Fish Shellfish Immunol 2026 Mar 06;:111262. doi: 10.1016/j.fsi.2026.111262.

A proliferative subpopulation of coelomocytes in sea cucumber is identified and characterized by single-cell RNA-seq after evisceration.

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Sea cucumbers possess a unique physiological function, evisceration, after which they regenerate new coelomocytes in the coelom before organ reformation. However, the recovered mechanism of coelomocytes in coelom after evisceration has not been studied enough. In this study, a total of nineteen subpopulations in sea cucumber Apostichopus japonicus were identified by scRNA-seq analysis for coelomocytes in coelom and water-vascular system, and further assigned by cell markers from homologous species. After evisceration, cluster 10 in coelom exhibits the highest increased proportion (15-fold) compared with that of normal conditions, which is identified as a moderately differentiated subpopulation associated with cell proliferation. It can directly differentiate into cluster 4, 0, or 5 at 6 h post evisceration (hpe). Furthermore, immunocytochemical staining of cluster 10 indicates they share consistent features with moderately differentiated cells reported in other holothurian animals. Moreover, we also find the cell proportion of cluster 10 in the water-vascular system after evisceration has the highest elevated fold compared to that in intact animals. Meanwhile, this subpopulation strongly exhibits a poorly differentiated level and property of cell proliferation and can differentiate into cluster 9 at 6 hpe. However, the achievements of the proliferative and differentiated capability for cluster 10 coelomocytes in the water-vascular system need to undergo a dedifferentiation process post-evisceration because these activities are absent in intact animals. Altogether, we provide comprehensive resources for accurately molecular classification for coelomocytes in sea cucumber and characterize the dynamics in compositions and functions of coelomocytes in coelom and water-vascular system after evisceration.

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