Observations on FGF immunoreactivity in the regenerating tail blastema, and in the limb and tail scars of lizard suggest that FGFs are required for regeneration

Abstract

Tail regeneration in lizards depends on the stimulation of growth factors, including Fibroblast Growth Factors (FGFs). Light and ultrastructural immunolocalization of FGFs was compared between the rege-nerating tail blastema and the limb where no regeneration occurs. A likely epithelial-mesenchymal transition occurs following amputation in both tail and limb and FGFs are present in the wound epidermis of both organs at 7-14 days post-amputation, and at lower intensity in mesenchymal cells of the blastema. Immunoreactivity for FGFs disappears in the limb wound epidermis after 14 days post-amputation and in the epithelium covering tails induced to form scars, whereas it remains in the apical tail epithelium. These observations suggest that scarring in the limb or the induced scarring in the tail correlate with the disappearance of FGFs. Basic FGF is concen-trated in the incomplete basement membrane between the epidermis and the tail blastema where the essential signaling process that allows the continuous growth of the regenerative blastema may occur. The study suggests that the successful regeneration of lizard tail is dependent on the presence of FGFs in the wound epidermis, which are probably released into the blastema.