Assessment of Thy-1 mRNA levels as an index of retinal ganglion cell damage.
OBJECTIVE
Thy-1 is primarily, if not entirely, expressed by the ganglion cells within the retina. This knowledge was used to index ganglion cell death after ischemia and excitotoxicity by studying changes in Thy-1 mRNA levels.


METHODS
Insults to the rat retina were delivered either by elevation of intraocular pressure for 60 minutes or by intravitreal injection of N-methyl-D-aspartate (NMDA). After a defined period, changes in Thy-1 immunoreactivity and mRNA levels of Thy-1 and NR1 (NMDA receptor subunit) were used to index ganglion cell sensitivity to damage. Opsin mRNA levels were used as an internal control because photoreceptors lack NMDA receptors.


RESULTS
Retinal Thy-1 immunoreactivity, associated with the ganglion cell and inner plexiform layers, is reduced by ischemia or intravitreal injections of NMDA in a dose-dependent manner. Using a semi-quantitative polymerase chain reaction (reverse transcription-polymerase chain reaction) methodology, the levels of total retinal Thy-1 and NR1 mRNAs were shown to be dramatically reduced after both transient ischemia and intravitreal injection of NMDA. The effect of NMDA was found to be both time- and dose-dependent. In contrast, no change occurred in the levels of opsin mRNA unless high levels of NMDA (200 nmoles) were administered.


CONCLUSIONS
Ischemia and NMDA-induced excitotoxicity caused retinal ganglion cell destruction, but the photoreceptors were unaffected. Measurement of total retinal Thy-1 mRNA levels provides a useful way of following ganglion cell death especially when combined with immunohistochemical localization of Thy-1. Additionally, the effect on other retinal cell types such as the photoreceptors can be followed in concert using this technique.
Nash
M S
MS
The Nuffield Laboratory of Ophthalmology, University of Oxford, United Kingdom.
Osborne
N N
NN
D000818:Animals; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D007150:Immunohistochemistry; D007267:Injections; D007511:Ischemia / Q000378:metabolism; D007536:Isomerism; D016202:N-Methylaspartate / Q000494:pharmacology; D009498:Neurotoxins / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000378:metabolism* / Q000473:pathology*; D012171:Retinal Vessels; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017299:Rod Opsins / Q000235:genetics; D018800:Thy-1 Antigens / Q000235:genetics* / Q000378:metabolism; D014822:Vitreous Body
D018690:Excitatory Amino Acid Agonists; D009498:Neurotoxins; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; D017299:Rod Opsins; D018800:Thy-1 Antigens; D016202:N-Methylaspartate