Cover: Primary cell populations isolated from neonatal rat myocardium co-cultured with human extraembryonic mesenchymal stem cells (FTM HUCPVCs). Human cells (purple nuclei) integrate with the primary rat cardiac tissue (blue nuclei) and assume cardiac phenotypes, including sarcomeric actinin (red) positivity. Endoplasmic reticulum labelling is applied as counterstain (green). Such phenotypical and lineage commitment changes are only detectable during long term maintenance of co-cultures, providing high homogeneity and high cell viability even with high starting cell numbers. Homogenous and long-lasting cultures from high seeding density were achieved using the column-augmented culture dish described in Szaraz et al. Image licensed under a Creative Commons Attribution 4.0 International license.