Is a novel medical use using, pluripotent stem cells (Muse cells) for. regenerative medicine, and the present invention provides a cell preparation and a pharmaceutical composition for improving and treating brain disorders caused by abnormal growth of, animals including SSEA-3 multipotent stem cells . The cell preparation. of the present invention is based on a mechanism for causing, cells to grow by administering, Muse cells to a subject having, disorders, thereby improving and treating, disorders.