Morphological Changes in Disused and Denervated Old Rat Achilles Tendon Fibrils

ABSTRACT

BACKGROUND: This study tried to compare the morphological changes of collagen fibrils between disused and denervated old rat Achilles tendons with those of young rats through quantitative analyses of collagen fibril diameters by transmission electron microscopy (TEM). METHODS: Old (18 months old) and young (6 months old) male Sprague-Dawley rats were divided into 3 groups (n=8 in each group): a control group, a complete denervation group for 4 weeks after the transection of the right sciatic nerve, and a disuse group with hindlimb unweighing by tail suspension. Each explanted Achilles tendon was used for TEM observation. Under TEM, quantitative analyses of collagen fibril diameters were performed. RESULTS: All groups comprising old rats had smaller mean diameters and showed more left-shifted distribution of collagen fibril diameters than young rats. In particular, the disuse group of old rats showed a more prominent mean fibril diameter decrease than young rats. CONCLUSION: Disuse might cause a more prominent decrease of collagen fibril size in the old than the young.