Alterations in the Local Axonal Environment Influence Target Reinnervation and Neuronal Survival after Postnatal Axotomy
UNIFORMED SERVICES UNIV OF THE HEALTH SCIENCES BETHESDA MD DEPT OF ANATOMY AND CELL BIOLOGY
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Following peripheral nerve injury in adult animals, Schwann cells SC proliferate and provide guidance in the local axonal environment by generating the infrastructure along which regenerating nerves grow. A portion of the SC in the peripheral nerves of postnatal rats undergo apoptosis during normal development, and this apoptosis is augmented at the injury site and the neuromuscular junction NMJ following sciatic nerve axotomy. The current work determined that SC apoptosis occurs in the distal but not the proximal nerve segment after postnatal transection of the hypoglossal nerve, suggesting that SC apoptosis is a general, age-related and location-specific response to peripheral nerve injury. Apoptotic SC were found in two strategic locations for guiding axonal outgrowth during peripheral nerve regeneration a capping the transected end adjacent to the injury site and b just proximal to the bifurcation of the nerve into medial and lateral branches. Electron microscopic EM analysis identified apoptotic and mitotic SC in close proximity within the distal nerve segment, supporting apoptosis and mitosis as closely related phenomena.
- Medicine and Medical Research