Androgen Regulates Neuritin mRNA Levels in an In Vivo Model of Steroid-Enhanced Peripheral Nerve Regeneration

ABSTRACT Following crush injury to the facial nerve in Syrian hamsters, treatment with androgens enhances axonal regeneration rates and decreases time to recovery. It has been demonstrated in vitro that the ability of androgen to enhance neurite outgrowth in motoneurons is dependent on neuritin–a protein that is involved in the re-establisment of neuronal connectivity following traumatic damage to the central nervous system and that is under the control of several neurotrophic and neuroregenerative factors–and we have hypothesized that neuritin is a mediator of the ability of androgen to increase peripheral nerve regeneration rates in vivo. Testosterone treatment of facial nerve-axotomized hamsters resulted in a ∼300% increase in neuritin mRNA levels 2 days post-injury. Simultaneous treatment with flutamide, an androgen receptor blocker that is known to prevent androgen enhancement of nerve regeneration, abolished the ability of testosterone to upregulate neuritin mRNA levels. In a corroborative in vitro ...