A HUMAN OSTEOBLASTIC CELL-LINE, MG-63, PRODUCES 2 MOLECULAR TYPES OF MACROPHAGE-COLONY-STIMULATING FACTOR

A human osteoblastic cell line, MG-63, mouse primary osteoblasts, and a mouse osteoblastic cell line, MC3T3-E1, were shown to produce macrophage-colony-stimulating factor (M-CSF) by bone-marrow-cell colony assay, using a specific neutralizing antibody for M-CSF. Immunoblot analysis of M-CSF, produced by MG-63 cells, revealed the presence of a higher-molecular-weight species of M-CSF, in addition to the 85-kDa M-CSF. The higher-molecular-weight species had a high affinity to the DEAE-Sephacel column and was sensitive to chondroitinase ABC and AC. These physico-chemical profiles were wholly compatible with those of the proteoglycan form of M-CSF (PG-M-CSF), which was recently identified by our group in the conditioned medium of Chinese hamster ovary cells transfected with the 4.0-kb cDNA of the M-CSF gene. Conditioned medium of MG-63 cells was fractionated by DEAE-Sephacel column chromatography, and the M-CSF of each fraction was measured by both enzyme-linked immunosorbent assay and bone-marrow-cell colony assay. The fractions eluted by 0.3-0.6 M NaCl, which were shown to contain only PG-M-CSF on immunoblot analysis, also have macrophage-colony-stimulating activity.