Procedures to produce a biologically active human TPO by mammalian cells in in vitro cultures are disclosed. Murine myeloma cells were genetically modified by introducing the gene of human thrombopoietin through a DNA construction which includes an immunoglobulin promoter associated to an immunoglobulin enhancer. The hTPO obtained is useful with methods of stimulating proliferation or development of hematopoietic cells of the megakaryocytic leneage in vitro and in vivo.