Quantitative Analysis of Mesenchymal Proliferation During Early Regeneration of Zebrafish Fins

Charles W Hunter IV


Epimorphic regeneration is a biological phenomenon with cellular mechanisms that are still unclear. Using a synthetic nucleotide analog BrdU, that incorporates into newly synthesized DNA, we studied cells induced into proliferation during the early phases of teleost fin regeneration. Adult Zebrafish caudal fins were first amputated and incubated in water containing BrdU. The regenerating fins were then harvested at different time points: 24, 36, and 48 hours post amputation (hpa). A monoclonal antibody specific to BrdU was then used to detect the proliferative cells. At 24 hpa, cell proliferation in the epithelial cells where already shown to be greatly induced, whereas only sparse BrdU labeled cells were detected in the mesenchyme. We found that cell proliferation within the mesenchymal tissue peaks at 36 hpa, leading the way for an essential group of cells called blastema to be formed. We analyzed fin cross sections and found that the average number of proliferating mesenchymal cells per section was 7.29 on average at 36 hpa. This number decreases to 3.57 by 48 hpa. By examining the longitudinal sections, we found that BrdU-labeled mesenchymal cells aggregated within the distal most 2 bone rays of the regenerate whereas the BrdU-labeled epidermis spread a much longer distance, ~5 bone rays, suggesting that there might be different regeneration signals in the epidermal and mesenchymal compartments. The disparities in activation of proliferation observed in the mesenchymal tissue during early regeneration suggest timely activation mechanism during regeneration induction. In summary, our results provide a quantitative understanding of epimorphic regeneration.


Epimorphic Regeneration, Zebrafish, Cell Proliferation

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