title: Rodent anterior ischemic optic neuropathy (rAION) induces regional retinal ganglion cell apoptosis with a unique temporal pattern.
abstract: OBJECTIVE
  Nonarteritic anterior ischemic optic neuropathy (NAION) results in optic nerve damage with retinal ganglion cell (RGC) loss. An NAION model, rodent anterior ischemic optic neuropathy (rAION), was used to determine AION-associated mechanisms of RGC death and associated regional retinal changes.
  
  
  METHODS
  rAION was induced in male Wistar rats, and the retinas analyzed at various times after induction. RGCs were positively identified by both retrograde fluorogold labeling and brain-expressed X-linked protein-1/2 (Bex1/2) immunoreactivity. RGC death was analyzed by fluorescein-tagged annexin-V labeling (FITC-annexin-V), as well as by terminal nucleotide nick-end labeling (TUNEL). Retinal flatmount preparations enabled regional retinal analysis of labeled dying cells. Apoptosis pathway activation was confirmed by Western analysis, with an antibody that recognizes cleaved caspase-3.
  
  
  RESULTS
  Post-rAION, RGCs die by apoptosis over a longer period than previously recognized. Cleaved caspase-3 immunoreactivity was greatest between 11 and 15 days. rAION-induced RGC death occurs regionally, with sparing of large contiguous regions of RGCs.
  
  
  CONCLUSIONS
  rAION results in later RGC death than in traumatic optic nerve damage models. Apoptosis, measured by FITC-annexin, occurs maximally in the second to third week after infarct. Cleaved caspase-3 activation confirms that after rAION, RGCs undergo apoptosis by the caspase activation pathway. The regional pattern in dying RGCs after rAION implies that a measure of retinotopic organization occurs in the rodent optic nerve. The prolonged period from insult to death suggests that the window for successful treatment after ON infarct may be longer than previously recognized.
authors.affiliation: Department of Ophthalmology, University of Maryland School of Medicine, Baltimore, Maryland, USA. slbernst@umaryland.edu
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Slater
authors.forename: Zara
authors.initials: Z
authors.lastname: Mehrabian
authors.forename: Yan
authors.initials: Y
authors.lastname: Guo
authors.forename: Allan
authors.initials: A
authors.lastname: Hunter
authors.forename: Steven L
authors.initials: SL
authors.lastname: Bernstein
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D020287:In Situ Nick-End Labeling; D008297:Male; D018917:Optic Neuropathy, Ischemic / Q000378:metabolism / Q000473:pathology*; D051381:Rats; D017208:Rats, Wistar; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000473:pathology*
chemical_list: D017304:Annexin A5; C477719:Bex2 protein, rat; D002352:Carrier Proteins; D053148:Caspase 3