Fig. 7. Fin blastema is not formed from slow cycling stem cells. Representative fins from long-term pulse-chase experiments are shown. All the fins had continuous BrdU treatment for 4 days, followed by chases of various times. BrdU is indicated by red and H3P by green. (A) Intact caudal fin after a 4-week chase showing a high number of labeled transit-amplifying (TA) cells, mostly in the epidermis. In whole-mount (B) and longitudinal sections (C) of intact caudal fins after an
8-week chase, most of the BrdU label is lost from TA cells and concentrated in basal epidermal cells (arrowheads in C). (D) Longitudinal section through regenerating fin 2 days post-amputation. Note that BrdU-positive cells in the regenerate are rare and strongly labeled (arrows), indicating that these cells had not likely undergone division. H3P-positive cells are not BrdU-positive, suggesting that proliferating blastemal cells in the regenerate are not derived from slow-cycling cells. Original magnification (in A and B): 50x.
