Apoptosis involves in intestinal regeneration via iPLA2 and EGFL7 signaling in Apostichopus japonicus

Apoptosis preserves organismal homeostasis by selectively eliminating unnecessary or damaged cells. Emerging evidence suggests that this programmed cell death also activates regenerative pathways and facilitates tissue remodeling. However, the regulatory mechanisms linking apoptosis to regeneration remain poorly defined, particularly in evolutionarily basal organisms. Using the sea cucumber (Apostichopus japonicus) intestinal regeneration model, we observed robust activation of apoptosis throughout the regenerative process. Suppression of apoptosis during the wound healing and mesenteric expansion phases critically impaired intestinal regeneration. Proteomic profiling by Direct data-independent acquisition (Direct DIA) apoptosis-inhibited specimens revealed coordinated downregulation of lipid metabolic pathways, notably Ca²⁺-independent phospholipase A2 (iPLA2) activity, which is typically upregulated during normal regeneration. In parallel, expression of the regeneration-associated factors WNT6 and EGFL7 was markedly reduced under apoptosis inhibition. Functional assays further confirmed that inhibition of iPLA2, EGFL7, or WNT6 significantly reduced both expansion area and cell proliferation in the regenerating intestinal primordia. These findings suggest two potential mechanistic pathways: apoptosis-mediated regeneration of lipid metabolism via iPLA2 and apoptosis-dependent activation of WNT6/EGFL7 signaling. This study offers foundational insights into apoptosis-regulated organ regeneration in invertebrates.