Restoration of myofiber continuity after transection injury in the rat soleus.

In a shearing type of muscle injury, scar formation prevents restoration of myofiber continuity and the transected myofibers may become permanently divided into two separate myofibers. We have analysed whether the injured myofiber stumps can fuse and continuity of the transected fibers be re-established, if the stumps are surgically closely apposed immediately after injury. 55 rat soleus muscles were transected, after which the epimysium was carefully sutured and the leg was immobilised for seven days. The animals were sacrificed at 2, 5, 7, 10, 14 and 25 days after surgery. All muscles were analysed by light and electron microscopy as well as by immunohistochemistry. Mechanical strength was also measured at day 10 and 25. We observed that suturing reduced the extent of the intervening scar and accelerated healing. More importantly our results indicate that fusion of the stumps and thus restoration of myofiber continuity, is possible after myofiber transection injury.