Optic Nerve Head Myelin-Related Protein, GFAP, and Iba1 Alterations in Non-Human Primates With Early to Moderate Experimental Glaucoma

PURPOSE. The purpose of this study was to test if optic nerve head (ONH) myelin basic protein (MBP), 2',3' -cyclic nucleotide 3'-phosphodiesterase (CNPase), glial fibrillary acidic protein (GFAP), and ionized calcium binding adaptor molecule 1 (Iba1) proteins are altered in non-human primate (NHP) early/moderate experimental glaucoma (EG). METHODS. Following paraformaldehyde perfusion, control and EG eye ONH tissues from four NHPs were paraffin embedded and serially (5 mu m) vertically sectioned. AntiMBP, CNPase, GFAP, Iba1, and nuclear dye-stained sections were imaged using subsaturating light intensities. Whole-section images were segmented creating anatomically consistent laminar (L) and retrolaminar (RL) regions/sub-regions. EG versus control eye intensity/pixel-cluster density data within L and two RL regions (RL1 [1-250 mu m]/RL2 [251-500 mu m] from L) were compared using random effects models within the statistical program R. RESULTS. EG eye retinal nerve fiber loss ranged from 0% to 20%. EG eyes' MBP and CNPase intensity were decreased within the RL1 (MBP = 31.4%, P < 0.001; CNPase =62.3%, P < 0.001) and RL2 (MBP = 19.6%, P < 0.001; CNPase = 56.1%, P = 0.0004) regions. EG eye GFAP intensity was decreased in the L (41.6%, P < 0.001) and RL regions (26.7% for RL1, and 28.4% for RL2, both P < 0.001). Iba1+ and NucBlue pixel-cluster density were increased in the laminar (28.2%, P = 0.03 and 16.6%, P = 0.008) and both RL regions (RL1 = 37.3%, P = 0.01 and 23.7%, P = 0.0002; RL2 = 53.7%, P = 0.002 and 33.2%, P < 0.001). CONCLUSIONS. Retrolaminar myelin disruption occurs early in NHP EG and may be accompanied by laminar and retrolaminar decreases in astrocyte process labeling and increases in microglial/ macrophage density. The mechanistic and therapeutic implications of these findings warrant further study.

Automated summary

This study aimed to investigate the alterations of several proteins in the optic nerve head in non-human primate early/moderate experimental glaucoma. The findings suggest that early retrolaminar myelin disruption, accompanied by decreases in astrocyte process labeling and increases in microglial/macrophage density, occurs in this glaucoma model.