Cell proliferation and movement during early fin regeneration in zebrafish

Cell proliferation and cell movement during early regeneration of zebrafish caudal fins were examined by injecting BrdU and Di-I, respectively. In nor mal fins of adult fish, a small number of proliferating cells are observed in the epidermis only. Shortly following amputation, epithelial cells cover ed the wound to form the epidermal cap but did not proliferate. However, by 24 hr, epithelial cells proximal to the level of amputation were strongly labeled with BrdU. Label incorporation was also detected in a few mesenchym al cells. Proliferating cells in the basal epithelial layer were first obse rved at 48 hr at the level of the newly formed lepidotrichia. At 72 hr, pro liferating mesenchymal cells were found distal. to the plane of amputation whereas more proximal labeled cells included mainly those located between t he lepidotrichia and the basal membrane. When BrdU-injected fins were allow ed to regenerate for longer periods, labeled cells were observed in the api cal epidermal cap, a location where cells are not thought to proliferate. T his result is suggestive of cell migration. Epithelial cells, peripheral to the rays or in the tissue between adjacent rays, were labeled with Di-I an d were shown to quickly migrate towards the site of amputation, the cells c loser to the wound migrating faster. Amputation also triggered migration of cells of the connective tissue located between the hemirays. Although cell movement was induced up to seven segments proximal from the level of amput ation, cells located within two segments from the wound provided the main c ontribution to the blastema. Thus, cell proliferation and migration contrib ute to the early regeneration of zebrafish fins. (C) 2001 Wiley-Liss, Inc.