A Review of Histocytological Events and Molecular Mechanisms Involved in Intestine Regeneration in Holothurians

SIMPLE SUMMARY: Many species of sea cucumber in Echinodermata may eviscerate most of or even all internal organs when encountering predators or adverse environments, and can achieve regeneration within a certain time. Although regeneration time varies, the mechanism is common. This paper reviewed the intestinal regeneration process of sea cucumbers from the perspectives of histocytology and molecular mechanism. Echinodermata has a special evolutionary position between achordate and chordate, so we hope to explore the common regeneration conserved signals between invertebrates and vertebrates by recording the intestinal regeneration of sea cucumbers. ABSTRACT: Most species of the class Holothuroidea are able to regenerate most of their internal organs following a typical evisceration process, which is a unique mechanism that allows sea cucumbers to survive in adverse environments. In this review, we compare autotomy among different type of sea cucumber and summarize the histocytological events that occur during the five stages of intestinal regeneration. Multiple cytological activities, such as apoptosis and dedifferentiation, take place during wound healing and anlage formation. Many studies have focused on the molecular regulation mechanisms that underlie regeneration, and herein we describe the techniques that have been used as well as the development-related signaling pathways and key genes that are significantly expressed during intestinal regeneration. Future analyses of the underlying mechanisms responsible for intestinal regeneration should include mapping at the single-cell level. Studies of visceral regeneration in echinoderms provide a unique perspective for understanding whole-body regeneration or appendage regeneration.