Tumor necrosis factor facilitates regeneration of injured central nervous system axons

The results of this study attribute to tumor necrosis factor (TNF) a role in regeneration of injured mammalian central nervous system (CNS) axons which grow into their own degenerating environment. This is the first time that a specific factor involved in axonal regeneration has been identified. The axonal environment is occupied mostly by glia cells, i.e., astrocytes and oligodendrocytes. Previous studies have shown that mature oligodendrocytes are inhibitory to axonal growth. Therefore, it seemed likely that application of a factor such as TNF, which has been shown to be cytotoxic to oligodendrocytes, would contribute to the creation of permissive conditions for axonal regeneration. In the present work, injured adult rabbit optic nerves were treated with human recombinant TNF (rhTNF). As a result, abundant newly growing axons (circa 9000, about 4% of the total estimated number of axons in an intact adult rabbit) were observed traversing the site of injury.