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Review Article

Exp Neurobiol 2012; 21(3): 83-93

Published online September 30, 2012

© The Korean Society for Brain and Neural Sciences

Sensory Axon Regeneration: A Review from an in vivo Imaging Perspective

Seung Baek Han1,2, Hyukmin Kim1,2, Andrew Skuba1,2, Alan Tessler1, Toby Ferguson1,3 and Young-Jin Son1,2*

1Shriners Hospitals Pediatric Research Center and Center for Neural Repair and Rehabilitation, 2Department of Anatomy and Cell Biology, 3Department of Neurology, Temple University School of Medicine, Philadelphia, PA 19140, USA

Correspondence to: *To whom correspondence should be addressed.
TEL: 1-215-991-8274, 1-215-926-9354, FAX: 1-215-843-9082


Injured primary sensory axons fail to regenerate into the spinal cord, leading to chronic pain and permanent sensory loss. Re-entry is prevented at the dorsal root entry zone (DREZ), the CNS-PNS interface. Why axons stop or turn around at the DREZ has generally been attributed to growth-repellent molecules associated with astrocytes and oligodendrocytes/myelin. The available evidence challenges the contention that these inhibitory molecules are the critical determinant of regeneration failure. Recent imaging studies that directly monitored axons arriving at the DREZ in living animals raise the intriguing possibility that axons stop primarily because they are stabilized by forming presynaptic terminals on non-neuronal cells that are neither astrocytes nor oligodendrocytes. These observations revitalized the idea raised many years ago but virtually forgotten, that axons stop by forming synapses at the DREZ.

Keywords: dorsal root entry zone, sensory nerve regeneration, NG2 glia, oligodendrocyte precursor cells, in vivo imaging, astrocytes