The observation of transplanted embryonic motoneurons in the denervated muscles of adult rats.

OBJECTIVE: To observe the survival of embryonic motoneurons after they were transplanted into the denervated skeletal muscles and to find a new method to retard the atrophy of denervated muscles. METHODS: Dissociated embryonic motoneurons prelabled with 5-bromo-2'-deoxyuridine (Brdur) on the embryonic days 12 were injected into the denervated gastrocnemius muscles of adult rats. Then gastrocnemius muscles were processed with Nissl staining, acetylcholinesterase staining and Brdur immunocytochemical staining to show the implanted motoneurons at 9 and 22 weeks post-transplantation. Myofibrillar ATPase staining was used to show the morphology of muscle fibers. The rats in experimental group were implanted with embryonic motoneurons in the predenervation muscles, while the rats in control group were injected with just culture medium without motoneurons. RESULTS: Embryonic motoneurons survived, developed and extended long axons to form neuromuscular junctions with the denervated muscles. The differentiation of muscle fibers and fiber type grouping occurred among bigger fibers in experimental group. The transverse area was smaller and there was no apparent fiber type grouping in control group. CONCLUSIONS: Embryonic motoneurons can survive, develop and reinnervate denervated muscles after being transplanted into denervated muscles. It is worth further investigating on ameliorating the atrophy of denervated muscle.