circUtrn is required for exercise-induced physiological cardiac hypertrophy. (A) The schedule of AAV9 injection and swimming training–induced physiological cardiac hypertrophy model establishment. (B) RT–qPCR analysis of circUtrn expression in mice hearts at indicated treatment group (**P < 0.01, n = 12/group). (C) Cardiac morphology, HW, and HW/TL of mice hearts at indicated treatment group (**P < 0.01, n = 12/group). (D) Representative images of immunofluorescence staining and quantification of WGA staining in mice hearts at indicated treatment (**P < 0.01, n = 6/group. Scale bar: 20 μm). (E) Representative images of immunofluorescence staining and quantification of EdU-positive and Ki67-positive cardiomyocytes in mice hearts at indicated treatment (**P < 0.01, n = 6/group. Scale bar: 20 μm). AAV9-shScramble, Scramble AAV9; AAV9-sh-circUtrn, circUtrn knockdown AAV9. Data are presented as means ± SD. (B, C, D, and E, two-way ANOVA with Tukey post hoc test).