Axotomized motoneurons can be rescued from cell death by peripheral nerve grafts: the effect of donor age.

Injury to neonatal nerves, unlike adult nerves, results in poor regeneration and extensive motoneuron death. We examined whether exposure to a more mature nerve environment could rescue axotomized motoneurons following neonatal injury. The sciatic nerve in 1 hindlimb of 3-day-old (P3) rats was transected and the cut end sutured to a nerve graft taken from donor rats, which ranged between P3 and P21. The extent of motoneuron survival and axon regeneration was established 7 days later. Since integrins play an important role in regeneration, we also examined the effect of manipulating integrin binding in nerve grafts. Following axotomy at P3 and implantation of nerve grafts from 3-day-old rats, approximately 38% of motoneurons survived. In contrast, grafts from rats aged 5 days and older resulted in an improvement in regeneration, and over 70% of motoneurons survived. This survival-promoting effect of P5 grafts was prevented by blocking beta1-integrins. In contrast, increasing beta1-integrin levels in grafts from P3 rats dramatically increased motoneuron survival. Thus, following neonatal nerve injury, exposure to a more mature nerve environment significantly increases motoneuron survival, an effect that is dependent upon beta1-integrin signaling. Therefore, pharmacological upregulation of beta1-integrins may significantly improve the outcome of neonatal nerve injuries.