ARF expressed under control of the endogenous human ARF promoter in ARF:ARF fish suppresses cardiac regeneration over time. (a) AFOG and troponin staining of WT and ARF:ARF heart cryosections at 1, 7, 15, and 30 dpi. The dotted lines demarcate the injury site. Red stains are for fibrin. Blue stains are for collagen. Brown stains are for muscle. Green stains are for troponin. (b) Myocardial recovery measured by troponin infiltration into the injury site. Infiltration quantified by imaging software shows decreased troponin in the injury site of ARF:ARF fish compared to WT fish from 7 dpi onward. N = 49 hearts. The grey and black lines are logarithmic approximations of the WT and ARF:ARF heart recovery trends respectively. Results are shown as mean ± standard error. The * represents a statistically significant difference.