Upregulated Retinal Neurofilament Expression in Experimental Optic Neuritis.

Area of Science:

• Neuroscience
• Ophthalmology
• Immunology

Background:

• Transient thickening of the macular retinal nerve fibre layer (RNFL) is observed in optic neuritis (ON) but its mechanism is unclear.
• Axonal diameter is linked to neurofilament (Nf) protein content, yet retinal Nf concentrations in ON are not well-documented.

Purpose of the Study:

• To investigate the concentration of neurofilament (Nf) proteins in the retina during experimental autoimmune encephalomyelitis (EAE)-induced optic neuritis (ON).
• To explore the relationship between Nf expression and RNFL changes in ON.

Main Methods:

• Utilized the myelin-oligodendrocyte-glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) rat model.
• Collected retinal tissues from rats with confirmed ON, rats without ON, and control animals 27 days post-immunization.
• Quantified retinal tissue Nf concentrations per total protein using spectrophotometry.

Main Results:

• Retinal tissue Nf concentrations were significantly higher in MOG-EAE rats with ON compared to MOG-EAE rats without ON and control rats.
• Median Nf concentration in rats with ON was 4.29 μg/mg, versus 1.14 μg/mg in MOG-EAE rats without ON and 0.93 μg/mg in controls.
• These results indicate elevated Nf levels preceding RNFL atrophy.

Conclusions:

• The study suggests that increased neurofilament (Nf) expression in retinal ganglion cells precedes RNFL atrophy in ON.
• This up-regulation of Nf plausibly explains the transient axonal diameter increase and RNFL thickening observed in optic neuritis.
• The findings provide a molecular explanation for early OCT observations in ON.