Clonal cell cultures from adult spinal cord of the amphibian urodelePleurodeles waltl to study the identity and potentialities of cells during tail regeneration

The urodele amphibians are nearly the only adult vertebrates able to regener- ate their missing or amputated tail. The most strik- ing feature of this model lies in the ability of the spinal cord (SC) to differentiate, within the regen- erating tail, a new ependymal tube from which the SC and the peripheral nervous system originate. A fundamental question is whether, in response to tail excision, the ependymoglia of the old SC stump behaves as an embryonic neuroepithelium. To evaluate this possibility, cell lines from primary cell cultures of adult SC were established for the first time in newts, and two cell clones, immuno- chemically characterized as ependymoglial cell populations, could be obtained. To analyze the po- tentialities of these clonal cells, after transplanta- tion in tail regenerates, cell-marking experiments, using either in vitro transfection with lac2 gene or the lineage tracer lysinated rhodamine dextran (LRD), were performed. One to 2 weeks postim- plantation, most of labeled derivatives were iden- tified as melanocytes. Interestingly, labeled cells were also seen integrated in the ependymoglia of the regenerating SC. Two to 6 weeks after implan- tation in young regenerates, we also observed LRD-labeled elongated cells close to nerves or myofibers which were unambiguously identified as Schwann cells by galactocerebroside staining. Taken together, these findings showed that clonal cells derived from adult newt SC cultures could largely find, in regenerate mesenchyme, suitable environmental conditions to differentiate into mel- anocytes or Schwann cells. Because these two cell types arise from neural crest cells during embryo- genesis, this supports the interesting view that multipotent cells are still present in the SC of adult urodeles.