Immunolocalization of serpins in the regenerating tail of lizard suggests a role for epidermal and neural barrier formation

Tail regeneration in lizard is stimulated from the apical epidermis and spinal cord, the principal sources of growth factors and signaling proteins that sustain regeneration. Immunolabeling shows that serpins (serine protease inhibitors), which genes are among those most up-regulated during tail regeneration, are prevalently inununolocalized in the regenerating epidermis and ependyma. Western blot detects main protein bands extracted from regenerating tail at 25-27 and 48-52 kDa. The former band may correspond to p27 serpin, a degraded immunogenic fragment of serpin detected in psoriasis and cancer. This suggests that also in lizard the degradation of these proteins occurs but is uncertain whether it is physiological with some function or the fragments derive from the extractive process. In the regenerating epidermis serpins are mainly accumulated in pre-corneous and corneous layers (alpha-layers), and also in the forming oberhautchen and hard beta-layer. In the tail tip serpin-immunolabeling is mainly seen in the ependymal tube and with lower intensity in blastema (mesenchymal) cells. Aside the control on endogenous proteases for the formation of a protective corneous barrier, serpins may also form a protective anti-microbial barrier for the ependyma. The protection of the epidermis and ependyma allows these tissue to continue the stimulation for tail regeneration.