Fig. 5

Administration of zCNTF reduces apoptosis and boosts initiation of heart regeneration after cryoinjury. a Experimental design for the apoptosis assay. zCNTF was injected into the pericardial cavity 72 h before cryoinjury. Hearts were collected at 6 and 12 h post-cryoinjury (hpci). b Transversal heart sections at 6 hpci stained for apoptotic cells using the TUNEL assay (green) and a myocyte nuclear marker Mef2 (red). Cryoinjured zone is encircled with a dashed line. Scale bar for the whole section, 500 μm; for the magnified area, 100 μm. cQuantification of TUNEL-positive nuclei at 6 and 12 hpci, in hearts injected with control proteins and zCNTF. n ≥ 4 hearts; ≥ 2 sections per heart; *P < 0.05; **P < 0.01. d Experimental design for assessment of the initiation of regeneration. zCNTF was injected into the pericardial cavity at 3 days before cryoinjury (dpci). Hearts were collected at 7 dpci. e, fImmunofluorescence staining of heart sections. Scale bar for the whole section, 500 μm; for the magnified area, 100 μm. e Transversal heart sections of transgenic fish cmlc2:DsRed2-nuc immunstained for MCM5 (green) display an enhanced number of proliferating CMs (arrows) after zCNTF injection. f Transversal heart sections of zCNTF/hIgG injected wild type fish immunostained for embCMHC (N2.261, green) and F-actin (red) comprise more abundant expression of embCMHC in the peri-injured ventricle within a distance of 100 μm from the wound tissue, which is delineated with a dotty line. g Quantification of MCM5-positive cardiac nuclei in hearts injected with control proteins and zCNTF. n ≥ 4 hearts; ≥ 2 sections per heart; *P < 0.05; **P < 0.01. h Proportion of the embCMHC-positive myocardium within the 100 μm peri-injury zone in hearts injected with control proteins and zCNTF. n ≥ 4 hearts; ≥ 2 sections per heart; ***P < 0.001