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Tissue remodeling is essential to multiple processes, including embryogenesis, regeneration, and disease progression. While most current regeneration studies have focused on mechanisms for the regulation of stem cells, much less is known about regenerative tissue remodeling. A wide variety of animal model systems are used to study regeneration, but the organs and tissues each organism regenerates is different, complicating cross species comparisons of regenerative shape changes. We hypothesized that there are conserved regenerative tissue remodeling mechanisms across species, which, if identified, would further our ability to design effective regenerative therapies. We examined tissue remodeling events during regeneration in three species of planarian flatworms: Schmidtea mediterranea and Dugesia japonica (which are closely related), and Phagocata morgani (which is more distantly related). Worms were cut into three fragments (head, pharynx, and tail), and 9 different metrics were analyzed over 25 days post amputation. Our data revealed that conserved regenerative kinetics exist in all species, such as the inability of head fragments to return to pre-regeneration tissue proportions. As predicted by our hypothesis, we also found remodeling events that occurred similarly in the closely related S. mediterranea and D. japonica species, but not in P. morgani. However, we also uncovered regenerative kinetics that did not track by phylogeny. Of these, the most surprising were the similarities between S. mediterranea and P. morgani. For example, in these two species the regeneration kinetics of having to regrow new organs was noticeably different than the kinetics of needing to prune existing organs to the proportions of the new smaller worm size. Together, our data reveal that regenerative tissue remodeling kinetics are quite complex and require further study.
Bolliet, Marine, "A comparative analysis of regeneration among various planarian species" (2017). Honors Theses. 2796.