Effect of Age and Neurovascular Grafting on the Mechanical Function of Medial Gastrocnemius Muscles of Fischer 344 Rats

Both aging and grafting of whole skeletal muscle are associated with decreased specific force and resistance to fatigue. This study tested the hypothesis that the recovery of mechanical function in nerve-repair skeletal muscle grafts in senescent rats would be impaired compared with recovery in similar grafts in younger animals. Following a 120-day recovery period, the contractile properties of grafted medial gastrocnemius (MGN) muscles from young-mature (6 months), middle-aged (12 months), and senescent (24 months) Fischer 344 rats were measured and compared to age-matched controls. Although there was full recovery of muscle mass, grafting and aging alone both were associated with diminished maximum twitch and tetanic tension, maximum power, and maximum sustained power. In addition, the deleterious effect of grafting on maximum tetanic tension, specific force, and sustained power of MGN muscle was significantly greater in old animals. These findings suggest that aging limits full recovery of the quality of muscle contractions from the nerve-repair grafting procedure, possibly due to an age-related impairment of reinnervation.