Stem Cell Migration in the Early Stages of Regeneration in Hofstenia miamia.

Abstract

The process of whole-body regeneration is a phenomenon seen broadly throughout animal species, and comparisons between the physiological mechanisms involved in the regenerative process between distantly-related organisms can shed light on the evolution of different processes in regeneration and development. The mobilization of cell types involved in tissue growth and replacement following amputation is an important aspect of regeneration across multiple species. The model organism Hofstenia miamia is an acoel worm capable of whole-body regeneration, with a stem cell population involved in tissue replacement following tissue amputation. The cellular and molecular response to injury, the reestablishment of body polarity and the development of regenerated structures have been studied previously in this organism, but little is known about the mechanisms of cell migration during regeneration. Single-cell RNA-sequencing data and fluorescent in-situ hybridization were used to evaluate the mechanics of cell migration during the early stages of regeneration in Hofstenia. As was expected, the cell cluster assumed by previous research to represent neoblasts in these animals appeared to be the sole cell type migrating towards the wound site, while other progenitor types either did not appear to express motility-related genes in the dataset, or did not migrate long distances to the wound site to repopulate missing tissues. Most of the genes associated with migration in other species, namely planarians, that were investigated during this research (such as homologues for planarian snail-1, zeb-1 and mmp) did not appear to be highly upregulated during regeneration; however, the wound response gene follistatin was expressed in neoblasts which may have been migrating, and two integrins- integrin α7 and integrin β6- were strongly expressed following amputation in cells surrounding neoblasts, potentially playing a role in neoblast motility.