Nestin expression reflects formation, revascularization and reinnervation of new myofibers in regenerating rat hind limb skeletal muscles.

This work provides a comprehensive view of expression and distribution patterns of the intermediate filament nestin in rat regenerating skeletal muscles. Regeneration was induced by heterochronous isotransplantation of extensor digitorum longus (EDL) or soleus muscles from 15-day-old rats into the EDL muscle of adult female inbred Lewis rats. Recipients were sacrificed by anesthetic overdose and the host muscles with the graft were excised after 7-, 16-, 21- and 29-day survival, fixed in 10% formalin solution and immunohistochemically stained. In the regenerating skeletal muscle maximal nestin expression was observed in newly formed myoblasts and myotubes and it decreased in the course of skeletal myofiber development. We demonstrate the phenomenon of a peripheral concentration of nestin expression within the differentiating myofibers called 'lateralization', which may represent a mechanism of nestin elimination during the development of skeletal myofibers. Furthermore, nestin has been detected in newly formed endothelial cells of blood vessels growing into the regenerated area and also in peripheral nerves innervating the graft as well as the host muscle. In conclusion, according to our results, nestin represents an ideal marker for skeletal muscle regeneration, as its expression reflects processes of development, revascularization and reinnervation of new myofibers.