Remodelling of the skin during metamorphosis in the Italian newt (Lissotriton italicus) (Amphibia, Urodela): localization pattern of keratins, stromelysin-3 (MMP-11), and pan-cadherin

During amphibian metamorphosis, modifications of several important body systems take place involving different molecular mechanisms driving, among other, cell differentiation, cell–cell adhesion, and extracellular matrix turnover. Amphibians have been used as a classic model to investigate organs remodelling, including the skin; however, previous studies on metamorphosis have examined, for the most part, anurans, whereas only a few reports have considered urodeles. The main goal of this study was to evaluate the presence of keratins in the epidermis of the Italian newt (Lissotriton italicus). In order to assess the putative differential expression of keratins, we immunodetected cytokeratin type I, type II, and high molecular weight (HMW) during the larval, pre-metamorphic, and adult phase. Our results clearly indicated that keratins expression changes as the epidermis modifies during the functional maturation; interestingly, HMW keratins showed a strong immunopositivity in adult, thus suggesting that, in urodeles, these keratins become expressed in adult epidermis. Moreover, by using a monoclonal antibody against pan-cadherin, we demonstrated that in L. italicus epidermis during pre-metamorphic stages, the conversion from larval to adult type is not completed in whole epidermis; we also showed the strong spatiotemporal correlation of stromelysin-3 expression with tissue remodelling in L. italicus skin. Considering that skin remodelling in urodeles is a topic relatively neglected, our findings will contribute to fill a gap in the existing research literature; moreover, these data emphasize that unexpected results could be obtained when different model systems were used.