Abstract
The early stages of regeneration after injury are similar to those of wound healing. The ascidian Botrylloides diegensis can regenerate an entire adult from a small fragment of vascular tunic following the removal of all zooids in an injury-induced regeneration model. We investigated the molecular and cellular changes following injury to determine the differences between the healing process and the initiation of whole-body regeneration (WBR). We conducted transcriptome analysis at specific time points during regeneration and wound healing to identify differentially expressed genes (DEGs) and the unique biological processes associated with each state. Our findings revealed 296 DEGs at 10 h post-injury (hpi), with 71 highly expressed in healed tissue and 225 expressed during the WBR process. These DEGs were predicted to play roles in tissue reorganization, integrin signaling, extracellular matrix organization, and the innate immune system. Pathway analysis of the upregulated genes in the healed tunic indicated functional enrichment related to tissue repair, as has been observed in other species. Additionally, we examined the cell types in the tunic and ampullae in both tissue states using histology and in situ hybridization for six genes identified by transcriptome analysis. We observed strong mRNA expression in cells within the WBR tunic, and in small RNA-positive granules near the tunic edge. We hypothesized that many of these genes function in the compaction of the ampullae tunic, which is a pivotal process for WBR and dormancy in B. diegensis, and in an immune response. These findings establish surprising similarities between ascidian regeneration and human wound healing, emphasizing the potential for future investigations into human regenerative and repair mechanisms. This study provides valuable insights into the gene sets specifically activated during regeneration compared to wound healing, shedding light on the divergent activities of these processes.