Early glial responses after acute elevated intraocular pressure in rats.
OBJECTIVE
To study the responses of glial cells to a short-term elevation in intraocular pressure (IOP) in rats.


METHODS
Adult Sprague-Dawley albino rats, 45 to 55 days old, were given India ink intracamerally. After 7 days, 200 spots of laser burn over 360 degrees were delivered by an Argon laser (620-637 nm; 200 mW; 200 mm; 0.2 seconds) aimed at the ink deposits in the trabecular meshwork. IOP was recorded and eye tissues at 12 hours and 1, 3, 5, 7, or 14 days after laser were examined by immunohistochemistry with antibodies against glial fibrillary acidic protein (GFAP), vimentin, S-100, ED1, and OX42. To evaluate neuronal loss, the number of cells in the retinal ganglion cell layer (RGCL) was counted on flat preparations of retinas at various times after elevation of IOP.


RESULTS
Significant elevation of IOP from 1 to 7 days and loss of cells in the RGCL from 3 days onward were noted after trabecular laser photocoagulation. In the inner retina, there was a gradual and sustained increase in GFAP and S-100 immunoreactivity, but only a transient increase in vimentin immunoreactivity. No remarkable changes in GFAP, vimentin, and S-100 immunoreactivity were noted at the optic nerve head (ONH). ED1- and OX42-labeled cells were noted in the choroidal plexus, the parapapillary region of the optic nerve, and the ONH from 3 days onward, whereas expression in the retina was unremarkable.


CONCLUSIONS
There is differential expression of glial cell markers in the retina and the ONH, with early loss of cells in the RGCL in response to the elevation of IOP. Macroglia such as astrocytes and Müller cells may be involved in the pathophysiology of retinal ganglion cell death or retinal repair, and activated microglial/phagocytic cells may play an important role in modulating the changes in the ONH that occur with the elevation of IOP.
Lam
Tim T
TT
Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Kowloon, Hong Kong.
Kwong
Jacky M K
JM
Tso
Mark O M
MO
D000208:Acute Disease; D000818:Animals; D015703:Antigens, CD; D000954:Antigens, Surface / Q000378:metabolism; D015415:Biomarkers / Q000032:analysis; D015153:Blotting, Western; D002452:Cell Count; D053331:Ectodysplasins; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D007124:Immunoenzyme Techniques; D020287:In Situ Nick-End Labeling; D007429:Intraocular Pressure; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D009457:Neuroglia / Q000378:metabolism / Q000473:pathology*; D009798:Ocular Hypertension / Q000473:pathology*; D009898:Optic Disk / Q000378:metabolism / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000473:pathology*; D009418:S100 Proteins / Q000378:metabolism; D014746:Vimentin / Q000378:metabolism
D015703:Antigens, CD; D000954:Antigens, Surface; D015415:Biomarkers; D053331:Ectodysplasins; D005904:Glial Fibrillary Acidic Protein; D008565:Membrane Proteins; D009418:S100 Proteins; D014746:Vimentin; C042739:antigens, CD200