Regenerative capacity of minced muscle tissue in newborn and adult guinea pigs.

Our data showed that the regenerative capacity of skeletal muscle in newborn guinea pigs was less than in adults. In newborn guinea pigs the active regeneration of muscle tissue was only observed during the 1st week after mincing of gastrocnemius muscle. The 14-day grafts were characterized by having smaller muscle fibers and greater amounts of interstitial connective tissue. Furthermore, the active growth of connective tissue was more pronounced. The grafts did not recover contractility. In 60 day grafts the ectopic formation of 2-3 bone-cartilage nodules was observed. In adult guinea pig grafts the quantity of muscle tissue was twice as great as in newborns. Muscle tissue was formed throughout the graft, but no bone-cartilage nodules were present. All 60 day grafts contracted when the tibial nerve was stimulated, but this contractility was very weak. However, the reestablishment of neuromuscular junctions had occurred. The age characteristics of skeletal muscle regeneration were the same both in the term guinea pig and in the rat.