Meeting Abstract
Tissue regeneration is widespread throughout the animal kingdom, although most regenerative animals have a limited capacity for the structures they can regenerate. The colonial cnidarian Hydractinia, however, has the remarkable ability to regenerate any structure throughout its lifespan, including regenerating its head structures (mouth, tentacles, neurons, stinging cells) within about 72 hours. Migratory stem cells, known as interstitial cells (‘i-cells’), typically reside in the body column of Hydractinia feeding polyps. Head regeneration is accomplished via the proliferation of these i-cells forming a blastema structure that gives rise to all head structures. In this study, we established a detailed timeline of head regeneration in Hydractinia symbiolongicarpus. To better understand this process at a cellular level, we performed a series of experiments including live imaging, immunohistochemistry, and cell proliferation assays over a time course of regeneration. Most polyps completely regenerated their head within ten days, with first tentacle buds occurring between 48 and 72 hours post dissection. Immunofluorescence staining showed wound closure within four hours, while nervous system regeneration and the appearance of stinging cells around the newly formed mouth and in the budding tentacles occurred between 48 and 72 hours after dissection. EdU staining and pulse-chase experiments revealed the essential contributions made by the pool of proliferating i-cells to all regenerated head structures. Our results confirm initial observations made in a sister species of Hydractinia and provide a more detailed understanding of the head regeneration process in Hydractinia that will be used as a basis for future studies of this highly regenerative species.
