Longitudinal profile of retinal ganglion cell damage assessed with blue-light confocal scanning laser ophthalmoscopy after ischaemic reperfusion injury.
OBJECTIVE
To longitudinally investigate retinal ganglion cell (RGC) expression of Thy-1, a cell-surface glycoprotein specifically expressed in RGCs, with a blue-light confocal scanning laser ophthalmoscope, following retinal ischaemia induced by acute elevation of intraocular pressure.


METHODS
A blue-light confocal scanning laser ophthalmoscope (bCSLO, 460 nm excitation and 490 nm detection) was used to image Thy1-cyan fluorescent protein (CFP) mice before and weekly for 4 weeks after transiently elevating the intraocular pressure to 115 mm Hg for 45 min (n = 4) or 90 min (n = 5) to induce ischaemic injury. Corresponding retinal areas before and after the intraocular pressure (IOP) elevation, during the period of ischaemic reperfusion, were compared, and the fluorescent spots (Thy-1 expressing RGCs) were counted. The longitudinal profile of CFP-expressing RGCs was modelled with a linear regression equation. The spatial distribution of RGC damage was analysed in the superior, nasal, inferior and temporal quadrants of the retina.


RESULTS
No significant change was found at 4 weeks after 45 min of IOP elevation (n = 4, p = 0.465). The average RGC densities before and 4 weeks after IOP elevation were 1660 (SD 242) cells/mm2 and 1624 (209) cells/mm2, respectively. However, significant loss of CFP-expressing RGCs was detected at 1 week following 90 min of IOP elevation (n = 5, p<0.001). After this initial RGC loss, no significant change was detected subsequently. The proportion of RGC fluorescence remaining was variable and ranged from 14.5% to 79.5% at 4 weeks after the IOP elevation. The average RGC densities before and 4 weeks after IOP elevation were 1443 (162) cells/mm2 and 680 (385) cells/mm2, respectively. Diffuse loss of fluorescent RGCs was observed in the spatial distribution analysis.


CONCLUSIONS
The longitudinal profile of Thy-1 expressing RGC fluorescence loss after ischaemic injury is non-progressive and unrelated to the duration of reperfusion.
Leung
C K S
CK
Hamilton Glaucoma Center, University of California, San Diego, La Jolla, CA 92093-0946, USA.
Lindsey
J D
JD
Chen
L
L
Liu
Q
Q
Weinreb
R N
RN
D000818:Animals; D018450:Disease Progression; D008137:Longitudinal Studies; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal / Q000379:methods; D008856:Microscopy, Fluorescence; D009887:Ophthalmoscopy / Q000379:methods; D020221:Optic Nerve Injuries / Q000150:complications / Q000473:pathology*; D015427:Reperfusion Injury / Q000150:complications / Q000473:pathology*; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000473:pathology*; D018800:Thy-1 Antigens / Q000032:analysis*
D018800:Thy-1 Antigens