CTX injection caused tissue damage apparent at 2 dpi that resolved by 4 wpi. Adult heat-shocked Tg(Bre:GFP) and Tg(Bre:GFP); Tg(HS-acvr1l_Q204D-mCherry) zebrafish injected with CTX (B, D, F, H, I–L) or PBS (A, C, E, G) were collected at 2 dpi (A–H) and 4 wpi (I–L). Paraffin sections of the lesion site were analyzed by H&E staining (A–D, I, J), Safranin O staining (K, L), and anti-pSmad2 IHC (E–H). Tissue damage is indicated by the dashed outline(A–H). The injury lesion and pSmad2 expression were apparent at 2 dpi (A–H), and not at 4 wpi (I–L). n = 1 zebrafish per PBS treatment group, n = 3 zebrafish per CTX treatment group at 2 dpi. n = 1 zebrafish per CTX treatment group at 4 wpi. (A–L) 5 × scale bar is 400 μm. CTX, cardiotoxin; PBS, phosphate-buffered saline.
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