Abstract
The fate of injured motor neurons could be determined by the balance of the protection and death signals, which expressed in the injured motor neuron. However recent studies implied the significances of surrounding non-neuronal cells for the protection of motor neurons in degenerative diseases and nerve injury. In periphery Schwann cell, macrophage and endoneurial fibroblast play crucial roles for the proper nerve regeneration. Schwann cell promotes infiltration of macrophage to remove debris of degenerated myelin and provides a scaffold and several growth factors for axon to elongate. The macrophage phagocytoses myelin debris and stocks lipids, which is re-used for re-myelination by Schwann cell. The fibroblast controls the localization of axon and Schwann cells during nerve regeneration. For those cellular functions several mediators among those cells are expressed. In CNS microglia and astrocytes would be the major players for the protection of motor neurons after injury. After nerve injury the activated microglia adhered to the injured motor neurons for a while and then the astrocyte took over, whereas in the dying motor neurons the initial behavior of the microglia was not observed. Glial behavior in CNS may be associated with the fate of injured motor neurons.
