The present disclosure relates to a method of expanding myeloid progenitor cells by culturing an initial population of cells in a medium comprising a mixture of cytokines and growth factors that promote growth and expansion of the myeloid progenitor cells. The expanded cell population provides a source of cells as therapeutic treatments for neutropenia and/or thrombocytopenia arising in patients subjected to myeloablative therapy and hematopoietic stem cell transplantation.