Cardiac regeneration capacity is lost at P7 in wild type mice.

<p>(A) Masson’s trichrome-stained cross sections of wild type mouse hearts showing fibrous tissue (blue) at the level of the ligature and below the ligature (stitch) 3 weeks post MI induced at P1 or P7. Plots represent quantification of the fibrous tissue area as percentage area of the left ventricle (LV). (B) Masson’s trichrome-stained sections showing fibrous tissue in the left ventricle of hearts that underwent apical resection at P1 or P7. Hearts were collected 3 weeks post-resection. Plots represent the fibrous tissue area. The scar area is outlined. Dotted lines show the mean in plots. Scale bar = 500 μm. * = p<0.05.