Hemopexin is synthesized in peripheral nerves but not in central nervous system and accumulates after axotomy

In adult mammals, injured axons regrow over long distances in peripheral nerves but fail to do so in the central nervous system. Analysis of molecular components of tissue environments that allow axonal regrowth revealed a dramatic increase in the level of hemopexin, a heme-transporting protein, in long-term axotomized peripheral nerve. In contrast, hemopexin did not accumulate in lesioned optic nerve. Sciatic nerve and skeletal muscle, but not brain, were shown to be sites of synthesis of hemopexin. Thus, hemopexin expression, which can no longer be considered to be liver-specific, correlates with tissular permissivity for axonal regeneration.