This is fascinating. Another article about olfactory system and regeneration:

Review

Spinal Cord (2006) 44, 406–413. doi:10.1038/sj.sc.3101948; published online 6 June 2006
Repair of spinal cord injury: ripples of an incoming tide, or how I spent my first 40 years in research

An Inaugural Lecture given by Geoffrey Raisman, DM, DPhil, FRS on appointment to the Chair of Neural Regeneration and the inception of the Spinal Repair Unit at the Institute of Neurology, University College London

G Raisman1

Abstract

Abstract of the inaugural lecture on appointment to the Chair of Neural Regeneration at University College London January 2006. Record of personal research. Electron microscopic observations led to the concept that the adult brain is capable of forming new synapses after injury, and the search for methods to repair brain and spinal cord injuries. It is proposed that the failure of regeneration after central axotomy is due to protective glial scarring leading to the loss of the aligned astrocytic pathways needed for axon elongation.

Taking advantage of the discovery that the adult olfactory system is capable of continual renewal, cultured olfactory ensheathing cells were transplanted into lesions of the spinal cord and spinal roots.

The transplants re-opened scarred glial pathways, allowed the regeneration of severed nerve fibres, and the restoration of various functions, including paw reaching, climbing, and supraspinal respiratory impulses to the phrenic nerve.