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Type: Journal article
Title: Expression of osteopontin in the rat retina: Effects of excitotoxic and ischemic injuries
Author: Chidlow, G.
Wood, J.
Manavis, J.
Osborne, N.
Casson, R.
Citation: Investigative Ophthalmology & Visual Science, 2008; 49(2):762-771
Publisher: Assoc Research Vision Ophthalmology Inc
Issue Date: 2008
ISSN: 0146-0404
Statement of
Glyn Chidlow, John P. M. Wood, Jim Manavis, Neville N. Osborne and Robert J. Casson
Abstract: PURPOSE: The cytokine osteopontin (OPN) has been localized to the retinal ganglion cell layer in the normal rodent retina, prompting the suggestion that it could serve as a useful marker for identifying and quantifying such neurons in models of retinal and optic nerve neurodegeneration. In the present study, we characterized the time course and cellular localization of OPN expression in the rat retina after excitotoxic and ischemic injuries. METHODS: Excitotoxicity and ischemia–reperfusion experiments were performed by using standard techniques. Rats were killed at various time points, and the retinas were removed either for mRNA analysis or to be processed for immunohistochemistry. RESULTS: In the normal retina, double-labeling immunofluorescence indicated that OPN is expressed by the majority of, if not all, RGCs, since OPN was associated with more cells than Brn-3, but was colocalized with Thy1.1. NMDA, kainic acid, and ischemia–reperfusion all caused decreases in the total retinal levels of Thy1 and Brn-3 mRNAs, reflecting injury to RGCs, but a dramatic, short-lived upregulation in OPN mRNA. The source of the increased OPN signal after excitotoxic–ischemic insults is unlikely to be injured RGCs, as no alteration in the intensity of OPN immunostaining in RGCs was apparent. Instead, additional cells, mostly contained within the IPL, were identified as positive for OPN. Double-labeling immunofluorescence showed that ED1 always colocalized with OPN in these cells, indicating their status as activated microglia. CONCLUSIONS: OPN is exclusively expressed by RGCs in the physiological retina, but in response to retinal neurodegeneration is synthesized de novo by endogenous, activated microglia.
Keywords: Retinal Ganglion Cells; Retina; Animals; Rats; Rats, Sprague-Dawley; Retinal Diseases; Reperfusion Injury; Kainic Acid; N-Methylaspartate; Antigens, Thy-1; RNA, Messenger; Excitatory Amino Acid Agonists; Fluorescent Antibody Technique, Indirect; Immunoenzyme Techniques; Reverse Transcriptase Polymerase Chain Reaction; Transcription Factor Brn-3; Osteopontin
Description: Copyright © 2008 by The Association for Research in Vision and Ophthalmology, Inc.
RMID: 0020080124
DOI: 10.1167/iovs.07-0726
Appears in Collections:Opthalmology & Visual Sciences publications

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