Fig. 2: Cardiomyocyte-specific ProTracer identifies highly regional cardiomyocyte cell-cycle activity in adult hearts.

a Schematic showing AAV9-Dre-induced tracing of cardiomyocyte cell-cycle activity. b Schematic illustrating the experimental design. c Immunostaining for GFP on heart sections prepared from Ki67-CrexER;R26-GFP mice treated with AAV9-control or R26-GFP mice treated with AAV9-Dre. d Immunostaining for GFP and TNNI3 on heart sections collected from Ki67-CrexER;R26-GFP mice treated with AAV9-Dre. Numbered regions (1,2,3,4) are magnified on the right. OMW outer myocardial wall, IMW inner myocardial wall, Pa. M papillary muscle, VS ventricular septum, RV right ventricle, LV left ventricle. e Illustration of cycling CMs (GFP) in the adult heart in 12 weeks. Quantification of the distribution of GFP⁺ CMs in different regions of the ventricles. Data are the mean ± s.e.m.; n = 5. f Representative images showing GFP⁺ CMs (arrows) in different regions of hearts. g Immunostaining for GFP and TNNI3 in transverse heart sections. The dotted line demarcates the inner core region of the LV that harbors the majority of the GFP⁺ cardiomyocytes in the ventricles. Numbered regions (1–5) are magnified on the right. Arrows, GFP⁺ cardiomyocytes. h Heat-map of GFP⁺ cardiomyocytes (CM) in transverse heart sections. The green color intensity indicates the average number of GFP⁺ CMs in each 0.0256 mm² square from five heart sections. The red dotted line demarcates the inner core region of the LV. Scale bars, yellow, 1 mm; white, 100 µm. Each image is representative of five individual biological samples.