Figure 1.

Higher Cell Cycle Activity of Human CMs in Moderate SaO₂ Conditions

(A) Representative Ki67-positive cardiomyocytes (CMs) in group B; cardiac troponin-T (cTnT) (red), Ki67 (green), and 4′,6-diamidino-2-phenylindole (DAPI) (blue) stainings are shown. The arrow indicates proliferating CMs. (B) Quantification of Ki67-positive CMs: 1-way analysis of variance (ANOVA), Student Newman Keuls (SNK), n = 10; ∗∗p < 0.01. (C) Representative phospho-histone H3 (pHH3)−positive CMs in group B; cTnT (red), pHH3 (green), and DAPI (blue) stainings are shown; the arrow indicates proliferating CMs and hatch sign indicates proliferating non-CMs. (D) Quantification of pHH3-positive CMs; 1-way ANOVA, SNK, n = 10; ∗∗p < 0.01. (E) Representative aurora B-positive CMs in group B; cTnT (red), aurora B (green), and DAPI (blue) stainings are shown; the arrow indicates proliferating CMs. (F) Quantification of aurora B-positive CMs; 2-way ANOVA, SNK, n = 10; ∗∗p < 0.01. We used quantitative polymerase chain reaction (qPCR) to analyze the expression of mRNA levels of (G) Ki67, (H) cyclin D2, and (I) AURKB in CMs treated with different levels of oxygen saturation (SaO₂). Our results indicated that Ki67, cyclin D2, and AURKB mRNA were significantly increased in the moderate SaO₂ group compared with the other 2 groups. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) served as a control; 1-way ANOVA, SNK, n = 10; ∗∗p < 0.01.