rh activin A 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 were injected with rh Activin A (B, D, F, H, J, L) or DMSO (A, C, E, G, I, K), collected at 2 dpi (A–H) and 4 wpi (I–L), paraffin sectioned, and analyzed by H&E staining (A–E, I–L) and anti-pSmad2 IHC (E–H). At 2 dpi, tissue damage was apparent, as indicated by a dashed line(A–H). In contrast, no tissue damage was apparent at 4 wpi (I–L). n = 2 zebrafish per treatment group, per time point. The 5 × scale bar is 200 μm (A–H), and the 20 × scale bar is 100 μm. (I–L). dpi, days postinjury; wpi, weeks postinjury.
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