Microglial responses around intrinsic CNS neurons are correlated with axonal regeneration.
BACKGROUND
Microglia/macrophages and lymphocytes (T-cells) accumulate around motor and primary sensory neurons that are regenerating axons but there is little or no microglial activation or T-cell accumulation around axotomised intrinsic CNS neurons, which do not normally regenerate axons. We aimed to establish whether there was an inflammatory response around the perikarya of CNS neurons that were induced to regenerate axons through a peripheral nerve graft.


RESULTS
When neurons of the thalamic reticular nucleus (TRN) and red nucleus were induced to regenerate axons along peripheral nerve grafts, a marked microglial response was found around their cell bodies, including the partial enwrapping of some regenerating neurons. T-cells were found amongst regenerating TRN neurons but not rubrospinal neurons. Axotomy alone or insertion of freeze-killed nerve grafts did not induce a similar perineuronal inflammation. Nerve grafts in the corticospinal tracts did not induce axonal regeneration or a microglial or T-cell response in the motor cortex.


CONCLUSIONS
These results strengthen the evidence that perineuronal microglial accumulation (but not T-cell accumulation) is involved in axonal regeneration by intrinsic CNS and other neurons.
Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK. p.anderson@ucl.ac.uk
Bahman N
BN
Shokouhi
Bernadette Z Y
BZ
Wong
Samir
S
Siddiqui
A Robert
AR
Lieberman
Gregor
G
Campbell
Koujiro
K
Tohyama
Patrick N
PN
Anderson
D000818:Animals; D001369:Axons / Q000502:physiology*; D019771:Axotomy; D016380:Brain Tissue Transplantation; D016923:Cell Death; D005154:Facial Nerve / Q000502:physiology / Q000601:surgery; D005260:Female; D005615:Freezing; D008297:Male; D017628:Microglia / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology; D009416:Nerve Regeneration / Q000502:physiology*; D009474:Neurons / Q000502:physiology* / Q000637:transplantation; D010525:Peripheral Nerves / Q000601:surgery; D011712:Pyramidal Tracts / Q000502:physiology / Q000601:surgery; D051381:Rats; D017207:Rats, Sprague-Dawley; D012012:Red Nucleus / Q000502:physiology* / Q000601:surgery; D013601:T-Lymphocytes / Q000502:physiology; D013787:Thalamic Nuclei / Q000502:physiology* / Q000601:surgery