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StemBook [Internet]. Cambridge (MA): Harvard Stem Cell Institute; 2008-. doi: 10.3824/stembook.1.32.1

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Figure 2. A Stages of zebrafish caudal fin regeneration as longitudinal sections.

Figure 2A Stages of zebrafish caudal fin regeneration as longitudinal sections.

(top) The dotted line demarcates the amputation plane. The wound is closed by migrating epithelial cells to form a wound epidermis within the first 12 hours postamputation (hpa). Over the next 12 hours, the wound epidermis thickens as cells near the amputation disorganize and migrate toward the amputation plane. By 24–48 hpa, a blastema has formed that contains cells expressing a number of molecular markers. Near the end of this period, the blastema has compartmentalized into proximal and distal zones that can be distinguished by the level of cell proliferation as well as the expression of molecular markers. This marks the onset of regenerative outgrowth. By 72 hpa the distal zone can be further subdivided by the expression of fgf20a. (bottom) Cell proliferation (blue) and gene expression (red) show the compartmentalization that occurs in the blastema. B The identification of progenitor cells in the zebrafish heart. (Upper panels – Left) Expression of Red Fluorescent Protein (RFP) driven by a heart muscle-specific promoter. Cells along the boundary of regenerating tissue exhibit reduced “dim” expression of this marker, which could indicate either that the cells are dedifferentiating and reducing the expression of tissue specific genes, or instead that progenitor cells are just beginning to express this gene for the first time. (Upper panels – Right) To distinguish these possibilities, Lepilina et. al. engineered fish to express both GFP and RFP from the same heart muscle-specific promoter. Because GFP folds faster than RFP and RFP is more stable once it is made, GFP+/RFP- cells should represent cells that have turned this gene on for the first time (stem/progenitor progeny) while GFP-/RFP+ cells should represent cells that have turned off the gene at this promoter (dedifferentiation). As illustrated, GFP+/RFP- cells are clearly present near the edge of the amputation, indicating that these “dim” cells are in the process of activating heart muscle-specific genes for the first time and therefore represent differentiating stem/progenitor cells. (Lower panels) After injection of the fluorescent dye near the heart of unamputated fish, epithelial cells around the exterior of the heart fluoresce red. During normal tissue homeostasis, these cells migrate inward and eventually give rise to vasculature within the heart, illustrating the unexpected dynamics of cellular activity in the unamputated zebrafish heart. Images are adapted from: (1) Tales of regeneration in zebrafish., Vol. 226, 2003, 202–210; Reprinted with permission of John Wiley & Sons, Inc. (2) Reprinted from Cell, 127, Lepilina, A., Coon, A. N., Kikuchi, K., Holdway, J. E., Roberts, R. W., Burns, C. G., and Poss, K. D., A dynamic epicardial injury response supports progenitor cell activity during zebrafish heart regeneration. 607–619, 2006, with permission from Elsevier. (3) Wills, A. A., Holdway, J. E., Major, R. J., and Poss, K. D. (2008). Regulated addition of new myocardial and epicardial cells fosters homeostatic cardiac growth and maintenance in adult zebrafish. Development 135, 183–192. Reproduced with permission of the Company of Biologists.

From: Stem cells in animal models of regeneration

Copyright: © 2008 Kyle A. Gurley and Alejandro Sánchez Alvarado.

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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