Wound repair during arm regeneration in the red starfish Echinaster sepositus

Abstract

Starfish can regenerate entire arms following their loss by both autotomic and traumatic amputation. Although the overall regenerative process has been studied several times in different asteroid species, there is still a considerable gap of knowledge as far as the detailed aspects of the repair phase at tissue and cellular level are concerned, particularly in post‐traumatic regeneration. The present work is focused on the arm regeneration model in the Mediterranean red starfish Echinaster sepositus; to describe the early cellular mechanisms of arm regeneration following traumatic amputation, different microscopy techniques were employed. In E. sepositus, the repair phase was characterized by prompt wound healing by a syncytial network of phagocytes and re‐epithelialisation followed by a localized subepidermal oedematous area formation. Scattered and apparently undifferentiated cells, intermixed with numerous phagocytes, were frequently found in the wound area during these first stages of regeneration and extensive dedifferentiation phenomena were seen at the level of the stump, particularly in the muscle bundles. A true localized blastema did not form. Our results confirm that regeneration in asteroids mainly relies on morphallactic processes, consisting in extensive rearrangement of the existing tissues which contribute to the new tissues through cell dedifferentiation, redifferentiation, and/or migration.

Post‐metamorphic ontogeny of Zoroaster fulgens Thomson, 1873 (Asteroidea, Forcipulatacea)

“…Recent work on the regeneration process in echinoderms, especially the regeneration of the asteroids and ophiuroids arms, has shown that regeneration follows a ‘distalization‐intercalation’ model (Ben Khadra et al. ,b, ; Czarkwiani et al. ).…”

“…The regeneration can be divided into three main phases: (i) the repair phase during the first hours/days post‐amputation; (ii) the early regenerative phase; and (iii) the advanced regenerative phase (Candia Carnevali & Bonasoro, ; Ben Khadra et al. ,b, ). It is during the early regenerative phase that ‘distalization‐intercalation’ occurs, i.e.…”

Tissue Extract Fractions from Starfish Undergoing Regeneration Promote Wound Healing and Lower Jaw Blastema Regeneration of Zebrafish

“…This cluster behavior has also been observed during arm regeneration in the red starfish7. It is unclear whether the injured tissues or water vascular canal area release bioactive substances that direct cell growth and behavior.…”

“…In addition to blastema structure, wound sealing, wound healing, wound epidermis reconstitution, and epithelial/mesenchymal interconversions represent the basic processes of nearly complete healing in both zebrafish and starfish2722. In contrast to zebrafish blastema, which is composed of a mass of undifferentiated mesenchymal cells with excessive extracellular matrices, starfish blastema-like structures are more likely to be an accumulation of proliferating cells in matrix and lack typical fibroblast features.…”

“…The arm regeneration in A. rollestoni was achieved synchronously by de novo arm-bud formation and growth and arm-stump elongation6. In E. sepositus , the repair phase was characterized by prompt wound healing and re-epithelialization, followed by formation of a localized subepidermal edematous area7. Most studies suggest that regeneration in asteroids mainly relies on cell dedifferentiation, cell proliferation, cell migration, and the formation of blastema-like structures.…”