De-novo myelination of grafted neural progenitor cells in the adult CNS

We previously reported that neural progenitor cells (NPCs) grafted into sites of spinal cord injury (SCI) exhibit extensive axonal outgrowth and formation of new synaptic connections with host neurons, forming novel functional neural relays across lesion sites. In the present study we performed a detailed characterization of axons emerging from NPC grafts. Rat embryonic spinal cord-derived NPCsderived NPCs, constitutively expressing EGFP, were grafted into adult C5 spinal cord hemisections. Three months after grafting, we examined graft-derived axonal diameter and myelination using transmission electron microscopy. In total, 104 graft-derived axons were characterized. Axon diameter ranged from 0.15 to 1.70 µm, and 23% of graft-derived axons were myelinated. The average diameter of myelinated axons (0.72 ± 0.3µm) was significantly larger than that of non-myelinated axons (0.61 ± 0.2µm, p<0.05). Notably, the Gratio of myelinated graft-derived axons was comparable to that of developmentally myelinated axons (0.77 ± 0.05 µm). 67 % of graft-derived axons were in direct contact with host myelin, suggesting that myelin does not repel axons extending from implants of early stage neurons.

Society for Neuroscience Chicago SCI Animal Models and Human Studies Trauma
Acknowledgements: Veterans Administration and the Adelson Medical Research Foundation Disclosures: M.A. Hunt: None. P. Lu: None. Mark.H. Tuszynski: None.
Authors: *M. A. HUNT1, P. LU2,3, Mark. H. TUSZYNSKI2,3; 1Biomed. Sci., 2Neurosci., Univ. of California San Diego, LA Jolla, CA; 3Veterans Affairs Med. Ctr., San Diego, CA

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