Neural Regeneration and Functional Recovery of the Inhalant Siphon in Ascidians After Obstruction

Following tissue injury, inflammatory responses play an important role in initiating the cellular and molecular events associated with tissue regeneration. Among vertebrates, neuroregenerative capacity is limited. Thus, the use of animal models with high regenerative capacity is essential for understanding the mechanisms underlying the interplay between injury, inflammation, and neural regeneration. Ascidians are chordates capable of regenerating organs, making them valuable models for investigating neural regenerative processes. Therefore, this study aims to investigate the morphological, functional, and neurobiological responses associated with regeneration following obstruction of the inhalant siphon (IS) in the ascidian Styela plicata. Animals were maintained in an aquatic vivarium, and regeneration was induced by tethering the siphon. Specimens were monitored at 0 to 7 days post-induction. Morphometric analyses, histological analyses, biochemical assessment and functional evaluation of siphon responses were performed. The formation of a new siphon was observed 2 days after obstruction. Morphometric analyses of the regenerated siphon revealed no statistically significant in length, number of tentacles, or oral pigment organs at this time point. However, siphon stimulation assays revealed significant functional differences for up to 6 days, characterized by delayed motor responses. AChE activity showed a significant alteration at 1.5 days, suggesting changes in cholinergic signaling during the early stages of the regenerative response. Additionally, immunofluorescence analyses revealed alterations in the CNS as early as 0.5 days. Together, these findings demonstrate that S. plicata exhibits a rapid and highly coordinated regenerative response following tissue injury. The temporal profile of these responses highlights the potential involvement of early injury-associated and inflammatory processes in coordinating neural and tissue regeneration.