In vitro and in vivo characterization of blastemal cells from regenerating newt limbs.

To better characterize the cells involved in newt limb regeneration, blastemal cells from accumulation and differentiation phase blastemas were grown in dissociated cell culture, and their morphology and antigenic phenotype determined using a variety of antibodies directed against intermediate filaments, cell adhesion molecules, and extracellular matrix molecules. In addition to previously described blastemal cell morphologies, many of the cells in these cultures had a round cell body, with an eccentrically placed nucleus and a cytoplasm filled with autofluorescent granules. The majority of accumulation phase blastemal cells labeled with antibodies against GFAP, vimentin, 22/18 as well as with antibodies against NCAM, L-1, laminin, and fibronectin. The majority of differentiation phase blastemal cells had a similar phenotype but lacked expression of vimentin and fibronectin. Comparison of the blastemal phenotype in vitro and in vivo showed similar expression characteristics. However, in differentiation phase blastemas, laminin immunoreactivity was concentrated in specific locations. In addition, the proliferation of cultured blastemal cells is stimulated by the addition of a crude brain extract, consistent with previous studies in vivo and in vitro. Taken together, these observations suggest that dissociated cultures of newt limb blastemal cells provide a suitable model for the analysis of the cell and molecular mechanisms involved in limb regeneration.