FIGURE 1.

Summary time line diagram of different events after spinal cord injury, which can be generally divided into acute, subacute and chronic, as indicated in the diagram. Acute time points include intraspinal bleeding, glutamate release, microglial activation cytokine expression such as TNFα and IL-1β. There is also neuron death over the first 1–2 days and vasospasm in spared tissue leading to ischemic damage. OPCs begin proliferating almost immediately upon injury and differentiate into new oligodendrocytes within 3 days. In the subacute time, OPC proliferation and differentiation continue, while early cytokines decline as others such as TGFβ increase. Growth factor expression such as CNTF and FGF-2 continues to rise and oligodendrocyte apoptosis is ongoing in degenerating axon tracts. This is also a time of robust monocyte infiltration and macrophage (mϕ) activation (derived from monocytes and microglia). In the chronic period, new oligodendrocyte and new myelin formation continues, and growth factors remain at levels significantly above naive