A temporal study of axonal degeneration and glial scar formation following a standardized crush injury of the optic nerve in the adult rat.

PURPOSE: In this methodological study, we describe a standardized optic nerve injury model in adult rats. The temporal pattern of the glial response is mapped in relation to axonal regeneration and degeneration.

METHODS: A standardized optic nerve crush injury was made in adult rats, using a fine pair of forceps with a preset pressure of 0.6 N during 10 seconds.

RESULTS: This crush injury resulted in a pronounced astroglial and microglial proliferation 2-7 dpi. Degenerative axons distal to the lesion presented a gradual decrease in neurofilament immunoreactivity. In contrast, Fluoro-Jade staining was gradually increased in these degenerative axons from 2-7 dpi. Regeneration was observed proximal to the lesion in sprouts double labeled with the tracer Fluoro-Gold and anti-GAP43.

CONCLUSION: The standardized optic nerve crush injury model used in the present study resulted in a reproducible degenerative pattern including a pronounced astroglial and microglial proliferation. The gradual decrease in Neurofilament immunoreactivity in degenerative axons, and a gradual increase in Fluoro-Jade staining was paralleled with a spontaneous regeneration proximal to the lesion, shown with tracing and GAP43-immunoreactivity. The combination of these markers and this experimental setup thus allows analysis of the entire degenerative/regenerative process in a standardized CNS axotomy model.