Purification and biochemical properties of a human monocyte-derived growth factor

A monocyte-derived growth factor (MDGF) that stimulates proliferation of fibroblast and smooth muscle cells was purified from mitogen-stimulated human peripheral blood lymphocyte conditioned medium by using anion-exchange, Bio-Sil TSK-250 HPLC gel-permeation chromatography, and NaDodSO4/PAGE. Purified MDGF exhibited acidic charge characteristics (pI 5.0) and migrated with an apparent Mr of 40,000 +/- 2000 in molecular sizing HPLC columns. Elution from NaDodSO4/polyacrylamide gels showed that the growth-promoting activity was associated with three or four protein bands. The highest molecular weight species representing the most intense silver-stained band corresponded to 42,000; the lowest molecular weight species was 33,000. MDGF activity was stable to treatment with acid (pH 2.0) or base (pH 10.0) and heating (100 degrees C, 5 min) but was inactivated upon reduction with 2-mercaptoethanol. The acidic MDGF did not effectively compete with platelet-derived growth factor (PDGF) for receptor binding and was not inhibited by PDGF antibodies. Previous studies have suggested that fibroblast growth-stimulating activity of macrophages is largely due to their secretion of interleukin 1 and a PDGF-like molecule. Our purification and biochemical characterization studies reveal the occurrence of multiple forms of fibroblast growth-stimulating activity in human monocyte conditioned medium. The MDGF activity characterized here appears to be structurally and functionally distinct from the previously described fibroblast growth-promoting activities including interleukin 1, basic fibroblast growth factor, and PDGF.