HISTOMORPHOLOGIC CHANGES IN EXPANDED SKELETAL-MUSCLE IN RATS

Tissue expansion is one of the powerful tools for various reconstructi ve procedures and has proven to provide more available local tissues. However, limited attention has been given to the characteristics of ex panded skeletal muscle. Using a rat model (n = 41), we expanded the ra t gracilis muscle and investigated the histomorphologic changes in the expanded skeletal muscle. By expansion, the gracilis muscle after 3 w eeks increased 50.4 to 58.4 percent in length and 60.5 percent in widt h and decreased 39.0 to 42.0 percent in thickness. Histologically, the expanded muscle demonstrated a normal striation and no signs of infla mmation or necrosis. The cross-sectional areas of muscle fibers indica ted that expanded muscle consisted of predominantly smaller fibers. Va sculature in the expanded muscle demonstrated a longer network of arte ries and a more obvious and developed arterial arcade. The average num ber of sarcomeres in a fiber estimated from the sarcomere length and f iber length was significantly greater (46.5 percent) in the expanded m uscle. These findings suggest that the expansion of skeletal muscle is not a ''stretching'' process of muscle but rather a growth process of the muscle accompanied by an increase in the number of sarcomeres per fiber. Furthermore, the expanded skeletal muscle appears to preserve normal skeletal muscle architecture, vasculature, and function while u ndergoing the ischemic stress of expansion.