Neuronal differentiation in vitro from precursor cells of regenerating spinal cord of the adult teleost Apteronotus albifrons

This study documents neuronal differentiation in vitro from undifferentiated precursor cells of caudalmost regenerating spinal cord of the teleost Apteronotus albifrons. At 11 days in vitro, cells from the caudalmost tip of the regenerating cord are flat and polygonal in shape, lack neuronal processes and do not stain with antibody against neuron-specific filaments. At 15 days in vitro, some of the caudalmost cells have developed short, neurite-like processes; at 18 days in vitro, some cells react positively with antibody against neuron-specific filaments. At 26 days in vitro, many of the caudalmost cells have long branching neurites and react positively with anti-neurofilament antibody. Addition of insulin-like growth factor-I to the medium accelerates the process of neuronal differentiation from the caudalmost precursor cells in vitro. The source of these precursor cells is ultimately cells of the ependymal layer of adult spinal cord. Further investigation of the factors that control production and differentiation of these cells will be important in defining the developmental potential possible for vertebrate spinal cord cells and may aid in creating an optimal environment for regeneration of axons within mammalian spinal cord.