[An experimental study on recovery of lacerated skeletal muscle: correlation between separation gap and the potential for recovery].

Skeletal muscle has a potential for recovery with muscle tissue when the lacerated stumps are maintained in contact. However, when there is no contact, this potential for recovery is unknown. Here we report our studies on the correlation between the recovery and the separation distance between the stumps in partially lacerated muscles in Wistar rat. The gastrocnemius muscle was subjected to a partial wedge-shaped laceration which allowed the surrounding tissue to hold a constant separation distance between the stumps throughout the duration of the study. Groups each of 7 rats were examined at 1, 2, and at 4 days, and at 1, 2, 2, and at 6 weeks after the laceration was performed. In each group, 5 rats underwent histological and immunohistological examinations, while the other 2 underwent electronmicroscopic examination. The muscle stumps initially degenerated, and then began to regenerate at 4 days after the laceration. During this period, local basement membranes remained intact allowing regeneration of muscle fibers. However, the absence of basement membrane between the stumps led to a random regeneration pattern of myotubes growing into the granulation tissue in the wedge-shaped gap. The electronmicroscopic findings showed that these growing myotubes had no basement membrane. The maximum growth of these myotubes was found to be 1.20 +/- 0.31 mm reached at 3 weeks after the laceration, suggesting that the maximum gap was approximately 1.0 mm across which there is a potential for recovery through regeneration.