Regeneration of ganglion cell axons into a peripheral nerve graft alters retinal expression of glial markers and decreases vulnerability to re-axotomy.
OBJECTIVE
To compare the effect of cutting the optic nerve versus replacing the cut optic nerve with a peripheral nerve (PN) graft on retinal glial markers, and to determine whether the PN graft can stabilize regenerating retinal ganglion cells (RGCs), thus preventing their death following re-axotomy.


METHODS
Retinas harvested after ganglion cell regeneration into a sciatic nerve graft were compared to untreated control retinas and retinas obtained following optic nerve axotomy. Glial-specific proteins such as glial fibrillary acidic protein (GFAP), Bcl-2 and complement-3 receptor (Ox-42) were examined using immunohistochemistry. Ganglion cells that survived the second axotomy were quantified on retinal flat mounts by retrograde labeling from the graft.


RESULTS
GFAP expression in astrocytes and Muller cells was elevated in axotomized retinas when compared to controls, and an additional up-regulation in Muller cells was found in retinas following ganglion cell regeneration. Increased GFAP expression in retinas containing regenerated neurons was accompanied by increased Bcl-2 expression with latter being confined to Muller cells. Moreover, re-axotomy of the regenerated axons within the graft did not result in significant retrograde degeneration of RGCs within 28 days.


CONCLUSIONS
The data suggest that the graft stabilizes the regenerating RGCs to an extent reminiscent of peripheral neurons, a process that may involve the interaction between neuronal and glial elements.
Schuetz
Erik
E
Department of Experimental Ophthalmology, University Eye Hospital Münster, School of Medicine, Domagkstr 15, 48149 Münster, Germany.
Rose
Karin
K
Thanos
Solon
S
D000818:Animals; D001369:Axons / Q000502:physiology*; D019771:Axotomy / Q000379:methods; D001562:Benzimidazoles / Q000493:pharmacokinetics; D002452:Cell Count; D002470:Cell Survival; D005260:Female; D005786:Gene Expression Regulation; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D009410:Nerve Degeneration / Q000378:metabolism / Q000503:physiopathology; D009416:Nerve Regeneration / Q000502:physiology*; D009900:Optic Nerve / Q000033:anatomy & histology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000166:cytology / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000502:physiology*; D012584:Sciatic Nerve / Q000637:transplantation*; D013997:Time Factors
D001562:Benzimidazoles; D005904:Glial Fibrillary Acidic Protein; C447680:hoechst 32258