A stem cell produced by culturing a monocyte in the presence of (i) M-CSF and (ii) at least one component selected from a group consisting of a ganglioside and a water-soluble plant extract to dedifferentiate the monocyte； a therapeutic agent for diseases associated with the damage of cells, tissues or organs； a cellular therapeutic agent； a method for producing a stem cell； a culture medium for inducing the dedifferentiation of a monocyte； a dedifferentiation-inducing agent； a kit for cellular therapy, or a kit for producing dedifferentiated cells； and a pharmaceutical composition.
