Immunolocalization of Shh and Chordin in the Regenerating Tail of the Lizard Podarcis muralis

The transcriptome of the regenerating tail in the wall lizard, Podarcis muralis , has indicated the up‐regulation of genes for chordin and shh, but the localization of these proteins in the regenerating tail is poorly known. The present immunohistochemical study has analysed early regenerating lizard tails. Chordin is almost exclusively present in the regenerating spinal cord, made of an ependymal epithelium surrounded by regenerating axons, and in sparse peripheral regenerating nerves. It is unknown whether chordin may stimulate differentiation in surrounding tissues. Chordin immunolocalization resembles that of shh in the regenerating spinal cord. Electron microscopy immunodetection of shh shows its prevalent localization in the cytoplasm of regenerating ependymal cells, from which it may be secreted into the mesenchyme of the regenerative blastema. Shh is also detected in the wound epidermis and regenerating scales but is scarce or completely absent in nerves, muscles, connective tissues and cartilage. In regenerating scales, shh appears localised in the differentiating epidermal layers, in particular in the new beta‐layer, suggesting that shh is also implicated in the stimulation of beta‐cell differentiation. The elective distribution of the two proteins in ependyma and epidermis suggests that they have a fundamental role in the stimulation of tail regeneration in lizards.