473:pathology*; D004195:Disease Models, Animal; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000502:physiology; D005901:Glaucoma / Q000150:complications* / Q000473:pathology*; D055551:HSP27 Heat-Shock Proteins / Q000378:metabolism; D004676:Myelin Basic Protein / Q000378:metabolism; D016202:N-Methylaspartate / Q000494:pharmacology; D009416:Nerve Regeneration / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009898:Optic Disk / Q000293:injuries / Q000473:pathology*; D009930:Organic Chemicals / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000473:pathology*; D013997:Time Factors
chemical_list: C417664:Alexa594; D016564:Amyloid beta-Protein Precursor; D018690:Excitatory Amino Acid Agonists; D055551:HSP27 Heat-Shock Proteins; D004676:Myelin Basic Protein; D009419:Nerve Tissue Proteins; D009930:Organic Chemicals; D012333:RNA, Messenger; D016202:N-Methylaspartate; D002772:Cholera Toxin