Immunolocalization of Matrix Metalloproteinases in regenerating lizard tail suggests that an intense remodelling activity allows for apical tail growth

Abstract Regeneration of the tail in lizards suggests that a continuous remodelling process is active in the developing tissues. The present immunological study has detected Matrix Metalloproteinases (MMPs), previously indicated from a transcriptome study, in the lizard Podarcis muralis . Immunoblots show a main labelled band for MMPs around 68 kDa, possibly a MMP16‐like. Immunofluorescence shows that MMPs are mainly present in the central apical region of the mesenchymal blastema, in the ependyma of regenerating spinal cord, and in the basal layer and basement membrane‐region of the apical wound epidermis. The immune‐labelling decreases or disappears in differentiating tissues present in proximal regions of the regenerating tail such as the epidermis and dermis, muscles, inner connective tissues and in the axial cartilaginous tube. The prevalent localization of MMPs in the central mesenchyme of the blastema indicates a continuous remodelling of the extracellular matrix that actively contributes to the progressive distal growth of the apical blastema into a new tail. The study stresses that in regenerating organs of amniotes, a massive growth can only occur where connective tissues are maintained loose by the continuous action of extracellular matrix proteases in concert with the high production of hyaluronate and consequent tissue hydration.