Synergistic activity for high-proliferative-potential colony-forming cell (HPP-CFC) development, stable to trypsin...

In this paper we describe a crude pregnant mouse uterus and embryo extract (PMUE) prepared from CFW/ep mice which was able to stimulate the proliferation of high-proliferative-potential colony-forming cells (HPP-CFC) of bone marrow of normal mice, in vitro, in semisolid agar culture system. The development of that primitive murine progenitor cells requires the presence of a macrophage-stimulating factor (CSF-1) plus a synergistic factor (SF). The biological activity of both factors was present in our extracts. The higher SF activity was found in uterine plus placental tissues extracts. The SF was precipitated over 45 per cent ammonium sulfate saturation, and behaved as a nondialyzable substance, remained unaffected by trypsin digestion, and was heat-stable (70 degrees C for 15 min).