Melanopsin-expressing retinal ganglion cells are more injury-resistant in a chronic ocular hypertension model.
OBJECTIVE
To investigate the survival of melanopsin-expressing retinal ganglion cells (mRGCs) after the induction of chronic ocular hypertension.


METHODS
Intraocular pressure (IOP) was elevated in adult Sprague-Dawley rats using an argon laser to photocoagulate the episcleral and limbal veins. IOP was measured with a calibrated tonometer and monitored for a period. Seven days before the animals were killed, a piece of sterile foam soaked with gold fluorescent dye was placed onto the superior colliculus (SC) to label the SC-projecting retinal ganglion cells (scRGCs) retrogradely. mRGCs were visualized by free floating immunohistochemistry on whole-mounted retinas. The number of surviving scRGCs and mRGCs were counted on flatmounted retinas. The branching pattern of dendrites and soma size of mRGCs were examined.


RESULTS
An approximately 1.7-fold increase of IOP and a significant loss of scRGCs were found in experimental eyes after laser photocoagulation. However, no significant cell loss or morphologic changes on mRGCs and their dendrites after the induction of chronic ocular hypertension are noticed over a 12-week period.


CONCLUSIONS
Although the degeneration of retinal ganglion cells (RGCs) is a major concern in glaucomatous damage, the findings show that mRGCs are less susceptible to death after the induction of chronic ocular hypertension. This result indicates that mRGCs carry some unique properties that are different from those of other subpopulations of RGCs. The immunohistochemistry approach can be used to distinguish easily these mRGCs from other subtypes. This method provides a useful tool to investigate their injury-resistant properties that are informative for the development of effective neuroprotective treatment for glaucoma.
Li
Rachel S
RS
Department of Anatomy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, China.
Chen
Bai-Yu
BY
Tay
David K
DK
Chan
Henry H L
HH
Pu
Ming-Liang
ML
So
Kwok-Fai
KF
D000818:Animals; D002452:Cell Count; D002470:Cell Survival / Q000502:physiology; D002908:Chronic Disease; D004195:Disease Models, Animal; D005260:Female; D007429:Intraocular Pressure; D009798:Ocular Hypertension / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000166:cytology* / Q000378:metabolism*; D017299:Rod Opsins / Q000378:metabolism*; D000099210:Melanopsin
D017299:Rod Opsins; D000099210:Melanopsin