In alternative embodiments, provided are chimeric cells, which in alternative embodiments are the so-called “cardiochimeras”, and methods for making and using them. In alternative embodiments, exemplary chimeric cells as provided herein comprise a cardiac stem cell of cardiac origin or a cardiac progenitor cell fused to either a mesenchymal progenitor cell or mesenchymal stem cell, an endothelial progenitor cell or endothelial stem cell, or a cardiac stem cell or a cardiac progenitor cell. In alternative embodiments, the chimeric cells as provided herein comprise an endothelial progenitor cell, which may or may not be of cardiac origin, fused to either a mesenchymal progenitor cell or mesenchymal stem cell, an endothelial progenitor cell or endothelial stem cell, or a cardiac stem cell or a cardiac progenitor cell. In alternative embodiments, methods for making chimeric cells as provided herein further comprise selecting a cell fusion product comprising a viable chimera of the fused cells. In alternative embodiments, methods for making chimeric cells as provided herein comprise use of any known cell fusion technique, for example, using a Sendai virus, such as a Sendai virus Hemagglutinating Virus of Japan Envelope (HVJ-E), a polyethylene glycol, liposomes or lipids, a fusion protein, electrofusion and/or equivalents thereof. In alternative embodiments, provided are cell lines, chimera (chimeric) cell lines or chromosomally-stable chimera cell lines, derived or made from chimeric cells as provided herein. In alternative embodiments, provided are methods for inducing cardiogenesis in a mammalian heart comprising administration to an individual in need thereof (for example, a human), chimeric cells as provided herein, or a cell line, a chimera cell line or a chromosomally-stable chimera as provided herein. In alternative embodiments, provided are methods for treating or ameliorating a heart injury, a congenital or genetic heart defect, or a heart dysfunction, comprisin
