Integrin-Alpha-6+ Cells Are Responsible for Blastema Formation During Oral Siphon Regeneration in Ciona robusta.

Ascidians exhibit remarkable regenerative capacity through epimorphosis regeneration, a process characterized by blastema formation containing highly proliferative progenitor cells. Characterization of blastemal cell types offers potential advantages for further exploration of cell origin, migration, and differentiation during regeneration. Here, we systematically delineated four morphologically distinct regeneration phases, with particular focus on blastemal morphogenesis using the oral siphon (OS) regenerative model in Ciona robusta. Our findings established IA6+ cells as essential components of the regenerative blastema based on their spatiotemporal accumulation patterns and IA6 knockdown phenotypes. RNA-sequencing analysis of regenerating siphon tissues revealed the activation of Wnt signaling during the blastema formation. Inhibition of the Wnt signaling pathway led to a decrease in the number of IA6+ cells at the blastema site, indicating that the recruitment of IA6+ cells to the blastema site is regulated by the Wnt pathway. Taken together, our findings demonstrate that the accumulated IA6+ cells in the blastema play critical roles in OS regeneration in ascidians, and this process was regulated by canonical Wnt signaling. These results offer new insights into the evolutionary conservation of regenerative mechanisms across deuterostomes.