A Morphological Study On Forelimb Regeneration Of A Salamander-Cynops Cynaurus

[Objectives]To establish an ideal model for regenerative biological study and observe the forelimb epimorphosis of a salamander-Cynops cynaurus,as well as to learn the cellular dedifferentiation during regenerative process through morphological and histological investigation.[Methods]The right forelimbs of fifteen wild typed adult male and female Cynops-cynaurus were amputated around the elbows under general anesthesia.The samples were obtained and observed morphologically and histologically at different intervals of 3,7, 12,15,20,30,45 days postoperatively.[Results]All experimental animals survived and limbs regenerated without any complications after amputations.At the third postoperative day,wound epidermis or called apical ectodemal cap formed where a population of round shaped mononuclear cells underneath streamed along the proximal-distal axis of residual stump. Meanwhile,some long and narrow shaped myoblast and fibroblast like cells migrated distally in which a myogenic-specific Myogenin expressed positively inside nuclei.At seventh to fifteenth days after amputation,blastemas emerged beneath the wound epidermis and the blastemal cell appeared immature with a manifested nucleole and an increasing karyoplasmic ratio while positive-expression area of Myogenin enlarged. At 20th to 30th days,blastemal cells redifferentiated to osteoblast and myoblast etc when the Myogenin still expressed positively in some osteoblast nucleus.At day of 45th,a new limb with a little color and size difference regenerated completely.[Conclusions](1) Cynops cynaurus looks like an ideal model of regenerative biology for its magical epimorphosis and wonderful organ regeneration.(2) Epimorphosis of cynops cynaurus' forelimb results from migration, dedifferentiation,proliferation and redifferentiation of proximal cells.(3) It seems dedifferentiated blastemal cells most likely derived from skeletal muscle because myogenic-specific Myogenin had been positively expressed in redifferentiated tissue during regeneration.