Effect of a Hematopoietic Promoting Factor Derived from Porcine Kidney on the Proliferation of Mouse Hematopoietic Progenitor Cells in Liquid Culture

We have partially purified a factor from porcine kidney, hematopoietic-promoting factor (HPF), which enhances granulocyte-macrophage colony-forming units (CFU-GM) and erythropoietic burst-forming unit (BFU-E) colony formation in the presence of various exogenous colony-stimulating factors (CSF) or erythropoietin (Epo) from mouse bone marrow cells. In this paper we examine the combined effects of HPF and/or stem cell factor (SCF) with interleukin-3 (IL-3) and interleukin-6 (IL-6) on the proliferation of primitive hemopoietic progenitor cells in liquid cultures for 7 or 14d. The combination of IL-3+IL-6+HPF could not increase the number of CFU-GM, BFU-E, and day-8 colony forming units in spleen (CFU-S) in the cultures of unfractionated bone marrow cells, while this combination resulted in a marked increase of progenitors in cultures of c-kit+ enriched cells. In contrast, expansion of progenitors was observed by IL-3+IL-6+SCF or IL-3+IL-6+SCF+HPF in the culture of both unfractionated bone marrow cells and c-kit+-enriched cells after 7 d. The number of CFU-GM and BFU-E in the combination of IL-3+IL-6+SCF+HPF for c-kit+ cells showed the largest increase, 109-fold and 38-fold respectively after 14 d. These results show that HPF has promoting activity on hematopoietic stem cells and acts synergistically with SCF in the early stages of hematopoiesis.