Fig. 3

Satellite-like cells in adult zebrafish skeletal muscle proliferate after mechanical injury. (A) Schematic of experimental procedure, in which mechanical injury is performed by a single needle-stick into tail skeletal muscle. The approximate position of needle-stick injury in the ventral myotome is indicated in cross-sectional view. EdU was administered (gray arrowhead) by intraperitoneal injection at each post-injury time-point, allowing for EdU incorporation into S-phase cells, and fish were sacrificed 4 h later (acute EdU labeling). Tissue was collected at 2, 3, 4, 5, 6, and 7 dpi. (B) Pax7-positive cell numbers increase at the injury site and peak at 4 days post-injury (dpi). (C) Acute EdU labeling indicates robust proliferation at the injury site at 2 and 3 dpi that declines thereafter. (D) Overlap of Pax7 and EdU at 3 dpi indicates satellite-like cell proliferation post-injury. (E) Quantification of Pax7 and EdU double positive cells at each post-injury time-point reveals a peak number of proliferating satellite-like cells at 3 dpi in a 375 µm² area encompassing the injury site; p*<0.05; p**<0.01. (F) Quantification of the percentage of Pax7-positive cells that are EdU-positive (out of total Pax7-positive cell population) at each post-injury time-point indicates that nearly 50% of Pax7-positive cells are proliferating at 2 dpi, and ~35% are proliferating at 3 dpi. The percentage of Pax7-positive cells that are EdU-positive at later post-injury time-points (4–7 dpi) is significantly less; p*<0.05; p**<0.01. One-way ANOVA followed by Tukey's multiple comparisons test was performed for statistical analyses. Scale bar in all panels is 75 µm.