Abstract: The subject of the present invention is to provide a means to producing an erythropoietin-producing organoid using mesenchymal stem cell derived from a mammal. It is a method for producing erythropoietin-producing organoid (organ-like structure) precursor, comprising the step of transplanting mesenchymal stem cell derived from a mammal into an embryo within a pregnant mammalian host or an embryo separated from a pregnant mammalian host to thereby induce the differentiation of the mesenchymal stem cell, in particular, a site to which the mesenchymal stem cell is to be transplanted is a nephrogenic site of the embryo, and a timing of transplantation corresponds to the stage in which a immune system of the host is still immunologically tolerant.

Abstract: The present invention provides a method for preparing an organ, particularly a kidney, for transplantation into mammals. In detail, the present invention provides a method for preparing autotransplantation of autologous organs, particularly a kidney, wherein the isolated autologous mesenchymal stem cells are transplanted into an embryo inside a pregnant mammalian host or into an embryo dissected from a pregnant mammalian host at a desired site to induce differentiation, which is then transplanted into the individual.