Influence of Age on Regeneration in the Peripheral Nervous System

Abstract

Studies on the influence of age on regeneration in the peripheral nervous system are reviewed. Observations in the human are limited, but clinical experience indicates that the efficiency of regeneration is less in later life. The results of experimental studies in animals, although sometimes variable, indicate a decline with age. This may be correlated with reduced axonal transport. At motor nerve terminals, the capacity to produce ultraterminal sprouting secondary to partial denervation is reduced, but not the capacity to eliminate terminal sprouts or reinnervation. Frequency and accuracy of reoccupation of the sites of motor nerve terminals are impaired. Nerve transection is more likely to result in loss of the parent neurons following nerve transection in young than in older animals. Chromatolysis is more intense and does not return to normal as rapidly in old animals, and the degree of retrograde axonal atrophy is less. This suggests a diminished dependence on peripheral growth factor support.

Neural control of aging skeletal muscle

“…Thus, histological examination conducted on isolated sciatic nerves and brachial plexuses revealed axonal degeneration and remyelination which was more pronounced in B6C3F1 and C3H than in C57BL mice (Tabata et al ., 2000). Impairment in nerve regeneration in animals and humans has been correlated with diminished anterograde and retrograde axonal transport (Kerezoudi & Thomas, 1999). Retardation in the slow axonal transport of cytoskeletal elements during maturation and aging has been reported (McQuarrie et al ., 1989).…”

Aging profoundly delays functional recovery from gustatory nerve injury

“…Regeneration is typically delayed and incomplete in elderly patients and in aged animals sustaining neural injury (Kerezoudi and Thomas, 1999, Verdu et al, 2000). The impact of aging on regeneration varies depending on the model system, nerve, and even subpopulation of peripheral neurons injured (Kovacic et al, 2009).…”

Aging and partial body weight support affects gait variability

“…In aging adults, peripheral nerves conduct impulses slower, resulting in decreased sensation, slower reflexes, and even clumsiness [ 29 , 30 ]. This is due to degeneration of myelin sheaths due to decreased blood flow which is accompanied with inability for axonal self-repair [ 29 , 30 ]. Aging is also associated with decreases in glial cells of the central nervous system [ 29 , 30 ].…”