sentences:  Once a signal is sent that remyelination is needed, OPC's will first migrate to damaged axon.This process may be signaled or enhanced by microglia or astrocytes at the injured axon site that stimulate migratory OPC pathways From there the cells must differentiate from being progenitors to being pre-oligodendrocytes, then premyelinating oligodendrocytes, and finally mature oligodendrocytes.These oligodendrocytes can then wrap damaged axons with new myelin sheaths.