An alteration in the lateral geniculate nucleus of experimental glaucoma monkeys: in vivo positron emission tomography imaging of glial activation.
We examined lateral geniculate nucleus (LGN) degeneration as an indicator for possible diagnosis of glaucoma in experimental glaucoma monkeys using positron emission tomography (PET). Chronic intraocular pressure (IOP) elevation was induced by laser trabeculoplasty in the left eyes of 5 cynomolgus monkeys. Glial cell activation was detected by PET imaging with [(11)C]PK11195, a PET ligand for peripheral-type benzodiazepine receptor (PBR), before and at 4 weeks after laser treatment (moderate glaucoma stage). At mild, moderate, and advanced experimental glaucoma stages (classified by histological changes based on the extent of axonal loss), brains were stained with cresyl violet, or antibodies against PBR, Iba-1 (a microglial marker), and GFAP (an activated astrocyte marker). In laser-treated eyes, IOP was persistently elevated throughout all observation periods. PET imaging showed increased [(11)C]PK11195 binding potential in the bilateral LGN at 4 weeks after laser treatment; the increase in the ipsilateral LGN was statistically significant (P<0.05, n = 4). Immunostaining showed bilateral activations of microglia and astrocytes in LGN layers receiving input from the laser-treated eye. PBR-positive cells were observed in LGN layers receiving input from laser-treated eye at all experimental glaucoma stages including the mild glaucoma stage and their localization coincided with Iba-1 positive microglia and GFAP-positive astrocytes. These data suggest that glial activation occurs in the LGN at a mild glaucoma stage, and that the LGN degeneration could be detected by a PET imaging with [(11)C]PK11195 during the moderate experimental glaucoma stage after unilateral ocular hypertension. Therefore, activated glial markers such as PBR in the LGN may be useful in noninvasive molecular imaging for diagnosis of glaucoma.
Department of Biofunctional Evaluation, Gifu Pharmaceutical University, Gifu, Japan.
Masamitsu
M
Shimazawa
Yasushi
Y
Ito
Yuta
Y
Inokuchi
Hajime
H
Yamanaka
Tomohiro
T
Nakanishi
Takuya
T
Hayashi
Bin
B
Ji
Makoto
M
Higuchi
Tetsuya
T
Suhara
Kazuyuki
K
Imamura
Makoto
M
Araie
Yasuyoshi
Y
Watanabe
Hirotaka
H
Onoe
Hideaki
H
Hara
D000818:Animals; D004195:Disease Models, Animal; D005829:Geniculate Bodies / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D005901:Glaucoma / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D053685:Laser Therapy; D008252:Macaca fascicularis; D009410:Nerve Degeneration / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D009457:Neuroglia / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000502:physiology; D009798:Ocular Hypertension / Q000000981:diagnostic imaging / Q000473:pathology; D009901:Optic Nerve Diseases / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D049268:Positron-Emission Tomography; D016896:Treatment Outcome