Abstract
Purpose :
We have previously reported optic nerve head (ONH) lamina cribrosa deformation, thickening and insertion migration in NHP early EG. Here we test the hypothesis that retrolaminar (RL) myelin alterations accompanied by alterations of astrocyte and microglial markers are also present in NHP early EG.
Methods :
Four unilateral early EG NHPs were sacrificed by 4% paraformaldehyde perfusion fixation. For each NHP, EG and Control (C) eye ONH tissues were trephined (10 mm circular blade), and cut vertically, embedded in paraffin and serially sectioned 5µm sections (Fig 1). For-each immunohistochemical (IHC) marker, n=4 near-adjacent ONH sections were deparaffinized, stained with the primary antibody [myelin basic protein (MBP), 2',3'-Cyclic-nucleotide 3'-phosphodiesterase, (CNPase), glial fibrillary acidic protein, (GFAP), or ionized calcium binding adaptor molecule 1, (Iba1)] incubated with fluorescent secondary antibodies and cover slipped using a NucBlue mountant. Whole section images were acquired and ONH anatomic landmarks were manually segmented, allowing signal intensity per unit area or cell density to be assessed in consistent RL anatomic regions. Animal specific (AS) and experiment wide (EW) EG versus C eye signal differences were analyzed using a series of linear mixed effects models.
Results :
CNPase and MBP decreased significantly in EG versus C eyes (EW, (p<0.001)) in both RL regions and in at least 1 RL region of 3 of 4 NHPs individually (AS, p<0.02) (Table 1). GFAP decreased and NucBlue and Iba1(+) cell counts increased in both retrolaminar regions (EW, p<0.01), and in 3 or 4 NHPs individually for (GFAP and NucBlue only). CNPase, GFAP and MBP expression decreased (EW, P<0.05) in the peripheral versus central (Fig 1) RL sub-regions in C eyes. EG vs control eye increases in Iba1(+) expression were greater peripherally than centrally (p=0.023).
Conclusions :
Decreased myelin–related protein expression within the immediate retrolaminar ONH tissues in NHP early EG is accompanied by decreased GFAP expression and increased NucBlue and Iba1(+) cell counts. Retrolaminar myelin homeostasis may be a neuroprotective target for enhancing axonal survival in glaucoma whether its disruption primarily contributes to axonal injury or is secondary to its occurrence.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.