Methods, compositions, and kits for repairing damaged myocardium and/or myocardial cells including the administration of cytokines, variants of cytokines, cardiac stem cells, or combinations thereof are disclosed and claimed. In addition, methods, compositions, and kits for forming coronary vasculature including the administration of cytokines, variants of cytokines, cardiac stem cells, or combinations thereof are described. In particular, administration of variants of hepatocyte growth factor, such as NK1, 1K1, and HP11, are useful for the repair and/or regeneration of damaged myocardium or formation of coronary vasculature. Methods of activating cardiac stem cells in vitro are also disclosed.