Natural tissue immortality: Indefinite survival of sea cucumber explants

Senescence and immortality are central biological paradigms. While regenerative capabilities in Deuterostomia are known, the fate of lost and discarded tissues has been presumed terminal. Here, we demonstrate that explanted epidermal, connective, neural, and muscle tissue from the sea cucumber Psolus fabricii (Holothuroidea: Echinodermata) healed and continued to grow in natural, nonaxenic seawater without supplementation for more than 3 years. In experimental trials, these explants, termed LiPfe (living immortal P. fabricii explants) displayed immune activity, cell cycling, tissue reorganization, and absorption of dissolved amino acids, underscoring their active living state. Comparative experiments conducted on explanted tissues from related species demonstrated no equivalent tissue survival, highlighting the unique properties of P. fabricii, which do not have parallels in the current literature. Our findings challenge conventional perceptions of tissue immortality and present a new class of experimental model, free from ethical concerns, with substantial implications for regenerative biology, biomedical research, and tissue engineering.