Figure 2.

Cellular response in spinal cord injury. In the healthy spinal cord, intact nerve bundles are surrounded by oligodendrocytes and supported by astrocytes. In the acute phase of injury, severed axons retract toward the soma, while their distal stumps and remaining myelin debris are phagocytosed by microglia and infiltrating macrophages. Damaged oligodendrocytes lead to demyelination of nearby intact axons. In the chronic phase, when the acute inflammatory response has been resolved, reactive astrocytes have proliferated and formed a dense glial scar, which includes trapped immune cells and dense networks of extracellular matrix, which is inhibitory to axons attempting reinnervation to the distal end of the injury. Remyelination may take place to once again envelop naked axons. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/wound