Sciatic nerve conditioning lesion increases macrophage response but it does not promote the regeneration of injured optic nerves.
Injured optic nerves in the matured central nervous system (CNS), alike injured neurons in other CNS regions, fail to regenerate. Interestingly, activation of inflammatory cells (macrophages) following optic lens injury or implantation of peripheral nerve fragments into the vitreous body, have been previously reported to stimulate retinal ganglion cells (RGCs) to regenerate axons across the injury site and into the distal optic nerve. In addition, the beneficial role of macrophage cells has also been demonstrated in the regeneration of lesioned spinal neurons following sciatic nerve injury. However, it is not known whether these locally activated macrophage cells also contribute to the regeneration of remotely injured neurons within the CNS. Adult Sprague Dawley rats received a conditioning sciatic nerve injury followed by an optic nerve crush (ONC). Retrograde and anterograde tracing results revealed that injured optic axons did not regenerate after peripheral dorsal root ganglion (DRG) lesion, as the beneficial effects of this injury extended only locally. However, a greater inflammatory infiltration/activation was found in injury-combined animals compared to controls, although this was not sufficient to trigger a systemic regenerative response. Proximity of cell body response to injury, accompanied by a timely macrophage activation are critical factors for regeneration of injured CNS neurons to occur. Immune cell surveillance into the CNS compartment was enhanced following peripheral nerve injury.


METHODS
nervous system development, regeneration and aging.
Salegio
Ernesto A Aguilar
EA
Department of Human Physiology and Centre for Neuroscience, Flinders University, GPO Box 2100, Adelaide 5001, Australia.
Pollard
Anthony N
AN
Smith
Malcolm
M
Zhou
Xin-Fu
XF
D000818:Animals; D002452:Cell Count; D005260:Female; D005727:Ganglia, Spinal / Q000276:immunology / Q000503:physiopathology*; D007150:Immunohistochemistry; D008262:Macrophage Activation / Q000276:immunology*; D009409:Nerve Crush / Q000379:methods; D009416:Nerve Regeneration; D009900:Optic Nerve / Q000503:physiopathology*; D020221:Optic Nerve Injuries / Q000276:immunology / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000503:physiopathology*; D020426:Sciatic Neuropathy / Q000276:immunology / Q000503:physiopathology*