A model for the easy assessment of pressure-dependent damage to retinal ganglion cells using cyan fluorescent protein-expressing transgenic mice.
OBJECTIVE
To establish an animal model for the easy assessment of pressure-dependent damage to retinal ganglion cells (RGCs) using the B6.Cg-TgN(Thy1-CFP)23Jrs/J transgenic mouse strain (CFP mouse), which expresses cyan fluorescent protein (CFP) in RGCs, and to evaluate pressure-dependent RGC death.


METHODS
In 20 CFP mice, right eyes were selected to receive laser-induced ocular hypertension eye and the contralateral eyes remained untouched to serve as controls. Intraocular pressure (IOP) was measured each week in both eyes using the microneedle method up to 8 weeks. Based on the line plot of time (x) and IOP (y) in laser-treated and control eyes, the area surrounded by both lines (∫ΔIOP(y) dx) was calculated as a surrogate value of the pressure insult. At 9 weeks, eyes were enucleated and RGCs expressing CFP were evaluated histologically in retinal whole mounts. The correlation between pressure insult and RGC density was evaluated in the whole eye, three concentric regions, and four quadrants.


RESULTS
Laser-treated eyes showed a significantly higher IOP than control eyes from 1 to 7 weeks (p<0.01). The pressure insult and the RGC density showed a significant negative correlation (y=-0.070x+97.2, r=0.75, p=0.0008). Moreover, the central, middle, and peripheral areas measured from the optic disc and each of four retinal quadrant areas also showed significant negative correlations. Our data demonstrate that each retinal area was almost evenly damaged by IOP elevation.


CONCLUSIONS
Laser photocoagulation causes a chronic elevation of IOP in CFP mice. The use of CFP mice enabled us to easily evaluate pressure-dependent RGC damage. This glaucomatous CFP mouse model may contribute to the molecular analysis of neurodegeneration and the development of neuroprotective drugs for glaucoma with a great increase in experimental efficiency.
Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo, Japan.
Hidekazu
H
Tsuruga
Hiroshi
H
Murata
Makoto
M
Araie
Makoto
M
Aihara
D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D005901:Glaucoma / Q000473:pathology*; D049452:Green Fluorescent Proteins / Q000737:chemistry / Q000235:genetics*; D007150:Immunohistochemistry; D007429:Intraocular Pressure / Q000528:radiation effects; D017075:Laser Coagulation; D007834:Lasers; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009798:Ocular Hypertension / Q000473:pathology*; D012165:Retinal Ganglion Cells / Q000473:pathology / Q000528:radiation effects*; D014065:Tonometry, Ocular
C485182:Cyan Fluorescent Protein; D049452:Green Fluorescent Proteins