Figure 5

Stat3 plays a key role in the regenerative response in the neonatal mouse heart. (A) Western blotting analyses of phospho-AKT and AKT, phospho-Erk1/2 and Erk1/2, and phospho-STAT3 and STAT3 between the sham and AR hearts at 1, 4 and 7 dpr. (B) Immunostaining for phospho-STAT3 (Tyr705) in the resected, ZA micro-injected and IL-6 micro-injected hearts at 1 day post-surgery in neonatal mouse hearts. The high-magnification views of the boxed areas are presented below. Scale bars, 200 μm. (C) Cardiomyocyte proliferation was identified by immunostaining for pH3 (green) and Ki67 (green) together with α-actinin (red) co-localization in the STAT3^+/+ and STAT3^−/− mice at 7 dpr in neonatal mice. Arrows indicate cardiomyocytes positive for pH3 or Ki67 staining. The inset is a high-magnification image of a pH3- or Ki67-positive cardiomyocyte which is denoted by an arrowhead. Scale bars, 75 μm. (D) The newly formed cardiomyocytes were shown as Brdu and α-actinin double-positive cells following a pulse-chase experiment in STAT3^+/+ and STAT3^−/− hearts at 21 dpr. Magnification images of the Brdu⁺ cardiomyocyte (arrow) are shown on the right. Scale bars, 25 μm. CMs, cardiomyocytes; n = 3 per group; values are presented as the mean ± SEM; ^*P < 0.05.