Regeneration in Echinoderms and Ascidians

Abstract

AbstractThe regenerative potential is expressed to a maximum extent in echinoderms and ascidians. They provide unique and valuable deuterostome models, closely related to vertebrates (man included), for an integrated approach exploring regeneration from tissue repair to asexual cloning. The comparison of results derived from different experimental models of echinoderms and ascidians and employing different approaches,in vivoandin vitro, provides an insight on specificity of regulatory mechanisms and processes governing large‐scale pattern formation and information signalling storage between cells and tissues allowing a living system to reliably regenerate and maintain a complex morphology. Since in these animals, regenerative phenomena involve progenitor cells present in the circulating fluids or in the tissues, the crucial questions opened are those related to (1) stemness properties of responsible cells, in terms of origin and derivation (stem cells or dedifferentiated cells) and (2) activities (proliferation and/or migration), plasticity and differentiation potential (derived cellular phenotypes).Key Concepts:Regeneration is a regulative and conservative developmental process complementary to asexual reproduction.Asexual reproduction (cloning) represents the highest expression of the regenerative potential of an organism.Regeneration processes generally imply the key‐contribution of pluripotential cells (stem cells or reprogrammed cells).Echinoderms utilise regeneration processes at all stages of their life cycle (embryo, larva and adult).Echinoderms can regenerate body parts and even complete individual from a fragment following self‐induced or traumatic amputation processes.In ascidians the potential for asexual development is expressed during colony formation by developing functional individuals from adult tissues.Ascidians are the unique adult chordates able to regenerate completely the ablated nervous system.