Regeneration of central nervous system: Its concept and strategy

It had been long believed that our adult mammalian central nervous system (CNS) does not regenerate after damage due to injuries or degenerative diseases, as Santiago Ramóny Cajal had indicated long time ago. Today, however, CNS came to be recognized as an important target of so called "regenerative medicine". We have been proposing that regeneration of CNS does include the following three concepts: i) re-growth of the damaged neuronal axons, ii) replenishment of lost neural (or neuronal) cells and iii) recovery of lost neural functions. Here, we would like to emphasize that to recapitulate normal neural development is an essential strategy for CNS-regeneration. In this review, we would like to take Parkinson's disease and spinal cord injury as examples to discuss actual strategy aiming for CNS-regeneration.