VIM and congenital heart disease: The surviving cells that form the C-spheres are more robust to culture conditions, and predominantly feature co-expression of c-kit and the mesenchymal marker vimentin (herein referred to as CMCs) (Fig 1A and 1B), as previously shown in the analysis of C-spheres derived from the atria of patients with congenital heart disease [5] and from adult myocardium [12].