Skeletal muscles undergo severe atrophy changes after denervation. Due to the slow growth velocity of the regenerating axons and the long distance they have to travel to reach the target muscle, skeletal muscles undergo irreversible atrophy before they are effectively reinnerated, and this is one of the major reasons for poor funtinal recovery following peripheral nerve surgery, despite the modern microsurgical techniques for nerve repair and technologic advances in equipment. Embryonic neural stem cells are multipotential cells derived from the embryo and can proliferate indefinitely in vitro while retaining multipotency. Neural stem cells can also be made to differentiate into a large variety of terminal cell types in vitro. Embryonic neural stem cells which transplanted into mammalian nervous system, especially the centrol nervous system, such as brain can survive, develop and repair some functional deficits by replacement of the damaged neurons and construction of new neural circuits. In this study, we explored the differention characteristic of neural stem cells both in vitro and in vivo, and evaluated the therapeutic effect of transplantation of neural stem cells on recovery of denervated skeletal muscle atrophy and motor function.Part One Study of Cultivation and Differentiation of Spinal Cord-derived Stem Cells in Embryonic Rats in vitro. AIMS: To establish procedures of neural stem cell culturing from embryonic rat spinal cord and study the characteristics of their proliferation and differentiation in vitro. METHODS: Neural stem cells were obtained from spinal cord of P16 day rats by dissociation. They were cultured in a serum-free medium containing basic fibroblast growth factor and epidermal growth factor. Single cell cloning was undertaken in order to purify the cells. The culture condition of stem cells was explored and the passaging method was investigated. Then, all neural spheres were attached to the bottom and induced to differentiate. Indirect immunoflurenscence cytochemistry were used to identify the neural stem cells and the differentiated cells with nestin as marker for neural stem cells, neurofilaments (NF) for neurons and glial fibrillary acidicprotein (GFAP) for astrocytes. RESULTS: Plenty of neural stem cells were obtained from the spinal cord by means of mechanical dissociation and serum-free culture medium. The obvious neural sphere can be observed in about 10 days and can be maintained in vitro for more than 8 weeks. The neural stem cells induced to differentiate in vitro can produce various types of neural cells. Indirect immunoflurenscence cytochemistry showed Nestin positive for the neural stem cells and NF, GFAP positive for the differentiated cells. CONCLUSIONS: Plenty of neural stem cells can be obtained from the spinal cord in embryonic rats and can be induced to differentiate into various types of neural cells such as neurons and astrocytes.