Fig. 5

Myocardial Polyploidization Creates a Barrier to Cardiomyocyte Proliferation and Heart Regeneration

(A–D) Adjacent sections from 45-dpr hearts from the indicated cohorts, immunostained for Tropomyosin and GFP (left) or stained with AFOG (right). n = 14 (12), 10 (9), 9 (9), and 19 (18) hearts (number of hearts that showed complete regeneration is indicated in parentheses), respectively. Asterisks indicate injured/regenerated area.

(E) Relative change in percentage of GFP⁺ cardiomyocytes in the regenerate compared with the surrounding region in hearts from the indicated cohorts (n = 12, 9, and 19, respectively). ^∗∗∗p < 0.001; ^∗∗p < 0.01; Kruskal-Wallis test followed by Dunn's multiple comparisons test.

(F) Quantification of the scar area of hearts from (A) to (D) normalized to the ventricular area (n = 14, 10, and 19 hearts; solid black line indicates the mean); n.s., not significant by Kruskal-Wallis test.

(G) BrdU pulse-chase strategy used to evaluate cardiomyocyte proliferation during regeneration in experiments from (G) and (H).

(H) Section from a 14-dpr mosaic heart composed of diploid (GFP⁻) and polyploid-enriched (GFP⁺) cardiomyocyte populations, immunostained for tropomyosin, GFP, Mef2, and BrdU. BrdU and Mef2/GFP signals of boxed region are shown at higher magnifications. Blue arrowheads indicate BrdU⁺ cardiomyocyte nuclei. Asterisks indicate injured/regenerated area.

(I) Cardiomyocyte BrdU labeling indices of GFP⁻ and GFP⁺ populations in injury sites in experiments from (F) and (G). Box-and-whisker plot. n = 7 hearts. ^∗∗p < 0.01, Mann–Whitney test.

CM, cardiomyocyte; ER, early recombination; HS, heat-shocked. Scale bars, 50 μm. See also Figure S6.