•There are number of factors that stop or hinder CNS regeneration:
•CNS injuries involve neurons’ cell bodies long with axons and the loss of neurons is irreversible.
•Oligodendrocytes are the cells that create myelin sheath in CNS. But they die when the axon is degenerated and so, the sheath is lost. Without the sheath, the axons form a non-functional messy ball of nerve fibres when they try to regrow.
•Astrocytes, the main supporting cells of the CNS start to form a scar at the injury site. This astroglial scar initially helps strengthen the injured tissue but later it physically bars the axons from growing across the injury site.
•When the axons degenerate after injury, they leave debris behind, which is not cleared efficiently in CNS. This left over debris also slows down re-growing axons.